Choosing The Correct Reticle Glass Diameter For Your Eyepiece (top of page)
microscope eyepieces (oculars) are designed to accept a reticle
on the inside of the bottom of the eyepiece. This is the end of
the eyepiece that normally sets in the microscope's eyetube,
which is the tube that is attached to the microscope.
order for the eyepiece to properly use a reticle it will need
two things. You can check for these by removing the eyepiece
from the eyetube, turning it over and looking down inside the
bottom of the eyepiece. 1) There must be a "shelf" of some kind
down inside the eyepiece for the reticle to rest on, and 2)
there must be a retaining mechanism of some kind to hold the
reticle in place. The shelf is very important as it positions
the reticle at the optical focal point of the eyepiece's lens.
This means the reticle is spaced correctly to be in focus when
you view it through the top of the eyepiece. The retaining
mechanism is typically a threaded ring that you unscrew from the
inside of the eyepiece. You then set the reticle down inside on
the shelf, and screw the retaining ring back in to hold the
reticle in place. Be very careful you do not over-tighten this
ring on the reticle as it may break or chip the reticle glass.
Often you will need a spanner wrench of some kind to remove and
re-install this threaded ring. If there is no retaining
device but there is a shelf for the reticle, then you can
buy a properly sized C-Ring Retainer to
hold the reticle in place. Choose the C-Ring size that matches
the reticle diameter (as determined in the next paragraph).
If there is no shelf for the reticle to rest on in the bottom of
the eyepiece, then either your eyepiece uses a different method
of holding its reticle, or more likely it is not able to use
one. Some eyepieces are designed so the reticle is installed
in-between two lenses instead of at the bottom, or possibly by
some other method. In this case you would need to refer to the
owner's manual or contact the manufacturer/dealer. Ask them if
the eyepiece can accept a reticle and how to determine the
proper glass diameter.
you have determined your eyepiece has the proper shelf inside
the bottom of the eyepiece, you would then measure the inside
diameter of the bottom of the eyepiece. Be sure you are
measuring against the inside wall of the eyepiece and not the
inside of any retaining ring that may be in there. This
measurement must be reasonably accurate. It will typically be a
fraction of a millimeter over a whole number. For example it may
measure 19.6 mm. You would then round down to the nearest
millimeter, in this case 19mm, and that would be the proper
diameter for the reticle. Another example is you measured
23.1 mm. You would then select a 23 mm reticle diameter. The
tolerance on the reticle's diameter is +0 / -0.005 in. so as
long as the inside diameter of the eyepiece is between 0.1mm and
0.9mm larger than the reticle diameter it should fit.
Please note that a typical eyepiece will have numbers written on
the outside such as WF10X/23MM. These numbers are not
specifying the diameter of a reticle for that eyepiece. They are
specifying the magnification of the eyepiece and its aperture
size. Unless you have the reticle diameter as specified by the
owner's manual or other manufacturer's specification, you must
measure per the instructions above.
Choosing The Correct Reticle Scale Value For Your Objective (top of page)
If you need to order a reticle for your application, use the
following to determine the correct scale value.
When ordering reticles, take into
consideration only your total objective magnification (don't add
eyepiece). On a typical zoom stereo microscope it would be between
1X and 5X. If you installed a 1.5X auxiliary objective lens on
that same stereo microscope, it would then be between 1.5X and
7.5X. On a compound microscope it would typically be between
4X and 100X.
Using the 3X objective lens on your stereo microscope, you
want to be able to measure .001" of your target specimen
for each division of your reticle. Therefore, use the following formula:
Formula: Desired value of Target x Objective = Value of Reticle
.001" x 3X = .003" per division
You can see you need a reticle that has
.003" per division.
If you want 100 divisions: .003" x 100 divisions = .300"/100
div. (Part #
If you want 200 divisions:
.003" x 200 divisions = .600"/200 div. (Part #
Below are examples of the different values
attained from this reticle when used with various objective
Part # S-14278: .300"/100
division equals .003" actual value.
.003" @ 1x objective setting = .003" at target
.003" @ 2x objecting setting = .0015" at target
.003" @ 3x objective setting = .001 " at target
If you already have a reticle, use the following to determine
its measurement resolution.
Example 2: You have a S-14340 reticle which has a 2mm scale
divided into 200 divisions. Therefore each division is 0.01mm (10
micron). If you use the 40X objective lens on your compound
microscope, you want to know the corresponding dimension of your
Formula: Reticle Value / Objective =
Value at Target Specimen.
0.01mm / 40 = 0.00025mm (0.25 micron or 0.25µ)
Below are examples of different values attained from this reticle
used with various objective settings.
# S-14340: 2mm/200 divisions, each division equals 0.010mm actual
0.01mm / 4 = 0.0025 (2.5µ) at target specimen.
0.01mm / 10 = 0.001 (1µ) at target specimen.
0.01mm / 100 = 0.0001 (0.1µ) at target specimen.
Calibrating Your Reticle With a Stage Micrometer (top of page)
FOR PRECISE MEASUREMENTS, EACH RETICLE MUST BE
CALIBRATED TO EACH OBJECTIVE USING A STAGE
PROCEDURE FOR CALIBRATING
Accurate measurement of microscopic objects requires
the use of an eyepiece reticle (a.k.a. eyepiece micrometer) and a stage
micrometer. The eyepiece reticle is a round glass disk on
which a scale has been etched. The eyepiece reticle is
inserted into one eyepiece and held in place in the correct
focal plane of the eyepiece. The
eyepiece and eyepiece reticle can be rotated 360 degrees in
the eyetube so the measuring scale can be aligned with or
superimposed over the image of your specimen. A typical eyepiece
reticle would be a 5mm or 10mm linear scale featuring 50 or
100 divisions. Before using the eyepiece reticle for accurate
measurements it is
necessary to calibrate the eyepiece reticle using a stage
micrometer. A stage micrometer is simply a microscope slide with
a pattern of known dimensions etched upon its surface. The stage micrometer
is placed directly on the stage of the microscope and brought
into focus. By rotating the eyepiece both scales can be
positioned parallel to each other. To calibrate the eyepiece
reticle you must first find out how many intervals of the
eyepiece reticle correspond to a certain distance on the
stage micrometer. You can then calculate the value of one
interval of the eyepiece reticle. Each microscope objective
must be calibrated independently.
Example: Let's say each division of the metric stage
micrometer above is 0.01mm or 10µ (10 micron). The eyepiece reticle
into 100 units. First determine how many divisions of the
eyepiece reticle correspond to a certain distance on the
stage micrometer and calculate the length which corresponds to
one division of the eyepiece reticle. In this example 30
divisions of the eyepiece reticle corresponds to 20 divisions
of the stage micrometer. Each division of the stage micrometer
equals 10µ so 20 divisions of the stage micrometer would equal
200u. To calculate the value of one division of the eyepiece reticle
we would divide 200µ by 30 and the result would be
6.67µ per reticle division. The reticle value, in this case 6.67µ,
would apply only to the objective for which the calibration was
made. Each microscope objective must be calibrated independently.
Important Note on Reticle Diameters & Patterns (top of page)
All geometric patterns available will not fit on all available
reticle diameters! Please keep this in mind when choosing a
For example: The S-14368 Scale
Reticle is a 20mm scale. If you order it on a 17mm diameter
Reticle, you can see that it will not completely fit. We
understand that sometimes this is intentional because you may want
the geometry to go right to the edge. So, if you order this, we
will make it! How will we orient the pattern on the glass?
Unless you tell us otherwise we
would do it just as if it was being printed on a larger diameter
piece of glass. The center of the geometry will be in the center
of the glass. Therefore in the above example, both ends of the
pattern will fall off the edge. We can orient it differently (left
justified for example), but you would need to
contact us before ordering to make
sure we know what you want. Please make sure you completely
understand what you will be getting since these types of
reticles are non-returnable!
If you have any doubt at all, please call
Custom Reticle and Stage Micrometer Designs (top of page)
We are capable of making custom products if you need a reticle
or stage micrometer with an artwork design, physical dimension
or substrate material that we do not carry as standard. Unless the design is very
simple, we will need you to supply us with an artwork drawing and
any other differing specifications.
RETICLES: Reticles with custom artwork have a minimum
cost of $715 for setup and $125/ea in small quantities.
These prices cover most designs we have been asked to do, but
may increase depending on the complexity and size of the artwork, product dimensions
and requested substrate material. An exception is if we
can use a standard artwork pattern but simply remove some of the
can typically be done less expensively. Also, reticles using one of our standard
artwork patterns but with a non-standard physical dimension or substrate
type can usually be made less expensively as well since they
would not require new artwork. Please
contact us for a firm quote.
STAGE MICROMETERS: Prices for custom stage
micrometers vary significantly depending on your requirements
so you will need to contact us with
your details for a
quote. However, like the reticles above, any new artwork
requirement will have a minimum $715 setup charge. Please note: it is less expensive to put one of our
standard reticle patterns on a stage micrometer than to create