JPH07169080A - Beam deflector for optical disk - Google Patents

Abstract

PURPOSE:To easily obtain desired damping characteristics and lock servo characteristics by providing gain regulating means for holding a gain of a rotating angle signal from rotating angle detecting means upon rotation of a galvanic mirror constant. CONSTITUTION:This beam detector detects a rotating angle of a galvanic mirror 1 as a change in a light quantity, and then differentially amplifies an electric output based on the change in the light quantity of a reflection type photodetector 2 by a sensor 3. In this case, an output signal of a differential circuit 5 is input to a negative terminal of a differential amplifier 6 thereby to negatively feed back a rotating angular velocity signal of the mirror 1 before a driver 7 of the mirror 1. In this case, speed-damped characteristics can be obtained as rotating characteristics of the mirror 1 corresponding to a signal obtained by D/A conversion of the signal from a CPU 9 with a D/A converter 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam deflecting device for an optical disk, and more particularly to a beam deflecting device for an optical disk which employs tracking control, focus control or lock servo control for drive control.

[0002]

2. Description of the Related Art In recent years, in an optical recording / reproducing apparatus (hereinafter referred to as "optical disk") using a laser beam such as a CD, it is possible to read the recorded content because the apparatus can be thinned and high-speed search can be performed. Using a separation optical system as an optical head to perform,
On top of this, in order to reduce the weight of the moving part on the linear motor, a galvanometer mirror (beam deflecting device) equipped on the fixed part was used as a tracking actuator (positioning mechanism for correctly tracking on the guide groove), and a CD and light source were used. Precise positioning in the tracking direction is performed by deflecting the laser that reciprocates between and.

By the way, as described in Japanese Patent Application Laid-Open No. 58-039273, in order to improve the damping of the galvano mirror and enhance the stability of the entire servo system,
It is useful to perform control by using a detector that detects the rotational angular velocity of the galvanometer mirror. Now, as the rotation angular velocity detector, the one using a simple reflection type optical sensor using an LED and an optical sensor is proposed in the above-mentioned Japanese Patent Laid-Open No. 58-039273. Hereinafter, FIG. 4, FIG. 5, and FIG.
The damping control device of this galvanometer mirror will be described using. FIG. 10 is a block diagram of a conventional damping control device for a galvanometer mirror. In this figure, 1
Reference numeral 2 denotes a galvano mirror that deflects the laser light by reflection, and 2 detects the rotation angle of the galvano mirror by a change in the amount of light reflected from a reflection mirror (not shown) for a rotation angle detection light source provided on the galvano mirror. It is a reflection type photodetector, and 13 is a sensor circuit. The reflection type photodetector 2
The sensor circuit 13 and the sensor circuit 13 are actually manufactured integrally, and also incorporate an LED for detecting the rotation angle, a circuit for converting a change in the detected reflected light into a change in the current, and the like. 5 is a galvanometer mirror 1 by differentiating the current from the sensor circuit.
6 is a differentiating circuit that changes the angle change of
Reference numeral 7 is a differential amplifier that obtains a required drive signal from the original target angle and the detected rotational angular velocity, and 7 is a drive circuit. As shown in this figure, this is the optical / electrical conversion by the reflection type optical sensor, and after detecting the change of the rotation angle of the galvanometer mirror as a current, this signal is passed through a differentiating circuit to be converted into an angular velocity signal. The damping control is performed by feeding back the angular velocity signal corresponding to the input velocity signal of the galvanometer mirror.

Next, the content of this control will be described using a transfer function. First, the transfer function G _T of the galvanometer mirror is shown. G _T = (Ka · ωa ² ) / (S ² + 2 · ζa · ωa · S + ωa ² ) ... (Equation 1) Here, Ka is the driving sensitivity coefficient of the galvanometer mirror,
ζa is the damping factor of the galvanometer mirror,
ωa is the primary resonance angular frequency of the galvanometer mirror. Further, “·” is used in place of “× (multiply)” in order to prevent misunderstanding of “X (ex)” and represents multiplication.

The relational expression between the damping factor ζa and the gain Qa at ωa is shown below. Qa = −20log (2ζa) (Equation 2) As shown in the Bode diagram of the galvanometer mirror before damping control in FIG. 4, ωa is 1.26K (ra).
d / Sec), Qa is 28 dB, and ζa is 0.02.

Reflection type optical sensor, transfer function G of differentiating circuit
Indicates _C. G _C = 2ζ c / (Ka ・ ω a) S (Equation 3) In the above equation, ζ c is a damping factor corrected by the damping control loop.

Under the above conditions, if damping control is performed,
The transfer function G _TD of the galvanometer mirror has the characteristics shown in the following equation. G _TD = (Ka · ωa ² ) / {S ² + 2 · (ζa + ζc) · ωa · S + ωa ² } ... (Equation 4) And, here, ζd = ζa + ζc ... (Equation 5) is a galvanometer mirror damping factor. is there.

By the damping control as shown in (Equation 4) and (Equation 5), the damping factor ζd of the galvanometer mirror ζd = 1 / √2, and the damping factor ζc = to be corrected.
At 0.687, the gain peak after control was damped to -3 dB. Based on the above, the Bode diagram of the galvanometer mirror after damping control has the characteristics shown in FIG.

Further, the above means and devices are such as a focus servo and a lock servo for properly holding (fixing) the position of the galvano mirror even when there is disturbance or vibration on the device body such as an optical head. It is also used in.

[0010]

However, as means for detecting the angular velocity of the galvanometer mirror, simply differentiating and feeding back the signal from the reflection type photodetector,
Manufacture of optical sensors that convert light quantity into current and output, individual differences in detection characteristics due to the limits of quality control, errors in optical sensor mounting position, changes in sensor detection sensitivity due to uncertainty in sensor circuit constants, and The gain of the damping control loop (amplitude of the rotation angle signal / amplitude of the input signal) tends to fluctuate due to variations in the rotation characteristics (galvano mirror transfer function) of the galvano mirror itself with respect to the drive signal of the galvano mirror, and inevitably. It becomes difficult to obtain desired damping characteristics.

A change in the damping characteristic of the galvanometer mirror when the gain of the damping control loop changes will be described below using a specific example. FIG. 6 is a Bode diagram of the galvanometer mirror after damping when the gain changes by +6 dB. In this figure, if the loop gain of damping control changes by +6 dB with respect to the target value, the gain Qa at the primary resonance frequency becomes −8.89 dB, and it can be seen that the desired damping characteristic cannot be obtained. On the contrary, in FIG. 7, the gain is -6d.
It is a Bode diagram of the galvanometer mirror after damping when B is changed. Also in this figure, when the loop gain of the damping control changes by -6 dB with respect to the target value, the gain Qa at the primary resonance frequency becomes 2.78 dB, and it can be seen that the desired damping characteristic cannot be obtained.

Further, when the above-mentioned reflection type optical sensor is used as a lock servo for holding the position of the galvanometer mirror as a means for compensating for disturbance vibration to the main body of the apparatus such as focus control and optical head, the lock servo is similarly used. It is not preferable because the gain of the loop fluctuates. For this reason, the gain of the loop is constant despite variations in characteristics and performance of each part caused by manufacturing, manufacturing, product assembly of component parts, etc.
Consequently, the emergence of a beam polarization device for an optical disk having a desired damping characteristic for drive control is desired. The present invention has been made for the purpose of solving such problems.

[0013]

In order to achieve the above object, in the invention of claim 1, the rotation angle detecting means for detecting the rotation angle of the galvanometer mirror and the rotation angular velocity based on the detection result of the rotation angle detecting means. In the beam deflecting device for an optical disk, which is provided with an angular velocity calculating means for obtaining a difference between the galvano-mirror drive signal and the rotational angular velocity signal, and is applied to the galvano-mirror, the rotation angle detecting means from the rotation angle detecting means according to the rotation of the galvano-mirror. It is characterized in that a gain adjusting means for keeping the gain of the rotation angle signal constant is provided.

According to a second aspect of the present invention, the rotation angle detecting means is a reflective photoreflector, and the gain adjusting means is a light source current variable element for varying the drive current of the reflective photoreflector light source. According to another aspect of the invention, a computer provided for converting the digital recording recorded on the optical disk into a predetermined significant signal is controlled by utilizing the surplus capacity of the light source current variable element. It is characterized in that it functions as a part.
In the invention of claim 4, the gain adjusting means is an arithmetic unit that compares the amplitude of the galvano-mirror rotation angle signal with the target amplitude and performs necessary calculation on the galvano-mirror rotation angle signal based on the error. To do.

According to a fifth aspect of the invention, the arithmetic unit is a divider. In a sixth aspect of the invention, the computer provided for converting the digital recording recorded on the optical disc into a predetermined significant signal makes use of the surplus capacity of the computer, and the arithmetic control unit of the arithmetic unit. It is characterized by the action of. In the invention of claim 7, the computer provided for converting the digital recording recorded on the optical disk into a predetermined significant signal, utilizes the surplus capacity of the division of the divider. It is characterized in that it functions as a control unit.

[0016]

With the above structure, in the invention of claim 1,
The gain adjusting means holds the gain of the rotation angle signal from the optical rotation angle detecting means in accordance with the rotation of the galvanometer mirror constant. In the invention of claim 2, the reflection type photo reflector detects the rotation angle of the galvanometer mirror. A drive circuit drives the galvanometer mirror based on the drive signal from the drive signal generator. The optical rotation angle detection means detects a change from the angle to be held by the galvanometer mirror through a change in the amount of light.

In the third aspect of the invention, the light source current variable element as the gain adjusting means adjusts the gain of the rotation angle signal of the galvanometer mirror by increasing or decreasing the drive current of the light source of the reflection type photo reflector. According to the fourth aspect of the present invention, the arithmetic unit as the gain adjusting means compares the amplitude of the rotation angle signal of the galvanometer mirror with the target amplitude, and performs the necessary calculation for the rotation angle signal of the galvanometer mirror based on the error.

In the fifth aspect of the invention, the arithmetic unit is a divider. In the inventions of claim 3, claim 6 and claim 7, the computer provided for converting the digital recording recorded on the optical disk into a predetermined significant signal utilizes its surplus capacity. Plays the role of gain adjustment means.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A beam deflecting device for an optical disk according to the present invention will be described below with reference to an embodiment centering on drive control which is a characteristic part thereof. FIG. 1 is a configuration diagram of an embodiment for a beam deflecting device for an optical disk according to the present invention.

In the figure, 1 is a galvanometer mirror, 2 is a reflection type photodetector, 3 is a sensor (photodetector) circuit, 5 is a differentiating circuit, and 6 is a differential amplifier. , Which are basically the same as those according to the prior art shown in FIG. Next, 4 is a divider, and 9
Is a microcomputer (MPCU) having a standardized ability whose original purpose is to make a digital signal significant information, 8 is an A / D converter, 10,
Reference numerals 11 and 12 are D / A converters.

As shown in the figure, in this embodiment, after the rotation angle of the galvanometer mirror 1 is detected by the reflection type photodetector 2 as a change in the light amount, the sensor circuit 3 detects the light amount of the reflection type photodetector 2. Differentially amplify the electrical output signal based on the change.
The contents of this differential amplification will be described later in detail. The drive current of the light source of the reflection type photodetector 2 can be adjusted by a voltage control resistor (VCR), and a signal from the CPU 9 is supplied to a terminal controlled by a voltage via the first D / A converter 11. It is connected. The output of the sensor circuit 3 is input to the divider 4, and the division signal input terminal of the divider 4 is a CPU.
The signal from 9 is connected via the second D / A converter 10. The output signal of the divider 4 is input to the differentiating circuit 5, whereby the rotation angle signal of the galvanometer mirror 1 detected by the reflection type photodetector 2 is converted into a rotation angular velocity signal,
This is connected to the negative terminal of the differential amplifier 6. Next, the output of the D / A converter 12 is connected to the positive terminal of the differential amplifier 6. The output of the differential amplifier 6 is connected to a drive circuit 7 that rotationally drives the galvanometer mirror 1. By inputting the output signal of the differentiating circuit 5 to the negative terminal of the differential amplifier 6, the rotational angular velocity signal of the galvano mirror 1 is negatively fed back to the drive circuit 7 of the galvano mirror 1. At this time, CP
A speed-damped characteristic can be obtained as the rotation characteristic of the galvanometer mirror 1 according to the signal obtained by D / A converting the signal from U9 by the D / A converter 12. The output of the divider 4 when the galvanometer mirror 1 is rotationally driven in response to a signal from the CPU 9 is input to the CPU 9 via the A / D converter 8 and the divider 4 receives a constant drive signal. The CPU 9 changes the division signal of the divider 4 via the second D / A converter 10 so that the sensor signal of the output of 1 has a constant amplitude.

Next, the positional relationship between the galvanometer mirror 1 and the reflection type photodetector 2 will be described with reference to FIG. here,
FIG. 2 is a perspective view of the galvanometer mirror 1 and the reflection type photodetector. In this figure, 1 is a galvanometer mirror, and 1
Reference numeral 01 denotes a mirror body that reflects laser light between the light source, the optical disk, and the reading unit, and the side portion of the reflecting surface is visible in the figure. Reference numeral 102 denotes a holder (mirror holder) for the mirror body, and a leaf spring 105 is attached to the end of the holder. Reference numeral 103 is a lightweight reflecting member that reflects light from an LED described later. Reference numeral 104 is a coil for rotationally driving the galvanometer mirror. Two thick straight lines 106 with arrows show laser light polarized by reflection on the mirror body 101, and a semicircular thick line 107 with arrows at both ends shows the rotation direction of the galvanometer mirror. 2 is a reflection type photodetector, 202 is an LED (light emitting diode), 201 and 203 are photosensors that electrically detect reflected light, and the two broken lines 108 and 109 are LEs.
It shows how the light from D202 reaches the upper and lower photosensors 201, 203. Then, as shown in the figure, the mirror body 101 and the mirror holder 102 are integrally overlapped with each other, and the reflection member 103 is adhesively fixed and fixed to the one side surface, and the reflection member 103 is provided at a position facing the reflection member 103. A reflection type photodetector 2 is arranged to detect the rotation of the mirror body 101 and the mirror holder 102.

Next, the operation of the reflection type photodetector 2 and its sensor circuit 3 will be described with reference to FIGS. 2 and 3. It should be noted that, although they are shown separately in the drawings for easy understanding of the content of the invention, both are actually manufactured integrally as in the conventional case. FIG. 3 is a circuit diagram of the reflective photosensor in this embodiment. As shown in this figure,
The Anode terminal of the LED 202 is connected to + 10V, and the Cathode terminal is connected (grounded) to the GND via the VCR and the resistor (R1). And VC
The voltage from the D / A converter 11 is applied to the R control terminal. The current flowing through the LED 202 is adjusted by the voltage applied to the control terminal. Upper and lower optical sensors (PR
1, PR3, 201 and 203 in FIG. 2) have collector terminals connected to +10 V, and emitter terminals having resistors (RE1,
It is connected to GND via RE2). The connection points of the upper and lower photosensors (PR1, PR2) and the resistors (RE1, RE2) are connected to the negative input terminal of the operational amplifier via the resistors (Ri1, Ri2), respectively. The negative input terminal of the operational amplifier is connected to the output terminal of the operational amplifier via the resistor (Rf1), and the positive input terminal is connected to the resistor (Rr1).
ef) to + 5Vref. LED
The light from 202 is reflected by the reflecting member 103 fixed to the side surface of the galvanometer mirror 1. Then, the reflected light is received by the upper and lower photosensors PR1 and PR2 and converted into light / voltage. At this time, if the galvanometer mirror 1 rotates as indicated by the thick arrow in FIG. 2, the distances between the upper and lower optical sensors 201 and 203 and the reflecting member 103 become unequal, so that
The result of voltage conversion is different at the top and bottom. Therefore, the operational amplifier determines this difference and then amplifies it. Thus, a detection signal corresponding to the rotation angle of the galvanometer mirror is obtained as a current value.

Next, the sensitivity adjustment of the sensor output, which is performed by controlling the current that drives (emits) the LED 202, will be described. First, the operation of the VCR will be described. One terminal of the VCR is connected to the Cathode of the LED 202 which is the light source of the reflection type photodetector 2, and the other terminal of the VCR is connected to the GND through the fixed resistor. Also, LE
The Anode of D202 is connected to the power source + 10V. The voltage control terminal of the VCR is connected to the CPU 9 via the first D / A converter 11, and the drive current of the LED 202 is determined by the fixed resistor R1 and the resistance value of the VCR. Then, when the voltage of the control terminal of the VCR is increased, the resistance value of the VCR becomes large, so that the LED drive current becomes small.
On the contrary, when the voltage of the control terminal of the VCR is lowered, its resistance value becomes small and the LED drive current becomes large.

FIG. 8 shows the photocurrent / forward current characteristics. The horizontal axis represents the forward current flowing through the LED 202. The vertical axis is
It is an optical sensor that is detected by the left and right reflected light detectors with respect to the forward current. It can be seen from FIG. 8 that the forward current and the photocurrent are in a proportional relationship. From this, it is understood that if the forward current flowing through the LED 202 is changed, the current detected by the reflected light detector also changes in proportion to this.

As a drive signal for the drive circuit 7, for example, 60H
When the galvanometer mirror 1 is rotationally driven using the sine wave of z and the speed damping control is off, a sine wave signal of 60 Hz is obtained as the sensor rotation angle signal of the output of the sensor circuit 3. The sensor output rotation angle signal from the divider 4 is A / D converted by the A / D converter 8 and input to the CPU 9. The CPU 9 is connected to the control terminal of the VCR via the first D / A converter 11. The applied voltage is changed so that the rotation angle signal amplitude of the sensor output becomes maximum. The range of change is 25 for the drive current.
It is preferably ± 10 mA with respect to mA. Therefore,
By changing the resistance value of the VCR according to the VCR control signal from the CPU 9, the LED drive current is controlled, and the sensitivity of the reflection type photodetector can be adjusted by this.

Here, the relationship between the mounting position of the reflection type photodetector and the detection characteristics will be described. The reflection type photodetector 2 is shown in FIG.
2 shows the position detection characteristics of. FIG. 9A is a diagram of FIG. 9B.
It is a characteristic of the relative photocurrent with respect to the distance when the reflecting member and the optical sensor are arranged as shown in FIG. In FIG. 9A, the horizontal axis represents the distance and the vertical axis represents the relative photocurrent detected by the optical sensor with respect to the distance. From this, it can be seen that the relative photocurrent greatly changes as the distance changes.

Next, the sensitivity adjustment of the sensor output by the divider 4 will be described. First, the operation of the divider 4 will be described. If the amplitude of the rotation angle signal output from the sensor circuit 3 is smaller than the amplitude that gives the originally desired gain, C
The input signal is amplified and the target amplitude is obtained by reducing the signal obtained by D / A converting the signal from the PU 9 by the D / A converter 10. On the contrary, when the amplitude of the rotation angle signal output from the sensor circuit 3 is large, the input signal is attenuated by increasing the signal D / A converted from the signal from the CPU 9 by the D / A converter 10. Get the target amplitude. It should be noted that the signal from the CPU 9 is D / A converted by the D / A converter 12 to drive the galvanometer mirror 1 with a 60 Hz sine wave drive signal to obtain the maximum amplitude value of the output signal of the divider 4. Is the CPU
In step 9, the output of the A / D converter 8 is sampled by the CPU 9 to obtain the maximum value or the minimum value of the sensor signal. The obtained maximum value or minimum value is compared with a value set in advance as a target value, and if the maximum value or minimum value of the sensor signal is larger than the target value, the CPU
9 increases the division signal set value output to the D / A converter 10. If it is smaller than the target, the CPU 9 reduces the division signal setting value. Therefore, the amplitude at the output of the divider 4 is adjusted to be constant with respect to the predetermined sinusoidal drive signal from the CPU 9. Therefore, an arithmetic unit as a device (hardware) for performing the calculation necessary for gain adjustment is simple. The reason why the divider is used as the arithmetic unit here is that it is adapted to the adjustment of the LED.

Next, the CPU will be described. In this embodiment, the CPU 1 is functionally equivalent to a microcomputer originally provided as an essential component of an optical recording / reproducing apparatus for extracting audio information from a digital signal stored in a laser disk. It is supposed to use the part. The driving characteristics of the galvanometer mirror 1, the LED 202 and the optical sensor 201,
In order to be able to deal with the aging of 203, when the reading switch of the laser disk is turned on and each part of the CPU 1 exerts its steady function, the differential signal is transmitted via the D / A converter 12 according to a predetermined program. It is programmed to apply a predetermined signal to the amplifier 6, drive the galvano mirror 1 by a predetermined amount based on this, check the output from the sensor circuit 3 and the like based on this, and perform the necessary gain adjustment.

After that, the optical disk reached steady rotation,
The reading unit driven by the linear motor reaches a predetermined position, and digital information is read on the reading unit.
U1 will serve its original purpose. In this case,
Even if the microcomputer is a device such as an LSI, it is widely used in addition to the optical recording / reproducing device, and therefore its performance, capacity, etc. are almost standardized. . For this reason, when used in an optical recording / reproducing apparatus, most of them have a surplus capacity for analogization of digital signals.
In addition, the ability and the amount of calculation required to exert the effects of the present invention are very small when compared with the original application of analogization of digital signals. Therefore, virtually no hardware is required for the present invention.

In addition to the above, dedicated devices (DSP, Digi
It is needless to say that a tal Signal Processor) may be used. Next, the control performance of this embodiment will be described based on the Bode diagram. FIG. 6 is a galvanometer mirror board diagram when the damping control gain is large by 6 dB. FIG. 7 is a galvanometer mirror board diagram when the damping control gain is 6 dB less. FIG. 5 is a galvanometer mirror board diagram when the damping control gain is just right. From this, it can be seen that appropriate control is being performed.

Although the present invention has been described above based on the embodiments, it goes without saying that the present invention is not limited to the above embodiments. That is, for example, (1) not only the drive control of the rotation angle of the galvanometer mirror but also the fixed control for compensating the position variation due to the disturbance, the focus control, and the like may be used. In these cases as well, there is no inconvenience such as the change of the gain intersection of the lock servo (the intersection with OdB in the Bode diagram) despite the individual difference of various components and the secular change of the dynamic characteristics, and it is constant. It is possible to obtain the lock servo characteristics and the like. (2) The operation and action according to the present invention may be performed by improving the hardware and software of the existing one. (3) One constituent element (element) of the present invention may be divided into a plurality of pieces for the convenience of manufacturing, or the plurality of pieces may be physically integrated. Alternatively, a part of the program may be configured. (4) The optical rotation angle means, the use of the LED or the like, and the adopted light may be infrared rays or ultraviolet rays.

[0033]

As described above, according to the present invention, when the signal from the reflection type optical sensor is used as the angular velocity detector of the galvano mirror, the detection characteristic of the optical sensor is limited due to the limitation of manufacturing and quality control of the optical sensor. Difference, error in mounting position of optical sensor, change in sensor detection sensitivity due to uncertainty in sensor circuit constant, individual difference in galvano-mirror rotation characteristics (galvano-mirror transfer function) with respect to galvano-mirror drive signal, and age of drive sensitivity Even if there is a change, it can be compensated simply by making the sensor detection sensitivity at the output end of the divider for the drive signal of the galvanometer mirror electrically constant. Moreover, in this case, by utilizing the surplus functions of the CPU originally installed, special parts and the like become unnecessary. As a result, it is possible to appropriately compensate for gain fluctuations when performing galvano-mirror damping control or lock servo, and it is possible to easily obtain desired damping characteristics and lock servo characteristics.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a beam deflecting device for an optical disc according to the present invention.

FIG. 2 is a perspective view showing how the reflection type photodetector is attached to the galvanometer mirror in the above embodiment.

FIG. 3 is a reflection type photodetector and a circuit diagram thereof in the above embodiment.

FIG. 4 is a Bode diagram of the galvanometer mirror before damping control.

FIG. 5 is a Bode diagram of the galvanometer mirror after damping control according to the present invention.

FIG. 6 is a Bode diagram of the galvanomirror after performing the damping control according to the present invention when the gain is reduced by 6 dB.

FIG. 7 is a Bode diagram of the galvanomirror after performing the damping control according to the present invention when the gain increases by 6 dB.

FIG. 8 is a characteristic diagram of photocurrent vs. forward current of an LED of a reflective photodetector.

FIG. 9 is a diagram for explaining characteristics of detection of a rotation angle of a galvano mirror by an optical sensor of a reflective photodetector.
(A) is a characteristic diagram of relative photocurrent with respect to distance.
(B) is a figure which shows the positional relationship of a reflection member and an optical sensor.

FIG. 10 is a configuration diagram of a conventional beam deflecting device for an optical disc.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Galvano mirror 101 Mirror body 102 Mirror holder 103 Reflecting member 2 Reflection type photodetector 201, 203 Optical sensor 202 LED 3 Sensor circuit 4 Divider 5 Differentiating circuit 6 Differential amplifier 7 Driving circuit 8 A / D converter 9 CPU 10 D / A converter 11 D / A converter 12 D / A converter

Claims (7)

[Claims] 1. A rotation angle detecting means for detecting a rotation angle of a galvanometer mirror, and an angular velocity calculating means for obtaining a rotation angular velocity from a detection result of the rotation angle detecting means, the galvanometer mirror drive signal and the rotation angular velocity signal. A beam deflecting device for an optical disk, which applies a difference to a galvanometer mirror, is characterized in that gain adjusting means for keeping a gain of a rotation angle signal from the rotation angle detecting means in accordance with rotation of the galvanic mirror constant is provided. Beam deflecting device for optical disk. 2. The rotation angle detecting means is a reflective photoreflector, and the gain adjusting means is a light source current variable element for varying the drive current of the reflective photoreflector light source. Beam deflecting device for optical disk. 3. A computer provided for converting a digital recording recorded on an optical disc into a predetermined significant signal, by utilizing the surplus capacity of the computer, an operation of a control unit of the light source current variable element. The beam deflecting device for an optical disk according to claim 2, wherein 4. The gain adjusting means is an arithmetic unit that compares the amplitude of the galvano-mirror rotation angle signal with a target amplitude and performs necessary calculation on the galvano-mirror rotation angle signal based on the error. Item 1. A beam deflecting device for an optical disc according to item 1. 5. The beam deflecting device for an optical disk according to claim 4, wherein the arithmetic unit is a divider. 6. A computer provided for converting a digital recording recorded on an optical disk into a predetermined significant signal, and utilizing the surplus capacity thereof, causes the operation of the arithmetic control unit of the arithmetic unit to operate. The beam deflecting device for an optical disk according to claim 4, wherein 7. A computer provided for converting a digital recording recorded on an optical disc into a predetermined significant signal, utilizing the surplus capacity of the computer, a computer of a division control unit of the divider. 6. The beam deflecting device for an optical disk according to claim 5, which operates.