Planar Diffractive Lens for Night Vision Overlay Display
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Solution Overview
Problem
Legacy analog night vision systems face challenges in integrating an overlay display due to the curved exit surface of the intensifier module, which complicates the addition of optical elements and affects the focus of both the intensified and display images, leading to design and compatibility issues.
Innovation Solution
The integration of a planar, diffractive lens within the intensifier module that induces a phase curvature matching the curved exit surface, allowing for a flat overlay display and ensuring both intensified and display light are in focus, along with the use of refractive lenses to correct phase curvature if necessary, maintaining compatibility with legacy systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a curved exit surface is used in the intensifier module, then the number of lens elements in the eyepiece is reduced, but the overlay display cannot be fabricated on the curved surface
Solution Approach 1:
A planar lens is introduced as an intermediary optical element between the flat overlay display and the curved exit surface. This planar lens serves as a mediator that converts the flat wavefront from the display into a curved wavefront that matches the curved exit surface, enabling both the flat display fabrication and the curved surface optical path to coexist without direct contact between the display and curved surface.
2Ease of manufacture
If additional optical elements are introduced to enable flat overlay display fabrication, then the overlay display can be fabricated on a flat surface, but the space allotted for the intensifier module is exceeded
Solution Approach 1:
The planar lens is implemented as a thin optical element with minimal thickness, allowing it to be integrated into the intensifier module without significantly increasing its volume. The thin-film nature of the planar lens enables it to fit within the constrained space while still providing the necessary wavefront transformation function.
3Volume of moving object
If the intensifier module is shortened to accommodate additional optical elements, then the space constraint is satisfied, but the optical path length is reduced affecting image quality
Solution Approach 1:
The planar lens is designed with specific optical parameters (refractive index, curvature radius, thickness) that are optimized to provide the necessary wavefront transformation within a compact form factor. By carefully selecting and adjusting these parameters, the lens achieves the required optical function while maintaining a minimal thickness that fits within the shortened intensifier module dimensions.
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 configuration allows for a compact, lightweight, and efficient integration of an overlay display in night vision systems, reducing neck strain and maintaining backwards compatibility by ensuring both intensified and display images are in focus, while minimizing space and mass within the intensifier module.
Implementation Method 1
a planar lens (e.g., a diffractive planar lens) that induces a phase curvature on the display light and that induces a same phase curvature on the direct-view light as on the display light
Implementation Method 2
transmitting the display light and the intensified light with the third phase curvature to an eye piece comprising lenses
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A~2B
AI summary
An apparatus and method are provided for a night vision system including a transparent overlay display that transmit direct-view light representing an intensified image and emits display light representing a display image. The night vision system includes an intensifier with a flat exit face, an overlay display that is flat/planar, and planar, diffractive lens. The direct-view light and the display light exit the overlay display with the same phase curvature (e.g., a flat phase curvature). The planar, diffractive lens induces a spherical phase curvature on the light exiting the overlay display. The phase curvature induced by the planar, diffractive lens matches the phase curvature of a legacy intensifier in which the final element is fiberoptic inverting element with a curved exit face. Accordingly, the combination of the intensifier, overlay display, and planar, diffractive lens can replace the legacy intensifier while maintaining the design specifications of the night vision system.