Cross correlator with automatic rotational alignment

Claim 2

In a correlator in which radiant energy is transmitted from an object through a variable density planar representation thereof to a detecting plane, apparatus for determining the rotational misalignment of said object and said representation, comprising, a radiant energy sensor positioned in said detecting plane for generating a unidirectional voltage indicative of the total amount of radiant energy falling thereon, means for subjecting said representation to oscillatory rotary motion about an axis perpendicular thereto, whereby said voltage varies in amplitude and includes a component varying at the frequency of said oscillatory rotary motion, means for generating an alternating voltage at the frequency of and in synchronism with said oscillatory rotary motion, and synchronous detector means controlled by said alternating voltage for generating a unidirectional error signal voltage the magnitude and polarity of which are indicative of the magnitude and phase respectively of said component with respect to said alternating voltage.

Claim 3

In a correlator in which radiant energy is transmitted from an object through a variable density planar representation thereof to a detecting plane, apparatus for determining the translational misalignment of said object and said representation, comprising, radiant energy sensing means positioned in said detecting plane for generating first and second unidirectional voltages, the magnitude and polarity of each of which is indicative of the amount and sense of the displacement of a spot of light from the center of said means in one of two orthogonal directions, means for subjecting said representation to oscillatory rotary motion about an axis perpendicular thereto, whereby each of said voltages varies in amplitude and includes a component varying at twice the frequency of said oscillator rotary motion, means for generating an alternating voltage at twice the frequency of and in syncHronism with said oscillatory rotary motion, and two synchronous detector means each controlled by said alternating voltage for generating first and second error signal voltages the magnitude and polarity of which are indicative of the magnitude and phase of said components of said first and second unidirectional voltages respectively with respect to said alternating voltage.

Claim 4

In a correlator in which radiant energy is transmitted from an object through a variable density planar representation thereof to a detecting plane, apparatus for determining the translational misalignment of said object and said representation, comprising, radiant energy sensing means positioned in said detecting plane for generating first and second unidirectional voltages, the magnitude and polarity of each of which is indicative of the amount and sense of the displacement of a spot of light from the center of said means in one of two orthogonal directions, means for subjecting said representation to oscillatory rotary motion about an axis perpendicular thereto, whereby each of said voltages varies in amplitude and includes a component varying at twice the frequency of said oscillator rotary motion, means for generating an alternating voltage at twice the frequency of and in syncHronism with said oscillatory rotary motion, and two synchronous detector means each controlled by said alternating voltage for generating first and second error signal voltages the magnitude and polarity of which are indicative of the magnitude and phase of said components of said first and second unidirectional voltages respectively with respect to said alternating voltage.

Claim 5

In a correlator for indicating the amount of mismatch between an illuminated body and a partially transparent image thereof located in spaced parallel relation thereto in which such mismatch is determined by a radiant energy sensing means positioned to receive radiation transmitted from said body through said image, the improvement which comprises, means for oscillating said image about an axis perpendicular thereto, whereby said sensing means generates signals having alternating current components at both the fundamental and the second harmonic of the frequency of oscillation, means for generating first and second voltages in synchronism with the oscillation of said image having frequencies equal to and twice that of said oscillation respectively, and means for synchronously detecting said signals using each of said first and second voltages as a reference, whereby error signals indicative of mismatch are generated.

Claim 6

In a correlator for indicating the amount of mismatch between an illuminated body and a partially transparent image thereof located in spaced parallel relation thereto in which such mismatch is determined by a radiant energy sensing means positioned to receive radiation transmitted from said body through said image, the improvement which comprises, means for oscillating said image about an axis perpendicular thereto, whereby said sensing means generates signals having alternating current components at both the fundamental and the second harmonic of the frequency of oscillation, means for generating first and second voltages in synchronism with the oscillation of said image having frequencies equal to and twice that of said oscillation respectively, and means for synchronously detecting said signals using each of said first and second voltages as a reference, whereby error signals indicative of mismatch are generated.

Claim 7

A correlator for indicating the amount of mismatch between an illuminated body and a partially transparent image thereof located in spaced parallel relation thereto, comprising, a radiant energy sensing means for generating first, second and third unidirectional voltages, said first voltage having a magnitude indicative of the total amount of radiant energy reaching said sensing means, said second and third voltages indicating by their amplitude and polarity the magnitude and sense of the displacement in orthogonal directions of a spot of incident energy from the center of said sensing means, said sensing means being positioned to receive radiant energy transmitted from said body through said image, means for oscillating said image at a convenient frequency about an axis perpendicular thereto, whereby the quality of the match between said body and said image varies periodically, and whereby each of said voltages varies in amplitude, means for generating fourth and fifth voltages in synchronism with the oscillation of said image and having frequencies equal to and twice that of said convenient frequency respectively, means for synchronously detecting the variations in amplitude of said first voltage using said fourth voltage as a reference, whereby there is derived a first error signal indicative of the rotational mismatch between said body and said image, and means for synchronously detecting the amplitude variations in each of said second and third voltages using said fifth voltage as a reference, whereby there are generated second and third error signals indicative of the translational mismatch of said image and said body in said orthogonal directions.

Claim 8

A correlator for indicating the amount of mismatch between an illuminated body and a partially transparent image thereof located in spaced parallel relation thereto, comprising, a radiant energy sensing means for generating first, second and third unidirectional voltages, said first voltage having a magnitude indicative of the total amount of radiant energy reaching said sensing means, said second and third voltages indicating by their amplitude and polarity the magnitude and sense of the displacement in orthogonal directions of a spot of incident energy from the center of said sensing means, said sensing means being positioned to receive radiant energy transmitted from said body through said image, means for oscillating said image at a convenient frequency about an axis perpendicular thereto, whereby the quality of the match between said body and said image varies periodically, and whereby each of said voltages varies in amplitude, means for generating fourth and fifth voltages in synchronism with the oscillation of said image and having frequencies equal to and twice that of said convenient frequency respectively, means for synchronously detecting the variations in amplitude of said first voltage using said fourth voltage as a reference, whereby there is derived a first error signal indicative of the rotational mismatch between said body and said image, and means for synchronously detecting the amplitude variations in each of said second and third voltages using said fifth voltage as a reference, whereby there are generated second and third error signals indicative of the translational mismatch of said image and said body in said orthogonal directions.

Claim 9

In a correlator in which an illuminated body and a partially transparent image thereof are located in spaced-apart parallel relation to each other, apparatus for rotationally positioning said image to obtain the best correlation between said image and said body, comprising, radiant energy sensing means for generating a unidirectional voltage indicative of the amount of radiant energy falling thereon, said sensing means being located to receive radiant energy transmitted from said body through said image, means for oscillating said image about an axis perpendicular thereto, whereby said unidirectional voltage varies in amplitude, means for generating an alternating voltage in synchronism with and at the frequency of the oscillation of said image, means for synchronously detecting the variations in amplitude of said unidirectional voltage by employing said alternating voltage as a reference, whereby there is obtained a unIdirectional error signal the polarity and amplitude of which are indicative of the sense and magnitude of the rotational misalignment of the mean position of said image, and means responsive to said error signal for rotationally positioning said image so as to minimize said error signal.

Claim 10

In a correlator in which an illuminated body and a partially transparent image thereof are located in spaced-apart parallel relation to each other, apparatus for rotationally positioning said image to obtain the best correlation between said image and said body, comprising, radiant energy sensing means for generating a unidirectional voltage indicative of the amount of radiant energy falling thereon, said sensing means being located to receive radiant energy transmitted from said body through said image, means for oscillating said image about an axis perpendicular thereto, whereby said unidirectional voltage varies in amplitude, means for generating an alternating voltage in synchronism with and at the frequency of the oscillation of said image, means for synchronously detecting the variations in amplitude of said unidirectional voltage by employing said alternating voltage as a reference, whereby there is obtained a unIdirectional error signal the polarity and amplitude of which are indicative of the sense and magnitude of the rotational misalignment of the mean position of said image, and means responsive to said error signal for rotationally positioning said image so as to minimize said error signal.

Claim 11

A correlator for indicating the translational mismatch between an illuminated body and a partially transparent image thereof located in spaced parallel relation thereto, comprising, radiant energy sensing means for generating first and second unidirectional voltages the amplitude and polarity of each of which are indicative of the amount and sense of the displacement of a spot of radiant energy from the center thereof in one of two orthogonal directions, said sensing means being located to receive radiant energy transmitted through said body through said image, means for oscillating said image about an axis perpendicular thereto, whereby said unidirectional voltages vary in amplitude, means for generating an alternating voltage in synchronism with and at twice the frequency of the oscillation of said image, means for synchronously detecting the variations in amplitude of each of said unidirectional voltages by employing said alternating voltage as a reference, whereby there are obtained two unidirectional error signals the amplitude and polarity of each of which are indicative of the magnitude and phase of the amplitude variations of one of said unidirectional voltages, means controlled by said error signals for moving said sensing means in said orthogonal directions so as to reduce said error signals to zero, and means for generating signals indicative of the position of said sensing means with respect to a reference position.

Claim 12

A correlator for indicating the translational mismatch between an illuminated body and a partially transparent image thereof located in spaced parallel relation thereto, comprising, radiant energy sensing means for generating first and second unidirectional voltages the amplitude and polarity of each of which are indicative of the amount and sense of the displacement of a spot of radiant energy from the center thereof in one of two orthogonal directions, said sensing means being located to receive radiant energy transmitted through said body through said image, means for oscillating said image about an axis perpendicular thereto, whereby said unidirectional voltages vary in amplitude, means for generating an alternating voltage in synchronism with and at twice the frequency of the oscillation of said image, means for synchronously detecting the variations in amplitude of each of said unidirectional voltages by employing said alternating voltage as a reference, whereby there are obtained two unidirectional error signals the amplitude and polarity of each of which are indicative of the magnitude and phase of the amplitude variations of one of said unidirectional voltages, means controlled by said error signals for moving said sensing means in said orthogonal directions so as to reduce said error signals to zero, and means for generating signals indicative of the position of said sensing means with respect to a reference position.