Research and Development of Reverse Plenoptic System: Design and Construction of Illumination Projection System platform
Date Issued
2015
Date
2015
Author(s)
Chen, Kuan-Ming
Abstract
More and more people are using smart phone to take photographs in recent years. Fill flash light is needed when there is not sufficient external lighting for illumination. However, fill exposure lights of the smart phone camera are usually designed to aim at objects located 1.5 meters in front of the lens. Since photographers are not always taking photograph at that distance, the fill light region usually exceeds the intended exposure area. This ineffective illumination wasted the fill light and resulted in shorter operating time for smart phones. In order to deal with the drawbacks mentioned above and to make sure the fill illumination light located only on the region covers the intended photograph subjects, this thesis developed a new fill illumination system. This system, called reverse plenoptic system, is based on the configuration of Plenoptic 2.0 camera except that the illumination light travels along the opposite direction. In this system, light sources are placed around the CCD/CMOS sensor. Each and every of the light sources has a micro lens mounted in front of it. Light beam goes through the micro lens and the main lens and finally illuminates on the subject. The fill illuminated range was found to match the intended photographic region. The reverse plenoptic system module was simulated by an optical simulation package CodeV first to set up the lens layout. The fill illumination was then simulated by using another simulation software LightTools. With the deviation of the light source and the main optical axis, a small view difference between the fill illuminated region and the intended photographic area was discovered. In the case of fixed focus lens simulation case, the fill illuminated range of the system light source is slightly larger than the captured range of 1/2.3” frame size. The fill illuminated range changes while the main lens zoom in or zoom out. The reverse plenoptic system analyzed in this thesis was set up by using a camera lens, a micro lens, LED and a CMOS camera. Exposure experiments were pursued to illuminate intended photographic objects located at different distance and different zoom ratio. The fill illuminated subject was captured by using CMOS camera. The effect of the fill illuminated range changes with the focusing depth were observed by using the side camera so as to separate the effect of the fill illumination and the back light noise created by placing the LED so close to the CMOS. In summary, for the reverse plenoptic system proposed in this thesis, both the simulation and the experiments were performed. With our design, the illuminated region was found to be slightly larger than the intended photographic region. However, both the simulation and the experimental results confirm the intended the results, i.e., the fill illuminated region almost matches the intended photographic region for different zoom ratio with respect to objects located at different distances in front of the photographic lens.
Subjects
Plenoptic
Light field
coaxial optic
illumination
Type
thesis
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