Wednesday, December 06, 2006

Canesta High DR Patent Granted

Yahoo-Finance: The new Canesta SunShield(TM) technology has been granted U.S. Patent No. 6,919,549, "Method and System to Differentially Enhance Sensor Dynamic Range."

A key challenge in uncontrolled lighting conditions, such as those common in automotive applications, has been dealing with both bright sunlight and the rapidly flickering shadows that often accompanies it. Canesta's native technology uses bursts of infrared light from tiny lasers or light-emitting diodes (LEDs) to illuminate the field of view, and then measures the "time of flight" that it takes the photons of infrared light to bounce off of nearby objects and return to the sensor. From this, the sensor chips form a real-time 3-dimensional image, at 30 frames per second or better, which can be used to detect objects.

In the presence of strong sunlight, however, the extremely low-level illumination from the laser or LED is, in effect, swamped out. If a system is made sensitive enough to perceive the infrared bursts, then it completely saturates in the presence of bright light, not unlike our eyes do when surprised by a camera flash. By contrast, if the system is configured to work at the highest levels of sunlight, then the infrared pulses become too faint to measure accurately.

Canesta solved this problem with a simple and elegant solution. Rather than allowing the sensor to saturate by having it observe the scene for too long a time - in this case the duration of one "frame," a series of shorter samples are taken that keeps the amount of ambient light for any one sample within the dynamic range of the sensor. During each sample, the system receives photons from both the ambient background and from the infrared ranging signals. At the end of the sample, the signal from the ambient sources is simply discarded, while the ranging signal is saved. When the time comes for the sensor array to output a frame - say, every 30th of a second - the results from each sample, which now only contain the ranging signal component, are added together to determine its final value.

1 comment:

  1. hahaha ... and the shot noise ???

    ReplyDelete

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