Orange Peel (effect) - Measurement

Measurement

The instruments used to measure orange peel simulate visual perception. Like our eyes, the instruments optically scan the wavy light / dark pattern. A laser point light source illuminates the specimen at a 60° angle and a detector measures the reflected light intensity at the equal but opposite angle. The orange peel meter is rolled across the surface and measures point by point the optical profile of the surface across a defined distance. The instruments analyze the structures according to their size. In order to simulate the human eye's resolution at various distances, the measurement signal is divided into several ranges using mathematical filter functions:

• Wa 0.1 ..... 0.3 mm wavelength
• Wb 0.3 ........ 1 mm wavelength
• Wc 1............ 3 mm wavelength
• Wd 3 ......... 10 mm wavelength
• We 10 ....... 30 mm wavelength
• SW 0.3 ..... 1.2 mm wavelength
• LW 1.2....... 12 mm wavelength

Simplified Measurement Diagram

Structures smaller than 0.1 mm also influence visual perception, therefore the instruments use a CCD camera to measure the diffused light caused by these fine structures. This parameter is referred to as "dullness".

The values of dullness and Wa to We form a "structure spectrum". This allows a detailed analysis of Orange Peel and its influencing factors, being material or application parameters. Example of a "structure spectrum"

The detailed information of the structure spectrum as well as LW and SW became the basis to correlate to specific scales and to the DOI as described in ASTM E430.