Neopath, Inc.

Tuan H Phan

James K Riley

Kim J Hansen

Keith L Frost

James A Stephanick

William C Lindow

William E Ortyn

Wayne A Biggs

Yuhui Cheng

Improving accuracy of frequency response measurements of linear systems using modulation transfer function test compensation. An optical imaging system illuminates and images an input test pattern. A processor measures a modulation transfer function. The processor determines a compensating factor for error in the input test pattern duty cycle. The driving function for the measurement is a test pattern having a periodic waveform approximating a square wave with an error in duty cycle. A windowed fast fourier transform on a greyscale image of the test pattern generates odd harmonics. Adjusting amplitude values of the odd harmonics corrects for the error in resolution target duty cycle.

Modulation transfer function test compensation for test pattern duty

A computer receives image data from a star-shaped optical target in the object plane and calculates angle-dependent boundary sharpness. The horizontal, x-direction, amplitude derivative and the vertical, y-direction, amplitude derivative are computed over a portion of each star pattern image from a Z panning sequence. A microscope slide stage, carrying the target, is moved vertically from a level just below where the target is in focus to a level just above where the target is in focus. For each small increment of vertical motion, Z panning, an image of the star pattern is captured for analysis. Computations are performed on the differentiated images to search for evidence of elongation of the point spread function and variation with stage Z position of the angle of long axis of such an out-of-round point spread function. The presence of a distorted point spread function that varies along the optical axis indicates astigmatism.

Astigmatism measurement apparatus and method based on a focal plane

Separation apparatus and method for measuring focal plane

Growing community of inventors

Lynwood, WA, United States of America

Tuan H Phan