Patent ID: 8817392

Claim:
A wide field athermalized orthoscopic lens system, comprising: a first optical group having a negative optical power; a second optical group having a positive optical power; a third optical group having a positive optical power; a fourth optical group having a positive optical power; and a fifth optical group having a negative optical power, wherein the first optical group comprises one optical element with a negative optical power, and the first optical group is arranged to diverge light received from the object and to direct the diverged light onto the second optical group, wherein the third optical group comprises a first and a second optical element having in order from the object a positive and a negative optical power, and is arranged to converge the light from the second optical group and to direct the converged light onto the fourth optical group, wherein the fifth optical group comprises one optical element with a negative optical power and directs the light from the fourth optical group onto the image plane, and wherein −0.26<Φ 1 /Φ<−0.14, 0.22<Φ 2 /Φ<0.38, 0.85<Φ 2 /Φ 3 <1.25, 1.45<Φ 4 /Φ<1.85, 0.65<Φ 3 /Φ 4 <1.05, 1.30< V 1 /V 2 <1.55, 1.35< V 31 /V 32 <1.55, 0.80< V 4 /V 5 <1.20, −2.60<( dn/dT ) 1 /( dn/dT ) 2 <−2.25, 0.45<( dn/dT ) 31 /( dn/dT ) 32 <0.65, and 8<( dn/dT ) 4 /( dn/dT ) 5 <10, where Φ is the optical power of the lens; Φ 1 , Φ 2 , Φ 3 , Φ 4 and Φ 5 are the optical powers of the first, second, third, fourth and fifth groups, respectively; V 1 , V 2 , V 4 and V 5 are Abbe values for the first second fourth and fifth optical groups respectively; V 31 and V 32 are the Abbe values for the first and second elements of the third optical group, respectively; (dn/dT) 1 , (dn/dT) 2 , (dn/dT) 4 and (dn/dT) 5 are temperature change in refractive indices for the first, second, fourth and fifth groups, respectively; and, (dn/dT) 31 , (dn/dT) 32 are temperature change in refractive indices for the first and second elements of the third optical group, respectively.