Technique for scanning a microfilm image moving at a variable sp

Details Technique for scanning a microfilm image moving at a variable sp Technique for scanning a microfilm image moving at a variable sp

1989-06-26

1990-06-19

Groody, James J

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358214, H04N 718

Patent

active

049348213

ABSTRACT:
A technique, particularly for use in an image retrieval or image management system, for scanning a succession of microfilm images that moves within a flim transport mechanism at a variable user adjusted speed in order to implement an effective "search" mode of operation. Specifically, this technique relies on operating a CCD scanner at a constant clock rate, e.g. its maximum clock rate, while individual lines in a microfilm image are moving in front of the scanner at a rate that is faster than the integration time of the scanner. As such, the scanner generates a succession of composite lines of pixel data in which each pixel in such a line represents an average value of a corresponding group of vertically adjacent full resolution line spacings situated across an area of the microfilm image, where the number of line spacings in the area equals the value of a ratio of the user controlled speed of the microfilm to the speed of the microfilm when scanned at full resolution. Each composite line of data is then replicated a number of times typically equal to the number of full resolution line spacings in the scanned area associated therewith in order to form an associated group of identical lines of pixel data which, in turn, is stored in successive lines in a frame store memory. The entire contents of the frame store memory are read in succession and applied to a video display terminal to provide a subsequent full size display of the scanned image. Although the invention technique imparts increasing degradation, specifically loss of image resolution, into the displayed image as the (search) speed of the microfilm increases, this degradation is not visible to a human observer inasmuch as the visual acutance of that observer decreases substantially as the speed at which successive images are displayed increases.

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