JPH0567345A - Optical substrate type optical information recording/ reproducing device - Google Patents

Abstract

PURPOSE:To improve the detection accuracy by forming integrally a diffraction grating for emitting light which is reflected in a transparent substrate and becomes a stray light to the outside, in a position turned aside from an original optical path of a laser light of the transparent substrate. CONSTITUTION:A diffraction grating 101 is formed on both end faces, as well in the longitudinal direction of a transparent substrate 10. That is, the diffraction grating 101 is formed on the whole surface of the transparent substrate 10 except the position of optical parts. According to such a constitution, in the same way, the stray light of an unnecessary degree containing a O-order light which is made incident on the peripheral part of an optical disk 7 and a hologram lens 23, a hologram beam splitter 15 and a diffraction grating 12 can be emitted surely to the outside of the transparent substrate 10. Accordingly, according to this device, it does not occur that a multi-division photodetector 16 detects a stray light which causes deterioration of an S/N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical substrate type optical information recording / reproducing apparatus used in the information processing field using laser light.

[0002]

2. Description of the Related Art In recent years, as in a compact disc device, a video disc device, a writable optical disc device, a rewritable optical disc device, an optical card device, etc., a minute light spot is formed on a medium such as an optical disc by using laser light. 2. Description of the Related Art Information devices that are formed and thereby reproduce or record information have been widely used.

By the way, the signal processing optical system constituting the central portion of the conventional compact disk device includes a large number of various lenses such as a collimator lens, a diffraction grating, a half prism, a mirror prism, an objective lens, a photodetector and a semiconductor laser. It was composed of optical components. Moreover, electric parts such as actuators for moving the objective lens toward and away from the optical disk are arranged in parallel.

As a result, the number of optical components is increased, and the device configuration becomes large, heavy and complicated.

Therefore, recently, an optical information recording / reproducing apparatus having a signal processing optical system called a hologram pickup has been proposed for the purpose of reducing the number of these optical components and downsizing them. FIG. 5 shows a conventional example of this type of hologram pickup. The outline of the configuration will be described below.

The laser light emitted upward from the semiconductor laser 1 passes through the diffraction grating 2, the hologram beam splitter 5 and the collimator lens 3, and then is focused on the optical disk 8 by the objective lens 4. The objective lens 4 can be moved toward and away from the optical disc 8 by an actuator (not shown), so that a focused spot is focused on a pit of the optical disc 8 in a focused state.

The diffraction grating 2 diffracts incident light into three light beams of 0th order and ± 1st order. The ± 1st order diffracted light is also focused on another position on the optical disk 8 and used to detect the tracking error signal.

On the other hand, the reflected light from the optical disk 8 passes through the objective lens 4 and the collimator lens 3 in the opposite route to the above, is diffracted by the hologram beam splitter 5, and is collected on the multi-segment photodetector 6. It is focused on the light spot. The recording signal, the focus error signal, and the tracking error signal are detected by using the light condensed at these condensing points.

Although this hologram pickup has the advantages that the number of parts is reduced and the apparatus structure is simplified, it has the drawback that it takes time to manufacture because it is necessary to adjust the positions of the optical parts. In addition, there is a limit in downsizing.

An optical integrated circuit (hologram pickup) proposed by the applicant of the present application in Japanese Patent Application No. 3-164621 has been proposed to solve the above-mentioned problems of the prior art. This is because most of the optical components that are the constituent elements of the optical integrated circuit are integrally formed on one transparent substrate made of glass or plastic, and the number of components is reduced, and the positions between the optical components are reduced. No adjustment required. Therefore,
According to this optical integrated circuit, it is possible to realize a signal processing optical system which is small in size, light in weight and improved in manufacturability. Therefore, by applying the optical integrated circuit, a thin, lightweight and high speed optical information processing device can be realized. .. The reason is shown below.

FIG. 6 shows the structure of this optical integrated circuit. A semiconductor laser 11 that emits laser light toward the inside of the transparent substrate 10 is mounted on one end face in the longitudinal direction of the block-shaped transparent substrate 10. Laser light emitted from the semiconductor laser 11 is diffracted into three light beams of 0th order and ± 1st order by the diffraction grating 12 formed on one end side of the lower surface 10a of the transparent substrate 10. Subsequently, the three light beams are transmitted to the transparent substrate 1
The hologram beam splitter 15 formed in the central portion of the upper surface 10b of 0 in the longitudinal direction, the hologram lens 23 formed on the other end side of the lower surface 10a of the transparent substrate 10 and the portion above the hologram lens 23 of the substrate upper surface 10b. It is condensed on the pits 8 of the optical disk 7 via the formed objective lens 14 to form three light spots.

This is a method for detecting a tracking error signal, which is a so-called three-beam method.
The pit information recorded in the pit 8 is detected by the next light spot, while the tracking error signal is detected by using the light spots on both sides of the ± 1st order light beam to detect the 0th order light spot as a desired track. Get the servo signal to fix to.

The laser beam focused on the optical disk 7 is reflected from the disk surface, passes through the objective lens 14 and the hologram lens 23, is diffracted by the hologram beam splitter 15, and is subsequently arranged on the diffraction grating 12 in parallel. 19
After being reflected by, the light is focused on the multi-segment photodetector 16. As a result, the reproduction signal focus error signal and the tracking error signal are detected.

In the signal processing optical system of this optical integrated circuit, since each optical component can be manufactured by integral molding, it is not necessary to adjust the positions of the optical components. Therefore, the manufacturability can be improved. In addition, since the laser light travels back inside the transparent substrate 10, the size and weight of the device can be reduced.

In the writable optical disk device, a semiconductor laser having three light emitting points is used instead of the diffraction grating 12 described above. That is, of the three light emitting points, the two light emitting points on both sides emit light with a low light output that is not written on the optical disk, and are used for detecting the tracking error signal. The laser light from the central light emitting point is emitted at a high light output for recording on the optical disk, while it is emitted at a low light output for information reproduction.

[0016]

However, in the above-described optical integrated circuit, the photodetector 1 is provided after the unnecessary laser light which is not subjected to signal processing is repeatedly reflected on the inner surface of the transparent substrate 10.
There was a problem of stray light entering 6. That is, there is a problem that the detection accuracy deteriorates due to the stray light. Particularly, in the optical integrated circuit having the above configuration, unnecessary diffracted light from the diffraction grating 12, the hologram beam splitter 15, and the hologram lens 23 is repeatedly totally reflected on the inner surface of the transparent substrate 10 and is incident on the photodetector 16. There is a problem that the S / N ratio of the signal light and the S / N ratio of the focus error signal and the tracking error signal are lowered, and malfunction often occurs.

The present invention solves the problems of the prior art as described above. The optical substrate is capable of reducing the size and weight of the device, reliably eliminating the adverse effects of stray light, and causing no malfunction. An object is to provide a pattern type optical information recording / reproducing apparatus.

[0018]

In the optical substrate type optical information recording / reproducing apparatus of the present invention, a wide variety of optical components are integrally formed on a block-shaped transparent substrate, and laser light propagates inside the transparent substrate. In the optical substrate type optical information recording / reproducing apparatus configured to perform the above, a diffraction grating that emits light that is reflected in the transparent substrate and becomes stray light to a position outside the original optical path of the laser light of the transparent substrate. Are integrally formed, whereby the above object is achieved.

In the optical substrate type optical information recording / reproducing apparatus of the present invention, various optical components such as a laser light source and a photodetector are integrally formed on a block-shaped transparent substrate, and the inside of the transparent substrate is formed. In an optical substrate type optical information recording / reproducing apparatus in which laser light is propagated, a polarization plane conversion optical component and a polarization plane selection optical component are provided in the path of the signal light detected by the photodetector. By doing so, the above object is achieved.

The polarization plane conversion optical component is preferably one having a function of converting linearly polarized light into circularly polarized light and elliptically polarized light, or one having a function of rotating the plane of polarization of linearly polarized light.

[0021]

If the stray light inside the transparent substrate is emitted to the outside by the diffraction grating as described above, the stray light is not detected by the photodetector in the optical component integrally formed on the transparent substrate. Therefore, the S / N ratio of the photodetector can be improved.

If the polarization plane converting optical component and the polarization plane selecting optical component are provided in the signal light path as described above, it is possible to prevent stray light components from entering the photodetector. Therefore, the S / N ratio of the photodetector that finally detects the signal light can be improved.

[0023]

EXAMPLES Examples of the present invention will be described below.

(First Embodiment) FIG. 1 shows a first embodiment of the optical substrate type optical information recording / reproducing apparatus of the present invention. The transparent substrate 1 has a block shape and is made of transparent glass or transparent plastic. One end face in the longitudinal direction corresponding to the left side of the transparent substrate 10 in the figure is an inclined surface 10c.
The semiconductor laser 11 is mounted on c. Laser light emitted from the semiconductor laser 11 travels inside the transparent substrate 10 and is incident on a diffraction grating 12 integrally formed on one end side of the lower surface 10 a of the transparent substrate 10. The diffraction grating 12 diffracts the laser light into three light beams of 0th order and ± 1st order.

Subsequently, the three light beams are transmitted to the transparent substrate 1.
The hologram beam splitter 15 formed in the central portion of the upper surface 10b of the 0 in the longitudinal direction, the hologram lens 23 formed on the other end side of the lower surface 10a of the transparent substrate 10, and the portion above the hologram lens 23 of the substrate upper surface 10b. It is condensed on the pits of the optical disk 7 through the formed objective lens 14 to form three light spots.

The pit information recorded in the pits is detected by using the 0th-order light spot in the center. Further, the tracking error signal is detected by utilizing the ± 1st order light spots located on both sides of the 0th order, and a servo signal for fixing the 0th order light spot to a desired track is obtained.

The laser light focused on the optical disk 7 is reflected from the disk surface, passes through the objective lens 14 and the hologram lens 23, is diffracted by the hologram beam splitter 15, and is subsequently arranged on the diffraction grating 12 in parallel. 19
After being reflected by, the light is focused on the multi-segment photodetector 16. As a result, the reproduction signal focus error signal and the tracking error signal are detected.

By the way, since the laser beam emitted from the semiconductor laser 11 has a wide radiation angle, it is also incident on the periphery of the diffraction grating 12. As indicated by the broken line in the figure, this incident light becomes unnecessary light, that is, stray light 102, which is reflected toward the inside of the substrate by the lower surface 10 a of the transparent substrate 10. Further, in the diffracted light diffracted by the diffraction grating 12, the above-mentioned 0
In addition to the ± 1st order diffracted light, there is also higher order diffracted light.
Since this high-order diffracted light also has a large diffraction angle, it becomes stray light 103 which is incident on the peripheral portion of the hologram beam splitter 15 and is reflected here toward the inside of the substrate.

If such stray light 102, 103 is left as it is, the S / N ratio of the multi-divided photodetector 16 is lowered as described above, which causes malfunction of the optical substrate type optical information recording / reproducing apparatus.
Therefore, in this embodiment, another diffraction grating 101, 101 is provided on the lower surface 10a and the upper surface 10b of the transparent substrate 10 including the peripheral portions of the diffraction grating 12 and the hologram beam splitter 15.
Of the diffraction gratings 101, 10
1, the stray light 102, 103 is effectively emitted to the outside of the transparent substrate 10.

As shown in the figure, the diffraction grating 101 is also formed on both end faces of the transparent substrate 10 in the longitudinal direction. That is, in this embodiment, the diffraction grating 101 is formed on the entire surface of the transparent substrate 10 excluding the positions of the optical components described above. According to such a configuration, similarly, an unnecessary order including return light from the optical disk 7 and the hologram lens 23, which is the 0th-order light incident on the periphery of the hologram lens 23, the hologram beam splitter 15, and the diffraction grating 12. The stray light can be reliably emitted to the outside of the transparent substrate 10.

Therefore, according to the optical substrate type optical information recording / reproducing apparatus of the present embodiment, the multi-segment photodetector 16 does not detect stray light which causes a decrease in S / N ratio.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention. In the second embodiment, a polarization plane conversion element (polarization plane conversion optical component) 111, that is, a so-called polarizer and a polarization plane selection element (polarization plane selection optical component) 112 are provided in the optical path in the transparent substrate 10. Form and by these stray light 103
Is prevented from being detected by the multi-segment photodetector 16.

The polarization plane conversion element 111 is formed on the incident side of the objective lens 14. The polarization plane conversion element 111 is made of, for example, a crystal plate having a desired crystal orientation and a desired thickness, and is attached and fixed to the upper surface 10b of the transparent substrate 10. The polarization plane conversion element 111 has a function of converting incident light from linearly polarized light to circularly polarized light.
Further, the polarization plane selection element 112 is formed on the incident side of the multi-split photodetector 16. The polarization plane selection element 112 has a function of detecting only light having a polarization plane perpendicular to the plane of the drawing. Therefore, the multi-split photodetector 16 that detects the incident light through the polarization plane selection element 112 similarly detects only the incident light having the polarization plane in this direction.

The details will be described below. However, the same numbers are attached to the portions corresponding to those in the first embodiment,
Details of the structure and the like are omitted.

The semiconductor laser 11 has a plane of polarization parallel to the plane of the paper, as indicated by the symbol ← → in the figure.
The laser light emitted from the inside of the transparent substrate 10 is reflected by the diffraction grating 12, the hologram beam splitter 15,
The polarization plane conversion element 111 passes through the hologram lens 23.
Incident on. This laser light is converted from linearly polarized light into circularly polarized light by the polarization plane conversion element 111. Then, the laser light is focused on the pit 8 of the optical disk 7 by the objective lens 14.

The laser light reflected from the optical disk 7 is re-incident on the optical polarization conversion element 111, and the polarization conversion element 1
It is converted into linearly polarized light by 11. At this time, the laser light has a plane of polarization perpendicular to the plane of the paper orthogonal to the emitted light of the semiconductor laser 11, as indicated by a symbol having a concentric circle with a black circle at the center in the figure. Then, the laser light is emitted from the hologram lens 2
3, the beam is separated by the hologram beam splitter 15, is then reflected by the mirror 19, and enters the multi-segment photodetector 16 through the polarization plane selection element 112.

As described above, since the polarization plane selection element 112 allows the multi-division photodetector 16 to detect only the laser light having the polarization plane perpendicular to the paper surface, the reflected light from the optical disk 7 having the polarization plane in the vertical direction. That is, the laser light is detected by the multi-segment photodetector 16.

On the other hand, stray light which is repeatedly reflected multiple times in the transparent substrate 10 is not detected by the multi-division photodetector 16. That is, as an example, stray light 103 indicated by a broken line in the figure will be described as an example. Since the stray light 103 does not pass through the polarization conversion element 111, it does not have a polarization plane perpendicular to the paper surface and the symbol ← As shown by →, the light has a horizontal plane of polarization on the paper. Therefore, the stray light 1
03 is a multi-segment photodetector 1 through the polarization plane selection element 112.
It is not detected by 6. Therefore, according to the present embodiment, the adverse effect of the stray light 103 can be reliably eliminated, and the S / N ratio of the multi-segment photodetector 16 can be improved.

In the above embodiment, the polarization plane conversion element 1 is used.
Although the element having a conversion function of linearly polarized light and circularly polarized light is used as 11, a polarization plane conversion element having a conversion function of linearly polarized light and elliptically polarized light may be used.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention. In the third embodiment, the polarization plane conversion element 111 is arranged in the peripheral portion of the hologram lens 23.
With such a configuration, the laser light passes through this portion four times, and the optical path length can be increased by that amount. Therefore, the thickness of the transparent substrate 10 is the transparent substrate 10 of the first and second embodiments.
1/2 of the thickness will be good. Therefore, according to this embodiment, not only the same effects as the above embodiments can be obtained, but also the weight of the optical substrate type optical information recording / reproducing apparatus can be further reduced.

The parts corresponding to those in the above embodiment are designated by the same reference numerals, and the detailed description will be omitted.

(Fourth Embodiment) FIG. 4 shows a fourth embodiment of the present invention. In the second and third embodiments, the polarization plane conversion element 11 is used.
Although the one having the conversion function of linearly polarized light and circularly polarized light was used as 1, the Bi-substituted garnet, YIG, and B are used in this embodiment.
A polarization plane conversion element having a function of rotating the plane of polarization of a linearly polarized wave, such as a Faraday rotator made of a material such as i ₁₂ SiO ₂₀ or ZnSe, is used.

As shown in FIG. 4, the Faraday rotation element 12
1 is formed on the periphery of the hologram lens 23,
Permanent magnets 122 that apply a magnetic field to the Faraday rotator 121 are disposed at corresponding positions on both front and rear surfaces of the transparent substrate 10.

The polarization plane selection element 112 of this embodiment is also used.
Is a prism 114 forming a part of the transparent substrate 10,
The incident surface of the prism 114, that is, the multi-segment photodetector 1
6 and a dielectric multilayer film 113 formed on the surface which becomes the incident surface of light. The polarization plane selection element 112 having such a configuration transmits the P polarization component and reflects the S polarization component.

After adhering the dielectric multilayer film 113, the prism 114 is adhered to one end face in the longitudinal direction of the transparent substrate by using an adhesive. After the adhesion, the inclined surface 1 of the transparent substrate 10
The semiconductor laser 11 and the multi-divided photodetector 16 are formed on one surface of the prism 114 that is 0c.

In this embodiment, the laser light emitted from the semiconductor laser 11, focused on the optical disk 7, and then reflected is detected by the multi-split photodetector 16 as follows. That is, the laser light emitted from the semiconductor laser 11 and having the plane of polarization in the direction perpendicular to the plane of the paper is reflected by the diffraction element 1
2, the hologram beam splitter 15, the hologram lens 23, and the Faraday rotator 121, and the light is focused on the optical disk 7 by the objective lens 14. When passing through the Faraday rotation element 121, the plane of polarization of the laser light is rotated by 45 °.

The reflected light from the optical disk 7 is the objective lens 1
4 through the Faraday element 121, then the hologram beam splitter 15, the mirror 19, and the polarization plane selection element 112 to be detected by the multi-segment photodetector 16. When the reflected light passes through the Faraday rotator 121, the plane of polarization is rotated by 45 ° again. Therefore, the polarization plane of the laser light emitted from the semiconductor laser 11 is 90 °.
It is incident on the multi-segment photodetector 16 in a rotated state. That is, since the laser light has a horizontal plane of polarization on the paper surface, the laser light is transmitted through the dielectric multilayer film 114 and the prism 1
It is detected by the multi-segment photodetector 16 through 13.

On the other hand, the Faraday rotation element 121
Unnecessary light that does not pass through, that is, stray light, has a plane of polarization perpendicular to the paper surface, and therefore cannot pass through the dielectric multilayer film 113 and does not enter the multi-segment photodetector 16. Therefore,
Also in this embodiment, the S / N ratio of the multi-segment photodetector 16 can be improved as in the above embodiment.

[0049]

According to the optical substrate type optical information recording / reproducing apparatus of the first aspect, the stray light generated inside the transparent substrate is surely emitted to the outside of the substrate by the diffraction grating. The S / N ratio of the detector can be improved. Therefore, the detection accuracy can be improved and no malfunction occurs. In addition, since various optical components including the photodetector are integrally formed on the transparent substrate, it is not necessary to adjust the positions of the optical components. Therefore, the manufacturability can be improved. Further, since the laser light travels back inside the transparent substrate, it has an advantage that the size and weight of the device can be reduced.

Further, according to the optical substrate type optical information recording / reproducing apparatus of the second to fourth aspects, the stray light component is incident on the photodetector by the polarization plane converting optical component and the polarization plane selecting optical component. Can be prevented, so that the S / N ratio of the photodetector that finally detects the signal light can be improved. Therefore, similarly to the optical substrate type optical information recording / reproducing apparatus according to the first aspect, the detection accuracy can be improved and no malfunction occurs. Similarly, it is possible to improve manufacturability and reduce the size and weight of the device configuration.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of an optical substrate type optical information recording / reproducing apparatus of the present invention.

FIG. 2 is a side view showing a second embodiment of the optical substrate type optical information recording / reproducing apparatus of the present invention.

FIG. 3 is a side view showing a third embodiment of the optical substrate type optical information recording / reproducing apparatus of the present invention.

FIG. 4 is a side view showing a fourth embodiment of the optical substrate type optical information recording / reproducing apparatus of the present invention.

FIG. 5 is a perspective view showing a conventional hologram pickup.

FIG. 6 is a perspective view showing an optical integrated circuit previously proposed by the applicant of the present application.

[Explanation of symbols]

 7 optical disk 10 transparent substrate 10a transparent substrate lower surface 10b transparent substrate upper surface 11 semiconductor laser 12 diffraction grating 13 collimator lens 14 objective lens 15 hologram beam splitter 16 multi-segment photodetector 19 mirror 101 diffraction grating 102, 103 stray light 111 polarization plane conversion Element 112 Polarization plane selection element 113 Dielectric multilayer film 114 Prism 121 Faraday rotator 122 Permanent magnet

Continuation of the front page (72) Inventor Shochika Kato 22-22 Nagaike-cho, Abeno-ku, Osaka City Sharp Corporation (72) Inventor Masumi 22-22 Nagaike-cho, Abeno-ku, Osaka City (72) Invention Toshimasa Hamada 22-22 Nagaike-cho, Nagano-cho, Abeno-ku, Osaka City Sharp Corporation (72) Inventor Matsui Kansai 22-22 Nagaike-cho, Abeno-ku, Osaka City Sharp Corporation

Claims (4)

[Claims] 1. An optical substrate type optical information recording / reproducing apparatus in which various kinds of optical components are integrally formed on a block-shaped transparent substrate, and laser light propagates inside the transparent substrate. 2. An optical substrate type optical information recording / reproducing apparatus integrally formed with a diffraction grating that emits light, which is reflected in the transparent substrate and becomes stray light, to a position outside the original optical path of the laser light. 2. An optical substrate type optical information in which a wide variety of optical components such as a laser light source and a photodetector are integrally formed on a block-shaped transparent substrate, and laser light propagates inside the transparent substrate. In the recording / reproducing apparatus, an optical substrate type optical information recording / reproducing apparatus in which a polarization plane conversion optical component and a polarization plane selection optical component are provided in the path of the signal light detected by the photodetector. 3. The optical substrate type optical information recording / reproducing apparatus according to claim 1, wherein the polarization plane converting optical component has a function of converting linearly polarized light into circularly polarized light and elliptically polarized light. 4. The optical substrate type optical information recording / reproducing apparatus according to claim 1, wherein the polarization plane converting optical component has a function of rotating a polarization plane of linearly polarized light.