Imaging system transfer function control method and apparatus
First Claim
1. A method to measure a system transfer function of an imaging system having an input and an image sampler with a discrete image output wherein the discrete image output can be represented by a frequency representation with aliased components and unaliased components, the method comprising the steps of:
- (a) providing an image primitive to the input, the image primitive comprising a substantially uniaxial pattern having a predetermined frequency representation, the image primitive being oriented at a predetermined angle relative to the image sampler wherein the predetermined angle is chosen to separate the aliased components from the unaliased components;
(b) obtaining a discrete image of the image primitive with the imaging system;
(c) computing a two-dimensional frequency representation of the discrete image;
(d) selecting a region of the two-dimensional frequency representation; and
(e) comparing the region to the predetermined frequency representation to compute the system transfer function.
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Abstract
Accurately measuring and controlling the system transfer function of an imaging system, by eliminating interference from aliases. An image is captured of an image primitive with a uniaxial pattern, oriented at an angle to the primary axes of a sampling array. In order to accurately measure the system transfer function, a two-dimensional frequency representation is computed. The aliased components of the representation are separated from the unaliased components by translation in frequency along the axis perpendicular to the axis of the image primitive. Accurate measurement of the system transfer function makes it possible to accurately control the system transfer function.
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Citations
32 Claims
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1. A method to measure a system transfer function of an imaging system having an input and an image sampler with a discrete image output wherein the discrete image output can be represented by a frequency representation with aliased components and unaliased components, the method comprising the steps of:
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(a) providing an image primitive to the input, the image primitive comprising a substantially uniaxial pattern having a predetermined frequency representation, the image primitive being oriented at a predetermined angle relative to the image sampler wherein the predetermined angle is chosen to separate the aliased components from the unaliased components; (b) obtaining a discrete image of the image primitive with the imaging system; (c) computing a two-dimensional frequency representation of the discrete image; (d) selecting a region of the two-dimensional frequency representation; and (e) comparing the region to the predetermined frequency representation to compute the system transfer function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An apparatus to measure frequency response of an imaging system having an input and an image sampler with a discrete image output wherein the discrete image output can be represented by a frequency representation with aliased components and unaliased components, the apparatus comprising:
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(a) an image primitive placed in view of the input, the image primitive comprising a substantially uniaxial pattern having a predetermined frequency representation, the image primitive being oriented at a predetermined angle relative to the image sampler wherein the predetermined angle is chosen to separate the aliased components from the unaliased components; (b) means, connected to the discrete image output, for computing a two-dimensional frequency representation of the discrete image output, having a computing output; (c) means, connected to the computing output, for selecting a region of the two-dimensional frequency representation, having a selected region output; and (d) means, connected to the selected region output, for comparing the region to the predetermined frequency representation to compute an optical transfer function, having an optical transfer function output. - View Dependent Claims (22, 23, 24, 25, 26)
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27. An imaging system control apparatus, for an imaging system having a transfer function control input, wherein the imaging system has a system transfer function and system transfer function control input, the imaging system control apparatus comprising:
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(a) means for measuring the system transfer function of the imaging system having a system transfer measure output; and (b) means for controlling the system transfer function in response to the system transfer measure output connected to the system transfer measure output, wherein the means for controlling the system transfer function is connected to the system transfer function control input. - View Dependent Claims (28, 29, 30, 31)
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32. A method of modifying a system transfer function of an image system comprising the steps of:
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(a) measuring an original system transfer function at multiple focal planes; (b) selecting a system transfer function with a highest modulation transfer function; (c) checking if the system transfer function is within predetermined limits; (d) calculating imaging system component values to optimize system transfer function; (e) checking if a modeled system transfer function is within the predetermined limits; (f) modifying the image system using the calculated components; (g) measuring a modified system transfer function at multiple focal planes; (h) selecting the system transfer function with the highest modulation transfer function; and (i) checking if the system transfer function is within the predetermined limits.
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Specification