Copying machine including a dielectric covered metal reflective device

Claim 2

A copying machine comprising an original table on which an original to be copied is laid; a lens system; a photosensitive medium which has characteristics of high sensitivity to light in a certain wavelength range; a light source for illuminating an object to be copied; and reflective means for reflecting light from the object to said photosensitive medium, said reflective means comprising a metal surface having a dielectric film provided thereon, wherein said dielectric film decreases the reflection factor of said metal surface for light of a wavelength to which said photosensitive member is highly sensitive, while retaining a relatively higher reflection factor for other light, and wherein said metal absorbs non-reflected light, so that the spectral wavelength characteristics of light coming from the light source match with the spectral sensitivity characteristics of said photosensitive medium.

Claim 3

A copying machine as claimed in claim 1, wherein said metal surface is provided on a glass substrate.

Claim 4

A copying machine as claimed in claim 1, wherein said dielectric film comprises a plurality, less than five, of alternate high and low refractive index layers.

Claim 5

A copying machine as claimed in claim 1, wherein said metal is aluminum.

Claim 6

A copying machine as claimed in claim 1, wherein said metal is silver.

Claim 7

A copying machine as claimed in claim 1, wherein said reflective means has at least two reflective metal surfaces, with a dielectric film formed, respectively, on each said metal surface.

Claim 8

A copying machine as claimed in claim 6, wherein said two or more reflective surfaces have different spectral reflectance characteristics.

Claim 9

A copying machine as claimed in claim 7, wherein the dielectric film on each reflective metal surface comprises alternate high and low refractive layers with the condition that the first layer in contact with said metal surface be a high refractive layer.

Claim 10

A copying machine as claimed in claim 8, wherein the last one of said alternate high and low refractive layers in said dielectric film is a high refractive layer.

Claim 11

A copying machine as claimed in claim 1, wherein said dielectric film comprises alternate high and low refractive layers with the condition that the first layer in contact with said metal reflective surface be a high refractive layer.

Claim 12

A copying machine as claimed in claim 10, wherein each the layer in said dielectric film has an optical film layer thickness approximately corresponding to 1/4 of the design wavelength λ which is about the center value of the wavelength range at which a reduction of reflectance is desired, with the provision that the first layer in contact with said metal reflective surface has an optical film layer thickness somewhat less than 1/4λ.

Claim 13

A copying machine comprising an original table on which an original to be copied is laid; a lens system; a photosensitive medium which has characteristics of high sensitivity to light in a certain wavelength range; a light source; at least one metal reflective surface and a dielectric film provided on said metal reflective surface and serving to match the wavelength characteristics of beam of light coming from an object with the spectral sensitivity characteristics of said photosensitive medium, wherein said dielectric film comprises alternate high and low refractive layers with the condition that the first layer in contact with said metal reflective surface be a high refractive layer, wherein each layer in said dielectric film has an optical film layer thickness approximately corresponding to 1/4 of the design wavelength λ which is about the center value of the wavelength range at which a reduction of reflectance is desired, with the provision that the first layer in contact with said metal reflective surface has an optical film layer thickness somewhat less than 1/4; and wherein the optical film layer thickness, nd of said first layer is given by: ##EQU2## wherein, n: refractive index of the first layer, d: geometrical film layer thickness of the first layer, n o , k: coefficients of the complex refractive index n o -i k on the metal reflective surface at the wavelength λ, and n H : refractive index of the high refractive layer.

Claim 14

A copying machine comprising an original table on which an original to be copied is laid; a lens system; a photosensitive medium which has characteristics of high sensitivity to light in a certain wavelength range; a light source; at least one metal reflective surface and a dielectric film provided on said metal reflective surface and serving to match the wavelength characteristics of beam of light coming from an object with the spectral sensitivity characteristics of said photosensitive medium, wherein said dielectric film comprises alternate high and low refractive layers with the condition that the first layer in contact with said metal reflective surface be a high refractive layer, wherein each layer in said dielectric film has an optical film layer thickness approximately corresponding to 1/4 of the design wavelength λ which is about the center value of the wavelength range at which a reduction of reflectance is desired, with the provision that the first layer in contact with said metal reflective surface has an optical film layer thickness somewhat less than 1/4; and wherein the optical film layer thickness, nd of said first layer is given by: ##EQU2## wherein, n: refractive index of the first layer, d: geometrical film layer thickness of the first layer, n o , k: coefficients of the complex refractive index n o -i k on the metal reflective surface at the wavelength λ, and n H : refractive index of the high refractive layer.

Claim 15

A copying machine as claimed in claim 11 or 12, wherein the last one of alternate high low refractive layers in said dielectric film is a high refractive layer.

Claim 16

An optical system comprising: a light source for illuminating an object; a photosensitive medium for sensing the light from said object, said photosensitive medium having characteristics of high sensitivity to light in a certain wavelength range; and reflective means disposed in the optical path between said light source and said photosensitive medium, said reflective means comprising a reflective metal surface having a dielectric film provided thereon, wherein said dielectric film decreases the reflection factor of said metal surface for light of a wave length to which said photosensitive member is highly sensitive, while retaining a relatively higher reflection factor for other light, and wherein said metal absorbs non-reflection light, so that the spectral wavelength characteristics of a beam of light coming from said light source match with the spectral sensitivity characteristics of said photosensitive medium.

Claim 17

An optical system comprising: a light source for illuminating an object; a photosensitive medium for sensing the light from said object, said photosensitive medium having characteristics of high sensitivity to light in a certain wavelength range; and reflective means disposed in the optical path between said light source and said photosensitive medium, said reflective means comprising a reflective metal surface having a dielectric film provided thereon, wherein said dielectric film decreases the reflection factor of said metal surface for light of a wave length to which said photosensitive member is highly sensitive, while retaining a relatively higher reflection factor for other light, and wherein said metal absorbs non-reflection light, so that the spectral wavelength characteristics of a beam of light coming from said light source match with the spectral sensitivity characteristics of said photosensitive medium.