JP2005148654A - Liquid crystal element for phase modulation, optical pickup, phase adjusting method, and optical aberration correcting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal element for phase modulation that is enabled to perform proper phase modulation by using a liquid crystal material and an optical pickup using the liquid crystal element for phase modulation, and to provide a phase correcting method and an optical aberration correcting method that enable proper phase correction by using a liquid crystal material. <P>SOLUTION: Used is the liquid crystal element which has the liquid crystal material 82, alignment films 83 and 84 arranged across the liquid crystal material 82 adjacenty to the liquid crystal material, and electrode films for applying a voltage to the liquid crystal material 82, and is constituted by modulating alignment processing of alignment films 83<SB>1</SB>and 83<SB>2</SB>, and 84<SB>1</SB>and 84<SB>2</SB>prescribing an alignment restricting force for the liquid crystal material 82 so that when the voltage 87 is uniformly applied to the electrode films 85 and 86, refractive index variation of the liquid crystal material 82 is partially modulated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a phase modulation liquid crystal element that partially modulates a phase and an optical pickup using the phase modulation liquid crystal element.
The present invention relates to a phase correction method and an optical aberration correction method using a liquid crystal element that partially modulates a phase without refracting transmitted light.

  Due to recent advances in computer technology and higher functionality in information network environments, recording media that record more information are desired. Both recording media that optically record and reproduce information (so-called optical disks) and recording media that magnetically record and reproduce information (so-called hard disks) are desired to have higher recording densities.

  The recording density in an optical disc is generally defined by the lens numerical aperture (NA) of the optical system and the wavelength of light. The higher the lens numerical aperture (NA) and the shorter the wavelength, the higher the recording density can be realized. However, increasing the lens numerical aperture (NA) and using a short wavelength tend to cause optical aberrations and narrow the margin of the optical system. Alternatively, a high recording density cannot be realized unless the optical system hardly generates optical aberrations.

In addition, the hard disk can form a recording film only in the very vicinity of the surface of the recording medium that is close to the recording / reproducing head. On the other hand, the optical disk can be a so-called multi-layer disk in which recording films are stacked with an interval that does not interfere optically. Recording and reproduction of a multi-layer disc is performed by forming an optical spot on each recording film that exists at a different depth from the surface of the recording medium, and thus recording and reproduction must be performed in an environment where aberration exists.
Therefore, in order to record / reproduce a multi-layer disc for high recording density, it must be performed in an environment where aberrations exist in a state where there are few optically acceptable aberrations.

  In view of such a situation, Mr. Iwasaki et al. In Non-Patent Document 1, by applying a voltage close to the shape of spherical aberration to a liquid crystal material injected into a region sandwiched between parallel electrode materials, It has been proposed to adjust the phase of the laser beam passing through the liquid crystal element to reduce the aberration of the focused spot. Before explaining the configuration of the phase adjusting device proposed by Mr. Iwasaki et al., The refractive index control (ECB) of the liquid crystal material by voltage application, which is the principle, will be described with reference to FIG.

Liquid crystal materials are classified into many types depending on their electrical characteristics or optical characteristics. Here, a nematic liquid crystal material having a positive optical anisotropy will be described as an example. Since the molecular structure of the liquid crystal material is not electrically symmetrical, the liquid crystal material is arranged regularly according to the alignment film subjected to the alignment treatment.
In the liquid crystal element 1 shown in FIG. 13, an alignment film 4 is formed on the inner surface of one electrode film 2 for applying a voltage 7 [7 ₁ , 7 ₂ ], and an alignment film 5 is formed on the inner surface of the other electrode film 3. The liquid crystal material 6 is filled between the alignment films 4 and 5. FIG. 13A shows the state of the liquid crystal material 6 when no voltage is applied to the electrode films 2 and 3, and the liquid crystal material 6 is arranged in the direction of the alignment treatment applied to the alignment films 4 and 5, respectively. When the dielectric anisotropy of the liquid crystal material 6 is positive, when a voltage 7 is applied between the electrode films 2 and 3 of the liquid crystal element 1, a voltage 7 applied from the outside as shown in FIGS. 13B and 13C. _1, 7 a liquid crystal material 6 in the _second direction (i.e. the liquid crystal molecules 6 of the liquid crystal material 6 ') is trying to change its direction. Here, the liquid crystal molecules 6 a ′ close to the alignment films 4 and 5 are aligned on the alignment films 4 and 5 compared to the liquid crystal molecules 6 b ′ located far from the alignment films 4 and 5. It is difficult to change the direction of molecules because it is greatly affected by the treatment. However, the direction of the liquid crystal molecules 6 'changes according to the magnitude of the electric field from the outside (voltages 7 ₁ and 7 ₂ ).

  The liquid crystal material 6 having optical anisotropy has a characteristic that the refractive index ne for polarized light in a direction parallel to the alignment direction of the liquid crystal material 6 varies depending on the angle of the liquid crystal material 6. Therefore, as a result, the refractive index changes due to external voltage application. In the liquid crystal material 6 having positive optical anisotropy, ne> no (no: refractive index with respect to polarized light in a direction perpendicular to the alignment direction of the liquid crystal material 6). The refractive index is greatest when parallel to the electric field direction (vertical direction in FIG. 13).

Next, consider a case where the electric field applied to the liquid crystal element is not uniform as shown in FIG. In the liquid crystal element 11 as a sample in FIG. 14, the high resistance conductive film 8 having the alignment film 4 is disposed on one side of the liquid crystal material 6, and the low resistance conductive film 8 is low on both ends of the high resistance conductive film 8. A resistive conductive film 9 [9a, 9b] is formed, and an electrode film 3 having an alignment film 5 is disposed on the other side of the liquid crystal material 6 therebetween. Then, the one voltage ₇₁ across the low-resistance conductive film 9a and the electrode film 3 is applied a voltage 7 ₁ greater than the voltage 7 ₂ is applied between the other of the low resistance conductive film 9b and the electrode film 3. As described above, since the refractive index ne of the liquid crystal material 6 changes according to the applied voltage, the light vertically incident on the liquid crystal element 11 as shown in FIG. Only a change in refractive index according to the applied voltages 7 ₁ and 7 ₂ is felt. In FIG. 14, a region 12 is a region having a small change in refractive index, and a region 13 is a region having a large change in refractive index. The fact that light feels a change in refractive index means that the difference in optical distance (refractive index × physical distance) is felt, so that the phase of the transmitted light changes according to the amount of voltage applied. .

  Iwasaki et al. Applied the basic characteristics of the liquid crystal material 6 described with reference to FIGS. 13 and 14 to the reproducing optical system of the optical disk apparatus. FIG. 15 shows the configuration of the optical pup-up of Mr. Iwasaki et al. FIG. 16 shows an electrode pattern formed on the liquid crystal element used by Mr. Iwasaki et al. FIG. 17 shows an example of phase adjustment performed by Mr. Iwasaki et al.

In FIG. 15, reference numeral 14 denotes a recording medium, that is, an optical disk, and 21 denotes an optical pickup. The recording medium 14 is formed by forming a recording layer 16 on a support 15 and a cover layer (for example, a cover glass layer) 17 thereon. The optical pickup 21 includes a semiconductor laser 22, a collimator lens 23 sequentially arranged along the laser beam emission direction, a polarization beam splitter (PBS) 24, an aberration correction element 25 described later using a liquid crystal element, and 1 / 4 wavelength plate (QWP) 26, an objective lens 27, and a photodetector 29 for detecting return light from the optical disk 14 via a condenser lens 28.
In this optical pickup 21, the laser light L1 emitted from the semiconductor laser 22 is collimated and collimated by the lens 23, and this parallel light passes through the polarization beam splitter 24, the aberration correction element 25, and the quarter wavelength plate, The light is condensed by the objective lens 27 and applied to the recording film 16 of the optical disk 14. That is, an optical spot is formed on the recording film 16. Then, the reflected light (so-called return light L 2) of the optical spot from the recording film 16 is incident again on the polarization beam splitter 24 through the objective lens 27, the quarter wavelength plate 26 and the aberration correction element 25. The light is reflected and received by the photodetector 29 via the condenser lens 28.

  Mr. Iwasaki et al. Used the aberration correction element 25 using the phase change of the liquid crystal element described in FIG. 13 and FIG. 14 described above, and caused spherical aberration that occurs when the thickness of the cover glass layer 17 of the optical disk 14 changes. In order to correct, the method of correcting the phase of the laser beam incident on the objective lens 27 in advance is adopted. That is, this is a method of giving a phase distribution that cancels the spherical aberration that occurs when the thickness t of the cover glass layer 17 of the optical disc 14 changes with respect to the parallel laser beam before entering the objective lens 27. .

FIG. 16 shows a liquid crystal element used in the aberration correction element proposed by Iwasaki et al. The liquid crystal element 31 has a configuration similar to that of FIG. 14 described above, and a high resistance transparent conductive film 32 having an alignment film on the inner surface is disposed on one side with a liquid crystal material interposed therebetween. A concentric first low resistance transparent conductive film 33, a second low resistance transparent conductive film 34, and a third low resistance transparent conductive film 35 are formed on 32. The third low-resistance transparent conductive film 35 is divided and formed in a circular shape. On the other side of the liquid crystal material, a transparent electrode film having an alignment film on the inner surface is formed. Lead lines 36, 37 and 38 are led out from the first, second and third low resistance transparent conductive films 33, 34 and 35, respectively. L indicates a laser beam incident on the liquid crystal element 31.
In the liquid crystal element 31, a predetermined voltage is applied to the first, second and third low-resistance transparent conductive films 33, 34 and 35, which are concentric low-resistance electrode patterns, and formed in other regions. 17B, the potential distribution shown in FIG. 17B, that is, a refractive index change that generates a phase distribution as shown in FIG. 17C occurs in the liquid crystal material. The voltage distribution is a. FIG. 17C is a distribution diagram of the refractive index change corresponding to the phase correction. The curve b indicates the ideal shape of the phase correction amount, and the curve c indicates the actual phase correction amount.
Technical Digest of Optical Data Storage 2001, 103-105, Santa Fe, New Mexico, April 2001

However, when the liquid crystal element 31 having the electrode-shaped low-resistance transparent conductive films 33, 34, and 35 as shown in FIG. 16 is used, there are the following problems.
First, in order to give a distribution to the voltage to be applied, two types of conductive films are required: a high-resistance conductive film having transparency and a low-resistance conductive film having transparency. . However, a conductive film made of an oxide such as an ITO (Indium Tin Oxide) material has increased conductivity due to the release of oxygen from its molecular structure. There is a problem of lack of nature. That is, when a voltage is uniformly applied to the entire surface, a highly transparent conductive film with high transparency can be used, but in order to have a distribution in the applied voltage, a low resistance conductive film with poor transparency is used. A membrane must be used. For this reason, the intensity distribution of the laser beam that passes through the phase adjustment element having the liquid crystal element 31, for example, the aberration correction element, is affected.

Second, in order to apply a voltage in a ring shape, lead lines 36 and 37 for applying a voltage to the inner low resistance transparent conductive films 33 and 34 must be arranged as shown in FIG. I must. For this reason, there is a problem that the distribution shape of the voltage applied by the lead lines 36 and 37 is disturbed. A portion 39 where the lead line is derived is an area where phase correction is not performed.
Third, it depends on the problem that the low resistance conductive film lacks transparency and the problem that the arrangement of the lead lines 36 and 37 causes disturbance in the applied voltage distribution. That is, because of these two problems, it is desired to reduce the number of lead-out lines by reducing the placement area of the low-resistance conductive film. However, the voltage distribution between them must be extrapolated and the electrode pattern faithful to the ideal phase adjustment pattern cannot be formed.

In view of the above-described points, the present invention provides a phase modulation liquid crystal element capable of appropriate phase modulation using a liquid crystal material, and an optical pickup using the phase modulation element.
The present invention provides a phase adjustment method and an optical aberration correction method that enable proper phase correction using a liquid crystal material.

  The liquid crystal element for phase modulation according to the present invention includes a liquid crystal material, an alignment film adjacent to the liquid crystal material with the liquid crystal material interposed therebetween, and an electrode film for applying a voltage to the liquid crystal material. The alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated so that the change in the refractive index of the liquid crystal material is partially modulated when the film is uniformly applied.

  In the liquid crystal element for phase modulation of the present invention, the refractive index change of the liquid crystal material is modulated when the voltage is uniformly applied by modulating the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material. . When light is transmitted through the liquid crystal element, the phase of the light is modulated.

  An optical pickup according to the present invention is an optical pickup that irradiates a recording medium with a laser beam using an optical lens and forms a focused spot on a recording film in the recording medium, and includes a liquid crystal in the optical path of the laser beam. A refractive index of the liquid crystal material when the voltage is uniformly applied to the electrode film having a material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material A phase modulation liquid crystal element in which the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated is arranged so that the change is partially modulated, and the laser light passing through the phase modulation liquid crystal element is arranged. The phase is partially modulated in accordance with the alignment treatment of the alignment film, and the aberration of the optical spot collected by the optical lens is corrected.

  The optical pickup according to the present invention is an optical pickup that irradiates a recording film in a recording medium with a laser beam using an optical lens, collects and reflects the reflected light from the recording film, and the laser pickup In the optical path, a phase modulation liquid crystal element similar to the above is disposed, and the phase of the laser light passing through the phase modulation liquid crystal element is partially modulated in accordance with the alignment treatment of the alignment film and collected by the optical lens. The configuration is such that the aberration of the reflected light from the recording film of the illuminated optical spot is corrected.

  In the optical pickup of the present invention, a laser that irradiates the recording medium by disposing a phase modulation element configured to partially modulate the refractive index change of the liquid crystal material in the optical path of the laser light. The aberration of light or reflected light reflected from the recording medium is corrected.

  The phase adjustment method according to the present invention includes a liquid crystal material, an alignment film adjacent to the liquid crystal material with the liquid crystal material interposed therebetween, and an electrode film for applying a voltage to the liquid crystal material, and the voltage is uniformly applied to the electrode film. A liquid crystal element in which the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated so that the change in the refractive index of the liquid crystal material is partially modulated when applied to Applying uniformly, the phase of the light transmitted through the liquid crystal material is partially modulated according to the alignment treatment of the alignment film.

  In the phase adjustment method of the present invention, by using a liquid crystal element that is configured such that the refractive index change of the liquid crystal material is partially modulated, the refractive index change does not occur when a uniform voltage is applied to the liquid crystal element. Partially modulated, the phase of light passing through the liquid crystal material is modulated.

  An optical aberration correction method according to the present invention is an optical aberration correction method for irradiating a recording medium with a laser beam using an optical lens and forming a focused spot on a recording film in the recording medium. A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material, and applying a voltage uniformly to the electrode film A liquid crystal device for phase modulation, in which a liquid crystal device for phase modulation, in which the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated, is arranged so that the refractive index change of the liquid crystal material is partially modulated. The phase of the laser beam that passes through is partially modulated according to the alignment treatment of the alignment film, and the aberration of the optical spot collected by the optical lens is corrected.

  The optical aberration correction method according to the present invention is an optical aberration correction method when a recording film in a recording medium is irradiated with laser light using an optical lens, and reflected light from the recording film is collected and received. A phase modulation liquid crystal element similar to the above is disposed in the optical path of the laser light, and the phase of the laser light transmitted through the phase modulation liquid crystal element is partially modulated in accordance with the alignment treatment of the alignment film, The aberration of the reflected light from the recording film of the optical spot condensed by the optical lens is corrected.

  In the optical aberration correction method of the present invention, a liquid crystal element for phase modulation in which the alignment treatment of the alignment regulating force that regulates the alignment regulating force of the liquid crystal material is modulated so as to generate a phase distribution that cancels the aberration. Then, the laser beam applied to the recording medium or the reflected light reflected from the recording medium is transmitted through the phase modulation liquid crystal element, whereby the aberration in the optical spot is corrected.

  According to the liquid crystal element for phase modulation according to the present invention, the alignment treatment of the alignment film that regulates the alignment regulating force is modulated so that the refractive index change of the liquid crystal material is modulated when a uniform voltage is applied. Therefore, the phase of light transmitted through the liquid crystal element can be modulated. Therefore, it is not necessary to use an electrode film having a different resistivity such as a low resistance electrode film and a high resistance electrode film as compared with the conventional example, so that a transparent conductive film giving priority to transparency can be used on the entire surface. There is no need to provide a lead wire for the electrode film. For this reason, it is possible to perform more faithful phase modulation without forming a region where the refractive index is disturbed by the lead line of the electrode film.

When the alignment film of the liquid crystal element for phase modulation has a partially different alignment regulating force due to the alignment treatment method of irradiating linearly polarized light of different energy, it can be easily manufactured and has high accuracy. An element can be provided.
When one of the alignment films has a partially different alignment regulating force and the other alignment film has a uniform alignment regulating force, the liquid crystal element for phase modulation has a different alignment for both alignment films. Compared with the case where the alignment treatment is performed so as to have a regulating force, alignment of alignment treatments of both alignment films is not required, and the liquid crystal element for phase modulation can be manufactured more accurately and easily. On the other hand, the alignment treatment of the alignment film can be a low-cost alignment treatment using a general rubbing cloth, and this type of liquid crystal element for phase modulation can be provided at a low cost.

According to the optical pickup of the present invention, the liquid crystal is formed by partially modulating the alignment treatment of the alignment film that defines the alignment regulating force so as to generate a phase distribution that cancels the aberration in the optical path of the laser beam. By arranging so-called aberration correction elements consisting of phase modulation liquid crystal elements in which the refractive index change of the material is partially modulated, laser light irradiated to the recording medium at the time of recording / reproducing of the recording medium such as an optical disk, or recording The aberration in the reflected light reflected from the medium can be corrected. As the aberration correction element, it is not necessary to use a conventional electrode film having a different resistivity such as a low resistance electrode film and a high resistance electrode film, so that a transparent conductive film giving priority to transparency can be used on the entire surface. The structure can be simplified. At the same time, since there is no need to provide a lead line for the electrode film, a region where the refractive index is disturbed by the lead line for the electrode film is not formed. Therefore, more accurate phase correction at the laser spot can be performed, and higher density recording / reproduction can be performed.
In the conventional method, it is possible to obtain a refractive index distribution shape by applying a voltage only with a voltage distribution formed by a plurality of concentric electrode patterns. However, in the present invention, in the liquid crystal element, a change in refractive index due to application of a voltage can be defined during the alignment treatment of the alignment film. Therefore, since almost any refractive index change pattern can be formed during the alignment processing of the alignment film, a more faithful phase correction pattern for canceling aberration can be realized.

When the liquid crystal material has a liquid crystal element for phase modulation in which the alignment direction of the liquid crystal material is composed of two liquid crystal elements orthogonal to each other and the alignment treatment of the alignment film that regulates the alignment regulating force of these liquid crystal elements is modulated, The aberration included in the optical spot focused on the recording film by the element can be corrected, and the aberration included in the optical spot focused on the reflected light from the recording film can be corrected by the other liquid crystal element.
When the alignment film of the liquid crystal element for phase modulation has a partially different alignment regulating force due to the alignment processing method of irradiating linearly polarized light of different energy, an aberration correction element that can be easily manufactured and is accurate Can be provided.
When one of the alignment films has a partially different alignment regulating force and the other alignment film has a uniform alignment regulating force, the liquid crystal element for phase modulation has a different alignment for both alignment films. Compared to the case where the alignment process is performed so as to have a regulating force, the alignment process of both alignment films is not required to be aligned, and the aberration correction element can be manufactured more accurately and easily. On the other hand, the alignment treatment of the alignment film can be a low-cost alignment treatment using a general rubbing cloth, and this type of liquid crystal element for phase modulation can be provided at a low cost.

  According to the phase adjustment method of the present invention, the alignment film alignment treatment that regulates the alignment regulating force of the liquid crystal material so that the refractive index change of the liquid crystal material is partially modulated when a voltage is applied uniformly. By using a liquid crystal element in which light is modulated and dropping light onto the liquid crystal element, the phase of the transmitted light can be modulated and the phase of the light can be adjusted. As a liquid crystal element, it is not necessary to use an electrode film with different resistivity, such as a low resistance electrode film and a high resistance electrode film, and a transparent conductive film giving priority to transparency can be used on the entire surface, and the electrode film can be drawn out. Since there is no need to install a line, a region where the refractive index is disturbed by the lead line is not formed, and more accurate phase adjustment can be performed.

When the alignment film of the liquid crystal element has a partially different alignment regulating force due to the alignment treatment method of irradiating linearly polarized light of different energy, this type of liquid crystal element with high accuracy can be obtained and a more accurate phase can be obtained. Correction can be performed.
When a liquid crystal device in which one alignment film has a partially different alignment regulating force and the other alignment film has a uniform alignment regulating force, different alignment regulating forces are applied to both alignment films. Compared with the case where the alignment treatment is performed, alignment of the alignment treatments of both alignment films is not necessary, and this type of liquid crystal element can be obtained with higher accuracy and more accurate phase correction can be performed. .

According to the optical aberration correction method of the present invention, the alignment processing of the alignment film that defines the alignment regulating force is partially modulated so as to generate a phase distribution that cancels the aberration in the optical path of the laser beam. By arranging a liquid crystal element for phase modulation in which the refractive index change of the liquid crystal material is partially modulated, a condensed spot is formed on the recording film of the recording medium or the reflected light from the recording film is condensed. Aberrations at the laser spot when receiving light can be corrected. As the liquid crystal element for phase modulation, it is not necessary to use an electrode film with different resistivity such as a conventional low resistance electrode film and a high resistance electrode film, and a transparent conductive film giving priority to transparency is used on the entire surface. In addition, since it is not necessary to provide a lead wire for the electrode film, a region where the refractive index is disturbed by the lead wire for the electrode film is not formed. Accordingly, more faithful phase correction at the laser spot is possible.
In the conventional method, it is possible to obtain a refractive index distribution shape by applying a voltage only with a voltage distribution formed by a plurality of concentric electrode patterns. However, in the present invention, in the liquid crystal element for phase modulation, the change in the refractive index due to the application of voltage can be defined during the alignment processing of the alignment film, so that almost any refractive index pattern can be formed during the alignment processing of the alignment film. It is possible to form a more faithful phase correction pattern for canceling aberrations.

When the alignment film of the liquid crystal element for phase modulation has a partially different alignment regulating force by the alignment treatment method of irradiating linearly polarized light of different energy, obtain this kind of liquid crystal element for phase modulation with high accuracy. Therefore, more accurate phase correction can be performed.
When one of the alignment films has a partially different alignment regulating force and the other alignment film has a uniform alignment regulating force, the liquid crystal element for phase modulation has a different alignment for both alignment films. Compared with the case where the alignment treatment is performed so as to have a regulating force, alignment of the alignment treatment of both alignment films is not required, and this type of phase modulation liquid crystal element can be obtained with higher accuracy, and a more accurate phase can be obtained. Correction can be performed.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a phase modulation liquid crystal element, an optical pickup using the phase modulation liquid crystal element, a phase adjustment method using a liquid crystal material, and an optical aberration correction method using a liquid crystal material according to the present invention will be described below with reference to the drawings. explain.

Before explaining the liquid crystal element for phase modulation according to the present invention and the optical pickup using the liquid crystal element for phase modulation, an alignment treatment method applied to the present invention will be described with reference to FIGS. 10, 11, and 12. FIG. .
FIG. 13 described above shows an example in which a uniform alignment process is performed on the entire surface of the alignment film. However, in the present invention, the alignment process is modulated. FIG. 10 shows a principle diagram of an alignment process using a generally used rubbing cloth. In the alignment treatment method using a rubbing cloth, a roll 44 around which the rubbing cloth 43 is wound is disposed on the substrate 42 on which the alignment film 41 is formed, and the rubbing cloth 43 wound around the roll 44 is rotated and oriented. This is a method of pushing against the film 41. The alignment film 41 is aligned in the direction 45 in which the rubbing cloth 43 is pressed. This method is suitable for the case where the alignment film 41 having a large area is subjected to the alignment treatment in a short time, and is used in a manufacturing process of a general liquid crystal display or the like.

Next, a recently developed alignment processing method using light will be described. In this method, the alignment film material is irradiated with linearly polarized light to cut off the alignment film in the direction corresponding to the polarized light and to give anisotropy to the polarization direction of the alignment film. In the alignment treatment using this light, that is, a so-called photo alignment method, the light to be irradiated needs to have a short wavelength (UV light is desirable) because it is necessary to break a chain in the molecule. Further, in this method, the remaining state of the chain changes depending on the energy of light irradiated to the alignment film. Therefore, by adjusting the irradiation energy of light, the alignment strength, that is, the alignment that regulates the alignment of the liquid crystal material. Regulating power can be controlled. More specifically, depending on the material of the alignment film, in the case of using a laser light source near 266 nm, the alignment regulating force is reduced by irradiating light energy of about 0.1 to 2.0 J / cm ^2. Can be adjusted.

FIG. 11 and FIG. 12 show an example of a photo-alignment processing method for the alignment film.
In the photo-alignment processing method using the photo-alignment processing apparatus 46 of FIG. 11, a linearly polarized UV light collected by a condensing lens 48 using a laser light source 47 (for example, a commercially available 266 nm UV laser light source) 47 is used. In this method, the alignment film 51 formed on the substrate 52 is irradiated with a laser beam 49. This optical alignment treatment device 46 includes a laser light source 47, a shutter 54 for opening and closing the laser light, an attenuator 55 for adjusting the irradiation energy of the laser light, a mirror 56 for changing the optical path, and a condensing lens 48. Further, the substrate 52 having the alignment film 51 is placed and an XY stage 53 that can move in the X direction and the Y direction is arranged. In this device 46, the linearly polarized UV laser light 49 from the laser light source 47 passes through the opened shutter 54, the irradiation energy is adjusted by the attenuator 55, and the alignment film 51 is irradiated via the mirror 56 and the condenser lens 48. Is done. According to this method, the portion of the alignment film 51 irradiated with the laser beam 49 has an alignment direction corresponding to the polarization direction of the irradiated laser beam 49 and corresponds to the irradiation energy of the irradiated laser beam 49. Alignment treatment with an alignment regulating force is performed. Accordingly, by arranging the attenuator 55 for adjusting the irradiation energy of the laser beam 49 and the stage 53 for controlling the irradiation position of the laser beam 49, the irradiation energy of the laser beam 49 can be partially controlled. That is, being able to partially control the irradiation energy of the laser light 49 enables partially controlling the alignment regulating force of the alignment film 51.

  FIG. 12 shows another specific example in which the alignment regulating force of the alignment film can be partially controlled using the photo-alignment process. This photo-alignment processing device 61 is modified so that light irradiated by an exposure machine used in a general photolithography process becomes linearly polarized light. The light source 62 uses a non-polarized light source that emits ultraviolet rays, such as a high-pressure mercury lamp, but only linearly polarized light is present in the path to the irradiation region to the alignment film 65 formed on the surface of the substrate 64. It has been improved. In FIG. 16, the polarization component separation mirror 66 made of a transparent dielectric substrate, that is, the dielectric substrate 67 is arranged at a position where the Brewster angle φ is set, so that only the S-polarized light component is irradiated on the alignment film 65. An example of arriving is shown. By using such a photo-alignment processing apparatus 61, a large area can be collectively irradiated without moving the substrate (sample) 64 on which the alignment film 65 is formed via the XY stage 63. That is, a partial alignment process can be performed by using a photomask 68 generally used in a semiconductor manufacturing process. By using several types of photomasks 68, it is possible to easily perform an alignment process in which there are several stages of alignment control force. Furthermore, if a photomask having a gray gradation is used, an alignment process in which the alignment regulating force changes almost continuously can be easily performed in a single exposure process for the photoresist film 69 on the alignment film 65. .

Next, the configuration and principle of operation of the liquid crystal element capable of phase modulation according to the present invention will be described with reference to FIGS.
The operation of the liquid crystal material when the alignment regulating force is different will be described with reference to FIG. FIG. 1A shows the state of the liquid crystal material of the liquid crystal element 71 when no voltage is applied. The liquid crystal element 71 is formed by forming an electrode film 75 having an alignment film 73 on one side with a liquid crystal material 72 interposed therebetween and forming an electrode film 74 having an alignment film 74 on the other side. FIG. 1B shows a state of the liquid crystal material 72 when a voltage 77 is applied to the liquid crystal element 71 ₁ having the alignment films 73 ₁ 74 ₂ subjected to the alignment treatment so that the alignment regulating force becomes stronger. Figure 1C shows a state of the liquid crystal material 72 upon application of the same voltage 77 to the liquid crystal element 71 ₂ having the orientation-treated alignment film 73 _2, 74 ₂ as alignment regulating force is weakened.

When the voltage 77 is not applied between both electrode films 75 and 76, the alignment regulating force of the alignment film of the liquid crystal material 71 ₁ and 1C that the alignment regulating force is alignment treatment so that stronger alignment film of Figure 1B the liquid crystal element ₇₁₂ together which is oriented process as weakened, the liquid crystal material 72 and an alignment film 73 as shown in FIG. 1A _[73 1, 73 _2], in the direction defined by 74 _[74 1, 74 _2] Arranged. On the other hand, when the voltage 77 is applied from the outside between the two electrode films 75 and 76, observing the state of the liquid crystal material 72 in the liquid crystal element ₇₁₂ of the liquid crystal element 71 ₁ and 1C in FIG. 1B. Even when the same voltage 77 is applied, the alignment film 73 _{2 in} FIG. 1C is aligned with the liquid crystal element 71 ₁ subjected to the alignment treatment so that the alignment regulating force of the alignment films 73 ₁ and 74 ₁ in FIG. 1B becomes stronger. , compared to the liquid crystal element 71 ₂ alignment regulating force of 74 ₂ is oriented treated to be weaker, the liquid crystal material 72 is strongly felt relatively orientation regulating force of the alignment films 73 _1, 74 _1. In the liquid crystal element 71 ₁ in this order Figure 1B, feels like voltage 77 from the outside as if small. That is, when a constant voltage 77 is applied, the alignment treatment is performed so that the alignment regulating force of the alignment film is increased, compared with the case where the alignment treatment is performed such that the alignment regulating force of the alignment film is weakened. As a result, the amount of change in the refractive index ne decreases.

Based on the above description, an embodiment (the principle configuration and operation) of the phase adjustment method using the liquid crystal element for phase modulation and the liquid crystal material according to the present invention will be described with reference to FIG.
As shown in FIG. 2, the phase modulation liquid crystal element 81 according to the present embodiment includes regions 83 ₁ and 84 ₁ that are aligned in the same device so that the alignment regulating force of the alignment films 83 and 84 is increased. When an example of the alignment-treated areas 83 _2, 84 ₂ is configured in a mixed such that the orientation regulating force is weak alignment film 83, 84. That is, the phase modulating liquid crystal element 81 includes an area 83 ₁ which respectively on one side across the liquid crystal material 82 and alignment process as alignment regulating force in contact with the liquid crystal material 82 is increased, the alignment regulating force is weakened and alignment-treated areas 83 ₂ is disposed an electrode film 85 having an alignment film 83 coexist as, region 83 1 of the alignment film 83 respectively on the side of the other sandwiching the liquid crystal material 82 in contact with the liquid crystal material _82, 84 as opposed to _1, the electrode film 86 having an alignment film 84 and the region 84 ₁ oriented treated as alignment regulating force is increased, and a region 84 ₂ oriented treated as alignment regulating force is weakened mixed It is arranged. In this example, the alignment treatment is performed so that the alignment regulating forces of the region 83 ₁ of the alignment film 83 and the region 84 ₁ of the alignment film 84 facing each other with the liquid crystal material 82 interposed therebetween are the same, and the region 83 _{2 of the} alignment film 83. alignment regulating force of the region 84 ₂ of the alignment layer 84 are oriented treated to be both the same as.

As shown in FIG. 2, the liquid crystal material 82 corresponding to the regions 83 ₁ and 84 ₁ subjected to the alignment treatment so that the alignment regulating force of the alignment films 83 and 84 is strong has a weak alignment regulating force of the alignment films 83 and 84. made as compared to the alignment treatment region 83 _2, 84 ₂ to the liquid crystal material 82 corresponding, even in a situation where equal electric field is applied, the variation of the refractive index ne is reduced. Therefore, in the phase modulation liquid crystal element 81 of the present embodiment, the amount of change in the refractive index of the liquid crystal material 82 can be modulated without modulating the applied voltage. The light perpendicularly incident on the phase modulation liquid crystal element 81 does not generate refraction, and only feels a change in refractive index according to the applied voltage 87. Therefore, when light is transmitted through the phase modulation liquid crystal element 81, the transmitted light changes the phase amount corresponding to the alignment regulating force of the alignment films 83 and 84. The phase amount of the transmitted light can also be changed by changing the voltage 87 to be applied. The light beam may be for example a strong region ₈₃ 1, 84 ₁ and the alignment regulating force of the alignment regulating force is transmitted through the device 81 to include a weakened region 83 ₂ and 84 _2.

According to the phase modulation liquid crystal element 81 shown in FIG. 2, it is not necessary to use conductive materials having different resistivity, such as a low-resistance conductive film and a high-resistance conductive film, as compared with the conventional example shown in FIG. Therefore, a transparent conductive film giving priority to transparency can be used on the entire surface, and there is no need to provide a lead wire. Note that, in the same liquid crystal element, regions 83 ₁ and 84 ₁ subjected to the alignment treatment so that the alignment regulating force of the alignment film becomes strong, and regions 83 ₂ subjected to the alignment treatment that weaken the alignment regulating force of the alignment film, the liquid crystal element 81 84 ₂ are mixed, can be easily created by alignment treatment method shown in FIGS. 11 and 12 described above.

Next, FIG. 3 shows the phase modulation liquid crystal element of the present invention, that is, the region subjected to the alignment treatment so as to increase the alignment regulating force of the alignment film in the same liquid crystal element, and the alignment regulating force of the alignment film becomes weak. Another embodiment of a liquid crystal element for phase modulation configured so as to coexist with such an alignment-treated region is shown.
In the phase modulation liquid crystal element 91 according to the present embodiment, the region 83 is subjected to alignment treatment so as to be in contact with the liquid crystal material 82 on one side with the liquid crystal material 82 in between and the alignment regulating force is increased as in FIG. ₁ and a region 83 ₂ oriented treated as alignment regulating force is weak is disposed electrode film 85 having an alignment film 83 that has a mixed orientation film subjected to constant alignment treatment on the other side of sandwiching a liquid crystal material 82 An electrode film 86 having 92 is arranged. Since other configurations are the same as those in FIG. 2, the corresponding portions are denoted by the same reference numerals and detailed description thereof is omitted.

Also in the phase modulation liquid crystal element 91 of the present embodiment, similarly to the case of FIG. 2, in the situation where the equal voltage 87 is applied, the region 83 is subjected to the alignment treatment so that the alignment regulating force of the alignment film 83 becomes strong. the amount of change in the refractive index ne of the liquid crystal material 82 corresponding to _1, compared to the amount of change in the refractive index ne of the liquid crystal material 82 corresponding to the region 83 ₂ oriented treated as alignment regulating force is weakened in the alignment film 83 And less. For this reason, the amount of change in the refractive index can be modulated without modulating the applied voltage. Therefore, when light is transmitted through the phase modulation liquid crystal element 91, the transmitted light can change the phase amount corresponding to the alignment regulating force of the alignment film 83. In addition, the same effects as in FIG.

4 and 5 show the principle implementation when the phase adjustment method using the liquid crystal element for phase modulation and the liquid crystal material of the present invention is applied to an aberration correction element and an aberration correction method for correcting an optical aberration. The form of is shown.
As shown in FIG. 4, the aberration correction element 94 according to the present embodiment includes a phase modulation liquid crystal element 100 in which a transparent electrode film 97 is formed on an alignment film 96. The transparent electrode film 97 having the alignment film 96 is formed on the inner surfaces of the opposing transparent substrates 98 and 99, and a liquid crystal material is filled between the transparent substrates 98 and 99. As the structure of the alignment film, the structure shown in FIG. In this aberration correction element 94, the change in the refractive index of the liquid crystal material due to the application of a voltage is positionally modulated in accordance with the alignment regulating force of the alignment film 96, and before the incident light enters the objective lens. As shown in FIG. 5, with respect to the parallel beam, the refractive index of the liquid crystal material is distributed so that the phase distribution cancels the spherical aberration that occurs when the thickness of the cover glass layer of the optical disk changes. Such alignment regulating force of the alignment film 94 is distributed.

In FIG. 4, the alignment film 94 is subjected to an alignment process so as to have a refractive index change that causes a phase change that cancels optical aberrations. FIG. 5A shows a change in the refractive index of the liquid crystal due to the application of an external voltage, which tends to be inversely proportional to the strength of the alignment regulating force of the alignment film. e is the refractive index distribution of the liquid crystal material. FIG. 5B shows the phase change due to the application of an external voltage. d is a phase distribution.
In the alignment film 96 of the present embodiment, as distribution e of the refractive index of 5 is obtained, and alignment treatment such that the orientation regulating force a circular central region 96 ₁ concentrically becomes stronger, circular ring-shaped region outside 96 ₂ alignment treatment such that the orientation regulating force is weak, it is possible to alignment treatment such that the orientation regulating force of the outermost region 96 ₃ is increased.

  Therefore, according to the aberration correction element 94 of this embodiment and the aberration correction method using the same, by applying a uniform voltage to the phase modulation liquid crystal element 100 constituting the aberration correction element, spherical aberration can be reduced. A canceling phase distribution (that is, phase change) d can be generated, and by transmitting the light beam 95 through the aberration correction element 94, spherical aberration can be corrected. In the aberration correction element 94 and the aberration correction method of the present embodiment, a conventional low-resistance conductive film or an unnecessary electrode such as a lead line required for forming a voltage distribution is not necessary, and in addition, a lead line It is possible to eliminate a region where the voltage distribution is disturbed by the presence of.

  Further, in the aberration correction method using the aberration correction element 94 to which the phase modulation liquid crystal element of the present embodiment is applied and the phase adjustment method using the liquid crystal material, the change in the refractive index due to the application of voltage is It can be defined in the alignment treatment of the alignment film. Therefore, in the conventional method for distributing the voltage, the refractive index distribution shape can be obtained only by the voltage distribution formed by a plurality of concentric electrode patterns. In the present embodiment, the alignment process of the alignment film is performed. In some cases, a refractive index distribution shape having an almost arbitrary pattern can be formed.

FIGS. 6, 7, and 8 show embodiments of optical aberration correction elements that can be incorporated into an optical pickup by applying the phase adjustment method using the phase modulation liquid crystal element and the liquid crystal material of the present invention. FIG. 6 shows a schematic configuration of the optical aberration correcting element. FIG. 11 is an exploded perspective view of the optical aberration correction element, and FIG. 12 shows a cross-sectional structure of the main part of the optical aberration correction element.
As shown in FIG. 6, the optical aberration correction element 101 for an optical pickup according to the present embodiment has transparent cover glass members 103 and 104 arranged on both surfaces of a transparent glass substrate 102 at a predetermined interval, A first liquid crystal element 105 and a second liquid crystal element 105 formed by injecting liquid crystal materials 107 and 108 between the glass substrate 102 and one cover glass member 103 and between the glass substrate 102 and the other cover glass member 104, respectively. The liquid crystal element 106 is configured. In the first liquid crystal element 105, a transparent glass substrate side electrode 110 and an alignment film 111 thereon are formed on one surface of a glass substrate, and a transparent cover glass member side electrode 112 is formed on the inner surface of the cover glass member 103. Then, an alignment film 113 is formed thereon, and a liquid crystal material 107 is injected between the alignment films 111 and 113. In the second liquid crystal element 106, a transparent glass substrate side electrode 115 and an alignment film 116 thereon are formed on the other surface of the glass substrate, and a transparent cover glass member side electrode 117 is formed on the inner surface of the cover glass member 104. The alignment film 118 is formed thereon, and the liquid crystal material 108 is injected between the alignment films 116 and 118.

  The glass substrate 102 is formed to have a larger area than both cover glass members 103 and 104. On one surface of the glass substrate 102, an electrode terminal 121 integrated with the glass substrate side electrode 110 and an electrode terminal 122 electrically connected to the cover glass member side electrode 112 are formed so as to be exposed to the outside. Similarly, an electrode terminal 123 integral with the glass substrate side electrode 115 and an electrode terminal (not shown) electrically connected to the cover glass member side electrode 117 are externally exposed on the other surface of the glass substrate 102. To be formed. The electrode terminals 121 and 123 integral with the glass substrate side electrodes 112 and 115 are formed, for example, at the center of the glass substrate 102. The electrode terminals connected to the cover glass member side electrodes 112 and 117 are the electrode terminals 121 and 123, respectively. It is formed on the end side of the glass substrate 102 in parallel.

  7 and 8 show the electrode connection configuration for applying a voltage to the liquid crystal materials 107 and 108, the region where the liquid crystal materials 107 and 108 are injected, and the alignment regulating force of the alignment films 113 and 116 described later. It is a figure for demonstrating more easily the area | region currently modulated. Since the glass substrate side electrodes 110 and 115 and the cover glass member side electrodes 112 and 117 face each other, it is not easy to connect them when a voltage is applied from the outside. Therefore, in the example shown in FIGS. 7 and 8, the anisotropic conductive adhesive in which the conductive particles 126 are dispersed in the insulating adhesive in order to define the thickness of the region into which the liquid crystal materials 107 and 108 are injected. Further, a spacer 125 is added to 127, and the cover glass member side electrodes 112 and 117 are connected to the electrode terminal 122 for the glass substrate formed on the glass substrate 102 by the anisotropic conductive adhesive 127.

  That is, the glass substrate 102 and the cover glass member 103 are joined together by the frame-shaped anisotropic conductive adhesive 127 via the spacer 125 as shown in FIGS. The electrode terminal 122 and the cover glass member side electrode 112 are electrically connected by an anisotropic conductive adhesive 127. Similarly, the glass substrate 102 and the cover glass member 104 are bonded to each other with a frame-shaped anisotropic conductive adhesive 127 via a spacer 125. An electrode terminal (not shown) and the cover glass member side electrode 117 are electrically connected by an anisotropic conductive adhesive 127. The liquid crystal material 107 is injected into a space surrounded by the frame-shaped anisotropic conductive adhesive 127, the glass substrate 102, and the cover glass member 103, and the frame-shaped anisotropic conductive adhesive 127, the glass substrate 102, and the cover glass member A liquid crystal material 108 is injected into the space surrounded by 104.

In the first liquid crystal element 105 and the second liquid crystal element 106, the alignment directions of the liquid crystal materials 107 and 108 are both parallel to the glass substrate 102, and the first liquid crystal element 105. In addition, the alignment directions of the liquid crystal materials 107 and 108 in the second liquid crystal element 106 are configured to be orthogonal to each other. The first and second liquid crystal elements 105 and 106 are configured such that the strength of the alignment regulating force of the alignment film is modulated so as to correspond to the optical aberration correction pattern. In this example, the alignment film is generated only in the alignment films 111 and 116 on the glass substrate 102 side so as to generate a phase distribution in which the refractive index change of the liquid crystal materials 107 and 108 when a voltage is applied cancels the spherical aberration. The orientation regulating force of 111 and 116 is positionally modulated.
In the alignment films 111 and 116 of this example, the circular center region is aligned in a concentric manner so as to increase the alignment regulating force so that the refractive index distribution e shown in FIG. It is possible to perform an orientation treatment so that the orientation regulating force is weakened, and an outermost region can be oriented so that the orientation regulating force is strong.

  Here, as in the configuration of FIG. 2 described above, the refractive index change of the liquid crystal materials 107 and 108 when a voltage is applied to the alignment films 111, 112, 116, and 118 on both sides of the liquid crystal materials 107 and 108 is a spherical aberration. It is also possible to adopt a configuration in which the alignment regulating force of the alignment films 111, 112 and 116, 118 is positionally modulated so as to generate a phase distribution that cancels. In this way, by adopting a configuration in which the alignment regulating force of the alignment films 111, 112, 116, and 118 on both sides of the liquid crystal materials 107 and 108 is positionally modulated, the applied voltage can be lowered and adjusted. There is an effect that the amount can be increased.

  Further, as shown in FIG. 6, alignment films on both sides of the liquid crystal materials 107 and 108 are generated so that a change in refractive index of the liquid crystal materials 107 and 108 when a voltage is applied generates a phase distribution that cancels the spherical aberration. In the case where only one of the alignment films (the alignment films 111 and 116 in FIG. 6) is subjected to the alignment treatment so that the alignment regulating force is positionally modulated, the other alignment film (the alignment films 112 and 116 in FIG. The orientation treatment 118) can be a low-cost orientation treatment using a general rubbing cloth. As a result, the cost of the aberration correction element can be reduced, and in the bonding process between the glass substrate 102 and the cover glass members 103 and 104, the alignment accuracy can be extremely relaxed.

  As described above, in the aberration correction element 101 of the present embodiment, in the alignment process of the alignment films of the liquid crystal elements 105 and 106, almost any distribution shape of refractive index change can be formed. A more faithful phase correction pattern can be realized.

FIG. 9 shows an embodiment of an optical pickup according to the present invention to which the aberration correction element and the aberration correction method of the present embodiment shown in FIG. 6 are applied. In FIG. 9, reference numeral 14 denotes a recording medium, that is, an optical disk, and 131 denotes an optical pickup according to the present embodiment. The optical disk 14 is formed by forming a single-layer or multilayer recording film 16 on a support 15 and forming a cover layer (for example, a cover glass layer) on the surface thereof.
The optical pickup 131 according to the present embodiment includes, for example, a semiconductor laser light source 132 serving as a light source, and a collimator lens 133 for sequentially converting the laser light emitted from the semiconductor laser light source 132 into parallel light along an optical path toward the optical disk 14. A polarization beam splitter 134, an aberration correction element 101 of the present invention, a quarter wave plate (QWP) 136, and an objective lens (PBS) 137, and the reflected light from the optical disk 14 is further converted into the polarization beam splitter. A condensing lens 138 and a photodetector 139 for detecting and detecting the return light are arranged in the optical path of the return light reflected by 134.

  The quarter-wave plate 136 is disposed between the aberration correction element 101 and the polarization beam splitter 134 so that linearly polarized light is incident on the liquid crystal elements 105 and 106 constituting the aberration correction element 101. As described above, the aberration correction element 101 is made to coincide with the polarization direction of the laser light transmitted through the alignment films of the liquid crystal elements 105 and 106, respectively. That is, in the aberration correction element 101, the alignment directions of the liquid crystal elements 105 and 106 are orthogonal to each other, and these alignment directions have the polarization direction of the laser light incident on the optical disc 14 and the reflected light from the optical disc 14, respectively. It is configured to match the polarization direction. For example, the alignment direction of the liquid crystal element 105 matches the polarization direction of the laser light incident on the optical disk 14, and the alignment direction of the liquid crystal element 106 matches the polarization direction of the reflected light from the optical disk 14. In this case, one liquid crystal element 105 is formed by positionally modulating the alignment regulating force of the alignment film so as to obtain a phase distribution that corrects the spherical aberration of the laser light incident on the optical disk 14. The other liquid crystal element 106 is formed by positionally modulating the alignment regulating force of the alignment film so as to obtain a phase distribution that corrects the spherical aberration of the return light reflected from the optical disk 14 and collected on the photodetector 139. Is done.

In the optical pickup 131 of the present embodiment, the laser light emitted from the semiconductor laser light source 132 is converted into parallel light by the cotometer lens 133 and is transmitted through the polarization beam splitter 134. The laser beam Lf that has passed through the polarization beam splitter 134 passes through the liquid crystal element 106 that is applied with a voltage so as to transmit the light in the aberration correction element 101, and is phase-modulated when it passes through the liquid crystal element 105. The light passes through the wave plate 136 and the objective lens 137 and is condensed on the recording film 16 of the optical disk 14. At this time, the laser light Lf is phase-modulated by the liquid crystal element 105, whereby the spherical aberration in the laser light Lf on the recording film 14 is corrected.
The reflected light reflected by the recording film 16 of the optical disk 14 is transmitted through the objective lens 137 again, converted to a linearly polarized light orthogonal to the polarization direction of the laser light Lf by the quarter wavelength plate 136, and applied to the aberration correction element 101. Incident. In the aberration correction element 101, the liquid crystal element 106 functions as an aberration correction element, and a voltage is applied to the liquid crystal element 105 so as to transmit light. Accordingly, the reflected light is transmitted through the liquid crystal element 105, phase-modulated by the liquid crystal element 106, enters the polarization beam splitter 134, is reflected here, and is received by the photodetector 139 as the return light Lr via the condenser lens 138. . At this time, the reflected light is phase-modulated by the liquid crystal element 106, whereby the spherical aberration in the return light Lr on the photodetector 139 is corrected.

  Therefore, the optical pickup 131 according to the present embodiment enables use of an environment in which aberrations exist in a state where there are few optically acceptable aberrations such as multi-layer recording and reproduction at a high recording density.

  In the above description of the present invention, no detailed explanation is given regarding the manufacturing process other than the description of the alignment treatment process of the alignment film. However, in the manufacturing process, it is easy to produce by a manufacturing process of a commercially available liquid crystal display device. It is. In the description of the liquid crystal element for phase modulation of the present invention, the optical pickup using the liquid crystal element for phase modulation, the phase adjustment method using a liquid crystal material, and the optical aberration correction method using a liquid crystal material, the phase correction and aberration correction However, in the liquid crystal element for phase modulation of the present invention and the optical pickup using the liquid crystal element for phase modulation of the present invention, a desirable form as an element as a general optical component, that is, a transmitted light amount It is possible to form an anti-reflection coating for enhancing the coating. Specific descriptions regarding the reflective film coat and the like are omitted.

  Furthermore, in the description of the present invention, the material of the alignment film that modulates the strength of the alignment regulating force is not defined, but the alignment film of the present invention only needs to be a material suitable for the photo-alignment treatment. . More specifically, an AL1254 material manufactured by JSR, which is an alignment film material that can be used in an alignment method using a conventional rubbing cloth, can be aligned by a photo-alignment method.

FIGS. 2A to 2C are explanatory views for explaining the fundamental configuration and operation of a liquid crystal element that enables phase modulation according to the present invention. FIGS. 1 is a configuration diagram showing a principle embodiment of a liquid crystal element for phase modulation and a phase adjustment method according to the present invention. It is a block diagram which shows other embodiment in principle of the liquid crystal element for phase modulations and phase adjustment methods concerning this invention. It is a block diagram which shows fundamental embodiment at the time of applying to the aberration correction element and aberration correction method which correct | amend the optical aberration which concerns on this invention. A is a distribution diagram of a change in refractive index of a liquid crystal material when an external voltage is applied to the aberration correction element of FIG. B is a distribution diagram of phase change when an external voltage is applied to the aberration correction element of FIG. It is a schematic block diagram which shows embodiment of the aberration correction element which concerns on this invention applied to an optical pick-up. FIG. 7 is an exploded perspective view of the aberration correction element of FIG. 6. A It is sectional drawing of the principal part on the AA line of FIG. B is a cross-sectional view of the main part on the BB line in FIG. It is a block diagram which shows one Embodiment of the optical pick-up based on this invention. It is a block diagram which shows an example of the orientation processing method applied to this invention. It is a block diagram which shows the other example of the orientation processing method applied to this invention. It is a block diagram which shows the further another example of the orientation processing method applied to this invention. It is explanatory drawing about the refractive index control of the liquid crystal material by AC voltage application. It is a block diagram with which it uses for description of the principle of the conventional liquid crystal element for spherical aberration correction. It is a block diagram which shows the example of the conventional optical pick-up. FIG. 16 is a schematic configuration diagram of an aberration correction element applied to the optical pickup in FIG. 15. A is a plan view of a region portion used for aberration correction of the aberration correction element of FIG. B is a distribution diagram of voltages applied to the liquid crystal material of the aberration correction element. C is a distribution diagram of a change in refractive index corresponding to a phase distribution to be corrected.

Explanation of symbols

14 ... optical disc, 15 ... support, 16 ... recording film, 17 ... cover layer, 71 ... liquid crystal element, 72 ... liquid crystal material, 73, 74 ... alignment film, 75, 76... Electrode film, 73 ₁ , 74 ₁ ... Alignment film with strong alignment regulating force, 73 ₂ , 74 ₂ ... Alignment film with weak orientation regulating force, 77. Liquid crystal element for phase modulation, 82... Liquid crystal material, 83 [83 ₁ , 83 ₂ ], 84 [84 ₁ , 84 ₂ ], 92... Alignment film, 85, 86. ..Voltage, 94... Aberration correction element, 95... Parallel light beam, 96... Alignment film, 97 .. Transparent electrode film, 98, 99. Distribution of refractive index change of material, d... Distribution of phase change, 101... Aberration correction element for optical pickup, 102. Glass substrate, 103, 104 ... Cover glass member, 105, 106 ... Liquid crystal element, 107, 108 ... Liquid crystal material, 110, 115 ... Glass substrate side electrode, 111, 113, 116, 118 ..Alignment film, 112, 117 ... cover glass member side electrode, 121, 122 ... electrode terminal, 125 ... spacer, 126 ... conductive particles, 127 ... anisotropic conductive adhesive , 131... Optical pickup, 132... Semiconductor laser light source, 133... Collimating lens, 134... Polarization beam splitter, 136. ..Condensing lens, 139 ... Photo detector

Claims (15)

A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material,
The alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated so that the refractive index change of the liquid crystal material is partially modulated when a voltage is uniformly applied to the electrode film. A liquid crystal element for phase modulation characterized by comprising: 2. The phase modulation device according to claim 1, wherein the alignment film that defines the alignment regulating force has a partially different alignment regulating force according to an alignment treatment method that irradiates linearly polarized light having different energy. Liquid crystal element. The liquid crystal element for phase modulation according to claim 1, wherein the one alignment film has a partially different alignment regulating force, and the other alignment film has a uniform alignment regulating force. An optical pickup that irradiates a recording medium with laser light using an optical lens and forms a focused spot on a recording film in the recording medium,
In the optical path of the laser beam,
A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material, and when the voltage is uniformly applied to the electrode film, A liquid crystal element for phase modulation formed by modulating the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is arranged so that the refractive index change of the liquid crystal material is partially modulated,
The phase of the laser light passing through the phase modulation liquid crystal element is partially modulated in accordance with the alignment treatment of the alignment film, and the aberration of the optical spot collected by the optical lens is corrected. An optical pickup characterized by that. An optical pickup that irradiates a recording film in a recording medium with a laser beam using an optical lens, collects and receives reflected light from the recording film,
In the optical path of the laser beam,
A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material, and when the voltage is uniformly applied to the electrode film, A liquid crystal element for phase modulation formed by modulating the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is arranged so that the refractive index change of the liquid crystal material is partially modulated,
The aberration of the reflected light from the recording film of the optical spot focused by the optical lens, the phase of the laser light passing through the liquid crystal element for phase modulation is partially modulated according to the alignment treatment of the alignment film An optical pickup characterized in that the correction is made. The phase modulation liquid crystal element is composed of two liquid crystal elements in which the alignment directions of the liquid crystal material are orthogonal to each other, and the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal element is modulated,
The aberration contained in the optical spot condensed on the recording film by the optical lens and the aberration contained in the optical spot condensed the reflected light from the recording film are corrected. The optical pickup described. 7. The alignment film that defines the alignment regulating force is partially different in alignment regulating force depending on an alignment treatment method that irradiates linearly polarized light having different energy. Optical pickup. 7. The optical pickup according to claim 4, wherein the one alignment film has a partially different alignment regulating force, and the other alignment film has a uniform alignment regulating force. . A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material,
The alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated so that the refractive index change of the liquid crystal material is partially modulated when a voltage is uniformly applied to the electrode film. Using the liquid crystal element
A phase adjustment method, wherein a voltage is uniformly applied to the liquid crystal element, and a phase of light transmitted through the liquid crystal material is partially modulated according to an alignment treatment of the alignment film. 10. The liquid crystal device according to claim 9, wherein the alignment film that defines the alignment regulating force has a partially different alignment regulating force depending on an alignment treatment method that irradiates linearly polarized light having different energy. Phase adjustment method. 10. The phase according to claim 9, wherein the one alignment film has a partially different alignment regulating force, and the other alignment film has a uniform alignment regulating force. Adjustment method. An optical aberration correction method for irradiating a recording medium with a laser beam using an optical lens and forming a focused spot on a recording film in the recording medium,
In the optical path of the laser beam,
A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material, and when the voltage is uniformly applied to the electrode film, A phase modulation liquid crystal element in which the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated so that the refractive index change of the liquid crystal material is partially modulated;
The phase of the laser beam transmitted through the phase modulation liquid crystal element is partially modulated according to the alignment treatment of the alignment film, and the aberration of the optical spot collected by the optical lens is corrected. Optical aberration correction method. An optical aberration correction method for irradiating a recording film in a recording medium with a laser beam using an optical lens, and collecting and receiving reflected light from the recording film,
In the optical path of the laser beam,
A liquid crystal material, an alignment film adjacent to the liquid crystal material across the liquid crystal material, and an electrode film for applying a voltage to the liquid crystal material, and when the voltage is uniformly applied to the electrode film, A phase modulation liquid crystal element in which the alignment treatment of the alignment film that regulates the alignment regulating force of the liquid crystal material is modulated so that the refractive index change of the liquid crystal material is partially modulated;
The aberration of the reflected light from the recording film of the optical spot that is partially modulated in accordance with the alignment process of the alignment film and focused by the optical lens, and the phase of the laser light transmitted through the phase modulation liquid crystal element An optical aberration correction method characterized by correcting the above. 13. The liquid crystal element according to claim 12, wherein the alignment film that defines the alignment regulating force has a partially different alignment regulating force according to an alignment treatment method in which linearly polarized light having different energy is irradiated. 14. The optical aberration correction method according to 13. 14. The liquid crystal element according to claim 12, wherein the one alignment film has a partially different alignment regulating force, and the other alignment film has a uniform alignment regulating force. Optical aberration correction method.

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