Until today, almost all objective lenses and windows of LIR imagers use crystal Germanium (Ge) as the optical material. Germanium is heavy, expensive and very sensitive to the environmental temperature change. When the temperature rises above 120°C, the lens becomes opaque. It is necessary to overcome these shortcomings.Using the analytic universal skew ray tracing formula and the automatic optical system design software developed by us, we successfully designed a 150mm/F1 objective lens using Ge and non-Ge materials for the LIR imager of the missile seeker and airborne surveillance. We also successfully designed a 25mm/F1 objective lens with large FOV of 30°x40°using only non-Ge materials for the LIR imager of the helmet mounted search and rescue system. Good image quality is obtained. The cost is less than half of the Ge lens and the high temperature resistance is much better. In order to increase the S/N ratio 4 times for the low-sensitivity UFPA, an immersed Ge lens for the UFPA is also successfully designed.Currently, most of UFPAs use high-cost Digital Signal Processing (DSP) module. The LIR imager needs at least two circuit boards. We present a design that uses low-cost Altera processor and the imager only needs one board without Thermal Electrical Cooler (TEC). Therefore, three "AA" batteries can operate the imager for more than 4 hours. By inserting data between pixels and enhance the contrast, the image from the 120x120/50µ UFPA is even better than the image from the 240x320/50µ array. This gives us an opportunity to reduce the imager cost to 2/3 of the larger format without degrading the image quality.These innovative researches give us a chance to build a small, lightweight, inexpensive, and good image quality LIR imager for homeland security and many other military and commercial applications. Two patents were pending and one was granted. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/21/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 4820 551 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/21/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
Since high resolution recording materials are not readily available in the infrared and laser diodes do not have a sufficient coherent length, it is difficult to make an infrared hologram for the LD directly. An infrared hologram for a simple object can be easily calculated by a computer. If the hologram is large and the spatial frequency is high (say, more than 1000 lines/mm), it is still an elaborated process to generate these holograms by an electron beam machine. Also because of the long writing time required for the hologram, the electron beam and the translation stage stability must be carefully maintained. The former is often affected by the static charge built up and the latter by temperature changes and mechanical vibrations. In this paper we describe a different approach to make the hologram. We first create a CGH for a visible wavelength for which high resolution recording media are available. The CGH is then used as the object to make the final IR hologram using visible wavelength. The CGH is designed in such a way that the wavefront distortion is precompensated. The CGH is drawn by a personal computer system which includes an MP 1000-01 plotter.
It has become increasingly important to include a hologram or HOE in an optical system for serious applications. It is, therefore, necessary to calculate quantitatively the wavefront reconstructed from a hologram. We have tried two methods to perform the calculation1: the optical path difference method; the tangent plane intersection (TPI) method. For holograms with simple geometries, such as those with planar or spherical waves, both methods yield the same results. For general holograms, particularly for those with small f/Nos. and large aberrations, the results are quite different. Our experiments show that the TPI method produces results more consistent with the assumptions. We are unable to explain why these two methods yielded different results.
The Segmented Gamma Scanner(SGS) technology is specially used for type identification and activity quantitative analysis of radioactive material in sealed containers, which mainly divided into the transmission measurement and the emission measurement. In actual measurement process, it cannot meet the need for rapid analysis because the efficiency calibration time takes up more than 60% of the whole detect time in the data analysis. Whereas most previous research have focused on theory or specific applications, this research groups aim to different aspects of the SGS technique and direct it at an audience with interests in the need for rapid analysis. The Monte Carlo simulation calculation models were established by the passive efficiency calibration method, and then the detection efficiency database was carried out based on the experimental verification. Lots of work was used to analysis the influence of crosstalk between layers and interpolation step. Furthermore, the database was implanted into the control and analysis system to complete the measurement experiments. The results show the measuring time of single waste drums is about 30 min, and the average relative deviation is less than 10%, so the problem that the time taken to calibrate the detection efficiency is too long has been solved effectively. The efficiency in the use of SGS technology has been increased.
Personal computers and peripherals have become very powerful and sophisticated. A CGH can now be readily made on a personal computer system. Our equipment consists of an IBM-PC, a Western Graphtec MP 1000-01 x-y plotter, and an IBM dot matrix printer. The serial port for asynchronous communication is used to transfer the data to the plotter. The parallel port is used for the printer for data or program printing. The MP 1000-01 plotter is very suitable for plotting holograms because it has a large plotting area (36 × 27 cm), adequate resolution, and best of all it has a built-in firmware spline routing for smooth curve plotting using only a few points. We have also added a switch (and an optional rom) so that the plotter can be changed from the MP-1000 to the popular HP-7475A mode. Because of the limited accuracy (and the speed, a minor factor), we have used a series expansion on the mathematical expressions to obtain the necessary precision. We have made holograms of two spherical waves. The quality of the plotting is comparable with that obtained from large computer systems. We also investigated ways to equalize the dark and white spacings so that the reconstruction efficiency will be more uniform across the hologram. This may also increase the reconstruction efficiency for a phase hologram. Experimental results and related technical problems are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.