Three field of view refractive afocal telescope

• US 5,229,880 A
• Filed: 03/09/1992
• Issued: 07/20/1993
• Est. Priority Date: 03/09/1992
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Cook, Lacy G., Spencer, Harvey M.
• Primary Examiner(s): Lerner, Martin
• Application Number:
  US07/848,632
• Time in Patent Office: 498 Days
• Field of Search: 359/350, 359/351, 359/353, 359/354, 359/355, 359/356, 359/357, 359/566, 359/672, 359/674
• US Class Current: 359/353
• CPC Class Codes: G02B 15/02 by changing, adding, or subtracting a part of the objective, e.g. convertible objective
• CPC Class Codes: G02B 17/02 Catoptric systems, e.g. image erecting and reversing system
• CPC Class Codes: G02B 23/12 with means for image conversion or intensification
• CPC Class Codes: G02B 27/0037 with diffracting elements G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence
• CPC Class Codes: G02B 27/4277 being separated by an air space
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08
• CPC Class Codes: G02B 5/1895 such optical elements having dioptric power

Abstract

An infrared refractive reimaging afocal telescope (10) has an objective lens group (12), an eyepiece lens group (14), and a switching lens group (16). The system (10) provides a plurality of magnification modes in a compact arrangement. The system (10) utilizes lenses (40, 42, 44, 46) with diffractive surfaces to provide for magnification changes and chromatic aberration correction. The system provides for excellent image quality in all modes using a minimum number of lens elements.

Claims

1. An infrared refractive reimaging afocal telescope comprising:

an objective lens group for receiving and focusing collimated radiation of a viewed object;

an eyepiece lens group receiving radiation from said objective lens group said eyepiece lens group recollimating and forming an exit pupil;

said objective lens group and said eyepiece lens group providing a first magnification and field of view; and

a switch lens group selectively positioned with respect to said objective lens group to receive and transmit said radiation for changing magnification of the telescope and providing two additional fields of view, and at least one optical element of said switch lens group having an optical diffractive surface for correcting chromatic aberration.

2. The telescope according to claim 1 wherein at least one lens in said eyepiece lens group includes a diffractive surface for correcting chromatic aberration.

3. The telescope according to claim 1 wherein said switch lens group includes four lenses grouped in first and second pairs with the first pair of said lenses positionable between said objective lens group and said eyepiece lens group to provide a second magnification and field of view and the second pair of lenses positionable between said objective lens group and said eyepiece lens group to provide a third magnification and field of view.

4. The telescope according to claim 3 wherein said first pair of lenses has one diffractive surface and said second pair of lenses has two diffractive surfaces.

5. An infrared refractive reimaging afocal telescope comprising:

a pair of objective lenses for receiving and focusing collimated radiation in the thermal infrared band of a viewed object;

switching lens group positioned between said pair of objective lenses to selectively receive and transmit radiation from one of said objective lenses for changing magnification of the telescope and providing three fields of view, at least one lens of said switch lens group having a diffractive surface for correcting chromatic aberration; and

an eyepiece lens pair receiving energy from said objective lens pair recollimating the radiation and forming an exit pupil, and one of said eyepiece lenses including a diffractive surface for correcting chromatic aberration.

6. The telescope according to claim 5 wherein said switch lens group includes four lenses grouped in pairs with a first pair of said lenses positioned to receive and transmit radiation to provide a desired magnification and field of view and a second pair of lenses positioned to receive and transmit radiation to provide another desired magnification and field of view.

7. The telescope according to claim 6 wherein said first pair of lenses has one diffractive surface and said second pair of lenses has two diffractive surfaces.

8. The telescope according to claim 5 further comprising a plurality of fold mirrors for compacting the telescope.

9. An infrared refractive reimaging afocal telescope comprising:

an objective lens group for receiving and focusing collimated radiation of a viewed object;

an eyepiece lens group receiving radiation from said objective lens group said eyepiece lens group recollimating and forming an exit pupil;

said objective lens group and said eyepiece lens group providing a first magnification and field of view; and

a switch lens group selectively positioned with respect to said objective lens group to receive and transmit said radiation for changing magnification of the telescope and providing two additional fields of view.