JPH03142715A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive optical disk device with satisfactory packaging efficiency by separating the detection signal of a photodetector into a low frequency band and a high frequency band so as to be used for reproducing format data and tracking control, further adding the both signals and reproducing the data. CONSTITUTION:An optical recording medium 1 is irradiated with a light beam and the reflected light is detected. Then, this detection signal is separated into the signal of the low frequency band and the signal of the high frequency band by a band separating means 27 and current / voltage conversion is executed to the signal of the high frequency band by operational amplifiers 17a and 17b of the high frequency band and low offset, for example, so that the signal can be used for reproducing the format data. The current / voltage conversion is executed to the signal of the low frequency band by operational amplifiers 17c and 17d of the low frequency band and high offset, for example, so that the signal can be used for the tracking control, and further the signals of all the frequency bands are generated from the signal of the low frequency band and the signal of the high frequency band. Then, these signals of all the frequency bands are made binary and the recorded data are reproduced. Thus, the inexpensive optical disk device excluding the influence of noise can be obtained with the satisfactory packaging efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention] (Industrial Application Field) The present invention relates to an optical disc device for recording and reproducing information on and from an optical recording medium such as an optical disc.

(Prior Art) Conventionally, in an optical disk device that optically records or reproduces information on an optical recording medium such as a write-once or erasable optical disk, a relatively small continuous beam of light is emitted from a semiconductor laser as a light source. While the information on the optical disk is read by the output, the information is recorded on the optical disk by the optical output which intermittently changes at a relatively large predetermined value or more.

In such an optical disc device, a laser beam generated from a semiconductor laser oscillator is irradiated onto the optical disc, and the reflected light is sent to a four-split photodetector 12 as shown in FIG.
The photoelectrically converted signal is subjected to photoelectric conversion, and predetermined calculations are performed on the photoelectrically converted signal to obtain various information.

First, data recorded on the optical disc is reproduced based on the sum signal of each detection cell of the four-division photodetector 12. That is, the photocurrent signal from the photodetection cells arranged as shown in FIG. A binarization circuit 24 binarizes the data to obtain reproduction≠−t. That is, the data reproduction signal SD is obtained by the following equation.

S(,=a+b+c+d　　　　-t.

Further, a tracking error signal for performing tracking servo is obtained as a signal of a difference between two photodetection cells divided in the track direction of the four-split photodetector 12. That is, the photocurrent signal from the photodetection cell is converted into a voltage signal by the current-voltage conversion circuit 18, and then the photodetection cell a.

A subtracter 19 subtracts the added value of d and the added value of photodetection cells b and d.
A difference signal is obtained by subtraction, and this is supplied to the tracking control circuit 16 to generate a signal used for tracking servo.

That is, the tracking error signal ST is obtained by the following equation.

St = (a + d) - (b + c) - (2) In addition, the reproduction of format data is based on the difference between two photodetection cells divided in a direction orthogonal to the track direction of the four-division photodetector 12. is required as a signal. That is,
The photocurrent signal from the photodetection cell is converted into a voltage signal by the current-voltage conversion circuit 18, and the added value of photodetection cells c and d and the added value of photodetection cells a and b are subtracted by a subtracter 40. A difference signal is obtained and binarized by a binarization circuit 41 to reproduce format data. That is, the format data reproduction signal S is determined by the following equation.

Sp = (c+d) - (a+b) - (3) Here, the data reproduction signal SD and format data reproduction signal SF are high-speed signals of 10 to 20 MHz, but as for the offset (DC), the data is binarized. This is a signal that can vary somewhat within a possible range. Further, the data reproduction signal SD has a full frequency band and a format data reproduction signal S.

is a signal that requires only a high frequency band of several tens of KHz or more. On the other hand, the tracking error signal St is 10
Although it is a low-speed signal of 0 KHz or less, since it is used for tracking servo, it is a signal whose offset (DC) should be as small as possible.

Focusing on the properties of each signal as described above, the conventional signal regeneration system uses high frequency band, low offset operational amplifiers 18a to 18a.
The photocurrent signals from the photodetection cells a to d are converted into current-to-voltage using four 18d, and then calculations such as addition and subtraction are performed to obtain the desired sum or difference signal. .

However, the high frequency band, low offset operational amplifier (indicated by r(H)J in the figure) is very expensive, and the number of circuits that can be housed in one package is small, so if you use it frequently, There were problems in that the equipment became expensive and the efficiency of implementation deteriorated. In addition, in order to handle high-speed signals (10 to 20 MHz), it is necessary to shorten the wiring distance from the 4-split photodetector 12 to the current-voltage conversion circuit 18. It is impossible to mount an operational amplifier on the optical head due to mounting area constraints, so if the operational amplifier is installed outside the optical head, it will be susceptible to noise and stray capacitance will increase, making it impossible to extend the bandwidth. There was a problem. Furthermore, the signal after current-voltage conversion is 3
Since the signal is supplied to two operational amplifiers 19, 23, and 40, there are various restrictions on the design of drive ability, resistance value, etc., which is a problem.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problem that using many high-frequency band, low-offset operational amplifiers increases the cost of the device and reduces the efficiency of implementation. Since it is not possible to mount a large number of high-frequency band, low-offset operational amplifiers on the optical head, installing an operational amplifier outside the optical head makes it susceptible to noise and increases stray capacitance, making it impossible to extend the bandwidth. Furthermore, since the signal of an operational amplifier that performs current-to-voltage conversion is supplied to multiple operational amplifiers, various restrictions have arisen in the design of drive capacity, resistance value, etc. The purpose of the present invention is to provide an optical disk device that is inexpensive, has high mounting efficiency, eliminates the influence of noise, can extend the bandwidth, and can significantly alleviate design limitations. .

[Structure of the Invention] (Means for Solving the Problems) An optical disc device of the present invention includes a light output means for emitting a light beam onto an optical recording medium, and a reflected light of the light beam emitted by the light output means. a detection means, a band separation means for separating the signal detected by the detection means into a low frequency band signal and a high frequency band signal, and a current-voltage converter for the low frequency band signal separated by the band separation means. tracking control means for generating a tracking control signal from a low frequency band signal converted into a current voltage by the first conversion means and performing tracking control; a second conversion means for converting a signal in a high frequency band into a current and a voltage; and a format data signal is generated from the signal in the high frequency band converted into a current and voltage by the second conversion means, and the format data signal is binarized. a format data reproducing means for reproducing format data recorded on a recording medium; a low frequency band signal converted into a current voltage by the first converting means; and a high frequency signal converted into a current voltage by the second converting means. a data signal means for generating a data signal of all frequency bands from a signal of the band; and a data signal means for binarizing the data signal of all frequency bands generated by the data signal means to reproduce data recorded on the optical recording medium. The present invention is characterized by comprising a data reproducing means.

(Function) The present invention irradiates an optical recording medium with a light beam, detects the reflected light from the irradiated optical recording medium, and divides this detection signal into a signal in a low frequency band and a signal in a high frequency band by band separation means. The signals in the high frequency band are converted into current and voltage using a high frequency band, low offset operational amplifier and used for format data reproduction, and the signals in the low frequency band are separated into signals in the low frequency band, for example. , a high-offset operational amplifier converts current to voltage and uses it for tracking control, and further generates a full frequency band signal from the low frequency band signal and high frequency band signal, and generates a full frequency band signal. Recorded data is reproduced by binarizing it.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Note that the same parts as those described in the conventional example will be described with the same reference numerals.

FIG. 2 shows a schematic configuration of an optical disc device according to the present invention. In the figure, an optical disk 1 is formed by coating the surface of a circular substrate made of glass or plastic with a donut-shaped metal coating layer such as tellurium or bismuth.

The optical disc 1 is rotated by a spindle motor 2. This spindle motor 2 is
A motor control circuit (not shown) that operates in response to a control signal from the control circuit 3 controls the start and stop of rotation, the number of rotations, and the like.

The control circuit 3 is composed of, for example, a microcomputer, and in addition to controlling the rotation of the spindle motor 2,
Controls various controls described below.

An optical head 4 is disposed below the optical disc 1 . This optical head 4 records or reproduces information on the optical disc 1, and includes a semiconductor laser oscillator 5, a collimator lens 6, and a polarizing beam splitter 7.
, objective lens 8, cylindrical lens and convex lens 1
The astigmatism optical system includes a well-known astigmatism optical system 11, a 4-split photodetector 12, a photodetector 13, and the like. This optical head 4 is configured to move in the radial direction of the optical disc 1 by a moving mechanism constituted by, for example, a linear motor (not shown). And control circuit 3
The track is moved to a target track for recording or reproduction in accordance with a control signal from the controller.

The semiconductor laser oscillator 5 generates a diverging laser beam (light beam) according to the drive signal S1 from the optical output control circuit 14, and when recording information on the recording film of the optical disc 1, the recording film is A strong laser beam whose light intensity is modulated according to the information to be stored is generated, and when information is read and reproduced from the recording film of the optical disc 1, a weak laser beam having a constant light intensity is generated. There is.

The diverging laser beam generated by the semiconductor laser oscillator 5 is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1.

The objective lens 8 is supported movably in a direction perpendicular to the optical axis by a lens actuator 15 as a lens drive mechanism. By being moved in a direction perpendicular to the optical axis by the servo signal S2 from the tracking servo circuit 16, the focused laser beam that has passed through the objective lens 8 is projected onto the surface of the recording film of the optical disc 1. The light is irradiated onto recording tracks formed on the surface of the recording film of the optical disc 1. In this state, the objective lens 8 is in a matching track state.

Further, the objective lens 8 is supported so as to be movable in its front axis direction by a lens actuator (not shown) serving as a lens drive mechanism. By being moved in the optical axis direction by a servo signal from a focus servo circuit (not shown), the focused laser beam that has passed through the objective lens 8 is projected onto the surface of the recording film of the optical disc 1.1.
The minimum beam spot is formed on the surface of the recording film of the optical disc 1. In this state, the objective lens 8 is in a focused state. In the focused track and focused state, information can be written and read.

On the other hand, the diverging laser beam reflected from the recording film of the optical disc 1 is converted into a parallel beam by the objective lens 8 when it is focused, and is returned to the polarizing beam splitter 7 again.

Then, it is reflected by this polarizing beam spooler 7 and guided onto a 4-split photodetector 12 by an astigmatism optical system 11, and an image is formed in a state where the tracking deviation is determined by the amount of reflected light. ing.

As shown in FIGS. 1 and 5, the 4-split photodetector 12 has four photodetection cells a, b, and c that convert the light imaged by the astigmatism optical system 11 into electrical signals. , d. The photocurrent signal output from this four-division photodetector 12 is supplied to a band separation circuit 27. As shown in FIG. 1, this band separation circuit 27 is composed of a resistor and a capacitor. Further, the frequency characteristics of this band separation circuit 27 are as shown in FIG. In other words, the signal output from the resistor side is rapidly attenuated in the frequency range of 1/(2πCR) or higher, and the signal output from the capacitor side is attenuated at a frequency of 1/(2πCR) or higher.
In the region below (2πCR), it attenuates rapidly. here,
The resistor R and capacitor C are selected so that the frequency 1/(2πCR) is several tens of KHz.

The signals output by the two photodetection cells a and b placed on the same side in the direction perpendicular to the recording track of the four-split photodetector 12 are extracted from the capacitor side of the band separation circuit 27. Only the signals in the high frequency band are extracted, further added, and supplied to the high frequency band, low offset operational amplifier 17a. In addition, the signals output by the other two photodetection cells C and d are taken out from the capacitor side of the band separation circuit 27 to extract only the signals in the high frequency band, and are further added to the high frequency band and the low frequency band. The offset signal is supplied to an operational amplifier 17b.

On the other hand, the signals output by the two photodetection cells a and d placed on the same side across the recording track from the four-split photodetector 12 are extracted from the resistance side of the band separation circuit 27, so that the signals are low. Only the frequency band signals are extracted, further added, and supplied to the low frequency band, high offset operational amplifier 17c. In addition, the other two photodetection cells b
The signals output by C and C are taken out from the resistance side of the band separation circuit 27 to extract only the low frequency band signals, which are further added and supplied to the low frequency band, high offset operational amplifier 17d.

The operational amplifiers 17a and 17b convert the photocurrent signal in the high frequency band into a voltage signal.
7c and 17d convert the photocurrent signal in the low frequency band into a voltage signal.

The low frequency band signals subjected to current-to-voltage conversion by the operational amplifiers 17c and 17d are supplied to the differential amplifier circuit 19 and the adder circuit 43. The signal differentially amplified by the differential amplifier circuit 19 is then supplied to the tracking control circuit 16 as a tracking error signal S7. Further, the low frequency band signals added by the adding circuit 43 are supplied to the adding circuit 23 and the tracking control circuit 16.

The tracking control circuit 16 includes a phase correction circuit 20 that corrects the phase of the tracking error signal S, and an analog switch 21 that controls whether or not the output signal of the phase correction circuit 20 is supplied to the driver 22. and a driver 22 that amplifies the signal from the analog switch 21 and drives the actuator 15. When the analog switch 21 is turned on by the tracking on/off signal S3 from the control circuit 3, the signal from the phase correction circuit 20 is supplied to the actuator 15 via the driver 22 to form a tracking servo loop. It has become.

Further, the high frequency band signal subjected to current-voltage conversion by the operational amplifiers 17a and 17b is supplied to an adder circuit 23. The addition circuit 23 includes operational amplifiers 17a, 1
The high frequency band signals subjected to current-voltage conversion are added in step 7b, and the low frequency band signals added in the adding circuit 43 are also added to generate a full frequency band signal. The output of the adder circuit 23 reflects the recorded content of the optical disc 1 and is sent to the binarization circuit 24. The binarization circuit 24 is composed of, for example, a comparator, and performs binarization by comparing the analog signal output from the addition circuit 23 with a predetermined threshold level. The reflected light signal S4 binarized by the binarization circuit 24 is supplied to the control circuit 3. After being subjected to predetermined processing in the control circuit 3, it is sent as a reproduction signal to a host device (not shown).

Further, the high frequency band signals subjected to current-to-voltage conversion by the operational amplifiers 17a and 17b are supplied to a differential amplifier circuit 40. This differential amplifier circuit 40 performs differential amplification of the high frequency band signals from the operational amplifiers 17a and 17b to obtain a difference signal. This difference signal is a front-back difference signal in the track direction, and this signal is supplied to the binarization circuit 41. The binarization circuit 41 is composed of, for example, a comparator, and performs binarization by comparing the analog signal output from the differential amplifier 40 with a predetermined threshold level. The high frequency band signals binarized by the binarization circuit 24 are data such as track addresses and sector addresses that have been preformatted on the optical disc 1, and are supplied to the control circuit 3. There is. In the control circuit 3, the optical head 4 currently faces the optical disk 1.
By knowing the upper position, the target position for subsequent recording or playback processing can be recognized.

The waveform shaping circuit 32 waveform-shapes the recording data S10,
A recording pulse signal S7 is passed through and supplied to a driver 28, which will be described later.

A photodetector 13 formed of a photoelectric conversion element such as a photodiode, which is provided opposite to a light emitting port of the semiconductor laser oscillator 5 on the opposite side to the light emitting port of the recording or reproducing laser beam, is connected to the semiconductor laser oscillator 5. By being irradiated with the monitor light from 5, the monitor light is converted into an electric signal (photocurrent) and supplied to the light output control circuit 14 as the light output monitor signal S5 of the semiconductor laser oscillator 5. .

The optical output control circuit 14 controls the optical output of the semiconductor laser oscillator 5 to keep it constant by inputting the optical output monitor signal S5 output from the semiconductor laser oscillator 5 and performing feedback control. This optical output control circuit 14 includes a current-voltage conversion circuit 25 and an error amplifier 26.
, and a driver 28. The current-voltage conversion circuit 25 inputs the optical output monitor signal S5 photoelectrically converted by the photodetector 13 and extracted as a current signal, and receives the light intensity received by the photodetector 13, that is, the optical output of the semiconductor laser oscillator 5. It is converted into a voltage signal S6 according to the voltage signal S6 and outputted. A voltage signal S6 outputted from this current-voltage conversion circuit 25 is supplied to an error amplifier 26.

The error amplifier 26 uses the voltage signal S6 as one input and the reference voltage Vs generated by a constant voltage source (not shown) as the other input, compares the two types of pressures S6 and Vs, and amplifies the difference. This is output as an error signal. The reference voltage Vs is a constant voltage for obtaining the optical output necessary for reproduction, and the voltage signal S6 is converted to the reference voltage Vs.
By feedback control to bring it closer to
A constant optical output can be obtained from the semiconductor laser oscillator 5. The error signal from the error amplifier 26 is supplied to a driver 28.

The driver 28 is supplied with a recording pulse signal S7 corresponding to the information to be recorded from the waveform shaping circuit 32 described above. This driver 28 is composed of a transistor Tri (not shown) that generates reproduction light and a transistor Tr2 (not shown) that generates recording light, and the voltage signal output from the error amplifier 26 is input to the base of the transistor Tri during reproduction. During recording, a voltage signal is input in which the voltage value manually input during the previous playback is held in a sample-and-hold circuit (not shown), and these two inputs vary depending on whether recording or playback is being performed. It is possible to switch.

In both recording and reproduction, feedback control is performed based on the level of optical output during reproduction.

The transistor Tr2 (not shown) generates a laser beam with high intensity during recording, and a recording pulse signal S7 corresponding to the recording data S10 output from the waveform shaping circuit 32 is supplied to the base of the transistor Tr2. ing. Then, in response to this recording pulse signal S7, the transistor Tr2
turns on and off, and the semiconductor laser oscillator 5 is driven by the superimposed signals of the respective collectors of the transistors Tri and Tr2 to emit intermittent laser light of high intensity, thereby recording information on the optical disk. ing.

Next, the operation of the optical disc device configured as described above will be explained.

First, an operator sets the optical disc 1 into the optical disc device. Then, a start switch (not shown) is operated to instruct the start of the operation. As a result, the optical disc device starts its initial operation. That is, first, the validity of the light emission output of the semiconductor laser oscillator 5 is checked. In this process, a control signal from the control circuit 3 drives a linear motor (not shown) to cause the objective lens 8 to face the non-recording area of the optical disc 1. This non-recording area is provided on the innermost or outermost side of the optical disc 1, and is a portion where no information is recorded. By initially moving the optical head 4 to such a position, even if the laser beam is abnormally emitted for some reason, the recorded data will not be destroyed. Also,
The spindle motor 2 is rotated to shift the optical disc 1 to a predetermined rotation speed. Next, the control circuit 3 disconnects a focus servo loop constituted by a focus control circuit (not shown). Thereby, the objective lens 8 is released from focusing control.

Next, in response to a signal from the control circuit 3, the objective lens 8 is forcibly moved to the position shown by the dotted line in FIG. 1 to create a defocused state.

In this defocused state, power is supplied to the optical output control circuit 14 to turn on the semiconductor laser oscillator 5 and start outputting a laser beam. As a result, the monitor light generated from the semiconductor laser oscillator 5 is converted into a current according to the light output by the photodetector 13 and output as a light output monitor signal S5. The current-voltage conversion circuit 25 converts this optical output monitor signal S5 into a voltage signal S6 and supplies it to the error amplifier 26. The error amplifier 26 compares the preset reference voltage Vs and the voltage signal S6, and outputs the error as an error signal.

This error signal is a signal that "reduces the optical output of the semiconductor laser oscillator 5 if the voltage signal S6>reference signal VsJ, and increases the optical output of the semiconductor laser oscillator 5 if the voltage signal S6<reference signal VsJ". A feedback loop is formed by supplying this error signal to the driver 28. Then, the reference voltage Vs and the voltage signal S6 are controlled to be equal, and thereby the optical output of the semiconductor laser oscillator 5 is kept constant. It is maintained.

When feedback control of the light emission output of the semiconductor laser oscillator 5 is started in this manner, the control circuit 3 drives an actuator (not shown) to move the objective lens 8 toward the focal point position. When the objective lens 8 reaches the focused position, the focus servo loop is connected and the initial operation is completed. Thereafter, automatic focusing control is performed by the focus servo loop.

Next, the control circuit 3 drives a moving mechanism constituted by a linear motor (not shown), etc., and performs rough access to move the optical head 4 in the radial direction of the optical disk 1 to the target track to be accessed. .

Next, the tracking on/off signal S3 is sent from the control circuit 3.
By outputting , the analog switch 21 is turned on. As a result, the tracking servo loop is connected, and tracking control of the objective lens 8 is started. That is, when the track is placed near the target track position by the rough access, the servo signal S2 is further driven to move the objective lens 8, and precise access is performed in which the objective lens 8 is placed on the target track. After turning on the target track, the tracking servo loop performs feedback control to maintain the turned-on state. That is, the diverging laser beam reflected from the recording film of the optical disk 1 is converted into a parallel beam by the objective lens 8 and returned to the polarizing beam splitter 7. The light is then reflected by the polarizing beam splitter 7 and guided onto the 4-split photodetector 12 by the astigmatism optical system 11, where it is imaged with the amount of reflected light depending on the tracking deviation.

From the photocurrent signal outputted by this four-split photodetector 12, a low frequency band signal is extracted by a band separation circuit 27, and two photodetection cells a and 2 placed on the same side with the recording track in between are extracted. The outputs of d are added to the operational amplifier 17c.
and converted into a voltage signal. Furthermore, the outputs of the two photodetection cells b and C placed on the opposite side of the recording track are added together and supplied to the operational amplifier 17d, where it is converted into a voltage signal. The two signals converted into currents and voltages by these operational amplifiers 17c and 17d are differentially amplified by one differential amplifier circuit to produce a tracking error signal St.
The signal is outputted as a signal and supplied to the phase correction circuit 20. Then, the phase is corrected by the phase correction circuit 20 and further supplied to the driver 22 via the analog switch 21. This driver 22 outputs the tracking error signal S20.
is amplified and provided to the actuator 15, thereby moving the objective lens 8 in a direction perpendicular to the optical axis. As a result, a tracking servo loop is formed, and control is performed so that no track deviation occurs. With such control,
The track is in focus and the focus is in focus, and recording or reproducing operation becomes possible.

Next, the format data playback operation is started.

That is, in the focused track and focused state, the semiconductor laser oscillator 5 emits laser light with a constant level of low optical output. This laser light is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1. The diverging laser beam reflected from the recording film of the optical disk 1 is converted into a parallel beam by the objective lens 8 and returned to the polarizing beam splitter 7 again. Then, it is reflected by this polarizing beam splitter 7 and imaged by an astigmatism optical system 11 onto a 4-split photodetector 12 . The photocurrent signal photoelectrically converted by the 4-split photodetector 12 is extracted as a signal in a high frequency band by a band separation circuit 27. photodetection cell a
and b are added and supplied to the operational amplifier 17a, where it is converted into a voltage signal.

Further, the outputs of the two photodetection cells C and d arranged on the opposite side in the direction perpendicular to the recording track are added together and supplied to the operational amplifier 17b, where it is converted into a voltage signal. The two signals subjected to current-voltage conversion by these operational amplifiers 17a and 17b are differentially amplified by a differential amplifier circuit 40, outputted as a format data signal SP, and supplied to a format data binarization circuit 41. The binarization circuit 41 binarizes the output of the differential amplifier circuit 40 at a predetermined level and supplies it to the control circuit 3. As a result, the control circuit 3 refers to the reproduced format data, recognizes the position to be recorded or reproduced, and starts the recording or reproduction operation.

The playback operation is performed as follows. That is, in the focused track and focused state, the semiconductor laser oscillator 5 emits laser light with a constant level of low optical output. This lens laser light is converted into a parallel light beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1. The diverging laser beam reflected from the recording film of the optical disk 1 is converted into a parallel beam by the objective lens 8 and returned to the polarizing beam splitter 7 again. Then, it is reflected by this polarizing beam splitter 7 and imaged by an astigmatism optical system 11 onto a 4-split photodetector 12 .

The photocurrent signal photoelectrically converted by the 4-split photodetector 12 is extracted as a signal in a high frequency band by a band separation circuit 27. The outputs of the photodetection cells a and b are added together and supplied to the operational amplifier 17a, where it is converted into a voltage signal. Further, the outputs of the two photodetection cells C and d arranged on the opposite side in the direction perpendicular to the recording track are added together and supplied to the operational amplifier 17b, where it is converted into a voltage signal. The two high frequency band signals converted into current and voltage by these operational amplifiers 17a and 17b are sent to an adder circuit 23.
is added. Furthermore, in parallel with the above operation, the adder 43
The low frequency domain signals added in are also added. As a result, the output signal of the adder circuit 23 is output as a signal of all frequency bands. The output signal of this adder circuit 23 is supplied to a recording data binarization circuit 24. The binarization circuit 24 binarizes the output of the adder circuit 23 at a predetermined level and supplies it to the control circuit 3. After being subjected to predetermined processing in the control circuit 3, it is sent as a reproduction signal to a host device (not shown).

The recording operation is performed as follows. That is, when the format data is reproduced and the position where the data should be recorded is determined, the recording data sent from the host device (not shown) is supplied to the control circuit 3, and as a result, the pulse-shaped recording data S10 is output from the control circuit 3. Output. This recording data S10 is supplied to the waveform shaping circuit 32 and subjected to waveform shaping, and then supplied to the driver 28 as a recording pulse signal S7. As a result, the semiconductor laser oscillator 5 emits intermittent high-output laser light according to the recording data S10. This laser light is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided to the polarizing beam splitter 7 passes through the polarizing beam splitter 7, enters the objective lens 8, and is focused by the objective lens 8 toward the recording film of the optical disc 1. Information recording is performed.

As described above, the optical disk 1 is irradiated with a laser beam, the reflected light from the optical disk 1 irradiated with this laser beam is detected by the 4-split photodetector 12, and this detection signal is sent to the band separation circuit 27 at a low frequency The signal in the high frequency band is separated into a signal in the high frequency band and a signal in the high frequency band. For example, the frequency band signal is converted into a current voltage by the low frequency band, high offset operational amplifiers 17c and 17d and used for tracking control, and then the low frequency band signal and the high frequency band signal are added together to obtain a total signal. Since the recorded data is reproduced by generating a frequency band signal and binarizing this entire frequency band signal, for example, the number of high frequency band, low offset operational amplifiers can be reduced (as described above). In the example, 6 pieces become 4 pieces),
It is cheaper and has better implementation efficiency. In addition, the number of high-frequency band, low-offset operational amplifiers used has been reduced, making it possible to mount them in the optical head 4, eliminating the effects of noise and extending the bandwidth, and further reducing design limitations. This can be significantly alleviated.

[Effects of the Invention] As detailed above, according to the present invention, it is inexpensive and has high implementation efficiency, and it is possible to eliminate the influence of noise and extend the band, and furthermore, it greatly alleviates design restrictions. It is possible to provide an optical disc device that can perform

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a circuit diagram showing a detailed configuration of a signal reproducing system, FIG. 2 is a block diagram showing a schematic configuration of an optical disc device, and FIG. Figure 3 is a diagram showing the characteristics of the band separation circuit, Figures 4 and 5 are for explaining the conventional signal reproduction system, and Figure 4 is a circuit diagram showing the detailed configuration of the signal reproduction system. , FIG. 5 is a diagram showing the configuration of a four-division photodetector. DESCRIPTION OF SYMBOLS 1... Optical disk (optical recording medium), 3... Control circuit, 5... Semiconductor laser oscillator (light output means), 12.
... 4-split photodetector (detection means), 16 ... Tracking control circuit (tracking control means), 17 ... Current-voltage conversion circuit, 17 a, 17 b ... Operational amplifier (second conversion means) ), 17c, 17d... operational amplifier (first conversion means), 19... differential amplification regeneration means) 27... band separation circuit (band separation means), 40
...Differential amplifier circuit (format data reproducing means),
41...Binarization circuit (format data reproducing means)
, 43...adder (signal generation means).

Claims (1)

[Claims] A light output means for emitting a light beam onto an optical recording medium; a detection means for detecting reflected light of the light beam emitted by the light output means; and a signal detected by the detection means at a low frequency. A band separation means for separating a signal in a high frequency band and a signal in a high frequency band; a first conversion means for converting a low frequency band signal separated by the band separation means into a current voltage; Tracking control means that performs tracking control by generating a tracking control signal from a low frequency band signal that has been converted into a current voltage; and a second conversion means that converts a high frequency band signal separated by the band separation means into a current voltage. and format data reproduction for reproducing the format data recorded on the optical recording medium by generating a format data signal from the high frequency band signal converted into current and voltage by the second conversion means and binarizing it. means for generating a data signal in all frequency bands from a low frequency band signal converted into current and voltage by the first conversion means and a high frequency band signal converted into current and voltage by the second conversion means; An optical disc device comprising: a signal means; and a data reproducing means for binarizing data signals of all frequency bands generated by the data signal means and reproducing data recorded on the optical recording medium. .