Beam Splitter Coating for Intraoral Scanner Stray Light Control

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Solution Overview

Problem

Existing intraoral scanning devices suffer from stray light interference, which affects color fidelity and requires the use of polarizing films that absorb significant amounts of light, making it difficult to reproduce true colors.

Innovation Solution

An intraoral scanning device with a light absorbing unit on the beam splitter, featuring an antireflective coating and an absorbing layer, minimizes stray light by absorbing it before it reaches the image sensor, and omits polarizing films, allowing for a broader wavelength transmission and lower excitation wavelengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If polarizing films are used to minimize stray light, then stray light is reduced, but short wavelength light is absorbed, reducing color fidelity

Engineering Contradiction:

Improvestray lightVSAvoidcolor fidelity

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent changes the material parameters of the beam splitter by applying an antireflective coating with specific optical properties (refractive index and thickness) to reduce reflections across the visible spectrum, particularly in short wavelengths. This allows the system to minimize stray light through optical design rather than light absorption, preserving color fidelity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The beam splitter is constructed as a composite structure combining a substrate material with an antireflective coating layer. This composite design enables the system to achieve both low stray light (through the coating's reflective properties) and high color fidelity (by transmitting short wavelengths that would be absorbed by polarizing films).

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If light absorbing materials are used to reduce stray light, then stray light is minimized, but light transmission is reduced, affecting image brightness

Engineering Contradiction:

Improvestray lightVSAvoidimage brightness

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The patent converts the harmful effect of light reflection (which causes stray light) into a beneficial feature by using the antireflective coating's controlled reflectivity to redirect stray light away from the image sensor while maintaining high transmission for useful light paths. The coating's optical properties are designed to benefit the imaging performance.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The antireflective coating acts as an intermediary layer between the beam splitter substrate and the surrounding medium. This intermediate layer with specific refractive index and thickness controls light reflection and transmission, mediating between the substrate and environment to minimize stray light while preserving image brightness.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If antireflective coating is applied to beam splitter, then stray light is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvestray lightVSAvoidmanufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent specifies particular parameter ranges for the antireflective coating (refractive index between 1.3-1.7, thickness 50-200 nm) that balance performance optimization with manufacturing feasibility. These parameter choices enable effective stray light reduction while remaining compatible with standard coating deposition processes.

Inventive Principle:

Principle #35Parameter changes

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 design enhances color fidelity by reducing stray light and absorption losses, enabling more accurate color reproduction and a cost-effective solution with improved signal-to-noise ratio.

Implementation Method 1

a light absorbing unit arranged on a surface of the beam splitter, said light absorbing unit comprising an antireflective coating

Methodology Applied

Scientific EffectAntireflective coating: Anti-Reflective Coating

Implementation Method 2

an absorbing layer configured to absorb light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 3

a beam splitter configured to split an incident beam of light into two beams, wherein at least one of said beams is linearly polarized

Methodology Applied

Scientific EffectPolarization: Polarisation

Implementation Method 4

a waveplate, such as a quarter-wave plate configured to alter the polarization state of light travelling through the waveplate

Methodology Applied

Scientific EffectWaveplate polarization alteration: Birefringence

Data Source

PatentUS12631862B2Intraoral scanner with optical system for minimizing stray light

Publication Date: 2026.05.19 3SHAPE AS

AI summary

The present disclosure relates to an intraoral scanning device including a light source configured for emitting light; a beam splitter configured for outputting linearly polarized light of a predefined orientation, wherein the beam splitter is arranged such that light from the light source is transmitted through the beam splitter; an image sensor configured for acquiring one or more images; and a light absorbing unit for minimizing stray light on the image sensor, said light absorbing unit arranged on a surface of the beam splitter. The present disclosure further relates to an optical system for an intraoral scanning device, said optical system configured for minimizing stray light in the system.