Dynamic range

Dynamic range of a detection system is established here as the ratio between the highest signal and electronic noise measuring a full spot containing 100 pixels. Electronic noise floor = square root of number of pixels x 5 counts per pixel. Maximum signal = number of pixels x 65 000 counts per pixel. Maximum signal results = 6.5 million counts/50 counts which yields five orders of magnitude difference.

The intrascenic dynamic range is important to quantify bright signal against low signal or background. An adjacent area to a very bright spot should not be influenced by the high signal value (about 60 000 counts mean) of the bright spot area. The image should have a background of close to zero in the spot pitch distance (about 10 pixels) of a bright spot. Almost all CCD systems have problems in achieving four logs here because they have broad area illumination and imaging capacity. They cannot excite and detect pixel-by-pixel and lack a confocal scanning mode (Figure 16.1).

Automatic sample load, focal adjustment and scan

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