JPS6240984A - Optical path control device - Google Patents

Abstract

PURPOSE:To enable focusing of a spot at the prescribed position without causing any fluctuation in the direction and position of the optical axis of a laser beam by controlling the turning of a mirror so that the beam is made incident on the prescribed position on the mirror in response to the position signal transmit ted from an optical position detector. CONSTITUTION:The irradiating position of a laser beam is controlled by a control circuit 16 so as to locate it at the center thereof in an optical position detector 15. The laser beam which transmitted a beam splitter 14 is set so that the distance l1 from the beam splitter 14 to the optical position detector 15 and the distance l2 from the splitter 14 to a mirror 22 become at the same value on the optical path further and the laser beam passes always through the point A of the mirror 22. In an optical position detector 19 further the direction of the reflecting beam from the beam splitter 18 and the position thereof become stable and in high accuracy always because of the point A being stable at one point of the space by the first servo system 10 when the irradiating position of the laser beam is controlled by a control circuit 22 so as to locate at the center thereof.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an optical path control device using laser light.

[Technical background of the invention and its problems]

BACKGROUND ART In recent years, writing on video disks has been carried out using microfabrication techniques using large gas lasers.

Methods of writing information into a video disc using laser light include focusing the laser light into a minute light spot and injecting it into a photosensitive chemical material, or using heat from the light spot to write the information onto the recording surface. Some methods do this by changing the shape or reflectance of the material. In this case, a high precision of 0.1 micrometers (μm) may be required as the precision on the machined surface.

However, the direction and position of the optical axis of this large gas laser changes due to the influence of heat from the equipment in use and external vibrations, and despite the high precision required as mentioned above, However, there was a problem in that the position of the light spot was shifted on the recording surface.

In addition, since the large gas laser is incorporated as part of the optical system, when the large gas laser is adjusted, the other optical systems must be adjusted accordingly, making it extremely difficult to operate. Met.

〔Effect of the invention〕

According to the present invention, the direction and position of the optical axis of the laser beam emitted from the laser oscillator can be adjusted even if there is an influence of heat from the external environment, such as the influence of heat from various devices in use or vibration from the outside. Spots can be connected to predetermined positions without causing fluctuations.

Furthermore, even if the laser oscillator is adjusted, there is no need to adjust other optical systems accordingly.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide an optical path control device d that connects a spot to a predetermined position without being influenced by the external environment.

[Summary of the invention]

The present invention includes a first mirror that reflects light emitted from an optical oscillator in an arbitrary direction, a second mirror that reflects the light reflected by the first mirror in an arbitrary direction, and a second mirror that reflects the light reflected by the first mirror in an arbitrary direction.
a third mirror that reflects the light reflected by the mirror;
a light splitting element for extracting a part of the incident light or emitted light from the second mirror; and a first light splitting element for detecting the incident position of the light on the second mirror-h from the light extracted by the light splitting element. an optical position detector; and a first optical position detector that rotationally controls the first mirror so that light is incident on a predetermined position on the second mirror in response to a position signal from the first optical position detector.
a light splitting element for extracting a part of the incident light or output light to the third mirror; and a control means for controlling the incidence of the light on the third mirror by 0c than the reflected light extracted by the light splitting element. a second optical position detector for detecting a position;
and second control means for controlling the rotation of the second mirror so that light is incident on a predetermined position on the third mirror in response to a position signal from an optical position detector. An optical path control device is provided.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained using FIG.
This will be explained in detail using figures.

FIG. 1 is a schematic configuration diagram of an optical path control device of the present invention. Laser light emitted from the laser oscillator 01) is supplied to the first servo system.

This first servo system (In is mirror 0211 beam splitter 11 optical position detector (15+, control circuit Q61
．． A laser beam emitted from a laser oscillator Qll consisting of a driving device 0 is irradiated to a three-dimensionally rotatable mirror 021 (trade name: Mirror Hold), and the laser beam reflected by this mirror 04 is transmitted to a fixed beam splitter 0. Injected into the water. One of the laser beams is directly transmitted toward the mirror e of the second servo system (2I8, which will be described later), and the other is reflected by the beam splitter I, where it is thermally transmitted to the optical position detector (I5), which will be described in detail later. The binary signal detected by this optical position detector (151) is input to the control circuit OQ, and this control circuit abl moves the drive device (131) that drives the mirror (12) three-dimensionally to a predetermined position. It is controlled so that

That is, in the first servo thread, first the mirror (2
) is always irradiated at the center point A.

The second servo string consists of a mirror Q, a beam splitter Ql, a light and sound detector 11 control circuit, and a driving device. The laser beam transmitted by the beam splitter TL of the first servo thread (11) is reflected by a three-dimensionally rotating mirror +24 (trade name: Mirror Hold), and is incident on the fixed beam splitter A mallet. .

Then, one side of the light goes around the mirror (171) and is reflected, and the other side of the light passes through and is irradiated onto the optical position detector 0, which will be described in detail later in the same way as above.

The control circuit c! binarized signal detected by this optical position detector u3! 1), and this control circuit (21j is
A driving device f231 that rotates the mirror riff in three dimensions is controlled to a predetermined position. That is, the optical axis of the laser beam is inserted in the second servo thread, and the laser beam irradiation surface 041 is irradiated.

The two optical position detectors mentioned above include, for example, a 4-split photodiode (3) and a 1j1m photodiode as shown in FIG.
A circuit (31) consisting of θ crossing is used.

If the laser beam is correctly irradiated to the center of the quadrant photodiode, the output signals Ia, Ib, Ic, and Id from the four parts a, b, c, and d will all be equal, but for example, if the laser beam is The point of contact is from the center in Figure 2,
When it moves upward, the output ti becomes larger than the magnitudes of 1a and Ib or lc and ld. Then, the calculation circuit θ
At υ, if we calculate (Ia + Ib) - (Ic + Id), we get (Ia - 1 - 1b) = (Ic + Ia)) U, and the downward movement H (l a - 1 - I b) - (I c
-1-I d) is obtained. Similarly, the amount of movement in the left and right direction in Fig. 2 (I a + I c) - (I b + l
d) Calculated in +ffjfT4 circuit G3d.

Then, each binarized data is outputted from the terminal 6 θ, and the above-mentioned control circuit and drive device are configured to always irradiate the central position of the 4-split photodiode α) with laser light. .

As shown above, the laser beam irradiation position of the optical position detector (151) is controlled to be located at the center.Furthermore, the laser beam transmitted through the beam splitter 04 is emitted from the beam splitter circle on the optical path. The distance 111i (ll) to the position detector (old) and the distance from the beam splitter I to the mirror (221 @ C12) are the same value (ls
= At). Then, the laser beam will always pass through the mirror (young point A).

Furthermore, when the optical position detector uLJ controls the laser beam irradiation position to be located at the center, point A becomes
Since the first servo system ulJl stabilizes the beam at one point in space, the direction and position of the reflected light from the beam splitter 0 barrel are always stable and highly accurate.

The data obtained from the experiment is shown below. Large Ar+L
, -f (4579A), the optical axis fluctuates for 2 to 3 hours after the start of oscillation.

The value was 200 to 300 μrod in angle and 500 to 600 μm in optical position.

For example, f is a common value for master recording of video discs.
(Focal length M of the objective lens that focuses the laser beam into a minute light spot) -2.5mm, m (The ratio of the beam expander that focuses the laser beam into a minute light spot)
=2. Using S, S (angle variation amount of optical axis) = 200 μrad, the amount of movement of the optical spot is determined by Δ(movement amount = variation amount) = f−tj/m, and it becomes approximately 0.2 μm. The track pitch of current video discs is between 1.35 and 1.35.
Even considering that it was 6 μm, the amount of variation of 0.2 μm could not be ignored.

However, by using this device, the amount of angular variation of the optical axis can be reduced to 5
It became within 0 μrod and within 50 μm at the position. At this time, a degree of clarity was obtained in which the variation of the light spot on the disk was within 0.05 μn1.

The reflected light obtained with this high precision is a mirror (Fig. 1 Q?))
It can be used in any direction.

In other words, in this embodiment, the laser oscillator 00 causes fluctuations in the direction and position of the optical axis even if there is a heat influence from various devices in use or external vibrations.
This prevents the spot from shifting on the laser beam irradiation surface (2+9).

Furthermore, since the first and second servo systems 1ll (2) are each independent and the laser oscillator is also configured independently, the other optical systems are adjusted according to the adjustment of the laser oscillator. This results in an extremely stable device that is unnecessary.

[Other embodiments of the invention]

In the above embodiment, the position of the optical position detector 19 shown in FIG. An optical position detector 1 provided on the optical path of the reflected light of the beam splitter 18 so as to be irradiated with the optical position detector 1
9 may be controlled by O. Note that the present invention is not limited to the above embodiments.

For example, a configuration as shown in FIG. 3 may be used.

In other words, the half mirror (14) shown in FIG. Even in a configuration in which the thread that is irradiated to point A of the mirror Q2) is placed after the second servo thread 0, the same effect as that of the embodiment described above can be obtained.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the optical path control device according to the present invention, FIG. 2 is a configuration diagram of an optical position detection device, and FIG. 3 is another embodiment of the optical path control device according to the present invention. FIG. 11, 22. 17... Mira -1
3.23...Kaku-J device 14.18...Beam splitter,

Claims (3)

[Claims] (1) A first mirror that reflects the light emitted from the optical oscillator in any direction, a second mirror that reflects the light reflected by this first mirror in any direction, and this second mirror. a third mirror that reflects the light reflected by the second mirror;
a light splitting element that takes out a part of the incident light or outgoing light of the mirror, and a first light position detection that detects the incident position of the light on the second mirror from the light taken out by the light splitting element. a first control means for rotating the first mirror so that the light is incident on a predetermined position on the second mirror in response to a position signal from the first optical position detector; ,
A light splitting element that takes out part of the incident light or output light to the third mirror, and detecting the incident position of the light on the third mirror from the reflected light taken out by the light splitting element. a second optical position detector; and a second optical position detector that rotationally controls the second mirror so that light is incident on a predetermined position on the third mirror in response to a position signal from the second optical position detector. 2
An optical path control device comprising a control means. (2) The optical path control device according to claim 1, wherein the control means comprises a control circuit and a drive device that performs three-dimensional driving using signals from the control circuit. (3) The optical path control device according to claim 1, wherein the light splitting element is a beam splitter.