Modified Petzval lens

• US 4,232,943 A
• Filed: 12/20/1978
• Issued: 11/11/1980
• Est. Priority Date: 09/13/1975
• Status: Expired due to Term

• Current Assignee: Pilkington PE Limited
• Original Assignee: Pilkington PE Limited
• Inventors: Rogers, Phillip J.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Sugarman, Scott J.
• Application Number:
  US05/971,481
• Time in Patent Office: 692 Days
• Field of Search: 350/202, 350/216, 350/175 SF
• US Class Current: 359/726
• CPC Class Codes: G02B 13/02 Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/12 operating by refraction only
• CPC Class Codes: G02B 5/04 Prisms
• CPC Class Codes: G02B 9/34 having four components only
• CPC Class Codes: G02B 9/60 having five components only

Abstract

A collimating magnifier lens which may be used in a head-up display has a focal length of F. The lens has a front part comprising at least one positive element with a focal length between +1 F and +3 F and a negative element with a focal length between -1.2 F and infinity, the focal length of the front part as a whole being between +1 F and +6 F and the negative element of the front part not being cemented to any other element, a rear part comprising a single positive element with a focal length between +0.4 F and +1.2 F, and a field flattener behind the rear part and comprising a single negative element with a focal length between -0.4 F and -1.1 F.

The negative element of the front part may have a refractive index less than or equal to 0.13 greater than that of any positive element of the front part and may be meniscus in shape having a focal length of at least 2.8 times that of the positive component and which produces overcorrect spherical aberration. A single positive element with a focal length between +1.4 F and infinity may be used as a middle part. The air gap in front of the rear part is preferably between 0.6 F and 1.1 F, and the air gap between the rear part and the field flattener is preferably between 0.01 F and 0.5 F. The front part of the lens may have two positive elements. A mirror may be interposed in the gap between the rear and front, or rear and middle.

Claims

1. A modified Petzval lens having a focal length F, the lens having a front part comprising at least one positive element with a focal length between +1F and +3F and a negative element with a focal length between -1.2F and infinity, the focal length of the front part as a whole being between +1F and +6F and the negative element of the front part not being cemented to any other element and having a refractive index less than or equal to 0.13 greater than the refractive index of any positive element of the front part, a rear part comprising a positive singlet element with a focal length between +0.4F and +1.2F, and a field flattener behind the rear part and comprising a single negative element with a focal length between 0.4F and -1.1F.

2. A lens as claimed in claim 1 wherein the negative element in the front part is meniscus in shape.

3. A lens as claimed in claim 1 further having a middle part located between the front and rear parts, the middle part comprising a single positive element with a focal length between +1.4F and infinity.

4. A lens as claimed in claim 1 having an air gap of between 0.6F and 1.1F in front of the rear part.

5. A lens as claimed in claim 1 having an equivalent air gap of between 0.01F and 0.5F between the rear part and the field flattener.

6. A lens as claimed in claim 1 in which the front part has two positive elements.

7. A lens as claimed in claim 6 in which the front positive element in the front part has a focal length between +6F and infinity.

8. A head-up display incorporating a lens as claimed in claim 1.

9. A modified Petzval lens having a focal length F, the lens having a front part comprising a positive component consisting of at least one positive element with a focal length between +1F and +3F and a relatively weak meniscus shape negative element having a focal length at least 2.8 times that of said positive component and which produces overcorrect spherical aberration, the focal length of the front part as a whole being between +1F and +6F and the negative element of the front part not being cemented to any other element, a rear part comprising a positive singlet element with a focal length between +0.4F and +1.2F, and a field flattener behind the rear part and comprising a single negative element with a focal length between -0.4F and -1.1F.

10. A lens as claimed in claim 9 further having a middle part located between the front and rear parts, the middle part comprising a single positive element with a focal length between +1.4F and infinity.

11. A lens as claimed in claim 9 having an air gap of between 0.6F and 1.1F in front of the rear part.

12. A lens as claimed in claim 9 having an equivalent air gap of between 0.01F and 0.5F between the rear part and the field flattener.

13. A lens as claimed in claim 9 in which the positive component of the front part consists of two positive elements.

14. A lens as claimed in claim 13 in which the front positive element in the front part has a focal length between +6F and infinity.

15. A head-up display incorporating a lens as claimed in claim 9.

16. A modified Petzval lens comprising lens elements 1 to 5 having faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, substantially in accordance with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +146.608 1 18.774 1.62040 60.3 -132.244 2.772 -115.569 2 2.903 1.74842 27.8 +744.569 0.138 +117.416 3 13.396 1.68880 49.5 -1530.615 89.823 +38.031 4 11.087 1.74400 44.7 +4964.771 4.404 -140.909 5 1.106 1.70035 30.3 +46.980 ______________________________________

said lens having an effective focal length of 100, aperture of F/1.08 and field of view of 20°

.

17. A modified Petzval lens comprising lens elements 6 to 10, and having a prism 12 with associated lens element 17 interposed between the lens elements 9 and 10, wherein the elements have faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, which substantially accord with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +132.916 6 15.676 1.51650 64.2 +1088.136 16.692 -154.232 7 5.080 1.62096 35.9 -215.741 0.290 +113.331 8 21.191 1.51650 64.2 PLANO 71.847 +50.157 9 13.063 1.71300 53.8 +205.750 2.758 PLANO 12 + 10 29.668 (12 +

     17) (34.835) 1.80518 25.4 +81.543 ______________________________________

said lens having an effective focal length of 100, aperture of F/0.8 and field of view of 20°

.

18. A modified Petzval lens comprising lens elements 18 to 21, and having a prism 22 interposed between the lens elements 20 and 21, wherein the elements have faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, which substantially accord with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +120.567 18 21.885 1.71300 53.8 -1506.931 7.003 -269.096 19 5.107 1.58406 37.0 -865.060 100.672 +47.597 20 21.885 1.74400 44.7 +1714.869 0.730 PLANO 22+21 32.098 1.95250 21.5 +72.951 ______________________________________

said lens having an effective focal length of 100, aperture of F/0.8 and field of view of 20°

.

19. A modified Petzval lens comprising elements 23 to 26 having faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, substantially in accordance with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +150.787 23 8.688 1.62040 60.3 -565.064 12.698 -69.808 24 4.277 1.51742 52.2 -73.358 65.040 +49.807 25 18.045 1.51650 64.2 +320.733 42.481 -38.163 26 1.711 1.74877 27.8 -106.497 ______________________________________

said lens having an effective focal length of 100, aperture of F/1.25 and field of view of 20°

.

20. A modified Petzval lens comprising lens elements 35 to 39 having faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, substantially in accordance with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +443.085 35 7.971 1.63854 55.5 +15816.588 0.145 +105.648 36 16.667 1.71300 53.8 +348.241 15.217 -192.474 37 5.072 1.48749 70.4 -231.826 91.487 +35.450 38 20.290 1.78443 43.9 +115.490 4.007 +94.291 39 1.739 1.74842 27.8 +36.232 ______________________________________

said lens having an effective focal length of 100, aperture of F/0.8 and field of view of 20°

.

21. A modified Petzval lens comprising lens elements 45 to 48 and 51, and having a prism 49 and block 50 interposed between the lens elements 48 and 51, wherein the elements have faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, which substantially accord with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +338.430 45 5.328 1.48749 70.41 +1200.222 0.355 +123.338 46 15.484 1.48749 70.41 -220.187 3.552 -152.639 47 3.374 1.80518 25.43 -253.324 87.036 +64.220 48 19.581 1.71300 53.83 -962.743 7.773 PLANO 49 15.096 1.80518 25.43 PLANO 50 13.155 1.62096 35.90 PLANO 4.700 -71.339 51 1.539 1.80518 25.43 +246.062 ______________________________________

said lens having an effective focal length of 100, aperture of F/1.10 and field of view of 20°

.

22. A modified Petzval lens comprising lens elements 45 to 48 and 51, and having a prism 49 and block 50 interposed between the lens elements 48 and 51, wherein the elements have faces with radii of curvature, axial thicknesses and separations, refractive indices Nd, and Abbe numbers Vd, substantially in accordance with the following table:

space="preserve" listing-type="tabular">______________________________________ REFRAC- AXIAL TIVE ABBE ELE- THICKNESS/ INDEX NUMBER MENT RADIUS SEPARATION Nd Vd ______________________________________ +171.490 45 6.803 1.48749 70.41 +846.481 0.363 +125.746 46 13.606 1.48749 70.41 -301.450 3.628 -201.061 47 3.447 1.80518 25.43 -462.319 87.076 +60.234 48 19.955 1.71300 53.83 -464.676 0.363 PLANO 49 15.420 1.80518 25.43 PLANO 50 6.794 1.62096 36.18 PLANO 7.987 -73.347 51 1.814 1.69895 30.07 +110.728 ______________________________________

said lens having an effective focal length of 100, aperture of F/1.104 and field of view of 25°

.

23. A modified Petzval lens having a focal length F, the lens having a front part comprising at least one positive element with a focal length between +1F and +3F and a negative element of focal length between -1.2F and infinity, and of at least 2.8 times that of the positive component and which produces overcorrect spherical aberration, the focal length of the front part as a whole being between +1F and +6F and the negative element of the front part not being cemented to any other element and having a refractive index less than or equal to 0.13 greater than the refractive index of any positive element of the front part, a rear part comprising a positive singlet element with a focal length between +0.4F and +1.2F, and a field flattener behind the rear part and comprising a single negative element with a focal length between 0.4F and -1.1F.