The Optical Surface Accuracy

Surface accurcay can simply be understood as referring to the flatness of the filter surface. It is like paving a road with cement or asphalt. A good road surface is smooth and smooth, and the car passes smoothly and quickly. If the paving is not good, the road surface ups and downs, potholes, the car can feel a very obvious sense of turbulence.

Surface accuracy refers to the deviation of the surface geometry of the optical element from the ideal shape. This deviation is generally quantified by a variety of parameters such as aperture number, local aperture number, PV, RMS, etc. Before figuring out the relationship between them, let's briefly understand the definition: the two parameters of aperture number (N) and local aperture appear more frequently in regular and complete optical drawings. Generally, it is mainly for the requirements of parts before processing. After processing, it is detected by interferometer and displayed with PV and RMS values. The PV value (Peak-to-Valley) is the height difference between the highest and lowest point of a surface. The RMS value (Root Mean Square) is the average of the data points in the detection area. In general, the PV value is 6-8 times the RMS value. So how to understand the relationship between aperture and PV? Simply remember: aperture is good, PV must be good. PV good, aperture is not necessarily good. Because PV is the relative value of the peak and trough of the aperture, the influence of local error is not considered. However, the influence of local aperture error should be considered when saying aperture.

The 3D model measured with the interferometer ‌ is generated by sampling data points, which visually and intuitively shows the convex and convex of the surface, which is helpful for the result evaluation. The interference fringe diagram ‌ provides detailed information about the surface topography, including the surface microstructure and interference phenomena.

Surface profile inspection of optical components is a complex and critical process that involves the integrated application of multiple parameters and techniques to ensure the performance and reliability of optical systems ‌.