JPS5845096B2 - optical recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to obtain an average intensity of light on a recording medium in any state in an optical recording/reproducing device.

In general, optical recording and reproduction of information involves irradiating an optical recording medium with a light beam, changing the optical transmittance or light reflectance of the optical recording medium using the energy of the light, and recording information. Information is reproduced by detecting changes in transmittance or light reflectance.

An optical recording/reproducing device using a disc-shaped optical recording medium includes a light source that generates a light beam for recording/reproducing, a light modulation element that modulates the light beam, an optical system such as a mirror or lens that guides and focuses the light beam, and an optical system such as a mirror or lens that guides and narrows the light beam. A light receiving element that detects changes in transmittance or light reflectance, a rotating device that rotates a disc-shaped optical recording medium,
It is composed of a transport device that relatively transports the disk-shaped optical recording medium and the optical system, and a control device that performs various controls.

When a disk-shaped optical recording medium is rotated at a constant rate by a rotating device, continuously moved relative to the optical system, and the recording light beam from the light source is modulated and focused and irradiated by a lens, it is concentrically shaped as shown in Figure 1. Information can be recorded in a spiral.

In FIG. 1, 1 is a disc-shaped optical recording medium, and 2 is an information recording section.

To reproduce information, the disk-shaped optical recording medium is rotated and transported in the same way as during recording, and the information recording section is continuously irradiated with a reproduction light beam. However, the energy of the light depends on the optical transmittance or reflectance of the optical recording medium. The light receiving element receives the transmitted light or reflected light.

The format of the information to be recorded and reproduced here is based on the gradation of the optical recording medium and other factors such as light transmission vehicle height (low light reflectance).
It is binary information of “0”, low light transmittance (light reflective vehicle height), “1” or vice versa, and indicates the geometric length of the light transmittance vehicle height area and the low light transmittance area (or reflectance). The time axis information is changed and arranged as shown in Fig. 2.

In FIG. 2, a indicates an information recording section, 3 indicates a light transmitting vehicle height region, 4 indicates a low light transmittance region, and b indicates a signal 5 corresponding to a detected by a light receiving element using transmitted light.

Changes in the light transmittance or light reflectance of an optical recording medium depend on the energy of the irradiated recording light beam.

Taking as an example an optical recording medium in which an amorphous semiconductor is deposited on the recording medium substrate, if the energy of the light beam exceeds a certain threshold, the light transmittance will change, and as the energy of the light beam increases, eventually Although it evaporates, the light transmittance has gradations depending on the energy of the light beam from the threshold value to evaporation, as shown in FIG.

In FIG. 3, a indicates the change in light transmittance of the amorphous semiconductor due to the energy of the light beam, 6 is the recording medium substrate, 7 is the amorphous semiconductor, and 8 is the energy of the irradiated light beam that exceeds the threshold value. If you can't hear it, 9
and 10 are cases where the energy of the light beam exceeds the threshold value, but the energy of the light beam is 9<10, and the light transmittance is 9>10.11 is the case where the amorphous semiconductor is evaporated, and b is the case where the light is received. A signal 12 corresponding to a detected by the transmitted light in the element is shown.

As mentioned above, when recording and reproducing information on a disc-shaped optical recording medium in an array of high and low light transmittance or light reflectance regions, the energy of the recording light beam must be determined by the optical recording medium and kept constant. , as is clear from the above,
Optimal information cannot be recorded or played back.

In other words, if the energy of the recording light beam is too large or too small, the recorded information will be missing from the input information and will no longer be the same information, even if the energy of the recording light beam is within the recording range. If the variation is large, the output level of the signal detected by the light-receiving element will differ, causing problems in recording and reproducing information.

By the way, in the above-mentioned optical recording and reproducing apparatus for a disc-shaped optical recording medium, assuming that the power of the light source during recording is constant, the disc-shaped optical recording medium rotates at a constant rate, and the rotation at the outer and inner peripheries is constant. The speeds are different, and the irradiation time of the light beam changes between the outer and inner circumferences, and the energy of the light beam is smaller at the outer circumference than at the inner circumference.

In addition, when the frequency of the information to be recorded is different (when the geometric lengths of high and low light transmittance or light reflectance regions are different), the irradiation time of the light beam is different, and the light beam with a higher frequency is The energy of the lower frequency will be smaller than that of the lower frequency.

Furthermore, the power of the light source is not always constant and varies.

Therefore, in order to optimally record and reproduce information, it is necessary to control the energy of the recording light beam during recording.

The present invention controls the recording and reproducing of information by controlling the outer circumference and inner circumference of the disk-shaped optical recording medium, and eliminating the difference in the energy of the recording light beam caused by the difference in the frequency of the information to be recorded and the fluctuation in the power of the light source. The purpose is to provide a device that performs this process properly.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 4, reference numeral 1' denotes a disc-shaped optical recording medium, which is mounted on a transparent turntable 14 fixed to the shaft 13' of 13 motors and rotated at a constant rate.

The motor 13 has a holding member 15 that meshes with the screw of the transfer screw 16.
is held by the transfer screw 16 with bearings 17 and 17
' and rotated by a motor (not shown), the disc-shaped optical recording medium 1' is rotated by a motor (not shown).
is transferred as shown by arrow 18.

Reference numeral 19 denotes a light source such as a laser that generates a light beam 20 for recording or reproducing.

21 is a modulation circuit into which information such as a video or audio signal is input, and 22 is an optical modulator that modulates the light beam 20 with an electric signal from the modulation circuit 21.

The light beam 20 passes through an optical system including an auxiliary lens 23, a mirror 24, a beam splitter 25, a lens 26, etc., is focused, and is irradiated onto the disc-shaped optical recording medium 1'.

At this time, focus control is necessary in order to keep the focused beam spot of the light beam 20 at a constant size and irradiate the medium.

Various methods can be considered for this focus control, but in this embodiment, it is performed, for example, by the position of the reflected light from the optical recording medium.

A light receiving element 27 is irradiated with reflected light 20' of the light beam 20 from the disc-shaped optical recording medium 1 by a beam splitter 25.

The light receiving element 27 is divided into two parts, and the reflected light 20'
moves in the direction of the arrow 28 depending on the vertical position of the disc-shaped optical recording medium 1', and by utilizing this, the difference between the two output signals of the light receiving element 27 is calculated by the differential amplifier 29 and used as a control signal.

The lens 26 is held by a holding member 30 having a structure such as a voice coil, and is operated by a drive circuit 46 in response to a control signal from a differential amplifier 29 to move the lens 26 up and down to control the focus.

31 is a filter that allows only light having the wavelength of the light beam 20 to pass through.

33 is a light source such as a laser that generates the auxiliary light beam 32, and the wavelength of the light from this light source 33 is different from the wavelength of the light from the light source 19.

The auxiliary light beam 32 includes a mirror 24 and a beam splitter.
The light beam passes through optical systems such as 25 and lens 26, is focused like the light beam 20, and is irradiated onto the disc-shaped optical recording medium 1'.

At this time, the irradiation position of the auxiliary light beam is on the rear side of the light beam 20 in the recording direction, as shown in FIG.

34 is a filter that allows only the 320 wavelengths of the auxiliary light beam to pass through.

Reference numeral 35 denotes a light receiving element, which receives transmitted light 37 that passes through the disc-shaped optical recording medium 1' and the turntable 14.

A control circuit 38 controls the energy of the light beam 20 during recording, and its configuration is as shown in FIG.

In FIG. 6, 39 is an amplification circuit that amplifies the signal from the light receiving element 35, and 40 is an integration circuit that integrates the amplified signal.

41 and 41' are reference signal level generation circuits;
2 and 42' are differential amplification circuits for the reference level signal and the signal from the integrating circuit 40, and 43 and 43' are comparison circuits such as Schmitt circuits. The analog gate circuits 44 and 44' generate output signals, and the signals of the differential amplifier circuits 42 and 42' are outputted as outputs 45 and 45'.

Information is recorded on the disc-shaped optical recording medium 1' as described above.
is rotated at a constant rate by a motor 13 and transferred by a transfer screw 16, a light beam 20 is generated from a light source 19, and is modulated by a light modulator 22 with a signal from a modulation circuit 21. This is done by focusing the light beam 20 using an optical system including a splitter 25 and a lens 26 and irradiating it onto the disc-shaped optical recording medium 1', thereby recording information as shown in FIG.

When recording this information, the light receiving element 27, the differential amplifier circuit 2
9. The control device composed of the drive circuit 30 and the holding member 30 is operated to perform focus control.

The filter 31 in front of the light receiving element is for eliminating the influence of reflected light from the auxiliary light beam 320 having a different wavelength.

Also, when recording information, an auxiliary light beam 3 is emitted from the light source 33.
2, the recording information is detected by the light receiving element 35, and the energy of the recording light beam is controlled.

This recording light beam is controlled as follows.

When recording information, an auxiliary light beam 32 is generated from a light source 33 and is transmitted to a mirror 24, a beam splitter 25, and a lens 26.
The light beam 32 is focused by an optical system such as the like, and is irradiated onto the disc-shaped optical recording medium 1'.

The position irradiated by the auxiliary light beam 32 is configured to be on the rear side in the recording direction of the light beam 20 as shown in FIG. When detected by the element 35, it becomes recorded information.

In front of the light receiving element 35, there is a filter 34, in which the light beam 20 and the auxiliary light beam 32 have different light wavelengths, so that only the auxiliary light beam is allowed to pass through, and the influence of the transmitted light of the light beam 20 can be prevented.

Note that the power of the auxiliary light beam 32 is set to a constant value that does not change the light transmittance or light reflectance of the optical recording medium.

In addition, it is necessary to keep the focused beam spot constant for the auxiliary light beam 32, but the light beam 20
Similarly, if the irradiation position of the auxiliary light beam 32 is brought sufficiently close to the irradiation position of the light beam 20, the beam spot can be made constant by the control operation of the lens 26.

The recording information signal detected by the light-receiving element 27 becomes as shown in FIG. 7a due to the above-described difference between the outer circumference and the inner circumference, the information, or the fluctuation of the light source 19.

In FIG. 7, a indicates the detected signal 46, and b indicates an integrated output signal 46' obtained by integrating the signal 46.

In Fig. 7, the signal output level between A and B is when the light transmittance of the optical recording medium 1' changes and there is no evaporation, and the light transmittance changes favorably. Indicates the output level range.

When the output signal 46' is above the output level A, the energy of the recording light beam is too thick, and when the output signal 46' is below the output level B, the energy of the recording light beam is too small.

This is the case when an optical recording medium such as an amorphous semiconductor illustrated in FIG. 3 is used as the disk-shaped optical recording medium 1'.

The detection signal as described above is input to the control circuit 38.

In the control circuit 38, the amplification circuit 39 first amplifies the
An integration circuit 40 integrates the detection signal 46.

The reference signal generation circuit 41 generates a signal at a level corresponding to output level A, and the reference signal generation circuit 41' generates a signal at a level corresponding to output level B. Dynamic amplifier circuit 42.42'
, a signal is generated from the comparison circuit 43, passed through the analog gate circuit 44, and the output of the differential amplifier circuit 42 is generated as a signal 45.

Further, the integrated output signal 46' is transmitted to the reference signal generation circuit 41'.
If the signal level does not exceed , a signal is generated from the comparison circuit 43', and the output of the differential amplifier circuit 42' is generated as the signal 45' through the analog gate circuit 44'.

For the signal 45, the level of the integral output signal 46' is the output level A.
Since the signal 45' corresponds to the case above the output level B, and the signal 45' corresponds to the case below the output level B, it can be used as a signal for controlling the energy of the recording light beam.

Signal 45 indicates that the energy of the recording light beam is too thick, and signal 45' indicates that the energy of the recording light beam is too small.

Therefore, these signals 45 and 45' are used as control signals,
The power of the light beam 20 is changed by the optical modulator 22 to perform energy control.

Although the optical modulator 22 is used to change the power of the light beam 20, it may be an optical modulator such as an acousto-optic modulator.

When the acousto-optic light modulator is used in the Bragg region, it is separated into 0th-order and 1st-order diffracted light by the applied ultrasonic wave, but the power of the 0th-order and 1st-order diffracted light depends on the applied ultrasonic wave, as shown in Figure 8. Varies depending on level.

In FIG. 8, 47 indicates the power of the O-order diffracted light, and 48 indicates the power of the 1st-order diffracted light.

By utilizing this fact, the optical power of the light beam 20 hitting the recording medium can be changed.

When using this acousto-optic light modulator, the recording and reproducing light beam may be either the O-order diffracted light or the 1st-order diffracted light, but it is necessary to use means for connecting the other.

Also, if the light source 19 is a semiconductor laser, etc.
No optical modulator 22 is required to vary the power or modulate the optical beam 20 (which can be done purely electrically).

Information is reproduced using the disc-shaped optical recording medium 1' in the same way as during recording.
is being rotated and transported, the light beam 20 is not modulated, the power is made smaller than that during recording by the optical modulator 22, and the reproduction light beam is narrowed down by the optical system of the auxiliary lens 23, the mirror 24, and the beam splitter 25. The information recording section is irradiated with the light, and the transmitted light 37 is detected by the light receiving element 35.

However, at this time, the filter 34 is moved and removed without generating the auxiliary light beam 32.

The focus control operation is similarly performed when reproducing information.

The information may be reproduced by adding the two output signals of the light receiving element 27 and reproducing the information using reflected light.

As described above, in an optical recording/reproducing device for a disc-shaped optical recording medium, recorded information is detected when information is recorded, and the energy difference of the recording light beam due to the difference in the rotational speed of the outer circumference and inner circumference and the frequency of the recorded information is detected. By eliminating this, there is no loss of information, the signal output level becomes constant during reproduction, and information recording and reproduction becomes optimal.

In addition, although a light source such as a laser is normally used as the light source for the recording light beam, it is possible to prevent the influence of energy changes in the recording light beam due to fluctuations in the output power of this light source, allowing long-term information recording and reproduction. is optimal and stable.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an information recording trajectory by an optical recording/reproducing device on a disc-shaped optical recording medium, and Figs. 2 a and b are enlarged views of the information recording section of the disc-shaped optical recording medium and the corresponding detection signals. Figure 3a. b is a diagram showing changes in light transmittance due to differences in energy of the recording light beam of an optical recording medium and a diagram showing corresponding detection signals; FIG. 4 is a configuration diagram of an embodiment of the present invention;
FIG. 5 is a diagram showing the position irradiated by the auxiliary light beam, FIG. 6 is a block diagram showing the energy control circuit in FIG. 4, and FIG. 7a. b is a diagram showing a detection signal of recorded information and its integrated output signal, and FIG. 8 is a characteristic diagram of the acousto-optic light modulation element. 11'... Disk-shaped recording medium, 14...
Turntable, 19...Light source, 20...
...Light beam, 21...1 drive circuit, 22...
... Light modulator, 27.35 ... Light receiving element,
29...Differential amplifier, 32...Auxiliary light beam, 33...Light source, 31.34...
- Filter, 38... Control circuit.

Claims (1)

[Claims] 1. An information recording light beam whose intensity is modulated according to the information signal to be recorded at the time of information recording is irradiated onto a disc-shaped recording medium whose light reflectance or light transmittance changes by irradiation with the light beam, and the information signal is optically recorded. In addition to sequentially recording information on the information recording track as a change in reflectance or light transmittance, an auxiliary light beam is irradiated onto the recorded information recording track near the information recording light beam, and reflected light or transmitted light of the auxiliary light beam is recorded. 1. An optical recording/reproducing apparatus characterized by detecting a change in the amount of light received by a light receiving element that receives light, and controlling the energy of the recording light beam in accordance with the detected signal.