JPS633022Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disc reproducing device such as a compact disc, and more particularly to a disc reproducing device having a means for detecting when a track servo mistracks due to dust or scratches.

When playing a digital audio disc (DAD) such as a compact disc, minute tracks are tracked by a servo, but if the disc is scratched, the track may not be seen or the track may jump to another track. If you are listening to music while playing a disc, you can determine that these track jumps have occurred and take corrective action, but it is not possible to perform operations such as dubbing the disc playback signal to a tape recorder, etc. Even if a track jump occurred in the middle of a tape playback, it would not be noticed until the tape was played back, which could lead to serious problems.

In view of these drawbacks, the present invention provides a disc playback device that can reliably detect a track jump and issue an output such as a warning. Therefore, in the present invention, a track error is detected by utilizing the continuity of address information such as a time code inserted into a disc.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. Figure 1 shows a system diagram of the present invention, and Figure 2 shows an explanatory diagram of waveforms.Address information and data such as time codes are input from the disk to the input terminal _T1 , and are added to the data separation circuit 1. . The data separation circuit 1 extracts address information such as a time code, and if it is correct by CRC or the like, derives an output clock shown in waveform B in FIG. The data separation circuit 1 further outputs the address data shown in FIG. 2A, loads the address data into the counter circuit 3, and outputs the output of the counter circuit 3 shown in FIG. 2H and the address data (FIG. 2A). The subtraction circuit 4 performs subtraction at the timing shown in FIG. 2B.The output shown in FIG. If the value is greater than or equal to the predetermined value, the second
The output shown in the figure is derived.

The reference level of the comparator 5 may be selected to be smaller than the amount of addresses that advance when the disk rotates once. Reference numeral 2 denotes an oscillator to which a count-up input to the counter 3 is applied, and the oscillation frequency of the oscillator 2 has a waveform as shown in FIG. 2D, which is the same as the address period.

Now, if the address information output separated from the input data is shown in Figure 2 A, it will be reproduced sequentially from 1 to 2,
Counter 3 is loaded with the pulse of FIG. 2C. Even if addresses 3 and 4 are missing due to dropout as shown in FIG. 2A, they are raised by the up pulse from the oscillator 2, and the output of the counter 3 becomes continuous as shown in FIG. 2H. Therefore, the output of the subtraction circuit 4 has 0 as shown in Figure 2. If a track jump occurs after address 5 and playback starts by jumping to another track, for example, address 51, the output will be 0. The output in FIG. 2 increases to 51-7=44, exceeding the set value of the comparator 5, and the output in _FIG . Here, 8 is a slight delay circuit that covers the delay in calculations such as 4 and 5, and the output of the comparator 5 is applied to one input of the gate circuit 7 via an inverter 6, and the clock output is also input to the gate circuit 7. (FIG. 2B) is applied to the other input through the delay circuit 8.

Even if the oscillator 2 is omitted in order to make the circuit described above simpler, it can still operate in the same way since the normal dropout is generally small, in which case the counter 3 is just a latch. It is also obvious that all of these circuits may be implemented using a microprocessor or the like.

Since the present invention is constructed as described above, even if data on the disk is lost due to dropout, if the laser beam of light is on the correct track, it will not output, and if it jumps to the wrong track, it will be detected reliably. , it is possible to issue a warning to stop unnecessary playback, or to display a mistrack.

[Brief explanation of the drawing]

Figure 1 is a system diagram of the disc playback device of the present invention.
FIG. 2 is a waveform explanatory diagram of FIG. 1. In the figure, 1...data separation circuit, 2...oscillator,
3... Counter, 4... Subtraction circuit, 5... Comparator, 6... Inverter, 7... Gate circuit,
8...Delay circuit.

Claims (1)

[Scope of utility model registration request] In a disc playback device that plays back a disc having multiple pieces of address information during one revolution, there is an address information separation circuit that separates the address information included in the playback signal, and a subtraction circuit that sequentially subtracts the separated consecutive address information. 1. A disc playback device comprising a circuit and a comparison circuit for detecting a track mistake by comparing the output of the subtraction circuit with a set reference value, and for detecting a track mistake and issuing an alarm.