KEYWORDS: Fluorescence lifetime imaging, Sensors, Luminescence, Photodetectors, Signal detection, Monte Carlo methods, Single photon, Analog electronics, Physics, Temporal resolution
GaAsP hybrid detectors, which is new kind of photodetector, has been known as its excellent performance in time correlated single photon counting technique. We have verified that this detector also shows excellent performance in analog mean-delay method, which is another kind of time-domain FLIM, so one can expect enhancement of performance in time-domain FLIM when using the hybrid detector.
Phasor plot analysis is one of the most powerful analysis technique in fluorescence lifetime imaging microscopy, especially for analysis of heterogeneous mixtures. Compared to frequency domain fluorescence lifetime measurement, time domain measurement offers information in various frequencies at once measurement, but needs high frequency sampling for stable signal acquisition, which requires a lot of memory in hardware and a long time for analysis, furthermore in TCSPC, acquisition time is extremely long due to low photon count rate. We suggest a new system with low pass filter, which leads to about 100 times faster measurement speed while maintaining precision and accuracy in usual modulation frequency.
KEYWORDS: Luminescence, Fluorescence lifetime imaging, Analog electronics, Signal processing, Signal detection, Super resolution, Photodetectors, Convolution, Microscopy, Fluorescence resonance energy transfer
Fluorescence lifetime imaging microscopy (FLIM) is a powerful imaging tool widely used in monitoring cells, organelles, and tissues in biosciences. Since fluorescence lifetimes of most probes are a few nanoseconds, 20 ps measurement resolution is normally required. This requirement is quite challenging even with the fastest available optical and electronic devices, and several brilliant time-domain super-resolution techniques have been proposed for FLIM. The analog mean-delay (AMD) method is a recently introduced time-domain super-resolution technique for FLIM. Detailed constraints in the AMD method and their impact on the performance of the AMD super-resolution lifetime measurement are presented with experiments and simulations.
In today's manufacturing of PCBs (Printed Circuit Boards), there is an increasing demand on 3-D inspection of mesoscale
objects for quality assurance. Two representative examples are the solder pastes on printed circuit board and bumps
on FC-BGA (Flip Chip - Ball Grid Array) substrates, of which heights and volumes are precisely controlled to avoid
defects in direct surface mounting of semiconductor chips. Despite the demand, no suitable 3-D inspection techniques
are available yet, especially for high speed real time quality control of FC-BGA bump heights. Well-established
monochromatic or white light interferometry is not easy to produce large measuring ranges up to a few millimeters and
become robust to the vibrations on factory floor, while widely-used optical triangulation techniques with structured light
illumination fail to provide the measurement precision usually required down to a few micrometers. Moire
interferometry may be considered as a hybrid approach that combines the two distinct principles of the monochromatic
light interferometry and optical triangulation. Thus, when appropriately configured, moire interferometry is capable of
filling the gap between the two principles in terms of measurement range and precision. In this paper we propose a new
method of 3-D inspection of meso-scale objects, which is in fact based upon the principle of grating projection moiré
interferometry. This method projects a series of line patterns with predetermined phase shifts onto the target object and
detects phase information leading to construction of 3-D profiles. Making the most of modern computer vision and
digital signal processing technology allows for high speed measurement of 0.6 sec per 15mm×15mm field of view, with
a resolution of 1μm for all three (x,y,z) axis.
White-light scanning interferometry uses a wide-band spectrum light source and observes the short coherent variation of interferometric intensity obtained while moving either the test surface or the reference surface along the optical axis of the interferometric optics. When one employs the scanning interferometry for gauging the step height between two separate surface points that are made of different materials, a significant amount of measurement error occurs due to the phase change on reflection. The phase change varies with wavelength and materials, so its effects on resulting interferograms are not easy to be precisely identified. In this paper, we present a practical method for compensating for the measurement error caused by the phase change on reflection in step height gauging. The method takes a first-order approximation to the wavelength-dependent nonlinear behavior of the phase change and then determines its precise value from the phase information of the Fourier-transformed intensity data in the spatial frequency domain. The method can be realized simply by performing two additional quasi-monochromatic phase-shifting interferometric measurements, or more conveniently by adopting a special form of light source that has two spectral peaks. Experimental results prove that the propose compensation method is capable of reducing the measurement error to an accuracy of +/- 2 nm.
One of main error sources in scanning white light interferometry is the inaccuracy of scanning mechanisms for which PZT piezoelectric ceramics actuators are widely used. In this paper, we propose a new calibration method being capable of identifying actual scanning errors directly by analyzing the spectral distribution of sampled interferograms. Experimental results prove that the method provides an effective means of in-situ self-calibration enhancing the measurement uncertainty by one order of magnitude.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.