JPS5590907A - Projector - Google Patents

Abstract

PURPOSE: To prevent the vignetting of the lens effective region by specifying the shape of the lens end face in the projection optical system using bar-form lenses, in the projection system of the copying machine.

CONSTITUTION: The 1st bar-form lens 73 which is telecentric on the exit side, which has a uniform outside diameter ϕ₂₁', whose length in the optical axis direction is longer than their effective diameter ϕ₂₁, which form the curved faces of an effective diameter ϕ₂₁ smaller than the outside diameter ϕ₂₁' on the end faces and whose portions 72 other than the effective diameter ϕ₂₁ are roughened and the 2nd bar-form lens 74 being telecentric on the incident side, are prepared. The 1st, 2nd bar-form lenses 73, 74 are fitted into a lens barrel 61 by way of clad materials 62, 63 which have nearly the same refractive index as that of the lenses per se and are provided with light-absorptivity and these are so fixed as to become perpendicularly coaxial to the object surface and projection surface. Thereby, the vignetting of the lens effective region owing to the parallel deviations between the core materials for the bar-form lenses and the recesses of dies in the manufacture of the 1st, 2nd bar- form lenses 73, 74 is prevented and working allowable errors are eased.

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