Performance of a photo-diode array cooled to low temperatures in image cytometry

It is hypothesized that the low-light-level performance of a solid-state imaging device can be significantly improved if it is cooled to temperatures in the range of 0 degrees to -40 degrees C, which is obtainable by a simple thermoelectric cooler design. To verify this, a linear charge-coupled photodiode array was cooled, and the dark current, dark current nonuniformity, and certain thermal spikes were measured from +40 degrees C and -40 degrees C. It was seen that the dark current decreased by three decades in this range, the dark current nonuniformity decreased by 97% from +40 degrees C to +10 degrees C, and the thermal spikes were nonexistent at -30 degrees C. Fluorescence and bright field microscopy images were also captured, and it was found that fluorescent images with an illuminance of approximately 10/sup -4/ lux can be detected at -40 degrees C and that the dynamic range of an image with a two second integration time is increased by over two decades from +40 degrees C to -40 degrees C.<>