JPH04252430A - Automatic focusing adjuster - Google Patents

Abstract

PURPOSE:To quickly correct out-of-focus by providing a focusing offset impression means which discriminates the out-of-focus direction from a focusing error signal, and corrects the out-of-focus based on the result of discrimination. CONSTITUTION:A focusing servo circuit is provided with a focusing error amplifier 11 which inputs focusing detectional signals (+) and (-), an adding point 12 for focusing servo, a focusing phase compensation circuit 13, and a focusing driving circuit 14. Also, it is provided with a focusing addition amplifier 15 which inputs the focusing detectional signals (+) and (-) in addition to the amplifier 11 for focusing servo and obtains a focusing sum signal B by performing addition and amplification, a polarity discrimination circuit 16 which inputs a focusing position error signal A at the focusing position of the amplifier 11 and the focusing sum signal B and obtains out-of-focus directional signals C, D, and an offset impression circuit 17 which outputs focusing offset signal output E corresponding to the out-of-focus directional signals C, D.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an automatic focus adjustment method, and more particularly, to an optical disc-based information recording and reproducing device, a focus servo is used to track a minute spot on the recording track of the optical disc. The present invention relates to an automatic focus adjustment device applied to a circuit.

0002

2. Description of the Related Art FIG. 3 shows a schematic configuration of a conventional focus servo circuit of this type.

That is, in the focus servo circuit shown in FIG. 3, focus detection signals (+) and (-) obtained by irradiating a light beam from an optical means onto an optical disk are sent to a focus error amplifier 1 and a focus detection signal (-). A focus servo is configured by passing through a phase compensation circuit 4 and a focus drive circuit 5, and for focus adjustment, a semi-fixed resistor 3 that is set to a desired value in advance is used.
This is done by applying the offset output to the focus offset addition point 2.

0004

However, in the case of the focus adjustment device in the conventional focus servo circuit having the above configuration, after adjusting the setting of the semi-fixed resistor 3,
Since the offset application amount is fixed, there is a problem in that it is not possible to quickly respond to changes in focus during use.

[0005] The present invention is an attempt to improve such conventional problems, and an object thereof is to provide an automatic focus adjustment device that can quickly respond to changes in focus in a focus servo circuit. It is something to do.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a focus shift polarity determining circuit and a focus offset application circuit, so that when a focus shift is detected, an offset voltage is automatically applied. The focus adjustment can be performed by applying the voltage.

That is, the present invention provides a focus servo circuit that irradiates a disk with a light beam from an optical means to obtain a focus error signal, and uses the focus error signal to track a minute spot on a recording track of the disk. , a focus shift polarity determining means for determining the focus shift direction from the focus error signal, and a focus offset applying means for correcting the focus shift based on the determination result of the focus shift polarity determining means, and automatic focus adjustment can be performed. This is an automatic focus adjustment device characterized by the following features.

[0008]

[Operation] Therefore, in the present invention, when a focus shift occurs due to focus fluctuation, the polarity of the focus shift is determined by the focus shift polarity determining means, and a focus offset is applied by the focus offset applying means to correct the focus shift. It is possible to correct this automatically in response to changes in focus.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an automatic focus adjustment device according to the present invention will be described in detail below with reference to FIGS. 1 and 2.

FIG. 1 is a schematic block diagram showing the configuration of a focus servo circuit to which this embodiment is applied, and FIG. 2 is an explanatory diagram showing the form of signal waveforms in the main parts of the same circuit.

The configuration of the circuit device according to the embodiment of FIG. 1,
In the signal waveform of the main part of the same circuit shown in FIG. It has an addition point 12 for servo, a focus phase compensation circuit 13, and a focus drive circuit 14.

The focus servo circuit includes a focus addition circuit which inputs focus detection signals (+) and (-) to the focus error amplifier 11 and adds and amplifies them to obtain a focus sum signal B. amplifier 1
5, a focus shift polarity determination circuit 16 which inputs the focus position error signal A of the focus error amplifier 11 and the focus sum signal B to obtain focus shift direction signals C and D, and each of the focus shift direction signals C,
This configuration includes an offset applying circuit 17 that outputs a focus offset signal E corresponding to the focus offset signal E.

Here, the focus shift direction signal C is set to "H" when the focus position error signal A shifts in the (-) direction, and similarly, the focus shift direction signal D is set to "H" when the focus position error signal A shifts in the (-) direction. If the error signal B is (
+) outputs "H" when the shift occurs in the direction.

Therefore, in the apparatus of the above embodiment, the focus detection signal (+) by the focus addition amplifier 15
, (-), when a focus shift is detected and a focus sum signal B is output, the focus shift polarity determination circuit 16 detects a focus shift based on the input focus position error signal A and focus sum signal B. At the same time as detecting the direction signals C and D, a focus offset signal E is applied from the offset application circuit 17 to the addition point 12 for focus servo in response to each of these focus shift direction signals C and D. The focus shift can be automatically corrected,
In this manner, in the case of the apparatus of this embodiment, defocus can be automatically detected and then quickly corrected.

[0015]

As is clear from the embodiments described above, the present invention irradiates the disk with a light beam from an optical means to obtain a focus error signal, and uses the focus error signal to create a minute image on the recording track of the disk. A focus servo circuit for tracking the spot is provided with a focus shift polarity determining means for determining a focus shift direction from a focus error signal, and a focus offset applying means for correcting the focus shift based on a determination result of the focus shift polarity determining means. Because I configured it as
When a focus shift occurs due to a change in focus, the polarity of the focus shift is determined by the focus shift polarity determining means, and the focus offset applying means applies a focus offset signal to the servo circuit to correct the focus shift. As a result, it has the advantage of being able to automatically correct for focus fluctuations at all times, and does not require offset adjustment means as in the past. It has excellent features such as the ability to eliminate adjustment of the circuit configuration itself.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the configuration of a focus servo circuit to which an embodiment of an automatic focus adjustment device according to the present invention is applied.

[Fig. 2] An explanatory diagram showing signal waveforms of main parts of the circuit according to the above embodiment.

[Figure 3] A schematic block diagram showing the configuration of a focus servo circuit to which a conventional focus automatic adjustment device is applied.

[Explanation of symbols] 11 Focus error amplifier 12 Focus offset addition point 13 Focus phase compensation circuit 14 Focus drive circuit 15 Focus addition amplifier 16 Focus shift polarity determination circuit 17 Focus offset application circuit (+), (-)
Focus detection signal A Focus position error signal B Focus sum signal C, D Focus shift direction signal E Focus offset signal

Claims (1)

[Claims] 1. A focus servo circuit that irradiates an optical disk with a light beam from an optical means to obtain a focus error signal, and uses the focus error signal to track a minute spot on a recording track of the optical disk. A focus deviation polarity determining means for determining the focus deviation direction from a signal, and a focus offset applying means for correcting the focus deviation based on the determination result of the focus deviation polarity determining means, so that focus can be automatically adjusted. An automatic focus adjustment device featuring: