Method and apparatus for three frame range imaging

Claim 2

Apparatus for imaging a scene comprising: means for illuminating said scene with a moving periodic modulation pattern; means, offset from said illuminating means, for converting light reflected from a plurality of points in said scene into electrical signals; and means for determining the relative phase with respect to said periodic modulation pattern of light reflected from each of said points in said scene using three of said electrical signals for each of said points generated at different times, said relative phase being related to the relative range of said points.

Claim 3

Apparatus as in claim 1 wherein said converting means includes an electronic camera.

Claim 4

Apparatus as in claim 1 wherein said determining means includes a computer responsive to said converting means.

Claim 5

Apparatus as in claim 1 wherein said illuminating means comprises: a source of light for illuminating said scene; a plate having a transmissiveness which varies with said periodic pattern in a first direction; and means for moving said plate along said first direction between said light source and said scene.

Claim 6

Apparatus as in claim 4 wherein said plate has transmissive regions separated by opaque regions in said direction.

Claim 7

Apparatus as in claim 1 wherein said illuminating means comprises: a source of light for illuminating said scene; a disk having a transmissiveness that varies with said periodic pattern circumferentially; and means for rotating said disk between said light source and said scene.

Claim 8

Apparatus as in claim 6 wherein said disk has transmissive regions separated by opaque regions in a circumferential direction.

Claim 9

Apparatus as in claim 1, wherein said periodic pattern has transmissive regions separated by opaque regions.

Claim 10

Apparatus as in claim 1 wherein said converting means integrates received light over a predetermined period of time.

Claim 11

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising: means for illuminating said scene with a moving periodic modulation pattern; means, offset from said illuminating means, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; and means for determining the relative phase with respect to said periodic modulation pattern of light reflected from each of said areas in said scene using three frames of said intensity values, said moving pattern having shifted in phase between consecutive ones of said three frames, said relative phase being related to the relative range of said areas.

Claim 12

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising: means for illuminating said scene with a moving periodic modulation pattern; means, offset from said illuminating means, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; and means for determining the relative phase with respect to said periodic modulation pattern of light reflected from each of said areas in said scene using three frames of said intensity values, said moving pattern having shifted in phase between consecutive ones of said three frames, said relative phase being related to the relative range of said areas.

Claim 13

Apparatus as in claim 10 further comprising means for summing said intensity values for each of said pixels, said sum being indicative of the intensity of light reflected from each of said pixels.

Claim 14

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising: a source of light for illuminating said scene; means, offset from the axis between said light source and said scene, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; means for modulating said light source to produce a moving, periodic pattern on said scene; means for obtaining first, second and third frames of values from said generating means such that said moving pattern shifts in phase with respect to said pattern by one-third cycle between consecutive frames; means for taking the difference between said values of each of said pixels in said first and third frames, and the difference between said values of each of said pixels in said second and third frames; and means for determining the angle of the vector formed by said differences for each of said pixels, said angle being indicative of relative range.

Claim 15

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising: a source of light for illuminating said scene; means, offset from the axis between said light source and said scene, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; means for modulating said light source to produce a moving, periodic pattern on said scene; means for obtaining first, second and third frames of values from said generating means such that said moving pattern shifts in phase with respect to said pattern by one-third cycle between consecutive frames; means for taking the difference between said values of each of said pixels in said first and third frames, and the difference between said values of each of said pixels in said second and third frames; and means for determining the angle of the vector formed by said differences for each of said pixels, said angle being indicative of relative range.

Claim 16

Apparatus as in claim 12 wherein said obtaining means, taking means and determining means include a digital computer.

Claim 17

Apparatus as in claim 12 wherein said modulating means includes: a disk having a transmissiveness that varies with said periodic pattern circumferentially; and means for rotating said disk between said light source and said scene.

Claim 18

Apparatus as in claim 14 wherein said disk has transmissive regions separated by opaque regions in a circumferential direction.

Claim 19

Apparatus as in claim 12 wherein said periodic pattern has transmissive regions separated by opaque regions.

Claim 20

Apparatus as in claim 12 wherein said generating means integrates received light over a predetermined period of time.

Claim 21

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising; a source of light for illuminating said scene; means, offset from the axis between said light source and said scene, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; means for modulating said light source to produce a moving, periodic pattern on said scene; first means for storing a first frame of said values; second means for storing a second frame of said values; third means for storing a third frame of values, said moving pattern having shifted in phase with respect to said pattern by 120° between consecutive frames; first means for determining first difference values related to the differences between said intensity values for each of said pixels in said first and third frames; second means for determining second difference values related to the differences between said intensity values for each of said pixels in said second and third frames; and means for determining the arc tangent of a value related to the quotient of the sum of said first and second difference values and the difference of said first and second difference values for each of said pixels, said arc tangent being indicative of relative range.

Claim 22

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising; a source of light for illuminating said scene; means, offset from the axis between said light source and said scene, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; means for modulating said light source to produce a moving, periodic pattern on said scene; first means for storing a first frame of said values; second means for storing a second frame of said values; third means for storing a third frame of values, said moving pattern having shifted in phase with respect to said pattern by 120° between consecutive frames; first means for determining first difference values related to the differences between said intensity values for each of said pixels in said first and third frames; second means for determining second difference values related to the differences between said intensity values for each of said pixels in said second and third frames; and means for determining the arc tangent of a value related to the quotient of the sum of said first and second difference values and the difference of said first and second difference values for each of said pixels, said arc tangent being indicative of relative range.

Claim 23

Apparatus as in claim 18 further comprising means for summing said intensity values for each of said pixels, said sum being indicative of the intensity of light reflected from each of said pixels.

Claim 24

Apparatus as in claim 18 wherein said first difference determining means, said second difference determining means and said arc tangent determining means include a digital computer.

Claim 25

Apparatus as in claim 18 wherein said modulating means includes: a disk having a transmissiveness that varies with said periodic pattern circumferentially; and means for rotating said disk between said light source and said scene.

Claim 26

Apparatus as in claim 21 wherein said disk has transmissive regions separated by opaque regions in a circumferential direction.

Claim 27

Apparatus as in claim 21 wherein: said disk has a transmissiveness that varies circumferentially with two periodic, superimposed patterns, one of said patterns having a frequency higher than the other said patterns; and said apparatus includes means for generating relative coarse and fine range data.

Claim 28

Apparatus as in claim 18 further comprising: second means for modulating said light source, said second modulating means producing a periodic pattern having a lower frequency than said modulating means; and means, responsive to intensity values while said second modulation means is actuated, for producing coarse, relative range data.

Claim 29

Apparatus as in claim 18 wherein said moving periodic pattern shifts one complete cycle for every three frames of intensity values generated by said generating means.

Claim 30

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising: a source of light for illuminating said scene; means, offset from the axis between said light source and said scene, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; means for modulating said light source to produce a moving, periodic pattern on said scene; first means for storing a frame of said values; second means for storing a frame of said values; control means for causing (1) a first frame of said values to be stored in said first storing means, (2) a second frame of said values to be stored in said second storing means, and (3) said values in said first and second storing means to be read out and subtracted from corresponding pixels in a third frame, the differences being stored in said first and second storing means, said moving pattern having shifted in phase with respect to said pattern by 120° between consecutive frames; and means for determining the arc tangent of a value related to the quotient of the sum of said first and second difference values and the difference of said first and second difference values for each of said pixels, said arc tangent being indicative of relative range.

Claim 31

Apparatus for creating an image of a scene, said image including a plurality of pixels, each pixel being associated with an area of said scene, said apparatus comprising: a source of light for illuminating said scene; means, offset from the axis between said light source and said scene, for generating intensity values for each of said pixels related to the amount of light reflected from said scene; means for modulating said light source to produce a moving, periodic pattern on said scene; first means for storing a frame of said values; second means for storing a frame of said values; control means for causing (1) a first frame of said values to be stored in said first storing means, (2) a second frame of said values to be stored in said second storing means, and (3) said values in said first and second storing means to be read out and subtracted from corresponding pixels in a third frame, the differences being stored in said first and second storing means, said moving pattern having shifted in phase with respect to said pattern by 120° between consecutive frames; and means for determining the arc tangent of a value related to the quotient of the sum of said first and second difference values and the difference of said first and second difference values for each of said pixels, said arc tangent being indicative of relative range.

Claim 32

Apparatus as in claim 26 wherein said periodic pattern has transmissive regions separated by opaque regions.

Claim 33

Apparatus as in claim 26 wherein: said modulating means includes means for modulating said light source to produce two moving periodic patterns on said scene, one of said periodic patterns having a frequency greater than the other periodic pattern; and said apparatus includes means for generating relative coarse and fine range data.

Claim 34

Apparatus as in claim 26 wherein said generating means includes an electronic camera.

Claim 35

Apparatus as in claim 26 wherein said control means and said determining means includes a digital computer.

Claim 36

Apparatus as in claim 26 wherein said moving periodic pattern shifts one complete cycle for every three frames of intensity values generated by said generating means.

Claim 39

A method as in claim 32 wherein said monitoring step includes the step of integrating said reflected light over a predetermined time.

Claim 42

A method as in claim 34 further comprising the step of summing said intensity values for corresponding pixels, said sum being indicative of the intensity of light reflected from each of said pixels.

Claim 45

A method as in claim 36 wherein said monitoring step includes the step of integrating said reflected light over a predetermined period of time.

Claim 48

A method as in claim 38 wherein: said illuminating step includes the step of illuminating said scene with first and second moving periodic modulation patterns, said first and second modulation patterns moving at different frequencies and having different periods; and said method further comprises the step of processing frames of intensity values to obtain coarse and fine range data.

Claim 49

A method as in claim 38 wherein said pattern shifts one complete cycle for every three frames of intensity values monitored in said monitoring step.