Wyniki wyszukiwania - BazTech

1

A study of distortion correction algorithms based on aspheric fisheye lens design

Li Dan, Zhang Baolong, Zhu Jiawei, Wang Qi, Zhu Zhenwei

Optica Applicata

|

2020

|

Vol. 50, nr 4

579--592

EN

A design method of aspheric fisheye lens has been proposed in this paper, based on the requirements of automobile surround view system. The study has designed a kind of ultra-wide-angle fisheye lens, which only consists of a spherical glass lens and three aspherical plastic lenses. The maximum diameter of imaging aperture is 15. 3 mm; the working distance behind is 2.158 mm; the total length of system is 11.44 mm; the focal length is 0.97 mm; the viewing angle is 210°, and the modulation transfer function (MTF) curve is 0.35 at 60 lp/mm. Furthermore, a kind of a distortion correction algorithm for fisheye lens has been created, which calculates the position of the ideal image point with the actual image point and the obtained distortion curve and distortion model. The algorithm can correct the distorted image taken by a fisheye lens to an image without distortion, which is suitable for the human eye. The algorithm, which is simple and effective, has been applied to the automobile surround view system. It has been verified to be accurate and reasonable, after the comparison is made between the real image taken by a fisheye lens and the corrected image.

2

Wide-angle vision for road views

Huang F., Fehrs K. K., Hartmann G., Klette R.

Opto-Electronics Review

|

2013

|

Vol. 21, No. 1

1-22

EN

The field-of-view of a wide-angle image is greater than (say) 90 degrees, and so contains more information than available in a standard image. A wide field-of-view is more advantageous than standard input for understanding the geometry of 3D scenes, and for estimating the poses of panoramic sensors within such scenes. Thus, wide-angle imaging sensors and methodologies are commonly used in various road-safety, street surveillance, street virtual touring, or street 3D modelling applications. The paper reviews related wide-angle vision technologies by focusing on mathematical issues rather than on hardware.

3

Zastosowanie zdjęć hemisferycznych w badaniach ekosystemów leśnych

Strzeliński P.

Roczniki Geomatyki

|

2006

|

T. 4, z. 4

93-112

EN

The main aim of the study is to discuss basic assumptions of taking hemispherical photographs in the context of their practical use in forest inventory. The work encompasses methodology of taking digital hemispherical photographs. Hemispherical photographs are most often taken for research on ecological conditions of plants. Usually the aim of such research is to obtain information on the amount of light which reaches selected height above the ground. It is important to observe a few rules in taking photographs (overcast, camera leveling, sensitivity, shutter speed, maximum resolution). The best equipment for this purpose is a digital reflex camera and fish-eye lens with the angle 180°. Another solution is a digital reflex camera smaller than 35 mm with suitable converter which together with lens will allow to obtain circular photo with retained angle of 180°. Gap Light Analyzer and WinSCANOPY are the most frequently used software packages for analysis of hemispherical photos. The following elements are expected to be determined as a result of analyses based on hemispherical photographs: absolute amount of light registered at measurement levels, crown density structure, spatial variability of stand foliage, leaf area index, general description of crowns (crowns deformation, viability of lateral shoots) the condition of assimilatory organs (number of annuals, crown light and decrement of assimilatory organs, distortion and discoloration of assimilatory organs) relationship between tree density and natural regeneration The following attempts will be undertaken with the use of hemispherical photos: to estimate biomass of assimilatory organs, to estimate density of photons flow in the process of photosynthesis under canopies and in gaps of stand, to register the infrared scope of radiation (in order to examine assimilation organs in stands), to prepare a photomap of canopies. The study encompasses a brief review of literature, a list of possible devices with basic software.