JPH02287141A - Defect inspecting device - Google Patents

Abstract

PURPOSE:To decide various defects without providing any other optical system by providing a defect detecting means and a defect deciding means and deciding the kind of the defect of a stamper from the detection result of the defect detecting means and the photodetection result of a photodetecting element. CONSTITUTION:This defect inspecting device is constituted by providing the defect detecting means (auto power control circuit) 4 which detects laser light carrying defect information and a defect deciding circuit 11. If there is a specific kind of defect is present on an optical disk original plate (stamper) 10, reflected laser light from the defect returns to a semiconductor laser 1 through polarization optical systems 16 - 13 and then the circuit 4 detects the defect through its pin 8. Then the circuit 11 consisting of a comparator and a logic element decides the kind of the defect on the stamper 10 through logical operation from the detection result of the circuit 4 and the photodetection result of a photodetecting element 19 which photodetects the reflected laser light reflected by a beam splitter 14, and outputs the decision result.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a defect inspection device that inspects defects on an optical disk master (hereinafter referred to as a stamper).

(Prior art) Techniques for inspecting defects in stampers include, for example, Japanese Patent Laid-Open No. 63-67550 and Japanese Patent Laid-Open No. 63-372.
There is a publication No. 45. Among these, JP-A-63-67550 discloses that a laser beam output from a laser light source is irradiated onto a stamper through a beam splitter, and the reflected laser beam from the stamper is reflected by the beam splitter and guided to a photodiode. A defect is detected when the amount of light received by this photodiode falls below a predetermined amount.In addition, Japanese Patent Laid-Open No. 63-37245 discloses that a laser beam output from a laser light source is connected to a polarizing beam splitter. If there is a defect in the stamper in this state, the reflected laser beam from the stamper will return to the laser light source through the polarizing beam splitter on the same optical path.However, if there is a defect in the stamper, If it exists, scattered light will be generated in the reflected laser light from the stamper.Since this scattered light has directionality, only the scattered light out of the reflected laser light from the stamper is reflected by the beam subrifter and divided into four parts. The light is guided to a light-receiving element.Defects can be distinguished from the output of this light-receiving element.

By the way, there are two types of standby defects: foreign matter adhesion and defects in the structure of the standby itself. Among these defects, defects due to adhesion of foreign matter are not transferred to the optical disk, but structural defects are transferred to the optical disk, causing defects in the optical disk.

Therefore, when these defects are to be detected separately, if the former of the above techniques is applied, the amount of light received by the photodiode similarly decreases to a predetermined amount or less for both defects, and the defect is detected as a defect. Therefore, it is not possible to distinguish between defects due to adhesion of foreign matter and structural defects. In addition, the latter technology has a configuration in which the laser light output from the laser light source is irradiated onto the standby bar through a polarizing beam splitter, and the scattered light caused by the defect is guided to a light receiving element divided into four parts. The optical system (big-up head) normally used for reading optical discs irradiates a stamper with laser light output from a laser light source through a polarizing beam splitter, and then reflects the reflected laser light with the polarizing beam splitter. These structures are completely different because the light is guided to the light receiving element. Therefore, in the latter technique, a separate optical system for defect inspection must be provided.

(Problems to be Solved by the Invention) As described above, it has been impossible to distinguish between defects due to adhesion of foreign matter and structural defects, and it has been necessary to provide a separate optical system.

Therefore, an object of the present invention is to provide a defect inspection device that can discriminate various defects without providing a separate optical system.

[Structure of the Invention] (Means for Solving Problem R) The present invention provides that when a laser beam output from a laser light source is irradiated onto an optical disc master through a polarizing optical system, the reflected laser light from the optical disc master is transmitted through a polarizing optical system. In a defect inspection device that uses an automatic power controller of a laser light source to inspect optical disk masters for defects based on the amount of light that is polarized by the action of a system and received by a light receiving element, a predetermined defect on the optical disk master is detected by a laser beam through a polarizing optical system. The above object is achieved by providing a defect detection means for detecting laser light returning to a light source, and a defect determination means for determining the type of defect in the optical disc master from the detection result of the defect detection means and the light reception result of the light receiving element. This is a defect inspection device.

(Function) By providing such a means, when a predetermined type of defect exists on the optical disc master, the reflected laser light from the defect returns to the laser light source through the polarization optical system and is detected by the defect detection means.

Then, the defect determining means determines the type of defect in the optical disk master from the detection result of the defect detection means and the light reception result of the light receiving element which polarized and received the reflected laser light from the optical disk master.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a defect inspection device, and shows a case where the defect inspection device is applied to a pickup head for an optical disk. In the figure, 1 is a semiconductor laser, and as shown in FIG. 2, it is equipped with a light emitting section 2 and a photodiode 3 for monitoring the amount of light emitted. An auto power controller (APC) circuit 4 is connected to the semiconductor laser 1, and a power source 7 is connected between the light emitting leg 5 and the common leg 6 of the semiconductor laser 1, and a monitor leg 8 is connected to the semiconductor laser 1. A current detection circuit 9 is connected between the common leg 6 and the common leg 6 . and,
The amount of current detected by the current detection circuit 9 is fed back to the power source 7, and the output voltage of the power source 7 is controlled, and the amount of light emitted from the semiconductor laser 1 is controlled to be constant through this control.

By the way, this APC circuit 4 has a function as a defect detection means. That is, when this semiconductor laser 1 is outputting laser light, if scattered light generated by foreign matter on the standber 10 is incident, the amount of light emitted from the laser light being output changes. As a result, the output voltage of the amplifier 28 changes depending on the amount of laser light emitted. Therefore, by detecting the output voltage of this amplifier 28, the standby 10
It will be detected that there is a defect in the power supply 7.
The output voltage is sent to the defect determination circuit 11.

On the other hand, a polarization optical system 12 is provided in the laser output direction of the semiconductor laser 1 . To explain the configuration of this polarizing optical system 12, a collimator lens 13, a polarizing beam splitter, a quarter wavelength plate 15, and an objective lens 16 are arranged in order from the light emitting part 2 of the semiconductor laser 1 toward the laser output direction. There is. A cylindrical lens 17 and a condensing lens 18 are arranged in the branching direction of the polarizing beam splitter 14.

A light receiving sensor 19 is provided at the condensing position of the condensing lens 18 . This light receiving sensor 19 outputs a voltage signal according to the amount of light received, and this voltage signal is sent to the defect determination circuit 11.

The defect determination circuit 11 has a function of determining structural defects among the defects in the standber 10 from the output voltage of the feedback amplifier 28 of the APC circuit 4 and the voltage signal from the light receiving sensor 19.

Its configuration includes comparators 20, 21, and 22, and the output voltage of the amplifier 28 is input to the "-" input terminal of one comparator 20 and the "10" input terminal of the comparator 21. DC power supplies 23 and 24 are connected to the "+" input terminal of the comparator 20 and the "-" input terminal of the comparator 20, respectively, for generating determination voltages Va and Vn for the returned laser beam. Therefore, when the output voltage of the amplifier 28 exceeds the judgment voltage Va, the comparator 20 sets the judgment signal P to a low level rLJ indicating defect detection.
The comparator 21 determines that the output voltage of the amplifier 28 is the judgment voltage v
When the value falls below b, the determination signal Q is set to rLJ indicating defect detection.

The voltage signal from the light receiving sensor 19 is input to the "+" input terminal of the other comparator 22, and the DC power supply 25 that generates the judgment voltage VC for defect determination is connected to the "-" input terminal. . Therefore, this comparator 21
When the voltage signal from the light receiving sensor 19 becomes lower than the judgment voltage Vc, the judgment signal R is set to low level rL indicating defect detection.
It is designed to output J. The output terminal of each comparator 20.2f is connected to each input terminal of a gate circuit 26, and the output terminal of this gate circuit 26 and the output terminal of the comparator 22 are connected to each input terminal of a gate circuit 27. However, this defect discrimination circuit 11 discriminates only the structural defects of the standber 10 according to the following table and outputs the discrimination result S.

Next, the operation of the apparatus configured as described above will be explained.

When laser light is output from the semiconductor laser 1, this laser light passes through the collimator lens 13. Polarizing beam splitter 1
The light passes through the 4.4/4 wavelength plate 15, is focused by the objective lens 16, and is irradiated onto the stand bar 10. Here, standby 10
If there is no defect in , the reflected laser light from the standber 10 is sent from the objective lens 16 through the quarter-wave plate 15 to the polarizing beam splitter 14 , and is reflected by the polarizing beam splitter 14 to be transmitted to the cylindrical lens 17 . guided by. Then, the reflected lens laser light passes through the condensing lens 18 to the light receiving sensor 1.
The light is focused on 9. Therefore, when there is no defect in the standber 10, the amount of laser light emitted from the ζ-semiconductor laser 1 is constant, and the output voltage of the amplifier 28 of the APC circuit 4 is constant. However, the output voltage of the amplifier 28 is between the judgment voltages VasVb and the comparator 2
From 0 and 21, high level rHJ judgment signals P, Q
At the same time, the voltage signal output from the light receiving sensor 19 is lower than the determination voltage, and the comparator 21 outputs a high level rHJ determination signal R. As a result, the gate circuit 27 outputs a determination result of high level rHJ indicating that no defect exists.

By the way, if a structural defect exists in the stamper 10, the amount of reflected laser light from the stamper 10 decreases. Then, this reflected laser light passes through the quarter wavelength plate 15 from the objective lens 16, is reflected by the polarizing beam splitter 14, is guided to the cylindrical lens 17, and is further focused onto the light receiving sensor 19 by the condensing lens 18. . At this time, the level of the voltage signal output from the light receiving sensor 19 decreases as the amount of received light decreases, and becomes lower than the determination voltage VC. Therefore, a low level rLJ signal is output from the combo barre 22. Note that at this time, the reflected laser light does not return to the semiconductor laser 1 because its polarization direction does not change, and the output voltage of the power source 7 remains constant. As a result, the gate circuit 25 outputs a determination result S of low level rLJ indicating a structural defect.

Next, in the case of a defect in which foreign matter is attached to the stand bar 10, scattered light is generated by this foreign matter. This scattered light, which is different from the polarization direction of the reflected laser light when the stamper 10 is normal, passes through the polarization beam splitter 14 without being partially reflected, and further returns to the semiconductor laser 1 through the collimator lens 13.

As a result, the amount of light emitted from the semiconductor laser 1 changes, but A
The PC circuit 4 controls the amount of light emitted from the semiconductor laser 1 to be constant. This control increases the output voltage of the amplifier 28. On the other hand, in this state, the amount of light received by the light receiving sensor 19 decreases. Therefore, the comparator 20 or 21 outputs the judgment signal P or Q of low level rLJ, and the comparator 22 outputs the judgment signal R of low level rLJ, and as a result, the gate circuit 27 confirms that there is no structural defect. A determination result S of high level rHJ indicating .

In this way, in the above embodiment, the scattered light that returns to the semiconductor laser 1 from the defect on the standber 10 through the polarizing optical system 12 is detected, and the reflected laser light from the standber 10 is reflected by the polarizing beam splitter 14 and received. Since light is received by the sensor 19 and only structural defects in the stamper 10 are determined from the scattered light and the amount of received light, only structural defects in the stamper 10 can be reliably determined. The structure can be easily constructed by simply adding the defect determination circuit 11 to the optical system of the optical disc, without using a separate optical system.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, although the above embodiment is configured to discriminate only structural defects, the circuit configuration of the defect discrimination circuit 11 may be changed to discriminate between defects due to adhesion of foreign matter and structural defects.

Furthermore, the polarizing optical system 12 may omit the cylindrical lens 17 as shown in FIG.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a defect inspection device that can discriminate various defects without providing a separate optical system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a defect inspection device according to the present invention, FIG. 2 is a block diagram of an auto power controller circuit in the same device, and FIG. 3 is a diagram showing a modification. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 2... Light emitting part, 3... Photodiode, 4... Auto power controller circuit, 10... Standber, 11... Defect determination circuit, 12
... Polarization optical system, 13 ... Collimator lens, 14
...Polarizing beam splitter, 15...1/4 wavelength plate, 16...Objective lens, 17...Cylindrical lens, 1
8... Condensing lens, 19... Light receiving sensor. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] The laser light output from the laser light source is irradiated onto the optical disc master through the polarization optical system, and the reflected laser light from the optical disc master is polarized by the action of the polarization optical system and received by the light receiving element. Based on the amount of received light, the optical disc master is detected. A defect inspection apparatus that performs defect inspection using an automatic power controller of a laser light source, the defect detection means detecting laser light that returns to the laser light source through the polarizing optical system due to a predetermined defect on the optical disk master; What is claimed is: 1. A defect inspection apparatus comprising: defect determining means for determining the type of defect in the optical disk master from the detection result of the detection means and the light reception result of the light receiving element.