JPH08178855A - Method for inspecting light-transmissive object or specular object - Google Patents

Abstract

PURPOSE: To evaluate an abnormal part easily and reliably with a simple configuration by a scattered light source with a geometrically known brightness change as a light source. CONSTITUTION: A light source 1 where brightness changes uniformly geometrically as a light source, is obtained, for example, by transmitting light from a surface-scattering light source through a filter whose transmittance changes continuously. Then, transmission light through an object 2 to be inspected or reflection light reflected from the object 2 to be inspected is received by a light reception device 4 and the amount of change in the quantity of light is used as an evaluation index for appearance deterioration of a failed part. Rays are bent and a brightness which is different from original brightness is detected at a part of a defect 3. Namely, where there is no defect 3, a known change rate is obtained and a detection signal is obtained where the brightness changes successively, but the order is inverted at the position of the defect 3 and no uniform change can be achieved, thus detecting the defect 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method for optically inspecting or measuring a transparent object or a specular object.

[0002]

2. Description of the Related Art Conventionally, in the case of inspecting glass or the like for abnormality in appearance such as abnormality in surface shape or abnormality in optical characteristics such as abnormality in refractive index inside, abnormality of abnormal portion is detected by a sensory inspection by an inspector. The degree is evaluated and judged, or a lattice pattern or the like is used to receive light through an object to be inspected and the amount of deformation thereof is used as an evaluation index for an abnormal portion. Further, in the inspection of the surface of the object to be inspected for scratches or the like, the object to be inspected is irradiated with light, the reflected light is received, and the intensity of scratches or the like is evaluated by the change in the amount of light.

[0003]

However, the sensory test by the inspector can be carried out in a short time while having a correlation with the strength of the defect on the appearance, but there are individual differences in evaluating the defect. It was difficult to obtain an objective evaluation index.

Further, in the inspection method using the deformation amount of the lattice pattern, an evaluation index for objective judgment can be obtained, but it is not easy to convert the measured value into the evaluation index, and high-speed and simple inspection cannot be performed. It was Further, the detection signal may be distorted or disturbed at the edge portion of the lattice pattern, and there is a problem that the inspection sensitivity is locally different because the change does not become uniform locally.

In addition, in the inspection method which uses the amount of reflected light as an index for inspecting for scratches and the like, a relatively simple determination index can be obtained, but the placement of the object to be inspected matches the placement of the light receiving device or the like. It may be evaluated that the degree of abnormalities of the scratches at the marked position is large, and there may be little correlation with the actual degree of defects such as the degree of visual appearance of the scratches, and the reliability of the inspection evaluation is low. It was

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an optical inspection method capable of easily evaluating a highly reliable abnormal portion with a simple structure.

[0007]

In order to achieve the above object, in the present invention, light is emitted from a light source, and this light is transmitted through a light-transmitting inspection object and is received by a light receiving device, or A method of inspecting or measuring an optical abnormal portion of the inspection object by receiving reflected light reflected by the inspection object having a specular surface with a light receiving device, wherein a brightness change geometrically known as the light source is used. Provided is a method for inspecting a translucent object or a specular object, which is characterized by using a scattered light source.

In a preferred embodiment, the scattering light source having the geometrically known brightness change is a planar light source, and a surface light source whose brightness increases or decreases along a certain direction on the plane. It is characterized by using.

In a further preferred embodiment, the change amount of the transmitted light or the reflected light by the light receiving device is
It is characterized by being used as an index of the strength of an abnormal portion in inspection or measurement.

In a further preferred embodiment, in addition to the strength index, geometric information such as the size of the abnormal portion is used as an evaluation index for the abnormal portion.

Further, according to the present invention, light is emitted from a light source, and the transmitted light transmitted through the transparent inspection object is received by a light receiving device or is reflected by the specular inspection object. A method for inspecting or measuring an optical abnormal portion of the inspected object by receiving light with a light receiving device,
There is provided a method of inspecting a translucent object or a specular object, characterized in that a surface light source having an edge having two brightness levels is used as the light source.

[0012]

When an optically abnormal portion of a translucent or reflective object is inspected, a scattered light source whose intensity changes geometrically and uniformly is used as a light source, and the transmitted light transmitted through the object to be inspected or The reflected light reflected by the object to be inspected is received by the light receiving device, and the amount of change in the amount of light is used as an index of strength, and geometrical information such as the size of the abnormal part is taken into consideration to determine the appearance It is used as an evaluation index. Therefore, an index that can be easily converted enables an inspection having a correlation with a sensory inspection for optical abnormality. Further, since the geometrical brightness of the light source changes uniformly, unlike the case where the above-mentioned lattice pattern is used, it is possible to give similar sensitivity to any part of the light source.

Further, by utilizing the focus shift of the light receiving device, the brightness can be continuously changed by using a light / dark two-step edge light source and a light source whose brightness is changed stepwise, which are relatively easy to obtain. The same operation and effect as in the case of using a changing light source can be brought about, and an abnormal portion can be easily inspected.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view of a schematic structure of an inspection apparatus for carrying out the method of the present invention. Reference numeral 1 is a scattered light source whose brightness changes geometrically uniformly. In this embodiment, for example, a case where a streak-like defect of glass is evaluated is assumed. Therefore, a light source whose light amount is continuously reduced in a certain direction is used. Depending on the shape of the defect, the method of the present invention can of course be realized by using a light source whose light amount changes radially. In the figure, a light source whose brightness is gradually reduced (from right to left) is drawn as the light source 1, but a light source whose brightness continuously and uniformly changes is desirable.

Reference numeral 2 is, for example, glass to be evaluated, and reference numeral 3 is, for example, streak-like defects. Reference numeral 4 is a light receiving (imaging) device such as a CCD camera, and 5 is an arithmetic processing device for processing and calculating an image signal obtained from the light receiving device 4.

The light source 1 can be realized by transmitting the light from the surface scattering light source through a filter whose transmittance continuously changes. Instead of using a light source that transmits such a filter, a large number of light-emitting elements with different brightness are sequentially arranged, or a surface that continuously changes from white to black is uniformly illuminated, or Also by combining, it is possible to obtain a light source in which the change in brightness is changed geometrically.

It should be noted that instead of a light source whose brightness continuously changes in a stepless manner, a light source whose brightness changes stepwise at appropriate intervals according to the image pickup range and resolution of the light receiving device may be used. Good.

FIG. 2 is a diagram for explaining the operation of the inspection apparatus shown in FIG. 1, and shows how the light beam from the light source 1 behaves due to the stripe defect 3. The figure shows a certain cross-section including the defects 3 of the glass 2, for example the AA ′ cross-section of FIG. In this figure, the light rays detected by the image sensor are represented by upper parallel lines, and indicate from which part of the light source 1 the light rays originate. In the portion of the defect 3, the light beam is bent and a brightness different from the original brightness is detected. That is, if there is no defect 3, a detection signal in which the brightness sequentially changes at a known change rate is obtained, but at the position of defect 3, the order is reversed and the change does not become uniform. Thereby, the defect 3 can be detected.

Since the inspection field is within the imaging visual field of the light receiving device 4, the light receiving device 4 is inspected for a range exceeding this range.
(Or glass 2) is moved to scan the entire inspection surface. In this case, if the light receiving device uses a line sensor, the entire surface of the glass can be inspected by scanning in the direction perpendicular to the line.

FIG. 3 is a block diagram of another embodiment of the present invention, and FIG. 4 is an explanatory view of its operation. In this embodiment, instead of using a light source whose light quantity changes continuously (or in a large number of steps) as in the previous embodiment, a scattering light source 6 having an edge whose light quantity changes in two steps of light and dark is used. Is. The light source 6 having such an edge (bright / dark boundary portion) is installed at a position displaced from the focus position of the light receiving device 4, and the glass 2 is installed at the focus position. As a result, the light from the light source 6 is received by the light receiving device in a blurred manner, so that it is possible to obtain a light source having a geometrically known luminance change so that the amount of light continuously changes easily.

Thus, as shown in FIG. 4, it is possible to see the change in the integral of the amount of light within the circle of confusion 10, which is the visual field range at the position of the light source surface. That is, the integral of the amount of light (corresponding to the white portion in the figure) from the circle of confusion 10 corresponding to each pixel position of the image pickup device 4 is obtained as a detection signal, so that FIG.
When there is no defect as described above, a detection signal in which the light amount continuously changes within the visual field range of the image pickup device is obtained. On the other hand, if there is a defect 3 at the position of one pixel in the field of view of the image pickup device, as shown in FIG. The obtained integrated data of the light amount does not change continuously and uniformly. In addition, 9 represents the position where the imaging system is focused.

As described above, even if the focus shift is used, the background of the image obtained by the image pickup device continuously changes due to the change of the area of the light source part (white part) in the circle of confusion, and thus The detection and evaluation can be performed according to the same principle as in the case of using the light source whose luminance continuously changes uniformly as in the above embodiment.
It is also possible to combine a continuously changing pattern with a mechanism for defocusing.

FIG. 5 shows an example of the detection signal of the light amount when there is no defect along the AA ′ cross section of FIG. 1, and FIG. 5A shows the light amount obtained along the AA ′ cross section. The graph shows that the amount of light changes uniformly regardless of the location, and is a straight line that rises to the right (the amount of light increases toward the right). FIG. 6B is a graph in which the light amount data of FIG. This is constant regardless of location.

On the other hand, if there is a convex defect 3 as shown in FIG. 2 or an abnormality such as a refractive index that causes a similar effect on the same AA 'cross section, the obtained light amount signal is as shown in FIG. Like The figure (a) shows the amount of detected light. In this figure (a), 13 is a defect part. The amount of change in this light amount is shown in FIG. In the figure (b), 14 is a defect part. The height of the defect portion 14 corresponds to the abrupt change of the light amount change. Thereby, the degree of abnormality of the defect 3 can be evaluated. In the detection data of the convex defect 3 (see FIG. 2) in FIG. 6,
As shown in (a), in the defect portion 13, a white portion is first detected and then a black portion is detected, so that a rapid change from convex to concave is detected on the graph.

FIG. 7 is a graph similar to FIG. 6 when there is a concave defect. In this case, since the light beam from the light source is bent in the defect portion 13 in the direction opposite to that of the convex defect, as shown in (a), the black portion is detected first and the white portion is detected thereafter. Therefore, a rapid change from concave to convex is detected on the graph.

In such a detection method, if a strong defect is a defect in which a light beam is greatly bent, a light beam emitted from a place farther from the place where it should be is detected as a stronger defect. In other words, the stronger the defect, the larger the change amount signal, and the quantitative evaluation of the defect strength becomes possible.

As a specific embodiment of the method of the present invention, a diffuse light source having an edge is used to focus on the object to be measured,
An optical system with a focal length of 55 mm and an F value of 4 was used as the focal point shift position with the distance from the light source to the object to be measured set to 100 mm, and a scratch-like defect called glass scratch was evaluated. It was confirmed that there is a correlation between the amount of change in the light amount obtained by using a differential (or difference) filter for viewing and the strength evaluation in the visual inspection. Further, an index obtained by multiplying the change amount of the light quantity by the length or size of the defect portion makes it possible to quantitatively evaluate the badness of the defect.

FIG. 8 is a constitutional view showing still another embodiment of the method of the present invention. In this embodiment, the present invention is applied to a reflection type inspection object instead of the transmission type inspection object. The light from the light source 1 whose brightness is uniformly changed as described above is reflected on the surface of the DUT 2 and the reflected light is detected by the imaging device 4. As a result, the defect 3 of the inspection object 2 can be evaluated in the same manner as in the above embodiment.

[0030]

As described above, in the present invention, the transmitted light or the reflected light from the object to be inspected is detected by using the light source having a known brightness change, and the abnormal portion is detected and measured by the change in the light amount. As a result, it is possible to quantitatively measure and evaluate optical anomalous parts easily by using an index close to human sensitivity in a short time, and it is possible to evaluate a large amount of inspected objects and gain confidence in complex processes. Highly efficient inspection can be achieved easily and efficiently.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an optical inspection device according to an embodiment of the present invention.

FIG. 2 is an explanatory view of the operation of the embodiment shown in FIG.

FIG. 3 is a structural explanatory view of another embodiment of the present invention.

FIG. 4 is an explanatory view of the operation of the embodiment shown in FIG.

FIG. 5 is a graph of detection data of a normal inspection object.

FIG. 6 is a graph of detection data of an inspection object having a convex defect.

FIG. 7 is a graph of detection data of an inspection object having a concave defect.

FIG. 8 is a structural explanatory view of yet another embodiment of the present invention.

[Explanation of symbols]

 1: Scattered light source whose brightness changes geometrically uniformly 2: Object to be inspected 3: Striped defect 4: Imaging (light receiving) device 5: Arithmetic processing device for arithmetic processing of signal 6: Bright and dark two-stage Light source having edge 9: Focus position of image sensor 10: Circle of confusion indicating the field of view on the light source surface of the image sensor

Claims (5)

[Claims] 1. A light receiving device receives light transmitted from a light source and transmitted through a light-transmitting inspection object, or reflected light reflected by a specular inspection object is received by the light receiving device. A method for inspecting or measuring an optical abnormal portion of an object to be inspected by receiving light, characterized in that a scattering light source having a geometrically known luminance change is used as the light source. Or an inspection method for specular objects. 2. A surface light source which is a planar light source and whose brightness increases or decreases along a certain direction on the plane is used as the scattering light source having a geometrically known luminance change. The method for inspecting a translucent object or a specular object according to claim 1. 3. The translucent object or the specular object according to claim 1, wherein the amount of change in the light amount by the light receiving device is used as an index of the strength of an abnormal portion in inspection or measurement. Inspection methods. 4. The translucent object or specularity according to claim 3, wherein geometric information such as the size of the abnormal portion is used as an evaluation index of the abnormal portion in addition to the strength index. How to inspect an object. 5. A light receiving device emits light from a light source, the transmitted light is transmitted through a light-transmitting inspection object, and the reflected light reflected by the specular object is received by the light receiving device. A method of inspecting or measuring an optically abnormal portion of an object to be inspected by receiving light, wherein a surface light source having an edge of brightness in two steps of brightness and darkness is used as a light source. Or an inspection method for specular objects.