초록 ▼

An apparatus and method for automatic character recognition is presented which automatically locates and recognizes alphanumeric characters in a scene viewed by a raster-scan type of sensor. By this method the apparatus can search the entire scene and recognize up to seven alphanumeric characters in

An apparatus and method for automatic character recognition is presented which automatically locates and recognizes alphanumeric characters in a scene viewed by a raster-scan type of sensor. By this method the apparatus can search the entire scene and recognize up to seven alphanumeric characters in a bounded area of known size by the correlation technique in less than 1.5 seconds. The technique used first locates the bounded area and alphanumeric characters and then performs the recognition. Two different feature extraction methods are used to locate the characters in the scene. The recognition function is performed by correlation using an incoherent electrooptical processor.

대표청구항 ▼

An apparatus for automatic location and recognition of alphanumeric characters in a bounded area of known size within a scene viewed by a raster-scan type video sensor which comprises: means, connected to receive a video signal from the raster-scanned type sensor, for converting said video signal in

An apparatus for automatic location and recognition of alphanumeric characters in a bounded area of known size within a scene viewed by a raster-scan type video sensor which comprises: means, connected to receive a video signal from the raster-scanned type sensor, for converting said video signal into a digital binary signal whereby the alphanumeric characters are represented by one of the binary signals and the background data is represented by the other binary signal; means, disposed to receive the output of the converting means, for locating a known bounded area containing alphanumeric characters in the scene viewed; means, connected to the locating means, for recognizing the alphanumeric characters contained in the known bounded area; and means, disposed to receive the output of the recognizing means, for further processing and displaying of the recognized alphanumeric characters; wherein the converting means comprises: means, disposed to receive the analog video signal from the video sensor, for presearching the scene viewed to locate probable bounded areas containing alphanumeric characters, wherein said means for presearching identifies horizontal and vertical coordinates representing the location of each probable bounded area containing alphanumeric characters; means, connected to receive a signal from the output of the presearching means, for setting a threshold to represent the background signal level; means, connected to the presearching means, for storing the horizontal and vertical coordinates representing the location of each probable bounded area containing alphanumeric characters; and means, connected to receive the analog video signal from the video sensor and also connected to receive the output analog signal from the threshold setting means, for digitizing those signals pertaining to probable bounded areas containing alphanumeric characters in a manner that signals pertaining to alphanumeric characters are set as a first binary coded signal level and the background signals are set at the second binary coded signal level; the apparatus further comprising: a threshold setting means which adjusts the threshold reference signal to relate in an absolute manner to analog signals pertaining to probable alphanumeric characters in a manner that possible alphanumeric characters are always treated similarly in relation to the background level whether the alphanumeric characters are light colored on a dark background or dark colored on a light background; and an analog comparator as the digitizing means, said analog comparator outputting a digital logic binary signal of “1”for data pertaining to alphanumeric characters and a digital logic signal of “0”for data caused by background signals; wherein the presearching means comprises: an input for receiving the video signals from the video sensor; a bit clock generator; a first analog delay circuit connected to receive the video sensor input, said delay circuit causing a delay of time length equal to one horizontal video line scan; a first analog differential comparator which receives input signals from the first analog delay circuit and from the video sensor input, said comparator outputting a signal when the input signals differ; a first AND gate which receives one input from the bit clock generator and a second input from the output of the first analog differential comparator, said AND gate emitting an output signal when signals occur simultaneously at both inputs; a first counter connected to receive the output of the first AND gate, said counter accumulating a total count representing the period during which the first AND gate is outputting a pulse signal; a first digital comparator connected to receive the count output (A) from the first counter and to compare this accumulating count against a preset test count (B) which represents the expected horizontal width of a single alphanumeric character, said comparator outputting a signal when A is less than or equal to B; a first D-flip flop unit connected to receive the output signal from the first digital comparator, said flip flop unit outputs a signal after it has been triggered by a first output signal from the first digital converter; a second D-flip flop unit connected to receive the output of the first D-flip flop unit and to receive the output signals from the first digital comparator, said second D-flip flop unit being activated by the output signal from the first D-flip flop unit which occurs when the first flip flop unit is activated by the first output signal emitted from the first comparator, and then is caused to emit a signal at its output when a second consecutive signal is emitted from the first comparator; a second counter connected to receive inputs from the bit clock generator which causes the counter to accumulate counts; a second digital comparator connected to receive the count output (C) from the second counter, and to compare this accumulating count against a preset test count (D) which represents the expected horizontal width of the area containing all alphanumeric characters of interest, said comparator outputting a signal when C is greater than or equal to D; a second AND gate which receives inputs from the second digital comparator and the second D-flip flop unit, said AND gate emitting an output signal when its input\s both simultaneously hold an input signal, whereby the tentative detection of a field of alphanumeric characters of interest against a clear background has been accomplished; a second analog delay circuit connected to receive the output of the first analog delay circuit, said second circuit causing a delay of time length equal to 10 bits along a horizontal video line scan; a second analog differential comparator connected to receive the output of the second analog delay circuit and the output of the first analog delay circuit, said second analog differential comparator outputting a signal when its input signals differ, said second differential comparator being connected to feed this output signal to the second counter and the first and second D-flip flop units whereby these respective devices are reset to restart their active functions over; a first OR gate connected to receive the output signals from the first and second analog differential comparators, said OR gate emitting a signal when either of the signals input from said first and second comparators exist, and said output of the OR gate connected to the first counter whereby this counter is reset to the start position when a signal from the OR gate output occurs; and a third analog delay circuit connected to receive the output video signal from said first analog delay circuit, said third delay circuit causing a delay of time length equal to one horizontal video line scan.