Dark-field detection method of shallow scratches on the super-smooth optical surface based on the technology of adaptive smoothing and morphological differencing

Abstract

There exist some shallow scratch defects on the super-smooth optical surface. Their detection has a low efficiency with the existing technologies. So a new detection method, dark-field detection of adaptive smoothing and morphological differencing (DFD-ASMD), is proposed. On one hand, the information of shallow scratches can be kept in dark-field images. On the other hand, their weak characteristics can be separated and protected from being overly reduced during the elimination of noise and background in the image. Experiments show the detection rate of shallow scratches is around 82%, and DFD-ASMD can lay a foundation for quality control of defects on the high-quality optical surface.

Detection and simulation of defects on precision optical surface

“…1(a), while the abscissa is the width and the ordinate is the height. The scratch is in the shape of "V", consistent with the literature [13] . The maximum depth and width of the scratch are 38.9 nm and 10.8μm respectively.…”

Super-resolution Imaging of Submicron Natural Defects on Optics Component by Structured Illumination Microscopy

“…And combined with the optical components defect detection technology in recent year's progress, it is possible to achieve fast and accurate measurement of defects with a size of ≥0.5μm. By special treatment of microscopic measurement defects, the actual damage resistance of post treatment optical components has been further improved, but it is still ~1 order of magnitude off the material intrinsic damage threshold [9,10]. Therefore, high-threshold defects with a scale ≤0.5 μm have become one of the only factors that limit the optical-damage-threshold of materials.…”

“…For this kind of defects, the existing detection methods mainly include microscopy, optical scattering imaging [10,11], interference method [12], laser confocal microscopy [13,14]. Restricted by the Rayleigh diffraction limit, normal optical microscopy, optical scatter imaging, and laser confocal microscopy just achieved defect detection with a scale >λ/2 [16,17].…”

Isotropy frequency-domain extension imaging and its application in detection of nanostructures

“…With the rapid development of precision manufacturing technology for optical components, effective control of defects above several micrometers has been achieved, and corresponding the damage threshold of optical elements has been greatly improved. However, it is still about an order of magnitude lower than the intrinsic threshold of materials, so the high damage threshold defects at the sub-micron scale have become a key limiting factor for further improvement of the damage resistance of fused silica optics [8,9]. How to effectively suppress sub-micron defects has become an important scientific problem in the fields of precision manufacturing and laser damage resistance.…”

“…If you want to suppress or eliminate it, the first rule is to find it. At present, the methods for characterizing surface defects of fused silica optics mainly include optical microscopy, optical scattering [9,10], interference [11], laser confocal microscopy (LCM) [12,13], scanning probe-based microscopy (SPM) [14], atomic force microscope (AFM) [3,15] and scanning electron microscope (SEM) [3,15]. Limited by the Abbe-Rayleigh diffraction limit, microscopy and optical scattering methods can only achieve defect detection within a certain range of scales (>λ/2) [16,17], and just can obtain two-dimensional morphological information of defects.…”