Digital correlation pattern tracker

Claim 5

The system of claim 2 wherein said detector means further comprises: digitizing means for receiving the outputs of each of said photosensor strips and comparing each of said outputs to at least one reference level during successive discrete intervals of time during a scan, producing as an output, digital wordS indicative of the relation of each sensor''s output to said reference level during each of said discrete intervals of time.

Claim 6

The system of claim 3 wherein said correlation means comprises: means for storing the digital words produced by at least two successive scans; means for repeatedly shifting the digital words resulting from a later scan in relation to the corresponding digital words resulting from the immediately preceding scan; means for comparing the digital words resulting from the later scan to the corresponding words from the immediately preceding scan, said comparison effected for each shifted position of said later scan words.

Claim 7

The system of claim 4 wherein said comparing means comprises: means for modulo-two adding each bit of a word from a later scan to the corresponding bit of the corresponding word from the immediately preceding scan, said adding means producing an output indicative of the total number of modulo-two additions wherein the corresponding bit values of corresponding words are dissimilar.

Claim 8

The system of claim 5 further comprising: means for determining which shifted position of each later scan word minimizes said adding means output, the number of shifts required to achieve said shifted position being a function of the motion of the pattern between the time of said later and said immediately preceding scan.

Claim 9

The system of claim 6 wherein said detector means further comprises: digitizing means for receiving the output of said photosensor strip and comparing said output to at least one reference level during successive discrete intervals of time during a scan, producing as an output, a digital word indicative of the relation of said sensor''s output to said reference level during each of said discrete intervals of time.

Claim 10

The system of claim 7 wherein said correlation means comprises: means for storing the digital words produced by at least two successive scans; means for repeatedly shifting the digital word resulting from a later scan in relation to the corresponding digital word resulting from the immediately preceding scan; means for comparing the digital word resulting from the later scan to the corresponding word from the immediately preceding scan, said comparison effected for each shifted position of said later scan word.

Claim 11

The system of claim 8 wherein said comparing means comprises: means for modulo-two adding each bit of the word from said later scan to the corresponding bit of the word from said immediately preceding scan, said adding means producing an output indicative of the total number of modulo-two additions wherein the corresponding bit values are dissimilar.

Claim 12

The system of claim 9 further comprising: means for determining which shifted position of each last scanned word minimizes said adding means output, the number of shifts required to achieve said shifted position being a function of the motion of the pattern in said scan direction between the time of said later and said immediately preceding scan.

Claim 15

Apparatus for determining the motion of an image of a pattern in the focal plane of a focusing means comprising in combinatiOn: an array of at least two strip shaped photosensor elements; drive means for repetitiously providing relative movement between said sensor array and the pattern image thereby causing said sensor array to repetitiously scan the pattern image; digitizing means receiving the output of each of said photosensor elements during each scan and comparing each such output to at least one referenced level during successive discrete intervals of time, said digitizing means providing as an output digital words indicative of the relation of each of said photosensor''s outputs to said reference level during each of said discrete intervals of time of a scan; means for repeatedly shifting the digital words resulting from a later scan in relation to the corresponding words from the immediately preceding scan; means for modulo-two adding each bit of a word from a later scan to each corresponding bit of the corresponding word from the immediately preceding scan, said adding means producing an output indicative of the total number of additions wherein the corresponding bit values of corresponding words are dissimilar; means for determining which shifted position of each later scan word minimizes said adding means output, the number of shifts required to achieve said shifted position being a function of the motion of the pattern between the time of said later and said immediately preceding scan.

Claim 16

Apparatus for determining the motion of an image of a pattern in the focal plane of a focusing means comprising in combinatiOn: an array of at least two strip shaped photosensor elements; drive means for repetitiously providing relative movement between said sensor array and the pattern image thereby causing said sensor array to repetitiously scan the pattern image; digitizing means receiving the output of each of said photosensor elements during each scan and comparing each such output to at least one referenced level during successive discrete intervals of time, said digitizing means providing as an output digital words indicative of the relation of each of said photosensor''s outputs to said reference level during each of said discrete intervals of time of a scan; means for repeatedly shifting the digital words resulting from a later scan in relation to the corresponding words from the immediately preceding scan; means for modulo-two adding each bit of a word from a later scan to each corresponding bit of the corresponding word from the immediately preceding scan, said adding means producing an output indicative of the total number of additions wherein the corresponding bit values of corresponding words are dissimilar; means for determining which shifted position of each later scan word minimizes said adding means output, the number of shifts required to achieve said shifted position being a function of the motion of the pattern between the time of said later and said immediately preceding scan.

Claim 17

The apparatus of claim 12 further characterized in that said photosensor array comprises: at least two aligned photosensor strips disposed along each of two coordinate axes.

Claim 18

In a telescope tracking system wherein an image of a pattern to be tracked is directed onto the focal plane of the telescope, and wherein said telescope is adapted to dither to sweep the image along a predetermined trajectory across said focal plane, means for determining motion of said pattern in said focal plane comprising: an array of at least two orthogonally disposed photosensor strips disposed in said focal plane; means for dithering said telescope to cause said image to repetitiously sweep consecutively across first one and then the other of the photosensor surfaces, thus repetitiously scanning said image across said sensor array; digitizing means for receiving the outputs of each of said photosensor strips and comparing each of said outputs to at least one reference level during successive discrete intervals of time during the course of a scan, producing as an output, digital words indicative of the relation of each sensor''s output to said threshold level during each of said discrete intervals of time; means for repeatedly shifting the digital words resulting from a later scan in relation to the corresponding digital words resulting from the immediately preceding scan; means for correlating the digital words resulting from a later scan to the corresponding words from the immediately preceding scan, said correlation effected for each shifted position of said corresponding later scan words; means for determining which shifted position of said later scan words results in maximum correlation with said corresponding prior scan words, the number of shifts required to achieve said shifted position being a function of the motion of said pattern in said image plane between the time of said later and said immediately preceding scan.

Claim 19

In a telescope tracking system wherein an image of a pattern to be tracked is directed onto the focal plane of the telescope, and wherein said telescope is adapted to dither to sweep the image along a predetermined trajectory across said focal plane, means for determining motion of said pattern in said focal plane comprising: an array of at least two orthogonally disposed photosensor strips disposed in said focal plane; means for dithering said telescope to cause said image to repetitiously sweep consecutively across first one and then the other of the photosensor surfaces, thus repetitiously scanning said image across said sensor array; digitizing means for receiving the outputs of each of said photosensor strips and comparing each of said outputs to at least one reference level during successive discrete intervals of time during the course of a scan, producing as an output, digital words indicative of the relation of each sensor''s output to said threshold level during each of said discrete intervals of time; means for repeatedly shifting the digital words resulting from a later scan in relation to the corresponding digital words resulting from the immediately preceding scan; means for correlating the digital words resulting from a later scan to the corresponding words from the immediately preceding scan, said correlation effected for each shifted position of said corresponding later scan words; means for determining which shifted position of said later scan words results in maximum correlation with said corresponding prior scan words, the number of shifts required to achieve said shifted position being a function of the motion of said pattern in said image plane between the time of said later and said immediately preceding scan.

Claim 20

The system of claim 14 further characterized in that said sensor array comprises: at least two aligned photosensor strips disposed along each of two coordinate axes.