JP2541042Y2 - Optical disk drive - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to an optical disk device.
In particular, it relates to an improvement in an optical pickup drive control system.

[0002]

2. Description of the Related Art A one-beam optical pickup system will be described with reference to FIG. The optical pickup system 40 includes an objective lens 4 that receives reflected light of the laser beam applied to the groove 51 or the land 52 on the optical disk 50.
1, including a beam splitter 42, a cylindrical lens 43, and a photodiode 44 as a photosensor. As shown in FIG. 8, the photodiode 44 is of a four-division type including divided photodiodes 44A to 44D divided into four equal parts vertically and horizontally. When the optical disk 50 is at the focal position of the optical pickup, a circular spot light is incident on the photodiode 44. However, when the optical disk deviates from the focal position, the spot light approaches an ellipse as shown by S2 or S3 in FIG. As described above, in order to detect a focus error indicating a defocus according to the shape of the spot light incident on the photodiode 44, and to detect a displacement of the optical pickup (objective lens) from the track center, that is, a tracking error. And a four-division photodiode. In this method, detection signals from the divided photodiodes 44A to 44D are added and subtracted. The focus error FE and the tracking error TE are expressed by the following equations. FE = (A + C)-(B + D) (1) TE = (A + B)-(C + D) (2) where A to D are each a divided photodiode 44A
It is assumed that the amount of light detected by .about.44D is represented. In FIG. 7, a waveform W1 indicates a change in the tracking error TE when the optical pickup moves in the radial direction with respect to the optical disk, and a sine waveform which becomes 0 at the center of the groove 51 (track center) and the center of the land 52 is shown. Present.

[0003]

In an optical disk apparatus standardized by ISO or the like, the sum of the return light from the optical disk (usually called track cross signal or radial contrast RC) is dark in the groove,
The light and darkness between the groove and the land is set so that the land becomes bright. Radial contrast RC (= A +
FIG. 7 shows a signal representing the ratio of light and dark on B + C + D).
A signal having a sine waveform as shown by 2 and represented by binary values of 0 and 1 based on the sine waveform is called a mirror signal.
In recent optical disk devices, radial contrast RC
There is a standard that the groove may be dark or bright, such as -0.1 <RC <0.1. On the other hand, in the drive control system of the optical pickup, when the actuator is driven for a track jump or the like, the drive is stopped when the tracking servo accelerates the actuator, and the drive to the actuator is applied when the actuator is decelerated. . However, such a control method is difficult to apply to the above-described standard in which it is difficult to determine the groove-land. In view of such a problem, an object of the present invention is to provide an optical disc device that enables reliable discrimination between a groove and a land and that can perform reliable drive control of an optical pickup.

[0004]

An optical disk apparatus according to the present invention includes a one-beam optical pickup having a photo sensor for detecting return light from an optical disk, and an optical pickup which processes a detection signal from the photo sensor. An optical disc apparatus comprising: a circuit for detecting a tracking error indicating a positional deviation from a track center of the track; and control means for controlling an actuator of the optical pickup based on an output of the tracking error detection circuit.
The photo sensor is moved four times with respect to the moving direction of the return light.
In the direction perpendicular to the moving direction, the division is made into an eight-segment type with two divisions, and four at the center are divided into four at the outside.
A first discriminating circuit for processing detection signals from the four photosensors closer to the center to discriminate the moving direction of the optical pickup; and an output of the first discriminating circuit and the tracking error. A second discrimination circuit that processes the output of the detection circuit and outputs a signal only when the optical pickup is at a position corresponding to the groove on the optical disc to discriminate a groove or a land; and a zero-cross point of the tracking error. And a sample circuit for sampling the output of the second determination circuit, wherein the control means controls the timing of driving the actuator by the output of the sample circuit.

[0005]

The first discrimination circuit according to the present invention discriminates whether the optical pickup is moving inside or outside the optical disk. On the other hand, the second discriminating circuit outputs two signals of high and low indicating the inclination (increase or decrease) of the detected tracking error detection signal. And the control means drives the actuator of the optical pickup only when receiving a signal from the sample circuit.

[0006]

Embodiments of the present invention will be described below.
FIG. 2 shows a photodiode 21 as a photosensor used in the present invention. The photodiode 21 is divided into four in the moving direction of the return light from the optical disk, and divided into two in the direction perpendicular to the moving direction.
It is an eight-segment type consisting of 1H, and 4
The two 21B, 21C, 21F, and 21G are smaller than the four 21A, 21D, 21E, and 21H on the outer side. The four divided photodiodes 21 near the center
The widths of B, 21C, 21F, and 21G are set such that the spot light SP is equally divided into four when the spot light SP is located at the center of the photodiode 21. FIG. 1 shows a drive control system of an actuator of an optical pickup,
In addition to the tracking error detection circuit 10 for detecting a tracking error indicating a position shift from the track center of the optical pickup based on the detection signals from the divided photodiodes 21A to 22H shown in FIG.
00 drive system 11 and divided photodiodes 21B,
A first determination circuit 12 that processes detection signals from 1C, 21G, and 21F to determine the moving direction of the optical pickup;
The output of the first discriminating circuit 12 and the output of the tracking error detecting circuit 10 are processed to output a signal only when the optical pickup is at a position corresponding to the groove on the optical disc to discriminate the groove and the land. And a sample circuit 14 for sampling the output of the second determination circuit 13 at the zero-cross point of the tracking error detection signal from the tracking error detection circuit 10. The tracking error detection circuit 10 generates a sum signal S (A + B + G + H) of the detection signals of the divided photodiodes 21A, 21B, 21G, and 21H and a sum signal S (C + D + E + F) of the detection signals of the divided photodiodes 21C, 21D, 21E, and 21F. The tracking error TE is calculated by the following equation (3). TE = (A + B + G + H)-(C + D + E + F) (3) The drive system 11 includes a CPU 11-1 and a switch circuit 11-2.
The CPU 11-1 controls the timing for driving the actuator 100 by turning on and off the switch circuit 11-2 by the output of the sample circuit 14, as described later. The second discriminating circuit 13 includes a differentiating circuit 13-1 for differentiating the tracking error detection signal, and a switch circuit 13-2 switched by the output of the first discriminating circuit 12.
A phase inverting circuit 13-3 for inverting the phase of the differentiated tracking error detection signal sent via the switch circuit 13-2, and a level comparing circuit 13-4.
And outputs a signal only when the level of the differentiated tracking error detection signal or the signal whose phase is inverted is equal to or higher than a certain value. As will be described later, the sample circuit 14 samples the output of the level comparison circuit 13-4 in a predetermined time zone around the zero cross point of the tracking error detection signal amplified by the amplification stage 11-3.

The first discriminating circuit 12 will be described with reference to FIG. The first determination circuit 12 generates a sum signal S (B + G) of detection signals of the divided photodiodes 21B and 21G.
And a sum signal S (C) of detection signals of the divided photodiodes 21C and 21F.
+ F), and a second binarizing circuit 12-2 for binarizing
And a D-type flip-flop 12-3 using the output of the binarization circuit 12-1 as a D input and the output of the second binarization circuit 12-2 as a clock input. Sum signal S (B +
G) and S (C + F) and FIG. 4 showing signals of respective parts in FIG.
The operation will be described also with reference to FIG. In FIG. 2, the brightness in the spot is divided by the divided photodiodes 21A to 21D.
To the sum signal S, as shown in FIG.
(B + G) and S (C + F) are signals having a certain phase difference. The sum signals S (B + G) and S (C + F) are first and second binarization circuits 12-1 and 12-2, respectively.
Are converted into binary signals S12-1 and S12-2. The flip-flop 12-3 has a function of sampling the binary signal S12-1 at the rising edge of the binary signal S12-2. That is, the output signal S12-3 of the flip-flop 12-3 becomes high if the binary signal S12-1 is high at the time of rising of the binary signal S12-2. In this way, when the brightness of the spot moves from the divided photodiodes 21A to 21D, the output of the flip-flop 12-3 becomes high. Conversely, when the brightness of the spot moves from the divided photodiodes 21D to 21A, as shown in FIG.
Since the output signal 12-1 is not sampled by the binary signal S12-2, the output of the flip-flop 12-3 remains low. As is apparent from the above description, the first determination circuit 12 has a function of determining the phase between the sum signal S (B + G) and S (C + F).

Returning to FIG. 1, the differentiating circuit 13-1 differentiates the tracking error detection signal TE and outputs a differentiated signal DTE advanced by 90 degrees in phase. The relationship between the tracking error detection signal TE and the differential signal DTE is as shown in FIG. In FIG. 5, GC indicates the center of the groove. Note that FIG.
FIG. 5b shows the relationship when moving from 1A to 21D, and FIG.
The relationship when moving toward A is shown. Switch circuit 1
3-2, when the output of the first determination circuit 12 is high,
The differential signal DTE is output to the OR gate 13-5. On the other hand, when the output of the first determination circuit 12 is low, the differential signal DTE is supplied to the phase inversion circuit 13-3. The phase inversion circuit 13-3 outputs a phase inversion signal of the differential signal DTE (FIG. 5).
b (shown by a broken line) is output to the OR gate 13-5. The level comparison circuit 13-4 outputs a high-level signal only when the signal from the OR gate 13-5 exceeds a predetermined level. The level comparison circuit 13-4 operates when the optical pickup is located before and after the center of the groove (FIG. 5).
a, a high-level signal is output in FIG. This means that the second discriminating circuit 13 has a function of discriminating grooves and lands on the optical disc. The sample circuit 14 further samples the mirror signal output from the level comparison circuit 13-4 in a predetermined time zone centered on the zero cross point of the tracking error detection signal TE. Output a signal. The CPU 11-1 uses the sample signal from the sample circuit 14 to switch the switch circuit 11.
By turning on -2, the tracking error detection signal amplified by the amplification stage 11-3 is supplied to the drive amplifier 11-4. Thus, the drive amplifier 11-4 drives the actuator 100 only when the actuator of the optical pickup is located at the timing when the brake is applied in the tracking direction. Referring to FIG. 6, the brake timing when the actuator is moving in a certain direction will be described. In FIG. 6A, the brake is activated when the servo system is turned on on the positive side of the tracking error TE, and the actuator is accelerated when the servo system is turned on on the negative side of the tracking error TE. FIG. 6B shows a mirror signal which is an output of the discriminating circuit 13. When the output of the discriminating circuit 13 is sampled by the sample circuit 14, FIG.
The tracking servo is turned on at the high level timing of this signal (FIG. 6d), and the brake is applied. The latter half of FIG. 6A shows that the track is traced normally by turning on the tracking servo. Although the present invention has been described with respect to an embodiment, the present invention is not limited to the illustrated configuration, and various modifications are possible.
For example, the differentiating circuit 13-1 may be a 90-degree phase delay circuit.

[0009]

As described above, according to the present invention, the drive control of the optical pickup such as a track jump can be accurately performed by reliably determining the groove and the land on the optical disk. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing an example of a photo sensor used in the present invention.

FIG. 3 is a block diagram illustrating a configuration of a first determination circuit in FIG. 1;

FIGS. 4A and 4B are diagrams showing signals of respective parts in the circuit of FIG. 3;

5A and 5B are diagrams showing a relationship between a tracking detection signal and a phase delay signal in the circuit of FIG.

FIG. 6 is a diagram for describing brake timing when an actuator is moving.

FIG. 7 is a diagram for explaining a relationship between an optical pickup system, an optical disk, and a tracking detection signal.

FIG. 8 is a diagram for explaining a relationship between the photodiode shown in FIG. 7 and a spot light reflected from the optical disc.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Drive system 13 Second discriminating circuit 11-3 Driving stage 11-4 Drive amplifier 13-4 Level comparison circuit 14 Sample circuit 41 Objective lens 42 Beam splitter 43 Cylindrical lens 44 Photodiode 50 Optical disk 51 Groove 52 Land

Claims (1)

(57) [Scope of request for utility model registration] 1. A one-beam optical pickup having a photosensor for detecting return light from an optical disk, and a tracking error indicating a displacement of the optical pickup from a track center by processing a detection signal from the photosensor. And a control unit for controlling an actuator of the optical pickup based on an output of the tracking error detection circuit, wherein the photo sensor is divided into four parts in the moving direction of the return light, In the direction perpendicular to the direction, an eight-segment type is divided into two parts, and the four parts near the center are made smaller than the four parts near the outside, and the detection signals from the four photosensors near the center are processed to generate the light. A first determining circuit for determining a moving direction of the pickup, an output of the first determining circuit, and the A second discrimination circuit that processes the output of the king error detection circuit and outputs a signal only when the optical pickup is at a position corresponding to the groove on the optical disc to discriminate between a groove and a land; An optical disk device, comprising: a sample circuit that samples an output of the second determination circuit at a zero crossing point, wherein the control unit controls the timing of driving the actuator based on an output of the sample circuit.