JP2002042363A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device capable of making it hard to receive influence of noise on an information signal RF, etc., even if a photoelectric converter and a controller are separated by a small distance. SOLUTION: In the photoelectric converter 21, a current-voltage conversion amplifier 22 having differential output terminals VRF+ and VRF- for calculating current output from specific photodiodes 12a to 12d in photodiodes 12a to 12f and differentially outputting the result of the calculation is used to output the result as a difference signal; thereby the influence of noise, even if the converter 21 and the controller are separated by a small distance can be made less likely. As a result, a signal amplitude can be reduced, to provide the optical disk device capable of fast operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical disk device.

[0002]

2. Description of the Related Art Generally, an optical disk device of this type uses a semiconductor laser as a light source, and has a laser power control device for appropriately controlling the laser power. FIG. 4 shows a schematic configuration example of an optical disk device provided with such a laser power control device. First, a semiconductor laser (laser diode) 1 that emits laser light to irradiate an optical disk (not shown) toward the front, receives laser light emitted from the semiconductor laser 1 toward the rear, and adjusts the light amount. A laser light source unit 3 integrally provided with a rear light monitoring element 2 that converts the output into a monitor current and outputs the same is provided. The configuration itself of the rear light monitoring element 2 is a so-called photodiode element. A driver 4 for driving the semiconductor laser 1 and a controller 5 for controlling the driver 4 are provided. The controller 5 is an automatic power control circuit (APC circuit) 6 for automatically controlling the output signal from the rear light monitoring element 2 and the power of the semiconductor laser 1.
Built-in. Further, the controller 5 detects a signal from a photoelectric conversion device (denoted as PD) 7 including a plurality of photodiodes (not shown) for receiving and detecting light reflected by the optical disk when the laser beam is irradiated from the semiconductor laser 1. Captures the signal and reproduces or tracks the information signal RF
Performs signal processing such as detection of a servo signal for focusing.

[0003] The driver 4 rarely causes the semiconductor laser 1 to turn on DC even when reading an optical disk.
In order to reduce optical noise, a high frequency current of several hundred MHz is superimposed. In addition, at the time of writing to the optical disk, the driver 4 turns the semiconductor laser 1 on and off (turns on / off) at a high speed. For this reason, such an optical disk device is structurally configured as shown in FIG. A laser light source unit 3, a driver 4, and a photoelectric conversion device 7 are mounted on an optical pickup 9 that can move in a radial direction shown by an arrow with respect to an optical disk 8 that is rotationally driven by a spindle motor (not shown). . As a result, the physical distance from the driver 4 to the semiconductor laser 1 is shortened (the influence of inductance due to wiring is minimized). On the other hand, the controller 5 is generally mounted on a circuit board 10 fixed in position in the optical disk device because it is difficult to mount the controller 5 on the optical pickup 9 even if it has an IC configuration. The circuit board 10 and the optical pickup 9 are electrically connected by a flexible cable 11.

FIG. 6 shows an example of the configuration of a photoelectric conversion device (PD) 7. Here, this is an example of the photoelectric conversion device 7 including six photodiodes 12a to 12f indicated by A to F. Among them, for example, four photodiodes 12a to 12d indicated by A to D receive four divided light beams. It is configured as an element and receives a main beam of light reflected from the optical disk 8, and is used for an information signal RF and a tracking / focusing servo. Output currents from the photodiodes 12a to 12f are one-to-one current / voltage conversion amplifiers 13a having corresponding output terminals VA to VF.
To 13f, which are output to the controller 5 side, and the output currents from the four photodiodes 12a to 12d involved in the information signal RF are subjected to arithmetic processing in which they are added by the current / voltage conversion amplifier 14 to calculate the voltage. And output from the output terminal VRF to the controller 5 side. A bias unit 15 for performing a predetermined bias process is connected to the current / voltage conversion amplifier 14.

Further, with respect to such an optical disk device, in an optical pickup having a plurality of optical systems,
Japanese Patent Application Laid-Open No. 11-7635 proposes an arrangement in which the number of signal lines is reduced by selecting an optical system to be used by a switch to reduce the load when the optical pickup is moved and to reduce the wiring cost. .

[0006]

However, according to the conventional general photoelectric conversion device 7 or the optical disk device as described above, since the controller 5 and the photoelectric conversion device 7 are physically separated from each other, the signal line has noise. The structure is easily affected. Further, the ground is structurally weak, and the structure is susceptible to noise other than the signal line. In particular, recently, the wavelength of the semiconductor laser 1 has been shortened for high-density recording, while the sensitivity of the photodiode tends to decrease as the wavelength becomes shorter. Further, it is necessary to widen the whole band in order to improve the data rate. These points are
/ N is worsened.

According to the example of Japanese Patent Application Laid-Open No. 11-7635, although the number of signal lines can be reduced, there is a possibility that the quality of signals is rather deteriorated by switching the switches.

Accordingly, the present invention provides an information signal RF, even if the photoelectric conversion device and the controller are somewhat apart from each other,
Tracking / focusing servo signals can be made less susceptible to noise. As a result,
It is an object of the present invention to provide an optical disk device capable of reducing the amplitude of these signals and operating at high speed.

[0009]

According to the first aspect of the present invention,
A semiconductor laser for emitting light to the optical disk, a driver for driving the semiconductor laser, a controller for controlling the driver, and a plurality of light-receiving and detecting lights irradiated with the laser light from the semiconductor laser and reflected from the optical disk And a photoelectric conversion device having a current / voltage conversion amplifier that converts a current output from these photodiodes to a voltage and outputs the voltage to the controller, wherein the photoelectric conversion device includes:
One-to-one with the photodiode as a voltage conversion amplifier
And a current / voltage conversion amplifier having a corresponding output terminal, and a current / voltage having a differential output terminal for calculating a current output from a specific photodiode among the photodiodes and differentially outputting the calculation result. A conversion amplifier.

Therefore, a current / voltage conversion amplifier having a differential output terminal for calculating a current output from a specific photodiode in the photodiode and differentially outputting the calculation result is used as a differential signal. By outputting to the side, signal transmission that is not easily affected by noise can be performed. Therefore, even if the photoelectric conversion device and the controller are slightly separated from each other, the influence of noise can be reduced. As a result, the signal amplitude can be reduced, and high-speed operation can be performed as the optical disk device.

According to a second aspect of the present invention, there is provided a semiconductor laser for emitting light to an optical disk, a driver for driving the semiconductor laser, a controller for controlling the driver, and a laser beam emitted from the semiconductor laser. A photoelectric conversion device having a plurality of photodiodes for receiving and detecting light reflected from the optical disc, and a current / voltage conversion amplifier for converting a current output from these photodiodes to a voltage and outputting the voltage to the controller. The photoelectric conversion device, as the current / voltage conversion amplifier, calculates a current output from each photodiode in one-to-one correspondence with the photodiode, and outputs a differential output of the calculation result. From a current / voltage conversion amplifier having a terminal and a specific photodiode among the photodiodes And a current-voltage conversion amplifier with a differential output terminal for outputting the calculated current output operation result in the differential.

Therefore, with respect to the output to the controller based on all the photodiodes, a current output having a differential output terminal for calculating a current output and differentially outputting the calculation result.
By using a voltage conversion amplifier to output all tracking / focusing servo signals and the like as differential signals, signal transmission that is less affected by noise becomes possible. Therefore, even if the photoelectric conversion device and the controller are slightly separated from each other, the influence of noise can be reduced. As a result, the signal amplitude can be reduced, and high-speed operation can be performed as the optical disk device.

According to a third aspect of the present invention, in the optical disk device according to the first or second aspect, the specific photodiode is a photodiode involved in the information signal RF.

Accordingly, since the information signal RF is converted into a differential signal and output to the controller side, the influence of noise can be reduced even if the photoelectric conversion device and the controller are somewhat apart from each other. As a result, the signal amplitude can be reduced, and high-speed operation as an optical disk device becomes possible.

The invention described in claim 4 is the first to third aspects of the present invention.
In the optical disc device according to any one of the above, a differential signal line from the differential output terminal of the current / voltage conversion amplifier having the differential output terminal to the controller side is a twisted pair line.

Therefore, in addition to the optical disk device according to any one of claims 1 to 3, the signal line itself for the differential signal uses a twisted pair wire which is less susceptible to attenuation and noise than a parallel line. Therefore, it is possible to further reduce the influence of noise.

[0017] The invention according to claim 5 is the invention according to claims 1 to 4.
In the optical disk device according to any one of the above, the semiconductor laser, the driver and the photoelectric conversion device are mounted on an optical pickup that is movable in a radial direction with respect to the optical disk, and the controller is mounted on a fixed circuit board. It is installed.

Therefore, more realistically, the photoelectric conversion device is mounted on the optical pickup, the controller cannot be mounted on the optical pickup, and the photoelectric conversion device and the controller are less likely to be affected by noise in a configuration in which the photoelectric conversion device and the controller are slightly separated. be able to.

[0019]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. 4 to 6 are denoted by the same reference numerals, and description thereof is omitted.

In the photoelectric conversion device (PD) 21 of the present embodiment corresponding to the photoelectric conversion device (PD) 7,
A differential-type current / voltage conversion amplifier 22 that outputs a single-ended information signal RF from the differential output terminals VRF + and VRF− to the controller 5 as a differential signal with the output terminal VRF of the voltage conversion amplifier 14. Is provided. That is, the current / voltage conversion amplifier 22
Is a specific photodiode 12 involved in the information signal RF.
The current outputs from a to 12d are added, and the addition result is output from the differential output terminals VRF + and VRF- as a differential signal.

Further, regarding the output from the photoelectric conversion device 21 to the controller 5, the differential output terminals VRF +, VRF
Twisted pairs 23 as signal lines for differential signals from RF-
Is used.

Therefore, according to the present embodiment, although the photoelectric conversion device 21 and the controller 5 are far apart,
Since the information signal RF from the photoelectric conversion device 21 is transmitted as a differential signal from the differential output terminals VRF + and VRF- of the current / voltage conversion amplifier 22, it is less affected by noise. As a result, the signal amplitude can be reduced, and high-speed operation as an optical disk device is possible. In particular, recently, for high density recording, the wavelength of the semiconductor laser 1 has been shortened, whereas the wavelength of the photodiode 1 has been reduced.
The sensitivity of 2a to 12f tends to decrease as the wavelength becomes shorter, and furthermore, the S / N of the information signal RF deteriorates in a situation where it is necessary to widen the whole band in order to improve the data rate. This is effective in solving the problem that is causing the problem. In addition, the transmission line for the differential signal from the photoelectric conversion device 21 to the controller 5 side also uses the twisted pair wire 23 that is less affected by attenuation and noise than the parallel line, so that the noise is further reduced. It can be less affected.

A second embodiment of the present invention will be described with reference to FIG. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the photoelectric conversion device 24 of the present embodiment, not only the current / voltage conversion amplifier 22 for the information signal RF but also the output terminals VA to VF of the current / voltage conversion amplifiers 13a to 13f are conventionally used as a single unit. Regarding the signal output at the end, the differential output terminals VA +, VA−,.
Differential current-to-voltage conversion amplifiers 25a to 25 that output from VF + and VF- as differential signals to the controller 5 side
f is provided. That is, all outputs from the photoelectric conversion device 24 to the controller 5 are converted into differential signals and transmitted. Correspondingly, twisted pair wires 23 for each differential signal pair are used for all signal lines related to output from the photoelectric conversion device 24 to the controller 5 side.

As described above, for the recent high-density recording, the sensitivity of the photodiodes 12a to 12f is reduced as the emission wavelength of the semiconductor laser 1 is shortened, and
Although the S / N ratio of a transmitted signal is deteriorated by widening the bandwidth for improving the data rate, each photodiode 12
Since the individual signals obtained based on a to 12f are used for the calculation of the tracking / focusing servo, it is obvious that if the S / N is deteriorated due to the above-mentioned cause, it becomes difficult to perform the servo operation. Servo control cannot be performed. In this regard, in the present embodiment, as in the case of the information signal RF, the signals obtained from the photodiodes 12a to 12f are also converted into differential signals and transmitted to the controller 5 side. Even if the photoelectric conversion device 24 and the controller 5 are far apart from each other, they are hardly affected by noise.
As a result, the amplitude of these signals can be reduced, and high-speed operation as an optical disk device is possible. In addition, the transmission line for the differential signal from the photoelectric conversion device 24 to the controller 5 side also uses the twisted pair line 23 that is less susceptible to attenuation and noise than the parallel line for each differential signal pair. Therefore, it is possible to further reduce the influence of noise.

In carrying out these embodiments, the optical disk 8 is not limited to a CD disk or DVD disk, but may be a so-called magneto-optical disk. In addition, the photoelectric conversion devices 21 and
The photodiode included in 4 is not limited to the combination of six photodiodes as in the embodiment, but can be similarly applied to an appropriate combination of photodiodes.

[0027]

According to the first aspect of the present invention, a current / voltage having a differential output terminal for calculating a current output from a specific photodiode in a photodiode and differentially outputting the calculation result. A conversion amplifier is used to output a differential signal to the controller side, so that the photoelectric conversion device and the controller can be less affected by noise even if they are slightly separated from each other. As a result, the signal amplitude can be reduced. And an optical disk device capable of high-speed operation can be provided.

According to the second aspect of the present invention, with respect to the output to the controller based on all the photodiodes, the current / voltage conversion having a differential output terminal for calculating a current output and differentially outputting the calculation result. Since an amplifier is used to output all of the tracking / focusing servo signals and the like as differential signals, even if the photoelectric conversion device and the controller are slightly separated from each other, it is possible to reduce the influence of noise. Accordingly, it is possible to provide an optical disk device capable of reducing the signal amplitude and operating at high speed.

According to the third aspect of the present invention, in the optical disk device according to the first or second aspect, particularly, the information signal RF
Is converted to a differential signal and output to the controller side. Therefore, even if the photoelectric conversion device and the controller are slightly apart from each other, it is possible to reduce the influence of noise, and as a result, the signal amplitude of the information signal RF is reduced. And an optical disk device capable of high-speed operation can be provided.

According to the fourth aspect of the present invention, in addition to the optical disk device according to any one of the first to third aspects, the signal line itself for the differential signal is more affected by attenuation and noise than the parallel line. Since the twisted pair wire that is hardly affected by noise is used, it is possible to further reduce the influence of noise.

According to the fifth aspect of the present invention, in the optical disk device according to any one of the first to fourth aspects, the photoelectric conversion device is more realistically mounted on the optical pickup and the controller is mounted on the optical pickup. In this case, the influence of noise can be reduced in a configuration in which the photoelectric conversion device and the controller are slightly separated from each other.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a photoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a structural example of the optical disk device.

FIG. 3 is a schematic circuit diagram illustrating a photoelectric conversion device according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing an optical disk device showing a conventional example.

FIG. 5 is a schematic configuration diagram showing a structural example of the optical disk device.

FIG. 6 is a schematic circuit diagram showing a conventional photoelectric conversion device.

[Explanation of symbols]

Reference Signs List 1 semiconductor laser 4 driver 5 controller 12a to 12f photodiode 13a to 13f current / voltage conversion amplifier 21 photoelectric conversion device 22 current / voltage conversion amplifier 23 twisted pair wire 24 photoelectric conversion device 25a to 25f current / voltage conversion amplifier VA to VF output Terminal VRF +, VRF- Differential output terminal VA +, VA-, ..., VF +, VF- Differential output terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D090 AA01 CC04 CC16 DD03 EE12 LL05 5D119 AA10 AA12 BA01 DA01 DA05 FA05 KA02 KA28 KA43 5F049 MA01 NA03 NA04 NB08 UA04 UA20 5F073 AB21 BA05 FA02 GA02 GA12

Claims (5)

[Claims] 1. A semiconductor laser for emitting light to an optical disk, a driver for driving the semiconductor laser, a controller for controlling the driver, and a laser beam emitted from the semiconductor laser and reflected from the optical disk And a photoelectric conversion device having a current / voltage conversion amplifier that converts a current output from these photodiodes into a voltage and outputs the voltage to the controller, and the photoelectric conversion device includes: A current / voltage conversion amplifier having an output terminal corresponding to the photodiode in a one-to-one correspondence with the current / voltage conversion amplifier, and calculating a current output from a specific photodiode in the photodiode; Having a current / voltage conversion amplifier having a differential output terminal for outputting the result differentially Optical disc apparatus according to claim. 2. A semiconductor laser for emitting light to an optical disk, a driver for driving the semiconductor laser, a controller for controlling the driver, and a laser beam emitted from the semiconductor laser and reflected from the optical disk. And a photoelectric conversion device having a current / voltage conversion amplifier that converts a current output from these photodiodes into a voltage and outputs the voltage to the controller, and the photoelectric conversion device includes: A current / voltage conversion amplifier having, as the current / voltage conversion amplifier, a differential output terminal for calculating a current output from each photodiode in one-to-one correspondence with the photodiode and differentially outputting the calculation result; A conversion amplifier and a current output from a specific photodiode among the photodiodes are calculated. Optical disk apparatus characterized by comprising a current-voltage conversion amplifier with a differential output terminal for outputting a differential calculation results of. 3. The optical disk device according to claim 1, wherein the specific photodiode is a photodiode involved in an information signal RF. 4. A current / voltage conversion amplifier having a differential output terminal, wherein a differential signal line from a differential output terminal to the controller side is a twisted pair line. An optical disk device according to any one of the above. 5. An optical pickup which is movable in a radial direction with respect to the optical disk, wherein the semiconductor laser, the driver, and the photoelectric conversion device are mounted, and the controller is mounted on a fixed circuit board. The optical disk device according to any one of claims 1 to 4, wherein: