Infra-red optical systems

Claim 2

An "eye-piece" system for use in a non-Gallilean afocal infra-red optical system or an afocal infra-red telescope in which an intermediate image is formed, the "eye-piece" system comprising at least three lens elements of infra-red transmitting material operative with radiation in at least one of the 3 to 5.5 and 8 to 13 micron wavebands, the three lens elements including a back element of positive power having a front surface which is convex and a curved back surface, and a pair of elements which are closely spaced to define a gas lens therebetween, the back element of the pair having a convex back surface and the front element of the pair having a concave front surface with an absolute value of radius of curvature equal to or greater than that of the convex back surface of the back element of the pair, the pair of elements in combination with the gas lens therebetween being of positive power.

Claim 3

An "eye-piece" system according to claim 1 in which said curved back surface of said back element of positive power has a radius of curvature whose absolute valve is less than that of the concave front surface of the front element of the pair.

Claim 4

An "eye-piece" system according to claim 1 or claim 2 in which said curved back surface of said back element of positive power is a concave surface.

Claim 5

An "eye-piece" system according to claim 1 in which said pair of elements comprises a front element of negative power and a back element of positive power.

Claim 6

An "eye-piece" system according to claim 4 in which said front element of negative power is of meniscus form with a convex back surface whose radius of curvature has an absolute value greater than that of its convex back surface.

Claim 7

An "eye-piece" system according to claim 4 or claim 5 in which said back element of positive power is of meniscus form with a concave front surface whose radius of curvature has an absolute value greater than that of its convex back surface.

Claim 8

An "eye-piece" system according to claim 1 in which the gas lens between the elements of the pair is of negative power.

Claim 9

An "eye-piece" system according to claim 7 in which said gas lens is bounded at the back by a front concave surface of the back element of the pair and at the front by a back convex surface of the front element of the pair having a radius of curvature with an absolute value greater than that of the front concave surface of the back element of the pair.

Claim 10

An "eye-piece" system according to claim 1 having an associated field or corrector lens element of positive power.

Claim 11

The invention of claim 1 and further comprising an objective lens system for collecting and transmitting infra-red radiation thereto, the combination being for use as a non-Gallilean afocal infra-red optical system or afocal infra-red telescope.

Claim 12

The invention of claim 10 in which the powered elements of the objective lens system are all refracting elements.

Claim 13

The invention of claim 11 comprising lens elements 23, 24, 25, 15, 16 and 17 whose surfaces R23 to R28 and R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R23 70.848 23 3.765 R24 58.69 2.54 R25 68.927 24 5.5883 R26 98.8331 81.4045 R27 372.363 25 6.35 R28 -6680.6943 38.1 R17 -44.7180 15 6.8 R18 -89.5669 2.54 R19 -44.3003 16 12.2 R20 -36.7068 0.25 R21 28.0132 17 4.5 R22 30.4512 ______________________________________

Claim 14

The invention of claim 11 comprising lens elements 23, 24, 25, 15, 16 and 17 whose surfaces R23 to R28 and R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R23 71.5668 23 3.7446 R24 57.2219 5.5898 R25 68.8225 24 6.0 R26 97.2005 75.8214 R27 273.4474 25 6.35 R28 -4597.7524 36.7173 R17 -43.1559 15 6.8 R18 -103.7221 2.6457 R19 -55.3904 16 13.8148 R20 -36.5331 0.25 R21 25.0986 17 4.5 R22 30.4513 ______________________________________

Claim 15

The invention of claim 11 comprising lens elements 26, 27, 28, 15, 16 and 17 whose surfaces R29 to R34 and R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R29 159.1069 26 8.9619 R30 238.2525 88.85 R31 281.1277 27 5.08 R32 149.2209 87.814 R33 54.5642 28 3.81 R34 105.2138 7.62 R17 -34.0261 15 2.54 R18 -263.2878 4.8014 R19 -49.9219 16 12.0382 R20 -34.0261 0.25 R21 27.0365 17 4.1065 R22 29.1954 ______________________________________

Claim 16

The invention of claim 11 comprising lens elements 29, 30, 15, 16 and 17 whose surfaces R35 to R38 and R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R35 163.93456 29 8.8545 R36 218.9659 76.60999 R37 -137.4706 30 5.7571 R38 -145.4383 136.9784 R17 -45.0241 15 3.4948 R18 -57.0621 1.8163 R19 -42.5843 16 8.3768 R20 -37.4844 0.25 R21 34.3084 17 4.3137 R22 43.0330 ______________________________________

Claim 17

The invention of claim 10 in which the objective lens system is a catadioptric system including reflecting powered elements.

Claim 18

The invention of claim 16 comprising lens elements 11 and 14 to 17 and mirrors 12 and 13 whose surfaces R11 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R11 -138.0862 11 7.5 R12 -159.2796 86.9752 12 R13 -217.2779 -86.9752 13 R14 -159.2796 83.3621 R15 -88.2180 14 7.2 R16 -80.7690 38.3071 R17 -44.7180 15 6.8 R18 -89.5669 2.54 R19 -44.3003 16 12.2 R20 -36.7068 0.25 R21 28.0132 17 4.5 R22 30.4512 ______________________________________

Claim 19

The invention of claim 1 and further comprising an objective lens system for producing a real image from infra-red radiation from a distant scene or object, said "eye-piece" system being arranged to receive infra-red radiation from said real image and to provide a collimated magnified view of the scene or object at a real exit pupil, and scanning and detector means operative at said exit pupil to scan the collimated magnified view via imaging means across infra-red detector means, for use as an infra-red optical system.

Claim 20

An "eye-piece" system according to claim 1 in which the infra-red transmitting material is selected from germanium and silicon.

Claim 21

An "eye-piece" system according to claim 1 comprising three lens elements 15, 16 and 17 whose surfaces R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Raadius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R17 -44.7180 15 6.8 R18 -89.5669 2.54 R19 -44.3003 16 12.2 R20 -36.7068 0.25 R21 28.0132 17 4.5 R22 30.4512 ______________________________________

Claim 22

An "eye-piece" system according to claim 1 comprising three lens elements 15, 16 and 17 whose surfaces R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R17 -43.1559 15 6.8 R18 -103.7221 2.6457 R19 -55.3904 16 13.8148 R20 -36.5331 0.25 R21 25.0986 17 4.5 R22 30.4513 ______________________________________

Claim 23

An "eye-piece" system according to claim 1 comprising three lens elements 15, 16 and 17 whose surfaces R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R17 -34.0261 15 2.54 R18 -263.2878 4.8014 R19 -49.9219 16 12.0382 R20 -34.0261 0.25 R21 27.0365 17 4.1065 R22 29.1954 ______________________________________

Claim 24

An "eye-piece" system according to claim 1 comprising three lens elements 15, 16 and 17 whose surfaces R17 to R22 have radii of curvature, and whose elements have axial thicknesses and separations, substantially as follows: ______________________________________ Radius of Axial Thickness/ Element Surface Curvature Separation ______________________________________ R17 -45.0241 15 3.4984 R18 -57.0621 1.8163 R19 -42.5843 16 8.3768 R20 -37.4844 0.25 R21 34.3084 17 4.3137 R22 43.0330 ______________________________________

Claim 25

An "eye-piece" system for use in a non-Gallilean afocal infra-red optical system or an afocal infra-red telescope, the "eye-piece" system comprising at least three lens elements including a back element of positive power having a back surface which is either convex or concave and a front surface which is convex, and a pair of singlet elements which are closely spaced to define a gas lens therebetween, the back singlet element of the pair having a convex back surface and the front singlet element of the pair having a concave front surface with an absolute value of radius of curvature equal to or greater than that of the convex back surface of the back singlet chamber of the pair, the pair of singlet elements in combination with the gas lens therebetween being of positive power.

Claim 26

An "eye-piece" system for use in a non-Gallilean afocal infra-red optical system or an afocal infra-red telescope, the "eye-piece" system comprising at least three lens elements including a back element of positive power having a back surface which is either convex or concave and a front surface which is convex, and a pair of singlet elements which are closely spaced to define a gas lens therebetween, the back singlet element of the pair having a convex back surface and the front singlet element of the pair having a concave front surface with an absolute value of radius of curvature equal to or greater than that of the convex back surface of the back singlet chamber of the pair, the pair of singlet elements in combination with the gas lens therebetween being of positive power.