Eastman-Kodak Company

John E Greivenkamp, Jr

Russell J Palum

David N Lambeth

James W Meyer

Kevin G Sullivan

Method and apparatus are disclosed for providing absolute Moire distance measurements of a diffusely reflective surface from a reference position. More particularly, a first grating is located, formed, or printed on the diffusely reflective surface. An image of the first grating is formed on a second grating or detector array by imaging means for generating a Moire pattern that is detected by a detector means. At the reference position of the diffusely reflective surface relative to the imaging means, the periods of the image of the first grating and the second grating match. Movement of the diffusely reflective surface from the reference position in a direction normal thereto, produces a spatially varying intensity pattern at the detector means which results from the shifting and magnification mismatch between the pattern of the image of the first grating and the pattern of the second grating. Measuring the amount of magnification differences between the two patterns provides information related to the instantaneous absolute distance of the diffusely reflective surface from the reference position. Various methods are disclosed for using the information from the detector means for determining the absolute distance measurements.

Method and apparatus for absolute Moire distance measurements using a

Method and apparatus are disclosed for providing Moire distance and displacement measurements of a diffusely reflective surface of an object or support. More particularly, a first grating is physically located, formed, or printed on the diffusely reflective surface. An image of the first grating is formed on a second grating by an imaging means for generating a Moire pattern behind the second grating. At an initial position of the diffusely reflective surface relative to the imaging means, the periods of the image of the first grating and the second grating match. Movement of the diffusely reflective surface in a direction normal thereto and away from the initial position produces a spatially varying intensity pattern caused by the Moire between a shifting and changing magnified pattern of the image of the first grating and a pattern of the second grating. The temporal intensity changs in the Moire pattern are detected and are used to produce information related to the instantaneous distance and displacement of the diffusely reflective surface from the initial position.

Moire distance measurements using a grating printed on or attached to a

A Moire distance measurement technique for measuring the distance that a diffusely reflecting surface moves involves projecting a first grating onto the surface, imaging the projected grating onto a second grating to form a Moire pattern, and measuring a change in the Moire pattern as the surfaces move to determine the distance that the surface has moved.

Moire distance measurement method and apparatus

A process for scanning halftoned images with a sampled or electronic imaging system includes the steps of first optically low-pass filtering the scene, then oversampling the scene at a rate several times that required for display bandwidth, and finally putting the resulting data through an electronic or digital low-pass filter/resampling operation to reduce the system data load. The oversampling advantageously shifts unwanted aliasing between the halftone and sampling frequencies to frequencies above the display bandwidth, so that the aliasing may then be filtered out without affecting signals within the bandwidth of the display.

System for scanning halftoned images

The measurement range of Moire contouring techniques is extended beyond the Nyquist frequency limit by constraining the reconstruction of a surface contour according to a priori knowledge about the surface. In one example the a priori knowledge is that the surface is smooth, being described by a function having continuous derivatives, and the location of a region where the surface changes by less than C/2 per sample. In another example, the a priori knowledge is the location and height of a step discontinuity to within C/2, where C is the contour interval.

Extended-range moire contouring

A technique is described for extending the measurement range of interferometry past the Nyquist limit of the sampling frequency of the interferogram. The absolute phase values measured by an interferometer are reconstructed by applying constraints based upon a priori knowledge of the absolute phase values. The constraints include the knowledge that one or more derivatives of the spatial distribution of phase values is a continuous function, and the knowledge of step heights to within .lambda./2.

Sub-nyquist interferometry

An optical spatial frequency filter of the type having a pair of birefringent elements with means for changing the polarization state of light between them is given a substantially color dependent spatial frequency response. The filter comprises a wavelength dependent means for changing the polarization state of light between the birefringent elements such that the polarization state of light of a first color is changed by a first amount and the polarization state of light of a second color is changed by a second amount sufficiently different from the first amount such that the spatial frequency response of the spatial frequency filter is substantially color dependent. The filter is particularly useful with a color image sensor of the type having a first sampling frequency in a first color and a second sampling frequency different from the first in a second color. The filter is made to have a frequency response in the first and second colors in relation to the respective first and second sampling frequencies of the sensor. The filter has the advantage that, when used with the color image sensor, aliasing is selectively reduced in each color without reducing resolution in the other colors.

Optical spatial frequency filter

A simple rangefinder device, suitable for two-zone ranging applications, comprises a single lens, a light emitter located with respect to the lens to produce a beam of light, and a light detector located with respect to the lens to define a field of view. The effective lens aperture for the emitter and the detector substantially coincide and the field of view of the detector overlaps the light beam in a detection region extending away from the lens for a predetermined distance. Signal processing electronics receive a signal produced by the light detector to produce a signal representing the presence or absence of a reflecting object in the detection region.

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Rochester, NY, United States of America

John E Greivenkamp, Jr