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1. (CA2234960) ASTIGMATISM MEASUREMENT APPARATUS AND METHOD

Office : Canada
Application Number: 2234960 Application Date: 18.10.1996
Publication Number: 2234960 Publication Date: 01.05.1997
Publication Kind : A1
Prior PCT appl.: Application Number:US1996016787 ; Publication Number: Click to see the data
IPC:
G06K 9/60
G01M 11/02
G PHYSICS
06
COMPUTING; CALCULATING; COUNTING
K
RECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
9
Methods or arrangements for reading or recognising printed or written characters or for recognising patterns, e.g. fingerprints
60
Combination of image acquisition and preprocessing functions
G PHYSICS
01
MEASURING; TESTING
M
TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
11
Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
02
Testing of optical properties
CPC:
G01M 11/0264
G01M 11/0242
Applicants: NEOPATH, INC.
Inventors: FROST, KEITH L.
LINDOW, WILLIAM C.
RILEY, JAMES K.
HANSEN, KIM J.
STEPHANICK, JAMES A.
PHAN, TUAN
Priority Data: 08/547,653 24.10.1995 US
Title: (EN) ASTIGMATISM MEASUREMENT APPARATUS AND METHOD
(FR) DISPOSITIF ET PROCEDE POUR LA MESURE DE L'ASTIGMATISME
Abstract: front page image
(EN) A computer (30) receives image data from a star-shaped optical target (18) 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 (83). A microscope slide stage (16), carrying the target (18), 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 (85, 86, 89). 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 (134). The presence of a distorted point spread function that varies along the optical axis indicates astigmatism (136).


Also published as:
EP0858638JPH11514445AU1996074583WO/1997/015898