JPH0495243A - Producing device for master optical disk - Google Patents

Abstract

PURPOSE:To easily equalize the intensity of recording laser beams between two master optical disks by providing a means which changes polarizing state of the recording laser beams and a polarized beam splitter and dividing a recording laser beam into two parts by the beam splitter. CONSTITUTION:A polarized beam splitter 7 is provided together with a means 6 which changes the state of the recording laser beam. Then a recording laser beam is divided into two parts by the splitter 7. A wavelength plate 6, for example, is provided between a laser device 4 and the splitter 7 as a means which changes the polarizing state of the recording laser beam. Thus the intensity ratio between two laser beams can be optionally changed up to 100:0 from 0:100 with use of a 1/2 wavelength plate 6. In other words, the intensity ratio can be changed between two laser beams when the plate 6 is turned against the optical axis of the incident light. As a result, the intensity of the recording laser beams can be equalized on a substrate 1.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to an apparatus for producing an optical disc master.The conventional technology for an optical disc master is to apply a photoresist to a substrate made of glass or the like with a polished surface, and record information signals on this. In order to increase the transfer rate of the information signal, two signals are recorded and played back at the same time. The power of using two laser devices to record two signals at the same time
It is necessary to divide the light emitted from two laser devices into two by a half mirror.If two laser devices are used, problems may arise with the stability of the two laser beams, and maintenance may become difficult. Although a method is used in which the light emitted from six laser devices is divided into two by a half mirror, there are problems such as time and effort. This mainly shows the laser beam irradiation configuration.

In FIG. 3, a substrate 1t coated with photoresist
−1 Rotationally driven by spindle 2 and to −
The recording laser beam emitted by the recording laser device 4 is transferred in the radial direction of the substrate 1 by the axis moving table 3, and is divided into two by the half mirror 21 after passing through the mirror 5. The beam diameter is expanded by beam expanders 9, 9a which receive intensity modulation according to the signal to be recorded by modulators 8, 8a, and are composed of two lenses having different focal lengths arranged so as to share a focal point. One side is reflected by the polarizing beam splitter 12 through the mirror 10, and the other side is reflected by the mirror 11.
After that, the plane of polarization is rotated by 90 degrees with a 1/2 wavelength plate 20 and transmitted through a polarizing beam splitter 12. Both lights are combined by a polarizing beam splitter 12, pass through a dichroic mirror 13 and a mirror 14, and then a lens actuator 15. The control laser beam focused and irradiated onto the substrate 1 by the control laser device 16 is for focus control, and is directed to the polarization beam splitter 17 and the quarter-wave plate 1.
8. After dichroic mirror 13 and mirror 14,
The control laser light that is narrowed down by the lens actuator 15 and irradiated onto the substrate 1 is reflected from the substrate 1 (daily mirror 14, dichroic mirror 13, 1
The incident light is separated from the incident light by a polarizing beam splitter 17 through a /4 wavelength plate 18 and sent to a light receiving element 19 for focal position detection.
Even if the lens actuator 11 is driven based on the signal obtained by the light receiving element 19 and the focus control is performed so that the recording laser beam is always focused on the substrate 1, the invention attempts to solve the problem. The intensity of the laser beam irradiated to the target substrate is influenced by the characteristics of optical parts such as mirrors that transmit or reflect after the laser beam is divided into two. In order to make the light equal, it is necessary to adjust the intensity ratio when dividing the laser beam into two parts according to the characteristics of the optical components. The plate is divided into two lights.
The intensity ratio of each laser beam cannot be changed without replacing the half mirror, and if the half mirror is replaced, it becomes necessary to readjust the optical components from the half mirror to the lens actuator. Although it is difficult to subtly change the ratio of reflection and transmission, the present invention is aimed at providing an optical disk master production device that eliminates the above-mentioned drawbacks. The apparatus of the present invention achieves the above object by having a means for changing the polarization state of a recording laser beam and a polarizing beam splitter, and dividing the recording laser beam into two by the polarizing beam splitter. By changing the polarization state of the recording laser beam, the ratio between the amount of transmitted light and the amount of reflected light from the polarizing beam splitter can be changed.
There is no need to readjust the optical components from the lens actuator to the lens actuator.In addition, the intensities of the two recording laser beams at the optical disc master can be easily adjusted and made equal. The invention will be explained in detail by way of examples.

FIG. 1 is a block diagram of an optical disc master production apparatus according to a first embodiment of the present invention. As a means for changing the polarization state of a recording laser beam, a wavelength Even if a board is installed, Figure (b)C
L is a front view of the substrate 1 and the vicinity of the mirror 14. The substrate 1 coated with photoresist is rotated by the spindle 2 and transferred in the radial direction of the substrate 1 by the uniaxial moving stage 3.

A linearly polarized recording laser beam 4L emitted by a recording laser device 4 passes through a mirror 5, the polarization state is converted by a wavelength plate 6, the S-polarized component is reflected by a polarizing beam splitter (hereinafter abbreviated as PBS) 7, and the P-polarized component is converted into a P-polarized component. The laser beam is transmitted and divided into two recording laser beams, and the laser beam reflected by the PBS 7 is intensity modulated by an intensity modulator 8 according to the signal to be recorded.
The beam diameter is expanded by the beam expander 9, reflected by the PBS 12, and transmitted through the PBS 7. The laser beam passes through the mirror 11 and undergoes intensity modulation by the intensity modulator 8a according to the signal to be recorded. Two laser beams with polarization planes different by 90 degrees pass through the PBS 12 whose beam diameter has been expanded by the beam expander 9a.
The synthesized recording laser beam is reflected or transmitted by the dichroic mirror 13 and the mirror 14, and is narrowed down to the substrate 1 by the lens actuator 15. Light whose polarization direction is parallel to the plane (incident plane) formed by the normal line of the reflecting surface (reflecting surface) and the optical axis of the incident light is called P-polarized light, and light whose polarization direction is perpendicular to the incident plane is called S-polarized light. .Linearly polarized light
There is circularly polarized light and elliptically polarized light, and the direction of the plane of polarization in the case of linearly polarized light includes the ellipticity in the case of elliptically polarized light.The focus control system using a laser device for control is the same as shown in Figure 3.Focus position Detection light receiving element 198 For example, in the Naifetsu method, the lens and the knife between the focal plane of the lens and the photodetector divided into two parts are used.In the astigmatism method, the cylindrical lens and the photodetector divided into four parts are included.A This invention In the explanation, such photodetectors capable of focus control are collectively referred to as light receiving elements for detecting focus positions, but as recording laser devices, for example, argon lasers, krypton lasers, excimer lasers, etc. are used as photodetectors. 1. Any laser device that generates a wavelength to which the resist is sensitive is acceptable. For example, a helium-neon laser can be used as a laser device for controlling the %.Any laser device, such as a semiconductor laser, that generates a wavelength to which the photoresist is not sensitive may be used. Even if a crystal plate with a certain thickness is used, depending on the angle between the crystal axis (two axes) of the crystal and the polarization plane of the incident light, the thickness of the crystal plate, and the wavelength of the incident light, linearly polarized light may be transmitted as is, or circularly polarized light may be transmitted as is. In the case of P-polarized light or S-polarized light, PB
100% transmission or 100% reflection due to S 4 When converted to circularly polarized light 41 Is the intensity of the P polarized light component and the S polarized light component equal?n When the light is divided into two lights of the same intensity by PBS7 is an ellipse When converted to polarized light, the intensities of the P-polarized light component and the S-polarized light component are different. By changing the angle with the wavefront, the intensity ratio of the two separated beams can be changed.If a 172 wavelength plate is used as a wavelength plate, the intensity ratio of the two laser beams can be changed to 0:1.
In this embodiment, the intensity ratio of the two laser beams can be changed by rotating the wavelength plate 6 with respect to the optical axis of the incident light. Although the intensity ratio of the two laser beams can be easily changed, the optical axis of the laser beam does not change even if the intensity ratio of the two laser beams is changed.
There is no need to readjust the optical components from the PBS 7 to the lens actuator 15. (When recording two information signals on one board, it is necessary to equalize the signal quality of the two information signals.) It is necessary to equalize the light intensity on the board.Due to variations in the characteristics of optical components from PBS7 to PBS12!, differences in characteristics due to the polarization plane of the incident light of optical components from PBS12 to lens actuator 15, etc. Even if the beams are divided into two beams with different strengths, the intensities irradiated onto the substrate often differ (as shown in this example). Therefore, the intensities of the recording laser beams on the substrate can be made exactly equal, or can be set to any intensity ratio as required. Next, FIG. 2 shows a second embodiment of the present invention. In this embodiment, as a means for changing the polarization state of the recording laser beam, the recording laser device is provided so as to be rotatable around the optical axis of the laser beam. is the same as Figure 1, except that the recording laser device that emits linearly polarized laser light is rotatable around the optical axis of the laser beam, and there is no wavelength plate, so the details of the figure are Although I will omit the detailed explanation, the plane of polarization of the recording laser beam emitted from the recording laser device can be changed from P polarization to S polarization with respect to the rotating L PBS by rotating the recording laser device. When the plane of polarization of the laser beam is parallel to the plane of the paper, that is, it is P-polarized light, it transmits 100% at i, t, and PBS7.

When the polarization plane of the recording laser beam is perpendicular to the plane of the paper, that is, S-polarized light 1;1. , 100% reflection on PBS7 When the plane of polarization of the recording laser beam is tilted with respect to the paper surface & above The ratio of transmission and reflection of PBS7 changes depending on the degree of tilt of the plane of polarization. By rotating the laser device around the optical axis of the laser beam, the intensity ratio of the two laser beams separated by PBS 7 can be easily changed. There is no need to readjust the optical components from the PBS 7 to the lens actuator 15 because the optical axis of the laser beam does not change. It is possible to change the intensity ratio of the two beams by changing the intensity ratio of the two beams.It is also possible to make the intensity of the recording laser beam on the substrate exactly equal, or it is possible to set the intensity ratio to an arbitrary value as needed. When recording an information signal on a substrate with a groove formed on it, there is a force required to record the signal along the groove (recording can be done by replacing the mirror 14 with a tracking mirror and adding a tracking control system to the focus control system). For example, the push-pull method involves a lens and a photodetector divided into two parts. Based on the signal obtained by the photodetector, the angle of the tracking mirror is changed and tracking control is performed so that the groove is always being tracked. In the case where we also have a tracking control system, k
The apparatus for producing an optical disk master according to the present invention is capable of precisely equalizing the intensity of recording laser beams on the substrate.It is also possible to set the intensity ratio to any desired intensity ratio as required.Effects of the Invention Apparatus of the present inventionFor recording It has means for changing the polarization state of the laser beam and a polarizing beam splitter, and by dividing the recording laser beam into two by the polarizing beam splitter, the polarization state of the recording laser beam is changed and the polarizing beam splitter is formed.・Although it is possible to change the ratio of the amount of light transmitted by the vine to the amount of reflected light, there is no need to change the polarization state of the recording laser beam and readjust the optical components from the polarizing beam splitter to the lens actuator. t~ This number It is possible to easily equalize the intensities of two recording laser beams on the optical disc master, and to obtain an easy-to-maintain and highly reliable optical disc master production apparatus.

[Brief explanation of drawings]

1. Fig. 2 is a block diagram of the first and second embodiments of the optical disc master production apparatus of the present invention. Fig. 3 is a block diagram of a conventional example of the optical disc master production apparatus of the present invention. ... Recording laser device 6 ... Wave plate 7 ... Polarizing beam splitter - 0 Name of agent Patent attorney Shigetaka Awano Figure 1 (a-) (b) S Mira

Claims (5)

[Claims] (1) An apparatus for producing an optical disc master on which a recording signal is recorded, which has a process of irradiating an optical disc substrate coated with a photoresist with a laser beam whose intensity is modulated according to a recording signal, and which changes the polarization state of the recording laser beam. 1. An apparatus for producing an optical disc master, comprising: a means for producing an optical disc master; and a polarizing beam splitter, the polarizing beam splitter splitting a recording laser beam into two. (2) A device for producing an optical disk master recording a recording signal, which includes a step of irradiating an optical disk substrate coated with a photoresist with laser light whose intensity is modulated according to the recording signal, and which uses a wavelength plate to emit linearly polarized laser light. An apparatus for producing an optical disc master, characterized in that the polarization state is changed using a polarizing beam splitter, and then the recording laser beam is divided into two recording laser beams with polarization planes different by 90 degrees. (3) The apparatus for producing an optical disc master according to claim (2), characterized in that a 1/2 wavelength plate is used as the wavelength plate. (4) By adjusting the wavelength plate and changing the ellipticity of the elliptically polarized light to change the ratio between the amount of transmitted light and the amount of reflected light from the polarizing beam splitter, the intensity of the two recording laser beams on the optical disk master can be made equal. Claim (2)
) or the optical disc master production device described in (3) (5) A device for producing an optical disc master on which a recording signal is recorded, which has a process of irradiating an optical disc substrate coated with a photoresist with a laser beam whose intensity is modulated according to the recording signal, and generates a linearly polarized recording laser beam. The optical disc master is characterized in that a laser device is rotatable around the optical axis of a recording laser beam, and the recording laser beam is split into two recording laser beams with polarization planes different by 90 degrees by a polarizing beam splitter. Creation device.