JP2618068B2 - Off-track detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an off-track detection device for detecting that a beam has deviated from a track in an optical disk device, a magneto-optical disk device, or the like.

2. Description of the Related Art In general, an optical disc apparatus detects a tracking error signal indicating a position shift of a beam with respect to a track on an optical disc, and controls an objective lens by a tracking servo so that the tracking error signal becomes “0”. Control to follow tracking.

When data is written to the optical disk, it is detected whether or not the beam follows the track based on the tracking error signal. If the beam is following, the data is written using the logical product signal of the write data and the write gate signal.

Conventionally, this type of optical disc apparatus detects off-track and inhibits data writing when a tracking servo signal is deviated by a disturbance or the like and a tracking error signal exceeds a predetermined level. Is configured so as to prevent data from being erroneously written.

SUMMARY OF THE INVENTION However, in the above-described conventional optical disc device, it is detected whether or not the beam follows the track by the tracking error signal, and when the beam follows, the logical product of the write data and the write gate signal is detected. Since it is configured to write data by signals, the tracking error signal rises due to the glitch etc. of the write gate signal at the start of writing, and it detects off-track even though the beam follows the track and writes it. There is a problem that bans.

In particular, since the optical disc is a write-once recording medium, a spare sector or a spare track serving as a spare recording area is provided. Therefore, in the above-described conventional optical disc apparatus, data is written in a writable sector or the like. There is a problem that the writing area is reduced by writing in a replacement sector or the like without writing.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an off-track detection device capable of accurately detecting a beam position deviation with respect to a track on a recording medium.

Means for Solving the Problems In order to solve the above problems, the present invention inhibits a tracking NG signal while a data write gate signal rises by a read signal from a recording medium, and by a gate signal and a tracking NG signal, This allows writing of data to a recording medium.

Effect of the Invention With the above structure, the tracking NG signal is inhibited while the data write gate signal rises, so that it is not erroneously detected as off-track even if the tracking error signal rises due to the glitch of the write gate signal at the start of writing. Therefore, it is possible to accurately detect the displacement of the beam with respect to the track of the recording medium.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing an optical disk device provided with an embodiment of an off-track detecting device according to the present invention, and FIG. 2 is a waveform diagram of main signals in the optical disk device of FIG.

In FIG. 1, reference numeral 1 denotes an optical disk as a recording medium. The optical disk 1 is formed with concentric or spiral tracks serving as recording areas, and the tracks are divided into a plurality of sectors in the radial direction of the optical disk 1. Has been split.

Each sector of the optical disc 1 includes an area in which a sector mark indicating a head of the sector, an address mark indicating a sector address, and the like are formed in advance, an area in which a user records data, and the like.

2 is a motor for rotating the optical disk 1, and 3 is
Focusing a beam from a semiconductor laser (not shown) in the optical pickup 4 and irradiating the track on the optical disc 1,
A lens for condensing the reflected light, a lens 3
Can be minutely moved in the radial direction of the optical disc 1 for beam tracking and fine seek, and can be minutely moved in the axial direction of the optical disc 1 for beam focusing.

Focus optical pickup 4 is movable together with the lens 3 due to the rough seek the beam in the radial direction of the optical disk 1, also showing the reflected light beam, and the read signal S _RF data such as defocusing of the beam In addition to the error signal (not shown), as shown in FIG. 2 (a), when the beam follows the track, the peak value is small. For example, when the beam jumps to an adjacent track by the still jump control. , the peak value is large and when to follow the track beam is jumped by a tracking servo, a peak value and outputs a low tracking error signal S _T.

5, the reading signal S _RF from the optical pickup 4, and outputs a write gate signal b as shown in the write data and the second view (b) as described below, the control circuit that drives the inhibit signal generating circuit 8 , 6a, respectively 6b, the tracking error signal S distance from the center line of the beam track predetermined by _T (e.g., the track distance 1.6
μm, if it is located within ± 0.2 μm),
Low level tracking OK as shown in FIG. 2 (c)
The window comparator 7 that outputs the signal c is a tracking OK signal c from the window comparators 8a and 8b.
Is an inverter that inverts

8 is controlled by a control circuit 5 is activated by the read signal S _RF of a sector mark indicating the beginning of a sector, a time width to cover the rise of the write gate signal b as shown in FIG. 2 (d), This is a prohibition signal generation circuit that outputs a low-level signal d that prohibits the tracking NG signal c.

Reference numeral 9 denotes a NAND circuit whose two input terminals are connected to the NG signal c and the output terminal of the inhibition signal generation circuit 8, respectively, and whose output terminal is connected to the clear terminal CLR of the flip-flop 10. The write gate signal b from the control circuit 5 is input to the T terminal of the flip-flop 10, and the Q terminal
It is connected to the input terminal of the gate 11.

The AND gate 11 outputs an AND signal of the output signal of the Q terminal of the flip-flop 10 and the write gate signal b from the control circuit 5 to the AND gate 12.
An AND signal of the output signal of the AND gate 11 and the write data from the control circuit 5 is output to the semiconductor laser of the optical pickup 4.

Next, the operation of the embodiment according to the above configuration will be described with reference to FIG.

First, when the peak value of the tracking error signal S _T is large, window comparator 6a, 6b outputs a high level signal, thus, the output signal of the NAND gate 9 becomes a low level by the inverted signal, the flip-flop The output signal of the Q terminal 10 goes low.

Then, the beam of the optical pickup 4 is smaller than the level threshold of the tracking error signal S _T to follow the track of the optical disk 1, the window comparator 6a, 6
b outputs a low-level tracking OK signal c, and therefore, the output signal of the NAND gate 9 goes high due to this inverted signal.

The control circuit 5 reads a signal from the optical pickup 4
The S _RF, a sector mark indicating the beginning of a sector, after the detection of the address mark or the like indicating a sector addresses, and outputs a write data and a write gate signal b in order to record the next recording area, inhibit signal generating circuit 8 To generate a low-level signal d that inhibits the tracking NG signal.

Therefore, the flip-flop 10 is set by the write gate signal b, the output signals of the AND gates 11 and 12 become high level, and the data from the control circuit 5 is written on the optical disk 1.

In this case, even if the tracking NG signal c is a high level rises tracking error signal S _T by glitch like writing gate signal b at the start writing, the output signal is the high level of the Q terminal flip-flop 10 is not reset And the data is written normally.

Effect of the Invention As described above, the present invention inhibits the tracking NG signal during the rise of the data write gate signal by the read signal from the recording medium, and writes the data to the recording medium by the gate signal and the tracking NG signal. Is allowed, so that even if a tracking error signal rises due to a glitch of a write gate signal at the start of writing, it is not erroneously detected as off-track. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an optical disc apparatus provided with an embodiment of an off-track detecting device according to the present invention.
FIG. 3 is a waveform diagram of main signals in the optical disk device of FIG. DESCRIPTION OF SYMBOLS 1 ... Optical disk (recording medium), 4 ... Optical pickup, 5 ... Control circuit, 6a, 6b ... Window comparator, 7 ... Inverter, 8 ... Prohibition signal generation circuit, 9 ...
… NAND gate, 10 …… Flip-flop, 11,12 …… AND
Gate.

Claims (2)

(57) [Claims] 1. A method for outputting data to be written on a recording medium and a gate signal of the data, and a tracking error signal indicating a displacement of the beam with respect to a track on the recording medium, to determine that the beam does not follow the track. Means for outputting a tracking NG signal, and means for inhibiting the tracking NG signal while the gate signal rises by a read signal from a recording medium, and a state in which the gate signal is present and the tracking NG signal is not present, Means for permitting writing of the data to a recording medium. 2. The off-track according to claim 1, further comprising means for prohibiting the writing of the data to the sector of the recording medium when the beam does not follow the track before the gate signal rises. Detection device.