Multiple effective focal length (EFL) optical system

Patent metadata

Field	Value
Publication number	US-12066609-B2
Application number	US-201916454988-A
Country	US
Kind code	B2
Filing date	Jun 27, 2019
Priority date	Jun 27, 2018
Publication date	Aug 20, 2024
Grant date	Aug 20, 2024

Abstract

A multi-band/multi-polarization reflective or catadioptric optical system yields differing effective focal lengths (EFLs) per band/polarization. This approach could be used to create an imaging system, for example. In such case, a sensor (imager, spectrometer, diode, etc.) is located at the one or more focal planes. On the other hand, it could also be used to create a projecting system or hybrid projecting and imaging system by locating an emitter such as an LED, laser, etc.) at the image or focal plane. The system employs polarizers and/or dichroic coatings nano patterns to create different focal lengths and/or fields of view using the same mirrors and/or lenses by, for example, including at least one dichroic coating optically in front of at least one additional mirror to separately reflect the different bands or polarizations.

First claim

What is claimed is:

1. A multi-band telescope optical system, comprising:
a concave primary mirror assembly comprising a primary mirror, a first spacer on the primary mirror, a first dichroic coating on the first spacer, and a second dichroic coating on the first spacer to separately reflect different optical bands to create different focal lengths and/or fields of view for each of the different optical bands;
a curved secondary mirror that reflects light through an aperture in the primary mirror assembly; and
a detector system for separately detecting the different optical bands with different image sensors.

2. The optical system of claim 1 , wherein the optical system has a segmented-circular profile.

3. The optical system of claim 1 , wherein at least one of the spacers includes Zinc Sulfide.

4. The optical system of claim 1 , wherein the spacers have graded thicknesses such that the spacer gets thicker moving radially, with the thicker portions being near an optical axis of the primary mirror assembly.

5. The optical system of claim 1 , wherein the different optical bands include long wave infrared, visible, short wave infrared, and mid-wave infrared and the primary mirror assembly separately reflects each of the long wave infrared, visible, short wave infrared, and mid-wave infrared.

6. The optical system of claim 1 , wherein the primary mirror assembly provides different focal points for the different optical bands.

7. The optical system of claim 1 , wherein the detector system includes a CMOS image sensor, an InGaAs image sensor, and an HgCdTe image sensor.

8. The optical system of claim 1 , wherein the secondary mirror is a secondary mirror assembly that comprises at least one dichroic coating optically in front of at least one additional mirror to separately reflect the different optical bands.

9. The optical system of claim 8 , wherein the dichroic coating of the secondary mirror assembly forms a convex mirror and the additional mirror of the secondary mirror assembly forms a concave mirror.

10. The optical system of claim 8 , further comprising nano-patterns etched into the mirror assemblies.

11. The optical system of claim 1 , wherein the secondary mirror comprises a lens substrate and a dichroic mirror coating on a front surface of the lens substrate for reflecting light of a first spectral band; and a mirror coating on a back surface of the lens substrate.

12. The optical system of claim 11 , wherein the lens substrate is a convexo-concave lens.

13. The optical system of claim 11 , wherein the lens substrate is a biconvex lens.

14. The optical system of claim 11 , wherein the mirror coating is bonded to the lens substrate.

15. The optical system of claim 11 , wherein the mirror coating is deposited to the lens substrate.

16. The optical system of claim 1 , wherein the primary mirror assembly further comprises a second spacer on the second dichroic coating and a third dichroic coating on the second spacer.

17. The optical system of claim 16 , wherein the third dichroic coating reflects long wave infrared but transmits shortwave infrared, mid-wave infrared and visible; the second dichroic coating that reflects mid-wave infrared but transmits shortwave infrared and visible, and the first dichroic coating that reflects shortwave infrared but transmits visible.

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Sinclair Matthew A
• Laine Juha-Pekka

Classifications

• G02B27/142

  Coating structures, e.g. thin films multilayers · CPC title

• G02B27/141

  using dichroic mirrors · CPC title

• G02B17/061

  on-axis systems with at least one of the mirrors having a central aperture · CPC title

• G02B17/0808 Primary

  on-axis systems with at least one of the mirrors having a central aperture · CPC title

• G02B17/0856

  comprising a refractive element with a reflective surface, the reflection taking place inside the element, e.g. Mangin mirrors · CPC title