JPH01144232A - Information processor - Google Patents

Abstract

PURPOSE:To inexpensively apply stable and accurate control on a convergence means by binarizing a signal corresponding to the incident light quantity of a detecting means and keeping the servo gain of a control circuit constant by selecting a gain corresponding to the signal obtained by the above binarization. CONSTITUTION:A laser beam emitted from a semiconductor laser 14 is converged on an optical disk 1 by using an objective lens 11, and two kinds of signals are detected by using light reflected on the optical disk 1, and a subtraction signal and an addition signal can be calculated by a detected detection signal, and a subtracted result and an added result are amplified by the gain corresponding to a resistance value in response to a signal in which the addition signal is binarized, and also, a track shift detection signal can be obtained by amplifying the subtracted result amplified by the gain corresponding to an amplified added result. And the objective lens 11 is driven by the track shift detection signal. In such a way, it is possible to realize the stable and accurate tracking inexpensively as a whole.

Description

Detailed Description of the Invention [Objective of the Invention 1 (Industrial Application Field) The present invention relates to an information processing device such as an optical disk device that records or reproduces information by irradiating an optical disk with Ritto light. .

(Prior art) In recent years, image information such as Bungata, which is generated in large quantities, is photoelectrically converted by two-dimensional optical scanning, and this photoelectrically converted image information is recorded or searched as necessary. Recently, an optical disk device (information processing 3!I! device) has been used as an image recording device in an image information file device that can reproduce and output as a hard copy or soft copy.

Conventionally, such optical disk devices use an optical disk that records information in a spiral or concentric pattern, and records or reproduces information using an optical head that moves linearly in the radial direction of the optical disk using a linear motor. It is becoming more and more popular.

In such a device, when tracking the objective lens in the optical head, the beam may not be irradiated at an appropriate position due to mounting errors or the like. For this reason, the objective lens is driven to the correct track position by taking the difference between two types of detection signals for tracking and passing a current corresponding to the signal difference to the objective lens drive coil. .

That is, as shown in FIG. 4, the beam light (laser light) from the semiconductor laser 14 (light source) is directed onto the optical disk (recording medium) 1 by the objective lens (focusing means) 11, and the reflected light is divided into two parts. The tracking control is performed so that the difference between the outputs of the detector (detection means) 16, that is, the outputs a and b of the amplifier circuits 41 and 42, becomes zero.

In an optical disk device, two detectors 16a are used because the laser beam output is large during recording.

The amount of light incident on the detector 16b also increases, so an analog divider is used to keep the loop gain of the control circuit constant and stabilize the servo system regardless of the magnitude of the incident light on the two detectors 16a and 16b. (The difference signal of two detection signals divided by the sum signal: normalization) 43 is used.

However, in the above-mentioned device, the analog divider 43 is used, but it is very expensive, has poor division accuracy, and is affected by temperature changes or the size of the denominator of the division, resulting in output loss. This has drawbacks such as an offset voltage is generated in the servo, and the servo is operated by the addition of the offset voltage, making it impossible to perform accurate tracking.

Furthermore, for the same reason, focusing control has the disadvantage that accurate focusing cannot be performed.

(Problems to be Solved by the Invention) This invention eliminates the disadvantages of not being able to perform stable and accurate control over the objective lens and being expensive. It is an object of the present invention to provide an information processing device that can perform stable and accurate control over means.

[Structure 1 of the Invention (Means for Solving Problems) The information processing apparatus of the present invention includes a focusing means for focusing light emitted from a light source onto a recording medium, and a focusing means for focusing light emitted from a light source onto a recording medium, and a focusing means for focusing light emitted from a light source onto a recording medium. a detection means for detecting the first and second signals using light; and a detection means for detecting the first and second signals using light; an incident light amount detection means that detects the amount of light incident on the detection means by adding a second detection signal; a binarization means that binarizes the signal from the incident light amount detection means; a first selector for selecting a gain corresponding to the signal binarized by the means;
and a second selection means, and a first selection means detected by the detection means.
．． calculating means for equalizing the signal controlling the focusing means by subtracting the second detection signal; and amplifying the signal obtained by the calculating means with the gain selected by the first selecting means. a first amplification means, a second amplification means for amplifying the signal obtained by the incident light amount detection means with a gain selected by the second selection means, and a signal amplified by the first amplification means. A control means for amplifying the signal with a gain controlled to be constant according to the signal amplified by the second amplification means, and a driving means for driving the focusing means according to the signal from the control means. It is configured.

(Operation) This invention binarizes a signal corresponding to the amount of incident light on the detection means, and selects a gain corresponding to the binarized signal to keep the servo gain of the control circuit approximately constant. , it is possible to use an inexpensive control means with a low dynamic range and a small offset voltage, and therefore the overall cost is low, and moreover, the control of the focusing means can be realized with high precision.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an information processing device, for example, an optical disk device, according to the present invention. That is, an optical disk (recording medium) 1 is moved by an optical head 1 by a motor 2.
It is designed to be rotated at a constant linear velocity with respect to zero. The above-mentioned optical disk 1 has a donut-shaped metal coating layer made of tellurium or bismuth coated on the surface of a circular substrate made of, for example, glass or plastic.

An optical head 10 for recording and reproducing information is provided on the back side of the optical disc 1.

This optical head 10 is configured as follows.

That is, 14 is a semiconductor laser (light source), and this semiconductor laser 14 generates a diverging laser beam.

In this case, when writing (recording) information onto the recording film of the optical disc 1, a laser beam whose light intensity is modulated according to the information to be stored is generated, and the information is read out (reproducing) from the recording film of the optical disc 1. ), a laser beam with a constant light intensity is generated.

The diverging laser beam generated by the semiconductor laser 14 is converted into a parallel beam by the collimator lens 13 and guided to the polarizing beam splitter 12. The laser beam guided to the polarizing beam splitter 12 is reflected by the polarizing beam splitter 12, enters an objective lens (focusing means) 11, and is focused by the objective lens 11 toward the recording film of the optical disc 1.

Here, the objective lens 11 is movably supported by coils 18° 17 in the direction of its optical axis and in the direction perpendicular to the optical axis, and when the objective lens 11 is positioned at a predetermined position, the objective lens 11 The beam waist of the focused laser beam emitted from the optical disc 1 is projected onto the surface of the recording film of the optical disc 1, and the minimum beam spot is
is formed on the surface of the recording film. In this state, the objective lens 11 is maintained in a focused state and a focused track state, and information can be written and read.

Further, the diverging laser beam reflected from the FIA of the optical disc 1 is converted into a parallel beam by the objective lens 11 when focused, and is returned to the polarizing beam splitter 12 again. This laser beam passes through a polarizing beam splitter 12 and is sent to a photodetector (detection means) 1 by a projection lens 15.
6.

The photodetector 16 is composed of photodetection cells 16a and 16b that convert the light imaged by the projection lens 15 into electrical signals.

The outputs of these photodetection cells 16a, 16b (first, second
(detection signal) becomes the output of the optical head 10. That is, the photodetection cells 16a, 1 as the output of the optical head 10
The output of 6b is used for tracking deviation correction and reproduction signal.

The outputs of the photodetection cells 16a and 16b are supplied to amplifier circuits 20 and 21, respectively. These amplifier circuits 20.
21 is the photodetection cell 16a.

It outputs signals obtained by individually amplifying the signals supplied from 16b.

The output of the amplification circuit 20 is a subtraction circuit (numbing means) 22.
The output of the amplifying circuit 21 is supplied to the inverting input terminal of the differential amplifier 22 in the differential amplifier 22a, and the output of the amplifying circuit 21 is supplied to the non-inverting input terminal of the differential amplifier 22a. Further, the outputs of the amplifier circuits 20 and 21 are respectively supplied to the inverting input terminal of an adder 23a in the adder circuit (incident light amount detection means) 23.

The output of the differential amplifier 22a is a resistor R having a different resistance value.
1, R2, and R3 to a selector (first selection means) 24, and the output of the adder 23a is a resistor having a resistance value proportional to the resistance value of each of the resistors R1, R2, and R3. r1. r2. The signals are respectively supplied to the selector (second selection means) 31 via r3. These selectors 24 and 31 binarize the output of the adder 23a using comparators 25a, 25b, etc.
According to the signal from the digitization circuit (binarization means) 25 (that is, the digital signal corresponding to the amount of light incident on the photodetector 16), the voltage from any one of the resistors R1 to R3 and the resistors r1 to r3 is It selects and outputs the respective signals to the gain adjustment amplifiers (first and second amplification means) 27 and 32, and is constructed of, for example, a very inexpensive C-MOS analog switch.

The gain adjustment amplifier 27 receives the signal from the differential amplifier 22a with a gain corresponding to the resistors R1 to R3 selected by the selector 24 based on the output of the binarization circuit 25 and the resistor R27 in the gain adjustment amplifier 27. That is, the difference between the outputs of the photodetecting cells 16a and 16b is amplified using a gain such that the loop gain of the servo system is approximately constant to obtain a difference signal f. Further, the gain adjustment amplifier 32 outputs the adder 23 with a gain corresponding to the resistors r1 to r3 selected by the selector 31 and the resistor r32 in the gain adjustment amplifier 32 based on the output of the binarization circuit 25.
amplify the signal from the photodetection cell 16a, that is, the photodetection cell 16a
, 16b is amplified by a gain such that the loop gain of the system is approximately constant to obtain a sum signal 9.

For example, in the gain adjustment amplifier 27, the selector 24
When resistor R1 is selected in , amplification is performed with a gain of R1/R27, and when resistor R2 is selected by selector 24, amplification is performed with a gain of R2/R27; If R3 is selected and 0, R3/
Amplification is performed with the gain of R27. On the other hand, in the gain adjustment amplifier 32, when the resistor r1 is selected by the selector 31, amplification is performed with a gain of r1/r32, and when the resistor r2 is selected by the selector 31, amplification is performed with a gain of r2/r:
The amplification is performed with a gain of 12, and when the resistor r3 is selected by the selector 31, the amplification is performed with a gain of r3/rqz. As a result, in the above difference signal f, the dynamic range is approximately 1/1 due to the resistances R1 to R3.
3, and in the sum signal 9, the dynamic range becomes about 1/3 due to the resistors r1 to r3 which are proportional to the resistors R1 to R3.

Therefore, even when the detection levels of the photodetection cells 16a and 16b differ due to differences in the intensity of the laser beams, such as during recording and reproduction, it is possible to always obtain a signal at a predetermined detection level. ing.

The output of the gain adjustment amplifier 27, that is, the difference signal f, is supplied to a variable feedback amplifier (control means) 33. Further, the output from the gain adjustment amplifier 32 is supplied to the variable feedback amplifier 33 via a current/voltage conversion circuit 34.

This current/voltage conversion circuit 34 includes the variable feedback amplifier 3
Current source 3 of the transconduction amplifier that constitutes 3
3a in accordance with the output of the gain adjustment amplifier 32, the gain (servo gain) of the variable feedback amplifier 33 is kept constant.

In this case, when the amount of light incident on the photodetector 16 increases, the output of the adder 23a, that is, the addition signal e, increases linearly as the amount of incident light increases, as shown in FIG. Ru. Comparator 25a is turned on at threshold 1lex of this addition signal e, comparator 25b is turned on at threshold e2, and selector 24.31 is switched. As a result, the sum signal q is changed as shown in FIG. Therefore, the dynamic range of the difference signal and the sum signal q is limited to the threshold value Q2/qt. Therefore, in the variable feedback amplifier 33, the signal dynamic range is limited to the threshold value Q2/qt.
A narrow dynamic range of x is necessary and sufficient, and drift and offset can be kept small.

In addition, the response of the variable feedback amplifier 33 is made sufficiently higher than the servo band.
Since the transient response in the direct attack of switching of 4.31 can be ignored, it can be equivalent to an analog divider with an extremely wide range as a whole. Moreover, it responds quickly enough to large changes in the amount of recording or reproducing laser light, and does not cause the servo loop to become unstable.

The output of the variable feedback amplifier 33 is supplied to the drive circuit (drive means) 28 as a track deviation detection signal. This drive circuit 28 is variable 9!13M! Tracking is performed by driving the objective lens 11 by supplying a corresponding N current to the coil 17 that drives the objective lens 11 in the horizontal direction with respect to the recording surface of the optical disk 1 according to a signal supplied from the amplifier 33. This is to correct the deviation.

In this way, even if the output of the adder 23a, that is, the amount of light incident on the photodetector 16 changes, the operation is performed so that the loop gain remains constant.

Next, the operation in such a configuration will be explained.

For example, during playback, the semiconductor laser 14 generates a (continuous) low-intensity laser beam, and during recording, a high current intermittently flows through the semiconductor laser 14 to generate intermittent high-intensity laser beams.

As a result, a laser beam of high intensity (
recording beam) and low-intensity laser beam (reproduction beam)
is uttered.

This laser beam is converted into a parallel light beam by a collimator lens 13, reflected by a polarizing beam splitter 12, and incident on an objective lens 11, and is focused by this objective lens 11 toward the recording film of the optical disc 1.

In this state, when recording information, bits are formed on the track on the optical disk 1 by irradiation with a laser beam of high intensity (recording beam light), and when reproducing information, bits are formed on a track of the optical disk 1 using a laser beam of low intensity. is irradiated with a laser beam (reproduction beam light). The reflected light from the optical disc 1 with respect to this reproduction beam light is converted into a parallel light beam by the objective lens 11, passes through the polarizing beam splitter 12, and passes through the projection lens 15.
irradiates onto the photodetector 16. Therefore, signals corresponding to the irradiated light are output from the photodetection cells 16a and 16b, and these signals are supplied to the amplifier circuits 20 and 21, respectively.

The tracking operation in such a state will be explained. That is, the signals from the amplifier circuits 20 and 21 are respectively supplied to the differential amplifier 22a and the adder 23a. Then, the differential amplifier 22a
The signal obtained by taking the difference between the detection signal from a and the detection signal from the photodetection cell 16b is transmitted to the resistors R1 to R3.
are output to the selector 24 via each of them. Further, the adder 23a adds two signals corresponding to the amount of light incident on the photodetector 16, which is obtained by adding the detection signal from the photodetector cell 16a and the detection signal from the photodetector cell 16b.
It is output to the selector 31 via the value converting circuit 25 and the resistors r1 to r3, respectively.

Thereby, the binarization circuit 25 transfers the digital signal corresponding to the signal supplied from the adder 23a to the selector 24.
Output to 31. Thereby, the selector 24 selects the resistors R1 to R3 according to the digital signal from the binarization circuit 25.
Gain adjustment amplifier 2 selects a signal from either one of the
Output to 7.

Further, the selector 31 selects a signal from any one of the resistors r1 to r3 according to the digital signal from the binarization circuit 25 and outputs the selected signal to the gain adjustment amplifier 32.

The gain WiJ1 adjustment amplifier 27 amplifies the signal from the differential amplifier 22a with a gain corresponding to the resistors R1 to R3 selected by the selector 24 and the resistor R27 in the gain adjustment amplifier 27, and is variable 9! i) Output to the far amplifier 33. Further, the gain adjustment amplifier 32 amplifies the signal from the adder 23a with a gain corresponding to the resistors r1 to r3 selected by the selector 31 and the resistor R32 in the gain adjustment amplifier 32, and performs current/voltage conversion. It is output to the variable feedback amplifier 33 via the circuit 34.

The variable*i amplifier 33 converts the difference signal f from the gain adjustment amplifier 27 into a gain according to the current source 33a controlled by the current/voltage conversion circuit 34 according to the signal @9 from the gain adjustment amplifier 32. It is amplified and output to the drive circuit 28 as a track detection signal. As a result, when recording,
Even when the detection levels of the photodetectors 18a and 16b differ depending on the intensity of the laser beam, such as during reproduction, a signal of a predetermined detection level can always be obtained.

The drive circuit 28 supplies a predetermined current to the coil 17 in accordance with the signal from the variable feedback amplifier 33, and supplies the objective lens 1 with a predetermined current.
1 is driven in a direction perpendicular to the optical axis of the laser beam to perform tracking. As a result, the beam spot formed by the objective lens 11 can be set at the optimum position relative to the tracking position.

Therefore, even when the detection level is different during recording and playback, the servo gain can always be kept constant regardless of the amount of light incident on the photodetector 16, and stable N
J can be performed. This makes it possible to perform accurate tracking.

In this way, the dynamic range required by the variable feedback amplifier 33 is made sufficiently small. As a result, the wider the dynamic range in which signal processing is possible, the greater the drift and offset can be suppressed by limiting the dynamic range. Furthermore, gain adjustment by the selector and resistor is determined by the characteristics of the gain adjustment amplifier. Therefore, the offset and drift are originally small, and therefore the offset and drift can be made extremely small as a whole.

Furthermore, the transient response immediately after switching, which is a problem when the gain is made variable only by the selector, can be ignored by making the response of the variable feedback amplifier sufficiently higher than the servo band. Therefore, as a whole, it can be equivalent to an analog divider with an extremely wide range.

As mentioned above, the signal corresponding to the amount of light incident on the detection means is
By converting the signal into a value and selecting the gain corresponding to the signal obtained by the binarization to keep the servo gain of the control circuit approximately constant, an inexpensive variable feedback amplifier with a low dynamic range and a small offset voltage can be created. Therefore, the overall cost is low, and the objective lens can be controlled with high accuracy.

That is, laser light emitted from a semiconductor laser is focused onto an optical disk using an objective lens, at least two types of signals are detected using the light reflected from the optical disk, and the detected detection signals are used to generate a subtraction signal. The subtraction result and the addition result are amplified with a gain corresponding to the resistance value corresponding to the signal obtained by binarizing the addition signal, and the addition result is amplified according to the amplified addition result (sum signal). A track deviation detection signal is obtained by amplifying the amplified subtraction result (difference signal) using a gain, and the objective lens is driven by this track deviation detection signal. This allows the servo loop gain of the control circuit to be adjusted at all times, regardless of the amount of incident light, by combining a gain adjustment amplifier whose resistors are switched with a switch and a variable feedback amplifier whose gain is variable analogously, without using expensive components. It is possible to realize automatic interest adjustment to keep it constant.

Therefore, the device is inexpensive as a whole and can perform stable and accurate tracking.

In addition, although the case of tracking control was explained in the said Example, it is not limited to this, and focus control can also be implement|achieved by the structure similar to the said tracking control.

In this case, the photodetection cells 16a and 16b detect the positional deviation between the optical disk 1 and the objective lens 11, and in response to this detection, the drive circuit 28 causes the coil 18 to move the objective lens 11 in the focusing direction. Good.

Further, although the present invention has been described using an example of applying the invention to an optical disk device, the present invention is not limited to this, and by slightly changing the configuration of the amplifier circuits 20, 21, etc., an analog divider that requires a wide range can be used. It can also be applied to various circuits used, such as laser card devices.

[Effects of the Invention] As detailed above, according to the present invention, it is inexpensive;
Furthermore, it is possible to provide an information processing device that can perform stable and accurate control of the focusing means.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing the configuration of an optical disk device that is an embodiment of the present invention, Figs. 2 and 3 are shown to explain the operation, and Fig. 2 shows the amount of incident light and the addition. FIG. 3 is a diagram showing the relationship between the amount of incident light and the sum signal, and FIG. 4 is a diagram showing the prior art and its problems. DESCRIPTION OF SYMBOLS 1... Optical disk (recording medium), 10... Optical head, 11... Objective lens (focusing means), 14... Semiconductor laser (light source), 16... Photodetector (detection means)
, 16a, 16b... photodetection cell, 17, 18...:1
20.21...Amplification circuit, 22...Subtraction circuit (calculation means), 22a...Differential amplifier, 23...Addition circuit (incident light amount detection means), 23a...Adder, 2
4.31... Selector (selection means), 25... Binarization circuit (conversion means), 27.32... Gain adjustment amplifier, 28... Drive circuit (drive means), 33... Variable feedback amplifier (control means), 34... current/voltage conversion circuit.

Claims (4)

[Claims] (1) a focusing means for focusing light emitted from a light source onto a recording medium; a detection means for detecting first and second signals by the light from the recording medium; and a first signal detected by the detection means. 1. An incident light amount detection means that detects the amount of light incident on the detection means by adding a second detection signal; A binarization means that binarizes the signal from the incident light amount detection means; the focusing means by subtracting the first and second selection means for selecting a gain corresponding to the signal binarized by the digitization means and the first and second detection signals detected by the detection means; a first amplification means for amplifying the signal obtained by the calculation means with the gain selected by the first selection means; The second signal
a second amplification means for amplifying the signal amplified by the first amplification means with a gain selected by the selection means; and a second amplification means for amplifying the signal amplified by the first amplification means
A control means for amplifying the signal amplified by the amplification means at a constant gain controlled according to the signal amplified by the amplification means, and a drive means for driving the focusing means according to the signal from the control means. information processing equipment. (2) The information processing apparatus according to claim 1, wherein the control of the focusing means is focusing control or tracking control. (3) A patent characterized in that the first and second selection means select a resistor that adjusts the gain so that the loop gain of the circuit that performs the focusing control or the tracking control is approximately constant. Claim 1
The information processing device described in the section. (4) The information processing apparatus according to claim 1, wherein the control means is constituted by a variable feedback amplifier.