JPH01182931A - Optical information reader - Google Patents

Abstract

PURPOSE:To attain small sized and light weight device entirely by arranging the optical element formed with a 2nd diffraction grating with different grating interval in a direction orthogonal to a 1st diffraction grating, radiating the radiated light from the optical element to the 4-split photodetector and applying focus servo. CONSTITUTION:The optical element 19 is arranged, which is formed with the 2nd diffraction grating 24 of linear shape with a different grating interval T orthogonal to the direction formed with the 1st diffraction grating 23 to the radiating face 22 receiving a light reflected from the reflecting face 21 through the transmission of the incident face 20 where the 1st diffraction grating 23 of a linear shape with different grating interval T is formed on the optical path of the reflected light reflected by a polarized beam splitter. Since the 4-split photodetector 25 is provided on the optical path of the light emitted from the light emitting surface 22 to attain focus servo by irradiating the radiated light from the optical element 19 onto the 4-split photodetector 25. Thus, number of component in the optical servo system is reduced and small size and light weight are attained.

Description

TECHNICAL FIELD The present invention relates to an optical information reading device of an optical information recording and reproducing apparatus that records and reproduces information by irradiating light from a semiconductor laser onto an optical information recording medium.

Prior Art A conventional optical information recording/reproducing device will be explained based on FIG. The light emitted from the semiconductor laser 1 is as follows.

The coupling lens 2 converts the light into parallel light, and the beam shaping splitter 3 transforms the plane of polarization from an ellipse to a circle. The circularly deformed light is transmitted by the first polarizing beam splitter 4 (this characteristic is that it transmits 100% of the P polarized light wave and reflects 66% of the S polarized light wave).

The same applies to a second polarizing beam splitter, which will be described later), so that only the S-polarized wave is irradiated onto the optical disc 7 via the polarizing prism 5 and the objective lens 6. Thereafter, the reflected light is reflected as a P-polarized light wave according to the magnetic direction of the optical disk 7 as an optical information recording medium.

After the reflected light passes through the first polarizing beam splitter 4, it is further divided into two parts by the second polarizing beam splitter 8, one of which is transmitted and guided to the magneto-optical detection optical system 9, and the other is reflected and sent to the servo motor. It is guided to a detection system 10.

In the magneto-optical detection optical system 9, the reflected light having the P-polarized wave that has passed through the first polarizing beam splitter 4 is divided into 1/2
It is tilted at 45 degrees by the wave plate 11, separated into ordinary light and extraordinary light by the Wollaston prism 12, and the detection lens 1
3 to the light-receiving element 14 having a two-part light-receiving surface.

A magneto-optical signal on the optical disk 7 is detected. As a result, the amounts of ordinary light and extraordinary light are determined, and it is detected whether the polarization direction has been changed.

Further, in the servo optical system 10, the S-polarized light reflected by the second polarizing beam splitter 8 is condensed by a condenser lens 15, and then split into two by a Knaifezi prism 16.

The light reflected by this knife prism 16 is guided to the track light receiving element 17 and detected as a track error signal, thereby performing tracking servo, while the separated light traveling straight is guided to the focus light receiving element 18. Focus servo is performed by detecting this as a focus error signal.

In the case of the conventional device as described above, it takes time to assemble and adjust because it has a large number of parts.

This poses a problem in that the device itself becomes large-scale, resulting in high costs.

Purpose The present invention was made in view of these points, and by reducing the number of parts, it is inexpensive and compact.

The purpose is to obtain a lightweight optical information reading device.

Structure The present invention is characterized in that linear first diffraction gratings with different grating intervals are formed on the incident surface on the optical path of the reflected light reflected by the polarizing beam splitter, and the light is transmitted through the incident surface and reflected by the reflective surface. An optical element having a linear second diffraction grating formed with a different grating interval in a direction perpendicular to the direction in which the first diffraction grating is formed is disposed on an exit surface through which light is guided, and the light is emitted by the exit surface. Since the 4-split light-receiving element is provided on the optical path of the light, focus servo can be performed by irradiating the 4-split light-receiving element with the light emitted from the optical element.This reduces the number of parts in the servo optical system. Therefore, it can be made inexpensive, small, and lightweight.

In addition, on the optical path of the reflected light reflected by the polarizing beam splitter, a linear first diffraction grating with different grating intervals is formed on the incident surface, and the light transmitted through this incident surface and reflected by the reflective surface is guided. An optical element in which a linear second diffraction grating is formed with a different grating interval in a direction perpendicular to the direction in which the first diffraction grating is formed is disposed on the output surface, and the light emitted from the output surface is A 4-split light-receiving element is provided on the optical path, and a 2-split light-receiving element is provided in contact with the reflective surface, so focus servo is performed by irradiating the light emitted from the optical element onto the 4-split light-receiving element. 2 touching
Tracking servo can be performed by irradiating the split light receiving element with light that has passed through the incident surface.
Since the number of parts and space in the servo optical system can be significantly reduced, it can be made cheaper, smaller, and lighter.

A first embodiment of the present invention will be described based on FIGS. 1 and 2. Note that the same reference numerals are used for the same parts as in the prior art.

The optical element 19 has a triangular prism shape, and includes an entrance surface 20 on which the reflected light from the optical disk 7 enters, a reflection surface 21 that reflects the light transmitted through this entrance surface 20, and a reflection surface 21 that reflects the light transmitted through this entrance surface 20. An exit surface 22 from which the emitted light is emitted is formed.

On the incident surface 20, there is a linear first diffraction grating 2 in which the grating interval T is coarse in the center and becomes denser toward the outside.
3 is formed along the X-axis direction. Further, a second diffraction grating 24 having a shape similar to that of the first diffraction grating 23 is formed on the output surface 22 along the Z-axis direction perpendicular to the direction in which the first diffraction grating 23 is formed. ing.

The optical element 19 is located on the optical path of the light reflected from the optical disk 7 by the second polarizing beam splitter 8 (see FIG. 5). Further, on the optical path of the light emitted by the output surface 22 of the optical element 19, a four-division light receiving element 25 for performing focus servo is provided.

In such a configuration, a method of performing focus servo using the optical element 19 will be described.

The light reflected by the second polarizing beam splitter 8 and incident on the incident surface 20 of the optical element 19 is focused in the Y-axis direction by the first diffraction grating 23, and the beam shape changes from a circle to an elongated ellipse in the X-axis direction. transformed into a shape. The deformed light is then reflected by the reflective surface 21 and directed to the output surface 22.
At this time, the deformed light is focused in the X-axis direction by the second diffraction grating 24, and its beam shape is deformed into an elongated ellipse in the Z-axis direction.

As a result, the light emitted from the output surface 22 of the optical element 19 becomes a beam with astigmatism. Therefore, by arranging the four-segment light receiving element 25 at a position P where the beam shape becomes a circle at one point on the optical path, focus servo can be performed using the well-known astigmatism method.

Next, a second embodiment of the present invention will be explained based on FIG. It made it possible. Therefore, a description of the focus servo will be omitted, and the tracking servo will be described here. Note that the same reference numerals are used for the same parts.

A two-part light receiving element 26 is directly attached to the optical element 19 in contact with its reflective surface 21 . The reflective surface 21 is set at a certain inclination so that the light transmitted through the incident surface 20 is transmitted on one side and enters the two-split light receiving element 26, and is reflected on the other side and guided toward the output surface 22. ing.

In such a configuration, a light beam that enters the entrance surface 20 of the optical element 19 and is deformed into an elongated shape in the X-axis direction by the first diffraction grating 23 passes through the reflection surface 21 and is guided to the two-split light receiving element 26. Accordingly, tracking servo can be performed by detecting a tracking error signal using the well-known push-pull method.

As described above in the first embodiment and the second embodiment, in the servo optical system that performs focus servo and tracking servo, the optical element 19 is used to control the condenser lens 15 and the Naifezi prism 16. The first diffraction grating 23. Second diffraction grating 24
There is no particular restriction other than that the lattice directions are orthogonal to each other.

If the grating spacings T of the diffraction gratings 23 and 24 are made the same, it is possible to duplicate them using one type of mold, thereby further improving manufacturing efficiency.

Note that, as shown in FIG. 4, by integrating the optical element 19 with the second polarizing beam splitter 8, the space can be significantly reduced, so the entire device can be made even smaller and lighter. .

Effects In the present invention, linear first diffraction gratings with different grating intervals are formed on the incident surface on the optical path of the reflected light reflected by the polarizing beam splitter, and the reflected light is transmitted through this human beam and reflected by the reflecting surface. An optical element in which a linear second diffraction grating is formed with a different grating interval in a direction perpendicular to the direction in which the first diffraction grating is formed is disposed on an exit surface through which the light is guided, and the light is emitted by the exit surface. Since a 4-split light receiving element is provided on the optical path of the emitted light, focus servo can be performed by irradiating the 4-split light receiving element with the light emitted from the optical element.This reduces the number of parts in the servo optical system. Since it can be reduced in number, it can be made inexpensive, small, and lightweight.

In addition, on the optical path of the reflected light reflected by the polarizing beam splitter, a linear first diffraction grating with different grating intervals is formed on the incident surface, and the light transmitted through this incident surface and reflected by the reflective surface is guided. An optical element in which a linear second diffraction grating is formed with a different grating interval in a direction perpendicular to the direction in which the first diffraction grating is formed is disposed on the output surface, and the light emitted from the output surface is A 4-split light receiving element is installed on the optical path.

Since the two-split light receiving element is provided in contact with the reflective surface, focus servo is performed by irradiating the light emitted from the optical element onto the four-split light receiving element, and the light receiving element that is divided into two parts in contact with one of the reflective surfaces is Tracking servo can be performed by irradiating light that has passed through the servo optical system, which can significantly reduce the number of parts and space in the servo optical system, making it inexpensive, small, and lightweight. It is.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a first embodiment of the present invention, Fig. 2 is a plan view of a four-division light receiving element including the circuit configuration, and Fig. 3 is a perspective view showing a second embodiment of the invention. 4 are perspective views showing a state in which the optical element is integrated with a second polarizing beam splitter, and FIG. 5 is a perspective view showing a conventional example.

Claims (1)

[Claims] 1. Information is recorded by irradiating light from a semiconductor laser onto an optical information recording medium, the reflected light from the optical information recording medium is separated by a polarizing beam splitter, and the reflected light is used for tracking. In an optical information recording and reproducing apparatus that performs servo detection of a servo and a focus servo, and also detects a signal of the optical information recording medium using the transmitted light and reproduces information, the light of the reflected light reflected by the polarizing beam splitter A linear first diffraction grating with different grating intervals is formed on the road on an entrance surface, and the first diffraction grating is formed on an exit surface to which light transmitted through the entrance surface and reflected by the reflection surface is guided. An optical element in which a linear second diffraction grating with a different grating interval is formed in a direction perpendicular to the direction is disposed, and a four-division light receiving element is disposed on the optical path of the light emitted by the emission surface. Optical information reading device. 2. Information is recorded by irradiating light from a semiconductor laser onto an optical information recording medium, and the reflected light from the optical information recording medium is separated by a polarizing beam splitter, and the reflected light controls the tracking servo and focus servo. In an optical information recording and reproducing apparatus that performs detection and reproduces information by detecting a signal of the optical information recording medium using the transmitted light, a lattice interval is provided on the optical path of the reflected light reflected by the polarizing beam splitter. Different linear first diffraction gratings are formed on the entrance surface, and light transmitted through the entrance surface and reflected by the reflection surface is guided to the exit surface in a direction perpendicular to the direction in which the first diffraction gratings are formed. An optical element in which a second linear diffraction grating with a different grating interval is formed is disposed, a four-split light receiving element is provided on the optical path of the light emitted by the output surface, and the light is received in two parts in contact with the reflective surface. An optical information reading device characterized by being provided with an element.