Researchers at Germany's Fraunhofer Institute for Microelectronic Circuits and Systems IMS said they have found a new way to dramatically improve the low-light capabilities of CMOS image sensors.
The technology is especially suited for applications such as fluorescence and astronomy, which require image cells that are substantially larger than those cells commonly used in mainstream chips in order to achieve sufficient light exposure.
CMOS image sensors typically used pinned photodiodes (PPD) to convert the light signals into electrical pulses. However, there are limits to PPD-based readout speeds, which creates a problem when high image rates a necessary. To solve the issue, the Fraunhofer scientists developed a "lateral drift field photodetector (LDPD)" which accelerates the electrons. 'With the PPD the electrons simply diffuse to the exit; a comparatively slow process but which is sufficient for many applications," saidWerner Brockherde from Fraunhofer. “But by integrating an internal electric field into the photoactive region of the component, we have managed to accelerate this process by a factor of up to a hundred.”
The invention has already been submitted as a patent and Brockherde expects the technology to be available for 0.35 µm mass production in 2013. It is unlikely that we will be seeing this feature in mainstream cameras anytime soon, but it is good to know that there are new low-light capabilities on the horizon.