JPH0227531A - Digital servo circuit - Google Patents

Abstract

PURPOSE:To attain non-adjustment by performing the A/D conversion of a reproducing level, a tracking error, and a focusing error, and performing the correction of the tracking error and the focusing error to reference values by using the reproducing level of a recording and reproducing signal. CONSTITUTION:An RF amplifier 3 which outputs the recording and reproducing signal 11 by amplifying the output of an optical pickup 2, an error generation circuit 6 which outputs the focusing error signal by inputting the output of the optical pickup 2, an A/D conversion circuit 5 which inputs and performs the digital conversion of a recording and reproducing signal level 15, the tracking error, and the focusing error, and a digital signal processing circuit 8 which performs the signal processing of the digital conversion values of those signals, etc., are provided. And the recording and reproducing signal level 15 can be obtained by detecting the reproducing level of the recording and reproducing signal 11 outputted from the RF amplifier 3 by a level detection circuit 4. In such a way, the non-adjustment can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital servo circuit, and particularly to a digital servo circuit used in an optical disk device.

[Conventional technology]

Conventionally, in this type of digital servo circuit, as shown in FIG. and output as a tracking error signal and a focus error signal.

These signals are converted to an A-D converter circuit 5. Digital signal processing circuit 8. After signal processing, the actuator coil in the optical pickup 2 is driven via the driver 7 to form a digital servo loop. At this time, differences in tracking error and focus error levels occur due to variations in the semiconductor laser, optical components, optical disk medium, etc., so the level is adjusted using a semi-fixed variable resistor etc. in the level adjustment circuit 26. Ta.

[Problem to be solved by the invention]

In the conventional digital servo circuit described above, differences in the amount of reflected light due to manufacturing variations in component parts are adjusted using semi-fixed variable resistors during device assembly, which increases the number of adjustment steps and leads to higher costs. Another drawback is that the level cannot be adjusted to account for differences in the amount of reflected light due to aging or changes in the optical disk medium.

[Means to solve the problem]

The digital servo circuit of the present invention includes a level detection circuit that detects a reproduction level of a recording/reproduction signal from an optical disc;
an error generation circuit that generates a tracking error and a focus error; an A-D conversion circuit that converts the playback level and the tracking error and focus error into analog and digital; and a tracking error and focus that are digitally converted based on the digitally converted playback level. and a digital signal processing circuit that performs error level correction.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

As shown in FIG. 1, an optical pickup 2 reads signals from an optical disk 1 rotated by a spindle motor 10, an RF amplifier 3 that amplifies the output of the optical pickup 2 and outputs a recording/reproduction signal 11, and an error generation circuit 6 which inputs an output and outputs a tracking error signal and a focus error signal; a level detection circuit 4 which inputs a recording and reproduction signal 11 and outputs a recording and reproduction signal level 15; and a recording and reproduction signal level 15. an A-D conversion circuit 5 which inputs and digitally converts tracking error and focus error; and a digital signal processing circuit 8 which processes the digitally converted recording/reproduction signal level and the digital conversion values of the tracking error signal and focus error signal. , a driver 7 , and a disk controller 9 .

That is, the difference from the embodiment and the digital servo circuit shown in FIG. That is what we are doing.

−m, in proportion to the amount of light reflected from the optical disk,
The recording/reproducing signal, the tracking error signal, and the focus error signal increase/decrease. Now, the amount of reflected light is A, the reference recording/reproducing signal level is RFo, the reference tracking error level is TEo, the reference focus error level is FE,
Then, the recording/reproduction signal level RF, the racking error level TE, and the focus error level FE are expressed as equations (1) to (3), respectively (where k is a proportionality constant).

RF = to -A-RFo - (1) TE = to -A-TEo - (2) FE = to -A-FEo - (3) Here, each reference level is the center value of the dispersion, This is the level used when designing the servo system. Formula (1
) to equation (3), equation (4) and equation (5) are derived.

TEa =RFo/RF-TE-(4)F
Eo = RF+) / RF-FE...1
5) Therefore, the reference tracking error level and reference focus error level can be derived from the recording/reproducing signal level RF.

FIG. 2 is a block diagram of the level detection circuit of FIG. 1.

As shown in FIG. 2, the level detection circuit 4 (see FIG. 1) is composed of an upper peak hold circuit 12, a lower peak hold circuit 13, and a difference circuit 14. The level detection circuit 4 holds the upper and lower peaks of the recording/reproduction signal 11, calculates the difference, and outputs the recording/reproduction signal level 15.

Next, the recording/reproduction signal level 15 and the tracking error signal and focus error signal from the error generation circuit 6 are converted into digital values by the AD conversion circuit 5.

FIG. 3 is a block diagram of the digital signal processing circuit of FIG. 1.

That is, as shown in FIG.
(See Figure 1) consists of a proportional calculation circuit 21 and a multiplication circuit 22-
．． 22b, and a digital loop filter 23. ．． 23b
It consists of

The proportional calculation circuit 21 is a circuit that receives the recording and reproduction signal level digital conversion value 18 and calculates RFo/RF in the above-mentioned equations (4) and (5). The output of the proportional calculation circuit 21 is input to the multiplication circuits 22- and '22b,
Multiplication circuit 22. is separately multiplied by a tracking error digital conversion value 19 inputted from the AD conversion circuit 5.

Further, the multiplication circuit 22b separately performs multiplication with the focus error digital conversion value 20 inputted from the AD conversion circuit 5.

After that, like a normal servo system, the digital loop filter 23-. 23b, a tracking actuator drive signal 24 and a focus actuator drive signal 25 are obtained, and the optical pickup 2 is controlled via the driver 7.

〔Effect of the invention〕

As explained above, the present invention automatically corrects the tracking error and focus error to the reference value using the playback level of the recording and playback signal, so it has the effect of eliminating the need for adjustment and stabilizing the servo system. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the level detection circuit of FIG. 1, FIG. 3 is a block diagram of the digital signal processing circuit of FIG. 1, and FIG. 4 is a block diagram of the level detection circuit of FIG. It is a block diagram of an example of a conventional digital servo circuit. 1... Optical disk, 2... Optical pickup, 3...
- RF amplifier, 4... Level detection circuit, 5, 5.・・・
- A-D conversion circuit, 6, 6. ...Error generation circuit, 7
...driver, 8, 8. . . . Digital signal processing circuit, 9 . . . Disk controller, 10 . ... Differential circuit, 15 ... Recording and reproduction signal level, 16 ... Upper peak hold signal, 17 ... Lower peak hold signal, 18 ... Recording and reproduction signal level digital change value, 19 ... Tracking error digital conversion value, 20... Focus error digital conversion value, 21... Proportional calculation circuit, 22. ．． 22b...
・Multiplication circuit, 23. ．． 23b... Digital loop filter, 24... Tracking actuator drive signal, 25... Focus actuator drive signal, 26... Level adjustment circuit. Agent Patent Attorney Uchihara Shinyuzu

Claims (1)

[Claims] A level detection circuit that detects a playback level of a recording/playback signal from an optical disc, an error generation circuit that generates a tracking error and a focus error, and an A-D conversion circuit that converts the playback level and the tracking error and focus error into analog-digital conversion. and a digital signal processing circuit that performs level correction of digitally converted tracking errors and focus errors using the digitally converted playback level.