JPS6025947B2 - optical reproduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical playback device that projects a light beam onto a disk-shaped recording medium (hereinafter referred to as a disk) to negotiate information signals, and more particularly relates to an optical playback device that projects an optical beam onto a disc-shaped recording medium (hereinafter referred to as a disk) and processes information signals. The present invention relates to an optical playback device that can perform both playback (for example, still image playback and reverse playback) favorably.

An example of a recently developed optical reproducing device will be described with reference to FIGS. 1 to 3.

A disk 1 on which information signals are recorded, for example, in the form of a spiral track, is rotated by a motor 2 at a constant speed of, for example, 180 p.m, and a light beam 4 is projected onto the disk 1 from a light beam projection device 3. Light beam projection device 3
The optical beam 4 is sent in the radial direction of the disk by a feeding device 5, and the optical beam 4 scans the disk in a spiral manner while collecting signals. More specifically, the laser light emitted from the laser light source 6 passes through a concave lens 7, a beam splitter 8, a 1'4 input plate 9, and a rotary mirror 10 for minutely moving the light beam.
, and a condensing lens 11 to form a reproducing light beam 4, which is projected onto the disk 1. When the recording track of the disk 1 is scanned with the light beam 4, a reflected light beam 12 corresponding to the presence or absence of a recording signal is obtained, and this reflected light beam 12 is sent to the condenser lens 11, the rotating mirror 10, 1'4^ The signal reaches a recording signal detection photodetector 13 via the plate 9 and the beam splitter 8, where it is converted into an electrical signal and sent to a demodulation circuit. A disk 1 used in the apparatus shown in FIG. 1 generally records an information signal such as a video signal or an audio signal in the form of a spiral track using optical recesses or bits 14, as shown in FIGS. 2 and 3. It is something.

The width of the bit 14 in this disk 1 is approximately 1 m,
The depth of the bit is approximately 1/4^ (where ^ is the wavelength of the laser light), and the length of the bit differs depending on the inner and outer sides of a video disc, for example, 1.5 to 6 bits. It is. In the case of a video disc, the part indicated by the dotted line 15 in FIG.
One round of 4a constitutes one frame. As shown in FIG. 3, a video disc 1 on which an information signal is recorded using bits 14 generally includes a transparent resin layer 16 having an uneven surface corresponding to the bits 14, a reflective film 17 covering the uneven surface of the resin layer, and a reflective film 17 covering the uneven surface of the resin layer. It consists of a protective film 18 that protects the film. In the above-mentioned apparatus, the track on which the information signal is recorded must be faithfully scanned with a light beam.

Contact-type disc players that use a stylus as a scanning element to scan a groove with the stylus do not require a special tracking mechanism, but non-contact disc brakes such as those described above that use an optical device as a scanning element do not require a special tracking mechanism. Since there is no mechanical guidance, a special tracking mechanism must be provided.
Therefore, whether or not the reproduction light beam 4 is projected onto the bit 14 of the predetermined track 14a is determined by the tracking light beam having a predetermined geometrical positional relationship with the reproduction light beam 4 as shown in FIG. 19 and 20 onto the disk 1 from the light beam projection device 3 and detecting the reflected light. The tracking light beams 19 and 20 are not positioned at the center of the track 14a, that is, the bit 14, when the reproduction light beam 4 is in the normal position, and the preceding tracking light beam 19 is positioned below the bit 14 (on the inner circumferential side). The tracking light beam 20 that follows is positioned unevenly above the bit (on the outer circumferential side). The reproduction light beam 4 and the tracking light beams 19 and 20 are respectively displaced in the disk radial direction following the displacement of the light beam projection position 3 in the disk radial direction, and are also displaced in the disk radial direction following the rotation of the rotating mirror 10. The disk is also displaced in the radial direction due to movement. Detection of whether the reproduction light beam 4 and the tracking light beams 19, 20 are projected at desired orientations and control based on the detection are performed by the apparatus shown in FIG.

In FIG. 4, 21 is a photoelectric converter that detects the reflected light of the beam 19, and 22 is a photoelectric converter that detects the reflected light of the beam 20. The beam reflected outputs obtained from these optical turtle converters 21 and 22 are transmitted to preamplifiers 23 and 2.
After being amplified by 4, band pass filter 25,
26, and here only high frequency components in a band corresponding to the recording frequency of the information signal are extracted, ie, only intermittent signals that change in accordance with the bit arrangement. Phil evening 25,
Each high frequency intermittent signal obtained from 26 is sent to the AM detector 2.
For example, the FM recording track 14a is subjected to envelope detection by 7, 28, and thereby the bits 14 are arranged intermittently.
Even though the reflected output is obtained by projecting the light beams 19 and 20 above, it is similar to the reflected output when scanning the track where the bits 14 are continuously arranged with the light beams 19 and 20. The output will be The respective outputs of the AM detectors 27 and 28 serve as inputs to a differential amplifier 29, and the difference between these inputs is output as a beam position detection signal. If the tracking light beams 19 and 20 are projected at the correct position, they will scan the bit 14 under the same conditions.
The reflected outputs are equal to each other, and the output of the differential amplifier 29 is zero. However, if the light beams 19 and 20 are displaced upward or downward in FIG. 2, the amounts of the spots of the light beams 19 and 20 applied to the bit 14 will differ, resulting in a difference in reflected output. Therefore, a positive or negative output is generated from the difference scale amplifier 29. By the way, track 14
a has a spiral shape as shown in FIG. 2, so if the disk 1 is rotated but the light beam 4 is not moved in the disk radial direction and light beam scanning is started, the light beam will move along the spiral track 14a. deviate from Therefore, the output of the differential amplifier 29 is connected to the adjusting resistor 30 and the integrating low-pass amplifier.
The light beam 4,
The light beam projection device 3 is displaced in the disk radial direction so that the light beams 19 and 20 are projected onto predetermined positions on the track 14a. If the response of the motor 33 is fast, tracking is possible only by the motor 33 feeding the light beam projection device 3 in the disk radial direction. However, since the response of the motor 33 is slow, in order to compensate for this, a rotating mirror 10 with a fast response is provided, and the output of the difference amplifier 29 is used to move the rotating mirror 10.
is rotated to project the light beams 4, 29, 20 onto a desired track. Rotating mirror 10. To adjust the position of the light beam, the output of the differential amplifier 29 is adjusted by adjusting the resistor 34 and the adder 3.
5 and a drive amplifier 36 to a coil 37 disposed in a permanent magnet to rotate the rotating mirror 10. The device for rotating the rotating mirror 10 has a structure in which the rotating mirror 10 is provided in place of the pointer of a galvanometer, and when a positive or negative current is passed through the coil 37, the rotating mirror 10 connected to the coil 37 The movable mirror 10 rotates clockwise or counterclockwise together with the coil 37 to displace the light beam, and when the current in the coil 37 disappears, the movable mirror 10 returns to the neutral position with a spring, and the beam also corresponds to this. It is configured to be in position. Since the above-mentioned rotating mirror 10 has a quick response, it is used for fine adjustment of the light beam position and for transferring (jumping) the light beam to another track. Fourth
In the figure, a jumping pulse generator 38 connected to an adder 35 generates jumping pulses when performing special reproduction such as steal, slow, and reverse direction. Generates jumping pulses in synchronization with the synchronization signal. When a jumping pulse occurs, the rotating mirror 10 shifts the light beam onto a predetermined adjacent track. By the way, when standard playback is started using the above-mentioned device, the drive voltage of the rotary mirror 10 is zero at first, but as the light beam scan progresses, it changes as shown in FIG. 5 in order to make the light beam 4 follow the spiral track. As shown, it gradually increases and reaches, for example, 11 volts at a certain point.

Since the rotating mirror 10 alone cannot cover the entire range of movement of the light beam 4 in the disk radial direction, when the rotating mirror drive voltage (bias voltage) becomes 11 volts,
The motor 33 of the feeding device is driven with a voltage corresponding to, for example, 11 volts to operate the feeding device 5, whereby the light beam projection device 3 including the spreading mirror 10 is gradually fed in the radial direction of the disk. Therefore, the center value of the spread mirror driving voltage is 11 volts as shown in FIG. 5. During still image playback (still playback), the light beam is moved in the radial direction of the disk by only one round of the track (one pitch), so the light beam is moved only by the rotating mirror 10.

Therefore, the rotating mirror driving voltage is changed as shown in FIG. 6B in synchronization with the jumping pulse generated every frame shown in FIG. 6A.
As shown in FIG. 2, the light beam changes in a mirror tooth shape with 0 volt as the center. For example, when the light beam scans from point a to point c in FIG. 2, it shifts from point c to point a, and then scans again from point a to point c. At this time, the feeding by the feeding device 5 is stopped. During reverse playback, a jumping pulse is generated for each field as shown in FIG. 7A, and the light beam moves to an adjacent track for each field (half-circle) scan.

For example, in Figure 2, if the direction from the outer circumference to the inner circumference is the opposite direction, after scanning one field from point d to point e, the light beam is transferred from point e to point c, and from point c Scan to point d. When point d is reached, the light beam is transferred from point d to point b and scanned from point b to point c. Therefore, the rotating mirror drive voltage becomes a sawtooth wave for each field as shown in FIG. Therefore, a negative voltage, for example, 11 volts, is applied to the DC motor 33 of the feeding device 5, and a feed corresponding to 11 volts is performed. For this reason, the rotating mirror drive voltage changes in a sawtooth pattern around, for example, 11 volts, and images are reproduced one after another in the opposite direction. In addition, during 1/2 slow forward playback, the operation returns one frame after scanning two frames. For example, the feed motor 33 of the feed device 5 is driven at 0.5 volts, and the rotating mirror drive voltage is, for example, 0.5 volts. It becomes serrated around the bolt.

As is clear from the above, the center voltage of the rotating mirror 10 changes depending on the mode.

That is, the voltage is 11 volts during forward standard playback, 0 volts during steel playback, 11 volts during reverse playback, and about 0.5 volts during 1/2 slow playback. By the way, since the condensing lens 11 is fixedly arranged with respect to the rotating mirror 10, the light beam 4 is caused to change when the turning angle of the rotating mirror 10 changes due to a change in the rotating mirror drive voltage. Even if it does not deviate from 11, it will pass through different positions in each mode. For this reason, when the light does not pass through the center of the condenser lens 11, signal reading performance deteriorates due to lens aberration. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical reproducing device that can maintain the rotation center angle of a rotary mirror substantially constant even if the signal processing mode changes.

To achieve the above object, the present invention includes a recording medium rotation mechanism that rotates a disk-shaped recording medium on which signals are recorded in a predetermined track form, and a reproducing light beam that moves in the radial direction of the disk-shaped recording medium. a rotating mirror for moving a light beam in a minute range capable of moving the light beam, and a condensing lens disposed between the rotating mirror and the disk-shaped recording medium to direct the reproduction light beam to the disk-shaped recording medium. a light beam projection device for projecting, a feeding device for sending the light beam projection device in the radial direction of the disk-shaped recording medium, and reflection or transmission of the reproduction light beam corresponding to the recording signal on the disk-shaped recording medium. a recording signal detector for detecting light; a beam position detection device for detecting whether the light beam is correctly projected onto a predetermined recording track; and a beam position detection device for detecting whether the light beam is correctly projected onto a predetermined recording track; a jumping signal generator for generating a jumping signal for abruptly transitioning the beam onto a track; and a jumping signal generator coupled to the beam position detection device and the jumping signal generator in response to the beam position detection signal and the jumping signal. , controlling the rotating mirror so as to project the reproduction light beam onto a predetermined track, and controlling the rotation mirror so as to transfer the reproduction light beam to another track when the jumping signal is generated; a pivoting mirror control device coupled to the jumping signal generator and the feeding device to control the feeding device in response to the jumping signal, the device being coupled to the jumping signal generator and the feeding device to maintain a substantially constant pivot angle of the pivoting mirror; The present invention relates to an optical reproducing device comprising a feeding device that controls the feeding device so as to maintain the same.

According to the present invention, the transition signal (jumping pulse)
The feeding device is controlled in accordance with the occurrence state of the beam, and the rotating center angle of the rotating mirror is configured to be constant, so that the light beam passes approximately through the center of the condensing lens in various modes. This makes it possible to converge the light beam onto the disk and perform reproduction with less influence of lens aberrations. Therefore, high performance signal reading is possible in various modes. Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The basic parts of a video disc player according to one embodiment of the present invention are constructed the same as the apparatus shown in FIGS. 1-4.

Therefore, we will discuss the different parts. FIG. 8 shows the optical beam control circuit of the disk player shown in FIG. 1. Compared to the secondary optical beam control circuit shown in FIG. 42
A smoothing circuit 43 and an adder 44 are added. That is, a jumping pulse generator 38 is connected to the trigger terminal of the monostable multipipelator 41, and a smoothing circuit 43 consisting of a low-pass filter is connected to the output terminal of the monostable multipipelator 41 via a resistor 42. Adder 4
4 is connected to an integrating low-pass filter 31 and a smoothing circuit 43, where both output signals are added. In this embodiment, the unit constant multipipulator 41 continues to generate an output of 11 volts in a stable state, and every time a trigger signal is applied from the jumping pulse generator 38, the generation cycle of the vertical synchronizing signal of the television signal is changed. (16.7 msec) or 1
It is configured to generate an output pulse having a pulse width equal to the field scan time and an amplitude of 11 volts. In the disc player configured as described above, if the Masamaki standard playback mode is used, the jumping pulse generator 38 does not generate any jumping pulses. Therefore, no negative output pulse is generated from the monostable multi/distributor 41, and its output voltage is maintained at 1 IV as shown in FIG. In this device, adder 44
When the output voltage of
Since the rotating mirror 101 is configured to move in the radial direction by an amount corresponding to the pitch, it is possible to perform almost tracking by feeding the rotating mirror 101 in the radial direction by the output of the monostable multipipulator 41. As shown in Figure 5, the applied voltage of 11 volts can be reduced to zero.
Therefore, the center value of the rotating mirror drive voltage is zero, and changes around this zero. On the other hand, condenser lens 1
1 is arranged so that the light beam passes through the center of the lens when the rotating mirror drive voltage is zero, so that the light beam 4 can be projected onto the disk with little influence of aberrations. In the case of still playback, a jumping pulse is generated in synchronization with a vertical synchronizing signal applied from the frame 39 every frame scan, as shown in FIG. 10A.

For example, if a jumping pulse occurs at t in FIG.
is triggered, with an amplitude of -1 volt and a pulse width of approximately 16.7 m.
Generates a pulse of sec. After the pulse, it returns to 11 volts at 2, but is triggered again at t3 to generate an output pulse corresponding to one field scanning time. As is clear from FIG. 10B, the output of the multipipulator 41 has a duty ratio of about 50% and varies between 11 volts and -1 volt, so if it is smoothed by the smoothing circuit 43, it becomes 0 volt. As a result, no voltage is applied to the motor 33 of the sending device 5, and the rotating mirror drive voltage changes as shown in FIG. 6B, allowing the rotating mirror 10 to send the light beam in the radial direction. In the case of reverse playback, a jumping pulse is generated corresponding to one field scanning time of about 16.7 msec, as shown in FIG. 11A.

That is, every time a vertical synchronizing signal is applied from the vertical synchronizing signal input terminal 39 to the jumping pulse generator 38, a jumping pulse is generated in synchronization with this, and the monostable multipipelator 41 is triggered by this. Since the output pulse width of the monostable multipipelator 41 is equal to one field scanning time, an output of 11 volts is ultimately sent out from the monostable multipipelator 41 continuously. Of course, the output of the smoothing circuit 43 is also -1 volt, and the motor 33 is -1 volt.
The rotation corresponds to the bolt. As a result, the light beam projection device 3 is gradually sent in the opposite direction at a speed symmetrical to -1 volt, so that the rotating mirror 10 is driven around the bias voltage of -1 volt as explained in FIG. There is no need to do this, and the center value of the rotating mirror drive voltage can be set to zero volts. In addition, in the case of 1/2 slow playback, a jumping pulse is generated every time four vertical synchronization signals are generated as shown in Fig. 12, so a jumping pulse is generated to move back one frame after scanning two frames. Therefore, the value obtained by adding the output of the monostable multipipulator 41 to the normal voltage is approximately 0.5 volt as shown by the dotted line.

Accordingly, the feed of the light beam projection device 3 by the feed device 5 is 0.
．． 5 volts, and can offset the 0.5 volt bias of the rotating mirror 10 in the conventional device. As is clear from the above, with the configuration as shown in FIG. It becomes possible to make the light incident almost at the center of the optical lens 11, and it becomes possible to proceed with reproduction in a pillow state with less influence of lens aberration.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be further modified. For example, instead of the feed control circuit including the monostable multipipulator 41 and the smoothing circuit 43, another circuit configuration may be used to perform the same function.
Furthermore, if the voltage accuracy, stability, and reliability of the circuit that controls the DC motor 33 using the output of the monostable multipipulator 41 is high, the open loop that controls the motor 33 using the output of the differential amplifier 29 may be omitted. . However, since it is difficult to maintain the output voltage formed by the multipipulator 41 and the smoothing circuit 43 at a desired value, an open loop configuration is desirable. Furthermore, in the embodiment, the beam position is detected using the two tracking light beams 19 and 20, but a beam position detection configuration may also be adopted in which one tracking light beam or reproduction light beam 4 is used. Furthermore, the present invention can also be applied to a reproducing apparatus for a disc having a 0-circular recording track configuration.

[Brief explanation of the drawing]

1 is an explanatory front view of a video disc player according to an embodiment of the present invention and a conventional example; FIG. 2 is an explanatory plan view of a disc used in the video disc player of FIG. 1; Fig. 3 is an enlarged cross-sectional view of the disc shown in Fig. 2, Fig. 4 is a block diagram showing a light beam position control device in a conventional video disc player, and Fig. 5 is an enlarged sectional view of the disc shown in Fig. 4. A waveform diagram showing changes in the rotating mirror drive voltage when performing standard playback, Figure 6 shows a case where steel playback is performed with the mount shown in Figure 4, A is a waveform diagram of the jumping pulse, B 7 shows the waveform of the rotating mirror drive voltage, FIG. 7 shows the case of reverse playback using the device shown in FIG. 4, A is the waveform of the jumping pulse, and B is the waveform of the rotating mirror drive voltage. A waveform diagram, FIG. 8 is a block diagram showing a light beam position control device according to an embodiment of the present invention, and FIG.
Figure 10 shows the output waveform of a monostable multipipelator when forward playback is performed using the device shown in the figure. Figure 10 shows the case where still playback is performed using the device shown in Figure 8. A is a waveform diagram of the jumping pulse, and B 11 shows the output waveform of the monostable multipipelator, and FIG. 11 shows the case of reverse playback using the device shown in FIG. Output waveform diagram, 12th
The figure shows the case of 1/2 slow playback using the device shown in Figure 8, where A is the waveform diagram of the vertical synchronizing signal, B is the waveform diagram of the jumping pulse, and C is the output of the monostable multipipelator. FIG. In addition, in the symbols used in the drawings, 1 is a disk,
2 is a motor, 3 is a light beam projection machine, 4 is a light beam, 5
1 is a feeding device, 6 is a laser light source, 10 is a rotary mirror for displacing a light beam, 11 is a condensing lens, 41 is a monostable multipipulator, 43 is a smoothing circuit, and 33 is a DC motor. Figure 1 Figure 2 Figure 8 Figure 4 Figure 5 Figure 6 Key? Figure 9 Figure 101 Figure 12

Claims (1)

[Claims] 1. A recording medium rotation mechanism that rotates a disc-shaped recording medium on which signals are recorded in a predetermined track form, and a reproducing light beam capable of moving a reproduction light beam in the radial direction of the disc-shaped recording medium. A light beam that projects the reproduction light beam onto the disc-shaped recording medium, including a rotating mirror for moving the optical beam in a minute range and a condensing lens arranged between the rotating mirror and the disc-shaped recording medium. a projection device, a feeding device for sending the light beam projection device in the radial direction of the disc-shaped recording medium, and detecting reflected or transmitted light of the reproduction light beam corresponding to the recording signal in the disc-shaped recording medium. a recording signal detector; a beam position detection device for detecting whether or not the light beam is correctly projected onto a predetermined recording track; a jumping signal generator for generating a jumping signal for rapid transition; and a jumping signal generator coupled to the beam position detection device and the jumping signal generator in response to the beam position detection signal and the jumping signal, and for the regeneration. Rotating mirror control for controlling the rotating mirror so as to project the light beam onto a predetermined track, and controlling the rotating mirror so as to transfer the reproduction light beam to another track when the jumping signal is generated. a device;
coupled to the jumping signal generator and the feeding device so as to control the feeding device in response to the jumping signal, and to control the feeding device so as to maintain a rotation center angle of the rotating mirror substantially constant; and a feed control device for controlling the optical reproducing device. 2. The disc-shaped recording medium is a video disc on which a television signal is recorded in one frame per round, and the feed control device is triggered by a jumping signal to change the voltage from a positive (or negative) first voltage value to the first voltage value. Negative (
a monostable multivibrator that generates an output pulse having an amplitude inverted to a second voltage value (or positive) and a pulse width equal to one field scanning time; and a control including a smoothing circuit that smoothes the output of the monostable multivibrator. The optical reproducing device according to claim 1, which is a circuit.