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US 4,215,924 AGranted
Method to control introduction of diffracted beam by means of diffraction element
AssigneeCanon Kabushiki Kaisha
InventorKazuya Matsumoto
Life of this patent
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Abstract
According to the present invention in the image forming light path a direction-selective diffraction element is provided in such a manner that the image forming beam having entered into said diffraction element is diffracted by means of the diffraction grating structure of said diffraction element and devided into a plurality of beams, whereby at least one of the diffracted beams is led to a photo detecting device while the not diffracted beam is made use of as the image forming beam.
Claims19
A method for measuring varying intensities of light comprising:
- exposing an image forming optical system to the varying intensities of light and directing the light along an optical path within the system;
- receiving the varying light by one of two flat faces of a planar optical system having an end face;
- intercepting at least a section of the varying light in the path with a diffraction element whose size within the path of the light remains constant;
- diffracting the light incident on the diffraction element out of the optical path so that at least a portion of the diffracted light reaches one of the flat faces of the planar optical system at a total reflection angle;
- internally reflecting the diffracted light by the flat faces toward said end face;
- and
- receiving the diffracted light projected from the end face by light detecting means;
- said intercepting step including orienting the element substantially perpendicular to the optical path.
5 more elements
A method for measuring portions of the light incident on an image forming optical system, comprising:
- forming an optical path with a portion of the system;
- intercepting at least a section of the light in the path with a transparent element having a plurality of diffracting parts each formed of a diffraction lattice whose size within the path of the light remains constant;
- diffracting the intercepted light in a plurality of directions separately of each other in accordance with each of said diffracting parts;
- and
- measuring the diffracted lights separately, by means of light detecting means, in each of the different directions,
- said intercepting step including orienting the element substantially perpendicular to the optical path.
3 more elements
A light guide comprising:
- a transparent plate having two flat faces and an end face forming a projection face, and a diffraction lattice formed on the transparent plate for diffracting light incident upon the transparent plate toward one of the two flat faces so that at least a portion of the diffracted light reaches the one of the two flat faces at a total reflection angle and so that the diffracted light is internally reflected toward the end face, said lattice covering an area less than the area of one of the faces and being surrounded on all sides within one of the faces by a non-diffracting surface and having an area less than the cross section of light to be directed thereon.
A light guide comprising:
- a parallel planar plate having an end face, and
- a diffraction lattice formed on the parallel planar plate, said diffraction lattice forming an angle at least other than a total reflection angle to the plane of the plate, and diffracting the incident light at least to one of the parallel planes at a total reflection angle and projecting the diffracted light which was totally reflected from the end face, said lattice covering an area less than the area of one of the faces and being surrounded on all sides within one of the faces by a non-diffracting surface and having an area less than the cross section of light to be directed thereon.
A light guide comprising:
- a parallel planar sheet having parallel faces and an end face, and
- a diffraction lattice on said parallel planar sheet, said diffraction lattice directing the light incident on one of the parallel faces at a non-total reflection angle toward the other parallel face at a total reflection angle and projecting the light totally reflected by the other parallel face from one of the parallel faces, said lattice covering an area less than the area of one of the faces and being surrounded on all sides within one of the faces by a non-diffracting surface and having an area less than the cross section of light to be directed thereon.
An apparatus for measuring portions of light incident on an image forming optical system, comprising:
- a diffraction element having a transparent sheet and a diffraction lattice of predetermined size carried by the sheet, said sheet having two flat faces, said lattice being arranged to intercept at least a section of the light of predetermined size and to diffract said intercepted light out of the optical path toward one of the two flat faces at a total reflection angle so that at least a portion of the diffracted light is internally reflected toward said end face, and
- light detecting means in the direction of at least a portion of the light diffracted from the optical path for measuring at least a portion of the light diffracted from the optical path.
An optical apparatus, comprising:
- an image forming optical system defining an optical path, a diffraction element of predetermined size in the optical path of the light arranged for diffracting a predetermined part of constant size, of the light incident on the image forming optical system outside of the optical path, and a light detecting means arranged in the direction of light diffracted by said diffraction element for measuring the different light, said element being surrounded by non-diffracting surfaces on all sides lying entirely within said optical path.
Dependencies are inferred from the claim text.