JPS62264444A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To detect a magneto-optical disk information signal, an amplitude modulation disk information signal, a focus error signal, and a tracking error signal, by converting a light quantity received at six photoreceiving areas in an optical detector to electrical signals, and performing arithmetic operations on the six electrical signals. CONSTITUTION:A light spot A and a light spot B on an optical detector 8 are polarized light intersecting orthogonally with each other, and their light quantities are almost equal. When a disk 5 is a magneto-optical disk, a difference between the electrical signals generated by the light spot A and the light spot B is taken. In other words, by taking the difference between the sum of the electrical signals generated at a photoreceiving plane (a), a photoreceiving plane (b), and a photoreceiving plane (c), and the sum of those generated at a photoreceiving plane (d), a photoreceiving plane (e), and a photoreceiving plane (f), the magneto-optical disk information signal can be obtained. When the disk 5 is an amplitude modulation disk, the amplitude modulation disk information signal can be obtained by taking the sum of all of the light quantities received at the optical detector 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to read-only optical disks such as compact disks that have already been commercialized, recording/reproducing optical disks whose reflectance changes when recording is performed, and recording devices whose recording portions are evaporated. An optical recording and reproducing device that can be used for both reproducing optical discs and magneto-optical discs that allow recording, reproducing and erasing, and can be applied to both consumer and professional audio equipment, video equipment, computer memory, etc. It is related to.

Conventional Technology The modern era is called the information age, and the technology development of high-density, large-capacity memory, which forms the core of this age, is actively being carried out.

In addition to the above-mentioned high density and large capacity, the capabilities required of memory include high reliability and high speed access, and optical disk memory is attracting the most attention as a device that satisfies all of these requirements. Optical disk memory is a device that optically records information on a recording medium, and recently a lot of research has been conducted on magneto-optical disks that can also erase recorded information. The present invention relates to an optical recording/reproducing device.

In the past, many reports have been made regarding technologies related to optical recording and reproducing devices.
There are publications such as No. 0-234235.

The conventional optical recording/reproducing device mentioned above will be explained below with reference to the drawings.

FIG. 3 is a schematic diagram of a conventional optical recording/reproducing device and a diagram explaining its operating principle.

In FIG. 3, 1 is a semiconductor laser which is a linearly polarized light source, 2 is a collimating lens, 3 is a half mirror, 14 is an objective lens, 6 is a disk which is an information recording medium, 12 is an objective lens actuator, 13 is a % wavelength plate, 14 is a polarizing beam splitter, 16 is a 2-split photodetector, 16.17 is a convex cylindrical lens, 18 is a 4-split photodetector, 19
, 20° 23 are subtracters, and 21, 22, and 24 are adders.

The operation of the conventional example configured as described above will be explained below.

The light emitted from the semiconductor laser 1 is converted into parallel light by a collimating lens 2, passes through a half mirror 3, and then passes through an objective lens 4 incorporated in an objective lens actuator 12.
As a result, the light is focused on the information recording medium 5 as a light spot with a diameter of about 1 μm.

The reflected light from the information recording medium 5 follows the opposite path, is reflected and separated by the half mirror 3, and enters the lunar wave plate 13. The semiconductor laser 1 is installed so that the polarization direction is parallel to the plane of the paper, and the frequency plate 13 is set to rotate the polarization direction of the reflected light by approximately 46 degrees.

The reflected light that has passed through the wavelength plate 13 is separated by the polarization beam splitter 14 into two mutually orthogonal polarization components, one of which is transmitted and enters the two-split photodetector 15, and the other is reflected and passes through the convex cylindrical lens. 16.4 after 17
The light enters the split photodetector 18. The two-split photodetector 16 is
It has a dividing line 15a as shown in FIG. 3, and the reflected light from the information recording medium 6 is shown by diagonal lines in the figure. 2
A tracking error signal is detected by subtracting electrical signals generated in each divided area of the divided photodetector 15 using a subtracter 20. This tracking error detection method is a method called a push-pull method.

The light reflected by the polarization beam splinter 14 passes through convex cylindrical lenses 16 and 17, which are optical means for detecting focus errors, and enters the four-split photodetector 18. The 4-split photodetector 18 has dividing lines 18a, as shown in FIG.
18b, and the reflected light from the information recording medium 5 is the shaded area in the figure. Of the electric signals generated in each divided area of the 4-split photodetector 1B, the sum of the electric signals generated in the opposing divided areas is calculated, and the subtracter 19 calculates the difference between the sums, thereby determining the focus. An error signal is being detected. This method is a focus error detection method called the astigmatism method.

Let us consider a case where a magneto-optical disk is used as the information recording medium 5 and information recorded on the disk is to be reproduced.

As described above, in FIG. 3, the frequency plate 13 is used to adjust the amount of light transmitted through the polarizing beam splitter 14 and the amount of reflected light to be approximately equal. When reproducing information recorded on a magneto-optical disk, the transmitted light and the reflected light of the polarizing beam splitter 14 become signal lights that have approximately the same amplitude and contain information that is in opposite phase to each other. Therefore, by converting this transmitted light and reflected light into electrical signals and taking the difference between them, the in-phase components are canceled out, and the information components that are in opposite phase are doubled to obtain a reproduced signal with a good S/N ratio. Is possible. This method is often used as a reproduction method for magneto-optical disks, and is called a differential detection method.

In FIG. 3, the electric signals detected by the two-split photodetector 15 are added by an adder 22, the electric signals detected by the four-split photodetector 18 are added by an adder 21, and the difference between each is added by a subtracter. 23, the above-mentioned differential detection method is realized, and it is possible to obtain a reproduction signal of the magneto-optical disk.

Next, a case will be considered in which a disc such as a compact disc on which information is recorded on uneven surfaces or a disc on which information is recorded as a change in reflectance is used as the information recording medium 5 and the information is reproduced. When reproducing information, the light emitted by the semiconductor laser 1 is kept substantially uniform, and the reflected light is modulated in light intensity by the signal recorded on the information recording medium 6. Therefore, the information signal lights incident on the two-split photodetector 15 and the four-split photodetector are in phase and have substantially equal amplitudes. Therefore, the output of the adder 22 which adds the electrical signals detected by the two-split photodetector 16 and the output of the four-split photodetector 18
The information signal can be efficiently reproduced by adding the electrical signals detected by the adder 24 and the output of the adder 21.

Problems to be Solved by the Invention However, although the above configuration is functionally sufficient, it has the disadvantage that it has a large number of component parts, making it difficult to achieve miniaturization and cost reduction of the optical system. . In addition, optical disk memory requires a high-speed access function that allows the optical system to move to a desired position on the disk at high speed and record and reproduce information, making it difficult to make the optical system smaller and lighter. , it was inevitably difficult to achieve high-speed access capabilities.

The present invention has been made in view of the above-mentioned problems, and provides a small, lightweight, and low-cost optical recording and reproducing device by reducing the number of component parts while maintaining the same optical characteristics as the examples shown in the prior art. The purpose is to provide

Means for Solving the Problems In order to achieve the above object, the optical recording and reproducing apparatus of the present invention includes a light source whose polarization direction is linear, and a light source that directs the light from the light source to a recording track on an information recording medium. a condensing means arranged to form a minute light spot having a polarization direction at an angle of 45 degrees with the direction of the recording track; a separating means for separating the light reflected by the information recording medium; and the separating means. a convex lens that converges the light separated by the means;
located in a convergent light beam of the convex lens, directing the convergent light beam of the convex lens in the direction of an optical image of the recording track;
an analyzer made of a polarizing prism arranged to polarize and separate two mutually orthogonal polarized components with a small polarization angle, and two parallel dividing lines that intersect approximately perpendicularly to the two parallel dividing lines. The light-receiving surface is divided into six parts by one dividing line, and two parts are formed by the convex lens and the polarizing prism.
When one of the book's converging light beams is in a convergent state and the other is in a divergent state after convergence, the sum of the light amounts received by the four outer light receiving surfaces and the sum of the light amounts received by the inner two light receiving surfaces are approximately equal, and the outer light It consists of a single photodetector installed to receive a substantially equal amount of light on four light receiving surfaces.

Operation The present invention has the above-described configuration, converts the amount of light received by the six light receiving areas of the photodetector into electrical signals, and calculates the six electrical signals to generate magneto-optical disk information signals and amplitude modulated disk information. It is possible to detect signals, focus error signals, and tracking error signals.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a schematic configuration diagram of an optical recording/reproducing apparatus according to an embodiment of the present invention, and the same parts as in FIG. 3 are given the same numbers.

In FIGS. 1(a), (b), and (C), 6 is a convex lens, 7 is an analyzer, and 8 is a photodetector. Figure 1 (
a) shows the disk 6 and objective lens 4 of FIG. 1(b+) viewed from the direction of arrow G;
C) shows the state of the light spot on the photodetector 8.

Note that the direction of the recording track on the disk 5 and the polarization direction of the light emitted from the objective lens 4 are set to form an angle of 46°.

The analyzer 7 is a polarizing prism that has the function of polarizing and separating the transmitted light beam into two mutually orthogonal light beams at a minute polarization angle, and examples thereof include a Wollaston prism, a Glan-Thompson prism, and a Rochon prism. .

When the light reflecting surface of the disk 6 matches the focal point of the objective lens 4, reflected parallel light from the disk 5 enters the convex lens e and is emitted as a convergent beam. After the light from the convex lens 6 passes through the analyzer 7, it is separated into two polarized lights that are perpendicular to each other, and converge at a focus P and a focus Q. The photodetector 8 has a light receiving surface divided into six by two parallel dividing lines and one dividing line that intersects the two dividing lines substantially perpendicularly. Analyzer A is set so that the line connecting focal points P and Q of convex lens 6 coincides with the track direction on disk 5, by rotating analyzer 7 by 45 degrees around the optical axis of the incident light. Like the analyzer 7, the photodetector 8 is rotated by 45 degrees and set so that the two parallel dividing lines are substantially parallel to the line connecting the focal points P and Q of the convex lens 6. Furthermore, the photodetector 8 is
The analyzer 7 is tilted so that one of the two convergent light beams is received in a convergent state and the other in a divergent state after convergence, and the sum of the amounts of light received by the four outer light receiving areas and the two inner light receiving areas are calculated. The setting is such that the sum of the amounts of light received by the two areas is approximately equal, and the four outer light receiving areas receive approximately equal amounts of light. FIG. 2(C) shows an enlarged view of the analyzer 7 and photodetector 8 surrounded by broken lines as seen from the direction G. Photospora) A and photospora) B are formed.

The operation of an embodiment of the optical recording/reproducing apparatus configured as described above will be explained below.

FIG. 2 shows an example of the connections and calculations after the photodetector 8 of the present embodiment shown in FIG. In Figure 2, e&
9q is an adder, and 1o is a subtracter.

The light spot A and the light spot B on the photodetector 8 are polarized lights perpendicular to each other, and have approximately the same amount of light.

When the disk 5 shown in FIG. 1 is a magneto-optical disk, the light receiving surface of the photodetector 8 is , by taking the difference between the sum of the electric signals generated on the light receiving surface b1 and the light receiving surface C and the sum of the light receiving surface d, the light receiving surface e, and the light receiving surface f. A disc information signal can be obtained. If the disk 5 is an amplitude modulation disk, an amplitude modulation disk information signal can be obtained by summing all the amounts of light received by the photodetector 8.

Next, the principle of detecting the focus error signal will be explained. In FIG. 1, when the light reflecting surface of the disk 5 is at the focal point of the objective lens 4, the light spot A and the light spora B on the photodetector 8 have substantially congruent shapes. At this time, the focus error signal obtained by subtracting the sum of the electrical signals generated at the light receiving surfaces A, D, and F from the sum of the electrical signals generated at the light receiving surfaces A, C, and E of the photodetector 8 is zero. . Here, assume that the disk 5 is slightly displaced in the direction of arrow G in FIG. 1, that is, in the direction toward the objective lens 4. At this time, since the light incident on the convex lens 6 becomes diverging light, both the focal point P and the focal point Q are slightly displaced in the direction of G. That is, since the focal point P moves away from the light receiving surface of the photodetector 8 and the focal point Q approaches, the optical spot A on the photodetector 8 has a large diameter, and the optical spot B has a small diameter. Therefore, the light receiving surfaces a, C and e of the photodetector 8
The amount of light received at the light receiving surfaces decreases, and the amount of light received at the light receiving surfaces S, d and f increases. Therefore, the light receiving surface of the photodetector 8 &,C
The focus error signal obtained by subtracting the sum of the electric signals generated at the light receiving surfaces S, d, and B from the sum of the electric signals generated at the light receiving surfaces S, D, and E becomes negative. When the disk 5 is slightly displaced in a direction away from the objective lens 4, the opposite phenomenon occurs and a positive focus error signal can be obtained. This method has the advantage that detection errors are less likely to occur even if the light spots A and B and the photodetector 8 change in the T direction and the R direction due to changes in environmental temperature.

Next, the tracking error signal detection means will be explained. In this embodiment, the photodetector 8 is
The two parallel dividing lines are approximately aligned in the track direction on the disk 5. Therefore, when focusing only on the optical spora (A) on the photodetector 8, it is possible to detect the tracking error signal by using the push-pull method similar to the conventional example by taking the difference between the electrical signals generated at the light receiving surface d and the center. . Since the light spot B is a light spot that once converges and then diverges, the diffraction image due to the track on the disk 5 in the light spora) B is opposite to that of the light spot A. Therefore, in the tracking error signal detection example shown in Fig. 2,
Light receiving surface a of photodetector 8.

The tracking error signal is detected by subtracting the sum of the electrical signals generated at the light-receiving surfaces c and d from the sum of the electrical signals generated at f.

As described above, according to this embodiment, a light spot having a polarization direction at an angle of 450 with respect to the direction of the recording track on the disc 5 is formed on the disc 5, and the transmitted light is minutely polarized into two polarized lights perpendicular to each other. An analyzer consisting of a polarizing prism that separates at an angle is set so that the plane containing the two transmitted optical axes coincides with the track direction, and two parallel dividing lines,
The photodetector 8 is divided into six by one dividing line that intersects the two dividing lines substantially perpendicularly to the two dividing lines, and the direction of the two parallel dividing lines is as follows.
By setting it to match the direction of the track,
It has the same function as the conventional example, and it becomes possible to eliminate the % wavelength plate 13 required in the conventional example, and furthermore, it becomes possible to reduce the number of photodetectors by one.

Note that in this embodiment, the same effect can be obtained even if the convex lens 6 is set at a position between the analyzer 7 and the photodetector 8.

Effects of the Invention The present invention provides an optical recording/reproducing device that includes a light source whose polarization direction is linear, and focuses the light from the light source onto a recording track on an information recording medium, and forms an angle of 46° with the direction of the recording track. a convex lens that converges the light reflected from the information recording medium; and a convex lens that directs the reflected light in the direction of an optical image of the recording track. , an analyzer made of a polarizing prism arranged to deflect and separate two polarized light components perpendicular to each other with a minute polarization angle, two parallel dividing lines, and the two parallel dividing lines. The light-receiving surface is divided into six parts by one dividing line that intersects substantially perpendicularly, and both receive two convergent beams formed by the convex lens and the polarizing prism, and both of the two parallel dividing lines are connected to the recording track. is parallel to the optical image of By installing it to receive light, it is possible to detect information on information recording media such as magneto-optical recording materials and width modulation recording materials, as well as focus error signals and tracking error signals.

In addition, by arranging the photodetector to receive one of the two convergent beams in a convergent state and the other in a divergent state after convergence, it is possible to maintain a stable focus error without being affected by changes in environmental temperature. It becomes possible to detect the signal.

Furthermore, the number of component parts can be significantly reduced, and a compact, lightweight, and low-cost optical recording/reproducing device can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an optical recording and reproducing device according to an embodiment of the present invention, FIG. 2 is a configuration diagram for explaining its operation, and FIG. 3 is a configuration diagram of a conventional optical recording and reproducing device. be. 1...Semiconductor laser, 2...Collimating lens, 3...Half mirror 14...
・Objective lens, 6...Disc, 6...
・Convex lens, 7...analyzer, 8...photodetector. Name of agent: Patent attorney Toshio Nakao and 1 other person - Ittetsu d -no
(Figure 2 Figure 3

Claims (3)

[Claims] (1) A light source whose polarization direction is a straight line, and the light from the light source is focused on a recording track on an information recording medium to form a minute light spot whose polarization direction is at an angle of 45 degrees with the direction of the recording track. a convex lens for converging the light reflected from the information recording medium; The light is received by an analyzer made of a polarizing prism arranged to deflect and separate the light with an angle of declination, two parallel dividing lines, and one dividing line that intersects approximately perpendicularly to the two parallel dividing lines. The surface is divided into six parts, both receive two convergent beams formed by the convex lens and the polarizing prism, and the two parallel division lines are both parallel to the optical image of the recording track, and the outer The sum of the amount of light received by the four light receiving surfaces and the inner 2
An optical recording/reproducing device characterized in that the sum of the amounts of light received by the two light receiving surfaces is substantially equal, and a photodetector is installed so that the sum of the amounts of light received by the four outer light receiving surfaces is substantially equal. (2) The optical recording and reproducing apparatus according to claim 1, characterized in that a convex lens is disposed between the analyzer and the photodetector. (3) Optical recording according to claim 1, characterized in that a photodetector is arranged to receive one of the two convergent beams in a convergent state and the other in a divergent state after convergence. playback device.