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Figure 1: The two components of reflection: specular and diffuse reflection. n

represents the surface normal, an imaginary line at 90° to the sample surface.

Traditionally, the accessory used to measure diffuse reflectance is the integrating

sphere. Applications include characterizing solar materials, color measurement and

characterization, and obtaining reflectance spectra of a painted surface. Integrating

spheres have also proven ideal for measuring the transmission of turbid, translucent or

opaque refractory materials where standard techniques proved inadequate due to loss

of light resulting from the scattering effects of the sample. Samples which distort the

beam of the instrument, such as a lens, can also be studied with the Diffuse

Reflectance accessory.

The Cary 4000, 5000 and 6000i Internal Diffuse Reflectance accessory (DRA)

consists of a 110 mm diameter integrating sphere. The coating is

Polytetrafluoroethylene (PTFE), which exhibits NIR performance that is superior to

traditional coatings

(1)

, whilst maintaining UV-Vis performance. The sphere is easily

installed by the lock down™ mechanism in the sample compartment of the

instrument. The three different versions of the DRA have different detectors that

determine the wavelength range at which measurements can be taken. These are

detailed in the Specifications

section.

Reflectance measurement of a sample is made relative to a reference material (either a

PTFE or a BaSO

plate) or a standard reference material. The reference material is

used to establish a baseline, and when the standard reference material is being used,

the absolute reflectivity of a sample may be calculated from that of the reference. For

further details, refer to the Reflectance measurements

section.

The DRA requires the Extended Sample Compartment, part number 00 00100798 00

(Cary 4000, 5000, 6000i and DeepUV).

Theory

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Mantis 5000 Specifiche Pagina 3