The OndaVia Analysis Instrument is a powerful, compact Raman spectrometer. The excitation and collection optics use a single aspheric lens positioned approximately four millimeters above the sample inside a microscope objective style housing. This lens has a high numerical aperture (NA) which helps collect a large amount of signal. However, this high NA places tighter constrains on focusing. The system includes a manual focusing ring that allows the user to adjust the focus. Simply twisting the ring right or left moves the lens up and down.
Our analysis software includes a “Focus” button. When selected, this option configures the spectrometer for rapid data collection. The integration time is significantly shortened, often as short as 100 milliseconds, which reduces the overall signal but increases the number of spectra per second. This increase in spectra collected provides rapid feedback to the user as to how well the focus is positioned. Because the integration time is short, the signal will likely be noisy; this noise is okay, although any numbers calculated should be ignored. The goal is to see peaks due to the sample over the noisy background. Adjust the focus ring while watching the spectra. Also pay attention to the intensity scale bar on the left. Although it may appear the spectra are not changing, the software could be adjusting the scale. Note that perfect focus is rarely necessary. During full data collection, the intensity will be much higher due to a longer integration time.
The following video demonstrates this process:
