Beam position locater with photodetector array
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorKenneth L. Smith
Life of this patent
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Abstract
An apparatus for accurately detecting and digitally displaying the centrum of the location where a luminous energy beam impinges a shift register scanned linear photodetector array. With the commencement of the array scan, clock pulses corresponding to successive photodiodes are accumulated in a counter, continuing until an illuminate photodiode, with a video response above the detection threshold, is encountered. Thereafter, clock pulses are locked out while only alternate video pulses reach the counter. The onset of the succeeding scan locks out the video pulses, leaving the counter display at the previously accumulated count for an extended period defined by a supplemental sample timing circuit. The sampling of scans provides a display sufficiently stable for visual monitoring.
Claims6
An apparatus for digitally locating the centrum of a luminous energy beam, comprising:
- a shift register scanned linear photodetector array generating a luminous energy actuated video output signal;
- a shift register clock generating pulses in correspondence to the sampling of array elements;
- a means for generating a start signal at the beginning of each array scan;
- a means for counting pulses;
- a means for transmitting clock pulses to the counting means;
- a flip-flop having a clock input connected to receive said video output signal and to trigger the flip-flop to change state only when the video output exceeds a given threshold value, so that it operates as a divide-by-two means;
- means connected to be triggered in response to the first change of state of said flip-flop during a scan to stop said transmission of clock pulses and to start the transmission of pulses output from the flip-flop to the counting means until the next succeeding start signal.
An electronic device for locating the centrum of a luminous energy beam, comprising:
- photodetector means including a serially scanned linear photodetector array of elements generating a luminous energy actuated series of "video" pulses whose amplitudes are functions of the light intensity on corresponding array elements, with the "video" pulses appearing on a "video" lead, generating clock pulses on a clock lead in correspondence to the sampling of array elements, and generating a start signal on a start lead at the beginning of each array scan;
- a first flip-flop having a clock input connected to said "video" lead and enabled so that only "video" pulses exceeding a given threshold level change the state of the flip-flop at an output thereof, whereby said first flip-flop acts as a divide-by-two means for "video" pulses which exceed said threshold level;
- a second flip-flop having a first input connected to said start lead, and a second input connected to the output of the first flip-flop, the second flip-flop being responsive to a start signal at its first input to set it to a first state and a pulse at its second input to set it to a second state, the second flip-flop having output means connected to first and second AND function gates so that in said first state the first AND function gate is enabled while the second is disabled, and in said second state the second AND function gate is enabled while the first is disabled, the first AND function gate having a second input connected to said clock lead, and the second AND function gate having a second input connected to the output of the first flip-flop;
- a counter coupled to outputs of said first and second AND function gates to count pulses transmitted via the second input of the one which is enabled;
- whereby in one scan cycle commencing with a start pulse, clock pulses transmitted via the clock lead and the first AND function gate are counted until a "video" pulse on the "video" lead exceeds said threshold, and then alternate "video" pulses exceeding the threshold are counted, after which there is no further advance of the counter for the remainder of the scan cycle.
Dependencies are inferred from the claim text.