New-Tech Europe Magazine | August 2017

Interline Transfer EMCCD Technology Enables a New Regime of Very Low Light Imaging

Michael DeLuca, Go to Market Manager, Industrial and Security Division, Image Sensor Group, ON Semiconductor

While light sensitivity is an important specification for all image sensors, some applications require devices that are capable of operating under very low lighting conditions, beyond the range where standard image sensors are useful. Whether detecting a fluorescent marker viewed under a microscope, an image of the retina captured with an ophthalmic fundus camera, or a surveillance image operating on a cloudless, moonless night, technologies that enable very low light imaging – enabling 30 fps image capture at illuminations down to 0.1 lux – can be critical to success. Historically, Electron Multiplication Charge Couple Device (EMCCD) technology has been very successful

in enabling the capture of scenes with very low light levels. This technology takes the very small charge detected in a pixel under low light and multiplies it many times before reaching the sensor’s amplifier, allowing the initially unresolvable low signal level to be raised above the amplifier noise floor for detection. While this technology excels at image capture under low light levels – even down to the detection of single photons – the electron multiplication cascade can overflow and create blooming artifacts if signal levels entering the EMCCD register are too high, limiting use of sensors with this technology to scenes that do not contain any bright components. In addition,

the Full Frame Transfer technology traditionally used for EMCCD designs limits the resolution available from these devices to approximately one megapixel or lower, restricting the spatial image quality available when using this technology in video applications. Interline Transfer EMCCD technology addresses these limitations directly by combining the low light sensitivity available from an electron multiplication output register with the image uniformity, resolution scaling, and electronic global shutter capabilities of Interline Transfer CCD. This combination enables the development of image sensors that can capture continuously from very low light to bright light in

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