JPS62280713A - Optical information recording device - Google Patents

Abstract

PURPOSE:To increase the stability of an optical axis at the time of recording and to eliminate the need to readjust an optical system by providing an automatic optical axis correcting function which detects and corrects the projection position and angle deviation of laser light. CONSTITUTION:Two servo mirrors 4 and 5 reflect light emitted by a laser oscillator 1 in optional directions and two light splitting elements 7 are provided behind the servo mirrors; and the two servo mirrors 4 and 5 are rotated under control based upon position control signals of photodetectors 10 and 11 which detect light beams split by the light splitting elements so that the light beams are incident on the light splitting elements at specific positions. Further, k0<k2<=k3, where k0 is the distance between the two servo mirrors 4 and 5, k2 is the distance between the 2nd servo mirror 5 and the 1st photodetector 10, and k3 is the distance between the two photodetectors 10 and 11. Consequently, an optical information recording device is obtained which is reduced in size and records information stably with high accuracy. Further, a variation in the optical axis of laser light is eliminated to eliminate the need to readjust the optical system.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) This invention relates to an optical information recording device capable of recording information using laser light.

(Prior art) Various methods of recording information have been developed in the past.
Among these, information recording using laser light is attracting particular attention.

Among these, signals are written on various disks using microfabrication techniques using large lasers. There are various ways to write signals on disks using this laser light, such as focusing the laser light into a tiny spot and exposing it to a photosensitive chemical material, and using heat from the light spot to change the shape of the recording surface. Some methods do this by changing the reflectance. In this case, the accuracy on the machined surface is 0.
．． High accuracy of less than 1 (μm) may be required.

However, devices using this large laser (for example, Ar+ laser) have various problems.

(2) Pointing stability (stability of the exit position and exit angle of the light emitted from the laser tube) immediately after the laser is turned on is not good enough to meet the requirements of the recording optical system. This situation can also be seen from the diagram shown in FIG. 8, which shows the M1 constant results of the pointing stability of the Ar'' laser.

■The large laser is incorporated as part of the optical system, so whenever this large laser is adjusted, other optical systems that require precise positioning accuracy must also be readjusted. Must be. Regarding this, the lifespan of a laser tube is usually about 10 (10 to 200 lH), so it is necessary to replace the laser tube every time it is used, and it is completely inconvenient to adjust the optical system each time. .

(2)Furthermore, vibrations from the outside cause optical axis fluctuations, resulting in misalignment of the optical spot on the recording surface. This is a technical problem that must be overcome in order to meet the demand for highly accurate recording of information on the order of submicrons.

From the above, it is no exaggeration to say that the problem of current optical recording technology is to solve these problems, such as the need for a large amount of warming-up time.

(Problems to be solved by the invention) This invention was made in order to solve the above-mentioned problems, and its purpose is to reduce the size of the device and to achieve high precision and stability. The present invention provides an optical information recording device that is capable of recording recorded information. Furthermore,
The present invention provides an optical information recording device that eliminates optical axis fluctuations of a laser beam due to various factors, eliminates the need for readjustment of an optical system, and significantly reduces laser warming-up time.

[Structure of the Invention] (Means for Solving the Problem) This invention comprises two servo mirrors that reflect light emitted from a laser oscillator in any direction, and two light splitting elements provided after these. Then, the two servo mirrors are rotationally controlled using a position control signal from a photodetector that detects the light split by each light splitting element so that the light enters a predetermined position on each of these light splitting elements. It is something to do. Furthermore, the distance between the two servo mirrors (ko) and the second
The distance between the servo mirror and the first photodetector (k2) and the distance between the two photodetectors (k3) satisfy the following conditions.

3 for ko<k2≦ (Function) The emission position of the laser beam is determined by the above-described configuration. By installing an automatic optical axis correction function that detects and corrects angular deviation,
The optical axis stability during recording is greatly increased, and readjustment of the optical system due to various factors can be eliminated.

(Example) An embodiment of the present invention will be described in detail below with reference to the drawings.

First, the optical system of this embodiment will be explained using the basic configuration diagram of the optical information recording apparatus shown in FIG. Further, the portions from the Ar+ laser device 1 to the servo mirror 5 shown in FIG. 1 that are not visible in this figure are shown in FIG.

First, the light emitted from the Ar+ laser device 1 (for example, 4
579 people) are mirrors 3 and 2 that make up the optical axis correction unit.
The optical axis is corrected to the optimum optical axis by the servo mirrors 4 and 5. Here, the two servo mirrors 4 and 5 constitute one of the features of the first embodiment, and will be described in detail later. A system in which the beam reflected by the servo mirror 5 is divided by a beam splitter into two beams for recording an information signal and a tracking signal at a desired spectral ratio will be described. One of the lights split by the beam splitter 7 passes through the optical modulator 12, where the light intensity is modulated by a signal and the light amount is controlled.

The light emitted from this optical modulator 12 is enlarged and collimated by a first collimator optical system consisting of two convex lenses 15 and 17 and a pinhole 16 via mirrors 13 and 14, and is incident on a mirror 18. Ru. In this mirror 18, the reflected light passes through a half prism 19 and passes most of the light amount (for example, 96%) to a beam splitter 36.
A portion (for example, 4%) is divided into the two-split photodetector 21 via the convex lens 20.

Here, the control signal output from this photodetector 21 is transmitted to the first convex lens 15 of the first collimator optical system.
is driven vertically to minimize optical axis fluctuations.

This beam position servo optical system will be described in detail later.

The other light split by the beam splitter enters the half prism 8 as a tracking signal recording beam, where it is further transmitted and sent to the mirror 2.
2, the other half prism 9 is reflected as a control signal.
is incident on the This half mirror 9 or less photodetector 10
．． 11 will be explained in detail later along with the above-mentioned servo mirror 4.5.

The tracking recording beam reflected by the mirror 22 is subjected to light intensity modulation and light amount control by a light modulator 23, and then enters a mirror 24. This mirror 24
The light reflected by the 1/2 plate 25 converts the direction of linear polarization from perpendicular to the surface plate surface 6 to horizontal direction, and passes through the mirror 26 to the two convex lenses 26 and 29 and the pinhole. The second (beam expansion) consisting of 28
The light is incident on the collimator optical system. In addition, the light reflected by the mirror 30 via this second collimator optical system is mostly transmitted by the half prism 31, further reflected by the mirror 35, and is sent to the deflection beam splitter as a tracking signal recording beam. 36 together with the information signal recording beam, and the two beams are superimposed here. On the other hand, the light split (reflected) by the half prism 31 is sent to the mirror 3 for detecting the optical axis angle displacement.
2 and a convex lens 33, the light is incident on a two-split photodetector 34. The control signal output from this photodetector 34 is transmitted to the first convex lens 27 of the second collimator optical system.
Here, fluctuations in the optical axis of the tracking signal recording beam are minimized. This is similar to the beam position servo optical system in the first collimator optical system described above, and will be described in detail later in the same way.

The two beams (one for information recording and one for tracking signal recording) superimposed in the deflection beam splitter 36 are reflected by a mirror 37, and most of the light amount (for example, 96%) is transmitted by a half prism 38 via a moving optical system (not shown). The information signal and the tracking signal are recorded on the recording medium. In this case, it is desirable that the relative positions (ie relative angles) of the two beams are always kept constant.

On the other hand, a part of the light amount (for example, 4%) is reflected here and totally reflected by the mirror 39, and the returned light is narrowed down by the converging lens 40, and the narrowed pattern is passed through the objective lens 41 (mirror 42. Huff prism (e.g. branch ratio 5
0%:50%)) and a beam shape viewing microscope consisting of an eyepiece 44, it can be visually observed from above. The other light split (reflected) by the half prism 43 is used to observe the beam shape and the interval between the two beams (information signal, tracking signal), and to check the beam shape of the reflected light from the recording medium mentioned above. The setting of the focus position is monitored using data from the camera 45.

Next, the principle of the above-mentioned beam position servo optical system will be explained using FIG. Components that are the same as those in FIG. 1 are given the same numbers. Also, the convex lens 15 is 27.17 is 2
The explanation will be given assuming that 9.20 is the same as 33 and that the photodetector 21 is the same as 34. The convex lenses 15 and 17 form a beam expander, and the convex lens 20 forms a photodetector P.
The light passing through the expander forms an image on D21. Assuming that the emission angle of the light in the vertical plane is displaced by Δθ, the amount of movement ΔL of the beam on the photodetector PD21 is: Point distance). Therefore, in order to return the position of this light to the position before movement, it is necessary to move the convex lens 15 in the vertical direction. The amount of movement of the convex lens 15 at the focal position corresponding to ΔL is flΔθ. Therefore, by forming a loop that controls the motor 69 directly connected to the convex lens 15 so that the photoelectrically converted ΔL becomes O, the beam position can always be kept constant.

However, when actually assembling the beam position servo optical system using this method, it is difficult to install the photodetector 21 at a predetermined position.

This situation is shown in FIG. The parallel component Δ! is applied to the desired input source indicated by the dotted line. When light including . Then, at a position where the upper parallel movement component Δ2 is 21, the convex lens 15 is corrected by the motor 69 as an angle correction value. In other words, although the parallel component is not a problem in this system, the parallel component is recognized as an angular displacement, resulting in a malfunction.

Therefore, in addition to this beam position servo optical system, we installed the following optical axis correction servo.

The optical axis correction servo system, which is one of the features of this embodiment, will be explained with reference to FIG. FIG. 3 is a diagram showing a hardware configuration for optical axis correction of light emitted from the Ar+ laser device 1. (For the sake of explanation, the mirror 3 is omitted from the drawing.) First, the light emitted from the Ar+ laser device 1 is transmitted by the first servo mirror 4 to the second servo mirror 5.
The light guided upward and reflected by this second servo mirror 5 is guided to half prisms 8 and 9. Note that the first and second servo mirrors 4.5 can be rotated as shown by the arrows in the figure. The light reflected by the half prism 8 is 4
The output of this photodetector 10 drives two motors 100° 101 as control signals. The four-division photodetector 10°11 is already known. For example, the error signal in the vertical direction of the first photodetector 10 is sent to the comparison amplifier 104, and the error signal in the left and right direction is sent to the comparison amplifier [05
The servo mirror 4 is detected according to each error signal.
motor 100. Drive a lot. Similarly, the vertical error signal and the horizontal error signal of the second photodetector 11 are detected by comparison amplifiers 106 and 107, respectively, and the motor 102. 103 is driven. What is important in configuring this front axis correction servo system is to transmit the control signal from the one of the two photodetectors closer to the Ar+ laser device 1, that is, the first photodetector 10 mentioned above, to the two servo mirrors. Of these, the one closest to the Ar+ laser device 1, that is, the first servo mirror 2 mentioned above, must be driven, and furthermore, after the light emitted from the Ar+ laser device 1 passes through the two servo mirrors 4.5, The light must be arranged in the order that the light is incident on the two photodetectors 10° and 11. According to experiments conducted by the inventor, the first photodetector detects the second servo mirror, and the second photodetector detects the first servo mirror.
If a control signal for driving a servo mirror is detected, the light emission position and angle deviation will be corrected, but divergence will occur.

In other words, the conditions for configuring this optical axis correction servo system are such that the light always passes through two predetermined points, so (1) the light is incident on the first and second servo mirrors; and a second photodetector.

(2) One control signal for rotating the first servo mirror is from the first photodetector.

can be mentioned.

Next, the conditions for the optical axis correction will be further discussed using FIGS. 4 and 5. FIG. 4 is a diagram schematically showing the configuration of FIG. 2. Components that are the same as those described above are given the same number. First, the distance from the first servo mirror 4 to the second servo mirror 5 is k; Or the distance from the first servo mirror 4 to the first photodetector (hereinafter simply referred to as PDl) 10 is +; servo mirror 5 to a second photodetector (hereinafter simply referred to as PD2).
Let the distance to 11 be 3. A coefficient indicating a distance of 1 to 3 to these becomes a variable gain coefficient.

Furthermore, the output angle variable of the light from the Ar laser device 1 is set to Δθ0. The emission position displacement is Δlo, and the drive angle displacement of the first and second servo mirrors 4.5 is Δθ Δθ PD
The angular displacement on +lO and the position degree of 11'012' are respectively Δθ2. Δ12. Also, the transfer functions of the first and second servo mirrors 4 and 5 are respectively PD+10. The angular displacement and positional displacement on F'D211 are (on mirror 4 to PD+10 of ml) (on second mirror 5 to PD211).

The addition point for this system is PD+10. If we focus on the fact that it is on the PD 211 and create blocks, we get something like the one shown in FIG. 5(a). Therefore, N+(s)-1Δ! 0+Δθ(,
k, N2 (S) - ΔθOka, the fifth
The result is as shown in Figure (b). First servo mirror 4. P
D+ (10) and second servo mirror 5゜PD2 (11
) is a minor loop whose characteristics can be determined independently. However, as can be seen from this figure, this loop has an expanded transmission number of 500. The combination transfer function 501 exists, and in order to stabilize the overall closed-loop characteristics, the selection of the conversion gain coefficient (distance between each element) is important.

Expanded transfer function 50 from addition point 502 (output EI(s))
The transfer function from 0 to the output E2(S) is as follows, and the stability condition for this is: k,≦3...(1).

Next, the closed loop transfer function is (N2 (S) = O.)
)−1111−N+ (s) (1++M+
(S)) (1+kzM2(s)) +2M2 (
s) The summing point 502 which is (1+kIM+ (s)) is part of the summing point on PD+lO. The driving change of the above servo mirror is 2 times 1 (0<k2...(2). From (1) and (2) above, the loop stability condition is k(1<k2≦k3-( 3) is obtained.In other words, this equation (3) is especially true for the first and second
In order to correct the interference of the orthogonal axes of the servo mirrors, eccentricity of the rotation center, etc., the distance (k2) between the second servo mirror 5 and the first photodetector PD+lθ must be It is optimal for stability to make the distance sufficiently larger than .5 distance M(ko).

As described above, a part of the tracking recording beam is classified,
An optical axis correction servo system that detects and corrects the emission position and angle deviation of the light from the Ar+ laser device using two 4-split photodetectors, and a
A beam position servo system detects positional deviation using a split photodetector and minimizes optical axis polarization by driving the first convex lens of each collimator system.
The relative position fluctuation between the information signal recording beam and the tracking signal recording beam described above could be suppressed to ±0.05 μIIl or less. Up to this point, the two beams have been described as an information signal recording beam and a tracking recording beam, but if the target recording medium is, for example, a write-once recording disk, as shown in the cross-sectional view of the disk in FIG. One of the two beams is used to form a guide groove (group) (where information is recorded), and the other is used to record sector information necessary for recording within a pitch of 1.8 μm. It can be used as The reason why such sector information can be recorded at normal track pitch intervals is that the relative position fluctuations of the two beams as shown above can be minimized.

[Effects of the Invention] According to the present invention, it is possible to connect a spot at a predetermined position with extremely high precision without causing any fluctuation in the optical axis direction and position of the light emitted from the laser oscillator.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of an optical information recording device showing one embodiment of the present invention, FIG. 2 is a partial configuration diagram showing one embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a schematic diagram showing the characteristic parts of the device according to an embodiment of the present invention. FIG. 5 is a block diagram showing the angular displacement and position displacement according to the embodiment of the present invention. 6 is a principle diagram of the beam position servo optical system, and FIG. 7 is a diagram for explaining the problems of the beam position servo optical system.
Figure S8 is a diagram showing pointing stability, No. 9
The figure is a sectional view of a new write-once recording disc.

Claims (2)

[Claims] (1) A first servo mirror that reflects light from a laser oscillator in any direction, a second servo mirror that reflects light reflected by this first servo mirror in any direction, and this second servo mirror. a first light splitting element that takes out a part of the light reflected by the mirror; and a first light splitting element that detects the incident position of the light on the first light splitting element using a part of the light split by the first light splitting element. 1
a photodetector; a first control means for rotationally controlling the first servo mirror so that light enters a predetermined position on the first light splitting element; a second light splitting element that takes out a part of the light; and a second light splitting element that detects the incident position of the light on the second light splitting element using the part of the light split by the second light splitting element.
a photodetector; and in response to a position control signal from the second photodetector,
a second control means for rotationally controlling the second servo mirror, the distance (k_0) between the first servo mirror and the second servo mirror, the distance between the second servo mirror and the first light; A light source characterized in that the distance to the detector (k_2) and the distance between the first photodetector and the second photodetector (k_3) each satisfy the relationship k_0<k_2≦k_3. Information recording device. (2) The optical information recording device according to claim 1, wherein the first and second photodetectors are divided into four parts.