Multi-Reflection Telescope Layout for Wide Field in Compact Volume

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Solution Overview

Problem

Existing compact long focal length telescopes face challenges in achieving a wide field of view and reduced volume without increasing sensitivity to positioning errors and chromatic aberration, particularly in Cassegrain and Korsch-type designs.

Innovation Solution

A telescope design utilizing coincident optical axes for two mirrors (concave and convex) with double or triple reflections, eliminating intermediate images and incorporating a plane mirror to direct light to the focal plane, reducing sensitivity to positioning errors and eliminating the rear cavity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the distance between M1 and M2 is reduced to achieve a more compact telescope, then the volume is reduced, but the sensitivity to positioning errors (particularly longitudinal position error of mirror M2) increases significantly

Engineering Contradiction:
Improvetelescope volumeVSAvoidsensitivity to positioning errors
Core Design Contradiction:
Volume of moving objectVSManufacturing precision

Solution Approach 1:

The optical path is segmented into multiple reflections (double or triple reflections between M1 and M2) instead of a single pass. This segmentation allows the light to traverse the optical path multiple times within the same physical space, effectively reducing the sensitivity to positioning errors while maintaining a compact volume. The multiple reflections create virtual images that compensate for the reduced physical distance between mirrors.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The telescope design nests the focal plane within the space between the two mirrors by using double or triple reflections. The focal plane is positioned in a location that would normally be occupied by the long focal length requirement, but the multiple reflections fold the optical path back on itself, nesting the effective optical path length within the compact physical volume between M1 and M2.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Volume of moving object

If Cassegrain-type telescope design is used to achieve compact volume, then the volume is reduced, but the field of view is limited

Engineering Contradiction:
Improvetelescope volumeVSAvoidfield of view
Core Design Contradiction:
Volume of moving objectVSArea of stationary object

Solution Approach 1:

The patent employs dynamic optimization of the mirror curvatures and distances to achieve a balance between compact volume and wide field of view. By carefully selecting the radii of curvature and the distance between mirrors for double or triple reflection configurations, the design dynamically adapts the optical path to cover a wide angular field while maintaining a compact physical footprint, overcoming the static limitations of traditional Cassegrain designs.

Inventive Principle:
Principle #15Dynamics

3Area of stationary object

If Korsch-type telescope design is used to achieve linear fields of view up to 2 or 3°, then the field of view is improved, but the overall volume increases due to the additional mirror in the rear cavity

Engineering Contradiction:
Improvefield of viewVSAvoidtelescope volume
Core Design Contradiction:
Area of stationary objectVSVolume of moving object

Solution Approach 1:

The patent extracts and eliminates the rear cavity mirror (M3) from the traditional Korsch-type telescope design. By using double or triple reflections between only two mirrors (M1 and M2), the design achieves similar or improved field of view performance without requiring the additional mirror and its associated rear cavity space, thereby significantly reducing the overall telescope volume while maintaining wide field capabilities.

Inventive Principle:
Principle #2Taking out (Extraction)

4Area of stationary object

If double or triple reflection is used between two mirrors, then the field of view is increased to greater than 30°, but the device complexity increases

Engineering Contradiction:
Improvefield of viewVSAvoidoptical path complexity
Core Design Contradiction:
Area of stationary objectVSDevice complexity

Solution Approach 1:

The two mirrors (M1 and M2) are designed to serve multiple functions simultaneously: they act as both the primary collecting mirrors and the focusing elements for multiple reflection passes. The same pair of mirrors handles all double or triple reflections, eliminating the need for separate auxiliary mirrors or complex optical components, thereby achieving wide field of view with relatively simple device architecture.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 design achieves a field of view greater than 30° with reduced volume and sensitivity to manufacturing precision, maintaining image quality and stability, while eliminating chromatic aberration and rear cavity volume.

Implementation Method 1

the first mirror is suitable for collecting an incident light beam and reflecting it towards the second mirror, to obtain a first reflected beam

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 2

the second mirror is suitable for reflecting the first reflected beam towards the first mirror, to obtain a second reflected beam

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 3

the plane mirror is suitable for modifying the axis of reflection of the last beam so that the last beam reaches the focal plane

Methodology Applied
Scientific EffectReflection: Reflection

Data Source

PatentEP4685541A1Telescope
Publication Date: 2026.01.28 THALES SA
  • EP4685541A1 patent drawingFigure 1
  • EP4685541A1 patent drawingFigure 2
  • EP4685541A1 patent drawingFigure 3

AI summary

The present invention relates to a telescope (10) comprising: - a first concave mirror (M1), - a second convex mirror (M2), - a focal plane (PF), the first mirror (M1) and the second mirror (M2) being arranged so that: - the optical axes of the first mirror (M1) and the second mirror (M2) are coincident, - each of the first mirror (M1) and the second mirror (M2) is used at least in double reflection, - no intermediate image is formed between the first mirror (M1) and the second mirror (M2).