透镜中心厚度测量设备是基于色差共焦原理，能快速自动测量透镜的中心厚度，且不接触透镜表面的一种新型设备。通过对该测量系统出射光光谱的研究，得到影响光谱带宽及系统测量精度的因素。研究结果表明，对于峰值波长λ0 的光，其在系统中的像方数值孔径NA ，以及小孔半径r 均会对出射光的光谱有影响。NA 越大，出射光带宽越小，系统测量精度越高；r 越小，出射光带宽越小，系统测量精度越高。根据这一研究结果进行测量系统的设计与仿真，确定了能满足系统测量精度要求的NA 和小孔半径r。

The equipment based on confocal principle is a kind of new setup, which can fast and automatically measure center thickness of lens without contact of lens surfaces. We investigate the spectral bandwidth of emergent light in order to obtain the factors influencing the spectrum bandwidth and the measurement precision. The result shows that the numerical aperture on image side and the confocal hole radius are the main factors. When the numerical aperture is larger, the spectral bandwidth is smaller and the measurement precision is higher. What is more, when the hole radius is smaller, the spectral bandwidth is smaller and the measurement precision is higher, too. Then, we adopt the result to guide the design and simulation, and we get a better numerical aperture and confocal hole radius, which can realize the precision of the measurement system.