Rearview Mirror Imaging With Row-Synced Transmissive Switching

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Solution Overview

Problem

Existing driver monitoring systems in vehicles often distract or overwhelm drivers due to visible components, compromising safety by diverting attention from the road.

Innovation Solution

An imaging system integrated into a rearview mirror that switches between reflective and transmissive modes using a twisted nematic liquid crystal cell, allowing covert installation and continuous rearview functionality while monitoring driver behavior.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If driver monitoring systems use visible cameras and components, then driver behavior can be monitored effectively, but the driver is distracted or overwhelmed, compromising safety

Engineering Contradiction:
Improvedriver behavior monitoring capabilityVSAvoiddriver distraction
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system uses a liquid crystal mirror element that changes its optical properties between reflective and transmissive states. This allows the camera to capture images of the driver through the mirror when it is in transmissive mode, while the mirror appears normal to the driver when in reflective mode, thus enabling monitoring without driver distraction

Inventive Principle:
Principle #32Color changes

Solution Approach 2:

The mirror element dynamically switches between reflective and transmissive modes in synchronization with the camera's scanning process. The control unit controls the mirror to be transmissive only during the brief period when the camera scans a row of pixels, and reflective during the period when the camera moves to the next row, making the switching imperceptible to the driver

Inventive Principle:
Principle #15Dynamics

2Adaptability or versatility

If the imaging system is integrated into the rearview mirror, then rearview functionality is maintained, but the system components become visible to the driver

Engineering Contradiction:
Improverearview mirror functionalityVSAvoidvisible components
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The imaging system is merged with the rearview mirror by placing the camera behind the mirror element and using the mirror's dual functionality. The same mirror element serves both as the rearview surface and as the optical element that allows camera access to the driver's image, eliminating the need for separate visible components

Inventive Principle:
Principle #5Merging (Combining)

3Measurement precision

If the mirror element switches between reflective and transmissive modes continuously, then covert imaging is achieved, but the switching frequency may distract the driver

Engineering Contradiction:
Improvecovert imaging capabilityVSAvoiddriver distraction from switching
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The mirror element performs periodic switching between reflective and transmissive modes that is synchronized with the camera's row-by-row scanning process. The switching occurs in brief, periodic intervals that are too fast and too brief to be perceived by the human eye, thus achieving covert imaging without driver distraction

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The system maintains continuous rearview functionality by keeping the mirror in reflective mode for the majority of the time, with only brief transmissive intervals for imaging. This ensures the useful rearview action continues uninterrupted from the driver's perspective while enabling periodic covert imaging

Inventive Principle:
Principle #20Continuity of useful action

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

Ensures unobtrusive driver monitoring by maintaining rearview functionality without distracting the driver, enhancing road safety through covert imaging and real-time alert systems.

Implementation Method 1

the mirror element includes: a twisted nematic (TN) liquid crystal cell; a first conductive glass panel and a second conductive glass panel being positioned at both sides of the twisted nematic liquid crystal cell

Methodology Applied
Scientific EffectTwisted nematic liquid crystal effect: Liquid Crystals

Implementation Method 2

The TN liquid crystal cell includes liquid crystal materials having long, rod-like molecules that can align themselves in a specific direction when an electric field is applied to the TN liquid crystal cell

Methodology Applied
Scientific EffectElectric field control of liquid crystal orientation: Electric Field

Implementation Method 3

a first polarizer and a second polarizer being positioned adjacent to the first conductive glass panel and the second conductive glass panel, respectively

Methodology Applied
Scientific EffectPolarization: Polarisation

Data Source

PatentEP4442512B1Imaging system
Publication Date: 2025.11.26 HARMAN BECKER AUTOMOTIVE SYST GMBH
  • EP4442512B1 patent drawingFigure 1~2
  • EP4442512B1 patent drawingFigure 3A~3B
  • EP4442512B1 patent drawingFigure 4A~4B

AI summary

An imaging system for a driver monitoring system, comprising: a mirror element; a camera comprising an imaging sensor, the camera being provided at a back side of the mirror element; and a control unit; wherein the control unit is configured to switch the mirror element from a reflective mode to a transmissive mode when the camera starts to scan a row of pixels of the imaging sensor, and switch the display from the transmissive mode to the reflective mode when the camera moves to a next row of pixels.