JPH0453043A - Optical disk tester - Google Patents

Abstract

PURPOSE:To detect the position of fine flaw by quantitatively detecting the fault position respectively in the radial and circumferential directions of a disk. CONSTITUTION:An RF signal (m) outputted from an optical head 13 is amplified to a prescribed level by an amplifier 29, and preformat is detected by a detection part 30 and outputted. When a flaw signal (h) is inputted from a comparator 26 to a latch 32, a counter 31 latches the count value at that time and on the other hand, each time a track is advanced, a counter 27 latches the count value of a Z phase, which is generated from an encoder 12, to a latch 28 simultaneously with the output of the flaw signal from the comparator, and outputs the count value to a bus 24 under the control of a CPU 23. Therefore, according to the outputs of the latches 28 and 32, the flaw positions of tracks and sectors can be recognized without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement of an optical defect tester for detecting defects in optical discs.

<Prior Art> FIG. 4 is a functional block diagram showing the configuration of a conventional optical disc tester. 1 is an optical disk, 2 is a spindle that rotates the optical disk 1 at a constant speed, and 3 is an optical head that irradiates the surface of the optical disk 1 with a laser beam and receives the reflected light with a divided photodiode. Reference numeral 4 denotes an error signal generation section which receives a light reception signal from the optical head and generates a tracking error and a focus error.

The tracking error signal is a signal indicating that the optical head is deviated from the spiral track formed on the surface of the optical disc 1 in the radial direction of the optical disc.
This is a signal that indicates that the distance between the 5 introduces the tracking error signal and the focus error signal, and based on the signals, the optical head 3
A servo unit 6 is a measuring unit that receives the output of the optical head 3 and detects defects in the optical disc 1. This optical disc tester rotates an optical disc 1 using a sub-driver 2, irradiates the optical disc 1 with a laser beam using an optical head 3, generates an error signal after receiving the reflected light, and outputs an optical signal using a servo unit 5. head 3
At the same time, the measuring section 6 evaluates the defect.

<R IJI to be solved by the invention> However, such an optical disc tester only detects whether there is a defect or not, but cannot detect where the defect is located on the optical disc. Therefore, there were problems in that quantitative inspection was not possible and the causes of defects could not be adequately investigated.

The present invention has been made to solve such problems, and an object of the present invention is to provide an optical disc tester that can identify the defect location 1 on the disc.

Means for Solving the Problems> The present invention irradiates an optical disk with laser light from an optical head, receives reflected light from the optical disk to control the position of the optical head, and generates an error signal from this reflected light. An optical disc tester that tests the optical disc by determining the error signal includes an AGC unit that converts the error signal into a signal that does not depend on the intensity of the laser beam and the reflectance of the optical disc; a first counter that counts the Z phase indicating the track position of the optical disk from the output of the spindle encoder; a first latch that latches the output of this counter; and a signal output from the optical head. a preformat detection section that detects a preformat that divides the optical disk into sectors; a second counter that counts the detection signal of this preformat detection section; and a second latch that latches the output of this counter. The optical head is brought into a non-stall state by a measurement start command, the first counter counts two-phase signals, the second counter counts a preformat signal, and the output of the comparator is used to turn the optical head into a non-stall state.
The count values of the first and second counters are latched by the second latch, and the position of the optical head immediately before entering the non-stall state, the track pitch, the reference position of the sector, and the first and second counter values are determined. This optical disc tester is characterized in that the position where an error signal is generated is specified from the value of the latch.

In the present invention, the optical head irradiates the optical disk with laser light, receives the reflected light, and performs AGC.
The error signal is converted into a signal that does not depend on the intensity of the laser beam and the reflectance of the optical disk. here,
The first counter counts the Z phase of the optical disc, and the second counter counts the Z phase of the optical disc.
The counter counts the preformat signals detected by the preformat detection section. The output of the AGC section is compared with a predetermined level by a comparator, and if an error is detected, the count values of the first and second counters are set to the first level.
and a second latch to identify the position of the track and the position of the sector in which the defect is detected.

<Example> The present invention will be described in detail below using the drawings.

FIG. 1 is a functional block diagram showing an embodiment of an optical disk tester according to the present invention. In FIG. 1, 10 is an optical disk, 11 is a spindle for rotating the optical disk 10,
Reference numeral 12 denotes an encoder directly connected to the spindle 11, which outputs a Z-phase signal every time the track rotates once. 1
3 is an optical head that irradiates a laser beam onto the optical disk 10 and detects the reflected light with a two-split photodiode;
Reference numeral 4 denotes a slide table for moving the optical head 13 in the radial direction of the optical disk 10, and reference numeral 15 denotes an encoder for moving the slide table 14 and measuring the distance traveled. 16 introduces the output signals of the two-split photodiode in the optical head 13, and amplifies these output signals 175. The preamplifier calculates the difference between them to obtain a tracking error signal a, and the sum thereof to obtain a signal proportional to the total optical cover entering the photodiode. 17 introduces the two outputs a and b of the preamplifier 16, and 5
, the tracking error signal is divided by a signal proportional to the total amount of light 3E L, , the AGC section outputs a signal C that is independent of the intensity of the laser beam and the reflectance of the optical disk 10, 18 is an AG
Output signal C of C section 17 and output signal e of servo control section 20
This is a servo circuit that receives input, and has a built-in phase compensation circuit and amplifier. ] 9 is a servo power amplifier to which the output of the -V--V circuit 18 is inputted and drives the actuator of the optical head 13. Here, the servo circuit 18, the servo power amplifier 19, and the servo control section 20 constitute a tracking servo, and the optical head 13 is made to follow one of the tracks of the optical disk 10.

The servo control section 20 controls the entire tracking servo and sends a clear signal f to the counter 27, latch 28, and latch 32. Furthermore, the servo control section 20 has a function of jumping tracks by outputting a signal e to the servo circuit 18 and controlling the servo circuit 18 using an analog signal d. By performing this jump once per rotation in synchronization with the Z-phase output of the encoder 12, the optical head 13 can be stopped on the same spiral track formed on the optical disk 10. This state is called a stale control state, but the non-stale state means that the optical head follows a spiral track. amplifier to amplify,
22 is a filter unit that matches the characteristics of the output of the amplifier 21 to the tracking servo band; 23 is a CPtJ that controls the entire circuit via a bus 24; 25 is CPtJ
a D/A converter that converts the digital value set in 23 into an analog signal, that is, in this case, a threshold level;
A comparator 26 compares the threshold level output from the D/A converter 25 with the servo error signal g output from the filter unit 22 as a reference voltage.

Comparator 26 sends a gII signal to latch 28 and latch 32 when a defect is detected by comparison, that is, when servo error signal g exceeds a threshold level. A counter 27 counts the Z phase output from the encoder 12, that is, counts the position of the track from the start of measurement, and is reset by a clear signal f from the servo control section 20. A latch 28 latches the current count value 1 of the counter 27 at the timing of input of the flaw signal from the comparator 26, and is reset by the clear signal f from the size control W section 20. The output signal j from the latch 28 indicates the position of the track where the defect exists. 29 is a preformat detection unit that detects a preformat from the output signal of the RFF signal amplifier 29; A preformat signal n is output every time a preformat is detected. The preformat here is a part that separates sectors on the disk. 31 is a preformat signal n from the preformat detection section 30
This is a counter that takes in and counts the position of the sector from the reference sector position, and is reset by inputting the two-phase signal k from the encoder 12. A latch 32 latches the current count value p of the counter 31 at the timing of input of the flaw signal from the comparator 26, and is reset by a clear signal f from the servo control section 20. The output signal q from this latch 32 indicates the position of the sector where the scratch exists. Reference numeral 33 denotes an interface that is interposed between the servo control section 20 and the servo control section 20 when signals are sent and received through the bus 24.

Next, the present invention will be explained in detail using FIGS. 1, 2, and 3. Components that are the same as those in FIG. 1 are given the same numbers and their explanations will be omitted. FIG. 2 is a block diagram showing details of an optical head and an optical disk, and FIG. 3 is a time chart showing the operation of the present invention.

In FIG. 2, reference numeral 34 indicates an origin index, and a spindle index 38 serves as a reference position on the optical disk 10.
When they match, a two-phase pulse is generated from an encoder 12 (not shown). A preformat 35 is used to distinguish sectors on the optical disk 10 from one another.

36 is a track, and 37 is a unit of one sector.

In this figure, it is divided into 17 sectors, but the number of sectors is determined by the ISO standard to be 17 sectors and 31 sectors. Move in one direction of arrow A-A in the figure. Further, the optical disc 10 rotates in the direction of arrow B (counterclockwise) in the figure. In FIG. 3, ■ is a time chart of the servo error signal g output from the filter unit 22, ■ is a time chart of the I signal output from the comparator 26, and ■ is a time chart of the servo error signal g output from the encoder 12.
Phase k, ■ is a time chart of the count value of the counter 27, ■ is a time chart of the preformat signal n output from the preformat detection section 30, and ■ is the time chart of the counter 3
A time chart of a count value of 1, ■ is a time chart representing the output of the latch 28, ■ is a time chart representing the output of the latch 32, and ■ is a clear signal f output from the servo control section.

First, a measurement start command from the CPU 23 is sent to the bus 24.
, is sent to the servo control section via the interface 33, and the servo 1vI 11 section 20 moves the optical head 13 to a non-stall state and starts testing the optical disk 10 under predetermined settings. The optical disk 10 is rotated by the spindle 11, and the optical disk 10 is irradiated with laser light from the optical head 13, and the reflected light is received by the head. At the same time, each time the track advances, the encoder 12
outputs a two-phase signal (■ in Figure 3). This two-phase output is realized by matching the origin index 34 and the spindle index 38 in FIG. 2, as described above. The light received by the optical head 13 is detected by a two-split photodiode, and the servo difference signal and servo sum signal are sent to the preamplifier 1.
6 is input.

The preamplifier 16 obtains a tracking error signal a and a focus error signal S, which are input to the AGC section 17. Here, the AGC section 17 outputs a signal C that is independent of the intensity of the laser beam and the reflectance of the optical disk 10. This signal C, the output signal e from the servo control unit 20, and the M control signal d based on the Z-phase input for position control of the optical head 13 are input to the servo circuit 18, and the servo circuit 1
The output of 8 is input to a servo power amplifier 19.

Thereafter, the actuator of the optical head 13 is driven by the output of the servo power amplifier 19. Preamplifier 16
The position of the optical head 13 is controlled by a tracking servo composed of an AGC section 17, a servo circuit 18, a servo power amplifier 19, and a servo control W section 20. The signal is amplified to a predetermined level and input to the filter section 22. The filter unit 22 outputs a servo error signal g whose characteristics are matched to the tracking servo band and has a waveform as shown in FIG. 3, for example. This servo error signal g is input to the comparator 26, and the D/
It is compared with the A conversion value (threshold level), and when it exceeds the threshold level, it is regarded as a defect and the flaw signal is output as a high level (Fig. 3 ■).
The counter 27 counts the Z phase generated by the encoder 12 (Fig. 3 ■), but when the comparator 26 outputs a flaw signal (see Fig. 3 ■), the latch 28
latches the count value signal I (■ in Figure 3) at that time, latches X in this case, and sends the latch output signal j (in Figure 3), X in this case, to the bus 24 based on the control signal of the CPU. Output. This latched value allows the track in which the defect exists to be known, and at the same time, the RF flaw signal output from the optical head 13 allows the sector in which the defect exists to be known. This operation will be explained below. The RF flaw signal output by the optical head 13 is amplified to a predetermined level by an RF signal amplifier 29.
A preformat detection section 30 detects the preformat. Here, the preformat detection unit 30 detects the preformat signal n(
Figure 3 ■) is output. In other words, the head outputs a high level every time the head crosses a preformat between sectors. The counter 31 counts this signal n (Fig. 3), and the comparator 26
At the same time, the latch 32 inputs the flaw signal from the counter 31 to the signal p(
Latch (■) in Figure 3. In this case, the count value y of the counter 31 is latched, and the latch output signal q (FIG. 3 ■), in this case y, is output to the bus 24 based on the control signal of the CPU 23. The position of the defective sector can be detected by this output signal q. Therefore,
The track and sector in which the defect exists can be determined by the output j of the latch 28 and the output q of the latch 32, and the position of the scratch on the disk can be determined with certainty. However, since the count of the counter 31 is the number of rotating sectors from the reference sector, when one rotation is made, that is, when moving to the next track, two phases are input from the encoder 12, and the signal is cleared by the counter 31. Reset as a signal. In this case, the count value is always set to represent 0 to 16, so that the sector position where the scratch exists can be detected. When one flaw is detected, a clear signal (■ in Figure 3) output from the servo control unit 20 is input to the latch 28 and the latch 32, and the contents of the latch are reset (■ in Figure 3). ), when testing the optical disk 10 continuously from one track to another, the count value of the counter 27 may be left as is, but when changing the setting of the range of tracks to be tested, the servo A clear signal f is input from the control 20 to the counter 27, and the counter is returned to zero.

In this way, the location of the error on the optical disc can be identified both in the radial direction and in the circumferential direction of the disc.

<Effects of the Invention> As explained in detail above, in the present invention, since the defect position of an optical disc can be identified in both the radial direction and the circumferential direction of the disc, the position can be reliably detected even with minute scratches. It became so.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of an optical disk tester according to the present invention, FIG. 2 is a configuration diagram showing details of an optical head and an optical disk, FIG. 3 is a time chart showing the operation of the present invention, and FIG. The figure is a functional block diagram showing the configuration of a conventional optical disc tester. lO...Optical disk 11...Spindle 1
2... Encoder 13... Optical head 14
... Slide feed table 15 ... Encoder 16 ... Preamplifier 17 ... AGC section 18
... Servo circuit 19 ... Servo power amplifier 20 ... Servo control section 21 ... Amplifier 22 ... Filter section 2
3...CPU 24...Bus 25...
・D/A converter 26... Comparator 27...
・Counter 28...Latch 29...RF
Signal amplifier 30... Preformat detection section 31... Counter 32... Latch 33...
・・Interface 34 ・・Origin index 35 ・・Preformat 36 ・・Tara・Yuri 37 ・・・Sector 38
...Spindle index Figure J Figure

Claims (1)

[Scope of Claims] Laser light is irradiated from an optical head to an optical disk, and reflected light from the optical disk is received to control the position of the optical head, and an error signal is obtained from the reflected light to test the optical disk. The optical disc tester includes: an AGC unit that converts the error signal into a signal that does not depend on the intensity of the laser beam and the reflectance of the optical disc; a comparator that receives the output of the AGC unit and compares it with a predetermined level; and a spindle. a first counter that counts the Z phase indicating the track position of the optical disc from the output of the encoder; a first latch that latches the output of this counter; and sectors of the optical disc from the signal output from the optical head. It is equipped with a preformat detection section that detects the preformat to be classified, a second counter that counts the detection signal of this preformat detection section, and a second latch that latches the output of this counter. The optical head is placed in a non-still state, the first counter counts the Z-phase signal, the second counter counts the preformat signal, and the output of the comparator counts the first signal.
The count values of the first and second counters are latched by the second latch, and the position of the optical head immediately before entering the non-still state, the track pitch, the reference position of the sector, and the first and second counters are latched. An optical disc tester characterized in that a position where an error signal is generated is specified from a latch value.