Ambient light variation detector

Claim 2

An ambient light intensity variation detector comprising: a. first means responsive to the variation in ambient light intensity for generating a trigger pulse when the variation in ambient light intensity with respect to time exceeds a predetermined rate, and b. second means responsive to said trigger pulse for producing a control signal, said second means further including means for sustaining said control signal for a predetermined control period independent of the ambient light intensity during said control period.

Claim 3

The detector as set forth in claim 1 further including third means for providing a bias voltage to said first means sufficient to cause operation of said first means, said first means being responsive to said control signal to reduce the bias voltage supplied to said first means below the level necessary for operation of said first means, thereby disabling said first means from detecting ambient light intensity variations occurring during said control period.

Claim 4

The detector set forth in claim 2 wherein said first means is a first amplifier with input coupled to a light sensitive photo-resistor, and said second means is a second amplifier with input coupled to the output of said first amplifier whereby said second amplifier provides a control signal when said first amplifier is activated by a resistance variation with respect to time in said photo-resistor of a predetermined rate in response to variation in the ambient light intensity.

Claim 5

Apparatus for providing a control signal in response to variation in ambient light intensity, said control signal occurring as a result of a variation in said light intensity with respect to time in excess of a predetermined rate and being sustained for a predetermined control period, said apparatus comprising: a. a photo-resistor, subjected to ambient light, for providing a resistance variation proportional to the variation of said light intensity with respect to time; b. a first amplifier stage coupled to said photo-resistor for providing a trigger pulse when the variation in resistance of said photo-resistor with respect to time exceeds a predetermined rate; c. a second transistor amplifier stage with inpUt coupled to the output of said first amplifier stage for providing a control signal when there is a presence of a trigger pulse at its input; d. a capacitor means coupling a bias voltage supply to said second transistor amplifier stage; e. feedback resistor means coupling the output of said second amplifier stage to its input, said feedback resistor means in combination with said capacitor means controlling the duration of said control signal; and f. means for applying said control signal to said photo-resistor to render said photo-resistor inoperative thereby preventing said first amplifier stage from providing trigger pulses to said second amplifier stage during said control period.

Claim 6

Apparatus for providing a control signal in response to variation in ambient light intensity, said control signal occurring as a result of a variation in said light intensity with respect to time in excess of a predetermined rate and being sustained for a predetermined control period, said apparatus comprising: a. a photo-resistor, subjected to ambient light, for providing a resistance variation proportional to the variation of said light intensity with respect to time; b. a first amplifier stage coupled to said photo-resistor for providing a trigger pulse when the variation in resistance of said photo-resistor with respect to time exceeds a predetermined rate; c. a second transistor amplifier stage with inpUt coupled to the output of said first amplifier stage for providing a control signal when there is a presence of a trigger pulse at its input; d. a capacitor means coupling a bias voltage supply to said second transistor amplifier stage; e. feedback resistor means coupling the output of said second amplifier stage to its input, said feedback resistor means in combination with said capacitor means controlling the duration of said control signal; and f. means for applying said control signal to said photo-resistor to render said photo-resistor inoperative thereby preventing said first amplifier stage from providing trigger pulses to said second amplifier stage during said control period.

Claim 7

An ambient light intensity detector comprising: a. a first transistor amplifier; b. bias control means coupled to the input of said first transistor amplifier; c. a photo-resistor coupled to said bias control means whereby a variation in resistance of said photo-resistor with respect to time in excess of a threshold amount will cause said bias control means to provide a bias voltage to said first transistor amplifier sufficient to cause operation of said first transistor amplifier; d. a second transistor amplifier stage coupled at its input to said first transistor amplifier for providing a control signal in response to the operation of said first transistor amplifier; e. capacitor means coupling a bias supply voltage to said second transistor amplifier stage; f. feedback resistor means coupling the output of said second transistor amplifier stage to its input, said feedback resistor means in combination with said capacitor means providing the control for the duration of said control signal; and g. means coupling the output of said second transistor amplifier stage to said bias control means to reduce the bias voltage supplied to said first transistor amplifier below the level necessary for operation of said amplifier during the presence of said control signal.

Claim 8

An ambient light intensity detector comprising: a. a first transistor amplifier; b. bias control means coupled to the input of said first transistor amplifier; c. a photo-resistor coupled to said bias control means whereby a variation in resistance of said photo-resistor with respect to time in excess of a threshold amount will cause said bias control means to provide a bias voltage to said first transistor amplifier sufficient to cause operation of said first transistor amplifier; d. a second transistor amplifier stage coupled at its input to said first transistor amplifier for providing a control signal in response to the operation of said first transistor amplifier; e. capacitor means coupling a bias supply voltage to said second transistor amplifier stage; f. feedback resistor means coupling the output of said second transistor amplifier stage to its input, said feedback resistor means in combination with said capacitor means providing the control for the duration of said control signal; and g. means coupling the output of said second transistor amplifier stage to said bias control means to reduce the bias voltage supplied to said first transistor amplifier below the level necessary for operation of said amplifier during the presence of said control signal.