Spatial frequency filter
First Claim
1. A spatial frequency filter having a two-dimensional spatial frequency plane whose first quadrant includes a first prescribed point, whose second quadrant includes a second prescribed point, whose third quadrant includes a third prescribed point and whose fourth quadrant includes a fourth prescribed point, said two-dimensional spatial frequency plane having a vertical axis and a horizontal axis, said spatial frequency filter comprising:
- primary filter means for providing a first trap line passing through said first prescribed point and a second trap line passing through said third prescribed point;
secondary filter means for providing a third trap line passing through said second prescribed point and a fourth trap line passing through said fourth prescribed point; and
tertiary filter means for providing a fifth trap line passing through said first and fourth prescribed points and a sixth trap line passing through said second and third prescribed points,wherein each of said first to fourth trap lines crosses over said vertical and horizontal axes so as to form a rhombic trap pattern, and a modulation transfer function of the image sensor becomes substantially zero on the respective trap lines.
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Accused Products
Abstract
A spatial frequency filter is adapted to an image sensor having a two-dimensional spatial frequency plane whose first quadrant includes a first prescribed point, whose second quadrant includes a second prescribed point, whose third quadrant includes a third prescribed point and whose fourth quadrant includes a fourth prescribed point. The two-dimensional spatial frequency plane has a vertical axis and a horizontal axis. The spatial frequency filter includes the combination of a primary filter part for providing a first trap line passing through the first prescribed point and a second trap line passing through the third prescribed point, a secondary filter part for providing a third trap line passing through the second prescribed point and a fourth trap line passing through the fourth prescribed point, and a tertiary filter part for providing a fifth trap line passing through the first and fourth prescribed points and a sixth trap line passing through the second and third prescribed points. Each of the first to fourth trap lines crosses over the vertical and horizontal axes. The spatial frequency filter of the present invention so arranged suppresses spurious information along the slant and horizontal (or vertical) axes of the image sensor.
69 Citations
30 Claims
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1. A spatial frequency filter having a two-dimensional spatial frequency plane whose first quadrant includes a first prescribed point, whose second quadrant includes a second prescribed point, whose third quadrant includes a third prescribed point and whose fourth quadrant includes a fourth prescribed point, said two-dimensional spatial frequency plane having a vertical axis and a horizontal axis, said spatial frequency filter comprising:
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primary filter means for providing a first trap line passing through said first prescribed point and a second trap line passing through said third prescribed point; secondary filter means for providing a third trap line passing through said second prescribed point and a fourth trap line passing through said fourth prescribed point; and tertiary filter means for providing a fifth trap line passing through said first and fourth prescribed points and a sixth trap line passing through said second and third prescribed points, wherein each of said first to fourth trap lines crosses over said vertical and horizontal axes so as to form a rhombic trap pattern, and a modulation transfer function of the image sensor becomes substantially zero on the respective trap lines. - View Dependent Claims (2, 3, 4, 5, 6, 7, 13, 14, 15, 16, 17, 18)
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- 11. A spatial frequency filter according to claim 11, wherein the polarizing axis of said primary filter means is inclined by substantially 45 degrees from the polarizing axis of said tertiary filter means, the polarizing axis of said secondary filter means is inclined by substantially 90 degrees from the polarizing axis of said primary filter means, and said tertiary filter means is sandwiched between said primary filter means and said secondary filter means.
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19. A spatial frequency filter having a two-dimensional spatial frequency plane whose first quadrant includes a first prescribed point, whose second quadrant includes a second prescribed point, whose third quadrant includes a third prescribed point and whose fourth quadrant includes a fourth prescribed point, said two-dimensional spatial frequency plane having a vertical axis and a horizontal axis, said spatial frequency filter comprising:
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primary filter means for providing a first trap line passing through said first prescribed point and a second trap line passing through said third prescribed point; secondary filter means for providing a third trap line passing through said prescribed point and a fourth trap line passing through said fourth prescribed point; and tertiary filter means for providing a fifth trap line passing through said first and second prescribed points and a sixth trap line passing through said third and fourth prescribed points, wherein each of said first to fourth trap lines crosses over said vertical and horizontal axes so as to form a rhombic trap pattern, and a modulation transfer function of the image sensor becomes substantially zero on the respective trap lines. - View Dependent Claims (20)
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21. A spatial frequency filter having a two-dimensional spatial frequency plane whose first quadrant includes a first prescribed point, whose second quadrant includes a second prescribed point, whose third quadrant includes a third prescribed point and whose fourth quadrant includes a fourth prescribed point, said two-dimensional spatial frequency plane having a vertical axis and a horizontal axis, said spatial frequency filter comprising:
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primary filter means for providing a first trap line passing through said first prescribed point and a second trap line passing through said third prescribed point; secondary filter means for providing a third trap line passing through said second prescribed point and a fourth trap line passing through said fourth prescribed point; and tertiary filter means for providing a fifth trap line passing through a fifth prescribed point in said first quadrant and a sixth prescribed point in said second quadrant, for providing a sixth trap line passing through a seventh prescribed point in said third quadrant and an eighth prescribed point in said fourth quadrant, for providing a seventh trap line passing through said fifth and eighth prescribed points and an eighth trap line passing through said sixth and seventh prescribed points, wherein each of said first to fourth trap lines crosses over said vertical and horizontal axes so as to form a rhombic trap pattern, and a modulation transfer function of the image sensor becomes substantially zero on the respective trap lines.
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22. A spatial frequency filter having a two-dimensional spatial frequency plane with orthogonal first and second axes, wherein said spatial frequency plane has a first quadrant containing a first prescribed point, a second quadrant containing a second prescribed point, a third quadrant containing a third prescribed point and a fourth quadrant containing a fourth prescribed point, wherein the absolute values of said first to fourth prescribed points with respect to said first axis are substantially the same, and wherein the absolute values of said first to fourth prescribed points with respect to said second axis are substantially the same,
said spatial frequency filter comprising: -
a first spatial frequency filter part having two sets of parallel trap lines, said parallel trap lines of one set passing through said first and third prescribed points, respectively, and crossing over said first and second axes, and said parallel trap lines of the other set passing through said second and fourth prescribed points, respectively, and crossing over said first and second axes, said two sets of parallel trap lines thereby forming a rhombic trap pattern; and a second spatial frequency filter part having one set of parallel trap lines which are symmetrical with respect to said first axis and are parallel to said first axis. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
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Specification