The rake includes a flat rake body with a flared portion provided with a plurality of prongs and a head portion opposite to the flared portion. The flat rake body has a first slot formed adjacent to a free end thereof and a second slot which has a second length that is shorter than a first length of the first slot and which is spaced from the first slot in a parallel manner. The rake further includes a resilient fastening unit that has a first inverted U-shaped member with two legs, a second inverted U-shaped member that is smaller than the first U-shaped member and that has two legs, and a connecting rod which interconnects one of the legs of the first and second U-shaped members. Each of a remaining one of the legs of the first and second U-shaped members has an extension that extends toward one another and that defines cooperatively a clearance therebetween. The two legs of the first and second U-shaped members respectively define first and second distances which are correspondingly equal to the first and second lengths of the first and second slots.

1. Field of the Invention
The invention relates to a rake with a rake body and a handling rod, more particularly to a rake with an improved fastening relationship of the handling rod to the rake body.
2. Description of the Related Art
A rake is used for drawing together fallen leaves, for smoothing soil, and for moving haystacks. Referring to FIG. 1, a conventional rake includes a wooden rod (2) and a rake body (1). The rake body (1) has a flared portion (1d) provided with a plurality of prongs (1e) and a head portion (1a) opposite to the flared portion (1d). The head portion (1a) has a blind connecting tube (1b) for receiving detachably one end of the wooden rod (2) and a pair of reinforcing ribs (1c) for strengthening the head portion (1a). When storing a plurality of conventional rakes, the rake bodies (1) are detached from the wooden rods (2) and are stacked in order to minimize storing space. The rake bodies (1) can not be stacked properly because the blind connecting tube (1b) and the reinforcing ribs (1a) project beyond a flat surface of the rake body (1), thus preventing an even stacking of the rake bodies (1).

San-An Li, Tien-Chung Chen, Changhua Hsien


A cyclone separator useable in a surface cleaning apparatus comprises a cyclone chamber and a dirt collection chamber exterior to, and surrounding at least a portion of the cyclone chamber. The dirt collection chamber is in communication with the cyclone chamber via a dirt outlet. An air flow passage extending to the cyclone air inlet travels generally axially through the dirt collection chamber.

Cyclonic separators, including those used in vacuum cleaners are known in the art. Typically, a cyclonic separator has an inlet for fluid (air, liquid or and air and liquid mix) to be treated and an outlet for treated fluid. Dirt may be collected either in the cyclone chamber itself (e.g. in the bottom) or in a collection chamber in fluid communication with the cyclone separator. Various such constructions are known in the art.
U.S. Pat. No. 7,086,119 (Go et al) discloses a dust-collecting unit for a vacuum cleaner. The dust-collecting unit includes a cyclone separator having a dirt collection chamber positioned adjacent one lateral side of the cyclone separator. A dirt outlet is provided in the upper wall of the cyclone such that dirt may enter the adjacent dirt collection chamber through the outlet in the upper wall of the cyclone separator. A second dirt collection chamber is positioned below the cyclone chamber and is accessed by an opening formed in a separating plate that separates the cyclone chamber and the second dirt collection chamber. An openable bottom is provided. However, when the bottom is opened, the cyclone chamber is still closed by the separating plate.
U.S. Pat. No. 7,160,346 (Park) discloses a cyclone for use in a vacuum cleaner having a dirt collection space positioned below the cyclone chamber. A dirt outlet is provided as an annular gap between the sidewall of the cyclone chamber and a separating plate for permitting dirt to travel downwardly from the cyclone into the dirt collection chamber. Accordingly, the dirt collection chamber is not exterior to the cyclone casing but is within the casing.

Configuration of a cyclone assembly and surface cleaning apparatus having same


An array coil to achieve more uniform RF excitation for high field magnetic resonance imaging. In the preferred embodiment, the array coil has a plurality of transmit-composite elements distributed around the object to be imaged. A composite element comprises up to three current loops preferably orthogonal to each another. The array coil has the capability to shape the distribution of all three orthogonal components (x, y, and z) of the RF B1 field.

The trend of development of MRI technology has been to use magnets of increasing strengths. However, current high-field (static field B0 strength approximately 1.5 T and higher) MRI technology is hampered by non-uniform B, amplitude distribution offered by conventional coil techniques. At high B0 field strengths the size of the human brain or other body parts is no longer small in comparison to the wavelength of the RF inside tissues. For human brain imaging above 3 T, the center of the brain shows brighter image intensity compared with the periphery, due to wavelength effects. The Maxwell equations dictate that a single RF component (Bx or By) cannot be uniform over a three-dimensional (3D) volume under these conditions. It is possible to manipulate the RF field distribution to make it more uniform in one plane but the field homogeneity along the perpendicular direction will decrease. Consequently, it has been very difficult to obtain a highly uniform 180° pulse through a large 3D sample volume. As used in the entire document, "field amplitude", "B1 field amplitude" and "RF field amplitude" all mean the amplitude of the transverse component of the B1 field unless specifically indicated otherwise, because the longitudinal component does not contribute to spin excitation.
Achieving uniform RF excitation in high field MRI scanners is not a trivial task. In the case of brain scans, because of the large relative dielectric constant of water in the tissue, images acquired with conventional volume coils show higher signal intensity at the center of the head. Although a totally homogeneous B1 field is unattainable over a 3D volume, allowing phase variation in space can lead to improvement in the B1 amplitude distribution. Modification of birdcage coils showed improvement in the homogeneity of RF excitation. Due to the short wavelength of the RF field inside the tissue, the field distribution is strongly affected by the shape of the object, and conventional hardware configurations do not provide optimal results at very high field strengths. Many approaches have been proposed to improve RF field homogeneity, including a multiple-port transverse electromagnetic (TEM) resonator driven with variable phase and amplitude at each port (Magn Reson Imaging 2001: 19: 1339-1347) and the use of an array coil to obtain uniform Bx and By in one plane (J Magn Reson Imaging 2000: 12: 46-67).
The RF magnetic field for spin excitation can be described by a steady state field B(r,t)=B(r)·e−iωt. Achieving uniform RF excitation in high field MRI scanners is desirable, but not a trivial task. Because of the large relative dielectric constant of water in the tissue, images acquired with conventional volume coils show higher signal intensity at the center of the head. (J Magn Reson 2004: 167: 12-24). Although a totally homogeneous B1 field is unattainable (J Magn Reson Imaging 2000: 12: 46-67), allowing phase variation in space can lead to improvement in the B1 amplitude distribution. Modification of birdcage coils showed improvement in the homogeneity of RF excitation. (Magn Reson Med 1992: 23: 287-301; Magn Reson Med 1998: 40: 49-54). Due to the short wavelength of the RF field inside the tissue, the field distribution is strongly affected by the shape of the object, and conventional hardware configurations are unable to provide optimal results at very high field strengths. Many approaches have been proposed to overcome this difficulty, including a multiple-port transverse electromagnetic (TEM) resonator driven with variable phase and amplitude at each port. (Magn Reson Imaging 2001: 19: 1339-1347). The use of an array coil to obtain uniform Bx and By field in one plane (J Magn Reson Imaging 2000: 12: 46-67) has also been proposed.

RF coil for a highly uniform B1 amplitude for high field MRI


Systems and methods to aid a welder or welding student. A system may provide a real-world arc welding system or a virtual reality arc welding system along with a computerized eyewear device having a head-up display (HUD). The computerized eyewear device may be worn by a user under a conventional welding helmet as eye glasses are worn and may wirelessly communicate with a welding power source of a real-world arc welding system or a programmable processor-based subsystem of a virtual reality arc welding system.

Providing information to a welding student in real time during a welding process (whether a real-world welding process or a simulated welding process) is important to aid the welding student in the learning process. Similarly, providing information to an expert welder in real time during a real-world welding process can aid the expert welder in the welding process. Furthermore, providing the ability for a welding student or an expert welder to easily communicate with (e.g., provide commands to) a welding system (real or simulated) can allow for a more efficient and user-friendly welding experience. Today, a welding helmet may be provided with simple light indicators representative of welding information which don't require a welder to be able to focus sharply on the light indicators, since the light indicators may be within one inch of the welder's eye. Simply being able to see that the color of a light indicator is red or green or yellow, for example, is provided. Thus, there is an ongoing need to improve how a welder or welding student interacts with a welding system and how information is provided and viewed in real time.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such systems and methods with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.

This patent is subject to a terminal disclaimer.

Systems and methods providing a computerized eyewear device to aid in welding


An exemplary light emitting diode illuminating device includes a light emitting diode (LED) light source, a heat dissipating device, a temperature detector, a power supply and a pulse width modulator. The heat dissipating device is thermally connected to the LED light source. The temperature detector is thermally connected to the LED light source and configured for detecting the working temperature of the LED light source. The power supply is electrically connected to the pulse width modulator for providing electric power to the pulse width modulator. The pulse width modulator has a direct current (DC) output mode and a pulse output mode.

1. Technical Field
The present invention generally relates to illuminating devices and, particularly, to a light emitting diode (LED) illuminating device capable of maintaining a stable working temperature.
2. Discussion of Related Art
Nowadays, light emitting diodes (LEDs) have been used extensively as light source for illuminating devices due to their high luminous efficiency and low power consumption.
However, radiant efficiency and lifespan of the LEDs may be distinctly reduced by high working temperature, thereby easily leads to low reliability of illuminating device employing the same.
Therefore, what is needed is a light emitting diode (LED) illuminating device capable of maintaining a stable working temperature.

Light emitting diode illuminating device


A fluorescent lampholder with a top portion for supporting a fluorescent lamp and a base portion with a wire opening located on the bottom surface of the base that receives wires without exposing the wires to the exterior surface of a fixture. The lampholder is capable of supporting various types and/or sizes of fluorescent lamps such as “tall”, “medium” and “small” T-8 fluorescent lamps as well as other types and/or sizes of fluorescent lamps.

As is well known, conventional fluorescent fixtures comprise an elongate frame which may include an integral reflector. At each end of the frame there is provided a lampholder for receiving the contact pins at the ends of the fluorescent lamp; the lampholder functions to support the lamp and provide electrical power. The lampholder has a top portion with a pair of spaced apart lamp pin contacts to engage the contact pins of the fluorescent lamp and a base portion with a wire opening located on the side surface of the base portion. During installation, wires are inserted through the wire openings of the lampholders and the wires are electrically connected to the lamp pin contacts of the lampholders to provide electrical power to the lamp. One wired lampholder is mounted at one end of a fixture and another lampholder is mounted at the other end of the fixture. A portion of the wires connected to the lampholder assemblies is typically exposed on the exterior surface of the fixture. There is a need for a fluorescent lampholder that connects to wires without exposing the wires to the exterior surface of the fixture.


System and methods are provided for clock calibration. A satellite navigation system includes: a timing component configured to determine a counting period for clock calibration; a counter network configured to determine a first number of local clock periods associated with a local clock of the satellite navigation system during the counting period and determine a second number of external clock periods associated with an external clock during the counting period; and a processor configured to perform calibration for the local clock based at least in part on the first number of the local clock periods and the second number of the external clock periods.

Satellite based navigation systems are widely used. Global navigation satellite systems (GNSS) include Global Positioning System (GPS) (United States), GLONASS (Russia), Galileo (Europe), and COMPASS (China). A GNSS often involves a plurality of satellites orbiting the Earth, and the plurality of satellites form a constellation of satellites. Each satellite transmits a navigation message periodically that can be received and used by a GNSS receiver to derive position, velocity, and/or time. For example, GPS navigation systems can acquire and track GPS satellite signals so that range measurements can be made between several satellites and a GPS receiver in order to compute a location for the receiver. A metric of acquisition performance is time to first fix (TTFF). The TTFF may depend on the accuracy of the receiver's previous estimate of GPS time within the receiver's local timing system.
Electronic devices (e.g., a mobile phone, a tablet computer, a camera, etc.) often include a GPS receiver. Different clocks may be used for different function modules in such electronic devices. For example, a clock used for the GPS receiver corresponds to a local clock of the GPS receiver, while other clocks may correspond to external clocks relative to the GPS receiver. The local clock of the GPS receiver provides a reference frequency source so as to generate a local carrier that is used for GPS signal down conversion in a radio frequency (RF) front end and GPS signal mixing in a baseband.

Systems and methods for clock calibration for satellite navigation


A receiver device is provided with: channel estimation unit which obtains channel estimation values for a frequency domain on the basis of pilot symbols disposed in an OFDM subcarrier; interpolation unit which performs interpolation so that the number of samples of channel estimation values obtained by the channel estimation unit is a power of 2; transformation unit which transforms the channel estimation values interpolated by the interpolation unit into a time domain to obtain a delay profile; and power peak position detection unit which detects a power peak position of the delay profile so as to obtain a propagation delay time. The power peak position detection unit references the signal power of the portion interpolated by the interpolation unit in order to detect a suitable power peak position in the delay profile.

A communication method making use of Orthogonal Frequency Division Multiplexing (OFDM), as represented by Long Term Evolution (LTE), now being discussed in 3rd Generation Partnership Project (3GPP), attracts attention as a communication method for the next generation. OFDM is a transmission method in which a bandwidth to be used is divided into multiple subcarriers, and then each data symbol is assigned to each subcarrier. Since the subcarriers are so arranged as to be orthogonal one another on a frequency axis, OFDM is excellent at frequency usage efficiency. Moreover, each subcarrier has a narrow bandwidth, and therefore an effect of multiple-path interference can be suppressed so that a high-speed large-capacity communication can be realized.
In a data transmission method using OFDM, generally at a transmission side, already-known pilot symbols besides data symbols are inserted at intervals in the frequency-wise direction and the time-wise direction, as shown in FIG. 13. At a receiver side, amplitude-phase variation of the pilot symbols is detected from a received signal, and then data symbols included in the received signal are demodulated, on the basis of the amplitude-phase variation. The amplitude-phase variation detected from the pilot symbols is called a channel estimation value.
To calculate a channel estimation value, a Cyclic Prefix (CP) part is removed from a received signal, and Fast Fourier Transform (FFT) in accordance with an effective symbol length of OFDM is carried out in order to extract pilot symbols, and then the pilot symbols extracted are verified with an already-known pattern. In this way, amplitude-phase variation of the symbols is calculated, and the amplitude-phase variation is deemed to be a channel estimation value.
A result of transforming channel estimation values of the frequency domain into the time domain by means of Inverse Fast Fourier Transform (IFFT) is called a delay profile. In a delay profile, peaks of power appear in response to propagation paths of a transmission line. A low-level part in the delay profile means that there is no propagation path, or a propagation path there is weak, so that noise power is dominant there. After replacing values of the delay profile at its low-level part with "0", transforming the data back into the frequency domain by means of FFT makes it possible to cancel noise components from the original channel estimation values. Moreover, a propagation delay time can be calculated according to the positions of power peaks in the delay profile.
The calculated propagation delay time is used for transmission time control. For example, if a mobile station for transmitting/receiving information to/from a base station by way of a wireless radio communication executes a transmitting process in accordance with timing of a received signal from the base station as it is, the transmission signal is received twice the one-way propagation time late, at the base station. In the meantime, the base station transmits/receives information to/from a plurality of mobile stations; and therefore, if a distance between the base station and each mobile station is different to others, there appears a time-wise overlap in received signals from the mobile stations so that interference occurs.
Explained below with reference to FIG. 14 and FIG. 15 is interference that occurs in the case where a mobile station executes a transmitting process in accordance with timing of a received signal from the base station as it is. For an easy understanding, an explanation is made here with a case example of transmission/receiving between one base station BS and two mobile stations MS1 and MS2.
As shown in FIG. 14, it is assumed that the mobile station MS1 receives a receiving frame "A" from the base station BS, and transmits a transmission frame "a" to the base station BS. Meanwhile, it is assumed that the mobile station MS2 receives a receiving frame "B" from the base station BS, and transmits a transmission frame "b" to the base station BS. Under the situation, if the mobile stations MS1 and MS2 transmit the transmission frame "a" and the transmission frame "b" in accordance with timing of signal receiving from the base station BS as it is, each transmission signal from the mobile stations MS1 and MS2 is received twice the one-way propagation time late, at the base station BS, as shown in FIG. 15.
Herein, a propagation delay time of the receiving frame "A" at the mobile station MS1 is defined as "t1", and a propagation delay time of the receiving frame "B" at the mobile station MS2 is defined as "t2". The transmission frame "a" from the mobile station MS1 is received "2t1" late at the base station BS, wherein "2t1" is twice a time needed for a propagation from the base station BS to the mobile station MS1. On the other hand, the transmission frame "b" from the mobile station MS2 is received "2t2" late at the base station BS, wherein "2t2" is twice a time needed for a propagation from the base station BS to the mobile station MS2. In this case, if the distance between the base station BS and the mobile station MS1 and the distance between the base station BS and the mobile station MS2 are different from each other, needed times for respective propagations are different (t1≠t2). Accordingly, at the base station BS, there appears a time-wise overlap in the transmission frame "a" from the mobile station MS1 and the transmission frame "b" from the mobile station MS2, so that interference occurs.
Explained next with reference to FIG. 16 and FIG. 17 is an adjustment of transmission timing at each of the mobile stations MS1 and MS2.
A propagation delay time measured at the mobile station MS1 is defined as "t1", and a propagation delay time measured at the mobile station MS2 is defined as "t2". Under this situation, the mobile station MS1 puts a transmission start timing of the transmission frame "a" in relation to the receiving frame "A" ahead twice the measured propagation delay time "t1", as shown in FIG. 16. In the meantime, the mobile station MS2 puts a transmission start timing of the transmission frame "b" in relation to the receiving frame "B" ahead twice the measured propagation delay time "t2", as shown in FIG. 16. According to this arrangement, each transmission frame coming from the mobile station MS1 and the mobile station MS2 is received without causing a time-wise overlap at the base station BS, accordingly having no interference, as shown in FIG. 17.
A measurement of a propagation delay time is explained below with reference to a flowchart of FIG. 18. In the following explanation, a mobile station, a transmit/receive terminal to be used as a mobile station, and a device to be used as a receiving unit of those mobile station and terminal are collectively called a "receiver device."
In order for a measurement of a propagation delay time, channel estimation values are calculated at first. For calculating a channel estimation values; CP is removed from a received signal (Step S21) as described above, FFT tailored to an effective symbol length of OFDM is carried out (Step S22), and pilot symbols are extracted (Step S23). Then, the extracted pilot symbols are verified with an already-known pattern, and an amplitude-phase variation of the symbols is calculated so as to obtain the channel estimation values (Step S24).
To measure a propagation delay time in accordance with the channel estimation values, the channel estimation values in the frequency domain is transformed into the time domain by means of IFFT (Step S26), and positions of power peaks are detected from a delay profile obtained (Step S27). Then, the propagation delay time can be calculated according to the positions of power peaks.
Moreover, with respect to a low-level part in the delay profile, by way of replacing values of the delay profile with "0" (Step S28) and transforming back into the frequency domain by using FFT (Step S29), it becomes possible to cancel noise components from the original channel estimation values.
At the time of carrying out IFFT with respect to channel estimation values in the frequency domain; the number of channel estimation values, namely pilot symbols, is sometimes not a power of 2. In such a case, IFFT of the number of samples of the channel estimation values is not carried out but IFFT of size larger than the number of samples of the channel estimation values is carried out. At the time, the channel estimation values are so placed as to fill a front end and its subsequent followers; and for any part with an insufficient number of samples is not filled with 0 but the channel estimation values are interpolated (Step S25). Thus, a signal power of a part with no propagation path decreases in the delay profile so that a canceling process on noise components can be improved (for example, refer to NPL 1).
Moreover, a technology of using an arrangement pattern of already-known samples, in which a noise effect is canceled by means of carrying out IFFT samples of the already-known pattern included in a received signal, is also known as a technology for calculating a delay profile (for example, refer to PTL 1).

Receiver device, transmit/receive terminal, propagation delay time measurement method and computer program


A tablet division feeder includes a moving unit to move a tablet T, a fixing blade located in a movement path of the tablet T, and a support plate extending from the fixing blade such that divided tablets T2 on the fixing blade are transferred and kept onto the support plate. The fixing blade divides the tablet T into upper and lower divided tablets as the tablet T is moved in such a manner that the lower divided tablet T1 is discharged and the upper divided tablet T2 is transferred from the fixing blade to the support plate by the moving unit and kept on the support plate. The upper divided tablet T2 is discharged from the support plate as the upper divided tablet T2 is further moved by the moving unit in such a manner that the upper divided tablet T2 is discharged from the moving unit.

According to a pharmaceutical feeding apparatus of a related art, tablet feeders provided in multiple steps in the entire circumference thereof with rotors are installed in a tablet receiving case, and tablets are selectively fed from the tablet feeders and wrapped based on the prescription (see, FIG. 1 of Patent document 1 and FIG. 38 of the present invention), or the tablet feeders are arranged in the form of a tray to selectively feed the tablets based on the prescription (see, FIG. 6 of Patent document 2 and FIG. 36 of the present invention).
In the tablet feeder, a rotor is installed in a container receiving a plurality of tablets, and a plurality of recesses are formed along an entire lateral side of the rotor at a regular interval to receive the tablets. As the rotor rotates, the tablets provided in the container are received in the recesses such that the tablets may move in the rotating direction of the rotor. When the recesses face a discharge port, the tablets are discharged from the recesses one by one through the discharge port (see, patent document 3).
Meanwhile, one dose of half-size tablets may be prepared according to the prescription. In this case, the half-size tablets are previously set in the tablet feeder to allow the tablet feeder to feed the half-size tablets.
A tablet divider divides the tablets into half-size tablets by using a rotary cutter while the tables are moved downward with being pinched between a pair of belt conveyers, (see, FIG. 1 of patent document 4). In addition, the tablets being moved into a tube are blocked by a shutter and a cutter of a tablet divider divides the tablet into half-size tablets in such a manner that a lower half-size tablet is dropped down and an upper half-size tablet is kept on the cutter and then dropped down as the cutter moves to its initial position (see, FIG. 6 of patent document 5).
Patent document 1: Japanese Patent Unexamined Publication No. 2003-63503.
Patent document 2: Japanese Patent Unexamined Publication No. 2008-162609.
Patent document 3: Japanese Patent Unexamined Publication No. 2005-59903.
Patent document 4: Japanese Patent Unexamined Publication No. 1990-29257.
Patent document 5: Japanese Patent Unexamined Publication No. 1999-226089.
Patent document 6: Japanese Patent Unexamined Publication No. 2005-272011.
Patent document 7: Japanese Patent Unexamined Publication No. 2007-75178.


A method of localizing the location of a received signal from a tire pressure sensor includes sending an AM identification signal. The AM signal is adjusted for speed such that the frequency of the signal equals a constant multiplied by the speed of the vehicle. Each of the tire locations on a vehicle have an expected sequence of black-out points in the signal received by a receiver at any point on the vehicle. That is, given a particular vehicle design, the AM signal described above would be received at a receiver with an expected sequence of received peaks and black-out points. Since the frequency of the signal is adjusted for speed, the received signal will accurately allow the location of black-out points to be utilized to identify the tire location for a particular signal.

This invention relates to the use of a signal being transmitted from tire pressure sensors wherein a signal is adjusted to have a frequency corrected for the speed of the vehicle. A control receives the signal and identifies characteristics in the signal to identify which tire has sent the signal.
Modern vehicles are being provided with more and more electronic diagnostic and sensing systems. In particular, tire pressure sensors are now incorporated into most modem vehicles. The tire pressure sensors typically send a wireless signal to a control. The signal will typically include a code, such that the control can identify to which tire the particular signal relates.
Such tire pressure monitoring systems require some way of initially identifying the code for each sensor and its associated tire with a control. Thus, means for "localization" are incorporated into tire pressure monitoring systems.
One proposed system looks at characteristics in the signal that would be distinct for each of the tire based sensor transmitters. As an example, due to the relative location of the receiver and the control and each of the sensors on each of the tires, there would be distinct "black spots" within the signal at which the receiver would not receive a portion of the signal. The pattern of black spots could thus be of value in identifying the location of the particular sensor sending the particular signal. A receiver could be programmed to expect a particular series of black spots at particular times, and identify which tire is reporting based upon those black spots. However, the speed of the vehicle would affect the expected timing of the black spots within the signal. Thus, the prior art discussed above is not a practical way of identifying the location of a sensor sending a particular transmission.

Tire sensor localization utilizing speed corrected frequency


A laser diode (LD) driver and method, in an optical recording and reproduction apparatus, to drive an LD determines a type of a loaded recording medium; and sets driving potentials corresponding to power levels of a laser signal output from the LD according to the determined type of the recording medium.

1. Field of the Invention
The present invention relates to a laser diode (LD) driver for driving an LD in an optical recording and reproducing apparatus, and more particularly, to an apparatus, which has an auto laser power control (ALPC) function and can drive two or more LDs using the LD driver, a method of driving the LD driver, and a method of initializing the optical recording and reproducing apparatus.
2. Description of the Related Art
FIG. 1 illustrates the structure of a laser diode (LD) driver 100 for driving an LD (not shown) currently used in optical recording apparatuses.
The components of the LD driver 100 include switches 10a through 10c, a multiplexer 12 for multiplexing the outputs of the switches 10a through 10c, an amplifier 14 for amplifying the output of the multiplexer 12 with a predetermined degree of amplification, an adder 16, and a high frequency modulator (HFM) 18.
Current such as peak current, bias current, and read current, or voltage correspond to power levels such as peak power level, bias or erase power level, and read power level of the LD, which are applied to the switches 10a through 10c. The power levels are turned on and off by control signals such as peak control, bias control, and read control.
The outputs of the switches 10a through 10c are multiplexed by the multiplexer 12. The output of the multiplexer 12 is applied to a recording medium. Because the LD cannot be fully driven by the output of the multiplexer 12 alone, the output of the multiplexer 12 is amplified through the amplifier 14.
The HFM 18 generates a high frequency modulation signal to remove optical interference noise from an optical pick-up (not shown). The adder 16 adds the high frequency modulation signal to the output of the amplifier 14 and outputs a driving signal to the LD. The LD, in turn, generates a recording signal corresponding to the driving signal from the adder 16. Here, the high frequency modulation signal is set to have the most effective frequency and magnitude for removing the optical interference noise and is primarily used in a read mode. Further, in the LD driver 100, the number of switches may include two to five switches according to the number of channels used (2 ch through 5 ch), which are the number of driving levels in a recording signal.
The LD changes according to an operating temperature. Specifically, referring to FIG. 2, an output characteristic of TOLD9452MB, which is an LD driver by Toshiba Co., Ltd. is illustrated. Here, when the LD is operating and a constant input current is applied, the operating temperature increases and the optical output decreases. For example, when an input current of 110 mA is applied, the optical output is reduced from 40 mW at 25° C. to about 20 mW at 70° C. The reduction of the optical output causes a recording function to either deteriorate or not be able to be performed.
To improve such reduction, conventional LD drivers use an automatic laser diode power control (ALPC). In the ALPC, the output of the LD is monitored through an additional monitor diode and the change in the output of the LD is fed back. Accordingly, the output of the LD is maintained uniform. However, the ALPC function cannot be realized only by the LD driver, but it must be realized by an additional circuit or an integrated circuit (IC). Accordingly, electromagnetic wave interference may cause mis-operation during an interface operation when supplying the LD output control signal provided by the ALPC to the LD driver. Furthermore, when recording speed increases, the interface operation may not be performed. The waveform of the LD is reduced to either 780 μm (in the case of a CD), 635 or 650 μm (in the case of a DVD), or 410 μm as a result of development of recording technology and increase in capacity. If a recording and reproducing apparatus includes a plurality of LDs, which lower compatibility and share between a recording medium, multiple circuit blocks for the ALPC corresponding to the respective LDs are necessary. Accordingly, a plurality of circuit blocks performing similar operations must be included. This is a big obstacle to making products small, light, and inexpensive.

Laser diode driver, method of driving the laser diode driver, and method of initializing an optical recording and reproducing apparatus