水下气泡高速摄影光学系统设计

为了研究水下气泡的粒径、速度和浓度特性,提出基于高速电荷耦合器件(CCD)的气泡照明和三维摄影光学系统.采用532nm半导体激光器,基于伽利略结构用三个柱面镜设计了厚度1.5mm,宽度44mm的片光源。设计物像距530mm,放大率为0.4,1,2.5倍(×)的摄影光学系统,每组均由共用前组镜和会聚镜组成,中间以平行光中继。通过同步移动片光源和共用前组镜实现60mm×40mm视场内二维高速成像和纵向5mm扫描,具有结构简单、性能可靠的特点。对设计结果进行评价,0.4,1,2.5×成像光学系统在0.707ω,50lp/mm时调制传递函数值分别为0.58,0.55和0.38,能够分辨粒径范围为10～450μm的气泡。

Design of High-Speed Photography Optical System for Air Bubbles in Water

For the purpose of study on diameter, velocity and concentration of air bubbles in water, an optical system of illumination and 3D photography based on high-speed imaging charge-coupled device is proposed. Based on Galileo structure with three cylindrical lens and semiconductor laser of wavelength 532 nm, a light sheet with thickness of 1.5 mm and width of 44 mm is designed. Three groups of imaging lens with magnification of 0.4×， 1× and 2.5×, having a uniform conjugate distance of 530 mm are designed. Each group relayed by collimated light includes frontal lens and focusing lens. A simple and reliable structure of 2D high-speed photography for the area of 60 mm×40 mm and 1D scan with length of 5 mm along the optical axis, is achieved by moving light sheet and frontal lens synchronously. The imaging quality of the optical system with magnification of 0.4×, 1× and 2.5× is evaluated, it shows that the modulation transfer function of 0.707ω has reached 0.58, 0.55 and 0.38 respectively at the spatial frequency of 50 lp/mm, as well as the diameter resolution of air bubbles in water has been from 10 μm to 450 μm.