Gain control circuit

Claim 2

Signal generating apparatus responsive to a first signal having a first frequency of occurrence for generating an output signal having the first frequency and a linearly changing waveform, and responsive to a second signal having a second frequency of occurrence and a reference signal having a first reference level for regulating the maximum level and the rate of change of the output signal, said signal generating apparatus comprising: a. first means responsive to the second signal for detecting the instantaneous level of the linearly changing waveform of the output signal; b. second means responsive to the detected instantaneous level of the output signal and the first reference level of the reference signal for producing a control signal having a control level related to the instantaneous level of the output signal and the reference level of the reference signal; c. third means for integrating the control level of the control signal during the period between successive occurrences of the first signal to produce the output signal having a rate of change related to the control level of the control signal; and d. fourth means for adjusting the level of the linearly changing waveform of the output signal to a second reference level at each occurrence of the first signal, whereby the waveform of the output signal linearly changes in response to the control level of the control signal from the second reference level to the maximum level in the period between successive occurrences of the first signal.

Claim 3

The apparatus of claim 1 wherein the output signal has a linearly changing sawtooth waveform, said first and second frequencies are equal, the second signal is 180* out-of-phase with respect to the first signal, and the instantaneous level of the sawtooth waveform output signal detected by the first means in response to the second signal is one-half the maximum level of the sawtooth waveform output signal.

Claim 4

The apparatus of claim 1 wherein the output signal has a linearly changing sawtooth waveform, and said third means further comprises an input terminal, a reset terminal and an output terminal; and wherein said second means is coupled to said input terminal of said third means to apply the control signal to said input terminal; said third means is responsive to the control signal to produce the sawtooth waveform output signal at said output terminal; and said first means is coupled to said output terminal to detect the instantaneous amplitude of the sawtooth waveform output signal.

Claim 5

The apparatus of claim 3 wherein said third means further comprises a signal inverting operational amplifier having said input terminal and said output terminal and an integrating capacitor coupled to said input and output terminals and adapted to integrate the control signal applied to said input terminal, and inverted by said signal inverting operational amplifier, over the period correspondIng to the first frequency of the first signal; and said fourth means further comprises a reset gate including said reset input terminal and having a predetermined signal conductive path coupled between said input terminal and said output terminal, whereby each occurrence of the first signal applied to said reset input terminal renders said reset gate conductive to discharge the integrating capacitor and to reset the sawtooth waveform output signal developed at said output terminal to said second reference level.

Claim 6

The apparatus of claim 4 wherein said first and second frequencies are equal, the second signal is 180* out-of-phase with respect to the first signal, and the instantaneous level of the sawtooth waveform output signal detected by the first means in response to the second signal is one-half the maximum level of the sawtooth waveform output signal.

Claim 7

The apparatus of claim 1 wherein said second means further comprises: a. means for comparing the detected instantaneous level of the output signal with the first reference level of the reference signal to produce the control signal having the control level, said control level being related to the difference in amplitude between the first reference level and the detected instantaneous level and being representative of the second frequency of the second signal. b. non-polar switching means responsive to the second signal to apply the instantaneous amplitude of the output signal to the comparing means; and c. means for storing the control level of the control signal during the successive periods of occurrence of the second signal.

Claim 10

The method of claim 7 wherein the output signal has a linearly changing sawtooth waveform, the first and second frequencies of the first and second signals are equal, the second signal is 180* out-of-phase with respect to the first signal, and the first reference level is one-half the maximum level of the sawtooth waveform output signal.

Claim 11

The method of claim 7 further comprising the step of storing the control level of the control signal during the period between successive occurrences of the second signal.

Claim 12

Signal generating apparatus responsive to first and second signals differing in phase by 180* and each having a first frequency of occurrence for generating first and second output signals differing in phase by 180* and each having the first frequency and a linearly changing waveform, and responsive to the second and first signals, respectively, and a third signal having a first reFerence level for regulating the maximum level and rate of change of the linearly changing waveforms of the first and second output signals, respectively, said apparatus comprising: a. first means responsive to the first signal for detecting the instantaneous level of the linearly changing waveform of the second output signal; b. second means responsive to the second signal for detecting the instantaneous level of the linearly changing waveform of the first output signal; c. third means responsive to the detected instantaneous levels of the first and second output signals and the first reference level of the reference signal for producing a control signal having a control level related to the instantaneous levels of the first and second output signals and the first reference level of the reference signal; d. fourth means for storing the control level of the control signal during the successive periods of occurrence of the first and second signals; e. fifth means responsive to the control signal and the first signal for integrating the control level of the control signal during the periods between successive occurrences of the first signal and for producing the first output signal having a linear rate of change related to the control level of the control signal and a maximum level related to the first reference level; and f. sixth means responsive to the control signal and the second signal for integrating the control level of the control signal during the period between successive occurrences of the second signal and for producing the second output signal having a linear rate of change related to the control level of the control signal and a maximum level related to the first reference level.

Claim 13

Signal generating apparatus responsive to first and second signals differing in phase by 180* and each having a first frequency of occurrence for generating first and second output signals differing in phase by 180* and each having the first frequency and a linearly changing waveform, and responsive to the second and first signals, respectively, and a third signal having a first reFerence level for regulating the maximum level and rate of change of the linearly changing waveforms of the first and second output signals, respectively, said apparatus comprising: a. first means responsive to the first signal for detecting the instantaneous level of the linearly changing waveform of the second output signal; b. second means responsive to the second signal for detecting the instantaneous level of the linearly changing waveform of the first output signal; c. third means responsive to the detected instantaneous levels of the first and second output signals and the first reference level of the reference signal for producing a control signal having a control level related to the instantaneous levels of the first and second output signals and the first reference level of the reference signal; d. fourth means for storing the control level of the control signal during the successive periods of occurrence of the first and second signals; e. fifth means responsive to the control signal and the first signal for integrating the control level of the control signal during the periods between successive occurrences of the first signal and for producing the first output signal having a linear rate of change related to the control level of the control signal and a maximum level related to the first reference level; and f. sixth means responsive to the control signal and the second signal for integrating the control level of the control signal during the period between successive occurrences of the second signal and for producing the second output signal having a linear rate of change related to the control level of the control signal and a maximum level related to the first reference level.

Claim 14

The apparatus of claim 10 wherein the fifth means further comprises means responsive to the first signal for adjusting the level of the first output signal to a second reference level, whereby the waveform of the first output signal linearly changes in response to the control level of the control signal from the second reference level to the maximum level in the period between successive occurrences of the first signal; and said sixth means further comprises means responsive to the second signal for adjusting the level of the second output signal to the second reference level, whereby the waveform of the second output signal linearly changes in response to the control level of the control signal from the second reference level to the maximum level in the period between successive occurrences of the second signal.

Claim 15

The apparatus of claim 11 wherein the first and second output signals have linearly changing sawtooth waveforms that are 180* out-of-phase with respect to each other.

Claim 16

The apparatus of claim 12 wherein said fifth and sixth means each further comprise: a. a signal inverting operational amplifier having an input terminal and an output terminal; b. an integrating capacitor coupled to said input and output terminals and adapted to integrate the control level of the control signal applied to said input terminal, and inverted by said operational amplifier, over the respective periods between successive occurrences of the first and second signals; and c. a reset gate including a reset input terminal and having a predetermined signal conductive path coupled between said input terminal and said output terminal, whereby each occurrence of the first and second signals applied to the reset input terminals of said fifth and sixth means, respectively, renders said reset gate signal conductive path operative to discharge the respective integrating capacitor and to reset the waveforms of the respective first and second output signals developed at said output terminals to said second reference level.

Claim 17

Signal generating apparatus for deriving a scanning signal having an irregular sawtooth waveform for application to scanning apparatus for scanning the image frames of continuously moving information bearing media having a Plurality of successive image frames disposed thereon, in response to a first signal having a first frequency of occurrence related to the rate of movement of the image frames with respect to said scanning apparatus and a second signal having a second frequency of occurrence related to the scanning rate of the scanning apparatus, said signal generating apparatus comprising: a. means responsive to the first signal for producing third and fourth signals differing in phase by 180* and each having a third frequency related to the first frequency of the first signal as a submultiple thereof; b. means responsive to the third and fourth signals for generating first and second output signals, respectively, each output signal having the third frequency and a linearly changing sawtooth waveform; c. first means responsive to the fourth signal for detecting the instantaneous level of the linearly changing sawtooth waveform of the third signal; d. second means responsive to the third signal for detecting the instantaneous level of the linearly changing sawtooth waveform of the second output signal; e. means for establishing a reference signal having a reference level; f. means responsive to the reference level of the reference signal and the detected instantaneous levels of the first and second output signals for producing a control signal having a control level related to the instantaneous levels of the first and second output signals and the reference level of the reference signal; g. means responsive to the control level of the control signal for regulating the rate of change of the waveforms of the first and second output signals; h. means responsive to the second signals for producing a third output signal having the second frequency and a linearly changing sawtooth waveform, the third output signal having a maximum level related to said reference level of the reference signal; and i. switching means responsive to each occurrence of the second signal that succeeds, in time, each occurrence of the third and fourth signals for combining complementary periods of the first and second output signals with the third output signal to produce the scanning signal having an irregular sawtooth waveform.

Claim 18

Signal generating apparatus for deriving a scanning signal having an irregular sawtooth waveform for application to scanning apparatus for scanning the image frames of continuously moving information bearing media having a Plurality of successive image frames disposed thereon, in response to a first signal having a first frequency of occurrence related to the rate of movement of the image frames with respect to said scanning apparatus and a second signal having a second frequency of occurrence related to the scanning rate of the scanning apparatus, said signal generating apparatus comprising: a. means responsive to the first signal for producing third and fourth signals differing in phase by 180* and each having a third frequency related to the first frequency of the first signal as a submultiple thereof; b. means responsive to the third and fourth signals for generating first and second output signals, respectively, each output signal having the third frequency and a linearly changing sawtooth waveform; c. first means responsive to the fourth signal for detecting the instantaneous level of the linearly changing sawtooth waveform of the third signal; d. second means responsive to the third signal for detecting the instantaneous level of the linearly changing sawtooth waveform of the second output signal; e. means for establishing a reference signal having a reference level; f. means responsive to the reference level of the reference signal and the detected instantaneous levels of the first and second output signals for producing a control signal having a control level related to the instantaneous levels of the first and second output signals and the reference level of the reference signal; g. means responsive to the control level of the control signal for regulating the rate of change of the waveforms of the first and second output signals; h. means responsive to the second signals for producing a third output signal having the second frequency and a linearly changing sawtooth waveform, the third output signal having a maximum level related to said reference level of the reference signal; and i. switching means responsive to each occurrence of the second signal that succeeds, in time, each occurrence of the third and fourth signals for combining complementary periods of the first and second output signals with the third output signal to produce the scanning signal having an irregular sawtooth waveform.

Claim 19

The apparatus of claim 14 wherein said switching means further comprises: a. means operative in a first or a second state, responsive to each occurrence of the second signal that succeeds, in time, each occurrence of the first signal for changing the operative state and for producing first and second switching signals, respectively, having respective complementary periods equal to the periods of said first and second states; b. first and second non-polar switches each having a gate input adapted to receive the first and second switching signals, respectively, first and second signal inputs adapted to receive the first and second output signals, respectively, and a common output terminal, said first and second non-polar switches being responsive to the first and second complementary switching signals for passing respective complementary periods of the first and second output signals to said output terminal; and c. means for combining the complementary periods of the first and second output signals at said output terminal with the third output signal to produce the scanning signal having a frequency equal to said second frequency and an irregular sawtooth waveform.