Capacitive Sensing for Optical Module DOE Shift Detection
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Solution Overview
Problem
Existing optical modules face challenges in reliably detecting shifts of diffractive optical elements (DOEs) and moisture incursion, which can compromise light beam integrity and performance, due to limitations in resistance measurement and susceptibility to electrical shorts.
Innovation Solution
An optical module with a capacitive sensing system using a connector with two conductive layers separated by a dielectric layer, forming a test circuit that inhibits emitter operation when capacitance changes exceed a threshold, ensuring robust detection of DOE shifts and moisture incursion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If resistance measurement is used to detect DOE shifts and moisture incursion, then the detection system is simple, but the reliability is compromised due to susceptibility to electrical shorts
Solution Approach 1:
The patent replaces the electrical resistance measurement system with a capacitive sensing system. The connector structure itself forms a capacitor where one conductive layer is connected to the enclosure and the other to the optical output assembly. Changes in capacitance detect DOE shifts and moisture incursion without being susceptible to electrical shorts, thus improving reliability while maintaining simplicity.
2Strength
If a mechanical seal is used to connect the optical output assembly, then the assembly is secure, but the detection of seal disruption requires additional conductive traces that may break
Solution Approach 1:
The patent replaces mechanical disruption detection using conductive traces with a capacitive sensing approach. The connector's capacitive structure continuously monitors the electrical characteristics across the mechanical seal. When the seal is disrupted or moisture intrudes, the capacitance changes, providing reliable detection without the fragility of thin conductive traces that can break.
3Ease of manufacture
If conductive adhesive is used to connect the connector to the enclosure, then the electrical connection is established, but the resistance measurement becomes unreliable due to variable contact resistance
Solution Approach 1:
The patent changes the measurement parameter from resistance to capacitance. The connector structure forms a capacitor where the conductive adhesive connections are part of the capacitive circuit rather than the measurement path. This eliminates the problem of variable contact resistance affecting measurements, as capacitance measurement is not influenced by the resistance of the conductive adhesive layers.
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 capacitive sensing system effectively shuts down the emitter upon detecting significant shifts or integrity loss, ensuring reliable operation and improved assembly verification, while avoiding issues with resistance measurement and electrical shorts.
Implementation Method 1
a connector, which includes two conductive layers separated by a dielectric layer, has a first side connected to the enclosure and a second side connected to the optical output assembly
Data Source
AI summary
An optical module includes an enclosure and an optical output assembly mounted on the enclosure. An emitter mounted in the enclosure is configured to emit a beam of light toward the optical output assembly. A connector, which includes two conductive layers separated by a dielectric layer, has a first side connected to the enclosure and a second side connected to the optical output assembly. An electrical trace disposed on the enclosure is connected to the first side of the connector so as to define a test circuit having a capacitance. Control circuitry is coupled to sense the capacitance of the test circuit, and configured to inhibit operation of the emitter upon sensing a change in the capacitance that exceeds a predetermined threshold.