Diffuse Reflectance Spectroscopy Instruments for Measuring Virtually Any Sample

Gamma Scientific provides unique, high-performance solutions for reflectance and transmission testing. These reflectivity measurement devices and light transmission testing systems capture complete spectral and colorimetric properties of thin film coatings with scan times typically less than one second. Uniquely, the 191F Specular Reflectometer can non-destructively measure first-surface reflectance on transparent substrates up to 0.3mm thick, with 100% exclusion of backside reflectance and no backside preparation or additional interference. Second-surface or second layer intermediate reflectance can also be characterized on intermediate surfaces by excluding reflectance from other surfaces within the substrate.

Our diffuse reflectance spectroscopy instruments are available in several configurations, optimized for the sample type and desired measurement result, including either polished (specular) or rough (diffuse) samples. The below product selection guide will help you configure the best system to fit your needs.


  • Anti-reflectance coating characterization
  • Flat-panel display glass testing
  • Touchscreen display glass testing
  • Optical filter / lens testing
  • Pyrolytic glass coating test & characterization
  • Characterization of flat panel displays, photovoltaic coatings, low-E architectural coatings, paint samples and diffuse plastics

The vast majority of our Display Measurement Solutions are custom-configured.

Installation and commissioning is option, though for the automated systems, highly recommended.

191F Series models are available in handheld, tabletop, semi-automatic and fully automatic configurations.

191F Series models have a fixed AOI as indicated above.  A handheld unit with 10-45º variable AOI is available under model number 191C.

191 T and 191 DR Series units are available in tabletop models only.


191 Series Optical Heads Specification Comparison Table
191 Series Optical Heads191F191T191C191DR
Measurement TypeSpecular Reflection
or Total Reflection
Total TransmissionSpecular ReflectionDiffuse Reflection
Sample TypesGlass, Plastic, Metal,
Polished Substrates
Glass, Plastic,
Transmissive Elements
Glass, Plastic, Metal,
Polished Substrates
Opaque Materials,
Matte Surfaces,
Rough Substrates
Illumination AngleFixed Angle at
0°, 10°, 20°, or 45° or
Dual Angle 10° & 45°
10° to 45° Variable45°
Viewing AngleMatches Selected Illumination
2π (180°)10° to 45° Variable45°
System ConfigurationHandheld, Tabletop,
Semi-Automatic, Fully Automated
TabletopHandheldTabletop (Sphere Based)
Minimum Sample ThicknessDependent on Angle
(transparent samples)
(transparent samples)
1.5mm (transparent samples)
None (opaque samples)
None (opaque samples)
Spectral Range365nm-900nm (default)
UV / IR Options
365nm-900nm (default)
UV / IR Options Available
UV / IR Options Available
Illumination Spot Size
(Area of Analyis)
1mm x 10µmØ 1mm, Ø 2mm, or
Ø 3mm
1mm x 65µmØ 1mm, Ø 2mm, or
Ø 3mm
Typical Measurement Speed
(Sample Dependent)
Optical Head DimensionsVaries Depending
on Model/Angle
Height: 350mm (13.75″)
Width: 205mm (8.0″)
Depth: 225mm (8.85″)
Weight: 3.5kg (7.75lbs)
Height: 230mm (9″)
Width: 150mm (6″)
Depth: 150mm (6″)
Weight: 1.6kg (3.5lbs)
Height: 300mm (12″)
Width: 1000mm (40″)
Depth: 300mm (12″)
Weight: 12kg (25lbs)
Spectral Reflectance/
Spectral Transmission
± 0.2%± 0.5%± 0.5%± 0.5%
(CIE 1931 X, Y, Z)
± 0.05± 0.05± 0.05± 0.05
(CIE 1931 x,y)
± 0.002± 0.005± 0.005± 0.005
LAB Color
(CIE 1976 L*, a*, b*)
L* ± 1.0 a*, b* ± 0.8L* ± 2.0 a*, b* ± 0.8L* ± 2.0 a*, b* ± 0.8L* ± 2.0 a*, b* ± 0.8
Reported Parameters
Spectral DataReflectance/Transmission as a function of wavelength
Colorimetric DataCIE Tristimulus X, Y, Z, with 2° or 10° View Angle, (L*, a*, b*), (x, y), (u’, v’), and other parameters
Illuminant WeightingIlluminant A, Illuminant B, Illuminant C, Illuminant D65, or User Specified Custom Illuminant
Specifications are subject to change without notice.


  • Gamma Scientific Model 191 Series Reflectometer Heads isolate the first surface reflection
  • The second surface is completely eliminated in a non-destructive manner
  • Light reflecting off each surface will be slightly offset
  • This offset is used to mechanically block light reflected off lower surfaces