JPS634434A - Optical pickup - Google Patents

Abstract

PURPOSE:To obtain an optical pickup capable of high speed operation having a small sized pickup head with high reliaiblity and long service life by providing a light emitting/light receiving section to an end of a head feeder and providing an actuator for automatic focus and automatic tracking to a collimator lens. CONSTITUTION:An optical head 11 fed in the radial direction of an optical disk 5 by a head feeder 12 consists only of a reflecting mirror 10 and a converging lens 6. Further, the collimator lens 2 is provided with an electromagnetic drive actuator comprising a magnet and a coil and the automatic focus and tracking are applied by using an automatic focus detection signal and a tracking detection signal detected by a light receiving element 8. The light emitting/light receiving sections 8, 11 provided at the end of the head feeder 12 are placed while utilizing the center of the optical disk 5 where no information is stored, then an isolator for return light prevention or the like is added without making the entire device large in size when high performance coping with high S/N ratio is called for.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical pickup used in optical information processing devices such as optical disk memories, video disks, and digital audio disks.

(Prior Art) Optical disk devices, which are optical information writing and reading devices, have made remarkable progress in recent years because they are capable of high-speed, large-capacity information processing. It is being Since semiconductor lasers have been used as light sources, the semiconductor laser and light receiving element are small and lightweight, so the pickup head that includes them is moved in the radial direction of the optical disc by a head feeding mechanism, and the information is transferred. Writing and reading are performed.

An example of a conventional pickup head of this type will be explained with reference to FIG. In the figure, the pickup head includes a semiconductor laser 1 that emits light with a fixed polarization direction, a collimating lens 2 that converts the light emitted from the semiconductor laser 1 into parallel light, and a lens that transmits light with the same polarization direction. - A polarizing beam splitter 3 that reflects light that does not match, a 174-wave plate 4 that converts the linearly polarized light transmitted by the polarizing beam splitter 3 into clockwise circularly polarized light, and the transmitted light of the 174-wave plate 4 is focused on an optical disk 5. At the same time, the reflected light from the optical disc 5 is transmitted through a converging lens 6 that converts it into parallel light, and the quarter-wave plate 4 described above, and becomes linearly polarized light again.The light is reflected at right angles by the polarizing beam splitter 3 described above. It is composed of a converging lens 7 that condenses light, and a light receiving element 8 that receives the converging lens.

The operation of the pickup head configured in this way will be explained.

The linearly polarized light emitted from the semiconductor laser 1, which is the light source, is
The collimating lens 2 converts the light into parallel light, and the light is incident on the polarizing beam splitter 3. The polarizing beam splitter 3 transmits light without loss because its transmission polarization direction matches the linear polarization direction of the semiconductor laser 1 described above. The linearly polarized light that has passed through the polarizing beam splitter 3 is converted into clockwise circularly polarized light when it passes through the 174-wave plate 4 , and is then focused onto the surface of the optical disk 5 by the converging lens 6 .

In the case of information writing, it is performed as described above, but when reading the information stored on the optical disc 5, reflected light from the surface of the optical disc 5 is used.

Therefore, the optical disc 5 usually has a metal mirror added thereto.

Converging lens 6 along the same path as when writing information as described above.
The clockwise circularly polarized light that has passed through the optical disc 5 undergoes a phase inversion when reflected by the metal mirror surface of the optical disk 5, and is converted into counterclockwise circularly polarized light. The circularly polarized light converted counterclockwise is again 1
When the light enters and passes through the 74-wavelength plate 4, it further rotates counterclockwise and is converted into linearly polarized light perpendicular to the linearly polarized light emitted by the semiconductor laser 1 described above. Therefore, the reflected light incident on the polarizing beam splitter 3 is reflected in the right angle direction without loss, is focused by the converging lens 7, and is received by the light receiving element 8. The light receiving element 8 detects information from the optical disc 5,
Performs automatic focus detection and tracking detection, and converts each into electrical signals.

The converging lens 6 that focuses light on the optical disk 5 is equipped with an electromagnetic actuator consisting of a magnet and a coil, and focusing and tracking are controlled by a signal detected by the light receiving element 8.

(Problems to be Solved by the Invention) However, in the above configuration, although the light source and light receiving element using semiconductor elements are small and lightweight, the collimating lens 2, the two converging lenses 6 and 7 A pickup head mounting optical system components such as the polarizing beam splitter 3 has a problem in that it is restricted by these optical system components and becomes large, making it difficult to reduce the size and weight.

In addition, the combination of the quarter-wave plate 4 and the polarizing beam splitter 3 prevents light returning to the semiconductor laser 1, which causes noise, but when a high-performance device with high S/H is required. In order to completely prevent the return light, it was necessary to use an isolator, which caused the problem that the pickup head became large.

Furthermore, since the semiconductor laser 1 is operated at high output when writing information, there is also the problem that temperature control is required to ensure reliability and longevity.

Furthermore, semiconductor laser 1. There is also a problem in that the electric wiring from the light receiving element 8 and the actuator comes out from the pickup head, which hinders smooth high-speed operation.

The present invention solves the above problems and provides an optical pickup that has a small pickup head, is capable of high-speed operation, is highly reliable, and has a long life.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a semiconductor laser, a collimating lens, a polarizing beam splitter, a 174
a light emitting/receiving section composed of a wavelength plate, a light receiving element, and a converging lens that focuses reflected light from the optical disk onto the light receiving element; a converging lens that focuses the emitted light of the semiconductor laser on the surface of the optical disk; An optical pickup is composed of an optical head section composed of a reflecting mirror and a head feeding device that moves the optical head section in the radial direction of the optical disk, and the light emitting/receiving section is installed at the end of the head feeding device. At the same time, actuators for automatic focusing and automatic tracking are provided in the collimating lens.

(for production) With the above configuration, a semiconductor laser and a light receiving element.

The light emitting/receiving section, which includes most of the optical system parts and actuators, is stationary, and the moving optical head section cannot be made small and lightweight, and there is no electrical wiring.

Smooth and high-speed operation is possible. Furthermore, since the light emitting/receiving section is fixedly placed at the end of the head feeding device, it is possible to add an isolator and a temperature control device to improve performance without increasing the size of the entire device.

(Example) An example of the present invention will be described with reference to FIG. Components that are the same as those in the conventional example shown in FIG. 2 are given the same symbols and their explanations will be omitted.

In the figure, an optical pickup according to the present invention includes a semiconductor laser 1. Collimating lens 2 that converts the emitted light into parallel light
, a polarizing beam splitter 3 that selectively transmits or reflects polarized light, converts the linearly polarized light from the semiconductor laser 1 into circularly polarized light, and converts the circularly polarized light reflected from the optical disk 5 back into linearly polarized light orthogonal to the above linearly polarized light. A fixed light emitting/receiving section consisting of a 174 wavelength plate 4 for conversion, a lens 7 for converging reflected light, a light receiving probe 8 for detecting information, and a temperature control device 9 for the semiconductor laser 1, and the surface of the optical disk 5. an optical head section 11 composed of a reflecting mirror 10 and a converging lens 6 that change the direction of a laser beam running parallel to the laser beam at right angles;
The optical head section 11 is arranged in the radial direction of the optical disk 5.
and a head feeding device 1112 that moves the head.

The operation of the optical pickup having such a configuration will be explained.

The light emitted from the semiconductor laser 1 becomes parallel light by the collimating lens 2 and enters the polarizing beam splitter 3. Since the polarization direction of the emitted light from the semiconductor laser 1 matches the transmission polarization direction of the polarizing beam splitter 3, the light is transmitted without loss and becomes clockwise circularly polarized light by the quarter-wave plate 4.

The light transmitted through the 174-wavelength plate 4 runs parallel to the surface of the optical disc 5, is converted into a direction perpendicular to the surface of the optical disc 5 by a reflecting mirror 10 installed in the moving optical head unit 11, and is converted into a direction perpendicular to the surface of the optical disc 5 by a converging lens 6. The light is focused on the surface of 5.

The reflected light from the optical disk 5 has its phase reversed and becomes counterclockwise circularly polarized light, becomes parallel light by the converging lens 6, changes direction by the reflector 10, runs parallel to the surface of the optical disk 5, and reaches the light emitting/receiving section. The light enters the quarter-wave plate 4 again. The incident light is further counterclockwise rotated by the 174-wave plate 4 and converted into linearly polarized light perpendicular to the linearly polarized light emitted from the semiconductor laser 1, reflected by the polarizing beam splitter 3, and sent to the light receiving element by the converging lens 7. Focus the light on 8.

'The optical head section 11, which is sent in the radial direction of the optical disk 5 by the head feeding device 12, is composed of only the reflecting mirror 1o and the converging lens 6, so it is small and lightweight, and there is no electrical wiring, so it can be moved smoothly. High-speed operation is possible.

Further, the collimating lens 2 is equipped with an electromagnetic actuator (not shown) consisting of a magnet and a coil.
Autofocus and tracking are performed by the autofocus detection signal and tracking detection signal detected by the light receiving element 8. Further, since the temperature of the semiconductor laser 1 is controlled by the temperature control device 9, the semiconductor laser 1 operates stably even at high output.

Furthermore, since the light emitting/receiving section installed at the end of the head feeding device 12 is installed using the central part of the optical disk 5 where no information is stored, it is possible to support a higher S/N ratio. When high performance is required, an isolator for preventing return light can be added without increasing the size of the entire device.

Further, in this embodiment, a configuration has been described in which the head feeding device is provided with a light emitting/receiving section on the center side of the optical disc 5, but it goes without saying that it may be installed on the outer diameter side of the optical disc 5.

(Effects of the Invention) As explained above, according to the present invention, the light emitting/receiving section and the optical head section are separated, and the optical head section, which is small and lightweight and has no electrical wiring, is fed by the head feeding device, so that it can be fed smoothly and at high speed. operation becomes possible.

In addition, since the light emitting and receiving parts can be installed in the empty space of the optical disk, it is possible to add isolators, temperature control devices, etc. without increasing the size of the entire device, and the influence of return light to the semiconductor laser is eliminated. It is possible to obtain a highly reliable and long-life optical pickup that can obtain a high S/N ratio and stable high-output operation.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical pickup according to the present invention, and FIG. 2 is a schematic diagram of a conventional optical pickup head. 1... Semiconductor laser, 2... Collimating lens, 3... Polarizing beam splitter, 4...
174 wavelength plate, 5... optical disc, 6.7...
Converging lens, 8... Light receiving element, 9... Temperature control device, 10... Reflecting mirror, 11... Optical head section, 12... Head feeding device.

Claims (1)

[Claims] A light emitting/receiving section including a semiconductor laser, a collimating lens, a polarizing beam splitter, a quarter wavelength plate, a light receiving element, and a converging lens that focuses reflected light from the optical disk onto the light receiving element, a reflecting mirror, and a converging lens. It is composed of an optical head section and a head feeding device, the light emitting/receiving section is installed at the end of the head feeding device, and the collimating lens is equipped with an actuator for automatic focusing and automatic tracking. An optical pickup featuring