Reflection Measurements



Flame color measurement
Reflection measurement using a fiber optic probe at 45 degrees – Spectrecology


% Reflection or reflectance is measured as the ratio of light reflected from a sample to light reflected from a reference material. It is usually expressed in a percentage scale (%R). Fixtures and probes are used to define the illumination and reflected light angles, allowing for the measurement of specular (mirror like) and/or diffuse reflection.

In a typical setup, the light source and spectrometer are connected by optical fibers to the reflection measurement fixture. In the illustration the fixture is a fiber optic probe held at 45 degrees to the sample.







45/45 reflection accessory
REF fixture set for 45/45 specular reflection with collimating lenses – Spectrecology


 SE-REF-KIT  45/45/90

This is an aluminum fixture for looking at reflection from flat surfaces. There are 3 ports to allow for illumination at 45, 90 and 135 degrees. The ports accommodate screw in  fiber optic collimators (2 are included with the kit) or black plugs to block light. An additional adapter will hold a 1/4″ OD reflection probe.

The ports fit our SE-112689 collimator with quartz, sapphire or AR coated lenses. The ports also accommodate the 74-UV and 74-ACR style lenses.



Model Number SE-REF-KIT
Materials Fused Silica, Aluminum (black anodized)
RoHS Compliant Yes
Max. Bake Temperature 80 °C
Max. Operating Temperature 80 °C
Max. Vacuum Level Air Service
Length / Height 2.30 Inch
ID 0.25 Inch
OD 1.00 Inch
Operating Wavelength 250~2000 nm
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R400-7 and R-600-7-UV-SWIR Fiber Optic reflection Probes

The 6 around 1 fiber reflection probe is multi-purpose. It can be used to measure specular or diffuse reflection from a surface, diffuse reflection from liquids, tissue and other translucent materials and fluorescence.

reFlection backscatter diffuse fiber probe - Spectrecology

Probes are available in any size fiber, but the R400-7-UV-VIS (or VIS-NIR) or our new R600-UV-SWIR probes are our most popular. They have a 3″ ferrule, 1/4″ OD and 2m long fibers that are bifurcated at the halfway point.

These probes can be used with holders such as the SE-REF above, or the RPH-1, to hold it at 45 or 90 degrees.  A white (diffuse) or specular reflection standard and a light source completes the setup.

Spectrecology UV-SWIR reflection probe

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The SE-112802 30 degree reflection adapter provides a large area flat quartz window to accommodate measuring powders, or soft surfaces that must be pressed into a flat surface. This provides essentially “dark field” reflection spectra by eliminating specular reflections in the measurement plane.




R400, R200 6 around 1
Premium grade R400 reflection probe – Spectrecology



Reflection Probe adapter for powders, slurries and wiggling anaimals - Spectrecology
Large Area Reflection Probe Adapter (SE-112802) for powders, slurries and wiggling animals – Spectrecology












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Engineering Specifications Premium-grade Reflection Probes
Probe ferrule material: Stainless steel
Probe ferrule length: 76.2 mm (3″)
Probe ferrule diameter: 6.35 mm (1/4″) unless otherwise noted (3.175 mm / 1/8″ for QR600 probes)
Probe fiber bundle: 6 illumination fibers around 1 read fiber
Numerical aperture: 0.22 ± 0.02 (equivalent to an acceptance angle of 24.8° in air)
Jacket: Standard fibers: Silicone-coated steel monocoil with a Nomex braid for superior strain relief and protection
“-BX” fibers: Stainless steel BX
Connectors: Precision SMA 905 with knurled ferrule
Length: 2 m
Breakout: Midway point of assembly at 1 meter
Fiber core size: 200 – 600 μm (see product variations table for options)
Wavelength range: XSR, SR, UV/VIS, VIS/NIR (see product variations table for options)
Fiber buffer: See Fiber Bend Radius and Mechanical Specifications for details
Bend radius: See Fiber Bend Radius and Mechanical Specifications for details
Operating temperature: -20 °C to 80 °C
Quarter reflection probe adapter, tilted 30° / 60° (from normal / optical axis) with large contact area 25mm diameter fused silica lens is ideal for large specimen study.

Model Number SE-112802
Materials Fused Silica, Aluminum (black anodized)
RoHS Compliant Yes
Max. Bake Temperature 80 °C
Max. Operating Temperature 80 °C
Max. Vacuum Level Air Service
Length / Height 2.30 Inch
ID 0.25 Inch
OD 1.00 Inch
Operating Wavelength 250~2000 nm
The spot size for reflection off a surface, and the active volume for fluorescence or back scatter vary with distance. Initially the signal increases as the overlap region grows. Then the signal decreases as the distance to the sample increases.

diffuse reflection R400
Diffuse reflection probe optics – overlap volume of illumination and read fibers varies with distance – Spectrecology


reflection probe sampling depth
Backscatter – reflection signal increases with the distance to the probe tip, then decreases. – Spectrecology













Integrating Spheres

ISP-R reflection integrating sphere
Integrating spheres for reflection measurements – Spectrecology


Integrating spheres are used to acquire reflection spectra from 180 degrees.  The typical setup is to have a collimated viewing angle of ~8 degrees from normal and diffuse illumination from a baffled light source in the sphere. A removable light trap at the opposite 8 degree angle can be used to eliminate specular reflection. 


ISP-R series fiber optic integrating spheres couple to Ocean Optics spectrometers to measure the total integrated reflectance of surfaces placed against the sphere’s sample port. ISP-R integrating spheres are well-suited for measurement of opaque or highly directional samples. The spheres are available in 6 mm and 8 mm sample port diameters and gloss-trap options are available that allow you to measure the specular component of the total integrated reflection.





Versatile – adaptable for diffuse or specular measurements

High reflectivity – PTFE sphere coating is >98% reflective from 400-1500 nm

Multiple options – available with sample port diameters of 6 mm and 8 mm


Engineering Specifications ISP-30-6-R ISP-50-8-R ISP-50-8-R-GT ISP-80-8-R
Dimensions: 59 mm diameter x 58 mm height 80 mm diameter x 78 mm height 80 mm diameter x 78 mm height 107 mm diameter x 117 mm height
Weight: 330 g 730 g 743 g 1,650 g
Spectral range: 200-2500 nm 200-2500 nm 200-2500 nm 200-2500 nm
Sphere diameter: 30 mm 50 mm 50 mm 80 mm
Sample port diameter: 6 mm 8 mm 8 mm 8 mm
Sphere coating: PTFE PTFE PTFE PTFE
PTFE reflectivity: >98% (400-1500 nm)>95% (250-2500 nm) >98% (400-1500 nm)>95% (250-2500 nm) >98% (400-1500 nm)>95% (250-2500 nm) >98% (400-1500 nm)>95% (250-2500 nm)
Reflectance measurements: Specular and diffuse Specular and diffuse Diffuse or specular and diffuse Specular and diffuse
Gloss trap: No No Yes No
Connector: SMA 905 SMA 905 SMA 905 SMA 905


Integrating sphere for measuring diffuse hemispherical reflection


Multi-purpose sample stage for reflection and transmission using fiber probes, lenses and/or integrating spheres – Spectrecology


The Stage-RTL-T is a clever sampling system that couples to Ocean Optics spectrometers and accessories for reflection and transmission measurements of samples ranging from organic materials such as grains and fertilizers to man-made materials including plastics, coatings and semiconductor wafers.

Thanks to its variable x-y axis rail design and adjust able platform, the Stage-RTL-T can be configured for several setups:

Attach an Ocean Optics ¼” (6.35 mm) OD reflection probe and position the probe for 90° measurements.

Position collimation lenses to measure transmission at 90° or reflection at 45°.

Add an optional integrating sphere adapter (ISP-RTL-ADP) to make diffuse reflection measurements using 30 mm and 50 mm diameter integrating spheres.





Multipurpose – adjustable for transmission and reflection measurements

Sample parameters – ideal for flat substrates and large specimens

Materials measured – everything from coatings and semiconductor wafers to vegetation and animal tissue


Engineering Specifications STAGE-RTL-T
Base dimensions: 206.3 mm diameter
Sample area dimensions: 152.4 mm diameter
Weight: 4.5 kg
Rail height: Adjustable to 400 mm
Components: Sample plate, rail, adapter, collimating lenses (2) and light trap
Collimating lens wavelength: 200-2000 nm
Stage material: Anodized aluminum
Integrating sphere adapter (optional): Item ISP-RTL-ADP, for attaching 30 mm or 50 mm ISP-series spheres


Reflection Standards

Diffuse Standards for Reflectance Measurements

We offer two types of diffuse reflectance standards. The WS-1 uses a PTFE optical diffuser, a Lambertian material distinguished by its white matte finish and reflectivity >98% from 250-1500 nm and >95% from 250-2200 nm.

For field work or unclean environments, the WS-1-SL can be a good option. Its Spectralon diffusing material can be smoothed, flattened and cleaned if it gets pitted or dirty. Reflectivity is 99% from 400-1500 nm and >96% (250-2000 nm).

  • Diffusing materials – choose from PTFE or Spectralon standards
  • High reflectivity over broad range – >95% reflectivity from 250-2200 nm
  • More options – additional Spectralon reflectance standards and targets also available
White standard – diffuse white reflection standard – Spectrecology
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Engineering Specifications WS-1 WS-1-SL
Dimensions: 38 mm diameter (housing) 32 mm OD, 10 mm thick (tile)
Weight: 30 g 30 g
Spectral range: 250-2000 nm 250-2500 nm
Diffusing material: PTFE Spectralon
Housing material: Aluminum Delrin
Reflectivity: >98% (250-1500 nm)>95% (250-2200 nm) 99% (400-1500 nm)>96% (250-2000 nm)
Spectralon white standard reflection spectra – Spectracology

Actual reflectivity values for the standards are available as an ASCII file. Spectrasuite and Oceanview can use that file to correct for deviations from 100%.

NIST traceable versions of the ehite standards are also available.


WS-1 white standard actual reflectivity (zoomed) - Spectrecology
WS-1 white standard actual reflectivity (zoomed) – Spectrecology


Specular Reflection Standards

Ocean Optics offers specular reflectance standards for measuring shiny surfaces such as machined metals and semiconductor materials and low-reflectivity surfaces such as anti-reflective coatings and thin film coatings.

The STAN-SSH varies in reflectivity from 87%-98% over the 200-2500 nm wavelength range and is available in a version (STAN-SSH-NIST) calibrated to a NIST master standard.  For measuring surfaces with low specular reflectivity, we recommend the STAN-SSL, which has ~4% reflectivity from 200-2500 nm. Add a STAN-HOLDER to keep your standards in place and to protect their coatings.

Specular reflection Standard – high reflectivity STAN-SSH – Spectrecology


Low reflection specular standard – Spectrecology
Engineering Specifications STAN-SSH STAN-SSH-NIST STAN-SSL
Dimensions (substrate): 31.75 mm OD x 6.35 mm height 31.75 mm OD x 6.35 mm height 31.75 mm OD x 6.35 mm height
Dimensions (housing): 38 mm OD x 19 mm height 38 mm OD x 19 mm height 38 mm OD x 19 mm height
Weight: 40 g 40 g 40 g
Reflectance material: Al mirror on fused silica substrate Al mirror on fused silica substrate Schott ND9 glass
Reflectivity: ~87%-93% (200-1000 nm) ~87%-93% (200-1000 nm) ~5% (200-950 nm)
~93%-98% (1000-2500 nm) ~93%-98% (1000-2500 nm) ~4% (950-2500 nm)