JPH1139704A - Optical information reader and recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read and record information in an arbitrary focus position by combining polarizing conversion and reflactive index anisotropy media. SOLUTION: This device has a function of reading optical information of an optical storage medium 105 which may have an arbitrary thickness by using a polarization converting device 103 composed of combined optical media having a polarization converting function and reflactive index anisotropy respectively, changing the polarizing direction of light to be incident upon the optical media and making a convergent position of a beam from a semiconductor laser 101 variable. Then, by changing a reflactive index distribution of a lens formed by the optical medium having deflactive index anisotropy, the degree of freedom of varying the focus position and controllability are enhanced. Moreover, since about 100% of the incident light beam can be converged, the light utilizing efficiency is high, and not only reading optical information but also recording information can be performed at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information system including an optical head and an optical pickup for recording and reading information recorded on an optical storage medium such as an optical disk or a magneto-optical disk using a laser beam. The present invention relates to a processing device.

[0002]

2. Description of the Related Art Developments in optical system design techniques and the shortening of the wavelength of semiconductor lasers as light sources have led to the development of optical disks having higher-density storage capacities than ever before. As an approach for increasing the density, it has been studied to increase the optical disk side numerical aperture (NA) of a condensing optical system that narrows a light beam onto an optical disk. At that time, a problem is an increase in the amount of aberration generated due to the tilt of the optical axis (so-called tilt). When the NA is increased, the amount of aberration generated with respect to the tilt increases. To prevent this, the thickness (substrate thickness) of the substrate of the optical disk may be reduced.

For the above reasons, it is desirable to reduce the thickness of the substrate in a high-density optical disk. For this reason, it is considered that the substrate thickness will be further reduced in next-generation high-density optical disks, such as compact disks (CDs) already on the market and digital video disks (DVDs) whose demand is expected to increase in the future. As a result, an optical information processing device capable of recording and reproducing both conventional optical disks and next-generation high-density optical disks is required. For that purpose, an optical head device having a condensing optical system capable of condensing a light beam to a diffraction limit on an optical disk having a different substrate thickness is required.

[0004] The main methods of an optical head device known to date are described below. There is a bifocal method using a hologram in which the lens regions of the objective lens are overlapped and formed twice. This is because a part of the light in the hologram at the center of the lens is given a refraction effect like a concave lens by diffraction, and when reproducing a CD, the light that fits the CD by the combination of the hologram and the objective lens Form spots. Peripheral light that is not diffracted by the hologram is converged by the objective lens and used to form a light spot for a high-density DVD or the like.

There is also a two-lens system in which reproduction is performed using two objective lenses for DVD and CD. There are two methods of switching the optical path and switching the lens. As a method of switching the optical path, two objective lenses are provided adjacent to each other, light from a semiconductor laser is incident on both objective lenses, and an optical system to be used is selected by a focus operation.

[0006] As a method of switching the objective lenses, a type in which two objective lenses are mounted on an actuator and the lenses are switched together with a tracking operation is used.

There is another method called an aperture limiting method.
This is a method of limiting the aperture of an objective lens designed for DVD to reduce spherical aberration of CD disks having different substrate thicknesses. Specifically, a liquid crystal shutter is arranged in the optical path of the optical pickup, and when the DVD is reproduced, the shutter is fully opened.
When reproducing a CD, information is read out by blocking the peripheral portion and passing only the light at the central portion.

[0008]

In the bifocal system, the number of components can be reduced by forming a hologram on the incident surface of the objective lens, and the cost can be reduced as much as an optical pickup for CD. Further, the configuration can be compactly stored.

However, since only the light at the center is used for CDs and only light at the periphery is used for DVDs, the light use efficiency in each case is reduced. Therefore, there is a problem that the light intensity is insufficient particularly at the time of writing, and it is difficult to simultaneously satisfy both the reading and the recording purposes.

[0010] The aperture limiting method uses a liquid crystal shutter or the like to block the light in the peripheral area, so that there is a problem that the light use efficiency is reduced for the same reason as described above.

In the two-lens system, since the lenses dedicated to CD and DVD are used, the light use efficiency can be kept optimal, and there is no problem such as insufficient light intensity.
However, the use of two lenses increases the number of parts, and a drive system for switching lenses must be newly added. Therefore, there arises a problem that the size of the system becomes large and the cost increases.

The present invention solves the above-mentioned problems of the prior art,
It is an object of the present invention to provide an optical information processing apparatus capable of simultaneously reading and recording optical information with a compact configuration.

[0013]

In order to achieve the above object, an optical information reading and recording apparatus according to the present invention comprises a laser emitting at least polarized light, and a light emitted from the laser converging on an optical storage medium. An optical lens, a light receiving element for detecting light reflected by the optical storage medium, wherein the optical lens is formed using an optical medium having a refractive index anisotropy, and the optical lens And a polarization conversion means for changing the polarization direction of the laser light incident on the laser beam.

In the above structure, it is preferable that the optical lens is formed using a uniaxial optical crystal having a refractive index anisotropy.

In the above configuration, it is preferable that the optical lens is configured to include liquid crystals arranged uniformly.

Further, in the above configuration, it is desirable that the polarization direction of the radiation light of the laser is substantially parallel or perpendicular to the optical axis of the optical medium forming the optical lens.

In the above arrangement, it is desirable that the polarization conversion means is made of a liquid crystal having birefringence or optical rotation.

Further, the optical information reading and recording apparatus according to the present invention comprises a laser emitting at least polarized light, an optical lens for converging light emitted from the laser on an optical storage medium, and a light reflected by the optical storage medium. The optical lens is formed by using an optical medium whose spatial refractive index distribution changes by application of an electric field.

Further, in the above configuration, it is desirable that the optical lens is configured to include liquid crystals arranged uniformly.

Further, in the above configuration, it is desirable that the polarization direction of the laser radiation is substantially parallel to the optical axis of the optical medium forming the optical lens.

Further, the optical information reading and recording apparatus according to the present invention comprises a laser emitting at least polarized light, an optical lens for converging light emitted from the laser on an optical storage medium, and a light reflected by the optical storage medium. The optical lens is formed using an optical medium having a refractive index anisotropy in which a spatial refractive index distribution is changed by application of an electric field, and A polarization converter for changing the polarization direction of the laser light incident on the optical lens is provided.

Further, in the above configuration, it is desirable that the optical lens is configured to include liquid crystals arranged uniformly.

In the above configuration, it is desirable that the direction of polarization of the emitted light of the laser is substantially parallel or perpendicular to the optical axis of the optical medium forming the optical lens.

In the above structure, it is desirable that the laser is a semiconductor laser.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows an optical information reading and recording apparatus using a polarization conversion device according to Embodiment 1 of the present invention.

Light emitted from a semiconductor laser 101 emitting polarized light is reflected by a beam splitter 102 and passes through a polarization converter 103. This polarization conversion device 103 has a structure in which a liquid crystal layer is sandwiched between glass substrates having transparent electrodes. As the liquid crystal layer, a twisted nematic liquid crystal having optical rotation or a ferroelectric liquid crystal having memory characteristics and capable of high-speed response can be used. Then, the liquid crystal molecules are switched by an input signal due to application of an electric field or the like, and the polarization direction of the light incident on the panel is substantially 90 degrees.
It has a function of changing degrees.

First, the case where the polarization conversion device 103 is configured using a twisted nematic liquid crystal will be described.
When no electric field is applied, the liquid crystal has the optical rotation of 90 degrees twisted between the entrance surface and the exit surface. Then, the light rays incident at an angle parallel or perpendicular to the long axis direction of the liquid crystal travel along a spiral in the panel, and the polarization direction is substantially 90 degrees at the end face of the panel.
It is emitted at an angle. When an electric field is applied to this panel, the spiral of the liquid crystal is unwound, and the liquid crystal molecules are in a homeotropic state arranged substantially perpendicular to the glass substrate. In this case, the incident light has no polarization conversion function, and the incident light passes through the panel while maintaining its polarization state.

As described above, by controlling the magnitude of the voltage applied to the polarization conversion device 103, it is possible to perform the function of tilting the polarization direction of the radiated light from the semiconductor laser by 90 degrees or passing the radiated light as it is.

Next, the case where the polarization conversion device 103 is formed using ferroelectric liquid crystal will be described. In a liquid crystal panel using a ferroelectric liquid crystal, liquid crystal molecules are aligned parallel to a glass substrate, and the liquid crystal molecules are uniformly arranged at substantially the same angle with respect to the thickness direction of the liquid crystal layer. Then, the liquid layer molecules switch between states having two certain angles corresponding to the positive and negative directions of the applied electric field. In addition, these two states have memory characteristics, and maintain an initial state when no electric field is applied. The angle between these two states is called the cone angle, which is approximately 45 degrees.

Therefore, light incident in a polarization direction parallel or perpendicular to the liquid crystal molecules passes through the panel while maintaining the polarization direction. Further, when the light is incident on the liquid crystal molecules at an angle difference of about 45 degrees, the polarization state changes as the light progresses in the liquid crystal layer. Therefore, by setting the thickness appropriately, it is possible to emit the light by switching the polarization direction to approximately 90 degrees with respect to the polarization direction on the incident surface. That is, λ /
It has the same function as a retardation plate such as 2, λ / 4. The switching of the liquid crystal can be performed by changing the direction of the electric field applied to the liquid crystal panel, and a high-speed response of about 1 kHz is possible.

The light that has passed through the polarization conversion device 103 is focused on an optical storage medium 105 by an objective lens 104 formed of an optical medium having refractive index anisotropy. Here, since the objective lens 104 has the refractive index anisotropy, the position where light is focused differs depending on the polarization direction of the incident light.

That is, when the light is incident in a polarization direction parallel to the optical axis (extraordinary light), the refractive index is Ne, and in the direction perpendicular to the optical axis (ordinary light), the refractive index is No. Here, Ne>
No. Therefore, since the phase delay of the light wave becomes large with respect to the extraordinary light, the radius of curvature of the wavefront of the light after exiting the objective lens is small. That is, the focal length is short. Conversely, the focal length of ordinary light is longer than that of extraordinary light.

By switching the polarization direction of the light incident on the objective lens by the polarization conversion device, the focal position of the light passing through the objective lens 104 can be changed.

The light reflected by the optical storage medium 105 returns to the original optical path, passes through the beam splitter 102, and
At 06, an information signal is detected.

In the configuration of FIG. 1, the beam splitter 10
A configuration in which 2 is a polarization beam splitter and a λ / 4 wavelength plate is inserted between the objective lens 104 and the optical storage medium 105 is also possible. At this time, the semiconductor laser 10
The light intensity of No. 1 is reflected by the polarization beam splitter by approximately 100%, and the light whose polarization direction has been changed by 90 degrees is transmitted through the return path by approximately 100% to improve the light utilization rate received by the photodetector. is there.

Further, a lens or a hologram is arranged in front of the photodetector 106, and a light intensity pattern is obtained on the photodetector 106 by diffracting or condensing the light reflected from the optical storage medium 105. Then, a configuration may be adopted in which a focus shift, a tracking shift, and a signal of information stored in the optical storage medium 105 are simultaneously detected.

Next, the principle of changing the focal position based on the polarization conversion of the present invention will be described. FIG. 2 shows a refractive index ellipsoid of a uniaxial optical crystal. (A) shows a refractive index ellipsoid when the optical axis is in the Y direction. In this case, light having a polarization direction in the Y direction becomes extraordinary light and shows the refractive index of Ne. In addition, light having a polarization direction in the XZ plane becomes ordinary light and shows a refractive index of No.

(B) shows a refractive index ellipsoid when the optical axis of the uniaxial optical crystal is tilted by 90 degrees from the Y direction. In this case, light having a polarization direction in the Y direction shows a No refractive index, and light having a polarization direction in the XZ plane also shows a No refractive index.

In the state where the optical axis is between (a) and (b), Ne and No (Ne> Ne) for light polarized in the Y direction.
No). On the other hand, for light whose polarization direction exists in the XZ plane, the refractive index is always No, regardless of the inclination of the optical axis.

As described above, the optical medium having the refractive index anisotropy has different refractive indexes of Ne and No depending on the incident polarization direction, and further, with the change of the inclination of the optical axis of the optical medium. It will take an intermediate value of the refractive index. In practical applications, it is considered that it is suitable to change the refractive index by changing the incident polarization direction for a uniaxial crystal.

The direction of the optical axis can be easily changed by applying a voltage to the liquid crystal. For this reason, there is an application in which the polarization direction of incident light is fixed and the voltage applied to the liquid crystal is controlled to spatially arbitrarily change the refractive index distribution of the liquid crystal with respect to the incident light.

FIG. 3 shows a lens 3 using a uniaxial optical crystal.
FIG. 1 shows an embodiment in which No. 01 is formed. In this figure, the optical axis of the uniaxial crystal exists in the Y direction. (A) shows that incident light acts as an extraordinary ray on the uniaxial lens 301, and (b) shows that it acts as an ordinary ray. Light incident parallel to the lens has a phase difference corresponding to its refractive index and thickness at each position according to the shape of the lens. Then, a curved surface corresponding to the phase difference is formed on the exit surface of the lens, and the light is focused to a certain focal position.

Now, comparing (a) and (b), both have the same lens shape, and the refractive index differs between Ne and No. Since Ne> No, the phase difference between the center and the periphery of the lens becomes larger in the case of (a) than in the case of (b), and the radius of curvature of the wavefront modulated by the lens becomes shorter in the case of (a) than in the case of (b). That is, in the case of (a), the focal length is shorter than that of (b) (fo> fe). The focal position can be changed by switching the polarization direction of the incident light beam with respect to the lens 301 formed of the optical medium having the refractive index anisotropy as described above. The change range of the focal position can be set to a necessary value depending on the anisotropy value of the optical medium used or the shape of the lens.

In the embodiment shown in FIG. 1, a case will be described in which a ferroelectric liquid crystal is used as the polarization conversion device 103 and a uniaxial optical crystal is used as the objective lens 104. Light emitted from the semiconductor laser 101 is reflected by the beam splitter 102 and enters the polarization conversion device 103. Here, in the initial state, the liquid crystal molecules of the polarization conversion device 103 and the polarization direction of the incident light are arranged in parallel.

For this reason, the light beam passes through the polarization converter while maintaining the initial polarization state, and enters the objective lens 104. Here, the uniaxial optical crystal constituting the objective lens and the polarization direction of the incident light are arranged so as to be parallel in the initial state. That is, it acts on the objective lens 104 as an extraordinary ray. Therefore, the light beam emitted from the objective lens 104 has a shorter focal length and is focused on the central portion of the substrate of the optical storage medium 105. That is, information on a high-density recording disk such as a DVD having a thin substrate can be read.

Next, an electric field was applied to the polarization conversion device 103 to change the direction of the liquid crystal molecules by about 45 degrees from the initial state.
At this time, since the polarization direction of the light beam incident on the polarization conversion device 103 and the liquid crystal molecules have an angle difference of about 45 degrees, the light is emitted with the polarization direction changed by approximately 90 degrees. Since this light ray acts on the objective lens 104 as an ordinary light ray, the focal length becomes longer than that in the earlier initial case. In other words, the light is condensed on a portion of the optical storage medium 105 that is deep. In this case, it is possible to read information on a disk such as a CD having a large substrate thickness.

As described above, by combining the polarization conversion device 103 and the objective lens 104 formed of a uniaxial crystal, laser beams are condensed at two different focal positions, respectively, and a disk or the like having a different substrate thickness is used. It was possible to read the information. Further, almost all of the light intensity incident on the front surface of the objective lens 104 at the two focal positions could be used. For this reason, the light use efficiency is high and not only the information reading but also the recording of the optical storage medium 105 can be performed at the same time.

(Embodiment 2) FIG. 4 is an example showing a spatial refractive index distribution by the liquid crystal element constructed in Embodiment 2 of the present invention. This is a nematic liquid crystal sandwiched by a glass substrate having a transparent electrode, and FIG. 4 shows this cross section. In the central part, the liquid crystal molecules are in a homogeneous alignment in which the optical axis is in the Y direction. A little outside the center, the optical axis of the liquid crystal molecules has an arrangement slightly inclined in the YZ plane. In the periphery, it is homeotropically oriented substantially perpendicular to the glass substrate. Such orientation can be performed by controlling the magnitude of the voltage applied to each portion of the transparent electrode on the glass substrate.

As described in the first embodiment with reference to FIG. 2 as an example, the refractive index of the liquid crystal molecules changes in accordance with the inclination of the optical axis. In the case of FIG. 4, the liquid crystal panel exhibits an Ne refractive index as an extraordinary ray in the central portion with respect to an incident ray having polarization in the Y direction, and the refractive index decreases according to the tilt angle of the liquid crystal toward the periphery. On the outermost side, the ordinary ray shows a refractive index of No.

Therefore, in the liquid crystal panel composed of the glass substrate 401 shown in FIG. 4, the incident wavefront undergoes phase modulation that gradually decreases from the center to the periphery due to the spatial refractive index distribution. For this reason, the incident light beam is subjected to the same operation as when it is incident on the convex lens, and converges to a certain point as a spherical wave after being emitted. In addition, an incident light beam having a polarization direction perpendicular to the Y direction is an ordinary light beam having a refractive index of No, regardless of the angle of the liquid crystal molecules. In this case, the liquid crystal panel only passes incident light as it is, and does not function as a lens.

As described above, by constructing the liquid crystal panel as shown in FIG. 4 using liquid crystals having a uniform homogeneous orientation, the liquid crystal panel has the same function as a lens with respect to light polarized in a specific direction. Can be made. Here, the focal position can be easily changed by changing the magnitude of the electric field at each position applied to the panel or the spatial position of the applied electric field. It is also possible to cope with this by changing the thickness of the liquid crystal layer. Accordingly, it is understood that the degree of freedom is high with respect to the variability of the focal position and the controllability is excellent.

Here, in the optical information reading and recording apparatus shown in FIG. 1, a system was constructed using the liquid crystal panel shown in FIG. This time, the polarization converter 103 was not used, and the polarization direction of the light beam from the semiconductor laser 101 was set to be parallel to the optical axis of the liquid crystal molecules used for the objective lens 104. The transparent electrodes of the liquid crystal panel were patterned concentrically, and a spatial refractive index distribution was generated by changing the voltage applied to each pattern.

First, the electric field applied to the liquid crystal panel was set to approximately 0 at the central portion, and a high voltage was applied to the peripheral portion until the liquid crystal was completely homeotropically aligned. At this time, the incident light from the semiconductor laser 101 passed through the objective lens 104 and was focused on the central portion of the optical storage medium 105. That is, it was found that it can be used for reading and recording information on a thin substrate.

Next, for the liquid crystal panel used as the objective lens 104, the gradient of the spatial electric field distribution was set to be gentler than the distribution of the electric field applied above. At this time, the incident light from the semiconductor laser 101 is
After passing through No. 4, light was condensed at a depth deeper than the substrate thickness of the optical storage medium 105. Therefore, it has been found that optical information can be read and recorded on a thick substrate as an optical storage medium.

(Embodiment 3) FIG. 5 shows the structure of a liquid crystal lens having a Fresnel structure used in Embodiment 3 of the present invention. The effective lens thickness can be reduced by forming a Fresnel structure using the periodicity of the phase at intervals of 2π with respect to the normal lens shape shown in FIG.

FIG. 5A is a sectional view, FIG. 5B is a view from the front, and FIG. 5C is an enlarged sectional view of a main part.
The surface of one of the glass substrates 501 was a concentric step-shaped structure. Although not shown in the figure, a transparent electrode is formed on the glass substrate, and the transparent electrode is patterned for each concentric circle shown in FIG. The structure is such that a different electric field can be applied to each electrode. A nematic liquid crystal was sealed therein as a uniform homogeneous alignment as in FIG.

The above-described Fresnel structure has the following advantages as compared with a case where a liquid crystal lens is formed in a convex lens shape as shown in FIG.

First, since the response speed of the liquid crystal is proportional to the square of the thickness, the response and recovery time become significantly slower as the cell thickness increases. Further, when the cell thickness is increased, there is a problem that the liquid crystal cell becomes cloudy due to the light scattering effect. Such a problem can be improved by making the thickness thinner by the Fresnel structure.

The liquid crystal lens having the Fresnel structure shown in FIG.
Since it has a stepped surface shape in the thickness direction, it exhibits a lens function having different refractive indices with respect to extraordinary rays and ordinary rays without applying an electric field. That is, it is possible to change the focal position by switching the polarization direction of the incident light beam. Further, it is also possible to change the focal length by changing the voltage applied to each electrode with respect to the extraordinary ray.

As described above, the focal position can be changed in both the polarization switching and the magnitude of the applied electric field.
By combining these, it is possible to improve the degree of freedom in changing the focal position. Further, in the configuration shown in FIG. 5, it is possible to further shorten the focal position by shortening the interval between the concentric circles and increasing the number of steps.

Now, an embodiment in which the liquid crystal lens having the Fresnel structure constructed in the third embodiment is used as the objective lens 104 shown in FIG. 1 will be described. Light from a semiconductor laser 101 is reflected by a beam splitter 102, passes through a polarization converter 103, and is focused on an optical storage medium 105 by an objective lens 104. First, the objective lens 1
The polarization direction was switched by the polarization converter 103 without applying a voltage to the liquid crystal lens having the Fresnel structure used as 04. It was confirmed that extraordinary rays were condensed at the central portion of the substrate thickness of the optical storage medium, and ordinary rays were condensed at a deeper position. This proved that optical information could be read and recorded on disks having different substrate thicknesses.

Next, several patterns of electric fields were applied to the electrodes at each position of the liquid crystal Fresnel lens used as the objective lens 104. At this time, it was confirmed that the light beam from the semiconductor laser 101 could be focused on an arbitrary position of the substrate thickness of the optical storage medium 105. From this,
In the future, it is considered that optical information can be read and recorded even when the optical recording capacity becomes higher than that of the current DVD disk and the substrate thickness becomes correspondingly thinner.

As described above, the present embodiment has described the function of changing the focal position of a lens in combination with polarization conversion for an optical medium having a refractive index anisotropy such as a liquid crystal or a uniaxial optical crystal.

As the uniaxial crystal, a uniaxial crystal having an electro-optical effect such as lithium niobate, KD2PO4, β-BaB ₂ O ₄ , PLZT or the like can be used, and a uniaxial crystal such as KTiPO4 can be used. The effect can also be exerted by using a medium having a refractive index anisotropy including an axial optical crystal and the like.

It goes without saying that the device can be used as a recording-only or read-only device.

[0067]

As described above, the present invention can arbitrarily change the focal position of a light beam by a combination of an optical medium having a polarization conversion function and a refractive index anisotropy, and can be used for discs having different thicknesses. It reads and records optical information.

A focus can be focused on an arbitrary position by a combination of the polarization conversion and the action of a lens such as a liquid crystal, so that the degree of freedom is high and the controllability is excellent. Further, since almost 100% of the light rays incident on the lens can be used, the light use efficiency is high, and not only reading but also writing of optical information is possible. In addition, since it is small and lightweight and can be manufactured at low cost, it can be widely used as an optical information device including an optical pickup, and has great value.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of an optical information reading and recording apparatus using a polarization conversion device of the present invention.

FIGS. 2A and 2B show examples of refractive index modulation based on a refractive index ellipsoid of a uniaxial optical medium.

3A and 3B are diagrams showing an example of a change in focal length of a lens made of a uniaxial optical medium.

FIG. 4 is a diagram showing an example of a spatial refractive index distribution by a liquid crystal.

5A is a sectional view showing an example of molecular orientation in a Fresnel structure liquid crystal lens. FIG. 5B is a view from the front.

[Explanation of symbols]

 Reference Signs List 101 semiconductor laser 102 beam splitter 103 polarization converter 104 objective lens 105 optical storage medium 106 photodetector 301 lens 401 glass substrate 402 transparent electrode 403 liquid crystal layer 501 glass substrate 502 liquid crystal layer

Claims (12)

[Claims] 1. A laser emitting at least polarized light, an optical lens for converging light emitted from the laser on an optical storage medium, and a light receiving element for detecting light reflected by the optical storage medium. The optical lens is formed using an optical medium having a refractive index anisotropy, and has a polarization conversion means for changing the polarization direction of laser light incident on the optical lens. Characteristic optical information reading and recording device. 2. The optical information reading and recording apparatus according to claim 1, wherein the optical lens is formed using a uniaxial optical crystal having a refractive index anisotropy. 3. The optical information reading and recording apparatus according to claim 1, wherein the optical lens includes liquid crystals arranged uniformly. 4. The optical information reading and recording apparatus according to claim 1, wherein the polarization direction of the laser radiation is substantially parallel or perpendicular to the optical axis of the optical medium forming the optical lens. 5. The optical information reading and recording apparatus according to claim 1, wherein the polarization conversion means is performed by a liquid crystal having birefringence or optical rotation. 6. A laser which emits at least polarized light, an optical lens for converging light emitted from the laser on an optical storage medium, and a light receiving element for detecting light reflected by the optical storage medium. The optical information reading and recording apparatus, wherein the optical lens is formed using an optical medium whose spatial refractive index distribution changes by application of an electric field. 7. The optical information reading and recording apparatus according to claim 6, wherein the optical lens includes liquid crystals arranged uniformly. 8. The optical information reading and recording apparatus according to claim 6, wherein the polarization direction of the emitted light of the laser is substantially parallel to the optical axis of the optical medium forming the optical lens. 9. A laser that emits at least polarized light, an optical lens for converging light emitted from the laser on an optical storage medium, and a light receiving element for detecting light reflected by the optical storage medium. The optical lens is formed using an optical medium having a refractive index anisotropy in which a spatial refractive index distribution changes by application of an electric field, and a polarization direction of laser light incident on the optical lens. 1. An optical information reading and recording apparatus, comprising: a polarization conversion means for changing the wavelength. 10. The optical information reading and recording apparatus according to claim 9, wherein the optical lens includes liquid crystals arranged uniformly. 11. The optical information reading and recording apparatus according to claim 9, wherein the polarization direction of the laser light is substantially parallel or perpendicular to the optical axis of the optical medium forming the optical lens. 12. An optical information processing apparatus capable of recording or reading information or recording and reading information, using a laser capable of emitting at least polarized light and an optical medium having a refractive index anisotropy. Optical lens means for converging laser light emitted from the laser onto an optical storage medium, light receiving means for detecting light reflected by the optical storage medium, and the optical storage medium The apparatus further includes at least a polarization conversion unit that is disposed on an optical path between the laser and the optical lens unit and changes a polarization direction of the laser light incident on the optical lens unit, and is configured such that a focal position of the laser light is variable. An optical information processing apparatus characterized by the above-mentioned.