Electro-Optical System Conformal Window Wavefront Correction
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Solution Overview
Problem
Conformal environmental windows in electro-optical systems often compromise on semi-diameter due to aerodynamic requirements, making it difficult to incorporate a steering mechanism and resulting in non-uniform wavefront error correction across the field of regard.
Innovation Solution
Designing the surface geometry of the environmental window and optical corrector using matched surface sagitta equations, including a base biconic equation and optional aspheric or freeform terms, to achieve uniform wavefront error and magnification across the field of regard.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a planer or spherical dome environmental window is used, then uniform light refraction and minimal aberrations are achieved, but aerodynamic performance deteriorates at high speeds
Solution Approach 1:
The environmental window employs different surface geometries in different regions: the external surface has an ogive shape for aerodynamic performance, while the internal surface maintains optical quality with appropriate curvature. This local differentiation allows each surface to fulfill its specific function without compromising the other.
Solution Approach 2:
A corrector plate is introduced as an intermediary optical element between the environmental window and the sensor. This corrector plate compensates for the aberrations introduced by the non-ideal ogive-shaped window, mediating between the aerodynamic requirement and the optical performance requirement.
2Object-affected harmful factors
If the semi-diameter of the environmental window is reduced to achieve desired fineness ratio, then aerodynamic performance is improved, but the ability to incorporate a steering mechanism deteriorates
Solution Approach 1:
The steering mechanism is relocated from the traditional position within the environmental window to a position behind the corrector plate. This dimensional relocation allows the steering mechanism to operate in a different spatial plane where it is not constrained by the reduced window semi-diameter, thereby maintaining full steering capability while preserving aerodynamic performance.
3Object-affected harmful factors
If a conformal environmental window with non-ideal geometry is used, then aerodynamic performance is improved, but wavefront error correction uniformity deteriorates
Solution Approach 1:
The corrector plate serves as an intermediary optical element that compensates for the non-uniform wavefront errors introduced by the ogive-shaped environmental window. By positioning the corrector plate at an optimized location, it can effectively correct aberrations across the entire field of regard, restoring wavefront error uniformity despite the conformal window geometry.
4Adaptability or versatility
If the line of sight of the sensor is moved to allow sensing over a wider field of regard, then versatility is improved, but image quality deteriorates due to increased aberrations
Solution Approach 1:
The corrector plate acts as a mediator that maintains image quality across the extended field of regard. As the sensor steers to different angles, the corrector plate compensates for the increased aberrations that would otherwise degrade image quality, thereby enabling wide field of regard operation while maintaining consistent image quality throughout the entire field.
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
This approach allows for improved aerodynamic properties, easier manufacturing and measurement, and uniform wavefront error correction, enabling a wider field of regard while maintaining aerodynamic performance.
Implementation Method 1
it is refracted uniformly to minimise aberrations such as coma and astigmatism
Implementation Method 2
correct for the aberrations created as a result of the non-ideal optical geometry of the environmental window
Data Source
AI summary
Many electro-optical systems include an environmental window that shield the sensor and optical train from environmental conditions. Where the electro-optical system is mounted on a high speed platform it can be necessary to shape the window away from the ideal optical shape of a hemisphere to one that is more aerodynamic. The optical train can include corrector elements to correct aberrations resulting from the non-ideal shape of the window. The exterior surface is configured to a specific biconic equation and that specified biconic equation is used to define the surfaces of the corrector element(s) of the optical train. This provides a more uniform wavefront error and magnification across the field of regard.