The WOSP RT-DESKTOP spectrometer system records absolute reflectance and transmittance spectra of glass panes or other flat and shiny samples. Measurements are done in a few seconds. A wide range of angles of incidence is possible. No reference standard is needed for reflectance.
The system consists of
- a mobile stabilized halogen light source (25 W)
- a mobile spectrometer unit (using a Zeiss MMS1 spectrometer and tec5 electronics)
- mechanical accessories that assist you in positioning all components.
Spectra are recorded in the range 380 … 1000 nm.
You need to provide a flat table (which is not part of the system) and electrical power. The spectrometer connects to a USB port of your computer. Alternatively, you can use an ethernet connection.
How it works
You can move and turn both the spectrometer unit and the light source on the table, performing the following sequence of actions:
- Pointing the field of view of the spectrometer away from the light source (to a dark surface, ideally) you record the dark spectrum, i.e. the detector signals for vanishing light intensity.
- Then you arrange the components in a way that the full intensity (100%) is recorded.
- From now on you can record absolute transmittance and reflectance spectra for various angles of incidence.
The image below shows a reflectance measurement taken at 45°:
You are not limited to absolute measurements – if relative measurements are more appropriate for a given problem, you are free to go this way as well.
You have plenty of time to do the measurements. The graph below shows the ‘100% line’ 5 minutes after the backgound signal has been measured:
The system is controlled by our CODE-NF software which allows to compute various technical data from measured spectra like color coordinates or integral transmittance and reflectance values. As an option you can upgrade to the full CODE software package which allows to obtain film thickness and optical constant values based on physical modelling.
In order to record high quality spectra the operators need to execute a few commands only. Both CODE-NF and CODE are very flexible concerning user interfaces. We recommend to provide large buttons for dark, reference and sample measurements. You can save measured spectra manually or automatically to folders or a MySQL database.
The screenshot below shows (in red) the measurement of the absolute reflectance of a silicon wafer (30° angle of incidence). The blue spectrum is a model computation based on literature data of silicon with a 4 nm native SiO2 layer on top – the agreement is excellent, also for other angles of incidence:
The next graph shows a more advanced example. 6 measured spectra (absolute T and R spectra, taken at 30°, 45° and 60°) have been used to fit an optical constant model for Schott Borofloat glass.
The obtained optical constants (real part n of the refractive index, absorption coefficient alpha) are shown here: