Types of deficiency
The so-called optical component surface defects mainly refer to surface rickets and surface contaminants. Surface rickets refer to various processing defects such as pitting, scratches, open bubbles, broken edges, and broken spots on the surface of polished optical components. The main reason is processing or subsequent processing. Scratches are the scratches on the surface of an optical component. Due to the length of the scratch, it can be divided into long scratches and short scratches, with a limit of 2 mm. If the scratch length is greater than 2 mm, it is a long scratch, and if it is less than 2 mm, it is a short scratch . For short scratches, the evaluation criterion is to detect their cumulative length. Relatively speaking, scratches are easier to detect than defects such as pitting.
Pitting refers to pits and defects on the surface of an optical component. The surface roughness in the pit is large, the width and depth are approximately the same, and the edges are irregular. Typically, defects with an aspect ratio greater than 4:1 are scratches, while defects less than 4:1 are pitting.
The bubbles are formed by gases that are not removed in time during the manufacture or processing of the optical component. Since the pressure of the gas in each direction is evenly distributed, the shape of the bubble is usually spherical.
Broken edges are a criticism of the edge of optical components. Although it is outside the effective area of the light source, it is also a source of light scattering, which also has an effect on optical performance.
Negative impact caused by the deficiency
Surface rickets, as a microscopic local defect caused by man-made process, have a certain influence on the surface properties of optical components, which may lead to serious consequences such as optical instrument operation errors. In short, the surface defects of optical components can be detrimental to the performance of optical systems, and the root cause is the scattering characteristics of light.
The damage of optical component surface defects to itself and the entire optical system is manifested in the following aspects:
(1) The quality of the beam is degraded. The surface scattering defect of the component produces a scattering effect of light, so that the energy of the beam is greatly consumed after passing through the defect, thereby reducing the quality of the beam.
(2) The thermal effect of defects. Since the area where the surface defects are located absorbs more energy than other areas, the thermal effect phenomenon may cause local particial deformation of the component, damage the film layer, etc., and thus damage the entire optical system.
(3) Damage to other optical components in the system. In a laser system, under the illumination of a high-energy laser beam, the scattered light generated by the surface of the component is absorbed by other optical components in the system, resulting in uneven light received by the component. When the damage threshold of the optical component material is reached. The quality of the transmitted light is affected, and the optical components are damaged, which is more likely to cause serious damage to the optical system.
(4) Rickets can affect the cleanliness of the field of view. When there are too many rickets on the optical components, it will affect the microscopic aesthetics. In addition, the cockroaches will leave tiny dust, microorganisms, polishing powder and other impurities, which will cause the components to be corroded, moldy, and foggy. Will significantly affect the basic performance of the component.