Ocean Optics IDRaman mini, Installation And Operation Manual, Page: 23 / 40

2: Set-up and Operation
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Note
If you do not disconnect and reconnect, the system will continue to act as an MSD and it
will not use your library to match.
If you intend to encrypt your files, you will need to use the Secure Library function when you are ready to
place them on the IDRaman mini. See
Building a Secure Library .
Acquiring a Reference and Spectrum
Spectra can be acquired several different ways depending on your application or on the sample’s
composition.
Button Function
Acquire Acquires a spectrum for the integration time . The laser turns on for a period of time
determined by the integration time. Some delays exist to allow for the laser
stabilization; however, the exposure time is precisely set by the integration time
selected.
Reference Acquires a dark reference for the set integration time. Normally the shutter closes
during this period and the reference spectrum is subtracted from the acquisition.
This removes any environmental background and it eliminates any fixed pattern
noise due to the CCD detector.
The slide switch at the top: Use Reference determines if a reference is used. Use
Reference (Yes) causes the reference to be subtracted; this is the default. Select
Use Reference (No) if you do not want the reference subtracted.
NOTE: It is essential to have the reference acquired for the same integration time as
the acquisition. If there is a mismatch, a new reference will be automatically
acquired at the new acquisition time.
Acquiring an Average
Averaging is used when your sample has a high background. Often samples will produce some or even
large amounts of fluorescence. The quality of a spectrum is determined by the signal-to-noise. The noise
is determined by “shot noise” which is equal to the square root of signal. This means that samples with
large backgrounds will inherently have poor signal-to-noise ratios. Increasing the integration time will
improve the signal-to-noise ratio, but with high background samples this may be impossible due to the
detector’s limited dynamic range.
Averaging allows one to take multiple short acquisitions and average them to improve signal to noise.
Until the detector becomes dark noise limited the signal to noise ratio will improve by the square root of
the number of averages.