US4121234A — Focusing and projection screen

Claim 1

Independent Claim 217 words

A screen adapted to be mounted in the optical viewing path of a camera with through the lens viewing where the lens is focusable to create an image of an object in a depth of focus, said screen comprising a multiplicity of light transmitting elements essentially uniformly arranged and closely spaced together, each element surrounded by a light absorbing material, the length (D) of each element being equal to or less than λ/NA 2 , the major cross-sectional dimension (φ) across each element being equal to or less than λ/n sin u where λ is the wavelength of light in the optical spectrum of the light entering the lens, n is the index of refraction of the material of the element, u is the half angle of the largest bundle of light rays which can be transmitted through each element, and Na is the smallest numerical aperture of the lens so that when the lens is not focused to include the elements in the depth of focus the screen darkens due to absorption of light by said light absorbing material and as the lens is focused to bring its depth of focus within the length of the screen an image formed by the lens appears to sharply come into focus and be brightly illuminated on the screen.

Claim 2

Dependent Claim 217 words

A screen adapted to be mounted in the optical viewing path of a camera with through the lens viewing where the lens is focusable to create an image of an object in a depth of focus, said screen comprising a multiplicity of light transmitting elements essentially uniformly arranged and closely spaced together, each element surrounded by a light absorbing material, the length (D) of each element being equal to or less than λ/NA 2 , the major cross-sectional dimension (φ) across each element being equal to or less than λ/n sin u where λ is the wavelength of light in the optical spectrum of the light entering the lens, n is the index of refraction of the material of the element, u is the half angle of the largest bundle of light rays which can be transmitted through each element, and Na is the smallest numerical aperture of the lens so that when the lens is not focused to include the elements in the depth of focus the screen darkens due to absorption of light by said light absorbing material and as the lens is focused to bring its depth of focus within the length of the screen an image formed by the lens appears to sharply come into focus and be brightly illuminated on the screen.

Claim 3

Dependent Claim 26 words

The screen of claim 1 wherein the elements are glass and the light absorbing material is glass of essentially the same refractory index as said elements.

Claim 4

Dependent Claim 42 words

The screen of claim 1 further including a larger screen having a recess therein behind an image-viewing surface, said screen disposed in said recess of said larger screen with the front and back surfaces thereof on opposite sides of said image-viewing surface.

Claim 5

Dependent Claim 10 words

The screen of claim 1 wherein said elements are air.

Claim 6

Dependent Claim 65 words

The screen of claim 1 in combination with a single lens reflex camera having an objective lens defining an exit pupil, means defining a film plane, and a viewing system, said screen positioned in said viewing system so that the front and rear surfaces thereof subtend a plane that is the same distance from the exit pupil of the lens as the defined film plane.

Claim 7

Dependent Claim 44 words

The screen of claim 1 further including a larger screen having a recess therein behind an image viewing surface, said screen disposed in said recess of said larger screen with the front and back surfaces thereof on opposite sides of said image viewing surface.

Claim 8

Dependent Claim 178 words

In a camera of the type arranged to mount interchangeable lens where the lens is focusable to create an image of an object in a depth of focus, means defining a focal plane, and a viewing system including a focusing screen subtending a plane that is the same distance from the exit pupil of a lens as the focal plane and is a continuation of the optical axis of the lens; said focusing screen comprising a multiplicity of light transmitting elements of finite length essentially uniformly arranged and closely spaced together, each element surrounded by a light absorbing and non-light transmissive material, said elements being of a length which resides within the focal range of a lens mounted to the camera and of a predetermined cross-sectional shape and dimension whereby only light of a predetermined angle of incidence or less is passed by said elements so that when the lens is focused such that its focus range includes the elements of said screen an image from said lens comes into sharp focus and bright illumination on said screen.

Claim 9

Dependent Claim 178 words

In a camera of the type arranged to mount interchangeable lens where the lens is focusable to create an image of an object in a depth of focus, means defining a focal plane, and a viewing system including a focusing screen subtending a plane that is the same distance from the exit pupil of a lens as the focal plane and is a continuation of the optical axis of the lens; said focusing screen comprising a multiplicity of light transmitting elements of finite length essentially uniformly arranged and closely spaced together, each element surrounded by a light absorbing and non-light transmissive material, said elements being of a length which resides within the focal range of a lens mounted to the camera and of a predetermined cross-sectional shape and dimension whereby only light of a predetermined angle of incidence or less is passed by said elements so that when the lens is focused such that its focus range includes the elements of said screen an image from said lens comes into sharp focus and bright illumination on said screen.

Claim 10

Dependent Claim 51 words

The camera of claim 7 wherein the length (D) of the light transmissive elements along the optical axis is given by D ≦ (λ/NA.sup.2 where λ is the wavelength of light in the optical spectrum of the light to be viewed and NA is the smallest numerical aperture of the lens.

Claim 11

Dependent Claim 68 words

The camera of claim 7 where each element has a major cross-sectional dimension φ and φ ≧ λ/(n sin u) where λ is the wavelength of light in the optical spectrum of the light to be viewed, n is the index of refraction of the material of the element, u is the half angle of the largest bundle of light rays which can be transmitted through each element.

Claim 12

Dependent Claim 26 words

The camera of claim 7 wherein the elements are glass and the light absorbing material is glass of essentially the same refractory index as said elements.

Claim 13

Dependent Claim 44 words

The camera of claim 7 further including a larger second screen having a recess therein behind an image-viewing surface, said screen disposed in said recess of said larger second screen with the front and back surfaces thereof on opposite sides of said image-viewing surface.

Claim 14

Dependent Claim 44 words

The screen of claim 7 further including a larger screen having a recess therein behind an image viewing surface, said screen disposed in said recess of said larger screen with the front and back surfaces thereof on opposite sides of said image viewing surface.

Claim 15

Dependent Claim 89 words

The camera of claim 7 where said elements have a length in said screen D and a major cross-sectional dimension φ and D ≦ FR, and φ ≧ λ/(n sin u) where FR is the maximum depth of focus of the lens, λ is the wavelength of light in the optical spectrum of the light to be viewed, n is the index of refraction of the material of the elements, u is the half angle of the largest bundle of light rays which can be transmitted through each element.

Claim 16

Dependent Claim 22 words

The combination of claim 13 wherein said elements ae glass, and the light-absorbing material is glass of the same index of refraction.

Claim 17

Dependent Claim 10 words

The screen of claim 13 wherein said elements are air.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1981-10-16	1982-04-17	1982-10-17	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1985-10-16	1986-04-17	1986-10-17	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1989-10-16	1990-04-17	1990-10-17	$7700.00	Window Closed / Lapsed

Focusing and projection screen

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