We describe the process of preparing an experimental study of a coded aperture in the visible spectral range. In the experiments, shadowgrams are supposed to be recorded with a conventional imaging sensor. A feature of the work is a proposed coded aperture implementation method based on surface evaporation by laser ablation. As a coded aperture base material, a glass substrate with a titanium film 500-nm thick deposited on it is used. To characterize and validate the fabricated coded apertures, a dual-metric method based on image processing techniques was developed. The method was used to optimize laser parameters, including the pulse power, the spot moving speed, and the pulse repetition rate. The coded aperture implemented with the parameter values determined was then used as the imaging device in the experimental stand and proved to form a high-contrast image. The double metric method allows one to optimize other laser parameters, along with the studied ones, for the given experimental conditions.
Different spatial alignment techniques for multimodal image fusion are presented in the paper. Main feature-based spatial alignment steps and operations as well as cross-correlation techniques are described. An experiment was carried out to compare spatial alignment methods. Experiment results are presented and conclusions are made. The text gives information about spatial alignment application for multimodal systems calibration.
KEYWORDS: Video, Cameras, Signal to noise ratio, Photodetectors, Interference (communication), Sensors, Power supplies, Temperature metrology, Light sources and illumination, Visualization
Digital video cameras are the main component of both visual and measuring optoelectronic devices. The parameters and characteristics of video cameras can be varied significantly for each instance. Since the characteristics of a video camera mostly determine the characteristics of the entire device, it is important to monitor them. This will ensure the stability of the characteristics of video cameras, and consequently, image stability and improvement of measurement accuracy in the case of using video cameras in optical-electronic measuring devices. This paper presents an experimental test bench designed to study the parameters of serial video cameras based on CMOS matrix photodetectors. Method are proposed for determining such camera parameters as irregularity of photosensitivity around the site, as well as change in the signal-to-noise ratio with variations in the level of exposure, exposure time and amplifier coefficient.
This work discusses coded aperture functioning in the visible spectral range. A MURA coded aperture was implemented using laser ablation by evaporation of titanium film from a transparent substrate. The optimal laser parameters to make a high-contrast aperture are shown. The paper also present an algorithm based on periodic correlation which has been developed for image reconstruction. Experiments were carried out with the aperture of rank 37 with a minimal element of 130 μm. The images obtained during the experiment demonstrate the effectiveness of the proposed aperture implementation method and the developed image processing algorithm.
A high-energy radiation imaging system is presented which is based on the scintillation method. To detect and visualize high-energy radiation, a SiPM array is used together with a CsI(Tl) scintillation crystal. At the current stage of development, gamma or X-ray sources are not used to verify the operation of the system and initiate scintillation. Instead of them, vacuum ultraviolet (VUV) radiation is used. The possibility of using a VUV lamp as a source of high-energy radiation has been proven computationally and experimentally. This allows eliminating the use of sources of gamma or X-ray radiation and special protective equipment at the initial stage of development. A coded aperture is used as an imaging device. It is made by laser evaporation of titanium sputtering from the surface of a transparent substrate. The results of this study show methods and materials which allow investigating the high-energy radiation imaging system at the initial stage without using sources of hazardous radiation.
In this work it is shown that high-intensity microprismatic tapes have a potential to be used as a good substrate for bright and cheap fiducial marks in machine vision metrology applications. The drawback of the tapes is that they have technological netting pattern distributed across the surface. The proposed image processing technique allows good suppression of the parasitic technological netting pattern by a harmonic mean image filtering followed by circle shape recovering based on Fourier descriptors. It was also shown that the combination can provide good results in mark position estimations. In experiments it was shown that subpixel accuracy of position estimation can be achieved after applying proposed image processing, while without filtering the error can exceed 4 pixels in some cases.
In this paper we show, how different optical elements affect the polarization state. We show it on the examples of elementary optical elements, such as refracting and reflecting surfaces and an anisotropic waveplate, and more complex elements: a plane-parallel plate, a Dove prism, a spherical lens, an image sensor. The method of considering the calculated influence on the example of Stokes polarimetry is also shown.
The paper is about field and special methods of radiation terrain mapping with the identification of their distinctive features, advantages and disadvantages of each of them. The applicability of methods in various situations of radiation contamination is shown. An analysis of sources of radioactive radiation and of the situation of radiation contamination in Russia has been carried out. Different detectors of ionizing radiation are compared. It is proved that SiPM combines high performance and operational characteristics most effectively, making it possible to use it in a gamma spectrometer for any type of radiation mapping.
3D position estimation of an object usually involve computer vision techniques, which require fiducial markers attached to the objects surface. Modern technology provides a high intensity retroreflective material in the form of a tape which is easy to mount to the object and can be used as a base for fiducial marks. But inevitable drawback of the tapes with the highest retroreflective intensity is the presence of technological pattern which affects spatial distribution of retroreflected light and deforms border of any print on tape's surface. In this work we compare various shapes of metrological pattern and examine Fourier descriptors based image processing to obtain estimation of accuracy of mark image position. To verify results we developed a setup consisting of a camera based on Sony ICX274 CCD, 25 mm lens, 800 nm LED lightning and high intensity microprismatic tape. The experiment showed that there is no significant difference between proposed mark shapes as well as between direct and indirect contrast when proposed image processing is used. The experiments confirmed that the image processing implemented without elimination of non-reflective netting pattern can only provide an accuracy of coordinates extraction close to 1 pix.
The paper deals with influence of orientation of matrix detector relative to incident light on its sensitivity area from the viewpoint of polarization. The calculation algorithm based on Jones matrix formalism is presented. The results obtained with calculations and experiment with Stokes polarimeter are shown.
The research of changes of the parameters for the polarized radiation output anisotropic linear phase-shifting elements, with their minor collimation turns about the source of spatial orientation in the optical scheme of measuring polarization device, is performed. Comparative analysis of the polarization and energy parameters of the radiation output retards of crystalline silica, magnesium fluoride, and polyvinyl alcohol are accomplished. The dependencies of changes of the ellipticity and azimuth of the output radiation, as well as the transmission coefficient of the phase plate with the changing spatial orientation from the hade on refracting side and azimuth of linearly polarized radiation at its input are considered.
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