Pattern detection in two dimensional signals
First Claim
1. A method of detecting a pattern feature in a two-dimensional electrical signal applied to a coordinate array of storage cells comprising, in a preliminary step, storing a plurality of template words, each template word being a plurality of storage cell address words, individual ones of which are associated with the individual values of one coordinate direction of the array and represent address values in the other coordinate direction, of cell locations coincident with a template, defining the pattern feature, mapped onto the array, and operationally applying a two-dimensional signal to said array of storage cells, extracting a stored template word addressing simultaneously a set of cells, one at each value of said one coordinate direction, at address values of said other coordinate direction defined by the template word, reading the signal levels of the addressed cells, determining whether substantially all of the levels of the addressed cells are characteristic of the levels of a pattern feature template, and in response to a successful determination, providing an indication that the pattern feature has been detected in the two dimensional electrical signal.
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Abstract
Detection of a pattern feature in a two dimensional signal e.g. as produced by scanning a linear array of detectors, is performed by apparatus 20 (FIG. 3) comprising an M×N array 21 of serial input shift registers 40 in which the signal, digitized to binary level samples and on M channels, is stored. Sampling and input occur at timing intervals controlled by timing means 29, previous samples being shifted one stage through the registers. Pattern features each comprising a binary level pattern formed on an M×N element map of the array and comprising only one element per row, are encoded as sets of M binary address words defining shift register addresses in M.log2 N-bit template words stored in ROM 23'"'"'. A ROM address register 33'"'"' points to a ROM location and extracts a template word on bus 25 which comprises M.log2 N lines so that all the address words are extracted in parallel. A 1-out of-N data selector connected to parallel outputs of each shift register is addressed by its own log2 N lines of bus 25 and in accordance with the value of the address word outputs the state of the appropriate shift register stage. The selectors produce outputs simultaneously to an M-input AND gate 55. If all inputs are `1` then the pattern feature defined by the signal distribution in the registers corresponds to the template word and detection of the pattern is signalled. In each timing interval a succession of clock pulses from timing means 29 indexes address register 33'"'"' to extract a succession of template words until detection is achieved. If detection is not achieved the template words are again extracted in the next timing interval with a new signal distribution in the registers.
20 Citations
14 Claims
- 1. A method of detecting a pattern feature in a two-dimensional electrical signal applied to a coordinate array of storage cells comprising, in a preliminary step, storing a plurality of template words, each template word being a plurality of storage cell address words, individual ones of which are associated with the individual values of one coordinate direction of the array and represent address values in the other coordinate direction, of cell locations coincident with a template, defining the pattern feature, mapped onto the array, and operationally applying a two-dimensional signal to said array of storage cells, extracting a stored template word addressing simultaneously a set of cells, one at each value of said one coordinate direction, at address values of said other coordinate direction defined by the template word, reading the signal levels of the addressed cells, determining whether substantially all of the levels of the addressed cells are characteristic of the levels of a pattern feature template, and in response to a successful determination, providing an indication that the pattern feature has been detected in the two dimensional electrical signal.
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4. Apparatus for detecting the presence of a two dimensional pattern feature in a two dimensional electrical signal, comprising a plurality of signal storage cells interconnected to define a coordinate array of M rows each of N cells corresponding to a two dimensional pattern field, input means arranged to apply temporally and spatially distributed electrical signals in discrete level samples to the array of storage cells to define a stored input pattern signal, template storage means operable to store a plurality of template words, each word comprising M address words associated individually with m adjacent rows of the storage array cells, where 1<
- m≦
M and each identifying the address of one only out of N adjacent cells, where 1<
n≦
N, of its associated row, said template word defining a two dimensional linear template pattern mapped onto the storage cell array and extending across said M rows of cells but of one cell width only in each row, array reading means operable to extract one template word at a time from the template storage means and, for each template word extracted, cause the address words thereof simultaneously to address the storage cells of the m lines defined thereby and read the sample levels of the input signals in the addressed cells, and decision means responsive to sample levels characteristic of a pattern feature output from substantially all of the simultaneously addressed storage cells to provide a detection signal indicative of the presence in the two dimensional electrical signal of the template pattern represented by the extracted template word. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- m≦
Specification