Low-light-level imaging and image processing

A charge-coupled imaging device for imaging a scene to produce a sequence of image frames of the scene at an image frame rate, R, of at least about 25 image frames per second, the charge-coupled imaging device comprising:

• a charge storage medium comprising a substrate having a front side and a backside;
• an array of pixels defined in the charge storage substrate by pixel interconnections supported on the front side of the substrate, exposure of the substrate to light from the scene producing charge packets in the pixels, the pixel interconnections providing selective electronic temporal control of transfer of charge packets from one pixel to another in the substrate;
• means for suppressing generation of dark current charge packet generation in the substrate pixels;
• and
• an output circuit for converting the charge packets in the pixels to an electrical pixel signal of output pixel values based on the light from the scene, a plurality of pixel values together forming an image frame, the output circuit characterized by a capacitance of less than about 10 femtoFarads;
• the output pixel values being characterized by noise-limited resolution of at least a minimum number, N.sub.M, of line pairs per millimeter, referred to the charge-coupled imaging device pixel array, in an image frame configured of the output pixel values as a function of illuminance of the light from the scene impinging the charge-coupled imaging device pixels, wherein for a scene characterized by a contrast of about 0.3, for a human observation time of about 0.05 seconds, and for an image scene frame rate of about 30 frames per second, N.sub.M is given as N.sub.M =1900 L.sup.0.51, where L is the value of illuminance of the input light impinging the charge-coupled imaging device pixels, for at least one illuminance value between a range of illuminance values of about 1.times.10.sup.-2 LUX and 1.times.10.sup.-7 LUX.

An imaging system for imaging a scene to produce a sequence of color image frames of the scene at a frame rate, R, of at least about 25 image frames per second, the imaging system comprising:

• an optical input port for accepting input light from the scene;
• a spectral range separator located in re lation t o the input port to receive the input light, the spectral range separator separating the input light into distinct spectral ranges;
• an imager system comprising at least one charge-coupled imager having an array of a plurality of pixels configured in a charge storage medium, the at least one charge-coupled imager being located in relation to the spectral range separator such that separated spectral ranges of input light impinge charge storage medium pixels, the at least one charge-coupled imager being characterized by monochromatic noise-limited resolution of at least a minimum number, N.sub.M, of line pairs per millimeter, referred to the imager pixel array, in an imaged scene as a function of illuminance of input light impinging the pixel array, wherein for a scene characterized by a contrast of about 0.3, for a human observation time of about 0.05 seconds, and for a monochromatic image scene frame rate of about 30 frames per second, N.sub.M is given as N.sub.M =1900 L.sup.0.51, where L is the value of illuminance of input light impinging the pixel array, for at least one illuminance value between a range of illuminance values of about 1.times.10.sup.-2 LUX and 5.times.10.sup.-7 LUX, the imager system producing a plurality of electrical pixel signals of analog pixel values based on the spectral ranges of input light that impinge the pixels, each electrical pixel signal corresponding to a distinct spectral range;
• an analog signal processor connected to receive each pixel signal for amplifying the pixel signals;
• an analog-to-digital processor connected to the analog signal processor for digitizing the amplified pixel signals to produce corresponding digital image signals having a dynamic range of digital pixel values represented by a number of digital bits, B, where B is greater than 8;
• and
• an image processor connected to receive the digital image signals and to combine together the digital image signals to produce a sequence of color image frames, each color image frame having pixel values based on the separated spectral ranges of input light, the sequence of color image frames being produced at the frame rate, R, with a latency of no more than about 1/R.