Quantum-dot sensor brings benefits to near-IR

Quantum-dot sensor brings benefits to near-IR

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By eeNews Europe

The SparkP2 is a 2-Mpixel NIR image sensor in a 1/7-inch physical format that the company claims brings a number of advantages to the NIR spectrum, where it can be used for gesture and iris recognition, security and surveillance in consumer, industrial and automotive applications.

SparkP2 operates at the 940nm near-infrared spectrum with 3 times higher light response and over 20 times lower power consumption than competing solutions even in extreme lighting conditions.

It follows on from the launch of the Q13, a 13-Mpixel visible-light image sensor based on quantum film technology, in November 2015 (see Quantum-dot image sensor launch threatens silicon). 

InVisage (Menlo Park, Calif.) was founded in October 2006 to develop a light sensitive material based on quantum dots. The quantum-dot material is a II-VI meta-chalcogenide broad-band light absorber where the band-gap is tuned by the physical size of the material bound together in an optically transparent carrier material. This material replaces the silicon photodiode in the CMOS image sensot IC.

The same QuantumFilm used in the Q13 visible light sensor is used in SparkP2 but tuned to the near-IR, Jess Lee, CEO of InVisage, told eeNews Europe. A key advantage of the QuantumFilm is its efficiency, which means that the film can be much thinner than the equivalent silicon photodiode. In the case of IR QuantumFilm’s advantage is increased with a thickness of 0.5-micron versus 5 to 10 microns of silicon. This produces better specifications in terms of pixel signal crosstalk.

The SparkP2 also provides a global shutter capability. As well as providing for sharper images of moving scenes this allows image taking to be synchronized with infrared illumination. By not having to provide continuous infrared illumination system-level power consumption can be significantly reduced. InVisage QuantumFilm global shutter works in tune with a pulsed LED, which optimizes the LED battery usage to be just 10 mW, versus 750 mW for LEDs used with rolling shutter NIR cameras. 

"Previous IoT NIR cameras have been difficult to use indoors and almost impossible to operate outside," said Lee, in a statement. "Indoors, users had to remain within a short range for the device to work. At the same time, conventional camera systems burn a continuous 1000 mW of illumination power, which produces a distracting red glow and drains battery life. Outside, the power requirement is even higher in order to overcome the power of the sun, which makes it challenging for compact IoT devices to see and detect obstacles. SparkP2 is the first solution to address all of these issues."

Next: A lighter NIR sensor

The overall combination also makes for a much thinner and lighter NIR image sensor, an advantage when it comes to design wins in drones where SparkP2 could be part of a collision avoidance system.

SparkP2 specifications. Source: InVisage.

The SparkP2 is expected to sample in 2Q16 and be in volume production in 4Q16.

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