Focusing system and method with adjustment for lens depth of focus
First Claim
1. The method of focusing a variable aperture objective lens of a photographic camera having a range finder to determine the distance from the camera to the near part of a subject to be photographed, focus control means for positioning said lens at a focus setting corresponding to the distance determined by said range finder and aperture control means for determining the effective lens aperture value for proper exposure of camera-contained film to said subject, said method comprising the steps of:
- generating a signal representative of objective lens depth of focus for the determined lens aperture value to be used; and
transmitting said signal to said focus control means to effect a focusing adjustment of said lens in accordance wth said determined aperture value to a focus setting corresponding to a distance greater than that determined by said range finder.
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Accused Products
Abstract
A focusing system and method for a photographic camera providing an automatic adjustment in the focus setting of the camera lens with aperture size to exploit the increased depth of focus available with a reduction in aperture size. In the illustrated embodiment, the aperture size is determined in accordance with scene light level, and the focus setting of the lens for a given camera/subject distance, as determined by an acoustical range finder, is adjusted automatically one or more positional increments toward the infinity focus setting of the lens to shift the in-focus field of the lens farther from the camera, in response to available subject illumination.
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Citations
14 Claims
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1. The method of focusing a variable aperture objective lens of a photographic camera having a range finder to determine the distance from the camera to the near part of a subject to be photographed, focus control means for positioning said lens at a focus setting corresponding to the distance determined by said range finder and aperture control means for determining the effective lens aperture value for proper exposure of camera-contained film to said subject, said method comprising the steps of:
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generating a signal representative of objective lens depth of focus for the determined lens aperture value to be used; and transmitting said signal to said focus control means to effect a focusing adjustment of said lens in accordance wth said determined aperture value to a focus setting corresponding to a distance greater than that determined by said range finder. - View Dependent Claims (2, 3, 4, 5)
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6. In an automatic focusing system for a photographic camera, said camera having a variable lens aperture, means for determining the effective value of said lens aperture employed in a given photographic scene, range finder means for determining camera/subject distance, and focus control means for positioning a lens element of said camera within a range of focus distance settings, the improvement comprising:
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means for generating a signal representative of the size of said lens aperture and correspondingly, the lens depth of focus; and means for adjusting said focus control system to position said lens element in response to both said range finding means and said aperture determining means to a focus distance setting corresponding to a camera/subject distance greater than the distance determined by said range finder so as to exploit the depth of focus variation with selected aperture value. - View Dependent Claims (7, 8, 9)
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10. In a photographic camera comprising an automatic exposure and focus control system having a shutter mechanism, means including a light integrating network for controlling the shutter mechanism to establish a lens aperture variable automatically with light levels illuminating a scene to be photographed, an objective lens having a lens element movable through a range of focus distance settings, a range finder means for generating a series of range pulses corresponding in number to camera/subject distance, focus control means including a lens movement detector for generating another series of lens pulses corresponding in number to focusing movement of said lens element in a direction from an infinity focus setting to a near distance focus setting, counter means for accumulating the total count of both said series of pulses and encoding means for fixing the focus setting of said lens element in response to a predetermined total count in said counter means, the improvement comprising:
means for transmitting to said counter means one or more additional pulses corresponding in number to successively increased light levels of subject illumination whereby said lens element will be positioned by said focus control means at a focus setting corresponding to a camera/subject distance greater than the distance represented by the number of pulses generated by said range finder means. - View Dependent Claims (11, 12, 13, 14)
Specification