Five-Mirror Afocal Optical System for Wide Field of View

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Solution Overview

Problem

Conventional afocal optical systems, such as three and four mirror anastigmat designs, are limited in their usable field of view and image quality, with most four mirror designs being excessively large and performance metrics like distortion and pupil aberrations restricting their usefulness to about 5-6 degrees circular field of view.

Innovation Solution

A five mirror afocal optical system with a balanced distribution of three positive-powered and two negative-powered mirrors, arranged to achieve a flat field condition and a collimated output beam, providing a wider field of view exceeding 5 degrees, superior image quality, and a more compact size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional three mirror anastigmat design is used, then the system achieves high magnification (>10X), but the usable field of view is limited to about 1.0 - 1.5 degrees

Engineering Contradiction:
ImprovemagnificationVSAvoidfield of view
Core Design Contradiction:
ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent divides the optical system into five separate mirror elements rather than using three mirrors, allowing each mirror to contribute to both magnification and field of view correction independently. This segmentation enables the system to achieve high magnification while simultaneously expanding the usable field of view to 5-10 degrees.

Inventive Principle:
Principle #1Segmentation

2Adaptability or versatility

If conventional four mirror anastigmat design is used, then the field of view is improved to about 5 - 6 degrees, but the system becomes excessively large in size

Engineering Contradiction:
Improvefield of viewVSAvoidsystem size
Core Design Contradiction:
Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent employs dynamic optimization of the five-mirror configuration, where the spacing and positioning of mirrors are carefully adjusted to achieve compact form factor. The system maintains 5-10 degree field of view while reducing overall system volume by optimizing the dynamic arrangement of optical elements rather than using fixed conventional configurations.

Inventive Principle:
Principle #15Dynamics

3Adaptability or versatility

If conventional four mirror anastigmat design is used, then the field of view is extended, but performance metrics such as image quality, distortion, and pupil aberrations deteriorate

Engineering Contradiction:
Improvefield of viewVSAvoidimage quality
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality optimization by assigning specific optical power distributions to individual mirrors within the five-element system. Each mirror is designed with tailored surface figures and optical powers to correct specific aberrations in different regions of the field, thereby maintaining superior image quality across the extended 5-10 degree field of view.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The system achieves improved image quality by carefully controlling and optimizing multiple parameters including mirror spacing, surface curvatures, and optical powers. The five-mirror configuration allows for greater parameter freedom to balance and correct various aberrations while maintaining high image quality across the extended field of view.

Inventive Principle:
Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The five mirror afocal optical system achieves a circular field of view of 6-10 degrees, improved image quality, and reduced physical size compared to conventional designs, while maintaining superior performance metrics like field distortion and pupil aberrations.

Implementation Method 1

five mirrors arranged to sequentially reflect from one another electromagnetic radiation received via a system entrance pupil to produce a collimated output beam of the electromagnetic radiation at a system exit pupil

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 2

optical powers of the five mirrors are balanced to achieve a flat field condition at the system exit pupil

Methodology Applied
Scientific EffectOptical power balancing:

Data Source

PatentEP3356874B1Five-mirror afocal wide field of view optical system
Publication Date: 2019.11.20 RAYTHEON CO
  • EP3356874B1 patent drawingFigure 1
  • EP3356874B1 patent drawingFigure 2
  • EP3356874B1 patent drawingFigure 3A

AI summary

A five-mirror all-reflective afocal anastigmat. I n one example, a five mirror afocal anastigmat includes five mirrors arranged to sequentially reflect from one another electromagnetic radiation received via a system entrance pupil to produce a collimated output beam of the electromagnetic radiation at a system exit pupil, the five mirrors consisting of three positive-powered mirrors and two negative-powered mirrors, wherein optical powers of the five mirrors are balanced to achieve a flat field condition at the system exit pupil.