A capacitive division imaging readout detector for light-sheet FLIM

Measuring the spatial position and lifetime distribution of the fluorophores enables users to discern vital information about the chemical environment within a biological system. It however, remains challenging since the photon count is usually extremely limited, requiring a high degree of efficiency within the system. The timing precision to measure the lifetimes are of the order of picoseconds. Traditional methods to achieve two dimensional images involve point scanning with a confocal or two photon microscope and collecting the photon timings with a point collector. This has the downside of being comparatively slow. High speed, photon timing counters with spatial imaging capabilities therefore offer a desirable option to decrease measurement times. We have developed a new solution to this problem. Our system side illuminated our sample with a sheet of excitation light produced by a pulsed laser diode at 470nm. The imaging path is then performed by two cameras: a high resolution EMCCD captures an intensity image allowing for alignment of the sample. The second path contains a multichannel plate (MCP) photomultiplier. To read the charge, time and position from the MCP remains a challenge. We have demonstrated an alternative technology; a Capacitive Division Imaging Readout (C-DIR) which has been developed by Photek Ltd. The device uses an array of capacitors to move the charge site from the MCP to four preamplifiers and time-over-threshold discriminators. The work here will present data on the measured frame rate,point spread function, and spatial and temporal resolution of the device. The microscope shows a excellent degree of time resolution and temporal repeatability. The spatial imaging exhibits some degree of geometric distortion and post measurement correction methods have been implemented to reduce this. Images of biological samples will be presented showing the two dimensional life time imaging of the system along with measurements of FRET.