Transmission experiments – Ocean Optics OOIPS2000 User Manual

Page 46

Sample Experiments

Palm-SPEC Operating Instructions

Transmission Experiments

Transmission is the percentage of energy passing through a sample relative to the amount that passes through
the reference. Transmission Mode also displays the portion of light reflected from a sample, since transmission
and reflection measurements use the same mathematical calculations. The transmission is expressed as a
percentage (%T

) relative to a standard substance (such as air). OOIPS2000 calculates %T

(or %R

) with the

following equation…

λλλλ

- D

λλλλ

- D

λλλλ

x 100%

…where S

is the sample intensity at wavelength

, D

is the dark intensity at wavelength

, R

is the reference

intensity at wavelength

Common transmission applications include measuring light through solutions, optical filters, optical coatings, and
other optical elements (such as lenses and fibers).

Perform the following steps to take a transmission measurement using OOIPS2000:

1. Place OOIPS2000 in scope mode by clicking the scope mode icon on the toolbar or selecting Spectra |

View Mode | Scope from the menu bar.

2. Ensure that the entire signal is on scale. The intensity of the reference signal should peak at about 3500

counts. If necessary, adjust the integration time until the intensity is approximately 3500 counts.

3. Place a sample of the solvent into a cuvette, place the cuvette into the sampling chamber, and take a

reference spectrum. You must take a reference spectrum before measuring transmission.

Note: Do not put the sample itself in the path when taking a reference spectrum, only the solvent.

Select Spectra | Store Reference Only from the menu to store the reference. This command merely
stores a reference spectrum in memory. You must select File | Save | Reference from the menu bar to
permanently save the spectrum to disk.

4. Take a dark sample by selecting Spectra | Store Dark Only from the menu. OOIPS2000 turns the light

source off, takes a dark sample, and turns the light source back on. This command merely stores a dark
spectrum in memory. You must select File | Save | Dark from the menu to permanently save the
spectrum to disk.

You must take a dark spectrum before measuring transmission.

5. Put the sample in place and verify that the light path is clear. Then, take a transmission measurement by

clicking the Transmission Mode icon on the toolbar or selecting Spectra | View Mode | Transmission
from the menu bar. To save the spectrum to disk, click the Save icon on the toolbar or select File | Save |
Processed from the menu bar.

Note: If you change any sampling variable (integration time, averaging, smoothing, etc.), you must store

a new dark and reference spectrum.