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8 March 2014 Improvement of image quality by polarization mixing
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Proceedings Volume 8992, Photonic Instrumentation Engineering; 89920U (2014)
Event: SPIE OPTO, 2014, San Francisco, California, United States
Information about the polarization of light is valuable because it contains information about the light source illuminating an object, the illumination angle, and the object material. However, polarization information strongly depends on the direction of the light source, and it is difficult to use a polarization image with various recognition algorithms outdoors because the angle of the sun varies. We propose an image enhancement method for utilizing polarization information in many such situations where the light source is not fixed. We take two approaches to overcome this problem. First, we compute an image that is the combination of a polarization image and the corresponding brightness image. Because of the angle of the light source, the polarization contains no information about some scenes. Therefore, it is difficult to use only polarization information in any scene for applications such as object detection. However, if we use a combination of a polarization image and a brightness image, the brightness image can complement the lack of scene information. The second approach is finding features that depend less on the direction of the light source. We propose a method for extracting scene features based on a calculation of the reflection model including polarization effects. A polarization camera that has micro-polarizers on each pixel of the image sensor was built and used for capturing images. We discuss examples that demonstrate the improved visibility of objects by applying our proposed method to, e.g., the visibility of lane markers on wet roads.
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Ryosuke Kasahara, Izumi Itoh, and Hideaki Hirai "Improvement of image quality by polarization mixing", Proc. SPIE 8992, Photonic Instrumentation Engineering, 89920U (8 March 2014);


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