Mary Masterman - Oklahoma Biological Survey - University of ...

Materials and Methods
6
Primary Materials
Drill press with various drill bits, C-clamps, taps, and screws; Lathe with 3-jaw and 4-jaw chucks; Various scrap aluminum
tubing, L-brackets, and plates; Black foamie w/ double-stick tape; Canon EOS 300D digital camera; 300 mm medium-format
camera lens; Mounting board with aluminum rails; 1200 lines / mm 5 cm^2 diffraction grating; Vice and files; Saw; Hand-drill;
Canon 50 mm camera lens; Chroma Corporation filter set (including barrier filter, excitation filter, and dichroic mirror); Thin brass
sheet to hold dichroic mirror in place; Canon 67 mm filter to hold barrier filter; 532 nm 5 mW green laser; Red laser, level, and ruler
(for calibration); Flat diagonal mirror with adjustment screws; Micrometer head (to adjust angle of grating).
Methods
Build Raman filter cube using square aluminum tubing. Carefully contruct brass sheet to hold dichroic mirror and drill holes in
filter cube for other filters. Very carefully, and with gloves, slide dichroic mirror into brass sheet so that it is at a 45° angle to filter
cube. Construct mounting board for Raman system using large wood board and aluminum rails. Attach lenses to rails using L-
brackets and and attach to mounting board. Construct holder for laser using aluminum tubing and screws. Attach barrier filter to lens
using 67 mm filter holder. Attach excitation filter to laser holder. Align optical system.
Construct backing-ring to attach Pentax 6x7 ring to Canon EOS 300D Camera. Construct holder for diagonal on lathe using
round aluminum tubing. Attach diagonal mirror to holder using double-stick tape. Construct grating holder using micrometer head,
brass rod for grating to turn on, and part of an aluminum L-bracket. Attach grating with double-stick tape. Align optical system.
Attach spectrograph to Raman head. Collect spectra. In the Raman system, the dichroic mirror was not initially at the correct 45º
angle, so that the filter cube had to be made tiltable and separate holders for the barrier and excitation filters had to be constructed.
Due to the necessity of placing the invisible Raman signal on the slit of the spectrograph, alignment of the Raman system’s
optical path was very challenging. The Raman system didn’t work at all until the sample focusing lens was replaced with a
microscope objective, which presumably dramatically intensed the intensity of the laser beam on the sample. It was very difficult to
design the Littrow spectrograph such that the diagonal and SCT ring would fit in the flange-to-film distance of the lens, partly
because the distance was not as published.
Alignment of the diagonal mirror so that the entrance image of the spectrograph resulted in a centered and focused image on the
camera chip proved to be tedious.