High-Speed X-ray Imaging

August 5, 2009

Scientists from the European Synchrotron Radiation Facility (France) the Forschungszentrum Karlsruhe, the Technische Universität Berlin and the Helmholtz Zentrum Berlin (all Germany) were able to make fast processes inside opaque objects visible, by using white synchrotron radiation to perform hard X-ray radioscopy with high spatio-temporal resolution. The required imaging detector was constructed out of a standard indirect detector in combination with a Photron SA1 CMOS-based camera. Thus, it was possible to investigate pore coalescence and individual cell wall collapse in an expanding liquid metal foam: the rupture of a film and the subsequent merger of two neighbouring bubbles could be recorded with a time sampling rate of 40000 frames per second (25 micorseconds exposure time). The results as published in the Journal of Synchrotron Radiation (http://journals.iucr.org/s/issues/2009/03/00/kv5057/ – open access) allowed to determine that the pore stability in a liquid metal foam is driven by intertia and not the viscosity of the melt. This knowledge is crucial in order to adapt metal foaming process for industrial production.

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Scientific CMOS Enables Rapid Frame Rates

Juni 18, 2009

At Laser 2009 – World of Photonics in Munich, Germany, the fastest CMOS ever was introduced. The Scientific CMOS chip enables image acquisitions at 100 frames per second.

Common Imaging Detectors

For CCDs it is feasible to achieve less than 3 electrons RMS readout noise, but due to the serial readout nature of conventional CCDs, this performance comes at the expense of frame rate. Conversely, when CCDs are pushed to faster frame rates, resolution and field of view are sacrificed (i.e. fewer pixels per frame to read out) or read noise and dynamic range suffer. These devices are capable of reading out at 20Mpixel/s per output port with a respectable read noise of only 5 to 6 electrons RMS. At this readout speed a single port 1.3 megapixel sensor can achieve 11 frames/s. The Electron Multiplying CCD (EMCCD) was introduced into the market in 2000 and represented a significant leap forward in addressing the mutual exclusivity of speed and noise. EMCCD cameras employ an on-chip amplification mechanism called ‘Impact Ionization’ that multiplies the photoelectrons that are generated in the silicon.

CMOS Imaging Sensors (CIS)
CIS are similar to CCD sensors, in so far as they are semiconductor devices with photosensitive areas in each pixel that convert incident photons into electrons. ‘Traditional’ CIS performance has generally been worse than CCDs and their acceptance into scientific markets has been limited due to a reputation of unacceptably high read noise and dark current, lower fill factors, and greater non-uniformity.

Hybrid CCD/CMOS Image Sensors
A hybrid focal plane array is comprised of CMOS Readout Integrated Circuits (ROICs) that are bump bonded to a CCD imaging substrate. By applying a column-parallel readout architecture, the speed versus noise limitations of a conventional CCD can be overcome.

The New Scientific CMOS
Scientific CMOS (sCMOS) can be considered unique in its ability to simultaneously deliver on many key performance parameters, overcoming the ‘mutual exclusivity’ that was earlier discussed in relation to current scientific imaging technology standards, and eradicating the performance drawbacks that have traditionally been associated with conventional CIS. The 5.5 megapixel sensor offers a large field of view and high resolution, without compromising read noise or frame rate. The sensor is capable of achieving 100 full frames/s with a read noise < 3 electrons RMS.

Performance Highlights of the First sCMOS Technology Sensor Include:
– Sensor format 5.5 megapixels 2560 (h) x 2160 (v)Read noise < 2 e- rms @ 30 frames/s; < 3 e- rms @ 100 frames/s
– Maximum frame rate 100 frames/sPixel size 6.5 μm
– Dynamic range 16,000:1 @ 30 frames/s
– QEmax 60%
– Read out modes (user selectable) Rolling and Global Shutter


Scientific CMOS Technology-A High-Performance Imaging Breakthrough

Scientific CMOS Technology-A High-Performance Imaging Breakthrough

New Type of Imaging: Fastest Camera

Mai 4, 2009

Researchers at the UCLA (University of California, Los Angeles, US) Henry Samueli School of Engineering and Applied Sciences have developed the serial time-encoded amplified microscopy (STEAM) technology. It is a novel, continuously running camera that enables real-time imaging at a frame rate of more than 6 MHz and a shutter speed of less than 450ps – roughly a thousand times faster than any conventional camera. Keisuke Goda, Kevin Tsia and team leader Bahram Jalali describe a new approach that does not require a traditional CCD (charge-couples device) or CMOS (complementary metal-oxide semiconductor) video camera. The new imager operates by capturing each picture with an ultrashort laser pulse. It then converts each pulse to a serial data stream that resembles the data in a fiber optic network rather than the signal coming out of the camera. Using a technique known as amplified dispersive Fourier transform, these laser pulses, each containing an entire picture, are amplified and simultaneously stretched in time to the point that they are slow enough to be captured with an electronic digitizer. Those cameras could be used for observing high-speed events such as shockwaves, communication between cells, neural activity or laser surgery.