Object detection and tracking with reduced error due to background illumination

摘要

An image sensor frame rate can be increased by “interlaced” mode operation whereby only half the number of lines of an image is transported to the readout circuitry. This halves the integration time but also halves the resolution of the sensor. Accordingly, in one embodiment, an image sensor operated in an interlaced fashion is first exposed to a scene under a first form of illumination (e.g., narrowband illumination), and a first set of alternating (horizontal or vertical) lines constituting half of the pixels is read out of the array; the sensor is then exposed to the same scene under a second form of illumination (e.g., existing ambient illumination with the illumination source turned off), and a second set of alternating lines, representing the other half of the pixel array, is read out. The two images are compared and noise removed from the image obtained under narrowband illumination.

主权项

1. An image capture and analysis system including:
a camera including an image sensor and a field of view, wherein the image sensor operates in an interlaced mode that alternately reads out sets of odd lines and even lines of pixels arranged in adjoining rows or columns; one or more light sources directed toward the field of view with existing ambient illumination; and at least one processor that generates control signals to coordinate activated and deactivated intervals of the light sources with the interlaced mode read out of the image sensor; wherein the control signals initiate the interlaced mode readout so that a successive pair of reads from the sets of the odd and even lines capture a non-illuminated image from a deactivated interval and an illuminated image from an activated interval; wherein the non-illuminated image from the deactivated interval is illuminated by the existing ambient illumination; wherein the processor further compares adjoining lines from the non-illuminated image with lines from one or more illuminated images and uses the comparison to modify the illuminated image to remove noise based on ratios of pixel values between the pixel values in illuminated and non-illuminated images, whereby signal-to-noise ratio between foreground object illumination and background object illumination or background lighting improves.