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difference between blank and sample measurement with and without illumination to reduce
the effect of liquid refraction and incident light.
Figure 5. Photometric Light Absorbance Method
4.2.3 Optical Light Scatter and Diffraction Method
Optical measurement of light scattering and diffraction is used to determine 5-part leukocyte
(LYM%, MON%, NEU%, EOS%, BAS%) differential parameters. An optical measuring head
contains a focused laser source that is used to illuminate a stream of leukocytes (WBC)
suspended in an optically clear diluent moving through a flow cell.
The cells scatter light as they flow through the path of the laser beam. An optical detector
senses changes in the intensity of the scattered laser light which are proportional to the cell
volume and granularity of the cell’s internal structure. The ‘ELite 5’ electronics convert these
changes to electrical pulses which are gathered and stored for analysis. Five part population
discrimination is based on analysis of the two dimensional volume and granularity distribution
scatter diagram.
Figure 6. ‘ELite 5’ Optical Head Block DIagram
Cells with greater volume or size or more granularity will tend to scatter greater amounts of
light. The intensity of scattered light is detected by an optical signal processing system.
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