JPH0644348B2 - Focus retractor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video disc using an optical pickup,
The present invention relates to a focus pull-in command device that outputs a drive start command to a focus servo device of an optical disk memory device such as a document file.

2. Description of the Related Art Conventionally, the focus pull-in operation of the optical disk memory device is performed several times until the focus is pulled in.
At this time, the focus pull-in operation is performed irrespective of the rotational phase of the recording or reproducing carrier disk (position in the disk circumferential direction).

FIG. 7 shows the relationship between the distance between the optical head and the disk and the focus shift detection signal during the focus pull-in operation in the conventional focus pull-in operation.
In the figure, the optical head 20 moves the disk 40 to X ₁ , X ₂ , X
_The signal level of the focus shift detection signal A changes to A ₁ , A ₂ , A ₃ , A ₄ , A ₅ as it approaches ₃ , X ₄ , X ₅ . When the focus pull-in detection point P of the pull-in detection level is reached, the focus servo loop is closed and the focus servo is activated.

Problems to be Solved by the Invention However, in the conventional configuration as described above, if the surface deviation of the disk is large, the focus pull-in operation is affected. An example will be shown below with reference to FIG. Immediately after the moment when the lens detects the focus pull-in detection point P, when the disk surface moves away from the optical head faster than the lifting speed of the lens due to surface fluctuation of the disk, the focus shift detection signal A'is detected in the normal case. The signal does not show the S-curve shown in FIG. The focus pull-in detection point P'is different from the actual pull-in detection point P (between X ₂ and X _{3 in} FIG. 7), and the optical head is located between X ₁ and X _{2 in} FIG. The focus servo is applied outside the control range) and the focus servo is not applied. If the focus pull-in operation is always performed at a position on the disk circumference where the change speed in the focus direction is large on the disk surface having such surface wobbling, there is a problem that the focus servo is not applied.

An object of the present invention is to relate the timing of pulling the focus to the rotation phase of the disc, and change the disc rotation phase (the position in the circumferential direction) of the focus pull-in detection point each time the focus pull-in operation is repeated, thereby causing the surface wobbling. This is to ensure that the focus is pulled in at a position on the disk circumference where the speed of change in the focus direction of the disk surface is small.

Means for Solving the Problems In order to solve the above conventional problems, the present invention provides
A focus servo device for an optical disk having a concentric or spiral information track, a time control means for outputting a signal when the focus pull-in operation is not performed within a predetermined time, and an optical disk corresponding to the output signal of the time control means. From the current position to the position where the focus pull-in is performed in the circumferential direction of the optical disc by θ ° (0 ° <θ ° <360 °)
A focus pull-in device having a phase control means for changing the phase. Specifically, the phase control means is a reference position detector for detecting a signal indicating a rotation reference position of an optical disc, and an initial setting is made by a detection signal of the reference position detector. A first timer that indicates the rotation phase of the optical disc, a counter that counts the number of times of the focus pull-in operation, and timing detection means that compares and detects a value corresponding to the value of the counter and the value of the first timer. And a time control means for initializing each focus pull-in operation and measuring a time during which the focus pull-in operation is performed.
When the focus pull-in is not completed and the value of the second timer exceeds the time required for the focus pull-in operation, the focus servo apparatus performs the focus pull-in operation according to the output from the timing detection means. It is configured.

Operation With the above-described configuration, first, the reference position detector 71 detects a signal indicating the rotation reference position of the disk, and the first timer 72 is initialized. The first timer indicates a rotation phase of the disc from the rotation reference position of the disc as an elapsed time from the rotation reference position. When the first timer 72 matches the timer value determined according to the counter value of the counter 74 that counts the number of times of the focus pull-in operation, the timing detection unit 73,
The focus pull-in operation start timing is output to the pull-in command means 75.

The pull-in command means 75 is the focus servo device 1
There is no focus pull-in detection signal from 0, and the second
When the timer 76 has exceeded the time required for the focus pull-in, and receives the timing output from the timing detecting means 73, the focus pull-in command is output to the focus servo device 10 to perform the focus pull-in operation.

The second timer 76 is initialized by the focus pull-in command, is driven as a timer for limiting the focus pull-in operation time, the counter is further counted up, and the first of the timing detection means is operated.
Change the comparison value with the timer of to change the disk rotation phase for starting the focus pull-in operation.

When the focus pull-in detection signal from the focus servo device 10 does not arrive before the second timer counts up, the pull-in command means outputs the focus pull-in command again in accordance with the timing output from the timing detecting means.

In this way, the focus pull-in operation is performed while changing the position (rotational phase) in the disc circumferential direction until the focus is pulled in. That is, since the lifting speed of the lens of the optical head is determined by the circuit constant and is constant, the focus pull-in detection point moves in the disk circumferential direction each time the focus pull-in operation is performed.

Embodiment A focus pull-in command device according to an embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 71 denotes a reference position detector that detects a signal indicating the rotation reference position of the disc 40 shown in FIG. 4, and initializes a first timer 72, and 72 denotes a disc from the rotation reference position of the disc 40. The first timer 73 indicates the rotation phase of 40 as the elapsed time from the rotation reference position, and 73 is a counter 7 that counts the number of times of the focus pull-in operation.
When the value of the first timer 72 matches the value determined according to the counter value of 4, the timing detecting means for outputting the focus pull-in operation start timing signal to the pull-in command means 75, 75 is the focus servo device 10 When the output signal from the timing detection means 73 is received in the state where the focus pull-in detection signal is not present and the value of the second timer 76 exceeds the time required for the focus pull-in, the focus pull-in command signal is set to the focus servo signal. It is a pull-in command means for outputting to the device 10 to perform a focus pull-in operation.

Here, the focus pull-in command signal causes the second
The timer 76 is initialized and driven as a timer for limiting the focus pull-in operation time, and the counter 74 is further counted up to change the comparison value with the first timer 72 of the timing detection means 73 to start the focus pull-in operation. Change the disk rotation phase. Then, when the focus pull-in detection signal from the focus servo device 10 is not input before the second timer 76 counts up, the pull-in command means 75 again uses the focus pull-in command signal as the timing output signal from the timing detecting means 73. Output together.

In this way, the focus pull-in operation is performed while changing the position (rotational phase) in the disc circumferential direction until the focus is pulled in. That is, since the lifting speed of the lens of the optical head is determined by the circuit constant and is constant, the focus pull-in detection point moves in the disc circumferential direction at each focus pull-in operation.

The phase control means includes the reference position detector 71, the first timer 72, the counter 74, and the timing detection means 7.
3 and the time control means includes a second timer 76.

FIG. 2 is a block diagram showing a more specific structure of an embodiment of the present invention. This embodiment will be described below with reference to FIG.

In FIG. 2, reference numeral 1 denotes a central processing unit (hereinafter referred to as cpu), which has an address bus AB, data buses DB and R.
It interfaces with peripheral devices by a control bus CB such as EAD / WRITE. Reference numeral 2 denotes a read-only memory (hereinafter, referred to as ROM), which stores a control program for cpu1. 3 is an arbitrary access memory (hereinafter referred to as RAM), which is a 2-bit counter memory 3
It is used as a data memory of cpu1 including a. 40
Is an optical disk, and as shown in FIG. 4, an index mark 41 indicating a rotation reference position, which has a reflectance different from that of the periphery, is recorded on the inner peripheral portion. A disk motor 30 rotates the disk 40 at a constant rotation speed.

Reference numeral 5 denotes a photo interrupter having a function as a reference position detector, which detects the index mark 41 of the disc 40. The first timer 6 is set so that the timer value per one rotation of the disc becomes T ₁ , and is reset every time the photo interrupter 5 detects the index mark 41.

The cpu1 determines the output timing of the focus pull-in command signal based on the value of the counter memory 3a in the RAM3. Now, let the value of the counter memory 3a be N. cpu
1 waits for the timer value of the first timer 6 to reach T1 / 4 · N, and the focus servo device 10 waits for I / O port 4
A focus pull-in command signal is output through the counter, the timer value of the second timer 7 is initialized and driven, and the counter memory 3a is counted up. If the pull-in detection signal (described in FIG. 3) from the focus servo device 10 cannot be detected through the I / O port 4 by the time the second timer 7 exceeds the time T ₂ required for one focus pull-in operation, If the focus pull-in operation is not performed correctly, the focus pull-in command signal is turned off, and the timing for turning on the next pull-in command is waited for. Next, the timing for turning on the focus pull-in command signal is the first timer 6 considering that the value of the counter memory 3a is counted up when the focus pull-in command signal is output before, that is, 1 is added here. The timer value turns on when the timer value becomes T1 / 4 (N + 1). Therefore, the position of the optical head 20 on the disk circumference when the focus is pulled in is shifted from the previous position by T1 / 4, that is, the disk 1/4 circumference, as a timer value. In this way, the focus pull-in operation is performed while changing the position in the disc circumferential direction until the focus is pulled in.

FIG. 3 shows an embodiment of a detector of a focus pull-in detection signal, in which the reflected light of the laser light from the disc is received by the two-divided photodetector 11 and the focus shift used for the focus servo from the difference signal of the two-divided photodetector 11. The detection signal is obtained and the disc 40 is obtained from the sum signal
The bit information recorded in 1 is obtained, and the sum signal is passed through the comparator 14 to detect the level, thereby obtaining the focus pull-in detection signal. Reference numeral 15 is a power source for generating a reference voltage.

The programs written in the ROM 2 are shown in flowcharts in FIGS. 5 and 6.

FIG. 5 shows a program of the pull-in command means 75,
In step 51, the focus pull-in detection signal is checked, and if the focus is pulled in, nothing is done and the process ends. If the focus is not pulled in, step 52
Do. In step 52, the value of the second timer 76 is read, and if the pull-in operation time is not over, that is, if the focus pull-in operation is in progress, go to step 51. If not, go to step 53 to turn off the focus pull-in command, and Proceed to 54. Step 54
Corresponds to the timing detecting means 73 (details are shown in FIG. 6). Here, when the timing for starting the focus pull-in is detected, steps 55 to 57 are executed. That is, the contents of the counter memory 3a in the RAM 3 for turning on the focus pull-in command (step 55), driving the second timer 76 for measuring the time limit of the focus pull-in operation (step 56), and storing the number of times of the focus pull-in operation. Count up (step 5
7) and returns to step 51.

FIG. 6 shows a program of the timing detecting means 73, and in steps 58 and 59, the lower two bits of the counter memory 3a.
The value of the bit is loaded into register A provided inside cpu1. In step 60, the on-timing of the pull-in command is calculated from the value of the counter memory 3a of the register A, and in steps 61 and 62, while checking the value of the first timer 72, wait until the on-timing of the pull-in command comes. After the on-timing, the focus pull-in command output program of step 55 and thereafter in FIG. 5 is executed. The surface wobbling cycle of the disk is one cycle for one rotation of the disk. Therefore, here, the timing of the focus pull-in command is shifted by 1/4 cycle (rotation phase 90 °), and the speed of the surface wobbling in the first focus pulling operation is performed. The focus pull-in detection point is detected at a position on the circumference of the disc where the surface run-out speed is low because the rotation phase of the pull-in timing is deviated by 90 ° in the second pull-in operation Therefore, the focus pull-in operation can be reliably performed, and the number of times of focus pull-in retries can be reduced. It is also possible to use a signal detected from the rotation reference signal of the motor 30 as the rotation reference position signal.

As described above, according to the present invention, the focus detection position on the disc changes along the disc circumferential direction each time the focus pulling operation is retried. It is possible to prevent the pull-in detection, and to reliably pull in the focus at a place where the surface wobbling speed is low. In addition, the number of retries for focus pull-in is reduced by making the amount of change in the output timing of the focus pull-in command 1/4 cycle by utilizing the property that the surface runout has one cycle for one rotation. In addition, the focus pull-in operation can be reliably performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a focus pull-in command device in one embodiment of the present invention, FIG. 2 is a block diagram showing the concrete configuration of the same embodiment, and FIG. 3 is a block of a focus signal detector section. 4 and 5 are a top view of the disk showing the disk shape of this embodiment, FIG. 5 is a flow chart of the pull-in command means in the present invention, FIG. 6 is a flow chart of the timing detection means, and FIG. FIG. 8 is a correlation diagram showing the relationship between the distance between the lens surface and the disk surface and the focus shift detection signal, and FIG. 8 is a waveform diagram showing the influence of surface wobbling on focus pull-in. 1 ... Central processing unit, 2 ... Read-only memory, 3
…… Arbitrary access memory, 4 …… I / O port, 5 ……
Photointerrupter, 6, 72 ... First timer,
7,76 Second timer, 10 Focus servo device, 11 Photo detector, 20 Optical head, 40 Optical disk, 41 Index mark, 71 Reference position detector, 73 Timing detection means, 74 ... Counter, 75 ... Pull-in command means.

Claims (6)

[Claims] 1. A focus servo device for an optical disk having a concentric circle or spiral information track, a time control means for outputting a signal when a focus pull-in operation is not performed within a predetermined time, and an output signal of the time limiting means. A focus pull-in device provided with phase control means for changing the focus pull-in position of the optical disc from the present position in the circumferential direction of the optical disc by θ ° (0 ° <θ ° <360 °). 2. The method according to claim 1, wherein the position for detecting the focus pull-in of the optical disc is changed by 1/4 cycle from the present position in the circumferential direction of the optical disc in response to the output signal of the time limiting means. Focus retractor. 3. The phase control means includes a reference position detector for detecting a signal indicating a rotation reference position of the optical disc, and a first timer which is initialized by a detection signal of the reference position detector and indicates a rotation phase of the optical disc. A counter for counting the number of times of the focus pull-in operation, and a timing detecting means for comparing and detecting a value according to the value of the counter and the value of the first timer, and the time control means is initialized for each focus pull-in operation. The focus servo apparatus is provided with a second timer that measures the time that is set and the focus pull-in operation is performed, and the focus servo apparatus has not completed the focus pull-in and the value of the second timer exceeds the time required for the focus pull-in operation. In this case, the patent contract is configured to perform the focus pull-in operation according to the output from the timing detection means Focus pull device ranging first claim of. 4. The timing detecting means, each time the counter counts the focus pull-in command signal, sets the value indicating the rotational phase deviated by 1/4 rotation from the rotational phase in which the focus pull-in operation is performed last time and the value of the first timer. The focus pull-in device according to claim 3, wherein the focus pull-in device is configured to perform comparative detection. 5. The focus pull-in device according to claim 3 or 4, wherein the rotation reference position of the optical disc is obtained by a signal corresponding to a mark provided on the optical disc. 6. The focus pull-in device according to claim 3, wherein the rotation reference position of the optical disc is obtained by a signal from a motor for rotating the optical disc.