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Sine Sectioning Illumination Method

IP.com Disclosure Number: IPCOM000044231D
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Hassebrook, LG: AUTHOR

Abstract

The topology of a surface can be determined by projecting a sinusoidal light pattern to the target surface at a determined incident angle. The reflected image is viewed from a different angle revealing lateral displacements and frequency changes related to the Z or elevation component of the topology. Basic Image Function I (x, y) The projected image (Fig. 1) contains two intensity component functions. The first function is: I1 (x, y) = K1 where K1 is a constant which sets the average intensity value I (x, y). The second function is a sine function: I2 (y) = K2 x sine (wy + K3) where K2 is a constant which controls the peak to peak value of intensity I (x, y), w is the frequency with respect to y and K3 is the phase angle with respect to y.

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Sine Sectioning Illumination Method

The topology of a surface can be determined by projecting a sinusoidal light pattern to the target surface at a determined incident angle. The reflected image is viewed from a different angle revealing lateral displacements and frequency changes related to the Z or elevation component of the topology. Basic Image Function I (x, y) The projected image (Fig. 1) contains two intensity component functions. The first function is: I1 (x, y) = K1 where K1 is a constant which sets the average intensity value I (x, y). The second function is a sine function: I2 (y) = K2 x sine (wy + K3) where K2 is a constant which controls the peak to peak value of intensity I (x, y), w is the frequency with respect to y and K3 is the phase angle with respect to y. The entire focused image is represented by: I (x, y) = I1 (x, y) + I2 (y) = K1 + K2 x sine (wy + K3) Incident Angle of Projection The image I (x, y) is projected at an incident angle Pi and the object reticle angle ro. ro is determined by exact focusing of the image onto the target surface. The pattern on the reticle is obtained by making a neutral density filter which is variable by the function L (I (x,y)), where L is the transformation due to the lens system used. It should be noted that the reflected or transmitted image I (x, y) is affected by scattering, absorption and Z positioning characteristics of the target topology. Lateral Distortion of Image (Fig. 2) Assume that the observation...