JPS6333651A - Optical disk inspecting device - Google Patents

Abstract

PURPOSE:To detect even a small defect existing on a guide groove of a disc, by varying the feed speed of a linear motor and revolutions of a spindle motor to always keep a scanning speed constant, when a fine spot of laser light scans over a guide groove in the surface of the disc. CONSTITUTION:A drive signal is outputted to a spindle motor 2 to scan along a guide groove in the surface of an object to be inspected placed on the spindle motor spirally with light irradiated from a light head 7 while a linear motor 4 is moved radially based on a radius position signal outputted from a radius position detector 5 so as to keep the scanning speed constant. The surface of a disc 1 is irradiated with a fine spot of laser light and an electrical signal of the reflected light thereof is converted into digital from analog synchronizing a rotation position signal, and the data thus converted is memorized 10 sequentially at a specified address. Thus, the length of a defect is determined 9 based upon the electrical signal and the results of inspecting the defect is displayed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical disc inspection device for inspecting defects such as dust and scratches on the surface of an object to be inspected such as an optical disc. In an optical disk inspection device that detects defects such as dust and scratches on the surface of an optical disk, the laser beam from the optical head scans along the guide groove of the optical disk, and the line of the laser beam is scanned by controlling the spindle motor and linear motor. By keeping the speed constant, the resolution for detecting the length of a defect can be kept constant regardless of the radial position of the disk.

[Conventional technology]

Conventional optical disk inspection equipment used a 10-gen lamp as a light source, so the beam spot on the disk surface was a large oval that spanned several guide grooves, and since the rotation speed of the disk was constant, the radius of the disk [Problem to be solved by the invention] However, with the above-mentioned conventional technology, defects smaller than the beam spot are not detected, and the defect detection resolution differs depending on the radial position of the disk. There is a problem.

The present invention is intended to solve these problems, and its purpose is to be able to detect even small defects that exist only on the guide groove of the disk, and to keep the defect detection resolution unchanged depending on the radial position of the disk. An object of the present invention is to provide an optical disc inspection device that can accurately detect the length and number of defects on the disc surface by doing this.

[Means for solving problems]

The optical disk inspection apparatus of the present invention is characterized by having the following configuration.

b) Irradiate the disc surface with a minute spot of laser light,
An optical head equipped with a photodetector that detects light reflected on the disk surface.

(b) A linear motor that drives the optical head in the radial direction of the disk.

(c) A radial position detector that outputs a radial position signal indicating the radial position of the optical head on the disk.

2) A spindle motor on which the object to be inspected is placed.

(E) A rotational position detector that outputs a rotational position signal indicating the rotational position of the spindle motor.

(f) A drive signal is output to the spindle motor to scan the surface of the object placed on the spindle motor in a spiral manner along the guide groove with the light emitted from the optical head, and the scanning speed is kept constant. A control unit that outputs a drive signal to the linear motor to move the linear motor in the radial direction based on the radial position signal output from the radial position detector.

(g) A temporary memory section that converts the electrical signal from the photodetector into analog-to-digital in synchronization with the rotational position signal and sequentially stores the analog-to-digital converted data at predetermined addresses.

(G) Comparator that determines the length of the defect from the electrical signal from the photodetector◎ (Display unit that displays the defect inspection results made by the male comparator.

[For production]

According to the above configuration of the present invention, the linear motor is controlled so that the scanning speed is always constant when scanning the minute spot of laser light over the guide groove on the disk surface based on the radial position signal output from the radial position detector. The feed rate and the rotation speed of the spindle motor can be successively changed.

〔Example〕

The present invention will be explained below with reference to the drawings.

FIG. 1 shows a block diagram of an optical disk inspection apparatus according to the present invention, in which 1 is an optical disk, 2 is a spindle motor, 3 is a rotational position detector for detecting the rotational position of the spindle motor, and 4 is an optical head. 5 is a radial position detector that detects the radial position of the linear motor; 6 is a radial position detector that detects the rotational position signal of the spindle motor and the optical head from the rotational position detector and the radial position detector; This is a control section that controls and outputs a spindle motor drive signal and a linear motor drive signal so that the linear velocity of the scanning beam is constant based on the disk radial position signal, and is made up of a microcomputer. Reference numeral 7 denotes an optical nozzle, which includes a semiconductor laser, an objective lens that focuses a minute spot on the guide groove of the optical disk, an actuator mechanism that makes the minute spot follow the guide groove when the disk rotates, and detects the reflected light from the optical disk as a RIP signal. It consists of a photodetector. 8 is a comparator that determines the length of the defect as an RP multiplied signal defect signal from the photodetector.

9 counts the number of defects of each length determined by the comparator, and a display unit 010 that displays the result displays position information on the optical disc of the defect signal in order to know the distribution of defects on the optical disc. A temporary memory section that stores. 11 is an RF wound signal. The rotational position signal from the 30-rotation position detector is 1 as the origin in the circumferential direction of the 0-index pulse, which has an index pulse that is output once per rotation of the spindle motor and a rotary encoder pulse that is output 1000 times. , The position of the scratch on the disk in the circumferential direction of the disk is determined by counting the rotary encoder pulses. ◎ Also, the number of tracks is counted by counting the index pulses. In this embodiment, if 100 tracks are counted,
The control unit 6 outputs a signal to the linear motor 4 to move it by 100 tracks, and at the same time outputs a signal to the spindle motor 3 to change the rotation speed so that the S speed of the scanning beam is constant. ing.

The embodiment shown in FIG. 2, which embodies the comparator 8 shown in FIG. 1, will be described. 11 is an RF scratch signal, which is a disc scratch signal. 12 is a comparator, 1 variable resistor 13 and 1
Reference numeral 4 sets the threshold level of the comparator 12, and reference numeral 15 indicates an OR circuit. 16 is a disc scratch signal output from the comparator.

FIG. 3 explains the operation of the comparator of FIG. 2.

In Figure 3, 17 is R? Scratch signals 18 and 19 are threshold levels of the comparator 12 set by variable resistors 15 and 14, and Al 20 is a disc scratch signal output from the OR circuit after being compared at the threshold levels 18 and 19. As shown in FIG. 3, the scratch signal 20 uniformly detects as a scratch on the disk whether the RIP signal 17 shifts to a positive level or a scratch shifts to a negative level. ◇The length of the scratch is determined from the scratch signal 20. Therefore, in this embodiment, the 4MHz clock pulse is used as the flaw signal 2.
This was done by counting only while 0 was rising.

〔Effect of the invention〕

As described above, according to the present invention, since the linear velocity of the scanning beam is constant regardless of the radial position of the disk,
Since the resolution for detecting the length of scratches on the disk is constant, it has the effect that the lengths of the scratches distributed on the disk can be detected with high accuracy. Furthermore, since the scanning beam is narrowed down to a minute spot and scanned along the guide groove, it is possible to accurately detect minute scratches existing on the guide groove that contribute to BER (pit error rate). .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the optical disc inspection apparatus of the present invention. FIG. 2 is a diagram showing a specific example of the optical disc inspection apparatus of the present invention. FIG. 6 is an operational waveform diagram of the circuit shown in FIG. 2. Control unit 7... Optical head 8... Comparator 9... Display unit 10... Temporary memory unit 11... RF scratch signal Applicant: Seiko Epson Corporation 5: Hand diameter I standing 1 荊fune tool b: @ straight J-1 fl Mo'aP 7-9 head pa 8: ni Zaku number j Figure I → Figure 2 Figure 3

Claims (2)

[Claims] (1) An optical disc inspection device characterized by having the following configuration. b) Irradiate a minute spot of laser light onto the disk surface,
An optical head including a photodetector for detecting light reflected from the disk surface. b) A linear motor on which the optical head is mounted and drives the optical head in the radial direction of the disk. c) A radial position detector that outputs a radial position signal indicating the radial position of the optical head on the disk. d) A spindle motor on which the object to be inspected is placed. e) A drive signal is output to the spindle motor to scan the surface of the object placed on the spindle motor in a spiral manner along the guide groove with the light irradiated from the optical head, and the scanning speed is increased. A control unit that outputs a drive signal to the linear motor to drive the linear motor to move the optical head in the radial direction based on the radial position signal output from the radial position detector so as to be constant. g) A temporary memory unit that performs analog-to-digital conversion of the electric signal from the photodetector in synchronization with the rotational position signal and sequentially stores the analog-to-digital converted data at predetermined addresses. H) A comparator that determines the length of the defect from the electrical signal from the photodetector. (i) A display unit that displays the defect inspection results made by the comparator. (2) The defect data stored in the temporary memory section has a length longer than a certain length determined by the threshold level set in each pixel area of a plurality of pixels obtained by dividing into polar coordinates around the rotation center of the disk. 2. The optical disc inspection apparatus according to claim 1, wherein the defect data is the defect data.