Rangefinder and digital single shot circuit

• US 4,159,873 A
• Filed: 09/27/1977
• Issued: 07/03/1979
• Est. Priority Date: 09/27/1977
• Status: Expired due to Term

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Farnsworth, Robert P.
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/836,937
• Time in Patent Office: 644 Days
• Field of Search: 307/273, 307/276, 307/232, 307/234, 328/207, 356/5, 343/13 R
• US Class Current: 356/5.03
• CPC Class Codes: G01S 13/16 using counters
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters

Abstract

This invention is an improved ranging system including an improved digital single shot circuit that has a resettable shift register therein so that a signal representative of the last target return occurring at any point of a predetermined range interval will be provided to the timing counter of the system. The digital single shot circuit includes a flip flop responsive to the first trigger pulse during the predetermined range interval, resetting the shift register so that, when the output pulse from the shift register representing the last target return is applied to the timing counter, it will terminate a fixed number of clock edges after the last trigger pulse determined by the number of stages of the shift register. The fixed delay in terminating the output of the shift register may represent the preset time of the readout counter.

Claims

1. A ranging system for providing the range of remote targets comprising:

(a) transmitting means for transmitting energy pulses to remote targets;

(b) detector means for receiving portions of the energy pulse reflected by the remote targets and for developing video pulses;

(c) first and second counters, said second counter coupled to said first counter for being controlled by said first counter when said first counter counts to a predetermined value; and

(d) digital single shot means responsive to the video pulses from said detecting means for applying reset pulses to said first counter, said digital single shot means including an enabling terminal further comprising first gating means coupled to said first and second counters and to said enabling terminal and responsive to predetermined counts of said counters for developing a pulse for enabling and disabling said digital single shot means.

2. A system for displaying the range of remote targets in space comprising:

(a) transmitting means for transmitting energy to remote targets, said transmitting means providing a reset signal;

(b) detector means for receiving portions of said energy reflected by the remote targets;

(c) a readout counter coupled to said transmitting means and responsive to said reset signal to be preset, said readout counter providing remote target information;

(d) a timing counter coupled to said readout counter, said timing counter at a full count controlling said readout counter to stop counting and provide range information of the remote target; and

(e) a digital single shot circuit including a flip flop and a shift register, said shift register having a plurality of stages coupled to said flip flop for being reset and having at least one stage coupled to said flip flop for clearing said flip flop when said shift register is reset, said flip flop being triggered by said detector means and enabled by a predetermined count of said timing counter, said shift register providing a reset signal to said timing counter.

3. The system of claim 2 further comprising clock oscillating means for providing a source of clock pulses to both said timing counter and to said readout counter and to said shift register.

4. The ranging system of claim 2 further comprising first gating means responsive to predetermined counts of said counters which provide a minimum and maximum range period for enabling said digital single shot circuit.

5. The ranging system of claim 2 further comprising second gating means coupled to said transmitting means and said detector means for developing, a count start signal.

6. The ranging system of claim 5 further comprising third gating means responsive to less than a full count of said second counter or to said count start signal for enabling said first and second counters.

7. The ranging system of claim 2 further including means to disable said digital single shot circuit by a predetermined count of said readout counter.

8. A ranging system for determining the range of a remote target within a selected interval comprising:

(a) means for transmitting energy;

(b) means for detecting the presence of said energy when reflected by a remote target located within said interval and for producing a return pulse signal indicative thereof;

(c) a digital single shot circuit to accept said return pulse signal and to produce an output responsive thereto, said output being a reset pulse;

(d) said digital single shot circuit including means for retriggering so that said digital single shot circuit is activated by and responsive to the application of a second return pulse during the duration of said reset pulse;

(e) a timing counter, said counter being reset by said reset pulse; and

(f) a readout counter, said counter being controlled by the count of said timing counter so that the count of said readout counter indicates the range of said target corresponding to the last return pulse signal at the time that said timing counter reaches its maximum count.

9. A ranging system as defined in claim 8 further characterized in that said digital single shot circuit additionally comprises:

(a) a flip flop, the state of said flip flop being controlled by said return pulse during said selected interval;

(b) a shift register, the output of at least one stage of which is utilized to provide said reset pulse;

(c) said shift register being coupled to an output of said flip flop so that the state of at least one stage of said shift register is changed by the change of state of said flip flop; and

(d) the output of said at least one stage of said shift register being utilized in turn to change the state of said flip flop so that the state of said flip flop is responsive to each return pulse applied to said digital single shot during said selected interval.

10. A resettable digital single shot circuit which comprises:

(a) a flip flop, said flip flop being transformed from a first state to a second state by the application of a triggering pulse to said digital single shot circuit;

(b) a shift register, the output of at least one stage of said shift register being utilized to produce the output of said digital single shot circuit;

(c) said shift register having a clearing means common to all stages thereof, said clearing means being coupled to an output of said flip flop so that all stages of said shift register are reset upon the transition of said flip flop from said first state to said second state; and

(d) the output of said at least one stage of said shift register being utilized in turn to return said flip flop to said first state so that the state of said flip flop is responsive to each triggering pulse applied to said digital single shot circuit, whereby said digital single shot circuit is responsive to all triggering pulses applied thereto.

11. A resettable digital single shot circuit as defined in claim 10 further characterized in that said digital single shot circuit is enabled during selected time intervals, whereby the output of said digital single shot circuit is responsive only to triggering pulses occurring during said selected intervals.