Pizza at 12:00 noon, Talks start at 12:15 pm

The next IMNS Seminar Series event will hear four short talks from members of the CMOS Sensors and Systems Group.  These are practice presentations for the upcoming IEEE International Conference on Communications ICC'15 - please come along and show your support:

TALK 1: Luca Parmesan - A 256 x 256 SPAD array with in-pixel Time to Amplitude Conversion for Fluorescence Lifetime Imaging Microscopy: A high resolution Time Correlated Single Photon Counting (TCSPC) image sensor based on sample and hold Time to Amplitude Converter (TAC) pixels and a global ramp voltage is presented. The 256 256 array achieves an 8 μm Pixel Pitch (PP), 19:63% Fill Factor (FF), output voltage range (0:7V) and time jitter of 368 ps at 10 fps employing an off-chip 14-bit differential Analogue to Digital Converter (ADC). A column-parallel flash ADCis also implemented, allowing coarse 3-bin TCSPC histogramming at 4 kfps for video rate fluorescence lifetime imaging.

TALK 2: Aravind Jalajakumari - An Energy Efficient High-speed Digital LED Driver for Visible Light Communications: Visible Light Communications (VLC) is a disruptive technology which could solve the RF spectrum crunch. VLC utilises light emitting diodes (LEDs) for transmitting data into free space. This talk details the development and experimental results of an integrated, energy efficient LED driver circuitry for VLC applications. . A current steering digital to analogue converter (DAC) based LED driver circuit supporting 4-channels with an 8-bit resolution is realized in a 180 nm complimentary metal oxide semiconductor (CMOS) technology. Each channel delivers a full-scale current of 255 mA and achieves up to 67% electrical efficiency when driving 250 MS/s orthogonal frequency division multiplexing (OFDM) signals. Optical differential drive capability is demonstrated by using two output branches of a single channel to drive two different LEDs with an SNR improvement (>5 dB). The chip is also capable of full digital control of color shift keying (CSK) using multi-color LEDs enabling lighting color-temperature adjustment, dimming and multiple-input and multiple-output (MIMO) optical communications.

TALK 3: Istvan Gyongy - Bit-plane Processing Techniques for Low-Light, High Speed Imaging with a SPAD-based QIS: Advances in SPAD sensor technology have recently yielded a >10kfps, 320x240 resolution imager that can be operated as a Quanta Image Sensor (QIS). This device, labelled SPCImager, thus combines the high speed and sensitivity afforded by SPAD devices with the negligible readout noise and logarithmic compression of QIS. These attributes open the door to a number of potential applications. This talk explores two applications: high speed imaging of fast moving objects and low light microscopy. Appropriate signal processing schemes are considered in both cases.

TALK 4: Neale Dutton - Oversampled ITOF Imaging Techniques using SPAD-based Quanta Image Sensors: The Quanta Image Sensor (QIS) or digital film sensor is an imaging array of photo-sensitive sites with single bit output (a jot). Binary field images (or jot bit planes) are oversampled in either the spatial or temporal domains to form a multi-bit intensity frame image, where each pixel in the image represents a summation of jots. Single photon avalanche diode (SPAD) based QVGA QIS image sensor have two significant advantages over photo-diode/photo-gate based CISs: the SPAD photo detection mechanism has both picosecond temporal resolution and single-photon sensitivity (typically 100ps RMS and >1V/ph respectively). This temporal resolution has previously been successful demonstrated in TOF imaging. The high sensitivity is ideal for connection to, and triggering of, a time-gated single bit memory pixel circuit or a single photon counter. Exploiting both these advantages, we propose two techniques applicable to oversampled QIS image sensors to implement two-bin ITOF imaging with and without background rejection. These are demonstrated for the first time using a time-gated SPAD-based QIS achieving 4.5x overexposure latitude in intensity and ITOF ranging with 38mm max σ in 60cm range.