JPH0430089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disc playback device such as a DAD player or a video disc player, and particularly relates to protection of playback of non-signal surfaces.

Since CD-type digital audio discs (DADs) are recorded at constant speed to increase recording density, when playing back discs, constant linear speed control (CLV) is used to change the rotation speed between the inner and outer circumferences.
(servo) is required. The control signal for this is a synchronization signal recorded on the disk. Also, the disc has single-sided recording, and the back side is a mirror surface on which no signals are recorded. For this reason, if a part of the disc where no signal is recorded or the back side is reproduced, a synchronizing signal cannot be obtained and the motor servo becomes uncontrollable, which may cause the disc to run out of control.

The purpose of the present invention is to:
An object of the present invention is to provide an information recording disk reproducing device that prevents runaway by determining the presence or absence of a recording signal and operating a CLV servo circuit only when there is a recording signal. Another object of the present invention is to provide a reproducing apparatus for an information recording disc which, when there is no recorded signal on the entire surface of the disc, determines that the disc is on the back surface, stops the reproducing operation, and issues a warning.

For this reason, the present invention provides a mirror surface detection means for detecting the presence or absence of a signal on the disk reproduction surface, and while the surface is a mirror surface, the disk is rotated at a constant rotation speed, and the pickup, which is an information reading device, is moved toward the outer periphery in the signal reproduction direction. The motor is moved a certain distance at a time, and the CLV servo is activated after detecting the signal surface to prevent the motor from running out of control. Further, if there is no signal even after the pickup moving device located at the outermost periphery is moved until the detection switch is turned on, it is determined that the disk is on the back side.

An embodiment of the present invention will be described below with reference to FIG. In FIG. 3, reference numeral 1 denotes an information recording disk, on which signals are recorded linearly from the inner circumference to the outer circumference at a constant linear velocity. 2 is a disk motor, 3 is an optical pickup, and 34 is a switch for detecting the outermost circumference of the pick-up moving device, which outputs a high level when the pick-up moves to the outermost circumference. 35 is a specular detector which outputs a high level when there is a recording signal in the pickup output, and a low level when there is no recording signal. 36 is a microcomputer, 37 is a microcomputer 36
38 is the feed motor of the pick-up moving device controlled by the microcomputer 36; 39 is the constant rotation of the disk motor-CLV servo switching device controlled by the microcomputer 36; be.
Here, the specular detector 35 will be explained. 35 in FIG. 1 is a specular detector proposed by the authors, and FIG. 2 shows the operation waveforms of each part of FIG. 1.

In FIG. 1, 1 is an information recording disk, 2 is a disk motor, 3 is an optical pickup that is a signal reading device, 4 is a photoelectric converter, 5 is a mirror surface level detector that detects the maximum level of the read signal,
6 is a pit surface level detector that detects the minimum level of the read signal; 16 and 18 are positive voltage supply terminals;
7 and 19 are negative voltage supply terminals, 7 is a voltage divider, and 8 is a comparator. In Fig. 1, when the motor 2 is rotating and the track servo that follows the signal track is not operating, the optical output of the optical pickup 3 is converted into a voltage by the photoelectric converter 4, and the output is shown in Fig. 2. As shown in output 4, a signal like a is output on the disc information recording surface, and a signal like b is output on the mirror surface.
It will be like this. By inputting these four outputs to level detectors 5 and 6, the maximum level and minimum level of the signal can be obtained at outputs 5 and 6, respectively. 5 is a well-known emitter follower detector that detects and holds the maximum value of a signal, which is connected to a transistor 10, a resistor 22,
It is composed of a capacitor 11, and the base-emitter voltage drop caused by the transistor 10 is corrected by the transistor 12. Therefore, the maximum level of the input signal is outputted from the mirror surface level detector 5. 6 is also a minimum level detector based on the same principle. The minimum level is detected by making the transistor 13 a PNP type. The pit surface level detector 6 has a second
Even when a signal whose minimum level envelope fluctuates over time is input as shown in the output in Figure a4, the minimum level can be adjusted by setting a large time constant determined by the capacitor 14 and resistor 23 with respect to the period of the envelope. It is possible to hold. In the case of information recording surface reproduction shown in FIG. 2a, maximum level 5 outputs and minimum level 6 outputs can be detected as shown in the diagram of 4 outputs. This minimum level is determined by the disk standard to be 0.6 or less when the maximum level is 1. Therefore, the partial pressure ratio of 7 is
If the value is 0.6 or more, as an example, 0.7, the input of the comparator 8 will have the 7th output higher than the 6th output, and the output 9 will be at a high level. On the other hand, when the mirror surface of the disk is reproduced, the output of the photoelectric converter 4 becomes as shown in FIG. 2b, and the outputs of the level detectors 5 and 6 both reach the maximum level and match. 7 output is 0.7 of 5 output
Therefore, the input of the comparator 8 becomes higher at the 6th output than the 7th output, and the output 9 becomes a low level so that a mirror surface can be detected.

A flowchart of the microcomputer 36 shown in FIG. 3 is shown in FIG. Following FIG. 4, the operation of FIG. 3 will be explained. FIG. 5 shows a timing chart. In FIG. 4, initialization is first performed. The pick-up moving motor 38 is driven to move the pick-up to the innermost circumference of the disk. Next, in order to read the signal, a focus servo loop (not shown in FIG. 3) that maintains a constant distance between the disk and the pick-up object lens is operated, and then the disk motor is switched to constant rotation. Next, since the output of the outermost limit switch 34 is at a low level, the output of the mirror detector 35 is referred to, and if the output is at a low level, it means that the pickup is located at the no-signal position on the innermost circumference of the disk. Then, a certain voltage is supplied to the feed motor 38 for a certain period of time to move the pickup to the outer periphery. Returning to the operation of referring to the outermost circumference limit switch again, repeat the above operation until the output of the mirror surface detector reaches a high level, then turn on the track servo that causes the pickup to follow the recording signal track, and turn on the disk motor switching device 39. Switching to CLV servo protects the disk motor from running out of control due to the CLV servo circuit malfunctioning due to the signal not being regenerated. In addition, when the back side of the disk is attached, as shown in the timing chart in Figure 6, the pickup continues to be sent until the output of the outermost position detection switch 34 reaches a high level. It is determined that no signal is recorded on the disk from the circumference to the outermost circumference, that is, the back side of the disk is loaded, and the focus servo loop and pick-up light source switch mentioned above are turned off to stop the playback operation and the back side indicator is turned off. 37 is lit to prompt the user to correctly attach the disc.

In this embodiment, the pick-up movement range was detected using the outermost position detection switch.
The moving range of the pick-up may be detected based on the amount of movement of the pick-up moving device at one time and the number of times the pick-up is moved.

As explained above, according to the present invention, it is possible to detect the unrecorded part of the innermost circumference of the disk, move the pickup to the signal recording area, and then switch to the CLV servo, thereby protecting the disk motor from runaway. effective. Furthermore, it is also possible to detect when the disk is mounted on the back side, stop the playback operation, protect against abnormal operation, and warn the user.

[Brief explanation of drawings]

Fig. 1 is a principle circuit diagram of a specular detector, Fig. 2 is an operation waveform diagram of the specular detector, Fig. 3 is a diagram showing an embodiment of the present invention, Fig. 4 is a flowchart of a microcomputer, and Fig. 5 is a diagram showing the operating waveforms of the specular detector. This figure and FIG. 6 are timing charts of the operation. 34...Outermost circumference position detection switch, 35...Mirror detector, 36...Microcomputer, 37
...Mirror indicator, 38...Feed motor for pick-up movement, 39...Constant rotation of disk motor - CLV servo switching device

Claims (1)

[Scope of Claims] 1. In an information recording disk reproducing apparatus having an information reading device and a moving device for moving the information reading device, no signal is recorded on the information recording disk from the output signal of the information reading device. and a control circuit that operates the moving device according to the output of the mirror surface detection means, and when the mirror surface detection means determines that the mirror surface has no signal recorded, the control circuit operates the moving device according to the output of the mirror surface detection means. A reproducing apparatus for an information recording disk, characterized in that the moving device is operated by a circuit to move the information reading device a certain distance, and the moving operation of moving the information reading device by the certain distance is continued until the mirror surface disappears. 2. An outermost circumferential position detecting means is provided for detecting the outermost circumferential position when the moving device continues the moving operation and moves to the outermost circumferential position of the information recording disk, and the outermost circumferential position is detected by the outermost circumferential position detecting means. 2. The information recording disk reproducing apparatus according to claim 1, wherein when the control circuit stops the moving operation of the moving device and drives a warning device.