Method For Multi-wavelength Wavefronts Testing Of Typical Transmission Systems

The transmitted wavefront contains a wealth of information which is a very important evaluation index of optical systems as well as studying the optical field.The wavefront of the transmission optical system needs to be tested at specific design wavelengths.From now on,wavefronts at only a few wavelengths can be accurately tested because of the limitation of instrument.With the development of technology,wavefront measurements of many of the much-needed optical system are still not perfect,especially for some special-purpose bands,such as near-infrared.Therefore,a novel method for measuring the wavefront aberration of an optical transmission system in a broad wavelength range is proposed,using existing technologies.The basic principle of multi-wavelength wavefronts testing is establishing the relationship between the transmitted wavefront and wavelength,using Zernike fringe coefficients to represent the wavefront.The transmitted wavefront at a specific wavelength can be calculated based on wavefronts measured at other wavelengths according to the Zernike coefficient function.From simulations of several different types of optical systems,we found that two formulas can be used to express Zernike-wavelength curves:the Conrady dispersion formula and a new formula that we have named the apochromatic characteristic formula.The Zernike-wavelength curves for most monochromatic systems and some achromatic systems can be expressed by the Conrady formula,while the apochromatic characteristic formula can express Zernike-wavelength of most optical systems,including monochromatic systems,achromatic systems and apochromatic systems.At the same time,relationships between other parameters and wavelength are analyzed by the two formulas.It is further proved that the two formulas can describe the wavelength dependent curves of optical systems.An algorithm which is the estimation of Zernike coefficients for arbitrary wavelength at defocus position is proposed.The method compensates the change of Zernike coefficients of defocus distance based on Zernike coefficients.The algorithm is verified by a doublet achromatic lens.The result shows that the proposed algorithm is effective for calculating Zernike coefficients related to position.While other Zernike term coefficients can be calculated by the data at defocus position.Five wavelength laser interferometers were built based on 632.8 nm laser interferometer.A single lens representing a monochromatic transmission system is measured by different wavelengths.The results show the monotonic Zernike-wavelength curves in 400¹000nm bandwidth can be predicted by binomial Conrady formula with two data points.Due to the influence of systemic errors in measured dataset,it is difficult to obtain the right curve by solving Conrady formula and apochromatic characteristic formula.Since,in general,the Zernike-wavelength curves of monochromatic systems are monotonic,at present this technique is only effective for these kinds of system.Then,the experimental setup is improved to test wavefront at defocus position.A doublet achromatic lens is measured at the focus position and the defocus position at different wavelengths.The measurement results are coincided with the defocusing algorithm.The calculated Z₃-wavelength curve is similar to the simulation result.It is feasible to estimate transmitted wavefronts in a broad bandwidth according to the experimental results.In addition,the method of measuring transmitted wavefronts in broad bandwidth using discrete points is verified by experiments.A standard spherical lens with variable wavelength is designed,and a method of testing focal length at arbitrary wavelength is proposed.In this thesis,a method to study the relationship between optical system parameters and wavelength is established,and we obtain two important expressions.The new method proposed in this thesis simplifies the testing of traditional transmitted wavefront,and is expected to become a universal method to meet the wavefront testing requirements of advanced optical systems in important fields such as industrial manufacturing,optoelectronic information and laser communication.Therefore,the development of new wavefront testing technology is of great significance for the high-precision testing of the quality and performance of modern optical systems.At the same time,the dispersion characteristics from our research can be applied in many aspects in the future,and have important value in the fields of optical design and optical computing,and will have certain influence in these optical related fields.