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光学杠杆式仪器,如:光学比较仪、超级光学比较仪等是常用的计量仪器,把光栅装于物镜焦面上,由标尺光栅的象和指示光栅实物形成“莫尔”条纹,以光电元件转变为电信号,就可以实现数字显示。光学杠杆式仪器数字化的优点是由于具有较高的光学杠杆放大率,因此可以用粗光栅实现高分辨率,而且光栅刻划误差对仪器精度的影响大为减少。但是光学杠杆式仪器数字化的难度较大,这是由于反射镜偏转时使用了物镜与照明光束的不同部位,象差与亮度的变化引起电信号幅值、直流电平与相位的变动,而且信号的频率较高。为了解决这些问题,须要严格控制物镜的象差;采用适当的光栅参数与结构,以及会聚光照明,现已研制成功的光学杠杆式仪器数字化的实例,有光学杠杆放大率为100~x与31.25~x、分辨率为0.1μ的数显光学比较仪,以及光学杠杆放大率为312.5~x、分辨率为0.01μ的数显超级光学比较仪。
Optical lever instruments such as optical comparators and super optical comparators are commonly used measuring instruments. The grating is mounted on the focal plane of the objective lens. The moire fringes are formed by the image of the scale grating and the indication grating. Into the electrical signal, you can achieve digital display. The advantage of optical lever instrument digitization is the high optical lenght magnification that enables high resolution with coarse gratings and a significant reduction in the impact of raster scribing errors on instrument accuracy. However, it is more difficult to digitize the optical lever instrument because the mirror uses different positions of the objective lens and the illuminating beam during the deflection. The aberration and the change of the brightness cause the amplitude, DC level and phase of the electrical signal to fluctuate, and the signal Higher frequency. In order to solve these problems, it is necessary to strictly control the aberration of the objective lens. With appropriate grating parameters and structures and converging light illumination, the digitalized examples of optical lever instruments that have been successfully developed have optical lever magnifications of 100 x and 31.25 ~ x, a resolution of 0.1μ digital optical comparator, and the optical lever magnification of 312.5 ~ x, a resolution of 0.01μ digital super optical comparators.