Spherical Mirror Projector for Wide-Field Camera Calibration
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Solution Overview
Problem
Current image scene generators and projectors are limited in producing ultra-wide field-of-view images, restricting the simultaneous testing and calibration of multiple camera systems with wide field coverage, such as those used in aircraft payloads with multiple visible and infrared cameras.
Innovation Solution
An image generator and projector system utilizing a convex spherical object surface with perforations and a large concave spherical mirror to create a collimated, wide-field test image that can be viewed by multiple cameras, providing a 76° field-of-view or more, with a corrector plate to correct spherical aberrations and maintain high resolution across the entire field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional image scene generator is used, then the device structure is simple, but the field-of-view is narrow and cannot accommodate multiple cameras simultaneously
Solution Approach 1:
The patent employs a spherical mirror with radius of curvature R to create a compact optical system that provides ultra-wide field coverage. The spherical geometry allows light rays from all directions within the field to reflect to the focal point, enabling simultaneous imaging by multiple cameras with different orientations without requiring a large linear footprint.
Solution Approach 2:
The patent places multiple cameras with different fields of view and orientations within a single turret, nesting them in a compact arrangement. The spherical mirror system is integrated into this nested structure, allowing all cameras to share a common optical source and testing environment while maintaining their individual viewing directions.
2Manufacturing precision
If the spherical mirror is placed close to the cameras to reduce system size, then the device complexity is reduced, but spherical aberration increases and degrades image quality
Solution Approach 1:
The patent introduces a corrector plate positioned between the spherical mirror and the cameras as an intermediary optical element. This corrector plate specifically addresses spherical aberration by modifying the wavefront of reflected light, thereby improving image quality without requiring the cameras to be placed at a distance that would increase system size.
Solution Approach 2:
The patent carefully selects and adjusts the radius of curvature R of the spherical mirror to optimize the balance between system compactness and image quality. By controlling the mirror's curvature parameter and its distance from the cameras, the system achieves ultra-wide field coverage while minimizing spherical aberration effects.
3Measurement precision
If the field-of-view is expanded to cover 50-80 degrees, then multiple cameras can be tested simultaneously, but the resolution and aperture are limited
Solution Approach 1:
The spherical mirror's curved surface is specifically designed to maintain consistent aperture size across the entire ultra-wide field of view. The geometry of the sphere ensures that the effective aperture remains constant from the center to the edges of the field, thereby maintaining high resolution imaging capability for all cameras regardless of their orientation within the 50-80 degree coverage range.
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
Enables simultaneous end-to-end testing and calibration of multiple camera systems with wide field coverage, ensuring that all cameras in the array receive a clear, collimated image, effectively addressing the limitations of existing technologies by providing a robust and efficient method for qualifying and calibrating imaging systems with ultra-wide fields of view.
Implementation Method 1
a spherical mirror having a concave side facing the aperture stop... Illumination of the object generates the target image, which is then reflected from the spherical mirror toward the aperture stop
Implementation Method 2
with a corrector plate to correct spherical aberrations and maintain high resolution across the entire field
Data Source
AI summary
A generator and projector system for providing a test target for testing sensing apparatus includes an aperture stop located adjacent to the sensing apparatus. Also included are a spherical mirror having a concave side facing the aperture stop and an object disposed between the spherical mirror and the aperture stop. The object includes various test targets for testing the sensing apparatus. A longitudinal optical axis passes through the aperture stop, the spherical mirror and the object. Illumination of the object generates the test target, which is then reflected from the spherical mirror toward the aperture stop, for testing the sensing apparatus.