To obtain satisfactory performance in characterizing optical freeform surfaces with local features, this paper proposes a model of a radial basis function with slope-based shape factor and distribution (RBF-SSD). Compared to previous RBF-slope models with only slope-based shape factors, the RBF-SSD model relates both shape factors and distribution with the surface slope, ensuring greater fitting ability can be achieved when fitting a surface with local features. Fitting experiments for two different surfaces demonstrated the fitting ability of the RBF-SSD model. An off-axis three-mirror system with 3 ° × 3.6 ° field of view was designed as an example to show the optical design efficacy of our model.
Distributed reconfigurable remote sensing satellite system can realize flexible and robust remote sensing network. Imaging system for distributed reconfigurable remote sensing satellite system should consume fewer power and be lighter to be installed on small or micro satellite. In this paper imaging system based on CMOS for distributed reconfigurable remote sensing satellite system was put forward. Circuits of CMOS sensor driving and CMOS data processing were detailed. In order to improve signal integrity circuits were divided into two sections which were connected with flexible printed circuit. CMOS sensor and its power circuits were placed in the focal plane printed circuit board. Imaging control box consisted of control and data processing circuits of CMOS sensor as well as communication and image data transferring circuits. Impedance matching was used to improve signal integrity of signals transmitted through flexible printed circuit between the focal plane printed circuit board and imaging control box. Results of experiments and analysis indicated that power dissipation of imaging system for distributed reconfigurable remote sensing satellite system was 4.05 W and the weight of imaging control box was 0.435 kg. SNR of each band of imaging system for distributed reconfigurable remote sensing satellite system was more than 41.28 dB as sun zenith angle is 20º and earth reflectance is 0.65.
Time delay and integration (TDI) CCD or CMOS sensors are widely used in space cameras to realize high resolution. Fixed TDI stages are often used when space cameras are working to avoid image saturation. As a result images obtained have problems such as short of digital number levels. In this paper an automatic on-orbit adjusting TDI stages method of space camera based on sun zenith angles was put forward. In this method radiance at entrance pupil of space camera was calculated in real time by nonlinear function fitting according to sun zenith angles of ground targets. Then optimal time of exposure could be obtained. Line transfer time for image compensation was calculated at the same time. Finally TDI stage was acquired by optimal time of exposure and line transfer time. In this way real-time calculation and adjustment of TDI stages were realized. Results of comparison of simulation by STK and computation by MODTRAN indicate that standard deviation of radiance fitting errors is about 0.175W/m2 ∙s and relative radiance fitting error is no more than 0.93% as sun zenith angle belongs to [5°, 65°]. Dynamic changes of SNR along with changes of time and sun zenith angle using adjusting TDI stages method and fixed TDI stages method were compared and analyzed. Results of analysis indicated that SNR would be improved from 23 dB to 39dB as sun zenith angle was 88.2° when automatic on-orbit adjusting TDI stages method was used in comparison with fixed TDI stages method.
Polarized LIDAR is defined as radar system which uses the polarization state of the laser to carry information. According to the different features, this paper divides the polarized LIDAR into non-imaging polarized LIDAR and imaging polarized LIDAR. The non-imaging polarized LIDAR can distinguish spherical particles and non-spherical particles by using the particle back polarization，which is used to study dust, haze, fog and other atmospheric phenomena. The imaging polarized LIDAR can instantly obtain the three-dimensional image of the target, which has many advantages such as high resolution, fast imaging speed and simple structure. Subsequently, the polarized LIDAR developed as an independent branch of the study, and a lot of excellent research results have been achieved. This paper mainly introduces the basic principle of polarization LIDAR, the realization way, the research progress at home and abroad.
It is of great importance to utilize a model to characterize the surfaces while designing an optical imaging system with freeform surfaces. For this purpose, a model with radial basis function based on surface slope (RBF-slope) for optical freeform surfaces was investigated by establishing the relationship between the shape factor and local surface slope, and improving the distributions of the basis functions for circular apertures. We performed the fitting experiment for “bumpy” paraboloids; the results demonstrated that the RBF-slope model has stronger fitting ability than conventional RBF model. A prototype of single mirror magnifier for head-worn display was designed and fabricated, in which the freeform mirror was described and characterized using the RBF-slope model. It can be proved by the design results that the RBF-slope model for optical freeform surfaces has obvious advantages in aberration balancing over conventional model. The primary experiments showed that the freeform surface was well fabricated and expected image display can be achieved.
In order to solve the problem that the conventional optical system can not be placed apart in different areas, fiber bundle imaging optical system is needed. With a flexible fiber bundle, the detection target can be imaged onto the sensor. This paper uses a fiber bundle with φ8mm, length 50mm, resolution 30lp/mm, hexagonal arrangement, and 0.3 numerical aperture as the main component. The front objective and rear magnifying optical system of the optical system are designed. It provides a complete imaging solution for fiber bundle imaging. Through the glass fitting of the designed optical system, the results show that the field of view of the system can reach 35°, the numerical aperture of the front objective is 0.29, the numerical aperture of the rear optical system is 0.3，.the modular transfer function of the front objective lens can reach 0.38 in 30 lp/mm,, and the modular transfer function of the rear magnifying optical system can reach 0.65 in 30 lp/mm,. It meets the requirements of field of view, numerical aperture matching, resolution and other parameters for fiber bundle imaging system. Furthermore, the selected glass are Chengdu Guangming's existing products, the system has high feasibility.
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.
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.
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.
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.