CN101587081A - Defect detecting method and device - Google Patents

Abstract

The invention relates to a defect detection method and device. The film was run between a first polarizer and a second polarizer arranged in cross Nicols. The halogen lamp irradiates light to the film through the first polarizer. There is only one glow line in the light from a halogen lamp. Light whose luminance has changed due to defects in the film or the like enters the photoreceiver via the second polarizer and the removal optical system. The output signal of the optical receiver is differentiated. A maximum signal and a minimum signal are detected from the differentially processed signal subjected to differential processing. The difference between the luminance value of the preset reference signal and the luminance value of the maximum signal is obtained as the first difference value, and the difference between the luminance value of the reference signal and the luminance value of the minimum signal is obtained as Second difference value. When the sum obtained by adding the first differential value and the second differential value is greater than a certain value, the maximum signal and the minimum signal are determined to be defect signals.

Description

Defect detection method and device

technical field

The invention relates to a defect detection method and device for optically detecting defects on a film.

Background technique

In recent years, with the increasing demand, as a protective film or optical compensation film for polarizers in liquid crystal displays, retardation films with optical anisotropy are often attached to the display screen. The retardation film (hereinafter simply referred to as "film") is produced by a process of forming an alignment film on a transparent support and a process of coating a liquid crystal on the support on which the alignment film is formed and drying to form a liquid crystal layer (for example, (Japanese) Patent Laying-Open No. 9 - Bulletin No. 73081). Although strict quality control is carried out in each process, defects such as molecular orientation defects (orientation defects) and uneven coating thickness of the liquid crystal layer (retardation defects) are caused by foreign matter in the manufacturing process. It is difficult to remove completely.

If there is a defect on the film, light is scattered due to this, so in the film manufacturing process, an optical defect detection device is installed to detect the defect of the film. This defect inspection device is composed of a photoirradiator for irradiating light to a film, a photoreceiver for receiving light from the film, and a processing circuit for analyzing an output signal from the photoreceiver. As this photoreceiver, a television camera having an imaging device (line sensor or area sensor) is used, and a scanning signal (imaging signal) obtained by line-scanning in the width direction of the film is output as an output signal.

In addition, a pair of polarizing plates may be arranged between the photoirradiator and the photoreceiver so that their polarization directions are perpendicular to each other (crossed Nichols). The pair of polarizers prevent light from entering the photoreceptor when there is no defect on the film, and when there is a defect on the film, scattered and diffused light enters the photoreceiver at the defect, thereby easily detecting the defect ((Japanese) Patent Laid-Open No. Bulletin No. 6-148095). In addition, by performing differential processing on the output signal from the optical receiver, not only the signal of the defect portion is enhanced, but also the signal other than the defect portion, that is, the so-called noise signal is reduced, so that the defect can be easily detected.

In recent years, in pursuit of higher-quality films, a defect detection method capable of high accuracy up to detection of fine defects has been desired. Generally, defect detection accuracy is represented by a value (S/N) of dividing a signal (defect signal) of a defect portion by a signal (noise signal) other than a defect portion in an output signal from an optical receiver, and the S/N The larger N is, the higher the defect detection accuracy is.

Therefore, in order to obtain a larger S/N, not only the defect signal needs to be improved, but also the noise signal needs to be suppressed to a minimum. As a method of increasing defect signals, it is generally considered to increase the intensity of light scattered and diffused at defects on the film by irradiating the film with high-intensity light.

However, for light irradiators that emit high-brightness light, such as metal halide lamps, there are often steep peaks, that is, bright lines. When light having such a plurality of glow lines is irradiated on a thin transparent body such as a film, interference fringes having bright light portions will be formed on the film. Therefore, since there is strong light even in a portion without a defect, the noise signal becomes large, resulting in a decrease in S/N. In addition, when a pair of polarizers are arranged on the cross Nicols and inclined to the slow axis of the film, since there is little light transmitted through the pair of polarizers without defects, if there are many bright When the light of the line is irradiated on the film, the noise signal will become larger due to the influence of interference fringes. Therefore, for a light irradiator with high luminance, in the case of having many bright lines, the S/N is conversely lowered due to the influence of interference fringes.

In addition, when a pair of polarizers are arranged on the cross Nicols to detect defects, the output signal from the photoreceiver will have a lower brightness in the center of the film width direction due to the optical characteristics of the film and the receiving characteristics of the photoreceiver. It is very high, and the luminance gradually decreases from the central part to both ends. When performing differential processing on such an output signal, the defect signal will affect its surrounding noise signals.

For example, as shown in FIG. 7(A), if there are a plurality of defects of the same degree on the film, and the output signal is differentiated when the brightness of the diffused light scattered at each defect is the same, then As shown in Figure (B), the defect signal in the region where the slope of the noise signal in the width direction of the film is negative is smaller than the defect signal in the region where the slope is positive. Therefore, as shown in FIG. 7(B), when the threshold value for defect detection is set to a constant luminance value Th, the defect signal in the region where the gradient of the noise signal is positive is detected at or above Th, On the other hand, a defect signal in a region with a negative inclination is not detected due to insufficient Th. Therefore, regardless of the degree of the defect, regardless of whether the luminance of scattered or diffused light is the same, there is a problem that the defect signal cannot be detected regardless of whether the slope of the noise signal is positive or negative.

Contents of the invention

An object of the present invention is to provide a defect detection method and device capable of detecting defects with high accuracy without reducing S/N.

Another object of the present invention is to provide a defect detection method and device capable of preventing detection errors of defective parts.

In order to achieve the above object and other objects, the present invention provides a defect inspection device which detects a film on the film in a state where a film is arranged between a first polarizing plate and a second polarizing plate arranged in a Cross Nicol manner. The defects are detected, and it has: a light irradiation part, which irradiates light with no glow line or only one glow line to the film through the first polarizer; a light receiving part, which passes through the second polarizer a sheet that receives light emitted from the film; and a defect detection section that detects a defect of the film based on an output signal from the light receiver.

Preferably, the film is a retardation film, and the polarization directions of the first polarizer and the second polarizer are 45° relative to the slow axis of the retardation film. Preferably, the light irradiation unit is a halogen lamp. Preferably, the first polarizer and the second polarizer are iodine-based polarizers.

The defect detection method of the present invention includes the steps of irradiating light with no bright line or only one bright line on the film through the first polarizer, and receiving the light by the light receiving part through the second polarizer. a step of emitting light from the film, and a step of detecting a defect of the film based on an output signal from the light receiving unit.

The present invention also provides a defect detection device for detecting a defect of a film, comprising: a light receiving unit having a plurality of pixels arranged in a line, scanning in the width direction of the film and outputting a time-series output signal; a differential processing unit that performs differential processing on the output signal; and an extreme value signal detection unit that detects a maximum luminance value within a predetermined pixel range from the differential processing signal obtained by the differential processing unit. signal and a very small signal with the smallest luminance value within a predetermined pixel range; a difference value calculation unit, which obtains the difference between the luminance value of the preset reference signal and the luminance value of the maximum signal as the first difference value, and obtain the difference between the luminance value of the reference signal and the luminance value of the extremely small signal as the second difference value; and a defect signal determining unit that determines the maximum signal and the minimum signal detected by the extreme value signal detection unit as a defect signal when the added value is equal to or greater than a certain value.

Furthermore, it is preferable to have: a first polarizer and a second polarizer arranged so that their polarization directions are orthogonal to each other; and the polarizer positioned between the first polarizer and the second polarizer The film is a light irradiation part that irradiates light. The film is a retardation film, and the polarization directions of the first polarizer and the second polarizer are 45° relative to the slow axis of the retardation film.

The present invention provides a defect detection method, comprising: scanning in the width direction of the film by a light receiving unit having a plurality of pixels arranged in a line to obtain a time-series output signal; and differentiating the output signal The process of processing; in the differential processing signal, the process of detecting the maximum signal with the largest luminance value within the specified pixel range and the minimum signal with the minimum luminance value within the specified pixel range; obtain the preset The difference between the luminance value of the reference signal and the luminance value of the maximum signal is used as the first difference value, and the difference between the luminance value of the reference signal and the luminance value of the minimum signal is obtained as the second difference. A step of difference value; a step of obtaining an added value obtained by adding the first difference value and the second difference value; and determining the maximum signal and the minimum signal when the added value is equal to or greater than a certain value Process that is a defect signal.

According to the present invention, since the film is illuminated using the light irradiation portion with few bright lines, it is possible to perform high-precision defect detection without lowering S/N. Furthermore, according to the present invention, since defects are detected using the maximum and minimum values of the differentially processed signal, it is possible to prevent detection errors of defective portions.

Description of drawings

Figure 1 is a schematic diagram of a retardation film production line.

Fig. 2 is a graph showing the spectral irradiation intensity of a halogen lamp.

Fig. 3 is a perspective view of a defect detection device.

Fig. 4 is a graph showing the relationship between the angle θ of the polarization direction of the first polarizing plate with respect to the slow axis of the film and the transmitted light ratio.

FIG. 5 is a graph showing the relationship between the retardation of the film and the transmitted light ratio.

FIG. 6 is a graph showing the spectral transmittance of a pair of polarizing plates arranged on cross Nicols.

FIG. 7(A) is a diagram showing an output signal, and FIG. 7(B) is a diagram showing a differentially processed signal obtained by performing differential processing on the output signal.

FIG. 8 is an explanatory diagram for explaining the defect detection method of the present invention.

Fig. 9 is a graph showing spectral irradiation intensities of halogen lamps, metal halide lamps, and fluorescent lamps.

FIG. 10 is a table showing the results of Example 1 and Comparative Examples 1 and 2. FIG.

Detailed ways

As shown in FIG. 1 , the retardation film production line 10 has an alignment film forming device 11 , a liquid crystal layer forming device 12 , a defect inspection device 13 , and a winding device 14 .

The alignment film forming apparatus 11 applies a coating solution containing a resin for forming an alignment film on the surface of the transparent resin film 15 conveyed from the film conveying roller 18, and heats and dries it. In this way, a resin layer is formed on the surface of the transparent resin film 15 . Thereafter, the alignment film forming apparatus 11 forms an alignment film by rubbing the resin layer.

The liquid crystal layer forming device 12 applies a coating liquid containing a liquid crystal compound on the alignment film, and heats and dries it after coating to form a liquid crystal layer. Then, the liquid crystal layer is irradiated with ultraviolet rays to join the alignment film and the liquid crystal layer. In this way, the retardation film 16 (hereinafter referred to simply as "film") in which the alignment film and the liquid crystal layer are formed on the transparent resin film 15 is obtained. The film 16 is wound up by the winding device 14 after passing through the defect detection device 13 . However, the conveyance direction of the film 16 is the X direction until the film conveyance roller 18 comes out and is wound up by the take-up device 14 .

The defect detection device 13 detects defects generated on the film 16 . As defects, for example, there are scratches, thickness defects, coating unevenness, molecular orientation defects, and the like. In addition, the inspection object of a defect inspection apparatus may be an antireflection film etc. other than a retardation film.

Defect detection device 13 includes guide rollers 20 , 21 , light irradiator 22 , light quantity adjustment unit 23 , light receiver 24 , first and second polarizers 25 , 26 , removal optical system 27 , and controller 28 . The guide rollers 20 and 21 are arranged along the transport path of the film 16 and rotate as the film 16 is transported. An encoder 30 is connected to the guide roller 21, and the encoder 30 generates an encoder pulse signal for each length of film 16 conveyed. The encoder pulse signal is sent to the controller 28 for determining the position of the defect in the length direction of the film 16 .

The light irradiator 22 is provided below the conveyance path of the film 16, extends in the width direction of the film 16, and illuminates in a strip shape. A halogen lamp is used as the light irradiator 22 . As shown in Figure 2, the halogen lamp has only one peak of illumination intensity between 600nm and 800nm wavelength, which is the glow line. Since the light emitted from the halogen lamp has only one bright line, substantially no interference fringes are formed on the film 16 . In addition, it is assumed that when interference fringes are formed, the luminance of the bright part of the light intensity is slightly larger than the luminance of the light emitted by the halogen lamp. Therefore, the interference fringes will not affect the defect detection accuracy. In addition, for light irradiators with no glow line or only one glow line, illuminator other than halogen lamp can also be used. In addition, a removal optical system for removing light having a wavelength of 600 nm or more may be disposed between the halogen lamp and the first polarizer to remove glow lines of light emitted by the halogen lamp.

The light amount adjustment unit 23 controls the light irradiator 22 based on a light amount detection signal detected by a sensor (not shown) provided near the light irradiator 22 . In this way, since it is possible to irradiate the film 16 with light having a uniform light intensity, it can be generally used for defect detection with the same sensitivity.

The first polarizer and the second polarizer 25, 26 are made of iodine-based polarizers, the first polarizer 25 is arranged between the light irradiator 22 and the film 16, and the second polarizer 26 is arranged between the film 16 and the light receiver 24 between. In addition, the first polarizer and the second polarizer 25, 26 are arranged so that the polarization directions 25a, 25b are perpendicular to each other (crossed Nichol). In addition, in terms of performance and price, although the first polarizer and the second polarizer use iodine-based polarizers, in addition, polarizers composed of dye-based polarizers, metal polarizers, calcite, etc. can also be used. piece.

By arranging the first polarizer and the second polarizer 25, 26 on the cross Nicols, in the absence of a defective film 16, the light emitted from the light irradiator 22 is polarized in the first polarizer 25 in the polarization direction 25a After polarization, it passes through the film 16 as it is, and is blocked by the other second polarizing plate 26 . Therefore, substantially no light transmitted through the normal portion enters the light receiver 24 . In this regard, in the case of a film 16 that is mixed with a foreign matter or has an orientation defect such as a scratch, the light emitted from the light irradiator 22 is polarized by the first polarizer 25 in the polarization direction 25a, and then occurs at the defect on the film 16. Scatter, diffuse. The scattered and diffused light passes through the other second polarizing plate 26 and enters the light receiver 24 due to a change in the polarization direction.

Scattered light is generated by orientation defects such as flaws on the film and contamination of foreign matter. By disposing the two first and second polarizers 25 and 26 in a cross-Nicol pattern, only the scattered light can pass through and be received by the light receiver. 24 detected. However, defects such as uneven coating thickness (retardation defects) cannot be detected in a structure in which the two first and second polarizers 25, 26 are arranged in a cross Nicols arrangement because they do not generate scattered light. However, the defect of uneven coating thickness passes through the retardation axis of the film 16 and the first polarizer in the state where the two first and second polarizers 25 and 26 are configured in a cross Nicol manner. The polarization directions 25a cross, so that detection is possible.

4 shows the ratio of the transmitted light quantity of the light transmitted through the two first and second polarizers 25, 26 when the angle θ of the polarization direction 25a of the first polarizer relative to the slow axis of the film 16 is changed. When the angle θ is 0°, it is in the extinction mode, and the transmitted light ratio (%) is "0.00". When the angle θ is 45°, it is a Boolean pattern (ブルーモード), and the transmitted light ratio (%) in this Boolean mode is about "0.80". If the angle θ is 45°, the amount of transmitted light is maximum. Here, the transmittance ratio (%) represents the ratio of the outgoing light emitted from the second polarizing plate 26 to the incident light entering the first polarizing plate 25 .

Also, if the angle θ is the same, as shown in FIG. 5 , the transmitted light amount ratio (%) varies due to the phase difference of the defective portion with respect to the normal portion of the film 16 . In FIG. 5 , "○" indicates that the angle θ is 0°, "□" indicates that the angle θ is 15°, "Δ" indicates that the angle θ is 30°, and "◇" indicates that the angle θ is 45°. The larger the phase difference, the larger the amount of transmitted light.

As above, in the state where the two first polarizers and second polarizers 25, 26 are arranged in a cross-Nicol manner, the angle θ of the polarization direction 25a of the first polarizer relative to the slow axis of the film 16 takes At 45°, uneven coating thickness (retardation defect) can be detected from the difference between the amount of transmitted light at the normal portion and the amount of transmitted light at the defective portion due to uneven coating thickness.

Wherein, in this embodiment, as shown in FIG. 3 , the angle θ of the polarization direction 25a of the first polarizer relative to the slow axis of the film 16 is set to 45°, and the polarization direction 26a of the second polarizer relative to the angle θ of the film 16 The angle (90°-θ) in the slow axis direction was 45°. In addition, the slow axis direction of the film may be the same as the film transport direction X.

FIG. 6 shows the light transmission characteristics of a pair of polarizers arranged in a cross Nicols arrangement. When there is no defect on the film, light with a wavelength less than 700nm is only rarely emitted from the first polarizer and the second polarizer 25, 26. From the characteristics of these polarizers, light with a wavelength exceeding 700nm will be transmitted with high rate leakage. The removal optical system 27 is composed of an infrared cut filter and is arranged before the light receiver 24 . This infrared cut filter cuts light (infrared rays) within a region 35 indicated by hatching. Therefore, light with a wavelength of 700 nm or more (infrared rays) is removed from the light emitted from the second polarizing plate 26 , and only light with a wavelength of less than 700 nm is incident on the light receiver 24 .

The photoreceiver 24 is constituted by a CCD camera, and is installed above the conveyance path of the film 16 . The CCD camera has an imaging device in which a plurality of light-receiving elements are arranged in a line in the width direction of the film 16, scans in the width direction of the film 16, and generates a scanning signal (imaging signal) as an output signal. This output signal includes, as shown in FIG. 7(A), a defect signal caused by a defect on the film 16 and a noise signal leaked only from the first and second polarizers 25 and 26 . Not only one optical receiver may be used, but a plurality of optical receivers may preferably be installed. In addition, as an imaging device, an image area sensor in which light receiving elements are two-dimensionally arranged can be used.

Normally, the photoreceiver 24 also performs photoelectric conversion of light having a wavelength exceeding 700 nm, but the removal optical system 27 removes light exceeding 700 nm. Therefore, only light based on defects on the film 16 is photoelectrically converted, so noise signals can be suppressed to a minimum, and sufficiently large S/N (defect signal/noise signal) can be obtained. For example, in the case of detecting a coating error due to uneven coating thickness, the S/N is "1.5" when the light of 700 nm or more is not removed by the optical system 27, and when the light of 700 nm or more is removed, , the S/N increased to "2.1".

As shown in FIG. 3 , the controller 28 has: a defect signal detection unit 32 that detects a defect signal based on an output signal (image signal) output from the optical receiver 24; 16. The defect position identification part 33 of the position of the defect in the longitudinal direction. The defect signal detection unit 32 includes a differential processing unit 32a, an extremum signal detection unit 32b, a luminance value calculation unit 32c, and a defect signal determination unit 32d.

The differentiation processing unit 32a performs differentiation processing on the output signal 40 as shown in FIG. 7(A) . In this way, as shown in FIG. 7(B), a signal 42 (hereinafter referred to as "differential processed signal") in which a portion with a large change in luminance value is emphasized is obtained. Then, as shown in FIG. 8 , the extremum signal detection unit 32b detects the maximum signals 50a, 51a, 52a with the largest luminance value within a certain pixel range and the signal with the minimum luminance value within a certain pixel range from the differential processing signal 42. Very small signals 50b, 51b, 52b.

The luminance value calculation unit 32c obtains differences LA1, LB1, and LC1 (hereinafter referred to as "first difference values") between the luminance values of the preset reference signal 55 and the luminance values of the maximum signals 50a, 51a, and 52a. Differences LA2, LB2, and LC2 between the luminance value of the reference signal 55 and the luminance values of the minimum signals 50b, 51b, and 52b (hereinafter referred to as "second difference values"). Among them, the reference signal 55 averages the noise signal, and is updated sequentially every time a defect detection is performed. Then, the luminance value calculation unit 32c obtains the added values LA, LB, and LC of the sums of the first difference values LA1, LB1, and LC1 and the second difference values LA2, LB2, and LC2.

The defect signal specifying unit 32d determines whether or not the added values LA, LB, and LC obtained by the luminance value calculating unit 32c are equal to or greater than a certain value. As a result of determination, when the added values LA, LB, and LC are equal to or greater than a certain value, the maximum signals 50a, 51a, and 52a and the minimum signals 50b, 51b, and 52b are identified as defect signals. In FIG. 8 , since all the added values LA, LB, and LC are equal to or greater than a certain value, all detected signals are identified as defect signals.

In the prior art, as shown in FIG. 7(B), a certain threshold Th is set for the differential processing signal 42, and a signal exceeding the threshold Th is regarded as a defect signal, and a signal with a large luminance change is below the threshold Th. In the case of the signal (the signal on the right side in FIG. 7(B) ), the defect signal was not detected. On the other hand, in the present invention, the defect signal is specified by the change amount of the luminance value instead of the threshold value Th, and the defect on the film 16 can be reliably detected.

Next, the action of the defect detection device of the present invention will be described. In the defect inspection device 13 , the film 16 is sent through the alignment film forming device 11 and the liquid crystal layer forming device 12 . The light irradiator 22 irradiates light to the film 16 running between the first polarizing plate 25 and the second polarizing plate 26 . Since the light irradiator 22 uses a halogen lamp, there is only one bright line of light, so no interference fringes, which are one of the reasons for increasing the noise signal, are generated on the film 16 .

The light from the light irradiator 22 is polarized by the first polarizing plate 25 in the polarization direction 25a. When there is an alignment defect such as contamination of foreign matter on the film 16 , the light from the first polarizing plate 25 changes its polarization direction due to scattering and diffusion at the defect, and the light is emitted from the second polarizing plate 26 . In addition, the same applies to the case where there are retardation defects such as coating unevenness. Due to the characteristics of the first and second polarizers 25 and 26, light having a wavelength of 700 nm or more passes through the first and second polarizers 25 and 26 as they are.

The light emitted from the second polarizing plate 26 enters the light receiver 24 after removing light having a wavelength of 700 nm or more by the removing optical system 27 . Since the photoreceiver 24 converts the incident light into an electrical signal, it sequentially reads out each pixel. The output signal 40 of the light receiver 24 is sent to the controller 28 .

The differential processing unit 32 a in the controller 28 performs differential processing on the output signal 40 from the optical receiver 24 . Based on the differentially processed signal 42 subjected to differential processing, the extreme value signal detection unit detects maximum signals 50a, 51a, and 52a and extremely small signals 50b, 51b, and 52b. Then, the differences between the preset luminance value of the reference signal 55 and the maximum signals 50a, 51a, and 52a are obtained by the luminance value calculation unit 32c as the first difference values LA1, LB1, and LC1, and the reference signal The difference between the luminance value of 55 and the luminance values of the minimum signals 50b, 51b, 52b is obtained as the second difference value LA2, LB2, LC2. In addition, the added values LA, LB, and LC of the sums of the first differential values LA1, LB1, and LC1 and the second differential values LA2, LB2, and LC2 are obtained by the luminance value calculation unit 32c. When the obtained added values LA, LB, and LC are equal to or greater than a certain value, the defect signal determination unit 32d compares the maximum signals 50a, 51a, 52a and the minimum signals 50b, 51b detected by the extreme value signal detection unit 32b , 52b is determined as a defect signal. Furthermore, the defect position identification part 33 specifies the defect position on the film 16 based on a defect signal and an encoder pulse signal. The results of the controller 28 are displayed on a display (not shown).

In addition, in the above-described embodiment, although an infrared cut filter is used as the removal optical system 27, a band-pass filter using a dielectric multilayer film, a monochromator, a wavelength cut filter, etc. can also be used. Filters, colored glass filters, diffraction gratings, etc. In addition, the wavelength region of the light removed by the removal optical system 27 is not limited to 700 nm or more, and can be appropriately changed according to the type of polarizing plate used for defect inspection.

Hereinafter, the present invention will be specifically described through Example 1 and Comparative Examples 1 and 2.

[Example 1]

Defects on the film 16 were detected using the defect detection device 13 shown in FIG. 3 . A light irradiator 22 for a halogen lamp is provided below the film 16 to be inspected, and a light receiver 24 is provided above it. A first polarizing plate 25 is provided between the light irradiator 22 and the film 16 , and a second polarizing plate 26 is provided between the film 16 and the light receiver 24 . In addition, the polarization direction 25a of the first polarizer is 45° with respect to the slow axis of the film 16, and the polarization direction 26a of the second polarizer is 45° with respect to the X direction. The first polarizer and the second polarizer 25, 26 use iodine-based polarizers, and the light receiver 24 uses a CCD line camera.

Before the light receiver 24, a removal optical system 27 composed of an infrared cut filter is provided. Of the light from the second polarizer 26 , light having a wavelength of 700 nm or more is removed by the removal optical system 27 . The light receiver 24 detects the light emitted from the removal optical system 27 and sends the detected signal to the controller 28 .

In the controller 28 , the differential processing signal 42 is obtained by performing differential processing on the signal obtained by the optical receiver 24 . Based on the differential processing signal 42, the maximum maximum signals 50a, 51a, 52a and the minimum minimum signals 50b, 51b, 52b within a certain pixel range are detected by the extreme value signal detection unit 32b. Then, the difference between the luminance value of the preset reference signal 55 and the luminance value of the maximum signals 50a, 51a, 52a is obtained as the first difference value LA1, LB1, LC1, and the luminance value of the reference signal 55 The difference between the luminance value and the luminance value of the minimum signal 50a, 51a, 52a is obtained as the second difference value LA2, LB2, LC2, and the first difference value LA1, LB1, LC1 and the second difference value LA2, LC1 are obtained. Added values LA, LB, and LC obtained by adding LB2, LC2. When the obtained added values LA, LB, and LC are equal to or greater than a certain value, the maximum signals 50a, 51a, and 52a and the minimum signals 50b, 51b, and 52b detected by the extreme value signal detection unit 32b are determined to be defects. Signal.

[Comparative example 1]

Defect detection was performed in the same manner as in Example 1, except that a metal halide lamp was used to emit light instead of a halogen lamp.

[Comparative example 2]

Defect detection was performed in the same manner as in Example 1 except that a fluorescent lamp was used instead of a halogen lamp to emit light.

[evaluate]

In the defect detection in the above-mentioned Example 1 and Comparative Examples 1 and 2, on the basis of evaluating the degree of formation of interference fringes on the film and the degree of S/N, comprehensive evaluation was performed for each of the Examples and Comparative Examples. In addition, the spectral irradiation intensity of the light irradiators of the respective examples and comparative examples was measured using a known spectrometer, and the number of glow lines was checked based on the measurement results.

Fig. 9 shows the spectral irradiation intensity measured in each embodiment and comparative example, curve 60 represents the spectral irradiation intensity of halogen lamp, curve 61 represents the spectral irradiation intensity of metal halide lamp, and curve 62 represents the spectral irradiation intensity of fluorescent lamp.

FIG. 10 shows the evaluation results of each Example and Comparative Example. The light irradiators in FIG. 10 show the types of light irradiators used in the respective examples and comparative examples, and the bright lines indicate the number of bright lines of light emitted by the light irradiators. In addition, interference fringes "◯" indicate that interference fringes are not generated on the film, and "×" indicate that interference fringes are generated on the film. In addition, "◯" of "S/N" indicates that S/N is 2 or more, and "△" indicates that S/N is 1.5 or more. In addition, "◯" in the evaluation indicates that a problematic defect on the product was detected, and "×" indicates that a problematic defect on the product could not be definitely detected. Moreover, when S/N is "2" or more, defect detection can be performed stably.

In Example 1, since there was only one bright line of light emitted from the halogen lamp, no interference fringes were formed on the film. On the other hand, in Comparative Examples 1 and 2, since two or more bright lines were present, interference fringes with clear bright and dark parts were formed on the film. Due to the influence of the interference fringes, the S/N is lowered, making it impossible to reliably detect defects that cause problems on products.

Claims (9)

1. defect detecting device, it detects the defective on the described film under the state of configuration film between first polaroid that disposes in cross Nicol mode and second polaroid, has:

Illumination part, its light that will not have bright line or only have a bright line shines on the described film via described first polaroid;

Light receiver, it is via the light of described second polaroid reception from described film; And

Defects detection portion, it is according to the defective that detects described film from the output signal of described optical receiver.

2. defect detecting device as claimed in claim 1 is characterized in that,

Described film is a phase retardation film, and the polarization direction of described first polaroid and described second polaroid is with respect to the slow axle mutually direction at 45 of described phase retardation film.

3. defect detecting device as claimed in claim 1 or 2 is characterized in that,

Described illumination part is a Halogen lamp LED.

4. as each described defect detecting device of claim 1 to 3, it is characterized in that,

Described first polaroid and described second polaroid are that iodine is polaroid.

5. defect inspection method, it detects the defective on the described film under the state of configuration film between first polaroid that disposes in cross Nicol mode and second polaroid, comprising:

The illumination that will not have bright line or only have a bright line via described first polaroid be mapped to operation on the described film,

By light receiver via described second polaroid receive from the operation of the light of described film and

Detect the operation of the defective of described film according to output signal from described light receiver.

6. defect detecting device, the defective that it is used to detect film has:

Light receiver, it has a plurality of pixels that wire is arranged, in the output signal of enterprising line scanning of the Width of described film and output time series;

The differential handling part, it carries out differential to described output signal and handles;

The extreme value signal detecting part, it detects the very big signal of brightness value maximum in the determined pixel scope and the minimum signal of brightness value minimum in the determined pixel scope in the differential processing signals that is obtained by described differential handling part;

Difference value calculating part, its difference of brightness value of trying to achieve the brightness value of predefined reference signal and described very big signal be as first difference value, and the difference of brightness value of trying to achieve the brightness value of described reference signal and described minimum signal is as second difference value;

Addition operation division, it tries to achieve the additive value that first difference value and the second difference value addition are obtained; And

The flaw indication determination portion, it is certain value when above at described additive value, will be defined as flaw indication by detected very big signal of described extreme value signal detecting part and minimum signal.

7. defect detecting device as claimed in claim 6 is characterized in that also having:

First polaroid that disposes according to the mode of each other polarization direction quadrature and second polaroid, and

Illumination part to the described film irradiates light between described first polaroid and described second polaroid.

8. as claim 6 or 7 described defect detecting devices, it is characterized in that,

Described film is a phase retardation film, and the polarization direction of described first polaroid and described second polaroid is with respect to the slow axle mutually direction at 45 of described phase retardation film.

9. defect inspection method, the defective that it detects film comprises:

The light receiver that utilization has a plurality of pixels that wire arranges scans and obtains the operation of seasonal effect in time series output signal at the Width of described film;

Described output signal is carried out the operation that differential is handled;

In described differential processing signals, detect the very big signal of brightness value maximum in the determined pixel scope and the operation of the minimum signal of brightness value minimum in the determined pixel scope;

Try to achieve the brightness value of predefined reference signal and described very big signal brightness value difference as first difference value and try to achieve the brightness value of described reference signal and the difference of the brightness value of described minimum signal as the operation of second difference value;

Try to achieve the operation of the additive value that first difference value and the second difference value addition are obtained; And

Be certain value when above at described additive value, described very big signal and minimum signal be defined as the operation of flaw indication.

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