Virtual Protective Housing for Eye-Safe Laser Projection

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Solution Overview

Problem

Laser projection systems, particularly those with high power visible laser devices, often fail to meet eye-safe standards without additional safety measures, posing a risk of eye damage.

Innovation Solution

The implementation of a scanning laser projection system with an automatic power reduction mechanism using a virtual protective housing circuit that employs infrared laser light to identify and reduce visible laser power in areas of the field of view containing objects, ensuring emissions remain below eye-safe levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If high power visible laser devices are used in projection systems, then projection brightness and visibility are improved, but eye safety is compromised and the system fails to meet eye-safe standards

Engineering Contradiction:

Improveprojection brightnessVSAvoideye damage risk

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary scanning with infrared laser light before projecting visible laser light to detect objects in the field of view. This advance detection allows the system to prepare safety measures (power reduction or blanking) before high-power visible laser exposure occurs, preventing eye damage while maintaining projection functionality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Infrared laser light serves as an intermediary between the projection system and visible laser light. The infrared scanner acts as a mediator that detects objects without the harmful effects of high-power visible laser, enabling safe operation by providing information about the field of view conditions before visible laser projection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If a physical protective housing is added to reduce accessible emission limits, then eye safety is improved, but device complexity and structural requirements increase

Engineering Contradiction:

Improveaccessible emission limitsVSAvoidprotective housing structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The system creates a virtual protective housing through software-controlled power reduction and blanking operations based on infrared scan data. Instead of implementing a physical protective housing structure, the system copies the safety function of a protective housing through digital processing and adaptive power control, eliminating complex mechanical structures while maintaining eye safety.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical protective housing system with an optical-electronic system. Instead of using physical barriers and mechanical safety structures, the system uses infrared laser scanning combined with real-time power adjustment and blanking control to achieve eye safety, substituting mechanical complexity with electronic control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If visible laser power is reduced in areas with detected objects, then eye safety is improved, but projection visibility and image quality in those areas deteriorate

Engineering Contradiction:

Improveemission levels in detected areasVSAvoidprojection visibility

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The system applies different power levels to different regions of the projection field based on local conditions detected by infrared scanning. Areas with detected objects receive reduced or zero power for safety, while areas without objects maintain full power for optimal visibility. This localized quality adjustment resolves the contradiction by making the projection adaptive to spatial variations in safety requirements.

Inventive Principle:

Principle #3Local quality

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 solution effectively reduces visible laser power in identified areas, providing a virtual protective housing that maintains accessible emission levels within safe limits, thereby preventing eye damage and meeting eye-safe standards without physical housing.

Implementation Method 1

illuminating objects in a field of view with a scanning infrared laser light pulse train and detecting reflections of the infrared laser light pulses from reflection points within the field of view with a photosensitive device

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

measuring at least one attribute of the reflections with a time of flight measurement circuit

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS11397317B2Automatic power reduction using a pre-scanned virtual protective housing

Publication Date: 2022.07.26 MICROVISION INC

AI summary

A scanning laser projection system includes a virtual protective housing circuit to automatically reduce power levels of visible laser light pulses when necessary to render the laser projection system eye-safe. IR laser light pulses are scanned out in front of visible laser light pulses in a field of view, and emitted power of visible laser light pulses is modulated based on attributes of reflections of the IR laser light pulses.