JPS5924456A - Tracking control system - Google Patents

Abstract

PURPOSE:To perform focus control even in a record erasure section on an optical disk, by biasing a beam position from its original correct track line to left or right in the record erasure section, and increasing the quantity of reflected light. CONSTITUTION:The 1st counter 11 counts a clock signal supplied from a clock source 10 and is used for detecting the erasure section; for example, when it counts clocks corresponding to length Td2, ''1'' is outputted to an AND gate 12. The AND gate 12 sets the 1st flip-flop 13 and then sets the 2nd flip-flop 14 to apply its Q output to an encoder 15 and an AND gate 17. The encoder 15 converts the input into a digital value necessary for generating an offset quantity ros, and a D-A converter 16 converts it into an analog signal, which is impressed as the offset quantity ros to a comparator 7. The 2nd counter 18 is used to detecting a beam spot exiting from the erasure section.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a tracking control method in an optical disk device. In the i-rack of an optical disk, when there are consecutive sections of low reflected light level due to record erasure, etc., it becomes impossible to obtain effective information necessary for irradiation beam spot focus control.

Focus control may become impossible.

The present invention relates to a tracking control method in which, in such a case, an offset is given to the tracking drive in the erasure period to create a slight tracking error, thereby increasing the level of reflected light of the irradiation beam spot.

[Technology background]

For example, an optical disk device irradiates pits (holes) with a diameter of 0 or 5 microns recorded on a track with a track pitch of about 1.6 microns with a laser beam having a spot diameter of 0.5 microns or less. to read and play. In this way, the optical disk device not only handles Mikun order objects.

Focus errors are likely to occur due to warpage of the disk itself and vibration of the single rotation mechanism, so precise focus control is performed to always obtain the optimum spot.

The focus control method is an equal-rate detection method that combines a cylindrical lens and a 4-part photodiode.

Alternatively, the beam decentering method is common, but all of these methods are based on the premise that the reflected light from the optical disk surface can be obtained at a sufficient level.

But on track 1 as shown in the September 11 figure.

When there are recording pits 2 and relatively long grooves 3 that are erased areas due to recording errors, etc., the irradiation beam spot 4 is located in the normal recording sections T1 and T when looking at A.
At m, a sufficient level of reflected light is obtained intermittently, but in the recording/erasing section Tt, the level of reflected light continuously decreases, making focus control virtually impossible. Therefore, a tracking error signal may not be obtained, and tracking control may not be possible. Alternatively, even if the recording erasure section T ends and the normal recording section T3 resumes, there may be a case where focus control is not possible, and it may become impossible to read the record. .

[Object and structure of the invention]

An object of the present invention is to enable focus control even in the recording/erasing section on an optical disk.
In the recording/erasing section, the beam position is biased from the originally correct track line to either the left or right or one side) so that the beam spot deviates from the erasing groove by a certain amount, thereby increasing the amount of reflected photoacid.

Therefore, the configuration of the present invention is to detect when a beam spot enters a recording erasing section when reading recorded information in an optical disk device equipped with a recorded information detection means, a tracking control means, and a focus control means. and means for detecting that the beam spot has escaped from the recording/erasing section, and when the two detecting means detect that the beam spot is within the erasing section.

The present invention is characterized in that a predetermined offset signal is supplied to the tracking control means to move the beam spot away from the track center line and increase the level of reflected light of the beam spot.

[Embodiments of the invention]

The present invention will be explained below based on examples.

3 and 2 are configuration diagrams of an embodiment of the present invention, and FIG. 3 is an operation timing chart thereof.

In the gf2 diagram, 5 is a track information detection section, 6 is a tracking servo circuit, and 7 is a comparator.

8 is a driver, 9 is a tracking coil, 10 is a clock source, 11 is an M'1 counter, 12 is an AND gate, 13 is a first flip-flop, 14 is a second flip-flop 7', 15 is an encoder, and 16 is a DA Converter, 17 is an AND gate, and 18 is a second counter.

The track information detection unit 5 detects the reflected light from the optical disk with respect to the irradiation beam, and generates a reproduction signal and a tracking error signal corresponding to the bit (hole).

Outputs a focus error signal to each control circuit.

Tracking servo circuit 61 Driver 8. The tracking coil 9 is a mechanism used in conventional devices, and is driven based on an input tracking error signal to shift the position of an optical system (not shown).

The irradiation beam spot is controlled to be positioned at the center of the track.

The comparator 7 is operated as shown in Fig. Af3 (α) during the Tos period, which includes the erasure section T'x on the track.

Place beam spot 4 in groove 3 with respect to track center line φ.
It has the function of giving off-cellar I-(No. 8 60S) to the tracking control signal so that even the distance of ROS applied to the edge of .

The circuit from the clock source 10 to the DA converter 16 is a tracking control circuit block for generating an offset according to the present invention.

The counter 11 is cleared by the recording pit reproduction signal generated at the leading edge and trailing edge of the recording pit shown in FIG. (See C1).The counter 11 is used to detect pits with a size longer than the recording pit length Td1 in one normal data, that is, an erase section.

For example, when counting the number of clocks corresponding to the length of Ta2 shown in the figure, 11N is output to the AND gate 12 (see Figure 3 (d)).

': Flip-flops 13 and 14 of Af1 and Fang2 are reset initially, and the AND gate 12 is
It is opened by the Q output of Fang2 flip-flop 14. Therefore, when the first counter 11 generates the z1i output, that is, when it detects that it has entered the erase period, the AND gate 12 sets the Fang 1 flip-flop 13 (see FIG. 3 (-)), and then Teme 11 flip flop 13.

1) AND gate 12 is closed by the Q output of second flip-flop 14 (see FIG. 3q)), and henceforth.

It does not respond to the output of the fang 1 counter 11.

When the first flip-flop 13 is set by the output of the AND gate 12, it is immediately reset by its own Q output, and has the function of generating a trigger pulse as shown in FIG. 3(6). This trigger pulse clears the g-2 counter 18 at the same time as it sets the shear 2 flip-flop 14 mentioned above.

When the second flip-flop 14 is set.

(7) Q output is encoder 15 and A N
I) Added to Kate 17.

When the encoder 15 receives an input, the offset amount'
Convert the os to the digital value necessary to generate it, and convert it to the D-A
Converter 16 is supplied. The D-A converter 16 is
To convert the digital value supplied from the encoder 15 into an analog signal, as shown in Figure 3 (see j+), apply the offset "os" to the comparator 7 as described above. As a result, as shown in Figure 3 (a), In addition, the beam spot 4'1 is offset by ros from the track center line φ, and a part thereof covers the high reflectance region without grooves.

By increasing the level of reflected light, a signal level that can be precisely controlled can be obtained.

Fang 2 counter 18 is used to detect when the beam spot escapes from the erasure section.

The AND gate 17 is kept open after the beam spot enters the erase section, and when the recording pit signal is detected again, it supplies it to the A.2 counter 18 (see Fig. 3 (σ)). ).

The second counter 18 counts a predetermined number of recorded pit playback signals and generates a count output when the count reaches 7 (
3(h)), it is determined that the beam spot has escaped from the erasure section, and the "Af2 flip-prop 14
is reset to return the entire circuit to its initial state. As a result,
Offset signal 11o supplied to comparator 7
s also becomes zero, and the beam spot returns to the original track center line φ, as shown in FIG. 3(α). In addition, there is also a second counter.

Similar to the first counter, it is also possible to modify the counter so that the clock signal is used as the count input.

〔Effect of the invention〕

As described above, according to the present invention (!), the level of reflected light is maintained high even in the erase section on the track.

Since it is possible to obtain a focus error signal with a sufficient level required for focus control, reading operation can be started immediately using an appropriate beam spot on C1 in the data recording section after exiting the erase section, and the optical The reliability of the disk device can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the relationship between the erase section on the optical disk and the reflected light of the beam spot, FIGS. A and 2 are block diagrams of an embodiment of the present invention, and FIG. In the figure, ■ is the track center line, and 2 is the par j2 recording bit. 3 is an erase groove, 4 is a beam spot, 5 is an l/rack information detection section, 6 is a tracking servo circuit 17 is a comparator, 8 is a driver, 9 is a tracking coil, 10
is the clock source, 11 is the 'A-1 counter, 12 is AND
13 is a flip-flop, 14 is a second flip-flop, 15 is an encoder, 16 is a DA converter, 17 is an AND gate, and 18 is a bottle 2 counter.

Claims (1)

[Claims] Recorded information detection means and tracking control means. In an optical disk device comprising a focus control means and - means for detecting that a beam spot enters a recording erasing section when reading recorded information. means for detecting that the beam spot has escaped from the recording erasing section, and when the two detecting means detect that the beam spot is within the erasing section, the tracking control means A tracking control method characterized by supplying an offset signal to move a beam spot away from a track center line to increase the level of reflected light from the Y-mus spot.