Extending Image Sensor Dynamic Range by Scene-aware Pixelwise-adaptive Coded Exposure

We present a method for extending the dynamic range of an image sensor by frame-to-frame adaptive adjustment of exposure of every pixel, based on changes in the brightness of the scene for that pixel. The method employs an image sensor with a coded-exposure-pixel (CEP) [1], where the exposure time of each frame is divided into N subframes, each of unary or binary-weighted duration. In each subframe the pixel is re-programmed with a 1bit binary code to be either on (code 1) or off (code 0), depending on the light flux captured by that pixel in the previous frame. The photo-generated charge is integrated across all subframes. The N 1-bit codes per pixel are computed by an off-sensor processor, and are loaded to a digital latch within that pixel, one per subframe. At the end of a frame, a high-dynamic-range (HDR) image is reconstructed by using that frame’s pixel codes to normalize the pixel digital outputs to a uniform exposure. The dynamic range is experimentally demonstrated to increase by up to 20log10(2 − 1) dB at the full frame rate and at the native resolution of the image sensor.