To satisfy a space patrol telescope system with high angular resolution, large space area and high stray light suppression, the stray light environmental characteristics at low earth orbit are summarized. In accordance with the parameters, which diameter is 1.5m, focal length is 20m, field of view is 1.1°×1°, and the optical and mechanical structure joint-design stray light suppression is compared and analyzed for on-axis cross type, off-axis back end type and off-axis sideway type. A method of optical and mechanical structure joint-design stray light suppression is proposed to reduce the stray light suppressing angle to enhance the efficiency of the observation time and sky patrol efficiency in orbit. The detailed stray light suppression design and optimization of off-axis sideway type is given. The simulation and analysis of total optical and mechanical periodic line is presented, and the major stray ray path is simulated and analyzed.Compared with the other two types, the off-axis sideway type presents the best performance of image quality and stray light suppression. The modulation transfer functions (MTF) approach the diffraction limit at all fields. When the evadable angle out of the field is 40°, the PST is less than 10-11 and the system can approach to the stray light suppression limitation.
A large-aperture, wide field-of-view, three-mirror optical system for a space borne astronomical survey telescope has been designed. The unobstructed optical system with a circular pupil has a 2 meter aperture, 1.7 deg2 FOV, and provides remarkably good imagery. Freeform surfaces and decentered/tilt surfaces are introduced to the system, which have the advantage of balancing the unsymmetrical aberrations, especially for the wide-field off-axis optical systems. The evaluation of image quality is that the value of the RMS wavefront error is 21 nm, the ellipticity is less than 6.5% in the main imaging area (about 1.1 deg2), and the maximum radius of Encircled Energy 80% (EE80) is less than 0.09arcsec.
With the development of new concepts and principles over the past century, helmet-mounted displays (HMDs) have been widely applied. This paper presents a review of avionic HMDs and shows some areas of active and intensive research. This review is focused on the optical design aspects and is divided into three sections to explore new optical design methods, which include an off-axis design, design with freeform optical surface, and design with holographic optical waveguide technology. Building on the fundamentals of optical design and engineering, the principles section primarily expounds on the five optical system parameters, which include weight, field of view, modulation transfer function, exit pupil size, and eye relief. We summarized the previous design works using new components to achieve compact and lightweight HMDs. Moreover, the paper presents a partial summary of the more notable experimental, prototype, fielded, and future HMD fixed-wing and rotary-wing programs.
Freeform surfaces provide more degrees of freedom for design of optical systems, and enhance the ability of
compensation and correction aberrations. Freeform surfaces are of advantage to balance the unsymmetrical aberrations, especially for the wide-field off-axis optical systems. This paper focus on an off-axis reflective optical system, which focal length is 550mm, F# is 6.5 and field of view (FOV) is 76°. The system adopts some freeform surfaces. We discuss the problems we noticed in processes of design, manufacture, measurement and alignment, and the solutions. At last, the periodical research result and the expected performance are given.
It is essential to analyze the gimbal displacement errors for a seeker due to the importance for cueing of targets and
tracking for the final approach. Otherwise, for a seeker electro-driven with a concentric glass dome, the large errors will
decrease the picking, pointing, and tracking precision rooted from the displacement errors existing between the rotation
center of the optical system and the gimbal. And the gimbaled camera system displacement errors are never eliminated
but reduced due to the geometric errors consists of geometric tolerances of gimbal structure, manufacture, installation
and vibration coming from working environment.
In this paper, the gimbal displacement errors in an electro-optically stabilized platform resulting from geometric errors
and environment errors were analyzed and shown in detail. The mathematical modal of the gimbal displacement errors
created based on multi-body dynamics demonstrated the connection between the gimbal displacement errors and the
stabilized platform. Taking a visible light image seeker as a case, the diameter is 120mm, and the geometric tolerances
came from the values of primary design and the vibration data came from the environmental vibration test on the
pitch-yaw seeker, and at the same time, the errors resulting from installation were considered too. Based on calculating,
the maximum gimbal displacement error will reach to 0.2mm for pitching angle smaller than 40° and yawing angle
smaller than 60°. However, the critical parts have been found out according to the probability theory and the reliability
analysis successfully used in the paper, and finally, the maximum gimbal displacement error reduced to 0.1mm, which is
acceptable corresponding to the picking, pointing and tracking precision for an optical imaging seeker.
When infrared optical system works in a large temperature range, the thermal effect of optical lens and optical tube will
produce image plane shift and lead to imaging quality deterioration. In order to eliminate the thermal aberration, the
athermalization design principles of infrared optical system were introduced, and some commonly used methods of
thermal difference compensation were described. Proceeding from single lens, the thermal difference caused by
temperature changing was analyzed, and the relationship between temperature and focus shift was obtained. Considering
optical tube thermal expansion, a set of equations to estimate the thermal difference of lens group was given. Finally, an
infrared optical imaging system that can work under the temperature range of -40°C to 60°C was design according to
athermal technique, in which a new mechanical passive temperature compensation was proposed. Through simulation,
the athermalization design could make imaging plane shift the smallest. The simulation results coincided with the
theoretical formula, and the design had reference value in engineering.
Electric-Optical (EO) imaging systems are modern systems, especially the one consists of aspheric optics and
image processing called wavefront coding system. The design concept of this kind system is totally different from
the traditional image system. The trade-off between the complexity of the image deconvolution and the depth of
focus extended should be considered. So we establish a simulation model consisting of optical optimization design,
system signal-to-noise ratio analysis and recovered image evaluation. The data can be exchanged among them. This
simulation tools will be very useful in system design process.
Narcissus can have a deleterious effect on image quality for cooled infrared imaging systems. Therefore, analysis of narcissus is important for designing both scanning and staring optics. Narcissus is generally assumed to be negligible in staring IR optical designs because the shading effects can be removed by calibration of the detector array data. However, the calibration usually decreases sensitiveness of the system and Narcissus variation may be noticeable for sensors when the conditions changes as follows: 1. warming and cooling the optical housing, 2. zooming optical elements, 3. movement of lenses for focus. In that case, it will result in shading and other image defects even after calibration. To minimize these effects, narcissus should be assessed and controlled during the design of staring array IR system. We provided a direct and fast method for analyzing the narcissus variation in the presence of software such as LightTools, TracePro and ASAP, and proposed the principles in optical design of staring IR systems to reduce narcissus. A cooled staring IR system with serious narcissus was estimated and reoptimized. Narcissus analysis of this IR system confirmed the efficiency of the analysis method.
It has been a significant issue in the imaging filed to provide the highest possible resolution of an electro-optical imaging system(E-O imaging system). CCD arrays are inherently undersampled and spatial frequency above Nyquist frequency is distorted so as to create ambiguity and Moire patterns for targets imaged by E-O system.. As to this drawback, a system-design project is introduced and discussed in the paper. It's well known that many image quality metrics are linked to MTF. However, CCDs don't satisfy MTF condition, namely, the shift-invariant property, so MTF synthesis can't appraise the whole system simply by the MTF product of the few sub-system ones in E-O imaging system. Then it is depicted how to solve this problem in the following. Finally the analyses and comparisons of the imaging performance parameters with and without super-resolved technologies are shown.
An infrared-optical zoom system using binary element is proposed in this paper. The two main advantages of the zoom system introducing here are: bigger F-number and lower cost. The primary optical properties are: F/#=1,zoom ratio =1:4,and dual field are 26.6°and 5.6°respectively. Wider field of view is used for search and the smaller one is used for imaging details. This system uses un-cooled infrared detector with 320×240 pixels and 45μm pixel size. The F-number matches the sensitivity range of the detector array. Three aspects are considered during design process to make the system more satisfactory and more achievable. First, the manner of zoom is accomplished by exchanging tow lenses into the smaller field of view system layout. The lens exchange manner faces the requirement of simple system structure and good image quality in both focal points. It can also make the system more feasible in the alignment process than mechanical-zooming manner and optical-zooming manner; Second, binary element is used to correct the chromatical aberration by taking the advantage of negative dispersion characteristics and the cost of the system is lower than that of conventional ones with Zinc Selenide (Znse) material at the same level. In the binary element is rotational symmetric with one step which is easy to fabricate; Others, in order to balance 5th spherical aberration, 5th coma aberration and 5th astigmatic aberration, high-order asphere surfaces with 2th order to 10thorder are also hired in the system. Asphere surface is useful in compressing the system and improving optical system transmittance. This kind asphere surface is on industrial level featuring low cost and easy to fabricate. It is shown that good image quality can achieved by implementing five Germanium lenses and the transmittance of system is 72%. All aberrations are diffraction-limited, both spherical aberration and astigmatic aberration are corrected. When the field of view(FOV) is 26.6°and the focal length is 152mm, MTF at Nyquist frequency(11lp/mm) is great than 0.7. The spherical aberration is -0.0073. The coma aberration is 0.0978 and the astigmatic aberration is -0.013. When the field of view(FOV) is 5.6°and the focal length is 38mm, MTF at Nyquist frequency is great than 0.8 with spherical aberration -0.0046,the coma aberration 0.055 and astigmatic aberration 0.034.
This paper summarizes the technical specifications of the Space-borne Imaging Spectrometer. The remote sensor consists of 20 bands including visible, near infrared, short wave infrared and thermal infrared channels. The engineering model (EM) was completed. Using the software CODEV, we discuss the influence of the space-borne environment, different temperature, especially different assembling material on this instrument. Data show that the main optical system is sensitive to the space-borne temperature; the space image quality is affected heavily by the assembling material and etc. The orbit environment analysis is of great advantage to the optical set-up, environment experimentations and cost saving.
Using broadband hybrid diffractive/refractive optical system, an athermalized imaging system without special optical and mechanical materials, which is the prototype for space borne small CCD camera, has been designed, evaluated, fabricated and tested. The comparison with conventional optical system is presented. Also, the paper analyzes and discusses the effect of parasite orders diffraction from binary optical element as the regular `stray light' on the image quality (MTF and contrast), and proposes an approach of image processing that can compensate such image quality degradation when broadband hybrid system is used in CCD camera.
In this paper we describe a low debris laser plasma source with cryogenic CO2 target developed in our institute, which can emit strong line radiation in EUV region even in water window. In particular the source is a very important candidate radiation source for the future EUV lithography production line.
Using refractive-diffractive hybrid system in multispectral camera to compensate thermal defocus effect is considered. The paper gives the design principle, the specification and layout, calculates the system MTF of a soaking environmental temperature and pressure variation compared to the conventional design.
Binary optics element (BOE) used to correct the aberrations of zoom lens, especially to control secondary spectrum in apochromatic zoom lens, are considered. Principles and methods are presented. The advantages in improving image quality and simplifying construction are illustrated through the design example.