Electron bombarded active pixel sensor camera incorporating gain control

A camera comprising:

• a photocathode operable in a night mode wherein electrons are generated in response to incident light;
• an active pixel sensor in spaced relation to said photocathode, said photocathode being positioned between said active pixel sensor and an object being imaged, said active pixel sensor comprising an array of pixels for sensing electrons in said night mode;
• a power supply for energizing said photocathode in said night mode in response to a power supply control signal, said power supply comprising a gated power supply and said control signal comprising a gating signal having a duty cycle that increases as the light level decreases;
• a power supply control circuit for providing said control signal to said power supply in response to the incident light level;
• and
• an integrated electron shielded light detector located within the image plane and shielded from electrons generated by said photocathode, said light detector generating a signal in response to incident light, wherein said power supply control circuit incorporates the output from said light detector and the output from the pixels to generate the power supply control signal.

A camera comprising:

• a photocathode operable in a night mode wherein electrons are generated in response to incident light and operable in a day mode in which a fraction of the incident light is transmitted through said photocathode and wherein pixels of an active pixel sensor sense light in said day mode;
• an active pixel sensor in spaced relation to said photocathode, said photocathode being positioned between said active pixel sensor and an object being imaged, said active pixel sensor comprising an array of pixels for sensing electrons in said night mode and light in said day mode;
• a power supply for energizing said photocathode in said night mode in response to a power supply control signal, said power supply comprising a gated power supply and said control signal comprising a gating signal having a duty cycle that increases as the light level decreases;
• a lens positioned between the object being imaged and said photocathode, a lens position actuator for moving said lens, in response to a position control signal, between a night position wherein an image of the object is focused on said photocathode, and a day position wherein an image of the object is focused on said active pixel sensor and a position control circuit for providing said position control signal to said lens position actuator in response to the incident light level;
• an electron shielded light detector that is shielded from the electrons generated by said photocathode, said light detector generating a light detector signal in response to incident light, wherein said position control circuit generates said position control signal in response to said light detector signal;
• and
• a power supply control circuit for providing said control signal to said power supply in response to the incident light level, wherein said power supply provides to said photocathode an average energy level that increases as the incident light level decreases.

A camera comprising:

• a photocathode operable in a night mode wherein electrons are generated in response to incident light and operable in a day mode wherein a fraction of the incident light is transmitted through said photocathode;
• an active pixel sensor in spaced relation to said photocathode, said photocathode being positioned between said active pixel sensor and an object being imaged, said active pixel sensor comprising an array of pixels, each capable of measuring the charge accumulated in said night mode or in said day mode;
• an integrated electron shielded light detector comprising a standard active pixel located within the image plane and shielded from electrons generated by said photocathode to generate a control signal to set the camera in day or night mode in response to light at said detector above a predetermined level;
• a power supply for energizing said photocathode in said night mode;
• a lens positioned between said object being imaged and said photocathode;
• a lens position actuator for moving said lens relative to said photocathode and said active pixel sensor, in response to a position control signal, between a night position wherein an image of the object is focused on said photocathode, and a day position wherein an image of the object is focused on said active pixel sensor;
• and
• a position control circuit for providing said position control signal to said lens position actuator in response to the incident light level at said electron shielded light detector, wherein said lens is moved to the night position in the night mode and is moved to the day position in the day mode.

A camera comprising:

• a photocathode operable in a night mode wherein electrons are generated in response to incident light and operable in a day mode wherein a fraction of the incident light is transmitted through said photocathode;
• a CMOS imager in spaced relation to said photocathode, said photocathode being positioned between said CMOS imager and an object being imaged, said CMOS imager comprising an array of pixels on the front side of said CMOS imager for sensing electrons in said night mode and for sensing light in said day mode;
• an electron shielded light detector associated with said CMOS imager to sense incident light levels, an automated gain control circuit associated with the CMOS imager to generate a control signal having a duty cycle which is less than a fraction of the field time of the CMOS imager and in which the field time includes read out and non read out times of the CMOS imager and in which charge is sensed on said CMOS imager during the read out times, a control circuit that transitions between energized and non-energized states during said non read out times;
• a vacuum enclosure containing said photocathode and said CMOS imager;
• a power supply for energizing said photocathode in said night mode in response to a power supply control signal, said power supply comprising a gated power supply;
• and
• a power supply control circuit for switching said power supply off in said day mode when the incident light level is greater than a predetermined value and for supplying the control signal as a gating signal having a duty cycle that increases as the incident light level decreases in said night mode when the incident light level is less than the predetermined value.