JPH0192644A - Detecting device for surface state - Google Patents

Abstract

PURPOSE:To remove vibration components and to extract only a component of variation due to a defect by comparing bright point position signals of two kinds of light beams which differ in beam diameter and generating their difference signal. CONSTITUTION:The surface of an object is irradiated with the two kinds of light beams which differ in beam diameter by laser beam irradiating devices 2 and 6 and 1st and 2nd bright point position detectors 5 and 8 detect their reflected light beams. A comparator 9 compares the bright point position signals I1 and I2 from two bright position detectors 5 and 8 with each other and outputs the signal I3 generated by removing their in-phase components. This signal I1 contains both a defect component and a vibration component. The bright point position signal I2, on the other hand, contains only the vibration component. The output signal I3 of the comparator 9 contains only the defect component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a surface condition detection device, and is particularly useful as a surface defect detection device for video disks, magnetic disks, mirrors, wafers, and the like.

[Conventional technology]

As a conventional surface condition detection device, an example of a video disc surface defect detection device will be described with reference to FIGS. 3 and 4.

This surface defect detection device 51 detects whether or not there is a defect d on the surface of the video disc D.The surface defect detection device 51 detects whether or not there is a defect d on the surface of the video disc D. a laser beam irradiation device 2 that irradiates toward the target, a beam splitter 3, a lens 4, and a bright spot position detector that receives the reflected beam a from the video disc D and outputs a signal corresponding to a change in the bright spot position. 5 and a filter 52.

10 is an examination table.

When the surface of the video disc D is scanned with the laser beam A, the angle of the reflected beam a differs between the position where the defect d is present and the position where there is no defect, so the presence of the defect d cannot be detected as a change in the position of the bright spot. I can do it.

However, since the bright spot position also changes due to the relative vibration between the device 51 and the video disc D, the output signal (2) of the bright spot position detector 5 includes both the change due to the presence of the defect d and the change due to the vibration. It becomes something. Such a bright spot position signal 1. is illustrated in FIG.

Therefore, in order to extract only the change due to the presence of the defect d, the filter 52 is used to remove the vibration component.

Furthermore, a vibration isolation table is used as the inspection table 10 to suppress vibration.

Another conventional technique is a surface defect inspection device disclosed in Japanese Patent Application Laid-Open No. 60-69539.

[Problem that the invention seeks to solve]

Even if the filter 52 is used as in the conventional device 51, if the defect component and the vibration component of the change in the bright spot position signal I are in the same phase, the same period, or close to it, only the vibration component is selectively removed. There is a problem that it cannot be done.

Furthermore, when using a vibration isolation table, a high-performance one is required to sufficiently suppress vibrations, which poses the problem of complicating the device.

Therefore, it is an object of the present invention to provide a surface state detection device that can eliminate the effects of vibration by means different from the filters and vibration isolation tables described above.

[Means for solving problems]

The surface condition detection device of the present invention includes a different diameter beam simultaneous irradiation means for simultaneously irradiating the surface of an object with 2N light beams having different beam diameters, and a means for receiving reflected beams of the two types of light beams, and each of the reflected beams. bright spot position detection means for outputting a signal according to a change in the bright spot/position of the loser beam, and comparison means for comparing the bright spot position signals of each of the loser beams with each other and outputting a difference signal. is a structural feature.

In the above configuration, it is preferable that the diameter of one of the two types of light beams be smaller than the size of the defect to be detected, and the diameter of the other beam be larger than the size of the defect.

[Effect]

For example, when detecting a defect on the surface of a video disc, the extent to which the bright spot position of the reflected beam changes due to the influence of the defect varies depending on the beam diameter. On the other hand, the magnitude of change due to the influence of vibration is constant regardless of the beam diameter.

Therefore, by comparing the bright spot position signals of two types of light beams with different beam diameters and obtaining a difference signal, it is possible to remove the vibration component and extract only the component of change due to the defect.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the drawings. Here, FIG. 1 is a conceptual diagram of the configuration of a video disc surface defect detection device which is an embodiment of the surface condition detection device of the present invention, and FIGS. 2 is a diagram of each signal waveform. Note that the present invention is not limited to the embodiment shown in the figure.

In the video disk surface defect detection device 1 shown in FIG. 1, a laser beam irradiation device 2. Beam splitter 3.
The lens 4 and the bright spot position detector 5 have the same configuration as the conventional device described with reference to FIG. 3, and are given the same reference numerals.

The output signal (1) of the bright spot position detector 5 is input to the comparator 9.

Further, a second laser beam irradiation device 6 is provided, and a second laser beam B is emitted onto the surface of the video disc D from a different angle to distinguish it from the first laser beam S emitted by the first laser beam irradiation device 2. is irradiated.

The beam diameter of the second laser beam B is larger than the size of the defect d to be detected, and is usually one order of magnitude larger than the beam diameter of the first laser beam A.

The reflected beam b of the second laser beam B is focused by a lens 7 and is received by a second bright spot position detector 8 .

The second bright spot position detector 8 inputs a signal 2 corresponding to a change in the bright spot position of the reflected beam b to the comparator 9.

The comparator 9 compares the bright spot position signals I+T2 from the two bright spot position detectors 5.8 and generates a signal I with the in-phase component removed.
3 is output.

Now, by laser beams A and B, video disc D is
When scanning the surface of , the output signal 1 from the bright spot position detector 5 becomes as shown in FIG. The bright spot position signal I2 output from the bright spot position detector 8 is, for example, as shown in FIG. It is almost unaffected by the presence or absence of light and contains only vibration components.And since laser beams A and B are simultaneously irradiated to the same position on video disc D, they are included in bright spot position signals II and I2. The vibration components are in phase.

Therefore, if the in-phase component is removed from both bright spot position signals ■1°I2 in the comparator 9, as shown in FIG. 2(C),
A signal (2) containing only defective components is obtained. In this way, even if the defect component and vibration component signals included in the bright spot position signal II have the same phase and the same period, only the vibration component can be selectively removed without any problem.

In another embodiment, instead of the laser beam B having a large beam diameter, a group of multiple laser beams having a narrow beam diameter and parallel to each other is irradiated. This is because this is essentially equivalent to increasing the beam diameter.

In addition, in Figure 1, the first laser beam A is irradiated vertically and the second laser beam B is irradiated obliquely, but the first laser beam A is irradiated obliquely and the second laser beam B is irradiated obliquely. It may also be irradiated vertically.

Furthermore, if the two light beams can be distinguished by a method other than the irradiation angle (for example, by changing the wavelengths of the two light beams), the irradiation angles of the two light beams may be made the same.

Furthermore, under the condition that the size of the light receiving surface of the bright spot position detectors 5 and 8 is sufficiently larger than the variation range of the reflected beams a and b,
Lens 4.7 may be omitted.

〔Effect of the invention〕

According to the present invention, 2M beams with different diameters are placed on the surface of the object.
different diameter beam simultaneous irradiation means for simultaneously irradiating different diameter light beams, and bright spot position detection means for receiving the reflected beams of the two types of light beams and outputting a signal according to a change in the bright spot position of each reflected beam. , a comparing means for comparing the bright spot position signals of the respective reflected beams with each other and outputting a difference signal. Since the influence of relative vibrations can be removed, the surface condition of the object can be suitably detected. Therefore, it is possible to detect minute irregularities, and furthermore,
There is also no need for a high-performance vibration isolation table to suppress relative vibrations.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the configuration of a video disk surface defect detection device which is an embodiment of the surface condition detection device of the present invention, and FIG. 2 (al.
, (bl, (C1 is a diagram of each signal waveform of the embodiment device shown in FIG. 1, FIG. 3 is a conceptual diagram of the configuration of a conventional video disc surface defect detection device, 2 is a diagram of each signal waveform of the conventional device shown in FIG.
Laser beam irradiation device 5...First bright spot position detection device 6...Second laser beam irradiation device 8...Second bright spot position detector 9...Comparator A... First laser beam B...Second laser beam D...Video disc d...Defect.

Claims (1)

[Claims] 1. Different-diameter beam simultaneous irradiation means for simultaneously irradiating two types of light beams with different beam diameters onto the surface of an object, and a means for receiving reflected beams of the two types of light beams and changing the bright spot position of each reflected beam. A surface condition detection device comprising: bright spot position detection means for outputting a corresponding signal; and comparing means for comparing bright spot position signals of the respective reflected beams with each other and outputting a difference signal. .