Cone Aperture Mechanism for Night Vision Goggles Depth of Field
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Solution Overview
Problem
Night vision goggles (NVG) face challenges in maintaining focus when used in environments with short object-to-goggle distances, such as simulators, due to limited depth of field, leading to image defocus with minor head movements, and existing aperture mechanisms reduce the field of view and cause light to illuminate undesirably.
Innovation Solution
An aperture mechanism with a cone-shaped aperture that attaches to the light admitting end of NVG, reducing light admission only through the inner portion of the lens, thereby increasing the depth of field and allowing for brighter images in simulator environments without compromising the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a panel with a small aperture is placed in front of the lens of NVG to filter light and improve focus, then the depth of field is improved, but the field of view is reduced and the image border appears altered and out of focus
Solution Approach 1:
The patent employs a conical aperture structure instead of a flat panel with a small hole. The conical shape allows light to pass through the apex while the sloped surfaces guide light away from the lens perimeter, maintaining a wide field of view while achieving deep focus. This geometric curvature resolves the contradiction by preserving both depth of field and field of view simultaneously.
Solution Approach 2:
The invention transitions from a two-dimensional flat aperture panel to a three-dimensional conical structure. This dimensional change allows the aperture to control light paths more effectively, enabling light to be directed precisely through the cone's apex while maintaining broad angular coverage, thus improving depth of field without sacrificing field of view.
2Measurement precision
If a panel aperture is displaced from the lens of the NVG to improve focus, then the depth of field is improved, but light is able to illuminate the panel undesirably, worsening the image quality
Solution Approach 1:
The conical geometry inherently directs light away from the panel surfaces through its sloped walls. Light passing through the cone's apex is guided along the conical surface and exits through the opening without illuminating the panel's outer surfaces, eliminating the harmful light reflection problem while maintaining focus improvement.
Solution Approach 2:
The conical structure converts the potential harmful light reflection off the panel into a beneficial light-guiding mechanism. The same conical surfaces that prevent undesirable illumination also serve to direct light efficiently through the aperture, transforming a problematic geometric feature into a solution for both focus and light control.
3Measurement precision
If the aperture mechanism is designed to block light from the outer extremity of the lens, then the depth of field is increased, but the amount of light admitted to the lens is reduced
Solution Approach 1:
The conical aperture structure selectively blocks only the peripheral light rays while allowing central light paths to pass through unobstructed. The geometry is designed so that the cone's walls intercept and redirect only the outer extremity light, preserving the majority of light intake while achieving the desired depth of field extension.
Solution Approach 2:
The aperture mechanism applies different light transmission characteristics to different regions of the lens. The conical structure creates localized light blocking only at the periphery while maintaining open transmission paths through the center, achieving selective light control that improves depth of field without significantly reducing overall light admission.
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 aperture mechanism doubles the focus range of NVG for short object-to-goggle distances, enabling clear images across a wider range of viewing positions without focus degradation and improving edge blending in multi-projector simulator systems by controlling light admission effectively.
Implementation Method 1
A cone portion opposite the lens engaging portion is preferably in contact with the light admitting part of the NVG and forms a cone shaped aperture for admitting light
Implementation Method 2
The recession extends from the back end of the aperture mechanism toward the front end and has a diameter which is less than the outer diameter of the aperture mechanism at the back end. This can provide a wall, the inner surface of which is a friction fit surface for engaging an outer surface of the end of the NVG
Data Source
AI summary
An aperture mechanism for night vision goggles (NVG) has a first end, a second end, a lens engaging portion, and a cone portion. A lens engaging portion has a recession allowing attachment of the aperture mechanism to a light admitting end of the NVG. A cone portion is opposite the lens engaging portion. Together the lens engaging portion and the cone portion form an aperture. The aperture mechanism increases the depth of field of the NVG for applications involving small object-to-goggle distances, such as in simulators or simulator environments. In a simulator system, the aperture mechanism can be attached to NVG such that at least a portion of light from a display screen is blocked. The light output of the display screen can be increased such that the depth of field remains higher but the image produced does not become darker.