KR100237561B1 - Focus servo lead in method and apparatus - Google Patents

Abstract

The present invention relates to a method and apparatus for refocusing a focus sub, and in the related art, when focusing fails, there is a problem of delaying focusing time by retrying from an initial operation. Accordingly, the present invention eliminates the initialization operation that is pulled down to the floor during the focus retraction operation and allows the fast refocusing operation to be performed immediately after the focus is released to enable the fast focusing operation.

Description

Focus servo reentry method and apparatus

1 is a block diagram of a conventional disc player.

2 is a block diagram of an optical pickup in FIG.

3 is a divided area diagram of a photodetector according to FIG. 2;

FIG. 4 is a light quantity distribution diagram incident on a four-segment photodetector in FIG.

5 is an explanatory diagram of a cylindrical lens for generating astigmatism in FIG. 2.

6 is a configuration diagram of a focus servo re-entry device of the present invention.

7 is a detailed circuit diagram of the objective lens positioning unit in FIG.

8 is an input / output waveform diagram of FIG.

9 is a flowchart illustrating an operation of the present invention.

* Explanation of symbols for main parts of the drawings

1: disc 2: optical pickup

3: spindle motor 4: motor drive part

6: Servo unit 7: Pick-up driving unit

8 digital signal processor 9 amplification / filter unit

10: system controller 11: objective lens positioning unit

In order to find the focusing position by controlling the focusing servo from the current position by detecting the current objective position without dropping the objective lens to the initial position when the focusing failure of the present invention, in particular, the focus retracted in the state where the focus is out of focus The present invention relates to a focus servo re-entry method and apparatus for operating at high speed by operating.

In the conventional disc reproducing apparatus, as shown in FIG. 1, an optical pickup 2 for converting an optical signal reflected from the disc 1 into an electrical signal and a linear linear velocity of the disc 1 are fixed. To control the spindle motor (3), and to drive the loading motor and the various motors not shown, and the electric signal of a predetermined level to the minute electrical signal output from the optical pickup (2) A focus error (FE) and a tracking error signal (TE) by using the high frequency amplification unit (5) for increasing the frequency and the signals (A, B, C, D, E, F) from the optical pickup (2). The servo unit 6 suitable for the focusing operation of the disc, the tracking and the sled servo operation, and the EFM (8-14 conversion) data outputted from the servo unit 6 are decoded to correct the data. Providing information about the rotation of the disk to the servo unit 6 by various data And amplification / filter unit 90 for amplifying the data output from the digital signal processing unit 9 and outputting a signal for driving the spindle motor by low pass filtering. A pickup driver 7 for controlling the focusing, tracking, and sled servo of the optical pickup 2 in response to the tracking error TE and the focus error FE from the unit 6, and the digital signal; And a system controller 10 for outputting drive control signals for driving a required motor in accordance with data and various signals input from the processing unit 8 and a switch input from the outside.

As shown in FIG. 2, the optical pickup 2 includes a diffraction grating (2) which receives a laser beam emitted from a laser diode (2-1) as a light source and makes a tracking subbeam. 2), an objective lens 2-3 for condensing the light passing through the diffraction grating 2-2 on the optical disk surface 1a, and a beam for changing the direction of reflected and diffracted light on the optical disk 1; A splitter 2-4, a cylindrical lens 2-5 for generating astigmatism for detecting a focus error in the light received from the beam splitter 2-4, and the cylindrical lens 2- 5) and a photodetector 2-6 which converts the collected light received from the cylindrical lens 2-5 into an electrical signal.

Referring to the prior art configured in this way in detail as follows.

The high frequency signal RF and the optical signals A, B, C, and D, which are converted into electrical signals by the optical pickup 2, are respectively input, and the high frequency signal RF is amplified to a predetermined level so that the servo unit 6 In addition, the focus error FE and the tracking error TE are obtained using the optical signals A, B, C, and D, and the obtained error is provided to the servo unit 6.

Then, the servo unit 6 picks up drive signals FE, TE, and SLED suitable for the disk focusing operation, the tracking operation, and the sled servo operation by the input focus error FE and the tracking error TE. The driving unit 7 outputs the high frequency signal RF, that is, the EFM signal, to the digital signal processing unit 8.

Accordingly, the pickup driver 7 outputs a signal for performing focus servo, tracking servo, and sled servo operation to the optical pickup 2, and the digital signal processor 8 synchronizes the EFM data to the synchronization signal input thereto. The digital signal is converted into digital data and output to the amplification / filter unit 9 and the system controller 10.

Accordingly, the amplification / filtering unit 9 amplifies and filters the input data as a driveable signal and outputs the same to the motor driving unit 4 to drive the spindle motor 3 and a loading motor (not shown). 10) to drive the necessary motor by the various switches (OPEN S / W, CLOSE S / W, LIMIT S / W) from the outside.

In addition, referring to FIG. 2 of the optical pickup 2, the diffraction grating 2-2 receiving the laser light from the laser diode 2-1 makes the tracking sub-beam to produce the objective lens 2. -3), the objective lens 2-3 is focused on the optical disk 1a.

At this time, the laser light focused by the diffraction grating 2-2 becomes the main beam 3-5 and the two sub beams 3-5a and 3-5b to focus on the optical disk 1, which is a double main beam. (3-5) is used for reading and focus error measurement (FE) of the information recorded on the disk surface 1a, and the subbeams 3-5a (3-5b) are used for tracking error measurement (TE).

When the main beams 3-5 and the sub beams 3-5a and 3-5b are reflected and diffracted to enter the beam splitter 2-4, the beam splitters 2-4 are loaded in different directions. Send to the decal lens (2-5).

Then, when the spherical condensed light enters the cylindrical lens 2-5, as shown in FIG. 5, two linear focuses 18 and 20 are generated, and the linear focuses 18 and 20 are generated. ) Occurs between the focal points (19), which is close to the cylindrical lens (2-5) of the two linear focal points (18) (20) and whose direction of length is parallel to the lens optical axis a, that is, the linear focal point (18). Is referred to as the primary prefocus, and the longitudinal direction is perpendicular to the optical axis a and occurs after the optimal focus 19, that is, the linear focus 20 is also referred to as the secondary prefocus.

In addition, the state in which the longitudinal direction of the prefocus is parallel to any axis a is defined as the state in which the prefocus is parallel to the a axis.

Then, the laser light passing through the cylindrical lens 2-5 enters the photodetector 2-6 while focusing the detection. The photodetector 2-6 is shown in FIG. In addition, it consists of a four-segment detector (21) consisting of four detectors (21-A, 21-B, 21-C, and 21-D) and tracking error signal detectors (22-1) and (22-2). The segmentation detector 21 forms a quadrangular shape as shown in FIG. 4 (a) and forms an angle of 45 degrees with the cylindrical lens 2-5 and the optical axis a.

When the distance between the objective lens 2-3 and the disk surface 1a becomes the correct image forming distance f, the photodetector 2-6 has the optimum focal length l from the cylindrical lens 2-5. ) Away from

Here, the recording information reading and focus error measurement (FE) and tracking error measurement (TE) by the main beams 3-5 and the sub beams 3-5a and 3-5b will be described.

First, the focus error (FE) measurement is performed when the main beam 3-5 is reflected by the optical disk surface 1a and again passes through the objective lens 2-3 to focus on the beam splitter 2-4. The reflected light is redirected by the beam splitter 2-4 and passes through the cylindrical lens 2-5 for generating astigmatism.

When the disk surface 1a is positioned at the correct image forming distance f from the objective lens 2-3, the detection focus 24 incident on the quadrant detector 21 from the cylindrical lens 2-5 is As shown in FIG. 4 (b), the best focus is achieved.

On the other hand, when the distance between the disk surface 1a and the objective lens 2-3 is close, the shape of the detection focus 24 approaches the shape of the primary prefocus as shown in FIG. 4 (a). When the distance between (1a) and the objective lens (2-3) increases, the shape of the detection focus 24 approaches the shape of the secondary prefocus as shown in FIG. 4 (c).

In this case, the amount of light detected by the four detectors 21-A, 21-B, 21-C, and 21-D of the four-part detector 21 is different, and the amount of light detected by each detector is A and B, respectively. , C and D, the focus error FE is FE = (A + C)-(B + D), and the total light amount FSUM, which is a signal corresponding to the information recorded on the disk surface 1a, is FSUM = It can be found as A + B + C + D. This is the total signal of light reflected from the disk 1.

Further, the tracking error is that the sub-beams 3-5a and 3-5b formed on the disk surface 1a are tracking error signal detectors of the optical detectors 2-6 along the optical path similar to the main beams 3-5. The tracking error signal detection beams 23-1 and 23-2 are formed in (22-1, 22-2), respectively. If the signals of the detectors are E and F, the tracking error signal TE is It can be obtained from TE = EF.

Use the same method as above to focus.

However, in the prior art as described above, when focusing (Focusing) is failed or when the deviation from the focusing position by the impact, etc. attempts to re-focus, at this time, by resetting the objective by pulling the objective lens to the bottom Due to the delay in focusing time, there is a problem that is not suitable for high-speed focusing.

Therefore, an object of the present invention for solving the conventional problems as described above is to eliminate the initialization operation to pull down to the floor during the focus operation of the focus servo and to perform the focus servo re-entry immediately in the state that the focus is out of the high-speed focusing operation It is to provide a focus servo re-entry method and apparatus to enable this.

In order to achieve the above object, the operation flow of the focus servo re-entry method according to the present invention is a method for identifying a relative position with respect to the focal point position of the recording surface of the objective lens when reading data from the recording medium, as shown in FIG. Step 1 and a second step of controlling the movement of the objective lens according to the identified relative position to re-enter within a predetermined distance when spaced more than a predetermined distance with respect to the focal position of the recording surface of the objective lens, and the recording medium during the movement The third step is to accumulate the focus ok signal FOK according to the output signal level reflected from the control panel.

An apparatus for performing the method consisting of each step includes an optical pickup 2 for converting an optical signal reflected from the disk 1 into an electrical signal, as shown in FIG. Servo unit that makes focus error (FE) and tracking error signal (TE) by using outgoing signals (A, B, C, D, E, F) to be suitable for disk focusing operation and tracking and sled servo operation ( 6) and the EFM (8-14 conversion) data output from the servo unit 6 are decoded to correct errors of the data, and information about the rotation of the disc is provided to the servo unit 6 by various data. A digital signal processor (8), an objective lens position checking unit (11) for checking a relative position of the focal point position of the objective lens recording surface in the optical pickup (2) when reading data from the disc, and the objective A predetermined distance with respect to the focal point position of the lens recording surface The system controller 10 which outputs a focus okay signal according to the output signal level reflected from the recording medium when detecting whether the detected distance is moved by the detected distance, and reentering it within a predetermined distance when the predetermined distance is separated from the predetermined distance. It consists of an objective lens driving control unit consisting of a motor driving unit 4 and the pickup driving unit 7 for controlling the driving of the objective lens in accordance with the relative position identified in the.

As shown in FIG. 7, the objective lens positioning unit 11 compares the signal FSUM representing the total amount of light with respect to the data reflected from the disk and the reference signal Vrefl, and thus the FSUM signal has a predetermined level. If this is the case, the comparator 111 for outputting the FOK signal is compared with the focus error signal FE indicating the focusing position and the reference signal Vref2 to detect whether the objective lens is upward based on the focal point position, and the corresponding signal ( UP-position detecting unit 112 for outputting UP and the focus error signal FE and the reference signal Vref3 are compared to detect whether the objective lens is downward based on the focal position, and accordingly the signal DOWN. And a logical operation of the down-position detector 113 and the FOK signal of the comparator 111 and the output signals of the up-position detector 112 and the down-position detector 113 of the objective lens for the focal position. Output by detecting relative position signal An up-and-down composed of the signal generating unit (114).

When described in detail with respect to the operation and effect of the present invention configured as described above.

When the system controller 10 outputs a drive signal to the motor driver 4 when reproducing the data recorded on the disk 1, the motor driver 4 is a spindle for making the rotational linear velocity of the disk 1 constant. The motor 3 and the loading motor are controlled, and the pickup driver 7 drives a signal for driving the optical pickup 2, that is, a drive for driving the focus servo of the optical pickup 2 as shown in FIG. 8 (a). Output the signal.

Accordingly, when the optical pickup 2 controls the objective lens to convert an optical signal from the disk 1 to an electrical signal and outputs the electrical signal to the high frequency amplifier 5, the high frequency amplifier 5 records the disk 1 on the disk 1. The total light quantity (FSUM), which is a signal corresponding to the obtained information, is obtained, and the signal corresponding to the total light quantity is amplified to a constant level to be output to the servo unit 6 to increase the electric signal of a predetermined level, and the objective lens position is confirmed. Output to section 11.

Then, the servo part 6 obtains the focus error signal FE and the tracking error signal TE from the total amount of light FSUM transmitted from the high frequency amplification part 5, and obtains the obtained signal from the pickup driving part 7 and the pickup driver 7. Output to the objective lens positioning unit 11, respectively.

In this case, the total light amount FSUM, the focus error signal FE, and the tracking error signal TE, which are signals corresponding to the information recorded on the disc 1, are obtained as shown in FIGS. 2 to 5, respectively. Since the operation process of the same as the prior art will be omitted.

Here, the signal corresponding to the total light amount FSUM is the same as in FIG. 8 (b), and the focus error signal F.E is the same as in FIG. 8 (c).

In the objective lens positioning unit 11, as shown in FIG. 7, first, the total light amount signal FSUM is input to the non-inverting terminal (+) of the comparator 111, and the focus error signal FE is up-. The non-inverting terminal (+) and the inverting terminal (-) of the comparator COMP1 and COMP2 in the position detecting unit 112 and the down-position detecting unit 113 are respectively input.

Accordingly, the comparator 111 checks whether the total light quantity signal FSUM of the disk is higher than or equal to a certain level by comparing with the reference signal Vrefl input to its inverting terminal (-). The OK signal FOK is outputted. As shown in FIG. 8 (d), the focus OK signal FOK of the comparator COMP1 outputs a high state when the total light quantity signal is above a predetermined level and a low state when it is below. do.

When the focus error signal FE having the waveform as shown in FIG. 8 (c) is in the high state, the comparator COMP1 of the up-position detecting unit 112 makes the high as shown in FIG. 8 (e). When the up position signal UP in a state is output and the focus error signal FE is in a low state, the comparator COMP1 outputs an up position signal in a low state. Likewise, the down-position detection unit 113 is a comparator. When the focus error signal FE is in the low state as shown in FIG. 8 (f) by the COMP2, the comparator COMP2 outputs the down position signal DOWN in the high state and the focus error signal FE. When is in the low state, the comparator COMP2 outputs the down position signal DOWN in the low state.

As described above, the up-position detecting unit 112 and the down-position detecting unit 113 output the up position signal UP and the down position signal DOWN, respectively, and the comparator 111 outputs the focus ok signal FOK. The relative position signal of the objective lens 2-3 (shown in FIG. 2) with respect to the focal position, i.e., through the logical combination of the AND gate and the RS flip-flop of the up-down signal generator 114, It outputs an UP-DOWN signal as shown in Fig. 8 (g).

When the objective lens position checking unit 11 outputs the relative position signal to the system controller 10, the system controller 10 determines the relative position of the objective lens 2-3 to determine the relative position of the objective lens 2-3. The pick-up driving unit 7 and the motor driving unit to move up from the position to find the focusing position, and if the objective lens 2-3 is above the focusing position, the objective lens 2-3 is moved down to move the focusing position. 4) outputs the drive signal.

As described above, when the system controller 10 transmits a driving signal to the pickup driver 7 to move the position of the objective lens 2-3 to the focusing position according to the up and down positions, the pickup driver 7 and the motor. The driving unit 4 drives the optical pickup 2, the spindle motor 3 and the loading motor to directly enter the focusing position from the current position.

Referring to FIG. 9 again for the above operation, the system controller 10 checks the focus ok signal FOK of the comparator 111 of the objective lens positioning unit 11 and focuses if it is high. Since it is in the correct position, the process is terminated. If the state is low, the position is not the focusing position. Therefore, the position of the objective lens 2-3 is checked.

As a result of the check, if there is no relative position, it moves from the initial position to the focusing position to read data from the disc 1, and if there is a relative position, whether the position of the objective lens 2-3 is above or below the focusing position. If it is above, the objective lens (2-3) is lowered to move to the focusing position, and if it is below, the objective lens (2-3) is raised to move to the focusing position and then the focus ok signal (FOK) and When the focus zero crossing signal * FZC changes from a high state to a low state, data is read from the disk 1.

In FIG. 9, FZC stands for Focus Zero Crossing signal, and the output is pulsed at the focal point of the objective lens 2-3.

As described above, the present invention allows the focus retracting operation to be performed at the position where the focus is out of focus when the focusing fails during the retracting operation of the focus so that the focusing time due to the initializing operation is not delayed. It is effective to make it suitable for high speed focusing.

Claims (5)

A first step of checking a relative position with respect to the focal point position of the recording surface of the objective lens when data is read from the recording medium; A focus servo comprising a second step of controlling the movement of the objective lens according to the identified relative position, and a third step of outputting a focus ok signal FOK according to the output signal level reflected from the recording medium during the movement. Re-entry method. The method of claim 1, wherein the determining of the relative position in the first step comprises: detecting a focus error signal from reflected light reflected from the recording medium, positive (+) for a predetermined level of the detected focus error signal, Detecting a negative change, and determining a relative position with respect to the focal point position of the recording surface of the objective lens according to the detected change. A digital signal processing unit for reading data and optical signals from a recording medium, an optical pickup for detecting and outputting a total amount of light (FSUM), an error signal, and the like from the optical signals inputted from the objective lens, and a digital signal processing unit A disc reproducing apparatus comprising a servo unit, comprising: objective lens position checking means for checking a state position with respect to a focal position of an objective lens recording surface when data is read from the recording medium, and at a vertex position of the objective lens recording surface; And a system controller that outputs a focus okay signal according to the output signal level reflected from the recording medium when it moves by the detected distance, and reenters it within a predetermined distance when it is spaced above the predetermined distance. To control the driving of the objective lens according to the relative position identified above Focus servo re-input device, characterized in that configured, including water, the lens control means. 4. The objective lens positioning means according to claim 3, wherein the objective lens positioning means compares the total amount of light reflected from the recording medium with a reference signal and outputs a focus ok signal if focusing is possible, and a focus error detected from the reflected light reflected from the recording medium. Position detecting means for detecting a positive (+) or a negative (−) change with respect to a predetermined level of the signal and outputting an up signal or a down signal, and at a position of the focal point of the recording surface of the objective lens according to the detected level change. And an objective lens relative position determining means for determining a relative position relative to the focus servo. 4. The method of claim 3, wherein the objective lens relative position determining means comprises: two AND gates each receiving an OR and DOWN signal from the focusing means of the comparing means and an up or down signal output from the position detecting means, and performing an AND operation on the AND signal; A focus servo re-entry device comprising a flip-flop each receiving an input terminal and outputting a movement signal by the input terminal.