JPH11183151A - Transparent sheet inspection equipment - Google Patents

Abstract

(57) [Problem] To provide a transparent sheet inspection apparatus for easily and accurately inspecting the surface properties and the like of a transparent sheet-like inspection object. An apparatus for inspecting an object to be inspected on a transparent sheet material, the irradiating means having a predetermined area on the surface of the object to be inspected, having substantially uniform intensity, and irradiating parallel light beams. 1, and a projection unit 5 that forms a transmitted light image of the inspection object irradiated by the irradiation unit 1 and projects the transmission light image on a predetermined imaging unit 7 via a mask 6. Based on the photoelectric conversion signal of the transmitted light image of the inspected object,
Inspect the test object. The emission angle of the transmitted light passing through the inspection object is caused by the front and back shapes and the state of the material inside, and appears as a difference in the light intensity distribution of the transmitted light image. A defect can be detected from the photoelectric conversion signal level difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent sheet inspection apparatus suitable for inspecting a transparent sheet, particularly a transparent sheet such as a transparent film or a transparent glass plate.

[0002]

2. Description of the Related Art Heretofore, as a method for inspecting the surface of a transparent sheet of this type for unevenness defects, for example, a so-called slit shape light beam is irradiated on the surface of an object to be inspected, and the surface shape is obtained from a change in the linearity of the light beam. The light-section method is known. Further, as an inspection apparatus, there is an inspection apparatus provided with a light source that emits a slit-like light beam and a light receiving system that detects a light beam linearity of a surface irradiated with the slit-like light beam, for example, an area sensor camera.

[0003]

However, according to the conventional surface inspection method and inspection apparatus, the light receiving magnification is increased particularly for an object to be inspected whose surface shape change is gradual and the surface irregularity change amount is minute. There is a need to. Therefore, there have been problems in the following points.

That is, 1. Positional fluctuations of the surface due to the movement and rotation of the inspection object disturb the focusing of the light receiving system, and also disturb the straight line and inclination of the light beam, making it difficult to detect a change in linearity due to a change in shape. . 2. In order to minimize position fluctuations, it is necessary to match the relative positions of the light source, the light receiving system, and the surface of the inspection object, which complicates the apparatus. 3. Since the light receiving magnification is increased with respect to the minute unevenness, the inspection field of view is narrowed, and the time required for full inspection of the inspection object is increased.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a transparent sheet inspection apparatus for easily and accurately inspecting the surface properties of a transparent sheet-like inspection object.

[0006]

SUMMARY OF THE INVENTION A transparent sheet inspection apparatus according to the present invention is an apparatus for inspecting an object to be inspected made of a transparent sheet material, and has a predetermined area on the surface of the object to be inspected and a substantially uniform strength. Irradiating means for irradiating parallel light beams, and projecting means for forming a transmitted light image of the inspection object irradiated by the irradiating means and projecting the transmitted light image to a predetermined imaging means via a mask. In addition, the inspection object is inspected based on a photoelectric conversion signal of a transmitted light image of the inspection object captured by the imaging unit.

Further, in the transparent sheet inspection apparatus according to the present invention, the irradiating means irradiates the object from a direction inclined at a predetermined angle with respect to the surface of the object to be inspected, and the imaging means illuminates the object through the object to be inspected. And transmitting a transmitted light image in an arrangement relationship facing the irradiation light.

Further, in the transparent sheet inspection apparatus of the present invention, the detected video signal for the inspected object is compared with the detected image signal for a non-defective product, and if the detected image signal is out of the specified value range, it is determined that the inspected object is abnormal. Features.

According to the first aspect of the present invention, the surface of the object is irradiated with the parallel light beam by the irradiating means, so that the emission angle of the transmitted light passing through the object is changed to the front and back shapes and the state of the material inside. It appears as a difference in the light intensity distribution of the transmitted light image. A defect can be detected from the photoelectric conversion signal level difference.

According to the second aspect of the present invention, the irradiating means irradiates the parallel light beam with respect to the surface of the inspection object from a direction inclined by a predetermined angle excluding the critical angle. It is more desirable that the predetermined angle be an acute angle with respect to the surface of the inspection object. This clearly shows a difference in the light intensity distribution of the transmitted light image between the gentle shape change surface and the non-defective surface, and it is possible to detect a shape change with a small unevenness change.

According to the third aspect of the present invention, for a video signal whose light intensity distribution of a transmitted light image has been photoelectrically converted by the imaging means, only a video signal portion corresponding to the transmitted light image is processed in the processing device. Then, the video signal level is compared with a non-defective detected video signal having no change in the surface shape of the inspection object stored in the processing device in advance. The detected image signal of a non-defective part of the same type of inspected object without any change in surface shape is stored in the processing unit in advance, and the stored image signal is compared with the image signal detected from the inspected object by the inspection to achieve a gentle shape. The signal difference between the changed surface and the non-defective surface can be detected. Further, by comparing the standard value with the standard value based on the comparison result, it is possible to reliably determine the surface shape defect.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a transparent sheet inspection apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram that best illustrates the features of the present invention, and shows a configuration example of the device of the present invention. In the figure, 1 is a He-Ne laser as a light source, 2 is a beam expander that expands the output light of the laser 1 and makes it parallel light, and 3 is the original shape of the inspection light to be irradiated on the surface of the inspection object. Defining mask board,
Reference numeral 4 denotes a transparent sheet as an object to be inspected, 5 denotes a plano-convex cylindrical projection lens that projects a transmitted light image transmitted through the object by irradiation of inspection light, and 6 denotes reception of a projected image by the plano-convex cylindrical projection lens 5. Light receiving mask plate for defining the range, 7
Is a CCD line sensor which receives the projected image of the surface which is defined by the light receiving mask plate 6 and passes through it, and converts the image into an electric signal. 8 is for processing a video output signal picked up by the CCD line sensor 7. Processing device.

In the above configuration, the laser 1 to the CC
Each component up to the D-line sensor 7 is covered by a light-shielding plate (not shown) for blocking external light, and is thereby arranged substantially in a dark place.

The inspection light source He-Ne (wavelength 63
(2.8 nm) The output beam 1a of the laser 1 is incident on a beam expander 2 arranged on the same optical axis. When irradiating the incident beam 1a as the inspection light beam 3a, the size is sufficiently larger than the size of the original shape of the mask plate 3 which determines the original shape, the light intensity distribution is enlarged to a uniform beam diameter, and the light is emitted as parallel light. It is converted into a light beam 2a.

The output light beam 2a thus converted is irradiated on a mask plate 3 which defines an original shape to be irradiated as an inspection light beam. The inspection light beam 3 irradiating the inspection object 4 with the mask plate 3
Only the original shape portion a is penetrated, and the other portions are shielded from light by the light shielding plate. The mask plate 3 is arranged perpendicular to the optical axis, and the center of the original shape of the penetrated inspection light beam 3a is located on the optical axis.

The inspection light beam 3a of the mask plate 3 has the original shape (3x = 5 mm, 3y = 14 mm).
a, the inspection beam 3a having a rectangular surface is illuminated by the mask plate 3 and passed therethrough as the original shape portion.
Is formed, and the surface of the inspection object is irradiated.

Here, 3x (5 mm) which is one side of the light beam having a rectangular surface of the inspection light beam 3a corresponds to, for example, the longitudinal direction of the transparent sheet 4 which is the inspection object 4. Also,
The other side, 3y (14 mm), corresponds to the width direction.

The inspection light beam 3a on the surface of the transparent sheet 4 as an object to be inspected is incident at an incident angle θ (60 to 87 °) which is within the incident angle θ (60 to 87 °) formed by the optical axis and the normal of the transparent sheet 4 surface. Irradiate diagonally. Thus, the irradiation length 4x of the inspection light beam 3a in the longitudinal direction of the transparent sheet 4 of the inspection object is sin (9
0 ° −θ) = 4x of 3x / 4x. For example, 3x which is one side of a light beam having a rectangular surface of the inspection light beam 3a
Is 5 mm and the incident angle [theta] is 80 [deg.], Since the inspection light beam 3a is a parallel light beam, the irradiation length 4x is about 2 mm.
9 mm, which is longer than the 3x = 5 mm, which is one side of the inspection light beam 3a having a rectangular surface after passing through the mask plate 3.

The other side of the rectangle 3y (= 14 mm) of the inspection light beam 3a is irradiated with an inspection light beam wider than the width of the inspection object. Thus, the surface of the transparent sheet 4 to be inspected is irradiated with the inspection light beam 3a at the incident angle θ,
The transmitted light image 4b of the transparent sheet 4 is incident on a plano-convex cylindrical projection lens 5 disposed on the optical axis in opposition to the transmitted light image of the transparent sheet 4 on the optical axis through the object to be inspected. .

With respect to the incidence of the transmitted light image 4b,
The plano-convex cylindrical projection lens 5 has no lens effect on the transmitted light image of the inspection light beam 3a in the 3x direction, and has a 3y
It is arranged to have a lens function for the transmitted light image in the direction. The distance between the irradiation position of the inspection light beam 3a on the surface of the object to be inspected and the plano-convex cylindrical projection lens 5 is larger than the focal length of the plano-convex cylindrical projection lens 5, and the plano-convex cylindrical projection lens 5 Are located.

As a result, the transmitted light image 4b incident on the plano-convex cylindrical projection lens 5 in the direction 3y of the inspection light beam 3a is formed at the focal length position, and 180 degrees away from it. The inverted image is inverted and enlarged depending on the distance and the lens magnification. In addition, the lens-emitted light image in the 3x direction is emitted with the width of the incident light beam because there is no lens action.

As described above, the transmitted light image 5a of the inspection object that has passed through the plano-convex cylindrical projection lens 5 defines a range in which the projected light image is received by the light receiving mask slit arranged on the optical axis. Thus, the light receiving range of the projection light image is determined by the slit of the light receiving mask plate 6, and the projection light image 6a passing through the slit is projected and received on the light receiving element surface of the CCD line sensor 7 arranged on the optical axis.

The CCD line sensor 7 has no imaging lens, and transmits a transmitted light image 5a of the object to be inspected that has passed through the plano-convex cylindrical projection lens 5 to a projection light image 6a that has passed through the slit of the light receiving mask plate 6. Only receive light directly. Also,
The light receiving element rows of the CCD line sensor 7 are arranged in the width direction of the inspection object (the 3y direction of the inspection light beam 3a) in the direction perpendicular to the optical axis similarly to the slit of the light receiving mask plate 6. The distance between the plano-convex cylindrical projection lens 5 and the CCD line sensor 7 is set in the vertical direction of the transmitted light image 5a of the inspection object enlarged by the plano-convex cylindrical projection lens 5 over the entire light receiving element array of the CCD line sensor 7. Are the irradiation positions.

A plano-convex cylindrical projection lens 5
The light-receiving mask plate 6 disposed between the CCD line sensor 7 and the slits provided therein are provided only on the entire surface of the light-receiving element array of the CCD line sensor 7 in the same manner as described above. It is provided to illuminate the area of the image in the vertical direction. The transmitted light image received by the CCD line sensor 7 is converted into an electric signal, and a video signal 7a
Is output to the processing device 8, and the processing device 8 determines whether the inspection object 4 is good or bad.

It should be noted that, for the input video signal 7a,
The video signal level for only the video signal corresponding to the transmitted light image is compared with a previously stored non-defective detected video signal of the inspection object having no change in surface shape. The result is compared with the upper and lower limit values of the standard level set in advance, as described above,
If the value deviates from the standard value, it is determined that a surface shape defect exists at that location. If the value is within the standard value, the surface at that location is determined to be good.

FIG. 2 shows that the parallel inspection light beam 3a is
Are illuminated with a certain range 4x of the surface at an incident angle θ, and the transmitted light is indicated by the presence or absence of a gradual change in the surface shape.
2, the front and back surfaces gentle irregularities no change surface in (4x _1, 4x ₃₎ For, the front and back surfaces to the longitudinal direction of the object to be inspected from the surface that the parallel is kept of the reference axis 4a of the object light beam irradiated to the incident on the inspection object by the refractive index of the object, the transmitted light beam to form a transmitted light image emitted from the object to be inspected (4b _1, 4b _3).

Next, in the case of a gently convex surface (4 × ₂ ), the surface loses parallelism with the reference axis 4a and has a tilt of x _n degrees with respect to the reference axis 4a. It becomes the incident angle theta _n of each irradiation position is _{θ-x n ° (= θ} n) relative to the surface, the inspection light beam at an incident angle theta with different incident angles to the surface in the absence of surface shape variation is irradiated.

With respect to the convex surface (4 × ₂ ), the incident angle θ _n
The light is incident on the surface of the object due to the refractive index of the object, and the transmitted light flux is emitted from the object to form a transmitted light image (4b ₂ ).

In the transmitted light range 4x 'of the incident angle θ and the transmitted / emitted angle θ' with respect to the range 4x of the surface of the inspection object irradiated with the inspection light beam 3a, a straight line perpendicular to the transmitted light at a certain position of the transmitted light. The transmitted light intensity distribution on 4c is
It is shown as 4d. A change in light intensity due to the convex shape of the surface appears as a change portion 4b ₂ ′, and the difference between the surface having no change in surface shape and the transmitted light intensity is obtained.

The transmitted light image thus obtained is passed through a plano-convex cylindrical projection lens 5 and a light receiving mask plate 6, and
When the light is received by the CCD line sensor 7, the change in light intensity is converted into a change in the voltage level of an electric signal. Further, after the converted electric signal 7a is input to the processing device 8,
This is compared with a non-defective video signal stored in advance, and then compared with upper and lower limits of a standard level to determine whether a shape change defect exists on the surface.

The transmitted light intensity due to the surface convex shape (4 × ₂ ) shown in FIG. 2 is converted as a change in the voltage level, and if any of the upper and lower limits of the standard level deviates, it is determined that a shape change exists.

In order to similarly inspect the entire surface of the transparent sheet 4 to be inspected, a feed mechanism for moving the inspected object in the direction of the reference axis 4a is provided (not shown). For example, the inspection object is moved at a constant speed in the direction of the reference axis 4a by the feed mechanism,
The surface of the inspection object is sequentially irradiated with the inspection light beam, and the light image transmitted through the inspection object at that time passes through the plano-convex cylindrical lens 5 and the light receiving mask plate 6 and is received by the CCD line sensor 7. As a result, the change in light intensity is converted into a change in the voltage level of an electric signal, and the entire test can be performed by inputting the change to the processing device 8. If any surface shape change defect exists, the test object is regarded as a defective product. Is determined.

[0033]

As described above, according to the present invention, both sides of this type of transparent sheet-like inspection object can be inspected at high speed. Furthermore, the inside of the inspection object can be inspected. Further, according to the present invention, since the object to be inspected is imaged obliquely with respect to the parallel irradiation light beam, irregularities including a defect with a constant thickness change on the surface of the object and abnormalities inside the object to be inspected, An image with a large refraction deformation can be taken, and a defect is reliably determined by signal processing of the photoelectric conversion signal. Therefore, both sides and the inside of the inspection object can be inspected at the same time, and the inspection can be performed efficiently and in a short time. By using an one-dimensional sensor as an imaging unit and performing one-dimensional imaging in the width direction of the inspection object and performing photoelectric conversion, inspection can be performed while the inspection object is continuously transmitted, and advantages such as faster inspection can be achieved. have.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main part configuration in an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a difference in intensity distribution of transmitted light due to a change in the shape of the surface of an inspection object according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 He-Ne laser 2 Beam expander 3 Mask plate 4 Transparent sheet 5 Plano-convex cylindrical projection lens 6 Light receiving mask plate 7 CCD line sensor

Claims (3)

[Claims] 1. An apparatus for inspecting an object to be inspected made of a transparent sheet material, said irradiating means having a predetermined area on the surface of the object to be inspected, having substantially uniform intensity, and irradiating parallel light beams. And a projection unit that forms a transmitted light image of the inspection object irradiated by the irradiation unit and projects the transmission light image on a predetermined imaging unit via a mask, wherein the transmitted light of the inspection object captured by the imaging unit is provided. A transparent sheet inspection apparatus, wherein the inspection object is inspected based on a photoelectric conversion signal of an image. 2. The irradiating means irradiates the object to be inspected from a direction inclined at a predetermined angle with respect to the surface of the object to be inspected, and the imaging means has an arrangement relationship with the illuminating means and the irradiation light via the object to be inspected. 2. A transmission light image is taken.
The transparent sheet inspection device according to the above. 3. The transparency according to claim 1, wherein the detected video signal for the inspected object is compared with the detected video signal for a non-defective product, and if the detected image signal is out of a specified value range, it is determined that the inspected object has an abnormality. Sheet inspection device.