Method and apparatus for contour measurement

Claim 2

Surface-contour-measuring apparatus comprising: a source of illumination casting illumination diverging outwardly toward an object space in which a surface of an object to be examined may be positioned; shadow-casting structure disposed in the optical path of said diverging illumination between said source of illumination and said object space, said shadow-casting structure having a periodically repetitive pattern of segments which are alternatively opaque and transmissive with respect to illumination from said source and which cast a periodically repetitive shadow pattern having a certain spatial frequency of bright and dark regions toward the object space for impingement onto a surface positioned therein; optical interference means positioned to receive an image of said periodically repetitive pattern reflected From such surface, said optical interference means having a periodically repetitive pattern of segments having the same characteristics of alternate opacity and transmissivity as said segments of said shadow-casting structure to establish optical interference between the reflected image and the periodically repetitive pattern of said optical interference means; and means operatively interrelated with said shadow-casting structure and said optical interference means for selectively translating said shadow-casting structure and said optical interference means in phase synchronism with each other in a direction substantially parallel to the direction of said periodic repetition.

Claim 3

Apparatus as in claim 1, wherein: said shadow-casting structure and said optical interference means comprise a unitary grid member having a periodically repetitive pattern of segments and being mounted for translational movement in a direction substantially parallel to the direction of said periodic repetition; said selectively translating means comprising motive means operatively connected with said grid member for selectively imparting translational movement thereto.

Claim 4

Apparatus as in claim 2, wherein said motive means is operative to translate said grid member at a substantially constant velocity.

Claim 7

The method as in claim 4, wherein said second spatial frequency is substantially equal to said first spatial frequency.

Claim 8

The method as in claim 4, wherein the amount of said phase shift is sufficient to cause at least some of said cyclically variable interference patterns to undergo at least one cycle of variation.

Claim 9

The method as in claim 4, wherein said phase shift occurs at a substantially uniform rate.

Claim 10

The method as in claim 4, wherein said first and second spatial frequencies are shifted in phase by one cycle.

Claim 11

The method as in claim 8, wherein said step of phase shifting comprises: spatially shifting the phase of said first and second spatial frequencies to each of a plurality of fixed phase positions spaced equidistant throughout a spatial frequency cycle; and combining the interference patterns present at each of said fixed phase positions to produce a composite interference pattern which is a summation of the fixed phase position interference patterns.

Claim 12

The method as in claim 7, wherein said rate of phase shift is sufficiently great that the instantaneous intensity of the interference pattern components which are cyclically varied by said phase shift is perceptually integrated to the average value of such cyclically varied components.

Claim 13

The method as in claim 4, wherein said steps of mixing and phase shifting comprise: pictorially recording the spatially modulated first spatial frequency at a number of predetermined discrete phase shift positions in a cycle of said first spatial frequency; mixing the image of each such pictorial record with the image of said reference pattern shifted in phase to the one of said discrete phase shift positions whereat the corresponding pictorial record was made to establish saId interference pattern of spatial frequency components for each of said discrete phase shift positions; and adding together said discrete phase position interference patterns for said spatial frequency cycle so that interference pattern components which are cyclically variable in the direction of spatial phase shift have an average value for said phase shift cycle.

Claim 14

The method as in claim 11, wherein the spatial phase separation between each of said phase shift positions is uniform.

Claim 15

The method as in claim 11, wherein said step of pictorially recording comprises: preparing a first pictorial record of the spatially modulated first spatial frequency at a first spatial phase position; preparing a second pictorial record of the spatially modulated first spatial frequency at a second phase position spatially displaced 90* in a predetermined direction from said first phase position; preparing a third pictorial record by making a negative duplicate of said first pictorial record; preparing a fourth pictorial record by making a negative duplicate of said second pictorial record; mixing the spatial frequency on said first record with an image of said reference pattern which is in phase with said first spatial position to establish said interference pattern for the first spatial position; mixing the spatial frequency on said second record with an image of said reference pattern which is spatially displaced 90* in said predetermined direction from said first phase position to establish said interference pattern for the second spatial position; mixing the spatial frequency on said third record with an image of said reference pattern which is spatially displaced 180* in said predetermined direction from said first phase position to establish said interference pattern for the third position; mixing the spatial frequency on said fourth record with an image of said reference pattern which is spatially displaced 270* in said predetermined direction from said first phase position to establish said interference pattern for the fourth position; and adding together all of said spatial position interference patterns for the cycle of spatial frequency so that interference pattern components which are cyclically variable in the direction of spatial phase shift have an average value.

Claim 18

The method as in claim 14, wherein said shift of both said patterns is substantially an integral number of repetitive periods in the direction of pattern repetition.

Claim 19

The method as in claim 14, wherein said shift of both said patterns takes place at a rate of shift sufficiently great that the instantaneous intensity of the portions of said interference pattern which are affected by said sHift is perceptually integrated to the average value of such shift-affected portions.

Claim 20

The method as in claim 14, wherein said step of shifting comprises: shifting both said pattern of periodically repetitive illumination and said viewing structure to each of a plurality of fixed positions spaced equidistant throughout said repetitive pattern; and combining the interference pattern present at each of said fixed positions to produce a composite interference pattern which is a summation of the fixed position interference patterns.