| Optical lens has been applied in many fields such as industrial inspection, security monitoring, defense and military. The lens central thickness is an important parameter of lens, which has a significant effect on the focal length of lens and image quality of optical system. Thus, it is necessary to develop a equipment with high precision in order to measure lens central thickness.The equipment introduced in this paper is based on confocal principle. It can fast simply measure lens central thickness with a high degree of precision.This paper’s main research work is as follow:1.Taking into consideration of the current technology and the future development trends of lens central thickness measuring equipment, the paper studies the method of measuring lens central thickness using chromatic confocal system. The chromatic confocal principle and the method of measuring lens central thickness using chromatic confocal system are introduced in detail. The research shows that it’s a feasible simple fast way to measure lens central thickness.2.The spectrum bandwidth of emergent light in the system is researched, and the results show that the image space numerical aperture and the confocal hole radius are main factors which influence the spectrum bandwidth of emergent light. The research provides a scientific guidance for the design and development of the opticalsystem.3.The design indexes of the equipment are established in consideration of the measuring principle and measuring demand. The equipment whose maximum measurable lens thickness is about 30 mm and measuring accuracy is within ±6 μm is required.4.The design of chromatic confocal system and its subsystem which consist of light source, chromatic lens, confocal hole and beam splitting system are introduced in this paper. It can provide a scientific guidance and reference for other confocal system.5.We devise a new way to make the optical axis of measured lens and the optical axis of chromatic lens collinear. In this way, we can minimize measuring time.6.The software of lens central thickness measurement is programmed.Algorithms of peak wavelength calculation and lens central thickness are researched.7.We develop the equipment successfully. And a series of measuring experiment using the equipment has been done, and the results show that the maximum measurable lens thickness is more than 30 mm by using this equipment.What’s more, the measuring accuracy is ±5.0 μm. So the equipment is suitable for measuring lens central thickness of the in large quantity. |
