JPS6019571B2 - optical recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for optically recording and reproducing signals on a recording medium at high density, and when recording signals at high density, it records whether recording is being performed reliably. The purpose is to provide a device that can simultaneously confirm the

First, one conventional example of a device for optically recording and reproducing signals at high density will be described.

In FIG. 1, 1 is a light source such as a laser, which generates a light beam a, and 2 is an optical modulator that uses, for example, Bragg reflection caused by ultrasonic waves. The light beam a is optically modulated and divided into zero-order light b and first-order light d. In other words, the optical modulator causes the total light intensity of the light beam a to be 0 at the recording site of the recording material during recording.
It becomes the second light b and is irradiated. The light beam irradiated onto the recording medium at this time is hereinafter referred to as a recording beam. Also, when reproducing a recorded signal or an unrecorded area, for example, 20% of the total amount of light beam a is zero-order light. b, remaining 8
0% is d of the first-order light, and the above 20% of the 0-order light is irradiated onto the recording medium.The light beam that is irradiated onto the recording medium when the above-mentioned 20% of the 0-order light is irradiated is hereinafter referred to as an unrecorded beam. call.
3 is a slit that allows only the 0th order light b to pass through.

4 is a projection lens which magnifies the light beam b and irradiates it onto the objective lens.

5 is a beam splitter, which changes the optical path of the reflected light c from the recording medium as shown in FIG.
3 is irradiated.

Reference numeral 6 denotes a total reflection mirror, which changes the optical path of the light beam b as shown in FIG. 1. The total reflection mirror changes the optical path of the light beam b as shown in FIG. Then, the light spot p is slightly rotated by the mirror driving device 14 and controlled so that the light spot p focused by the objective lens 7 follows the recorded information track 8.

Hereinafter, this control will be referred to as tracking control. Reference numeral 7 denotes an objective lens, for example, a microscope objective lens is used, and the light beam b is narrowed down to a minute spot of about 1 m, for example.
It has the function of irradiating the recording medium. 8 is an information track recorded on the recording medium.

9 is an objective lens driving device.

Even if the recording medium vibrates in the direction of the arrow y due to rotation or the like, the objective lens driving device 9 causes the objective lens 7 to vibrate up and down in the direction of the arrow y, so that the objective lens 7 is not affected by the vibration of the recording medium in the direction of the arrow y. It is controlled so that the distance between the objective lens 7 and the information track 8 is always constant, and has the function of always irradiating the light spot p onto the information track 8. control is called focus control). As the objective lens driving device, it is possible to use a device based on a driving principle such as a voice coil of a speaker, for example. 10 and 11 are photodetectors;
By detecting the transmitted light of the information track 8, reproducing the recorded signal, and comparing the amounts of received light incident on each of the photodetectors 10 and 11, a signal for the tracking control is obtained. The tracking control, which is applied to the mirror drive circuit 14 to perform tracking control, is not directly related to the present invention, so a description thereof will be omitted here.

Note that photoelectric conversion elements such as pin diodes are used for the photodetectors 10 and 11. Photodetectors 12 and 13 are irradiated with reflected light c reflected from the recording medium.

As shown in FIG. 1, the incident light on the objective lens 7 is incident at a position slightly deviated from the center of the objective lens in the direction of the arrow y, so the irradiation position of the incident light c on the photodetector is as follows. , moves in the direction of arrow y according to the distance between the objective lens 7 and the information track 8. Therefore, the photodetector 1
A signal for controlling the focus is obtained by comparing the amount of light received by the lenses 2 and 13, and the signal is applied to the objective lens driving device 9 to perform focus control. Note that focus control is not directly related to the present invention, so a description thereof will be omitted. 14 is a mirror drive layer; 15 is a recording medium which is rotated in the direction of arrow Q and transported in the direction of arrow X, and the information track 8 is recorded in a spiral shape.

In addition, the recording medium is made of a material that is exposed to strong light (for example, the amount of light when the total light amount of the light beam a is narrowed down to about 1 peak m) and exhibits light-blocking properties on a transparent disc-shaped base. The signal is e.g. FM
Data is recorded bit by bit using changes in the modulated light blocking rate. FIG. 2 shows the objective lens 7 shown in FIG.
FIG. 2 is a diagram of a recording medium 15 and photodetectors 10 and 11 viewed from the arrow x direction.

The light beam b incident on the objective lens 7 is focused as shown by a light beam q, and is irradiated onto the recording medium 15.

A portion of the amount of the irradiated light beam q is transmitted through the recording medium 15, and the transmitted light b,' is applied to the photodetectors 10 and 11. A portion of the light beam b is reflected by the surface of the recording medium and becomes a light beam C, which returns to the objective lens 7. The light beam c that has passed through the objective lens 7 is used for the focus control. Reference numeral 17 denotes an objective lens holder, which holds the objective lens and vibrates together with the objective lens 7 following the vibration of the recording medium in the direction of the arrow y when the focus is controlled.

An optical video disc is generally well known as a playback-only device that uses a recorded disc with the above configuration, and has a minimum recording bit length and a track width of 1.
A high-density reproduction device with a track pitch of about 1.6 Am has been realized.

The present invention uses a high-density recording material (for example, M old i, amorphous semiconductor, etc.) whose optical properties change in real time in response to irradiation light.
An object of the present invention is to provide a new device configured using the above-mentioned device for checking (recording monitor) whether or not a signal is being recorded reliably when recording a signal.

In addition, as a method for such recording monitoring, two types of lasers with different wavelengths are used when recording signals, and one
A method in which a recording light is composed of a laser beam of one wavelength to record a signal, and another laser beam of a different wavelength is irradiated immediately after the information track recorded by this recording beam to reproduce and confirm the recorded signal. However, since this method essentially requires two types of lasers, it is difficult to put it to practical use as a recording/reproducing device.

The details of the present invention will be explained below with reference to drawings showing embodiments.

In order to simplify the explanation, elements common to those in the conventional example are given common numbers and their explanation will be omitted. In FIGS. 3 and 4, reference numeral 18 denotes a light reflecting plate made of transparent glass, which is attached to the recording medium 1.
A portion of the amount of light beam b reflected from the light beam b is reflected again to form a light beam c2. A holder 19 holds the microlens 20 and the dummy microlens 21.

20 is a microlens, and the light beam c2 that is about to spread
The two microlenses, which have the function of focusing the light beam again and irradiating the light beam onto the recording medium as shown in c3, are made of, for example, a light converging light guide.

A dummy microlens 21 has the same weight as the microlens 20, and the weight is balanced between the two microlenses.

Note that the 21 dummy microlenses mentioned above do not necessarily have to have a lens function. In addition, each part of 18 to 21 is
The center of the objective lens is positioned so as to be balanced with respect to the x and Y directions of the arrows in FIG.

In addition, each of the parts 17 to 21 is glued together to form a single piece, and by performing the focus control, the recording medium 15
Even if vibrates in the direction of the arrow y, each of the integrated parts vibrates in the direction of the arrow y so as to follow the recording medium 15 together with the objective lens 7. Therefore, the distance between the objective lens 7 and the above-mentioned parts and the recording medium 15 is always kept constant, and the relationship between the light beams shown in FIG. 3 does not change even if the recording medium 15 vibrates in the direction of the arrow y. . Therefore, if the light beam b is made incident on the objective lens 7 in the relationship shown in FIG. 1, during recording in step 3, the signal is first recorded on the recording medium by the light beam q, and an information track is formed. Ru. Next, it becomes possible to irradiate the information track of the recorded signal with the light beam c3, and while recording information on the recording medium by detecting the transmitted light of the light beam c3, the information track is recorded with the light beam 0 just before. It becomes possible to read out the signals of the information track. 22
A photodetector detects the light beam c'3 of the light beam c3 that passes through the recording medium.

The output of the photodetector 22 thus contains information of the signal recorded by the light beam q. FIG. 5 shows another embodiment of the invention.

The structure is almost the same as the embodiment of the present invention shown in FIG. 3, but the light reflecting plate is partially inclined only in the direction of the arrow y, as shown at 18'. With the above configuration, it is possible to separate the photodetectors 10, 11 and the photodetector 22 further, and the signal obtained from the light beam b' and the signal obtained from the light beam c'3 can be separated. This makes it possible to completely separate the signals from the Note that in FIG. 3, the light beam c3 is the reflected light of the light beam q from the recording medium 15 and the light reflection plate 18, and therefore has a weaker light intensity than the light beam b. It is inconceivable to re-record the information track that has been recorded.

However, during recording, the light beam c3 is also optically modulated by the optical modulator 2 in accordance with the recording signal in order to record the signal on the recording medium using bit noy pits. therefore,
It is difficult to directly obtain a recording monitor signal from the output of the photodetector 22. Hereinafter, an embodiment in which a signal almost recorded on a recording medium by the light beam b is generated from the output of the photodetector 22 will be described using FIGS. 6 to 10. FIG. 6 is a diagram for explaining one embodiment for obtaining a signal recorded on a recording medium from the output of the photodetector 22.

In FIG. 6, the horizontal axis indicates the passage of time, and the vertical axis in each of the figures from 7 to 7 in FIG. 6 indicates that the direction of the arrow 22 is the direction in which the amount of light increases. Each figure will be explained. FIG. 6A shows the information track irradiated by the light beam c3 among the information tracks recorded by the light beam q.
For example, numeral 23 is a recording site and has light blocking properties. 24 is an unrecorded portion and is transparent to light.

The signal at the left in FIG. 6 is obtained from the photodetectors 10 and 11, which is t seconds ahead of the signal at FIG. 6A. This is because the light beams q and c are separated in the direction of the arrow y (see FIG. 3). FIG. 6C shows a signal obtained from the photodetector 22. The signal will be explained in a little more detail. In FIG. 6C, L, indicates when the light beam q is the recording beam, that is, when the light beam q reaches the light intensity indicated by 25 at the beginning of FIG. This is the level obtained from the photodetector 22 when irradiated with . L is the level obtained from the photodetector 22 when the light beam c irradiates the recording site at the above time.

Further, L3 indicates that when the light beam q is the unrecorded beam, that is, when the light beam b reaches the light intensity indicated by 26 in Figure 6, and the light beam C irradiates the recorded area, the light is detected. This is the level obtained from the device 22.

Similarly, L is the level obtained from the photodetector 22 when the recording region is irradiated with the light beam c. The beam described below is smaller than the recording beam, and the amount of light that passes through the recorded area is smaller than the amount of light that passes through the unrecorded area. FIG. 6 2 is a signal obtained by subtracting the signal shown in FIG. 6 from the signal shown in FIG. 6 c.

To make it easier to understand, I have shown the exit signal in Figure 6 as a broken line in Figure 6C. If you look at Figure 6 2, you can see that it corresponds to Figure 6 A, although there are some irregularities. Therefore, if the amplitude is limited by setting the reference level to 27, which is approximately the median value of the signal, in Fig. 6 2, as shown in the tree of Fig.
The signal read out from Figure A is obtained. The tree in FIG. 6 is a signal that immediately reads out the information track that was just recorded by the light beam b, and recording monitoring becomes possible by FM demodulating this signal. Note that the signals in Figure 6 are obtained from the photodetectors 10 and 11, so there may be differences in the recording medium.
Therefore, even if there is a difference in light transmittance, this effect can be avoided.

Next, the seventh step for obtaining the recording monitor signal explained above.
The block circuit diagram shown in the figure will be explained.

A signal from the photodetector 10 is applied to the terminal R, a signal from the photodetector 11 is applied to the terminal S, and a signal from the photodetector 22 is applied to the terminal T. Amplifiers 32, 33, and 34 amplify the signals from each detector to a desired magnitude.

36 is an adder for taking the sum of the output signals from the amplifiers 32 and 33, 36 is a subtracter for taking the difference between the signals from the adder 35 and the amplifier 34, and 37 is an amplitude limiter.

The signal at the opening in Figure 6 is the output signal from the adder 35, the signal at Figure 6 C is the output signal from the amplifier 34, the signal at Figure 6 2 is the output signal from 36, and the signal at Figure 6 E is the amplitude Limiter 37
represents the output signal of FIG. 8 shows another embodiment for obtaining a recording monitor signal from the output signal of the photodetector 22, and FIG. 9 is a diagram for explaining FIG. 8.

It should be noted that the tree A to I in FIG. 9 corresponds to the tree A to I in FIG. 6, so a detailed explanation will be omitted. In FIG. 8, 28 is a switching element such as an analog gate, and 29 and 30 are amplifiers with different gains. A signal shown in FIG. 9C, that is, a signal from the photodetector 22 is applied to the terminal J. Terminal K
K is the signal shown at the beginning of FIG.
When the signal reaches the level 25, the signal input from the terminal J is applied to the amplifier 29, and when the signal level is 26, the signal input from the terminal J is applied to the amplifier 29. 301 items will be added. For example, for ease of understanding, the gain G of amplifier 29 is 1, and the gain G of amplifier 3 is
Assuming that the gain G2 of 0 is greater than 1, consider the signal level output from the terminal M. In FIG. 9, it is shown, for example, at level 26. Only when the light beam L is the unrecorded beam, the signal input to the terminal J is amplified.
, L4, the amplitude increases as shown by the broken line in FIG. 9C. However, L2 G2 x L3, L2 G2 x
The gain of the amplifier 30 is adjusted so that the relationship of L is obtained. In the end, the signal output from terminal M becomes as shown in FIG. 9-2.

For example, if the reference level is set to Vc and the amplitude is limited, a signal shown in the tree of FIG. 9 is obtained. The signal shown in FIG. 9(e) is a signal obtained by reading out the information track just recorded by the light beam b shown in FIG. 9(a), and recording monitoring is possible by FM demodulating this signal. Although the principle is the same, it is also possible to obtain the signal shown in FIG. 9-2 with the configuration shown in FIG. 10.

That is, the signal shown in FIG. 99C is applied from the terminal N, and the signal shown in FIG. 9 is applied to the terminal P. Reference numeral 31 denotes an amplifier whose gain changes according to the level of the signal applied from the terminal P. For example, when the level is 25 as shown in the opening of FIG. 9, the gain G is 1, and when the level is 26, the gain G is 1. Assuming that G2 is the signal shown in FIG. 9, the signal shown in FIG.
This makes it possible to monitor recordings. In the above embodiments, the optical properties of the recording medium are changed and the amount of transmitted light is limited to the amount of transmitted light, but the same applies to the amount of reflected light.

As described above, according to the configuration of the present invention, since only one light source is required to enable recording monitoring with one light source, the cost is very low, and the optical axis of the light beam for recording monitoring can be adjusted easily. It becomes easier. Furthermore, it is easy to detect and confirm when recording cannot be performed reliably due to a defect in the recording medium or instability in the optical system or control system.

[Brief explanation of the drawing]

FIG. 1 is a conceptual block diagram of an optical recording/reproducing device according to an embodiment of the conventional technology, FIG. 2 is a schematic diagram of the main parts of FIG. 1, and FIG. 4 is a schematic exploded perspective view of the main parts of FIG. 3, FIG. 5 is a schematic diagram of the main parts of a different embodiment of the present invention, and FIGS. Main part block circuit diagrams of different embodiments of the electrical signal processing system according to the present invention, FIGS. 6 and 9, are operation explanatory diagrams of FIGS. 7 and 8, respectively. 7...Objective lens, 10,11...Photodetector,
15... Recording medium, 17, 19... Holder, 18... Light reflecting plate, 20...
Microlens, 22...Photodetector. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Scope of Claims] 1. In an apparatus for optically recording and reproducing signals on a recording medium by making an information light beam incident on a position away from the center of a condensing lens and condensing the light beam, A light reflecting plate for reflecting light reflected from a recording medium toward the recording medium is disposed between the condensing lens and the recording medium so as to maintain a constant distance from the recording medium, and the light reflecting plate A first photodetector that converts the light reflected from the plate and transmitted through the recording medium into an electrical signal, and a second photodetector that converts the information light beam transmitted or reflected from the recording medium into an electrical signal. , an optical recording/reproducing apparatus characterized in that a signal recorded on the recording medium is monitored and reproduced from an electric signal transmitted through the first and second photodetectors. 2. The optical recording/reproducing device according to claim 1, wherein the light beam that enters the second photodetector is a light beam that passes through a condenser lens. 3. An optical recording/reproducing device according to claim 1 or 2, characterized in that an optical system for condensing light beams passing through a reflector is fixed to the reflector supporting object. 4 In claim 3, the difference ( An optical recording/reproducing apparatus characterized in that the optical recording/reproducing apparatus monitors and reproduces a signal recorded on the recording medium.