Automatic gain control circuit

Claim 2

In Combination: signal source means producing reference signals: circuit means responsive to a gain control signal for amplifying the signals produced by said signal source; counter means adapted to continuously store a count representative solely of said gain control signal; means for initially placing in said counter means a reference count corresponding to a signal of given amplitude produced by said circuit means in response to the reference signal produced by said source; means for translating the count stored in said counter means to said gain control signal and applying the same to said circuit means; and means responsive to a change of more than a given amount in the amplitude of the amplified reference signal produced by said circuit means for changing the count in said coUnter means in a sense to restore the amplified reference signal to its previous level.

Claim 3

In combination: signal source means producing reference signals; circuit means responsive to a gain control parameter of a control signal for amplifying the signals produced by said signal source; counter means adapted to count in one direction at a given rate and to count in another direction at a different rate; means for initially placing in said counter means a reference count corresponding to a signal of given amplitude between two preselected limits produced by said circuit means in response to the reference signal produced by said source; means responsive to said amplified signals for producing a first signal to change the count in said counter means in said one direction whenever said amplified signals exceed the larger one of said preselected limits; means also responsive to said amplified signals for producing a second signal to change the count in said counter means in said another direction when said amplified signals are lower than the other of said preselected limits; and means for translating the count stored in said counter means to said control signal and for applying the same to said circuit means in a sense to restore the amplified reference signal to its previous level.

Claim 4

In combination: signal source means producing reference signals; circuit means responsive to a gain control parameter of a control signal for amplifying the signals produced by said signal source; counter means adapted to count in one direction at a given rate and to count in another direction at a different rate; means for initially placing in said counter means a reference count corresponding to a signal of given amplitude between two preselected limits produced by said circuit means in response to the reference signal produced by said source; means responsive to said amplified signals for producing a first signal to change the count in said counter means in said one direction whenever said amplified signals exceed the larger one of said preselected limits; means also responsive to said amplified signals for producing a second signal to change the count in said counter means in said another direction when said amplified signals are lower than the other of said preselected limits; and means for translating the count stored in said counter means to said control signal and for applying the same to said circuit means in a sense to restore the amplified reference signal to its previous level.

Claim 5

The combination as set forth in claim 2 wherein said parameter has upper and lower limits and further including means responsive to the count in said counter going outside of preselected limits corresponding to the upper and lower limits of said parameter for producing an alarm signal.

Claim 6

In combination: a reference target; means producing a light beam the intensity of which may vary with time; means for scanning said light along a path which intercepts said reference target; light responsive means positioned to receive light from the path illuminated by said scanning light for producing a signal the amplitude of which is a function of the light received by said light responsive means and also a function of an external gain control signal; means producing a target signal indicative of a scan over said reference target; counter means; means responsive to the count in said counter for producing said external gain control signal for controlling the amplitude of said signal produced by said light responsive means to be within first and second preselected limits; and means responsive to the target signal and responsive to a signal from the light responsive means outside of the preselected limits and producing a signal for changing the count in said counter in a sense to restore the light responsive means signal to within said preselected limits.

Claim 7

In combination: a reference target; means producing a light beam the intensity of which may vary with time; means for scanning said light along a path which intercepts said reference target; light responsive means positioned to receive light from the path illuminated by said scanning light for producing a signal the amplitude of which is a function of the light received by said light responsive means and also a function of an external gain control signal; means producing a target signal indicative of a scan over said reference target; counter means; means responsive to the count in said counter for producing said external gain control signal for controlling the amplitude of said signal produced by said light responsive means to be within first and second preselected limits; and means responsive to the target signal and responsive to a signal from the light responsive means outside of the preselected limits and producing a signal for changing the count in said counter in a sense to restore the light responsive means signal to within said preselected limits.

Claim 8

The combination as set forth in claim 4 wherein said means responsive to the count in said counter comprises a digital-to-analog converter producing an analog signal proportional to the count in said counter and also comprises means responsive to changes in said analog signal for changing the amplitude of said signal from said light responsive means.

Claim 9

The combination as set forth in claim 4 further including means responsive to the signal for changing the count in said counter for controlling the rate at which said counter counts.

Claim 10

In Combination: means producing, during discrete time intervals, an optical reference signal; transducer means adapted to receive said reference signal and responsive to a gain control signal for producing an output signal corresponding to said reference signal; counter means; digital-to-analog converter means coupled to said counter means for producing an analog signal corresponding to the count in said counter means; means responsive to said analog signal for producing said gain control signal and continuously applying the same to said transducer means; first comparison means receptive of said transducer output signal, for producing a first signal when said transducer signal is greater in amplitude than a first reference level for changing the count in said counter means during said discrete time intervals in a sense to restore said transducer output signal to a level below said first preselected limit; second comparison means receptive of said transducer output signal for producing a second signal when said transducer signal is lower in amplitude than a second reference level, lower than said first for changing the count in said counter means during said discrete time intervals in a sense to restore said transducer output signal to a level above said second preselected limit; and means for preventing the count in said counter means from changing between said discrete intervals.

Claim 11

In Combination: means producing, during discrete time intervals, an optical reference signal; transducer means adapted to receive said reference signal and responsive to a gain control signal for producing an output signal corresponding to said reference signal; counter means; digital-to-analog converter means coupled to said counter means for producing an analog signal corresponding to the count in said counter means; means responsive to said analog signal for producing said gain control signal and continuously applying the same to said transducer means; first comparison means receptive of said transducer output signal, for producing a first signal when said transducer signal is greater in amplitude than a first reference level for changing the count in said counter means during said discrete time intervals in a sense to restore said transducer output signal to a level below said first preselected limit; second comparison means receptive of said transducer output signal for producing a second signal when said transducer signal is lower in amplitude than a second reference level, lower than said first for changing the count in said counter means during said discrete time intervals in a sense to restore said transducer output signal to a level above said second preselected limit; and means for preventing the count in said counter means from changing between said discrete intervals.

Claim 12

In Combination: signal source means producing, during discrete spaced time intervals, reference signals; circuit means coupled to said signal source means and responsive to a gain control signal for producing a signal having a parameter the value of which is a function of the value of said gain control signal and of the reference signals produced by said signal source; counter means means for translating the count stored in said counter means to said gain control signal and applying the same to said circuit means; means responsive to a change in the value of said parameter to a value outside preselected limits for changing the count in said counter means in a sense to restore the value of said parameter to one within said preselected limits; and means for preventing the count stored in said counter means during each said discrete time interval from changing until the following discrete time interval.

Claim 13

In Combination: signal source means producing, during discrete spaced time intervals, reference signals; circuit means coupled to said signal source means and responsive to a gain control signal for producing a signal having a parameter the value of which is a function of the value of said gain control signal and of the reference signals produced by said signal source; counter means means for translating the count stored in said counter means to said gain control signal and applying the same to said circuit means; means responsive to a change in the value of said parameter to a value outside preselected limits for changing the count in said counter means in a sense to restore the value of said parameter to one within said preselected limits; and means for preventing the count stored in said counter means during each said discrete time interval from changing until the following discrete time interval.

Claim 14

In Combination: signal source means producing reference signals, said signal source means comprising an energy producing means, the energy level of which may vary with time and an energy target means adapted to transmit a fixed fraction of the energy received by it to said circuit means during spaced time intervals; circuit means responsive to a gain control signal for amplifying the signals produced by said signal source; counter means; means for initially placing in said counter means a reference count corresponding to a signal of given amplitude produced by said circuit means in response to the reference signal produced by said source; means for translating the count stored in said counter means to a gain control signal and applying the same to said circuit means; and means responsive to a change of more than a given amount in the amplitude of the amplified reference signal produced by said circuit means for changing the count in said counter means in a sense to restore the amplified reference signal to its previous level.

Claim 15

In Combination: signal source means producing reference signals, said signal source means comprising an energy producing means, the energy level of which may vary with time and an energy target means adapted to transmit a fixed fraction of the energy received by it to said circuit means during spaced time intervals; circuit means responsive to a gain control signal for amplifying the signals produced by said signal source; counter means; means for initially placing in said counter means a reference count corresponding to a signal of given amplitude produced by said circuit means in response to the reference signal produced by said source; means for translating the count stored in said counter means to a gain control signal and applying the same to said circuit means; and means responsive to a change of more than a given amount in the amplitude of the amplified reference signal produced by said circuit means for changing the count in said counter means in a sense to restore the amplified reference signal to its previous level.

Claim 16

In Combination: means intermittently producing an optical reference signal; transducer means adapted to receive said reference signal and responsive to a gain control signal for producing a signal corresponding to said reference signal: counter means; digital-to-analog converter means for producing an analog signal corresponding to the count in said counter means; means responsive to said analog signal for producing said gain control signal; a first comparison means for producing a first signal when said transducer signal goes above a first preselected limit for changing the count in said counter means in a sense to restore said transducer signal below said first preselected limit; a second comparison means for producing a second signal when said transducer signal goes below a second preselected limit for changing the count in said counter means in a sense to restore said transducer signal above said second preselected limit; and means producing a presence signal indicating unambiguously the presence of said reference signal and wherein said first signal and said presence signal in combination change the count in said counter and wherein said second signal and said presence signal in combination change the count in said counter.

Claim 17

In Combination: means intermittently producing an optical reference signal; transducer means adapted to receive said reference signal and responsive to a gain control signal for producing a signal corresponding to said reference signal: counter means; digital-to-analog converter means for producing an analog signal corresponding to the count in said counter means; means responsive to said analog signal for producing said gain control signal; a first comparison means for producing a first signal when said transducer signal goes above a first preselected limit for changing the count in said counter means in a sense to restore said transducer signal below said first preselected limit; a second comparison means for producing a second signal when said transducer signal goes below a second preselected limit for changing the count in said counter means in a sense to restore said transducer signal above said second preselected limit; and means producing a presence signal indicating unambiguously the presence of said reference signal and wherein said first signal and said presence signal in combination change the count in said counter and wherein said second signal and said presence signal in combination change the count in said counter.

Claim 18

The combination of: sourcE means producing a reference signal; receiver means receptive of said reference signal and responsive to a gain control signal for amplifying said reference signal in an amount dependent upon the value of said gain control signal; counter means having an input circuit and an output circuit; comparison means for comparing, during discrete, spaced time intervals, the amplified reference signal produced by said receiver means with first and second reference levels said first level higher than said second, for producing a first count correction signal when the amplified reference signal is greater in amplitude than the first level and for producing a second count correction signal when the amplified reference signal is smaller in amplitude than the second level; means for coupling the count correction signal produced by said comparison means to said input circuit of said counter means during said discrete, spaced time intervals to thereby, during each such interval, change the count stored in said counter means in one sense if a first signal is present, in the opposite sense if a second signal is present, and to leave the count unchanged if neither signal is present; means for retaining the count stored in the counter means during each said discrete time interval until the following discrete time interval, comprising means for effectively blocking said input circuit of said counter means during the periods between said spaced discrete time intervals; and means coupled to said output circuit of said counter means and to said receiver means for continuously translating the count stored in said counter means to a gain control signal and applying the latter to said receiver means in a sense to maintain said amplified reference signal within said first and second levels.

Claim 19

The combination of: sourcE means producing a reference signal; receiver means receptive of said reference signal and responsive to a gain control signal for amplifying said reference signal in an amount dependent upon the value of said gain control signal; counter means having an input circuit and an output circuit; comparison means for comparing, during discrete, spaced time intervals, the amplified reference signal produced by said receiver means with first and second reference levels said first level higher than said second, for producing a first count correction signal when the amplified reference signal is greater in amplitude than the first level and for producing a second count correction signal when the amplified reference signal is smaller in amplitude than the second level; means for coupling the count correction signal produced by said comparison means to said input circuit of said counter means during said discrete, spaced time intervals to thereby, during each such interval, change the count stored in said counter means in one sense if a first signal is present, in the opposite sense if a second signal is present, and to leave the count unchanged if neither signal is present; means for retaining the count stored in the counter means during each said discrete time interval until the following discrete time interval, comprising means for effectively blocking said input circuit of said counter means during the periods between said spaced discrete time intervals; and means coupled to said output circuit of said counter means and to said receiver means for continuously translating the count stored in said counter means to a gain control signal and applying the latter to said receiver means in a sense to maintain said amplified reference signal within said first and second levels.

Claim 20

The combination as set forth in claim 11 wherein said source means includes means producing an optical signal and wherein said receiver means includes a photomultiplier, said gain control signal being applied to said photomultiplier.

Claim 21

The combination as set forth in claim 12 wherein said source means comprises an optical target, means for periodically scanning a beam of light over said target and means for blocking said beam of light during spaced time intervals which may recur aperiodically at a relatively low rate compared to the periodic scanning rate.

Claim 22

The combination as set forth in claim 11 wherein said means coupled to the output circuit of said counter means includes digital to analog converter means.