tecan ls series Operating Manual page 24

4. Technical Description
4-2 Operating Manual for the LS Series Scanner No. 30001798 Rev. No. 1.5
Scanning is done in a first direction with the excitation beam. This very fast
scanning mechanism scans 40 lines per second. The overall scanning speed and
scanning time in this direction is independent from both pixel resolution and scan
width. The second scanning dimension is achieved by moving the sample in a
perpendicular direction. This movement is exactly synchronized with the first scan
axis to create a 2-dimensional fluorescence image. For example at 10 µm
resolution 4 mm are scanned within 10 s ((4 mm / 40 lines / s) * (100 lines / mm
) = 10 s). For this second direction the scanning speed is reciprocal
10 µm pixel size)
to the resolution and the overall scanning time depends linearly on the scan
length.
Fluorescence light is collected with a high aperture lens with exceptional working
distance (up to 6.5 mm). This long working distance is the key for the ability to
measure flexible sample formats other than slides.
A second lens refocuses the collected light onto a pinhole, thus creating a
confocal detection scheme.
Three pinholes of different sizes are mounted on an automatic slide carrier. The
smaller the pinhole, the lower the focal depth of the detected volume. The larger
pinholes typically create images with a slightly lower signal to background ratio
but offer the choice to measure bulky samples or uneven surfaces as well.
Behind the pinhole the fluorescence light passes through a bandpass filter that
rejects light of the excitation wavelength and all other spectral contributions that
are not within the detection bandwidth of the selected filter. Filters are arranged in
filter slides that can hold up to four different filters. Each filter slide has five
positions, but one of them has to stay open for autofocus purposes.
Filter slides can easily be removed or exchanged; up to 8 different slides can be
automatically identified by the instrument firmware when they are inserted in the
filter slots.
In the dual channel instrument a dichroic beamsplitter separates the two emission
wavelengths of the first and the second dye (e.g. Cy3 and Cy5) and lets them
pass trough two different emission filters and to two different photomultiplier tubes
(PMT's). The two different filters are located on two different filter slides in that
case.
A reference diode monitors laser power before each measurement.
Figure 4.2
(=
2004-11