Problem: Previous images of time-gated luminescence have been obtained with a cooled CCD camera by digitally
summing a series of sequential images. The data acquisition rate of approximately 10 one millisecond exposure images
per second was rate limiting and too slow for standard research and clinical use. An annoying undulating background was
present, which could not be totally removed by subtraction of an unexposed, control image.
Solution: An analog approach to this problem is to use an interline transfer, electronically shuttered camera. After each
exposure, the storage line is not readout; instead, the electrons from the acquisition pixels are transferred to the storage
pixels and thus are added to those previously stored. The length of the exposure is limited by the capacity of the storage
pixels and the rate of generation of background (noise) electrons. This electronic concept was tested with a Point Grey
Dragonfly2 640 by 480 pixel monochrome camera equipped with a Sony 1/3" progressive interline scan, electronically
shuttered CCD, which since it did not have any cooling, was operated at room temperature. Pulsed excitation was from a
Nichia UV LED.
Results: Five and 0.5 micron uniform europium complex stained microspheres could at room temperature be imaged with
time-gated excitation and acquisition times of 1 millisecond each and analog summation of 50 images.
Conclusion: The analog integration solution apparently works; however, a cooled scientific grade camera with the same
capacity for multiple transfers into storage pixels would be better suited for use with dimmer luminescent objects.