Prism plates for compact optical viewers

Claim 2

A dual function transparent, optical prism sheet, the prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prism elongation each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of the prisms monotonically continuously varying along the length of the prism sheet in a direction normal to the direction of elongation of the said prisms, whereby light incident upon the prism faces from the prism side of the prism sheet at greater than the critical angle is totally reflected at the flat surface of the prism sheet, and whereby light incident upon the prism sheet at an angle less than said critical angle is transmitted through the prism sheet, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 3

The prism sheet of claim 1 wherein the sides of the prisms are isosceles in transverse cross-section.

Claim 4

A dual function optical ensemble comprising a viewing screen and a transparent, optical prism sheet, the viewing screen and the prism sheet being parallel to each other and being spaced from each other by a gap, said prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the viewing screen being on that side of the prism sheet which carries the prisms, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prism elongation, each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of the prisms monotonically continuously varying along the length of the prism sheet in a direction normal to the direction of elongation of the said prisms, whereby light incident upon the prism faces at greater than the critical angle is totally reflected at the flat surface of the prism sheet, and whereby light incident upon the prism sheet at an angle less than said critical angle is transmitted through the prism sheet and strikes the viewing screen, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 5

A dual function optical ensemble comprising a viewing screen and a transparent, optical prism sheet, the viewing screen and the prism sheet being parallel to each other and being spaced from each other by a gap, said prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the viewing screen being on that side of the prism sheet which carries the prisms, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prism elongation, each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of the prisms monotonically continuously varying along the length of the prism sheet in a direction normal to the direction of elongation of the said prisms, whereby light incident upon the prism faces at greater than the critical angle is totally reflected at the flat surface of the prism sheet, and whereby light incident upon the prism sheet at an angle less than said critical angle is transmitted through the prism sheet and strikes the viewing screen, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 6

The optical device of claim 1 comprising two of the prism sheets of claim 1, the flat surfaces of which are substantially parallel and adjacent to but spaced from each other, homologous faces of the ridges of the two sheets being parallel to each other in transverse cross-section.

Claim 7

An optical system comprising a sheet of transparent material, the sheet having a plurality of optical prisms formed on a first surface thereof and having a substantially flat second surface which is substantially parallel to the plane of the first surface, a ray of light impinging on one of the prisms of said first surface from a first direction being substantially totally reflected from the second surface, while a ray of light impinging on one of the prisms of the first surface from a second direction is substantially totally transmitted completely through the sheet, and means for directing a ray of light reflected from the second surface back towards the prism sheet for impinging thereon for transmission completely through the prism sheet.

Claim 8

An optical system comprising a sheet of transparent material, the sheet having a plurality of optical prisms formed on a first surface thereof and having a substantially flat second surface which is substantially parallel to the plane of the first surface, a ray of light impinging on one of the prisms of said first surface from a first direction being substantially totally reflected from the second surface, while a ray of light impinging on one of the prisms of the first surface from a second direction is substantially totally transmitted completely through the sheet, and means for directing a ray of light reflected from the second surface back towards the prism sheet for impinging thereon for transmission completely through the prism sheet.

Claim 9

An optical system as set forth in claim 5 in which said means is a mirror.

Claim 10

A dual function transparent, optical prism sheet, the prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prism elongation, each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of each prism being ninety degrees, one shorter face of any one of said prisms in said transverse cross-section making an angle alpha with the said flat surface of the prism sheet, the other shorter face of said any prism making an angle beta with the said flat surface of the prism sheet, the sum of the angles alpha and beta being ninety degrees, the angle alpha monotonically continuously varying from one prism to the next, the said two shorter faces being flat, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 11

A dual function transparent, optical prism sheet, the prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prism elongation, each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of each prism being ninety degrees, one shorter face of any one of said prisms in said transverse cross-section making an angle alpha with the said flat surface of the prism sheet, the other shorter face of said any prism making an angle beta with the said flat surface of the prism sheet, the sum of the angles alpha and beta being ninety degrees, the angle alpha monotonically continuously varying from one prism to the next, the said two shorter faces being flat, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 12

A dual function optical ensemble comprising a viewing screen and a prism sheet, the viewing screen and the prisms sheet being parallel to each other and being spaced from each other by a gap, said prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the viewing screen being on that side of the prism sheet which carries the prisms, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prisms elongation, each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of each prism being ninety degrees, one shorter face of any one of said prisms in said transverse cross-section making an angle alpha with the said flat surface of the prism sheet, the other shorter face of said any prism making an angle beta with the said flat surface of the prism sheet, the sum of the angles alpha and beta being ninety degrees, the angle alpha monotonically continuously varying from one prism to the nxt, the said two shorter prism faces being flat, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 13

A dual function optical ensemble comprising a viewing screen and a prism sheet, the viewing screen and the prisms sheet being parallel to each other and being spaced from each other by a gap, said prism sheet being flat on one surface and having a plurality of integral and elongated parallel prisms on its other surface, the viewing screen being on that side of the prism sheet which carries the prisms, the prisms being shaped such that, in transverse cross-section of the prism sheet normal to the direction of prisms elongation, each prism face makes an angle between 0° and 90° to the surface of the prism sheet, the apex angle of each prism being ninety degrees, one shorter face of any one of said prisms in said transverse cross-section making an angle alpha with the said flat surface of the prism sheet, the other shorter face of said any prism making an angle beta with the said flat surface of the prism sheet, the sum of the angles alpha and beta being ninety degrees, the angle alpha monotonically continuously varying from one prism to the nxt, the said two shorter prism faces being flat, whereby rays of light striking the prisms at different angles are accommodated and are totally internally reflected and are rendered parallel to each other upon exiting from the prism sheet.

Claim 14

The optical device of any one of claims 1 to 8 wherein the said prisms are curved along their lengths, and have a common center of curvature, said common center of curvature lying beyond said prism sheet and on the same plane as the plane containing the prism sheet, the radii of curvature of the said curved prisms continuously monotonically varying, no two prisms having the same radius of curvature, whereby all of the light rays lying within a cone of light which strikes a given prism of the prism sheet are incident on that prism at the same angle.