Glare Spots Research Articles

GR-GAN: A unified adversarial framework for single image glare removal and denoising

In this paper, we introduce the single image glare removal (SIGR) task. SIGR aims to eliminate glare or light caused by external environment in lighting scene. To efficiently improve natural image quality and usability, many research tasks, such as image deraining and shadow removal, have been investigated a lot. However, SIGR is still underexplored. Therefore, we propose to construct a dataset and explore deep learning-based models for SIGR. Our contributions can be summarized as follows: (1) We establish a new benchmark dataset for SIGR, termed De-Glare, aiming to propel research of SIGR. This dataset comprises pairs of {glare, glare-free} images sourced from both real-world and synthetic data, utilized for training and evaluating models. (2) We conduct a comprehensive benchmarking of extensive state-of-the-art (SoTA) methods on the constructed De-Glare dataset and provide insightful analyses based on the results. (3) An innovative approach for single image glare removal employing a multi-scale generative adversarial network (GR-GAN) model is proposed. Glare images typically exhibit irregular glare shapes and cluttered backgrounds. To address these irregular glare patterns, we introduce a deformable convolution-based glare attention detector (GAD) designed to generate an attention map which specifics glare spots or rays in the input image. In pursuit of enhancing the perceptual quality of output image, GR-GAN adaptively filters out irrelevant noises and enhances salient features through a generator with cascaded pyramid neck (CPN) network. This work can provide useful insights for developing better SIGR models. Without specific tuning, our method achieves the SoTA results on multiple computer vision tasks, including the image deraining and image shadow removal.

РОЗРОБКА МОДИФІКОВАНОЇ МОДЕЛІ ШЛІКА ДЛЯ ВИЗНАЧЕННЯ СПЕКУЛЯРНОЇ СКЛАДОВОЇ КОЛЬОРУ

The most common bidirectional reflectance distribution functions (BRDF), among which the Schlick function is included, were analyzed. Compared to Blinn and Phong's BRDF, this function has a smaller degree, which makes it possible to use it in dynamic computer graphics tools. The Schlick function uses the specularity coefficient of the surface and the cosine of the angle between the vector normal to the surface and the median vector for calculation. The disadvantage of the function is the unrealistic reproduction of glare in the attenuation zone. In order to realistically reproduce both the glare epicenter and its blooming, a new modification of the Schlick function using correction coefficients and exponents is proposed. A program for selecting powers and coefficients has been developed. A diagram of the program with a detailed description is given. Mathcad 2001 Professional tools were used to perform a comparative analysis of the Schlick, Blinn BRDFs and modified function. The advantage of the modified function compared to Schlick's BRDF in the fall speed in the attenuation zone is proved. A smaller value of the relative error of approximation of the modified Schlick BRDF at the level of the glare epicenter was proven. Graphs of the dependences of the maximum relative and absolute approximation errors of the modified Schlick's BRDF compared to Blinn's BRDF depending on the specularity coefficient of the surface are plotted. An argument was found in which the modified BRDF reaches the sludge level. The monotonic decrease of the proposed BRDF on the interval of arguments [0, ] is proven. The intervals for calculating the specular color component were calculated for the proposed BRDF, Schlick and Blinn BRDFs. The limit values of the intervals were used when finding the ratio of the size of the glare spots for the modified BRDF and Blinn BRDF, Schlick and Blinn BRDFs. Spot size ratios for BRDFs are illustrated by three-dimensional graphs. It was proven that the blooming zone for the modified BRDF is calculated on a shorter interval than for Schlick's BRDF. The modified BRDF can be used in high-performance rendering systems and provides increased realism in the formation of reflections compared to Schlick's BRDF.

Rainbows in the grass I External-reflection rainbows from pendant droplets

In the mid-morning on a sunny day one can sometimes see glare spots associated with uncolored "rainbow" (i.e., fold) caustics due to the sunlight reflected from the surface of dew or guttation drops. We show that these dewdrop reflection rainbows are due to places on the droplet (i.e., from an "inflection circle") where its Gaussian curvature becomes zero. We work out the theory of such caustics with horizontally incident light and present a comparison of the theory to measurements made in the laboratory.

Rainbows in the grass II Arbitrary diagonal incidence

We consider external reflection rainbow caustics due to the reflection of light from a pendant droplet where the light rays are at an arbitrary angle with respect to the horizontal. We compare this theory to observation of glare spots from pendant drops on grass; we also consider the potential application of this theory to the determination of liquid surface tension.

Numerical study of glare spot phase Doppler anemometry

The phase Doppler anemometry has (PDA) been developed to measure simultaneously the velocity and the size of droplets. When the concentration of particles is high, tightly focused beams must be used, as in the dual burst PDA. The latter permits an access to the refractive index of the particle, but the effect of wave front curvature of the incident beams becomes evident. In this paper, we introduce a glare spot phase Doppler anemometry which uses two large beams. The images of the particle formed by the reflected and refracted light, known as glare spots, are separated in space. When a particle passes through the probe volume, the two parts in a signal obtained by a detector in forward direction are then separated in time. If two detectors are used the phase differences and the intensity ratios between two signals, the distance between the reflected and refracted spots can be obtained. These measured values provide information about the particle diameter and its refractive index, as well as its two velocity components. This paper is devoted to the numerical study of such a configuration with two theoretical models: geometrical optics and rigorous electromagnetism solution.

Development of a Method for the Measurement of Particle Size and Velocity based on Projection onto a Variable Frequency Grating

AbstractIrregular particles down to approximately 3.8 μm have been sized by imaging them onto a variable frequency grating using laser illumination. Velocity can also be determined. The method was successful for certain particle types that were rough or irregular, partly absorbing or translucent. It was not successful for transparent spheres that display glare spots in the image, or other particles that produce localised regions of high brightness.

Aerosol particle microphotography and glare-spot absorption spectroscopy

The relative intensities of glare spots in the image of an electrodynamically trapped aerosol droplet are measured experimentally with an aerosol particle microscope and calculated theoretically. The theoretical calculations are in good agreement with these experiments and indicate that the intensities of these spots are extremely sensitive to the imaginary part of the refractive index. Experimentally, we obtain the molecular absorption spectrum of an impurity within a droplet by recording the spectrum of an individual glare spot produced by broadband illumination.

Non-Debye enhancements in the Mie scattering of light from a single water droplet

The glare spots usually seen on a single water droplet which has been illuminated by a plane wave are produced by geometrical rays which correspond to the different terms of the Debye series expansion of the Mie scattered field. Recently other glare spot enhancements have been predicted which correspond to scattering resonances coupling to the orbiting rays associated with high-order geometrical rainbows. We observed the non-Debye enhancement of the eleventh-order rainbow glare spot at an observation angle of 90 degrees on a 3.5-mm water droplet illuminated by polarized He-Ne laser light.

Theory of the observations made of high-order rainbows from a single water droplet

Over a dozen rainbows have been observed in a single water droplet. They appear as glare spots on the water droplet which take on coloration at the appropriate rainbow angles. The appearance of rainbows as colored glare spots in this situation is understood in terms of the caustics created in the vicinity of the droplet by the refracting light rays. The angular positions of the glare spots are understood in terms of the Fourier transform of the geometric scattering amplitude. The rainbow glare spots are also found to appear numerically in the Fourier transform of the Mie scattered fields. An additional glare spot produced by rays at grazing incidence and not attributable to geometric optics also appears numerically in the Fourier transformed Mie fields.

PRINCIPLES OF THE USE OF NON-REFLECTING FILMS IN OPTICAL INSTRUMENTS*

WHEN light from an object passes through an optical system to form an image, a small fraction is reflected at each air-glass surface instead of being transmitted. For normal incidence, the reflectivity is usually between 4 and 7 per cent, depending on the refractive index of the glass. This affects the image in three ways. First, the brightness of the image is reduced. Secondly, the reflected light, eventually reaching the image plane after two or more reflexions at the lens surfaces, invades the dark parts of the image and gives rise to a haze called ‘veiling glare’. This reduces the contrast in the image. Thirdly, the reflected light may concentrate near the imago plane to form ‘glare spots’ and ‘ghost images’.