A document for transmission has ruled lines such as borders printed at predetermined locations thereon which do not constitute usable information. The main scan direction is perpendicular to the ruled lines. Each main scan line is pre-scanned to determine if the line contains information other than the ruled lines, and the main scan line is scanned again for transmission if information is encountered and skipped if information is not encountered. A gating signal is generated in synchronism with the pre-scanning step, but the gating signal is suppressed while the portions of the main scan line intersecting the ruled lines are being pre-scanned. If the gating signal and electrical signals resulting from pre-scanning usable information contained in the main scan line are sensed simultaneously, the line is scanned for transmission.

A positioning control circuit for locating a document image frame with respect to the scanning field of a camera in which the video and sync signals output from the camera are processed to determine the existence of a document reference mark within the camera field, as well as the coordinate location relative to the camera field, of a specific point within the reference mark. The actual coordinate position of the specific point within the reference mark is compared with a desired coordinate location, and the document image repositioned relative to the camera field in response to any difference existing between the actual and desired coordinate positions. This process is repeated during each successive field scanning operation until the mark coincides with the desired position, whereupon further signal processing and document image repositioning is terminated.

In a digital storage system for oscilloscope trace data, in order to obtain precisely the ordinate of an oscilloscope trace at the intersection of a scanning line therewith in a television camera image of the trace, a scan/trace intersection profile signal is compared with a multiplicity of threshold values to generate a set of rectangular pulses of a duration equal to the threshold-override interval, and the pulse for the highest threshold is selected and processed to determine the true intersection ordinate by forming the half-sum of the ordinates of the leading and trailing edges of the pulse. This ordinate and the line scan number are provided as a pair of digital quantities (addresses) for storage in a digital memory.

A television camera which scans an image provides a camera video signal having an amplitude representative of light received from an element of the image being scanned. Prior to a scan a sync pulse is generated which increments a raster counter. Accordingly, the roster counter provides a signal representation of a cumulative number of scans of the image. During the scanning, clock pulses increment a horizontal deflection counter which provides a signal representation of a horizontal deflection number corresponding to the horizontal coordinate of the line of sight. When the cumulative number of scans equals the horizontal deflection number, a comparator provides a gating signal which causes a sample and hold circuit to store a sampled video signal having an amplitude equal to the amplitude of the camera video signal. The sampled video signal is provided to the input of an analog to digital converter for conversion to digital signals which may be stored in a digital computer. A succession of sampled video signals is representative of the image when the cumulative number of scans exceeds a maximum horizontal deflection number.

An automatic scanning and control apparatus determines the location of a predetermined segment of an image field being scanned. The predetermined segment presents an image which is optically differentiatable from the surrounding area of the image field. The apparatus includes a beam device for selectively scanning the image field and producing an output signal thereof. The beam device includes means for modulating the output signal in accordance with variations in the image field. The predetermined segment of the image field causes modulation of the output signal of the beam device by providing an inflection therein when the beam scans across the segment. An analyzing circuit is adapted to accept the output signal from the beam device. Means generate a locating signal in predetermined time relation to the scanning. Comparator means compare the inflection in the output signal with the locating signal so that the location of the predetermined segment of the image field can be determined. A method compares an image field to be inspected with a standard image field. A standard image field is scanned with a beam and a video signal is modulated in accordance with intensity variations in the standard field. The video signal is recorded on a recording member. The field to be inspected is then scanned by the beam and a second video signal is generated. Both the video signals are reproduced and passed to a comparator means. A point to point comparison is made between the inflections and variations in each signal resulting from the scanning image areas of contrasting intensity of generating pulse signals during the intervals that the areas do not coincide. The pulse signals are then automatically analyzed.