Introduction

Mitutoyo provides microscope objectives of a great quality. My choice is motivated by:

  • The long working distance of these objectives.
  • Apochromatic objectives (corrected for three wavelengths).
  • The broad range of magnifications (versatility).
  • C-mount tube are pretty standard, could be used elsewhere.

Because such kind of objectives are corrected at infinity, we need a Lens tube to make the image on the camera sensor.

Edmund optics provides explanations for the setup. Actually, they provide two setups, I will come back to this point later. Before, I would like to comment Thorlabs solution I didn't retain because:

  • Their lens tube are optimized for Nikon lenses.
  • Nikon lenses have a shorter working distance.
  • Nikon lenses have less possibilities in terms of magnifications.
  • The solution uses Thorlabs tubes, which does not sound as reusable as C-mount tubes.

However, it's noteworthy that Thorlabs solution is cheaper (about $500). Nevertheless, it's an equipment you keep for a long time, I prefer to invest in versatile equipment instead.

This argument holds also for the choice between the two Edmund Optics setups. The seven component system allows to add extra components between the lens and the objective (example).

Bright field microscopy

Items

The typical price of my setup for one lens is $1800 and for two lenses $2600, without the camera and optical rails.

 Optics and adapters

Note that Edmund also provides a lens tube with 2x magnification. The same adapter works as well. To place the lens tube in the adapter, you need to unscrew the 4 outer screws and then inside, the 3 screws which are used to hold the lens. Rings are available to make sure that it fits perfectly. I used only the thinner one.

Tubes

The distance between the lens tube MT-1 to the end of the C-mount tube must be 200mm, but the adaptor takes 10mm. Thus, the tube must be 190mm long if a C-mount camera is behind. I will use a Nikon D7100 with a Fotodiox Lens Mount Adapter, C-mount to Nikon. Note that the Flange flocal distance is different for a C-mount and a Nikon mount. For this configuration, the tube length must be 190 - (46.5 - 17.5) = 161 mm.

Tube between the lens and the camera.

For the C-mount version:

For the SM1 version:

The advantage with this version is that you can put easily a 1' filter in the beam path.

For the tube between the lens and the objective. The manufacturer advises 57 mm. We can make a small deviation around that:

Setup

Microscope fully assembled with a Nikon D7100 and mitutoyo x5

Microscope fully assembled with a Nikon D7100 and mitutoyo x5

The shiny part near the first post is the lens tube.

Optional elements

Epifluorescence microscopy

We are now interested in upgrading the previous setup for fluorescence microscopy. Edmund optics gives an example. They use a beam splitter 50/50 and a filter wheel with longpass filters. I'm not really convinced by their proposition.

  • The light source is not filtered in their example. This means that the sample receives light at wavelengths for which the fluorophore emits.
  • 50% of the incoming light is trashed (well, ok), but also 50% of the emitted light is lost. The ratio signal/noise won't be optimized on that point too.
  • In the list, they suggest a light source but without optical fiber bundle and other accessories. Items are missing there.

Here, I propose to make a full fluorescence microscope. We need

  • Excitation + emission filters and a dichroic filter. These bandpass filters are narrow, the choice is optimized for only few fluorophores.
  • A cube to hold everything
  • A light source

Filters

A filter kit is about $650.

  • Dichroic 25.2x35.6mm
  • Excitation 25mm diameter
  • Emission 25mm diameter

 FITC - FITC-dextran - Fluosphere yellow-green

FITC is a common fluorophore. Edmund has a kit for this one.

corresponding to

Filter cube

Cheap filter holder (on C-mount cube)

The idea is to hold the filters in tubes. SM1 tubes have the right inner diameter for that. The filter can be hold between the male part and the retaining ring.

This is an alternative to this C-mount filter holder which is 4-5 times more expensive (Their filter holder makes things a little bit easier to swap filters, but something we don't really need for a filter cube)

Light

Setup

Fluorescence microscope fully assembled with a Nikon D7100 and mitutoyo 5x

Fluorescence microscope fully assembled with a Nikon D7100 and mitutoyo 5x

My first picture with fluorescent microspheres (yellow-green, 2 um). The inset shows the real resolution with a Nikon D7100 and mitutoyo 5x. It's a first test, a better job can be done for sure! :)

My first picture with fluorescent microspheres (yellow-green, 2 um). The inset shows the real resolution with a Nikon D7100 and mitutoyo 5x. It's a first test, a better job can be done for sure! :)

Bibliography