Wednesday, September 16, 2015
Hamamatsu ToF Sensor Principle Revealed
So far, Hamamatsu ToF image sensor operation principles have not been presented to the broad public. University of Siegen, Germany, MSc Thesis "Analysis of a pulse-based ToF camera for automotive application" by Simon Theiß fills this gap. The work is based on Hamamatsu S11963-01CR sensor:
Actually, Hamamatsu seems not to work with a short and long shutter but with two subsequent shutters and a draining gate to get rid of background light, as is actually illustrated in the datasheet to which also said MSc thesis refers (pg. 4 in):
ReplyDeletehttp://www.hamamatsu.com/resources/pdf/ssd/s11963-01cr_kmpd1142e.pdf
To my knowledge the short/long shutter sequence illustrated above originates from O. Elkhalili et al. - see ESSCIRC06, JSSC04; and O. Schrey - see EP 2263103 B1 (Fraunhofer IMS/Siemens AG).
I'm leaning out really far now and please teach me different if I'm making false assumptions - but to my "knowledge" Hamamatsu collaborates to some extent with Shizuoka University. At least there are plenty of papers with Hamamatsu and Shizuoka Univ. affiliations. Now looking at one set of papers they've written together about ToF based on gates-on-field-oxide structures, one finds the same timings (or at least very similar ones) that Hamamatsu quotes in their datasheet – c.f. e.g. S. Kawahito et al. “A CMOS Time-of-Flight Range Image Sensor With Gates-on-Field-Oxide Structure” IEEE Sensors Journal Vol. 7, No. 12., Nov 2007. Thus now I'd bet to find something like this in their imagers - but this is a job for e.g. Chipworks or Hamamatsu to confirm ;-D
The sequence looks a lot like US Patent No.6,452,666 - Optical Range Finder that Sandor Barna and I filed in 1998 at Photobit.
DeleteWell, the thesis claims that Hamamatsu sensor uses the long and short shutter approach. Or, at least, this is one of the possible modes of the sensor.
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