Apparatus and method for high dynamic range imaging using spatially varying exposures

A system for high dynamic range imaging comprising:

• an image sensor comprising an array of light sensing elements, the image sensor sensing an image of a scene and providing corresponding pixel values representing light intensities impinging on respective ones of the light sensing elements, the image sensor providing a saturated pixel value when the intensity of light impinging on a corresponding one of the light sensing elements is greater than a first threshold level and providing a blackened pixel value when the intensity of light impinging on a corresponding one of the light sensing elements is below a second threshold level, the image sensor having a low dynamic range relative to the range of intensities of the image of the scene;
• a mask interposed between the scene and the array of light sensing elements of the image sensor, the mask having a multiplicity of light transmitting cells that attenuate the intensity of scene light transmitted through the mask on to the light-sensing elements, wherein the light-transmitting cells are configured so that the intensity of scene light transmitted on to the light sensing elements is attenuated by brightness level amounts that vary spatially across the array of light-sensing elements, and whereby the scene is exposed to the light sensing elements in a spatially varying manner, each of the light sensing elements having a corresponding exposure value indicative of the transparency of the cells through which light impinging on the light sensing element passes, the transparency of each of the cells of the mask being alterable by applying a respective exposure control signal to the mask;
• a mask controller coupled to the image sensor for receiving the pixel values provided thereby and for computing, and applying to the mask, exposure control signals for minimizing the number of saturated pixel values and blackened pixel values from the image sensor, and providing exposure values corresponding to the applied exposure control signals;
• and
• an image processor coupled to the image sensor for receiving the pixel values provided thereby, the image processor comprising a normalizer for mapping the pixel values by a function of the exposure values to derive corresponding normalized pixel values.