JPH08129758A - Optical disk device - Google Patents

Abstract

PURPOSE: To improve an S/N ratio, a C/N ratio without deteriorating a transient response characteristic of a read RF signal even when a linear velocity is different according to a radial position. CONSTITUTION: An optical disk device is provided with rotation angle speed information 31 from a rotary encoder 17 connected to a motor 16 rotation driving a disk medium and a delay amount control circuit 15 calculating the linear velocity based on radial position information 32 from a linear encoder 19 connected to an actuator 18 driving a photosensor 11. Then, a delay amount added to the output of the first half part 11F of the photosensor is controlled to one according to the linear velocity by the delay amount control circuit 15, and a signal adding the output of a delay circuit 13 to the output of the second half part 11R of the photosensor is formed by an addition circuit 14 to be outputted as the read RF signal 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, such as a CAV type optical disk device.
The present invention relates to an optical disk device whose linear velocity changes according to the radial position of a disk medium.

[0002]

2. Description of the Related Art In an optical disc device, information recorded on a recording medium is read by introducing reflected light obtained by irradiating the disc medium with light to an optical sensor using an optical system. . At that time, the distance between the disk medium and the optical sensor (optical system) may change due to the warp of the disk medium, and the focus may not be achieved. It is also necessary to accurately introduce the reflected light from the location where information is stored into the optical sensor. Therefore, in an optical disk device, normally, a plurality of optical sensors (split type optical sensors) receive the reflected light from the disk medium to detect a focus shift and a tracking shift, and detect the shift amount according to the shift amount. Then, the position of the optical sensor is controlled.

Further, in the optical disk device using the split type optical sensor as described above, in order to improve the S / N ratio and the C / N ratio, reproduction of a recorded information signal is performed by using each output of the split type optical sensor. RF signals are being created.

For example, in the pit type optical disk device disclosed in Japanese Patent Laid-Open No. 60-23932, a reproduction RF signal is created by using four outputs from a four-division optical sensor.

FIG. 4 shows an outline of a pit type optical disk device disclosed in Japanese Patent Laid-Open No. 60-23932. As shown in the figure, in this pit type optical disc device, two output signals from the first half portion (51 _F1 , 51 _F2 ) of the four-division optical sensor 51 are input to the adder 52 _F , and the latter half portion ( 51 _R1 and 51 _R2 ), the two output signals from the adder 5
2 _R is input. The output signal of the adder 52 _F is input to the adder 54 via a delay device 53 that is a circuit that adds a predetermined delay to the input signal and outputs the added signal.
The output signal of _R is directly input to the adder 54.
Then, the output of the adder 54 is taken out as the reproduction RF signal 30.

In this technique, it is the CLV (Cons) that delays the output of the first half of the four-division optical sensor 51.
In the pit-type optical disk device of the tant Lenear Velocity) system, as shown schematically in FIG. 5, the output (b) of the latter half of the optical sensor is constant for a certain period of time with respect to the output (a) of the first half of the optical sensor. This is because it is delayed by t. In this optical disk device, the delay unit 53 is used to delay the output of the first half portion by t and add it to the output of the second half portion to make the time change profile dull. Without S
We are trying to improve the / N ratio and C / N ratio.

The same processing is also performed in the magneto-optical disk device, for example, Japanese Patent Application Laid-Open No. 3-152042.
In the magneto-optical disk device described in the publication, the information output is obtained by delaying the phase of the output of the first half by 90 ° and adding it to the output of the second half.

The pit depth is usually about λ /
Since it is set to 5, there is always a phase difference between the output of the first half and the output of the latter half, but when the pit depth is λ / 4, there is no phase difference between both output signals. . For this reason, when there is a pit with a pit depth of λ / 4, the above-mentioned processing adversely deteriorates the time change profile of the reproduction RF signal. Japanese Unexamined Patent Publication No. 63-58625 discloses a pit type optical disc device configured to cope with such a case. Pit optical disk apparatus according to this publication, as shown in FIG. 6, the adder 52 _F,
A phase difference detection circuit 55 for detecting whether or not there is a phase difference in the output of 52 _R , and a switch 56 for switching the delay time of the output of the adder 52 _F to t or "0" are added.
When there is no phase difference between the outputs of the adders 52 _F and 52 _R (that is, when the pit depth is λ / 4), the signal obtained by directly adding both outputs is output as the reproduction RF signal 30. It

[0009]

As described above, according to the conventional technique, the output signal of the first half portion of the split type optical sensor is delayed by a certain time so that the output signal of the latter half portion has the same phase. Is generated and the signal is added to the output signal of the latter half part to obtain the information output.

However, an optical disk device whose linear velocity differs depending on the radial position to be read, for example, C
When the above-mentioned conventional technique is applied to an AV (Constant Anglur Velocity) type optical disc device, when the delay time t is set to an appropriate value for the outer track, as shown in FIG.
As schematically shown in (a) and (b), the time difference t'appearing between the output of the first half portion and the output of the latter half portion is smaller than the set value t when information is read on the inner circumferential side track having a slow linear velocity. Since it becomes large, the profile of the obtained reproduction RF signal becomes distorted as shown in (c), and the effect of adding the delay cannot be sufficiently obtained.

Therefore, an object of the present invention is to improve the S / N ratio and the C / N ratio without deteriorating the transient response characteristic of the read RF signal even if the linear velocity varies depending on the radial position. To provide a device.

[0012]

The optical disk device of the present invention comprises: (a) a disk medium from which recorded information is read out by light; and (b) an optical disk divided into front and back in the signal reading direction of the disk medium. A sensor, (c) an optical system for introducing the reflected light from the disk medium into the optical sensor, (d) a detecting means for detecting the linear velocity of the portion to be read by the optical sensor, and (e) this detection. Delaying means for adding a delay corresponding to the linear velocity detected by the means to the output signal of the first half of the optical sensor; and (f) the signal delayed by this delaying means and the output signal of the second half of the optical sensor are added. And a read signal output means for outputting the signal as a read signal.

When the disk medium is driven at a constant angular velocity, the linear velocity is detected based on the radial position information on the disk medium of the portion to be read as the detecting means. You can use what you do,
When the disk medium is not driven at constant acceleration, the linear velocity detection is performed as the detection means based on the radial position information of the portion to be read on the disk medium and the rotational angular velocity information of the disk medium. Any of the above can be used.

The optical system used in the present invention comprises an objective lens for collimating the reflected light from the disk medium into parallel light, and a focusing lens for converging the reflected light that is collimated by the objective lens. It is desirable that the optical sensor is arranged near the focusing point of the focusing lens.

Further, as the delay means, for example, one that adds a delay corresponding to the linear velocity to the output signal of the first half portion of the photosensor by changing the base resistance of the transistor and the junction capacitance between the base and the emitter is used. be able to. Further, as the optical sensor, one that outputs a digital signal (optical sensor + A / D converter) may be used, and the optical disk device may be configured to perform delay based on the digital signal.

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples.

First, the outline of the configuration and operation of the optical disk device according to the embodiment will be described with reference to FIG. In the optical disk device of the embodiment, the recording mark on the disk medium is irradiated with the laser beam from the laser diode (not shown), and the reflected light is reflected by the optical system 24 including the objective lens and the condenser lens. It is introduced into the two-division optical sensor 11. The two-division optical sensor 11 is arranged at a position slightly different from the condensing point of the condensing lens so that the division line 26 is orthogonal to the moving direction 25 of the recording mark of the disk medium, and the first half of the light is detected. The output of the sensor 11 _F is the amplifier 12
Is inputted to _F, the output of the second half of the optical sensor 11 _R is inputted to the amplifier 12 _R.

The output signal of the amplifier 12 _F is delayed by the delay circuit 13 and then added to the adding circuit 14 _F.
At, the output signal of the amplifier 12 _R is added,
The output of the adder circuit 14 is taken out as the reproduction RF signal 30.

As described above, the phase difference appearing between the output signal of the first half portion and the output signal of the latter half portion of the optical sensor 111 differs depending on the linear velocity of the portion to be read. In the optical disk device of the embodiment, the delay amount control circuit 15 controls the delay circuit 13 so that the delay amount added to the output signal of the amplifier 12 _F corresponds to the linear velocity. Signals of the same phase are always input to 14.

The delay amount control circuit 15 is connected to a rotational angular velocity information 31 from a rotary encoder 17 connected to a motor 16 that rotationally drives a disk medium, and an actuator 18 for moving an optical sensor. The radial position information 32 from the linear encoder 19 that has been read is input, and the delay amount control circuit 15 calculates the linear velocity of the portion currently being read from the information, and the calculated linear velocity is obtained. The corresponding control signal 35 is output to the delay circuit 14.

Details of the adder circuit and the delay circuit in the optical disk device of the embodiment will be described below with reference to FIG. As shown in the figure, the output signal of the first half 11 _{F and} the output signal of the second half 11 _R of the optical sensor are respectively passed through an amplifier 12 and a transistor 4 whose base is grounded.
It is inputted to the emitters (E) of 1, 42.

In the optical disk apparatus of the embodiment, basically, both signals are added by connecting the collectors (C) of the transistors 41 and 42. However, the totem pole is added to the emitter input of the transistor 42. A varicap 46 is provided between the base and emitter of the transistor 44 arranged as a structure, and as is clear from the figure, the varicap 46 is provided with a reverse bias according to the control signal 35 from the delay amount control circuit 15. Is being applied.
As a result, the base resistance 45 of the transistor 44 and the capacitance between the base and the emitter are changed, and as a result, a signal delayed from the signal output of the first half portion 11 _F of the photosensor by the amount corresponding to the linear velocity is generated. , Will be output to the collector of the transistor 43.

The collector output of the transistor 41 and the collector output of the transistor 43 are input between the base and the emitter of a collector installation circuit (emitter follower) composed of the transistor 44, and the signal extracted from the emitter of the transistor 44 is output. After being impedance-matched, the read RF signal 30 is output.

As described above, in the optical disk device of the embodiment, the output of the first half portion of the optical sensor is delayed by the linear velocity and then added to the output of the latter half portion of the optical sensor to read it. Since the configuration is such that an RF signal can be obtained, in an optical disc device in which the linear velocity is not constant,
The S / N ratio and C / N ratio of the read RF signal can be improved without deteriorating the transient response characteristic.

Since the optical disk device of the embodiment is designed so that the rotational angular velocity of the disk medium can be changed,
Although the rotational angular velocity information is input to the delay amount control circuit, when the rotational angular velocity of the disk medium is constant, only the radial position information is input to the delay amount control circuit. The device may be configured.

Further, in the optical disk device of the embodiment, the output of the optical sensor is processed in an analog manner, but the signal processing can be performed in a digital manner.

Modification

FIG. 3 shows a variation in which signal processing is performed digitally.
An outline of the optical disk device of the embodiment is shown. Modified optical disc
In the optical device, as shown in FIG._F,
11 _RThe output of each is the amplifier 12_F, 12_RIncrease
After being widened, A / D (analog / digital) converter 2
0_F, 20_RIs converted into a digital signal by. And A
/ D converter 20_FThe signal output by the digital delay circuit
In response to the control signal 35 from the delay amount control circuit 15,
Is delayed by an amount corresponding to
Read the output signal from the latter half of the optical sensor
It is taken out as an RF signal.

The delay amount control circuit 15 is the same circuit as described in the embodiment, calculates the linear velocity based on the rotational angular velocity information 31 and the radial position information 32, and outputs a control signal according to the linear velocity. 35 is output to the delay circuit 21.

[0030]

As described above, according to the present invention, by adding a delay corresponding to the linear velocity to the output of the first half portion of the optical sensor and then adding it to the output of the latter half portion of the optical sensor, Since the reading RF signal is obtained, the reading R can be performed in the optical disk device in which the linear velocity is not constant.
The S / N ratio and C / N ratio of the F signal can be improved without deteriorating the transient response characteristic.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of a delay circuit and an addition circuit in the optical disc device of the embodiment.

FIG. 3 is a schematic diagram showing an outline of an optical disc device according to a modification of the present invention.

FIG. 4 is a block diagram showing an outline of an optical disk device described in Japanese Patent Laid-Open No. 60-23932.

FIG. 5 is an explanatory diagram showing an outline of the operation of the optical disc device described in Japanese Patent Laid-Open No. 60-23932.

FIG. 6 is a block diagram showing an outline of an optical disk device disclosed in Japanese Patent Laid-Open No. 63-58625.

FIG. 7 is a schematic diagram for explaining a problem that occurs in a conventional optical disk device that obtains a read RF signal by combining outputs of a plurality of optical sensors.

[Explanation of symbols]

 11, 51 Split-type optical sensor 12 Amplifier 13 Delay circuit 14 Addition circuit 15 Delay amount control circuit 16 Motor 17 Rotary encoder 18 Actuator 19 Linear encoder 20 A / D (analog / digital) converter 21 Digital delay circuit 22 Digital addition circuit 24 optical system 25 moving direction of disk medium 26 division line 30 read RF signal 31 rotational angular velocity information 32 radial position information 35 control signal 41, 42, 43, 44 transistor 45 resistor 46 varicap 52, 54 adder 53 delayer 55th position Phase difference detection circuit 56 switch

Claims (6)

[Claims] 1. A disk medium from which recorded information is read out by light, an optical sensor divided into front and rear with respect to a signal reading direction of the disk medium, and reflected light from the disk medium is introduced into the optical sensor. An optical system, a detection means for detecting the linear velocity of the portion to be read by the optical sensor, and a delay corresponding to the linear velocity detected by the detection means in the output signal of the first half portion of the optical sensor. An optical disc device comprising: a delay unit for adding the signal; and a read signal output unit for outputting a signal obtained by adding a signal delayed by the delay unit and an output signal of the latter half of the optical sensor as a read signal. . 2. The linear velocity detection device according to claim 1, wherein the detection means detects the linear velocity based on the radial position information on the disk medium of the portion to be read. Optical disk device. 3. The linear velocity is detected based on radial position information of the portion to be read on the disk medium and rotational angular velocity information of the disk medium. The optical disk device according to claim 1. 4. The optical system includes an objective lens that collimates the reflected light from the disk medium into parallel light, and a focusing lens that focuses the reflected light that is collimated by the objective lens. 4. The optical disk device according to claim 1, wherein the sensor is arranged near the focusing point of the focusing lens. 5. The delay means adds a delay according to a linear velocity to an output signal of the first half portion of the photosensor by changing a base resistance of a transistor and a junction capacitance between a base and an emitter. The optical disk device according to claim 1, wherein 6. The optical disk device according to claim 1, wherein the output signal of the optical sensor is a digital signal.