|
Things to keep in mind while
using this calculator and selecting a reticle
|
|
Results too big or too small:
|
|
|
|
While the results displayed will
be calculated based on the data input, they will not necessarily make sense.
|
|
|
|
You can see by entering a
desired resolution of 0.001" and an objective of 40x it will show a
division spacing of 0.04". A typical reticle with 50 or 100 divisions
would need to be 2" or 4" wide. This would, of course, not fit in a
microscope's eyepiece (although we could make the reticle as a special
order). You could always get a reticle with smaller spacing, such as
0.01" (our no.'s S-14362, S-14311, etc.) and just count every 4 division
lines to measure your feature.
|
|
|
|
Another example: you enter a
desired resolution of 1 micron and a 5x objective and you get a division
spacing of 5 micron. This is too close together considering the typical width
of each line on a reticle is 5 micron. It would also be very difficult to see
in the eyepiece.
|
|
|
|
Also consider that dimensions
below 0.2 micron are below the capabilities of optical glass, and 0.2 would
be obtainable only under the very best circumstances. For very small
features, a suggested expectation would be 0.5 micron and above using a
high-power objective.
|
|
|
|
Scale should fit in the eyepiece field diameter
|
|
|
|
Using a desired resolution of
0.01mm and a 20x objective lens results in a 0.2mm spacing. A reticle with
100 divisions (our no. S-14334) has a total scale of 20mm. This will only fit
on a reticle with a physical diameter larger than 20mm, and would only be
completely visible in a eyepiece with a field diameter (a.k.a. aperture
size), larger than 20mm (typically at least 1mm larger). Also, it is usually
more difficult to read the scale at the very edges of the visible field. The
field diameter number is written on the outside of the eyepiece. E.g.
WF10X/18MM means it is a 10X eyepiece with an 18mm field diameter. Note the
18mm does NOT denote the physical diameter of the reticle it will accept. The
reticle will be physically larger than the field diameter.
|
|
|
|
Of course, if you want the scale
or grid to "fall off" the edge of the reticle then simply order a
scale larger than the physical or field diameter. We do not require the
selected scale/grid to fit on the selected physical diameter.
|
|
|
|
You can use a scale/grid with a smaller division spacing
|
|
|
|
Let's say when you entered your
data it came up with a division spacing of 0.008" (our no.'s S-14360,
S-14309). It also works to use a scale with a 0.004" spacing (S-14100,
S-14283, S-14310, etc.) and just count two lines to measure the feature you
need. Why would you want to do this? It may be that 0.004" gives you
more flexibility to use other objectives in addition to the one you used for
this calculation. Generally, however, a coarser scale is easier to use.
|
|
|
|
What is "objective" magnification for this
calculator?
|
|
|
|
This is the total magnification
between the reticle's mounting position and the microscope stage. In most
configurations this is pretty easy to determine. The reticle is usually at
the bottom of the eyepiece, below its lens system (the field lens), so the
eyepiece magnification is not considered, and the objective is the lens
closest to the target.
|
|
|
|
However sometimes there are
other considerations:
- on a stereo microscope there may be an additional auxiliary lens attached
below the zoom lens system.
- the reticle may mount above one of the eyepiece lenses (in-between its
lenses). This is common in higher magnification eyepieces such as 15x or
20x.
- in an example where the reticle is mounted in a 15x eyepiece above a 1.5x
field lens, on a stereo microscope in the 4x position, with a 1.5x auxiliary
lens attached, the total magnification between the reticle and the stage
would be 1.5 x 4 x 1.5 = 9x.
|
|
|
|
If the total magnification
between the reticle and the target is not known you can measure it by using a
stage micrometer and a reticle.
|