JP4362335B2 - Inspection device - Google Patents

Description

  The present invention relates to an inspection apparatus for inspecting a defective portion of a plate-like transparent body.

As an inspection device for inspecting defects in a glass substrate for a liquid crystal panel as a plate-like transparent body, a laser beam is projected from the light projecting system onto the glass substrate, and regular reflection light that is regularly reflected by hitting the front and back surfaces of the substrate is filtered. Two positions separated by the CCD image sensor, receiving the surface scattered light and back scattered light that are diffusely reflected from the defect when the surface or back surface of the substrate is removed and a laser beam hits it. An apparatus using a method for discriminating between front and back defects on a glass substrate that determines whether the defect is on the front surface or the back surface depending on the position is proposed. (See Patent Document 1).
JP-A-9-258197 (Description of Claims, FIGS. 1 and 2 and Related Description)

  However, the inspection apparatus using such a method uses irregularly reflected light having a considerably reduced amount of light without using regular reflected light directly reflected from the front and back surfaces of the glass. Because it is necessary to irradiate with spot light so that the laser beam is strongly applied, and the entire surface of the substrate is inspected by moving the substrate by an XY two-dimensional moving stage, the inspection apparatus becomes complicated and expensive. When the inspection surface moves, the effect of regular reflection light transmitted from the front surface and reflected from the rear surface is inevitable, so that reliable front / back determination cannot be performed, that is, there is no defect on the back surface, or a surface defect or between the front and back surfaces. If there is an internal defect and this defect moves to reach a position where it directly blocks the reflected light from the back surface, the scattered light forms an image, so the front and back surface defects cannot be accurately determined, There is a problem that is not determined from the beginning for Recessed.

  On the other hand, the quality standards have become higher due to the recent spread of liquid crystal panels, and in addition to the surface at the time of inspection on which circuit patterns are formed, internals related to image distortion and color misregistration when people view images In addition, defects on the back surface at the time of inspection are also regarded as important. For example, in a large plasma display panel used for a television screen or the like, the defect size on the front surface, inside, and back surface is set to 50 to 100 μ, 200 to 300 μ, and It may be regulated to be 300 to 500 μm or less.

  Therefore, the present invention solves the above-mentioned problems in the prior art, and can inspect defective portions on the front, inside and back surfaces of a plate-like transparent body such as a liquid crystal display panel at a low cost with a simple configuration. It is an object to provide an apparatus.

In order to solve the above-mentioned problems, the invention of claim 1 is an inspection apparatus for inspecting a defective portion of a plate-like transparent body.
An optical system composed of a light projecting unit and a light receiving unit arranged at a fixed relationship position, and the plate-shaped transparent body and the optical system so as to be relatively movable in a certain direction. A moving mechanism that enables movement of either the transparent body or the optical system, and a determination unit; and the light projecting unit configured to project laser light on the plate-shaped transparent body The light receiving unit is configured to receive the front surface regular reflection light regularly reflected from the surface of the plate-like transparent body and the back regular reflection light regularly reflected from the back surface of the laser light so that an image can be formed. The determination unit takes in the image formed by the light receiving unit, and the abnormal image is included in one place or within a predetermined short time when the image includes the defective portion as an abnormal image. If there are two or three places in a certain direction, It determines that there is the defect portion in the middle or the surface of the a serial Front Back characterized.

  As described above, according to the present invention, in the first aspect of the present invention, an inspection apparatus for inspecting a defective portion of a plate-like transparent body includes a light projecting portion and a light receiving portion that are arranged at fixed positions. It has a configured optical system, the light projecting unit is configured to project laser light onto the plate-shaped transparent body, and the light receiving unit from the surface of the plate-shaped transparent body among the laser light projected It is configured so that it can receive the regular reflected light from the front surface and the back reflected light from the back surface to form an image, so when there is a defective part on the surface, the laser that hits the defective part Since light is diffusely reflected and only extremely weak light reaches in the direction of specular reflection, there is a large difference in the amount of light from the surrounding regular reflection light, and an abnormal image in which a defective part is photographed is detected on the light receiving part. It is formed. Further, most of the laser light enters the plate-like transparent body from the periphery of the defective portion, and the back-side regular reflection light reflected by the back surface of the plate-like transparent body also forms an abnormal image on the light receiving portion. Therefore, when there is a defective portion on the surface, an abnormal image is formed twice at two different positions of the light receiving portion at the same time at a certain position of the plate-like transparent body.

  On the other hand, when the defective portion is present at the intermediate position or the back surface in the plate-like transparent body, since there is no defective portion on the surface, an abnormal image is not formed by the front regular reflection light, or directly from the periphery of the defective portion at the intermediate position. An abnormal image is formed in the backside regular reflection light that reaches the backside and is regularly reflected from the backside. That is, at a certain position of the plate-like transparent body, an abnormal image is formed only once at the back surface image forming position of the light receiving portion for the back surface or the defective portion inside.

  In this case, since such an image is formed by specularly reflected light, the amount of light is much higher than when scattered light is used. Therefore, a long line-shaped light without using laser light as spot light. Thus, the inspectable range can be made sufficiently long.

  In addition, since the plate-like transparent body and the optical system have a moving mechanism that makes it possible to move either the plate-like transparent body or the optical system so that they can move relative to each other in a fixed direction. The position of the plate-like transparent body that receives light can be moved, and a certain width of the plate-like transparent body can be inspected two-dimensionally with a line-shaped laser beam. Therefore, when the plate-like transparent body is large, the entire area of the plate-like transparent body can be inspected by arranging as many optical systems as necessary in the direction perpendicular to the moving direction.

  In this case, when there is a defective portion on the surface or intermediate position of the plate-like transparent body, an abnormal image can be detected simultaneously by the front and back regular reflection light or the front regular reflection light as described above, and the defective portion is plate-shaped. If you move a small distance about the thickness of the transparent body, even if the influence of the defective part on the surface disappears, the defective part itself moves, so that the defective part comes on the back regular reflected light line, and the back regular reflected light As a result, an abnormal image is formed again. In other words, this abnormal image is added within a short distance and therefore within a short time, and eventually, within a short distance and within a short time, the abnormal image is detected three times or twice in three locations for a defective portion on the surface or an intermediate defective portion. It will be formed twice. On the other hand, when there is a defective part on the back side, once an image including this is formed, the defective part does not come again at the position of the front or back regular reflection light even if the plate-like transparent body moves. An abnormal image is formed only once at a defective portion on the back surface.

  Then, a determination unit that can be configured by a microcomputer or the like is provided as an image memory, an image processing program, or the like, thereby taking in the image formed by the light receiving unit as described above, and the image includes a defective part as an abnormal image. If there are two or three abnormal images in a certain direction where the abnormal image moves within a predetermined short time enough to move the distance of the thickness of the plate-like transparent body, the back side or the surface respectively. Since it is determined that there is a defective portion in the middle or on the front surface, the presence and position of the defective portion can be reliably determined including not only the front surface but also the back surface and the internal position.

  In such an inspection apparatus, the plate-like transparent body only needs to be moved in a one-dimensional direction, so that the apparatus configuration can be simplified and reliably operated at low cost.

FIG. 1 shows an example of the entire configuration of an inspection apparatus to which the present invention is applied.
The inspection apparatus is an apparatus for inspecting a defect D which is a defective portion such as a flaw, a distortion, a foreign matter or a bubble of a glass plate W made of a glass substrate for a plasma display or a liquid crystal display as a plate-like transparent body, The optical system 3 includes a laser marker 1 as a light projecting unit and a CCD camera 2 as a light receiving unit, a line transport device 4 as a moving mechanism, an image processing device 5 as a determination unit, and the like.

  The laser marker 1 is configured to be capable of projecting a laser beam L onto a glass plate W, and has a laser diode 11 that emits laser beam, a condensing lens 12 that converges the emitted laser beam, and is converged. Cylindrical lenses 13 and the like are provided in which a laser beam is directed toward the glass plate W in a direction perpendicular to the paper surface in the drawing and spreads in the horizontal X direction shown in FIG. .

The CCD camera 2 is capable of forming an image by receiving specularly reflected light composed of the front surface regular reflection light M and the back surface regular reflection light N that are specularly reflected from the front surface H and the rear surface R of the glass plate W in the laser light L, respectively. The imaging lens 21 and the CCD light receiving element 22 are provided. The front and back regular reflection lights M and N are imaged at different positions P ₁ and P ₂ of the CCD light receiving element 22, respectively.

  The CCD light receiving element 22 is constituted by a large number of minute sections so that the position of the minute defect D on the glass plate W can be accurately understood. As described above, the laser marker 1 and the CCD camera 2 are arranged at fixed positions so as to be able to project and receive light to form the optical system 3. In this example, the incident angle and reflection angle of light projection and light reception are 45 °. The laser light L is refracted by a certain angle to the glass plate W and is incident and reflected.

  The line transfer device 4 moves either the glass plate W or the optical system 3 so that the glass plate W and the optical system 3 can move relative to each other at a constant speed in the vertical Y direction. In this example, the glass plate W is movable as shown by an arrow. As such a line conveying device 4, a roller conveyor device is usually used. Reference numeral 41 denotes a rotary encoder that transmits a pulse signal corresponding to the amount of movement of the glass plate W being conveyed to the image processing apparatus 5.

  In this example, the conveyance mechanism is a line conveyance device 4 composed of a roller conveyor that continuously conveys the glass plate W. However, depending on the convenience of the manufacturing process, the glass plate W is sequentially stopped at a fixed position, and the optical A mechanism for reciprocating the system 3 on a glass plate may be used.

  The image processing apparatus 5 includes an image memory 51 and a defect determination unit 52. The image memory 51 takes in the image formed by the CCD camera 2, and the defect determination unit 52, when this image includes a defect D as an abnormal image, the abnormal image is in one place or within a certain short time t. If there are two or three in the longitudinal Y direction, it is determined that the defect D exists as a defect Db, Di, or Df, respectively, on the rear surface R or the intermediate I between the front surface H and the rear surface R or on the front surface H.

The above defect determination means will be described in detail with reference to FIGS.
FIG. 2 (a) targets only the laser beam on the surface side, and the surface defect Df at the position A shown in FIG. It shows the state of the laser beam when it reaches the position Q, and the positions A ₁ and A ₂ without the defect Df before and after the defect Df in the longitudinal Y direction of the glass plate W pass through the position Q, and the laser beam there. The state of the laser beam when irradiated with is shown virtually before and after the position Q. The XY plane state when the defect Df photographed by the CCD camera 2 and the image data before and after the defect Df are taken into the image memory unit 51 of the image processing device 5 is shown in the image f _{1 in} the upper diagram of FIG. As shown.

As shown in the figure, when the defect Df reaches the Q position, a part of the laser beam L that hits the defect Df in the X-Y direction is irregularly reflected to become scattered light m having a very low light intensity. On the other hand, the light for illuminating the CCD light receiving element 22 does not reach the CCD light receiving element 22, while the laser light L that does not strike the defect Df and the laser light L that irradiates the A ₁ and A ₂ positions before and after the defect Df at the Q position. ₁ and L ₂ are specularly reflected by about 5% from the glass surface and become specularly reflected light Lm, M ₁ , and M ₂ that are much lighter than the scattered light. turning on those a range of P ₁ position of the house. As a result, the defect Df is imaged and its state is stored in the image memory 51 as shown in FIG. The laser beam L has a length 1 in the X direction and a width of, for example, about 0.1 mm in the Y direction, and the number of Lm and the like is from 1 or less to about 10 depending on the size of the defect Df. .

Image r ₁ in the upper diagram of FIG. (B) and (e) shows the state of the back reflected light at the same defect position as (a) and the image f _1. The portion of the laser beam L that hits the defect Df in the part in the XY direction becomes the reflected and transmitted scattered light m, and does not turn on the CCD light receiving element 22 even when reflected by the back surface R, but on the defect Df. Most of the laser light L ₁ and L ₂ irradiated to the laser light L that does not hit and the A ₁ and A ₂ positions before and after the defect Df at the Q position pass through the front surface H and are usually about 5% from the rear surface R. The regular reflection light Ln, N ₁ , and N _2, which are specularly reflected and have much more light than the scattered light, have a certain range of P ₂ position different from the surface of the CCD light receiving element 22 of the CCD camera 2. Light things up. As a result, the defect Df is picked up and the state thereof is stored in the image memory 51 as shown in the r ₁ image of FIG.

As described above, when the defect Df at the A position reaches the Q position, the f ₁ and r ₁ images are simultaneously formed twice. The image memory 51 takes in the image data as numerical values, but normally, such image data can be written on a virtual screen corresponding to the glass plate W. In this case, the front image f ₁ and the back image r ₁ are usually displayed on different screens for the subsequent process of determining the defect Df. When the screens of (d) and (e) are overlaid, the position of the defect Df coincides with the actual position, and both defects are displayed overlapping each other at that position. That is, both images f ₁ and r ₁ are displayed at the same position in the X direction and at the same position in the Y direction.

Images r ₂ and f _{2 in} the lower diagrams of FIGS. 2C, 2E, and 2D show that the glass plate W further advances in the Y direction, and the A position of the defect Df is shifted from the Q position to the Q ₁ position. It shows the state when moving to. At this time, as shown in the drawing, the surface regular reflection light of the laser light of L, L ₁ , L _{2 at} the Q position is not affected by the defect Df and becomes completely regular reflection light M, M ₁ , M ₂ . A part of the back surface regular reflection light N transmitted from the front surface H in the X direction is just blocked by the defect Df, and after passing through the defect Df, the N is bent by the defect Df to become scattered light n. ), The back surface regular reflection lights Ln, N ₁ and N ₂ light the CCD element, and the image r ₂ shown in the lower figure of (e) is formed.

This image r ₂ is formed at the same position in the X direction and away from Q in the Y direction by the distance s between Q and Q ₁ where the defect Df has moved, and the image of r ₁ as a predetermined short time. Is formed at a time delayed by t = s / v from the formation of. v is the conveyance speed of the glass plate W. s corresponds to the thickness a of the glass plate W and is a distance slightly shorter than a by the amount of light refracted. At this time, an image by surface regular reflection light is also formed at the Q point of the laser beam irradiation position, but since there is no defect Df at the Q position, an image f _{2 in} which no defect is shown as shown in the lower figure of (d). Represented as:

  From the above, in the defect Df generated on the surface H, a small distance close to the thickness a of the glass plate W at a certain position in the transverse X direction perpendicular to the Y direction, which is the moving direction of the glass plate W, and An abnormal image including the defect Df is formed three times in total in the image memory 51 within a short time of defect movement corresponding to this.

3, the glass plate W has moved in the Y direction, and the defect Dr on the back surface R that was at the B position in FIG. 1 has slightly moved from the laser light irradiation position Q to reach the back surface irradiation position Q ₂ of the laser marker 1. The state of time is shown. When there is a defect Dr on the back surface R, there is no defect Dr at the front surface irradiation position Q. Therefore, the front surface irradiation light L is regularly reflected together with L ₁ and L ₂ , and as shown in the upper diagram of FIG. The defect Dr does not appear in the front image f _1, but the defect Dr appears in the back image r ₁ as shown in the upper diagram of FIG. When the defect glass plate W is further moved in the Y direction Dr leaves the Q ₂ position, the subsequent will not come defect D to Q and Q ₂ position, under (c) and (d) FIG. It does not occur image defects like the image f ₂ and r ₂ of the. Therefore, in the case of the defect Dr occurring on the back surface R, an image including the defect Dr is formed only once in the image memory 51 within the small distance and a small time corresponding to the small distance.

4, the glass plate W moves in the Y direction, and the intermediate Di defect Di at the position C in FIG. 1 slightly moves from the laser light irradiation position Q to reach the intermediate irradiation position Q ₃ of the laser marker 1. The state of time is shown. When there is a defect Di in the middle I, since there is no defect Di at the surface irradiation position Q, the surface irradiation light L is regularly reflected together with L ₁ and L ₂ , and as shown in the upper diagram of FIG. Although the defect Di does not appear in the front image f ₁ , as shown in the upper diagram of FIG. 4D, a part of the laser beam L is blocked by the defect Di, and the defect Di appears in the back image r ₁ .

Then, when the glass plate W further moves in the Y direction by the distance s ₂ and the defect Di comes from the Q ₃ position to the Q ₄ position, the laser light L is reflected by the back surface R and a part thereof is blocked by the defect Di. The back surface regular reflection light Ln is generated, and the defect Di appears again in the image r ₂ on the back surface. Therefore, in the defect Di generated in the intermediate I, an image including the defect Di is formed twice in the image memory 51 within the small distance and the small time corresponding thereto. The distance s _{2 is} also a small distance corresponding to the thickness of the glass plate W. For example, when the defect Di is at the center position of the thickness of the glass plate, s ₂ is ½ of s ₁ .

  As described above in detail with reference to FIGS. 2 to 4, when the defect is on the front surface, the back surface, or the middle, the image data including each defect appears three times, once or twice in the image memory 51. The defect determination unit 52 of the image processing device 5 detects the presence / absence of image data including the defect D in which the CCD light receiving element 22 of the CCD camera 2 is not turned on from the taken image data, and thus the defect image is detected. Then, a defect image is further obtained within a small distance close to the thickness a of the glass plate W in the Y direction, which is the moving direction of the glass plate W, at a certain position in the lateral X direction and within a short time of defect movement corresponding thereto. When it is detected whether or not there is an abnormal image at only one place, or at two or three places, it is determined that there is a defect Dr or Di or Df on the back, middle or front, respectively. In this example, the position of the defect in the Y direction is given by detecting the amount of movement of the glass plate W by the rotary encoder 41.

  If there is a defect and it is determined in this way, then the size and brightness of the defect are measured by a normal inspection means, and a certain inspection standard corresponding to the front, back or intermediate defect type. Accordingly, whether or not the defective part can be used as a product is determined, and a process for eliminating the product part including the defect or determining whether or not the whole product is acceptable is performed.

FIGS. 5 and 6 show the results of photographing an image including defects on the glass plate W on the CCD light receiving element 22 of the CCD camera 2 by the optical system 3 shown in FIG.
FIG. 5A is an image at positions P ₂ and P ₁ in FIGS. 2A and 2B. In the figure, the white and thick part in the black background shows the part hit by the specular reflection light, and the small black part in it shows the surface defect Df where the specular reflection light is scattered and hardly hits the light. The included image appears at two locations. Note that the upper and lower images are at the P ₂ and P ₁ positions, respectively. The white portion has a length of about 10 mm in the X direction centering on the defect Df. Therefore, it was confirmed that the defect Df was reliably imaged even when the laser beam was not a spot beam but a line beam having a length of 10 mm. FIG. 5B is an image at the P ₂ and P ₁ positions in FIG. 2C where the glass plate W is slightly moved. The defect Df appears only at one place on the back regular reflection light side. Therefore, it was also clarified that the surface defect Df is imaged twice at two locations at the same time, and once at one location with a short time delay, three times at a total of three locations.

FIGS. 6A and 6B are images at positions P ₂ and P ₁ in FIGS. 4A and 4B, respectively. The white portions of the upper and lower back surfaces and the regular specular reflection light respectively correspond to the diagrams of (d) and (c) of FIG. As shown in the figure, it was confirmed that at the intermediate defect Di, the image of the defect Di appears twice at two positions in the conveyance direction of the glass plate W by the backside regular reflection light of the same line-shaped laser beam.

  According to the defect inspection apparatus as described above, since an image including the defect D is formed only by specular reflection light having a constant light intensity, the glass plate W can be simply moved linearly in a fixed direction. According to the configuration, it is possible to reliably determine defects on the front surface, the middle, or the back surface. For example, when there are two or more defects in the vicinity of the back surface R of the glass plate W, there is no possibility of misjudging this as a surface or intermediate defect. Since, for example, a large number of 1.2 m square glass plates to be inspected have a frequency that occurs at one place, the same one glass plate is placed at the same position in the X direction and within a very short distance. Since it can be said that there are no defects of more than one location, the inspection apparatus of the present invention can determine the defect position substantially reliably.

FIG. 7 shows an example of an optical system of an inspection apparatus to which the present invention is applied.
The inspection apparatus of this example is an apparatus for a glass plate W having a dimension Ws = 1200 mm square, and an optical system 3 is constituted by 34 laser markers 1 and 24 CCD cameras 2. In the figure, the number of these corresponding portions is omitted. Further, the incident angle and the reflection angle of the laser beam L and the front and back regular reflection lights M and N with respect to the glass plate W are set to 45 °, but the plan view is shown in the figure. The optical path lengths S ₁ and S ₂ are 1064 mm and 152 mm, respectively.

  The field of view lc of one CCD camera 2 is 50 mm, and laser light emitted from nine laser markers is received within this range. Therefore, the effective length of the line-shaped laser light emitted from one laser marker is 6.25 mm. In the experimental results shown in FIGS. 5 and 6, since the defect D of the glass plate could be photographed with a laser beam having a length of about 10 mm, 6.25 mm is a value with a sufficient margin. The number of laser markers can be further reduced by projecting the regular reflection light once onto the screen and photographing the laser line reflected on the screen. Then, by moving only one of the optical system and the glass plate W, the 1200 mm width of the glass plate W can be photographed at a time. The part of the image processing device 5 is constituted by a microcomputer or the like as a device capable of processing as described above. According to such an inspection apparatus, the presence of a defect in the glass plate W and its position in the glass thickness direction can be determined under a reliable operation by a simple mechanism that performs a one-dimensional operation.

  The present invention is particularly advantageously used as a glass plate inspection apparatus used for liquid crystal panels, large-sized plasma display panels, and the like.

It is explanatory drawing which shows an example of the whole structure of the test | inspection apparatus to which this invention is applied. (A) thru | or (e) is explanatory drawing of the image formation state of the surface defect of the glass plate by the said apparatus. (A) thru | or (d) is explanatory drawing of the image formation state of a back surface defect. (A) thru | or (d) are explanatory drawings of the image formation state of the defect of an intermediate position. (A) And (b) is explanatory drawing which shows the state which image | photographed the surface defect with the actual camera. (A) And (b) is explanatory drawing which shows the state which image | photographed the defect of the intermediate position with the actual camera. It is a top view of the optical system of the inspection apparatus of the Example to which this invention is applied.

Explanation of symbols

1 Laser marker (light projecting part)
2 CCD camera (light receiving unit)
3 Optical system 4 Line conveyor (moving mechanism)
5 Image processing device (determination unit)
D, Df, Dr, Di Defects, front, back and intermediate defects (defective part)
F surface f ₁ , f ₂ , r ₁ , r ₂ image H surface I intermediate L, L ₁ , L ₂ laser light M, Lm, M ₁ , M ₂ surface regular reflection light N, Ln, N ₁ , N ₂ back surface Regular reflection light R Back surface W Glass plate (plate-like transparent body)
Y Longitudinal direction (constant direction)
t Predetermined short time

Claims (1)

In the inspection device for inspecting the defective part of the plate-like transparent body,
An optical system composed of a light projecting unit and a light receiving unit arranged at a fixed relationship position, and the plate-shaped transparent body and the optical system so as to be relatively movable in a certain direction. A moving mechanism that enables movement of either the transparent body or the optical system, and a determination unit; and the light projecting unit configured to project laser light on the plate-shaped transparent body The light receiving unit is configured to receive the front surface regular reflection light regularly reflected from the surface of the plate-like transparent body and the back regular reflection light regularly reflected from the back surface of the laser light so that an image can be formed. The determination unit takes in the image formed by the light receiving unit, and the abnormal image is included in one place or within a predetermined short time when the image includes the defective portion as an abnormal image. If there are two or three places in a certain direction, Serial surface inspection apparatus characterized by determines that the there is a defective portion in the middle or the surface of said back face.