混凝土结构裂缝宽度波前编码测量系统的设计

Design of wavefront coding system for measuring crack width in concrete structure

为了克服基于传统光学成像技术设计的手持式混凝土裂缝宽度测量系统焦深小、准确调焦困难,以及由于存在像差和混凝土表面凹凸过大致使视场内图像无法完全清晰等缺陷,采用波前编码技术重新进行缝宽检测系统的设计,以便有效地拓展景深(焦深)。讨论了波前编码立方型相位板规一化参数及其与实际系统相位板设计参数之间的关系,利用CODEV光学设计软件完成了手持式裂缝宽度波前编码测量系统的设计,加工制作了立方型相位板并进行了初步实验。实验表明,采用基于单透镜的波前编码系统设计,在满足分辨率为50μm,F数为6的前提下,可将景深拓展为15mm,达到传统光学系统相同F数时景深理论值的4.5倍。该系统能够满足混凝土结构裂缝宽度测量中扩大景深和成像的基本要求。

In order to remedy some defects in a traditional handy system for measuring the crack width in a concrete structure ,such as the difficulty inaccuracy focusing and the blur image due to the small focus depth and aberrations, a new system based on a wave-front coding was designed to extend the focus depth.The normalized parameters of a cubic phase plate and the relationship between these parameters and their corresponding real design parameters were discussed. Then a handy measurement system based on the wavefront coding with CODE V was designed. Finally, the cubic phase plate was fibricated and a preliminary experiment was carried out. Experimental results indicate that the field depth of the wavefront coding system based on a single lens can be extended to 15 mm when the resolving power is 50 μm and the F number is 6, which is 4.5 times as deep as that of traditional optical systems in theory at the same F number. The system can satisfy the requirements of extending focus depth and imaging in measuring the crack width of a concrete structure.