Sarah Bohndiek

Publication Details

• Characterization studies of two novel active pixel sensors

  Bohndiek SE, Arvanitis CD, Royle GJ, Speller RD, Clark AT, Crooks JP, Prydderch ML, Turchetta R, Blue A, O'Shea V. Optical Engineering. 2007; 46 (12): 124003

  A United Kingdom consortium (MI3) is founded to develop advanced CMOS image sensors for scientific applications. "Vanilla," a 520×520 array of active pixels with 25-μm pitch is fabricated in the 0.35-μm 4M2P (4 metal, 2 poly) CMOS process and uses a 3.3-V supply. It has flushed reset circuitry to attain low reset noise and random pixel access for high-speed region-of-interest (ROI) readout. "OPIC" is a 64×72 test structure array of digital pixels with 30-μm pitch, fabricated in 0.25-μm 5M1P (5 metal 1 poly) CMOS process with a 3.3/2.5-V supply. It can perform thresholding via an in-pixel comparator for sparse readout at a high frame rate. Characterization of both sensors is performed under optical illumination and x-ray exposure. For x-ray characterization, both sensors were coupled to a structured thallium-doped cesium iodide (CsI:Tl) scintillator via a fiber optic plate. Vanilla has been found to exhibit 34±3 e- read noise and a spectral response of 225±5 mAW at 500 nm and can read a 6×6 ROI at 24,395 framess. OPIC has 46±3 e- read noise and can perform sparse readout at up to 3700 framess. Based on these results, Vanilla could be employed for applications where only a small portion of the image contains relevant information, while OPIC is suited to high-speed imaging applications.