Variable Angle Reflection Accessory

Harrick's Variable Angle Specular Reflection Accessory is the industry standard for variable angle specular reflectance spectroscopy. It is ideal for specular reflection studies of films on metallic substrates, coatings, contaminants on reflective surfaces, and measurements of film thickness. The sample stage is readily adapted for absolute reflectance measurements or convenient horizontal reflectance measurements at a 12° incident angle. Models available for use in all FT-IR spectrometers and most UV-Vis spectrometers.

Variable Angle Reflection Accessory
Variable angle specular reflection accessory
Model No.
VRX-XXX
Price
N/A
NOTE: A Model No. ending in "XXX" denotes spectrometer code.

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Features
  • Incident angle variable from 30° to 85°.
  • Accommodates samples larger than 12mm x 12mm, up to 12mm thick.
  • Maintains alignment for all incident angles.
  • Optional Reflectance Reference for mid-infrared absolute reflectance measurements.
  • Adaptable for variable angle, fixed angle, and absolute specular reflection studies.
  • Optional sample stages for absolute specular reflectance and horizontal sampling.
  • Models available for a wide range of FT-IR spectrometers and UV-Vis spectrometers.
Includes
  • Optical base unit with variable angle specular reflectance sample stage.
  • Mating hardware for the specified UV-Vis or FT-IR spectrometer.
 
Model No. Product Description Price
DPS-R4V Depolarizer

Polarization scrambler for Vis-NIR

N/A
PGT-S1V Glan Taylor Polarizer™

Vis-NIR Polarizer

N/A
PTH-SMP Glan Thompson Polarizer™

Vis-NIR Polarizer

N/A
PWG-U1R Wire Grid Polarizer

Slide plate mounted FTIR polarizer (KRS-5 substrate)

N/A
RRF-00J Reflectance Reference

Mid-Infrared Ge reference

N/A
 
Model No. Product Description Price
VR1-HRS 12º Stage for VRX Horizontal sampling stage for Variable Angle Reflection Accessory N/A
VR1-RMA-LSS Large Sample Support for VRX N/A
VR1-VWA-12 12º Absolute Reflection Stage for VRX VW reflection sampling stage for Variable Angle Reflection Accessory N/A
VRC-OPC Purge Cover/Light Shield for VRC Sample stage enclosure N/A
VRC-PLL Polarizer Mount for VRC Mount for the Wire Grid, Glan Taylor and Glan Thompson Polarizers N/A
VRX-VWA-45 45º Absolute Reflection Stage for VRX VW reflection sampling stage for Variable Angle Reflection Accessory N/A
Reference & Mirrors
Model No. Product Price
MOP-114 32 x 50 x 3.2mm Mirror $84.00
MOP-115 25 x 50 x 3.2mm Mirror $84.00
Windows
Model No. Product Price
WPD-U38-P Window, protected KBr, 40 x 3 mm N/A
Variable Angle Specular Reflection Accessory

The Variable Angle Reflection Accessory is ideal for specular reflection studies of films on metallic substrates, coatings, contaminants on reflective surfaces, and measurements of film thickness. This accessory is the industry standard for variable angle specular reflectance studies. Three different models are available to suit the various optical designs of commercial FT-IR and UV-Vis spectrometers.

The incident angle can be continuously varied from approximately 30° to 80°. Samples with a minimum size of ½” x ½” and up to 0.5” thick can be readily examined. This accessory works best with samples up to 0.5” thick.

The incoming radiation is directed by mirrors to the sampling stage, where it reflects from the sample stage mirror and the sample. This mirror and the sample are coupled to rotate together. This configuration ensures that, once the Variable Angle Reflection Accessory is aligned, it remains aligned for all incident angles.  Some typical applications are shown in Figures 1 and 2.

For polarization measurements, Harrick Scientific’s Brewster’s Angle or Wire Grid Polarizers can be easily mounted onto the sample stage. For sampling versatility, there are four different reflectance sampling stages available: a continuously
variable angle rotational stage, included with the accessory; 12º absolute reflectance stage; 45º absolute reflectance stage and a 12º horizontal stage.

Figure 1. Specular Reflectance of an SiO₂ Coated Mirror at an Incident Angle of 75°.

Figure 2. Specular Reflectance of a Mylar Film at an Incident Angle of 20°.

Absolute Reflectance Sample Stages

Figure 3. The 12° Absolute Reflectance Accessory.

The two fixed angle absolute reflectance sample stages are available, featuring incident angles of 12º and 45º. Both utilize the ‘V-W’ double reflection technique illustrated in Figure 3. Using this technique, the reference spectrum is obtained in the ‘V’ mode. The beam is directed by mirrors to the sample stage mirror and back to the detector. To collect the sample spectrum, the stage is rotated (12º model) or inverted (45º model) to the ‘W’ mode. In this mode, the beam is directed from the sample to the stage mirror. The sample stage mirror reflects the beam back to the sample. The beam is then directed via mirrors to the detector of the spectrometer.

This configuration maintains the alignment, optical pathlength and polarization for
both the sample and the reference spectra. Note that the quantity measured is the ratio of the spectrum with the sample to the spectrum without the sample, is R2. Other incident angles are available on special order.

Horizontal Reflection Stage

The Horizontal Reflection Stage (see Figure 4) is used in combination with the Variable Angle Reflection Accessory for reflectance measurements at a 12° angle of incidence (near normal). The sample rests sample side down on a horizontal stage, making surface scanning and sample exchange straightforward.

Figure 4. Horizontal Reflection Stage.

This sample stage incorporates a single mirror that reflects the radiation from the sample stage mirror to the horizontal sample and then directs the light reflected from the sample back to the sample stage mirror.