This paper emphasizes on the stability of the diffused signal acquired by a time domain diffuse optical tomography system. The robustness of the system is enhanced to make it perform consistently over a longer period of time.
As a new time-resolved method which combines the spread spectrum time-resolved method with single photon counting,
pseudo-random single photon counting (PRSPC) has been proved to have the potential for high speed data acquisition
due to high count rate achievable. A continuous wave laser modulated by a pseudo-random bit sequence is used to
illuminate the sample, while single photon counting is used to build up the optical signal in response to the excitation.
Periodic cross-correlation is performed to retrieve the temporal profile. Besides the high count rate, PRSPC also offers
low system cost and portability which are not with the conventional time-correlated single photon counting (TCSPC). In
this paper, we report a high speed PRSPC system that can be used for real time acquisition of the temporal spread
function (TPSF) of diffuse photons. We also present preliminary experimental work of human blood glucose testing
studies by utilizing the PRSPC system.
Pseudo-random single photon counting (PRSPC) is a new time-resolved method combining the spread spectrum timeresolved
optical measurement method with single photon counting. A continuous wave laser diode is modulated with a
pseudo-random bit sequence, while a single photon detector is used to record the pulse sequence in response to the
modulated excitation. Periodic cross-correlation is performed to retrieve the impulse response. Compared with
conventional time-correlated single photon counting (TCSPC), PRSPC enjoys many advantages such as low cost and
high count rate without compromising the sensitivity and time-resolution. In this paper, we report a PRSPC system that
can be used for high speed acquisition of the temporal spread function of diffuse photons. It can reach a photon count
rate as high as 3Mcps (counts per second). Experimental work has been conducted to demonstrate the system
Time-correlated single photon counting (TCSPC) is popular in time resolved techniques due to its prominent
performance such as ultra-high time resolution and ultra-high sensitivity. However, this technique is limited by low
counting rate and high system cost. In this paper, we report a new time-resolved optical measurement method which
aims to achieve faster data acquisition without losing the key benefits of TCSPC. The new method is based on the spread
spectrum time-resolved optical measurement method combined with single photon counting. A pseudo-random bit
sequence is used to modulate a continuous wave laser diode, while the pulse sequence in response to the modulated
excitation is recorded by a single photon detector. The impulse response is then retrieved by periodic cross-correlation.
Both simulation and experimental work have been conducted to validate our approach. Experimental results with our
prototype have shown a time-resolution better than 200 picoseconds. Besides the faster data acquisition and high timeresolution,
the new method also affords other benefits such as portability and low cost.