Panasonic says it has developed an image sensor 100 times as sensitive to light as existing technology, enabling self-driving cars to spot pedestrians, traffic signals and other objects instantly even at night.
The Japanese manufacturer aims to have a practical version ready as early as 2020 or so.
With the race to build road-ready autonomous cars heating up, so too is the competition in the electronics needed to make them work.
Image sensors, found in digital cameras like those embedded in smartphones, convert light into electrical signals. Sony enjoys a market-leading 40% global share and is chasing demand for automotive applications. Panasonic had scaled back its presence amid declining profitability in its semiconductor business. But the prospect of growth in high-end sensors has prompted it to resume development.
The company's new design is made from a thin film of organic material rather than silicon, the stuff of most microchips. Panasonic developed the basic technology with Fujifilm. A proprietary circuit design reduces noise when converting light to electrical signals, while a modified electrode structure helps detect even faint light efficiently.
Conventional image sensors tend to get blinded by headlights or other sources of glare -- a shortcoming that limits their ability to discern objects at night. Panasonic says its new sensor is sharp-eyed enough to make out the license plate number of a speeding car. The company envisions a range of uses besides self-driving cars, including surveillance cameras and medical equipment.
Sony, which has strength in CMOS image sensors, will begin mass-producing them for automotive applications in May. The company reports pushing its technology to the level of taking color images in nighttime settings less bright than starlight.
Press Release:
Panasonic Develops the APD-CMOS Image Sensor to Realizes Sharp Color Imaging under 0.01 lux Illuminance.
Panasonic Corporation today announced that it developed the CMOS image sensor (APD-CMOS) that uses avalanche photodiodes (APDs)*1in each pixel. The company has succeeded in obtaining 10,000 times multiplied*2 electric signals by means of the APDs' multiplication of photoelectrons that are generated by photoelectric conversion in the photodetector. This allows you to take sharp color images even under starlight (illuminance of 0.01 lux) or in other similarly dark places.
*1 Photodiodes that are capable of obtaining large electric signals from weak light (i.e. small numbers of photons). Large output signals can be obtained by multiplying photoelectrons that are generated in the photoelectric conversion layer.
*2 In comparison with image sensors without a multiplication function (according to our own research as of February 3, 2016)
This new image sensor allows for highly sensitive imaging through the multiplication of photoelectrons, realizing high-gradation color imaging without the need to increase the exposure time even in dark places. In addition, the multiplication of photoelectrons can be controlled instantly by changing the voltage applied to the APDs depending on the illuminance at the time of imaging, allowing you to take images at various illuminances from bright places to dark places. Its expected applications include surveillance cameras that require color imaging with a wide dynamic range and industrial cameras that require ultra-highly sensitive imaging.
This development brings the following advantages.
- Highly sensitive color imaging:
40 million/lux･sec･μm² (10,000 times sensitive in comparison to conventional devices)
- Wide dynamic range:
100 dB (+ 40 dB in comparison to conventional CMOS image sensors)
This development has been realized on the basis of the following technologies:
- APD picture element design technology in which avalanche photodiodes and charge storages are incorporated in the photoelectric convertor for not only multiplying but also accumulating photoelectrons that contain generated color information
- Variable sensitivity technology in which multiplication is controlled in a thousandth of a second by controlling the voltage applied to the APDs, realizing 30-fps video imaging that can follow the changes in illuminance
With conventional image sensors, photoelectrons that are photoelectric-converted during imaging in dark places may fall below the noise level, thereby limiting the imaging environment to no less than moonlight (illuminance of 0.1 lux) or so. This is why imaging under illumination of a near-infrared light source and imaging using photo multipliers have been carried out. However, near-infrared light sources have the drawback of the inability of color imaging, whereas photo multipliers have the drawback of forcing cameras to be upsized due to the necessity of a large-capacity power supply.
This development result was announced in the 2016 International Solid-State Circuits Conference, which was held in San Francisco on February 1, 2016.
Fig. : Comparison of images without multiplication and with multiplication
About Panasonic
Panasonic Corporation is a worldwide leader in the development of diverse electronics technologies and solutions for customers in the consumer electronics, housing, automotive, enterprise solutions and device industries. Since its founding in 1918, the company has expanded globally and now operates 468 subsidiaries and 94 associated companies worldwide, recording consolidated net sales of 7.715 trillion yen for the year ended March 31, 2015. Committed to pursuing new value through innovation across divisional lines, the company uses its technologies to create a better life and a better world for its customers. To learn more about Panasonic: http://www.panasonic.com/global.
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