JP4285172B2 - Optical head device - Google Patents

Description

  The present invention relates to an optical head device that records on or reproduces from an optical recording medium such as an optical disk.

  In recent years, in order to increase the recording density of an optical recording medium such as an optical disk, a method of shortening the wavelength of light emitted from a light source and increasing the numerical aperture of an objective lens has been put into practical use. However, shortening the wavelength of the emitted light and increasing the numerical aperture of the objective lens have seriously affected the effects of coma and spherical aberrations on the reading and writing of information from the optical recording medium.

  As one method of correcting coma aberration, spherical aberration, etc. when recording or reproducing information on an optical recording medium, a phase correction element is provided between the objective lens and the light source to provide coma aberration, spherical aberration, etc. There is a method for correcting wavefront aberration. In a correction method using a phase correction element, a voltage applied to a birefringent material such as a liquid crystal by dividing the electrode provided on the phase correction element into a plurality of parts and controlling the potential of each electrode obtained by the division. Is controlled to change the refractive index to correct the wavefront aberration of the light emitted from the light source.

However, in this method of dividing the electrodes provided in the phase correction element, the amount of change in the wavefront of the light passing through each electrode is determined, and it is difficult to continuously change the wavefront between adjacent electrodes. Met. Therefore, a technology has been developed to continuously change the wavefront in a region where the amount of change in wavefront aberration is large by arranging a plurality of power supply units and taking a method of generating a voltage distribution by causing a potential drop between the power supply units. (For example, refer to Patent Document 1). And as a material of the electrode which comprises a phase correction element, the zinc oxide (GZO) thin film, the tin oxide thin film, etc. which were mainly doped with gallium are used.
JP 2003-228871 A

  However, in such a conventional optical head device, when GZO is used as a material for an electrode, there is a problem that the electrical resistance value of the electrode (hereinafter simply referred to as a resistance value) changes with time and the device is likely to fail. When a tin oxide film is used, there is a problem that it is difficult to control the resistance value of the electrode to be formed, resulting in variation in characteristics.

  The present invention has been made to solve such a problem, and provides an optical head device capable of reducing a change in resistance value of an electrode constituting a phase correction element with time and suppressing variation in performance. It is.

In view of the above points, the invention according to claim 1 includes a light source, an objective lens for condensing the light emitted from the light source on an optical recording medium, and between the light source and the objective lens. An optical head device comprising: a phase correction element that changes the wavefront of the emitted light; and a control voltage generation unit that generates a control voltage for controlling the phase correction element to change the wavefront of the emitted light. in the phase correction device includes a pair of substrates, and the anisotropic optical medium for changing a wavefront of the previous SL emitted light is sandwiched between the pair of substrates, one of the anisotropic optical medium A common conductor provided in the vicinity of the side surface, a power supply side conductor provided in the vicinity of the side surface facing the side surface of the anisotropic optical medium in which the common conductor is provided in the vicinity, the common conductor, and the The control voltage can be applied to the power supply conductor And a plurality of power supply portions provided, at least the power supply side _{conductors, Sn x Si (1-x} ) O y ( provided that 0.5 ≦ x <1,1 <y ≦ 2) thin film The power feeding portion is formed of a conductive thin film, and Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2), the sheet resistance value of the thin film is 10 ³ times or more and 10 ¹⁰ times or less the sheet resistance value of the conductive thin film forming the power feeding portion .

With this configuration, since the power supply-side conductor is formed of a thin film of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2), the phase correction element is configured. Thus, it is possible to realize an optical head device capable of reducing the change in resistance value of the electrode to be performed with time and suppressing variation in performance.
Further, the sheet resistance value of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2 ₎ forming the power supply side conductor forms the power supply unit. Since the sheet resistance value of the conductive thin film is 10 ³ times or more and 10 ¹⁰ times or less, it is possible to realize an optical head device capable of satisfactorily reducing the influence of the potential drop in the power feeding section and improving the performance. .

The invention according to claim 2, Oite to claim 1, a plurality of power supply portions provided on the power supply side conductor is provided so as to divide the power supply side conductors into a plurality of regions, the Of the plurality of power supply units provided on the power supply-side conductor, a predetermined power supply unit is connected to each other through a thin film resistor so as to be conductive.

With this configuration, in addition to the effect of the first aspect, since the predetermined power supply portion provided on the power supply side conductor is connected to be conductive through the thin film resistor, the resistance value of the thin film resistor is adjusted within a predetermined range. Thus, it is possible to realize an optical head device capable of reducing the number of control voltage terminals applied to the partial power supply side conductor.

According to a third aspect of the present invention, in the second aspect , the thin film resistor is a Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film. It has the structure formed.

With this configuration, in addition to the effect of the second aspect , at least the power supply side conductor and the thin film resistance are Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2). ) Since it is formed of a thin film, even when the resistance value of the material varies from lot to lot, the influence of variation is offset, and an optical head device capable of improving performance uniformity can be realized.

According to a fourth aspect of the present invention, there is provided the invention according to the first or second aspect , wherein at least the power supply side conductor contains Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <Y ≦ 2) formed as a thin film, and the nitrogen is contained to control the resistance value of the thin film.

According to this configuration, in addition to the effect of claim 1 or 2 , at least the power supply-side conductor is Sn _x Si _(1-x) O _y containing nitrogen (where 0.5 ≦ x <1, 1 <y ≦ Since the resistance value of the thin film can be controlled by adjusting the amount of nitrogen contained, an optical head device capable of further improving the uniformity of performance can be realized.

The invention according to claim 5 is the invention according to claim 2 , wherein at least the power supply side conductor and the thin-film resistor contain Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1 1 <y ≦ 2), and the nitrogen is contained to control the resistance value of the thin film.

With this configuration, in addition to the effect of the second aspect , at least the power supply side conductor and the thin film resistor are Sn _x Si _(1-x) O _y containing nitrogen (where 0.5 ≦ x <1, 1 <y Since it is formed as a thin film (even if it is ≦ 2), even if the resistance value of the material varies from lot to lot, the influence of variation is offset, and the resistance value of the thin film can be controlled by adjusting the amount of nitrogen contained Therefore, it is possible to realize an optical head device capable of further improving performance uniformity.

As described above, in the present invention, the power supply side conductor is formed of a thin film such as Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2). Therefore, it is possible to realize an optical head device capable of reducing the variation with time of the resistance value of the electrodes constituting the phase correction element and suppressing the variation in performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  An optical head device according to an embodiment of the present invention is provided between a light source, an objective lens for condensing emitted light from the light source on an optical recording medium, and between the light source and the objective lens. It has a configuration comprising a phase correction element that changes the wavefront, and a control voltage generating means that generates a control voltage for controlling the phase correction element to change the wavefront of the emitted light.

  Here, the light source is constituted by, for example, a semiconductor laser. The optical recording medium refers to a recording medium that is read and written by irradiating light from a light source such as an optical disk or a DVD. In the following, the term “optical disk” represents an optical recording medium unless otherwise specified.

  In addition, the optical system of the optical head device passes through the polarizing beam splitter for separating the emitted light from the light source and the reflected light from the optical recording medium, the collimating lens for converting the light that has passed through the polarizing beam splitter into parallel light, and reciprocating the light. In this case, a quarter-wave plate for changing the polarization direction by 90 ° may be included. In such a configuration, the linearly polarized light emitted from the light source (for example, a semiconductor laser) passes through the polarization beam splitter and is then converted into parallel light by the collimator lens, and the phase correction element, quarter wavelength. The light is sequentially transmitted through the plate and condensed on the optical disk by the objective lens.

  The information is recorded by changing the intensity of the light condensed on the optical disc in accordance with, for example, encoded information (for example, “0”, “1”). In addition, when reproducing information, the light collected on the optical disk is reflected by the optical disk, and the objective lens, quarter-wave plate, phase correction element, and collimator lens are sequentially reversed in the direction opposite to that for information recording. The light passes through, is distributed by the polarization beam splitter, and enters the photodetector.

  The control voltage generating means generates a signal (hereinafter simply referred to as “control signal”) for controlling the phase correction element so that information can be accurately recorded on the optical disc and the recorded information can be accurately reproduced. The phase correction element is controlled via the voltage (control voltage) of the control signal. This control voltage is adjusted by the control voltage generating means according to the aberration generated by the tilt of the optical disc or the shift of the objective lens.

  The phase correction element is provided so as to correct the phase and aberration of light so that information can be accurately read from and written to the optical recording medium. Control is performed to change the correction amount. Specifically, control is performed so as to optimize, for example, the spot diameter of the light condensed on the optical disc, or to optimize the light intensity incident on the photodetector.

  The medium that changes the phase of the light in the phase correction element is an anisotropic optical medium, and the anisotropic optical medium is refracted continuously with good reproducibility and with respect to the magnitude of the voltage by an externally applied voltage. What can change the rate is good. As the anisotropic optical medium, a lithium niobate single crystal, liquid crystal, or the like can be used. However, a liquid crystal is preferable because the refractive index can be changed at a low voltage and the productivity of the phase correction element is high. Hereinafter, the anisotropic optical medium will be described as a liquid crystal unless otherwise specified.

  FIG. 1 is a diagram showing a cross-sectional structure of a phase correction element constituting an optical head device according to an embodiment of the present invention. In FIG. 1, a phase correction element 100 is sandwiched between a pair of substrates 11, 17, a pair of substrates 11, 17, an anisotropic optical medium (liquid crystal) 14 for changing the wavefront of emitted light, and a pair In the vicinity of one side surface of the sealing materials 18 and 19, the alignment plates 13 and 15, and the anisotropic optical medium (liquid crystal) 14 that hold and seal the anisotropic optical medium (liquid crystal) 14 together with the substrates 11 and 17. A common conductor 12 provided, a power supply side conductor 16 provided in the vicinity of the side surface facing the side surface of the anisotropic optical medium (liquid crystal) 14 provided in the vicinity of the common conductor 12, and a power supply side conductor A plurality of power supply units 20 (other power supply units are provided in a direction perpendicular to the paper surface of FIG. 1) provided so that a control voltage can be applied to 16 and the common conductor 12. The power supply unit 22 is included.

  The substrates 11 and 17 need only be transparent to the wavelength of light used, and glass, acrylic resin, epoxy resin, vinyl chloride resin, polycarbonate resin, etc. can be used. From the viewpoint of easiness, glass is preferable. Although not shown, an antireflection coat may be applied to the outer surfaces of the substrates 11 and 17, that is, the surface not facing the anisotropic optical medium (liquid crystal) 14.

  The alignment plate 13 is disposed at a position sandwiched between the substrate 11 or the common conductor 12 and the anisotropic optical medium (liquid crystal) 14, and the alignment plate 15 is formed of the substrate 17 or the power supply side conductor (partial power supply side conductor). ) 16 and the anisotropic optical medium (liquid crystal) 14 are arranged between the liquid crystal molecules and the liquid crystal molecules are aligned in a predetermined direction when a control voltage is not applied to the anisotropic optical medium (liquid crystal) 14. It is provided to make it.

  As conceptually shown in FIG. 1, the sealing material 18 includes conductive beads 21, and electrical connection between the power supply unit 22 and the common conductor 12 is ensured through the conductive beads. Here, the conductive beads can be formed, for example, by coating the surface of the resin beads with metal.

A control voltage is applied between the common conductor 12 and the power supply side conductor 16 via power supply units 20 and 22, and the power supply side conductor 16 and the common conductor 12 are, for example, transparent conductive Consists of a membrane. At that time, at least the power supply side conductor 16 is a Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film (hereinafter referred to as an SSO thin film). It shall be formed. The common conductor 12 may also be formed as an SSO thin film.

Further, a Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film (hereinafter referred to as an SSON thin film) containing nitrogen instead of the SSO thin film. It may be used. This is because the sheet resistance of the thin film can be controlled to a desired value by adjusting the nitrogen content. A thin film (for example, an SSO thin film, an SSON thin film, etc.) for forming the power supply side conductor 16 and the common conductor 12 may be formed by sputtering, for example, but may be other methods.

  When different control voltages are applied between the power supply units 20 and 22, current flows in the power supply side conductor 16 due to a potential difference generated between the adjacent power supply units 20, and the power supply side conductor 16 A potential distribution is generated. As a result, the voltage applied between the power supply side conductor 16 and the common conductor 12 has a voltage distribution, and the refractive index distribution of the anisotropic optical medium (liquid crystal) 14 is determined according to this voltage distribution. Will be.

  Therefore, the refractive index distribution can be controlled by adjusting the control voltage applied to the plurality of power supply units 20, and the wavefront of the light passing through the anisotropic optical medium (liquid crystal) 14 is the anisotropic optical medium. Since it changes according to the refractive index of the (liquid crystal) 14, the wavefront aberration of the light passing through the anisotropic optical medium (liquid crystal) 14 can be corrected via the control voltage.

In general, in the phase correction element 100, it is desired that the potential drop generated in the power supply unit 20 is negligibly small compared to the potential drop generated in the power supply side conductor 16. For this purpose, the ratio ρ _T / ρ _S between the sheet resistance ρ _T of the power supply side conductor 16 and the sheet resistance ρ _S of the power supply unit 20 is preferably 10 ³ or more and 10 ¹⁰ or less. When ρ _T / ρ _S is less than 1000, a voltage drop occurs in the power feeding unit 20, making it difficult to obtain a desired potential distribution in the power feeding side conductor 16. Further, if the ratio ρ _T / ρ _S exceeds 10 ¹⁰ and the sheet resistance ρ _T of the power supply side conductor 16 is too high, the conductivity of the power supply side conductor 16 becomes low, and an appropriate potential distribution may be generated. It becomes difficult. Therefore, it is desirable to make the sheet resistance ρ _S of the power supply unit 20 as low as possible. Specifically, it is preferable to set the sheet resistance ρ _S to about 0.1 to 10Ω / □. ρ _T is preferably about 100 to 100 kΩ / □.

Thus, the thin film for the power supply side conductor 16, a transparent and sheet resistance as long as the range of the above-mentioned [rho _T but, and ease of implementation of the sheet resistance of such a range, From the viewpoint of little change in sheet resistance with time after the thin film is formed, it is preferable to use the SSO thin film or the SSON thin film as the thin film for the power supply side conductor 16.

The power supply unit 20 may be a transparent thin film with ρ _S of 0.1 to 10Ω / □, and metals such as Cr, Ag, and Al are preferable in terms of good durability, and are low resistance SSO thin films and SSON thin films. A transparent electrode such as a low-resistance ITO thin film is preferable in that a light-shielding portion does not occur and the light transmittance is improved.

  FIG. 2 shows that in an optical system in which the numerical aperture NA of the objective lens is 0.65 and the wavelength of the light emitted from the light source is 0.4 μm, the thickness of the optical disk having a design value of 0.6 mm is 0.03 mm thick. It is a figure which shows the pattern of the wavefront aberration (spherical aberration) which generate | occur | produces when becoming. When the optical disc is thicker than the design value, the intermediate portion B (vertical hatching) sandwiched between both of the effective pupil central portion A (right tilted hatching) and the peripheral portion C (left tilted hatching). ) Phase is advanced. FIG. 2 shows the phase shift as a distance in units of “nm”.

  FIG. 3 is a plan view showing an example of an arrangement pattern (hereinafter simply referred to as “arrangement pattern”) of the power supply side conductor 16 and the power supply unit 20 formed to correct the spherical aberration of the pattern as shown in FIG. FIG. In FIG. 3, the hatched portion indicates a portion where the substantially circular feeding-side conductor 16 is formed, and the feeding portion 20 surrounds the central portion (the feeding portion is labeled 201) and concentrically around it. The power supply side conductor 16 is divided into annular regions by the power supply units 202 to 204. The power supply side conductor 16 is divided into annular regions by the power supply units 202 to 204. Below, the part which belongs to the electric power feeding parts 20 other than the electric power feeding parts 201-204 is called wiring.

  As shown in FIG. 3, a control voltage is applied to the power feeding units 201 to 204 via the wirings 31 to 33. Here, the wirings 31 to 33 are electrically insulated from the power supply side conductor 16 except in the vicinity of the junction with the power supply units 201 to 204 so that the concentric potential distribution is not changed.

By applying different control voltages V ₁ , V ₂ , and V ₃ to the wirings 31 to 33 to generate a potential drop in the plane of the power supply side conductor 16, a substantially concentric continuous potential distribution is developed. . The spherical aberration and the like can be corrected by adjusting the voltage applied to the power feeding units 201 to 204 in the radial direction distribution of the concentric continuous potential distribution. FIG. 6 is a diagram in which the amount of wavefront aberration and the amount of correction are compared on the cut surface of the phase correction element, and the potential distribution indicated by the solid line is realized by appropriately setting the control voltages V ₁ , V ₂ , and V ₃ . Then, the phase amount corrected by the phase correction element can be matched with the aberration distribution shape shown by the broken line.

  As shown in FIG. 1, when a plurality of power supply units 20 are provided on any one of the opposing substrates 11 and 17 (substrate 17 in FIG. 1), a predetermined power supply unit 20 is provided. As shown below, the control voltage output from the control voltage generator and applied to the phase correction element is divided, and the divided voltage is divided into another control voltage by conducting a conductive connection through a thin film resistor. It may be used as. This is preferable because the number of control voltages to be output from the control voltage generating means can be reduced.

  FIG. 4 is a diagram showing a configuration in which a thin film resistor 42 made of a conductive thin film is provided between the wiring 31 and the wiring 32 shown in FIG. With this configuration, when a current flows through the power supply unit 202 via the thin film resistor 42, a potential difference is generated between the power supply unit 201 and the power supply unit 202, and the resistance value of the thin film resistor 42 is adjusted. This potential difference can be adjusted. Therefore, the control voltage applied via the wiring 32 shown in FIG. 3 can be omitted in the configuration shown in the figure.

FIG. 5 is a circuit diagram showing an equivalent circuit of the components of the phase correction element shown in FIG. Points 51 to 54 correspond to the power feeding units 201 to 204, respectively, and resistors R ₁ , R ₂ , and R ₃ respectively represent the power feeding unit 201 and the power feeding unit 202, the power feeding unit 202 and the power feeding unit 203, and the power feeding unit 203 and the power feeding unit 204. The equivalent resistance by the electric power feeding side conductor 16 is shown. The resistor R _S represents the equivalent resistance of the thin film resistor 42 and divides the control voltage V ₁ applied to the point 55 so that the desired potential is obtained at the position of the point 52. Hereinafter, the potentials of the point 53 and the point 55 are set to V ₂ and V ₁ , respectively. At this time, the potential V _{3 at} the position of the point 52 is expressed by the following equation (1) according to Ohm's law.

Here, if the resistors R ₁ and R ₂ and the potentials V ₁ and V ₂ are known, the potential V ₃ can be set to a predetermined value by appropriately setting the resistor R _S. By providing the thin film resistor 42 and appropriately setting the resistance value of the thin film resistor 42 in this manner, the power supply unit 202 can be set to the potential V _3, which is preferable because it is not necessary to separately apply a control voltage.

Here, the thin film forming the power supply side conductor 16 and the thin film resistor 42 has resistance values R ₁ , R ₂ , R ₃ so that the value of the potential V ₃ shown in the above equation (1) becomes a desired value. Must be realized. In general, it is preferable to make the resistance value of a thin film used in an optical head device in the range of 100 to 1000 kΩ because it is easy to produce. Furthermore, the thin film forming the power supply side conductor 16 and the thin film resistor 42 is manufactured using the same material. Even if the resistance value of the material varies from lot to lot, the influence is as shown in the equation (1). Since they are offset between molecules, the influence of variations on the potential V ₃ can be greatly reduced, which is preferable.

Therefore, it is preferable to form both the power supply side conductor 16 and the thin film resistor 42 by an SSO thin film. Furthermore, Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film (the above SSON thin film) containing nitrogen is supplied to the power supply side conductor 16 and the thin film. It is preferable to use the resistor 42 because the resistance value of the thin film can be easily controlled by adjusting the nitrogen content.

  The optical head device of this embodiment includes a phase correction element that corrects spherical aberration caused by thickness unevenness of the optical disk. The element structure of this phase correction element is the same as that shown in FIG. The arrangement pattern of the power supply side conductor 16 and the power supply unit 20 of the phase correction element in this embodiment is as shown in FIG. 4, and the equivalent circuit is as shown in FIG.

  In FIG. 4, the power supply side conductor 16 (shaded portion) is formed of an SSO thin film, and the power supply portions 201 to 204 (annular gray regions) are formed using an etching technique after the chromium thin film is formed. It is. The wirings 31 and 33 and other wirings are formed on the same substrate surface as the power supply unit on the same surface as that of the power supply unit.

  The thin film resistor 42 is formed of an SSO thin film on the same substrate surface as the substrate surface on which the power feeding unit is formed. A control voltage is applied to the power feeding units 201 to 204 via a chromium thin film wiring. Note that a control voltage is applied to the power feeding unit 202 via a chromium thin film wiring 31 and a thin film resistor 42 formed of an SSO thin film.

  Here, the line widths of the power supply units 202 to 204 are approximately 100 μm, the average diameters of the power supply units 202 to 204 are approximately 0.5, 1.5, and 2.2 mm, respectively, and the diameter of the power supply unit 201 is approximately 50 μm. It was a circle.

  The arrangement pattern of the power supply side conductor 16 and the power supply units 201 to 204 was formed as follows. First, a chromium film was deposited on a glass substrate by a sputtering method, and then unnecessary portions other than a portion to be left as an arrangement pattern were removed using an etching technique to form power supply portions 201 to 204. The same applies to the wiring.

  Next, an SSO thin film is formed by sputtering on the substrate on which the power supply portions 201 to 204 are formed, and unnecessary portions are removed by a lift-off method using a photoresist, thereby forming the power supply side conductor 16 and the thin film resistor 42. did. The sheet resistance of the power supply side conductor 16 and the thin film resistor 42 and the sheet resistance of the thin film used for the power supply units 201 to 204 were 100 kΩ / □ and 1Ω / □, respectively.

The values of the electrical resistance (corresponding to equivalent resistances R ₁ , R ₂ , R ₃ shown in FIG. 5) of the power supply side conductor 16 between the power supply units 201 to 204 were 50, 28, and 20 kΩ, respectively.

Here, the resistance value and shape of the thin film resistor 42 were determined as follows. 2V potential V ₁ of the feed section 201 and 204, the potential V ₂ of the feed 202 and 3V, when approximately 2.15V potential of the power supply unit 202, which corresponds to 52 points shown in FIG. 5, the resistance value of the thin film resistor R _S is determined to be 5.48 kΩ based on the equation (1). Further, since the sheet resistance ρ _L is 100 kΩ / □, when the line width W of the thin film resistor is 100 μm, the length L is determined to be about 5.5 μm by the relational expression R _S = ρ _L × L / W. Thus, in this example, a thin film resistor having a width of 100 μm and a length of 5.5 μm was formed, and a resistance value of 5.5 kΩ was obtained.

  Next, polyimide was spin-coated on the substrate on which the power supply side conductor 16 and the thin film resistor 42 were formed, and heated at 300 ° C. for 1 hour to be lowered to form an alignment film. The same applies when an alignment film is formed on the other substrate. The polyimide film formed on the substrate was subjected to an orientation treatment by a rubbing method, and then an epoxy resin was printed on the substrate to form a sealing material.

  After aligning and stacking the substrate obtained by performing each of the above treatments with an opposing substrate subjected to the same treatment as this substrate, it is pressure-bonded at a pressure of 0.06 MPa and heated at 170 ° C., An empty cell was created by curing the sealing material. When printing the sealing material, liquid crystal is injected from a previously prepared injection port by a vacuum injection method, and the injection port is sealed with a sealing material made of UV-curable acrylic resin, and the phase correction element is Completed.

As described above, in the optical head device according to the embodiment of the present invention, the power supply-side conductor is Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2 Since the thin film and the nitrogen-containing Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film are formed, good wavefront aberration is achieved. It is possible to achieve an optical head device that can obtain correction performance, reduce a change with time in the resistance value of an electrode constituting the phase correction element, and suppress variation in performance.

Further, the sheet resistance value of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2 ₎ forming the power supply side conductor forms the power supply unit. Since the sheet resistance value of the conductive thin film is 10 ³ times or more and 10 ¹⁰ times or less, it is possible to satisfactorily reduce the influence of the potential drop in the power feeding section and improve the performance.

  In addition, since the predetermined power supply units are connected to be conductive through a thin film resistor, the control voltage from the control voltage generating means is divided and applied to the predetermined power supply unit connected through the thin film resistor. The number of control voltage outputs to be output from the control voltage generating means can be reduced.

In addition, since at least the power supply side conductor and the thin film resistor are formed of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film, Even when the resistance value of each of these varies from lot to lot, the influence of variation is offset and the uniformity of performance can be improved.

In addition, since at least the power supply side conductor is formed as a thin film of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2 ₎ containing nitrogen, Since the resistance value of the thin film can be controlled by adjusting the amount of nitrogen contained, the performance uniformity can be further improved.

Further, at least the power supply side conductor and the thin film resistor are formed as Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) thin film containing nitrogen. As a result, even when the resistance value of the material varies from lot to lot, the influence of variation is offset, and the resistance value of the thin film can be controlled by adjusting the amount of nitrogen contained, thus improving the uniformity of performance. be able to.

In the optical head device according to the present invention, the power supply-side conductor is formed of a thin film of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2). In the industrial field etc. of the optical head device that has the effect of reducing the variation with time of the resistance value of the electrodes constituting the phase correction element and suppressing the variation in characteristics, and reading and writing information using light It can be applied to other uses.

FIG. 3 is a conceptual cross-sectional view showing an example of a fundamental configuration of a phase correction element that constitutes the optical head device according to the embodiment of the invention. The figure which shows the wavefront aberration which generate | occur | produces when the thickness of an optical disk becomes 0.03 mm thick from a design value. The figure which shows an example of the arrangement pattern of the electric power feeding side conductor and electric power feeding part which were formed in the phase correction element which comprises the optical head apparatus which concerns on embodiment of this invention. The figure which shows another example of the arrangement pattern of the electric power feeding side conductor formed in the phase correction element which comprises the optical head apparatus which concerns on embodiment of this invention, and an electric power feeding part. FIG. 5 is a circuit diagram showing an equivalent circuit of the phase correction element shown in FIG. 4. The figure which shows an example of the amount of phase changes produced | generated using the phase correction element which comprises the optical head apparatus which concerns on embodiment of this invention.

Explanation of symbols

11, 17 Substrate 12 Common conductor 13, 15 Orientation plate 14 Anisotropic optical medium (liquid crystal)
16 Feeding side conductors 18, 19 Sealing material 20, 22 Feeding part 21 Conductive beads 31, 32, 33 Wiring 42 Thin film resistors 51-54 Points corresponding to feeding parts 201-204 in the equivalent circuit 100 Phase correction elements 201-204 Feeding part

Claims (5)

A light source, an objective lens for condensing outgoing light from the light source on an optical recording medium, a phase correction element provided between the light source and the objective lens, and changing a wavefront of the outgoing light; In an optical head device comprising control voltage generating means for controlling the phase correction element to generate a control voltage for changing the wavefront of the emitted light,
Wherein the phase correcting element, and the anisotropic optical medium for changing a pair of substrates, the wavefront before SL emitted light is sandwiched between the pair of substrates, one side near the anisotropic optical medium A common conductor provided on the side, a power supply side conductor provided near the side surface of the anisotropic optical medium provided near the common conductor, the common conductor and the power supply side A plurality of power supply units provided so as to be able to apply the control voltage between conductors;
At least the power supply-side conductor is formed as a thin film of Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) ,
The power feeding portion is formed of a conductive thin film, and Sn _x Si _(1-x) O _y (where 0.5 ≦ x <1, 1 <y ≦ 2) is a thin film forming the power feeding side conductor . An optical head device characterized in that a sheet resistance value is 10 ³ times or more and 10 ¹⁰ times or less of a sheet resistance value of a conductive thin film forming the power feeding portion . The plurality of power supply units provided in the power supply side conductor are provided so as to divide the power supply side conductor into a plurality of regions, and are determined in advance among the plurality of power supply units provided in the power supply side conductor. The optical head device according to claim 1, wherein the fed power supply portions are connected to each other through a thin film resistor so as to be conductive. The thin film resistor is Sn _x Si _(1-x) O _y 3. The optical head device according to claim 2, wherein the optical head device is formed of a thin film (where 0.5 ≦ x <1, 1 <y ≦ 2). At least the power supply-side conductor is Sn containing nitrogen. _x Si _(1-x) O _y 3. The light according to claim 1, wherein the light is formed as a thin film (where 0.5 ≦ x <1, 1 <y ≦ 2), and the nitrogen is contained to control a resistance value of the thin film. Head device. At least the power supply side conductor and the thin film resistor are Sn containing nitrogen. _x Si _(1-x) O _y 3. The optical head device according to claim 2, wherein the optical head device is formed as a thin film (where 0.5 ≦ x <1, 1 <y ≦ 2), and the nitrogen is contained to control the resistance value of the thin film. .

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