Onto Innovation Inc.

4d Technology Corporation

Ad Technology Corporation

Brad Kimbrough

Erik Novak

James E Millerd

Neal Brock

Goldie Goldstein

A pixelated color mask is combined with a pixelated polarization mask in dynamic interferometry. The color mask includes a wavelength-selective bandpass filter placed in front of each camera pixel such that each set of contiguous four camera pixels is covered by two green bandpass filters, a red bandpass filter, and a blue bandpass filter. The pixelated phase mask is coupled to the color filters such that one polarization filter covers one set of color filters. At least three polarization filters are used to calculate phase. In addition, the color signals can be used, for example, to encode the motion of the interferometer, to provide very high speed autofocus or tip/tilt feedback, to create a color image of the object being measured, to automatically focus the system at different positions for different measurements conducted with different color sources, and to perform heterodyne interferometry with a single, vibration-immune measurement.

Interferometry with pixelated color discriminating elements combined with pixelated polarization masks

A cycloidal diffraction waveplate is combined with a pixelated phase mask (PPM) sensor in a dynamic fringe-projection interferometer to obtain phase-shifted interferograms in a single snap-shot camera operation that provides the phase information required to measure test surfaces with micrometer precision. Such mode of operation enables a portable embodiment for use in environments subject to vibration. A shifting mechanism coupled to the cycloidal waveplate allows temporal out-of-phase measurements used to remove noise due to test-surface characteristics. Two or more pixels of each unit cell of the PPM are combined to create super-pixels where the sum of the phases of the pixels is a multiple of 180 degrees, so that fringes are eliminated to facilitate operator focusing. By assigning colors or cross-hatch patterns to different ranges of modulation measured at the detector, the areas of best focus within the field of view are identified quantitatively to ensure measurements under best-focus conditions.

Single snap-shot fringe projection system

A substrate is tested with an interferometer in-line in a roll-to-roll processing operation to detect defects and exclude them from further processing. A tilt is introduced in the illumination path of the interferometer to allow detection of best fringes in a selected measurement field of view (FOV) that is smaller than the camera FOV in the direction transverse to the fringes. At each acquisition frame, the measurement FOV is shifted to track the best-fringe position within the camera field of view based on irradiance acquired at the previous step. As a result, the system is able to accommodate substrate flutter and roller runout and maintain focus on the substrate that allows precise identification of defects and their isolation for subsequent processing.

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Tucson, AZ, United States of America

Brad Kimbrough