JP4910939B2 - Color filter inspection method and apparatus using diffraction image - Google Patents

Description

The present invention relates to a method and apparatus capable of detecting RGB cells of a color filter and detecting abnormalities of various defects (missing, foreign matter, etc.) with high resolution.

High definition of liquid crystal display devices is progressing day by day, and in particular, high definition of liquid crystal panels for portable terminals is remarkable. The QVGA panel has already become a standard, and the speed of high definition is very fast, such as a 3 inch wide VGA panel being commercialized. Along with this, high definition of the color filter advances at the same speed. In such a color filter for a liquid crystal panel, the cell size is several tens of microns, and in the black matrix, the width is 10 microns or less.

Such a high-definition color filter is required to have an inspection with a very high resolution. In principle, a resolution of 1.7 microns is required to reliably detect defects of size 5 microns.

However, in order to capture such a high-resolution image with a conventional camera, a considerably large facility is required. First, the resolution of an ordinary industrial camera lens is about 10 microns, and even a high resolution lens is about 5 microns. If it has a resolution higher than this, it becomes a custom-made product considering aberrations and the like, and is very expensive. Moreover, when the resolution is about 2 microns, the depth of focus is very shallow, and it is necessary to accurately control the camera position so that the distance between the lens and the object to be inspected falls within a certain range.

One method for obtaining high resolution without being constrained by such measurement conditions is to use diffraction. A conceptual diagram is shown in FIG. This method irradiates a test object with a laser from below and acquires a diffraction image with a camera.

Diffraction is a phenomenon in which light wraps around where it has been blocked. For example, if there is a missing part as shown in FIG. 7 (a), the light that has escaped from it spreads out, and as shown in FIG. When a part of the light is blocked, light gradually goes around that part.

The diffraction image can theoretically be obtained from the original image by Fresnel transformation if the irradiation light wavelength, the object to be inspected, and the optical distance of the camera are known. Therefore, conversely, if the irradiation wavelength, the optical distance of the object to be inspected, and the camera are known and a diffraction image can be captured, the original image can be predicted.

The resolution of the method for calculating the original image from this diffraction image is about the same as the pixel size of the camera used. Some currently available cameras have a pixel size of 2 microns or less, and with such a camera, a resolution of 2 microns or less can be obtained. When imaging is performed according to this principle, an imaging system can be established at low cost because no lens is used, and the focus position and depth of focus are not a concern. This method is a technique called phase recovery.

Phase recovery is a method for estimating an original image from a diffraction image, and its main principle was devised by Gerchberg (see Non-Patent Document 1). Subsequently, Fienup et al. Improved this technique (see Non-Patent Document 2). In these methods, the original image is reproduced by adding some additional constraint condition to the diffraction image. However, it is very difficult to set additional constraint conditions that can be used universally for measurement objects of various shapes. Eventually, additional constraint conditions must be prepared for each measurement object. There are many difficulties in practical use.

However, Pedrini et al. Developed a method for reproducing an original image from a plurality of diffraction images obtained by changing the distance between a measurement object and a camera (see Non-Patent Document 3). This method is considerably more realistic than the above two examples because it does not require additional constraint conditions.
R. W. Gerchberg, Nature, 240, 404 (1972) J. et al. R. Fienup, Appl. Opt, 21, 2758 (1982) Yan Zhang, Opt. Express, 11 (24), 3234 (2003)

Diffraction image analysis is usually performed using irradiation light of one type of wavelength, but since the color filter includes filters for at least three color gamuts (for example, RGB), the wavelength of irradiation light is only one type. It can be inconvenient. In other words, if the wavelength of the irradiation light is one type, light in the near infrared region of 900 to 2000 nanometers in the wavelength region having the same transmittance for all filters will be selected. Since light has a very high transmittance, it is convenient for detecting foreign matters, but it cannot detect abnormalities such as leakage.

For example, when the color filter is irradiated with red laser light, the R (red) portion of RGB shows transmission characteristics. However, in the G (green) and B (blue) portions, red laser light is hardly transmitted. Therefore, with the red laser beam, foreign matter in the R (red) part can be detected, but no leakage can be detected. In the G (green) and B (blue) parts, leakage can be detected, but foreign matter cannot be detected. This means that it cannot be detected, which is inconvenient in performing defect inspection.

An object of the present invention is to provide an inspection method and an inspection apparatus that solve the above-described problems when a diffraction image analysis is performed on a color filter having a plurality of color filters.

In order to achieve the above object, in claim 1 of the present invention, a color filter inspection apparatus comprising:
A plurality of monochromatic light irradiation means for irradiating the color filter with monochromatic light of different wavelengths;
A diffraction image capturing means for capturing at least one diffraction image of the color filter when irradiated with each monochromatic light;
Analyzing the diffraction image of each monochromatic light imaged by the diffraction image imaging means by a phase recovery method, and reproducing the original image with each monochromatic light,
Image combining means for converting the original image for each monochromatic light reproduced by the analyzing means into one composite image;
Inspection determination means for performing image inspection processing for determining the presence or absence of a predetermined defect on the composite image or the original image for each single color light based on the combination of the color filters on each color filter and the wavelength of each single color light And a color filter inspection apparatus.

2. The color filter inspection according to claim 1, wherein the plurality of monochromatic light irradiation means are four types of a near-infrared laser, a red laser, a green laser, and a blue laser. It is a device.

In claim 3, further comprising an optical path length adjusting means for adjusting an optical path length between the color filter and the diffraction image imaging means,
A plurality of diffracted images of the color filter in a state where the optical path length between the color filter and the diffracted image capturing unit is different by the optical path length adjusting unit are captured by the diffracted image capturing unit with each monochromatic light. And
3. The color filter according to claim 1, wherein the analyzing unit analyzes a plurality of diffraction images for each monochromatic light by a phase recovery method and reproduces an original image with each monochromatic light. This is an inspection device.

Further, in claim 4, a color filter inspection method,
A monochromatic light irradiation step of irradiating the color filter with a plurality of monochromatic lights having different wavelengths;
A diffraction image imaging stage in which at least one diffraction image of the color filter when irradiated with each monochromatic light is imaged by the diffraction image imaging means;
Analyzing the diffraction image for each monochromatic light imaged in the diffraction image imaging stage by a phase recovery method, and reproducing the original image with each monochromatic light;
An image synthesis step in which the original image for each monochromatic light reproduced in the analysis step is made into one composite image;
An inspection determination step for performing an image inspection process for determining the presence or absence of a predetermined defect on the composite image or the original image for each monochromatic light based on a combination of each color filter on the color filter and the wavelength of each monochromatic light And a color filter inspection method.

Further, in claim 5, the irradiation light in the monochromatic light irradiation stage is four types of near infrared laser light, red laser light, green laser light, and blue laser light. This is a color filter inspection method.

Further, in claim 6, further comprising an optical path length adjusting step of adjusting an optical path length between the color filter and the diffraction image imaging means,
A plurality of color filter diffraction images in a state where the optical path length between the color filter and the diffracted image capturing means is different by the optical path length adjusting step are captured at the diffracted image capturing step with each monochromatic light. And
6. The color filter according to claim 4, wherein, in the analysis step, a plurality of diffraction images for each monochromatic light are analyzed by a phase recovery method to reproduce an original image with each monochromatic light. This is an inspection method.

The color filter defect detection by the apparatus and method according to claims 1 and 4 of the present invention is much more effective than the color filter defect detection using an image obtained by using a conventional standard lens and camera. It is characterized by high resolution and high reliability. Further, by analyzing the diffraction image for each monochromatic light by the phase recovery method and reproducing the original image with each monochromatic light, it is possible to detect defects even for color filters having a plurality of color gamuts.

Moreover, according to the apparatus and method of Claims 2 and 5, by making the monochromatic light irradiated to the color filter into four types of near-infrared laser light, red laser light, green laser light, and blue laser light, There is an advantage that defects of each color filter on the color filter can be easily detected.

Further, according to the apparatus and the method described in claims 3 and 6, the method of Pedrini described in Non-Patent Document 3 includes the optical path length adjusting means and the step for adjusting the optical path length between the color filter and the diffraction image imaging means. Thus, a plurality of diffraction images necessary for obtaining the original image can be obtained for each monochromatic light.

Table 1 shows the relationship between the color of the irradiated light and whether or not it can be detected for the foreign matter defect and the missing defect of each color filter of the color filter. “○” in the table indicates that detection is possible, and “x” indicates that detection is not possible.

There are different combinations of detectable defect items and filter colors for each of the four types of irradiation light, near infrared, red, green, and blue, so that the filter color, defect item, etc. can be identified. FIG. 3 shows an example of inspection of the red filter portion. (A) is a figure at the time of irradiating a near-infrared laser beam, (b) (c) (d) is a figure at the time of irradiating red, green, and blue laser beams, respectively.

In the case of the red filter, the transmittance of the red laser light (see FIG. 3B) is high, and if there is a foreign substance, the portion is shielded from light and can be detected. However, with respect to the leakage, it is difficult to detect the difference in light intensity between the leakage portion and the filter portion. The same applies to near-infrared laser light (see FIG. 3A), and foreign objects can be detected, but leakage is difficult to detect.

On the other hand, with respect to green and blue laser beams (see FIGS. 3C and 3D), the red filter portion has a small transmittance and it is difficult to detect foreign matter. However, if there is any leakage, it will be easy to detect because the light is transmitted through only that portion. Therefore, in the case of a red filter, it is easy to detect with red and near infrared laser light, but it is easy to detect with foreign matter, green and blue laser light.

The same applies to other filter colors, and combinations of detectable defect items and irradiation light are as shown in Table 1. As described above, the filter color and the defect item to be detected are determined by the combination of the four types of irradiation light, so that highly reliable information can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a color filter inspection apparatus according to an embodiment of the present invention. Reference numerals 101 to 104 denote near-infrared, red, green, and blue laser light sources, respectively. Each of the laser light sources 101 to 104 has shutters 301 to 304 that can be operated independently, and can transmit or block light at an arbitrary timing.

As the dichroic mirrors 201 to 204, those having a function of reflecting light of wavelengths of the laser light sources 101 to 104 and transmitting light of other wavelengths are selected. The laser light sources 101 to 104 are arranged so that the optical axes of the irradiated light are parallel to each other and the optical paths of the irradiated light overlap after passing through the dichroic mirror 204 from the object 407. The dichroic mirrors are arranged parallel to each other and at an angle of 45 ° with respect to the optical axis of the corresponding laser light source. With such an arrangement, the optical paths of the irradiation light from each laser light source can be overlapped, and the irradiation light can be applied to the same position of the object 407.

Reference numeral 405 denotes a beam expander, which is installed to widen the spot diameter of the laser light after passing through the dichroic mirror 204 and widen the area where the irradiation light hits the object 407. If the spot diameter of the laser beam is sufficiently large from the beginning, it may not be installed.

Reference numeral 406 denotes a mirror that reflects the laser light after passing through the beam expander 405 and irradiates the object 407. In this embodiment, in order to reduce the size of the apparatus, the mirror 406 is used to bend the optical path of the irradiation light. However, when the laser beam can be directly irradiated to the object 407, it may not be installed.

Reference numeral 408 denotes a diffractive image imaging means capable of imaging a two-dimensional area, which is a camera using various imaging elements. In this embodiment, a CCD camera is used. The diffraction image imaging unit 408 captures a diffraction image obtained by diffracting each irradiated laser beam by the object 407 as an image.

The data of the diffraction image captured by the diffraction image capturing unit 408 is sent to the image analysis / inspection determination unit 409. The image analysis / inspection determination unit 409 includes a storage unit (not shown) and a calculation unit that performs analysis, image synthesis, inspection determination, and the like.

The storage means (not shown) stores the image data of the diffraction image sent from the diffraction image imaging means 408, the original image reproduced by the phase recovery method, the composite image obtained by combining the original images, and the like. The calculation means (not shown) includes an analysis for reproducing the original image from the image data of the diffraction image by the phase reproduction method, an image synthesis for synthesizing the original image to create a synthesized image, and a defect for the obtained synthesized image. Inspection determination for performing image processing for detection is performed. As the image analysis / inspection determination means 409, a computer or workstation provided with various storage devices such as a hard disk and a memory can be used.

In addition, when obtaining the original image for each monochromatic light by the Pedrini method described in Non-Patent Document 3, it is necessary to capture a plurality of diffraction images having different diffraction conditions for each monochromatic light. The optical path length adjusting unit 401 can change the optical path length between the object 407 and the diffracted image capturing unit 408, and by performing imaging by changing the optical path length, a plurality of diffracted images having different diffraction conditions can be obtained. Can be obtained.

The optical path length adjustment unit 401 may be a mechanism that adjusts the distance between the object 407 and the diffraction image imaging unit 408, or a plurality of plane mirrors may be provided between the object 407 and the diffraction image imaging unit 408. It may be a mechanism that adjusts the distance until the diffracted light from the object 407 reaches the diffraction image capturing means 408 by arranging and changing the position of the plane mirror.

When the original image for each monochromatic light can be obtained by the Gerchberg method described in Non-Patent Document 1 or the Fienup method described in Non-Patent Document 2, it is not necessary to provide the optical path length adjusting means 401. .

In this embodiment, it is necessary to acquire at least four diffraction images having different irradiation light wavelengths. Finally, the four original images calculated from each of these diffraction images are compared and synthesized. The degree of coincidence of the hour position is very important, and coincidence on the micron order is necessary. Since the time required to acquire about four images is 1 second or less, it is considered that there is not much influence if it is low-frequency vibration, but high-frequency vibration is a major obstacle. Therefore, the present invention is preferably performed on a vibration absorbing material such as rubber.

Furthermore, since the laser light often has stripes from the vicinity of the oscillation exit, a more accurate result can be obtained if uniform irradiation is possible with a spatial filter or the like.

FIG. 2 shows a flowchart of the operation of the color filter inspection apparatus of the present invention.
First, the color filter that is the object is transported to the imaging position of the color filter inspection apparatus of the present invention and stops (step S01).

Near-infrared laser light is irradiated (step S02), and at least one diffraction image by the near-infrared laser light is captured (step S02). The diffraction image by the near infrared laser light is analyzed by the phase recovery method (step S13), and an original image by the near infrared laser light is obtained.

For laser beams of other wavelengths, diffraction image capturing, analysis, and original image creation are performed in the same procedure (steps S04 to S09, S15, S17, and S19).

The original images obtained by the respective laser beams are synthesized to obtain a synthesized image (step S20). The synthesis process here is, for example, the following procedure. Since the amount of transmitted light is basically small except for the transmitting portion, the luminance is low, that is, black. Thus, the simplest is to apply an appropriate correction coefficient to such a portion, and then add the original images to obtain a composite image. The correction coefficient is determined in consideration of the color sensitivity of the camera and the light intensity of the irradiation light source. Simply adding the colors together makes it difficult to distinguish the color of the color filter, so it is easier to see the colors after adding the colors to distinguish red, green, and blue.

A process for detecting a defective portion is performed on the composite image, and a quality inspection of the color filter is determined (step S21). As an example of defect detection processing, a cross comparison method is generally used. In this method, as shown in FIG. 8, four comparison positions 91 are set at predetermined intervals in the x and y directions from the inspection target position 90 on the image, and the determination is made by numerical comparison between these four points and the target position. is there. Luminance, chromaticity, etc. are used for numerical values used for judgment.

The defect detection process can also be performed on the original image by each laser beam. For example, when it is desired to detect foreign matter defects, foreign matter defects can be detected for all filter colors by performing defect detection processing on the original image using near-infrared laser light.

The obtained inspection results are output to output means such as various display devices, printers, storage devices (step S22).

A schematic diagram of the embodiment is shown in FIG. As the monochromatic light irradiation means, a green laser light source 41 and a red laser light source 42 were used. The optical paths of the green and red laser beams are made coincident and guided to the beam expander 45 by the dichroic mirror 43. The spot diameter of the laser beam was expanded with a beam expander 45, and further irradiated with a cubic mirror 46 from below the color filter 47, and the diffraction image was acquired with the camera 48. Each laser light source is provided with a shutter 44, which can transmit or block light at an arbitrary timing, and separately acquire red and green diffraction images.

Next, according to the flowchart of FIG. 2, the original image was reproduced by performing inverse Fresnel transformation on the diffraction image obtained by irradiating each laser beam. FIG. 5A shows a diffraction image when the red laser beam is irradiated, and FIG. 5B shows a diffraction image when the green laser beam is irradiated.

FIG. 6 shows a composite image obtained by combining FIGS. 5 (a) and 5 (b). In FIG. 6, the blue filter portion does not transmit the red laser beam and the green laser beam, and thus appears black. In this embodiment, a CCD camera in which one pixel is 5.2 microns is used. However, if a camera having a small pixel size is used, a higher-definition image can be acquired.

1 is a schematic diagram of a color filter inspection apparatus according to an embodiment of the present invention. The flowchart of operation | movement of the color filter test | inspection apparatus of this invention. In the color filter inspection apparatus of this invention, the figure which showed typically how a defective part looks when each laser beam is irradiated to a red filter part. 1 is a schematic diagram of a color filter inspection apparatus used in an example of the present invention. The image of the diffraction image of a color filter obtained with the color filter inspection apparatus of the Example of this invention. The composite image obtained with the color filter test | inspection apparatus of the Example of this invention. The conceptual diagram of a diffraction image. Explanatory drawing of the cross comparison method.

Explanation of symbols

101-104 ... Laser light sources 201-204 ... Shutters 301-304 ... Dichroic mirror 401 ... ... Optical path length adjusting means 405 ... ... Beam expander 406 ... ... Mirror 407 ...・ Color filter (object)
408 ... Diffraction image imaging means 409 ... Image analysis / inspection judging means 1 ... Base glass 2 of color filter ... Black matrix 3 of color filter ... Red filter of color filter Part a ··· Break defect b ··· Foreign matter defect 41 ··· Green laser light source 42 ··· Red laser light source 43 · · · Dichroic mirror 44 · · · Shutter 45 · · · Beam expander 46 ···・ Mirror 47 ... Color filter (object)
48 ... Camera 49 ... Image capturing computer 71 ... Irradiation laser beam 72 ... Object to be inspected (pinhole)
73 ... Diffracted light 81 ... Irradiation laser light 82 ... Inspected object (foreign matter)
83... Diffracted light 90... Inspection target position on image in defect detection processing 91... Comparison position on image in defect detection processing

Claims (6)

A color filter inspection device,
A plurality of monochromatic light irradiation means for irradiating the color filter with monochromatic light of different wavelengths;
A diffraction image capturing means for capturing at least one diffraction image of the color filter when irradiated with each monochromatic light;
Analyzing the diffraction image of each monochromatic light imaged by the diffraction image imaging means by a phase recovery method, and reproducing the original image with each monochromatic light,
Image combining means for converting the original image for each monochromatic light reproduced by the analyzing means into one composite image;
Inspection determination means for performing image inspection processing for determining the presence or absence of a predetermined defect on the composite image or the original image for each single color light based on the combination of the color filters on each color filter and the wavelength of each single color light An inspection apparatus for a color filter, comprising: 2. The color filter inspection apparatus according to claim 1, wherein the plurality of monochromatic light irradiation means are four types of a near infrared laser, a red laser, a green laser, and a blue laser. An optical path length adjusting means for adjusting an optical path length between the color filter and the diffraction image imaging means;
A plurality of diffracted images of the color filter in a state where the optical path length between the color filter and the diffracted image capturing unit is different by the optical path length adjusting unit are captured by the diffracted image capturing unit with each monochromatic light. And
3. The color filter according to claim 1, wherein the analyzing unit analyzes a plurality of diffraction images for each monochromatic light by a phase recovery method and reproduces an original image with each monochromatic light. Inspection device. A color filter inspection method,
A monochromatic light irradiation step of irradiating the color filter with a plurality of monochromatic lights having different wavelengths;
A diffraction image imaging stage in which at least one diffraction image of the color filter when irradiated with each monochromatic light is imaged by the diffraction image imaging means;
Analyzing the diffraction image for each monochromatic light imaged in the diffraction image imaging stage by a phase recovery method, and reproducing the original image with each monochromatic light;
An image synthesis step in which the original image for each monochromatic light reproduced in the analysis step is made into one composite image;
An inspection determination step for performing an image inspection process for determining the presence or absence of a predetermined defect on the composite image or the original image for each monochromatic light based on a combination of each color filter on the color filter and the wavelength of each monochromatic light And a color filter inspection method. 5. The color filter inspection method according to claim 4, wherein the irradiation light in the monochromatic light irradiation stage is four types of near infrared laser light, red laser light, green laser light, and blue laser light. An optical path length adjusting step for adjusting an optical path length between the color filter and the diffraction image imaging means;
A plurality of color filter diffraction images in a state where the optical path length between the color filter and the diffracted image capturing means is different by the optical path length adjusting step are captured at the diffracted image capturing step with each monochromatic light. And
6. The color filter according to claim 4, wherein, in the analysis step, a plurality of diffraction images for each monochromatic light are analyzed by a phase recovery method to reproduce an original image with each monochromatic light. Inspection method.