Monochrome/color dual-slope traffic camera system
First Claim
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1. A video traffic system, comprising:
- a dual-slope, high dynamic range CMOS camera with photodiodes that integrate the darker pixels over the full shutter period, but that reset the integration of bright pixels to an adjustable percentage of maximum;
a light sensor for positioning outdoors in an area to be imaged by the CMOS camera, and for providing a white plate measurement of the lighting conditions near an image target;
an automatic dynamic range (ADR) processor for computing, from a measurement returned by the light sensor, an optimum set of shutter, dual-slope integration reset time, and dual-slope integration reset thresholds for the CMOS camera to avoid oversaturation of said image; and
an output for image transfer.
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Abstract
A video traffic system comprises a dual-slope, high dynamic range CMOS camera. Shutter, gain, and pedestal control and set-points for the dual-slope integration knee threshold and trigger time are computed from an operational model of the camera response using an input from a wireless light sensor. Darker pixels can integrate over the full shutter period, but bright pixels that are integrating too quickly and will saturate are reset to an adjustable level around 78% of maximum. Such reset occurs at an adjustable time about 93% of the full shutter period. The bright pixels are released to integrate from that point until the shutter closes.
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Citations
10 Claims
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1. A video traffic system, comprising:
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a dual-slope, high dynamic range CMOS camera with photodiodes that integrate the darker pixels over the full shutter period, but that reset the integration of bright pixels to an adjustable percentage of maximum; a light sensor for positioning outdoors in an area to be imaged by the CMOS camera, and for providing a white plate measurement of the lighting conditions near an image target; an automatic dynamic range (ADR) processor for computing, from a measurement returned by the light sensor, an optimum set of shutter, dual-slope integration reset time, and dual-slope integration reset thresholds for the CMOS camera to avoid oversaturation of said image; and an output for image transfer. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of high dynamic range camera operation in which:
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shutter control and set-points for a dual-slope integration knee threshold and trigger time are computed from an operational model of a camera response using an input from a wireless light sensor; wherein, darker pixels can integrate over a full shutter period, but bright pixels that are integrating too quickly and that will saturate are reset to an adjustable level some percentage of maximum; and wherein a reset occurs at an adjustable time some percentage of the a shutter period, such that any bright pixels are released to integrate from that point until said shutter closes. - View Dependent Claims (8, 9, 10)
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Specification