Polarization information is valuable for image de-scattering in turbid media. Previous polarimetric image de-scattering methods tend to employ the illumination with a fixed polarization state, while ...the effect of the polarization state of active illumination on the target is less considered. In this paper, a computational polarization differential imaging de-scattering method based on 3 × 3 Mueller matrix and active illumination modulation is proposed. We extend the influence of active illumination polarization state on the imaging quality, and we realize a comprehensive de-scattering method based on both the input (active illumination modulation when imaging) and output (polarization processing after imaging) dimensions of the system by combining the traditional polarization differential method and the active polarization illumination filtering. Theoretical analysis and experimental results demonstrate the superiority of active illumination modulation and verify that our method can significantly improve the global quality of de-scattered images. In addition, the proposed method can achieve a better performance in image detail recovery for target detection and recognition even in strong scattering media.
•An improved polarization differential imaging method for underwater imaging is proposed.•The active illumination modulation is involved for improving the imaging quality.•Our method has a better performance in detail preservation and image recovery.•Our method is effective for both highly and low polarized objects.
While sensing in high temporal resolution is necessary for a wide range of applications, it is still limited nowadays due to the camera sampling rate. In this work, we try to increase the temporal ...resolution beyond the Nyquist frequency, which is limited by the sensor's sampling rate. This work establishes a novel approach to temporal super-resolution that uses the object-reflecting properties from an active illumination source to go beyond this limit. Following theoretical derivation and the development of signal-processing-based algorithms, we demonstrate how to increase the detected temporal spectral range by a factor of six and possibly even more. Our method is supported by simulations and experiments, and we demonstrate (via application) how we use our method to dramatically improve the accuracy of object motion estimation. We share our simulation code on GitHub.
In this study, we introduce a novel hyperspectral imaging approach that leverages variable filament temperature incandescent lamps for active illumination, coupled with multi-channel image ...acquisition, and provide a comprehensive characterization of the approach. Our methodology simulates the imaging process, encompassing spectral illumination ranging from 400 to 700 nm at varying filament temperatures, multi-channel image capture, and hyperspectral image reconstruction. We present an algorithm for spectrum reconstruction, addressing the inherent challenges of this ill-posed inverse problem. Through a rigorous sensitivity analysis, we assess the impact of various acquisition parameters on the accuracy of reconstructed spectra, including noise levels, temperature steps, filament temperature range, illumination spectral uncertainties, spectral step sizes in reconstructed spectra, and the number of detected spectral channels. Our simulation results demonstrate the successful reconstruction of most spectra, with Root Mean Squared Errors (RMSE) below 5%, reaching as low as 0.1% for specific cases such as black color. Notably, illumination spectrum accuracy emerges as a critical factor influencing reconstruction quality, with flat spectra exhibiting higher accuracy than complex ones. Ultimately, our study establishes the theoretical grounds of this innovative hyperspectral approach and identifies optimal acquisition parameters, setting the stage for future practical implementations.
This work demonstrates a novel, state-of-the-art method to reconstruct colored images via the dynamic vision sensor (DVS). The DVS is an image sensor that indicates only a binary change in ...brightness, with no information about the captured wavelength (color) or intensity level. However, the reconstruction of the scene’s color could be essential for many tasks in computer vision and DVS. We present a novel method for reconstructing a full spatial resolution, colored image utilizing the DVS and an active colored light source. We analyze the DVS response and present two reconstruction algorithms: linear-based and convolutional-neural-network-based. Our two presented methods reconstruct the colored image with high quality, and they do not suffer from any spatial resolution degradation as other methods. In addition, we demonstrate the robustness of our algorithm to changes in environmental conditions, such as illumination and distance. Finally, compared with previous works, we show how we reach the state-of-the-art results. We share our code on GitHub.
This paper aims to present a novel concentrator-photovoltaic window (CPVW) for the building application, which is able to provide a uniform daylighting environment. In order to study the daylighting ...performance of the CPVW, the ray-tracing simulation model for the complex window systems are built and validated by the outdoor experimental results. The daylighting uniformity of the proposed window system is analyzed and compared with the state-of-the-art semi-transparent photovoltaic window system (STPVW). The coefficient of variation (CV) is developed to evaluate the daylighting uniformity of photovoltaic windows. It was found that with the use of the CPVW, the daylighting uniformity can be significantly enhanced, while enlarging the active daylighting area at the same time: the CV values are decreased from 0.647, 0.642, 0.606, 0.595, 0.639, 0.624, 0.764 (for the STPVW) to 0.011, 0.044, 0.054, 0.054, 0.113, 0.171, 0.220 (for the CPVW) at various incidence angles. Due to the sun rays reallocation of the concentrator, the active daylighting area can also be enlarged: the ratio of the active illumination area offered by the CPVW to that by the STPVW can be up to 6.69 × . Thus, with the use of the concentrator-photovoltaic window system on the building, not only can the solar energy utilization be greatly enhanced and does suit the building energy demands well, but also it improves the daylighting uniformity and active natural daylighting area significantly.
•A novel concentrator based multi-functional BIPV window was introduced.•The daylighting performance of the concentrator-PV window was investigated through validated ray-tracing simulation modell.•The concentrator-PV window can provide much more uniform daylighting environment.•The concentrator-PV window can illuminate as larger area as up to 6.7 times of its own size.
Highlighted depth-of-field photography Kim, Jaewon; Horstmeyer, Roarke; Kim, Ig-Jae ...
ACM transactions on graphics,
05/2011, Letnik:
30, Številka:
3
Journal Article
Recenzirano
We present a photographic method to enhance intensity differences between objects at varying distances from the focal plane. By combining a unique capture procedure with simple image processing ...techniques, the detected brightness of an object is decreased proportional to its degree of defocus. A camera-projector system casts distinct grid patterns onto a scene to generate a spatial distribution of point reflections. These point reflections relay a relative measure of defocus that is utilized in postprocessing to generate a highlighted DOF photograph. Trade-offs between three different projector-processing pairs are analyzed, and a model is developed to help describe a new intensity-dependent depth of field that is controlled by the pattern of illumination. Results are presented for a primary single snapshot design as well as a scanning method and a comparison method. As an application, automatic matting results are presented.
Spectral reflectance or transmittance measurements provide intrinsic information on the material of an object and are widely used in remote sensing, agriculture, diagnostic medicine, etc. Most ...reconstruction-based spectral reflectance or transmittance measurement methods based on broadband active illumination use narrow-band LEDs or lamps combined with specific filters as spectral encoding light sources. These light sources cannot achieve the designed spectral encoding with a high resolution and accuracy due to their low degree of freedom for adjustment, leading to inaccurate spectral measurements. To address this issue, we designed a spectral encoding simulator for active illumination. The simulator is composed of a prismatic spectral imaging system and a digital micromirror device. The spectral wavelengths and intensity are adjusted by switching the micromirrors. We used it to simulate spectral encodings according to the spectral distribution on micromirrors and solved the DMD patterns corresponding to the spectral encodings with a convex optimization algorithm. To verify the applicability of the simulator for spectral measurements based on active illumination, we used it to numerically simulate existing spectral encodings. We also numerically simulated a high-resolution Gaussian random measurement encoding for compressed sensing and measured the spectral reflectance of one vegetation type and two minerals through numerical simulations. We reconstructed the spectral transmittance of a calibrated filter through an experiment. The results show that the simulator can measure the spectral reflectance or transmittance with a high resolution and accuracy.
To overcome the dependence on sunlight of multi-spectral cameras, an active light source multi-spectral imaging system was designed and a preliminary experimental study was conducted at night without ...solar interference. The system includes an active light source and a multi-spectral camera. The active light source consists of four integrated LED (Light Emitting Diode) arrays and adjustable constant current power supplies. The red LED arrays and the near-infrared LED arrays are each driven by an independently adjustable constant current power supply. The center wavelengths of the light source are 668 nm and 840 nm, which are consistent with that of filter lens of the Rededge-M multi-spectral camera. This paper shows that the radiation intensity measured is proportional to the drive current and is inversely proportional to the radiation distance, which is in accordance with the inverse square law of light. Taking the inverse square law of light into account, a radiation attenuation model was established based on the principle of image system and spatial geometry theory. After a verification test of the radiation attenuation model, it can be concluded that the average error between the radiation intensity obtained using this model and the actual measured value using a spectrometer is less than 0.0003 w/m
. In addition, the fitting curve of the multi-spectral image grayscale digital number (DN) and reflected radiation intensity at the 668 nm (Red light) is
= -3484230
+ 721083
+ 5558, with a determination coefficient of R
= 0.998. The fitting curve with the 840 nm (near-infrared light) is
= 491469.88
+ 3204, with a determination coefficient of R
= 0.995, so the reflected radiation intensity on the plant canopy can be calculated according to the grayscale DN. Finally, the reflectance of red light and near-infrared light can be calculated, as well as the Normalized Difference Vegetation Index (NDVI) index. Based on the above model, four plants were placed at 2.85 m away from the active light source multi-spectral imaging system for testing. Meanwhile, NDVI index of each plant was measured by a Greenseeker hand-held crop sensor. The results show that the data from the two systems were linearly related and correlated with a coefficient of 0.995, indicating that the system in this article can effectively detect the vegetation NDVI index. If we want to use this technology for remote sensing in UAV, the radiation intensity attenuation and working distance of the light source are issues that need to be considered carefully.
•Reviewed the advantages of self-illuminating systems for optical tracking.•Developed a model to evaluate the performances of such systems.•Presented the results of LEDSAT orbit determination (OD) ...feasibility analysis.•Explored the potentialities of light curves analysis and data fusion.•Results show that significant improvements of OD for LEO objects are achievable.
LEDSAT is a 1U CubeSat developed by S5Lab team of Sapienza – University of Rome in collaboration with the Astronomy Department of University of Michigan. The main goal of the mission is to demonstrate that a LED-based active illumination system may be used to achieve orbit and attitude determination. LEDSAT will be placed into a Low Earth Orbit (LEO) and observed by a network of ground-based telescopes. A LED-based system may improve the accuracy in monitoring LEO spacecraft. A simple model is developed to estimate the features of an optical link between a ground station and a self-illumination system. The reliability of orbit determination and the precision of the orbit reconstruction is evaluated.
Multi-tap CMOS pixels that are composed of a single photodiode, multiple sets of a charge transfer gate and storage diode, and a draining gate can implement functional imaging. In this paper, imaging ...systems based on the multi-tap CMOS pixel are categorized into those with synchronized active illuminations and those using coded exposure. Applications for quantitative wide-field imaging based on spatial frequency domain imaging (SFDI) using structured light projection and multi-exposure laser speckle contrast blood flow imaging (MELSCI) utilizing multiple exposure times are shown. The multi-tap CMOS pixel provides additional benefits like suppression of ambient light and motion artifact with SFDI and efficient sampling at a video rate with MELSCI.
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