JPH0580983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a defect inspection device for information recording masters such as glass masters and resist masters.

BACKGROUND ART There is an optical method as a method for recording video, audio information, etc. on a disk-shaped recording medium. In this optical method, a resist master is created by applying photoresist to the surface of a glass master, which serves as a substrate, and forming a resist film. The device is exposed to light using a so-called bit-by-bit method in which it flickers in response to video or audio information, and then the information is recorded based on the length of the pits (dents) obtained and their repetition period.

By the way, in the case of optical discs, signal defects, usually called dropouts, are a formidable enemy.For this reason, during the production stage of the Gilest master disc, it is necessary to check for defects such as dust and scratches on the surface of the master disc, which can cause dropouts. It needs to be inspected.

In this defect inspection, defects on the disc surface are detected by a detecting means that is movable in the radial direction while rotating the master disc, and information on the radial position R of the detecting means and information on the angle θ of the master disc is obtained. This is done by obtaining positional information on the master disc of the defect detection position based on the defect detection position. At this time, it is necessary to determine the reaction between the R-θ distribution of the detected defective portion on the master and the actual distribution on the master, and for this purpose, the origin in the circumferential direction must be made to coincide.

In the past, a method was used to match the origin in the circumferential direction by using, for example, an identification number attached to the master disc as a reference position, but with this method,
It has been difficult to accurately correlate the R-θ distribution of the detected defective portion on the master with the actual distribution on the master.

Summary of the Invention The present invention has been made to eliminate the drawbacks of the conventional ones as described above, and is capable of accurately matching the R-θ distribution of the detected defective portion on the master with the actual distribution on the master. The purpose of the present invention is to provide a defect inspection device for information recording master disks.

The information recording master defect inspection device according to the present invention includes:
The detecting means for detecting defects on the surface of the master includes means for attaching a reference position mark to a portion outside the information recording area on the master prior to defect inspection, and the detection means for detecting defects on the surface of the master records a line relative to the master with the reference position mark as a reference. It is configured to scan at a constant speed to detect defects.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, an information recording master, for example, a resist master disc 1 is supported by a turntable 2 and rotated by a spindle motor 3. As shown in FIG. An optical head 4 is provided above the resist master disk 1 for optically inspecting for defects on the surface of the master disk. The optical head 4 is screwed onto a helical shaft 5 extending in the radial direction of the resist master disk 1 via a member not shown, and as the shaft rotates, it moves in a direction corresponding to the direction of rotation. The helical shaft 4 is rotationally driven by a feed motor 6. A radial position detector 7 for detecting the radial position of the optical head 4 is provided, and the detector supplies radial position information corresponding to the radial position of the optical head 4 to the motor control circuit 8. As this radial position detector 7, well-known means such as a variable resistor whose resistance value changes as the optical head 4 moves may be used.

A pulse generator 9 is provided which continuously generates pulses at regular intervals in synchronization with the rotation of the spindle motor 3, and this pulse generator 9 generates, for example, 1000 pulses per rotation of the spindle motor 3. As this pulse generator 9, for example, an optical means consisting of 1000 slits arranged at a constant pitch in the circumferential direction and a photo sensor arranged opposite to the slits can be used. Further, a one-rotation sensor 10 is provided that generates a pulse every time the spindle motor 3 makes one rotation, and an optical fiber sensor or the like can be used as this one-rotation sensor 10. The motor control circuit 8 controls the movement position of the optical head 4 by controlling the rotational speed and direction of the feed motor 6, and also controls each movement position of the optical head 4 based on the radial position information from the radial position detector 7. The spindle motor 3 is set to CLV so that the linear velocity of the resist master 1 at
(Constant Linear Velocity) control.

The reason why the spindle motor 3 is controlled by CLV is as explained below. That is, as shown in FIG. 2, it is assumed that there is a scratch A with a constant width t (mm) in the radial direction from the inner circumference to the outer circumference on the master of the resist master 1, and the rotational speed of the master is f
(times/sec) and the inspection radius (radius of the moving position of the optical head 4) is R (mm), then the detection pulse width W obtained by inspection by the optical head 4 is W=t/2πR・f (sec ), and if the rotation speed f of the master is constant, the inspection radius R
Therefore, the test pulse width W changes. In order to use this detection pulse width W as a reference for the size of a defect by inspection, the detection pulse width W must also be output at a constant value for a constant width t. Therefore, it is necessary to perform the inspection with 2πR·f=V (linear velocity) constant. Inspecting with CLV control means f = K/R (K: a certain constant), which makes W = t/2πK, and the flaw width t and detection pulse width W are proportional regardless of the inspection radius R. I will do it.

Next, the specific configuration of the optical head 4 for optically inspecting the surface of the resist master 1 for defects will be described based on FIG.
The laser beam emitted from the mirror 12 is reflected by the mirror 12, passes through the diverging lens 13, the beam splitter 14, and the λ/4 plate 15, and enters the objective lens 16, where it is converged by the objective lens 16 to form a minute spot on the resist. The light is irradiated perpendicularly onto the surface of the master disc 1. The objective lens 16 is configured to be driven in the direction of its optical axis by a focus actuator 17. A glass plate 18 is provided between the objective lens 16 and the resist master 1 to prevent dust generated by the sliding movement of the focus actuator 17 from falling onto the resist master 1 and contaminating the resist surface. It is being

The laser beam reflected from the surface of the resist master disk 1 enters the beam splitter 14 via the glass plate 18, the objective lens 16 and the λ/4 plate 15, and is vertically reflected by the beam splitter 14. This reflected laser light enters the beam splitter 20 via the λ/2 plate 19, and is separated by the beam splitter 20 into a laser light for focus error detection and a laser light for defect detection. Ru. A laser beam for focus error detection passes through a cylindrical lens 21 and enters a so-called 4-split photodetector 22 whose light receiving surface is divided into four parts. The four-division photodetector 22 generates an output at a level corresponding to the amount of light received by each light-receiving surface, and supplies it to the focus control circuit 23. A focus control circuit 23 generates a focus error signal based on the four outputs of the four-part detector 22, and controls the height position of the objective lens 16 with respect to the resist master 1 so that this error signal is always zero. This focus error signal detection method is based on the so-called astigmatism method, and is a well-known detection method in the field of optical disc playback devices.

The laser light for defect detection separated by the beam splitter 20 enters, for example, a PIN photodiode 24, which converts it into an electrical signal corresponding to the amount of light and supplies it to a defect detection circuit 25. When a defect such as a scratch exists on the surface of the resist master 1, the signal level of the output signal of the PIN photodiode 24 partially decreases as shown in FIG. By setting the voltage level Vth, a defect detection pulse as shown in FIG. 4b can be obtained. The pulse width W of this detection pulse corresponds to the width t of the defective portion as described above, and the size of the defective portion can be determined from this pulse width.

Referring again to FIG. 1, pulses continuously generated from the pulse generator 9 in synchronization with the rotation of the spindle motor 3 are counted by the counter 26. This counter 26 is reset by a one-rotation pulse generated from the one-rotation sensor 10 every time the spindle motor 3 makes one rotation. The count value of the counter 26 is determined by the D/A (digital/analog) converter 27.
is converted into a sawtooth signal. This sawtooth wave signal is transmitted to the oscilloscope 28 every one rotation as angle θ information corresponding to the position in the circumferential direction from the reference position of the resist master 1 during one rotation.
is applied to the X axis of Radial position R information from the radial position detector 7 is applied to the Y-axis of the oscilloscope 28, and defect detection pulses from the defect detection circuit 25 are applied as brightness information to the Z-axis.
As a result, when there is a defective part on the surface of the resist master 1, the position of the defective part on the master 1 is displayed on the cathode ray tube of the oscilloscope 28, with the angle being the X axis and the radial position being the radial position. The Y axis is
It is displayed as an R-θ distribution in which the brightness change is the size of the defective portion represented by the pulse width of the defect detection pulse.

In addition, R-θ of the detected defective part on the master 1
In order to match the distribution with the distribution on the actual master 1, the resist master 1 is moved in response to a one-rotation pulse generated from the one-rotation sensor 10 prior to defect inspection.
A marking device 29 is provided for applying a single mark on the top. This reference position mark is placed outside the information recording area so as not to affect the recorded information, such as the outermost area of the resist master disk 1 where no information is recorded, or when defect inspection is performed from the inner circumference direction. It is applied to the innermost circumferential area of the resist master disk 1 rather than the recording area. Further, the reference position mark can also be provided on the outermost end surface. As a marking method by the marking device 29, for example, a method of applying a latent image mark by irradiating the surface of the resist master 1 with a laser beam containing a wavelength within the photosensitive range of the photoresist can be considered. This latent image mark is a mark that becomes visible only after it is developed. Other marking methods include methods of changing the geometric shape of the photoresist, such as bubble formation using thermal energy of light and mechanical unevenness formation.

In this way, prior to defect inspection, a single reference position mark is applied to the surface of the resist master disk 1 in response to a one-rotation pulse, and defects are detected using this reference position mark as a reference. −
For example, the origin of the θ distribution can be made to coincide with a predetermined point on the resist master disc, so that the R-θ distribution of the detected defective portion on the master disc 1 can be made to correspond accurately to the distribution on the actual master disc 1. This is possible. The attached reference position mark can be used for defect inspection as well as
It can be effectively used as a reference point for contamination control and inspection in each process.

In the above embodiments, a case has been described in which the present invention is applied to a defect inspection of a resist master disk, but the present invention is not limited to this, and can also be applied to a defect inspection of a glass master disk. In this case, as a marking method using the marking device 29, it is not possible to adopt a method of applying a latent image mark or forming a bulb, so a method of changing the geometrical shape of the surface of the glass master, such as mechanically forming unevenness, is mainly adopted. become.

Effects of the Invention As explained above, the information recording master defect inspection apparatus according to the present invention has a configuration in which a reference position mark is provided outside the information recording area on the surface of the master disc, and defect inspection is performed using this position as a reference. Therefore, it is possible to accurately match the R-θ distribution of the detected defective portion on the master with the actual distribution on the master. Further, since the detection means moves at a constant linear velocity in the scanning direction on the surface of the master disc, the type and size of the defect on the surface can be easily determined from the pulse width of the detection signal from the detection means.
In addition, since the inspection starts with a reference position mark added before the inspection, compared to the case where marks are attached to the master disc in advance, there is no need to spend time searching for marks on the master disc loaded into the device, which shortens the inspection time. It can be done in time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure shows a case where there are scratches on the surface of the resist master disk, FIG. 3 is a configuration diagram showing a specific example of the internal structure of the optical head in FIG. 1, and FIG.
It is a waveform diagram of the output signal a of the PIN photodiode 24 and the detection pulse b of the defect detection circuit 25 in the figure. Explanation of symbols of main parts, 1...Resist master,
3...Spindle motor, 4...Optical head, 7
...Radial position detector, 9...Pulse generator, 10
...One rotation sensor, 11...Laser light source, 14,
20...Beam splitter, 15...λ/4 plate,
19...λ/2 plate, 22...4-division photodetector, 24...PIN photodiode, 25...
Defect detection circuit, 28...Oscilloscope, 29...
...marking device.

Claims (1)

[Claims] 1. A spindle motor that rotationally drives an information recording master disc, a detection means that detects defects on the disc surface of the master disc while moving in the radial direction of the master disc, and a detecting means that detects a moving position of the detection means in the radial direction of the master disc. means for outputting radial position information by the spindle motor; means for generating a one-rotation pulse every time the spindle motor makes one rotation; and means for generating a one-rotation pulse for each rotation of the spindle motor; an information recording master defect inspection apparatus for obtaining position information on the master of a defect detection position by the detection means on the basis of the radial position information and the angle information, means for applying a reference position mark to a portion of the master disc outside the information recording area before the start of defect inspection, and the spindle motor rotates so that the master disc is scanned at a constant linear velocity by the detection means. A defect inspection apparatus for an information recording master disc, wherein the detecting means detects the defect using the reference position mark as a reference.