On-axis four mirror anastigmat telescope stray light suppression
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Solution Overview
Problem
On-axis reflective anastigmatic telescopes face significant stray light issues and high polarization sensitivity, which are not effectively addressed by existing designs, particularly in applications requiring tight packaging and high-performance infrared imaging.
Innovation Solution
An on-axis four mirror anastigmat telescope design with a mirror assembly featuring coaxial reflective surfaces, a field stop integrated into the first reflective surface, and an entrance pupil at the conjugate image of the aperture stop, which includes a Lyot stop to enhance stray light suppression and reduce polarization sensitivity, while the central obscuration of the tertiary mirror prevents the detector from seeing the obscuration of the secondary mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an on-axis reflective anastigmatic telescope design is used, then the telescope can be packaged within a tight cylindrical volume, but significant stray light issues arise
Solution Approach 1:
The optical path is segmented into four separate reflective surfaces arranged in sequence along the optical axis. This segmentation allows for controlled light reflection at each surface, enabling the use of light-blocking structures between surfaces to suppress stray light while maintaining the compact on-axis geometry.
Solution Approach 2:
Light-blocking structures are introduced as intermediary elements between the reflective surfaces to intercept and block stray light before it reaches the detector. These intermediaries suppress harmful stray light paths without interfering with the main optical path, resolving the contradiction between compact on-axis design and stray light suppression.
2Object-affected harmful factors
If an off-axis reflective anastigmat telescope design is used, then stray light issues are minimized, but the telescope does not fit well within a tight cylindrical volume
Solution Approach 1:
Instead of using off-axis geometry to suppress stray light, this invention inverts the approach by using on-axis geometry with intentionally introduced light-blocking structures. The stray light suppression is achieved not by geometric offset but by deliberate blocking at strategic locations within the on-axis path.
3Object-affected harmful factors
If an off-axis telescope design is used, then stray light is reduced, but polarization sensitivity increases
Solution Approach 1:
Rather than using off-axis geometry to reduce stray light, this invention employs on-axis geometry with light-blocking structures to achieve stray light suppression. This approach maintains lower polarization sensitivity compared to off-axis designs, as the on-axis reflective surfaces introduce less polarization-dependent phase shifts.
4Volume of moving object
If existing on-axis reflective anastigmatic telescope designs are used, then the telescope fits within tight packaging, but stray light suppression is insufficient
Solution Approach 1:
The optical system is divided into four distinct reflective surfaces with light-blocking structures positioned between them. This segmentation creates multiple opportunities to intercept stray light while maintaining the compact on-axis configuration, significantly improving stray light suppression compared to existing designs.
Solution Approach 2:
Light-blocking structures are strategically positioned as intermediaries between the four reflective surfaces to intercept stray light paths. These structures block stray light without interfering with the main optical path, achieving superior stray light suppression while maintaining compact packaging.
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 superior stray light suppression and low polarization sensitivity, making it suitable for applications with tight packaging constraints, such as missile seekers or endoscopes, while maintaining high imaging performance and fitting within a cylindrical volume.
Implementation Method 1
The mirror assembly is configured to receive light from the image on a common axis and to reflect the light successively by the four coaxial reflective surfaces
Data Source
AI summary
An on-axis four mirror anastigmat telescope includes an entrance pupil configured to receive light from an image, and a mirror assembly. The mirror assembly has a first reflective surface having a central aperture formed therein, a second reflective surface, a third reflective surface having a central aperture formed therein, a fourth reflective surface, and an aperture stop. The mirror assembly is configured to receive light from the image on a common axis and to reflect the light successively by the four coaxial reflective surfaces through the aperture stop. The telescope further comprises a detector configured to receive light from the mirror assembly. The central aperture formed in the first reflective surface defines a field stop to limit the field of view.