The perception of colour is primarily determined by two objective factors: the wavelengths of light that are reflected from a surface; and the colour of the illuminating light. White light is a combination of lights of different wavelengths in the visible spectrum. A surface will absorb and reflect proportions of these wavelengths dependent upon its colour, for example, vibrant red surfaces will absorb light of shorter wavelengths and reflect wavelengths of >700nm. However, this assumes that the surface is uniform and defect-free.
Specular reflection measurements analyse the light that is rejected from a surface into a singular outgoing direction. The Law of Reflection states that the angle of an incident ray of light is equal to the angle of reflection; provided that the surface is smooth, glossy, and free of defects. Rough or matte materials tend to exhibit diffuse reflection when struck by incident light. This refers to the scattering of wavelengths in multiple directions and is associated with reduced colour saturation and vibrancy.
Reflection measurements are ubiquitously used in product development and quality control (QC) for optical materials and devices such as plastic films, coated glass, and phosphor plates.
This blog post will explore the performance of reflection measurements in more detail.
Reflection Measurements: SCE vs SCI
The colorimetric characteristics of products are routinely assessed to maintain batch-to-batch consistency and support diagnosis of variations in production environments. These reflection measurements can be loosely divided into two subcategories: specular component excluded (SCE); and specular component included (SCI).
Reflection measurements operating on SCE methodology use a reflective probe at 45° to measure a surface’s true colour irrespective of gloss. This uses a stable incident light source such as the Steropes LED, to illuminate the surface and measure reflectance across multiple angles. SCI reflection measurements, meanwhile, use a straight probe at 0° to measure colour and gloss for total measurement of the surface’s appearance.
The latter method requires the integration of the Steropes LED light source to a reflective probe. SCE reflection measurements may also use an M8 optical fibre connection to ensure stability and repeatability for true colour analysis. Admesy supplies both 200 micrometre (μm) and 400 μm reflective probes suitable for interfacing with the Steropes LED light source and our full range of colorimeters.
This setup provides the most accurate form of reflection measurements for R&D and QC purposes.
Reflection Measurements with Admesy
Admesy specialises in the development and supply of ultra-precise optical measuring equipment for industrial and commercial applications. Our reflection measurement instrumentation provides a comprehensive solution for assessing the colorimetric behaviour of specular or diffuse surfaces.
If you would like any more information about our light measurement capabilities, read our previous blog post: What are Transmission Measurements? Or, if you have any questions simply contact us directly.