This disclosure describes hybrid chine hulls, marine vessels including hybrid chine hulls and methods of manufacturing and using hybrid chine hulls. An exemplary hybrid chine hull includes a keel, a single chine section, and a double chine section distinct from the single chine section with respect to a longitudinal direction of the keel and positioned aft of the single chine section.

Inland push boats generally have a single chine hull design or a double chine hull design. The majority of inland push boat hulls have a single chine hull, i.e., a single "hard edge" or sharp transition between a keel or hull bottom and sidewalls of the hull on both sides (i.e., port and starboard) of the hull. Some inland push boats have double chines hulls to increase efficiency and improve maneuvering, i.e., two "hard edges" or sharp transitions between the keel or hull bottom and sidewalls of the hull on both sides (i.e., port and starboard) of the hull. To illustrate, the double chine hulls include an intermediate angled portion between the keel or hull bottom and sidewalls of the hull. Although, double chine hull boats have increased efficiency and improved maneuvering, they are more costly to build. For example, double chine hulls often require additional welds, sometimes including multiple passes, along the entire length of the hull to join frame sections of the hull. Additionally, double chine hulls are less stable and slide more when flanking, when the boat is twisting to impart torque on a barge to turn the barge, as compared to single chine hulls. Double chine hulls have increased maintenance costs and service times, as compared to single chine hulls. To illustrate, double chine hulls are harder to dry dock, as compared to single chine hulls, because of the two chines have to be supported and the intermediate angled portion has to be supported. Furthermore, double chine hulls have less capacity for in boundary tanks, often as much as 10-20 percent less as compared to single chine hulls. Accordingly, double chine hull boats have 10-20 percent less operational time and require more frequent stops to fill up on supplies, e.g., water and fuel.

Hybrid chine boat hull and methods of manufacture and use


A multi-homed network node comprises an interface that is addressable using a primary network address and a secondary network address. Network packets identifying the primary network address traverse a first network path and packets identifying the second network address traverse a second network path that is routed physically separately from the first network path. A transport layer network protocol association is established in the network between a first node and the multi-homed node. One or more data messages are sent to the second node and identify the primary network address. Network feedback information indicates one or more performance characteristics of the first network path. In response, the data messages are automatically modified to identify the secondary network address.

The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Stream Control Transmission Protocol (SCTP) is defined in IETF RFC 2960. This description assumes the reader has familiarity with and understands RFC 2960. SCTP is also described in R. Stewart et al., "Stream Control Transmission Protocol" (Boston: Addison-Wesley, 2001) ("Stewart et al." herein).
SCTP can support of multi-homed network nodes, which are network elements such as routers and switches that can be reached using any of several network addresses. SCTP nodes and intermediate nodes in a network may be configured so that traffic from one node to another travels on physically different routed paths if different destination network addresses are used in a packet. In such a configuration, SCTP associations become tolerant against physical network failures.
In present practice, only a loss of connectivity will cause an SCTP implementation to change the destination network address of a destination node. Thus, the use of multi-homed nodes with SCTP associations is limited. Network path characteristics can change over the lifetime of an association, but when performance of a network path to a first destination of an address declines, presently there is no way to change the destination network address to a second address that may provide better performance.

Selecting paths in multi-homed transport-layer network associations


A method is disclosed. The method includes providing a plurality of blades, movably connecting the plurality of blades to an outer member via a plurality of arm members, disposing the plurality of blades in a human or animal body, and moving the plurality of blades from a first position outward to a second position when the plurality of blades are disposed in the human or animal body. The plurality of blades are disposed further from each other in the second position than the first position. Moving the plurality of blades outward from the first position to the second position includes moving the plurality of arm members. Moving the plurality of blades includes maintaining equidistance between the plurality of blades as the plurality of blades move from the first position to the second position.

Surgical retractors are used to hold an injured portion of a patient's body or incision open while a surgeon works on the patient. The surgical retractor thereby provides access for the surgeon during a surgical procedure at a given region of tissue.
Some soft tissue retractors are handheld, while others attach to a fixed ring. Conventional retractors are expandable, typically expanded by hand, one blade at a time. Some retractors are plier-type instruments, in which squeezing the handles of the instruments expands two of the blades of the instrument. However, these instruments typically have a third blade that is expanded separately from the other blades. Such conventional instruments may create uneven pressure on soft tissue, leading to bruising and post-surgical pain. Additionally, expanding the blades separately takes additional time during surgeries in which every precious second counts for providing positive patient outcomes.
Furthermore, such conventional retractors are typically large and bulky. Conventional retractors including a fixed ring are typically much larger than desired, to allow the blades of the instruments to slide. The plier-type retractors typically have larger metal handles. These large, bulky retractors can get in the way of the surgeon and may obstruct x-ray and other imaging that are performed during a procedure.
The exemplary disclosed system and method of the present disclosure is directed to overcoming one or more of the shortcomings set forth above and/or other deficiencies in existing technology.


The present invention provides a picture synthesizing apparatus comprising a first synthesis means for synthesizing base picture data with mix picture data to be synthesized with said base picture data; a single-color-picture generating means for generating a piece of single-color picture data or a plurality of pieces of single-color picture data; a select means for selecting one of said pieces of single-color picture data generated by said single-color-picture generating means to be used in fade processing of said base picture data and said mix picture data; and a second synthesis means for synthesizing an output of said first synthesis means with an output of said select means. Accordingly, the picture synthesizing apparatus of the present invention is capable of carrying out processing to synthesize a base picture and a mixing picture and fade processing in an integrated and coordinated manner as well as being capable of carrying out cross-fade processing in addition to single-color-fade processing.

The present invention relates to a picture synthesizing apparatus for carrying out a picture synthesis on base-picture data and mixing picture data at a transmittance ratio and for carrying out a fade processing based on the transmittance ratio and gain information in an integrated and coordinated manner. The present invention also relates to a picture processing apparatus for synthesizing an input picture and mixing picture data to produce a picture to be recorded and for synthesizing reproduced picture data and mixing picture data to produce an output picture by means of the picture synthesizing apparatus.
There has been becoming popular a digital camera which allows picture data to be recorded into recording media such as a semiconductor memory, a magnetic disc and an optical disc. In order to make such a digital camera capable of carrying out a fade-in process, a fade-out process and a process to synthesize a mixing picture, the related art digital camera is provided with a fade processing circuit 102 and a mixing processing circuit 103 as shown in FIG. 1. In such a configuration, the fade processing circuit 102 is used for carrying out fade-in and fade-out processes whereas the mixing processing circuit 103 is used for performing a synthesis process.
In the digital camera shown in FIG. 1, base picture data to undergo a fade processing is supplied to the fade processing circuit 102 by way of an input terminal 101. A white-color picture signal, a black-color picture signal and gain data are also supplied to the fade processing circuit 102.
The fade processing circuit 102 synthesizes the base picture data with the white-color picture signal or the black-color picture signal in accordance with the gain data in order to carry out fade-in and fade-out processes.
To put it in detail, a fade-in process is carried out by initially setting the gain for the white-color or black-color picture signal at a large value and the gain for the base picture data at a small value and then gradually decreasing the gain for the white-color or black-color picture signal while gradually increasing the gain for the base picture data. If the white-color picture signal is selected in the fade-in process, a picture will appear gradually from a white-color display. If the black-color picture signal is selected in the fade-in process, on the other hand, a picture will appear gradually from a black color display.
On the contrary, a fade-out process is carried out by initially setting the gain for the white-color or black-color picture signal at a small value and the gain for the base picture data at a large value and then gradually increasing the gain for the white-color or black-color picture signal while gradually decreasing the gain for the base picture data. If the white-color picture signal is selected in the fade-out process, a picture will disappear gradually, turning into a white-color display. If the black-color picture signal is selected in the fade-out process, on the other hand, a picture will disappear gradually, turning into a black color display.
A base picture output by the fade processing circuit 102 is supplied to the mixing processing circuit 103. The mixing processing circuit 103 superposes an OSD (On Screen Display) picture on the base picture. OSD data is supplied to the mixing processing circuit 103 by way of an input terminal 104 thereof. On the other hand, transmittance data is supplied to the mixing processing circuit 103 by way of an input terminal 105 thereof.
The mixing processing circuit 103 superposes the OSD (On Screen Display) data received through the input terminal 104 on the base picture received from the fade processing circuit 102. The transmittance indicates a priority given in a synthesis of the OSD picture on the base picture. To be more specific, an opaque transmittance indicates that the OSD picture is to be displayed on a portion where the base picture overlaps the OSD picture. A semi-transparent transmittance indicates that an intermediate value between the base picture and the OSD picture is to be displayed on a portion where the base picture overlaps the OSD picture. A transparent transmittance indicates that the base picture is to be displayed on a portion where the base picture overlaps the OSD picture. A result produced by the mixing processing circuit 103 appears at an output terminal 106 thereof.
Examples of the OSD picture are a design pattern and an animation character picture. In this case, a design pattern and/or an animation character picture is superposed on a base picture. In addition, a shrunk picture of an already picked-up picture used as an OSD picture makes a thumbnail showing a typical configuration of a picture display system of a digital camera employing a fade and mixing processing circuit implemented by the fade processing circuit 102 and the mixing processing circuit 103 described above. In FIG. 2, reference numerals 111 and 112 each denote a fade and mixing processing circuit. The fade and mixing processing circuits 111 and 112 each comprise the fade processing circuit 102 and the mixing processing circuit 103 as shown in FIG. 1. The fade and mixing processing circuit 111 carries out fade processing and mixing processing on a picture received from the camera. On the other hand, the fade and mixing processing circuit 112 carries out fade processing and mixing processing on a playback picture.
A memory 113 is used for storing a variety of mixing pictures such as a design pattern, an animation character picture and a shrunk picture of an already picked-up picture. Picture data to be superposed on a base picture in a camera-picture recording operation is read out from the memory 113 and set in an OSD-data processing circuit 114. On the other hand, picture data to be superposed on a base picture in a playback operation is read out from the memory 113 and set in an OSD-data processing circuit 115.
In an operation to record a camera picture signal, picture data generated by a camera-signal processing circuit 116 and picture data generated by the OSD-data processing circuit 114 to be superposed on the base picture are supplied to the fade and mixing processing circuit 111. The fade and mixing processing circuit 111 carries out fade-in as well as fade-out processes and superposes picture data received from the OSD-data processing circuit 114 on picture data received from the camera-signal processing circuit 116. Picture data output by the fade and mixing processing circuit 111 is supplied to a recording processing circuit 117 which records the picture data into recording media such as a semiconductor memory, a magnetic disc and an optical disc.
In an operation to play back picture data from the recording media, on the other hand, picture data generated by a playback processing circuit 118 and picture data generated by the OSD-data processing circuit 115 to be superposed on the base data upon playback of picture data recorded in advance are supplied to the fade and mixing processing circuit 112. The fade and mixing processing circuit 112 carries out fade-in as well as fade-out processes and superposes picture data received from the OSD-data processing circuit 115 on picture data received from the playback processing circuit 118. Picture data output by the fade and mixing processing circuit 112 is supplied to a video-output-signal processing circuit 119.
As described above, in order to make the related art digital camera capable of carrying out a fade-in process, a fade-out process and a process to synthesize a mixing picture, it is necessary to provide the digital camera with the fade processing circuit 102 and the mixing processing circuit 103 as shown in FIG. 1. In addition, in the configuration of the related art digital camera, the fade processing circuit 102 and the mixing processing circuit 103 are independent of each other.
In the configuration shown in FIG. 1, however, after the fade processing circuit 102 carries out a fade-in or fade-out process, the mixing processing circuit 103 synthesizes a mixing picture. For this reason, neither fade-in process nor fade-out process can be carried out on a mixing picture. In order to perform a fade-in or fade-out process on a mixing picture, it is necessary to provide another fade processing circuit at a stage behind the mixing processing circuit 103. Such another fade processing circuit will make the circuit configuration complicated.
In addition, in the configuration like the one shown in FIG. 1, the fade processing circuit 102 is designed to carry out only a black or white fade processing. With such a configuration, a cross fade processing can not be performed. In order to make the fade processing circuit 102 capable of carrying out a cross fade processing too, a processing circuit is further needed, making the circuit configuration complicated.
Furthermore, in the configuration of a related art picture display system of a digital camera like the one shown in FIG. 2, processing of a recording system is carried out in a manner completely independent of the processing of the playback system. Thus, the recording system is provided with the OSD-data processing circuit 114 and the mixing processing circuit 111 while the playback system is provided separately with the OSD-data processing circuit 115 and the mixing processing circuit 112. As a result, the circuit is large in size.

Integrated fading and mixing for a picture processing apparatus


A display device includes a first substrate, pixel electrodes located in correspondence with pixels above the first substrate, a first partition covering ends of a group of the pixel electrodes, a second partition covering ends of another group of the pixel electrodes, the second partition being lower than the first partition, a solid filler located above the first partition and the second partition, and a second substrate facing the first substrate, the second substrate being away from the first substrate by a distance kept by the first partition, the second partition and the filler.

Recently, display devices for uses in mobile devices are increasingly strongly desired to have higher definition and consume less power. Examples of display devices for uses in mobile devices are liquid crystal display devices (LCDs), display devices using light emitting elements, for example, organic light-emitting diode (OLED) display devices, electronic paper display devices, and the like.
Organic light-emitting diode display devices and electronic paper display devices, among the above, do not require a backlight unit or a polarization plate, which is required in liquid crystal display devices. These display devices are a target of attention as thin light emitting display devices consuming low power. Especially, top emission-type organic EL display devices using white light emitting elements and color filters for light emission to realize full-color display have been progressively developed. Such top emission-type organic EL display devices realize both of a higher numerical aperture of pixels and higher definition, and therefore attract a significant attention.
It is known regarding a high-definition top emission-type organic EL display device that in the case where the distance between a light emitting layer and a counter substrate is different among a plurality of pixels, non-uniform display is caused by a difference in the optical path length. In order to suppress the non-uniform display, a technology of locating spacers between an array substrate having a light emitting layer and a transistor layer formed thereon, and the counter substrate, has been developed (e.g., Japanese Laid-Open Patent Publication No. 2006-252988). In the case where the spacers have a height equal to, or larger than, the thickness of a filler located between the array substrate and the counter substrate, the distance between the array substrate and the counter substrate is controllable by adjusting the height of the spacers.
In the meantime, when the filler located between the array substrate and the counter substrate is thick in a high-definition display device, there occurs a problematic phenomenon that light emitted from the light emitting layer passes an adjacent pixel to be output outside (light leak between adjacent pixels). Especially in a structure in which color filters are located on the side of the counter substrate, colors are mixed due to the light leak between the adjacent pixels. In order to suppress such color mixing, the distance between the light emitting layer and the color filters needs to be shortened. For example, a structure of using partitions demarcating the pixels and a filler as spacers, instead of using conventionally used spacers, has been developed. In the case of this structure, the spacers and the filler located on the spacers are held between the array substrate and the counter substrate. The height of the spacers and the thickness of the filler need to be controlled to be uniform in a planar direction of the substrates.

Display device keeping a distance between a light emitting layer and a counter substrate uniformly


A driver of a semiconductor memory device and driving method thereof is disclosed, which relates to a technology for reducing consumption of a leakage current not required for a driver circuit of a semiconductor memory device. The driver of the semiconductor memory device includes a drive controller configured to selectively provide a first voltage and a second voltage, that have different levels in response to a power-down signal, to a first node; an input driver configured to selectively output a voltage received from the first node in response to a decoding signal; and an output driver configured to be driven in response to an output voltage of the input driver.

1. Technical Field
Embodiments of the present invention generally relate to a driver of a semiconductor memory device, and more particularly to a technology for reducing consumption of a leakage current not required for a driver circuit of a semiconductor memory device.
2. Related Art
Generally, according to a memory unit of a dynamic random access memory (DRAM), a plurality of unit cells, each of which has one transistor and one capacitor, is configured in the form of a matrix in a manner that the unit cells are arranged in a plurality of rows and a plurality of columns.
In addition, the semiconductor memory device includes a memory array, a row decoder, a column decoder, a sense amplifier, and pairs of input/output (I/O) lines. A memory array includes a plurality of memory cells, and a plurality of word lines and pairs of bit lines are coupled to the memory cells. Pairs of bit lines and pairs of I/O lines are coupled to the sense amplifier. In addition, the pairs of I/O lines are controlled by a plurality of column selection lines so as to be electrically coupled to the sense amplifier.
A row decoder decodes a row address received from an external part so as to select some of word lines, and a column decoder decodes a column address received from an external part so as to select some of column selection lines. In addition, the row decoder includes drivers for driving a plurality of word lines in an output end, and the column decoder includes drivers for driving a plurality of column selection lines in an output end.
Specifically, each MOS transistor contained in each of the row decoder and the column decoder of the semiconductor memory device configured to use a low power-supply voltage has a very small gate width, such that a leakage current occurs even when there is a small voltage difference between a source and a drain of each MOS transistor in a standby mode of the row decoder and the column decoder.
The small amount of a leakage current occurs in the MOS transistors, such that it does not greatly affect power consumption of the semiconductor memory device when a small number of row decoders and a small number of column decoders are used. However, with the increasing integration degree of the semiconductor memory device, the number of row decoders and the number of column decoders are rapidly increased in proportion to the increasing integration degree of the semiconductor memory device. Specifically, if the number of row decoders and the number of column decoders are increased, the amount of leakage current is also increased such that total power consumption of the semiconductor memory device is also increased.
In order to reduce the amount of leakage current of the decoder, the related art has widely used a method for blocking a power source of a transistor. However, there is needed a much larger-sized driver for facilitating supply of a power source. The higher the frequency, the larger the number of transistors to be driven, so that the related art may have difficulty in achieving smooth power supply. In addition, if a leakage current of the driver is increased, a direct current (DC) failure occurs, resulting in reduction of productivity.
In recent times, systems configured to use semiconductor memory devices have been rapidly developed to have smaller sizes and lower power consumption. Therefore, it is impossible for high power-consumption semiconductor memory devices to be used for small-sized or portable-sized systems, such that commercial viability thereof is greatly decreased. Especially, a leakage current encountered in products (such as mobile phones) that have low power-consumption as important elements for high product competitiveness is directly associated with such product competitiveness.

Driver of semiconductor memory device and driving method thereof


A head-mountable flow generator is configured to deliver a flow of breathable gas at a continuously positive pressure with respect to ambient air pressure to a patient interface in communication with an entrance to a patient's airways including at least an entrance of the patient's nares, while the patient is sleeping, to ameliorate sleep disordered breathing. The flow generator includes a motor, an impeller assembly and housing that encases the motor and the impeller assembly. The housing is configured to be mounted on the patient's head and comprises an inlet to receive the flow of breathable gas and a pair of opposing outlets to deliver the flow of breathable gas. In addition, the impeller assembly is configured to pressurize the flow of breathable gas received from the inlet, and the housing is configured to convey the pressurized flow of breathable gas through both outlets.

Obstructive Sleep Apnea (OSA) is a sleep breathing disorder (SBD). For those who have OSA, when they sleep the soft tissue in their throat and airway relax and collapse thus blocking the airway and preventing airflow to the lungs. This cessation of breathing, known as an apnea, can last for up to one minute before the blood oxygen levels reach a critical point where the patient has an arousal and their airway reopens. Most OSA suffers do not remember these arousals, however each arousal places extra strain on a patient's heart and destroys the quality of their sleep.
The treatment for OSA may include continuous positive airway pressure (CPAP). CPAP involves the patient wearing a nasal or facemask that delivers positive pressure into the patient's airway. This acts as a pneumatic splint and holds the patient's airway open to prevent apneas.
A typical respiratory apparatus for CPAP therapy includes a flow generator, including for example an air blower, that generates a flow of pressurized breathable gas, e.g. air, to a patient interface configured to be worn by the patient in sealing engagement with the patient's face. The patient interface may be, for example, a nasal mask, a full face mask, or nasal pillows. The flow generator and the patient interface are connected by a tube that delivers the flow to the patient interface.
The typical respiratory apparatus for CPAP therapy has several disadvantages. The patient interface and tube tend to be bulky, and the tube may be rather long, e.g. from about 2-3 m in length. The headgear used to maintain the patient interface in contact with the patient's face may also be bulky and/or complicated to correctly put on and/or adjust. These factors may make a patient reluctant to start CPAP therapy. These factors may also make it difficult for the patient to find a comfortable sleeping position. During sleep, the patient may change position, and the tube may exert a force, i.e. tube drag, on the patient interface which may disrupt the seal between the patient interface and the patient's face. This may result in a leak in the patient interface, which reduces the efficacy of the treatment. Leakage from the patient interface may also irritate the patient, or the patient's sleeping partner, thus further damaging the quality of the patient's sleep.
Patients using a typical CPAP apparatus for therapy may also find it difficult to travel with the apparatus. The flow generator, tube, and mask may be difficult to pack in luggage, and may take up a lot of room within the luggage. The patient may also find it difficult to use the apparatus away from home as the flow generator typically includes a power cord that must be plugged into a power source, e.g. an AC wall socket, which may not be accessible, or available, at the location the patient is visiting.


A projection display apparatus that is lightweight and provides bright, high quality images is provided. The projection display apparatus comprising a color separation and synthesis optical system 4, that performs color synthesis, generating an image, after separating light of the three primary colors of determined polarities into the respective three colors, and modulating those three color lights in relation to respective image signals therefor, and a projection lens 106. The color separation and synthesis optical system 4 comprises polarized light separating means 8, 9, 11 and 16 disposed in respective diagonal directions therein and reflecting spatial light modulating elements 12, 13 and 14 disposed to perform light modulation coordinated to an image signal for each respective color, for light separated according to polarization by the four polarized light separating means 8, 9, 11. Three spatial light modulating elements 12, 13 and 14 are disposed on the outer side of the polarized light separating means 9, 11 and 16, other than the polarized light separating means 8, that is disposed on that side of incident light, at least two from among the four polarized light separating means 8, 9, 11 and 16 are wire grid polarized light separating plates and an astigmatism correcting lens 21 is provided between the polarized light separating means 16 disposed on that side at which projection is performed and at least one of the spatial light modulating elements.

Color projection display apparatuses breakdown each of the three primary color red, green and blue light components from white light and lead those components to the respective corresponding spatial light modulating elements, where the color lights modulated in coordination to an image signal are synthesized and projected, causing color images to be displayed on screen.
Systems using reflective type spatial light modulating elements for a projection display apparatus are beneficial for producing high resolution, however there is a tendency for such apparatuses to have complex optical structures. A projection image display apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. 2001-174755, pp. 8–9, FIG. 8.
Japanese Patent Application Laid-Open Publication No. 2001-174755 discloses a structure comprising a lens for focusing light of the three primary colors, already made into p-polarized light as light of indeterminate polarity passes a polarizing panel or the like, a dichroic mirror, inclined at a 45° angle to the optical axis, that reflects green p-polarized light from this white light source and passes other p-polarized lights, a primary polarized light beam splitter prism that passes green p-polarized light reflected at the dichroic mirror and reflects s-polarized green light, a wavelength selective phase plate for red light, that rotates the plane of polarization of red light among the other p-polarized lights passing the dichroic mirror 90° and passes p-polarized blue light, and a secondary polarized light beam splitter prism that reflects red light, made into s-polarized light at the wavelength selective phase plate for red light and passes p-polarized blue light.
Further, the system comprises, spatial light modulating elements for green light, operating on the side of the primary polarized light beam splitter prism of passed green light, that modulate p-polarized green light in relation to an image signal, forming that light into s-polarized light and reflecting it, spatial light modulating elements for red light, operating on the side of p-polarized red light reflected at the secondary polarized light beam splitter prism, that modulate s-polarized red light in relation to an image signal, forming that light into p-polarized light and reflecting it, spatial light modulating elements for blue light, operating on the side of the secondary polarized light beam splitter prism of passed p-polarized blue light, that modulate p-polarized blue light in relation to an image signal, forming that light into s-polarized light and reflecting it, and a wavelength selective phase plate for blue light, that rotates 90° the plane of polarization of blue light from among p-polarized red light passing the secondary polarized light beam splitter prism and s-polarized blue light reflected at the secondary polarized light beam splitter prism, making that blue light into p-polarized light and passing p-polarized red light.
Moreover, that system comprises a tertiary polarized light beam splitter prism that reflects s-polarized green light reflected at the primary polarized light beam splitter prism and passes p-polarized blue and red lights passing the wavelength selective phase plate for blue light, and a projection lens for projecting p-polarized red, green and blue lights emitted from the tertiary polarized light beam splitter prism.
Further, that system comprises a λ/4 phase plate disposed between the primary polarized light beam splitter prism and the spatial light modulating elements for green light, that forms p-polarized green light emitted from the primary polarized light beam splitter prism into linearly polarized light and linearly polarized light from the spatial light modulating elements for green light into elliptically polarized light without green light reflected at the spatial light modulating elements for green light being slantingly injected into the primary polarized light beam splitter prism and suffering polarity degradation.
A secondary λ/4 phase plate the same as the above-mentioned plate is disposed between the secondary polarized light beam splitter prism and the spatial light modulating elements for red light, and a tertiary λ/4 phase plate the same as the above-mentioned two plates is disposed between the secondary polarized light beam splitter prism and the spatial light modulating elements for blue light.
The optical structure resulting from this projection display apparatus is simple and it is difficult for light beams to become mixed, thereby enabling a projection image having high contrast to be obtained at low cost.
The polarized light separating surfaces used in the primary, secondary and tertiary polarized light beam splitter prisms are formed of an optical membrane of tens of dielectric membranes deposited on the inclined face part of a right angle prism, as shown in FIG. 1A and FIG. 1B, the angle of incidence being a parameter for the rate of permeability for this optical membrane.
FIG. 1A shows wavelength dependence of the rate of permeability p-polarized light in visible wavelength regions when the angle of incidence β of incident light L1 to the transmittance face of a polarized light beam splitter prism 30 is a parameter as shown in FIG. 1B.
FIG. 1A shows the cases for the angle of incidence β of light incident L1 to the transmittance face of the polarized light beam splitter prism 30 where 'a' is 0°, 'b' is 6°, 'c' is 15°, 'd' is +6° and 'e' is +15°.
The angle of incidence β is the angle where incident light L1 to the polarized beam splitter prism provides the optical axis 30.
As shown in FIG. 1A and FIG. 1B, when the angle of incidence β of light incident L1 to the transmittance surface of a polarized light beam splitter prism 30 is within ±6° wavelength dependence of the rate of permeability of p-polarized light is relatively uniform, however when this angle of incidence is exceeded there is substantial wavelength dependence and the rate of permeability deteriorates.
Normally, because main light source input parallel with the optical axis or light incident at angles other than the angles prescribed input to a polarized light separating surface are included in light of indeterminate polarity, even if a main light beam is input to the polarized light separating surface parallel with the optical axis, light other than that main light cannot be input parallel with the optical axis. Thus, as described above, when light of indeterminate polarity is input to the polarized light separating surfaces color reproducibility deteriorates because permeability at those polarized light separating surfaces differs according to wavelength.
As a solution to this, it is possible to consider making the angle of incidence of light of indeterminate polarity input to the polarized light separating surfaces narrower, reducing the wavelength dependence of the rate of permeability, however this causes light of indeterminate polarity other than such light to become external light which is not used by the projection display apparatus, resulting in deteriorating brightness.
Further, heat distribution arises as light of the three primary colors is absorbed by the primary, secondary and tertiary polarized light beam splitter prisms, the refractive index changing due to differences of temperatures in the primary, secondary and tertiary polarized light beam splitter prisms and double refraction occurs leading to deteriorating image quality. This is because light polarizing surfaces within the prisms forming a polarized light beam splitter prism partially rotate. In order to prevent these problems from occurring it is necessary to use material having a low photo elasticity factor to suppress the double refraction of glass material used, however this is more costly.
Moreover, as it is becoming desirable for projection display apparatuses to be increasingly miniaturized, these polarized light beam splitter prisms, being the heaviest component within the apparatus, must be made lighter. Again, as the size of display elements increases the size of these prisms increases also, making these prisms increasingly weighty.
With the foregoing in view it is an object of the present invention to provide a lightweight projection display apparatus producing high-quality images.


Systems configured to inspect a wafer are provided. One system includes an illumination subsystem configured to simultaneously form multiple illumination areas on the wafer with substantially no illumination flux between each of the areas. The system also includes a scanning subsystem configured to scan the multiple illumination areas across the wafer. In addition, the system includes a collection subsystem configured to simultaneously and separately image light scattered from each of the areas onto two or more sensors. Characteristics of the two or more sensors are selected such that the scattered light is not imaged into gaps between the two or more sensors. The two or more sensors generate output responsive to the scattered light. The system further includes a computer subsystem configured to detect defects on the wafer using the output of the two or more sensors.

1. Field of the Invention
This invention generally relates to systems configured to inspect a wafer.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
Inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to promote higher yield in the manufacturing process and thus higher profits. Inspection has always been an important part of fabricating semiconductor devices. However, as the dimensions of semiconductor devices decrease, inspection becomes even more important to the successful manufacture of acceptable semiconductor devices because smaller defects can cause the devices to fail.
Improved sensitivity to particles, anomalies, and other defect types, while maintaining overall inspection speed (in wafers per hour), is desired in wafer inspection systems. Dark field optical inspection systems typically use laser light to illuminate the wafer in a specific pattern—individual spots, lines, or areas—and collection optics to direct the scattered light on a corresponding set of sensors.
One advantage of an inspection system where a large area (on the order of 1 mm by 1 mm) of the wafer is illuminated at once, as opposed to a spot (on the order of microns) or a line (on the order of microns wide by mm long), is that there exist many varieties of two-dimensional sensors that can capture information on thousands to millions of individual detectors in parallel. Furthermore, spot-illuminated inspection systems are practically limited to dozens of spots due to the complexities of illumination optics and of integrating individual sensors thereby limiting achievable throughput. One further disadvantage of spot and line scanning systems is the illumination energy is concentrated in relatively small areas, increasing the power density on the inspected surface, which can undesirably alter the sample properties.
It is well known that an XY (or serpentine) inspection sequence offers lower inspection throughput than a spiral sequence; therefore, a spiral trajectory (commonly known as R-Theta) is desirable under some circumstances. Examples of spiral inspection systems include the SP1 and SP2 instruments, commercially available from KLA-Tencor Corporation, Milpitas, Calif.
Despite the advantage of area inspection systems, as described above and in the art (e.g., U.S. Pat. No. 7,286,697 to Guetta), implementation of this configuration on an R-Theta platform has proven challenging, as there is an inherent mismatch of the spiral sequence of generated images with the rectilinear nature of most two-dimensional array sensors. Detection of defects by the aligning and registration of polar images in real time is a computationally intensive activity. Furthermore, the additional noise added to the measurement by most two-dimensional silicon-based sensors, as compared to discrete detectors such as photomultiplier tubes (PMTs), has in practice reduced the sensitivity performance of such systems. On XY-based area inspection systems, the coordinate mismatch problem does not exist, but previous embodiments of such systems have not been able detect all defects of interest at high speeds due to lack of flexibility of the illumination and collection subsystems.
Accordingly, it would be advantageous to develop inspection systems and/or methods that do not have one or more of the disadvantages described above.


A flexible and non-conductive, artificial, implantable nerve plate has an module of about 3000-1000 N/mm.sup.2 and a thickness of <50 .mu.m for placement and insertion between the fascicles of a nerve bundle. Multiple electrodes are arranged on the two sides of the nerve plate, which is connected via conducting lines inside the nerve plate to a cable integrated with the nerve plate; and the cable is connectable to a control and signal receiver unit.

The present invention relates to a flexible and nonconductive, artificial, implantable nerve plate ("flexible nerve plate", or FNP) for placement or insertion between the fascicles of a nerve bundle.
In the field of neuroprosthetics, new possibilities are being sought to contact nerve bundles and nerve fibers as gently as possible to a multiplicity of electrodes in order to derive multilocal and simultaneous nerve signals and/or stimulate nerve fibers. In this manner, by utilization of technical aid systems, it should also be possible to restore failed bodily functions by registering nerve signals and by stimulating nerves in the peripheral nerve system.
Interfascicular derivation techniques are used to detect nerve signals within a fascicle. (A fascicle is an organizational unit of nerve fibers within a nerve bundle.) Interfascicular electrodes are single bipolar electrodes, which derive both the electrical potential in the nerve fascicle and the electric potential at the nerve surface thereby making a differential measurement possible, which largely eliminates the disturbances caused by electromagnetic interferences. The signals from the sensory touch nerves of the front paws of cats were recorded with implanted interfascicular electrodes. Furthermore, motor nerves were successfully stimulated by means of implanted interfascicular electrodes.
The time and work consumed for precise placement of the electrodes, however, is considerable. As wire electrodes, the electrodes are single channel. Although new multi-channel silicon embodiments are in development, neither single nor multi-channel embodiments are sufficiently suited for permanent implantation. Moreover, the perineurium (the membrane around the fascicles) is damaged when the electrodes are inserted.
Shaft electrodes especially developed for the needs of an intracortical implantation, i.e. an implantation penetrating the pachymenix of the cerebral cortex or transmural, intracardial implantation, are known from IEEE Transactions on Biomedical Engineering vol. 39, No. 3, 1992, p. 271-279 and No. 5, p. 474-481. Insertion of a 125 .mu.m thick Kapton foil between the fascicles in peripheral nerves is inconceivable, however, because the nerve is so badly degenerated, due to movement of the electrode as a consequence of muscle movement as well as due to the weight load and the momentary load on the nerve from the microelectrode as a result of gravity, that a derivation and simulation is not possible.
Kovacs has already demonstrated single-fiber contacting of proximal nerve stumps branching into meshlike microstructures. In order to aid the branching of the nerve stumps, a resection (removal of the fibrous-altered nerve section by cutting with a scalpel) must be conducted on the proximal stumps. This surgery does not seem suited for contacting large peripheral nerves (e.g. ischaeticus, n. femoralis) or for nerves without a total loss of continuity of function. Mesh electrodes are not suited for contacting healthy nerves, because free nerve endings are needed for branching through the mesh.
Since the 1970s, attempts have been made to stimulate and record neurograms with extraneural cuff-like electrodes, so-called cuff electrodes, which are placed encircling the nerve. Cuff electrodes have meanwhile become the most successful form of construction of biomedical electrodes and have found use in many fields. There are several U.S. patents for various forms of construction: for example, U.S. Pat. Nos. 3,774,618; 3,738,368; and 3,654,933. Some electrodes have been safely in use for 15 years. The number of electrodes is limited to three or four. Only a limited local resolution of the stimulation within the nerve can be achieved (tripolar electrodes). Drawback: multilocal stimulation (with more than four electrodes) of the nerve is only possible to a limited extent. Deeper structures can be achieved only with an increased stimulation current. Simultaneous stimulation and derivation is not possible.
One object of the present invention is therefore to permit simultaneous stimulation of the nerve and derivation of the nerve signal by means of an implant.
This object is achieved in accordance with the present invention, by means of a double-sided electrode arrangement and an interfascicular (between the fascicles) implantation, which permits successful direct multi-contacting of fascicles. An illustration of this advantage requires embarking on a brief explanation of neurophysiology.
A fascicle is a bundle of fibers, which is surrounded by the so-called perineurium, a type of enclosing layer, which compared to the epineurium (which gathers the fascicles, literally, to a nerve), is harder and also represents a protective layer for the nerve fibers. The concept of implanting nerve plates provides for implantation between the fascicles, so that the perineurium remains undamaged; therefore, less traumatization of the nerve or the nerve fibers is to be expected than with electrode concepts, in which the shaft electrodes are stuck into the nerve or the fascicle, thereby fundamentally risking injury to the perineurium. These fascicles are disposed functionally in the distal parts of the peripheral nerves, i.e. specific nerve fiber bundles are allocated to specific organs or parts of the body. Proximally peripheral and proximally central, this separation is frequently not clear. Due to the nerve plate concept, functional parts of the body or organs can be intentionally acted upon via the fascicles. By implanting of a flat, flexible structure in the nerve (and not around the nerve as in the case of cuff electrodes), deeper structures can be stimulated with small currents in such a manner that functional damage to the nerve from high currents due to the construction concept can be ruled out. Furthermore, damage to the nerve from pressure from post-operative aedema, as can occur with cuff electrodes, are avoided by means of this principle of construction at the peripheral nerve.
The double-sided arrangement of the electrodes permits simultaneous stimulation (on the one side of the plate) and derivation of the nerve signals (on the other side of the plate). If multiple electroneurograms are derived, the signal can be temporally-spatially resolved. By means of the many electrodes on both sides, stimulation and derivation of the nerve signals can also occur simultaneously on both sides with respective spacing of the electrodes or electrode blocks (FIG. 1), thereby improving the ability to detect or contact many nerve ends.
Hitherto attempts with electrodes, such as described above, have always used only one-sided electrodes, because in classical silicon technology, thinning wafers is conducted using a selective, wet chemical etching process in which the structure of the electrodes at the beginning of the process have to be defined by a diffusion of boron into the silicon substrate. Following this diffusion step, it is impossible to deposit or insert electrodes deeper into the substrate on the bottom diffusion front. After etching the samples free by means of EDP, it is also no longer possible, using semiconductor technology and micromechanics, to apply and to structure metal using thin film technology, to provide it with an insulating covering layer and then to open electrode windows. Giving up silicon in favor of polymer materials (polyimide) and the development of a process of double-sided placement of electrodes on a flat structure using multilayer technology, therefore, is a great improvement over the state of the art.
With the implanted, flexible nerve plate according to the invention, multi-local and simultaneous nerve signals can be permanently derived along multiple fascicles or nerve fibers, and nerves can be stimulated with little stimulation and without severing the nerve or traumatizing it permanently. This is the prerequisite for a multifunctional neuroprosthesis.
The FNP measures the cumulative action impulses in the interfascicular region and can only stimulate there. Single fiber contacting is not possible and not intended. The advantage of the present invention is the minimal traumatization with this implantation.
Procedures that were originally developed for cuff electrodes can be employed for electrode configuration and the design of the stimulation log. Using tripolar electrodes with control currents permits limiting the field to the immediate surroundings of the electrodes so that small fiber groups are stimulated. Differentiated stimulation logs using subtle prepulses also permits selectively stimulating more distant fascicles from the nerve plate. The nerve fibers can be excited according to their size by using block techniques (e.g. anodic block) or in the event of simultaneous stimulation by multiple adjacent electrodes.
Improvement and Advantages Over the State of the Art
Direct multiple contacting of fascicles and nerve fibers within a nerve bundle. PA1 Simultaneous stimulation (e.g. of one side of the plate) and derivation (on the other side of the plate) is possible. PA1 Multiple electrodes are located on a flat, flexible substrate, resulting in minimal traumatization of the nerve. PA1 Mechanical stability by embedding the flexible nerve plate within the nerve fiber. PA1 High temporal-spatial signal resolution.
The concept of the flexible nerve plate also represents a new approach in the technology of fabricating electrodes. In the microelectrodes hitherto fabricated using state of the art silicon technology, there is a clear separation of the substrate (mechanical stability), Metallization (electrodes and feed lines) and isolation layers and passivation layers (biocompatability, isolation of strip conductors). By means of the selection of a flexible, isolating material, such as polyimide, the prepared layers above and below the electrode metallization are used simultaneously for isolation and granting mechanical stability.
The flexible nerve plate is composed of a polymer and connection conducting lines inside the polymer or the polymer layers; that is, polyimide or silicon under slight tension, on both sides of which metal microelectrodes (e.g. platinum, iridium) are located. The microelectrodes can be printed on or vapor deposited. Along the longitudinal axis of the nerve plate there are 20-30 rows of electrodes, which may be of any desired configuration in order to be able to utilize the same FNP in principle both for derivation of electroneurograms and for stimulation. Strip conductors lead from the microelectrodes inside the nerve plate to a flexible, multi-layer band conductor (cable) integrated in the nerve plate. Signal-preprocessing microchips can be located on this multi-layer band conductor as can amplifiers or also antennas for an inductive coupling. In view of the fact that with polyimide the mentioned components cannot be monolithically integrated, a hybrid construction, e.g., the state of the art electronic components have to be constructed to form a circuit. These components having the respective miniaturized circuit can be disposed on the band conductor itself. The integrated construction of the band conductor with the nerve plate can eliminate a major source of errors: parting of the cable at the point of connection.
On the other hand, the band conductor can also be led through the skin and the control and signal receiver unit can be carried outside the body. If these components are also implanted on the band conductor, energy and signals can be transmitted in both directions (into and out of the body) by means of inductive coupling. An energy carrier, e.g. durable batteries, can also be implanted along with the nerve plate. In this case too, transmission of the signals occurs to electronics, in particular for evaluating the electroneurograms, which are disposed outside the body.
If the aim is essentially to stimulate and only a limited processing of the receiver electroneurograms is required, e.g. in electrotherapy, the electronic processing can also be carried out directly in the signal receiver unit provided on the band conductor.
Furthermore, an element of the present invention is that the implant is fabricated using multilayer technology.
In an especially advantageous process of fabrication, a silicon wafer or another carrier is employed essentially as a "processing aid" on which all the process steps occur. Alternately, a thin (2-20 .mu.m) polyimide layer composed of a fluid prefabricated product is spun on and hardened by baking, and a metal layer is deposited and structured using thin film technology. The final layer is another polyimide layer. The polyimide of the created multilayer buildup is finally structured using a dry etching process (reactive ion etching:RIE). When fabricating numerous nerve plates on a single carrier, singling the nerve plates also occurs by means of RIE, making any desired shape of the exterior form (of the nerve plate) possible with greater precision, including the long, integrated cable to each nerve plate. At the end of the multilayer-nerve plate process, the nerve plates with the respective integrated cable can be detached from the silicon wafer. Their thickness is then approximately 10-30 .mu.m.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung e.V.


A scanner uses a hinge to connect the cover and the scanner body. The scanner further comprises a brake apparatus and a force-dispersing mechanism. The brake apparatus interferes the lifting cover at a predetermined interfering angle for avoiding the cover to thump at the scanning surface. The force-dispersing mechanism is used to disperse a stress resulted from the cover is lifted to be over a predetermined safety angle with respect to the scanning surface of the scanner.

Recently, with the advent of multimedia, digital image data can be seen everywhere. In order to digitize an image, various kinds of image-capturing devices were introduced to the market, such as digital cameras, digital video recorders, surveillance equipments, scanners . . . etc. Among all, the scanner plays a very important role in capturing plane images.
Refer now to FIG. 1a and FIG. 1b, in which FIG. 1a shows a conventional scanner 2 and FIG. 1b is a cross-sectional view of the scanner 2 of FIG. 1a. The scanner 2 is composed of a scanner body 4 including components such as an image capturer, an image processor, mechanisms . . . etc. (not shown in the image). The image capturer captures a plan image of an object posited upon the scanner body 4 through light scanning. For providing a standard environmental sensitivity, a cover 6 is posited upon the scanner body 4 to cover the object. In order to open or close the cover 6 more quickly and accurately over a scanning surface 10 of scanner body 4, a hinge 8 is located on a side of the cover 6. Through the hinge 8 pivotal shaft, the cover 6 can joint pivotally the scanner body 4.
In the prior art, when a user opens the cover 6 within a lifting angle less than 90 degree between the cover 6 and scanner body 4, the user must hold the cover 6 manually to avoid the cover 6 dropping back to the scanning surface 10. Once the lifting angle is over 90 degree, the user then needn't to hold the cover 6 anymore. However, at this moment, if the scanner 2 is further moved or accidentally shaken, the cover 6 may be disturbed and fall automatically back to hit at the scanning surface 10. Definitely, under such an incident, damage can be foreseen.
Besides, if the cover 6 is opened further after the 90-degree angle is achieved, the hinge 8 will hit a dead point at a predetermined angle to prevent the cover 6 from being over turned. This predetermined angle is usually called a safety angle. Nevertheless, while the cover 6 is opened to the safety angle and, at this point, only a little portion of the hinge 8 is used to contact with the cover 6, any abrupt action from the user onto the cover 6 will quite possible damage the hinge 9. In the dark side, such a damage at the hinge 8 may wreck the scanner 2.
Hence, to provide a brake apparatus or a force-dispersing mechanism to the hinge for resolving the problem mentioned above is definitely worthy in the art.

Hinge structure for mounting a cover onto an electronic device


Systems and methods may be provided for coupling together semiconductor devices. One or more of the semiconductor devices may be provided with an array of bump contacts formed in an etch back process. The bump contacts may be indium bumps. The indium bumps may be formed by depositing a sheet of indium onto a surface of a device substrate, depositing and patterning a layer of photoresist over the indium layer, and selectively etching the indium layer to the surface of the substrate using the patterned photoresist layer to form the indium bumps. The substrate may be an infrared detector substrate. The infrared detector substrate may be coupled to a readout integrated circuit substrate using the bumps.

During fabrication of some types of semiconductor devices, it can be desirable to mate or couple one semiconductor device to another. The mated semiconductor devices are mated to physically attach the devices to each other and to provide a large number of electrical interconnects between the mated semiconductor devices (e.g., to allow electrical conduction of signals between the semiconductor devices).
For example, infrared components may use this type of interconnect technology, with one semiconductor device optimized to perform a detection function (e.g., an infrared detector) and the other semiconductor device optimized to perform detector biasing, signal integration, signal processing, and/or multiplexing functions (e.g., a read-out integrated circuit (ROIC)). The interconnect array for these devices physically and electrically interconnects the infrared detector to the ROIC, with the interconnect array typically forming thousands to millions of electrical interconnects.
For example, one type of imaging device uses a focal plane array (FPA) to detect infrared radiation. An FPA is typically formed from a detector device having an array of infrared detector elements, with each infrared detector element functioning as a pixel to produce a two-dimensional image, and a mated ROIC. A change in a signal level output of each infrared detector element due to corresponding changes in received incident infrared radiation is translated into a time-multiplexed electrical signal by the readout integrated circuit (ROIC). The combination of the ROIC and the infrared detector array is commonly known as a FPA or infrared FPA. FPAs (e.g., microbolometer FPAs) are described in further detail in U.S. Pat. Nos. 5,756,999, 6,028,309, and 6,852,976, which are herein incorporated by reference in their entirety.
In a typical semiconductor mating approach, the array of electrical interconnects includes indium bump interconnects formed in a wafer level process that grows the indium bumps in place either by thermally evaporating the indium bumps through a photoresist liftoff layer or using a plating process to provide bump material into openings in a photoresist layer as described in further detail in U.S. Pat. No. 7,884,485 issued Feb. 8, 2011 which is herein incorporated by reference in its entirety. A potential drawback of these conventional approaches is that, if care is not taken, control of the indium bump uniformity (e.g., the post liftoff uniformity) can vary depending on the indium bump height, indium bump base width, photoresist geometry, and/or pattern loading effects (i.e., pattern loading effects in a plating process). In these approaches, if care is not taken, as the pitch of the detectors becomes smaller, bump non-uniformities can increasingly negatively affect the detector yield.
As a result, there is a need for improved techniques for forming interconnects between semiconductor devices.

Method and systems for coupling semiconductor substrates


In an I-Q receiver, I-Q baseband mixer receives a real signal, and outputs an in-phase baseband information signal and a quadrature baseband information signal, a decoupling compensator multiplies in-phase baseband information signal and the quadrature baseband information signal by a trained decoupling matrix that, based on adaptive training in response to purely in-phase and purely quadrature phase training signals, decouples the in-phase baseband information signal from a quadrature component of the I-Q signal, and decouples quadrature-phase baseband information signal from an in-phase component of the I-Q signal. Optionally, a trained I-arm-Q-arm imbalance compensator performs a filter compensation on one or both of the decoupled in-phase baseband signal and the quadrature-phase baseband signal output by the trained decoupling matrix. Optionally, the filter is trained based on training signals generated by inputting equal in-phase and quadrature phase training signals to the I-Q baseband mixer, and multiplying the result by the trained decoupling matrix.

Communication of information using carrier signals having an in-phase component signal and an out-of-phase component signal is well known.
The in-phase component of the two-dimensional carrier signal may be a sinusoid, e.g., cos(ωt), and the out-of-phase component may be a 90 degree phase-shift of the in-phase component, e.g., sin(ωt). Referenced to a complex plane having a "real" and an imaginary or "j" axis, the carrier signal may be represented as cos(ωt)−j sin(ωt), and the in-phase component signal, cos(ωt), may be referenced as the "I" signal, and the out-of-phase component signal may be referenced as the "quadrature" or "Q" signal. Such communication may therefore be referred as "two-dimensional" signaling.
Quadrature-amplitude modulation (QAM) is one example of a two-dimensional signaling. In QAM, symbols, e.g., binary bits or groups of binary bits, are encoded as amplitude-phase states of a transmission signal, each of the states being from a constellation of amplitude-phase states defined on the complex plane by the particular QAM coding scheme. As known, there may be N different ones of the states within the constellation, or different changes of states, representing different symbols.
Illustrative examples of QAM include, but are not limited to, binary phase shift keying (BPSK), which has a two-state constellation, quadrature phase shift keying (QPSK), having a four-state constellation and, more generally, M-ary phase-shift keying, having an M-state constellation.
A typical QAM receiver extracts the symbol sequence from the QAM transmission using a local baseband oscillator, having (within an acceptable accuracy and stability) the same frequency as the oscillator used by the transmitter, and a phase-shift arrangement to generate a local in-phase and quadrature-phase baseband mixing signal.
However, as also known, because QAM encodes information using relative amplitude and phase between I and Q signals, QAM systems are necessarily sensitive to the inaccuracies, e.g., imbalances, occurring within I and Q generation, mixers and propagation paths.


A bidirectionally amplifying rare earth doped fiber optical amplifier having an equalized gain at multiple wavelengths is disclosed for use in dense wavelength multiplexed bidirectional fiber transmission applications. In a first embodiment, a four port circulator is utilized with two amplifying fibers; one for each direction of propagation and a multiplicity of gratings configured to equalize the gain at the different wavelengths. Different embodiments utilizing three port and four port circulators are utilized. A more general amplifier device with equal gain at multiple wavelengths is disclosed.

The introduction in recent years of optical amplifiers with wide wavelength operating range in the 1520 to 1580 nm spectral region into fiber communication systems has enabled the practice of dense wavelength division multiplexing (DWDM). In DWDM systems a group of sixteen or even as many as sixty four wavelengths are simultaneously transmitted in a fiber, each wavelength being modulated by a data stream as fast as 10 Gb/s. Such high capacity communication systems consist of optical transmitters, cabled fiber, optical amplifiers, wavelength multiplexers and optical receivers and need to be closely monitored to detect any malfunction that may corrupt the information transmission. The bit error rate (BER) is a measure defined as the number of errored bits divided by the total number of bits received in a given time period. BER is sensitive to several parameters of the transmission system such as the optical power at the receiver, the quality of the transmitter, but particularly to the ratio of signal power to noise power, known as the signal to noise ratio (SNR) at the receiver. In turn the SNR is determined by the addition of receiver thermal noise shot noise and noise added by optical amplifiers in the system.
One of the most important parameters of optical amplifiers is the gain at the various wavelengths. For proper operation the receivers operating at the various wavelengths expect a common and substantially equal optical signal to noise ratio as well as substantially equal optical power. Since transmitters generally output substantially equal amounts of power at various wavelengths, the amplifiers in the system are expected to provide equal gain at the various channel wavelengths.
Several methods of equalizing or flattening the gain of optical amplifiers have been explored in the literature. The book titled "Erbium Doped Optical Amplifiers" by Emmanuel Desurvire discusses such gain flattening techniques on page 480. The article "Flat-gain amplifiers and transmission in WDM networks", paper FA1-1 presented at the "Optical amplifiers and their applications" conference by Bertrand Clesca also compares gain flattening techniques. In Erbium doped fibers the gain at any given wavelength has contributions from several broadened atomic resonances. Each of these resonances is centered at a slightly different wavelength in the 1520 to 1580 nm range and originates from a different pair of Stark sublevels in Erbium. The material of the glass matrix containing the Erbium as well as dopants in that matrix, affect the position and broadening of the atomic resonances in Erbium. One of the known techniques for flattening the gain curve is the use of aluminum co-doping of Erbium doped fiber. Another technique utilizes fluoride glass instead of silica glass as the fiber material. Yet other techniques insert specially shaped spectral filters in line with the amplifiers to compensate for the difference in gain at different wavelengths. U.S. Pat. No. 5,050,949 by Di Giovanni and Giles, describes the use of two stage fiber amplifiers to achieve flattened gain. The drawback of the two stage approach is that it still lacks enough suppression of the gain in the 1520 to 1535 nm spectral region to achieve the desired degree of flatness.
More recently, U.S. Pat. No. 5,557,442 by Huber describes a technique involving the use of a circulator, a series of fiber Bragg reflectors imprinted into a fiber and a set of attenuators to achieve gain flattening. Circulators are optical devices with three or more fiber ports that channel the light from port I into port I+1, Bragg gratings are periodic index of refraction gratings imprinted into the fiber core by UV light and reflect fiber propagating light at specific wavelengths matching the periodicity of the gratings. In U.S. Pat. No. 5,557,442 the light enters the amplifier then the circulator and is channeled into the chain of Bragg reflectors and attenuators. The light at a first wavelength W1 which experiences little gain in the amplifier is reflected from the first Bragg grating and thus suffers no attenuation before returning to the circulator and being channeled out. Light at a second wavelength W2 which experiences somewhat higher gain than W1 is reflected by a subsequent Bragg grating thus having to go through one or more attenuators before it returns to the circulator and gets channeled out. Light at a wavelength W3 experiencing the highest gain in the amplifier is reflected back by the last Bragg grating in the fiber thus forcing it to go through the whole attenuator chain twice before it reaches the circulator and gets channeled out.
Several drawbacks of U.S. Pat. No. 5,557,442 are apparent. The multitude of attenuators required adds to the cost of the device and to the complexity of its construction since such attenuators are generally bulk optical devices which include lenses and involve stringent alignment requirements in manufacturing. Furthermore such attenuators may exhibit temperature dependence and are required to be spliced between the Bragg gratings one at a time. Finally the Huber device allows unidirectional operation only.
Recently it has become generally accepted that optical amplifiers allowing bidirectional transmission in WDM networks offer several advantages. The advantages of bidirectional amplifiers and a specific embodiment of a bidirectional amplifier are described in U.S. Pat. No. 5,633,741 by Giles. Giles teaches the use of two four-port circulators in conjunction with fiber gratings to achieve a bidirectional amplifier.
A generally useful device in fiber optics whose function is to transfer or channel light from one fiber to the next fiber in an ordered set of fibers is known as the circulator. For example a circulator device will channel light from the first fiber in a set to the second fiber and from the second fiber to the third. The point of connection between a fiber and the circulator is referred to as a port and generally the ports are numbered to indicate their ordering. Circulators with three and four ports are commercially available from companies such as Etek of San Jose, Calif. and The Kaifa Group of Sunnyvale, Calif.
Referring to FIG. 1, light at frequencies f2 and f4 enters the first port P1 of the first circulator C1 and is channeled to the second port P2 where it enters a fiber with Bragg gratings G2 configured to reflect at f2 and f4 back into the circulator C1 and out to the third port P3 which is connected to the amplifier A1. The output of the amplifier A1 is then fed to the fourth port P4 of a second circulator C2 and from there f2 and f4 exit through the first port P1 of the second circulator C2. The wavelengths or frequencies f1 and f3 propagating in opposition to f2 and f4 are input through the first port P1 of the second circulator C2 and follow a similar if reverse path to f2 and f4. Other types of bidirectional amplifiers have been described as in U.S. Pat. No. 5,604,627 to Kohn where two wavelength division multiplexing devices (WDM) are utilized in place of the circulators to separate the counter-propagating light streams.
The drawback of the devices shown in the prior art is their failure to provide flat gain profiles especially in the 1533 nm spectral range as well as bidirectional operation. It is therefore a first objective of this invention to provide an erbium doped amplifier with a flat gain profile which is capable of bidirectional operation.
Another objective of this invention is to simplify the construction of the amplifier and to reduce the cost of its manufacturing.
A third objective is to eliminate the use of attenuators and their temperature dependence in either unidirectional or bidirectional amplifiers.
A fourth objective is to reduce the number of circulators and circulator ports used.
A fifth objective is to eliminate the need for fiber couplers or wavelength routers required in the prior art to couple the pump and signal lights into the doped fiber.
It is a further objective of this invention to remedy the general drawbacks described in the background section.

Bidirectional optical amplifier having flat gain