JPH06243480A - Focus servo pull-in controller - Google Patents

Abstract

PURPOSE:To provide a focus servo pull-in controller which can quickly pull an objective lens into a focus servo position where the objective lens is focused on the surface of a recording medium. CONSTITUTION:When an objective lens 4 passes through its in-focus position, the focus signal level is measured by a signal level measuring means 11. Then a measurement end detector means 15 detects that the measurement of the focus signal level is complete. Thus the shifting direction of the lens 4 is inverted by a shifting direction inverter means 16 based on the detection signal of the means 15. Then the lens 4 is pulled into a focus servo position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus servo pull-in control device for pulling an objective lens of an optical pickup in an optical recording / reproducing apparatus into a focus servo which is a position where its focus is focused on the surface of a recording medium. .

[0002]

2. Description of the Related Art In recent years, for example, optical disk devices have been used for recording and reproducing video signals and audio signals. The optical disk devices are equipped with the focus servo pull-in control device as described above.

An example of a conventional focus servo pull-in control device provided in the optical disk device will be described below with reference to FIGS. 3 and 4.

FIG. 3 is a block diagram showing a configuration of a conventional focus servo pull-in control device, and FIG. 4 is a graph showing temporal changes of a focus signal and a lens drive instruction signal in the same device. In the figure, 1 is a recording medium on which an information signal is recorded, 2 is a spindle motor for rotating the recording medium 1, 3 is a light source for generating a light beam, 4 is an objective lens for collecting the light beam from the light source 3, Reference numeral 5 is a half mirror that changes the direction of light reflected by the recording medium 1, 6 is lens driving means that moves the objective lens 4 to change the focus position, and 7 is reflected light from the recording medium 1 via the half mirror 5. A light receiving element for receiving the light, 8 is a focus signal generating means for generating a focus signal, 9 is a focus position detecting means for detecting a focus position, and 10 is a focus servo pull-in drive output for reversing the moving direction of the objective lens 4. Focus servo pull-in drive output generating means for generating
Reference numeral 1 is a signal level measuring means for measuring a focus signal level, which is information indicating the position of the objective lens 4 in the focus direction, and 12 is a focus servo loop filter for outputting a signal for pulling the objective lens 4 into the focus servo. A switch 13 selectively switches between a state in which the focus servo pull-in drive output generating means 10 and a state in which the focus servo loop filter 12 issues an operation instruction to the lens driving means 6.

Next, the operation of the focus servo pull-in control device having the above structure will be described. First, the light beam emitted from the light source 3 is condensed by the objective lens 4 on the recording medium 1 rotated by the spindle motor 2, and is irradiated onto the recording surface of the recording medium 1 to be reflected. This reflected light is
The direction is changed by the half mirror 5 and the light receiving element 7 is irradiated with the light. The signal indicating the amount of light detected by the light receiving element 7 is
It is converted into a focus signal by the focus signal generating means 8.

When the objective lens 4 is pulled into the focus servo whose focus is on the surface of the recording medium 1 at the focus position, a drive instruction to the lens driving means 6 is issued to the focus servo pull-in drive output generating means 10. one contact 14 ₁ of the switch 13 to perform from the state of FIG. 3
Switch to the side. Then, a drive instruction signal is sent from the focus servo pull-in drive output generating means 10 to the lens driving means 6, and the objective lens 4 is sent based on the drive instruction signal.
Is moved to the lowest point once, and then the level of the focus signal is measured by the signal level measuring means 11 at the in-focus position while pulling up from the lowest point, and based on the measurement result, the focus servo system loop filter 12 Adjust the sensitivity of. Following this, the in-focus position detecting means 9 is pulled down while lowering the objective lens 4 that has moved to the highest point.
The in-focus position is detected by means of the switch, and if the in-focus position is detected, the switch 13 is moved to the other contact 14 _{2 as} shown in FIG.
Switch to the side. Then, a drive instruction signal is sent from the focus servo system loop filter 12 to the lens driving means 6, and the objective lens 4 is driven based on the drive instruction signal to pull in the focus servo.

In the above operation, the temporal changes of the focus signal at the point a and the lens drive instruction signal at the point b in FIG. 3 are as shown in FIG.

[0008]

However, in the conventional focus servo pull-in control device, the objective lens 4 is once moved to the in-focus position, the level of the focus signal is measured, and then the objective lens 4 is moved again. After returning to the initial position, the objective lens 4 is moved and pulled into the focus servo.

Therefore, there is a drawback that the moving distance of the objective lens 4 becomes long and the objective lens cannot be quickly pulled into the focus servo after measuring the focus signal level.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a focus servo pull-in control device capable of quickly pulling the objective lens into the focus servo after measuring the focus signal level. .

[0011]

In order to achieve the above object, the focus servo pull-in control device of the present invention comprises a measurement completion detecting means for detecting the completion of the measurement of the focus signal level, and a measurement completion detecting means of the measurement completion detecting means. And a moving direction reversing means for reversing the moving direction of the objective lens in order to draw the objective lens into the focus servo based on the detection signal.

[0012]

According to the present invention, when the measurement completion detecting means detects that the focus signal level measurement is completed, the moving direction reversing means reverses the moving direction of the objective lens based on the detection signal. Then, the objective lens is pulled into the focus servo, which is the position where the focal point of the objective lens is focused on the surface of the recording medium. This minimizes the moving distance of the objective lens until the focus servo pull-in is completed, and the objective lens can be pulled into the focus servo promptly after measuring the focus signal level.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the focus servo pull-in control device of the present invention will be described below with reference to FIGS. 1 is a block diagram showing the configuration of a focus servo pull-in control device according to an embodiment of the present invention, FIG.
3 is a graph showing temporal changes of a focus signal and a lens drive instruction signal in the same device.

Reference numeral 1 is a recording medium on which an information signal is recorded, 2 is a spindle motor for rotating the recording medium 1, 3 is a light source for generating a light beam, 4 is an objective lens for focusing the light beam from the light source 3, 5 Is a half mirror that changes the direction of the light reflected by the recording medium 1, 6 is a lens driving unit that moves the objective lens 4 to change the focus position, and 7 is the half mirror 5 that reflects the reflected light from the recording medium 1. A light receiving element for receiving light, 8 is a focus signal generating means for generating a focus signal, 9 is a focus position detecting means for detecting a focus position,
Reference numeral 10 is a focus servo pull-in drive output generating means for generating a focus servo pull-in drive output for reversing the moving direction of the objective lens 4, and 11 is a signal for measuring the focus signal level, which is information indicating the focus direction position of the objective lens 4. The level measuring means 12 is a focus servo loop filter that outputs a signal for pulling the objective lens 4 into the focus servo. A switch 13 selectively switches between a state in which the focus servo pull-in drive output generating means 10 and a state in which the focus servo loop filter 12 issues an operation instruction to the lens driving means 6.

Further, between the signal level measuring means 11 and the focus position detecting means 9, there is provided a measurement completion detecting means 15 for detecting that the measurement of the focus signal level by the signal level measuring means 11 is completed. , between one of the contact 14 ₁ of the focus servo pull-in drive output generating means 10 and the switch 13, the drive output direction reversing means 16 which reverses the direction of the focus servo pull-in drive output is provided.

Next, the operation of the focus servo pull-in control device having the above structure will be described. First, the light beam emitted from the light source 3 is condensed on the recording medium 1 rotated by the spindle motor 2 by the objective lens 4, and is irradiated onto the recording surface of the recording medium 1 to be reflected. This reflected light is
The direction is changed by the half mirror 5 and the light receiving element 7 is irradiated with the light. A signal indicating the amount of light detected by the light receiving element 7 is converted into a focus signal by the focus signal generating means 8.

Here, when the objective lens 4 is pulled into the focus servo, the switch 13 is set to the state shown in FIG. 1 so that the focus servo pull-in drive output generating means 10 and 11 give a drive instruction to the lens driving means 6. From one contact 14 _a side. Then, a drive instruction signal is sent from the focus servo pull-in drive output generating means 10 to the lens driving means 6, and the objective lens 4 is once moved to the lowest point based on the drive instruction signal.
While raising from the lowest point, the level of the focus signal is measured by the signal level measuring means 11 at all focal positions, and the sensitivity of the focus servo system loop filter 12 is adjusted based on the measurement result. Subsequent to this, if the measurement completion detecting means 15 detects the measurement completion of the focus signal level, the drive output inverting means 1
6, the moving direction of the objective lens 4 is reversed, the focusing point emitting means 9 detects the focusing point while pulling down the objective lens 4, and if the focusing point is detected, the switch 13 is shown in FIG. As described above, the contact is switched to the other contact 14 _b side. Then, a drive instruction signal is sent from the focus servo system loop filter 12 to the lens drive means 6, and based on the drive instruction signal, the objective lens 4 is driven and pulled into the focus servo.

In the above operation, the temporal changes of the focus signal at point a and the lens drive instruction signal at point b in FIG. 1 are as shown in FIG. As is clear from FIG. 2, in the device of the present invention, the moving distance of the objective lens 4 is shorter than that of the conventional device, and the objective lens is quickly pulled into the focus servo after the measurement of the focus signal level is completed. Is something that can be done.

[0019]

As described above, according to the focus servo pull-in control device of the present invention, the movement distance of the objective lens is minimized, and the fluctuation of the focus signal is adjusted and the objective lens is pulled into the focus servo. Therefore, there is an effect that the time from the completion of the measurement of the focus signal level to the completion of the drawing of the objective lens into the focus servo can be shortened by about 30% as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a focus servo pull-in control device according to an embodiment of the present invention.

FIG. 2 is a graph showing temporal changes of a focus signal and a lens drive instruction signal in the same device.

FIG. 3 is a block diagram showing a schematic configuration of a conventional focus servo pull-in control device.

FIG. 4 is a graph showing a temporal change of a focus signal and a lens drive instruction signal in the same apparatus in the related art.

[Explanation of reference numerals] 1 recording medium 4 objective lens 10 focus servo pull-in drive output generating means 16 focus servo pull-in drive output direction reversing means (moving direction reversing means) 11 focus signal level measuring means 15 measurement completion detecting means

Claims (1)

[Claims] 1. A focus servo pull-in control device for pulling an objective lens of an optical pickup in an optical recording / reproducing apparatus into a focus servo, which is a position where its focus is focused on the surface of a recording medium. Measurement completion detecting means for detecting that the measurement of the focus signal level, which is information indicating the focus direction position of the object, is completed, and the objective for pulling the objective lens into the focus servo based on the detection signal of the measurement completion detecting means. A focus servo pull-in control device, comprising: a moving direction reversing means for reversing a moving direction of a lens.