Photometric device with a plurality of measuring fields

Claim 2

In an optical system for a photometer in which light to be measured from a scene is directed along an optical path defined by an objective lens having a focal plane, a relay lens in said optical path having a focal plane at the objective lens, and a photosensor having a light responsive surface at the back focal plane of the relay lens, and in which light from the scene being viewed is directed along an optical path from the focal plane of the objective lens to a viewing eye piece, the combination of: aperture mirror means located at the focal plane of the objective lens, said aperture means having a mirror surface for directing light to the viewing light path, said aperture means having a plurality of apertures of different area in said mirror surface selectively positionable in said focal plane at the optical axis of the objective lens, each aperture when positioned in said focal plane at the optical axis limiting the field being examined by said photosensor in said measuring light path.

Claim 3

In a system as stated in claim 1 wherein said aperture means includes a wheel-like member mounted for rotation about its center, and wherein said plurality of apertures are circularly arranged about said axis.

Claim 4

In an optical system as stated in claim 2 wherein said wheel-like member is disposed at an angle to the optical axis of the measuring light path.

Claim 5

In a system as stated in claim 1 wherein said apertures are of non-circular shape with respect to the plane of the aperture means.

Claim 6

In an optical system for a photometer which includes a measuring light path and includes a viewing light path of the area from which light is to be measured, the combination of: an objective lens of varifocal type in said measuring light path to receive light from said area and having a back focal plane; an aperture mirror means rotatable about an axis inclined to the measuring light path and having a plurality of apertures of different area, each aperture being positionable in the back focal plane of the varifocal lens, a relay and integrator lens and a photosensor in said measuring light path, said relay lens having conjugate focal planes at said varifocal lens and at said photosensor; and means at said photosensor including an aperture for compensating the transmission of T-stop variations of said varifocal objective lens.

Claim 7

In an optical system for a photometer which includes a measuring light path and includes a viewing light path of the area from which light is to be measured, the combination of: an objective lens of varifocal type in said measuring light path to receive light from said area and having a back focal plane; an aperture mirror means rotatable about an axis inclined to the measuring light path and having a plurality of apertures of different area, each aperture being positionable in the back focal plane of the varifocal lens, a relay and integrator lens and a photosensor in said measuring light path, said relay lens having conjugate focal planes at said varifocal lens and at said photosensor; and means at said photosensor including an aperture for compensating the transmission of T-stop variations of said varifocal objective lens.

Claim 8

In an optical system for a photometer including the combination of: an objective lens having a back focal plane, a relay lens in said path having a focal plane at the objective lens, and a photosensor having a light responsive surface at the back focal plane of the relay lens, said objective lens, relay lens, and photosensor defining a light path for measuring characteristics of light admitted to said objective lens; means including an inclined apertured mirror in the measuring light path limiting the field being examined and directing light along a separate viewing light path and delineating the area from which light is to be measured; and means including an aperture located at a focal plane of the relay lens at said photosensor whereby said relay lens and aperture located at the focal plane of the relay lens at said photosensor compensate for variations in light transmission as focal length of the objective lens is changed.

Claim 9

In an optical system for a photometer including the combination of: an objective lens having a back focal plane, a relay lens in said path having a focal plane at the objective lens, and a photosensor having a light responsive surface at the back focal plane of the relay lens, said objective lens, relay lens, and photosensor defining a light path for measuring characteristics of light admitted to said objective lens; means including an inclined apertured mirror in the measuring light path limiting the field being examined and directing light along a separate viewing light path and delineating the area from which light is to be measured; and means including an aperture located at a focal plane of the relay lens at said photosensor whereby said relay lens and aperture located at the focal plane of the relay lens at said photosensor compensate for variations in light transmission as focal length of the objective lens is changed.

Claim 10

In an optical system as stated in claim 6, wherein said apertured mirror includes a plurality of apertures of different area selectively positionable in said focal plane.

Claim 11

In an optical system as stated in claim 6, wherein said objective lens is a varifocal lens; said relay lens having conjugate focal planes at said varifocal lens and at said aperture in proximity to said photosensor; whereby said relay lens and aperture forms a T-stop system for automaTically compensating for variations in lens transmission as the focal length of the objective lens is varied.

Claim 12

In an optical system as stated in claim 1 including; said mirror surface including a reflectant coating, and a portion of said coating being removed to provide a selected nonreflecting light transmitting area positionable to pass light along said measuring light path.

Claim 13

In a luminance-radiance photometer having a viewing light path for observing the area from which light is being measured and a separate light path to measure characteristics of said light, the combination of: an objective lens; a mirror member positioned in the path of light transmitted by said objective lens and reflecting all wave lengths of said light at virtually unchanged intensity to said viewing light path; an opening in said mirror member at the focal plane of the objective lens to transmit light from an area to be measured along the light measuring path, said opening being viewable in said viewing light path as a black area; a relay lens in said light measuring path focused at a point which is the position of maximum clear aperture of the objective lens when the objective lens is focused on the nearest object; a photosensor having a photoresponsive surface upon which said clear aperture of said objective lens is projected by said relay lens; and a T-stop aperture means adjacent the photoresponsive surface of the photosensor to attenuate the intensity of light being measured as transmitted by said relay lens and without modification of the intensity of light reflected by said mirror member; said T-stop aperture means maintaining the light intensity of measured light reaching the photoresponsive surface at a constant level independently of the focal position of the objective lens.

Claim 14

In a luminance-radiance photometer having a viewing light path for observing the area from which light is being measured and a separate light path to measure characteristics of said light, the combination of: an objective lens; a mirror member positioned in the path of light transmitted by said objective lens and reflecting all wave lengths of said light at virtually unchanged intensity to said viewing light path; an opening in said mirror member at the focal plane of the objective lens to transmit light from an area to be measured along the light measuring path, said opening being viewable in said viewing light path as a black area; a relay lens in said light measuring path focused at a point which is the position of maximum clear aperture of the objective lens when the objective lens is focused on the nearest object; a photosensor having a photoresponsive surface upon which said clear aperture of said objective lens is projected by said relay lens; and a T-stop aperture means adjacent the photoresponsive surface of the photosensor to attenuate the intensity of light being measured as transmitted by said relay lens and without modification of the intensity of light reflected by said mirror member; said T-stop aperture means maintaining the light intensity of measured light reaching the photoresponsive surface at a constant level independently of the focal position of the objective lens.