Real-time single-exposure ROI-driven HDR adaptation based on focal-plane reconfiguration

Abstract

This paper describes a prototype smart imager capable of adjusting the photo-integration time of multiple regions of interest concurrently, automatically and asynchronously with a single exposure period. The operation is supported by two interwined photo-diodes at pixel level and two digital registers at the periphery of the pixel matrix. These registers divide the focal-plane into independent regions within which automatic concurrent adjustment of the integration time takes place. At pixel level, one of the photo-diodes senses the pixel value itself whereas the other, in collaboration with its counterparts in a particular ROI, senses the mean illumination of that ROI. Additional circuitry interconnecting both photo-diodes enables the asynchronous adjustment of the integration time for each ROI according to this sensed illumination. The sensor can be reconfigured on-the-fly according to the requirements of a vision algorithm.

Pixel-wise parameter adaptation for single-exposure extension of the image dynamic range

“…This approach has been proved to work inside a region of interest (ROI) in [8]. Within a ROI, correlation between light intensities is usually high.…”

“…The two chips reviewed in this paper [8] [9] work with a single exposure. They evaluate the illumination conditions locally and concurrently with image acquisition, and they have the necessary elements to correct pixel parameters to accommodate a wider intra-scene DR.…”

“…They evaluate the illumination conditions locally and concurrently with image acquisition, and they have the necessary elements to correct pixel parameters to accommodate a wider intra-scene DR. In [8] this evaluation allows for the local adaptation of the integration time. In [9] the voltage range is extended as needed by the asynchronous tagging of saturation events at each pixel.…”

“…Then we will explain that saturation conditions can be assessed without having to wait to the end of exposure, allowing for concurrent adaptation of the pixel parameters. After that, we will review the characteristics of a sensor chip that adapts the integration time of each pixel to the local illumination average [8]. Then, a prototype sensor whose pixels self-reset after asynchronously tagging the saturation events is described [9].…”