Technique for scanning a microfilm image moving at a variable speed
First Claim
1. A method for scanning at a variable resolution a visual depiction of a discrete image portion moving at a defined speed and for forming a bit-mapped representation of the image portion in a frame store memory, the method comprising the steps of:
- measuring a duration of an interval of time during which the image portion moves a pre-determined distance past a scanner;
determining, in response to the measured duration, a first number of adjacent full resolution image line spacings in an area in said image portion that are to be exposed to the scanner;
scanning said area to form a line of composite pixel values, wherein the value of each pixel in said composite line is a function of the value of a corresponding full resolution pixel occurring across said area;
generating, in response to the pixel values in said composite line, a group having a second number of successive lines of pixel values; and
storing the group of lines of pixel values in a corresponding area of a frame store memory.
1 Assignment
0 Petitions
Accused Products
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.
43 Citations
34 Claims
-
1. A method for scanning at a variable resolution a visual depiction of a discrete image portion moving at a defined speed and for forming a bit-mapped representation of the image portion in a frame store memory, the method comprising the steps of:
-
measuring a duration of an interval of time during which the image portion moves a pre-determined distance past a scanner; determining, in response to the measured duration, a first number of adjacent full resolution image line spacings in an area in said image portion that are to be exposed to the scanner; scanning said area to form a line of composite pixel values, wherein the value of each pixel in said composite line is a function of the value of a corresponding full resolution pixel occurring across said area; generating, in response to the pixel values in said composite line, a group having a second number of successive lines of pixel values; and storing the group of lines of pixel values in a corresponding area of a frame store memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
-
-
24. Apparatus for scanning at a variable resolution a visual depiction of a discrete image portion moving at a defined speed and for forming a bit-mapped representation of the image portion in a frame store memory, the apparatus comprising:
-
means for measuring a duration of an interval of time during which the image portion moves a pre-determined distance past a scanning means; means for determining, in response to the measured duration, a first number of adjacent full resolution image line spacings in an area in said image portion that are to be exposed to the scanning means; said scanning means for scanning said area to form a line of composite pixel values, wherein the value of each pixel in said composite line is a function of the value of a corresponding full resolution pixel occurring across said area; means for generating, in response to the pixel values in said composite line, a group having a second number of successive lines of pixel values; and means for storing the group of lines of pixel values in a corresponding area of a frame store memory. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
-
Specification