Leica DM R Serie Mode D'emploi page 35

Functional description
In all microscopes with infinite tube length (∞)
the objective theoretically forms the image at
infinity, which would be of no use to the
microscopist.
Therefore microscopes with infinite tube length
always need a tube lens that projects the
intermediate image into the eyepiece. The
magnification of an objective for tube length ∞
thus depends not only on the focal length of the
objective, but also on the focal length of the tube
lens, which is 200 mm. The magnification of this
system, i.e. objective + tube lens, is engraved on
the objective, while the tube factor is defined as
1x and therefore does not need to be engraved
(according to DIN and ISO standard). Infinity
objectives that comply with these conditions are
identified by the code nos. beginning with the
figure 506. . . , 556. . ., 557. . . , 566. . ., 567.
Objectives for ∞ microscopes with conventional
reference focal length f
used, but the engraved magnification factor
must be corrected with the value 200 : 250 = 0.8x.
However, as the visible field is then enlarged by
the factor 1.25x, the edges of the image may be
blurred. The code nos. of these objectives for
tube lens focal length 250 mm begin with 559. . .,
and 569. . . ; an adapter (spacer ring 32/RMS or
25/RMS is also necessary due to the RMS
objective thread (see Fig. 39). The mount
(labelled collar) may also require modification.
= 250 mm can also be
B
Another important function of the tube lens is
correction of chromatic and other image
aberrations, such as astigmatism. This used to
be performed by the eyepieces in former
microscopes. Additional correction by the tube
lens, however, has proved to be far more
advantageous. Optimum
cannot be carried out by one single lens – a
system of several lenses, some of them
cemented, is used, so that it is more accurate to
speak of a tube lens system. The tube lens
system is permanently integrated in the top
plane of the stand (22.1), designated as cover
plate in the instruction manual, except for the
tube module HC L (→ p. 36). This module is
available in interchangeable versions.
Conversion of tube optics
Remove the 4 fixing screws (22.1) using the hex-
agonal screwdriver, remove the tube optics by
pulling upwards and mount the module of your
choice with extreme care.
!
Attention:
Make sure the components are completely
clean – it is particularly important to check that
there is no dust or fingerprints on the
underneath of the tube lens. Screw in the four
fixing screws loosely, so that you are still able to
move the module.
colour correction
35