Diffractive Element with Lenticules for Enlarged Exit Pupil
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Solution Overview
Problem
Conventional optical instruments have a fixed and relatively small exit pupil size, requiring precise alignment of the observer's eye, and often include expensive field lens arrangements that can be cumbersome and costly.
Innovation Solution
The use of a diffractive element with an array of lenticules at an intermediate image plane, configured radially outwardly to produce a single, enlarged exit pupil through diffractive interference, eliminating the need for a field lens arrangement and allowing light to be relayed to a common region on a viewing plane without additional lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional optical system is used, then the exit pupil size is determined by numerical aperture and magnification, but the exit pupil remains small and requires precise alignment
Solution Approach 1:
The diffractive element divides the single exit pupil into an array of multiple exit pupils through the array of lenticules. Each lenticule generates one exit pupil, and the collective array appears as a single enlarged exit pupil to the observer, effectively increasing the usable area without requiring precise alignment
Solution Approach 2:
The invention transforms the exit pupil from a two-dimensional aperture into a three-dimensional array of pupils at different lateral positions. The lenticules are arranged in a radial pattern outward from the optical axis, creating exit pupils distributed across a larger area that the observer can access from multiple positions
2Area of stationary object
If field lens arrangement is added to enlarge exit pupil, then exit pupil size increases, but device complexity and cost increase
Solution Approach 1:
The invention replaces the mechanical field lens arrangement with a diffractive optical element. Instead of using additional refractive lens components to relay and enlarge the exit pupil, a single diffractive element with an array of lenticules performs the pupil enlargement function through diffractive interference, simplifying the optical system
Solution Approach 2:
The diffractive element serves multiple functions: it creates the array of exit pupils, relays light to a common region on the viewing plane, and eliminates the need for separate field lens components. This multi-functionality reduces overall device complexity while achieving the desired pupil enlargement
3Ease of manufacture
If field lens arrangement is added to relay light, then light can be directed to viewing plane, but manufacturing cost increases due to precision-ground glass components
Solution Approach 1:
The invention replaces expensive precision-ground and polished glass field lens components with a diffractive element that can be manufactured using more cost-effective techniques. The diffractive structure achieves the same light relaying function without requiring the high-precision mechanical grinding and polishing of traditional glass lenses
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 provides greater optical clarity and flexibility in viewing, allowing observers to view images from anywhere within the enlarged exit pupil without the need for precise alignment and reduces costs by eliminating the field lens component.
Implementation Method 1
the lenticules each comprising an irregular feature having a plurality of surfaces; wherein the diffractive units are disposed progressively radially outwardly from the optical axis of the diffractive element and configured progressively to provide for an increasing angular offset, such that, independent of location on the aperture of the diffractive element, light from the received image is relayed to a common region on a viewing plane across the aperture of the diffractive element
Data Source
AI summary
An optical instrument for producing an optical image to be viewed by an observer, the optical instrument comprising: an optical system for producing an optical image of an object which is viewable by an observer at an exit pupil; and a diffractive element located at an image plane of the optical system for producing an array of the exit pupils, which are perceivable as a single, enlarged exit pupil by the observer; wherein the diffractive element comprises a surface which has an array of diffractive units, each of which generates one of the exit pupils of the array of exit pupils, the diffractive units each comprising a lenticule, which is effective to produce diffractive interference of light and generate a plurality of exit pupils which are displaced relative to one another in the form of an array of exit pupils, the lenticules each comprising an irregular feature having a plurality of surfaces; wherein the diffractive units are disposed progressively radially outwardly from the optical axis of the diffractive element and configured progressively to provide for an increasing angular offset, such that, independent of location on the aperture of the diffractive element, light from the received image is relayed to a common region on a viewing plane across the aperture of the diffractive element.