Angle Selective Filter Assembly for Optical Noise Reduction

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Solution Overview

Problem

Optical filters experience performance degradation and increased noise due to angle of incidence changes, leading to stray light and cross-talk issues, especially at angles greater than a threshold value.

Innovation Solution

A composite optical filter assembly comprising a bandpass filter and an angle shift filter, where the bandpass filter allows light at configured angles and the angle shift filter blocks or reflects light at greater angles, ensuring minimal noise and cross-talk by shifting unwanted light to non-interfering wavelengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the angle of incidence changes from configured incidence to threshold angle of incidence, then the optical filter selects light at specific wavelengths, but the band edges experience blue shift to shorter wavelengths and polarization effects become significant

Engineering Contradiction:

Improvewavelength selection accuracyVSAvoidfilter performance stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies a wavelength shift filter that intentionally introduces a controlled blue shift to counteract the unwanted wavelength shift caused by angle of incidence changes. By converting the harmful wavelength drift into a compensated effect, the system maintains accurate wavelength selection even when light enters at varying angles, thus resolving the contradiction between measurement precision and reliability

Inventive Principle:

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

Solution Approach 2:

The patent changes the optical parameters of the filter system by introducing a wavelength shift filter with specific transmission characteristics that vary with wavelength. This filter is designed to shift the transmitted wavelengths in the opposite direction of the angle-induced blue shift, thereby compensating for the parameter changes and maintaining stable filter performance across different angles of incidence

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the angle of incidence increases beyond threshold value, then light filtering occurs, but noise and cross-talk increase due to stray light

Engineering Contradiction:

Improvesignal accuracyVSAvoidnoise and cross-talk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The wavelength shift filter converts the harmful stray light at high angles into shifted wavelengths that fall outside the bandpass filter's transmission window. By intentionally shifting the wavelengths of stray light, the system transforms this harmful effect into a beneficial separation, where stray light is redirected to non-interfering wavelengths, thus reducing noise and cross-talk while maintaining signal accuracy

Inventive Principle:

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

3Device complexity

If a single optical filter is used, then the device complexity is low, but the filter performance degrades at threshold angle of incidence

Engineering Contradiction:

Improvefilter assembly structureVSAvoidfilter performance consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent merges two filter functions into a single integrated assembly: a bandpass filter for wavelength selection and a wavelength shift filter for angle compensation. By combining these functions in close proximity with optimized optical alignment, the system achieves high performance consistency across varying angles without significantly increasing device complexity, as the two filters work together as a unified optical element

Inventive Principle:

Principle #5Merging (Combining)

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

The solution effectively restricts angle of incidence, reducing noise and cross-talk in optical sensors by allowing only configured light to pass through while blocking or reflecting light at higher angles, thereby maintaining filter performance and accuracy.

Implementation Method 1

an angle shift filter with at least a second threshold level of angle shift at the configured center wavelength and at angles of incidence greater than a configured value

Methodology Applied

Scientific EffectAngle shift: Refraction

Implementation Method 2

a bandpass filter with at least a first threshold level of transmissivity at a configured center wavelength

Methodology Applied

Scientific EffectBandpass filtering: Filter (optical)

Data Source

PatentUS20250004185A1Angle selective filter

Publication Date: 2025.01.02 VIAVI SOLUTIONS INC(US)

AI summary

In some implementations, an optical filter assembly includes a first optical filter disposed on a first side of a substrate, wherein the first optical filter is a bandpass filter; and a second optical filter disposed on a second side of the substrate, wherein the second optical filter is associated with a threshold amount of angle shift at a threshold angle of incidence.