JPH02162531A - Optical information processor - Google Patents

Abstract

PURPOSE:To execute the detection of a focal point in a short time by moving a condensing means along an optical axis and moving the condensing means at a low speed near the focal point based on the output signal of a photo- detecting means. CONSTITUTION:When an objective lens 14 is moved to a prescribed position on the optical axis by a driving coil 15 for focusing, an optical beam is converged on an optical disk 7 through the lens 14. A reflected light goes reversely and is incident through a polarizing beam splitter 13 and condenser lens 16 to an optical detector 17. The output signal is inputted to a D/A converter 18 and inputted through an adder 19 and A/D converter 23 to a main control circuit 1. When a switch 21 is opened at first and a signal corresponding to a driving DS value is inputted from the circuit 1 through the D/A converter 18 to the coil 15, the lens 14 is moved at a high speed from the position, which is most separated from the disk 7, to the disk 7. When a sum signal from the adder 19 is increased and close to the focal point, the lens 14 is moved at the low speed. When the sum signal reaches a threshold, the switch 21 is closed and it is confirmed that a focus difference signal is 0.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an optical information processing device using, for example, an optical disk, and particularly relates to an optical information processing device that improves the initial focusing operation for a previous disk. Regarding equipment.

(Prior art) Conventionally, in the initial focusing operation of focusing a laser beam onto an optical disk, an objective lens is moved at a constant speed in a direction approaching the optical disk while being irradiated with a laser beam, and during this movement, an objective lens is moved toward the optical disk at a constant speed. The focal point was detected.

However, since the focal point position of the laser beam is an extremely minute distance compared to the entire moving distance of the objective lens, it is difficult to detect the focal point position.

Therefore, it is conceivable to move the objective lens slowly to reliably detect the focal point, but in this case, it takes a long time to detect the focal point and is not practical.

(Inventive power (problem to be solved)) This invention solves the problem that it takes a long time to reliably detect the in-focus point, and its purpose is to detect the in-focus point in a short time and The present invention aims to provide an optical information processing device that can perform reliable detection.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a light emitting means for emitting light and a concentrator for condensing the light emitted by the light emitting means onto a recording medium. a light-receiving means for receiving light from a recording medium via the light-collecting means; moving the light-collecting means along an optical axis; and adjusting the light-collecting means based on an output signal of the light-receiving means. A moving means for moving at a low speed near the focal point is provided.

(Function) That is, the present invention irradiates the recording medium with light emitted from the light emitting means via the condensing means, receives the light reflected from the recording medium by the light receiving means via the condensing means, When detecting a focused point from this received light output, the moving means moves the focusing means along the optical axis of the focusing means, and the focusing means is moved at a low speed near the focused point, making it shorter than conventional methods. This makes it possible to reliably detect the focused point in a short amount of time.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, a main control section 1 controls the entire apparatus. A motor control section 2, a linear motor control section 3, a laser control section 4, a focusing control section 5, a tracking control section (not shown), etc. are connected to the main control section 1.

The motor control section 2 drives a motor 6 in accordance with a control signal supplied from the main control section 1, and the optical disk 7 is rotated by the motor 6 at, for example, a constant speed.

Information is recorded and reproduced on the optical disc 7 using an optical head 8.
carried out by This optical head 8 is driven by a linear motor 9. The linear motor control section 3 includes:
According to the control signal supplied from the main controller 1, the linear motor 9 is driven and controlled, and the optical head 8 is moved to the optical disk 7.
It moves in the radial direction.

The optical head 8 is provided with a semiconductor laser 1o. This semiconductor laser 10 is controlled by the laser control section 4. That is, the laser control section 4
According to the control signal supplied from I, the semiconductor laser 10
to drive. Further, a detector 11 is provided near the semiconductor laser 10 to detect monitor light output from the semiconductor laser 10. This detector 11 is connected to a laser control section 4, and the laser control section 4 controls the light emission output of the semiconductor laser 10 according to the output signal of the detector 1].

On the other hand, the diverging laser beam generated by the semiconductor laser 10 is converted into a parallel beam by the collimator lens 12 and guided to the polarizing beam splitter 13. The laser beam guided to the polarizing beam splitter 13 passes through the polarizing beam splitter 13 and is focused onto the recording surface of the optical disk 7 by the objective lens 14 .

The objective lens 14 is supported movably in the front axis direction and in the direction perpendicular to the optical axis by a support body (not shown), and is supported by a focusing drive coil 15 and a tracking drive coil (not shown). It is about to be moved. When the objective lens 14 is moved to a predetermined position on the optical axis, the beam waist of the laser beam focused by the objective lens 14 is aligned with the optical disc 7.
The minimum beam spot is formed on the surface of the recording film of the optical disc 7. In this state,
The objective lens 14 is maintained in a focused state and in a state where tracking control is possible (in-track state), and information can be written and read.

Further, the laser beam reflected from the recording surface of the optical disk 7 is incident on the polarizing beam splitter 13 via the objective lens 14 . This laser light is transmitted to the polarizing beam splitter 1
3 and is irradiated onto the photodetector 17 by the condensing lens 16.

This photodetector 17 converts the light irradiated by the condensing lens 17 into an electrical signal, and is composed of, for example, two photodetection cells.

The output terminal of this photodetector 17 is connected to an error amplifier (D.

A) 18 and an adder (ADD) 19.

The error amplifier 18 generates a focus difference signal from the signals output from the two photodetection cells constituting the photodetector 17. This focus difference signal is the A/D
The signal is supplied to the main control unit 1 via the converter 20 and to the driver 22 of the drive coil 15 via the switch 21 . The output signal of this error amplifier 18 is transmitted to the objective lens 14 during the initial focusing operation.
used to detect the focal point position.

Further, the adder 19 adds the output signals of the two photodetection cells constituting the photodetector 17 to generate a focus sum signal. This focus sum signal is A
The signal is supplied to the main control section 1 via the /D converter 23.

The output signal of the adder 19 is used to determine whether the objective lens 14 approaches the in-focus position during the initial focusing operation.

The switch 21 is turned on and off according to a control signal supplied from the main controller 1. That is, when performing the initial focusing operation, the switch 21 is turned off,
When the initial operation is completed, it is turned on and a focus servo loop is played.

The driver 22 includes an OP amplifier 24, a resistor 25 connected between the inverting input terminal of the OP amplifier 24 and the switch 21, a resistor 26 connected between the inverting input terminal and the output terminal,
and a resistor 27 whose one end is connected to the inverting input terminal.

The other end of this resistor 27 is connected to the output end of a D/A converter 28. The input end of this D/A converter 28 is connected to the main control section 1. This D/A converter 28 receives a drive value D of the objective lens 14 supplied from the main controller 1.
S is converted into an analog signal and supplied to the OP amplifier 24.

In the case of an initial focusing operation in which the switch 21 is turned off, the driver 22 drives the drive coil 15 according to the output signal of the D/A converter 28, and
When turned on, the drive coil 15 is driven according to the output signal of the error amplifier 18, and the objective lens 14 is moved.

In the above configuration, the initial focusing operation will be explained with reference to FIG.

When performing the initial focusing operation, the main controller 1 first turns off the switch 21 (step 5T1), rotates the optical disk 7, and drives the semiconductor laser 10 by the laser controller 4 (step 5T1). 5T2). When a laser beam is emitted from the semiconductor laser 10, the control circuit 9 outputs a drive value DS for driving the objective lens 14 at every predetermined timing, and this is supplied to the D/A converter 28 (step 5T3).

FIG. 3(a) shows the drive value DS.

This drive value DS has a fast moving speed when the objective lens 14 moves between the initial position farthest from the optical disc 7 and the vicinity of the in-focus point, and between the vicinity of the in-focus point and the closest position to the optical disc 7. The moving speed of the objective lens 14 is set to be slow. The maximum speed for driving the objective lens 14 can be set up to about 30 cm/s.

Furthermore, when detecting a focused point, it is necessary to detect a change in the focus difference signal, so it is necessary to move the objective lens 14 at the slowest possible speed. However, since surface wobbling occurs in the rotating optical disk, if the moving speed of the objective lens 14 is made slower than the speed of the surface wobbling, the rising speed of the optical disk 7 will be faster than the rising speed of the objective lens 14. The in-focus point cannot be detected. Therefore, the speed of surface runout (and the amount of runout 3
(2) If the rotational speed is 600 rpm, the speed needs to be slightly faster than 6 mm/s).

When the driver 22 receives a signal corresponding to the drive value DS from the D/A converter 28, it supplies the signal to the drive coil 15. Therefore, the objective lens 14 is first moved from the initial position farthest from the optical disc 7 in a direction approaching the optical disc 7 at high speed according to the drive value DS.

With this movement of the objective lens 14, it is determined whether the objective lens 14 is approaching the in-focus point. This determination is made based on the output signal of one of the adders, that is, the focus sum signal. This focus sum signal is shown in Fig. 3(b).
As shown in FIG. 2, the signal level has a property that it reaches a maximum at the focal point position FP and decreases as it moves away from the focal point. Therefore, it is determined whether or not this focus sum signal has reached a predetermined threshold value TH (step 5T4).

As a result, if it is less than or equal to the threshold value TH, the drive value of the objective lens 14 is increased (step 5T5), and it is determined whether this drive value has reached the maximum value (step 5T6).

As a result, if the drive value has not reached the maximum value, the objective lens 14 is moved in the direction approaching the optical disk 7 as described above. Furthermore, if the drive value has reached the maximum value, it is determined that focusing has failed, the objective lens 14 is returned to the initial position, and the above-described operation is repeated.

On the other hand, if it is determined in step ST4 that the focus sum signal has reached the threshold value TH, it is determined whether or not the focus position is reached (step 5T8). That is, the focus difference signal output from the error amplifier 18 is as shown in FIG. 3(c).
As shown in the figure, it is determined whether or not it has become "0". As a result, if the focus difference signal is not "0", the drive value DS is further increased (step 5T9), and it is determined whether this drive value DS has reached the maximum value (step 5TIO). As a result, if the maximum value has not been reached, the above operation is repeated.

Further, in step ST8, when the in-focus point is detected, the switch 21 is turned on, and from then on, the focus point is
Servo is performed (step 5TII).

On the other hand, if the in-focus position cannot be detected and it is determined in step 5T10 that the drive value DS has reached the maximum value, it is determined that the objective lens 14 is closest to the optical disc 7. , the objective lens 14 is moved in a direction away from the optical disc 7. That is, the driving value DS of the objective lens 14 is decreased as shown by the dotted line in FIG. Step 5T1B). As a result, if the in-focus point is detected, the switch 21 is turned on as described above (step 5).
T11), if the in-focus point is not detected, it is determined whether the drive value DS has reached the minimum value (step 5T14).
). As a result, if the drive value DS has not reached the minimum value, the above operation is repeated; if the drive value DS has reached the minimum value, it is determined that the focusing operation has failed, and the above operation is performed again (step 5T15). ).

According to the above embodiment, in the initial focusing operation, the objective lens 14 is moved at a high speed at a position away from the in-focus position, and at a low speed at a position close to the in-focus position. . Therefore, the in-focus point can be reliably detected, and since the objective lens 14 is moved at a low speed in a small range near the in-focus point, the focusing operation can be performed in a shorter time than in the past. It is something.

Furthermore, if the objective lens 14 is moved in a direction approaching the optical disk 7 and the focused point cannot be detected, the objective lens 14 is moved in a direction away from the optical disk 7 to detect the focused point. Therefore, since there is an opportunity to detect the in-focus point twice while the objective lens 14 is moving at a low speed, the in-focus point can be detected more reliably than in the past.

In the above embodiment, if the vicinity of the focused point cannot be detected in step ST6, the same operation is repeated from the beginning, but the present invention is not limited to this. If this is not possible, the vicinity of the in-focus position may be detected with the objective lens 14 moving away from the first disk 7, similarly to steps 5T12 to 5T14.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, the light emitted from the light emitting means is irradiated onto the recording medium via the condensing means, and the light reflected from the recording medium is reflected by the condensing means. When the light is received by the light receiving means via the light receiving means and the focused point is detected from the received light output, the moving means moves the light collecting means along the optical axis of the light collecting means, and the light collecting means is moved at low speed near the focused point. By doing so, it is possible to provide an optical information processing device that can reliably detect a focused point in a shorter time than conventional ones.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the invention, and FIGS. 2 and 3 are diagrams for explaining the invention in detail. DESCRIPTION OF SYMBOLS 1... Main control part, 7... Optical disk, 8... Optical head, 14... Objective lens, 15... Drive coil, 17... Photodetector, 18... Error amplifier, 19・
...Adder. Applicant's agent Patent attorney Takehiko Suzue P

Claims (1)

[Scope of Claims] A light emitting device that emits light; a light focusing device that focuses the light emitted by the light emitting device onto a recording medium; and a light receiving device that receives light from the recording medium via the focusing device. and a moving means for moving the light condensing means along the optical axis and moving the light condensing means at a low speed near the focal point based on the output signal of the light receiving means. Information processing device.