Proc. SPIE. 10884, Single Molecule Spectroscopy and Superresolution Imaging XII
KEYWORDS: Photodetectors, Super resolution, Microscopy, Luminescence, Signal processing, Convolution, Fluorescence lifetime imaging, Fluorescence resonance energy transfer, Analog electronics, Signal detection
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.
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.
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.
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.