Lens system for panoramic imagery

• US 4,395,093 A
• Filed: 05/21/1981
• Issued: 07/26/1983
• Est. Priority Date: 05/21/1981
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Dykes, Wiley V., Rosendahl, Gottfried R.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Dzierzynski, Paul M.
• Application Number:
  US06/265,874
• Time in Patent Office: 796 Days
• Field of Search: 350/441
• US Class Current: 359/725
• CPC Class Codes: G02B 13/06 Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces

Abstract

An optical system for 360° image transfer in which spaced primary secondary hyperbolically surfaced mirrors are combined with a refractive lens system and are held in spaced relation by a transparent envelope having inner and outer surfaces generated from the near focal point of the primary mirror to avoid image impairing aberrations, and in which the mirrors are so spaced and concentrically arranged that the entrance pupil of the lens system coincides with the near focal point of the primary mirror, which is centrally apertured to form an aperture diaphragm, and the near focal point of the secondary mirror approximates the apex of the primary mirror, the far focal points of the mirrors coinciding to form a confocal set of mirrors. The refractive lens system, in turn, consists of four lens groups, the first lens group of which bends chief rays of image forming light approximately parallel to an optical axis and corrects for field curvature, the second lens group of which corrects for primary and secondary color, the third lens group of which bends the chief rays towards an image plane and provides additional field curvature and secondary color correction, and the fourth lens group of which provides additional secondary color correction and renders the chief rays incident upon the image plane at an angle of approximately 90°.

Claims

1. An optical system for 360°

annular image transfer having mirror means positioned upon a predetermined optical axis so as to form an entrance pupil for said optical system adapted for passing therethrough chief rays and marginal rays of image forming light, and thereby reduce the vertical field angles of said chief rays and marginal rays of image forming light to a predetermined magnitude wherein the improvement comprises, in combination;

first lens means spatially disposed downstream from said mirror means on said optical axis for providing a positive power to correct for negative field curvature caused by said mirror means, and for bending the marginal rays of image forming light toward said optical axis and into a position approximately parallel to said optical axis, said first lens means having first and second negative lenses spatially disposed downstream from said mirror means on said optical axis, each negative lens of which has a low refractive index, and each negative lens of which is spaced for air cooling so as to prevent heat damage, and first, second, third and fourth positive lenses spatially disposed downstream from said second negative lens on said optical axis, each positive lens of which has a high refractive index, and each positive lens of which is spaced for air cooling so as to prevent heat damage;

second lens means spatially disposed downstream from said first lens means on said optical axis and having an overall power of zero for providing primary and secondary color correction;

third lens means spatially disposed downstream from said second lens means on said optical axis for bending the marginal rays of image forming light from the aforesaid position approximately parallel to said optical axis toward a predetermined image plane, and for providing additional field curvature correction and secondary color correction; and

fourth lens means spatially disposed downstream from said third lens means on said optical axis for adding a positive Petzval curvature such that an image may be formed at said image plane, for bringing the chief rays of image forming light incident upon said image plane at a predetermined angle, and for providing additional field curvature correction and secondary color correction.

2. The optical system of claim 1, wherein said first and second negative lenses are fabricated from silica, and said first, second, third, and fourth positive lenses are fabricated respectively from Schott SK5, Schott SK16, Schott LAK8, and Schott SK51.

3. The optical system of claim 1, wherein said second lens means comprises:

a first lens pair spatially disposed downstream from said first lens means on said optical path providing primary color correction;

a second and a third lens pair spatially disposed downstream from said first lens pair on said optical path providing primary and secondary color correction;

the first lens and the second lens of said first lens pair respectively being a negative lens and a positive lens of approximately equivalent refractive index;

the first lens and the second lens of said second lens pair respectively being a negative lens and a positive lens of approximately equivalent refractive index; and

the first lens and the second lens of said third lens pair respectively being a negative lens and a positive lens of approximately equivalent refractive index.

6. The optical system of claim 1, wherein said fourth lens means comprises:

first and second positive lenses spatially disposed downstream from said third lens means on said optical axis;

a first negative lens spatially disposed downstream from said second positive lens on said optical axis;

second and third negative lenses spatially disposed downstream from said first negative lens adapted for providing strong field curvature correction, and secondary color correction;

a third positive lens spatially disposed downstream from said third negative lens on said optical axis adapted for bringing the chief rays of image forming light incident upon said image plane at said predetermined angle; and

said first and second positive lenses and said first negative lens adapted for providing additional field curvature correction.

7. The optical system of claim 6, wherein each positive and negative lens of said fourth lens means is fabricated from a glass which is highly resistant to thermal shock.

4. An optical system for 360°

annular image transfer having mirror means positioned upon a predetermined optical axis so as to form an entrance pupil for said optical system adapted for passing therethrough chief rays and marginal rays of image forming light, and thereby reduce the vertical field angles of said chief rays and marginal rays of image forming light to a predetermined magnitude, wherein the improvement comprises in combination;

first lens means spatially disposed downstream from said mirror means on said optical axis for providing a positive power to correct for negative field curvature caused by said mirror means, and for bending the marginal rays of image forming light toward said optical axis and into a position approximately parallel to said optical axis;

second lens means spatially disposed downstream from said optical axis and having an overall power of zero for providing primary and secondary color correction;

third lens means spatially disposed downstream from said second lens on said optical axis for bending the marginal rays of said image forming light from the aforesaid position to approximately parallel to said optical axis toward a predetermined image plane, and for providing additional field curvature correction and secondary color correction, said third lens means having first and second positive lenses spatially disposed downstream from said second lens means on said optical axis, and a negative lens positioned between said first and second positive lenses on said optical path; and

fourth lens means spatially disposed downstream from said third lens means on said optical axis for adding a positive Petzval curvature such that an image may be formed at said image plane for bringing the chief rays of image forming light incident upon said image plane at a predetermined angle, and for providing additional field curvature correction and secondary color correction.

5. The optical system of claim 4, wherein each positive and negative lens of said third lens means is fabricated from a glass which is highly resistant to thermal shock.