Diffractive optical elements (DOEs) are widely used in different kinds of optical systems with its special dispersion characteristics, which include the dual-band lens. However, the single-layer DOEs (SLDOEs) suffer from the problem that the diffraction efficiency decreases significantly as the wavelength deviates from the design wavelength. So the selection of DOE is not necessary. A high diffraction efficiency of the multilayer diffractive optical element in the dual frequency band was investigated, Based on the scalar diffraction theory. The relationship between substrate material selection and diffraction efficiency of obliquely incident dual-band multi-layer diffractive optical elements under universal working conditions is derived. The influence factors of diffraction efficiency are analyzed. A material selection for quickly obtaining high-bandwidth integral diffraction efficiency is proposed. By this method, the optimal base material combination of the multilayer diffractive optical element can be quickly selected in a large-angle dual-band system. A medium wave-long wave infrared double frequency lens is designed by the ZEMAX commercial software.The transfer function of the system is greater than 0.4 in the medium wave and greater than 0.3 in the long wave. So the chromatic aberration of hybrid lens is corrected in infrared dual-band, and high image quality can be achieved.
Network technology has become a creative tool of changing human productivity, the rapid development of it has brought profound changes to our learning, working and life. Network technology has many advantages such as rich contents, various forms, convenient retrieval, timely communication and efficient combination of resources. Network information resources have become the new education resources, get more and more application in the education, has now become the teaching and learning tools. Network teaching enriches the teaching contents, changes teaching process from the traditional knowledge explanation into the new teaching process by establishing situation, independence and cooperation in the network technology platform. The teacher's role has shifted from teaching in classroom to how to guide students to learn better. Network environment only provides a good platform for the teaching, we can get a better teaching effect only by constantly improve the teaching content. <p> </p>Changchun university of science and technology introduced a BB teaching platform, on the platform, the whole optical classroom teaching and the classroom teaching can be improved. Teachers make assignments online, students learn independently offline or the group learned cooperatively, this expands the time and space of teaching. Teachers use hypertext form related knowledge of applied optics, rich cases and learning resources, set up the network interactive platform, homework submission system, message board, etc. The teaching platform simulated the learning interest of students and strengthens the interaction in the teaching.
In this paper, the effect of environmental temperature change on multilayer diffractive optical elements (MLDOEs) is evaluated from the viewpoint of the diffraction efficiency and the polychromatic integral diffraction efficiency (PIDE). As environmental temperature changes, the microstructure heights of MLDOEs expand or contract, and refractive indices of substrate materials also change. Based on the changes in microstructure height and substrate material index with environmental temperature, the theoretical relation between diffraction efficiency of MLDOEs and environmental
temperature is deduced. A practical 3-5μm Mid-wave infrared (MWIR) optical system designed with a MLDOE, which made of ZNSE and GE, is discussed to illustrate the influence of environmental temperature change. The result shows that diffraction efficiency reduction is no more than 85% and PIDE reduction is less than 50% when environmental
temperature ranges from -20°C to 60°C. According to the calculated diffraction efficiency in different environmental temperatures, the MTF of hybrid optical system is modified and the modified MTF curve is compared with the original MTF curve. Although the hybrid optical system achieved passive athermalization in above environmental temperature range, the modified MTF curve also remarkably decline in environmental temperature extremes after the consideration of diffraction efficiency change of MLDOE. It is indicated that the image quality of hybrid optical system with ZNSE-GE MLDOE is significantly sensitive to environmental temperature change. The analysis result can be used for optical engineering design with MLDOEs in MWIR.
This paper discusses the optical design of an uncooled dual-band MWIR/LWIR optical system using a circular
unobscured three-mirror system which is particularly suitable for wide spectral range , large aperture and small volume
imaging systems. The system is designed at focal length 310mm, F-number 1.55 with field of view 1.77°×1.33°. A
coaxial three-mirror system is calculated by the paraxial matrix as a starting point. With the condition that the focal point
of each conic mirror is placed to coincide successively, elements in the system are tilted and decentered properly to make
the system unobscured and the mirrors are arranged to form a round configuration for compactness. The optical path is
folded inside the region surrounded by the mirrors. Zernike polynomial surfaces which are limited to be symmetric about
tangential plane are used to correct aberrations and to improve the image quality. The modulation transfer function of
this system is above 0.65 in MWIR band and above 0.5 in LWIR band all over the field of view at the Nyquist frequency
of 20 line pairs per millimeter. The result shows that the space can be utilized efficiently, the system is compact and
image quality is favorable.