SURFACE MEASUREMENT INSTRUMENT AND METHOD
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Abstract
A method of characterising the surface of an aspheric diffractive structure includes using a metrological apparatus to perform a measurement on the surface of the structure so as to provide a measurement profile representing the z-direction deviations of the surface of the structure; determining parameters relating to the aspheric and diffractive components of the aspheric diffractive structure; producing data having the determined parameters; and comparing the produced data with the measurement profile to determine residual error data.
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Citations
119 Claims
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1-62. -62. (canceled)
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63. A method of characterising the surface of an aspheric diffractive structure, the method comprising:
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receiving measurement data representing the results of a measurement operation performed on the surface of the aspheric diffractive structure; fitting an equation having an aspheric component to the received data; producing fitted data based upon the fitted equation; subtracting the fitted data from the received data to produce first subtracted data; subtracting data representing a polynomial component of a diffractive component of the aspheric diffractive structure from the first subtracted data to produce second subtracted data having one or more steps; and identifying one or more step edge locations and/or step heights in the second subtracted data. - View Dependent Claims (64, 65, 66, 67, 68)
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69. Apparatus for characterising the surface of an aspheric diffractive structure, the apparatus being configured to:
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receive measurement data representing the results of a measurement operation performed on the surface of the aspheric diffractive structure; fit an equation having an aspheric component to the received data; produce fitted data based upon the fitted equation; subtract the fitted data from the received data to produce first subtracted data; subtract data representing a polynomial component of a diffractive component of the aspheric diffractive structure from the first subtracted data to produce second subtracted data having one or more steps; and identify one or more step edge locations and/or step heights in the second subtracted data.
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70-93. -93. (canceled)
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94. A data processor for characterising a diffractive aspheric workpiece having an aspheric and a diffractive component, the data processor comprising:
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a data receiver configured to receive measurement data produced from the measurement operation; a data component remover configured to fit an equation representing the aspheric component to the measurement data to produce fitted data and to subtract the fitted data from the measurement data to produce subtracted data having a series of steps; and a data feature finder configured to produce transformed data from the subtracted data having features at locations in the transformed data that correspond to the locations in the subtracted data of the steps, and to identify the locations of the features taking into account a polynomial component of the diffractive component, whereby the step edges characterise a stepped component of the diffractive component. - View Dependent Claims (95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118)
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119. A non-transitory storage medium carrying computer-readable instructions for causing a processor to execute the steps of:
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receiving measurement data representing the results of a measurement operation performed on the surface of the aspheric diffractive structure; fitting an equation having an aspheric component to the received data; producing fitted data based upon the fitted equation; subtracting the fitted data from the received data to produce first subtracted data; subtracting data representing a polynomial component of a diffractive component of the aspheric diffractive structure from the first subtracted data to produce second subtracted data having one or more steps; and identifying one or more step edge locations and/or step heights in the second subtracted data.
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Specification