CROSSING POINT DETECTOR, CAMERA CALIBRATION SYSTEM, CROSSING POINT DETECTION METHOD, CAMERA CALIBRATION METHOD, AND RECORDING MEDIUM
First Claim
1. A crossing point detector, comprising:
- a memory that stores a captured image obtained by imaging a checker pattern; and
a processor that reads out at least a partial image of the captured image from the memory as an image to process, and detects a crossing point of two boundary lines in the checker pattern depicted in the image to process, whereineach of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process,the processordecides multiple parameters of a function model that treats two-dimensional image coordinates as variables, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, andcomputes a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, andthe function model uses a curved surface that is at least first-order differentiable to express the first region and the second region in a two-dimensional coordinate system, and also pixel values at respective positions in the two-dimensional coordinate system at a boundary between the first region and the second region.
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Accused Products
Abstract
A crossing point detector includes memory and a crossing point detection unit that reads out a square image from a captured image in the memory, and detects a crossing point of two boundary lines in a checker pattern depicted in the square image. The crossing point detection unit decides multiple parameters of a function model treating two-dimensional image coordinates as variables, the parameters optimizing an evaluation value based on a difference between corresponding pixel values represented by the function model and the square image, respectively, and computes the position of a crossing point of two straight lines expressed by the decided multiple parameters to thereby detect the crossing point with subpixel precision. The function model uses a curved surface that is at least first-order differentiable to express pixel values at respective positions in a two-dimensional coordinate system at the boundary between black and white regions.
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Citations
22 Claims
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1. A crossing point detector, comprising:
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a memory that stores a captured image obtained by imaging a checker pattern; and a processor that reads out at least a partial image of the captured image from the memory as an image to process, and detects a crossing point of two boundary lines in the checker pattern depicted in the image to process, wherein each of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process, the processor decides multiple parameters of a function model that treats two-dimensional image coordinates as variables, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, and computes a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, and the function model uses a curved surface that is at least first-order differentiable to express the first region and the second region in a two-dimensional coordinate system, and also pixel values at respective positions in the two-dimensional coordinate system at a boundary between the first region and the second region. - View Dependent Claims (2, 3, 7, 8, 9)
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4. A crossing point detector, comprising:
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a memory that stores a captured image obtained by imaging a checker pattern; and a processor that reads out at least a partial image of the captured image from the memory as an image to process, and detects a crossing point of two boundary lines in the checker pattern depicted in the image to process, wherein each of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process, the processor decides multiple parameters of a numerical model, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, and computes a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, and the numerical model is a model that simulates a pixel integration effect when imaging a step edge by assigning pixel values to respective regions inside a pixel divided by a straight line, and deciding a pixel value of the overall pixel. - View Dependent Claims (5, 6)
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10. A crossing point detection method, comprising:
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reading out, from a memory storing a captured image obtained by imaging a checker pattern, at least a partial image of the captured image as an image to process; and detecting a crossing point of two boundary lines in the checker pattern depicted in the image to process, wherein each of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process, the detecting of the crossing point includes deciding multiple parameters of a function model that treats two-dimensional image coordinates as variables, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, and computing a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, and the function model uses a curved surface that is at least first-order differentiable to express the first region and the second region in a two-dimensional coordinate system, and also pixel values at respective positions in the two-dimensional coordinate system at a boundary between the first region and the second region. - View Dependent Claims (11, 12, 16, 17, 18)
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13. A crossing point detection method, comprising:
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reading out, from a memory storing a captured image obtained by imaging a checker pattern, at least a partial image of the captured image as an image to process; and detecting a crossing point of two boundary lines in the checker pattern depicted in the image to process, wherein each of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process, the detecting of the crossing point includes deciding multiple parameters of a numerical model, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, and computing a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, and the numerical model is a model that simulates a pixel integration effect when imaging a step edge by assigning pixel values to respective regions inside a pixel divided by a straight line, and deciding a pixel value of the overall pixel. - View Dependent Claims (14, 15)
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19. A non-transitory computer-readable recording medium storing a program, the program causing a computer to execute processing including:
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reading out, from a memory storing a captured image obtained by imaging a checker pattern, at least a partial image of the captured image as an image to process; and detecting a crossing point of two boundary lines in the checker pattern depicted in the image to process, wherein each of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process, the detecting of the crossing point includes deciding multiple parameters of a function model that treats two-dimensional image coordinates as variables, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, and computing a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, and the function model uses a curved surface that is at least first-order differentiable to express the first region and the second region in a two-dimensional coordinate system, and also pixel values at respective positions in the two-dimensional coordinate system at a boundary between the first region and the second region. - View Dependent Claims (21)
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20. A non-transitory computer-readable recording medium storing a program, the program causing a computer to execute processing including:
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reading out, from a memory storing a captured image obtained by imaging a checker pattern, at least a partial image of the captured image as an image to process; and detecting a crossing point of two boundary lines in the checker pattern depicted in the image to process, wherein each of the two boundary lines is a boundary line between a first region made up of multiple pixels having a first pixel value and a second region made up of multiple pixels having a second pixel value greater than the first pixel value in the image to process, the detecting of the crossing point includes deciding multiple parameters of a numerical model, the parameters being parameters for optimizing an evaluation value based on a difference between respective pixel values represented by the function model and respective pixel values in the image to process, and computing a position of a crossing point of two straight lines expressed by the decided multiple parameters, and thereby detects with subpixel precision the crossing point of the two boundary lines in the image to process, and the numerical model is a model that simulates a pixel integration effect when imaging a step edge by assigning pixel values to respective regions inside a pixel divided by a straight line, and deciding a pixel value of the overall pixel.
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22. A coordinate position determiner, comprising:
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a memory that stores an image obtained by imaging a checker pattern, the checker pattern including a first crossing point of a first line and a second line; and a processor that reads out the image from memory and determines a coordinate position of a second crossing point, in a two-dimensional coordinate system, indicating a crossing point in the image that corresponds to the first crossing point, wherein provided that a position of each pixel in the image is expressed by coordinate position (xk, yk) in the two-dimensional coordinate system, a pixel value at the coordinate position (xk, yk) in the image is I(xk, yk), where k is a natural number less than or equal to n, and n is a total number of pixels included in the image, the second crossing point is a crossing point of a first boundary line and a second boundary line, the first boundary line being located on a boundary between a region that includes a first region included in the image and a second region included in the image, and a region that includes a third region included in the image and a fourth region included in the image, and the second boundary line being located on a boundary between a region that includes the first region and the third region, and a region that includes the second region and the fourth region, each pixel value of the pixels included in the first and fourth regions is greater than each pixel value of the pixels included in the second and third regions, the processor decides parameters of M(x, y) that optimize an evaluation value based on a difference between M(x=xk, y=yk) and I(xk, yk), M(x, y) indicates a pixel value at the coordinate position (x, y) in the two-dimensional coordinate system, the processor computes the position of the crossing point of the first boundary line and the second boundary line expressed by using the multiple parameters to thereby obtain the second crossing point with a precision by which a resolution in an x-axis direction of the two-dimensional coordinate system is less than (xk+1−
xk) and a resolution in a y-axis direction of the two-dimensional coordinate system is less than (yk+1−
yk), andM(x, y) uses a curved surface that is at least first-order differentiable to express the first region, the second region, the third region, and the fourth region in the two-dimensional coordinate system, and pixel values at respective positions in the two-dimensional coordinate system on the first boundary line and the second boundary line.
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Specification