An integrated optical device with a loop resonator is provided, having at least one closed waveguiding loop which has losses. A coupler and at least one input waveguide is coupled to the loop resonator, An adjustment unit controls a coupling coefficient K1 of the coupler, and a second coupler is coupled to the loop resonator. At least one output waveguide is coupled with the second coupler to the loop resonator. Another adjustment unit is configured to control coupling coefficient K2 of the second coupler, being related to the value of K1, accordingly to the following equation K2=f{K1,ξ}, providing Q{K2}=Max {Q}, where (1−ξ) are the total optical losses within the loop resonator and Q is a resonator characteristic.

In the expanding integrated optical technology, a number of discrete structures have been proposed to serve as optical building blocks for controlling optical signals of specific wavelengths. Such structures include devices with circular, ring, disc, or sphere shaped active or passive cavities, which are useful components for wavelength filtering, routing, switching, lasing, modulation, multiplexing/demultiplexing, and sensing applications.
Loop or ring resonators are well known integrated waveguide components, see for example cascaded ring resonator described in, C. K. Madsen, "General IIR optical filter design for WDM applications using all-pass filters," IEEE J. Lightwave Technol., Vol. 18, pp. 860–868, 2000.
The basic schematic diagram of this device shown in FIG. 1. An input beam 1 propagates in an input waveguide 2. This waveguide 2 is coupled to a loop resonator 3 by a coupler 4 that has an adjustment (tuning) element 5. An output signal 6 from an output waveguide 7 varies correspondingly to a driving signal 8 applied to the adjustment element 5.
Integration of two couplings to the same loop resonator thus separating an input and output waveguides is also well known in prior art. See for example, FIG. 4 in the U.S. Pat. No. 6,856,641, incorporated herein by references. The schematic basic element of such device is shown in FIG. 2. An input beam 9 propagates along an input waveguide 10. The input waveguide 10 is coupled to a loop resonator 11 by a first coupler 12. A second coupler 13 connects the loop resonator 11 and an output waveguide 14. An output beam 15 depends on coupling ratios of the couplings 12 and 13. Note that the couplers 12 and 13 have the same characteristics in prior art. No separate tuning of the coupling parameters elements was suggested.
Passive or active loops have been realized in material structures such as glass, lithium niobate (LN), polymer-waveguides, doped silica waveguide, optical fibers and others. Most of the proposed micro-ring structures are based on micro-ring waveguide with a large lateral index contrast (air-substrate) such as whispering-gallery-mode (WGM) cavities. Having small diameters and relatively small bending loss, the strongly guiding micro-cavity can be up to orders of magnitude smaller than the weakly guiding waveguide, such as, for example, of LN Ti-indiffused technology.
The major physical design characteristics underlying such performance criteria as FSR, quality-factor, transmission at resonance, and extinction ratio, are the size and material of the cavity, wavelength, the input and output coupling ratio(s) (analogue of a Fabry-Perot etalon reflectivities), as well as the various components of losses, including coupling, scattering from surface irregularities, bending radiation loss, substrate leakage loss or whispering gallery loss, Raleigh scattering, and absorption due to molecular resonances.
The critical gaps, separating the micro-ring cavity from the tangential waveguides or fibers, determine the input and output coupling ratios of the resonator, which, in turn, define the magnitude of the finesse and the at-resonance transmittance. Because of the high optical confinement and short coupling distances, the coupling coefficients are not readily tuned once the device is fabricated, especially in an independent fashion. Tuning of the refractive index typically serves only to adjust the resonant frequencies. In particular, it is difficult to ensure that the two coupling gaps/lengths on two sides of the resonator cavity are matched. The finesse and the extinction ratio of the resonator would be impaired if the coupling factors and resonator phase are not matched for desirable conditions. Such a coupling management problem is relevant also for add/drop coupling in disk/sphere-shaped cavities having proximity-coupled tapered fiber or prisms, see, for example, "Microphotonic modulator for microwave receiver" by D. A. Cohen, M. Hossein-Zadeh, and A. F. J. Levi in Electron. Lett., vol. 37, pp. 300–301, 2001.
In general, while providing the high-density integration potential, small dimensions make efficient adjustments of cavity parameters a challenging task, limiting their direct implication within various optical systems. Alternative methods may require adjustments of intrinsic gain or loss (i.e. rate of energy flow), thus modifying the response shape or use of thermal tuning, see, for example, B. E. Little and Sai T. Chu, "Theory of loss and gain trimming of resonator-type filters", IEEE Photonics Technol. Lett., Vol. 12, No. 6, pp. 636–638, 2000. The speed and accuracy of thermal tuning, however, are not sufficient for high-speed applications.
Recently, Y-junction reflectors were proposed for effective change in propagation direction in weakly guided planar Ti-diffused LN structures "Tunable lithium niobate waveguide loop" by J. X. Chen at al IEEE Photonics Technol. Lett., Vol. 16, 2090–2092, 2004. In such embodiments, potentially, the add/drop coupling ratios can be readily tuned independently via applied electric fields along with the resonance frequency of the loop. Thus, the speed/accuracy and, as a result, applicability can be much improved over those obtained with thermal or electro-optical tuning with inseparable controls of cavity parameters (coupling and phase), such as, LN-based WGM cavities. Weakly guided technology also may mitigate the additional problem of fiber/waveguide alignment, which should provide an effective coupling between fiber and the micro-cavity and vise versa.
The generic unidirectional coupling between a ring resonator and a waveguide was discussed in the prior art and basic equations describing the manipulation of coupling between optical waveguides and microresonators were obtained for the case of the lossless cavity and/or simplified coupling operator model. For instance, it was shown in A. Yariv, "Universal relations for coupling of optical power between micro-resonators and dielectric waveguides," Electronics letters, Vol.36, No.4, pp. 321–322, 2000, that full transfer of power from the input port to the output port occurs when the two following conditions are satisfied: 1) all internal losses are negligible, and 2) couplings between the cavity and two waveguides are identical.
Reported methods for adjustable coupling are limited to single coupler tuning by using thermal or electro-optical perturbations of the refractive index, which is inseparable with the cavity phase change. Another reported techniques include additional phase matching structures (e.g. gratings) installed near coupled guides, e.g. waveguides, prisms (half blocks), or (tapered) fibers. Immersing the resonator cavity couplers in liquids may also improve the coupling by reducing the optical fiber modes confinement. Alternatively, the angle of light incidence with respect to the normal of the coupling face could be controlled. U.S. Pat. No. 6,393,186 suggests using "athermal" waveguides and couplers in order to separate thermal phase modulation (considered to be parasitic) and coupling modulation, which is done specifically by thermo-grating elements.
Coupling elements of δβ-reversal coupler configuration are disclosed in, "Directional coupler switches, modulators, and filters using alternating Δβ techniques" by R. Schmidt, R. Alferness in IEEE Trans. on Circuits and Systems, Vol. 26, No. 12, pp, 1099–1108, 1979. The δβ-reversal couplers may have advantages in terms of at-resonance stabilization of the structure since they are not introducing undesired phase shift to the cavity wave.
None of the above described prior art technologies proposed a separate adjustment of coupling ratios of the input and output waveguides coupled to a loop resonator with losses. This fact limits boundaries of loop resonator structures not allowing dynamic, such as real time, optimization of resonator output/performance. In addition, lack of mentioned resonators tunability disables an effective compensation of fabrication errors and/or changes in environmental conditions, thus decreasing the manufacturing yield and productivity.
There is a need for integrated optical devices that allow compensating of losses inherent to loop resonator structures. This compensation must be dynamic to follow changing environmental conditions.

Integrated loop resonator with adjustable couplings and methods of using the same


The loudspeaker magnetic circuit is an external-magnet type, and has a magnet, an upper plate, and a lower plate. The magnet is sandwiched between the upper plate and the lower plate. At least one of the lower plate and the upper plate is formed of magnetic powder or a mixture of a magnetic powder and resin.

1. Technical Field
The present disclosure relates to a loudspeaker magnetic circuit used for various types of acoustic equipment, video equipment, and information communications equipment, including in-car use, and also relates to a loudspeaker using the same.
2. Background Art
Hereinafter, a conventional loudspeaker magnetic circuit is described with reference to the drawings. FIG. 9 is a sectional view of conventional loudspeaker magnetic circuit 4. In magnetic circuit 4, magnet 1 of ferritic material is sandwiched between upper plate 2 and lower plate 3. Magnet 1 is produced by sintering a magnetic material. Lower plate 3 is formed in a manner that a metallic plate is processed by a multistage former method. Center pole 3A is formed in the center of lower plate 3.
Magnetic gap 5 is formed between upper plate 2 and center pole 3A. A voice coil is inserted into magnetic circuit 4 and vibrates in the vertical direction by magnetic force. Therefore, the width of magnetic gap 5 has to be determined with extremely high accuracy.

Magnetic circuit for loudspeaker, and loudspeaker using same

Panasonic Intellectual Property Management Co., Ltd.


In a process for producing a magnetic disk cartridge by welding two cassette shell halves for constituting a cassette shell of a magnetic disk cartridge to each other, a first fitting part is formed on an inner side of one of the two cassette shell halves. The first fitting part serves to adjust the position of the one cassette shell half with respect to the position of the other cassette shell half. A second fitting part is formed on an inner side of the other cassette shell half, which second fitting part is to be fitted to the first fitting part in order to adjust the position of the other cassette shell half with respect to the position of the one cassette shell half. Projections for ultrasonic welding are formed on a fitting surface of at least either one of the first and fitting parts. While the first and second fitting parts are being fitted to each other, energy of ultrasonic welding is concentrated upon the projections for ultrasonic welding, and the two cassette shell halves are thereby welded to each other.

1. Field of the Invention
This invention relates to a magnetic disk cartridge and a process for producing the magnetic disk cartridge. This invention particularly relates to a magnetic disk cartridge, which comprises a cassette shell formed by welding two cassette shell halves to each other, and a process for producing the magnetic disk cartridge.
2. Description of the Prior Art
Magnetic disk cartridges comprise a thin cassette shell and a magnetic disk, which is incorporated in the cassette shell such that it can rotate and on which analog or digital signals are to be recorded magnetically. The cassette shell takes on the form of a flat prismatic shape and comprises an approximately square top surface having an area slightly larger than the area of the magnetic disk, a bottom surface having an opening, through which a center core for supporting the center of the magnetic disk is exposed to the exterior, and a side surface having a narrow width and extending between the periphery of the top surface and the periphery of the bottom surface. The cassette shell is constituted by locating an upper cassette shell half and a lower cassette shell half such that they stand facing each other, and securing them to each other with screws, welding, or the like. The magnetic disk cartridge is provided with openings for insertion of a magnetic head, through which the magnetic head for magnetically recording and reproducing signals is to be inserted from the exterior such that the magnetic head can be brought into contact with the surfaces of the magnetic disk or can be brought to positions close to the surfaces of the magnetic disk. Also, the magnetic disk cartridge is provided with a shutter for opening and closing the openings for insertion of the magnetic head. When the magnetic disk cartridge is not being used, the shutter closes the openings for insertion of the magnetic head such that dust, debris, or the like, may not enter into the magnetic disk cartridge.
Recently, a magnetic disk cartridge, which has a recording capacity that is 50 times as large as the recording capacity of conventional magnetic disk cartridge (3.5-inch FD) by virtue of high-density recording (and is slightly larger than 3.5 inches), has been developed. In the developed magnetic disk cartridge, the magnetic disk is rotated at a markedly higher speed than the speed at which the magnetic disk in the conventional magnetic disk cartridges is rotated. Also, when signals are recorded on the magnetic disk accommodated in the developed magnetic disk cartridge and are reproduced therefrom, the position of the magnetic disk must be adjusted with a very high accuracy with respect to a magnetic head.
In order to satisfy the requirements for the high positioning accuracy, the accuracy of the dimensions of the cassette shell of the magnetic disk cartridge must be high. In particular, the positions of the two cassette shell halves to be combined and secured to each other must be adjusted accurately and must then be secured to each other. For such purposes, welding is advantageous over the use of screws. With welding, there is no risk that looseness or disengagement of the cassette shell halves is produced after they have been secured to each other. However, in order for ultrasonic welding to be carried out, projections or protruding strips (both will hereinbelow be referred to as the projections), which serve as energy directors (ED's) for concentrating energy of ultrasonic waves, must be formed on the surface to be welded. In addition, it is necessary to use a combination of a positioning pin and a pin receiver for accurately adjusting the positions of the two cassette shell halves with respect to each other during the welding. In particular, the projections for the welding are formed on the surfaces of the two cassette shell halves, which face each other. Therefore, if the projections are formed on the surfaces perpendicular to the fitting direction, along which the two cassette shell halves are moved towards each other and brought into contact with each other during the fitting step, the thickness of the entire cassette shell after being formed by the fitting of the two cassette shell halves to each other will fluctuate in accordance with the extent of the welding. Further, shift in positions of the two cassette shell halves and warp thereof occur depending on how the positioning pin and the pin receiver are formed. These problems are detrimental for the cassette shell, which is required to have accurate dimensions.
Also, besides the combination of the positioning pin and the pin receiver described above, it is necessary for protruded structures to be located on the inner surfaces of the cassette shell halves. From the viewpoint of the cost of molds for the molding step, prevention of deformation after the molding step, and product management, it is not desirable to have protruded structures provided on the inner surfaces of the cassette shell halves.
Therefore, it is desired that the structures of the cassette shell halves to be welded to each other by the ultrasonic welding are kept as simple as possible.

Magnetic disk cartridge in which shell halves are accurately positioned and process for producing the same


A hybrid regulator incorporates both linear and switching-type regulator circuits. While such a combination may at first be thought undesirable as simply compounding the flaws of one design with the flaws of the other, in fact the present design is well suited for many applications. In the preferred embodiment, the linear and switching circuits are cascaded. The switching circuit runs in open-loop fashion--without adaptive control. However, a feedback signal is derived from the output of the switching circuit and is used to control the linear regulator, effecting net control of the entire circuit. In this manner, a simple, low cost power supply is provided that provides the excellent regulation and simple over-current protection characteristic of a linear supply, together with the boost capabilities of switching topologies.

Prior art power supplies typically fall into one of two classes. The first, "linear" power supplies, regulate an output parameter (current or voltage) by linearly changing a variable impedance in response to load conditions so as to maintain a fixed output. The second, "switched" power supplies, regulate an output parameter by controllably storing energy in a reactive component (typically an inductor) and discharging this energy to the load.
Linear regulators offer a number of advantages, one of which is good regulation. However, they also suffer from several drawbacks, the primary one of which is inefficiency. Power that is not consumed by the load is dissipated as heat. Linear regulators often have efficiencies below fifty percent.
Switching regulators also offer a number of advantages, a primary one of which is high efficiency--often above 85%. Also, switching regulators can provide "boost." That is, the DC output voltage may be greater than the DC input voltage. However, switching regulators also have a number of drawbacks. One is that they cannot provide precision (i.e. <0.1%) regulation. Another is that the control circuitry used to dynamically control the switching characteristics (i.e. duty cycle) of a switching regulator to effect regulation in response to changing load conditions is generally complex, especially at high switching frequencies. Yet another is that the output signal usually includes some output ripple due to the switching operation. Finally, over-current protection is somewhat difficult to implement in many topologies.
In accordance with the present invention, a hybrid regulator is provided that incorporates both linear and switching-type circuits. While such a combination may at first be thought undesirable as simply compounding the flaws of one design with the flaws of the other, in fact the present design is well suited for certain applications.
In the preferred embodiment, the linear and switching circuits are cascaded. The switching circuit runs in open-loop fashion--without adaptive control. However, a feedback signal is derived from the output of the switching circuit and is used to control the linear regulator, effecting net control of the entire circuit. In this manner, a simple, low cost power supply is provided that provides simple over-current protection, characteristic of a linear supply, together with the boost capabilities of some switching topologies.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.