1. Technical Field
The present invention relates to the field of imaging system, and, more particularly, to active and/or passive imaging by multiple gated low noise pixel per readout frame method.
2. Discussion of Related Art
U.S. Pat. No. 7,733,464 B2, titled “vehicle mounted night vision imaging system and method” teaches a device and method for improving visibility conditions in a motor vehicle during low-visibility environment (nighttime or nighttime with poor visibility conditions such as rain, snow etc.). The system described in the aforementioned patent is based on gated imaging technology (i.e. the imaging sensor utilizes reflected light signal). In addition, the aforementioned system implements a sensor that is based on image intensification technology using photocathode and/or micro-channel plate. This type of image intensification technology has inherent drawbacks in vehicular environment; sensitivity lose due to high temperature (above 50 deg Celsius), sensitivity lose due to solar irradiance, burn effect due to a constant static image projection to the photocathode, temporal noise and blooming (saturation) in an inter-scene dynamic range above 50 dB. This type of image intensification technology is also defined as an export control item under the WASSENAAR arrangement or equivalent export control jurisdictions which cause difficulties in civilian application such as Advanced Driver Assistance Systems (ADAS). In addition, the system described in the aforementioned patent does not offer the driver any daytime imaging capabilities due to above drawbacks.
European Patent No. EP 1 118 208 B1, titled “measuring distances with a camera”, teaches a device and method for measuring distances with a camera referred to as a “3D camera”. Several gated pixel designs are described with a reset switch and at least a single gate switch or with a reset switch and at least a single modulator by a Field Effect Transistor (FET). These pixel designs have an integrator which is comprised of a storage capacitor and an amplifier. These gated pixel designs described in '208 B1 patent has low performance in low light level signal (such as in gated imaging vehicular applications) due to reset noise levels (also known as “KTC” noise) which are inherent in the integrator mechanism presented with the amplifier feedback in the pixel. In addition, noise levels and signal accumulation in the pixel integrator are not referred while gate off in the aforementioned patent. Anti-blooming ratio between pixel to the pixel apart is an important feature in an imaging sensor based on an array of gated pixels coupled and synchronized to a light source. In such a system configuration, a gated pixel can be bloomed (i.e. saturated even up to three magnitudes more than a nominal unsaturated signal) due to highly reflected objects (i.e. retro-reflector, mirror perpendicular to imaging sensor/light source etc.) in the viewed and/or measured scenery. Anti-blooming ratios between adjacent pixels are not described in the aforementioned patent.