JP2000353337A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical pickup device capable of high precision servo control in which offsetting is prevented from occurring in a focusing error signal or a tracking error signal. SOLUTION: The optical pickup device 1 is constituted such that a light flux separating means 6 is arranged before a light receiving element 7 and that only such reflected light as reflected by a light information recording medium (d) having a polarizing component different from the light flux of the laser beam emitted from a light source 2 is made incident on the light receiving element 7. A flare, which is caused by the laser beam from the light source 2 being reflected by a polarizing hologram element 8, suppresses the state that enters the light receiving element 7. Consequently, it is possible to perform the high precision servo control in which offsetting is prevented from occurring in a focusing error signal or a tracking error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device for optically recording / reproducing information on / from an optical information recording medium.

[0002]

2. Description of the Related Art Conventionally, in an optical pickup device for optically recording / reproducing information on an optical information recording medium, a signal light reflected on a recording surface of the optical information recording medium is detected by a light receiving / detecting section (light receiving element). Various optical components are used to guide light (beam splitting) to (). As this optical component, a prism type beam splitter or a non-polarization type hologram element has been often used. Since the prism type beam splitter and the non-polarization type hologram element are expensive, the non-polarization type hologram element is often used.

[0003] However, the non-polarization type hologram element is excellent in terms of miniaturization of parts, but the ratio of the amount of light reaching the optical information recording medium to the amount of light emitted from a light source such as a semiconductor laser (utilization efficiency) is high. It was small, and the round trip utilization efficiency (round trip efficiency) was limited to about 7%.

Therefore, a proposal for using a polarization hologram element in an optical pickup device instead of a non-polarization hologram element has been made in Japanese Patent Application Laid-Open No. 9-102138. Here, FIG. 13 is a longitudinal sectional side view showing an example of a conventional polarization hologram element. As shown in FIG. 13, this polarization hologram element 100 has an uneven groove portion (depth: 1.2 μm, pitch: 9 μm) having a rectangular cross section on the surface.
A glass substrate (refractive index: 1.54) 101 provided with
A glass substrate 103 having a polyimide film 104 as an alignment film on its surface;
And a liquid crystal 106 injected between them and sealed with an epoxy resin 105. Further, a λ / 4 film 107, a photopolymer 108, and a glass substrate 109 are laminated on the polarization hologram element 100, and a diffraction element 110 is formed. As a result, miniaturization of the optical pickup device and simplification of component assembly are achieved.

When such a polarization hologram element 100 is used in an optical pickup device and a P-wave having a wavelength of 678 nm is incident on the polarization hologram element 100 from the glass substrate 101, the transmittance of the P-wave is about 97%. there were. Further, when the reflected light from the optical information recording medium converted into the S wave by the λ / 4 film 107 is incident on the polarization hologram element 100, the diffraction efficiency of the + 1st-order diffracted light is 33%.
The diffraction efficiency of the -1st-order diffracted light was 33%. As a result, the outgoing route utilization efficiency (outgoing route efficiency) was about 97%, and the round trip efficiency was about 33%. That is, it is understood that the reciprocating efficiency is improved when the polarization hologram element is used, as compared with the case where the non-polarization hologram element is used.

FIG. 14 is a vertical sectional side view showing another example of a conventional polarization hologram element. As shown in FIG. 14, this polarization hologram element 200
1 is formed by covering the polarization hologram 203 injected into the concave-convex groove 202 formed in 1 with a glass substrate 204. The polarization hologram element 20
At 0, a λ / 4 film 205 and a glass substrate 206 are laminated, and a diffraction element 207 is formed. Further, on both surfaces of the diffraction element 207, an anti-reflection film 208 is provided.
Is given.

Next, a case where the diffraction element 207 is used in an optical pickup device will be described. Here, FIG.
FIG. 1 is a vertical sectional side view showing an example of a conventional optical pickup device. As shown in FIG.
Is composed of a semiconductor laser 210, a diffraction element 207, a collimating lens 211, an objective lens 212, and a light receiving element 213. Note that the semiconductor laser 210 and the diffraction element 207 are disposed so that the polarization direction of the laser wavefront of the laser light emitted from the semiconductor laser 210 is set to the polarization direction that is not diffracted by the polarization hologram 203 of the diffraction element 207. I have. That is, the laser light emitted from the semiconductor laser 210 is not affected at all when passing through the polarization hologram 203.

In such a configuration, the semiconductor laser 2
The light beam of the laser light emitted by the laser beam 10 is made incident on the polarization hologram element 200 side of the diffraction element 207. Diffraction element 207
Is transmitted through the polarization hologram element 200 of the diffraction element 207 and is incident on the λ / 4 film 205.
The light beam incident on the λ / 4 film 205 is converted into circularly polarized light, and is incident on the collimator lens 211. The light beam incident on the collimator lens 211 is converted into parallel light and then condensed by the objective lens 212, and is irradiated as a light spot on the optical information recording medium d. Thereafter, the optical information recording medium d
The reflected light flux transmitted through the objective lens 212 and the collimating lens 211 is incident on the diffraction element 207 again. The light beam that has re-entered the diffraction element 207 has its polarization direction rotated by 90 degrees in the λ / 4 film 205. Therefore, when the light beam passing through the λ / 4 film 205 enters the polarization hologram element 200, the light beam is diffracted by the polarization hologram element 200 and enters the light receiving element 213 because the polarization direction is rotated by 90 degrees. Will do. The light receiving element 213 detects a tracking signal, a focus signal, and an information signal based on a light receiving signal of the incident light beam.

[0009]

By the way, the above-mentioned diffraction element 207 prevents reflection of light by providing antireflection films 208 on both surfaces thereof, but it is impossible to make it completely non-reflective. is there. In particular, since the coating of the antireflection film 208 is insufficient at the groove 202 into which the polarization hologram 203 has been injected, reflection remains. Therefore, the diffraction element 207 functions as a reflection type, although it should be a transmission type. The light that is incident on the light receiving element 213 by being reflected by the diffraction element 207 in this manner is unnecessary light, and is called “flare”. Here, FIG. 16 is a schematic diagram showing a state of occurrence of flare. As shown in FIG. 16, a part of a light beam L1 (shown by a solid line) of the laser light centered at C emitted from the semiconductor laser 210 is specularly reflected by the diffraction element 207 and reflected by a light beam R (shown by a dashed line). )become. A part of the light flux R of the reflected light enters the light receiving element 213. When the polarization hologram 203 functions as a reflection diffraction element, light emitted from a collimating lens 211 which is a virtual light source located at a line symmetric position with respect to the diffraction element 207 becomes a light flux of a dashed line L2 centered on C. After proceeding, it proceeds as if diffracted by the polarization hologram 203 of the diffraction element 207. Therefore, the 0th-order diffracted light becomes the same as the reflected light flux R. On the other hand, this polarization hologram 20
The diffracted light flux D (indicated by a two-dot chain line), which is the first-order diffracted light diffracted at 3, is divergent light centered on the diffracted light D1. A part of the diffracted light beam D enters the light receiving element 213.

As described above, a part of the reflected light beam R and the diffracted light beam D
Is incident on the light receiving element 213, the reflected light beam R and the diffracted light beam D
Since the light receiving element 213 has an anisotropic intensity distribution due to the influence of tolerances such as the light intensity distribution of No. 10 and the mounting angle of the diffraction element 207, the amount of light incident on the plurality of light receiving portions of the light receiving element 213 differs. Will be. For this reason,
This causes an offset in the focus error signal and the tracking error signal. That is, a part of the reflected light beam R and a part of the diffracted light beam D are flares that cause an offset.

In particular, the reflectivity of a two-layer optical information recording medium such as a DVD or a phase-change optical information recording medium such as a CD-RW has a CD.
-Since the absolute value of the signal light amount at the time of reproduction or recording becomes small due to the lower reflectivity of a single-layer optical information recording medium such as a ROM, a two-layer optical information recording medium such as a DVD or a CD-RW The phase change type optical information recording medium is susceptible to flare. Also, during normal recording, the output power is made larger than during reproduction. However, since the flare changes in proportion to the output power of the semiconductor laser, the offset amount of the signal changes due to the output power, and a normal servo signal can be obtained. There is a problem of disappearing. Furthermore, in an optical pickup device used in a system for recording / reproducing both an optical information recording medium having a low reflectance and an optical information recording medium having a high reflectance, in order to keep a reproduction signal level constant, an optical pickup device having a low reflectance is used. Since the output power must be increased during reproduction of the optical information recording medium, the offset amount also changes in such a case.

An object of the present invention is to provide an optical pickup device capable of performing high-accuracy servo control while preventing occurrence of an offset in a focus error signal and a tracking error signal.

An object of the present invention is to provide an optical pickup device capable of accurately controlling the light amount of a light source.

[0014]

According to the first aspect of the present invention,
A light source that emits laser light, a quarter-wave plate provided downstream of the light source in the laser emission direction, and a focusing optic that spot-irradiates the laser light passing through the quarter-wave plate onto an optical information recording medium. A polarization hologram element disposed in an optical path between the light source and the quarter-wave plate and diffracting only light having a polarization component different from that of the laser light emitted from the light source; A light receiving element that receives the diffracted light diffracted by the hologram element, and a light beam that is disposed in an optical path between the light receiving element and the polarization hologram element and has the same polarization component as the light beam of the laser light emitted from the light source And a light beam separating means for eliminating incidence on the light receiving element.

Therefore, the laser light emitted from the light source is transmitted through the polarization hologram element and the quarter-wave plate, is reflected by the optical information recording medium, is again incident on the quarter-wave plate, and has a polarization direction of 90 degrees. Rotated by degrees. The reflected light whose polarization direction is rotated by 90 degrees has a polarization component different from that of the laser light emitted from the light source, and is diffracted when it is again incident on the polarization hologram element. The incidence on the light receiving element is not excluded by the light beam separating means. As a result, light having the same polarization component as the light beam of the laser light emitted from the light source does not enter the light receiving element, and optical information recording having a polarization component different from the light beam of the laser light emitted from the light source is prevented. Only the light reflected by the medium is incident.

According to a second aspect of the present invention, in the optical pickup device of the first aspect, the quarter-wave plate and the polarization hologram element are integrally laminated as a diffraction element.

Accordingly, it is possible to reduce the size of the apparatus and simplify the assembly of parts.

The third aspect of the present invention is the first or second aspect.
5. The optical pickup device according to claim 1, wherein the optical information recording device is provided between the quarter-wave plate and the condensing optical system, and the laser beam emitted from the light source passes through the quarter-wave plate. The laser light that is not applied to the medium as a light spot is reflected and diffracted, and the reflected diffracted light is again reflected in the 1
A reflection / diffraction element formed in a region so as to pass through a / 4 wavelength plate; and a monitoring light receiving element built in the light receiving element.

Therefore, of the laser light emitted from the light source, the laser light which is not irradiated as a light spot on the optical information recording medium passes through the polarization hologram element and the quarter wavelength plate and then collects with the quarter wavelength plate. After being reflected by the reflection / diffraction element provided between the optical system and the optical system, the light is again incident on the quarter-wave plate and the polarization direction is rotated by 90 degrees. Also,
The reflected light whose polarization direction has been rotated by 90 degrees has a polarization component different from that of the laser beam emitted from the light source, and the incidence on the light receiving element is not excluded by the light beam separating means. Thereby, the reflected light reflected by the reflection diffraction element enters the light receiving element similarly to the reflected light reflected by the optical information recording medium, and is monitored by the monitoring light receiving element built in the light receiving element. A sufficient amount of light is ensured as the monitor front emission light, and accurate light amount control of the light source can be performed.

The invention described in claim 4 is the invention according to claim 1 or 2
In the optical pickup device described above, provided between the light source and the polarization hologram element, of the laser light emitted from the light source, while reflecting and diffracting laser light that is not irradiated as a light spot on the optical information recording medium. The reflected diffraction light is provided separately from the reflection diffraction element formed as an area so as not to pass through the polarization hologram element, and the light receiving element. A monitoring light receiving element for receiving light.

Therefore, of the laser light emitted from the light source, the laser light that is not irradiated as a light spot on the optical information recording medium is reflected by the reflection diffraction element provided between the light source and the polarization hologram element. In addition, the reflected light reflected by the reflection diffraction element has the same polarization component as the light flux of the laser light emitted from the light source, and is prevented from being incident on the light receiving element by the light beam separating means. Is received by a separately provided monitoring light receiving element. Thereby, the reflected light reflected by the reflection diffraction element is monitored by the monitoring light receiving element provided separately from the light receiving element, so that a sufficient amount of light is secured as the monitor front emission light, and the accurate light amount of the light source is obtained. Control becomes possible.

[0022] The invention according to claim 5 is the invention according to claims 1 to 3.
In the optical pickup device according to any one of the above, the light beam separating means is a polarization filter that transmits only the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element.

Therefore, the polarization filter that transmits only the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element is applied as the light beam separating means, so that the incidence of flare on the light receiving element is surely suppressed. Becomes possible.

The invention according to claim 6 is the invention according to claims 1 to 3
In the optical pickup device according to any one of the above, the light beam separating means reflects or transmits the laser light emitted from the light source to enter the polarization hologram element,
A total reflection prism that transmits or reflects the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element.

Therefore, the laser beam emitted from the light source is reflected or transmitted and made incident on the polarization hologram element.
Applying a total reflection prism that transmits or reflects the diffracted light diffracted by the polarization hologram element to the light receiving element as a light beam separating means, it is possible to reliably suppress the incidence of flare to the light receiving element. Become.

The invention according to claim 7 is the invention according to claims 1 to 3
In the optical pickup device according to any one of the above, the light beam separating means is a total reflection prism that transmits or reflects the diffracted light diffracted by the polarization hologram element and makes the diffracted light incident on the light receiving element.

Therefore, the total reflection prism which transmits or reflects the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element is applied as the light beam separating means, so that the incidence of flare on the light receiving element is surely suppressed. It becomes possible to do.

[0028] The invention according to claim 8 is the invention according to claims 1 to 4.
In the optical pickup device according to any one of the above, the light beam separating means reflects or transmits the laser light emitted from the light source to enter the polarization hologram element,
A polarizing beam splitter that transmits or reflects the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element.

Therefore, the laser light emitted from the light source is reflected or transmitted and made incident on the polarization hologram element.
A polarizing beam splitter, which transmits or reflects the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element, is applied as a light beam separating means, so that it is possible to reliably suppress the incidence of flare on the light receiving element. Become.

The ninth aspect of the present invention provides the first to fourth aspects.
In the optical pickup device according to any one of the above, the light beam separating means is a polarization beam splitter that transmits or reflects the diffracted light diffracted by the polarization hologram element and causes the diffracted light to enter the light receiving element.

Therefore, the polarization beam splitter which transmits or reflects the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element is applied as a light beam separating means, so that the incidence of flare on the light receiving element is surely suppressed. It becomes possible to do.

According to a tenth aspect of the present invention, in the optical pickup device according to any one of the first to fourth aspects, the light beam separating means transmits the diffracted light diffracted by the polarization hologram element to the light receiving element. Is a second polarization hologram element to be made incident on the second polarization hologram element.

Therefore, the second polarization hologram element, which transmits the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element, is applied as the light beam separating means, so that the flare can be surely incident on the light receiving element. It becomes possible to suppress.

According to an eleventh aspect of the present invention, in the optical pickup device according to any one of the first to fourth aspects, the light beam separating means diffracts the diffracted light diffracted by the polarization hologram element to the light receiving element. Is a third polarization hologram element that is made incident on the third polarization hologram element.

Therefore, the third polarization hologram element, which diffracts the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element, is applied as a light beam separating means, so that the flare can be surely incident on the light receiving element. It becomes possible to suppress.

[0036]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. Here, FIG. 1 is a longitudinal sectional side view schematically showing the optical pickup device 1. As shown in FIG. 1, an optical pickup device 1 includes a semiconductor laser 2, which is a light source for emitting laser light, a diffractive element 3, a collimator lens 4 for converting the laser light into substantially parallel light, and a laser light for an optical information recording medium. A condensing optical system composed of an objective lens 5 that irradiates d with a light spot, a polarization filter 6 that transmits light in a predetermined polarization direction, and a monitor light receiving element (not shown) are provided. The light receiving element 7 is provided.

Next, the diffraction element 3 will be described in detail. Here, FIG. 2 is a longitudinal sectional side view schematically showing the diffraction element 3. As shown in FIG. 2, the diffraction element 3 has a polarization hologram element 8, and the polarization hologram element 8
, A λ / 4 film 9 functioning as a 波長 wavelength plate and a glass substrate 10 are laminated. Further, the polarization hologram element 8 is formed by covering the polarization hologram 13 injected into the concave and convex grooves 12 formed on the glass substrate 11 with the glass substrate 14. That is, the diffraction element 3 is configured by stacking the polarization hologram element 8, the λ / 4 film 9, and the glass substrate 10 in this order from the semiconductor laser 2 side. Further, antireflection films 15 are formed on both surfaces of the diffraction element 3 in the vertical direction (the traveling direction of the laser beam).

The diffraction element 3 and the semiconductor laser 2 are arranged such that the polarization direction of the laser wavefront of the laser light emitted from the semiconductor laser 2 is set to a polarization direction that is not diffracted by the polarization hologram 13 of the polarization hologram element 8. It is arranged in. That is, the laser light emitted from the semiconductor laser 2 is not affected at all when passing through the polarization hologram 13.

In such a configuration, the semiconductor laser 2
Make the light beam of the laser light emitted from the diffracting element 3 incident on the polarization hologram element 8 side. The light beam incident on the diffraction element 3 passes through the polarization hologram element 8 of the diffraction element 3 and
4 enters the film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. After that, the reflected light reflected by the optical information recording medium d passes through the objective lens 5 and the collimator lens 4 and then enters the diffraction element 3 again. The light beam incident again on the diffraction element 3 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the light beam passing through the λ / 4 film 9 enters the polarization hologram element 8, the polarization direction is changed to 9
Since the light beam is rotated by 0 degrees, the light beam is diffracted by the polarization hologram element 8 and enters the polarization filter 6. Here, the polarizing filter 6 is formed so as to transmit only a light beam in a polarization direction parallel to light obtained by rotating the polarization direction of the light beam reflected by the optical information recording medium d by 90 degrees. I have. That is, the polarization filter 6 functions as a light beam separating unit by transmitting only the light diffracted by the polarization hologram element 8 and making the light incident on the light receiving element 7. Therefore, light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8 is suppressed from entering the light receiving element 7. The light receiving element 7 on which the diffracted light is incident detects a tracking signal, a focus signal, and an information signal based on a signal of the incident diffracted light.

Here, by providing a polarizing filter 6 in the optical path between the diffractive element 3 and the light receiving element 7 for transmitting only the light flux of the light in the polarization direction parallel to the diffracted light, the diffracted light which is flare is provided. Light in the orthogonal polarization direction (the laser light emitted from the semiconductor laser 2 is
It is possible to reduce the ratio of reflected light (specularly reflected on the side) to the light receiving element 7. As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the same parts as those described in the first embodiment of the present invention are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 3 is a longitudinal sectional side view schematically showing the optical pickup device 20. As shown in FIG. 3, in the optical pickup device 20 of the present embodiment, a total reflection prism 21 is provided instead of the polarization filter 6 provided in the optical pickup device 1 of the first embodiment.

The total reflection prism 21 is arranged on the optical path between the semiconductor laser 2 and the diffraction element 3 and is arranged on the optical path between the diffraction element 3 and the light receiving element 7 and emitted from the semiconductor laser 2. The laser light emitted from the semiconductor laser 2 is reflected by the laser beam reflected by the total reflection surface and made incident on the diffraction element 3, and the diffracted light of the diffraction hologram element 8 of the diffraction element 3 is transmitted and made incident on the light receiving element 7. The light beam is separated from the light beam of the diffracted light in the polarization hologram element 8 of the diffraction element 3.

The total reflection prism 21 has the following characteristics. Here, FIG. 4 is a graph showing the relationship between the reflectance of the total reflection prism 21 and the incident angle. As shown in FIG. 4, P-polarized light (linearly polarized light whose vibration direction of light incident on the total reflection prism 21 is included in a plane including the normal direction of the total reflection prism 21) and S-polarized light (incident on the total reflection prism 21) The direction of vibration of the reflected light is the total reflection prism 2
(Linearly polarized light perpendicular to a plane including the normal direction of 1) has a different reflection intensity depending on the incident angle. The reflectance of S-polarized light increases as the incident angle increases. On the other hand, in the case of P-polarized light, the reflectance temporarily decreases as the incident angle increases, and when the incident angle approaches 56 degrees (Brewster angle).
, The reflectance becomes “0”. Thereafter, as the incident angle increases, the reflectance also increases. Therefore, by setting the diffraction angle of the polarization hologram element 8 by the polarization hologram 13 to a predetermined angle, the light diffracted by the polarization hologram element 8 (the light in the P polarization direction) is transmitted and the laser emitted from the semiconductor laser 2 is emitted. It becomes possible to reflect the reflected light (light in the S-polarized direction) which is regularly reflected on the polarization hologram element 8 side of the diffraction element 3. In the present embodiment, the angle of diffraction by the polarization hologram 13 of the polarization hologram element 8 is set so that the angle of incidence of the light diffracted by the polarization hologram element 8 on the total reflection prism 21 becomes φ (see FIG. 4). ing.

In such a configuration, the semiconductor laser 2
Make the light beam of the emitted laser light incident on the total reflection prism 21. The total reflection prism 21 totally reflects the incident laser light on the total reflection surface in the direction of the diffraction element 3 and makes the laser light incident on the polarization hologram element 8 side of the diffraction element 3. The light beam incident on the diffraction element 3 is transmitted through the polarization hologram element 8 of the diffraction element 3 and is incident on the λ / 4 film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. After that, the reflected light reflected by the optical information recording medium d passes through the objective lens 5 and the collimator lens 4 and then enters the diffraction element 3 again. The luminous flux incident on the diffraction element 3 again has a polarization direction of 9 in the λ / 4 film 9.
It will be rotated 0 degrees. Therefore, this λ /
When the light beam passing through the 4 film 9 enters the polarization hologram element 8, the light beam is diffracted by the polarization hologram element 8 and enters the total reflection prism 21 because the polarization direction is rotated by 90 degrees. . Here, the total reflection prism 21 transmits the light diffracted by the polarization hologram element 8 (light in the P-polarization direction), and the laser light emitted from the semiconductor laser 2 becomes positive on the polarization hologram element 8 side of the diffraction element 3. It is formed so as to reflect the reflected light (light in the S polarization direction). That is, the total reflection prism 21 functions as a light beam separating unit by transmitting only the light beam of the light diffracted by the polarization hologram element 8 and causing the light beam to enter the light receiving element 7. Therefore, for light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8, the light receiving element 7
Is suppressed. The light receiving element 7 on which the diffracted light is incident detects a tracking signal, a focus signal, and an information signal based on a signal of the incident diffracted light.

Here, the optical path between the semiconductor laser 2 and the diffraction element 3 and the optical path between the diffraction element 3 and the light receiving element 7 are:
By providing the total reflection prism 21 for separating the light beam of the laser light emitted from the semiconductor laser 2 and the light beam of the diffracted light in the polarization hologram element 8 of the diffractive element 3, the polarization direction orthogonal to the diffracted light that is a flare is provided. (Reflected light in which the laser light emitted from the semiconductor laser 2 is specularly reflected on the polarization hologram element 8 side of the diffraction element 3)
It is possible to reduce the ratio of incident light.
As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, a third embodiment of the present invention will be described with reference to FIG. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 5 is a longitudinal sectional side view schematically showing the optical pickup device 30. As shown in FIG. 5, the optical pickup device 30 of the present embodiment differs from the optical pickup device 1 of the first embodiment in that a total reflection prism 21 is provided instead of the polarizing filter 6 of the optical pickup device 1 of the first embodiment. The optical pickup device 20 is the same as that of the
The optical pickup device 20 according to the second embodiment is different from the optical pickup device 20 according to the second embodiment in that the optical pickup device is not disposed on the optical path between the semiconductor laser 2 and the diffraction element 3 but is disposed only on the optical path between the diffraction element 3 and the light receiving element 7. Are different.

In such a configuration, the semiconductor laser 2
Make the light beam of the laser light emitted from the diffracting element 3 incident on the polarization hologram element 8 side. The light beam incident on the diffraction element 3 passes through the polarization hologram element 8 of the diffraction element 3 and
4 enters the film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. After that, the reflected light reflected by the optical information recording medium d passes through the objective lens 5 and the collimator lens 4 and then enters the diffraction element 3 again. The light beam incident again on the diffraction element 3 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the light beam passing through the λ / 4 film 9 enters the polarization hologram element 8, the polarization direction is changed to 9
Since the light beam is rotated by 0 degrees, the light beam is diffracted by the polarization hologram element 8 and enters the total reflection prism 21. Here, the total reflection prism 21 transmits the light diffracted by the polarization hologram element 8 (light in the P-polarization direction), and the laser light emitted from the semiconductor laser 2 becomes positive on the polarization hologram element 8 side of the diffraction element 3. It is formed so as to reflect the reflected light (light in the S polarization direction). That is, the total reflection prism 21 transmits only the light diffracted by the polarization hologram element 8,
By making the light incident on the light receiving element 7, it functions as a light beam separating means. Therefore, light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8 is suppressed from entering the light receiving element 7. The light receiving element 7 on which the diffracted light is incident detects a tracking signal, a focus signal, and an information signal based on a signal of the incident diffracted light.

Here, in the optical path between the diffraction element 3 and the light receiving element 7, the light beam of the laser beam emitted from the semiconductor laser 2 and the light beam of the diffracted light in the polarization hologram element 8 of the diffraction element 3 are totally separated. By providing the reflecting prism 21, light in a polarization direction orthogonal to the diffracted light that is a flare (a reflected light in which the laser light emitted from the semiconductor laser 2 is specularly reflected on the polarization hologram element 8 side of the diffraction element 3) Can be reduced in the ratio of light entering the light receiving element 7. As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, a fourth embodiment of the present invention will be described with reference to FIG. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 6 is a longitudinal sectional side view schematically showing the optical pickup device 40. As shown in FIG. 6, the optical pickup device 40 of the present embodiment is different from the optical pickup device 20 of the second embodiment in that a polarization beam splitter 41 is provided instead of the total reflection prism 21. is there.

The polarization beam splitter 41 is disposed on the optical path between the semiconductor laser 2 and the diffraction element 3, and
The laser beam emitted from the semiconductor laser 2 is disposed on an optical path between the diffraction element 3 and the light receiving element 7, is reflected by a polarization plane, is incident on the diffraction element 3, and is diffracted by the polarization hologram element 8 of the diffraction element 3. By transmitting the light and making it incident on the light receiving element 7, the light beam of the laser light emitted from the semiconductor laser 2 is separated from the light beam of the diffracted light in the polarization hologram element 8 of the diffraction element 3.

Such a polarization beam splitter 41 is
This element utilizes the fact that the light obliquely incident on the dielectric multilayer film separates the characteristics (separation of P-polarized light and S-polarized light) by the polarization component. The incident angle to the interface in the multilayer film becomes the Brewster angle. When the condition is satisfied, the reflectance of the S-polarized light component increases, and the reflectance of the P-polarized light component becomes “0”. That is, in the polarization beam splitter 41 of the optical pickup device 40 according to the present embodiment, the light diffracted by the polarization hologram element 8 (the light in the P polarization direction) is transmitted, and the laser light emitted from the semiconductor laser 2 is diffracted by the diffraction element. It is possible to reflect the reflected light (light in the S-polarized direction) that is specularly reflected on the side of the third polarization hologram element 8.

In such a configuration, the semiconductor laser 2
The luminous flux of the laser light emitted by the polarization beam splitter 41
Incident on The polarization beam splitter 41 totally reflects the incident light beam of the laser light on the polarization plane in the direction of the diffraction element 3, and transmits the laser light to the polarization hologram element 8 of the diffraction element 3.
Incident on the side. The light beam incident on the diffraction element 3 is transmitted through the polarization hologram element 8 of the diffraction element 3 and is incident on the λ / 4 film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. Thereafter, the optical information recording medium d
The reflected light reflected by is transmitted through the objective lens 5 and the collimator lens 4 and is incident on the diffraction element 3 again. The light beam incident again on the diffraction element 3 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the light beam that has passed through the λ / 4 film 9 enters the polarization hologram element 8, the light beam is diffracted by the polarization hologram element 8 because the polarization direction is rotated by 90 degrees, and the light beam is transmitted to the polarization beam splitter 41. Will be incident. Here, the polarization beam splitter 41 transmits the light diffracted by the polarization hologram element 8 (light in the P polarization direction), and the laser light emitted from the semiconductor laser 2 is positively polarized on the polarization hologram element 8 side of the diffraction element 3. It is formed so as to reflect the reflected light (light in the S polarization direction). That is, the polarization beam splitter 41
By transmitting only the light diffracted by the polarization hologram element 8 and making it incident on the light receiving element 7, it functions as a light beam separating means. Therefore, light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8 is suppressed from entering the light receiving element 7.
The light receiving element 7 on which the diffracted light is incident detects a tracking signal, a focus signal, and an information signal based on a signal of the incident diffracted light.

Here, the optical path between the semiconductor laser 2 and the diffraction element 3 and the optical path between the diffraction element 3 and the light receiving element 7 are:
By providing the polarization beam splitter 41 for separating the light beam of the laser light emitted from the semiconductor laser 2 and the light beam of the diffracted light in the polarization hologram element 8 of the diffractive element 3, the polarization direction orthogonal to the flare diffracted light is provided. (Reflected light in which the laser light emitted from the semiconductor laser 2 is specularly reflected on the polarization hologram element 8 side of the diffraction element 3) can be reduced in the ratio of incidence on the light receiving element 7. As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, a fifth embodiment of the present invention will be described with reference to FIG. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 7 is a longitudinal sectional side view schematically showing the optical pickup device 50. As shown in FIG. 7, the optical pickup device 50 of the present embodiment differs from the optical pickup device 20 of the second embodiment in that a polarization beam splitter 41 is provided instead of the polarization filter 6 of the optical pickup device 20 of the second embodiment. In the same manner as the optical pickup device 40 of the embodiment, the polarization beam splitter 41 is not arranged on the optical path between the semiconductor laser 2 and the diffraction element 3 but is arranged only on the optical path between the diffraction element 3 and the light receiving element 7. This is different from the optical pickup device 40 according to the fourth embodiment in the point described above.

In such a configuration, the semiconductor laser 2
Make the light beam of the laser light emitted from the diffracting element 3 incident on the polarization hologram element 8 side. The light beam incident on the diffraction element 3 passes through the polarization hologram element 8 of the diffraction element 3 and
4 enters the film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. After that, the reflected light reflected by the optical information recording medium d passes through the objective lens 5 and the collimator lens 4 and then enters the diffraction element 3 again. The light beam incident again on the diffraction element 3 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the light beam passing through the λ / 4 film 9 enters the polarization hologram element 8, the polarization direction is changed to 9
Since the light beam has been rotated by 0 degrees, the light beam is diffracted in the polarization hologram element 8 and the polarization beam splitter 41
Will be incident. Here, the polarization beam splitter 41 transmits the light diffracted by the polarization hologram element 8 (light in the P polarization direction), and the laser light emitted from the semiconductor laser 2 is positively polarized on the polarization hologram element 8 side of the diffraction element 3. It is formed so as to reflect the reflected light (light in the S polarization direction). That is, the polarization beam splitter 41 functions as a light beam separating unit by transmitting only the light diffracted by the polarization hologram element 8 and making the light incident on the light receiving element 7. Therefore, light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8 is suppressed from entering the light receiving element 7. The light receiving element 7 on which the diffracted light is incident detects a tracking signal, a focus signal, and an information signal based on a signal of the incident diffracted light.

Here, in the optical path between the diffraction element 3 and the light receiving element 7, a polarized light for separating the light flux of the laser light emitted from the semiconductor laser 2 and the light flux of the diffracted light in the polarization hologram element 8 of the diffraction element 3. By providing the beam splitter 41, the light in the polarization direction orthogonal to the diffracted light as a flare (the laser light emitted from the semiconductor laser 2
(The light reflected specularly on the side of the polarization hologram element 8) can be reduced to enter the light receiving element 7. As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, a sixth embodiment of the present invention will be described with reference to FIG. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 8 is a longitudinal sectional side view schematically showing the optical pickup device 60. As shown in FIG. 8, in the optical pickup device 60 of the present embodiment, a polarization hologram device 61 as a second polarization hologram device is used instead of the polarization filter 6 provided in the optical pickup device 1 of the first embodiment. Is provided.

The polarization hologram element 61 does not diffract light in the polarization direction parallel to the light obtained by rotating the polarization direction of the light flux of the reflected light reflected by the optical information recording medium d by 90 degrees. Therefore, the light receiving element 7 is arranged at a position where the light transmitted through the polarization hologram element 61 can be received.

In such a configuration, the semiconductor laser 2
Make the light beam of the laser light emitted from the diffracting element 3 incident on the polarization hologram element 8 side. The light beam incident on the diffraction element 3 passes through the polarization hologram element 8 of the diffraction element 3 and
4 enters the film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. After that, the reflected light reflected by the optical information recording medium d passes through the objective lens 5 and the collimator lens 4 and then enters the diffraction element 3 again. The light beam incident again on the diffraction element 3 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the light beam passing through the λ / 4 film 9 enters the polarization hologram element 8, the polarization direction is changed to 9
Since the light beam is rotated by 0 degrees, the light beam is diffracted by the polarization hologram element 8 and enters the polarization hologram element 61. Here, the polarization hologram element 61
Is formed so as to transmit only light in a polarization direction parallel to light obtained by rotating the polarization direction of the reflected light beam reflected by the optical information recording medium d by 90 degrees. In other words, the polarization hologram element 61 functions as a light beam separating unit by transmitting only the light diffracted by the polarization hologram element 8 and making the light incident on the light receiving element 7. Therefore, light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8 is suppressed from entering the light receiving element 7. The light receiving element 7 on which the diffracted light is incident detects a tracking signal, a focus signal, and an information signal based on a signal of the incident diffracted light.

Here, by providing a polarization hologram element 61 for transmitting only the light in the polarization direction parallel to the diffracted light in the optical path between the diffractive element 3 and the light receiving element 7, it is orthogonal to the diffracted light which is a flare. It is possible to reduce the ratio of the incident light in the polarization direction (the reflected light of the laser light emitted from the semiconductor laser 2 specularly reflected on the polarization hologram element 8 side of the diffraction element 3) to the light receiving element 7. ing. As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, a seventh embodiment of the present invention will be described with reference to FIG. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 9 is a longitudinal sectional side view schematically showing the optical pickup device 70. As shown in FIG. 9, in the optical pickup device 70 of the present embodiment, a polarization hologram device as a third polarization hologram device is used instead of the polarization hologram device 61 provided in the optical pickup device 60 of the sixth embodiment. 71 is provided.

The polarization hologram element 71 is configured to diffract light in a polarization direction parallel to light obtained by rotating the polarization direction of the light flux of the reflected light reflected by the optical information recording medium d by 90 degrees. Therefore, the light receiving element 7 is arranged at a position where the light diffracted by the polarization hologram element 71 can be received.

In such a configuration, the semiconductor laser 2
Make the light beam of the laser light emitted from the diffracting element 3 incident on the polarization hologram element 8 side. The light beam incident on the diffraction element 3 passes through the polarization hologram element 8 of the diffraction element 3 and
4 enters the film 9. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light, and is incident on the collimator lens 4. The light beam incident on the collimator lens 4 is converted into parallel light and then condensed by the objective lens 5 and radiated as a light spot on the optical information recording medium d. After that, the reflected light reflected by the optical information recording medium d passes through the objective lens 5 and the collimator lens 4 and then enters the diffraction element 3 again. The light beam incident again on the diffraction element 3 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the light beam passing through the λ / 4 film 9 enters the polarization hologram element 8, the polarization direction is changed to 9
Since the light beam is rotated by 0 degrees, the light beam is diffracted in the polarization hologram element 8 and enters the polarization hologram element 71. Here, the polarization hologram element 71
Is formed so as to diffract only light in a polarization direction parallel to light obtained by rotating the polarization direction of the reflected light beam reflected by the optical information recording medium d by 90 degrees. That is, the polarization hologram element 71 functions as a light beam separation unit by diffracting only the light diffracted by the polarization hologram element 8 and making the light incident on the light receiving element 7. Therefore, light in the polarization direction orthogonal to the diffracted light in the polarization hologram element 8 is suppressed from entering the light receiving element 7. In the light receiving element 7 on which the diffracted light has entered, a tracking signal based on the signal of the incident diffracted light,
A focus signal and an information signal are detected.

Here, by providing a polarization hologram element 71 for diffracting only the light in the polarization direction parallel to the diffracted light in the optical path between the diffractive element 3 and the light receiving element 7, the light is orthogonal to the diffracted light which is flare. (The laser light emitted from the semiconductor laser 2 is polarized by the polarization hologram element 8 of the diffraction element 3).
It is possible to reduce the ratio of reflected light (specularly reflected on the side) to the light receiving element 7. As a result, high-accuracy servo control in which the occurrence of an offset in the focus error signal and the tracking error signal is prevented is reliably performed.

Next, an eighth embodiment of the present invention will be described with reference to FIG.
It will be described based on. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 10 is a longitudinal sectional side view schematically showing the diffraction element 80. As shown in FIG. 10, the diffraction element 80 of the present embodiment is different from the diffraction element 3 in that the reflection type hologram region 81 is further provided on the glass substrate 10 side of the diffraction element 3. It is provided in place of the diffraction element 3 provided in the optical pickup devices 1, 20, 30, 40, 50, 60, 70 of the embodiment.

The diffraction element 80 will be described in detail. As shown in FIG. 10, the diffraction element 80 is provided with a reflection hologram area 81 on the glass substrate 10 side of the diffraction element 3 described above. In this reflection hologram area 81,
An opening 82 is formed. The opening 82 is formed to allow a light beam, which is irradiated as a light spot on the optical information recording medium d, of the laser beam from the semiconductor laser 2 incident on the diffraction element 80 to pass therethrough. In other words, the reflection hologram region 81 functions as a reflection diffraction element that reflects a light beam that is not irradiated as a light spot on the optical information recording medium d among the light beams of the laser light from the semiconductor laser 2 incident on the diffraction element 80. Become.

In such a configuration, the semiconductor laser 2
Make the light beam of the laser light emitted from the diffraction element 80 incident on the polarization hologram element 8 side. The light beam incident on the diffraction element 80 passes through the polarization hologram element 8 of the diffraction element 80 and is incident on the λ / 4 film 9. The luminous flux converted into circularly polarized light in the λ / 4 film 9 is reflected by the reflection type hologram area 8.
Proceed to 1.

The light beam that has proceeded to the opening 82 of the reflection hologram area 81 passes through the opening 82 as it is,
It proceeds to the optical information recording medium d. On the other hand, the luminous flux that has traveled to portions other than the opening 82 of the reflection hologram region 81
The light is reflected by the reflection type hologram area 81 and again λ /
4 enters the film 9. The luminous flux of the reflected light that has reentered the λ / 4 film 9 is rotated by 90 degrees in the polarization direction in the λ / 4 film 9. Therefore, when the reflected light beam that has passed through the λ / 4 film 9 is incident on the polarization hologram element 8, since the polarization direction is rotated by 90 degrees, it is not excluded by the light beam separating means. Therefore, the luminous flux of the reflected light reflected by the reflection type hologram area 81 enters the light receiving element 7 like the luminous flux of the reflected light reflected by the optical information recording medium d, and is monitored by the monitoring light receiving element. And is used for controlling the amount of light of the semiconductor laser 2.

Here, a reflection type hologram area 81 is provided on the glass substrate 10 side of the diffraction element 3, and among the light beams of the laser light emitted from the semiconductor laser 2, the light beam which is not irradiated as a light spot on the optical information recording medium d is set. Reflected light receiving element 7
By monitoring with the monitoring light receiving element built in the monitor, a sufficient amount of light is secured as forward emission light for monitoring,
Accurate light quantity control of the semiconductor laser 2 becomes possible.

Next, a ninth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Note that the same parts as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, FIG. 11 is a longitudinal sectional side view schematically showing the diffraction element 90. As shown in FIG.
The diffraction element 80 according to the eighth embodiment of the present invention
While the reflection hologram region 81 is provided on the glass substrate 10 side, the diffraction element 90 of the present embodiment is different from the diffraction element 90 in that the reflection hologram region 81 is provided on the polarization hologram element 8 side of the diffraction element 3. Is different. The diffraction element 90 of the present embodiment is the same as the diffraction element 3 provided in the optical pickup devices 40, 50, 60, and 70 of the above-described embodiments.
Is provided in place of.

The diffraction element 90 will be described in detail. As shown in FIG. 11, the diffraction element 90 is provided with a reflection hologram region 81 on the polarization hologram element 8 side of the diffraction element 3 described above. This reflection hologram area 81
Has an opening 82 formed therein. This opening 82
Is formed to allow a light beam irradiated as a light spot on the optical information recording medium d from among the light beams of the laser light from the semiconductor laser 2 incident on the diffraction element 90. That is, the reflection hologram region 81 functions as a reflection diffraction element that reflects a light beam that is not irradiated as a light spot on the optical information recording medium d among the light beams of the laser light from the semiconductor laser 2 incident on the diffraction element 90. Become.

Subsequently, an optical pickup device 91 which is an example of an optical pickup device provided with the diffraction element 90 is shown in FIG.
This will be described with reference to FIG. As shown in FIG. 12, an optical pickup device 91 includes a diffractive element 90 instead of the diffractive element 3 provided in the optical pickup device 50 of the fifth embodiment, and a light receiving element 92 instead of the light receiving element 7. A monitoring light receiving element 93 is provided. In such a configuration, the light beam of the laser light emitted from the semiconductor laser 2 is made incident on the polarization hologram element 8 side of the diffraction element 90.
Opening 82 of reflection hologram area 81 of diffraction element 90
The luminous flux that has traveled to the portion passes through the opening 82 as it is, passes through the polarization hologram element 8 and passes through the λ / 4 film 9.
Incident on. The light beam incident on the λ / 4 film 9 is converted into circularly polarized light and travels to the optical information recording medium d. on the other hand,
The light beam that has traveled to a portion other than the opening 82 of the reflection hologram region 81 is reflected in the reflection hologram region 81 without being affected by the diffraction element 90 at all.

According to the optical pickup device 91, the light flux of the reflected light reflected by the optical information recording medium d is light in the P-polarized direction, so that it passes through the polarization beam splitter 41 as it is and is received by the light receiving element 92. , A tracking signal, a focus signal and an information signal are detected,
The luminous flux of the reflected light reflected by the reflection hologram area 81 is light in the S-polarized direction, is reflected by the polarization beam splitter 41, is received by the monitor light receiving element 93, and is used for controlling the light amount of the semiconductor laser 2. In this case, the luminous flux of the reflected light reflected by the reflection type hologram area 81 is transmitted to the monitor light receiving element 93 together with the flare.
The monitoring light-receiving element 93 monitors the amount of light emitted from the semiconductor laser 2,
There is no problem in receiving the flare.

Here, a reflection type hologram area 81 is provided on the side of the polarization hologram element 8 of the diffraction element 3, and among the luminous fluxes of the laser light emitted from the semiconductor laser 2, the luminous flux which is not irradiated as a light spot on the optical information recording medium d. Is reflected and monitored by the monitoring light-receiving element 93 provided separately from the light-receiving element 92, whereby a sufficient amount of light is secured as the monitor front emission light, and the light amount of the semiconductor laser 2 can be accurately controlled. become.

The optical pickup device 91 of the fifth embodiment is the same as the optical pickup device 91 of the fifth embodiment.
Although the element provided with the diffraction element 90 instead of the diffraction element 3 provided at 0 is applied, the invention is not limited to this, and any element provided with an optical element having polarization selectivity upstream of the light receiving element may be used. An optical pickup device 40 according to the fourth embodiment,
The diffraction element 3 provided in the optical pickup device 60 of the sixth embodiment and the optical pickup device 70 of the seventh embodiment
Instead, a diffraction element 90 may be provided, and a monitoring light receiving element 93 may be provided at a predetermined position.

In each of the embodiments, the diffraction element 3 in which the polarization hologram element 8 and the λ / 4 film 9 are laminated is used. However, the present invention is not limited to this. May be provided separately.

[0077]

According to the first aspect of the present invention, the laser light emitted from the light source is transmitted through the polarization hologram element and the quarter-wave plate, and then reflected by the optical information recording medium. Incident on the wave plate and rotate the polarization direction by 90 degrees,
The reflected light has a polarization component different from that of the laser light emitted from the light source, and after the reflected light is diffracted by the polarization hologram element, the incident light to the light receiving element by the light beam separating means is not excluded. The light having the same polarization component as that of the laser beam emitted from the light source does not enter the light receiving element, and is reflected by the optical information recording medium having a polarization component different from that of the laser beam emitted from the light source. Since only the reflected light is incident on the light receiving element, for example, it is possible to suppress the incidence of flare generated by reflection of the laser light emitted from the light source by the polarization hologram element on the light receiving element,
High-precision servo control in which occurrence of an offset in a focus error signal or a tracking error signal is prevented can be performed.

According to the second aspect of the present invention, in the optical pickup device according to the first aspect, the quarter wavelength plate and the polarization hologram element are integrally laminated to form a diffraction element, thereby miniaturizing the apparatus. And simplification of component assembly.

According to the third aspect of the present invention, in the optical pickup device according to the first or second aspect, of the laser light emitted from the light source, the laser light that is not irradiated as a light spot on the optical information recording medium is polarized hologram. Element and 1 /
After passing through the four-wavelength plate, it is reflected by the reflection / diffraction element provided between the quarter-wavelength plate and the condensing optical system, and then is incident on the quarter-wavelength plate again to rotate the polarization direction by 90 degrees. The reflected light has a polarization component different from that of the laser light emitted from the light source, and the reflected light reflected by the reflection diffraction element is prevented by not excluding the incident light to the light receiving element by the light beam separating means. Since monitoring can be performed by the monitoring light receiving element built in the light receiving element, a sufficient amount of light can be secured as the monitor front emission light, and the light amount control of the light source can be accurately performed.

According to a fourth aspect of the present invention, in the optical pickup device according to the first or second aspect, of the laser light emitted from the light source, the laser light that is not irradiated as a light spot on the optical information recording medium is used as the light source. The reflected light is reflected by the reflection / diffraction element provided between the polarization hologram element, and the reflected light has the same polarization component as the light flux of the laser light emitted from the light source. By eliminating the light and receiving the light by the monitoring light receiving element provided separately from the light receiving element, the reflected light reflected by the reflection diffraction element can be monitored by the monitoring light receiving element provided separately from the light receiving element. Therefore, a sufficient amount of light can be secured as the monitor front emission light, and the light amount control of the light source can be accurately performed.

According to a fifth aspect of the present invention, in the optical pickup device according to any one of the first to third aspects, only the diffracted light diffracted by the polarization hologram element is transmitted and incident on the light receiving element. Is applied as a light beam separating means, it is possible to reliably suppress the flare from entering the light receiving element.

According to a sixth aspect of the present invention, in the optical pickup device according to any one of the first to third aspects, the laser beam emitted from the light source is reflected or transmitted to be incident on the polarization hologram element, and the polarized light is polarized. By applying a total reflection prism that transmits or reflects the diffracted light diffracted by the hologram element and makes it incident on the light receiving element as the light beam separating means, it is possible to reliably suppress the flare from being incident on the light receiving element.

According to a seventh aspect of the present invention, in the optical pickup device according to any one of the first to third aspects, the diffracted light diffracted by the polarization hologram element is transmitted or reflected and incident on the light receiving element. By applying the reflecting prism as the light beam separating means, it is possible to reliably suppress the flare from entering the light receiving element.

According to an eighth aspect of the present invention, in the optical pickup device according to any one of the first to fourth aspects, the laser beam emitted from the light source is reflected or transmitted and made incident on the polarization hologram element, and By applying a polarizing beam splitter, which transmits or reflects the diffracted light diffracted by the hologram element and makes it incident on the light receiving element, as a light beam separating means, it is possible to reliably suppress the flare from being incident on the light receiving element.

According to the ninth aspect of the present invention, in the optical pickup device according to any one of the first to fourth aspects, the polarized light which transmits or reflects the diffracted light diffracted by the polarization hologram element and enters the light receiving element. By applying the beam splitter as the light beam separating means, it is possible to reliably suppress the flare from entering the light receiving element.

According to the tenth aspect of the present invention, the first aspect
In the optical pickup device according to any one of the above items (4) to (4), a second polarization hologram element which transmits the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element is applied as a light beam separating means, thereby receiving the flare light. The incidence on the element can be reliably suppressed.

According to the eleventh aspect, in the first aspect,
In the optical pickup device according to any one of (4) to (4), a third polarization hologram element that diffracts the diffracted light diffracted by the polarization hologram element and makes it incident on the light receiving element is applied as a light beam separating means, thereby receiving the flare light. The incidence on the element can be reliably suppressed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view schematically showing an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view schematically showing a diffraction element.

FIG. 3 is a vertical sectional side view schematically showing an optical pickup device according to a second embodiment of the present invention.

FIG. 4 is a graph showing a relationship between the reflectance of a total reflection prism and an incident angle.

FIG. 5 is a vertical sectional side view schematically showing an optical pickup device according to a third embodiment of the present invention.

FIG. 6 is a vertical sectional side view schematically showing an optical pickup device according to a fourth embodiment of the present invention.

FIG. 7 is a vertical sectional side view schematically showing an optical pickup device according to a fifth embodiment of the present invention.

FIG. 8 is a vertical sectional side view schematically showing an optical pickup device according to a sixth embodiment of the present invention.

FIG. 9 is a vertical sectional side view schematically showing an optical pickup device according to a seventh embodiment of the present invention.

FIG. 10 is a vertical sectional side view schematically showing a diffraction element according to an eighth embodiment of the present invention.

FIG. 11 is a longitudinal sectional side view schematically showing a diffraction element according to a ninth embodiment of the present invention.

FIG. 12 is a vertical sectional side view schematically showing an optical pickup device.

FIG. 13 is a vertical sectional side view showing an example of a conventional polarization hologram element.

FIG. 14 is a vertical sectional side view showing another example of a conventional polarization hologram element.

FIG. 15 is a vertical sectional side view showing an example of a conventional optical pickup device.

FIG. 16 is a schematic diagram showing a state of occurrence of flare.

[Explanation of symbols]

1, 20, 30, 40, 50, 60, 70, 91 Optical pickup device 2 Light source 3, 80, 90 Diffraction element 4, 5 Condensing optical system 6, 21, 41, 61, 71 Light beam separating means 7, 92 Light receiving Element 8 Polarization hologram element 9 1
/ 4 wavelength plate 81 Reflection / diffraction element 93 Monitor light receiving element d Optical information recording medium

Claims (11)

[Claims] 1. A light source for emitting a laser beam, a quarter-wave plate provided downstream of the light source in a laser emission direction, and a laser beam passing through the quarter-wave plate is spotted on an optical information recording medium. A condensing optical system for irradiating, and disposed in an optical path between the light source and the quarter-wave plate,
A polarization hologram element that diffracts only light having a polarization component different from the light flux of the laser light emitted from the light source; a light receiving element that receives the diffracted light diffracted by the polarization hologram element; An optical pickup device that is disposed in an optical path between the hologram element and a light beam separating unit that excludes a light beam having the same polarization component as the light beam of the laser light emitted from the light source from entering the light receiving element. 2. The optical pickup device according to claim 1, wherein the quarter-wave plate and the polarization hologram element are integrally laminated as a diffraction element. 3. A laser light, which is provided between the quarter-wave plate and the condensing optical system and which is emitted from the light source and passes through the quarter-wave plate, is used for the optical information recording medium. A reflection / diffraction element formed to reflect and diffract laser light not irradiated as a light spot and allowing the reflected / diffracted light to pass through the quarter-wave plate again; and a monitoring light receiving element built in the light receiving element. The optical pickup device according to claim 1, further comprising: 4. A laser light provided between the light source and the polarization hologram element and emitted from the light source,
A reflection / diffraction element, which is formed so as to reflect and diffract a laser beam not irradiated to the optical information recording medium as a light spot and the reflected / diffracted light does not pass through the polarization hologram element, is provided separately from the light receiving element. 3. The optical pickup device according to claim 1, further comprising: a monitoring light receiving element configured to receive light whose incidence on the light receiving element is excluded by the light beam separating means. 5. The optical pickup device according to claim 1, wherein the light beam separating means is a polarization filter that transmits only the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element. . 6. The light beam splitting means reflects or transmits laser light emitted from the light source to enter the polarization hologram element, and transmits or reflects the diffracted light diffracted by the polarization hologram element, and The optical pickup device according to any one of claims 1 to 3, wherein the optical pickup device is a total reflection prism that enters the light receiving element. 7. The light according to claim 1, wherein the light beam separating means is a total reflection prism that transmits or reflects the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element. Pickup device. 8. The light beam splitting means reflects or transmits laser light emitted from the light source and makes the laser light incident on the polarization hologram element, and transmits or reflects the diffracted light diffracted by the polarization hologram element to produce the laser light. 5. A polarizing beam splitter for entering a light receiving element.
An optical pickup device according to any one of the above. 9. The light according to claim 1, wherein the light beam separating means is a polarization beam splitter that transmits or reflects the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element. Pickup device. 10. The polarization hologram element according to claim 1, wherein the light beam separation means is a second polarization hologram element that transmits the diffracted light diffracted by the polarization hologram element and makes the light incident on the light receiving element. Optical pickup device. 11. The device according to claim 1, wherein the light beam separating means is a third polarization hologram element that diffracts the diffracted light diffracted by the polarization hologram element and causes the diffracted light to enter the light receiving element. Optical pickup device.