Wide angle telecentric projection lens assembly

Claim 2

A wide angle telecentric lens assembly comprising: a first meniscus lens element of negative power; a second meniscus lens element of positive power, said first and second lens elements being bonded together to form a front lens doublet; an aperture stop positioned behind said front lens doublet;

Claim 3

a third meniscus lens of negative power positioned behind the aperture stop;

Claim 4

a third meniscus lens of negative power positioned behind the aperture stop;

Claim 5

a fourth meniscus lens of positive power positioned behind and adjacent said third lens element to provide an air space therebetween, the third and fourth lens elements having radii of curvatures reversed to that of said front doublet; a fifth biconvex lens element positioned behind said fourth lens element, generally close thereto; and a sixth biconvex lens element positioned behind said fifth lens element, said third, fourth, fifth and sixth lens elements forming a rear lens group adapted to refract light from an object through said aperture stop and said front lens doublet adapted to correct the light rays transmitted through said aperture stop for essentially precise focusing on an image plane, said lens assembly having a relative long back focal distance as compared to the equivalent focal length of the lens assembly.

Claim 6

a fourth meniscus lens of positive power positioned behind and adjacent said third lens element to provide an air space therebetween, the third and fourth lens elements having radii of curvatures reversed to that of said front doublet; a fifth biconvex lens element positioned behind said fourth lens element, generally close thereto; and a sixth biconvex lens element positioned behind said fifth lens element, said third, fourth, fifth and sixth lens elements forming a rear lens group adapted to refract light from an object through said aperture stop and said front lens doublet adapted to correct the light rays transmitted through said aperture stop for essentially precise focusing on an image plane, said lens assembly having a relative long back focal distance as compared to the equivalent focal length of the lens assembly.

Claim 7

A lens assembly according to claim 1, wherein the radii of curvature R' I /R" I through R' VI /R" VI , the indices of refraction Nd I through Nd VI , the Abbe numbers Vd I to Vd VI and the thicknesses and axial spacings are defined, within desired tolerances by the following data: TABLE I ______________________________________ Radius Axial of Between Lens Curvature(mm) Surfaces(mm) N.sub.d V.sub.d ______________________________________ -- -- +106.07(R'.sub.I) I 100.0 1.60310 65.41 +37.06(R".sub.I) 0 +37.06(R'.sub.II) II 12.0 1.68893 31.18 +59.76(R".sub.II) 73.86 A.S. -- -- -- -- 25.54 -23.53(R'.sub.III) III 10.6 1.68893 31.18 -211.36(R".sub.III) 1.11(air space) -85.05(R'.sub.IV) 1.62014 63.52 IV 8.50 -32.75(R".sub.IV) 0.50 +346,78(R'.sub.V) V 11.80 1.62014 63.52 -66.97(R".sub.V) .50 +119.38(R'.sub.VI) VI 9.90 1.52054 69.71 -228.92(R".sub.VI) ______________________________________ where lens I is said first meniscus lens element, lens III is said third meniscus lens element, lens IV is said fourth meniscus lens element, lens V is said fifth lens element, lens VI is said sixth lens element and A.S. is said aperture stop.

Claim 8

A lens assembly according to claim 2 wherein the tolerances for said lens assembly are such that lens concentricities of all said lens elements are within about ±0.002", the axial air space between lens elements II and III is within about ±0.010" and the axial air spaces between lens elements IV and V and between lens elements V and VI are within about ±0.005".

Claim 9

A lens system according to claim 2 which further includes a prism element positioned behind said sixth biconvex lens element, and a cover plate positioned between said prism and the object.

Claim 10

A lens assembly according to claim 4, wherein the front surface of said prism element is spaced about 5.0 mm from said sixth lens element and said prism about 100 mm thick, having an index of refraction of about 1.45846 and an Abbe number of about 67.83 and wherein said cover plate is about 12.5 mm thick and is positioned with its front surface about 4.93 mm from said prism, said cover plate having an index of refraction of about 1,45846 and an Abbe number of about 67.83.

Claim 11

A lens system according to claim 5, wherein the tolerances for said lens assembly are such that lens concentricities of all said lens elements are within about ±0.002", the axial air space between lens elements II and III is within about ±0.010" and the axial air space between lens elements IV and V and between lens elements V and VI is within about ±0.005".

Claim 12

A lens system according to claim 4, wherein the front surface of said prism element is spaced about 5.0 mm from said sixth lens element and said prism is about 75 mm thick, having an index of refraction of about 1.6727 and an Abbe number of about 32.21, and wherein said cover plate is about 12.5 mm thick and is front surface about 4.93 mm from said prism, said cover plate having an index of refraction of about 1.45846 and an Abbe number of about 67.87.

Claim 13

A lens system according to claim 7, wherein the tolerances of said lens assembly are such that lens concentricities of all said lens elements are within about ±0.002", the axial air space between lens elements II and III is within about ±0.010" and the axial air space between lens elements IV and V and between lens elements V and VI is within about ±0.005".

Claim 14

A lens system according to claim 1 which further includes a prism element positioned behind said sixth biconvex lens element, and a cover plate positioned between said prism element and the object.