JPS647428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reproducing device for reproducing information from a rotationally driven disc-shaped record carrier (hereinafter referred to as a disk) using a pickup device, and is configured to enable high-speed retrieval operations. be.

Generally, a type of address signal called an address signal is recorded on a disk along with information signals such as video signals in order to quickly play back a desired part, and is used for a program cue operation called random access. There is.

That is, in random access, the address signal recorded on the disk is read, a desired location is found, and the beginning of the program is found. On the other hand, since the address signal is only recorded intermittently on a portion of the disk's information track, if the pickup device is moved diametrically across the disk at a very high speed, it will not be possible to fully read the address signal. There were times when I couldn't do it. As a result, the time required to cue becomes longer,
As a playback device, it sometimes became inconvenient. Furthermore, in conventional playback devices, the structure for moving the pick-up device was, for example, a rack and pinion type using a speed reducer, etc., or a screw feed system, so it was difficult to move the pick-up device at high speed. It wasn't easy either.

The present invention has been proposed in view of these points, and one embodiment thereof will be shown and explained below.

In FIG. 1, 1 is a disk whose rotation is controlled by a motor 3 via a clamper 2. In FIG. 4 is a pickup device, in which a laser beam is generated from a light source 5, passes through a diffraction grating 6, a lens 7, and a beam splitter 8, and is reflected by a tracking mirror 11. The laser beam is focused onto the disk 1 by a reading lens 12. After passing through the lens 12, mirror 11, and beam splitter 8 again, the reflected light passes through the cylindrical lens 9 and enters the photodetector 10, where the information signal recorded on the disk 1 is read. The configuration of this pickup device 4 is well known, so a detailed explanation will be omitted. This pick-up device 4 is coupled to a moving coil section 16 of a linear motor 13, and this moving coil section 16 is moved in the direction of an arrow 18 by a magnetic field generated by a magnet on the same principle as the voice coil of a speaker. The amount of movement is
It can be controlled by the voltage applied to the coil 16.

17 is a potentiometer, the movable contact 17a of which is fixed to the pick-up device 4, and the position of the pick-up device 4 can be detected by the resistance value. In the embodiment, one of the terminals is connected to the ground and the other to the voltage source _V1 , so the position of the pickup device 4 is converted into voltage and obtained from the movable contact piece 17a.

A part of the output of the photodetector 10 is input to a tracking error detection circuit 22, and is input to an adder 32 and a tracking error detection circuit 22.
The signal is applied to the control coil 11a that controls the tracking mirror 11 via the DC amplifier 23. Further, a part of the output of the DC amplifier 23 is inputted to the terminal A of the switch _S1 after the AC component is removed by the low-pass filter 30.

Since the operating range of the tracking mirror 11 is generally quite limited, the linear motor 13 is moved before the output light of the reading lens 12 follows the track of the disk 1 and reaches its limit. It is necessary to set the operating position appropriately. Therefore, the DC drive voltage of the tracking mirror 11 is sent to the differential circuit 20 via the switch _S1 .
The components are added, a current is supplied to the coil 16 via the DC amplifier 21, and the pickup device 4 is moved. The amount of movement is determined by the potentiometer 17.
This appears as a change in the output voltage of the linear motor ₁₃ , so this change is detected by the capacitor C1 and fed back to the differential circuit 20, thereby making the operation of the linear motor 13 more stable.

In this case, if the output of the potentiometer 17 is not fed back, for example, if a disturbance is applied to the pickup device 4 in the direction of the arrow 18, and it is assumed that the pickup device 4 is slightly displaced in the direction of the arrow 18, the tracking mirror 11 will be moved in the direction of the arrow 18. The tilt angle changes by the same amount, and attempts to follow the information track on disk 1. In other words, since the inclination of the tracking mirror 11 changes in response to a disturbance, the linear motor 13 cannot sufficiently counter the disturbance.

Therefore, in order to make the reproducing device stable even against disturbances, the above-mentioned feedback loop is necessary. The above description has been made regarding the normal playback of the present disc playback device.

Next, the cueing operation called random access will be described.

Reference numeral 28 is a key input terminal for inputting the address of a desired location.

For example, suppose that addresses consisting of consecutive integers from 0 to 54,000 are recorded on disk 1.

Now, if 5000 is input to the key input terminal 28, the pickup device 4 will detect the information track having the address 5000 and stop it. The input signal “5000” is stored in the memory device 27 and input to the D/A converter 29. Here, the position of the pickup device 4 is indicated by the output voltage of the potentiometer 17, and the output voltage and address signal are transferred to the D/A.
Configure it so that it corresponds to the converted voltage.
FIG. 2 illustrates this relationship.

Therefore, if address 5000 is input from key input terminal 28, 5000 will be stored in memory device 27,
The output of the D/A converter 29 is 0.5V. Thereafter, both switches S ₁ and S ₂ are connected to the B contact, current is supplied to the coil 16 until the output of the differential circuit 20 becomes 0, and then the switches S 1 and S 2 are connected to the B contact.
S ₁ and S ₂ are returned to A contacts. The output of the potentiometer 17 is 0.5V, ie, the pickup device 4 is moved to the vicinity of the information track with the address signal 5000.

At the same time, the signal output of the pickup device 4 is obtained from the photodetector 10 and demodulated by the demodulator 24, and the address signal is read by the address detector 25.
The digital comparator 26 compares it with the address signal input from the key input terminal 28, and applies the difference signal to the jumping pulse generating means 31. This jumping pulse generating means 31 generates a number of recording track jumping pulses corresponding to the difference signal, applies them to the adder 32, drives the tracking mirror 11, and outputs the reproduction address signal and the memory device 27. The search operation ends at the point where the stored address matches.

In the embodiment, the potentiometer output is fed back through the capacitor _C1 , but this is merely to remove the DC component. Therefore, it is possible to use the circuit shown in FIG. 3 in place of this capacitor _C1 .

That is, in FIG. 3, the output of the potentiometer 17 is converted into a signal having no DC component by the resistors R ₁ , R ₂ and the capacitor C ₂ provided on the input side of the differential amplifier 33. The signal is obtained as an output, and is fed back to the differential circuit 20 in the same manner as in the embodiment described above, and is controlled so that the pickup device does not move due to disturbance.

As described above, according to the present invention, first, the location of the pickup device is moved to the vicinity of the desired address.
Since the movement is performed without using a reproduction address signal, high-speed movement is possible, and accordingly, rapid random access operation is possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a playback device according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing the correspondence between address signals on a disk and outputs of a D/A converter, and FIG. 3 is a diagram of a reproduction apparatus according to an embodiment of the present invention. FIG. 7 is an electrical wiring diagram of main parts of another embodiment. DESCRIPTION OF SYMBOLS 1...Disk, 3...Motor, 4...Pickup device, 10...Photodetector, 11...Tracking mirror, 13...Linear motor, 17...
Potentiometer, 20...differential circuit, 21,2
3...DC amplifier, 22...Tracking error detection circuit, 24...Demodulator, 25...Address detector, 26...Digital comparator, 27...Memory device, 28...Key input terminal, 29... D/A converter, 31...jumping pulse generator,
33...Adder.

Claims (1)

[Claims] 1. An information signal including an address signal is recorded as a concentric or spiral recording track, and a pickup means for reproducing the information signal from the recording track of a rotationally driven disk-shaped recording medium, and a pickup means for reproducing the information signal from the recording track. a pickup device having tracking servo means for controlling the pickup device to scan; a linear motor for moving the pickup device in a direction in which the pickup device crosses the recording track; a position detection means of the pickup device for generating an output signal, and an address signal input means for inputting an address signal of a recording track desired to be reproduced;
a signal generating means for generating an output signal corresponding to the input address signal from the address signal input means; and a signal corresponding to the difference signal between the output signal of the signal generating means and the output signal of the position detecting means to drive the linear motor. The driving means compares the reproduced address signal from the pickup means and the input address signal, drives the tracking servo means according to the difference, and removes a DC component from the output signal of the position detection means. 1. A reproducing apparatus for a disc-shaped recording medium, comprising means for driving the tracking servo means using the signal and a tracking error signal in the tracking servo means to match the reproduction address signal and the input address signal.