UBC Theses and Dissertations
A television camera to computer interface Yusuf, Tundey
This is an instrumentation thesis. The interface system discussed is a link between an ordinary TV camera and a computer for storage of visual data. The same system can also be used as a link between the computer and a display monitor. Because of its wide bandwidth, a video signal cannot be sampled at the Nyquist rate and presented to a computer. Previous interface systems overcame the problem by scanning slowly on an element-by-element basis using a special scanner and then presenting the samples to the computer. After processing, the data would be read out at the same slow rate and displayed on a special display monitor. The interface described in this thesis will accept material obtained from an ordinary TV camera scanning at standard rate. By using a "stroboscope" sampling technique the samples are presented to the computer slowly enough for it to process. After processing, the data is displayed in a similar manner on a normally scanned monitor for evaluation. Basically the interface operates as follows: A TV camera video signal is sampled at a rate slow enough for computer acceptance. The camera scans the same picture several hundred times until all the points representing the picture have been sampled and stored, the sampling is controlled such that all the points are each sampled only once. Because of the sampling method consecutive samples in the computer do not correspond to adjacent points on the picture being stored. It may therefore be necessary to programme the computer to arrange the samples such that adjacent data in the computer represent consecutive picture points before processing. After processing, the samples may be rearranged and read out for display in the same order they were stored. The horizontal resolution of the picture being stored can be varied quite easily in steps. For example, a system designed to have a maximum of 480 points/line will also have the ability to provide such lower resolutions as 60, 120 and 240 points/lines. This variation is made possible by the design of the hardware. By software the vertical resolution can be varied between an upper limit of 525 lines per picture and such near submultiples of this as 263 and 131 lines/picture. The thesis is discussed in relation to the PDP-9 computer on which most of the work described was done. However, the system interfaces readily with other computers.
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