JPS6030014B2 - Recording plate setting position detection method in optical recording/reproducing device and recording plate used therein - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording plate setting position detection method in an optical recording/reproducing apparatus and a recording plate used therein.

In recent years, research and development of optical memory materials that can be optically recorded and reproduced have been actively conducted.

As main optical memory materials, silver salts, amorphous materials, magnetic amorphous materials, MnBi, thermoplastics, and the like have been widely studied. Looking at these materials from the usage perspective,
Items that record information such as images on a surface, such as photographic film,
Alternatively, the object may be one in which digital information from a computer or analog information such as images and audio signals is recorded in series. The latter application of point recording and playback is carried out by attaching the recording medium to a tape-shaped or disc-shaped base material, but basically recording and playback is realized by irradiating the surface of the recording material with a light beam. Ru.

That is, to record information, an incident light beam is modulated by a light modulation element or the like and the recording material is irradiated with the modulated light beam. Further, when reproducing recorded information, a light beam is sequentially irradiated onto each point of the recording material, and changes in light such as transmitted light or reflection are detected by a light receiving element or the like. In order to shorten the recording wavelength and record and reproduce high-density information using such optical memory materials, for example, a light source with good coherency such as a laser is used, and this light is focused into the smallest possible spot and directed onto the recording material. Irradiation is performed.

If we assume that the size of this small light spot is 1 f0, then a recording density of 1 pbit/s can be obtained. As described above, when recording and reproducing information by irradiating a recording material with a minute light spot, it is necessary to precisely align the recording material with the light spot image position.

For example, if a laser beam is narrowed down to a minimum light spot of 1 French ◇ by using a lens system, the size of the light spot will be 1.
If we define the depth of focus as the distance on the optical axis that falls within the size of 2 mm, the depth of focus will be approximately 4 mm. That is, it is necessary to place the recording material within the focal point with an accuracy of four degrees. In general, in a reproduction-only machine in which information has already been recorded, it is possible to check whether recording material is set near the focal plane by monitoring the quality of the reproduced signal.

However, in a recording/reproducing device, information to be monitored is usually not recorded during recording, and some means is required to bring the recording material within the focal depth of the light beam. In the present invention, when performing high-density recording as described above on a recording slope in which the recording material is attached to a base material,
This paper proposes a method for detecting the focal plane and setting the recording plate at that position.

Still another object is to provide a recording plate whose focal plane can be easily detected.

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows the overall configuration for recording information, where 1 indicates a light source such as a laser, and a indicates the optical axis of the light beam generated from the laser. 2 is an optical modulator that modulates the intensity of light a according to an electrical signal input from a terminal.

Reference numeral 3 denotes a mirror lens, which is used to enlarge the diameter of the incident light a.

A half mirror 4 reflects a reflected light beam b from a recording plate (described later) toward a photoelectric detector (described later).

5 is a total reflection mirror that changes the direction of incident light a and reflected light b.

6 is an optical device configured using a microscope objective lens or the like to focus the incident light beam a into a minute spot; 7 is a recording material;
Reference numeral 7a indicates a base material to which the recording material 7 is attached, and these constitute a recording disk 8 as a recording plate.

Generally, the recording material 7 is thinly and uniformly attached on a base material 7a, and the base material 7a here uses a transparent plate or sheet of glass or polyester. Reference numeral 9 denotes a motor for rotating the recording disk 8.

Reference numeral 10 denotes a device for supporting the motor 9, which supports the rotating shaft of the motor 9 with a bearing or the like.

Reference numeral 11 denotes a transfer device for moving the motor 9 and the recording disk 8, for example, in the direction of arrow A in accordance with the rotation of the motor 9.

The light focused by the objective lens 6 creates a minute light spot at the X point on the recording disk 8, part of this light passes through and becomes light C, and part reflects at the X point to generate reflected light b. do.

The reflected light b passes through the objective lens 6, is reflected by the total reflection mirror 5, is further reflected by the half mirror 4, and is sent to the light receiving elements 13, 1.
It's number 4. Although only the optical axis of the reflected light b is shown to simplify the drawing, in reality, the light is spread out. 12
is a screen for observing the optical image of the transmitted light C.

The light receiving elements 13 and 14 are arranged side by side, and 15 is a storage plate on which the two light receiving elements 13 and 14 are mounted. 19 accurately indicates the position of this storage plate 15 using arrow B.
This is a fine movement device for moving in the direction of.

A differential amplifier 16 amplifies the outputs of the two light receiving elements 13 and 14 and outputs the difference.

17 is a drive circuit that amplifies the output of the differential amplifier 16 and generates an output for driving the lens drive device 18; 18 is a drive circuit that holds the objective lens 6;
This is a lens drive device that slightly moves the lens in the vertical direction.

When the distance d between the objective lens 6 and the recording disk 8 in FIG. The position of the storage plate 15 can be set using a fine movement device 19.

At this time, the differential amplifier 16 does not generate an output, so the lens driver 18 maintains its position. On the other hand, distance d
When d becomes a value outside the above depth of focus, there is a difference in the amount of light received by the light receiving elements 13 and 14, as shown in FIG. 2, and the differential amplifier 16 generates a positive or negative output depending on the deviation of the distance d. , the lens driving device 18 is operated accordingly to control the distance d so that it falls within the depth of focus. FIG. 2 shows that the amount of reflected light hitting the light receiving elements 13 and 14 varies depending on the distance d between the objective lens 6 and the recording disk 8 in FIG. 1, and the same components as in FIG. The same numbers as in Figure 1 are given.

In FIG. 2, the optical axis a of the light incident on the objective lens 6 is slightly shifted from the optical axis of the lens itself. 7' indicates the upper surface of the recording disk 8, when the mouth position is within the depth of focus, the position A is closer to the lens than the focal point, and the position C is farther from the lens than the focal point. show.

When the upper surface of the recording disk 8 is at the position of the mouth, if the location is selected so that the amount of light received by the light receiving elements 13 and 14 is equal as described above, as is clear from the figure, the recording disk surface 7' is placed in the hole. At some point, the amount of light received by the light receiving element 14 becomes larger than that of the light receiving element 13. The opposite occurs when the recording disk surface 7' is in the position C. In this way, the objective lens 6
It is possible to obtain an output according to the distance between the recording disk surface and the recording disk surface. FIG. 3 shows an example of the structure of the lens drive device 18.

FIG. 3 shows an example in which the objective lens is driven up and down by electromagnetic force. The objective lens 20 and the cylindrical coil 21 are connected to the leaf spring 2
2, the coil 21 is inserted between the cylindrical magnets 23. Therefore, when a current is passed between portions C and D of the coil 21, the electromagnetic force of the coil acts, and the objective lens moves up and down depending on the direction of the current. The method of keeping the distance d between the objective lens 6 and the recording disk 8 constant has been described above.

However, in general, when newly recording information on the recording disk 8 on which no information has been recorded, it is necessary to determine in advance whether the distance d is within the depth of focus. The above-mentioned distance d needs to be kept constant within a range of about 2 mm, assuming that the diameter of the light spot irradiated onto the recording disk 8 is at least 1 mm as described above, and the allowable range is within 1.2 mm. Therefore, due to variations in the thickness of the recording disk 8, variations in the stable point of the objective lens driving device 18, or variations in the position of the light-receiving element storage plate 15, there is a risk that the distance d will go outside the depth of focus. Therefore, when installing a different recording disk 8, it is necessary to check whether the distance d is within the depth of focus. A method of confirming the distance d will be explained below.

Figure 4 shows the locus of the optical path when the optical beam is focused by a lens. E indicates the incident light east, and F indicates the output light east of the shins. Let's take the distance on the Z-axis from the lens 6 that gives the minimum spot diameter, and then set the distance to the allowable diameter location closer to the lens 6 as d.
Assuming that the distance to the allowable diameter farthest from the lens is flat, d,
The interval between and d2 becomes the depth of focus. In the figure, 8 indicates the recording disk. Near this focal point, for example, a transparent glass plate 31 uniformly having a flaw 30 on one side only, where the minimum light beam diameter is equal to or smaller than the beam diameter, is replaced with the recording disk 8 shown in FIG. 4, and the transmitted light image is obtained. When observed, it looks like Figure 5. That is, Figure a shows a diagram when the surface of the glass plate 31 is located at a distance Z<d from the center of the lens. In this case, since the light beam irradiated onto the glass surface is thick, more flaws 30 on the glass surface are irradiated, and the light beam is scattered and transmitted. Therefore, when the screen S is placed at the position Z=Z· and the projected image is observed, more striped patterns are observed as shown in FIG. 6a. The same thing can be said in the case of Z> as shown in FIG. 5C, and many striped patterns can be seen as shown in FIG. 6C. On the other hand, when the glass surface is placed at Z=F as shown in FIG. 5b, the number of scratches 30 on the irradiated glass surface is the smallest, so the number of scratches 30 on the screen S is the smallest as shown in FIG. 6b. A large striped pattern is observed. This change can be clearly observed and identified with the naked eye. Furthermore, by placing an appropriate light receiving element at the screen S, the above state can be detected as the maximum value of the amount of light received.
For example, as shown in FIG. 7, the recording disk 40 is coated with a recording material 42 on a portion of radius y in a glass disk 41 with radius R,
A flaw 44 smaller than or equal to the maximum diameter of the light beam is formed on a part of the outer periphery, for example, the part 43 in FIG. By observing this, it can be determined whether the recording disk 40 has entered the depth of focus.

The flaws 44 on the disc 40 can be achieved by lapping a glass or polyester film with fine powder, or by blowing hard fine particles (for example, alumina) at high speed. Although the flaw 44 in FIG. 7 is shown as being on the outer periphery, it may also be on the inner periphery of the disc 40.

Alternatively, if the disc 40 of FIG. 7 is opaque, a partially transparent material can be used to achieve the above objective. Furthermore, the coating thickness of the recording material is thin, and the granularity of the material itself can sometimes be used to observe a transmitted image. Next, referring to FIG. 1, a method for maintaining the distance d between the lens 6 and the recording disk 8 within the depth of focus will be explained.

First, before recording information on the recording disk, the rotation of the recording disk is stopped, and a light spot X is irradiated onto the portion of the recording disk that has minute scratches. At this time, an image of the flawed surface formed by the transmitted light C is projected onto the screen 12, and this image is observed. On the other hand, the light-receiving element storage plate 15 receiving the reflected light b at point X on the recording disk is moved in the direction of arrow B by the fine movement device 19.
As a result, the ratio of the amount of light received by the light receiving elements 13 and 14 changes, and the output of the differential amplifier 16 also changes accordingly. Therefore, as the fine movement device 19 moves, the lens drive device 18 also operates, and the distance d between the lens 6 and the recording disk 18 is
change continuously. Therefore, while moving the fine movement device 19, observe the transmitted image on the screen 12, and set the fine movement device 19 at a position where the image of the flaw has the largest area as shown in FIG. 6b. For example, the recording disk 8 is set within the depth of focus of the lenses 6.
By rotating the recording disk 8 in this state and operating the transfer device 11, it is possible to irradiate the recording disk 8 with light having a desired spot diameter and perform recording with a desired bit size.

Note that during recording, the reflected light b in FIG. The distance d is controlled to always be kept constant in response to surface rash and unevenness. That is, automatic focus control is performed. As described above, according to the present invention, even if there is no record plate, it is very easy to set the objective lens within the depth of focus, and even if there is a change in the thickness of the record plate, the record plate can be set outside the depth of focus. This completely eliminates the problem of "difficulty in recording data", making it possible to perform high-density recording.

Furthermore, as a means for finely moving the objective lens, the objective lens driving means of the control device can be used to finely move the light receiving means used in the automatic focus control device for detecting the displacement of the position where the reflected light reaches. . Furthermore, in the present invention, since the set position of the recording plate is detected using the uneven pattern for detecting the set position formed on a part of the recording plate, an adjustment plate separate from the recording plate is used to detect the set position. There is no need for any troublesome operations such as detecting the set position using a [lattice pattern] and replacing the adjustment plate on the recording plate after the detection is completed.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram;
Figure 2 shows the variation in the distance between the objective lens and the recording disk surface,
An explanatory diagram showing the relationship between the arrival positions of the reflected light on this surface, Fig. 3 is a specific configuration diagram of the lens driving device, Fig. 4 is an explanatory diagram of the depth of focus of the light focused by the objective lens, and Fig. 5
The figure is an explanatory diagram showing the interaction between a minute flaw made on a transparent plate and focused light, and Figure 6 is a diagram of a transmitted light image of the minute flaw.
FIG. 7 is a diagram showing a specific example of a recording disk. 1...Light source, 2...Light modulator, 6...
...Objective lens, 7,42... Recording material, 8,
40...Record disc (recording board), 12...
・Screen, 15... Light receiving element storage plate, 18
. . . Lens drive device, 19 . . . Light receiving element storage plate fine movement device, 30, 43 . . . Minute flaws. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. When recording and reproducing information signals on a recording plate through an objective lens with a light beam, an area other than the area where information is to be recorded on the recording surface of the recording plate is irradiated with minute particles. The objective lens is provided with a part that diffracts and scatters light, such as a concavo-convex pattern having a size equal to or smaller than that of the light spot, and the objective lens is slightly moved while observing changes in the amount of light diffracted and scattered by the minute light spot irradiated on the part. A recording plate setting position detection method in an optical recording/reproducing apparatus, characterized in that the recording plate is set within the depth of focus of the objective lens by setting the recording plate within the depth of focus of the objective lens. 2. A recording plate used in the recording plate setting position detection method according to claim 1, wherein at least a portion of the recording plate other than the portion coated with the recording material is configured to be transparent, and the surface of the portion is A recording board characterized by having minute scratches. 3. A recording plate used in the method for detecting a recording plate setting position according to claim 1, characterized in that a fine-grained recording material is coated and at least a part of the coated portion is configured to be transparent. Record board.