JPS5977638A - Controlling device of focus servo in optical type disc reproducing device - Google Patents

Abstract

PURPOSE:To prevent a focus actuator from ringing at the feeding of an optical pickup by reducing the gain of a focus servo loop. CONSTITUTION:When a feed request signal is applied to a system controlling circuit 37, the optical pickup is fed through th circuit 37 and a feed detecting signal from a feed detecting circuit 63 turns a switch SW1 of a muting circuit 64 in a focus servo circuit 13. Consequerntly, the gain of the circuit 13 is switched, a focus difference signal outputted from the circuit 13 is attenuated and the focus actuator is prevented from ringing to be generated at the feeding of the optical pickup.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus servo in a production device for an optical disc (911, video disc, digital audio disc), and the loop gain of the focus servo loop is adjusted when an optical pickup head is fed. This is to prevent the focus actuator from making a so-called "6-hee" noise.

The entire control system of the digital audio disc playback device group is configured as shown in FIG.

In FIG. 1, a disc 1 is placed on a turntable 2.
# and is driven by the disk rotation motor 3. The optical pickup head 4 houses a semiconductor laser, an optical system, a light receiving element, a focus 11□ control coil 5, and a tracking control coil 6, and irradiates the recording surface of the disk 1 with laser light from an objective lens 7. The reflected light is received by an objective lens 7. The optical pickup head 4 is fed in the radial direction of the disk 1 by a feed motor 8.

Optical pickup head 4mm detected, 1 (No. i is free amplifier 9, AGC (Auto Galn Cont
rol) 1 via the circuit 10 and the waveform shaping circuit 11
The signal is sent to the ρ adjustment circuit 12.

The focus servo circuit 13 detects scorching of the laser beam based on the light reception signal 111. , focus on the recording surface of disc 1. Drive the coil 5. The tracking servo circuit 14 detects the deviation of the laser beam with respect to the bit string by the dragging 1-millimeter difference detection circuit 15 based on the light reception signal, and drives the tracking; 1B+i 11 coil 6 to correct the deviation. As the playback of the disc progresses, if the tracking displacement becomes large enough that the tracking control 111 coil 6 can no longer handle it, the tracking displacement detection circuit issues a signal indicating that the tracking displacement should not be detected, and the system control circuit 37 sends a signal to the feed motor drive circuit. The feed motor 8 is rotated via the feed motor 40.

The 4g output from the waveform shaping circuit is sent to the grinding circuit 12 and is also used to create a detection signal in a constant linear velocity (CLV) disk rotation servo.

That is, the output signal of the waveform shaping [91 path 1] is applied to the clock 1 generation circuit 16, where the clock signal is regenerated. The synchronization signal detection circuit 17 detects the synchronization signal included in the IB force signal of the waveform shaping circuit 11.

This same) υj times the signal is output. The synchronizing signal output from the synchronizing signal output circuit 17 is frequency-divided by a frequency dividing circuit 18 and applied to a phase comparator circuit 19. The phase comparison circuit 19 compares the phases of this signal and a signal obtained by dividing the master clock generated from the master clock generation circuit by the frequency dividing circuit 2I, and controls the disk rotation servo circuit n so that these phases match. The disc rotation motor 3 is controlled through the disc rotation motor 3.

The demodulation circuit 12 uses an EFM (Eight to Four
1) Remove the original 8-bit signal K 0 MIAI L from the modulated and recorded signal of the disc 1, as well as remove uneasy items such as the combination bit and synchronization signal. On the error correction circuit n and memory circuit side, the data control circuit deinterleaves the signal +'-J (signal of the interleaved disc) output from the demodulation circuit 12 and converts it to the original data. The presence or absence of an error is checked based on the signal, and if there is an error, the error is corrected by the error correction circuit r, and if it is uncorrectable, it is corrected. In addition, by temporarily storing the corrected and corrected signal in the memory circuit at the timing of the reproduced clock code and outputting it at the timing of the master clock, it is possible to align the arter and absorb rotational irregularities of the turntable 2. What are you doing?

The signals read from the memory circuit side (signals in which right channel signals and left channel signals are arranged alternately in a time division manner) are applied to D/A converters 2'J and 31J, respectively.
The signal is separated into left and right channels at the timing of the master clock and converted into the original analog signal (audio signal).

The subcode detection circuit detects a subcode (address, track number, time code, etc.) from the signal demodulated by the demodulation circuit 2 and sends it to the system control circuit 37. The system control circuit 37 manually inputs the address, track number, etc. specified by the operation keypad via the decoder 39, compares it with the detected subcode, and adjusts the feed motor hull 1 circuit 40 so that they match. The feed motor 8 is driven through the feed motor 8. Also, system control 1^1
A path 37 displays the detected subcode on a display section 42 via a drive circuit 41.

The entire digital audio disk caterpillar device is constructed as described above.

By the way, the focus servo circuit 13 in the apparatus shown in FIG. 1 has conventionally been configured as shown in FIG. In FIG. 2, the photodetector 50 has a capacity of 11% in the optical big head 4, and is a photodiode divided into four parts.

5(1b, 50c, 5(ld). The reflected light from the disk passes through a cylindrical lens (not shown) and forms an image 5! on the photodetector. When the recording surface is at the focal point of the objective lens 7, it becomes circular and light is evenly distributed on the bamboo strips of the photodiodes 50a-50d, but when the recording surface of the disk is at the focal point of the objective lens 7, , when I'm close to you, when I'm lucky,)
'Due to non-imaginary aberration of DI+lens, near clearance: 1S-t
It becomes an ellipse with different directions depending on the shape Qli. Then, signals from diagonally opposite photodiodes 50a-8Jd are added by IJ circuits 52 and 53, respectively, to generate a focus error detection circuit (differential amplifier).
By performing ftCn- in step 54, a focus error detection signal corresponding to the direction of the focus error and its effect can be obtained. Therefore, this signal is sent to the focus Hill in the optical big amplifier head 4 via the loop filter 55 and the focus coil IQ,<J<h circuit 5 (j).
#In addition to the coil 5, set the 0 position of the objective lens 7 to 11
Then, you will be able to record Tinuku and make a conclusion.

By the way, in the above configuration, when the optical pickup \RAD 4 is fed in the radial direction of the disk for random access etc.
a) As shown by the arrow, set track 1a of the optical start-up head 4 and 1 screen 1 (lust 2), focus ii day difference detection 1)
b) contains a large number of certain frequencies (audible frequencies), resulting in No. 46. Therefore, this 'i1
The normal rule: ・'Gain City T1 made, hindered 3 trees,
So]-kas1lilj ji+1. : Coil 5 has 4 turbulence, and due to this, the current actuator (
The pair 4i+, the device for driving the 7 lenses 7 (h) "ノJ: The combination of the focus control coil 5 and the magnetic circuit vibrates due to the components in the audio frequency band. ``Hee'', which is 14-, exceeds 1.￥(9
As a g1 nail, it is not surprising that the system noise is large. However, if I turned off the focus servo during feeding to write something new, it would take some time for the focus servo to stabilize from 411°C after the feed was finished, and it would get stuck. Also, if the focus servo is turned off during feeding, the focus will be far off from the disk recorder, making it impossible to obtain a playback signal.Especially in the CLV (Constant Linear Velocity) method, the disk rotation servo required for the disk rotation servo Rotation information (by PJ Lukrock)
Since it is difficult to obtain information for ν), the disk rotation servo is often used as an example. In this state, even if the feed operation is ended at 1.7 and the current servo is turned on at t7, the fourth servo remains at 1.7. Even disc time 4
+, (-Lee--Bo will move '[゛, so
111-It takes more time for the raw signal to reach a stable state.

This invention was made in view of the problem of child connection, and prevents the focus actuator from being distorted when feeding the optical pickup head, and also prevents the focus actuator from being distorted when feeding the optical pickup head.
Optical disc playback scissors that can switch to the raw state immediately after the playback (in 6); 4-Cass servo fii
lJ (f11 device).

In this case, the focus servo is not completely turned off during feeding, but the loop gain is appropriately reduced.

In this way, it is possible to attenuate the squeal of the Akuzu unit, and although the focus error is larger than during normal playback, the general playback signal is still very low. , you can see the outline of the disk rotation status information required for the CI, V-buf type disk rotation servo, and the same rotation speed of the secondary disk motor is also 11. The black side becomes the ih side, and after the end of the feed movement i'1 (
ilJ+ crop is faster until the start of t1 cows 4).

Please refer to the drawings L'+ and 1 for the embodiments of this invention.
2 I will explain. Does this embodiment work with the circuits of FIGS. 1 and 2? ) The same code is used for the 11th minute.

In the embodiment of FIG. 4, -C1 subcode detection circuit 36
detects subcodes such as address information, face information, time code information, etc. from the Tisp playback signal.

The detected sub-1-mode is sent via the drive circuit 41 to the ℃ display tone (displayed on the puller 42).The operation key is used to specify the random number, track number and address for access, and is output via the decoder 39. , and sends it to the system control circuit 37. At the system control circuit 37, the comparator circuit 60 compares the subcode detected by the subcode detection circuit 36 and the command type of operation key +38. death,
1) Send a request for sending the specified order and send a request for the feed direction. The tracking displacement detection circuit 24 detects the dragging displacement h4 caused by the tracking servo, and when it reaches a predetermined value, foot request No. 18 (7'
The person who requests the feed amount and the feed direction ÷ 3)
Output. Sysbuno Control
The pulse generator 61 in the pulse generator 37 outputs a sending direction signal of 1㎜ pulses based on the output of the comparison circuit 60 and the output of the dragging displacement detection circuit 24. Based on the output of the feed motor control code generator 62 and the pulse generator 61, an 18-second control code is output that encodes the amount and direction of rotation of the feed motor 8, and the feed motor drive circuit The feed motor 8 is operated by kA via 7 through 40. The feed detection circuit 63 detects that a feed operation is being performed based on the comparison circuit mark indicating that the feed request signal is 133 times oscillating, and outputs a feed detection signal. Feed detection (K) is added to the focus servo circuit 13 and used for switching the loop gain of the focus servo.

The light reception signals output from each piece 5 (l a-50d) between the photodetectors are diagonally connected to each other by an adder circuit 52 g 53
These added p values are further subtracted by the focus difference detection circuit 54 to detect a focus error signal. This focus error signal passes through a muting circuit 64, a loop filter ij5, and a focus coil drive circuit 56 in the focus servo circuit 13, drives the focus coil 5, moves the objective lens 7, and performs focus control.

By the way, the above-mentioned muting circuit 04 traces the focus error signal as it is during normal playback, and attenuates and outputs the focus error signal when upper ie feed detection (i<) is added (i.e., switches the loop gain). Here, this muting 1 and 1 path 64
is formed by a resistor divider circuit with resistors R1 and R2, and the above loop gain switching operation is realized by turning off the muting switch SWl during normal playback and turning it on when the feed detection signal is applied. .

As explained above, according to the present invention, the loop gain of the focus servo loop is reduced when the optical picker 7 is fed, so that it is possible to prevent the focus actuator from squealing. Furthermore, since the loop gain is not completely turned off, it is possible to shift to the regeneration state immediately after the feed operation ends.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an optical digital audio disc playback device, FIG. 2192 is a block diagram showing the conventional configuration of the focus servo circuit 13 shown in FIG. 1, and FIG. 3(b) is a waveform diagram of a focus error detection signal obtained during the operation of FIG. 3(al), and FIG. 4 is an embodiment of the present invention. 0 1...Disk, 1a...Track, 2...Turntable, 3...Disk rotating motor, 4...Optical pickup head, 5... Focus control 1 coil, 6...Tracking'+1jll (iβI coil, 7...Even)l! ! ? I lens, m)...master clock generation circuit, n...disk rotary blade--bo circuit, 42...display' section, gate...four-division photodetector,
64...Muding circuit, SWI...Muting month] switch.

Claims (1)

[Claims] A focus servo-controlled iMI device for an optical disc playback device, comprising means for reducing the loop gain of a focus servo loop during a feed operation of an optical pickup head.