CROSS REFERENCE TO RELATED APPLICATION
This application claims priority of Taiwan Application No. 107119186 filed on 2018 Jun. 4.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a Demura system, and more particular, to a Demura system for a non-planar screen.
2. Description of the Prior Art
Mura is a visual problem which appears on displays as regions of low contrast and non-uniform brightness in various shapes and sizes. The irregular pattern or region causes uneven screen uniformity and influences viewer experience.
There are many manifestations of the Mura condition and the causes are quite diverse. Several possible causes of Mura include manufacturing defects and non-uniform luminance distribution of the backlight. In a prior art correction method of Mura (commonly known as Demura), a specific image is input to the display panel and a camera is used to capture the screen image under various gray scale conditions. By analyzing the non-uniformity in brightness or contrast based on the acquired optical information, an algorithm may be implemented for compensating Mura by adjusting the luminance and the chromaticity of each pixel to produce images with an entirely uniform appearance. In order to tackle insufficient resolution of cameras or Moiré pattern, a panoramic photography technique may be adopted in which the location of a camera changes in a predefined pattern so as to capture partial images of a screen section by section and then composite the partial images for subsequent Mura analysis.
Non-planar screens (also known as curved screens) provide more immersive visual experience than planar screens. When applying a prior art Demura method on a non-planar screen, several problems may occur when the camera captures partial images at different locations. Since the distance between the camera and the non-planar screen changes as the camera moves in a predefined manner, the partial images displayed on different sections of the non-planar screen may have different brightness or distortions caused by different pixel angles, thereby requiring a complicated algorithm for compensating the errors when calculating the brightness of the composited image from the partial images. Therefore, there is a need for a Demura system for use in non-planar screen.
SUMMARY OF THE INVENTION
The present invention provides a Demura system which includes a camera, a distance detection module, a location calibration module, and a processing circuit. The camera module is configured to capture an image displayed on a non-planar screen during an image-capturing period. The distance detection module is configured to detect a distance between the camera module and the non-planar screen during a test period. The location calibration module is configured to carry the camera module and the distance detection module, adjust an angle of the distance detection module, adjust an angle of the camera module and adjust a location of the camera module. The processing circuit is configured to control the location calibration module according to data acquired by the distance detection module during the test period so as to move the camera module to a predetermined location.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a functional diagram of a Demura system according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating the operation of a Demura system according to an embodiment of the present invention.
FIG. 3 is a diagram of a Demura system according to an embodiment of the present invention.
FIG. 4A is a diagram illustrating the operation of the Demura system when performing the calibration operation on camera location according to an embodiment of the present invention.
FIG. 4B is a diagram illustrating the operation of the Demura system when performing the calibration operation on camera location according to another embodiment of the present invention.
FIG. 4C is a diagram illustrating the operation of the Demura system when performing the calibration operation on camera location according to another embodiment of the present invention.
FIGS. 5A and 5B are diagrams illustrating the operation of a Demura system during the image-capturing period according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating the operation of a Demura system when performing image composition according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating the operation of a Demura system during the image-capturing period according to another embodiment of the present invention.
FIG. 8 is a diagram of the Demura system according to another embodiment of the present invention.
FIG. 9 is a diagram of a Demura system according to another embodiment of the present invention.
FIG. 10 is a diagram of a Demura system according to another embodiment of the present invention.
DETAILED DESCRIPTION
FIG. 1 is a functional diagram of a Demura system 100 according to an embodiment of the present invention. The Demura system 100 includes a camera module 20, a distance detection module 30, a processing circuit 40, and a location calibration module 50. The Demura system 100 may be implemented in a non-planer screen 10 which may be, but not limited to, a curved screen, a spherical screen, or an arc virtual reality (VR) screen. The camera module 20 includes one or multiple cameras, and the distance detection module 30 includes one or multiple proximity sensors. Each proximity sensor of the distance detection module 30 is disposed at a location associated with a corresponding camera of the camera module 20 for detecting the distance between the corresponding camera and the non-planar screen 10. For example, each proximity sensor may be disposed on a corresponding camera, or adjacent to a corresponding camera. The location calibration module 50 is configured to carry the camera module 20 and the distance detection module 30, adjust the angle of each camera in the camera module 20 so as to capture the image displayed on the non-planar screen 10 using a panoramic photography technique, and adjust the location of each camera in the camera module 20 according to the data acquired by the distance detection module 30.
FIG. 2 is a flowchart illustrating the operation of the Demura system 100 according to an embodiment of the present invention. The flowchart in FIG. 2 includes the following steps:
Step 210: determine a predetermined location.
Step 220: activate the distance detection module 30 and adjust the angle of the distance detection module 30 with a predetermined speed during a test period.
Step 230: determine whether the current location of the camera module 20 deviates from the predetermined location according to the data acquired by the distance detection module 30.
Step 240: adjust the location of the camera module 20.
Step 250: activate the camera module 20 and adjust the angle of the camera module 20 with a predetermined speed during an image-capturing period.
Step 260: the camera module 20 sequentially captures multiple images IMAGE1˜IMAGEM during the image-capturing period.
Step 270: the processing circuit 40 acquires multiple sub-images SUB1˜SUBM respectively from the multiple images IMAGE1˜IMAGEM and composites the multiple sub-images SUB1˜SUBM into a planar image for Demura purpose.
FIG. 3 is a diagram of the Demura system 100 according to an embodiment of the present invention. In this embodiment, the non-planar screen 10 is circular-shaped curved screen having a constant curvature. The camera module 20 includes a camera CAM, and the distance detection module 30 includes a proximity sensor SR which may be disposed on the camera CAM or adjacent to the camera CAM. The location calibration module 50 includes two slide guides 41 and 42, a swiveling base 44, and a pillar 46. The slide guides 41 and 42 provide two tracks perpendicular to each other (represented by dotted lines in FIG. 3), along which an object may move towards or away from the non-planar screen 10, or move from one end of the non-planar screen 20 to another end. The swiveling base 44, disposed on one end of the slide guide 41, is capable of rotating 360 degrees and moving along the track of the slide guides 41 and 42. The track of the slide guide 41 and the track of the slide guide 42 cross each other at an intersection point which may be fixed to the pillar 46. The height of the pillar 46 may be adjusted, such as using an electrical air pump. In the Demura system 100 depicted in FIG. 3, the camera CAM and the proximity sensor SR may be disposed on the swiveling base 44 of the location calibration module 50, and the processing circuit 40 (not shown in FIG. 3) may determine whether the current location of the camera CAM deviates from the predetermined location according to the data acquired by the proximity sensor SR, wherein the predetermined location is at a constant distance from the set of all points in the surface of the non-planar screen 10 (circular-shaped curved screen) which are at the same height of the predetermined location.
As well-known to those skilled in the art, PPI (pixel per inch) is a measurement of pixel density (the number of pixels printed in a one inch square area) of a planar screen, while PPD (pixel per degree) is a measurement of pixel density (the number of pixels per degree of the viewing) of a non-planar screen. In step 210, the distance between the predetermined location and the non-planar screen 10 may be determined based on the PPD specification of the Demura system 100, while the height of the predetermined location may be determined based on the vertical viewing range of the non-planar screen 10 or the camera module 20.
After determining the predetermined location, steps 220 and 230 are executed for performing a calibration operation on camera location. In step 220, the swiveling base 44 of the location calibration module 50 is rotated with a predetermined speed and in a predetermined direction during the test period so as to adjust the angle of the proximity sensor SR in the distance detection module 30. In step 230, the processing circuit 40 is configured to determine whether the current location of the camera CAM deviates from the predetermined location according to the data acquired by the proximity sensor SR.
FIGS. 4A-4C are diagrams illustrating the operation of the Demura system 100 when performing the calibration operation on camera location according to embodiments of the present invention. For illustrative purpose, it is assumed that the proximity sensor SR detect the location of the camera SR 3 times during the test period, wherein R1˜R3 represent the data associated with the distance between the camera CAM and the non-planar screen 10 and sequentially acquired by the proximity sensor SR during the test period. When the processing circuit 40 receives data indicating R1=R2=R3, it means the camera CAM is currently located at the predetermined location (represented by a star sign in FIG. 4A), as depicted in FIG. 4A. When the processing circuit 40 receives data indicating R1>R2>R3, it means the camera CAM is currently located to the right of the predetermined location (represented by a star sign in FIG. 4B), as depicted in FIG. 4B. When the processing circuit 40 receives data indicating R1<R2<R3, it means the camera CAM is currently located to the left of the predetermined location (represented by a star sign in FIG. 4C), as depicted in FIG. 4C.
When determining that the current location of the camera CAM deviates from the predetermined location according to the data acquired by the proximity sensor SR in step 230, the processing circuit 40 is configured to instruct the location calibration module 50 to adjust the location of the camera CAM in step 240. For example, the swiveling base 44 may move along the slide guides 41 and 42 in order to adjust the location of the camera CAM with respect to the non-planar screen 10. In an embodiment of the present invention, steps 220 and 230 may be executed repeatedly until the camera CAM of the camera module 20 arrives at the predetermined location.
When the processing circuit 40 determines that the camera CAM is currently located at the predetermined location according to the data acquired by the proximity sensor SR in step 230, the lens of the camera CAM may be maintained at the same distance from the set of all points in the surface of the non-planar screen 10 at the same height of the camera CAM when the angle of the camera CAM is adjusted by rotating the swiveling base 44. Under such circumstance, steps 250 and 260 are then executed for performing an image capturing operation. In step 250, the swiveling base 44 of the location calibration module 50 may rotate with a predetermined speed and in a predetermined direction in order to adjust the angle of the camera CAM in the camera module 20. In step 260, the camera CAM may sequentially capture multiple images IMAGE1˜IMAGEM during the image-capturing period, wherein M is an integer larger than 1.
FIGS. 5A and 5B are diagrams illustrating the operation of the Demura system 100 during the image-capturing period according to an embodiment of the present invention. For illustrative purpose, it is assumed that the camera module 20 captures 3 images (M=3) during the image-capturing period, wherein the camera CAM is rotated from left to right and sequentially captures the images IMAGE1˜IMAGE3, as depicted in FIG. 5A. Since the camera CAM is confirmed to be located at the predetermined location in the prior calibration operation on camera location, the images IMAGE1˜IMAGE3 captured in step 260 have the same resolution, as depicted in FIG. 5B.
In step 270, the processing circuit 40 is configured to acquire the multiple sub-images SUB1˜SUBM respectively from the multiple images IMAGE1˜IMAGEM and composites the plurality of sub-images SUB1˜SUBM into a planar image for Demura purpose. FIG. 6 is a diagram illustrating the operation of the Demura system 100 when performing image composition according to an embodiment of the present invention. Also assuming M=3, the processing circuit 40 may acquire the sub-images SUB1˜SUB3 respectively from the images IMAGE1˜IMAGE3 and composite the sub-images SUB1˜SUB3 into a planar image IMAGE0. In an embodiment of the present invention, the size of the sub-images SUB1˜SUBM may be determined based on the resolution of the camera CAM and the number of image-capturing (M) during a rotation cycle of the camera CAM.
As previously stated, the image displayed on the non-planar screen 10 may be an initial image which is output with different grey scale conditions. The processing circuit 40 is configured to analyze the difference between the planar image IMAGE0 and the initial image, thereby compensating the Mura of the non-planar screen 10 using an algorithm.
FIG. 7 is a diagram illustrating the operation of the Demura system 100 during the image-capturing period according to another embodiment of the present invention. For illustrative purpose, it is assumed that the proximity sensor SR detects the location of the camera SR N times during the test period and the camera module 20 captures N images during the image-capturing period, wherein N is an integer larger than 1. R1˜RN represent the data associated with the distance between the camera CAM and the non-planar screen 10 and sequentially acquired by the proximity sensor SR during the test period. When the non-planar screen 10 is a spherical screen or an arc VR screen having distinct curvatures, the lens of the camera CAM may not be at the same distance from the set of all points in the surface of the non-planar screen 10 at the same height of the camera CAM even when the camera CAM is located at the predetermined location (R1≠R2≠R3≠ . . . ≠RN). Therefore, in this embodiment, the camera module 20 of the Demura system 100 may include a zoom camera CAM for taking the images IMAGE1˜IMAGEM using a plurality of focuses F1˜FN at the distances R1˜RN, thereby compensating the variance in curvature of the non-planar screen 10 for allowing the images IMAGE1˜IMAGEM to have the same resolution.
FIG. 8 is a diagram of the Demura system 100 according to another embodiment of the present invention. In this embodiment, the non-planar screen 10 is a spherical screen or an arc VR screen having distinct curvatures. The camera module 20 includes multiple cameras CAM1˜CAMN (N is an integer larger than 1) with distinct focuses, and the distance detection module 30 includes multiple proximity sensors SR1˜SRN which may be disposed on the cameras CAM1˜CAMN or adjacent to the cameras CAM1˜CAMN, respectively. The location calibration module 50 includes two slide guides 41 and 42, a swiveling base 44, and a pillar 46. The slide guides 41 and 42 provide two tracks perpendicular to each other (represented by dotted lines in FIG. 8), along which an object may move towards or away from the non-planar screen 10, or move from one end of the non-planar screen 10 to another end. The swiveling base 44, disposed on one end of the slide guide 41, is capable of rotating 360 degrees and moving along the tracks of the slide guides 41 and 42. The track of the slide guide 41 and the track of the slide guide 42 cross each other at an intersection point which may be fixed to the pillar 46. The height of the pillar 46 may be adjusted, such as using an electrical air pump. In the Demura system 100 depicted in FIG. 8, the cameras CAM1˜CAMN and the proximity sensors SR1˜SRN may be disposed on the swiveling base 44 of the location calibration module 50, wherein the locations of the cameras CAM1˜CAMN are aligned with the same straight line parallel to a side of the swiveling base 44. The processing circuit 40 (not shown in FIG. 8) may determine whether the current location of the swiveling base 44 deviates from the predetermined location according to the data acquired by the proximity sensors SR1˜SRN, wherein the height of the predetermined location is determined based on the height of the non-planar screen 10 or the vertical viewing range of the cameras CAM1˜CAMN. When the swiveling base 44 is at the predetermined location, at least one of the cameras CAM1˜CAMN provides the PPD specification which matches that of the non-planar screen 10. In the embodiment illustrated in FIG. 8, the camera module 20 includes multiple cameras CAM1˜CAMN capable of capturing images using distinct focuses, thereby compensating the variance in curvature of the non-planar screen 10 for allowing the images IMAGE1˜IMAGEM to have the same resolution.
FIG. 9 is a diagram of the Demura system 100 according to another embodiment of the present invention. In this embodiment, the non-planar screen 10 is a spherical screen or an arc VR screen having distinct curvatures. The camera module 20 includes multiple cameras CAM1˜CAMN (N is an integer larger than 1) with the same focus, and the distance detection module 30 includes multiple proximity sensors SR1˜SRN which may be disposed on the cameras CAM1˜CAMN or adjacent to the cameras CAM1˜CAMN, respectively. The location calibration module 50 includes two slide guides 41 and 42, a swiveling base 44, and a pillar 46. The slide guides 41 and 42 provide two tracks perpendicular to each other (represented by dotted lines in FIG. 9), along which an object may move towards or away from the non-planar screen 10, or move from one end of the non-planar screen 10 to another end. The swiveling base 44, disposed on one end of the slide guide 41, is capable of rotating 360 degrees and moving along the tracks of the slide guides 41 and 42. The track of the slide guide 41 and the track of the slide guide 42 cross each other at an intersection point which may be fixed to the pillar 46. The height of the pillar 46 may be adjusted, such as using an electrical air pump. In the Demura system 100 depicted in FIG. 9, the cameras CAM1˜CAMN and the proximity sensors SR1˜SRN may be disposed on the swiveling base 44 of the location calibration module 50, wherein the locations of the cameras CAM1˜CAMN are aligned with different horizontal straight lines parallel to a side of the swiveling base 44. The processing circuit 40 (not shown in FIG. 9) may determine whether the current location of the swiveling base 44 deviates from the predetermined location according to the data acquired by the proximity sensors SR1˜SRN, wherein the height of the predetermined location is determined based on the height of the non-planar screen 10 or the vertical viewing range of the cameras CAM1˜CAMN. When the swiveling base 44 is at the predetermined location, at least one of the zoom cameras CAM1˜CAMN provides the PPD specification which matches that of the non-planar screen 10. In the embodiment illustrated in FIG. 9, the camera module 20 includes multiple fixed-focus cameras CAM1˜CAMN located at different distances with respect to the non-planar screen 10 at a given point of time during the image-capturing period, thereby capable of capturing the images IMAGE1˜IMAGEM of different resolutions. At each image-capturing during the image-capturing period, the processing circuit 40 may acquire the sub-images SUB1˜SUBN from one of the images IMAGE1˜IMAGEM captured at each point of time during the image-capturing period and having the specific resolution, thereby compensating the variance in curvature of the non-planar screen 10.
FIG. 10 is a diagram of the Demura system 100 according to another embodiment of the present invention. In this embodiment, the non-planar screen 10 is circular-shaped curved screen having a constant curvature. The camera module 20 includes a camera CAM, and the distance detection module 30 includes a proximity sensor SR which may be disposed on the camera CAM or adjacent to the camera CAM. The location calibration module 50 includes two slide guides 41 and 42, a swiveling base 44, and a pillar 46. The slide guides 41 and 42 provide two tracks perpendicular to each other (represented by dotted lines in FIG. 10), along which an object may move towards or away from the non-planar screen 10, or move from one end of the non-planar screen 10 to another end. The track of the slide guide 41 and the track of the slide guide 41 cross each other at an intersection point which includes a pivot structure 48 fixed to the pillar 46. The height of the pillar 46 may be adjusted, such as using an electrical air pump. The slide guides 41 and 42 are pivotally connected to the pillar 48 via the pivot structure 48, thereby capable of rotating around the pillar 46 by an angle of θ degree for adjusting the angle of the swiveling base 44. In the Demura system 100 depicted in FIG. 10, the camera CAM and the proximity sensor SR may be disposed on the swiveling base 44 of the location calibration module 50, and the processing circuit 40 (not shown in FIG. 10) may determine whether the current location of the swiveling base 44 deviates from a predetermined location. Similarly, the Demura system 100 depicted in FIG. 8 or FIG. 9 may also adopt the pivot structure 48 of FIG. 10 for adjusting the angles of the cameras CAM1˜CAMN and the proximity sensors SR1˜SRN.
In conclusion, the present invention provides a Demura system for use in a non-planar screen. During the process of capturing the image displayed on the non-planar screen, a camera is rotated so that the distance between the lens of the camera and the non-planar screen may be kept at a constant value. Also, a single zoom camera, multiple cameras with distinct focuses, or multiple cameras with the same focus but disposed at different locations may be used to compensate the variance in curvature of the non-planar screen. Therefore, regardless of the type of the non-planar screen, the present Demura system can keep one or multiple cameras at an appropriate distance and an appropriate angle with respect to the non-planar screen for Mura compensation.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Patent Grant
10872544
