Range measurement by a digital camera using flash

Naoya Ogawa; Kazunori Umeda

doi:10.1117/12.647730

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6 December 2005 Range measurement by a digital camera using flash

Naoya Ogawa, Kazunori Umeda

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Proceedings Volume 6051, Optomechatronic Machine Vision; 605108 (2005) https://doi.org/10.1117/12.647730
Event: Optomechatronic Technologies 2005, 2005, Sapporo, Japan

Abstract

Various methods have been proposed until now for range measurement or three dimensional shape reconstruction. However, most of them need a large-scale equipment or a special environment. This paper proposes a technique which obtains a range image easily under a general environment using only an off-the-shelf digital camera. Distance is calculated by obtaining the irradiance of scene lighted by the flash of a digital camera using the fact that the intensity of reflected light of the flash is inversely proportional to the square of the distance from the object. The irradiance is obtained by subtracting an image without the flash from an image with the flash. The image without the flash is used to obtain the reflectance ratio at each pixel. The intensity of reflected light of the flash is affected by the inclination of the object surface. A method to estimate the inclination at each pixel is proposed which uses the change of the irradiance in adjacent pixels. The inclination is formulated as the function of the rate of change, and thus the inclination can be calculated by the rate which is easily obtained from the image. Additionally, color information is simultaneously obtained because visible light is used. Assumptions in the method are that the object surface has no specular reflection and the flash is set at the same position as the center of the lens. Experiments show that a range image is roughly obtained by the proposed method, and furthermore, that proper distance is obtained for inclined surfaces.

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Naoya Ogawa and Kazunori Umeda "Range measurement by a digital camera using flash", Proc. SPIE 6051, Optomechatronic Machine Vision, 605108 (6 December 2005); https://doi.org/10.1117/12.647730

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