A CMOS Luminescence Sensor for Intensity and Lifetime Dual Sensing
Fu, Guoqing.
2018
-
Abstract:
Luminescence is an important phenomenon in nature used extensively in biology, life
sciences, biomedical and environmental applications. It is the light emitted by a
substance not resulting from heat after absorbing a certain amount of excitation energy.
Measurements of luminescence could involve measuring its intensity or measuring its
lifetime. Sensing based on luminescence intensity ... read moresuffers from the variation of many
factors such as the optical path, excitation light intensity and the concentration of
luminescent indicator used. Instead, sensing using luminescence lifetime is more
reliable as it is immune to these factors. Both luminescence intensity and lifetime
detection techniques can be applied to luminescence-based optical sensors since the
emission intensity and lifetime of the luminescent indicator varies as a function of the
concentration of a certain substance in the environment. In this dissertation, we
propose a CMOS (complementary metal-oxide-semiconductor) sensor that combines both
luminescence intensity and lifetime detection on a single chip. It applies multi-cycle
charge modulation for lifetime extraction realized by capacitive transimpedance
amplifier (CTIA) based circuitry. The designed in-pixel CTIA-based structure is able to
capture the weak luminescence-induced voltage signal by accumulating photon-generated
charges in 25 discrete gated 10ms time windows and 10us pulse width. A pinned photodiode
on chip with 1.04pA dark current is utilized for luminescence detection. The proposed
CTIA-based circuitry can achieve 2.1 mV/(nW/cm2) responsivity and 4.38 nW/cm2 resolution
at 630 nm wavelength for intensity measurement and 45 ns resolution for lifetime
measurement. The sensor chip is employed for measuring time constants and luminescence
lifetimes of an InGaN-based white LED at different wavelengths. In addition, we
demonstrate accurate measurement of the lifetime of an oxygen sensitive chromophore with
sensitivity to oxygen concentration of 7.5%/ppm and 6%/ppm in both intensity and
lifetime domain. This CMOS enabled oxygen sensor was then employed to test water quality
from different sources (tap water, lakes, and rivers). However this sensor required an
external analog to digital converter and, its operation was restricted to a dark room
due to the sensor saturation caused by ambient light. In order to solve these issues, an
improved CMOS image sensor for luminescence imaging was also designed. In addition to
the combined intensity and lifetime sensing feature, this new image sensor converts the
integrated output voltage into digital pulses. Ambient light compensation is also
realized with an on-chip charge-pump based compensation circuitry. Driven by a 10 KHz
clock signal with 20 us pulse width as the integration time window, the proposed
circuitry can achieve 93 Hz/(uW/cm2) responsivity and 19nW/cm2 resolution at 575 nm. 2D
luminescence images of a white LED are obtained with this proposed image sensor. Since
common luminophores may exhibit different lifetimes one can use lifetime as a means of
discriminating them. This enables the paradigm of "filterless" imaging. We verify this
hypothesis for filter-less imaging for two fluorescent samples with similar emission
wavelength ([Ru(dpp)3Cl2] and [Ru(bpy)3Cl2]) but different lifetimes. According to the
measurement results, the proposed image sensor can easily distinguish two fluorescent
indicators. Benefiting from this feature, in addition to the dual sensing of
fluorescence intensity and lifetime, the proposed CMOS image sensor has the potential to
be used in fluorescence imaging systems applying multiple fluorescent indicators without
selective optical filters.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Electrical Engineering.
Advisor: Sameer Sonkusale.
Keyword: Electrical engineering.read less - ID:
- 6h4415215
- Component ID:
- tufts:24316
- To Cite:
- TARC Citation Guide EndNote
