JPH0648399Y2 - Non-contact micro surface abnormality detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to minute scratches and dust on the surface of an object to be inspected from the change in the amount of the reflected laser beam from the surface of the object to be inspected having a surface that reflects light. The present invention relates to a non-contact micro surface abnormality detection device for detecting a surface abnormality such as a non-contact.

(Prior Art) Generally, in a so-called coating operation for coating a surface of a lens, a prism or the like with a single-layer film or a multilayer film, if the surface of the lens, the prism or the like before coating has a surface abnormality such as a scratch or dust, it is uniform. It is not possible to form a coating film on the substrate, which causes inconvenience.

For this reason, an operator visually inspects the surfaces of lenses, prisms, etc. to detect surface defects such as scratches and dust on the surfaces.

(Problems of the prior art) However, if a large amount of lenses, prisms, and the like are inspected by such operator's visual inspection, the inspection work is an inhuman and simple operation, so the inspection amount of the lenses, prisms, etc. As the number of defects increases, the number of defects (inspection errors) on these surfaces and dusts increases, resulting in a decrease in inspection efficiency.

That is, there is a demand to free the operator from such simple work and to carry out an efficient automated inspection without an inspection error by the inspection device.

There is also a problem that it is very difficult to visually detect surface defects such as scratches and dust.

(Purpose of the Invention) The present invention has been made in view of the background as described above, and detects non-contact micro surface abnormalities by detecting microscopic scratches on the surface of a test object or surface abnormalities such as dust by contact. The purpose is to provide a device.

(Means for Solving the Problems) Therefore, the non-contact micro-surface abnormality detecting device according to the present invention includes a laser light source that emits a laser beam that irradiates the surface of an object that reflects light, and a plurality of laser beams that emit the laser beam. Beam splitting means for splitting the beam into beams, an optical system for focusing the plurality of beams split by the beam splitting means on the surface of the object to be examined, and the plurality of beams reflected on the surface of the object to be examined. Focusing means for adjusting the focus of the laser beam on the surface of the object to be inspected based on the intensity of at least one of the reflected beams, and at least one of the plurality of beams reflected by the surface of the object to be inspected. Surface abnormality detecting means for detecting an abnormality on the surface of the object to be inspected based on the difference in intensity between the two reflected beams.

With the above configuration, by detecting the change in the light amount of the reflected laser beam from the surface of the object to be inspected, it is possible to detect surface abnormalities such as minute scratches and dust that cannot be visually observed by contact.

(Embodiment of the Invention) Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view showing a main part of an optical system in an embodiment of the non-contact micro surface abnormality detecting device according to the present invention.

FIG. 1 shows the main part of the optical system of the optical pickup unit PU. The main part of the optical system is the laser diode 1,
It is composed of a collimator lens 2, a diffraction grating 3, a beam splitter 4, a mirror 5, an objective lens 6, a plano-convex lens 7 and a photosensor 8.

A laser beam LB emitted from the optical pickup unit PU to the surface of the object to be inspected (not shown) inspects the surface of the object to be inspected for surface defects such as minute scratches or dust.

The object to be inspected may be anything as long as it has a surface that reflects light. However, if the surface of the laser beam is mirror-treated with glass, a lens, a prism, etc., the reflectance of the light on the surface is high, or if the reflectance of the light on the surface is high as with the above-mentioned laser beam.
Since LB is reflected well, even minute surface abnormalities can be accurately inspected.

The laser beam LB from the laser diode 1 has its cross-sectional shape shaped into a perfect circle by the collimator lens 2, passes through the diffraction grating 3 and the beam splitter 4, is reflected by the mirror 5, and is guided to the objective lens 6. And
The laser beam LB is focused by the objective lens 6 on the surface of the test object.

The laser beam reflected from the surface of the object to be examined passes through the objective lens 6 in the opposite direction to the above case, is reflected by the mirror 5, and is guided to the beam splitter 4. Then, the light is reflected by the beam splitter 4 in the arrangement direction of the photosensor 8 and introduced into the photosensor 8 via the plano-convex lens 7. Then, the reflected laser beam from the surface of the inspection object introduced into the photodetector 8 through the above-mentioned path is converted by the photodetector 8 into an electric signal corresponding to the amount of light.

It should be noted that the objective lens 6 is controlled by a control unit to be described later so that the optical axis direction of the laser beam LB (Z direction shown in FIG. 1) and a certain direction orthogonal to the optical axis of the laser beam LB (X direction shown in FIG. 1). Direction) is configured to be movable in two directions.

FIG. 2 is a schematic configuration diagram of a control unit that controls the objective lens 6 of the optical pickup unit PU.

The control unit of the objective lens 6 is composed of a focusing actuator 9, a vibration actuator 10, an error amplifier 11, an oscillator 12, an amplifier 13 and the above-mentioned photodetector 8.
Movement control of the objective lens 6 in the above two directions is performed.

To move the objective lens 6 in the directions Z _U and Z _D shown in FIG. 2 (the optical axis direction of the laser beam LB), the photosensor 8, the error amplifier 11, and the focusing actuator 9 are connected in the order described. Feedback control is performed by the focus control means. That is, when the focus of the laser beam LB deviates from the surface of the object to be inspected, the light quantity of the reflected laser beam changes, and this light quantity change causes a change in the output signal of the photosensor 8. Therefore, the focus control means controls as follows. To be done.

The output signal of the photosensor 8 is input to the error amplifier 11, amplified by the error amplifier 11, and output to the focusing actuator 9 as the error signal E. Then, the focusing actuator 9 moves the objective lens 6 to one of the arrows Z _U and Z _D shown in FIG. 2 based on the error signal E to shift the focus of the laser beam LB on the surface of the test object. To fix.

On the other hand, the movement of the objective lens 6 in the directions X _L and X _R shown in FIG. 2 (a certain direction orthogonal to the optical axis of the laser beam LB) is
The oscillator 12, the amplifier 13, and the vibration actuator 10 are connected and controlled in this order. That is, the oscillation output of the oscillator 12 (which is a sine wave oscillation output in this embodiment) is input to the amplifier 13, and the output signal of the amplifier 13 is applied to the vibration actuator 10.
Entered in. The vibration actuator 10 vibrates the objective lens 6 in the above direction by a predetermined width based on the output signal of the amplifier 13.

FIG. 3 is an explanatory diagram showing a schematic configuration of an abnormality detecting means provided in the optical pickup unit PU for detecting a minute surface abnormality on the surface of the test object. In the figure, 14 is a test object such as a glass plate, and 15 is an operational amplifier. The object to be inspected 14
Is shown on its side.

The laser beam LB from the laser diode 1 passes through the diffraction grating 3 and goes straight to the object to be inspected 14 in the same optical path as the laser beam LB ₀ , and the optical path is slightly deviated symmetrically with respect to the laser beam LB ₀ . The laser beams LB ₁ and LB ₂ are split into three beams.

These three laser beams LB ₀ , LB ₁ , and LB ₂ are focused on the surface of the object to be inspected 14 in such a manner that the beam diameters are very narrow and narrowed, and are reflected on the surface of the object to be inspected 14 respectively. Are guided to the beam splitter 4. And each reflected laser beam LB
₀ ′, LB ₁ ′, and LB ₂ ′ are reflected by the beam splitter 4 and introduced into the photosensor 8.

The photodetector 8 is configured by providing a photosensing unit 8a at the center thereof and photosensing units 8b and 8c on both sides of the photosensing unit 8a. The light sensing portion 8a has a configuration in which its detection site is divided into four.

The above three reflected laser beams LB ₀ ′, LB ₁ ′, LB ₂ ′
Are introduced into the light sensing portions 8a, 8b, 8c of the light sensor 8, respectively.

The output signal of the photo detector 8a is input to the error amplifier 11 described above. That is, the photodetector 8 constituting the above-mentioned focus control means is, in detail, the photodetector 8a of the photosensor 8.

On the other hand, the output signals of the photo detectors 8b and 8c are input to the two input terminals of the operational amplifier 15. The output signal of the operational amplifier 15 is a signal S. Then, the photo-sensing units 8b, 8c (photo-sensing device 8) and the operational amplifier 15 constitute an abnormality detecting means for detecting a surface abnormality such as a minute scratch or dust on the surface of the object 14 to be inspected. is there.

FIGS. 3A and 3B show laser beams LB (LB ₀ , L
A part of the surface of the test object 14 irradiated with B ₁ and LB ₂ ) and the output signal waveform (signal S) of the operational amplifier 15 are shown. In addition,
In the same figure, the arrow SD indicates the scanning direction of the laser beam LB, and the optical pickup unit PU is scanned in the arrow SD direction, or the object 14 itself is scanned in the direction opposite to the arrow SD. It Further, O ₁ and O ₂ are surface defects (abnormal parts) such as minute scratches or dust on the surface of the object to be inspected 14, respectively.

When the laser beam LB ₁ or LB ₂ is irradiated to the abnormal portion O ₁ or O ₂ on the surface of the object to be inspected 14 by the scanning of the optical pickup unit PU in the direction of the arrow SD, the abnormal portion O ₁ or O ₂ Therefore, the light quantity of the reflected laser beam LB ₁ ′ or LB ₂ ′ changes. This change in the amount of light results in a change in the output signal of the photo-sensing section 8b or 8c of the photo-sensing device 8, so that the signal S of the operational amplifier 15 changes as shown in FIGS.

That is, the abnormal portion O ₁ or O _{2 on the} surface of the object 14 to be examined is changed in waveform S ₁ or S ₁ of the signal S of the operational amplifier 15 as the optical pickup unit PU (laser beam LB) scans in the direction SD. ₂ or detected as S ₁ ′.

Now, when trying to inspect a minute abnormal portion over the entire surface of the object 14 to be inspected, the detection of the abnormal portion is accompanied by the scanning of the laser beam LB in the arrow SD direction as described above. A very fine scan of the object 14
It will be necessary to do it over the entire surface. Therefore, in this embodiment, as shown in FIG.
Are scanned.

FIG. 4 is an explanatory view showing the scanning direction of the laser beam LB on the surface of the test object 14.

Although the vibration of the objective lens 6 in the X direction shown in FIG. 1 is not shown in the explanatory view of FIG. 3, the laser beam LB vibrates at a predetermined amplitude as shown in FIG. To be scanned. That is, the optical pickup unit PU itself is scanned along the path of the arrow SD shown in FIG. 4, and along with this, the objective lens 6 is shown in FIG. 2 by a predetermined width D in the direction orthogonal to the arrow SD. It is vibrated by the vibration actuator 10.

By scanning the optical pickup unit PU in this manner, the scanning of the entire surface of the object 14 to be inspected can be performed by rough scanning that follows the path of the arrow SD.

FIG. 5 shows an optical pickup unit as shown in FIG.
FIG. 7 is an explanatory diagram of detecting an abnormal portion on the surface of the test object 14 when the PU is scanned. In the figure, O ₃ is an abnormal part such as a minute scratch or dust on the surface of the test object 14.

As the optical pickup unit PU scans in the direction of the arrow SD, the laser beam LB ₁ vibrates at a predetermined amplitude and the object to be inspected 1
4 When the abnormal portion O ₃ on the surface is irradiated, the output signal S of the operational amplifier 15 has a waveform as shown in FIG. That is, in the signal S, a waveform change corresponding to the number of times of irradiation of the abnormal portion O _{3 due} to the vibration of the laser beam LB ₁ itself appears.
Both end portions a and Hajimeri a of the waveform change and termination b are abnormalities O _3,
It corresponds to b respectively.

According to the above configuration, when there is a surface abnormality (abnormal portion) such as a minute scratch or dust on the surface of the object to be inspected 14, a change in the light amount of the reflected laser beam due to the abnormal portion is output from the operational amplifier 15. It will appear as a change in the signal S. Further, since the beam diameter of the laser beam LB for detecting an abnormal portion is narrowed down and condensed on the surface of the object to be inspected 14, it is very difficult to visually inspect the surface of minute scratches or dust. Abnormality can be easily detected.

That is, according to the non-contact micro surface abnormality detection device of the present invention, it is possible to detect non-contact surface defects such as minute scratches or dust that are very difficult to visually inspect the surface of the object to be inspected 14. It is possible to achieve efficient automated inspection.

The test object 14 may be a lens or the like whose surface is a distorted curved surface. That is, since the focus of the laser beam LB is controlled by the focus control means to always match the surface of the object to be inspected, even if the surface of the object to be inspected is a distorted curved surface, within the range of focus control of the focus control means, The surface can be inspected without problems.

Further, in the present embodiment, the abnormality detection means uses the laser beam LB (LB ₀ , LB ₁ , LB ₂ ) decomposed into three beams by the diffraction grating 3, but is not limited to this. is not. For example, the abnormality detecting means may be configured as shown in FIG.

In the abnormality detecting means shown in FIG. 6, the reflected light on the surface of the object to be inspected 14 due to the irradiation of the laser beam LB is guided to the light sensing portions 8b and 8c, and the change in the quantity of the reflected light is output from the output signal S of the operational amplifier 15. It is detected as fluctuation.

That is, since the reflection direction of the reflected light changes due to surface defects such as minute scratches or dust on the surface of the inspection object 14,
If the change in the amount of reflected light introduced into the light sensing portions 8b and 8c is detected by the configuration shown in FIG. 6, the above-mentioned surface abnormality is detected.

(Effects of the Invention) As described above, according to the non-contact micro surface abnormality detecting device of the present invention, the surface abnormality such as minute scratches or dust that is very difficult to visually inspect the surface of the inspection object is detected. It is detected in a non-contact manner from the change in the light amount of the laser beam reflected from the surface. This makes it possible to carry out an efficient automated inspection without an inspection error.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing a main part of an optical system in an embodiment of a non-contact micro-surface abnormality detecting device according to the present invention, and FIG. 2 is an optical pickup unit PU shown in FIG. FIG. 4 is a schematic configuration diagram of a control unit for controlling the objective lens 6, and FIG. 3 is an explanatory diagram showing a schematic configuration of an abnormality detecting means provided in the optical pickup unit PU for detecting a surface abnormality of a surface of an object to be inspected. Is an explanatory view showing the scanning direction of the laser beam LB on the surface of the object 14 to be inspected, and FIG. 5 is an explanatory view for detecting an abnormal portion on the surface of the object to be inspected 14 when the optical pickup unit PU is scanned as shown in FIG. , FIG. 6 is a diagram for explaining the operation of the abnormality detecting means in another embodiment. PU ... Optical pickup unit (detection head) 1 ... Laser diode (laser light source) LB ... Laser beam LB '... Reflected laser beam 2 ... Collimator lens 3 ... Diffraction grating 4 ... Beam splitter 5 ... Mirror 6 ... Objective lens 7 ... Plano-convex lens 8 ... Photosensor 8a, 8b, 8c ... Photosensor 9 ... Focusing actuator 10 ... Vibration actuator 11 ... Error amplifier 12 ... Oscillator 13 ... Amplifier 14 ... Test object 15 ... Operational amplifier

Claims (1)

[Scope of utility model registration request] 1. A laser light source that emits a laser beam that irradiates a surface of an object that reflects light, a beam splitting unit that splits the laser beam into a plurality of beams, and a beam splitting unit that splits the laser beam. An optical system for condensing the plurality of beams on the surface of the object to be inspected, and the object to be inspected based on the intensity of at least one reflected beam of the plurality of beams reflected on the surface of the object to be inspected. Focus adjustment means for adjusting the focus of the laser beam on the surface, and abnormality of the surface of the object to be inspected based on a difference in intensity of at least two reflected beams among the plurality of beams reflected by the surface of the object to be inspected. And a surface abnormality detecting means for detecting the non-contact minute surface abnormality detecting apparatus.