JP2005207808A - Defect inspecting apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which can surely perform inspection having proper reproducibility and which contributes to management and improvement in quality. <P>SOLUTION: An inspection apparatus comprises imaging means 11 and 12 for imaging a light emission surface 5a from a first direction in which the light-emitting surface is approximately perpendicular to the optical axis 11a and for imaging the light-emitting surface 5a with respect to a second direction intersecting the first direction; a black spot detection means 15A for detecting a black spot part having brightness lower than a first threshold from the imaged image from the first direction; and a white spot detection means 15B for detecting a white spot part having luminance higher than a second threshold from the imaged image with respect to the second direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for inspecting a defect of a light emitting surface such as a backlight used as a surface light source in a liquid crystal display device, for example.

When an inspector visually inspects the light emitting surface such as the backlight, the following problems are pointed out and improvement is desired. That is,
(1) A defect is overlooked or not mistaken as a defect.
(2) It is difficult to find objectivity in the determination, and inspection results vary due to differences in determination criteria and physical condition among inspectors.
(3) Since the defects are minute and the contrast is low, it is difficult to increase the inspection accuracy.

Further, Patent Document 1 proposes a method for detecting foreign matter or scratches on the backlight unit by visual observation or using a camera.
JP 2002-341345 A

  However, in the method described in Patent Document 1, the backlight is turned off, and oblique illumination is performed from an oblique direction with respect to the front direction. The above-described problems in the visual inspection cannot be solved, and in particular, there is a problem that it is difficult to see a high-intensity white spot portion by visual inspection.

  The present invention has been made in view of the above problems, and its purpose is to solve the above-mentioned problems of visual inspection, and can be inspected without relying on the subjective judgment of the inspector. It is to provide technology that contributes to the management and improvement.

  In order to solve the above-described problems and achieve the object, an inspection device for a light emitting surface of a lighting device according to the present invention is a device for inspecting a defect of a light emitting surface of a lighting device, the light emitting surface and an optical axis. Imaging means 11 and 12 for imaging the light emitting surface from a first direction in which the light emitting surface is substantially vertical, and imaging the light emitting surface from a second direction intersecting the first direction, and from the first direction A black spot detecting means 15A for detecting a black spot portion having a luminance lower than the first threshold value from the captured image, and a white inspection for detecting a white spot portion having a luminance higher than the second threshold value from the captured image from the second direction. Providing means 15B.

  The apparatus further includes a determination unit that determines that the illumination device is a non-defective product when neither the black spot portion nor the white spot portion is detected in the detection results of the detection means.

  Moreover, in the above apparatus, the imaging unit intersects the first direction with a first imaging unit that images the light emitting surface from a first direction in which the light emitting surface and the optical axis are substantially perpendicular to each other. And second imaging means for imaging the light emitting surface from a second direction.

  The apparatus further includes changing means for changing the direction of the light emitting surface with respect to the imaging means from the first direction to the second direction.

  In any of the above-described apparatuses, when imaging from the second direction, the depth of field of the imaging unit is set larger than the depth of the illumination apparatus in the inclined posture.

  In any of the above-described apparatuses, when imaging from the second direction, the focal position of the optical lens included in the imaging unit is tilted with respect to the normal focal position.

  Further, in any one of the above devices, when imaging from the second direction, the imaging unit is moved back and forth with respect to the illumination device, and different portions of the illumination device are photographed at different focal positions, Each detection means detects a black spot part and a white spot part using the image of each photographing location.

  In any of the above apparatuses, the imaging unit includes a line sensor in which a plurality of CCDs are linearly arranged.

  Also, the inspection method for the light emitting surface of the illumination device according to the present invention is a method for inspecting a defect in the light emission surface of the illumination device, and the light emission from the first direction in which the light emission surface and the optical axis are substantially perpendicular. An imaging step of imaging a surface and imaging the light emitting surface from a second direction intersecting the first direction, and a black spot portion having a luminance lower than the first threshold value from the captured image from the first direction. In the black spot detection step for detecting, the white spot detection step for detecting a white spot portion having a luminance higher than the second threshold from the captured image from the second direction, and the detection result in each detection step, the black spot portion And when the white spot portion is not detected, the lighting device includes a determination step of determining that the lighting device is non-defective.

  Note that a program for executing the defect inspection procedure may be created and recorded on a recording medium or the like, and read from the recording medium and executed by a computer when necessary.

  As described above, according to the present invention, since the problems of the conventional visual inspection are solved and the inspection can be performed without depending on the subjective judgment of the inspector, the inspection can be performed with high reliability and reproducibility. There is an effect that contributes to improvement.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiment described below is an example as means for realizing the present invention, and the present invention can be applied to a modified or modified embodiment described below without departing from the spirit of the present invention.
[Backlight unit]
FIG. 1 is a cross-sectional view of a liquid crystal display device including a backlight unit exemplified as an embodiment according to the present invention.

  The illumination device exemplified as an embodiment of the present invention is a backlight unit that illuminates an electro-optical (liquid crystal, LCD) panel from the back.

  The backlight unit U includes a light source 1, a light guide plate 2, a reflection plate 3, a diffusion sheet 4, and a prism sheet 5, and is provided on the back surface of a transmissive or transflective LCD panel 6 in which a plurality of pixels are formed in a matrix. It is arranged as a surface light source device.

  The liquid crystal display device including the LCD panel 6, the backlight unit U, and the light source 1 is mounted as a display of, for example, a mobile phone or a small electronic device.

  The light guide plate 2 is a plate-like optical component made of a light-transmitting material such as a transparent polycarbonate resin, for example, and receives light rays from a plurality of point light sources (white LEDs, etc.) 1, and the incident light rays This is a side light type member that is scattered and reflected and emitted toward the LCD panel 6.

Light rays emitted from the light guide plate 2 pass through the diffusion sheet 4 and the prism sheet 5 to illuminate the LCD panel 6 from the back side.
[Defect inspection equipment]
The defect inspection apparatus of the present embodiment is mixed between the members 2 to 5 when manufacturing the backlight unit U or scratches existing on the members such as the light guide plate 2, the reflection plate 3, the diffusion sheet 4, and the prism sheet 5. Inspect for defects in the light emitting surface of the backlight unit caused by foreign matter.

  Specifically, as shown in FIG. 2, in the defect inspection apparatus, the backlight unit U emits light in the first direction (the light emitting surface 5a and the optical axis 11a are substantially perpendicular to each other). A first CCD camera 11 (first image pickup means) that picks up an image from a first direction) and a second direction (in the first direction) in which the optical axis 12a is inclined by about 30 ° to 45 ° with respect to the light emitting surface 5a. A second CCD camera 12 (second image pickup means) that picks up an image from a certain optical axis 11a) is connected to each of the first and second CCD cameras via a communication cable 13, and a picked-up image is obtained. An image processing function 14 that performs AD conversion to generate digital image data and performs necessary image processing such as correction processing, and a detection function 15A (black spot detection means) that detects the presence or absence of black spot portions and white spot portions in the digital image data White point detection means) A computer 16 having a determination function 15B (determination means) for determining whether the backlight unit U is a non-defective product or a defective product by integrating the detection results.

  The computer 16 includes means for executing programs such as a keyboard, a mouse, an auxiliary storage device (such as a ROM and a hard disk), a CPU and a main storage device (RAM), an external storage device such as a CRT, a printer and a CD-ROM device, and a magnetic device. A recording medium such as a disk or a CD-ROM disk.

  The first and second CCD cameras 11 and 12 include, for example, a sensor in which a CCD (imaging device) having about 2000 pixels is arranged in a planar shape or a linear shape so that the entire light emitting surface can be imaged. The CCD camera may be provided with the image processing function.

  The computer 16 executes the image processing function by an image processing circuit (hardware) and an image processing program (software), and charges 1 accumulated in each of the first and second CCDs (imaging devices) for each pixel. Digital image data is generated by converting into luminance data (pixel value) of bytes (value of 0 to 255).

  Further, the computer 16 executes the detection function 15A by a detection circuit (hardware) and a detection program (software), and image data in the effective region R1 of the light emitting surface 5a in front view shown in FIG. For each pixel, a portion whose luminance data is lower than a first threshold (for example, a pixel value of 200) is detected as a black dot portion. Similarly, for each pixel of image data from an oblique direction shown in FIG. A portion higher than a second threshold (for example, a pixel value of 50) is detected as a white point portion. Then, the detection results are integrated, and when neither the black spot portion nor the white spot portion is detected, or the detection location or size is smaller than the predetermined value, there is no defect on the light emitting surface, and the backlight unit U is a non-defective product. Is determined.

  On the other hand, the computer 16 executes the determination function 15B by a determination circuit (hardware) and a determination program (software), and when at least one of a black spot portion and a white spot portion is detected from the detection result. The pixel position and size are displayed as defect information on a display device 17 such as a CRT, and are also stored in a recording device 18 such as a hard disk or a CD-R.

  Note that the number of computers is not limited to one, and each CCD camera can be installed for parallel processing. In this case, the processing time can be shortened.

  The cause of the black spot portion (low luminance portion) is that the light guide plate 2, the reflection plate 3, the diffusion sheet 4, the prism sheet 5, etc. are damaged by each member itself or between the members when the backlight unit is manufactured. It is conceivable that the emission of light is blocked by foreign matters mixed in, and a low-luminance portion is formed in front view, which is originally high-luminance.

Further, the cause of the occurrence of the white spot portion (high luminance portion) is that the light emission direction is normal due to scratches or the like existing on each member such as the light guide plate 2, the reflection plate 3, the diffusion sheet 4, and the prism sheet 5. It is conceivable that the high luminance portion is formed in the state of being inclined from the direction and viewed from the oblique direction which is originally low luminance.
[Defect detection processing]
FIG. 4 is a flowchart showing the defect detection processing of the backlight unit by the defect inspection apparatus.

  In FIG. 4, in step S <b> 1, the computer 16 acquires information related to the captured image from the CCD cameras 11 and 12.

  In step S3, image processing is performed on the acquired image information.

  In step S5, the presence / absence of a black spot portion and a white spot portion is detected based on the image processed image data.

  If at least one of the black spot portion and the white spot portion is detected in step S7, the pixel position and size are displayed on the display device as defect information in step S9 and recorded in the recording device or the like. .

  If neither a black spot portion nor a white spot portion is detected in step S7, it is determined in step S11 that the backlight unit is a non-defective product, and the result is displayed on the display device.

  Next, the image processing procedure in step S3 will be described with reference to FIG.

  In FIG. 5, in step S21, the captured image acquired from each CCD camera is binarized.

  In steps S23 and S25, contraction processing and expansion processing are executed for each pixel.

  In step S27, it is recognized as a block of pixels.

  In step S29, a small block is removed from the recognized block of pixels.

  In step S31, the number of lumps after the removal is counted.

  According to the above embodiment, since the problems of the conventional visual inspection can be solved and the inspection can be performed without depending on the subjective judgment of the inspector, the inspection can be surely performed with good reproducibility, and the effect of contributing to quality management and improvement. There is.

Note that the program for executing the defect detection process incorporates a program module including codes corresponding to the steps of the flowchart, and can be used as an electronic computer by an electronic, electromagnetic, or optical method. It is recorded on a hard disk device or a recording medium with a computer-readable code.
[Modification]
FIG. 6 is a diagram illustrating a defect inspection apparatus according to a modification of the present embodiment.

  In FIG. 6, the difference from the above embodiment is that the direction of the light emitting surface 5a with respect to the optical axis 11a of the CDD camera 11 is changed from the first direction to the second direction instead of using one CCD camera 11. The rotation mechanism 21 (changing means) is provided. The rotating mechanism 21 has a function of holding the backlight unit U and rotating the backlight unit U around the intersection A between the light emitting surface 5a and the optical axis 11a.

  In this modification, first, the light emitting surface 5a is imaged in a state in which the light emitting surface 5a of the backlight unit U is installed so as to be substantially perpendicular (first direction) to the optical axis 11a of the CCD camera 11. The computer detects the black spot.

  Next, the control unit 25 controls the motor M to drive the rotation mechanism 21, and the backlight unit U is inclined with respect to the CCD camera 11 (second direction in which the light emitting surface 5a intersects the optical axis 11a of the camera). Then, the computer detects the white spot portion by imaging the light emitting surface in this state.

  And the presence or absence of a defect is determined combining each detection result by the defect detection procedure mentioned above.

In the above modification, by providing the rotation mechanism 21 that rotates the backlight unit U with respect to the CCD camera 11, the same effect as in the above embodiment can be obtained with one CCD camera, and at the same time, the apparatus cost can be reduced. .
[Other aspects]
The first and second CCD cameras 11 and 12 have resolutions that are optimal for detecting defects in the inspection object, and the optical lens mounted on the camera and the angle of the light emitting surface of the backlight unit are uniform. Therefore, a sufficient distance between the lens and the light emitting surface is taken.

Note that any of the following (1) to (4) is performed at the time of photographing in an oblique direction by the CCD camera, and there is an effect of preventing the shift of the focal position at the time of photographing. That is,
(1) As shown in FIG. 7, the distance between the light emitting surface and the CCD camera is narrowed down, and the depth of field d of the second CCD camera is determined based on the depth D of the backlight unit U in an inclined posture. (D> D).
(2) A tilting mechanism that changes the attitude of the optical lens of the CCD camera is provided, and the focal position of the lens is tilted by about 2 ° with respect to the normal focal position, so that the imaging plane is perpendicular to the optical axis. Regardless of focus.
(3) In particular, in the case of d ≦ D, the CCD camera is moved back and forth with respect to the backlight unit to photograph different portions of the light emitting surface at different focal positions, and black spots and Detect the presence or absence of white spots.
(4) Using a line sensor in which the CCD is linearly arranged, the line sensor is positioned and scanned so that the distance between the light emitting surface and the CCD is the same.

It is sectional drawing of the liquid crystal display device containing the backlight unit illustrated as embodiment which concerns on this invention. 1 is a block diagram of a defect inspection apparatus according to an embodiment of the present invention. It is a figure explaining the defect detection method of this embodiment. It is a flowchart which shows the defect detection process of this embodiment. It is a flowchart which shows the image processing procedure in the defect detection process of this embodiment. It is a figure which shows the defect inspection apparatus of the modification of this embodiment. It is a figure which shows the other aspect of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide plate 3 Reflection plate 4 Diffusion sheet 5 Prism sheet 6 LCD panel 11, 12 CCD camera 11a, 12a Optical axis 13 Communication cable 14 Image processing function block 15 Judgment processing function block 16 Computer 17 Display device 18 Recording device 21 Rotation Mechanism 25 Control unit

Claims (9)

A device for inspecting a defect on a light emitting surface of a lighting device,
Imaging means for imaging the light emitting surface from a first direction in which the light emitting surface and the optical axis are substantially perpendicular, and imaging the light emitting surface from a second direction intersecting with the first direction;
Black spot detecting means for detecting a black spot portion having a luminance lower than the first threshold value from the captured image from the first direction;
An apparatus comprising: white point detecting means for detecting a white point portion having a brightness higher than a second threshold value from a captured image from the second direction. 2. The apparatus according to claim 1, further comprising a determination unit that determines that the illumination device is a non-defective product when neither the black spot portion nor the white spot portion is detected in the detection results of the detection means. . The imaging means includes: a first imaging means for imaging the light emitting surface from a first direction in which the light emitting surface and an optical axis are substantially perpendicular; and the light emission from a second direction intersecting the first direction. The apparatus according to claim 1, further comprising a second imaging unit that images the surface. The apparatus according to claim 1, further comprising a changing unit that changes the direction of the light emitting surface with respect to the imaging unit from the first direction to the second direction. 5. The apparatus according to claim 1, wherein, when imaging from the second direction, the depth of field of the imaging unit is set to be greater than the depth of the illumination device in an inclined posture. 6. apparatus. 5. The apparatus according to claim 1, wherein when imaging from the second direction, the focal position of an optical lens included in the imaging unit is tilted with respect to a normal focal position. 6. When imaging from the second direction, the imaging means is moved back and forth with respect to the illumination device, and different portions of the illumination device are photographed at different focal positions,
5. The apparatus according to claim 1, wherein each of the detection units detects a black spot portion and a white spot portion using an image of each photographing location. The apparatus according to claim 1, wherein the imaging unit includes a line sensor in which a plurality of CCDs are linearly arranged. A method for inspecting a defect of a light emitting surface of a lighting device,
An imaging step of imaging the light emitting surface from a first direction in which the light emitting surface and the optical axis are substantially perpendicular, and imaging the light emitting surface from a second direction intersecting the first direction;
A black spot detection step of detecting a black spot portion having a luminance lower than the first threshold value from the captured image from the first direction;
A white point detection step of detecting a white point portion having a luminance higher than the second threshold from the captured image from the second direction;
An inspection method comprising: a determination step of determining that the illumination device is a non-defective product when neither the black spot portion nor the white spot portion is detected in the detection result in each detection step.

Images