Levenhuk 850B Biological Binocular Microscope - Manual (Page 4)

Принцип работы
The numerical aperture (N.A.) of this high quality condenser is 1.25. Its position may be adjusted by turning the locking
screws, without any additional tools:
rotate the revolving nosepiece until either a 4x or a 10x objective lens is locked in place;
rotate the iris diaphragm to reduce its diameter;
lower the condenser until the diaphragm image is somewhat sharp;
focus the view by loosening or tightening the locking screws.
The condenser has been aligned with the objective lens during production. If this alignment hasn't been performed, the
field of view will be very irregular, with parts of it very bright, and others very dark. The rack-and-pinion mechanism
moves the condenser up and down within a 20 mm (0.79 in) range. Generally, you would want to raise the condenser when
using high-power objective lenses (40x, 100x) and lower it with low-power objective lenses (4x, 10x). The highest position
of the condenser is locked at 0.2 mm away from the stage.
If the condenser-objective lens alignment has somehow gone awry, you have to perform the following operations:
loosen the nut on the locking screw;
place a slide with a specimen on the stage;
raise the condenser to its highest position;
tighten the locking screw until the condenser touches the bottom of the stage;
retighten the nut on the locking screw.
Rotate the iris diaphragm to adjust its diameter in 2–30 mm (0.08–1.18 in) range, so that it corresponds with the N.A. of
the objective lens currently in use. When the iris diameter is approximately 70–80% of the objective lens N.A., the
observed image is sharp and clear. Remove one of the eyepieces and look through the tube. You will see the iris
diaphragm. You can use a color filter with the diaphragm for additional contrast and detail on the image. The filters come
in blue, green or yellow.
These microscopes are equipped with a 140 mm x 155 mm (5.5 in x 6.1 in) stage with coaxial controls. Press the stage
clip lever and place a slide with a specimen on the stage. Release the lever and it will securely lock the slide in place.
You can move the stage horizontally by using the coaxial controls below the stage. It moves within 70 mm (2.76 in) range
in 0.1 mm (0.004 in) increments.
Stage
The state of the art nosepiece provides for smooth rotation and easily locks in place on the desired objective lens. The
parfocal objective lenses used in these microscopes provide for simple switching from one magnification to the other,
without having to refocus your view over and over again.
Revolving nosepiece
The binocular head of these microscopes may be inclined at a 30° angle and rotated 360 degrees. The interpupillary
distance adjustment range is 55–75 mm (2.16–2.95 in), the diopter adjustment range is from +5 to -5 diopters on each
eyepiece.
Binocular head
Abbe condenser
The coarse and fine focus systems are operated with a rack-and-pinion mechanism. The coaxial design of the focus system
allows you to adjust coarse and fine focus without any difficulties. Fine focus system adjusts in 0.002 mm (0.00008 in)
increments; total adjustment range is 25 mm (0.98 in). You can use the coarse focus knob to quickly raise or lower the
stage, and fine-tune the view with the fine focus knob.
Upon moving the stage into a desired position, you can secure it in place with the stage locking screw. Rotate it clockwise
to lock the stage in its current position. It will remain in this position until you loosen the locking screw. If you are
observing a large and heavy specimen, you might want to increase the coarse focus system knob tension. Rotate the
adjustment ring on the focus knob and the stage will be lowered slowly and steadily, even with heavy specimens.
Focus system
Generally, a 6V/20W halogen lamp is used in the illumination system of a microscope. To adjust its brightness, rotate the
corresponding knob, to better illuminate the observed specimen. The illumination should not be too bright with low-
powered objective lenses and vice versa. When changing the lamp to a new one, make sure to align it along the optical
axis, otherwise, the quality of your views will be significantly decreased.
To change the old lamp, loosen the screw on the bottom of the base, remove the cover and replace the lamp.
Illumination
Unpack your new microscope with great care. Check if all the parts and accessories are present. Note that some parts
might have been disassembled for easier shipping, therefore, you will have to assemble them before you can begin your
observations.
Assembly