Abstract: Data to be stored in a frame buffer (12) that stores data representing an image are drawn from a look-up table (34). The look-up table (34) contains conversion data and is addressed by the output of a multiplexer circuit (24). The multiplexer circuit (24) receives its inputs from the data output port of the frame buffer (12), from a register (42), and from an analog-to-digital converter (22) that converts the output of a video camera (20) to digital signals. In response to different values on selection-signal lines (36), the multiplexer circuit (24) assembles the address that it applies to the look-up table (34) from different combinations of the outputs of the frame buffer (12), the register (42), and the analog-to-digital-converter (22).

Abstract: Level data on an output line (24) carrying the digitized output of a video camera and analog-to-digital converter (12) is processed by a combination circuit (10) to store in an acquisition memory (16) the results of a feature-identification or histogram operation. In a histogram operation, the memory locations of the acquistion memory (16) represent the bins into which the levels represented by the level data are sorted, and the contents of those locations indicate the number of picture elements whose levels fall in those bins. In feature identification, the contents of successive memory locations in the acquistion memory (16) contain the positions of those picture elements whose levels have a selected feature. Common circuitry performs both the histogram and feature-identification functions.

Abstract: A grid of electrical conductors for locating the position of a stylus utilizes a reduced number of line drivers. The grid utilizes twice as many conductors as required by conventional grids for a given resolution. The conductors are divided into coarse and fine sets which are interleaved and coextensive in the long dimension of the conductors. The coarse set is divided into subsets which consist of a predetermined number of conductors in close proximity to each other, adjacent coarse conductors being separated by only one fine conductor. The fine set is divided into a number of subsets equal to the number of conductors in each coarse subset. The number of conductors in each fine subset equals the number of coarse subsets. Each of the conductors of the fine subsets is spaced one from the other by a number of fine conductors equal to the number of coarse subsets. The conductors of each subset are connected to each other and to the output of a single driver.