Diffuse reflection or diffuse reflectance (DR) spectroscopy is a widespread non-contact analysis technique that is currently being used in a broad variety of applications such as biology, geology, food analysis, paint characterization, etc. Arcoptix offers several instruments and dedicated accessories that will help specialist and researchers obtain accurate DR measurements of their specific samples. Thanks to the usage of high-end MCT detectors, which display superior detectivity compared to pyroelectric detectors (DLATGS), Arcoptix is able to offer highly performant solutions to achieve DR in the mid-infrared as well.
Fibered reflection probes are flexible bundles of optical fibers that can effectively bring light to your sample and collect the resulting DR back to the spectrometer. Illumination is usually carried out by several cores (6-7), evenly spread around the central, collecting core. These fibered probes can either be installed in a dedicated stand or even operated by hand by the end-user. This makes it a versatile tool for a laboratory environment or a field application.
DR measurement using a fibered reflection probe
The ARCSPHERE-NIR is an integrating sphere with internal illumination. Compared to a passive integrating sphere, where light is brought externally using e.g. an optical fiber, the ARCSPHERE-NIR displays a much stronger signal, resulting in higher quality measurements. The ARCSPHERE-NIR is ideal for solid or powdered samples. Its sapphire window makes it robust against scratches even with hard samples (e.g. rocks or minerals).
ARCSPHERE-NIRSeveral options are available from Arcoptix to collect diffuse reflectance spectra. Fibered spectrometers, which are then directly compatible with our fibered accessories as well as other fibered systems, are available both in NIR and VIS-NIR versions. The VIS-NIR-FIB is actually a combination of our FT-NIR spectrometer and a grating spectrometer that covers the visible region of the electromagnetic spectrum.
FTNIR-L1-025-2TE
VIS-NIR-FIB
VIS-NIR-DRThe Arcoptix VIS-NIR-DR is an instrument designed to act as a convenient tool for the characterization of the reflectivity of paints, textiles, inks or other samples that are exposed to sunlight. Its sampling port leads to our integrating sphere with internal illumination, which ensures repeatable measurements. Light is then sent to both our FT NIR unit as well as a multichannel grating spectrometer that measures in the visible. Our software then merges the data from both instruments and also yields the total solar reflectance (TSR) or SRI (solar reflection index) value of the sample according to ASTM norms G173 and E903.
Fibered reflection probes are also available in the mid-infrared and operate on the same working principle as their NIR counterparts. MIR optical fibers suffer however from several drawbacks compared to their fused silica based equivalent, as they display significantly larger loss, which makes the system throughput inherently lower. Arcoptix thus recommends the usage of a liquid nitrogen cooled infrared detector when using diffuse reflection probes in the MIR, as their unparalleled detectivity ensures maintaining a sufficient signal quality.
ARCSPHERE-NIRAs an alternative to fibered probes, Arcoptix developed a common-path accessory that allows to build an efficient and compact setup for DR measurement. By mounting this input/output accessory on our OEM FTIR and adding a parabolic reflector, an elegant system for diffuse reflectance measurement is readily available, which displays significantly larger throughput compared to the fibered probes and also avoids being limited to the transparency windows of the fiber in use.
Common-path accessory operating principle (left), Arcoptix OEM010 with a common-path I/O and a parabolic reflector for free-space DR measurement (right)
The ARCSPHERE-MIR is an integrating sphere with internal illumination, which displays a significantly larger signal compared to a passive integrating sphere illuminated from an external source. In order to maximize throughput and SNR, The ARCSPHERE-MIR is directly coupled (free-space) to our FTMIR spectrometer. This optimized combination is unique on the world market. Both the FTIR and the sphere volumes are cleaned using a desiccant, which minimizes parasitic absorptions from water and CO2 molecules.
ARCSPHERE-MIR coupled to the FTMIR-L1-120-4TE