Aperture aberration reducing device

Claim 2

An arrangement of doubly refracting crystals for the reduction of aperture defects comprising first doubly refracting crystal means comprising a first doubly refracting crystal, said crystal having its optic axis at an oblique angle with respect to the system axis, a second doubly refracting crystal means comprising a second doubly refracting crystal substantially identical with said first doubly refracting crystal, and an element for rotating the polarization plane of divided ray bundles, said element being positioned between said first and second means, said second crystal being rotated by 90* about the system axis with respect to said first crystal.

Claim 3

The arrangement of claim 1 in which said first crystal means further comprises a third doubly refracting crystal and said second crystal means further comprises a fourth doubly refracting crystal, said third and fourth crystals being substantially identical with said first and second crystals respectively and being rotated by 90* with respect to said first and second crystals respectively, whereby the path length difference between the ordinary and extraordinary divided ray bundles is corrected.

Claim 4

The arrangement of claim 2 wherein said doubly refracting crystals are planoparallel plates.

Claim 5

An aperture aberration reducing system of birefringent crystals including means for correcting path length difference between ordinary and extraordinary partial beams, said aberration reducing system comprising first and second systems each having a plurality of birefringent crystals, and means for rotating a polarization plane of any partial ray beams by 90*, said crystal systems and rotating means having a common axis, said first system including first and second crystals positioned to deflect light of different relatively perpendicular polarizations, said second system including third and fourth crystals geometrically similar to said first and second crystals, said third and fourth crystals being positioned to deflect light of different relatively perpendicular polarizations, said rotating means being positioned between said first and second systems, said third crystal having its optic axis oriented to deflect light of the same polarization as said second crystal but which, due to the rotating means, deflects partial ray beams of light not deflected by said second crystal, whereby the path length difference between ordinary and extraordinary partial ray beams is corrected.

Claim 6

An aperture aberration reducing system of birefringent crystals including means for correcting path length difference between ordinary and extraordinary partial beams, said aberration reducing system comprising first and second systems each having a plurality of birefringent crystals, and means for rotating a polarization plane of any partial ray beams by 90*, said crystal systems and rotating means having a common axis, said first system including first and second crystals positioned to deflect light of different relatively perpendicular polarizations, said second system including third and fourth crystals geometrically similar to said first and second crystals, said third and fourth crystals being positioned to deflect light of different relatively perpendicular polarizations, said rotating means being positioned between said first and second systems, said third crystal having its optic axis oriented to deflect light of the same polarization as said second crystal but which, due to the rotating means, deflects partial ray beams of light not deflected by said second crystal, whereby the path length difference between ordinary and extraordinary partial ray beams is corrected.

Claim 7

The aperture aberration reducing device according to claim 4, wherein said double refracting crystal means of the first and second crystal system comprise plane parallel disks.

Claim 8

The aperture aberration reducing device according to claim 5, wherein said plane parallel disks have a thickness corresponding to 1/ Square Root 2 of the thickness of respective crystals in a device without correction of the aperture aberration.

Claim 9

The aperture aberration reducing device according to claim 4, wherein said double refracting crystal means forming the second crystal system have parameters which differ from the parameters of respective crystal means forming said first crystal system, except for the aperture aberration sO that the crystal means of the first and second crystal system have the same aperture aberration.

Claim 10

The aperture aberration reducing device according to claim 7, wherein the crystal means of the second crystal system have a light deflection which is equal to the light deflection of the respective crystal means of the first crystal system.

Claim 11

The aperture aberration reducing device according to claim 7, wherein said crystal means of the first and second crystal systems comprise plane parallel disks.

Claim 12

An aperture aberration reducing device, comprising a first crystal system comprised of a plurality of double refracting crystal means, a second crystal system comprised of a corresponding plurality of double refracting crystal means, said crystal system having a common axis, said crystal means of the first crystal system including at least one crystal oriented to deflect light of a polarization which is perpendicular relative to the polarization of light deflected by another crystal means of said first system, said crystal means of the second system comprisng at least one crystal which is rotated by 90* in a given rotation direction relative to said common axis whereby said rotated crystal of the second system in the absence of intervening ray rotating means deflects light of the same polarization as said other crystal means of the first system, said crystal means of the second system further comprising another crystal means oriented to deflect light of a polarization perpendicular with respect to the light deflected by said one crystal means of the second system, said another crystal means of said second system being rotated by 90* relative to said common axis with respect to said one crystal of said second system but in a direction opposite to said given rotational direction, and means between said systems for rotating a polarization plane of any partial ray beams by 90*, whereby the distance between ordinary and extraordinary partial ray beams is corrected.

Claim 13

An aperture aberration reducing device, comprising a first crystal system comprised of a plurality of double refracting crystal means, a second crystal system comprised of a corresponding plurality of double refracting crystal means, said crystal system having a common axis, said crystal means of the first crystal system including at least one crystal oriented to deflect light of a polarization which is perpendicular relative to the polarization of light deflected by another crystal means of said first system, said crystal means of the second system comprisng at least one crystal which is rotated by 90* in a given rotation direction relative to said common axis whereby said rotated crystal of the second system in the absence of intervening ray rotating means deflects light of the same polarization as said other crystal means of the first system, said crystal means of the second system further comprising another crystal means oriented to deflect light of a polarization perpendicular with respect to the light deflected by said one crystal means of the second system, said another crystal means of said second system being rotated by 90* relative to said common axis with respect to said one crystal of said second system but in a direction opposite to said given rotational direction, and means between said systems for rotating a polarization plane of any partial ray beams by 90*, whereby the distance between ordinary and extraordinary partial ray beams is corrected.

Claim 14

The aperture aberration reducing device according to claim 10, wherein said polarization plane rotating means for rotating said partial ray beams by 90* is a wafer having a thickness equal to lambda /2.

Claim 15

The aperture aberration reducing device according to claim 10, wherein said double refracting crystal means of the first and second crystal system comprise plane parallel disks.

Claim 16

The device of claim 2 in which said third and fourth crystals are rotated in the same direction relative to said first and second crystals respectively.

Claim 17

The device of claim 2 in which said third and fourth crystals are rotated in opposite directions relative to said first and second crystals respectively.

Claim 18

The aperture aberration reducing device according to claim 4, wherein said polarization plane rotating means for rotating said partial ray beams by 90* is a wafer having a thickness equal to lambda /2.