Reflection Characteristics Of Objects Research Articles

Image-Based Measurement of Structural Color using Spectral Camera

We perceive structural colors by optical phenomena such as light interference and diffraction caused by a fine structure of the object surface. One of the characteristics of structural colors is that a wavelength distribution of light changes depending on an incident angle of a light source and a viewing angle. Generally, for color evaluation and reproduction, it is required to acquire reflection characteristics of objects. Therefore, BRDF (Bidirectional Reflectance Distribution Function) is often used as a function that represents reflection characteristics depending on incident and viewing angles. In this study, we measured BRDF of structural colors based on a method to acquire image-based material reflection characteristics using a spectral camera. The measurement was performed by aligning an optical axis of a spectral camera with a structural color sample and changing an irradiation angle of a light source. Reflection characteristics were represented by using a radiance factor, which was a ratio between a spectral radiance of white material and that of structural color. From measurement results, we confirmed an angle-dependent radiance factor. Finally, based on a measured spectral radiance of a structural color sample, we spectrally reproduced the structural color using a spectral projector based on model fitting of spectral data.

Automatic Compensation for Defects of Laser Reflective Patterns in Optics-Based Auto-Focusing Microscopes

Since the optomechatronic system is characterized by a high energy density and high response speed, system performance can be substantially improved by integrating optical components with electromechanical systems. For micro-processing, conventional machining has been commonly replaced with laser processing. Auto-focusing plays a crucial role in processing, so developing an autofocus (AF) system with high precision and speed is vital. AF modules integrated with the knife edge method typically use a reflective semicircular laser image to calculate the defocus distance for the optical instrument and evaluate the accuracy. On the stage of an optical instrument, a reflective image is typically not a standard semicircular segment because of the different reflection characteristics of objects or the positioning error of the devices. In this study, a novel method is proposed to automatically compensate for these defects and errors. In addition to the compensation part, the improved adaptive anisotropic diffusion filter and wavelet-based edge detection are both proposed for pattern smoothing and enhancement, and pattern edge detection. For reflective patterns obtained using an image sensor in an optics-based AF module, the proposed method, compared with six state-of-the-art approaches in terms of several metrics, such as compensation accuracy, sensitivity, specificity, Dice coefficient, mean absolute distance, Hausdorff distance, and speed / computation time, enables and facilitates accurately reconstructing the complete semicircular segment. Experimental results show that the proposed method yields more satisfactory, stable and accurate results in comparison with six other approaches in performance analysis and statistical evaluation.

A method of comparing the effective scattering area of small objects with a coherent form of reflection in a converging beam of laser radiation

The basic ideas of a method of comparing the effective scattering areas of reflectors in the form of segments of specular spherical surfaces and retroreflectors, used as standard and working measures when measuring the reflection characteristics of objects when using active lidar, are developed. The systematic errors of the method are analyzed and recommendations are made on methods of reducing them.

A method of comparing the effective dispersion area of specular reflectors in a parallel beam of probe radiation

The fundamental assumptions of a method of comparison of the effective dispersion area of specular reflectors in the form of spherical mirror surfaces used in measurements of the reflection characteristics of objects in the case of active laser sensing conditions. An analysis of the systematic errors of the method is carried out and recommendations for decreasing this error are developed.

Remote sensing from space—present and future applications in forestry, nature conservation and landscape management

Past studies have suggested that sound knowledge about the reflectance characteristics of objects could be of great value in understanding the physical, chemical, and the spatial properties of features on our planet. These characteristics can be assessed remotely, and the available techniques hold considerable promise for the inventory and monitoring of natural resources. However, a significant lack of information concerning the full potential of this recent technology has resulted in an inadequate appreciation of the many possible applications in various domains. This paper presents the current situation regarding the development of satellite remote sensing technology within the fields of forestry, nature conservation, and landscape management in terms of resource assessment and monitoring. Future applications are reported on by having a closer look at the new generation of sensor systems and satellites, since methods currently used for environmental monitoring and resource survey appear to be fairly inappropriate or even inadequate in some cases. Forestry and associated environmental applications are reviewed in more detail with focus on projects being carried out in the southern part of Africa. Satellite remote sensing as a powerful and suitable tool for mapping purposes, forest mensuration and inventory, and forest disease and stress assessment is discussed. In addition, issues such as fire management, the assessment of soil erosion, the mapping of land cover, as well as wildlife habitat evaluation are raised.

Detecting and analyzing the body reflection characteristics of objects

We investigate the intrinsic color characteristics used in accomplishing color constancy. The surface reflectance of an object can be divided into two parts: interface reflectance and body reflectance. The body component is the physical basis for determining the surface color characteristics of objects, but it is influenced by geometrical factors in measurement. To eliminate the effect of illumination and geometrical factors we adopt the normalized deviation reflectance, which was suggested by Tominaga, to describe the body reflection characteristics. Then, according to a finite-dimensional linear model, the body reflection characteristics are expressed in terms of weighting coefficients of the constrained basis functions, so as to reduce its dimensionality and make it easy to use in color classification. We choose objects made of inhomogeneous dielectric material as samples and use a grating spectrometer to measure their surface spectral reflectance, from which the description of intrinsic color characteristics can be derived based on normalized deviation reflectance and a finite-dimensional linear model. The experimental results show that this description is very stable under different conditions and also compact, so that it can serve well for color classification.