Micromirror Capacitance Sensing for Stuck Tilt Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital micromirror devices (DMDs) face issues with individual micromirrors becoming stuck or missing, which prevents them from rotating between desired tilt angles, leading to inefficiencies in image formation and heat management.
Innovation Solution
Incorporating a measurement circuit within each micromirror cell that measures capacitance between electrodes and the micromirror at different tilt angles to determine if the micromirror is stuck or missing, allowing for electrical detection and remedial actions such as adjusting bias voltage to unstick the mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection methods are used to detect stuck or missing micromirrors, then detection can be performed, but the process is time-consuming and requires manual intervention
Solution Approach 1:
The patent replaces manual visual inspection with an automated electrical measurement system. The measurement circuit electrically determines micromirror status by measuring capacitance values between electrodes and micromirrors, substituting the mechanical/visual detection process with an automated electrical measurement process that is both faster and more precise.
Solution Approach 2:
The measurement circuit is integrated within the DMD device itself, allowing the device to self-diagnose stuck or missing micromirrors without external inspection equipment. The circuit automatically measures capacitance values and generates status signals, enabling the system to service itself.
2Reliability
If no measurement circuit is integrated, then the device structure remains simple, but stuck or missing micromirrors cannot be detected
Solution Approach 1:
The measurement circuit serves multiple functions: it measures capacitance values to detect stuck micromirrors, identifies missing micromirrors, and provides diagnostic information for remedial actions. This multi-functional approach improves reliability without proportionally increasing device complexity.
Solution Approach 2:
The measurement circuit acts as an intermediary between the control system and the micromirrors. It provides electrical connectivity between the measurement circuit and electrodes, enabling indirect detection of micromirror status through capacitance measurements without requiring direct physical access to each micromirror.
3Productivity
If capacitance measurement is performed at only one tilt angle, then the measurement process is faster, but stuck micromirrors cannot be reliably distinguished from properly functioning mirrors
Solution Approach 1:
The system performs preliminary measurements at one tilt angle, then conditionally performs additional measurements at a second tilt angle only when needed. This approach maintains fast measurement speed for normal operation while enabling accurate detection of stuck micromirrors when anomalies are detected.
Solution Approach 2:
The measurement process is made dynamic by adjusting the number of measurement angles based on the detected capacitance values. The system adapts its measurement strategy in real-time, performing single-angle measurements for efficiency and multi-angle measurements for diagnostic accuracy when required.
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
Enables the DMD to electrically determine and address stuck or missing micromirrors without visual inspection, ensuring proper operation and reducing manufacturing defects.
Implementation Method 1
measure a first value indicative of a capacitance between a first electrode and the micromirror and to measure a second value indicative of a capacitance between a second electrode and the micromirror
Implementation Method 2
The micromirrors can be individually controlled to one tilt state or another through electrostatic forces created by voltages on electrodes adjacent each micromirror
Data Source
AI summary
A digital micromirror device includes a plurality of micromirror cells on a semiconductor die. Each respective cell includes a memory circuit and an electrode selection circuit. At least some of the micromirror cells include a micromirror and each respective memory circuit controls a micromirror tilt angle. For a given memory circuit controlled to a first tilt angle, a measurement circuit measures a first value indicative of a capacitance between a first electrode and the micromirror and measures a second value indicative of a capacitance on the second electrode. For a second micromirror tilt angle, the measurement circuit measures a third value indicative of a capacitance between the first electrode and the micromirror and measures a fourth value indicative of a capacitance on the second electrode. The measurement circuit generates a signal indicative of whether the micromirror is stuck at a particular angle or missing.