KR100243176B1 - An optical pickup device - Google Patents

Abstract

The present invention detects a change in the amount of emitted light by irradiating the optical recording medium with a constant amount of light on information optically recorded on a predetermined optical recording medium, modulating the amount of light with a modulator to record a desired signal on the optical recording medium, and to reproduce the information. An optical pickup / reproducible optical pickup apparatus is also provided.

That is, in the optical pickup device according to the present invention, the light receiving portion is disposed in the starting portion, and the optical path with the fixing portion is adopted as a flexible material called an optical fiber, so that the optical pickup can be easily assembled and the distance between the disk and the light receiving portion is short. There is an advantage that the effect of vibration and the change over time during operation is small, there is no change in the incident optical axis due to the vibration during operation, there is also an advantage that can adjust the distance between the fixed part and the moving part arbitrarily. Particularly, in the present invention, a quarter wave plate is formed by using a part of the optical fiber itself, and this serves as a phase retarder, so that polarization conversion is possible.

Description

Optical pick device

1 is a layout diagram of a conventional optical pickup device.

2 is a layout diagram of an optical pickup device according to a preferred embodiment of the present invention.

3 is a layout diagram of an optical pickup device according to another embodiment of the present invention.

4 is a diagram showing the actual arrangement of the optical pickup device of the second embodiment.

FIG. 5 is a diagram showing the actual arrangement of the optical pickup device of the embodiment of FIG.

6 is a layout diagram of an optical modifiable optical input device used in an optical pickup device according to the present invention.

7 is a layout diagram of an optical output device used in the optical pickup device according to the present invention.

8 is a structural diagram of a movable part of the optical pickup device according to the present invention.

9 is an overall structural diagram of an optical pickup device according to the present invention.

FIG. 10 is a structural diagram showing the structure of a coil portion having a quarter-wave plate function shown in FIG.

<Explanation of symbols for main parts of drawing>

1 light source 2 light modulator

3: beam expander 4: beam split

5 movable part 6 reflector

7: objective lens 8: disc

9: spindle motor 10: transport carrier

11 light source 12 light modulator

13: beam expander 14: beam splitter

15: movable portion 16: reflector

17: objective 18: disc

19: spindle motor 20: transport carrier

21: photo detector 22: objective lens actuator

33: optical fiber 23: light receiving portion

45, 49: reflectors 46, 52, 66, 67, 96: focusing lens

47, 48: Lens (beam expander configuration) 50: Grating

52, 66, 67, 96: focusing lens 53: cylindrical lens

68: pinhole 75: optical fiber support

76: actuator 77: actuator support

89: shaft 101: optical input

102: light output device 103: the objective lens actuator

The present invention detects a change in the amount of reflected light by irradiating the optical recording medium with a constant amount of light on information optically recorded on a predetermined optical recording medium, modulating the amount of light with a modulator, recording a desired signal on the optical recording medium, and reproducing. An optical pickup / reproducible optical pickup apparatus is also provided.

The optical pickup which projects light onto the optical recording medium and reproduces information carried by the light reflected therefrom is basically a light generating element for generating light, an objective lens for focusing the light on the optical recording medium, and an optical recording. There is a need for a light detecting element that detects an electrical signal such as a reproduction signal from the reflected light reflected from the medium. The optical pickup also requires the addition of several optical components along the path of light through each element, depending on the placement of its basic elements. Therefore, in the optical pickup, by simplifying the light path, the required number of optical components can be reduced, as well as the installation space thereof.

FIG. 1 is a layout diagram of a conventional optical pickup device. In addition to the basic components of the light receiving unit 23 such as the light source 1, the objective lens 7, and the light detecting element, the beams emitted from the light source are predetermined light. A light modulator (2) for modulating the signal, a beam expander (3) for converting the beam into parallel light, a beam splitter (4) for changing the path or going straight according to the polarization direction, and reflecting the parallel light while moving A main reflector 6, a transfer carrier 10 for smoothly moving the movable part including the reflector, an actuator 22 for moving the objective lens 7, and a spindle motor 9 for rotating the disk. And the like.

The optical pickup device having such a configuration is configured to operate as follows.

The light emitted from the light source 1 is modulated by the optical modulator 2 into a predetermined optical signal (of course, the optical modulator is not used for reproduction only), and then becomes parallel light while passing through the beam expander 3. . This parallel light passes through the beam splitter 4 again and enters the movable part 5 which is a system instability factor in the optical pickup. In the movable part 5, the reflector 6 and the objective lens 7 are mounted, and there is an actuator 22 which moves the objective lens 7 in the vertical and horizontal directions so that the light path can be changed smoothly. have.

On the other hand, parallel light incident on the movable portion 5 is reflected by the reflector 6 and irradiated onto the disk via the objective lens 7. At this time, the light passing through the objective lens 7 is connected to the diffraction limit and reaches the optical disk 8 in the form of a minute spot. The disk 8 is driven to rotate by the spindle motor 9.

The light reflected from the disk 8 is then incident on the beam splitter 4 via the objective lens 7 and the reflector 6, where the reflected light is slightly polarized on the disk 8 surface, It is separated and is incident on the light receiving portion 23. The light receiving portion 23 is separated from the movable portion 5 in a separate position. The light receiver 23 does not move unlike the movable unit 5.

The problem occurring with the conventional optical pickup as described above is also as follows.

As a first assembly problem, a beam expander 3 is required to provide a beam of a constant diameter regardless of the position of the movable part 5, and also a difficult assembly process so that the optical axis is always aligned regardless of the position of the movable part 5. This is necessary. That is, the optical axis between the light receiving optical axis and the optical component of the light receiving portion 23 needs to be assembled so as to be constant.

As a second problem in operation, the optical axis of the received light is displaced due to the inclination due to the vibration of the disk 8 during operation, which causes errors in signal detection due to the optical axis displacement, and furthermore, the disk. The farther the distance between (8) and the light receiving portion 23 is, the larger the error becomes.

In addition, when the light source 1, the disk 8, and the light receiving unit 23 is far apart, malfunction is likely to occur due to vibration, and optical characteristics due to changes over time, that is, changes in the adhesive part of the optical component. Of course, a linear optical path is required between the light source 1, the disk 8, and the light receiving portion 23, and this is a great limitation for the compaction of the optical pickup device.

The present invention was devised to improve the problems of the conventional optical pickup apparatus as described above. In the optical pickup in the case where it is difficult to move together to form an optical spot at a predetermined position of the optical recording medium because the weight of the light source is heavy, For operational stability and ease of assembly when the light and light condensing and light receiving portions are separately used, and further, the light source and the light condensing and light receiving portions are connected by a separate connection medium to provide flexibility in the optical path. The object of the present invention is to provide a highly stable optical pickup device that can be easily assembled and tolerate changes and vibrations over time.

In order to achieve the above object, the optical pick-up device according to the present invention is fixedly installed and movable with respect to the recording medium and the fixed optical system for generating light and focusing projection of the light generated from the fixed optical system to the recording medium An optical pickup apparatus having a movable optical system, the optical pick-up device comprising a optical waveguide that guides light, and wherein the movable optical system includes a photodetecting element that receives light reflected from the recording medium and performs photoelectric conversion.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

First, Figure 2 is a preferred embodiment of the optical pickup device according to the present invention, characterized in that the light-receiving unit including the light detecting element is provided in the movable portion. A specific arrangement is shown in FIG. The configuration is as follows.

A light source 11 composed of a laser diode or the like, a reflector 45 for changing an optical path as necessary, a focusing lens 46 for focusing light, and light for modulating the light to obtain maximum efficiency The modulator 12 and the beam expander 13 and the reflector 49 which produce parallel light so that light of constant thickness is incident on the movable part irrespective of the distance to the movable part 15 are output from the optical modulator. The fixing part is made.

And a grating 50 for providing a separation angle and the like for forming the track control in a three-beam manner, and a beam splitter 14 for separating incident light and reflected light by the polarization direction, regardless of the position of the movable part. An objective lens 17 for focusing incident light from the beam splitter 14 to the track of the disk 18 to a polarization limit, and a focusing lens 52 for focusing the reflected light from the beam splitter 14; , A cylindrical lens 53 which is a kind of astigmatism lens for detecting the focus error of the objective lens 17 from the reflected light by the astigmatism method, and finally the photodetector 21 for detecting the electrical signal from the reflected light. The furnace movable part 15 is made.

The biggest difference from the conventional structure of the present invention as described above is that the photodetector 21 is mounted on the movable part. Based on these characteristics, the operation of the present configuration will be described.

The light emitted from the light source 11 is modulated into a desired optical signal through the optical modulator 12 and then converted into parallel light by the beam expander 13. This parallel light is reflected by the reflector 49 and is incident on the movable part 15.

In addition, the light incident on the movable part is first reflected by the reflector 16 through the grating 50 for the three-beam track, passes through the beam splitter 14, and is then focused by the objective lens 52 to enter the disc.

The light reflected from the disk 18 again passes through the objective lens 17 and is branched by the beam splitter 14 to the light receiving unit mounted on the movable unit to detect the optical signal. The reflected light incident on the light-receiving part is incident on the cylindrical lens 53 via the focusing lens 52 to form a focus signal to detect the focusing error and the tracking error of the objective lens and is detected by the photodetector 21.

Meanwhile another embodiment is shown in FIG. This embodiment is characterized in that an optical fiber having a function of? / 4 waveplate is used instead of the beam expander 13 as an optical input means to the movable part in the previous embodiment. Output 102 is added to facilitate the use of optical fibers. Herein, a method for manufacturing an optical fiber having a quarter wave plate function is described in detail in 1993 Patent Application No. 22959, which is a prior invention. Referring to this prior application specification, the coil portion 315 of the optical fiber as shown in Fig. 10A having only a quarter wavelength function has a phase delay function. That is, the refractive index of the optical waveguide 310 is changed due to the birefringence generated by the bending of the optical waveguide 310, so that the phase delay according to the winding condition of the coil unit 315 is possible. Referring to FIG. 10 (b), the radius of the cross section of the optical waveguide 310 is r, and the winding radius of the coil portion 315 of the optical waveguide 310 is R. The difference in the refractive indices of the mutually orthogonal X and Y axes in the vertical plane is as follows.

^{_{Δn X = (n 3/4}} ) (p 11 - 2σp 12) (r / R) 2 = n e -n

^{_{Δn Y = (n 3/4}} ) (p 12 - σp 12 σp 11) (r / R) 2 = n o -n

Where σ is the Poisson's ratio (e.g. 0.16 for silica)

p _ij is a photoelastic tensor

r is the radius of the optical waveguide 10 cross section

R is the radius of curvature of the optical waveguide 10

At this time, by repeating the optical waveguide 310 N times to make the coil portion 315 having a radius R, the following phase delays can be obtained.

2πδNR = λ / m

Provided that δ = n _e -n _o , m = 2, 4, 8.

In conclusion, N and R of the optical waveguide 310 and the coil unit 315 may be selected to configure phase delays such as a quarter wave plate or a half wave plate, which are optical phase delays.

On the other hand, in the coil part 315 provided in the optical waveguide 310 of the present invention, as shown in FIG. 10C, the coil part 315 is tilted at a predetermined angle α from the coil part 315. The polarization direction of the light guided by 315 can also be adjusted.

As described above, when the coil portion 315 of the optical waveguide 310 has a phase delay function of a quarter wave plate, the incident of the optical waveguide 310 from the semiconductor laser diode is shown in FIG. However, the linearly polarized light incident to the stage goes straight, and the linearly polarized light is changed into circularly polarized light by the coil part 15. The circularly polarized light is focused onto the optical disk 18 by the objective lens 17.

The reflected light reflected from the non-recorded portion of the optical disk 18, that is, the portion where the pits are not formed, is circularly polarized light. The circularly polarized light passes through the coil part 315 of the optical waveguide 310 and is converted into linearly polarized light again. By the way, the linearly polarized light of the reflected light has a different polarization angle from the linearly polarized light of the incident light when the coil part 315 is rotated by a predetermined angle α as shown in FIG. Therefore, the reflected light does not pass through the polarization filter (not shown) and is received by the four-segment photodetector 21 via the cylindrical lens 53, which is a kind of non-low aberration lens, in the detector. As described above, when the coil unit 315 is disposed in the optical fiber 33, the optical fiber 33 of the light receiving units 21, 52, and 53 may pass through the coil unit 315 again to reflect light from the optical disk 18. The position must be changed toward the front end of the.

As described above, the quarter wave plate coil unit 315 serves as a phase retarder to increase light efficiency and is composed of the optical fiber itself. In addition, instead of changing the positions of the light receiving parts 21, 52, and 53 as described above, the coil part 315 may be disposed between the optical fiber end part and the objective lens.

Next, only the portions that differ from the embodiment of FIG. 2 will be described with reference to FIG. 5, which is a specific arrangement diagram of the optical pick-up apparatus of FIG.

First, in the configuration, the parts up to the optical modulator 12 before the optical input unit 101 and after the optical output unit 102 in the movable portion are the same as in the embodiment of FIG.

The optical input unit 101 is composed of an actuator 75 for exciting the focusing lens 66 and the optical fiber 33 and an actuator support 77 for supporting the actuator, as shown in FIG.

In addition, the optical output unit 102 is composed of a focusing lens 66, a pinhole 68, and a focusing lens 67, as shown in FIG.

The operation of the optical fiber adding device having the above configuration is as follows.

Light emitted from the optical modulator 12 is focused by the focusing lens 66 (FIG. 6) of the optical input device 101 to the size of the diameter of the optical fiber. The input end of the focusing lens 66 and the optical fiber 33 serves as an optical connecting element. The optical fiber is used to efficiently transmit a wavelength suitable for the operating wavelength of the light source 11, in particular, the polarization of the polarization incident on the input terminal is output to the output terminal while the polarization direction of the polarized light is maintained as it is, and the polarization suitable for the use of a magnetic disk drive, etc. Retention optical fibers are used.

In addition, since the light input device of the present invention focuses light once by the focusing lens 66 and focuses on the optical fiber input end, the end of the optical fiber is attached to the fixing support 75, and the fixing support is attached. Excitation with an actuator 76, such as a piezo element, changes the spot size of the light at the optical fiber end. That is, the amount of light incident on the optical fiber 33 can be adjusted by having an actuator, thereby adjusting the amount of light incident on the focusing lens 66. In general, when the piezoelectric element is used as an actuator, several tens of micrometers of the excitation range can be adjusted in a band of 10 MHz or more, which is an extremely advantageous method for reducing the cost and size of the optical pick-up.

And the output end of the optical fiber 33 (FIG. 7) is connected to the movable part 15. FIG. The light emitted from this output stage is usually about 15 to 30 degrees of divergence angle, and aberration occurs in the light by the optical fiber. In order to remove such aberration, a fine spot is formed with the focusing lens 66, and then a pinhole 68 is placed at the spot, having a hole almost the same size as the optical wavelength and serving as a filter such as a spatial frequency filter. This pinhole eliminates aberration caused by the optical fiber. In addition, the light passing through the pinhole is diverged and focused by the focusing lens 67 to be converted into parallel light, and then proceeds to the beam splitter 14.

8 shows the structure of the movable part of the optical pick-up apparatus according to the present invention, and FIG. 9 shows the overall structure of the optical pick-up apparatus according to the present invention.

As described above, the optical pick-up apparatus according to the present invention arranges the light receiving part in the movable part and adopts the optical path with the fixing part as a flexible material called an optical fiber, so that the optical pick-up is easy to assemble and the distance between the disk and the light receiving part. It is short and has the advantage of less influence from the vibration and the change over time during operation, there is no change in the incident optical axis due to the vibration during operation, there is also an advantage that can arbitrarily adjust the distance between the fixed part and the movable part. Particularly, in the present invention, only a λ / 4 wavelength is formed by using a part of the optical fiber itself, and this serves as a phase delayer, so that polarization conversion is possible.

Claims (5)

An optical pick-up apparatus comprising a fixed optical system fixedly installed and movable optically mounted to a recording medium and movable optical system for focusing and projecting light generated from the fixed optical system onto the recording medium, wherein the fixed optical system and the movable optical system are provided. Optical fibers for guiding light between optical systems; A photodetecting device for receiving and photoelectrically converting light reflected from the recording medium by the movable optical system; And an actuator for exciting any one end of the optical fiber such that the intensity of light guiding the optical fiber is modulated. The optical pick-up apparatus according to claim 1, wherein the optical fiber is designed to have a polarization maintaining optical fiber for maintaining the polarization angle of the waveguided light. The optical pick-up apparatus according to claim 2, wherein the polarization maintaining optical fiber is designed to have a λ / 4 wave plate capable of adjusting its polarization direction. The optical pick-up apparatus according to claim 1, wherein the actuator comprises a lens for focusing light incident on an input end of the optical fiber and a piezo element for vibrating the input end of the optical fiber in an optical axis direction. The optical fiber of claim 1, further comprising: an aperture having a pinhole and a lens for focusing light from the output end of the optical fiber to the pinhole to remove aberration of light transmitted from the optical fiber to the fixed optical system. Optical pick-up device, characterized in that.