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US 2003/0197867 A1Published application
Video camera-based visibility measurement system
AssigneeRegents of the University of Minnesota
InventorTaek Mu Kwon
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AssigneeRegents of the University of Minnesota
InventorTaek Mu Kwon
Estimating the term…
A visibility measurement system that computes relative visibility by comparing an images of an environment against a benchmark image. A sensing device receives an image and a digital conversion system maps the image into a two-dimensional data array. A processor converts the digital data to a value that represents visibility by identifying a region in the image that has a uniform distance from the sensing device over time, computing a benchmark visibility index for the region as a summation of measurable visual characteristics that influence visibility in the region under a benchmark environmental condition, computing a second visibility index for a second environmental condition, and computing a relative visibility value as the ration of the second visibility index in relation to the benchmark visibility index.
A visibility measurement system comprising an image sensing device for sensing at least a first and a second image of an environment, the visibility meansurement system comprising a digital conversion system that maps the image of the environment into a two-dimensional data array, and a processor that computes a benchmark visibility index as a summation of measurable visual characteristics that influence visibility under a benchmark environmental condition, computes a second visibility index for a second environmental condition, and computes a relative visibility value as the ratio of the second visibility index to the benchmark visibility index.
A method for computing visibility comprising:
A relative visibility measurement system comprising:
A relative visibility measurement system comprising:
A relative visibility measurement system comprising:
A relative visibility measurement system comprising:
A system for measuring relative visibility, comprising:
Dependencies are inferred from the claim text.
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Systems in which incident light is modified in accordance with the properties of the material investigated: transmissivity
Within a flowing fluid, e.g. smoke: for determining atmospheric attenuation and visibility
Investigating or analysing materials by determining their chemical or physical properties
Term end not estimated
A. Field of the Invention
The present invention pertains generally to automated methods of measuring atmospheric visibility and, more particularly, to a video camera-based system for measuring atmospheric visibility.
B. Description of the Background
FIG. 1 is a schematic illustration of one implementation of the present invention.
FIGS. 2-5 illustrate daylight targets that can be used with the present invention.
FIG. 6 is a front view of a night target that can be used with the present invention.
Visibility may be measured using a video camera and a computer system. A series of targets may be used to measure visibility directly. Alternatively, visibility may be measured without specialized targets by computing a relative visibility from images of objects in view of a video camera. Systems using each of these techniques are described in detail below.
Relative visibility may be considered to be analogous to the relative humidity. Humidity is more accurately represented by measuring it relative to 100% humidity for a given temperature. In a similar manner, the visibility is dependent upon not just atmospheric conditions, but also the contrasts of the objects available from the scene viewed by the camera or human eye. More specifically, under the same atmospheric conditions, a location with higher contrasts such as an urban area with many buildings will have higher absolute visibility than a location with lower contrasts such as ocean. Essentially, visibility is a measurement of opacity in the visual path, and the degree of opacity is dependent not only on the air thickness or density but also the strength of the object contrasts behind.
Target-based Systems