Optical Projector Using DOE and MBG for Miniaturization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing miniaturized optical projection systems for 3D surface measurements, such as those used in smartphones for facial recognition, face challenges in reducing the 0th order beam intensity ratio to prevent eye damage while maintaining sufficient dot pattern density, which limits miniaturization and increases manufacturing costs.

Innovation Solution

A compact optical projector module is developed using a holographic diffractive optical element (DOE) in conjunction with a multiple beam grating (MBG) and a lens, where the DOE generates a dot pattern that appears as virtual images from a plane around the laser emitting point, and the MBG splits the pattern to maintain equal intensity across duplicated images, reducing the 0th order beam intensity and enabling miniaturization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a single laser beam and diffractive optical element are used to generate dot pattern, then the optical projector can be miniaturized, but the 0th order beam intensity ratio becomes too large causing potential eye damage

Engineering Contradiction:

Improveoptical projector sizeVSAvoid0th order beam intensity

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent divides a single laser beam into multiple beams (e.g., 5 beams) using a beam splitter, and each beam illuminates a separate diffractive optical element. This segmentation reduces the 0th order beam intensity ratio by distributing the laser power across multiple beams, minimizing the harmful effect on user eyes while maintaining sufficient dot pattern density for 3D surface measurements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a beam splitter as an intermediary component between the laser source and the diffractive optical elements. This mediator divides the incoming laser beam into multiple lower-intensity beams, allowing each subsequent DOE to receive reduced power and thereby reducing the overall 0th order beam intensity that reaches the user's eye

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If multiple diffractive optical elements are used to minimize 0th order beam ratio, then the harmful effect is reduced, but the device complexity and space requirements increase

Engineering Contradiction:

Improve0th order beam intensityVSAvoidoptical system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent combines multiple diffractive optical elements and their corresponding lenses into a single integrated optical element. This merging approach maintains the benefit of reduced 0th order beam intensity through multiple beam paths while simplifying the overall device structure, reducing the number of separate components, and enabling miniaturization suitable for smartphone integration

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent designs the integrated optical element to perform multiple functions simultaneously: it acts as both the diffractive optical element that generates the dot pattern and as the lens that focuses and projects the pattern. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity while maintaining the multiple beam structure that minimizes harmful effects

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 allows for a more miniaturized and cost-effective optical projection system that effectively generates a dense dot pattern for 3D surface measurements without eye damage risks, enhancing the accuracy of facial recognition and depth mapping applications.

Implementation Method 1

Optical projection of a pattern is used in applications such as 3D surface measurements. The positions of a pattern of dots caused by beams projected onto a flat surface can be determined.

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

Methodology Applied

Scientific EffectHolography:

Implementation Method 3

U.S. Patent Application Publication 2009/0185274, and uses two diffractive optical elements (DOEs). In one embodiment, the first DOE acts as a beam-splitter which splits the emitted beam into a multiple beams

Methodology Applied

Scientific EffectDiffraction grating: Diffraction Grating

Implementation Method 4

A lens projects the non-collimated pattern to a single DOE which is used to produce multiple replicas of the pattern.

Methodology Applied

Scientific EffectLens focusing: Lens

Data Source

PatentUS10317684B1Optical projector with on axis hologram and multiple beam splitter

Publication Date: 2019.06.11 K LASER TECH

AI summary

In one embodiment, the light from a single laser is used to illuminate a pattern-generating optical element to generate a pattern. The pattern-generating optical element in various embodiments can be, for example, a holographic diffractive optical element (DOE) or an array of micro-lenses. A multiple beam grating (MBG) duplicates the pattern multiple times to provide a multiple pattern image. A lens is used to project the patterns onto an object. In one embodiment, the lens is located between the pattern-generating optical element and the multiple beam grating (MBG).