Technology

Caeleste's technology is based on IP that enables the realization of the most challenging optical or radiation detector readout circuits, single pixel, one- and two-dimensional arrays.

You need a sensor that goes beyond state of the art in noise, sensitivity, dynamic range, geometry, spectral range? Or a sensor that combines these all and operates with CDS in versatile electronics shutter regimes?

Pixels which combine CDS (correlated double sampling), full pipelined synchronous shutter and high fill factor (Caeleste patent pending), both in front- and backside illumination.

Caeleste has the IP to design monolithic image sensors with high fill factor, not needing microlenses, and still compatible with regular CMOS technology.

Monolithic CMOS image sensors with high fill-factor.

The “8T” pixel (Caeleste patent pending), being the only CMOS pixel with synchronous shutter, CDS, low parasitic sensitivity and no in-pixel attenuation.

Hyperspectral image sensor, backside illuminated, operating in rolling shutter, snapshot shutter, synchronous shutter, NDR and random row addressing. Courtesy e2v+Caeleste

Detail of a Y-peripheral register

How to image X-rays with “photon counting” accuracy and energy discrimination (color X-ray)

Apart from our established approach to design “integrating” X-ray imagers, Caeleste developed a family of techniques (Caeleste patents pending) to realize the holy grail of X-ray imaging: photon counting.  Unlike state-of-the-art X-ray sensors that "integrate" secondary photocharge in classic CMOS or TFT pixels with associated noise and imperfections, photon counting allows true quantum limited imaging.  Quantum limited pixels can also discriminate photon energy, resulting in features as diagnostic "color X-ray", sharper  and lower dose X-ray images.  Large arrays ≥ 1 dm² and high yield are now possible. Photon counting enables unprecedented performance in noise floor, energy discrimination “color X-ray” and sharpness (MTF). Indirect detection photon counting is demonstrated (more…). Caeleste’s 91x90 pixel two-color X-ray photon counting demonstrator is soon available (more…).

16x16 pixel photon X-ray photon counting demonstrator

Realtime measurement of indirect detection events with the 16x16 pixel demonstrator

90x92 pixel Photon counting X-ray image sensor

An example of design-supporting R&D: “On the diagnostic value of Color X-ray”.

How Caeleste became involved in proving the mere “medical” diagnostic value of “color X-ray” is a story on its own. Initially we invented a compact low transistor count photon counting X-ray pixel. Quickly we noticed that photon counting has the optional feature of energy discrimination. However, is this a useful feature? Before investing time and money in the development, we needed the have some proof of value. Apart from bone densitometry and border control X-ray, which are based on energy discrimination of heavy atoms (Calcium, metals) as compared to light matter, no relevant medical records exits. Together with the UZB we pioneered multiple exposure color X-ray. So the added chrominance channels in the images label C-rich (fat) and O-rich (water) tissue, as well as intermediate C/O ratios (proteins, DNA, cancers).

Figs. Color mammography: B&W X-ray absorption and color X-ray images from the same mammary resection specimen (Breast carcinoma specimen “Poorly differentiated invasive duct” type). In this color X-ray image, hue codes the oxygen/carbon ratio (here blue=carbon-rich, red=oxygen-rich). [more...]

The key spec of your image sensor is Ultra Low Noise

Caeleste masters the art of CMOS pixel design with very low read noise (Noise electrons, noise photons, noise equivalent power NEP, noise equivalent flux NEF, etc). Our present (as of FEB 2011) record is 1.5 noise electrons RMS, as median of the imager, in nominal conditions, including the ADC discrimination. Our internal R&D aims to push this even further down (Caeleste patent pending).

We design for you image sensors that survive the highest doses of gamma or particle radiation

Total dose gamma and heavy particles: ionization damage, charge built-up (X, γ), and displacement damage (e-, H+, ions, hadrons). Caeleste personnel’s historical background in radiation tolerant design, and our experience in design X-ray pixels, allowed us to develop pixels that outperform any other published radiation tolerance (see graph).

Single event hardness (SEE, SEU, SEL). Caeleste can design image sensors with very high inherent immunity to single events.

Fig. Plot of dark current versus gamma total ionizing dose. Caeleste’s LAP, LAP DS, LAP DX and LAP XS radiation tolerant pixels “do not even move” as compared to State of the Art literature radhard imagers.

Your image sensor has depth information in every pixel.

Using Caeleste’s unique time-gating and time-of-flight pixels in standard CMOS technology (Caeleste patent US7564022). With this technology one is able to gate incoming light with sub-nsec accuracy. Applications in fluorescence imaging, TOF ranging, 3D imaging, in-the-pixel demodulation. Although the technique is pure CMOS based, it is superior compared to the established CMOS based techniques as these is absolutely no noise penalty due to the addition of multiple charge packets.

Visible light photon counting image sensors using APD (avalanche photo diode) / SPAD (Single photon avalanche diode) .

Caeleste designs and produces photon counting SPAD (single photo avalanche diode) imagers. These can be both hybrid and monolithic in standard CMOS technology [more…]

Detail of hybrid APD (left) wire bonded to a ROIC (right). Courtesy SensL+Caeleste.

Readout trace of photon counting avalanche photodiode