Proc. SPIE. 9142, Selected Papers from Conferences of the Photoelectronic Technology Committee of the Chinese Society of Astronautics: Optical Imaging, Remote Sensing, and Laser-Matter Interaction 2013
Since full-polarization parameter measurement can not be well combined with hyperspectral imaging technology yet , a new full-polarization hyperspectral imaging measurement structure using a dual optical path system was investigated. We utilized the hyperspectral<sup>1</sup> interference imaging technology and polarization modulation technology based on electro-optic effect in our research. The polarization information, spectral information and spatial image information were acquired at the same time, which means the simultaneous measurement of hyperspectral information and full-polarization parameter was achieved. In this artical, the principle of the full-polarization parameter measurement was introduced at first. Then the experiment setup was shown and the optical elements were illustrated. Also,the detailed formula derivation steps of the full-Stokes vector was given. At last, some computer simulation data and experimental results were given. Through the combination of spectral imaging and full-polarization parameter measurement, the detecting information of the object is greatly enriched. This work will definitely be helpful to many optical remote sensing technology areas such as resources survey, environmental monitoring and military reconnaissan.
The fusion of infrared and visible light images can effectively improve the ability of detail description and hot taget representation. For this purpose, a novel image fusion algorithm based on nonsubsampled shearlet transform (NSST) was presented in this paper. Firstly, the NSST was adopted to decompose the two source images at different scales and directions, and the low-frequency and high-frequency sub-band coefficients of the images were obtained. Secondly, we used a modified fusion rules. For the low-frequency coefficients of the fused image, we summed up the low-frequency coefficients of two source images, and then subtracted the average of the mean values of the two low-frequency coefficients. Meanwhile, considering that adjacent pixels had strong correlation, an improved selection principle based on the local energy matching was developed for the high-frequency coefficients of the fused image, which was also consistent with the characteristics of the human vision system. Finally, the fused image was reconstructed by performing the inverse NSST on the combined coefficients. Experimental results demonstrate that the proposed algorithm can effectively integrate important information from infrared and visible light images. And comparing with some other image fusion algorithms, the proposed algorithm can further enhance the contrast of fused images and protect more detail information of source images. Both visual quality and objective evaluation criteria show that the method has a higher performance.
Due to the low contrast ,lack of details and difficulties to distinguish target from background in traditional infrared(IR) imaging systems, the detection and recognition probability of camouflage infrared target is relatively low. Compared with the traditional IR imaging systems, the method of polarimetric imaging uses polarization information, which can help detect and isolate manmade objects from the natural environment in complex. The method of infrared polarimetric imaging is proposed in this paper. The experiment builds the IR polarimetric imaging system. An IR polarizer made of BaF2 is assembled before the IR camera. By rotating the IR polarizer, twelve polarization images are obtained at every thirty degree. The gray levels of the images are calculated by program. Stokes polarization vector representation is introduced to calculate I of stokes vector and degree of linear polarization (DoLP) with polarization images. According to the character of parameter I of stokes vector and DoLP, we propose an IR polarization fusion method based on Shearlets using regional saliency analysis. This method can highlight the target area and have good performance in the fusion of IR radiation information and IR polarization characteristics. To test the effectiveness of this method, we use mid-wave infrared (MWIR) camera and long-wave infrared(LWIR) camera to get real images. Compared with original image, both the subjective and objective evaluation results indicate that the enhanced images obtained by our method have much more image details and polarization information, which is useful for target detection and recognition.
Two layers of buried optical waveguides are manufactured in silicate glass substrate. Using ion-exchange process, this procedure is composed of two successive cycles of buried waveguide fabrication. Characterizations of these waveguides show that the two layers have similar dimensions for both waveguide core and for mode field, and thus similar optical properties. Loss analysis indicates that coupling loss of top and bottom layer waveguide with single-mode-fiber being 0.80 dB/facet and 0.75 dB/facet, respectively.
Due to the Joule heating effect induced by the use of an assisting electric field, glass wafer temperature is experimentally found to increase synchronically with the flow of current during the process of field-assisted ion diffusion. A theoretical analysis demonstrates that the amplitude of the glass wafer temperature increase is dictated by competition between two factors, heat generation and heat dissipation. Heat generation and heat dissipation both become stronger as the glass wafer temperature increases. Studies have shown that the Joule heating effect can influence the waveguide manufacturing process profoundly, including aspects such as the stability of ion diffusion, theoretical modeling of the ion-diffusion process, and waveguide depth uniformity over the glass wafer.
We propose a design of a Mueller-matrix-microscopic system that can efficiently capture the parameter image with two liquid-crystal modulators (LCMs). The usage of the LCMs can significantly reduce the measurement time for Mueller-matrix parameters. This system employs one LCM to realize real-time measurement of all subimages derived from the Stokes vector and the other one to change the light sources. Seven experimental results, acquired by using incident light with LCM-modulated light sources, are enough for biological research. An error analysis for m44 of the Mueller matrix is involved in order to present the error evaluation. The corresponding error evaluation shows that the measurement errors could be controlled under 0.07 deg.
In this paper an Optical Circular-Polarization Modulator (CPM) based Liquid Crystal (LC) is presented. Using the electric birefringence of LC material, the device can output polarized light with two circular-polarization states. Detailed illumination of the device's structure
and its testing investigation are also presented.
The planar waveguide optical couplers are of prime importance in optical communication and optical signal processing system. Comparing with the optical fiber coupler (OFC) which fabricated by fused biconical taper technology, the planar waveguide couplers are more compact size, lower loss, better uniformity, easier manufacture and integration. Multimode interference (MMI) couplers have many advantages, such as compact size, wavelength and polarization insensitivity, fabrication tolerances and low loss, etc., which concentrate more and more attention.
Conventional MMI devices are based on the uniform index waveguides. When the number of input/output waveguides becomes larger, the intrinsic propagation constant error, which will cause bad uniformity of output power, can’t be neglected. In fact, most waveguide devices are graded-index. With the enhanced compatibility of MMI coupler, the performance can be improved at the same time. Prior study shows that graded-index MMI couplers reach the best performance under certain index contrast. Among many available materials, glass is chosen to be the substrate of the coupler, because of its good features, such as low loss, ease fabrication, cheap cost, and so on. In this paper, an 8×8 MMI optical coupler is designed based on the principle of graded-index MMI. The coupler is composed of a waveguide, which is designed to support a large number of modes, and several access (usually single-mode) waveguides, which are used to launch light into and recover light from that multimode waveguide. The total length of the device is less than 3.5 centimeter, including S-bends which lead the multiple images to the output of the device with the spacing D=250μm to make the device fiber compatible.
In this paper, we describe an experimental realization of the 8×8 graded-index MMI optical coupler and the measurement of its performance with the testing laser of the wavelength of 1.55μm. The device is fabricated by ion-exchange on BK7 glass substrate. During the ion-exchange process, a melting mixture of AgNO<sub>3</sub> : (KNO<sub>3</sub> : NaNO<sub>3</sub>) (molar ratio, 0.001:1) is used at 350~380°C for different times (range from 8 to 18 hours) to fabricate the coupler. The experimental results show that the performance of the optical coupler is quite promising. For instance, while launching light from No.5 waveguide, the uniformity of the device is approximately 0.72dB. Optimization of design and fabrication is going on to improve the total performance of the optical coupler.
Single mode tapered waveguide (spot-size converter) can transmit the optical field with low loss. The less loss is very important for highly integrating optic devices. For the integrating optic device use the weak waveguide in order to keep the small ellipse field, like 2-3um. But standard single mode fiber has a large diameter like 9-11um, and a round field. If we want to get the effective coupling, the spot-size converter must be used.
These kinds of spot-size converter waveguide are designed so that the effective values of the normalized frequency are nearly the same everywhere and the shape of the mode field is basically kept Gauss. Then it can get the low loss coupling between the integrated waveguide and fiber with Gauss field. In this paper, an optimal method was used to find the lateral of the spot-size converter after give both the end size. It must point out that this paper's conclusion is just the theoretical computation conclusion.
In general, the BPM method can be used to design the low loss tapered waveguide. In this paper, under the background of FD-BPM method, the neural network' nonlinear property was used to find the optimal low loss boundary of the taper waveguide through the net learning.
This paper describes a process of design a waveguide spot-size converter lateral side. After the process, the spot-size converter waveguide can get low radiation loss and coupling in highly effect. And the paper also presents a method for finding the optimal boundary of the SSCs.