Table of Contents
Slit Aperture
B
Circular Aperture
C
1. The image of a rectangular slit illuminated by the light from the tungsten
lamp is focused into the flowcell and onto the photodiodes on the scatter and
absorption PC boards. The detected signal pulses from cells passing through
the slit image are proportional to the optical power scattered into defined
angles and the optical power absorbed or lost. The resulting scattering and
absorption of the light from each white blood cell is due to the size and
staining characteristics of each cell.
2. The dark field stop intersecting the light beam going to the scatter
photodiode only accepts light scattered at angles between 5° and 10°.
3. The absorption signals are collected over a 0° and 10° angular interval.
4. The photodiode converts the optical scatter and absorption signals from each
white blood cell into two signal currents for each of the two channels (scatter
and absorption). Preamplifiers convert these optical signals into signal
voltages.
Laser Optical Assembly
A
The laser optical assembly consists of the illuminator, flowcell, and detector
assemblies. A laser diode, housed in the illuminator assembly, is used as the light
source.
The image of a slit illuminated by light from the laser diode is focused into the
flowcell. The sample/sheath stream in the flowcell contains iso-volumetrically
sphered red blood cells (RBC).
The RBCs and reticulocytes that pass through the slit image in the flowcell
scatter light at low and high angles; the stained reticulocytes also absorb a
percentage of the light. The scattered light is detected by the two scatter
photodiodes and generates the following signals:
•
A high-angle scatter signal corresponding to light scattered at angles between
5° and 15°
1-8
Beam Splitter
F
B
Welcome to the ADVIA 2120/2120i Hematology System
Scatter PC Board
I
Illuminator
A
Assembly
Flowcell
B
Location
Detection
C
Assembly
C
Chapters
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Troubleshooting
