Image Combining Viewer Dichroic Mirror Parallax Reduction
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Solution Overview
Problem
Existing devices for combining visible light images with images from other wavelengths, such as infrared, fail to minimize parallax and image shift effectively, making them unsuitable for use as firearms sights or daytime telescopic sights, and lack resistance to temperature changes and impacts.
Innovation Solution
An image combining viewer with a dichroic fold mirror and objective lens configuration that overlays an image from a non-visible wavelength, like infrared, onto a visible light image, using dichroic coatings to transmit and reflect specific wavelengths, ensuring minimal image shift and alignment errors, and allowing for use with firearms sights without requiring sight adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If visible light images are combined with images from other wavelengths (e.g., infrared), then the viewing capability is enhanced, but parallax and image shift increase making the device unsuitable for firearms sights
Solution Approach 1:
The optical system is divided into separate channels for different wavelengths (visible light and infrared), with dedicated objective lenses and beam splitters for each channel. This segmentation allows independent optimization of each wavelength path while maintaining precise alignment through a common optical axis, resolving the parallax issue by ensuring both images originate from the same optical center.
Solution Approach 2:
A beam splitter acts as an intermediary element that combines the visible light and infrared image paths without introducing significant parallax. The beam splitter is positioned at a specific angle (typically 45 degrees) in the common optical path, allowing both wavelength channels to be merged while maintaining precise registration through careful optical design and alignment.
2Adaptability or versatility
If multiple wavelength images are combined, then scene viewing is improved, but the device becomes sensitive to temperature changes and impacts
Solution Approach 1:
The optical system is designed with a common objective lens and optical path that can handle multiple wavelengths simultaneously. The beam splitter and subsequent optical components are configured to process both visible light and infrared images through the same mechanical structure, ensuring that temperature changes and impacts affect both channels equally, thereby maintaining relative alignment and improving overall reliability.
Solution Approach 2:
The optical components, particularly the objective lenses and beam splitter, are selected and designed with specific thermal expansion coefficients and mechanical properties that minimize sensitivity to temperature changes. The system parameters (focal lengths, spacing, angles) are optimized to maintain alignment stability across a range of temperatures and mechanical conditions.
3Adaptability or versatility
If a beam splitter is used to combine images, then multiple wavelengths can be viewed, but about 70-80% of light is directed away from the image intensifier reducing efficiency
Solution Approach 1:
Instead of using a single beam splitter that divides light between multiple paths, the system creates separate optical copies for different wavelengths. Dedicated objective lenses and beam splitters are provided for each wavelength channel (visible and infrared), allowing each channel to efficiently direct its light to the appropriate detector without significant loss. This copying approach eliminates the need for one beam splitter to handle all wavelengths, thereby improving overall light transmission efficiency.
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 solution provides a stable and accurate overlay of thermal infrared and visible light images, maintaining the original aiming point relationship, and is insensitive to mirror alignment and vibrations, enabling effective use with firearms sights and telescopic sights.
Implementation Method 1
The fold mirror includes a front surface having a dichroic coating applied thereto. This dichroic coating is adapted to transmit visible light, and to reflect a wavelength outside the visible spectrum, for example, infrared or ultraviolet.
Implementation Method 2
An objective lens is provided between the front surface of the mirror and the sensor. The objective lens is optimized for the wavelength reflected by the front surface of the mirror.
Implementation Method 3
A display structured to convert the image received by the sensor into a visible light image is secured within the housing
Data Source
AI summary
An image combining viewer transmits a daylight image directly through the viewer, while reflecting at least one wavelength other than visible light towards a sensor. A display for displaying the image received by the sensor in a visible wavelength is reflected by the back surface of the mirror back along the optical path, combining the displayed image with the daylight image so that they appear to be a single image.