Objective Lens Backlash Reduction via Biasing Element
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Solution Overview
Problem
Objective lens assemblies experience backlash due to the loose fit between threaded components, leading to focus and resolution errors, requiring disassembly and repair.
Innovation Solution
Incorporating a biasing element, such as a belleville washer or snap-ring washer, configured for relaxed and compressed modes to reduce backlash between the objective lens cell and the optical bench, ensuring consistent focus and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a loose fit is used between threaded components, then ease of assembly is improved, but backlash increases causing focus and resolution errors
Solution Approach 1:
A biasing element (spring or elastomeric member) is introduced as an intermediary component between the objective lens cell and the optical bench. This biasing element applies continuous axial force to maintain thread engagement, eliminating backlash while preserving the loose fit configuration that enables easy assembly and tolerance accommodation.
Solution Approach 2:
The biasing element pre-applies a compressive force in the opposite direction of the intended movement, continuously pushing the lens cell against the threads of the optical bench. This preliminary counter-force ensures that the threads remain engaged under all operating conditions, preventing the development of backlash before it can occur during normal operation.
2Manufacturing precision
If a biasing element is added to reduce backlash, then focus precision is improved, but device complexity increases
Solution Approach 1:
The patent employs simple, well-understood mechanical elements (springs or elastomeric biasing members) with standardized geometric parameters. By selecting appropriate spring rates, pre-loads, and dimensions, the biasing element can be integrated into existing assemblies without requiring complex mechanisms or specialized components, thus minimizing the increase in device complexity.
Solution Approach 2:
The biasing element serves multiple functions simultaneously: it eliminates backlash, maintains thread engagement, accommodates manufacturing tolerances, and provides continuous contact between components. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in overall device complexity despite the addition of the biasing element.
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 biasing element effectively reduces backlash, maintaining resolution settings and allowing for a space-efficient design that only requires biasing during sensitive focus ranges, minimizing the need for disassembly and repair.
Implementation Method 1
a biasing element configured for a relaxed mode of operation and a compressed mode of operation
Data Source
AI summary
An objective lens assembly for night vision goggles including an objective lens cell having a threaded portion, an optical bench having a mating threaded portion for receiving the objective lens cell, and a snap-ring washer for reducing backlash between the objective lens cell and the optical bench. The objective lens cell includes a first wall radially extending away from an axial neck portion, the optical bench includes a second wall radially extending toward the axial neck portion and oriented substantially parallel to the first wall, and the snap-ring washer circumferentially surrounds the axial neck portion of the objective lens cell. The biasing element is configured for a relaxed mode of operation and a compressed mode of operation. In the relaxed mode, the snap-ring washer is inactive, and in the compressed mode, the snap-ring washer reduces backlash between the lens cell and the optical bench.