Method and apparatus for automatically focusing an image-acquisi

Details Method and apparatus for automatically focusing an image-acquisi Method and apparatus for automatically focusing an image-acquisi

1989-08-28

1991-08-13

Razavi, Michael

Image analysis

Histogram processing

For setting a threshold

382 1, 358227, 358448, 358458, G06K 900

Patent

active

050402285

ABSTRACT:
Autofocusing of a lens (18) on a television camera (12) is achieved by first processing the image captured by the camera to establish a histogram of the intensity gradients for each of a plurality of small areas (pixels) in the captured image. From the histogram of the pixel intensity gradients, a focus index value, indicative of the sharpness of focus of the captured image, is established. The just-computed focus index value is then compared to the previously established value which is initially set to zero. The difference between the just- established and previously established focus index values establishes the direction in which the lens is incrementally stepped to more sharply focus the image. The steps of (a) capturing the image, (b) establishing the intensity gradient histogram, (c) comparing focus index value to the previously established value, and (d) incrementally stepping the lens are repeated as long as the just-established focus index values exceeds the previous value. Once the focus index value no longer exceeds the previously established value, the lens is stepped by an amount dependent on the just-established and previously established focus index values to sharply focus the image.

REFERENCES:
patent: 3932733 (1976-01-01), Olsen et al.
patent: 4601057 (1986-07-01), Tsugi et al.
patent: 4700225 (1987-10-01), Hara et al.
patent: 4814889 (1989-03-01), Covey
patent: 4816919 (1989-03-01), Coates
Yoda et al., An Automatic Wafer Inspection System Using Pipelined Image Processing Techniques, Jan. 1988, 4-16.

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