JP2008014790A - Brightness calculation method, brightness calculation system, inspection system, brightness calculation program and computer-readable recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection system for detecting a flaw with high precision correlated with visual sensitivity by calculating the brightness value of a flaw pixel, a brightness calculation system, and to provide a brightness calculation method. <P>SOLUTION: The brightness calculation system is equipped with: a normal brightness estimation part 18 for calculating a normal brightness value being the brightness value when a normal pixel is imaged by an imaging element showing an abnormal brightness value; a flaw pixel ratio calculation part 20 for calculating a flaw pixel ratio being the ratio of the area in the imaging range of a certain imaging element of a flaw pixel opening part being the cause of the abnormal brightness value and the area of the imaging range of; and a brightness correction part 19 for calculating the brightness value of the flaw pixel opening part by multiplying the difference between the abnormal brightness value and the normal brightness value by the reciprocal of the flaw pixel ratio and adding a standard brightness, which is the normal pixel having the same color as the flaw pixel, to the obtained value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for inspecting a display panel such as a liquid crystal panel, and more particularly to a method and apparatus for calculating a luminance value of a picture element included in the display panel.

  The display device is inspected for quality by turning on the panel in the latter half of the manufacturing process. This inspection includes a visual inspection in which a lit display device is visually inspected by an operator, and an automatic processing for processing a signal obtained by imaging the lit display device with a sensor camera such as a line sensor or an area sensor. There is an inspection.

  However, in the case of visual inspection, there are variations in determination due to oversight or individual differences. In addition, display devices have become more sophisticated in recent years, and the number of display pixels is on the order of millions of pixels, so the defect location and defect type found visually can be recorded accurately for correction and process improvement. It is difficult to make feedback information. The display pixel is a unit composed of three picture elements (display picture elements) of R, G, and B.

  Further, in the case of automatic inspection, since the tact limit is severe, it is difficult to inspect with high resolution, and the imaging resolution is near the pixel pitch that is the interval between R, G, and B pixel elements, or 1 / 2 Macro inspection that matches to about 2 is the mainstream.

  A description will be given of what kind of problem occurs when imaging is performed with such an imaging resolution. A display device such as a liquid crystal panel has a structure in which picture elements such as RGB are regularly arranged. In this picture element, RGB filters are regularly arranged on a glass substrate, but a black matrix (hereinafter referred to as BM) is arranged in the gaps between the filters so as not to leak light. Yes. Therefore, the region through which RGB light actually passes is a region smaller than the pixel pitch (this region is referred to as a pixel aperture).

  When such a display device is imaged with a sensor camera, the imaged image data is obtained by sampling the regularly arranged picture elements in the display device with the regularly arranged imaging elements of the sensor camera. . Therefore, for example, when a defective picture element that becomes a bright spot is sampled by the imaging device, the aperture of the defective picture element and the BM are averaged together, and therefore a value lower than the actual luminance is taken. Output as image data.

  Furthermore, since both the display device and the image sensor have a regular lattice pattern, a frequency component corresponding to the difference between the spatial frequencies of the two patterns is generated, and a moire is generated. This moire becomes a noise component and decreases the inspection accuracy.

  Therefore, a technique for removing the influence of moire and improving inspection accuracy has been proposed. For example, in the invention described in Patent Document 1, a plurality of moire components are extracted from captured image data, a cycle of the moire components is detected, pixel values arranged for each cycle are connected, and defective components are removed. A smooth curve is obtained. Then, the difference between the pixel values located on the plurality of smooth curves and the original image data is obtained to obtain defect image data, the average of the plurality of smooth curves is obtained, and smooth image data not including moire is obtained. Have acquired. Further, the smooth image data and the defect image data are added, and the addition result is used as inspection image data. Thereby, it becomes possible to detect a defect without being affected by the moire component.

In the invention described in Patent Document 2, the positional relationship between the picture element and the sensor camera is set as a reference position, and the luminance information obtained by the image sensor is multiplied by the corresponding position correction coefficient extracted at the reference position. Light intensity information is generated.
Japanese Patent Laid-Open No. 11-352011 (released on December 24, 1999) Japanese Patent Laid-Open No. 5-240802 (published on September 21, 1993)

  However, the following problems occur in the prior art.

  In the invention described in Patent Document 1, even if the moire component is removed, the actual luminance of the pixel opening cannot be calculated. Accordingly, there is a possibility that a weak defect having a very low luminance without being correlated with the visual sensitivity is buried in a noise component and cannot be detected.

  In the invention described in Patent Document 2, as in the invention of Patent Document 1, the calculated defect luminance value is not the luminance of the pixel opening. Further, in the means for setting the reference position in advance and creating the corresponding correction coefficient, there is no means for correcting when a positional deviation occurs on the inspection panel.

  The present invention has been made to solve the above problems, and its purpose is to detect defects with high accuracy correlated with visual sensitivity by calculating the luminance value of the defective pixel opening itself. An inspection device, a luminance calculation device, and a luminance calculation method are provided.

  In order to solve the above-described problem, the luminance calculation method according to the present invention images a display panel in which a plurality of picture elements are arranged in a certain direction with an imaging unit having an imaging element, and obtains the obtained captured image data. A luminance calculation method in a luminance calculation apparatus included in an inspection apparatus that inspects the display panel by analyzing and detecting an abnormal luminance value that is a luminance value that is out of a reference range, the imaging showing the abnormal luminance value A normal luminance value calculating step for calculating a normal luminance value that is a luminance value when the element is imaging a normal picture element, and a certain imaging element at the opening of the defective pixel element that causes the abnormal luminance value A defective pixel rate calculation step of calculating a defective pixel rate that is a ratio of an area in the imaging range to the area of the imaging range, and the defective pixel rate in the difference between the abnormal luminance value and the normal luminance value Multiply the reciprocal of Is characterized in that it comprises a luminance value correction step of calculating a luminance value of the opening by adding the standard luminance value is the luminance value of the normal pixels of the defect pixel of the same color.

  In order to solve the above-described problem, the luminance calculation apparatus according to the present invention images a display panel in which a plurality of picture elements are arranged in a certain direction with an imaging unit having an imaging element, and obtains the obtained captured image data. Analyzing and detecting an abnormal luminance value that is a luminance value out of a reference range, the luminance calculating device provided in the inspection device that inspects the display panel, the imaging device showing the abnormal luminance value is normal A normal luminance value calculating means for calculating a normal luminance value, which is a luminance value when a picture element is being imaged, and an aperture of a defective pixel element that is the cause of the abnormal luminance value, within an imaging range of a certain imaging device A defective pixel rate calculating means for calculating a defective pixel rate that is a ratio between the area of the image area and the imaging range, and a difference between the abnormal luminance value and the normal luminance value multiplied by an inverse number of the defective pixel rate. Normal picture of the same color as the above defective picture element Is characterized in that it comprises a luminance value correction means for calculating a luminance value of the opening by adding the standard luminance value is a luminance value of.

  When a display panel in which picture elements are arranged in a certain direction is imaged by the imaging means, the positional relationship between the imaging range of the image sensor and each picture element is not constant. That is, the ratio of the area of the picture element included in the imaging range of a certain imaging device is not constant. For this reason, even when a display panel in which picture elements having a constant luminance value are arranged is picked up, the luminance value of each image sensor is not constant. Therefore, when a defective pixel is determined, an accurate luminance value of the defective pixel cannot be obtained, and the accuracy of the defect determination is reduced.

  According to the above configuration, the defective pixel rate calculating unit calculates the defective pixel rate, and the luminance value correcting unit calculates the luminance value of the defective pixel using the defective pixel rate. At this time, the luminance value correcting means multiplies the difference between the abnormal luminance value and the normal luminance value calculated by the normal luminance value calculating means by the reciprocal of the defective pixel rate, and adds the standard luminance value to the obtained value. The luminance value of the defective picture element is calculated.

  Therefore, the luminance value of the defective pixel opening itself can be calculated without being affected by the positional relationship between the imaging range of the imaging element and the picture element. Therefore, by applying the luminance calculation device to the inspection device, accurate defect determination correlated with the visual sensitivity of the defective picture element can be performed.

  Note that the standard luminance value may be set in advance, or may be input every time a luminance value is calculated via an input unit provided in the luminance calculation device.

  Further, it is preferable to further include a pixel determination step of determining which color the defective pixel is and setting the standard luminance value corresponding to the determination result.

  The luminance calculation apparatus further includes a pixel determination unit that determines which color the defective pixel is, and outputs the standard luminance value corresponding to the determination result to the luminance value correction unit. It is preferable to provide.

  According to the above configuration, the pixel determination unit determines which color the defective pixel is, and outputs a standard luminance value corresponding to the determined color to the luminance value correction unit. Therefore, the luminance value of the defective pixel opening can be accurately calculated regardless of the color of the defective pixel.

  Further, the luminance calculation method includes a signal dividing step of forming a signal component waveform by plotting a signal component of the imaging data at intervals corresponding to the number of moire in the pixel arrangement direction, which occurs in the captured image data. Before the pixel determination step, and in the pixel determination step, by comparing the coordinates of the peak of the waveform with the coordinates of the signal component caused by the defect pixel, It is preferable to determine whether the pixel is a color picture element.

  In addition, the luminance calculation device includes a signal dividing unit that forms a waveform of a signal component by plotting a signal component of the imaging data at intervals corresponding to the number of moire in the pixel arrangement direction that occurs in the captured image data. The picture element determination means compares the coordinates of the peak of the waveform with the coordinates of the signal component caused by the defective picture element to determine which color picture element the defective picture element is. It is preferable to determine.

  According to the above configuration, the signal dividing unit plots the signal component (pixel value) of the imaging data at intervals corresponding to the number of moire in the pixel array direction, and forms the waveform of the signal component, thereby capturing the captured image data. Remove the moire generated. Then, the picture element determination means compares the coordinates of the peak of the formed waveform with the coordinates of the signal component caused by the defective picture element. Since the position of the peak of the waveform corresponds to the type (color) of the picture element, it is possible to determine the color of the defective picture element by the above comparison.

  Further, the defective pixel rate calculation means calculates a distance between the center line of the defective picture element and the center line of the imaging range of the imaging device that images the defective picture element, and based on the distance, It is preferable to calculate the area of the opening within the imaging range.

  With the above configuration, the distance between the center line of the defective picture element and the center line of the imaging range of the imaging device that images the defective picture element is obtained, and from this distance, the defective pixel opening portion within the imaging range is obtained. The area can be calculated. Therefore, the defective pixel rate can be easily calculated.

  In addition, a display panel in which a plurality of picture elements are arranged in a certain direction is imaged by an imaging means having an imaging element, and the obtained captured image data is analyzed, and an abnormal luminance value that is a luminance value out of the reference range is obtained. An inspection apparatus for inspecting the display panel by detecting the luminance, and the display panel by comparing a luminance value of the defective pixel calculated by the luminance calculation apparatus and the luminance calculation apparatus with a reference value. An inspection apparatus provided with inspection means for reinspecting the defects is also included in the technical scope of the present invention.

  Also included in the technical scope of the present invention are a luminance calculation program for causing a computer to function as each of the means of the luminance calculation device and a computer-readable recording medium recording the luminance calculation program.

  The luminance calculation method according to the present invention, as described above, a normal luminance value calculation step of calculating a normal luminance value that is a luminance value when the imaging element that indicates an abnormal luminance value has captured a normal picture element, A defective pixel rate calculation step of calculating a defective pixel rate that is a ratio of an area within the imaging range of a certain imaging device and an area of the imaging range of the opening of the defective pixel that is the cause of the abnormal luminance value. And the difference between the abnormal luminance value and the normal luminance value multiplied by the reciprocal of the defective pixel rate, and the resulting value is a standard luminance value that is the luminance value of a normal pixel of the same color as the defective pixel And a luminance value correction step of calculating the luminance value of the opening by adding the above.

  As described above, the luminance calculation apparatus according to the present invention includes a normal luminance value calculation unit that calculates a normal luminance value that is a luminance value when the imaging element that indicates the abnormal luminance value captures a normal pixel. A defective pixel rate calculating means for calculating a defective pixel rate that is a ratio of an area of an imaging element in an imaging range of an aperture of a defective pixel that is an abnormal luminance value to the imaging range; Multiply the difference between the abnormal luminance value and the normal luminance value by the reciprocal of the defective pixel rate, and add the standard luminance value, which is the luminance value of the normal pixel of the same color as the defective pixel, to the obtained value Thus, a brightness value correction unit that calculates the brightness value of the opening is provided.

  Therefore, the luminance value of the defective pixel opening itself can be calculated without being affected by the positional relationship between the imaging range of the imaging element and the picture element. Therefore, by applying the luminance calculation apparatus to the inspection apparatus, there is an effect that accurate defect determination correlated with the visual sensitivity of the defective picture element can be performed.

  An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 2 is a schematic diagram showing the configuration of the inspection apparatus 1 of the present embodiment. As shown in FIG. 2, the inspection apparatus 1 includes an imaging apparatus 2, a stage 4 on which a display device 3 (display panel) is placed, a lighting circuit 5 that supplies a drive signal to the display device 3, and a contact portion with the display device 3. 6, illumination 7, and control device 8 (inspection device).

  The imaging device 2 is for imaging the display device 3, and has a plurality of imaging elements arranged in a matrix. Examples of the imaging device 2 include a CCD camera and a cMOS camera.

  The control device 8 controls the inspection device 1. FIG. 3 is a schematic diagram showing the configuration of the control device 8. As shown in FIG. 3, the control device 8 includes an input unit 9 for inputting various set values, an output unit 10 for outputting a defect detection result, a main control unit 11 for controlling each unit, and an inspection unit 12 for performing inspection. (Inspection means) and a correction unit 13 (brightness calculation device) that performs luminance correction.

  The inspection unit 12 analyzes the captured image data obtained by the imaging device 2 imaging the display device 3, and detects an abnormal luminance value that is a luminance value out of the reference range, thereby detecting a defect in the display device 3. This is to detect picture elements. The inspection unit 12 outputs the detected coordinates of the defective picture element and the luminance value data of the captured image captured by the imaging device 2 to the correction unit 13, and corrects the luminance value of the opening of the defective picture element. The defect determination is performed by comparing the calculated luminance value with a preset inspection threshold value (reference value). At this time, the defect detection algorithm of the inspection unit 12 may be a generally known algorithm.

  Here, a defective picture element is a picture element having a luminance value outside the reference range, and a normal picture element is a picture element having a luminance value within the reference range.

  In the following description, a captured image of the display device 3 captured by the imaging device 2 is simply referred to as a captured image, and data forming the captured image is referred to as captured image data.

  The correction unit 13 calculates the luminance value of the opening of the defective picture element detected by the inspection unit 12 based on the captured image data. The correction unit 13 outputs the calculated luminance value of the defective pixel opening to the inspection unit 12.

  FIG. 1 is a schematic diagram illustrating the configuration of the correction unit 13. As shown in FIG. 1, the correction unit 13 includes an input unit 14 that inputs correction information necessary for correction, such as coordinates of defective picture elements output from the inspection unit 12 and captured image data, and correction results (defective picture elements). Output unit 15 that outputs the luminance value of the aperture), a signal dividing unit 16 (signal dividing unit) that divides the signal component of the captured image data, and calculates the type and ratio of the picture element included in the abnormal portion from the captured image data. Picture element determination unit 17 (picture element determination unit), normal luminance estimation unit 18 (normal luminance value calculation unit) for estimating the luminance value of the imaging region when the defective pixel is normal, luminance of the opening of the defective pixel A luminance correction unit 19 (luminance value correction unit) that calculates a value and a defective pixel rate calculation unit 20 (defect pixel rate calculation unit) that calculates a defective pixel rate described later are provided. Details of each unit constituting the correction unit 13 will be described later.

  Note that the abnormal part means an imaging region of the imaging element corresponding to the coordinates of the defective picture element output from the inspection unit 12.

(Configuration of display device 3)
Next, the configuration of the display device 3 to be inspected by the inspection apparatus 1 will be described with reference to FIG. FIG. 4 is a schematic diagram showing the configuration of the display device 3.

  The display device 3 is a color filter in which picture elements 3a to 3c of three colors R (red), G (green), and B (blue) are arranged in a matrix. As shown in FIG. 4, the rectangle indicates each picture element, and a repetitive array of R picture element 3a, G picture element 3b, and B picture element 3c is formed in a line on the filter. Such a direction of arrangement of picture elements is referred to as a picture element arrangement direction (direction of arrow 21).

  The distance between the picture elements in the picture element arrangement direction is referred to as a picture element pitch. More precisely, the picture element pitch is a distance between the center line of the picture element perpendicular to the picture element arrangement direction and the center line of the picture element adjacent to the picture element. Between each picture element, BM which is a light absorptive film | membrane is exposed.

  When such a display device 3 is imaged, the imaging device 2 is arranged so that the pixel arrangement direction and the imaging element arrangement direction of the imaging device 2 are parallel to each other. In FIG. 4, the grid indicates the imaging range (imaging area) of each imaging element. The imaging range of each imaging element is substantially square, and the length of one side of this square is called imaging resolution. In FIG. 4, the imaging resolution is slightly smaller than the picture element pitch.

  Since the picture elements are arranged two-dimensionally, the picture element arrangement direction is also present in a direction perpendicular to the direction of the arrow 21, but in the following, in order to simplify the explanation, the direction of the arrow 21 A description will be given of the pixel arrangement direction.

(Example of image sensor output signal)
Next, an example of an output signal of the image sensor obtained when the display device 3 is imaged will be described with reference to FIG. FIG. 4A shows an output signal of the image sensor obtained when the imaging resolution is 1.5% smaller than the pixel pitch, and FIG. 4B shows the imaging resolution 21.5% larger than the pixel pitch. The output signal of the image pick-up element obtained when it is small is shown. Both (a) and (b) display the output signal of the image sensor in the pixel array direction of the display device 3 for one line (for example, a round frame in FIG. 4).

  As shown in FIG. 5A, moire is generated as a low-frequency component when the image is picked up with a resolution close to the pixel pitch. On the other hand, as shown in FIG. 5B, moire is generated as a high-frequency component when imaging is performed with such a resolution that the difference between the imaging resolution and the pixel pitch is large. Thus, the moire generation pattern changes depending on the imaging resolution of the imaging apparatus 2. Such moire hinders accurate detection of defects in the display device 3.

(Details of each part constituting the correction unit 13)
(Signal division method in the signal division unit 16)
The signal dividing unit 16 receives data of the captured image from the input unit 14 and divides the signal component in the pixel arrangement direction of the captured image. FIG. 6 is a diagram for illustrating an example of signal division in the signal division unit 16. As shown in the figure, when imaging is performed with a resolution such that the imaging resolution is close to the pixel pitch, three signal components (waveforms A, B, and C) that are out of phase are obtained. By plotting every two signal components in the pixel array direction and connecting these output signals, a divided signal is obtained.

  That is, the waveform A is a waveform obtained by connecting the 3n (n is a positive integer) th output signal, the waveform B is the waveform obtained by connecting the 3n + 1th output signal, and the waveform C is a waveform obtained by connecting the 3n + 2nd output signal. is there. For example, when imaging is performed with a resolution such that the imaging resolution is close to 1/2 of the pixel pitch, six signal components having a phase shift are obtained. In this case, every five signal components in the pixel array direction are plotted, and these output signals are connected to obtain a divided signal.

  Note that how many plots are to be plotted may be set in advance or may be input by the operator via the input unit 9.

  The signal dividing unit 16 outputs the divided signal component to the pixel determining unit 17 and the defective pixel rate calculating unit 20.

(Pixel type determination method in the pixel determination unit 17)
The pixel determination unit 17 determines which RGB pixel or the BM is sandwiched between the defective pixels of the display device 3 included in the abnormal portion of the captured image data. That is, the picture element determination unit 17 calculates the positional relationship between the picture element of the display device 3 and the image sensor.

  The reason why the three signal components are obtained as described above is that the spectral sensitivity characteristics for the R, G, and B of the image sensor are different. Here, the pixel determination is performed based on the signal components plotted (divided) by the signal dividing unit 16.

  For example, it is assumed that the signal component resulting from the defective pixel is included in the waveform A among the plotted signal components.

  In this case, first, the maximum, minimum peak value, and intermediate value are calculated from the waveform A. As a calculation method, the display device 3 may be imaged in advance, a divided signal may be calculated, and the operator may set the maximum, minimum peak value, and intermediate value based on the spectral sensitivity characteristics of the image sensor, or dynamically It may be calculated.

  FIG. 7 is a diagram for explaining a method of calculating a peak value from a waveform of a signal component, (a) is a graph showing the waveform of the signal component, and (b) is a graph plotting adjacent difference values. is there. As a method of dynamically calculating, for example, as shown in FIG. 7B, adjacent difference values of the waveform A are calculated and plotted, and coordinates where the difference value sandwiches 0 are set as the maximum and minimum peak values. Among these peak values, the one that has a negative slope of the straight line connecting the plotted difference values is the maximum peak value, and the one that is positive is the minimum peak value.

  That is, the maximum and minimum peak values are calculated by detecting a point where the slope of the tangent line drawn with respect to the waveform of the signal component is parallel to the horizontal coordinate axis (X axis).

  Next, in the range between the maximum peak value and the minimum peak value, the middle of the wider range is set as the intermediate peak value. The position of the intermediate value depends on the arrangement order of the RGB picture elements. FIG. 8 is a diagram for explaining a method for determining the type of defective picture element based on the waveform of the signal component. FIG. 8A is a diagram showing the waveform of the signal component, and FIG. It is a figure which shows the allocation part. Here, as shown in FIG. 8A, among the correction information input in advance, the sensitivity corresponding to the R, G, and B of the image sensor corresponds to the pixel corresponding to the maximum peak value and the minimum peak value. The pixel type corresponding to the pixel type and the intermediate peak value is determined. That is, since the sensitivity characteristic of the image sensor is R <B <G, the picture element corresponding to the maximum peak value is G, the picture element corresponding to the minimum peak value is R, and the picture element corresponding to the intermediate peak value is B.

  Therefore, as shown in FIG. 8B, by determining which region of the region delimited by the maximum peak value, the intermediate peak value, and the minimum peak value the signal caused by the defective picture element belongs, It is possible to determine which color the picture element is. In FIG. 8B, a region between the minimum peak value and the maximum peak value is referred to as an RG pixel allocation portion, and a region between the maximum peak value and the intermediate peak value is referred to as a GB pixel allocation portion. A region between the peak value and the minimum peak value is referred to as a BR picture element allocation portion. In FIG. 8B, the signal due to the defective pixel is in the GB pixel allocation portion.

  When there is a signal due to a defective picture element in the GB picture element allocation portion, a signal due to the defective picture element is also generated in other divided signals. For example, when G is a defective picture element, the defective picture element is assigned to the RG assigned part of another divided signal, and when B is a defective picture element, the defective picture element is assigned to the BR assigned part of the other divided signal. The resulting signal is generated. That is, in cases other than the case where there is a signal due to a defective pixel at the peak position of the waveform of the signal component, a signal due to the defective pixel is generated in a plurality of divided signals.

  Therefore, the picture element determination unit 17 determines which color picture element the defective picture element is by comparing the waveforms of a plurality of signal components (three in the example shown in FIG. 6).

The pixel determination unit 17 outputs the determination result of the defective pixel to the normal luminance estimation unit 18, the luminance correction unit 19, and the defective pixel rate calculation unit 20.
(Luminance estimation method in normal luminance estimation unit 18)
FIG. 9 is a diagram for explaining a normal luminance value calculation method in the normal luminance estimation unit 18, and the lower diagram in FIG. 9 is an enlarged view of a part of the upper diagram. As shown in FIG. 9, the normal luminance estimation unit 18 calculates the average value of the luminance values of the signals located on both sides of the signal caused by the defective pixel included in the plotted signal component, and calculates the average value. The luminance value of the image sensor when the defective picture element is normal (hereinafter referred to as a normal luminance value).

  The normal luminance estimation unit 18 outputs the calculated normal luminance value to the luminance correction unit 19.

(Defect pixel rate calculation method in the defective pixel rate calculation unit 20)
Next, a defective pixel rate calculation method in the defective pixel rate calculation unit 20 will be described with reference to FIGS. 10 and 11. FIG. 10 is a diagram for explaining a method of calculating the defective picture element rate. FIG. 11 is a diagram for explaining a method of calculating the distance between the center line of the image sensor that images the defective pixel aperture and the center line of the pixel aperture. The case where the signal resulting from a defective pixel opening part is located in the middle is shown.

  The defective pixel rate calculation unit 20 uses the signal component output from the signal dividing unit 16 and the determination result of the defective pixel output from the pixel determination unit 17 to detect a defect within the imaging range of a certain image sensor. The defective pixel rate, which is the ratio of the area (Ar) of the picture element opening and the area of the imaging range, is calculated as follows.

Assuming that the R picture element has a bright spot defect, as shown in FIG. 10, the area (Ar) of the defective picture element opening can be calculated by the following equation.
Ar = Lr * S
Here, Lr is the width in the pixel arrangement direction of the defective pixel opening (R picture element) included in the imaging range of the imaging element, and S is the imaging resolution.

The Lr can be calculated by the following formula.
Lr = S / 2−Lbm1
Here, Lbm1 is the BM width in the pixel arrangement direction in the image sensor of interest, and is the distance between the defective pixel opening and the center line of the image sensor.

  Furthermore, Lbm1 can be calculated by the following equation.

Lbm1 = N−Pm / 2
Here, the value of N is the distance between the center line of the image sensor that images the defective pixel aperture and the center line of the defective pixel aperture (R pixel) adjacent to the center line of the image sensor. It is. Pm is the width of the picture element opening in the picture element arrangement direction.

  As shown in FIG. 11, the value of N is obtained by combining the coordinates of the signal caused by the defective pixel and the peaks located on both sides of the signal (a combination of any two of the maximum peak, the intermediate peak, and the minimum peak). It can be calculated from the difference from the coordinates.

  Note that Pm is a unique value (design value), and may be stored in a memory (not shown) provided in the control device 8, or may be input by the operator each time. These values are output to the defective pixel rate calculation unit 20 via the input unit 14.

In summary, the defective pixel rate calculation unit 20 calculates the area (Ar) of the defective pixel opening by the following equation.
Ar = {S / 2- (N-Pm / 2)} * S
That is, the defective pixel rate calculation unit 20 calculates the distance between the center line of the defective pixel opening and the center line of the imaging range of the imaging device that captured the defective pixel, and the defective pixel element is calculated from this distance. The area within the imaging range of the opening is calculated.

  Then, the defective pixel rate calculation unit 20 calculates the defective pixel rate by dividing the area (Ar) in the imaging range of the defective pixel opening by the area (Accd) of the imaging range of the imaging device. The defective pixel rate calculation unit 20 outputs the calculated defective pixel rate to the luminance correction unit 19.

(Brightness correction method in the brightness correction unit 19)
The luminance correction unit 19 calculates the actual luminance value of the defective pixel opening from the luminance value of the imaging element that images the region including the defective pixel opening. More specifically, the luminance correction unit 19 outputs the defective pixel element determination result output from the pixel element determination unit 17, the normal luminance value output from the normal luminance estimation unit 18, and the defective pixel element rate calculation unit 20. Based on the defective pixel rate, the luminance value of the actual defective pixel opening is calculated.

  FIG. 12 is a diagram illustrating the positional relationship between the imaging range of the imaging device and the picture elements. Since the luminance value of the imaging element is the average of the imaging range, as shown in FIG. 12, when the average value of the luminance values of the defective pixel opening and the BM is obtained (upper stage in FIG. 12), or the defective pixel There is a case where the average value of the luminance values of the opening, the adjacent opening, and the BM is obtained (lower part of FIG. 12). The luminance correction unit 19 calculates the luminance value of the defective pixel element opening from the luminance value of such an image sensor.

  FIG. 13 is a diagram illustrating a correspondence relationship between the divided signal components and the imaging range of the imaging device. For example, as shown in FIG. 13, there is a bright spot defect in the R pixel opening, and a part of the defective pixel opening is included in the imaging range of the imaging elements P1 and P2 adjacent to each other. A case will be described in which the element P1 includes a part of the G picture element opening, and the imaging element P2 includes a part of the B picture element opening.

  In this case, the luminance value of the imaging device including the defective pixel opening is an average value of the luminance values of the defective pixel opening, the pixel opening adjacent to the defective pixel opening, and the BM.

At this time, if the luminance values (abnormal luminance values) of the image sensors P1 and P2 that image the defective pixel aperture are YrP1 and YrP2, respectively, the following equations (1) and (2) are related to the luminance values of the image sensors. To establish.
YrP1 = (Yrd * Ar1 + Yg * Ag + Ybm * Abm1) / Accd (1)
YrP2 = (Yrd * Ar2 + Yb * Ab + Ybm * Abm2) / Accd (2)
Here, Yrd is the luminance value of the actual R picture element luminescent spot opening, Yg is the luminance value of the G picture element opening, and Ybm is the luminance value of BM. Ar1 is the area of the R picture element luminescent spot opening in the image sensor P1, Ar2 is the area of the R picture element luminescent spot opening in the image sensor P2, Ag is the area of the G picture element opening in the image sensor P1, Ab Is the area of the B pixel opening in the image sensor P2, Abm1 is the area of the BM in the image sensor P1, and Abm2 is the area of the BM in the image sensor P2. Among these parameters, the luminance value (standard luminance value) of the actual R, G, and B pixel apertures in the absence of a defect and the luminance value of the BM are set in advance at a high resolution. The captured image data is acquired in advance.

Next, assuming that YrPn1 and YrPn2 are the luminance values of the imaging elements P1 and P2 when the defective pixel opening is normal, that is, the normal luminance values calculated by the normal luminance estimating unit 18, YrPn1 and YrPn2 The following formulas (3) and (4) are established.
YrPn1 = (Yr * Ar1 + Yg * Ag + Ybm * Abm1) / Accd (3)
YrPn2 = (Yr * Ar2 + Yb * Ab + Ybm * Abm2) / Accd (4)
Here, Yr is the luminance value (standard luminance value) of the R picture element opening when it is normal. Therefore, from the expressions (1) and (3), the luminance value Yrd of the R picture element bright spot opening can be expressed by the following expression (5).
Yrd = {Accd * (YrP1-YrPn1) / Ar1} + Yr (5)
Here, the value of Accd / Ar1 is the reciprocal of the defective pixel rate output from the defective pixel rate calculation unit 20.

  Similarly, the luminance value of the R picture element bright spot opening can be calculated from the equations (2) and (4) (omitted). In this case, the luminance value of the R picture element bright spot opening may be calculated using the luminance value of one of the image sensors P1 and P2. If the accuracy is further improved, the luminance value of the R picture element bright spot opening may be calculated using the luminance values of both of the image sensors P1 and P2, and the average value thereof may be taken.

Abm1 and Abm2 can be calculated as follows. Below, the case where (4) Formula is applied is demonstrated. If the imaging resolution is S and the BM width in the imaging device of interest is Lbm, Ab and Abm2 are
Ab = Lb * S,
Abm2 = Lbm * S,
It can be expressed as.

(Processing flow in the control device 8)
Next, the flow of processing in the control device 8 will be described with reference to FIG. FIG. 14 is a flowchart showing the flow of processing in the control device 8. As shown in FIG. 14, first, the inspection unit 12 detects a defective picture element from the captured image in accordance with a command from the main control unit 11 (S10).

  The defect detection algorithm may be a general algorithm. For example, there is an algorithm for comparing every image sensor with the luminance value of its neighboring elements. At this time, the defective pixel region may be detected across a plurality of image sensors in setting the imaging resolution, but the portion with the highest luminance value (or the lowest portion) may be used as the defect coordinate.

  In addition to the defective picture element, foreign matter on the surface of the display device 3, foreign matter on each layer constituting the display device 3, and color filter breakage may be detected as defects. Only a defective pixel may be corrected by shape comparison or pattern matching. Hereinafter, a defect means a defect of a picture element.

  The inspection unit 12 outputs the detected coordinates of the defective picture element to the signal dividing unit 16 via the input unit 14 of the correction unit 13.

  Next, the signal dividing unit 16 stores the signal components in the pixel arrangement direction in a temporary storage memory (not shown) provided in the signal division unit 16 based on the coordinates of the defective pixel obtained by the inspection unit 12, and displays the picture. The signal components in the element array direction are plotted at intervals according to the moire number (S11) (picture element dividing step). The signal dividing unit 16 outputs the plotted signal components to the pixel determination unit 17, the normal luminance estimation unit 18, and the defective pixel rate calculation unit 20.

  Next, the pixel determination unit 17 performs defective pixel determination using the plotted signal components (S12) (pixel determination step), and the determination result is used as a luminance correction unit 19 and a defective pixel rate calculation unit. 20 output.

  On the other hand, when the signal component plotted from the signal dividing unit 16 is received, the normal luminance estimating unit 18 calculates a normal luminance value using the signal component (S13) (normal luminance value calculating step). Then, the normal luminance estimation unit 18 outputs the calculated normal luminance value to the luminance correction unit 19.

  When the defective pixel rate calculation unit 20 receives the signal component plotted from the signal dividing unit 16 and the pixel determination result from the pixel determination unit 17, the defective pixel rate calculation unit 20 calculates the defective pixel rate as described above. (S14) (Defect picture element rate calculation step). The defective pixel rate calculation unit 20 outputs the calculated defective pixel rate to the luminance correction unit 19.

  When the pixel determination result is received from the pixel determination unit 17 and the normal luminance value is received from the normal luminance estimation unit 18, the luminance correction unit 19 calculates the luminance value of the defective pixel opening by the method described above (S15). (Luminance value correction step). Then, the brightness correction unit 19 outputs the calculated brightness value of the defective pixel opening to the output unit 15.

When receiving the luminance value of the defective pixel element opening, the output unit 15 outputs the luminance value to the inspection unit 12 (S16).
(Processing flow in the inspection apparatus 1)
Next, the flow of processing in the inspection apparatus 1 will be described with reference to FIG. FIG. 15 is a flowchart showing the flow of processing in the inspection apparatus 1. As shown in FIG. 15, first, after the display device 3 is placed on the stage 4, the display device 3 is disposed so as to contact the contact portion 6 (S <b> 1).

  When detecting that the display device 3 is arranged, the main control unit 11 gives a drive signal to the display device 3 via the lighting circuit 5 (S2).

  Upon receiving this drive signal, the display device 3 displays an inspectable image. If the contact fails, it is necessary to redo the contact (return to S1).

  Next, the main control unit 11 adjusts the illuminance of the illumination 7 so as to be suitable for the captured image (S3). In addition, when the display device 3 is a self-luminous type, the light emission amount is adjusted.

  Next, the main control unit 11 controls the stage 4 holding the display device 3 (S4). Then, the imaging device 2 images the display device 3 with a preset resolution (S5).

  Then, the main control unit 11 detects a rotation deviation of the display device 3 and outputs an alignment error (S9) when it is larger than a preset rotation angle limit value (YES in S6), A message indicating that it is necessary to control the stage 4 or contact the display device 3 again is output.

  As a method for detecting the rotation deviation of the display device, a generally known method may be used. For example, the corners of the display unit of the display device may be calculated from edge components in the x direction and the y direction, or pattern matching may be performed.

  When the rotational deviation of display device 3 is smaller than the rotation angle limit value (NO in S6), defect detection is performed by inspection unit 12, and the luminance of the detected defect is calculated by correction unit 13. .

  Then, the inspection unit 12 performs defect detection processing by comparing the luminance value calculated by the correction unit 13 with a preset inspection threshold (S7). When the presence / absence of a defect is determined, the main control unit 11 outputs the inspection result and ends the series of processes.

(Effect of inspection device 1)
As described above, in the inspection apparatus 1, first, the inspection unit 12 tentatively detects the defective pixel of the display device 3 from the luminance value of the imaging element (the luminance value of the imaging range including the defective pixel opening), The correction unit 13 calculates the luminance value of the opening of the defective picture element itself. The inspecting unit 12 compares the luminance value calculated by the correcting unit 13 with the inspection threshold value to inspect again whether or not the defective picture element is really defective.

  Therefore, the inspection accuracy of the defective picture element can be increased, and an inspection correlated with the visual inspection can be performed.

  In addition, since the signal dividing unit 16 removes the influence of moire, the inspection accuracy can be further increased.

  In addition, the picture element determination unit 17 determines which color picture element the defective picture element is by comparing the coordinates of the peak of the waveform of the signal component with the coordinates of the signal component caused by the defective picture element. Therefore, the color of the defective picture element can be determined even when imaging is performed at a low resolution (about the picture element pitch or more).

  In addition, the inspection apparatus 1 can perform inspection at low cost. In order to accurately capture the luminance of only the picture element opening, either a high pixel camera or a plurality of cameras is required. Further, the method of attaching a micro inspection camera (a method of inspecting the whole with a macro camera and inspecting defect candidates in detail with a micro camera) requires a tact. In the inspection apparatus 1, even with a camera configuration that does not have sufficient resolution (below the pixel opening), the inspection cost can be reduced by correctly estimating the defective pixel.

(Example of change)
The display device 3 may be a color filter or a filter for monochrome display. Also, the types of picture elements are not limited to three. Further, the arrangement order of the picture elements is not limited to the above.

  In the above description, a defective pixel having a luminance value higher than the reference range has been described. However, the present invention can also be applied to the case of detecting a defective pixel having a luminance value lower than the reference range.

  Each block of the inspection apparatus 1 described above, in particular, the control device 8, the inspection unit 12, and the correction unit 13 may be configured by hardware logic, or may be realized by software using a CPU as follows. Good.

  That is, the inspection apparatus 1 includes a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, a RAM (random access memory) that expands the program, A storage device (recording medium) such as a memory for storing the program and various data is provided. An object of the present invention is to record the program code (execution format program, intermediate code program, source program) of the control program (luminance calculation program) of the inspection apparatus 1 which is software that realizes the above-described functions so that it can be read by a computer. This can also be achieved by supplying the recording medium to the inspection apparatus 1 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and disks including optical disks such as CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  Further, the inspection apparatus 1 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The present invention can also be expressed as follows.

  According to the display device brightness calculation method of the present invention, the display screen of a display device having a color filter is used as an inspection screen. A method of inputting the number of moire in one of the X-axis direction and the Y-axis direction generated in the captured image data, and plotting pixel values of the captured data at intervals corresponding to the number of moire A step of detecting an abnormal portion from the plotted data sequence, a step of determining a type and a ratio of display picture elements included in the detected abnormal portion, and the detected abnormal portion being normal. The brightness of the defective pixel is calculated from the step of calculating the data of the case, the type and ratio of the determined display picture element, the abnormal part data, and the data when the abnormal part is normal. It contains a degree.

  The step of determining the type and ratio of the display picture element included in the abnormal portion includes calculating the maximum, minimum peak value, and intermediate value from the plotted data string, and the maximum sensitivity from the spectral sensitivity characteristics of the image sensor. Preferably, the method includes a step of associating the minimum peak value, the intermediate value, and the pixel pattern of the color filter, and a step of determining the type and ratio of the display pixel included in the abnormal portion from the plotted data string.

  The process of calculating the luminance of the defective picture element is performed by imaging in advance in a high resolution state, inputting the display picture element of the obtained display device and the luminance of the black matrix, and the display picture element included in the abnormal part. It is preferable to include a step of calculating the luminance of the defective pixel from the type and ratio of the pixel and the input display pixel of the display device and the luminance of the black matrix.

  The brightness calculation apparatus for a display device according to the present invention uses the display screen of a display device having a color filter as an inspection screen, captures an image with an imaging unit, and calculates the brightness in an inspection that determines the quality of the display device based on the captured image data obtained. A device for inputting the number of moire in either the X-axis direction or the Y-axis direction generated in the captured image data, and plotting pixel values of the captured data at intervals corresponding to the number of moire Means, means for detecting an abnormal part from the plotted data string, means for determining the type and ratio of display picture elements included in the detected abnormal part, and the detected abnormal part is normal The brightness of the defective picture element is calculated from the means for calculating the case data, the type and ratio of the determined display picture element, the abnormal part data, and the data when the abnormal part is normal. And a stage.

  The means for determining the type and ratio of the display picture element included in the abnormal part is a means for calculating the maximum, minimum peak value, and intermediate value from the plotted data string, and the maximum sensitivity from the spectral sensitivity characteristics of the image sensor. Means for associating the minimum peak value, the intermediate value with the pixel pattern of the color filter, and means for determining the type and ratio of the display picture element included in the abnormal portion from the plotted data string. preferable.

  The means for calculating the luminance of the defective picture element is preliminarily imaged in a high resolution state, the means for inputting the display picture element of the obtained display device, the luminance of the black matrix, and the display picture element included in the abnormal part And means for calculating the luminance of the defective pixel from the input display picture element of the display device and the luminance of the black matrix.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope shown in the claims, and an implementation obtained by appropriately combining technical means disclosed in the embodiment. The form is also included in the technical scope of the present invention.

  Since defect detection with high accuracy correlated with visual sensitivity can be performed, the present invention can be applied to an inspection apparatus for a display panel such as a liquid crystal panel.

It is the schematic which shows the structure of the correction | amendment part with which the inspection apparatus of one Embodiment is provided. It is the schematic which shows the structure of the test | inspection apparatus of one Embodiment. It is the schematic which shows the structure of the control apparatus with which the inspection apparatus of one Embodiment is provided. It is the schematic which shows the structure of a display device. (A) is a graph which shows the output signal of an image pick-up element obtained when an imaging resolution is 1.5% smaller than a pixel pitch, (b) is an imaging resolution 21.5% smaller than a pixel pitch. It is a graph which shows the output signal of the image sensor obtained in the case. It is a figure for showing the example of the signal division in the signal division part with which the inspection device of one embodiment is provided. It is for demonstrating the method of calculating a peak value from the waveform of a signal component, (a) is a graph which shows the waveform of a signal component, (b) is a graph which plotted the adjacent difference value. It is for demonstrating the method of determining the kind of defective pixel based on the waveform of a signal component, (a) is a figure which shows the waveform of a signal component, (b) shows the allocation part of a pixel. FIG. It is a figure for demonstrating the normal luminance value calculation method in the normal luminance estimation part with which the inspection apparatus of one Embodiment is provided. It is a figure for demonstrating the method to calculate a defect pixel rate. It is a figure for demonstrating the method of calculating the distance between the centerline of the image pick-up element which imaged the defective pixel opening part, and the centerline of a pixel element opening part. It is a figure which shows the positional relationship of the imaging range of an image sensor, and a picture element. It is a figure which shows the correspondence of the signal component divided | segmented by the signal division part, and the imaging range of an image pick-up element. It is a flowchart which shows the flow of the process in a control apparatus. It is a flowchart which shows the flow of the process in a test | inspection apparatus.

Explanation of symbols

1 Inspection device 3 Display device (display panel)
3a R picture element (picture element)
3b G picture element (picture element)
3c B picture element (picture element)
8. Control device (inspection device)
12 Inspection Department (Inspection means)
13 Correction unit (luminance calculation device)
16 Signal division part (signal division means)
17 Picture element judging unit (picture element judging means)
18 Normal luminance estimation unit (normal luminance value calculation means)
19 Luminance correction unit (luminance value correction means)
20 Defect pixel rate calculation unit (defect pixel rate calculation means)
P1 image sensor P2 image sensor

Claims (10)

A display panel in which a plurality of picture elements are arranged in a certain direction is imaged by an imaging means having an image sensor, and the obtained captured image data is analyzed to detect an abnormal luminance value that is a luminance value outside the reference range. A luminance calculation method in a luminance calculation apparatus provided in an inspection apparatus for inspecting the display panel by
A normal luminance value calculating step of calculating a normal luminance value, which is a luminance value when the imaging element showing the abnormal luminance value is capturing a normal picture element;
A defective pixel rate calculation step of calculating a defective pixel rate that is a ratio of an area within the imaging range of a certain imaging device and an area of the imaging range of the opening of the defective pixel that is the cause of the abnormal luminance value. When,
Multiply the difference between the abnormal luminance value and the normal luminance value by the reciprocal of the defective pixel rate, and add the standard luminance value, which is the luminance value of the normal pixel of the same color as the defective pixel, to the obtained value And a luminance value correction step of calculating a luminance value of the opening by performing a luminance calculation method.   The luminance calculation according to claim 1, further comprising: a pixel determination step of determining which color the defective pixel is and setting the standard luminance value corresponding to the determination result. Method. A signal dividing step for forming a signal component waveform by plotting signal components of the imaged data at intervals corresponding to the number of moire in the pixel arrangement direction, which occurs in the imaged image data, is performed before the pixel determining step. Further including
In the picture element determination step, by comparing the coordinates of the peak of the waveform and the coordinates of the signal component caused by the defective picture element, it is determined which color picture element the defective picture element is. The luminance calculation method according to claim 2, wherein: A display panel in which a plurality of picture elements are arranged in a certain direction is imaged by an imaging means having an image sensor, and the obtained captured image data is analyzed to detect an abnormal luminance value that is a luminance value outside the reference range. A brightness calculating device provided in an inspection device for inspecting the display panel by
A normal luminance value calculating means for calculating a normal luminance value which is a luminance value when the image pickup device showing the abnormal luminance value has picked up a normal picture element;
A defective pixel rate calculating means for calculating a defective pixel rate that is a ratio of an area of an imaging element in an imaging range of an opening of a defective pixel that is a cause of the abnormal luminance value to the imaging range;
Multiply the difference between the abnormal luminance value and the normal luminance value by the reciprocal of the defective pixel rate, and add the standard luminance value, which is the luminance value of the normal pixel of the same color as the defective pixel, to the obtained value And a luminance value correcting means for calculating the luminance value of the opening.   2. The image processing apparatus according to claim 1, further comprising: a pixel determination unit that determines which color the defective pixel is and outputs the standard luminance value corresponding to the determination result to the luminance value correction unit. 4. The luminance calculation device according to 4. Further comprising signal dividing means for forming the waveform of the signal component by plotting the signal component of the imaging data at intervals corresponding to the number of moire in the pixel array direction, which occurs in the captured image data,
The picture element determination means determines which color picture element the defective picture element is by comparing the coordinates of the peak of the waveform with the coordinates of the signal component caused by the defective picture element. The brightness | luminance calculation apparatus of Claim 5 characterized by the above-mentioned.   The defective pixel rate calculation means calculates a distance between a center line of the defective pixel and a center line of an imaging range of an imaging element that images the defective pixel, and based on the distance, The luminance calculation apparatus according to claim 4, wherein an area within the imaging range is calculated. A display panel in which a plurality of picture elements are arranged in a certain direction is imaged by an imaging means having an image sensor, and the obtained captured image data is analyzed to detect an abnormal luminance value that is a luminance value outside the reference range. An inspection apparatus for inspecting the display panel by
The luminance calculation apparatus according to any one of claims 4 to 7,
An inspection apparatus comprising: inspection means for reinspecting a defect of the display panel by comparing the luminance value of the opening calculated by the luminance calculation apparatus with a reference value.   A brightness calculation program for causing a computer to function as each of the means of the brightness calculation apparatus according to claim 4.   A computer-readable recording medium on which the luminance calculation program according to claim 9 is recorded.

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