JP2003050317A - Optical element, optical head, optical recording and reproducing device and method for manufacturing optically active polymer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head which can instantly switch recording and reproducing. SOLUTION: The optical head is used for recording or reproducing signals on or from an optical recording medium and the head is equipped with an optical element 3 between a light source 1 and an optical recording medium 9. The optical element 3 has an optically active polymer film in which the optical rotation property changes with respect to an applied voltage, a pair of conductive transparent thin films to apply a voltage to the optically active polymer film, and a transmittance polarization anisotropic part which is disposed on one of the conductive transparent thin film and has different transmittance with respect to the polarization direction. The light quantity of the linearly polarized light transmitting through the optical element 3 can be instantly changed by varying the voltage applied to the optically active polymer film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element, an optical head and an optical recording / reproducing apparatus used for optical information processing or optical communication. The present invention also relates to a method for producing an optically active polymer film.

[0002]

2. Description of the Related Art In recent years, a digital versatile disc (DVD) stores digital information in a compact disc (C).
Since it can record at about 6 times the recording density of D),
It has attracted attention as a large-capacity optical recording medium. However, there is a demand for a higher density optical recording medium as the information capacity increases. Here, in order to achieve higher density than DVD (wavelength 660 nm, numerical aperture (NA) 0.6), it is necessary to shorten the wavelength of the light source and increase the NA of the objective lens. For example, using a blue laser of 405 nm and an objective lens of NA 0.85, DV
A recording density of 5 times that of D is achieved.

However, in the high-density optical disk device using the blue laser described above, the reproduction margin is very strict, and the quantum noise of the light source becomes a problem. Therefore, an optical head that can reproduce high quality with low noise by suppressing the quantum noise of the semiconductor laser while suppressing deterioration of the optical disk and erasing of data by suppressing the surface power of the optical disk to a low level is a special feature. It is proposed in Kai 2000-195086.

An example of the above-mentioned conventional optical head will be described with reference to the drawings.

FIG. 20 is a schematic diagram showing the structure of a conventional optical head described in Japanese Patent Laid-Open No. 2000-195086.

Here, 161 is a light source, 162 is an intensity filter, 163 is a beam splitter, 164 is a collimator lens, 165 is a mirror, 166 is an objective lens, and 167.
Is an optical disk, 168 is a multi-lens, and 169 is a photodiode.

The light source 161 is a GaN-based blue light emitting semiconductor laser, and is a light source for outputting coherent light for recording and reproduction to and from the recording layer of the optical disc 167. The intensity filter 162 is an element on which an absorption film is formed, and is provided so that it can be inserted into and removed from the optical path. The beam splitter 163 is an optical element for separating light, the collimator lens 164 is a lens for converting divergent light emitted from the light source 161 into parallel light, and the mirror 165 reflects incident light to reflect the incident light on the optical disk 167. The objective lens 166 is a lens that focuses light on the recording layer of the optical disc 167, and is a multi-lens 168.
Is a lens that collects light on the photodiode 169, and the photodiode 169 receives light reflected by the recording layer of the optical disc and converts the light into an electric signal.

The operation of the optical head configured as described above will be described. Here, the intensity filter 162 is inserted in the optical path at the time of reproduction and is put out of the optical path at the time of recording. The light emitted from the light source 161 passes through the intensity filter 162 at the time of reproduction, so that the light amount is attenuated, and at the time of recording, the intensity filter 162 is out of the optical path, so the amount of light is not attenuated. Next, the light that has passed through the intensity filter 162 (the light emitted from the light source during recording) is reflected by the beam splitter 163 and converted into parallel light by the collimator lens 164. The collimated light is mirror 1
The optical disc 1 is reflected by 65 and is reflected by the objective lens 166.
It is focused on 67. Next, the light reflected from the optical disk 167 passes through the objective lens 166, is reflected by the mirror 165, is transmitted through the collimator lens 164, is transmitted through the beam splitter 163, and is collected by the photodiode 169 by the multi-lens 168. . The photodiode 169 outputs a focus error signal indicating the focused state of light on the optical disc 167 by using the astigmatism method,
It also outputs a tracking error signal indicating the light irradiation position.

Based on the focus error signal, the focus control means (not shown) controls the position of the objective lens 166 in the optical axis direction so that the light is always focused on the optical disk 167 in a focused state.

A tracking control means (not shown) emits light based on the tracking error signal.
The position of the objective lens 166 is controlled so that it is focused on a desired track on 67.

Further, the photodetector 169 is an optical disc 167.
Play the information recorded in.

According to this structure, at the time of reproduction, the power of the light source is set to the power at which the quantum noise is sufficiently low, and the surface power of the light source is suppressed to a low power at which the deterioration of the optical disk and the erasure of data do not occur. It is possible to perform the reproduction by using the power of the light source as it is at the time of recording.

[0013]

However, in the optical head having the above-described structure, the intensity filter 162 needs to be put in and taken out at the time of switching between recording and reproduction, and in the case where recording is performed instantly after address reproduction, The speed at which the intensity filter 162 is taken in and out becomes a problem. For example, DVD
For the next-generation high-density optical disc with higher density, switching of about 100 ns is required, but it is very difficult to achieve such speed by mechanical loading and unloading.

Further, in order to move the intensity filter 162 in and out, a mechanism (mechanism) for realizing this is required, which increases the size of the optical head, which is suitable for downsizing the optical head. It doesn't.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an optical element capable of instantaneously switching between recording and reproduction.

Further, according to the present invention, by using this optical element, the power of the light source is set to the power at which the quantum noise is sufficiently lowered, and the surface power of the light source is low so that the deterioration of the optical disk and the erasure of data do not occur. It is possible to perform reproduction while suppressing the power, and at the time of recording, it is possible to perform recording by using the power of the light source as it is. Furthermore, it is possible to instantaneously switch between recording and reproduction, and an optical head suitable for downsizing The purpose is to provide.

Another object of the present invention is to provide an optical recording / reproducing apparatus capable of instantaneously switching between recording and reproduction and suitable for downsizing and high density recording.

A further object of the present invention is to provide a method for producing an optically active polymer film capable of forming the above-mentioned optical element of the present invention. Another object of the present invention is to provide a method for producing an optically active polymer film which can be easily mass-produced.

[0019]

In order to achieve the above object, the present invention is configured as follows.

The optical element of the present invention comprises an optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and an optically active polymer film for applying a voltage to the optically active polymer film. Conductive transparent thin films arranged on both sides, and one of the conductive transparent thin films, which is arranged on the opposite side of the optically active polymer film, has different transmittance with respect to the polarization direction. Polarization anisotropy. And a part. As a result, the polarization direction of the linearly polarized light after passing through the optically active polymer film changes according to the voltage applied from the outside, and the amount of light transmitted by the transmittance polarization anisotropy part changes. It is possible to switch.

The optical element of the present invention comprises an optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and the optically active polymer for applying a voltage to the optically active polymer film. Conductive transparent thin films arranged on both sides of the film,
An optically active polymer film thickness correction unit that is arranged on the opposite side of the one of the conductive transparent thin films from the optically active polymer film and corrects optical rotation caused by a film thickness deviation of the optically active polymer film; It is characterized by having. Thereby, the polarization direction of the incident light can be changed at high speed according to the voltage applied from the outside. Further, it becomes possible to obtain linearly polarized light having a desired polarization direction by the optically active polymer film thickness correction unit without applying an external voltage or by short-circuiting.

Further, the optical element of the present invention comprises an optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and the optically active polymer for applying a voltage to the optically active polymer film. Conductive transparent thin films arranged on both sides of the film,
An optically active polymer film thickness correction unit that is arranged on the opposite side of the one of the conductive transparent thin films from the optically active polymer film and corrects optical rotation caused by a film thickness deviation of the optically active polymer film; And a polarization-anisotropic portion having a transmittance different from that of the conductive transparent thin film, the transmittance-polarization anisotropic portion being disposed on the side opposite to the conductive transparent thin film. . This changes the polarization direction of the linearly polarized light after passing through the optically active polymer film according to the voltage applied from the outside,
Since the amount of transmitted light changes depending on the transmittance polarization anisotropic portion, the amount of transmitted light can be switched at high speed. Further, it becomes possible to obtain a desired transmittance by applying an optically active polymer film thickness correction unit without applying an external voltage or by short-circuiting.

In the above optical element of the present invention, it is preferable that the optically active polymer film is composed of a polylactic acid film. As a result, the response characteristic to the external voltage becomes very fast.

In the above-mentioned optical element of the present invention, it is preferable that the change of the transmittance of the transmittance polarization anisotropic portion is caused by the change of the absorptance according to the polarization direction. This makes it possible to realize a transmittance polarization anisotropic portion.

In the above-mentioned optical element of the present invention, it is preferable that the transmittance polarization anisotropic portion is composed of an analyzer film. As a result, wafer processing becomes possible and an optical element with excellent mass productivity can be obtained.

In the above-mentioned optical element of the present invention, it is preferable that the change of the transmittance of the transmittance polarization anisotropic portion is caused by the change of the diffraction efficiency depending on the polarization direction. This makes it possible to realize a transmittance polarization anisotropic portion.

In the above-mentioned optical element of the present invention, it is preferable that the transmittance polarization anisotropic portion is composed of a polarization hologram. As a result, wafer processing becomes possible and an optical element with excellent mass productivity can be obtained.

In the above-mentioned optical element of the present invention, it is preferable that the change in the transmittance of the above-mentioned transmittance / polarization anisotropic portion is caused by the change in the reflectance depending on the polarization direction. This makes it possible to realize a transmittance polarization anisotropic portion.

In the above-mentioned optical element of the present invention, it is preferable that the transmittance polarization anisotropic portion is composed of a multilayer film including a birefringent film. As a result, wafer processing becomes possible and an optical element with excellent mass productivity can be obtained.

In the above-mentioned optical element of the present invention, it is preferable that the optically active polymer film thickness correction portion is composed of a K / 2 wavelength plate (K is an odd number of 1 or more). As a result, the optically active polymer film thickness correction unit can be realized.

In the above-mentioned optical element of the present invention, it is preferable that the optically active polymer film has a multilayer structure. This reduces the externally applied voltage required to achieve the desired characteristics.

Next, the optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
It is characterized in that it includes a light source and the above-mentioned optical element of the present invention arranged between the light source and the optical recording medium, and the voltage applied to the optical element is switched between recording and reproducing. As a result, the power of the light source during playback is set to a level at which quantum noise is sufficiently low, while the transmittance of the optical element is reduced, so that the surface power of the board is suppressed to a low power that does not cause deterioration of the optical disk or erasure of data. It is possible to perform the reproduction by using the power of the light source as it is by increasing the transmittance of the optical element at the time of recording. Further, since it becomes possible to switch the transmittance of the optical element at high speed by an electric signal from the outside, it becomes possible to instantaneously switch between recording and reproduction. In addition, it does not require a mechanism for inserting and removing the intensity filter as in the conventional case, and thus is suitable for downsizing.

Further, when the optically active polymer film thickness correction unit is provided, the desired transmittance can be obtained without applying an external voltage or by short-circuiting, so that the stability of the optical head is improved. improves.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A recording signal is formed by including a light source and the above-described optical element of the present invention arranged between the light source and the optical recording medium, and forming a recording signal by changing a voltage applied to the optical element. This makes it possible to record information on the optical recording medium even with a light source that is difficult to record and modulate. Further, when the optically active polymer film thickness correction unit is provided, the desired transmittance can be obtained without applying an external voltage or by short-circuiting, so that the stability of the optical head is improved.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
It is characterized by including a light source and the above-mentioned optical element of the present invention arranged between the light source and the optical recording medium, and detecting a tracking error signal using diffracted light generated by the optical element. As a result, the diffracted light generated by the optical element can be used as a sub-beam required to obtain the tracking error signal, and thus the optical element used for detecting the tracking error signal is replaced by the optical element of the present invention. It is possible to combine the functions, and it is suitable for downsizing and cost reduction of the optical head.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, the optical element of the present invention arranged between the light source and the optical recording medium, a light amount control means for receiving light emitted from the light source and controlling the light amount of the light source, and the optical element. And an optical element control means for controlling the characteristics of the element. As a result, the characteristics of the optical head do not change even if the temperature changes, and the control of the optical element is completed.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
The optical element includes a light source, the above-mentioned optical element of the present invention arranged between the light source and the optical recording medium, and a polarization splitting means arranged between the optical element and the optical recording medium. The feature is that the applied voltage is switched between recording and reproduction. As a result, the power of the light source during playback is set to a level at which quantum noise is sufficiently low, while the transmittance of the optical element is reduced, so that the surface power of the board is suppressed to a low power that does not cause deterioration of the optical disk or erasure of data. It is possible to perform reproduction by using the power of the light source as it is by increasing the transmittance of the optical element during recording. Further, since it becomes possible to switch the transmittance of the optical element at high speed by an electric signal from the outside, it becomes possible to instantaneously switch between recording and reproduction. In addition, it does not require a mechanism for inserting and removing the intensity filter as in the conventional case, and thus is suitable for downsizing.

Further, when the optically active polymer film thickness correction unit is provided, the desired transmittance can be obtained without applying an external voltage or by short-circuiting, so that the stability of the optical head is improved. improves.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
The optical element includes a light source, the above-mentioned optical element of the present invention arranged between the light source and the optical recording medium, and a polarization splitting means arranged between the optical element and the optical recording medium. It is characterized in that a recording signal is formed by changing an applied voltage. This makes it possible to record information on the optical recording medium even with a light source that is difficult to record and modulate. Further, when the optically active polymer film thickness correction unit is provided, it is possible to obtain linearly polarized light having a desired polarization direction without applying an external voltage or by short-circuiting the optical head stability. Is improved.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, the above-mentioned optical element of the present invention arranged between the light source and the optical recording medium, a polarized light separating means arranged between the optical element and the optical recording medium, and emitted from the light source. It is characterized by comprising a light quantity control means for receiving light and controlling the light quantity of the light source, and an optical element control means for controlling the characteristics of the optical element. As a result, the characteristics of the optical head do not change even if the temperature changes, and the control of the optical element is completed.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, disposed between the light source and the optical recording medium,
The optically active polymer includes an optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and polarized light separating means arranged between the optically active polymer film and the optical recording medium. The feature is that the voltage applied to the film is switched between recording and reproduction. As a result, the power of the light source during playback is set to a level at which quantum noise is sufficiently low, while the transmittance of the optical element is reduced, so that the surface power of the board is suppressed to a low power that does not cause deterioration of the optical disk or erasure of data. It is possible to perform reproduction by using the power of the light source as it is by increasing the transmittance of the optical element during recording. Further, since it becomes possible to switch the transmittance of the optical element at high speed by an electric signal from the outside, it becomes possible to instantaneously switch between recording and reproduction. In addition, it does not require a mechanism for inserting and removing the intensity filter as in the conventional case, and thus is suitable for downsizing.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, disposed between the light source and the optical recording medium,
The optically active polymer includes an optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and polarized light separating means arranged between the optically active polymer film and the optical recording medium. The recording signal is formed by changing the voltage applied to the film. This makes it possible to record information on the optical recording medium even with a light source that is difficult to record and modulate.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, disposed between the light source and the optical recording medium,
Optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, polarized light separating means arranged between the optically active polymer film and the optical recording medium, and light emitted from the light source. It is characterized by comprising a light amount control means for receiving the light and controlling the light amount of the light source, and an optical element control means for controlling the characteristics of the optically active polymer film. This allows
The characteristics of the optical head do not change even if the temperature changes, and the control of the optically active polymer film is completed.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, disposed between the light source and the optical recording medium,
An optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and a film thickness deviation of the optically active polymer film, which is disposed between the optically active polymer film and the optical recording medium. The optically active polymer film thickness correction unit that corrects the generated optical rotation, and the polarized light separating means arranged between the optically active polymer film thickness correction unit and the optical recording medium, The feature is that the applied voltage is switched between recording and reproduction. As a result, the power of the light source during playback is set to a level at which quantum noise is sufficiently low, while the transmittance of the optical element is reduced, so that the surface power of the board is suppressed to a low power that does not cause deterioration of the optical disk or erasure of data. It is possible to perform reproduction by using the power of the light source as it is by increasing the transmittance of the optical element during recording. Further, since it becomes possible to switch the transmittance of the optical element at high speed by an electric signal from the outside, it becomes possible to instantaneously switch between recording and reproduction. In addition, it does not require a mechanism for inserting and removing the intensity filter as in the conventional case, and thus is suitable for downsizing.

Further, since the desired transmittance can be obtained by the optically active polymer film thickness correction unit without applying an external voltage or by short-circuiting, the stability of the optical head is improved.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, disposed between the light source and the optical recording medium,
An optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and a film thickness deviation of the optically active polymer film, which is disposed between the optically active polymer film and the optical recording medium. The optically active polymer film thickness correction unit that corrects the generated optical rotation, and the polarized light separating means arranged between the optically active polymer film thickness correction unit and the optical recording medium, It is characterized in that a recording signal is formed by changing an applied voltage. This makes it possible to record information on the optical recording medium even with a light source that is difficult to record and modulate. In addition, since the optically active polymer film thickness correction unit can obtain linearly polarized light having a desired polarization direction without applying an external voltage or by short-circuiting, the stability of the optical head is improved.

The optical head of the present invention is an optical head for recording or reproducing a signal on or from an optical recording medium,
A light source, disposed between the light source and the optical recording medium,
An optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and a film thickness deviation of the optically active polymer film, which is disposed between the optically active polymer film and the optical recording medium. An optically active polymer film thickness correction unit that corrects the generated optical rotation, a polarized light separating unit disposed between the optically active polymer film thickness correction unit and the optical recording medium, and receives light emitted from the light source. And a light quantity control means for controlling the light quantity of the light source, and an optical element control means for controlling the characteristics of the optically active polymer film. This provides complete control of the optically active polymer film.

Next, the optical recording / reproducing apparatus of the present invention is an optical recording / reproducing apparatus for recording / reproducing a signal on / from an optical recording medium, and an optical head for recording / reproducing a signal on the optical recording medium. And the optical head is the optical head of the present invention. As a result, the power of the light source can be set to a level at which quantum noise is sufficiently low during playback, and the playback can be performed while suppressing the board power to a low level that does not cause deterioration of the optical disc or data deletion. Sometimes, recording can be performed using the power of the light source as it is. Further, since it becomes possible to switch the transmittance of the optical element at high speed by an electric signal from the outside, it becomes possible to instantaneously switch between recording and reproduction. In addition, it does not require a mechanism for inserting and removing the intensity filter as in the conventional case, and thus is suitable for downsizing.

Further, when the optically active polymer film thickness correction section is provided, the desired transmittance can be obtained without applying an external voltage or by short-circuiting, so that the stability of the optical head is improved. improves.

Next, in the method for producing an optically active polymer film of the present invention, the first substrate provided with a conductive transparent thin film and the second substrate provided with a conductive transparent thin film are treated with the above-mentioned conductive material. The transparent thin films face each other, and are arranged so that a desired gap is formed between the both conductive transparent thin films, and the optically active polymer in a molten state is arranged between the both conductive transparent thin films. It is characterized in that cooling is performed while maintaining the orientation direction of the molecules constituting the. By doing so, it becomes possible to manufacture an optically active polymer film with good orientation, and it becomes possible to manufacture an optically active polymer film in which the optical rotation greatly changes in a shorter time depending on the applied voltage. Become.

Further, if an optical head or an optical recording / reproducing device is constructed using this optically active polymer film, it becomes possible to switch between recording and reproducing in a shorter time.

In the above-mentioned manufacturing method, the optically active polymer in the molten state is placed above the conductive transparent thin films in the solid state and heated to a temperature equal to or higher than the melting point of the optically active polymer. It is preferably formed by By doing so, it is easy to dispose a desired weight of the optically active polymer between the substrates.

In the above manufacturing method, it is preferable that the orientation direction of the molecules is maintained in a desired direction by applying an electric field to the optically active polymer in the molten state. This makes it possible to easily hold the orientation direction of the optically active polymer in a desired direction.

In the above manufacturing method, it is preferable that the orientation direction of the molecules is maintained in a desired direction by applying a standing wave of ultrasonic waves to the optically active polymer in the molten state. This makes it possible to easily hold the orientation direction of the optically active polymer in a desired direction.

In the above manufacturing method, it is preferable that the standing waves of the ultrasonic waves are formed by the ultrasonic waves interfering with each other by applying the ultrasonic waves from different directions. By doing so, the phase and magnitude of the ultrasonic waves are controlled for each of the applied ultrasonic waves, so that the standing wave applied to the optically active polymer can be easily managed.

In the above manufacturing method, it is preferable that the standing wave of the ultrasonic wave is formed by the interference between the applied ultrasonic wave and the reflected wave of the ultrasonic wave. If you do this,
The circuit configuration of the ultrasonic standing wave control becomes simple.

In order to achieve the above-mentioned object, the method for producing an optically active polymer film of the present invention comprises a first substrate provided with a conductive transparent thin film and a second substrate provided with a conductive transparent thin film. , The conductive transparent thin films are opposed to each other, arranged so that a desired gap is formed between the both conductive transparent thin films, and the optically active polymer in a solid state is arranged between the both conductive transparent thin films, Focusing the ultrasonic wave on a part of the optically active polymer in the solid state, melting only the optically active polymer at the position where the ultrasonic wave is focused, and moving the position where the ultrasonic wave is focused over time. Is characterized by. By doing so, it becomes possible to manufacture an optically active polymer film with good orientation, and it becomes possible to manufacture an optically active polymer film in which the optical rotation greatly changes in a shorter time depending on the applied voltage. Become.

Further, if an optical head or an optical recording / reproducing device is constructed using this optically active polymer film, it becomes possible to switch between recording and reproducing in a shorter time.

In the above manufacturing method, the optically active polymer in the solid state is preferably a powder. By doing so, it is easy to control the weight of the optically active polymer to be arranged.

In the above manufacturing method, it is preferable that the optically active polymer in the solid state is a film. By doing so, it is easy to control the weight of the optically active polymer to be arranged. Further, in the method of sequentially melting only the optically active polymer at the position where the ultrasonic waves are converged, since the polylactic acid film with good orientation is formed by melting a part of the film, the orientation to be produced The thickness of the optically active polymer film having good properties is the thickness of this film. Therefore, it becomes possible to form a void having a desired size without using a separate member.

In the above production method, the optically active polymer is preferably polylactic acid. This makes it possible to switch for a few nanoseconds.

In the above manufacturing method, it is preferable that the gap is formed by disposing a member having a desired size between the first and second substrates. With this configuration, the void having a desired size can be accurately formed.

In the above manufacturing method, it is preferable that the member is transparent. In this way, incident light will not be lost.

In the above manufacturing method, it is preferable that the refractive index of the member is substantially equal to the refractive index of the optically active polymer. In this way, incident light will not be lost.

In the above manufacturing method, it is preferable that the glass transition point of the member is equal to or higher than the melting point of the optically active polymer. With this configuration, the void having a desired size can be formed more accurately.

[0066]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In Embodiment 1, an example of the optical head of the present invention will be described.

FIG. 1 is a block diagram of the optical head 17 of the first embodiment. The optical head 17 of the first embodiment is an optical head including the optical element of the present invention.

In FIG. 1, 1 is a light source, 2 is a first beam splitter, 3 is an optical element of the present invention, 4 is a diffraction grating,
5 is a second beam splitter, 6 is a collimator lens,
7 is a mirror, 8 is an objective lens, 9 is an optical recording medium, 10 is a first condenser lens, 11 is a second condenser lens, 12 is a first photodetector, and 13 is a second photodetector. , 14 is a third photodetector, 15 is a light amount control circuit, and 16 is an optical element control circuit. Here, the condensing optical system is composed of a collimator lens 6 and an objective lens 8, the light quantity control means is composed of a first photodetector 12 and a light quantity control circuit 15, and the optical element control means is , A second photodetector 13 and an optical element control circuit 16.

Here, the light source 1 is, for example, a GaN-based semiconductor laser element (wavelength 405 nm), and is a light source for outputting coherent light for recording and reproduction to the recording layer of the optical recording medium 9. The first beam splitter 2 has 90
The optical element has a transmittance of 10% and a reflectance of 10%.
As will be described in detail later, the optical element 3 of the present invention is an optical element whose transmittance changes according to an external signal (that is, a control signal from the optical element control circuit 16). The diffraction grating 4 is a grating formed by patterning a desired pattern on the glass surface using photolithography and then etching, and its characteristics are that the 0th-order diffraction efficiency is approximately 90% and the ± 1st-order diffraction efficiency is approximately 10%. . The second beam splitter 5 is an optical element having a transmittance of about 50% and a reflectance of about 50%. The collimator lens 6 is a lens that converts divergent light emitted from the light source 1 into parallel light. The mirror 7 is an optical element that reflects incident light and directs it toward the optical recording medium 9. The objective lens 8 is a lens that focuses light on the recording layer of the optical recording medium 9. The first condenser lens 10 is a lens that condenses a part of the light emitted from the light source 1 and transmitted through the optical element 3 of the present invention on the second photodetector 13.
The second condenser lens 11 is a lens that condenses the light reflected by the optical recording medium 9 on the third photodetector 14. The first, second, and third photodetectors 12, 13, and 14 receive light and convert the light into electric signals.

The operation of the optical head thus constructed will be described with reference to FIG. The linearly polarized light emitted from the light source 1 enters the first beam splitter 2. The light reflected by the first beam splitter 2 is incident on the first photodetector 12, and the transmitted light is incident on the optical element 3 of the present invention. Here, the light incident on the first photodetector 12 is converted into an electric signal and becomes an electric signal for monitoring the quantity of light emitted from the light source 1, and this signal is the light quantity control circuit 1
The light source 1 is controlled so that the light amount is input to 5 and outputs the optimum light amount (the light amount of the light source 1 is controlled by the light amount control means). Next, the light that has passed through the first beam splitter 2 and is incident on the optical element 3 of the present invention is attenuated in the light amount in the case of reproduction and is not attenuated in the case of recording. See below).

Most of the light transmitted through the optical element 3 of the present invention is transmitted by the diffraction grating 4 and a part thereof is diffracted. The light that has passed through the diffraction grating 4 (both the transmitted light and the diffracted light) is incident on the second beam splitter 5. The light reflected by the second beam splitter 5 is incident on the condenser lens 10,
The light is incident on the second photodetector 13 by the condenser lens 10. Further, the light transmitted through the second beam splitter 5 is incident on the collimator lens 6. Here, in the electric signal output from the second photodetector 13, since the light amount of the light emitted from the light source 1 is controlled by the first photodetector 12 and the light amount control circuit 15, The electric signal is an electric signal obtained by monitoring the amount of light transmitted according to the transmittance of the optical element 3.

Therefore, this signal is transmitted to the optical element control circuit 16
To the optical element 3 by the optical element control circuit 16 so that the transmittance of the optical element 3 of the present invention is optimized (the optical element control means sends a signal for controlling the transmittance of the optical element 3 to the optical element 3). ). The light incident on the collimator lens 6 is collimated by the collimator lens 6. The light transmitted through the collimator lens 6 is reflected by the mirror 7, travels in a direction bent 90 degrees from the traveling direction thereof, and is condensed on the optical recording medium 9 by the objective lens 8.

Next, the light reflected from the optical recording medium 9 passes through the objective lens 8, is reflected by the mirror 7, is transmitted by the collimator lens 6, is reflected by the second beam splitter 5, and is reflected by the second beam splitter 5. It is condensed by the optical lens 11 and is incident on the third photodetector 14. The third photodetector 14 outputs a focus error signal indicating the focused state of light on the optical recording medium 9, and also outputs a tracking error signal indicating the irradiation position of light. In this case, for example, the phase difference method is used in the case of the read-only optical recording medium, and the tracking error signal is obtained in the case of the recording optical recording medium by the three-beam method using the sub-beam created by the diffraction grating 4.

Based on the focus error signal, the focus control means (not shown) controls the position of the objective lens 8 in the optical axis direction so that the light is always focused on the optical recording medium 9. The tracking control means (not shown) controls the position of the objective lens 8 based on the tracking error signal so that the light is focused on a desired track on the optical recording medium 9. The information recorded on the optical recording medium 9 is also obtained from the third photodetector 14.

Here, the optical element 3 of the present invention will be described in detail. FIG. 2 shows a sectional view of the optical element of the present invention. In FIG. 2, 21 is the first glass and 22 is the first ITO.
A film, 23 is a polylactic acid film, 24 is a second ITO film, 25 is an analyzer film, and 26 is a second glass. Here, the optically active polymer film is composed of the polylactic acid film 23, the conductive transparent thin film is composed of the first and second ITO films 22 and 24, and the transmittance polarization anisotropy portion is detected. It is composed of the photonic film 25. Here, the analyzer film 25 is a film in which an iodine compound is added to the film and is a film having different absorptances of linearly polarized light beams orthogonal to each other. The operation of the optical element thus configured will be described.

The polylactic acid film 23 has a helical structure and has a large optical rotatory power. Further, when a voltage is applied to this film, the optical rotatory power is changed (see Functional Material, July 2000 issue, vol. 20, No. 7). Here, the material having a spiral structure has molecules of a right-handed helix and molecules of a left-handed helix, and the optical rotation is reversed in that direction. Although a polylactic acid film having a rightward spiral structure is used here, there is no problem even if a polylactic acid film having a leftward spiral structure is used. As shown in FIG. 3A, when linearly polarized light is incident on the polylactic acid film 23, a certain voltage (V1) is applied to the polylactic acid film 23 via the first and second ITO films 22 and 24. At this time, the polarization direction of the transmitted light becomes linearly polarized light having the same polarization direction as the incident light. On the contrary,
As shown in FIG. 3B, when a different voltage (V2) is applied to the polylactic acid film 23, the polarization direction of the transmitted light becomes linearly polarized light in the direction orthogonal to the polarization direction of the incident light. here,
The linearly polarized light shown on the right side of FIGS. 3A and 3B indicates the polarization direction of each polarized light as seen from the traveling direction of light. Further, since the response characteristic of the optical rotatory power with respect to this voltage is several GHz, the switching of 100 ns required by the optical head becomes possible. Polylactic acid has a very fast response characteristic. The same effect can be achieved with liquid crystal, but the response characteristic of liquid crystal is limited to several MHz and cannot respond to switching for 100 ns.

Next, the analyzer film 25 will be described. In the analyzer film 25, since the iodine compound is oriented in a certain direction, the absorptance changes depending on the direction of linearly polarized light. That is, 100% of the linearly polarized light in a certain direction is transmitted, and 100% of the linearly polarized light in the direction orthogonal to this polarization direction is absorbed. As such an analyzer film 25, for example, an analyzer film having an iodine doping amount of 10% or less can be used.

Therefore, the analyzer film 25 is set in such a direction that almost 100% of light having the same polarization direction as the light incident on the optical element 3 is transmitted and almost 100% of light orthogonal to this polarization direction is absorbed. . With this configuration, a certain voltage (V
When 1) is applied, the light transmitted through the polylactic acid film 23 becomes the same linearly polarized light as the incident light and 100% is transmitted through the analyzer film 25. Therefore, the optical element 3 of the present invention has a transmittance of 100%.

Next, when a voltage (V2) of another magnitude is applied, the light transmitted through the polylactic acid film 23 becomes linearly polarized light in the direction orthogonal to the incident light and is absorbed 100% by the analyzer film 25. Therefore, the optical element 3 of the present invention has a transmittance of 0%.

At a voltage between V1 and V2, the light transmitted through the polylactic acid film 23 becomes linearly polarized light in a direction slightly rotated from the polarization direction of the incident light, and passes through the analyzer film 25 to some extent. Therefore, the optical element 3 of the present invention can change its transmittance according to the applied voltage. here,
If the analyzer film 25 is set in such a direction that almost 100% of the light emitted in the polarization direction emitted from the light source 1 is transmitted and almost 100% of the light orthogonal to the polarization direction is absorbed, V1 is set at the time of recording.
100% of the light is transmitted by applying the voltage of 1, and a certain amount of light is absorbed by the application of an appropriate voltage between V1 and V2 during reproduction, so that the amount of light is attenuated.

Now, let us consider the film thickness of the polylactic acid film 3. Since the polylactic acid film has optical rotatory power as described above, the incident linearly polarized light is rotated even if no voltage is applied. Therefore, a certain voltage (V1) is applied so that the polarization directions before and after transmission of the optical element 3 of the present invention coincide with each other, and another voltage (V2) is applied so that the polarization directions before and after transmission are orthogonal to each other. I have to. Here, in order to improve stability against disturbance such as a change in the polarization direction of light transmitted through the polylactic acid film 3 due to drift of the applied voltage, for example, no voltage is applied or the first IT
When the O film 22 and the second ITO film 24 are short-circuited, if the polarization directions of the linearly polarized light before and after the light is transmitted through the polylactic acid film 3 are the same, the stability of the device characteristics is further improved. For that purpose, it is necessary to make the film thickness in consideration of the optical rotatory power of the polylactic acid itself.

For example, since the optical rotation with respect to the thickness of polylactic acid is as high as 7200 ° / mm, if the film thickness is 50 μm, the optical rotation will be 360 °, and the direction of linear polarization will be before and after transmission without applying a voltage. Match. However, since the optical rotation is large as described above, it is difficult to match the polarization directions before and after the transmission without applying a voltage, considering the variation in the film thickness. Therefore, consider an optical element in which the optical rotation due to the deviation of the film thickness is corrected. FIG. 4 shows a cross-sectional view of an optical element in consideration of the film thickness deviation of polylactic acid. In FIG. 4, 41 is 1 /
It is a two-wave plate (here, a half-wave plate is used, but it is not necessarily limited to this, and a K / 2 wave plate (K is an odd number of 1 or more) may be used).

Here, the optically active polymer film is the polylactic acid film 2
3, the conductive transparent thin film is made up of the first and second ITO films 22 and 24, and the transmittance polarization anisotropic portion is made up of the analyzer film 25. The molecular film thickness correction unit is composed of a half-wave plate 41. This half-wave plate can be formed by stretching a polyimide resin, for example. The operation of the optical element thus configured will be described.

First, when no voltage is applied or a voltage of 0 V is applied (the first ITO film 22 and the second ITO film 24 are short-circuited) (FIG. 5).
A), linearly polarized light incident by the polylactic acid film 23 is shown in FIG.
The linearly polarized light of incident light such as B is converted to linearly polarized light in a direction rotated to some extent. By setting the azimuth axis of the half-wave plate 41 here to divide the azimuth angle of the polarization direction of the linearly polarized light before and after transmission into two equal parts (see FIG. 5B), the linearly polarized light in the same direction as the incident linearly polarized light is obtained. It becomes possible to convert. That is, by rotating the half-wave plate 41, it becomes possible to match the polarization directions of the linearly polarized light before and after the transmission. Therefore, by setting the analyzer film 25 in the same manner as described above, it is almost 100% when no voltage is applied.
It will be transmitted. In this way, the half-wave plate 41
It becomes possible to compensate for the amount of rotation of the linearly polarized light due to the optical rotatory power caused by the thickness of the polylactic acid film 23 by providing.

Next, the voltage applied to the optical element of the present invention will be described. As described above, the optical rotation of the polylactic acid film 23 is changed by applying a voltage, but the polarization direction of the linearly polarized light of the transmitted light is changed from the same direction as the polarization direction of the linearly polarized light of the incident light to the orthogonal direction. In order to achieve this, the amount of change in the optical rotation must be changed from at least 0 degrees to 90 degrees, and for that purpose, it is necessary to apply a large voltage of about 50V. Therefore, consider an element structure that can obtain the same effect even when the applied voltage is lowered. FIG. 6 is a cross-sectional view of an optical element having a multi-layered structure of a polylactic acid film, which has a structure capable of reducing an applied voltage (here, it has a two-layer structure).

In FIG. 6, 61 is the first glass and 62
Is a first ITO film, 63 is a first polylactic acid film, 64 is a second ITO film, 65 is a second polylactic acid film, 66 is a third ITO film, and 67 is a second glass. The characteristics of the optical element thus configured will be described. First, for example, a voltage of 25 V is applied to the first ITO film 62,
A voltage of 0 V is applied to the ITO film 64. By doing so, a voltage of 25 V is applied to the first polylactic acid film 63, and the first polylactic acid film 63 has an optical rotation of 45 degrees. Further, when the same voltage as that of the first ITO film 62 is applied to the third ITO film 66, an electric field corresponding to 25 V is applied to the second polylactic acid film 65, so that the second polylactic acid film 65 is applied. Also has an optical rotation of 45 degrees. Therefore, both the first and second polylactic acid films 63 and 65 can have an optical rotation of 90 degrees. Therefore, by forming the polylactic acid film in multiple layers, it is possible to reduce the voltage applied to the optical element in order to have the required optical rotation. Since the analyzer film 25 has been described above, its explanation is omitted. Here, 2 of polylactic acid film
Although the layered structure has been described, if the polylactic acid film is further multilayered, the applied voltage can be reduced accordingly.

In the case of a material in which the optical rotation is reversed in the direction of the electric field, it is necessary to form a multilayer structure having opposite spiral structures.

Next, the control of the voltage applied to the optical element 3 of the present invention will be described in detail. In the case of recording, the transmittance of the optical element 3 of the present invention is set to 100%, and in the case of reproduction, the transmittance of the optical element 3 of the present invention is set to an appropriate value. Here, the amount of light emitted from the light source 1 changes when the temperature of the light source 1 changes, even if a constant voltage is applied. Further, since the optical element 3 of the present invention also has temperature dependency in the optical activity of the polylactic acid film, the polarization direction after transmission changes even when a constant voltage is applied due to temperature change, and thus the transmittance of the optical element 3 changes. Will change.

Therefore, if only one monitor that receives the light after passing through the optical element 3 is used, it cannot be determined whether the light amount of the light source 1 has changed or the transmittance of the optical element 3 has changed. If all of them are dealt with by changing the light amount of the light source 1, there is a possibility that more light than expected will reach the optical recording medium 9 and erase the information recorded during reproduction. Therefore, by monitoring the light quantity of the light source 1 to keep the light quantity of the light source 1 constant, and monitoring the light quantity of the light after passing through the optical element 3, which is dedicated to monitor the transmittance of the optical element 3, And the control of the transmittance of the optical element 3 can be perfected. In the present embodiment, as a monitor of the light amount of the light source 1, the light is split by the first beam splitter 2 and received by the first photodetector 12 to be converted into an electric signal. It is also possible to monitor (light emitted from the rear side of the laser chip), or there is no problem if light emitted from the light source 1 but emitted from a component used for the optical head is used. . These cases are useful because the light used is not lost.

As described above, by using this optical element in the optical head, the power of the light source during reproduction is set to the power at which the quantum noise is sufficiently low, while the transmittance of the optical element of the present invention is lowered. As a result, it is possible to perform reproduction while suppressing the surface power of the disc to a low power that does not cause deterioration of the optical recording medium or erasing of data, and at the time of recording, the transmittance of the optical element of the present invention is set to 100% to achieve Recording can be performed using the power as it is. Also, since the transmittance is switched very quickly, it is possible to record immediately after the address reproduction. Moreover, since the transmittance is switched by an electric signal from the outside, it is easy to miniaturize the optical head.

The optical element of the present invention is shown in FIGS.
It is not limited to the case where the laminated integrated structure is adopted as shown in FIG. For example, a polylactic acid film and ITO films on both sides thereof,
An optical element having a structure in which the analyzer film and the half-wave plate are separated from each other may be used.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. The present embodiment is different from the above-described first embodiment only in that the structure of the optical element of the present invention is different and also serves as a diffraction grating, and other than that, the first embodiment is different. Is the same as. Therefore, in the present embodiment, those not specifically described are the same as those in the first embodiment, and constituent members given the same reference numerals as those in the first embodiment are as follows.
Unless otherwise specified, it has the same function as that of the first embodiment.

FIG. 7 is a block diagram of an optical head according to the second embodiment of the present invention. In FIG. 7, reference numeral 71 is an optical element of the present invention. The operation of the optical head thus configured will be described with reference to FIG. The linearly polarized light emitted from the light source 1 enters the first beam splitter 2. The light reflected by the first beam splitter 2 is
The light that has been incident on the photodetector 12 and has been transmitted is incident on the optical element 71 of the present invention. Here, the light incident on the first photodetector 12 is converted into an electric signal and becomes an electric signal for monitoring the amount of light emitted from the light source 1. This signal is input to the light amount control circuit 15 to obtain the optimum amount of light. The light source 1 is controlled so as to output

Next, the light transmitted through the first beam splitter 2 and incident on the optical element 71 of the present invention is transmitted to some extent in the case of reproduction, and the rest is diffracted to attenuate a considerable amount of light. , In the case of recording, most are transparent,
Some are diffracted. As for the diffraction efficiency in this case, 90% is transmitted and 10% is diffracted as described in the first embodiment (this will be described later in detail).

The light (both the transmitted light and the diffracted light) transmitted through the optical element 71 of the present invention is incident on the second beam splitter 5. From this point, the process until the light focused on the optical recording medium and reflected by the optical recording medium returns to the photodetector is the same as that described in the first embodiment, and therefore its explanation is omitted.

The third photodetector 14 outputs a focus error signal indicating the focused state of light on the optical recording medium 9 and a tracking error signal indicating the irradiation position of light. In this case, for example, the phase difference method is used in the case of the read-only optical recording medium, and the tracking error signal is obtained in the case of the recording optical recording medium by the three-beam method using the sub-beam created by the optical element 71 of the present invention. The focus control means (not shown) is based on the focus error signal,
The position of the objective lens 8 is controlled in the optical axis direction so that the light is always focused on the optical recording medium 9. The tracking control means (not shown) controls the position of the objective lens 8 based on the tracking error signal so that the light is focused on a desired track on the optical recording medium 9. The information recorded on the optical recording medium 9 is also obtained from the third photodetector 14.

Now, the optical element 71 of the present invention will be described in detail. The present embodiment is different from the above-described first embodiment only in that a portion that changes the transmittance according to the polarization direction of linearly polarized light is different, and other than that, the first embodiment is different. It is similar to the form. Therefore, in the present embodiment, those that are not particularly described are the first
The same members as those of the first embodiment, and the constituents given the same reference numerals as those of the first embodiment have the same functions as those of the first embodiment unless otherwise specified.

FIG. 8 shows a sectional view of the optical element 71 of the present invention. In FIG. 8, 81 is a polarization hologram, 82 is a birefringent polyimide film, and 83 is an isotropic material.
It is a V-curable resin. Here, the transmittance polarization anisotropic portion is composed of the polarization hologram 81. Here, the polarization hologram 81 is constructed by etching a polyimide film 82 which is a birefringent material and burying a UV curing resin 83 which is an isotropic material (see Japanese Patent Laid-Open No. 63-026604).

As another structure, a predetermined part of a lithium niobate substrate having birefringence is proton-exchanged,
The proton exchange part is formed by etching (see JP-A-6-27322).

The operation of the optical element thus configured will be described. First, as described in the first embodiment, the incident linearly polarized light is converted into the linearly polarized light in the same direction as the incident light or the linearly polarized light of the incident light depending on the magnitude of the voltage applied to the polylactic acid film 23. Is converted to linearly polarized light in a slightly rotated direction.

Next, the polarization hologram 81 will be described.
As described above, since the polarization hologram 81 is formed by using the birefringent material, the diffraction efficiency for a certain polarized light and the diffraction efficiency for a polarized light in the direction orthogonal to the polarized light are different. Therefore, for example, 90% transmission and 10% diffraction characteristics are given to a certain polarized light, and 50% transmission and 50% diffraction characteristics are given to a polarized light in a direction orthogonal to the polarized light. Then, the polarization hologram 81 is set in such a direction that approximately 90% of the linearly polarized light of the incident light on the optical element 71 is transmitted and approximately 50% of the linearly polarized light in the direction orthogonal to the linearly polarized light is transmitted.

With this configuration, a certain voltage (V1)
When light is applied, the light transmitted through the polylactic acid film 23 becomes the same linearly polarized light as the incident light, and 90% is transmitted through the polarization hologram 81 and is diffracted by 10%. Therefore, the optical element of the present invention is 90%
Of the sub-beam (± 1
Second diffracted light) can be formed. Next, when a voltage (V2) of another magnitude is applied, the light transmitted through the polylactic acid film 23 becomes linearly polarized light in the direction orthogonal to the incident light, and 50% is transmitted by the polarization hologram 81. Therefore, the optical element of the present invention has a transmittance of 50%.

By using this optical element in the optical head, the power of the light source is set to the power at which the quantum noise is sufficiently reduced during reproduction, and the transmittance of the optical element of the present invention is lowered to increase the optical power of the board. It is possible to perform reproduction while suppressing to a low power that does not cause deterioration of the recording medium or erasure of data, and at the time of recording, most of the light source power is used by setting the transmittance of the optical element of the present invention to 90%. Recording can be performed, and a sub beam required for tracking can be formed.

Further, since the transmittance is switched very quickly, it is possible to record immediately after the address reproduction. Moreover, since the transmittance is switched by an electric signal from the outside, it is easy to miniaturize the optical head.

In the above description, the transmittance during reproduction is set to 5
Although it is set to 0%, the transmittance of the polarization hologram 81 may be set to an optimum value according to the amount of light emitted from the light source 1.

Further, the polarization direction of the light transmitted through the polylactic acid film 23 is set to either the same direction as the incident light or the orthogonal direction, but if the efficiency of the polarization hologram 81 is appropriately selected, the light passes through the polylactic acid film 23. The angle of the polarization direction of the latter light can be different from the above.

Further, although FIG. 8 shows the optical element 71 in which the polylactic acid film 23 sandwiched between the ITO films 22 and 24 and the polarization hologram 81 are laminated and integrated, both may be separated.

The optical element having the structure shown in FIG. 9 can be used as the optical element which changes the diffraction efficiency to change the transmittance. In FIG. 9, 91 is the first glass, 92 is the first ITO film, 93 is liquid crystal, 94 is the second ITO film, 9
Reference numeral 5 is a second glass having a grating. The characteristics of the optical element thus configured will be described with reference to FIG. The liquid crystal 93 changes its refractive index according to the applied voltage. Therefore, if the refractive index of the liquid crystal 93 is changed, the diffraction efficiency changes. Therefore, as described above, it is 9 when recording.
It is possible to transmit 0%, diffract 10%, perform tracking control using the diffracted light, and transmit 50% to attenuate the light during reproduction. However, since liquid crystal has a slow response characteristic of the refractive index, recording cannot be performed instantly after reproduction, so a waiting time is required after the refractive index stabilizes, that is, after the transmittance stabilizes. Becomes

Further, since it is possible to change the optical rotation of the liquid crystal, it is impossible to record immediately after reproduction as described above, but there is a waiting time of recording after the transmittance is stabilized. If provided, the liquid crystal can be used as an optically active polymer film of the optical element of the present invention.

Further, since the liquid crystal can change its retardation, the same effect can be obtained. In this case as well, recording cannot be carried out instantly after reproduction as described above, but if a waiting time is provided for recording after the transmittance is stabilized, the liquid crystal is used as the optically active polymer of the optical element of the present invention. It can be used as a membrane.

In the optical elements of the first and second embodiments, in order to change the transmittance according to the polarization direction, the absorptance is changed according to the polarization direction or the diffraction efficiency is changed. However, there is no problem even if the transmittance is changed by changing the reflectance. For example, FIG. 10 shows a cross-sectional view of an optical element that changes the reflectance in the polarization direction. In FIG. 10, 101 is an obliquely evaporated film of tantalum oxide, 1
02 is a silicon dioxide thin film. Here, the oblique deposition film 1
Since 01 has birefringence, if a multilayer film is formed with the isotropic thin film 102, the reflectance can be changed according to the polarization direction. Also in this case, the polylactic acid film 22 and the ITO films 22 and 24 on both sides of the polylactic acid film 22 may be separated from the laminated body of the obliquely evaporated film 101 and the silicon dioxide thin film 102.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings. This embodiment is different from the above-described first embodiment in that second harmonic generation (SHG) including a near-infrared semiconductor laser as a light source and a quasi-phase-matching polarization inversion waveguide device is used. It is the same as the first embodiment except for using a blue laser (SHG light source) and changing the light amount at the time of recording with the optical element of the present invention. Therefore, in the present embodiment, those that are not particularly described are the same as those in the first embodiment, and constituent members given the same reference numerals as those in the first embodiment are used unless otherwise specified. It has the same function as that of the first embodiment.

FIG. 11 is a block diagram of an optical head according to the third embodiment of the present invention. In FIG. 11, 111
Is a light source, and is configured by using a second harmonic generation (SHG) blue laser (SHG light source) including a near-infrared semiconductor laser 112 and a polarization inversion waveguide device 113 of a quasi phase matching method. The optical element 3 is the one described in the first embodiment.

The operation of the optical head thus constructed will be described with reference to FIG. The linearly polarized light emitted from the light source 111 enters the first beam splitter 2. The light reflected by the first beam splitter 2 is incident on the first photodetector 12, and the transmitted light is incident on the optical element 3 of the present invention. Here, the light incident on the first photodetector 12 is converted into an electric signal and becomes an electric signal for monitoring the light amount emitted from the light source 111, and this signal is input to the light amount control circuit 15 to obtain the optimum light amount. The light source 111 is controlled so as to output Here, it is assumed that the light source 111 always emits a constant amount of light both during reproduction and during recording. Next, the light that has passed through the first beam splitter 2 and is incident on the optical element 3 of the present invention has its light amount attenuated in the case of reproduction, and the light amount attenuated in the case of recording a mark in the case of recording. If the mark is not recorded, the mark is attenuated to some extent (this will be described in detail later).

Most of the light transmitted through the optical element 3 of the present invention is transmitted by the diffraction grating 4 and a part thereof is diffracted. The light that has passed through the diffraction grating 4 (both the transmitted light and the diffracted light) is incident on the second beam splitter 5. The light reflected by the second beam splitter 5 is made incident on the first condenser lens 10, and is made incident on the second photodetector 13 by the condenser lens 10. Further, the light transmitted through the second beam splitter 5 is incident on the collimator lens 6.

Here, the signal output from the second photodetector 13 is the main signal because the light amount of the light emitted from the light source 1 is controlled by the first photodetector 12 and the light amount control circuit 15. The signal is a signal obtained by monitoring the transmittance of the optical element 3 of the invention. This signal is input to the optical element control circuit 16 and is controlled by the optical element control circuit 16 so that the transmittance of the optical element 3 of the present invention becomes optimum.

The light incident on the collimator lens 6 is collimated by the collimator lens 6. The light transmitted through the collimator lens 6 is reflected by the mirror 7, travels in a direction bent 90 degrees from the traveling direction thereof, and is condensed on the optical recording medium 9 by the objective lens 8.

Next, the process until the light reflected by the optical recording medium returns to the photodetector is the same as that described in the first embodiment, and therefore its explanation is omitted.

The third photodetector 14 outputs a focus error signal indicating the focused state of light on the optical recording medium 9 and a tracking error signal indicating the light irradiation position. In this case, for example, the phase difference method is used in the case of the read-only optical recording medium, and the tracking error signal is obtained in the case of the recording optical recording medium by the three-beam method using the sub-beam created by the diffraction grating 4. Based on the focus error signal, the focus control means (not shown) controls the position of the objective lens 8 in the optical axis direction so that the light is always focused on the optical recording medium 9. The tracking control means (not shown) controls the position of the objective lens 8 based on the tracking error signal so that the light is focused on a desired track on the optical recording medium 9. The information recorded on the optical recording medium 9 is also obtained from the third photodetector 14.

Here, it is considered that the light quantity change of writing the mark at the time of recording is performed by using the optical element 3 of the present embodiment. The light source 111 used in this embodiment is SHG.
The light source is a near infrared semiconductor laser 112 of this light source.
The conversion efficiency of the light (wavelength 810 nm) emitted from the light into the wavelength-converted light (wavelength 405 nm) is proportional to the amount of light incident on the quasi-phase matching polarization inversion waveguide device 113, and Since the quantity of converted light is proportional to the quantity of light emitted from the near-infrared semiconductor laser 112, the quantity of light converted in wavelength is the square of the quantity of light emitted from the near-infrared semiconductor laser 112. It will be proportional. Therefore, when recording is performed using an ordinary semiconductor laser light source, the recording signal input to the light source cannot be used as it is.

When the light emission amount of the semiconductor laser is changed to change the recording light amount, that is, when the light amount of the light input to the quasi-phase-matching polarization inversion waveguide device 113 is changed, the wavelength is slightly changed at the same time. To do. Here, since the polarization inversion waveguide device 113 is very sensitive to wavelength,
When used for recording, it is very difficult to perform stable recording because it is necessary to design the circuit in consideration of the wavelength variation. Therefore, the modulation of the light quantity is performed by using the optical element 3 of the present embodiment having a high response speed, and the light source 111 emits a DC-like constant light quantity (a quantity of light that the mark can write on the optical recording medium).

As described in the first embodiment, since the optical element 3 of the present invention can change the transmittance,
When writing a mark at the time of recording, the transmittance of the optical element 3 is set to 100%, and when the mark is not recorded, the transmittance of the optical element 3 is reduced to attenuate the light amount. Further, in the case of reproduction, the transmittance of the optical element 3 is lowered to reduce the light amount to such an extent that no mark is written on the optical recording medium. Further, since the response speed of the optical element 3 of the present invention is several GHz, it can correspond to the switching speed (several n seconds) required for recording.

As described above, by using the optical element of the present invention for light amount modulation at the time of recording, an optical head capable of recording by using a light source such as an SHG light source which is difficult to perform light amount modulation is provided. Can be configured.

Further, at the time of reproduction, the power of the light source is set to the power at which the quantum noise is sufficiently lowered, and the transmittance of the optical element of the present invention is lowered to reduce the surface power of the optical recording medium and erase the data. It is possible to perform reproduction while suppressing to a low power that does not cause noise, and it is also possible to perform modulation at the time of recording with this element.

Therefore, the light source is required to always emit a constant amount of light both during reproduction and during recording, so that stability with respect to temperature and the like increases. Also, since the switching of transmittance is very fast,
Recording can be performed instantly after address reproduction. Moreover, since the transmittance is switched by an electric signal from the outside, it is easy to miniaturize the optical head.

Although the SHG light source is used as the light source in the above description, there is no problem even if the semiconductor laser used in the first embodiment is used.

Although the non-polarization optical system is used in the first to third embodiments, there is no problem even if the polarization optical system is used.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to the drawings. The present embodiment is different from the above-described first embodiment in that the optical system of the optical head is a polarization optical system and that the optical element has a configuration not including the analyzer film 25 in FIG. Other than that, it is similar to the first embodiment. Therefore, in the present embodiment, those that are not particularly described are the same as those in the first embodiment, and constituent members given the same reference numerals as those in the first embodiment are used unless otherwise specified. It has the same function as that of the first embodiment.

In FIG. 12, reference numeral 121 denotes a polylactic acid film (not shown, but an ITO film is provided on both surfaces), 12
Reference numeral 2 is a polarization beam splitter, and 123 is a quarter wavelength plate. Here, the condensing optical system is composed of a collimator lens 6 and an objective lens 8, and the light quantity control means is composed of a first photodetector 12 and a light quantity control circuit 15.
The optical element control means is composed of the second photodetector 13 and the optical element control circuit 16, and the polarization separation means is composed of the polarization beam splitter 122 and the quarter wave plate 123.

Here, the polarization beam splitter 122 transmits 100% of the linearly polarized light emitted from the light source 1,
1 linearly polarized light in a direction orthogonal to the linearly polarized light emitted from
00% reflection. The quarter-wave plate 123 is an optical element that converts linearly polarized light into circularly polarized light, and is made of, for example, a birefringent material such as quartz. Here, a quarter wave plate is used, but an L / 4 wave plate (L is an odd number of 1 or more) may be used.

The operation of the optical head thus constructed will be described with reference to FIG. The linearly polarized light emitted from the light source 1 enters the first beam splitter 2.
The light reflected by the first beam splitter 2 is incident on the first photodetector 12, and the transmitted light is incident on the polylactic acid film 121. Here, the light incident on the first photodetector 12 is converted into an electric signal and becomes an electric signal for monitoring the quantity of light emitted from the light source 1, and this signal is the light quantity control circuit 1
The light source 1 is controlled so that the light amount is input to the light source 5 and outputs the optimum amount of light.

Next, the light that has passed through the first beam splitter 2 and is incident on the polylactic acid film 121, in the case of reproduction,
It is converted to linearly polarized light that rotates the polarization direction by a certain angle,
In the case of recording, it is converted into linearly polarized light rotated by an angle different from that during reproduction. Most of these lights are transmitted by the diffraction grating 4 and a part thereof is diffracted. The light transmitted through the diffraction grating 4 (transmitted light and diffracted light) is incident on the polarization beam splitter 122. Here, the separation of transmitted light and reflected light differs depending on the rotation angle of linearly polarized light. That is, the amount of light that passes through the polarization beam splitter 122 changes during reproduction and during recording. (More on this later).
The light reflected by the polarization beam splitter 122 is incident on the first condenser lens 10, and is incident on the second photodetector 13 by the first condenser lens 10. Further, the light transmitted through the polarization beam splitter 122 is incident on the collimator lens 6.

Here, the signal output from the second photodetector 13 is such that the light amount of the light emitted from the light source 1 is controlled by the first photodetector 12 and the light amount control circuit 15. The signal is obtained by monitoring the polarization direction of linearly polarized light rotated by the polylactic acid film 121. This signal is input to the optical element control circuit 16 and is controlled by the optical element control circuit 16 so that the optical rotation of the polylactic acid film 121 is optimized. The light incident on the collimator lens 6 is
Is converted into parallel light by and is incident on the quarter-wave plate 123. The linearly polarized light is converted to circularly polarized light by the quarter-wave plate 123, and the circularly polarized light is reflected by the mirror 7 and travels in a direction bent 90 degrees from the traveling direction thereof, and then is directed onto the optical recording medium 9 by the objective lens 8. Collected.

Next, the light reflected from the optical recording medium 9 passes through the objective lens 8, is reflected by the mirror 7, and enters the ¼ wavelength plate 123. The circularly polarized light is converted by the quarter-wave plate 123 into linearly polarized light having a polarization direction orthogonal to the polarization direction of the linearly polarized light emitted from the light source 1, passes through the collimator lens 6, and is polarized by the polarization beam splitter 122. It is reflected and is condensed by the second condenser lens 11 and
Is incident on the photodetector 14 of. The third photodetector 14 is
A focus error signal indicating the focused state of light on the optical recording medium 9 is output, and a tracking error signal indicating the light irradiation position is output. In this case, for example, the phase difference method is used in the case of the read-only optical recording medium, and the tracking error signal is obtained in the case of the recording optical recording medium by the three-beam method using the sub-beam created by the diffraction grating 4.

The focus control means (not shown) controls the position of the objective lens 8 in the optical axis direction based on the focus error signal so that the light is always focused on the optical recording medium 9 in a focused state. The tracking control means (not shown) controls the position of the objective lens 8 based on the tracking error signal so that the light is focused on a desired track on the optical recording medium 9. The information recorded on the optical recording medium 9 is also obtained from the third photodetector 14.

Here, it will be described in detail that the light amount of the light passing through the polarization beam splitter 122 changes during reproduction and during recording. The polylactic acid film 121 has the optical rotatory power as described above, and the optical rotatory power changes according to the voltage applied from the outside. Therefore, when regenerating, polylactic acid film 12
A voltage of V3 is applied to 1 so that the polarization direction of the linearly polarized light transmitted through the polylactic acid film 121 is rotated by the angle a from the polarization direction of the linearly polarized light of the incident light. This is shown in Figure 13A.

When recording, V is applied to the polylactic acid film 121.
A voltage of 4 is applied so that the polarization direction of the linearly polarized light transmitted through the polylactic acid film 121 is rotated by an angle b from the polarization direction of the linearly polarized light of the incident light. This is shown in FIG. 13B.
Is shown in.

This rotated light is incident on the polarization beam splitter 122. In the polarization beam splitter 122, the light amount It (reproduction) of transmitted light and the light amount Ir (reproduction) of reflected light and recording in the case of reproduction are performed. In the case of, the transmitted light amount It (recording) and the reflected light amount Ir (recording) are
The quantity of incident light is I, the transmittance of the polarization beam splitter 122 for polarized light emitted from the light source 1 is T1, the reflectance is R1, and the transmittance for linearly polarized light orthogonal to the polarized light emitted from the light source 1 is T2. When the reflectance is R2, it is expressed as follows.

[0140]   It (reproduction) = T1 × I × cos (a) + T2 × I × sin (a) (Equation 1)   Ir (reproduction) = R1 × I × cos (a) + R2 × I × sin (a) (Equation 2)   It (record) = T1 × I × cos (b) + T2 × I × sin (b) (Equation 3)   Ir (record) = R1 × I × cos (b) + R2 × I × sin (b) (Equation 4)

Therefore, if the transmittance and the reflectance of the polarization beam splitter 122 are set as described above and the angle a is set to 60 degrees, 40% of the amount of light from the light source is transmitted and 60% is reflected. Further, when the angle b is set to 25 degrees, almost 90% of the amount of light from the light source is transmitted and 10% is reflected. In this way, by applying different voltages to the polylactic acid film 121 during reproduction and during recording, it is possible to change the amount of light transmitted through the polarization beam splitter.

Further, as described in the first embodiment,
Consider not applying a voltage or short-circuiting during reproduction or recording in order to stabilize the optical rotation. A cross-sectional view of an optical element that does this is shown in FIG. Figure 1
In FIG. 4, 141 is the first glass and 142 is the first I
TO film, 143 is polylactic acid film, 144 is second ITO
The film, 145 is a half-wave plate, and 146 is a second glass. Here, the same voltage is applied to the first and second ITO films 142 and 144 so that no voltage is applied to the polylactic acid film 143. At this time, the optical rotation due to the deviation of the film thickness of the polylactic acid film 143. It is possible to correct the shift amount by providing the half-wave plate 145. Since this has been described in the first embodiment, description thereof will be omitted.

With the above arrangement, the power of the light source during reproduction is set to a power at which the quantum noise is sufficiently low, and the transmittance of the polarization beam splitter 122 is reduced to reduce the surface power of the optical recording medium. It is possible to perform reproduction while suppressing to a low power that does not cause deterioration or data deletion, and at the time of recording, the power of the light source can be used considerably by recording by setting the transmittance of the polarization beam splitter 122 to 90%. it can. Also, since the transmittance is switched very quickly, it is possible to record immediately after the address reproduction. Moreover, since the transmittance is switched by an electric signal from the outside, it is easy to miniaturize the optical head. Further, since the polarization optical system is used, the amount of light emitted from the light source can be used efficiently.

In the above example, the polarization beam splitter 122 transmits 100% of the linearly polarized light emitted from the light source 1 in the same direction as the linearly polarized light emitted from the light source 1 and is orthogonal to the linearly polarized light emitted from the light source 1. Although it has a characteristic of 100% reflection with respect to polarized light, the amount of light transmitted through the polarization beam splitter 142 is as shown in (Equation 1) to (Equation 4). The rate may be other than the above values.

Also, the polylactic acid film 121 and the half-wave plate 1
An optical element (see FIG. 14) in which 45 is integrated is used,
It goes without saying that the same effect can be obtained even if the polylactic acid film and the half-wave plate are separately arranged. In this case, the half-wave plate can be rotated and removed after the rotation deviation of the linearly polarized light emitted from the light source is incorporated in the optical head, which is advantageous. In addition, in the structure shown in FIG.
It is possible to perform the modulation at the time of recording as described in the above embodiment.

Further, the optical head of the fourth embodiment uses the polarization optical system, but even the non-polarization optical system has no problem if it has a polarization beam splitter and changes the transmittance.

Further, although the optical elements of the present invention described in the above first to fourth embodiments have a structure in which they are sandwiched by glass, it is only performed to improve reliability. Does not mean that there is no need.

Although the optical element of the present invention is not coated with a non-reflective coating, it is advantageous to provide a non-reflective coating because the loss in the optical element is eliminated.

(Fifth Embodiment) In the fifth embodiment,
An example of the optical recording / reproducing apparatus of the present invention will be described. Fifth
The optical recording / reproducing device of the embodiment is a device for recording / reproducing a signal on / from an optical recording medium. FIG. 15 schematically shows the configuration of the optical recording / reproducing device 150 of the fifth embodiment. The optical recording / reproducing device 150 includes an optical head 151, a motor 152, and a processing circuit 153. Optical head 1
Reference numeral 51 has been described in the first embodiment. Since the optical head 151 is the same as that described in the first embodiment, duplicated description will be omitted.

Next, the operation of the optical recording / reproducing apparatus 150 will be described. First, when the optical recording medium 9 is set in the optical recording / reproducing device 150, the processing circuit 153 outputs a signal for rotating the motor 152 to rotate the motor 152.
Next, the processing circuit 153 drives the light source 1 to emit light, and gives a command to the light amount control circuit 15 to control the emitted light amount. Further, a command is also given to the optical element control circuit 16 so that the transmittance of the optical element 3 becomes an optimum value during reproduction and recording. The light emitted from the light source 1 is reflected by the optical recording medium 9 and enters the third photodetector 14. Third
The photodetector 14 outputs the focus error signal indicating the focused state of light on the optical recording medium 9 and the tracking error signal indicating the irradiation position of the light to the processing circuit 153. Based on these signals, the processing circuit 153 outputs a signal for controlling the objective lens 8 to focus the light emitted from the light source 1 on a desired track on the optical recording medium 9. Further, the processing circuit 153 reproduces the information recorded in the optical recording medium 9 based on the signal output from the third photodetector 14.

As described above, since the first optical head of the embodiment is used as the optical head 151, the optical power of the present invention is set while the power of the light source is set to the power at which the quantum noise becomes sufficiently low during reproduction. By lowering the transmittance of the element 3, it is possible to perform reproduction while suppressing the board power to a low power that does not cause deterioration of the optical recording medium or erasure of data, and at the time of recording, the transmittance of the optical element 3 of the present invention is reduced. By setting the power to 100%, it is possible to configure an optical recording / reproducing apparatus capable of recording by using the power of the light source as it is.

Also, since it is possible to reproduce by reducing the quantum noise of the light source, an optical recording / reproducing apparatus which can obtain stable control signals and reproduced signals can be constructed. Also, since the transmittance is switched very quickly, it is possible to record immediately after the address reproduction. Moreover, since the transmittance is switched by an electric signal from the outside, the optical head can be easily miniaturized, which is suitable for miniaturization of the optical recording / reproducing apparatus.

Although the optical head of the first embodiment is used as the optical head, there is no problem even if the optical heads described in the second to fourth embodiments are used. Furthermore,
By using the optical head of the third embodiment, stable recording is possible.

Although the objective lens 8 is a single lens, there is no problem even if it is a compound lens having a high NA. Further, the use of a lens with a high NA enables a higher density, and the stability of the reproduced signal against the noise of the light source becomes strict, so the present invention is very useful.

Although the embodiments of the present invention have been described above with reference to the examples, the present invention is not limited to the above-described embodiments and can be applied to other embodiments based on the technical idea of the present invention. it can.

Further, although the infinite optical head is shown in the first to fifth embodiments, a finite optical head not using a collimator lens may be used.

In the first to fifth embodiments described above, the optical recording medium in which information is recorded only by light has been described.
It is needless to say that the same effect can be obtained by using the optical element of the present invention for an optical recording medium that records information by light and magnetism.

Although the polylactic acid film is used as the optically active polymer film, any material can be used as long as the optical rotation of the film changes depending on the voltage applied from the outside, and for example, a polysilane film may be used.

In the above embodiments, the case where the optical recording medium is an optical disk has been described, but the present invention can be applied to an optical information recording / reproducing apparatus that realizes a similar function such as a card-shaped optical recording medium. .

As described above, the polylactic acid film has the same function as liquid crystal. Further, by combining with the transmittance polarization anisotropic portion, the transmittance of incident light can be changed according to the voltage applied from the outside. Therefore, the polylactic acid film can be applied to a video device. In this case, the image can be switched faster than the image device using the liquid crystal, so that it is possible to realize the image device in which the afterimage at the time of image switching is hardly noticed.

The optical heads of Embodiments 1 to 5 described above are provided with an optical element having an optically active polymer film whose optical rotation is changed by an electric signal. A polylactic acid film has been illustrated as an example of such an optically active polymer film. However, the optical rotation of the polylactic acid film with respect to the applied voltage varies greatly depending on its manufacturing method. For example, JP-A-9-266918
In a method of heating to a temperature below the melting point above the glass transition point and stretching as disclosed in Japanese Patent Laid-Open Publication, the orientation of polylactic acid is not oriented in a certain direction, so the crystallinity is low and the voltage applied from the outside The optical rotation hardly changes even when applied, and it cannot be used as the optically active polymer film of the present invention.

Therefore, a method for producing an optically active polymer film, which enables formation of an optical element that enables switching between recording and reproduction in a shorter time and is easy to mass-produce, will be described below. To do.

(Embodiment 6) In Embodiment 6, an example of the method for producing an optically active polymer film of the present invention will be described.

16A to 16E are process diagrams showing a method for producing a polylactic acid film which is an example of an optically active polymer.
Here, 201 is a first glass substrate, 202 is a second glass substrate, 203 is a first ITO (indium-tin-oxide alloy) film, 204 is a second ITO film, 205 is a filler, and 206 is Powdered polylactic acid, 207 is molten polylactic acid, and 208 is a thinned polylactic acid film.
Here, the first and second ITO films 203 and 204 are
It is a conductive transparent thin film, and the filler 205 is a glass sphere whose size is strictly controlled.

The polylactic acid film 2 will be described with reference to FIGS. 16A to 16E.
The manufacturing method of No. 08 will be described. First, the first and second
First and second ITO films 203 and 204, which are conductive transparent thin films, are formed on one surface of the glass substrates 201 and 202 by sputtering (FIG. 16A). Next, a polylactic acid powder 206 (or pellet) is placed on the first ITO film 203 formed on the first glass substrate 201,
Furthermore, a filler 205 for determining the size (for example, a thickness of 300 μm) of the gap between the first and second glass substrates 201 and 202 is arranged. This void determines the thickness of the manufactured polylactic acid film 208. Further, the second glass substrate 202 is arranged so that the second ITO film 204 faces the first ITO film 203 (FIG. 16).
B). Next, in this state, the polylactic acid 206 in the powder state is heated to a temperature equal to or higher than the melting point (for example, 180 ° C.) to form the polylactic acid 207 in the molten state (FIG. 16C). The upper limit of the heating temperature at this time is not particularly limited, but it is preferably 250 ° C. or lower in order to prevent thermal decomposition of polylactic acid. By this step, the polylactic acid is in a liquid state, so that the polylactic acid molecules vibrate randomly. next,
A voltage (for example, 6 kV / mm) is applied to the first and second ITO films 203 and 204 in order to apply an electric field to the polylactic acid while the polylactic acid is molten (FIG. 16D). Through this step, the direction of the molecules of polylactic acid can be maintained in the direction parallel to the electric field generated by the voltage applied from the random direction (the direction perpendicular to the glass substrates 201 and 202). Next, cooling is performed with a voltage applied to form a thin film of polylactic acid (FIG. 16E). By this step, it becomes possible to solidify the polylactic acid while keeping the direction of the molecules of the polylactic acid in the direction perpendicular to the substrate.

Next, a filler 205 is placed between the first and second glass substrates 201 and 202 to form the polylactic acid film 20.
Controlling the thickness of No. 8 will be described. Polylactic acid film 2
Since the optical rotatory power of 08 is as high as 7200 ° / mm, the optical rotatory power of the polylactic acid film 208 greatly changes depending on its thickness. Therefore, when it is desired to set the initial optical rotation to a certain value, for example, 0 degree (which is an integral multiple of 360 degrees), it is necessary to control the thickness of the polylactic acid film 208, and it is easy to use the filler 205. Moreover, the thickness of the polylactic acid film can be controlled.

Next, the filler 205 will be described. As shown in FIG. 16E, the filler 205 is also present in the region through which light is transmitted, so considering the light utilization efficiency,
It is better that the transmittance is close to 100%. Further, it is preferable that the refractive index of the filler 205 is almost equal to that of polylactic acid. Specifically, it is preferable that the difference in refractive index between the two is 0.3 or less. If the refractive indexes of the filler 205 and polylactic acid are significantly different, reflection occurs at the interface between the filler and polylactic acid, resulting in poor light utilization efficiency. However, in the case where the filler is arranged at a place where light does not pass, the transmittance and the refractive index may be any. Although the filler is made of glass, it may be made of plastic. Further, the glass transition point of this filler needs to be higher than the melting point of polylactic acid.

The polylactic acid film 208 formed by such a manufacturing method has a very good molecular orientation, and thus has a very good crystallinity, and the optical rotation greatly changes according to the voltage applied from the outside. For example, when 50 V is applied, the optical rotation changes by 90 degrees. If there is such a large change, it can be used as an optical element of the above-described optical head. Furthermore, since the change time of the optical rotation of the polylactic acid film is several nanoseconds, when the optical element using the polylactic acid film manufactured by the manufacturing method described in this embodiment is mounted on the optical head, it is very fast. It is possible to switch from playback to recording. In addition, in this manufacturing method, a large-area polylactic acid film is formed instead of forming small optical elements one by one, and then the optical element having a required size is formed by cutting, which facilitates mass production. Is.

Here, the cooling in the step of FIG. 16E may be slow cooling or rapid cooling. The reason for this is that the crystallinity is not affected by the cooling method because the direction of the molecules of polylactic acid is determined by the electric field applied from the outside. Here, when the polylactic acid film is formed by slow cooling, internal stress does not remain in the polylactic acid film, so that the change in the transmitted wavefront of the optical element using the polylactic acid film with respect to the temperature change becomes small. In the case of rapid cooling, the cooling time may be short, so that the production time of the polylactic acid film is shortened. In addition, the transparency of the polylactic acid film is improved when it is rapidly cooled.

Although a DC voltage is applied in the step of FIG. 16D, there is no problem even if AC voltage is applied.

Here, in the present embodiment, the polylactic acid in the powder state is placed between the first and second substrates and then heated to be in a molten state. However, the polylactic acid in the film is placed and then heated. It may be in a molten state, or polylactic acid that has been in a molten state in another step may be poured between the substrates. here,
In the case of disposing solid polylactic acid as described in the present embodiment, it is easy to dispose a desired weight of polylactic acid between the substrates. In particular, when polylactic acid in a powder state is placed, weight control is easier.

(Embodiment 7) Next, a method for producing a polylactic acid film according to a seventh embodiment of the present invention will be described with reference to the drawings. The present embodiment is different from the above-described sixth embodiment only in that the method for controlling the alignment state of the molecules of polylactic acid is different, and other than that, the sixth embodiment is different.
This is the same as the embodiment. Therefore, in the present embodiment, those which are not particularly described are the same as those in the sixth embodiment, and components having the same reference numerals as those in the sixth embodiment are, unless otherwise specified, It has the same function as that of the sixth embodiment.

17A to 17E are process drawings showing a method for producing an optically active polymer film according to the seventh embodiment of the present invention.

A method of manufacturing the polylactic acid film 208, which is an example of the optically active polymer film, will be described with reference to FIGS. 17A to 17E. First, the first and the second I, which are conductive transparent thin films, are formed on one surface of the first and second glass substrates 201 and 202.
The TO films 203 and 204 are formed by sputtering (FIG. 17A). Next, polylactic acid powder 206 is formed on the first ITO film 203 formed on the first glass substrate 201.
(Or pellets) are arranged, and further a filler 205 for deciding the size of the voids of the first and second glass substrates 1 and 2 is arranged. This void determines the thickness of the manufactured polylactic acid film 208. Further the second I
The second glass substrate 202 is arranged so that the TO film 204 faces the first ITO film 203 (FIG. 17B). Next, in this state, the powdery polylactic acid 206 is heated to a temperature equal to or higher than the melting point of the powdery polylactic acid 206 so that the powdery polylactic acid 20 is melted.
7 (FIG. 17C). By this step, the polylactic acid is in a liquid state, so that the polylactic acid molecules vibrate randomly. Next, while the polylactic acid is molten, ultrasonic waves 210 are applied to the polylactic acid from the outer surfaces of the first and second glass substrates 201 and 202 so as to face each other (FIG. 17).
D). By this step, the standing wave of the ultrasonic wave can be formed in the place where the polylactic acid exists, so that the direction of the molecules of the polylactic acid is changed from the random direction to the direction of the standing wave of the ultrasonic wave (here, the glass substrate 201). And the direction perpendicular to 202)
Can be arranged in. Next, cooling is performed in a state where a standing wave of ultrasonic waves is formed to form a thin film of polylactic acid (FIG. 17E).
By this step, it becomes possible to solidify the polylactic acid while keeping the direction of the molecules of the polylactic acid in the direction perpendicular to the substrate.

The polylactic acid film 208 formed by such a manufacturing method has a very good molecular orientation, so that the crystallinity is very good, and the optical rotation greatly changes according to the voltage applied from the outside. For example, when 50 V is applied, the optical rotation changes by 90 degrees. If there is such a large change, it can be used as an optical element of the above-described optical head. Furthermore, since the change time of the optical rotation of the polylactic acid film is several nanoseconds, when the optical element using the polylactic acid film manufactured by the manufacturing method described in this embodiment is mounted on the optical head, it is very fast. It is possible to switch from playback to recording. In addition, in this manufacturing method, a large-area polylactic acid film is formed instead of forming small optical elements one by one, and then the optical element having a required size is formed by cutting, which facilitates mass production. Is.

Here, the cooling in the step of FIG. 17E may be slow cooling or rapid cooling. The reason for this is that the crystallinity is not affected by the cooling method because the direction of the polylactic acid molecule is determined by the ultrasonic waves applied from the outside. Here, when the polylactic acid film is formed by slow cooling, internal stress does not remain in the polylactic acid film, so that the change in the transmitted wavefront of the optical element using the polylactic acid film with respect to the temperature change becomes small. In the case of rapid cooling, the cooling time may be short, so that the production time of the polylactic acid film is shortened. Also,
The transparency of the polylactic acid film is improved when it is rapidly cooled.

Here, in the step of FIG. 17D, opposing ultrasonic waves are applied and the standing waves of ultrasonic waves are formed by the interference, but as shown in FIG. 18, the outer surface of the second glass substrate 202 is The ultrasonic wave is applied from the side, the ultrasonic wave is reflected by the reflector 212 installed on the outer surface side of the first glass substrate 201, and the standing wave is formed by the interference between the ultrasonic wave 201 and the reflected wave 210 ′. Is also good.

When ultrasonic waves are applied from the front and back of the polylactic acid film as in this embodiment, the phase and magnitude of the ultrasonic waves are controlled for each of the ultrasonic waves applied from the front and back. It is easy to control the standing wave applied to the polylactic acid film. Further, when the ultrasonic wave is reflected, only one control of the ultrasonic wave is required, so that the circuit configuration of the standing wave control of the ultrasonic wave becomes simple.

(Embodiment 8) Next, an eighth embodiment of the present invention will be described with reference to the drawings. The present embodiment is different from the above-described sixth embodiment only in that the method for controlling the alignment state of the molecules of polylactic acid is different, and other than that is similar to the sixth embodiment. Is.
Therefore, in the present embodiment, those which are not particularly described are the same as those in the sixth embodiment, and components having the same reference numerals as those in the sixth embodiment are, unless otherwise specified, It has the same function as that of the sixth embodiment.

19A to 19F are process drawings showing a method for producing an optically active polymer film according to the eighth embodiment of the present invention.

A method of manufacturing the polylactic acid film 208, which is an example of the optically active polymer film, will be described with reference to FIGS. 19A to 19F. First, the first and the second I, which are conductive transparent thin films, are formed on one surface of the first and second glass substrates 201 and 202.
The TO films 203 and 204 are formed by sputtering (FIG. 19A). Next, polylactic acid powder 206 is formed on the first ITO film 203 formed on the first glass substrate 201.
(Or pellets) are arranged, and filler 205 for determining the size of the voids of the first and second glass substrates 201 and 202 is further arranged. This void determines the thickness of the manufactured polylactic acid film 208. Further, the second glass substrate 202 is arranged so that the second ITO film 204 faces the first ITO film 203 (FIG. 19).
B). Next, in this state, the polylactic acid 206 in the powder state is heated to a temperature equal to or higher than the melting point of the polylactic acid 206 in the powder state to form the polylactic acid 207 in the molten state (FIG. 19C). By this step, the polylactic acid is in a liquid state, so that the polylactic acid molecules vibrate randomly. Next, the polylactic acid film 208 is formed by cooling and solidifying (FIG. 19D). Here, the orientation direction of the molecules of polylactic acid is a random direction. Next, the ultrasonic waves 214 are converged on a part of the polylactic acid film 8 using the lens 216 (FIG. 19E). As a result, a part of the polylactic acid film 208 is melted by the energy of the ultrasonic waves 214, and the vibration of the ultrasonic waves holds the orientation direction of the molecules of the polylactic acid film 208 in a desired direction. Next, the focused ultrasonic wave 214
Are moved parallel to the surface of the second glass substrate 202 (FIG. 19F). As a result, the position where the ultrasonic waves 214 are converged is moved and rapidly cooled, so that the ultrasonic waves are solidified while maintaining the molecular orientation state. Next, at the newly moved position, the polylactic acid is melted in the same manner as described above, and the orientation direction of the molecules becomes the desired direction.

The polylactic acid film 208 formed by such a manufacturing method has very good molecular orientation, and thus has very good crystallinity, and its optical rotation greatly changes according to the voltage applied from the outside. For example, when 50 V is applied, the optical rotation changes by 90 degrees. If there is such a large change, it can be used as an optical element of the above-described optical head. Furthermore, since the change time of the optical rotation of the polylactic acid film is several nanoseconds, when the optical element using the polylactic acid film manufactured by the manufacturing method described in this embodiment is mounted on the optical head, it is very fast. It is possible to switch from playback to recording. In addition, in this manufacturing method, a large-area polylactic acid film is formed instead of forming small optical elements one by one, and then the optical element having a required size is formed by cutting, which facilitates mass production. Is.

Here, in this embodiment, after the polylactic acid in the powder state is placed between the first and second substrates, the polylactic acid of the film is placed between the substrates by heating to a molten state and then cooling. However, the polylactic acid of the film formed in another step may be arranged, or the polylactic acid in the powder state may be arranged and the ultrasonic waves may be partially applied as it is.

Here, if polylactic acid in a powder state is arranged between the substrates as described in the present embodiment, the weight control of polylactic acid is easy. In the case of arranging the polylactic acid of the film formed in another step, since the polylactic acid film with good orientation is formed by melting a part of the film,
The thickness of the produced polylactic acid film having good orientation is the thickness of this film. Therefore, it becomes possible to form a void of a desired size without using a separate member (filler 205).

Although the embodiment of the method for producing an optically active polymer film of the present invention has been described above with reference to the examples, the present invention is not limited to the above-mentioned embodiments and is based on the technical idea of the present invention. Can be applied to the embodiment.

Further, in the above sixth to eighth embodiments, the polylactic acid is applied with an electric field or an ultrasonic wave in a molten state to control the molecular arrangement of the polylactic acid, but the same effect can be obtained by controlling by another method. It goes without saying that it will be done.

In the sixth to eighth embodiments, the filler is used to control the thickness of the void in the glass substrate, but it is not always necessary.

Although polylactic acid is used as the optically active polymer in the sixth to eighth embodiments, there is no problem even if another substance is used.

Since polylactic acid can instantly switch the polarization direction of incident light on the basis of an external signal, it can be used for an apparatus (monitor, etc.) or device using liquid crystal. Is faster than liquid crystal, which improves device and device characteristics.

[0190]

The optically active polymer film in the optical element according to the present invention can change the polarization direction of the incident light according to the applied voltage and emit the light.

Therefore, in the optical element of the present invention in which the optically active polymer film is combined with the transmittance polarization anisotropic portion, the amount of light to be transmitted can be switched at high speed.

Further, in the optical element of the present invention in which the optically active polymer film thickness correcting section is combined with this optically active polymer film, linearly polarized light having a desired polarization direction is shorted without applying an external voltage. It becomes possible to obtain it.

The optical head of the present invention is provided with the above-mentioned optical element of the present invention, so that the power of the light source is set to the power at which the quantum noise is sufficiently lowered, and the surface power of the optical disk is deteriorated or the data is erased. It is possible to perform reproduction while suppressing to a low power that does not cause such a phenomenon, and at the time of recording, it is possible to perform recording by using the power of the light source as it is. Moreover, recording and reproduction can be switched instantly, which is suitable for downsizing.

Further, when the optical element has the optically active polymer film thickness correction section, the stability of the characteristics of the optical head is improved.

Furthermore, the optical recording / reproducing apparatus of the present invention can switch recording and reproduction instantaneously, and is suitable for downsizing and high-density recording.

The method for producing an optically active polymer film of the present invention is suitable for forming the above-mentioned optical element of the present invention and facilitates mass production of the optically active polymer film.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an optical head according to a first embodiment of the invention.

FIG. 2 is a sectional view showing an example of the optical element according to the first embodiment of the present invention.

3A and 3B are views for explaining changes in the polarization direction of linearly polarized light before and after transmission by a voltage applied to the optically active polymer film of the present invention.

FIG. 4 is a sectional view showing another example of the optical element according to the first embodiment of the present invention.

5A and 5B are views for explaining the relationship between the polarization direction of linearly polarized light and the direction of the azimuth axis of the half-wave plate before and after transmission in the optical element shown in FIG.

FIG. 6 is a sectional view showing still another example of the optical element according to the first embodiment of the present invention.

FIG. 7 is a schematic diagram showing an example of an optical head according to a second embodiment of the invention.

FIG. 8 is a sectional view showing an example of an optical element according to a second embodiment of the present invention.

FIG. 9 is a cross-sectional view showing another example of the optical element according to the second embodiment of the present invention.

FIG. 10 is a sectional view showing still another example of the optical element of the present invention.

FIG. 11 is a schematic diagram showing an example of an optical head according to a third embodiment of the invention.

FIG. 12 is a schematic diagram showing an example of an optical head according to a fourth embodiment of the invention.

13A and 13B are views for explaining the polarization directions of linearly polarized light before and after transmission in the optical element according to the fourth embodiment of the present invention.

FIG. 14 is a sectional view showing an example of an optical element according to a fourth embodiment of the present invention.

FIG. 15 is a schematic diagram showing an example of an optical recording / reproducing apparatus of the present invention.

16A to 16E are cross-sectional views showing an example of a method for manufacturing a polylactic acid film according to Embodiment 6 of the present invention in the order of steps.

17A to 17E are cross-sectional views showing an example of a method for manufacturing a polylactic acid film according to Embodiment 7 of the present invention in the order of steps.

FIG. 18 is a diagram showing another example of a method for forming a standing wave of ultrasonic waves in the seventh embodiment of the present invention.

FIG. 19A to FIG. 19F are cross-sectional views showing an example of a method for producing a polylactic acid film according to Embodiment 8 of the present invention in the order of steps.

FIG. 20 is a schematic diagram showing an example of a conventional optical head.

[Explanation of symbols]

1 light source 2 First beam splitter 3,71 Optical element 4 diffraction grating 5 Second beam splitter 6 Collimator lens 7 mirror 8 Objective lens 9 Optical recording medium 10 First condenser lens 11 Second condenser lens 12 First photodetector 13 Second photodetector 14 Third photodetector 15 Light intensity control circuit 16 Optical element control circuit 17 Optical head 21, 61, 91, 141, 201 First glass 22, 62, 92, 142, 203 First ITO film 23, 63, 65, 143, 208 Polylactic acid film 24, 64, 94, 144, 204 Second ITO film 66 Third ITO film 25 Analyzer membrane 26, 67, 95, 146, 202 Second glass 41,145 1/2 wave plate 81 Polarization hologram 82 Polyimide film 83 UV curable resin 93 LCD 101 Tantalum oxide oblique deposition film 102 Silicon dioxide thin film 111 light source 112 Near infrared semiconductor laser 113 Polarization Inverted Waveguide Device 121 Polylactic acid film 122 Polarizing beam splitter 123 1/4 wave plate 150 Optical recording / reproducing apparatus 151 optical head 152 motor 153 processing circuit 205 filler 206 Polylactic acid in powder form 207 Polylactic acid in molten state 210, 214 Ultrasound 210 'Ultrasonic reflected wave 212 reflector 216 lens

Continued front page    (72) Inventor Shinichi Kadowaki             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Hiroaki Yamamoto             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Daisuke Ogata             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2H049 BA05 BA27 BA42 BA47 BB03                       BB62 BC09 BC21                 2K008 AA00 DD12 DD23 EE01                 4F100 AK01A AK41A AR00B AR00C                       AR00D AR00E BA05 BA06                       GB41 JG01B JG01C JN01B                       JN01C JN06D JN06E JN08D                       JN08E JN10D JN10E JN18D                       JN18E JN30A                 5D090 AA01 BB05 CC16 FF11 HH01                       LL03                 5D119 AA01 AA09 AA21 AA22 BA01                       BB04 JA63

Claims (41)

[Claims] 1. An optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and an optically active polymer film disposed on both sides of the optically active polymer film for applying a voltage to the optically active polymer film. A conductive transparent thin film, and one of the conductive transparent thin films, which is disposed on a side opposite to the optically active polymer film, and has a transmittance polarization anisotropic portion having a different transmittance with respect to a polarization direction. An optical element characterized by the above. 2. An optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and an optically active polymer film disposed on both sides of the optically active polymer film for applying a voltage to the optically active polymer film. A conductive transparent thin film, and one of the conductive transparent thin films, which is arranged on the side opposite to the optically active polymer film, has an optical activity high value for correcting optical rotation caused by a film thickness deviation of the optically active polymer film. An optical element comprising: a molecular film thickness correction unit. 3. An optically active polymer film whose optical rotation changes with respect to a voltage applied from the outside, and an optically active polymer film disposed on both sides of the optically active polymer film for applying a voltage to the optically active polymer film. A conductive transparent thin film, and one of the conductive transparent thin films, which is arranged on the side opposite to the optically active polymer film, has an optical activity high value for correcting optical rotation caused by a film thickness deviation of the optically active polymer film. Molecular thickness correction unit, the optically active polymer film thickness correction unit, the transparent transparent thin film, which is arranged on the opposite side of the conductive transparent thin film, the transmittance polarization anisotropy unit having different transmittance with respect to the polarization direction, An optical element having: 4. The optical element according to claim 1, wherein the optically active polymer film is composed of a polylactic acid film. 5. The optical element according to claim 1, wherein a change in the transmittance of the transmittance-polarization anisotropic portion is caused by a change in the absorptance depending on the polarization direction. 6. The optical element according to claim 5, wherein the transmittance polarization anisotropy portion is composed of an analyzer film. 7. The optical element according to claim 1, wherein the change of the transmittance of the transmittance polarization anisotropic portion is caused by the change of the diffraction efficiency depending on the polarization direction. 8. The optical element according to claim 7, wherein the transmittance polarization anisotropic portion is composed of a polarization hologram. 9. The optical element according to claim 1, wherein the change of the transmittance of the transmittance polarization anisotropic portion is caused by the change of the reflectance depending on the polarization direction. 10. The polarization anisotropy portion for transmittance is composed of a multilayer film including a birefringent film.
The optical element described. 11. The optical active polymer film thickness correction unit is K /
The optical element according to claim 2 or 3, wherein the optical element comprises a two-wave plate (K is an odd number of 1 or more). 12. The optical element according to claim 1, wherein the optically active polymer film has a multilayer structure. 13. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a light source disposed between the light source and the optical recording medium. And an optical element for switching the voltage applied to the optical element between recording and reproduction. 14. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a light source disposed between the light source and the optical recording medium. And an optical element for forming a recording signal by changing a voltage applied to the optical element. 15. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and the optical element according to claim 7, which is arranged between the light source and the optical recording medium. An optical head, wherein a tracking error signal is detected by using diffracted light generated by the optical element. 16. An optical head for recording or reproducing a signal on an optical recording medium, comprising: a light source; and a light source disposed between the light source and the optical recording medium. An optical element, a light amount control unit that receives the light emitted from the light source and controls the light amount of the light source, and an optical element control unit that controls the characteristics of the optical element. head. 17. An optical head for recording or reproducing a signal on an optical recording medium, comprising: a light source; and a light source disposed between the light source and the optical recording medium. 2. An optical head comprising: the optical element, and a polarization splitting unit arranged between the optical element and the optical recording medium, and a voltage applied to the optical element is switched between recording and reproduction. 18. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a light source arranged between the light source and the optical recording medium. 2. An optical head comprising: the optical element of 1) and a polarization splitting means arranged between the optical element and the optical recording medium, and forming a recording signal by changing a voltage applied to the optical element. 19. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a light source disposed between the light source and the optical recording medium. An optical element, a polarization separation means arranged between the optical element and the optical recording medium, a light amount control means for receiving light emitted from the light source and controlling the light amount of the light source, the optical element And an optical element control means for controlling the characteristics of the optical head. 20. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a voltage applied from the outside arranged between the light source and the optical recording medium. An optically active polymer film having a changed optical rotation, and a polarized light separating means disposed between the optically active polymer film and the optical recording medium are included, and a voltage applied to the optically active polymer film is recorded and reproduced. An optical head characterized by switching with. 21. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a voltage applied from the outside arranged between the light source and the optical recording medium. An optically active polymer film whose optical rotation changes, and a polarization separation means arranged between the optically active polymer film and the optical recording medium, by changing the voltage applied to the optically active polymer film. An optical head characterized by forming a recording signal. 22. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a voltage applied from the outside arranged between the light source and the optical recording medium. An optically active polymer film whose optical rotation changes, a polarization separation means arranged between the optically active polymer film and the optical recording medium, and receives the light emitted from the light source to change the light amount of the light source. An optical head comprising: a light amount control means for controlling; and an optical element control means for controlling characteristics of the optically active polymer film. 23. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a voltage applied from the outside arranged between the light source and the optical recording medium. An optically active polymer film whose optical rotation changes, and an optically active polymer which is disposed between the optically active polymer film and the optical recording medium and which corrects optical rotation caused by a film thickness deviation of the optically active polymer film. It includes a molecular film thickness correction unit and a polarization splitting unit arranged between the optically active polymer film thickness correction unit and the optical recording medium, and switches the voltage applied to the optically active polymer film between recording and reproduction. An optical head characterized by that. 24. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a voltage applied from the outside arranged between the light source and the optical recording medium. An optically active polymer film whose optical rotation changes, and an optically active polymer which is disposed between the optically active polymer film and the optical recording medium and which corrects optical rotation caused by a film thickness deviation of the optically active polymer film. A recording signal by changing the voltage applied to the optically active polymer film, including a molecular film thickness correction unit and a polarization splitting unit arranged between the optically active polymer film thickness correction unit and the optical recording medium. Forming an optical head. 25. An optical head for recording or reproducing a signal on or from an optical recording medium, comprising: a light source; and a voltage applied from the outside arranged between the light source and the optical recording medium. An optically active polymer film whose optical rotation changes, and an optically active polymer which is disposed between the optically active polymer film and the optical recording medium and which corrects optical rotation caused by a film thickness deviation of the optically active polymer film. A molecular film thickness correction unit, a polarization separation unit disposed between the optically active polymer film thickness correction unit and the optical recording medium, and receives light emitted from the light source to control the light amount of the light source. An optical head comprising: a light quantity control means; and an optical element control means for controlling the characteristics of the optically active polymer film. 26. An optical recording / reproducing apparatus for recording or reproducing a signal on or from an optical recording medium, comprising an optical head for recording or reproducing a signal on the optical recording medium, wherein the optical head comprises a light source. An optical recording / reproducing apparatus comprising: the optical element according to any one of claims 1 to 3. 27. An optical recording / reproducing apparatus for recording or reproducing a signal on or from an optical recording medium, comprising: an optical head for recording or reproducing a signal on the optical recording medium, wherein the optical head comprises: An optical recording / reproducing apparatus, which is the optical head according to any one of 20 to 25. 28. A first substrate provided with a conductive transparent thin film and a second substrate provided with a conductive transparent thin film are arranged such that the conductive transparent thin films face each other, and the conductive transparent thin film is provided between the two conductive transparent thin films. Arranged so that a desired void can be formed, and the optically active polymer in a molten state is disposed between the conductive transparent thin films, and the orientation direction of the molecules constituting the optically active polymer is maintained in a desired direction. A method for producing an optically active polymer film, which comprises cooling as it is. 29. The optically active polymer in a molten state is formed by arranging the optically active polymer in a solid state between the conductive transparent thin films and heating it to a temperature equal to or higher than the melting point of the optically active polymer. 29. The method for producing an optically active polymer film according to claim 28, wherein 30. The method for producing an optically active polymer film according to claim 28, wherein the orientation direction of the molecules is maintained in a desired direction by applying an electric field to the optically active polymer in the molten state. 31. The optically active polymer film according to claim 28, characterized in that a standing wave of ultrasonic waves is applied to the optically active polymer in the molten state to maintain the orientation direction of the molecule in a desired direction. Manufacturing method. 32. The optically active polymer according to claim 31, wherein the standing waves of the ultrasonic waves are formed by the ultrasonic waves interfering with each other by applying the ultrasonic waves from different directions. Membrane manufacturing method. 33. The optically active polymer film according to claim 31, wherein a standing wave of the ultrasonic wave is formed by the interference between the applied ultrasonic wave and the reflected wave of the ultrasonic wave. Production method. 34. A first substrate provided with a conductive transparent thin film and a second substrate provided with a conductive transparent thin film are arranged such that the conductive transparent thin films face each other, Arranged so that a desired void can be formed, an optically active polymer in a solid state is disposed between the conductive transparent thin films, and ultrasonic waves are converged on a part of the optically active polymer in the solid state, A method for producing an optically active polymer film, characterized in that only the optically active polymer at the position where the ultrasonic waves are converged is melted, and the position where the ultrasonic wave is converged is moved with time. 35. The method for producing an optically active polymer film according to claim 29, wherein the optically active polymer in the solid state is powder. 36. The method for producing an optically active polymer film according to claim 29, wherein the solid state optically active polymer is a film. 37. The method for producing an optically active polymer film according to claim 28, wherein the optically active polymer is polylactic acid. 38. The optically active polymer film according to claim 28, wherein the void is formed by disposing a member having a desired size between the first and second substrates. Manufacturing method. 39. The method for producing an optically active polymer film according to claim 38, wherein the member is transparent. 40. The method for producing an optically active polymer film according to claim 38, wherein the refractive index of the member is substantially equal to the refractive index of the optically active polymer. 41. The glass transition point of the member is equal to or higher than the melting point of the optically active polymer.
The method for producing an optically active polymer film according to item 1.