Study On Technology Of Writing Mesh On The Convex Surface

The aircraft is generally equipped with high-precision electro-optical detector for object recognition and identification. In order to prevent the electromagnetic radiation to affect target detection accuracy and radiation caused by internal devices to leak and become the target of anti-radiation weapon, the optical window in front of the detector should be improved to deal with electromagnetic shielding. Meanwhile, the optical window must have the property of high infrared and visible light transmission which means low effect on the performance of detector. A lot of studies and practices show that, the optical window coated with a layer of metallic mesh has proved to have the perfect property of electromagnetic shielding and high infrared and visible light transmission.Generally, the metallic mesh is square because this type can be easily fabricated and relatively speaking, have fine electromagnetic shielding effectiveness. To illustrate the electromagnetic shielding effectiveness of metallic mesh in different shape, we use Finite Difference Time Domain (FDTD) numerical simulation method to analysis. The study shows that when the incident electromagnetic wave is in horizontal polarization, the shielding effectiveness of triangular mesh with the same length is higher than the square one; in the case of equal area, the shielding effectiveness of mesh shows this trend:triangle>square>hexagon. We conclude that in the same infrared transmission, the triangular mesh has better shielding effectiveness than square one.At present, making a concave mesh takes a lot of time which leads to low production. So, combined with the mask lithography technology in micron-machining field, we propose to use convex surface mask to fabricate concave spherical mesh. Then we build a laser direct writing platform for the convex surface mask and develop the corresponding software for tilting table control and algorithm for constant exposure on convex surface. The platform is able to process metallic mesh with ±20 degree at most on the convex surface. Not only mesh, but also concentric ring and grating can be processed by vector model.Based on the convex surface laser direct writing platform, we realize to fabricate the patterns on the convex surface with the diameter about 50mm and the radius of curvature about 51.64mm. Among these, the square grid with period about 400μm and feature size about 10μm has been get. The platform has proved to have capacity to process pattern on the convex surface which lays a solid base for future application.