CMOS image sensors have long since been the solution of choice for digital photography. They are much cheaper to produce than existing sensors, and they are also superior in terms of power consumption and handling. Consequently, leading manufacturers of cell-phone and digital cameras fit CMOS chips in their products almost without exception. This not only reduces the demands made of the battery, it also makes increasingly smaller cameras possible.
Yet these optical semiconductor chips are now reaching their limits: while miniaturization in consumer electronics is leading to increasingly smaller pixels around 1 micrometer across, certain applications require larger pixels in excess of 10 micrometers. Particularly in areas where only minimal light is available, such as in X-ray photography or in astronomy, having a larger pixel area compensates for the lack of light. Pinned photodiodes (PPD) are used to convert the light signals into electrical pulses. These optoelectric components are crucial for image processing and are built into the CMOS chips. “Yet when the pixels exceed a certain size, the PPDs have a speed problem”, explains Werner Brockherde, head of department at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS. Low-light applications tend to call for high image rates. “But the readout speed using PPD is too low”, says Brockherde.
The Fraunhofer researchers have now come up with a solution to this problem – it is unique and has already been patented. The scientists have developed a new optoelectronic component, the lateral drift field photodetector (LDPD). “In this component, the charge carriers generated by the incident light move at high speed to the readout node,” explains the researcher. With the PPD the electrons simply diffuse to the exit; a comparatively slow process but which is sufficient for many applications. “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.”
To produce the new component, the Fraunhofer researchers improved upon the currently available CMOS chip manufacturing process based on the 0.35 µm standard: “The additional LDPD component must not be allowed to impair the properties of the other components,” says Brockherde. Using simulation calculations the experts managed to meet these requirements – and a prototype of the new high-speed CMOS image sensors is already available. “We expect to get approval for series production next year,” says Brockherde.
The high-speed CMOS sensors are ideal candidates for applications that require large pixels and a high readout speed: astronomy, spectroscopy or state-of-the-art X-ray photography are among the potential applications. But the sensors are also ideally suited for use as 3-D sensors based on the time-of-flight process, whereby light sources emit short pulses that are reflected by the objects. The time-of-flight of the reflected light is then recorded by a sensor and used to create a fully-fledged 3-D image. This technology is a compelling proposition for applications such as crash protection, as the sensors can precisely record their environment in three dimensions. The Fraunhofer researchers have already developed this kind of area sensor based on the unique pixel configuration for TriDiCam GmbH.
Werner Brockherde | Fraunhofer Research News
New AI system manages road infrastructure via Google Street View
19.06.2019 | RMIT University
'Alexa, monitor my heart': Researchers develop first contactless cardiac arrest AI system for smart speakers
19.06.2019 | University of Washington
The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.
Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...
The well-known representation of chemical elements is just one example of how objects can be arranged and classified
The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...
Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.
Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...
Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.
The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...
Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.
The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....
29.04.2019 | Event News
17.04.2019 | Event News
15.04.2019 | Event News
19.06.2019 | Physics and Astronomy
19.06.2019 | Information Technology
19.06.2019 | Materials Sciences