US 4,060,725 AGranted

Focal plane detecting device

AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha

InventorShuji Hoshika

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Abstract

A focal plane detecting device is disclosed which uses an optical fiber system located within a rotating motor shaft or the like to scan an image plane and to deliver the scanned light to a stationary means, such as a photoconductor for developing a contrast signal. The optical system includes at least one optical fiber having its light incident end a fixed distance away from the axis of rotation of the shaft, but facing in the axial direction so as to scan a circular-like pattern of the plane wherein the light incident surface exists. The optical fiber extends through the shaft and exits in such a manner as to direct light therefrom upon a light detector at least part of the time that the shaft is rotating. Preferably the optical system includes a pair of optical fibers each having light incident ends symmetrically about the axis of rotation of the shaft and separated by a distance of .DELTA.Z along the axis of rotation. The axial separation results in the two optical fibers scanning corresponding potions of two image planes separated by .DELTA.Z. This permits the development of image signals representing the slightly separated planes and the comparison of said signals with each other to determine the position of the focal plane relative to the two image planes.

Claims10

Dependent claims

Apparatus for developing a signal indicative of the contrast of an image of scene, said apparatus comprising a motor having a rotary body having first and second ends and a means for imparting rotation to said rotary body about a rotary axis, the first said end of said rotary body being adapted to have an image plane of a scene impinging thereon, optical fiber means positioned within said rotary body and extending generally in the direction of said rotary axis from said first end to said second end of said rotary body, the first and second ends of said optical fiber means being in light communication with the area just outside the first and second ends of said rotary body, whereby light in an image plane falling on said first end of said optical fiber is carried to the second end and directed outwardly of said second end of said optical fiber and said rotary body, the said first end of said optical fiber means being displaced from said axis of rotation to effect a circular scan of said image plane as said rotary body rotates, and photoconductor means positioned rearwardly of and stationary relative to said second end of said optical fiber means and said rotary body means for developing an electrical signal dependent upon the scene brightness in the image plane scanned circuit means separating and integrating said electrical signal for developing a further signal indicative of the contrast of said image, said optical fiber means comprising at least a first and a second optical fiber bundle, the first ends of both said optical fiber bundles being positioned symmetrically about said rotary axis, and the first end of said first optical fiber bundle being displaced axially a predetermined amount .DELTA.Z relative to the first end of said second optical fiber bundle to effect scans of two image planes separated by .DELTA.Z by said first and second optical fiber bundles, respectively.

Dependencies are inferred from the claim text.