Palm MicroBeam - Laser Energy Adjustment; Laser Focus Correction

20 PALM
®
MicroBeam User Manual - 0202 Z
How to Prepare the PALM
®
MicroBeam for the Application
6.4.1 Laser Energy Adjustment
The nitrogen laser emits a fixed laser energy. For
precise laser micromanipulation a precise laser
energy adjustment is required.
A neutral density filter is mounted into the laser
beam path, which allows to continuously adjust
the laser energy to the individual requirements
without beam displacement. This gradually coated
filter is turned by a high precision DC stepping
motor, which is conveniently regulated on the
monitor screen by means of the of the PALM
®
RoboSoftware (please see the PALM
®
RoboSoft-
ware Manual).
6.4.2 Laser Focus Correction
Precise laser focus alignment allows laser cutting
with a nearly diffraction limited laser focus. The
coincidence of the laser focus with the optical focus
of the microscope is mandatory for precise laser
micromanipulation.
Every wavelength is diffracted differently. When
performing laser micromanipulation at a greater
distance from the specimen slide or within a
thicker or strongly refracting object, the offset of
the laser focus position has to be compensated.
The same applies when using different objectives.
To compensate for the so called chromatic aberra-
tion the laser focus position has to be changed,
independent from the microscope focus.
The Laser Focus Correction is done motorized: A
high precision DC stepping motor moves the cor-
responding lens. Focus setting is conveniently con-
trolled and regulated on the monitor screen by
means of the of the PALM
®
RoboSoftware. The dis-
play allows relocating selected laser focus settings.
Laser energy and focus is predefined by P.A.L.M.
Microlaser Technologies AG over the factory set-
tings for each objective (please refer to the PALM
®
RoboSoftware Manual). Only the sample specific
values have to be defined by the individual user.
These user specific values can be stored in a spe-
cial file for each user and/or application.
Figure 15 Laser focus in specimen plane
Figure 16 Laser focus above specimen plane
Figure 17 Laser focus below specimen plane
Notice
- The automated laser focus and energy set-
tings have been adjusted to the objectives
supplied by P.A.L.M. Microlaser Technolo-
gies AG (all of a comparable lens configura-
tion).
- Please contact P.A.L.M. Microlaser Technol-
ogies AG prior to the use of other objec-
tives.
- For the catapulting and microdissection, a
LD 40x objective has proved successful in
most of the applications.
For the visualization of catapulted specimen
with the LD 40x objective, you need a cap with
a flat, non-frosted clear surface and a rim,
which is not higher than 2mm (available from
P.A.L.M. Microlaser Technologies AG).