JPH0391133A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To make a device small in size and light in weight by integrating and providing an optical path separating element which transmits or reflects light with a diffraction grating type polarizing plate which polarizes and separates the reflected light from an optical information recording medium and has a diffraction grating formed so that the grating directions are orthogonally crossed with each other. CONSTITUTION:The optical path separating element 8 which transmits or reflects the light and the diffraction grating type polarizing plate 9 which polarizes and separates the reflected light from the optical information recording medium 10 and has the diffraction grating formed so that the grating directions are orthogonally crossed with each other are integrated to be provided on the optical path of the light emitted from a laser light source 7. Then, the light emitted from the laser light source 7 is reflected by the optical path separating element 8 and guided to the optical information recording medium 10. The light reflected on the medium 10 is guided to the optical path separating element 8 again and transmitted through there. Then, the light is polarized and separated by the diffraction grating type polarizing plate 9 having the diffraction grating and guided to a signal detection optical system. Therefore, the information is reproduced and a focusing error signal and a tracking error signal, etc., are detected. Thus, the number of parts in a signal detection optical system is reduced and the entire device is made small in size and light in weight.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording/reproducing apparatus that detects a focus error signal, a track error signal, etc. using reflected light from an optical information recording medium.

2. Description of the Related Art A diffraction grating type polarizing plate 1 used as one of polarization separation means in a conventional optical information recording/reproducing device is shown in FIGS. 4 and 5.
This will be explained based on the diagram. A grating 3 is placed on the substrate 2.
is formed (in the Y-axis direction), and this grating 3
A liquid crystal 4 and a cover glass 5 are provided on the top of the screen.

In this case, the diffraction grating type polarizing plate 1 has a Y
The polarized light component in the axial direction is emitted as O-order light T, and the polarized light component in the Z-axis direction is emitted as ±1st-order light. On the other hand, if linearly polarized light in the 45° direction is incident, the O-order light T and ±
It can be seen that the intensity difference in the primary light is O. Therefore, by using the diffraction grating type polarizing plate 1 having such a structure, it is possible to replace the Wollaston prism, Glan-Thompson prism, etc. that have been used as polarization separation elements for a long time, and this makes it possible to reduce the thickness and cost. can be dealt with.

Problems to be Solved by the Invention As described above, by using the diffraction grating type polarizing plate 1, it is possible to provide a polarization separation function and to reduce the size and weight of the device. However, in the conventional device, there is no device that uses the diffraction grating type polarizing plate 1 and has a structure that has a beam splitter and Naifezi prism function, and considers application to a magneto-optical pickup optical system. For this reason, it has not been possible to further reduce the size and weight of the entire device.

Means for Solving the Problem Therefore, in order to solve such problems, claim 1
In the described invention, light emitted from a laser light source is focused by an objective lens to form a light spot, and the light spot is irradiated onto an optical information recording medium to record information, and the reflected light from the optical information recording medium is recorded. By guiding the signal to the detection optical system and detecting it with the photodetector, information can be reproduced, focus error signals,
In an optical information recording/reproducing device that detects a track error signal, on the optical path of the light emitted from the laser light source,
An optical path separation element that transmits or reflects light and a diffraction grating type polarizing plate having a diffraction grating in which the grating directions for polarizing and separating the reflected light from the optical information recording medium are orthogonal to each other are integrated.

Further, in the invention according to claim 2, the light emitted from the laser light source is focused by an objective lens to form a light spot, and the light spot is irradiated onto an optical information recording medium to record information, and the light is recorded on the optical information recording medium. In an optical information recording and reproducing apparatus that reproduces information and detects focus error signals and track error signals by guiding reflected light from the laser beam to a signal detection optical system and detecting it on a photodetector, the light emitted from the laser light source A diffraction grating type polarizing plate is mounted on the optical path of the optical information storage medium, the semi-transparent film being formed on one surface and the other surface having a diffraction grating in which the grating directions for polarizing and separating the reflected light from the optical information recording medium are orthogonal to each other. A beam shaping prism was installed.

According to the invention according to claim 1, the light emitted from the laser light source is reflected by the optical path separation element and guided to the optical information recording medium, and the light reflected from this is guided to the optical path separation element again and transmitted therethrough, The polarized light is separated by a diffraction grating type polarizing plate having a diffraction grating and guided to a signal detection optical system, whereby information can be reproduced and a focus error signal and a track error signal can be detected.

According to the second aspect of the invention, the light emitted from the laser light source is reflected by the semi-transparent film of the beam shaping prism and guided to the optical information recording medium, and the light reflected from this is guided again to the semi-transparent film and is then guided to the semi-transparent film. The transmitted light is polarized and separated by a diffraction grating-type polarizing plate having a diffraction grating, and guided to a signal detection optical system, whereby information can be reproduced and a focus error signal and a track error signal can be detected.

Embodiment First, an embodiment of the invention as claimed in claim 1 is shown in FIGS. 1 and 2.
This will be explained based on the diagram. On the optical path of the light emitted from the semiconductor laser 7 as a laser light source, there is a half mirror 8 as an optical path separating element having an optical path separating function and a diffraction grating 9a having a polarization separating function.

A diffraction grating type polarizing plate 9 having a polarizing plate 9b is integrally provided. The grating direction of the diffraction gratings 9a and 9b is the second
As shown in the figure, they are formed perpendicular to each other. Further, a collimating lens 11 is integrally provided on one surface of the half mirror 8 on the side facing the magneto-optical disk 1o as an optical information recording medium, and between this collimating lens 11 and the magneto-optical disk 10. An objective lens 12 is disposed therein. Further, within the signal detection optical system 13 located on the side of the diffraction grating type polarizing plate 9, four light receiving elements 14 as photodetectors are provided.

In such a configuration, the light emitted from the semiconductor laser 7 is reflected by the half mirror 8, becomes parallel light by the collimating lens 11, is focused by the objective lens 12, and is irradiated onto the surface of the magneto-optical disk 1o, thereby transmitting information. Records will be made. Also, the magneto-optical disk 1
The reflected light from 0 is again guided to the half mirror 8, transmitted therethrough, and incident on the diffraction grating type polarizing plate 9.

In this diffraction grating type polarizing plate 9, diffraction gratings 9a and 9b are divided into two parts with the center line on the disk as a boundary, and the grating directions are perpendicular to each other, so that the light incident thereon is polarized. separated. That is, now, for example, when the magneto-optical disk 1o is set to the left and right diffraction gratings 9a, the polarization direction of the reflected light is
, 9b, when transmitted through this and guided onto the four light-receiving elements A, B, C, and D, the (A10) The output value and the output value of (B + D) become equal, and the value of the reproduced magneto-optical signal Mo = (A + G) (B + D) becomes 0 and is not detected.However, the actually incident magneto-optical signal The signal value is not 45@ but light with a polarization direction of (45±θ)°, and the Mo signal will be detected accordingly.Furthermore, the focus error signal F is Element 8
By dividing the surface into two, the spot shape on the surface becomes semicircular, so that signal detection can be performed using the well-known Knifezi method.

In this case, detection can be performed in the same way on the surface of the light receiving element, and in order to increase detection sensitivity, detection can also be performed using both light receiving elements B and D. Furthermore, the tracking error signal T can be easily detected by the well-known bush-pull method by dividing the light-receiving element A or C into two and making the dividing line direction perpendicular to the light-receiving elements B and D. can.

As described above, by integrating the half mirror 8 with the optical path separation function and the diffraction grating type polarizing plate 9 with the polarization separation function, the number of parts in the signal detection optical system 13 can be significantly reduced. As a result, the overall configuration of the device can be made smaller and lighter, which makes it possible to further increase the speed of access of the optical pickup optical system. Since it is possible to simultaneously detect the optical signals of 1 to 2, it is possible to apply this to a magneto-optical pickup optical system.

Next, an embodiment of the invention according to claim 2 will be described based on FIG. 3. A beam shaping prism 15 is disposed on the optical path of the light emitted from the semiconductor laser 7. This beam shaping prism 15 has a semi-transparent film 16 formed on one surface that has an optical path separation function, and a diffraction grating 9 formed on the other surface that has a polarization separation function and whose grating directions are perpendicular to each other.
A diffraction grating type polarizing plate 9 having elements a and 9b is integrally attached.

In such a configuration, the light emitted from the semiconductor laser 7 enters the semi-transparent film 16 of the beam shaping prism 15. This semi-transparent film 16 also serves as a kind of half mirror, and the light transmitted through it is directed to the beam shaping prism 1.
5, the beam is shaped into parallel light by a collimating lens 11, focused by an objective lens 12, and irradiated onto the surface of the magneto-optical disk 10, thereby recording information. Then, the reflected light from the magneto-optical disk 10 is transmitted again to the semi-transparent film 16 of the beam shaping prism 15.
The light is then reflected and guided to the light receiving element 14 in the signal detection optical system 13, where various signals are detected.

In the case of this device, in addition to being able to obtain the same effects as in the above-described embodiment, the use of the beam shaping prism 15 improves the light utilization efficiency.

An advantage is that the beam profile is also equidirectional.

Furthermore, since the direction of the dividing line of the light-receiving element 14 is made to match the direction of spot deviation due to wavelength fluctuation, which is a drawback of diffraction gratings, stable signal detection can be performed even in the face of wavelength fluctuation. be.

It should be noted that the signal detection method can be performed in the same manner as in the above-described embodiment, so a description thereof will be omitted here.

In addition, when a sample servo method is used to detect the track error signal, the light receiving element 14 is used as in the above embodiment.
There is no need to divide it into two parts.

Effects of the Invention The invention according to claim 1 is characterized in that an optical path separating element that transmits or reflects light and a grating that polarizes and separates the reflected light from the optical information recording medium are arranged on the optical path of the light emitted from the laser light source. Since it is integrated with a diffraction grating type polarizing plate having orthogonal diffraction gratings, the light emitted from the laser light source is reflected by the optical path splitting element and guided to the optical information recording medium, where it is reflected. The emitted light is again guided to the optical path separation element, transmitted therethrough, polarized by a diffraction grating type polarizing plate having a diffraction grating, and guided to the signal detection optical system, which reproduces information, focuses error signals, and tracks. Since it is possible to detect error signals, etc., it can be applied to magneto-optical pickup optical systems.
Since the number of parts in the signal detection optical system can be significantly reduced, the overall configuration of the device can be made smaller and lighter, making it possible to further increase the speed of access for the optical pickup optical system. be.

The invention according to claim 2 is characterized in that a semi-transparent film is formed on one surface on the optical path of the light emitted from the laser light source, and on the other surface, the grating directions for polarizing and separating the reflected light from the optical information recording medium are orthogonal to each other. Since a diffraction grating type polarizing plate having a diffraction grating formed by the laser light source is attached, the light emitted from the laser light source is reflected by the semi-transparent film of the beam shaping prism, guided to the optical information recording medium, and reflected from this. The light is guided to the semi-transparent film again, transmitted through it, polarized by a diffraction grating type polarizing plate having a diffraction grating, and guided to the signal detection optical system, where it is used to reproduce information, focus error signals, and track errors. In addition to being able to detect signals, it is also possible to significantly reduce the number of parts in the signal detection optical system, making it possible to reduce the size and weight of the entire device. This makes it possible to further improve access.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the invention as claimed in claim 1,
FIG. 2 is an optical path diagram showing the traveling direction of light incident on the diffraction grating type polarizing plate, FIG. 3 is a configuration diagram showing an embodiment of the invention as claimed in claim 2, and FIG. 4 is a conventional diffraction diagram. FIG. 5 is a configuration diagram of a grating type polarizing plate, and a side view thereof. 7... Laser light source, 8... Optical path separation element, 9...
Diffraction grating type polarizing plate, 9a, 9b... Diffraction grating, 10.
...Optical information recording medium, 12...Objective lens, 13...
・Signal detection optical system, 14... Photodetector, 15... Beam shaping prism, 16... Semi-transparent film Applicant Ricoh Co., Ltd. -Jδun

Claims (1)

[Claims] 1. The light emitted from the laser light source is focused by an objective lens to form a light spot, and the light spot is irradiated onto an optical information recording medium to record information, and to record information from the optical information recording medium. In an optical information recording and reproducing device that reproduces information and detects focus error signals and track error signals by guiding reflected light to a signal detection optical system and detecting it on a photodetector, the light emitted from the laser light source is used. On the road, an optical path separation element that transmits or reflects light and a diffraction grating type polarizing plate having a diffraction grating formed with grating directions orthogonal to each other that polarize and separate the reflected light from the optical information recording medium are integrated. An optical information recording/reproducing device characterized in that: 2. The light emitted from the laser light source is focused by an objective lens to form a light spot and irradiated onto an optical information recording medium to record information, and the reflected light from the optical information recording medium is detected by signal detection optics. In an optical information recording and reproducing device that reproduces information and detects a focus error signal and a track error signal by guiding the light into the system and detecting it with a photodetector, a semicircular light beam is placed on the optical path of the light emitted from the laser light source. A beam shaping prism is provided on which a transmission film is formed and a diffraction grating type polarizing plate having a diffraction grating formed with grating directions for polarizing and separating the reflected light from the optical information recording medium being orthogonal to each other is attached to the other surface. An optical information recording/reproducing device characterized by: