JPS6089840A - Automatic focus locking device - Google Patents

Abstract

PURPOSE:To attain sure focus servo by transmitting a signal cancelling the effect of face deflection or warp to an optical disc having defects larger than the detecting range of a focus error signal so as to move the optical system into the vicinity of the focal point. CONSTITUTION:When the focus error signal having changed in the order of D' D B C' reaches a position E to eliminate the face deflection of an optical disc, a search voltage of an objective lens is held by a signal hold control section 19. A switch SW2 is closed at the same time and a step voltage sufficiently faster than the relative speed of the information plane to the optical system due to the face deflection of the optical disc and corresponding to a distance from the point E to the point A is fed from a voltage generator 24 so as to move the optical system in the vicinity of the focal point A forcibly. Then sure servo locking is applied and accurate focus servo is conducted further so as to attain stable and sure operation.

Description

[Detailed Description of the Invention] Technical Field The present invention uses f1 to match the focal positions of the optical system of an optical big amplifier for recording and reproducing information on an optical disk or the like.
71J This invention is inspired by an automatic focus pull-in device used in an optical recording/reproducing device having a focus servo circuit.

Conventional technology In the autofocus circuit of a normal optical recording/reproducing device, the optical system such as the objective lens of the optical pick amplifier is compared with the level of the focus/processor signal and the return from the optical disk surface. , IL, and the focus servo loop is closed when the returned light is maximum and the error signal is zero. However, since the tracking servo is open during autofocus retraction,
Due to the eccentricity of the optical disk, the distance between the returning lights varies depending on the presence or absence of data (pits), groups, etc., and the maximum light Ef
This causes a problem in the detection accuracy of t, making it difficult to achieve stable focus pull-in. There is also a method of detecting the in-focus point without referring to the focus error number only, but there is an optical system in which the focus error number 1a includes an inverted r''IIS component (focus error number 1a) as shown in Figure 1. Detection method) is simply a focus error.

In the method of detecting the level of the disc, there is a possibility that the focus servo loop closes near the 8th point, and furthermore, the disk surface moves away from point B before the optical system is drawn into the great focal point of point A. When the lens moves in the direction, the polarity of the focus control word is reversed and the lens moves further away from point B.

It is possible to reduce this polarity reversal part to the extent that it hardly causes any trouble, but in this case, the optical system for detecting the focus error 1@, including the adjustment, becomes very complicated and undesirable. .

There is a method to fractionate the focus error signal and draw it into the servo while comparing and referring to the level of its run value and the level of the focus error signal, but in cases such as the critical angle method where there is a large polarity reversal part, When servo pull-in is performed while the optical disk is rotating, the shape of the differential waveform of the focus error rd@ changes greatly as shown in Figure 2 due to surface wobbling of the optical disk, resulting in poor detection accuracy and stability. There is a drawback that proper servo pull-in is not performed.

Purpose □ The present invention provides a focus system that controls the warping and surface wobbling of an optical disc so that the information surface of the optical disc coincides with the focal position of the optical system of an optical pickup for recording and reproducing information. In an optical recording and reproducing device having a servo circuit, even for an optical disk with surface wobbling or warping that is larger than the focus error fa @ detection range, the optical system is moved to the detectable range and the optical disc is stably drawn into the focus servo. It is an object of the present invention to provide an automatic focus retraction device iIt.

The automatic focus pull-in device of the optical 117 report recording and reproducing device of the present invention comprises an optical disc, an optical pick amplifier for recording and reproducing 117 reports toward the disc, and means for moving the optical system to a focus error government detection range. , 11. The distance between the focal position of the optical distribution system and the disk surface of the optical disk is J.
means for roughly illuminating the optical system on the disc surface of the optical disc so as not to be affected by surface wobbling of the optical disc until the position where fi is equal, and the distance between the focal position of the optical system and the information surface of the optical disc is equal. The present invention will now be described in detail with reference to the drawings.

The automatic focus retrieval device ri of the present invention shown in FIG. 8 includes a two-segment bin photodiode detector 10 of an optical big amplifier that detects the returning light from an optical disk, and a detector amplifier that adds and subtracts the outputs to obtain a focus error signal. 11, a switch SW8 that opens and closes the servo loop,
A focus actuator drive circuit 15 consisting of a phase compensation circuit 12, an actuator driver 13, and a drive voltage detection circuit 14, a window comparator OOMPI, and a window comparator OOMP2 for obtaining the timing to bring the focus into focus while monitoring the focus error signal. , a focus error signal detection circuit 16 consisting of a flip-flop 1i'F1, a flip-flop FF2, and a flip-flop FF8, a discharge control section 17, and a charge control section for moving the objective lens of the optical system of the optical pickup to a predetermined position. 18, signal hold control section 19, mirror area circuit 20. delay circuits 21 and 22, an inverter 28, a switch SW for switching connections between the actuator driver 18, and a step voltage generator 24.
, an adder 25, and a lens search tolerance voltage generation circuit 26 consisting of a switch and SW for switching the connection of the voltage generator 24 and the adder 25.

Fig. 4 shows the output Ill pressure waveform of the actuator driver 18? In the figure, ■ is the voltage waveform at the discharge 1 control section 17, ■ is the charge control section 1B, ■ is the switch sw2, ■ is the signal hold control section 19, ■ is the switch sw8, and ■ is the voltage waveform at the switch SW□.

In the automatic focus retrieval device of the present invention configured as described above, when the focus servo loop is open, the objective lens of the optical pickup is stationary at a position where it does not make sufficient contact with the disk with surface wobbling or warpage. do.

When the automatic focus pull-in device starts operating, the switch SW shown in FIG. A lens search voltage is generated under control of the mirror area circuit 20 to move the objective lens away from the optical disk from its rest position and then to move the objective lens closer to the disk surface at a constant speed. As the objective lens approaches the optical disc, the focus error signal is in the order of A' → A → B → C' → B → C → A, as shown in Figure 5, assuming that the objective lens is only facing the optical disc. It's going to change.

The flip-flops FFI and NFFIII of the 81-unit monitor the focus error signal, and the focus error signal causes the objective lens to gradually approach the focused point A of the optical system from the position where it is separated by light. After confirming that it has passed, close switch SW8 near point A,
Create an IQ to lock the focus servo. However, in reality, optical discs have surface wobbling of a few hundred micrometers to one gate, so the temporal change of the focus error signal is disrupted, and changes in the order of A'→A→B→C'→4. The focus error signal that came from continued to change from mouth to ha'-)
It may change from B to A. In other words, when the speed at which the optical system is moving away from the focal point (relative speed of the information surface to the optical system due to surface wobbling of the optical disk) is greater than the speed at which it approaches the focal point, the comparator OOMPI, Since the comparator GOMP 2 supplies timing pulses of the same color as when the optical system moves from mouth to c to A to the 7-lip front blocks FF2 and FF8 and closes the switch SW8 near point B, the polarity of the focus ftjf control is The direction of reversal, that is, the optical system becomes stable at 16 as it moves further away from A'.

Therefore, according to the present invention, in order to eliminate engravings caused by surface wobbling on the optical disc, the objective lens is turned off when the focus error signal, which has changed in the order of A' → A → B → C', reaches the IP lens at about the mouth. The search for Ichikawa is held by the signal hold control unit 19, and at the same time the switch SW2 is closed, so that the relative speed of the information surface to the optical system due to the vibration of the optical disc is sufficiently faster (this is specific to each optical system). A step-like voltage (fourth point) corresponding to the distance G to point A
By supplying the waveform (■) in the figure from the voltage generator 24 and moving the optical system to the vicinity of the focused point A under the @ constraint, precise servo pull-in is performed. I try to do it.

In other words, in the present invention, monitoring of the focus error signal is started from the point when the point A is closer to the in-focus point A than point 8, and the focus error signal is started from the point when the focus point A has passed ', and the influence of the surface area n of the optical disc is sufficiently canceled when the signal reaches the mouth position. While moving the optical system to the vicinity of the in-focus point as much as possible, the focus error signal is monitored to ensure that the focus servo is started at the in-focus point A. When the focus servo loop is closed and focus servo is started, the switch SW□ is opened and the lens search circuit is separated from the focus servo loop.

Effects of the Invention As is clear from the above, according to the present invention, even for optical discs with blood blur or warpage that is larger than the detection range of the focus error signal, a signal can be generated that sufficiently cancels out the effects of these blurs or warps. By supplying this, the optical system of the optical pickup is moved relaxedly to a focus error signal detectable range near the in-focus point, thereby stably and reliably performing focus servo.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the shape of a focus error signal that generally occurs, FIG. 2 is a waveform diagram illustrating the processing method thereof, and FIG. 8 is a circuit diagram showing the configuration of the automatic focus pull-in device of the present invention. FIG. 4 is an explanatory diagram showing waveforms of the output of the device shown in FIG. 3, and FIG. 5 is a waveform diagram showing signals at various points in the automatic focus retrieval device of the present invention shown in FIG. 10... Photodetector 11... Detector amplifier 12... Phase complement circuit 18... Actuator driver 14... Drive voltage detection circuit 15... Actuator drive circuit 16... Focus error signal detection Circuit 17...Discharge control unit 18...Charging control unit 19...Signal hold control unit 20...Miller integration circuit 21.22...Delay circuit 28...Inverter 24...Step-like Voltage generator 26...Writer 26...Lens search voltage generation circuit SW, ~SW,...Switch 00MPI...Window comparator 00MP2i...
...Comparator Ii'! 1 to FFf9...Flipf9p〇Patent originator Olympus Optical Industries Co., Ltd.% formula% Figure 4■ Figure 5 Procedural amendment (voluntary) April 24, 1980 Patent Application No. 197888 2 , Title of the invention: Automatic focus retraction device 3, Relationship to the amended person's case Patent applicant address: 2-48-2 Hatagaya, Shibuya-ku, Tokyo Name (
Name> (08?) Olympus Optical Industry Co., Ltd. President Satoshi Shimoyama Department 4, Agent 8 Contents of amendment (1) “■” on page 8, line 4 of the specification indicates switch SW,
The description “J” will be deleted. 9. Attachment, Catalog of Classes (1) Attachment, l Attachment [2. Claim 1: An optical disk, an optical pickup for recording and reproducing information on the disk surface of the optical disk, and an optical pickup for the optical pickup. a means for moving the system to a focus-error signal detection range; and a means for moving the optical system to a position where the focal position of the optical system and the distance between the disk surfaces of the optical disk are approximately equal, so as not to be affected by surface wobbling of the optical disk. It is characterized by comprising means for bringing the optical disk closer to the disk surface, and means for closing a focus servo loop when the distance between the focal point position of the optical system and the information surface of the optical disk becomes equal. Automatic focus retraction device. 2. The means for moving the optical system of the pickup that records and reproduces information on the disk surface to the focus error signal detection range includes a photodetector that detects the return light of the optical disk and a detector that amplifies the output of the photodetector. The focus signal is calculated by adding and subtracting the output signals of the amplifier and the detector amplifier.
It is characterized by comprising an arithmetic circuit that obtains an error signal, a phase correction circuit that receives the output of the focus error signal detection circuit to stably operate the servo system, and an actuator drive circuit that drives the actuator of the optical pickup. An automatic focus retraction device according to claim 1. 8. The means for bringing the optical system closer to the disk surface to a position where the distance between the focal point of the optical system and the disk surface is approximately equal so as not to be affected by surface wobbling of the optical disk includes a lens search voltage '□ generation circuit. An automatic focus retraction device according to claim 1, characterized in that: 4. The lens search voltage generation circuit includes a discharge control section, a dust amount control section, a signal bold control section, a Miller integration circuit controlled by these control sections, and a stepped 11 output of the Miller integration circuit. 9. The automatic focus pull-in device according to claim 8, further comprising a step for supplying a pressure, a tube-like voltage, and a generating circuit. ”

Claims (1)

[Scope of Claims] L An optical disk, an optical pickup for recording and reproducing information on the disk surface of the optical disk, means for moving an optical system of the optical pickup to a focus error signal detection range, and a means for moving the optical system of the optical pickup to a focus error signal detection range. Focus position and I! The distance between the discs (2) of the optical disc 01 is determined by means of bringing the optical system closer to the disc surface of the optical disc 01 so as not to receive Ie* of surface wobbling of the optical disc to the point where the distance between the discs 2 and 2 of the optical disc 01 is "buried," etc. - an automatic focus pull-in device characterized by comprising: means for closing a focus servo loop when the focal position of the optical system and the distance between the information surfaces of the optical disk become equal; The means for moving the pickup optical system for recording and reproducing information to the rheocus error signal detection range includes a photodetector for detecting the return light of the optical disk, a detector amplifier for amplifying the output of the photodetector, A phase correction circuit for the output U of the detector amplifier, a focus error signal detection circuit, and an actuator drive circuit that receives the outputs of the phase correction circuit and the focus error signal detection circuit and drives the actuator of the optical pink-up. The automatic focus retracting device according to claim 1, characterized in that it is not affected by surface wobbling of the optical disk until the focal position of the optical system and the distance between the disk surfaces are approximately equal. The automatic focusing device according to claim 1, wherein the means for bringing the optical system closer to the disk surface includes a lens search voltage generation circuit. The discharge fli control section, the charge '% 1ljlJ riAI section, and the rg number*/
k t' 117111 inl R ((t1, comprising a mirror circuit 1111 controlled by these control units and a step dt pressure circuit 6 which supplies a step pressure to the output of the mirror differential circuit) patents characterized by
Claims v, f (Automatic focus retraction device according to claim 8).