Optical Sighting Eyebox Adjustment With Dynamic Exit Pupil Alignment
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Solution Overview
Problem
Optical sighting devices, such as rifle scopes and spotting scopes, suffer from small exit pupil sizes, making it difficult for operators to maintain their eyes within the effective eyebox, especially under conditions of physical exertion or stress, leading to vignetting or loss of the observed image due to axial movement of the eye.
Innovation Solution
The solution involves an optical sighting device with a digital signal processor that adjusts the eye relief actuator to translate an aperture stop or control a varifocal lens along the optical axis, aligning the real exit pupil with the user's eye by compensating for axial movement, using a range-finder to measure the distance and an encoder to track the aperture stop's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exit pupil size is kept small to maintain optical performance, then the eyebox becomes difficult to maintain, but maintaining a larger exit pupil would degrade optical performance
Solution Approach 1:
The patent implements dynamic adjustment of the exit pupil position along the optical axis using an eye relief actuator. The system continuously tracks the user's eye position and automatically adjusts the aperture stop or varifocal lens to maintain proper alignment, transforming the static eyebox into a dynamic system that adapts to user movements.
Solution Approach 2:
The system employs a feedback mechanism where a range-finder measures the axial distance to the user's eye, and this information is fed to control circuitry that adjusts the eye relief actuator accordingly. This closed-loop feedback ensures the exit pupil remains aligned with the user's eye despite movements.
2Ease of operation
If the eyebox depth is increased to accommodate axial eye movement, then the apparent field of view must be reduced, but a larger apparent field of view is desired
Solution Approach 1:
Instead of increasing the static eyebox depth, the system dynamically adjusts the exit pupil position along the optical axis in real-time. This allows the system to maintain a large apparent field of view while accommodating axial eye movements through active tracking and adjustment.
Solution Approach 2:
The patent replaces the traditional mechanical approach of increasing eyebox depth with an optical/electronic solution using a range-finder, control circuitry, and variable optical elements (aperture stop or varifocal lens) to achieve the same goal of accommodating eye movement.
3Ease of operation
If manual adjustment of eye relief is provided, then the user must manually align their eye, but automatic alignment would improve ease of operation
Solution Approach 1:
The system performs automatic eye relief adjustment without requiring manual intervention from the user. The range-finder continuously measures eye position, and the control circuitry automatically actuates the eye relief actuator to maintain proper alignment, making the system self-adjusting.
Solution Approach 2:
The automatic adjustment is achieved through a feedback loop where the range-finder provides continuous eye position data to the control circuitry, which then adjusts the aperture stop or varifocal lens position accordingly. This closed-loop control eliminates the need for manual alignment.
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 adjustment maintains visual contact with the viewed image by dynamically aligning the eyebox with the user's eye, preventing vignetting and loss of the field of view even with head movements, without significantly affecting the optics or magnification.
Implementation Method 1
an infrared illuminator positioned to direct infrared electromagnetic radiation onto the eye. The range-finder may be configured to measure the range from the range-finder to the eye based on reflections of the infrared electromagnetic radiation from the eye.
Implementation Method 2
an eyepiece positioned to receive optical radiation along an optical axis and configured to produce a real exit pupil located remote from the eyepiece
Data Source
AI summary
An optical sighting device includes an eyepiece positioned to receive optical radiation along an optical axis to produce a real exit pupil located remote from the eyepiece. The real exit pupil is positioned at an eye relief distance from the eyepiece along the optical axis. A digital signal processor determines an axial distance from the eyepiece to an eye positioned proximate the real exit pupil along the optical axis. An aperture stop is centered along the optical axis to direct the optical radiation in a direction of the eyepiece. The eye relief distance is based at least in part on a position of the aperture stop along the optical axis. The optical sighting device further includes an eye relief actuator to translate the aperture stop along the optical axis to null a spatial offset between the eye relief distance and the axial distance to the eye.