A 72 × 60 Angle-Sensitive SPAD Imaging Array for Lens-less FLIM

Changhyuk Lee; Ben Johnson; TaeSung Jung; Alyosha Molnar

doi:10.3390/s16091422

A 72 × 60 Angle-Sensitive SPAD Imaging Array for Lens-less FLIM

Sensors (Basel). 2016 Sep 2;16(9):1422. doi: 10.3390/s16091422.

Authors

Changhyuk Lee^{1

2}, Ben Johnson^{3

4}, TaeSung Jung^{5

6}, Alyosha Molnar⁷

Affiliations

¹ School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA. cl678@cornell.edu.
² Department of Electrical Engineering, Columbia University, New York, NY 10027, USA. cl678@cornell.edu.
³ School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA. bcj25@cornell.edu.
⁴ Cortera Neurotechnologies, 2150 Shattuck Ave., PH, Berkeley, CA 94704, USA. bcj25@cornell.edu.
⁵ School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA. tj85@cornell.edu.
⁶ Department of Electrical Engineering, Columbia University, New York, NY 10027, USA. tj85@cornell.edu.
⁷ School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA. molnar@ece.cornell.edu.

Abstract

We present a 72 × 60, angle-sensitive single photon avalanche diode (A-SPAD) array for lens-less 3D fluorescence lifetime imaging. An A-SPAD pixel consists of (1) a SPAD to provide precise photon arrival time where a time-resolved operation is utilized to avoid stimulus-induced saturation, and (2) integrated diffraction gratings on top of the SPAD to extract incident angles of the incoming light. The combination enables mapping of fluorescent sources with different lifetimes in 3D space down to micrometer scale. Futhermore, the chip presented herein integrates pixel-level counters to reduce output data-rate and to enable a precise timing control. The array is implemented in standard 180 nm complementary metal-oxide-semiconductor (CMOS) technology and characterized without any post-processing.

Keywords: 3-D image sensor; CMOS avalanche photodiodes; SPAD; SPAD arrays; exponential decay; fill-factor; fluorescence imaging; highly sensitivity photodetectors; in-vitro; lab-on-chip; lifetime microscopy; low power imaging; photo-detector; photon timing; point-of-care; rangefinder; single photon detectors; time-correlated measurements.