JP2011007661A - Screen inspection system and method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screen inspection system for determining the quality of a screen, by quantitatively analyzing the existence of local strain on the screen.SOLUTION: The screen inspection system includes a photographic device for photographing the screen from the direction facing the screen; a projecting device for projecting light from an oblique direction of the direction facing the screen; and an image processor for determining the degree of unevenness in the brightness, resulting from the local strain of the screen based on the photographed image of the screen obtained from the photographic device.

Description

 The present invention relates to a screen inspection system and a screen inspection method.

  In recent years, as a projector capable of saving space, as shown in FIG. 7A, the projector is installed at a close position of the screen SC (in the drawing, near the lower end of the screen SC), and an image is displayed on the screen SC from the close position. A proximity projection type projector PJ that projects image light for displaying the image has attracted attention. In many cases, the image light projected from such a proximity projection type projector PJ is incident on the screen SC at an acute angle. For this reason, if local distortion (for example, convex-concave part) exists in the screen SC, distortion will generate | occur | produce in a projection image in the part of the local distortion.

  For example, as shown in FIG. 7B, assuming that there is a local distortion (convex portion d) on the screen SC, a pixel to be projected to a position P1 on the screen SC that does not have the convex portion d. Is actually projected at a position P1 ′ on the convex portion d. For this reason, assuming that the viewer's line-of-sight direction is perpendicular to the screen SC, the viewer sees the distortion of the projected image at the convex portion d of the screen SC. Note that even when a concave portion exists as a local distortion in the screen SC, the projection image is distorted by the same principle.

  On the other hand, there are many techniques for correcting distortion of an image projected on a screen by a projector. For example, Patent Document 1 below discloses a technique for correcting distortion of an image projected on a quadric curved screen using a plurality of projectors. Patent Document 2 listed below discloses a technique for correcting trapezoidal distortion of a projection image generated due to a mutual relationship between a projector installation position and a screen installation position.

JP 2009-005044 A JP 2004-31690 A

  As mentioned above, if there is local distortion on the screen, the projected image will be distorted. Therefore, the screen inspection can be performed to quantitatively analyze the presence of local distortion on the screen in advance and judge the quality of the screen. System development is required. However, since the techniques disclosed in Patent Documents 1 and 2 do not correct the distortion of the projected image caused by the local distortion of the screen, the presence of the local distortion on the screen cannot be quantitatively analyzed. Therefore, it is difficult to apply to a screen inspection system.

 The present invention has been made in view of the above-described circumstances, and provides a screen inspection system and a screen inspection method capable of quantitatively analyzing the presence of local distortion in a screen and determining whether the screen is good or bad. For the purpose.

In order to achieve the above object, a screen inspection system according to the present invention projects an imaging device that images the screen from a direction facing the screen, and projects light from a direction oblique to the screen from the direction facing the screen. And a projection device and an image processing device that determines a degree of brightness unevenness caused by local distortion of the screen based on a captured image of the screen obtained from the imaging device.
When local distortion exists on the screen, when light is projected from a direction oblique to the direction facing the screen, brightness unevenness due to the local distortion of the screen occurs in the light projection area on the screen. Such unevenness of brightness is caused by the difference in brightness between the portion where the local distortion exists in the light projection area on the screen and the peripheral portion thereof, so that there is a lot of local distortion. Also, the amount of occurrence of uneven brightness increases. In other words, by determining the degree of brightness unevenness based on the captured image of the screen obtained from the imaging device, it is possible to quantitatively analyze the presence of local distortion on the screen, and to determine whether the screen is good or bad. It becomes possible.

In the screen inspection system, the image processing device calculates a non-uniformity amount indicating the degree of non-uniformity of brightness based on the photographed image, and determines the non-uniformity of brightness based on the non-uniformity amount. It is desirable.
As described above, the more local distortion exists on the screen, the greater the amount of brightness unevenness. Thus, by calculating the amount of unevenness indicating the degree of brightness unevenness (amount of occurrence), it is possible to easily determine the degree of brightness unevenness.

In the screen inspection system, it is preferable that the image processing apparatus sets an image corresponding to a light projection area on the screen included in the captured image as a processing target image.
When a screen is photographed by the photographing device from the direction facing the screen, a photographed image obtained from the photographing device often includes a background image in addition to an image corresponding to the light projection area on the screen. Such a background image is a noise image that is unnecessary when performing image processing for calculating the amount of unevenness in brightness. Therefore, by setting an image corresponding to the light projection area on the screen included in the captured image as a processing target image, it is possible to reduce the load of image processing and improve the calculation accuracy of the amount of unevenness.

In the screen inspection system, the image processing device creates a histogram of the captured image, and an image corresponding to a light projection area on the screen included in the captured image based on the histogram and a background image A brightness threshold value for distinguishing between the pixels, and among the pixels constituting the captured image, an image constituted by pixels having a brightness equal to or higher than the brightness threshold value is recognized as an image corresponding to the light projection area. It is preferable to set the image to be processed.
Thereby, the image corresponding to the light projection area on the screen included in the photographed image can be easily distinguished from the background image, and as a result, the processing load on the processing target image can be reduced.

In the screen inspection system, the image processing device performs an averaging process on the processing target image, and performs a difference process between the processing target image after the averaging process and the processing target image before the averaging process. Preferably, a difference image is created by performing the calculation, and the amount of unevenness is calculated based on the difference image.
When projecting light from a direction oblique to the direction facing the screen, a phenomenon occurs in which the area far from the projection device in the light projection area on the screen becomes dark and the area near the projection device becomes bright. (In particular, this phenomenon becomes more prominent as light is projected at an acute angle with respect to the screen). That is, in the brightness unevenness present in the captured image, brightness unevenness due to local distortion of the screen and brightness unevenness due to the light projection direction are mixed. Therefore, in order to calculate the unevenness amount of the brightness unevenness caused by the local distortion of the screen, it is necessary to remove the brightness unevenness due to the light projection direction. By performing the above-described averaging process and difference process (difference image creation), it is possible to remove brightness unevenness caused by the light projection direction.

In the screen inspection system, the image processing device divides the processing target image into a plurality of regions, performs an averaging process for each of the plurality of regions, It is preferable that a difference image is created by performing a difference process with the processing target image before the averaging process, and the amount of unevenness is calculated based on the difference image.
As a result, it is possible to more accurately remove brightness unevenness caused by the light projection direction.

In the above screen inspection system, the image processing apparatus may calculate a ratio between the total number of pixels constituting the difference image and the number of pixels having brightness other than the maximum value among the pixels constituting the difference image. It is preferable to calculate the amount of unevenness.
As a result, it is possible to easily calculate the amount of unevenness indicating the amount of brightness unevenness caused by the local distortion of the screen, and to reduce the load of the calculation process.

In the screen inspection system, it is preferable that the image processing apparatus compares the unevenness amount with a preset quality determination threshold value and determines the quality of the screen based on the comparison result.
If the amount of unevenness can be calculated, the user can determine the quality of the screen by comparing the amount of unevenness and the pass / fail judgment threshold based on the calculation result, but the image processing device automatically determines the pass / fail of the screen. By providing the function of performing the inspection, the burden on the user can be reduced and the inspection efficiency can be improved.

In the screen inspection system, it is preferable that the projection device is a projector that projects image light for displaying a predetermined inspection image on the screen as the light.
As described above, by using the projector as the projection device, it is possible to project an arbitrary inspection image onto the screen. Depending on the specifications of the screen, the state of occurrence of uneven brightness differs depending on the color of image light to be projected, and it may be difficult to accurately calculate the amount of unevenness. In such a case, by projecting an inspection image of an appropriate color according to the specifications of the screen onto the screen, it is possible to maintain the unevenness amount calculation accuracy, that is, the screen pass / fail judgment accuracy.

In the screen inspection system, the inspection image is preferably an all-white image.
By projecting an all-white image, which is the brightest image, onto the screen as an inspection image, brightness unevenness due to local distortion of the screen occurs more clearly, and the unevenness calculation accuracy, that is, the screen The pass / fail judgment accuracy can be improved.

In the screen inspection system, the projection device is preferably a light source that projects predetermined color light onto the screen.
In this way, even if a light source is used as a projection device, it is possible to calculate the amount of unevenness in brightness due to local distortion of the screen and to reduce the system cost compared to the case where a projector is used as the projection device. Can be reduced.

Further, the screen inspection method according to the present invention includes a step of photographing the screen from a direction facing the screen, a step of projecting light from a direction oblique to the direction facing the screen, and a photographing of the screen. And a step of determining a degree of brightness unevenness caused by local distortion of the screen based on an image.
According to the screen inspection method having such characteristics, it is possible to quantitatively analyze the presence of local distortion on the screen and determine the quality of the screen.

1 is a schematic configuration diagram of a screen inspection system 1 according to an embodiment of the present invention. 1 is a block configuration diagram of a screen inspection system 1. FIG. 4 is a flowchart illustrating image processing performed by an image analysis unit 33b of the image processing apparatus 30 in the screen inspection system 1. It is a 1st supplement explanatory drawing about the image processing which image analysis part 33b performs. It is a 2nd supplement explanatory drawing about the image processing which the image analysis part 33b performs. It is explanatory drawing regarding the modification of this embodiment. It is explanatory drawing regarding the local distortion of the conventional proximity projection type projector PJ and the screen SC.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a screen inspection system 1 according to the present embodiment. The screen inspection system 1 according to the present embodiment is a system that quantitatively analyzes the presence of local distortion in the screen SC and determines whether the screen SC is good or bad, and includes a camera (imaging device) 10 and a projector (projection device). 20 and an image processing apparatus 30.

  The camera 10 is installed at a position facing the screen SC (specifically, a position on the axis AX extending from the center of the screen SC in a direction perpendicular to the screen SC), and the screen is viewed from the direction facing the screen SC. The SC is photographed, and data indicating the photographed image (hereinafter referred to as photographed image data) is output to the image processing device 30. The projector 20 is a proximity projection type projector installed in the proximity position of the screen SC (in the vicinity of the lower end of the screen SC in FIG. 1), and the image light based on the display image data input from the image processing device 30 is applied to the screen SC. And project from a direction oblique to the direction facing directly.

  The image processing apparatus 30 is, for example, a notebook PC (Personal Computer), and is connected to the camera 10 and the projector 20 via a signal cable so as to communicate with each other. The image processing apparatus 30 generates data (display image data) indicating an image to be displayed on the screen SC and outputs the data to the projector 20, while the local area of the screen SC is based on the captured image data input from the camera 10. It has a function of calculating the unevenness of the brightness unevenness caused by the mechanical distortion and determining the quality of the screen SC based on the calculated unevenness.

  FIG. 2 is a block diagram of the screen inspection system 1 described above. As shown in FIG. 2, the camera 10 includes a sensor optical system 11, a CCD (Charge Coupled Devices) sensor 12, and a CCD control circuit 13. The projector 20 includes a projection optical system 21, a lamp 22, a liquid crystal panel 23, and a display control circuit 24. The image processing device 30 includes an operation input device 31, a CPU (Central Processing Unit) 32, an image processing processor 33, a storage device 34, and a display device 35.

  In the camera 10, the sensor optical system 11 includes optical parts such as various lenses and mirrors necessary for receiving image light projected on the screen SC and forming an image on the CCD sensor 12. The CCD sensor 12 is an imaging device that is driven in accordance with a control signal supplied from the CCD control circuit 13, and outputs an analog signal corresponding to the light reception intensity in each pixel to the CCD control circuit 13. The CCD control circuit 13 supplies a control signal to the CCD sensor 12 and outputs an analog signal input from the CCD sensor 12 to the brightness of each pixel (gradation value: for example, a value from 0 to 255 for 8 bits). The gradation data is converted into gradation data, and the gradation data is output to the image processing apparatus 30 as photographed image data. That is, the captured image data is a group of gradation data indicating the brightness of each pixel constituting the captured image of the screen SC.

  In the projector 20, the projection optical system 21 includes optical components such as various lenses and mirrors necessary for projecting image light formed by a later-described lamp 22 and liquid crystal panel 23 onto the screen SC. The lamp 22 is, for example, a white halogen lamp, and emits light with a predetermined light amount corresponding to the drive current supplied from the display control circuit 24. The liquid crystal panel 23 is a light modulation element that forms image light by intensity-modulating light emitted from the lamp 22 in accordance with a drive signal supplied from the display control circuit 24, and includes R (red), G (green), Three are provided corresponding to each of B (blue). The display control circuit 24 generates a drive signal to be supplied to the liquid crystal panel 23 and a drive current to be supplied to the lamp 22 based on display image data input from the image processing device 30.

  In the image processing device 30, the operation input device 31 is composed of, for example, a keyboard, a mouse, and the like, receives an operation input by the user, and outputs an operation input signal corresponding to the operation input to the CPU 32. The CPU 32 controls the overall operation of the image processing device 30 based on an OS (Operating System) program and application program stored in the storage device 34 and an operation input signal input from the operation input device 31. It is a processing device.

  The image processing processor 33 is a processor that mainly performs various arithmetic processes related to image processing in accordance with instructions from the CPU 32, and includes an image generation unit 33a and an image analysis unit 33b as functional elements thereof. The image generation unit 33 a generates display image data indicating an image to be displayed on the screen SC according to an instruction from the CPU 32 and outputs the display image data to the display control circuit 24 of the projector 20. The image analysis unit 33b calculates the unevenness amount of the brightness unevenness due to the local distortion of the screen SC based on the captured image data temporarily stored in the storage device 34, and the screen is based on the calculated unevenness amount. The quality of the SC is judged and the result of the quality judgment is notified to the CPU 32.

  The storage device 34 includes an HDD (Hard Disk Drive), a flash memory, a RAM (Random Access Memory), and the like. The storage device 34 stores an OS program, an application program, and other various setting data in advance, and is controlled by the CPU 32. In response to this, the captured image data input from the camera 10 and other various data are temporarily stored. The display device 35 is, for example, a liquid crystal display provided in the image processing device 30 and displays a predetermined image in accordance with control by the CPU 32. Note that the image displayed on the display device 35 includes an image showing the quality determination result of the screen SC.

Next, the operation of the screen inspection system 1 according to the present embodiment configured as described above will be described in detail.
First, when the CPU 32 of the image processing apparatus 30 detects that a start instruction for the screen inspection application has been received from the user based on the operation input signal input from the operation input apparatus 31, the CPU 32 stores the screen inspection application in the storage apparatus 34. Various processes related to the screen inspection described below are executed based on the application program for screen inspection.

  That is, the CPU 32 first instructs the image generation unit 33a of the image processor 33 to generate an inspection image. The image generation unit 33 a generates display image data indicating an inspection image to be displayed on the screen SC in accordance with an instruction from the CPU 32 and outputs the display image data to the display control circuit 24 of the projector 20.

 Here, as the inspection image, it is preferable to use an image in which the entire screen has a uniform color so that uneven brightness due to local distortion of the screen SC appears clearly. In the present embodiment, as an example, an image in which the entire screen is white (an all-white image) is used as an inspection image. As described above, by using the all-white image having the highest brightness as the inspection image, the brightness unevenness due to the local distortion of the screen SC appears more remarkably.

  When the display image data indicating the inspection image (full white image) is input from the image generation unit 33a of the image processing processor 33 as described above, the display control circuit 24 of the projector 20 receives the liquid crystal based on the display image data. By generating a drive signal to be supplied to the panel 23 and a drive current to be supplied to the lamp 22, image light indicating an inspection image is formed on the lamp 22 and the liquid crystal panel 23. The image light thus formed is projected onto the screen SC via the projection optical system 21, and an inspection image is displayed on the screen SC.

  On the other hand, the camera 10 captures the screen SC from the direction facing the screen SC, and outputs captured image data indicating the captured image to the image processing device 30. Specifically, the CCD control circuit 13 of the camera 10 supplies a control signal to the CCD sensor 12 to drive the CCD sensor 12, and an analog signal input from the CCD sensor 12 is used to indicate the brightness of each pixel. The tone data is converted into tone data, and the tone data is output to the image processing apparatus 30 as photographed image data.

  When the captured image data is input from the camera 10 as described above, the CPU 32 of the image processing device 30 temporarily stores the captured image data in the storage device 34, and then the image analysis unit 33 b of the image processing processor 33. To instruct image processing based on the captured image data. Hereinafter, the image processing performed by the image analysis unit 33b will be described in detail with reference to FIGS.

  FIG. 3 is a flowchart showing a procedure of image processing performed by the image analysis unit 33b. First, the image analysis unit 33b sets, as a processing target image, an image corresponding to the light projection area on the screen SC included in the captured image based on the captured image data stored in the storage device 34. (Step S1).

 FIG. 4A shows an example of a photographed image obtained by photographing a screen SC on which an inspection image, that is, an all white image is displayed (projected). When the screen SC is imaged by the camera 10 from the direction facing the screen SC, the captured image obtained from the camera 10 includes an image corresponding to the light projection area on the screen SC (inspection image Ie) and its background image Ib. Are often included together. Such a background image Ib is a noise image that is unnecessary when performing image processing for calculating the amount of unevenness in brightness. Therefore, by setting the inspection image Ie on the screen SC included in the captured image as a processing target image, it is possible to reduce the load of image processing and improve the calculation accuracy of the amount of unevenness.

  Specifically, as the process of step S1, the image analysis unit 33b first creates a histogram of the captured image based on the captured image data (step S1a). FIG. 4B shows an example of the created histogram. As shown in this figure, the histogram is a graph of the number of pixels for each brightness (gradation value) of the photographed image, and represents the distribution tendency of pixels having a predetermined brightness.

Subsequently, the image analysis unit 33b sets a brightness threshold for distinguishing between the inspection image Ie and the background image Ib included in the photographed image based on the histogram created in step S1a (step S1b). For example, if the brightest gradation value in the histogram is “250” and the darkest gradation value is “20”, the image analysis unit 33b sets an intermediate value “135” between the two calculated by the following equation (1). Set as brightness threshold.
Brightness threshold = (250−20) / 2 + 20 = 135 (1)
Note that such a brightness threshold setting method is not limited to the above equation (1), but a known threshold setting method used in image processing such as binarization processing (for example, the threshold value is determined from the average value and standard deviation of the histogram). A setting method or the like may be used.

Then, the image analysis unit 33b compares the gradation value of each pixel constituting the photographed image with the brightness threshold set as described above, and pixels having brightness equal to or higher than the brightness threshold (that is, FIG. An image composed of pixels included in the right peak portion in the histogram shown in b) is recognized as an inspection image Ie and set as a processing target image (step S1c).
Through the processing in steps S1a, S1b, and S1c as described above, the inspection image Ie included in the photographed image is set as the processing target image.

  Next, the image analysis unit 33b performs unevenness in brightness unevenness caused by local distortion of the screen SC based on the gradation data of the pixels constituting the processing target image (inspection image Ie) set as described above. The amount is calculated, and the quality of the screen SC is determined based on the calculated amount of unevenness (step S2).

As shown in FIG. 4A, when image light is projected from an obliquely downward direction of the screen SC, the upper area of the screen in the inspection image Ie on the screen SC becomes dark and the lower area of the screen becomes bright. A phenomenon is likely to occur (in particular, this phenomenon becomes more prominent as light is projected at an acute angle with respect to the screen SC). That is, in the brightness unevenness existing in the captured image, brightness unevenness due to local distortion of the screen SC and brightness unevenness due to the light projection direction are mixed. Therefore, in order to calculate the amount of unevenness in brightness due to local distortion of the screen SC, it is necessary to first remove the unevenness in brightness due to the light projection direction.
In FIG. 4A, symbols m1 and m2 indicate brightness unevenness caused by local distortion of the screen SC.

  Specifically, as the process of step S2, the image analysis unit 33b first performs an averaging process on the processing target image based on the gradation data of the pixels constituting the processing target image (step S2a). Here, the averaging process refers to a process for making the brightness of the processing target image uniform, and a known technique such as using an averaging filter or a low-pass filter can be employed. Hereinafter, the processing target image before the averaging process is referred to as an original image, and the processing target image after the averaging process is referred to as an average image.

Subsequently, the image analysis unit 33b creates a difference image by performing a difference process between the average image and the original image (step S2b). More specifically, the gradation data of each pixel constituting the original image is Do (x, y), the gradation data of each pixel constituting the average image is Dave (x, y), and each pixel constituting the difference image. Is Ddif (x, y), the image analysis unit 33b calculates the gradation data Ddif (x, y) of each pixel constituting the difference image using the following equation (2). Note that x and y are variables indicating the horizontal (X-axis) and vertical (Y-axis) coordinates of each pixel. The maximum gradation value is “255” if it is 8 bits.
Ddif (x, y) = maximum gradation value− | Dave (x, y) −Do (x, y) | (2)

  FIG. 5A is an example of an average image, and FIG. 5B is an example of a difference image. As can be seen from these figures, by performing the above-described averaging process and difference process (creation of a difference image), it is possible to remove brightness unevenness due to the projection direction of the projector 20 and to cause local distortion of the screen SC. The brightness unevenness m1 and m2 to be emphasized can be emphasized.

  Then, the image analysis unit 33b calculates the unevenness amount of the brightness unevenness caused by the local distortion of the screen SC based on the gradation data Ddif (x, y) of the difference image (Step S2c). Specifically, the image analysis unit 33b has C1 as the total number of pixels constituting the difference image, and pixels having gradation values other than the maximum gradation value (white) among the pixels constituting the difference image (that is, FIG. 5). If the number of brightness irregularities m1 and m2 in (b) is C2, the ratio K (= C2 / C1) between C1 and C2 is calculated as the amount of unevenness.

  Then, the image analysis unit 33b compares the quality determination threshold value Kth set in advance with the unevenness amount K calculated as described above, and determines the quality of the screen SC based on the comparison result (step S2d). Specifically, the image analysis unit 33b determines that the screen SC is defective when the unevenness amount K is equal to or higher than the pass / fail determination threshold value Kth. For example, if C1 = 24000 pixels and C2 = 1520 pixels, the unevenness amount K is 6.3%. Here, if the pass / fail judgment threshold value Kth is set to 5%, the unevenness amount K is a value equal to or greater than the pass / fail judgment threshold value Kth, and therefore the screen SC is determined to be defective.

 The image analysis unit 33b notifies the CPU 32 of the quality determination result of the screen SC obtained by performing the image processing in steps S1 and S2 as described above. Then, the CPU 32 causes the display device 35 to display the pass / fail determination result of the screen SC. The user can determine whether or not the screen SC should be replaced by checking the pass / fail judgment result of the screen SC displayed on the display device 35.

 As described above, when local distortion exists in the screen SC, when light is projected from a direction oblique to the direction facing the screen SC, the local distortion of the screen SC is caused in the light projection area on the screen SC. The resulting brightness unevenness occurs. Such brightness unevenness is caused by the difference in brightness between the portion where the local distortion exists in the light projection area on the screen SC and the peripheral portion thereof, and therefore there is a lot of local distortion. As the brightness unevenness increases, the amount increases. That is, according to the screen inspection system 1 according to the present embodiment, the presence of local distortion in the screen SC is quantified by calculating the amount of unevenness in brightness based on the captured image of the screen SC obtained from the camera 10. Therefore, it is possible to judge the quality of the screen SC.

In addition, this invention is not limited to the said embodiment, The following modifications are mentioned.
(1) In the above embodiment, the averaging process and the difference image creation process are performed for all the regions of the processing target image. For example, the processing target image is divided into a plurality of regions F as illustrated in FIG. It is possible to divide and perform averaging processing for each of the plurality of regions F, and create a difference image by performing difference processing between the processing target image after the averaging processing and the processing target image before the averaging processing. good. As a result, it is possible to remove brightness unevenness caused by the projection direction of the projector 20 with high accuracy.

(2) In the above embodiment, as the unevenness amount indicating the amount of occurrence of brightness unevenness due to local distortion of the screen SC, the total number C1 of pixels constituting the difference image and the maximum of the pixels constituting the difference image Although the ratio K (= C2 / C1) with the number C2 of pixels having gradation values other than the gradation value (white) is calculated, the method of calculating the amount of unevenness is not limited to this. When the projector 20 is used as the projection device, an arbitrary inspection image can be displayed on the screen SC. For example, when an inspection image having feature points arranged at predetermined intervals is displayed on the screen SC,
Since the inspection image is distorted in a portion where local distortion exists, the position of the feature point changes. That is, by obtaining the distance between feature points in the photographed image, the density of feature points, or the like, the amount of unevenness indicating the amount of occurrence of unevenness in brightness can be calculated.

(3) Each image processing shown in FIG. 3 is performed based on photographed image data, that is, gradation data of each pixel constituting the photographed image, but gradation data on all pixels constituting the photographed image. Is treated as processing target data, the load of image processing increases, and the processing time increases. For this reason, the gradation data of the processing target data may be sampled at regular intervals instead of treating the gradation data of all the pixels constituting the captured image as the processing target data. Moreover, such sampling may be performed only by the process of step S1 of FIG. 3, or may be performed only by the process of step S2.

(4) Although the case where the projector 20 is used as the projection device has been illustrated in the above embodiment, a light source that projects predetermined color light onto the screen SC may be used as the projection device. FIG. 6B is a schematic configuration diagram of the screen inspection system 2 including a light source 40 that projects predetermined color light (for example, white light) on the screen SC instead of the projector 20. As described above, even when the light source 40 is used as the projection device, the unevenness amount of the brightness unevenness caused by the local distortion of the screen SC can be calculated, and compared with the case where the projector 20 is used as the projection device. System cost can be reduced. Further, when the light source 40 is used as the projection device, it is not necessary to provide the image processing device 30 with a function for generating an inspection image.

  On the other hand, an advantage of using the projector 20 as a projection device is that an arbitrary inspection image can be projected onto the screen SC. Depending on the specifications of the screen SC, the state of occurrence of brightness unevenness differs depending on the color of image light to be projected, and it may be difficult to calculate the amount of unevenness with high accuracy. In such a case, by projecting an inspection image of an appropriate color on the screen according to the specifications of the screen SC, it is possible to maintain unevenness calculation accuracy, that is, pass / fail judgment accuracy of the screen SC.

 DESCRIPTION OF SYMBOLS 1, 2 ... Screen inspection system, 10 ... Camera (imaging device), 11 ... Sensor optical system, 12 ... CCD sensor, 13 ... CCD control circuit, 20 ... Projector (projection device), 21 ... Projection optical system, 22 ... Lamp , 23 ... Liquid crystal panel, 24 ... Display control circuit, 30 ... Image processing device, 31 ... Operation input device, 32 ... CPU, 33 ... Image processing processor, 33a ... Image generation unit, 33b ... Image analysis unit, 34 ... Storage device 35 ... display device 40 ... light source SC ... screen

Claims (12)

A photographing device for photographing the screen from the direction facing the screen;
A projection device that projects light from a direction oblique to the screen from the direction facing the screen;
An image processing apparatus that determines the degree of brightness unevenness caused by local distortion of the screen, based on the captured image of the screen obtained from the imaging apparatus;
A screen inspection system comprising:   2. The image processing apparatus according to claim 1, further comprising: calculating a non-uniformity amount indicating the degree of non-uniformity of brightness based on the photographed image, and determining the non-uniformity of brightness based on the non-uniformity amount. Screen inspection system.   The screen inspection system according to claim 1, wherein the image processing device sets an image corresponding to a light projection area on the screen included in the captured image as a processing target image.   The image processing apparatus creates a histogram of the captured image, and sets a brightness threshold for distinguishing an image corresponding to the light projection area on the screen included in the captured image and a background image based on the histogram. Setting, recognizing an image composed of pixels having a brightness equal to or higher than the brightness threshold among pixels constituting the captured image as an image corresponding to the light projection area, and setting the image as the processing target image The screen inspection system according to claim 3.   The image processing device performs an averaging process on the processing target image, creates a difference image by performing a difference process between the processing target image after the averaging process and the processing target image before the averaging process, The screen inspection system according to claim 3, wherein the amount of unevenness is calculated based on the difference image.   The image processing apparatus divides the processing target image into a plurality of regions, performs an averaging process for each of the plurality of regions, and processes the processing target image after the averaging processing and the processing target image before the averaging processing, The screen inspection system according to claim 3, wherein a difference image is created by performing the difference process, and the amount of unevenness is calculated based on the difference image.   The image processing device calculates, as the amount of unevenness, a ratio between the total number of pixels constituting the difference image and the number of pixels other than the maximum brightness among the pixels constituting the difference image. The screen inspection system according to claim 5 or 6.   8. The image processing apparatus according to claim 2, wherein the unevenness amount is compared with a predetermined quality determination threshold value, and the quality of the screen is determined based on the comparison result. The screen inspection system according to item.   The screen inspection system according to claim 1, wherein the projection device is a projector that projects image light for displaying a predetermined inspection image on the screen as the light. .   The screen inspection system according to claim 9, wherein the inspection image is an all-white image.   The screen inspection system according to claim 1, wherein the projection device is a light source that projects predetermined color light onto the screen. Photographing the screen from the direction facing the screen;
Projecting light from a direction oblique to the screen from the direction facing the screen;
A step of determining a degree of brightness unevenness due to local distortion of the screen based on a captured image of the screen;
A screen inspection method characterized by comprising:

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