Multifunctional Sky Camera System for Total Sky Imaging and Spectral Radiance Measurement
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Abstract
A multifunctional sky camera system and techniques for the use thereof for total sky imaging and spectral irradiance/radiance measurement are provided. In one aspect, a sky camera system is provided. The sky camera system includes an objective lens having a field of view of greater than about 170 degrees; a spatial light modulator at an image plane of the objective lens, wherein the spatial light modulator is configured to attenuate light from objects in images captured by the objective lens; a semiconductor image sensor; and one or more relay lens configured to project the images from the spatial light modulator to the semiconductor image sensor. Techniques for use of the one or more of the sky camera systems for optical flow based cloud tracking and three-dimensional cloud analysis are also provided.
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Citations
21 Claims
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1-11. -11. (canceled)
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12. A method for cloud tracking, the method comprising the steps of:
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(a) obtaining a time-lapsed series of sky images using a sky camera system including (i) an objective lens having a field of view of greater than about 170 degrees, (ii) a spatial light modulator at an image plane of the objective lens, wherein the spatial light modulator is configured to attenuate light from objects in images captured by the objective lens, (iii) a semiconductor image sensor, and (iv) one or more relay lens configured to project the images from the spatial light modulator to the semiconductor image sensor; and (b) computing a velocity of one or more pixels in the time-lapsed series of sky images using optical flow analysis, wherein pixels in the time-lapsed series of sky images corresponding to cloud regions have a finite velocity and pixels in the time-lapsed series of sky images corresponding to non-cloud regions have a zero velocity. - View Dependent Claims (13, 14, 15)
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16-18. -18. (canceled)
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19. A method for three-dimensional cloud tracking, the method comprising the steps of:
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(a) obtaining sky images from each of at least one first sky camera system and at least one second sky camera system, wherein the first sky camera system and the second sky camera system each includes (i) an objective lens having a field of view of greater than about 170 degrees, (ii) a spatial light modulator at an image plane of the objective lens, wherein the spatial light modulator is configured to attenuate light from objects in an image captured by the objective lens, (iii) a semiconductor image sensor, and (iv) one or more relay lens configured to project the image from the spatial light modulator to the semiconductor image sensor, and wherein the first sky camera system and the second sky camera system are located at a distance of from about 100 meters to about 1,000 meters from one another; (b) measuring a position of clouds in the images based on x,y,z axes coordinates of each of the first sky camera system and the second sky camera system; (c) measuring an x′
,y′
,z′
orientation of each of the first sky camera system and the second sky camera system with respect to zenith and north as references;(d) determining an orientation of the clouds with respect to the zenith and north using the position of the clouds in the images measured in step (b) and the orientation of each of the first sky camera system and the second sky camera system with respect to the zenith and north determined in step (c); and (e) calculating a position and a vertical height of the clouds in the sky using triangulation based on the orientation of the clouds with respect to the zenith and north from step (d) and three-dimensional coordinates of the first sky camera system and the second sky camera system. - View Dependent Claims (20, 21)
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Specification