Optical fstop/resolution apparatus and method for specified depth-of-field
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsMark J. DiPippo, Bruce J. Bates
Life of this patent
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Abstract
A method and apparatus to determine the fstop that provides optimal image resolution for a predetermined depth-of-field. An approximate and exact method and apparatus are provided to determine the optimal resolution fstop. The optimal resolution fstop is a function of the lens focal length, depth-of-field in front of the object, wavelength of light, and distance of the object to the lens center. Once the optimal resolution fstop is determined, the camera is adjusted to the closest discrete fstop available. When the approximate field technique is utilized, the camera must be adjusted to the discrete fstop closest to, but not exceeding, the computed fstop.
Claims17
A method for setting a camera fstop, comprising:
- selecting a fixed focal length, f;
- determining a single distance, o, between said camera and an object to be focused;
- inputting a desired depth-of-field, d, in front of said object;
- computing an optimal fstop as a function of said depth-of-field, said distance and said focal length;
- and
- adjusting said camera fstop to a discrete fstop closest to said computed optimal fstop.
An apparatus for setting a camera fstop, comprising:
- a focal length f selector;
- a range finder to measure a distance o between said camera and an object to be focused and to measure a depth-of-field d in front of said object;
- a light wavelength selector λ;
- a module to compute an optimal fstop as a function of said depth-of-field, said distance and said focal length, wherein the module computes the optimal fstop from the relationship:
- fstop=f*sqrt (d/(2.44*λ*o*(o−d)));
- and
- a camera fstop adjuster to set said camera fstop to a discrete fstop closest to said optimal fstop.
A method for setting a camera fstop, comprising:
- selecting a focal length, f;
- determining a distance, o, between said camera and an object to be focused;
- a depth-of-field, d, in front of said object;
- computing an optimal fstop as a function of said depth-of-field, said distance and said focal length by specifying a wavelength of light, λ, and determining the optimal fstop from the relationship
- fstop=f*sqrt (d/(2.44*λ*o*(o−d)));
- and
- adjusting said camera fstop to a discrete fstop closest to said computed optimal fstop.
The method of claim 14, wherein determining the optimal fstop from the relationship further comprises:
- inputting the focal length, the distance, the depth-of-field and the wavelength into a processor;
- operating the processor to compute the relationship;
- and
- outputting the optimal fstop.
Dependencies are inferred from the claim text.