Determination of ambient light level changes in visual images

Details Determination of ambient light level changes in visual images Determination of ambient light level changes in visual images

1990-09-11

1992-09-29

Razavi, Michael

Image analysis

Histogram processing

For setting a threshold

382 37, 382 4, 358105, G06K 900

Patent

active

051519453

ABSTRACT:
A visual image comparison method is provided, including the steps of: obtaining a first digital representation of a first visual image, where the first digital representation comprises a first plurality of pixels, and each pixel has a gray scale indicative of light intensity; obtaining a second digital representation of a second visual image, where the second digital representation comprises a second plurality of pixels, and each pixel has a gray scale indicative of light intensity; and selectively making a first predetermined number of comparisons of corresponding pixels from the first and second digital representations to determine whether a difference in ambient light intensity exists between the first and second visual images, and, selectively making a second predetermined number of comparisons of corresponding pixels from the first and second digital representations if and only if no difference in ambient light intensity exists between the first and second visual images, and indicating an alarm condition when a percentage of the second predetermined number of comparisons result in pixels having a difference in gray scale of a predetermined amount. Apparatus is also described for the purpose of implementing the method.

REFERENCES:
patent: 4337481 (1982-06-01), Mick et al.
patent: 4408224 (1983-10-01), Yoshida
patent: 4455550 (1984-06-01), Iguchi
patent: 4679077 (1987-07-01), Yuasa et al.
patent: 4737847 (1988-04-01), Araki et al.

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