JPS58212633A - Focus controller - Google Patents

Abstract

PURPOSE:To stabilize the transmission and reception of information between a device and a medium, by automatically compensating the variation of offset of s focus servo device in an optical information storing device. CONSTITUTION:An optical beam is irradiated to a recording medium 5 through a half mirror 20, a focus actuator 2 and an objective lens 4 and the reflected light is formed in accordance with the recording status. The reflected light is refracted by the half mirror 20 through the objective lens 4 and the focus actuator 3 and detected by an optical detector 6. A signal read out from the optical detector 6 is supplied to a read amplifier 7 and a focus error detector 1 to detect the quantity of defocusing of the optical beam irradiated to the recording medium 5. A DC amplifier 2 connected to the focus error detecting circuit 1 amplifies the output signal from the focus error detecting circuit 1 and drives the foucs actuator 3 to drive the objective lens 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a focus system Ni
Regarding equipment.

Conventionally, in the original academic type information storage device, in order to stably write information to the recording medium or continue writing information to the recording medium, the rc source focus TiSd is always connected to the recording medium surface by 1°, following the fluctuation of the recording medium surface. - Has manual equipment.

Generally, the original beam in this type of device has a depth of focus of about 1 μm when focused on the medium surface, but if we assume that the deflection of the medium surface relative to the objective lens when the servo is opened is 500 μm, ``In order to make the objective lens follow the medium surface with an accuracy of about 1 μm in the range of the focal point RK by the servo means, a large servo gain of approximately 500 times L is required. For this reason, in conventional servo means, even if a slight offset occurs in the servo system due to temperature changes or the like, the focus of the original beam may deviate from the medium surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a focus control device that fully automatically corrects the offset change of a focus servo device in an optical information storage device and supports information exchange between the device and the medium.

According to the present invention, there is a redundant heap t on a rotating disc-shaped recording medium.
- A servo means for focusing, a successive means for reading out multiple information from a recording medium by the reflected light of the original beam, and an envelope detection of the successive signal of the information in the original information storage device tIt. a detection means, a memorization level for storing a detection blade at a certain point in time, a comparative means for comparing the stored detection blade and a currently detected detection output; and an output of the comparison means. and an offset correction intermediate wave that outputs a control output in the direction of offset (7) for determining the offset (7) of the servo means, and outputting a control output in the direction of offsetting the offset (1).
A focus control device is obtained in which the reliability of the data is improved by correcting the offset signal of the servo means by the output of the positive means, and securing φ such as the S/N ratio amplitude of the successive signal.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an original academic-style information storage device which is an embodiment of the present invention. In FIG. 1, this embodiment includes a rotatable disk-shaped recording medium, means for focusing the original beam on the recording medium 5, servo means thereof, and offset correction means for offsetting the servo means. The original beam from the light source passes through the half mirror 20° focus actuator 3 and the objective lens 4 and is irradiated onto the recording medium. The recording medium 5 generates reflected light depending on its recording state. This reflected light passes through the objective lens 4 and the focus actuator 3, is refracted by the half mirror 20, and is detected by the photodetector 6. The readout signal from the photodetector 6 is supplied to the readout amplifier 7 and the focus error detection circuit 1, and the focus error detection circuit 1 detects the amount of defocus of the original beam irradiating the recording medium 1. The DC amplifier 2 connected to the focus error detection circuit 1 receives the output signal from the focus error detection circuit 1? i- podium width, objective lens 4t-
The focus actuator 3 to be driven is driven.

The output amplifier 7 sends out its output signal as read information and also supplies it to the envelope detector 8. The envelope detector 8 generates an envelope of the readout signal and supplies the output signal to the memory 9 and the comparator 10. The memory 9 is, for example, an analog memory, and holds an analog 111tt of the envelope at the falling edge of the control signal 11 of the procedure controller 12 based on an index signal to be described later. The comparator IO compares the cutting edge signal of the envelope detector 8 with the output of the memory 9, and supplies the output 16, 17t, and procedure controller 121C of the comparison result.

The procedure controller 12 performs the functions shown in the flowchart of FIG.
- has a recording medium and is activated by an index signal indicating the position of information in the rotating recording medium. The blade signal of this procedure controller 12 is a digital signal 16, and the L)/A converter 13
supplied to The L)/A converter 13 supplies the cutting signal to the DC amplifier 2 and controls the DC amplifier 2t. Based on this, the DC amplifier 2 operates the focus actuator 3 to move the objective lens 4t closer to or farther from the medium.

In such a configuration, for example, when an offset occurs in the DC amplifier 2 due to a temperature change or power supply fluctuation, the actuator 3 is driven to change the distance between the medium surface and the lens 4, so that the combination on the medium surface is The focal state is distorted and the beam spot becomes broad, making it impossible to irradiate only the information bits recorded at about 1 .mu.m. A decrease in the readout level can also occur due to dirt on the medium surface or a decrease in the amount of irradiation source, but the irradiation light has a loop that monitors the source violet near the light source and feeds back to the light source driver to keep the amount of light emitted constant. If you create it, it will be stable. When a laser diode is used as a light source, the amount of light changes greatly depending on its temperature characteristics, so the above method has been generalized. In addition, dirt on the surface of the medium mainly occurs due to fogging caused by friction and changes in temperature and humidity, but such dirt can be prevented in the next state when the medium is attached to an apparatus.

Therefore, it can be concluded that the changes in the readout level in closely spaced time periods are due to offset in the focus servo system.

For the above-mentioned reasons, this embodiment attempts to determine the degree of focus based on the change in the readout level that is actively applied to the focus servo system.

First, let me explain with reference to the flowchart 7 in Figure 2.
The procedure controller 12 uses an index signal to store the current read level and the output of the envelope detector 8 in a memory 9.
to be memorized. Next, the DC amplifier 2 is biased in a direction that brings the lens 4 slightly closer to the medium. At this time, the output of the envelope detector 8 and the output of the memory 9 are compared, and if the output of the envelope detector 8 is larger, it is assumed that this is in focus better than the previous state, and the bias is applied to this position. to be fixed. If the output of the storage device 9 is larger, the DC amplifier 2t is biased in a direction that moves the lens 4t away from the medium twice as much as the previously moved tray.

Similarly, the output of the memory device 9 and the output of the envelope detector 8 are compared, and if the output of the envelope detector is large, the bias gold is fixed. If the edge of the memory device 9 is larger, it is assumed that the initial state was the optimum value, and the bias is completely changed and fixed so that the lens 4t returns to its original position. The amount of movement of the lens 4 is suitably about 1 μm, which is equivalent to the depth of focus of the beam spot. Since this operation uses information that has already been recorded, it is not convenient in areas where no information is recorded, such as on a direct read after write (DRAW) medium. Further, it is preferable that the information to be referred to be uniform so that the envelope is constant. For this reason, as shown in FIG. 3, it is more effective to use a medium on which certain information, as shown in FIG. 4, is pre-recorded in a certain part.

As explained above, the present invention is directed to the offset servo system that occurs in the shift focus servo system by adopting such a configuration. compensate,
The effect of improving the reliability of continuous information can be seen.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart of a control procedure, FIG. 3 is a diagram showing an embodiment of a medium according to the present invention, and FIG. FIG. 2 is a diagram illustrating one embodiment of information pre-recorded on a medium according to the present invention. 1...Focus error detector, 2...
・DC amplifier, 3... Focus actuator, 4... Track/objective lens, 5... Medium, 6...
...Photodetector, 7...Readout amplifier, 8.
... Envelope detector, 9... Group memory, 10...
... Comparator, ll ... Memory control notes, 12
...Procedure controller, 13...1)/A rhombus switch, 15...Index No. 16, 17...
...Comparison result signal, 3o1...Glue layer information area. Mine 3 anti○ 0 0 Mr. Gu Hayabusa+I Ki wo+Kuni

Claims (1)

[Claims] (1) An original academic information storage system comprising means for focusing an original beam on a rotating disk-shaped recording medium, a servo means thereof, and a successive means for reading out information from the recording medium using a reflection source of the original beam. fjlii[: a detection means for envelope detection of the successive notes of the information, and a storage means for storing the detection output at a certain point in time. The stored nine detection waves, the currently detected detection output, and t
Comparing means for determining the base plate, and offset correcting means for determining the offset 1 of the first move based on the output of the comparing means and generating a control output in a direction to offset the offset If, and the offset correcting means A focus control device that corrects the offset of said servo means based on the output of said servo means. 2) The focus control device according to claim 1, wherein the disc-shaped recording medium is a medium on which information t, which is a reference for detecting off-cell tracking, is pre-recorded.