Polarization-Canceling Optical Filter for Accurate Light Measurement

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing optical measurement apparatuses suffer from measurement errors due to the minute level of polarization dependence in thin film filters, which is not accounted for in calibration, leading to inaccuracies when measuring bright and dim lights.

Innovation Solution

An optical filter design with a first and second optical function layer, each having a high transmittance axis, is configured such that the angle between these axes is within 90°±30°, minimizing polarization dependence and reducing measurement errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a thin film filter is used to regulate the amount of received light, then the dynamic range of the optical measurement apparatus is widened, but measurement errors occur due to polarization dependence of the filter

Engineering Contradiction:

Improvedynamic rangeVSAvoidmeasurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The filter is divided into multiple optical function layers (first optical function layer and second optical function layer) with different transmittance characteristics. Each layer is designed to have specific high transmittance axes that are oriented at different angles, allowing the combined system to cancel polarization dependence while maintaining the desired light regulation function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The high transmittance axis of the first optical function layer and the high transmittance axis of the second optical function layer are oriented at angles that are not equal (specifically within 90°±30°). This asymmetric orientation causes the polarization dependence effects of the two layers to cancel each other out, resolving the measurement accuracy issue while maintaining the filter's light regulation capability.

Inventive Principle:

Principle #4Asymmetry

2Ease of manufacture

If the transmittance of the thin film filter is measured during calibration, then a correction factor is stored, but the actual transmittance differs from the stored correction factor due to polarization dependence

Engineering Contradiction:

Improvecalibration processVSAvoidtransmittance accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The multi-layer filter structure is designed to be self-correcting regarding polarization dependence. The asymmetric orientation of the high transmittance axes of the different layers automatically compensates for polarization effects without requiring additional calibration adjustments or correction factors, making the system self-sufficient in maintaining accurate transmittance measurements.

Inventive Principle:

Principle #25Self-service

3Device complexity

If a single optical function layer is used, then the device complexity is low, but polarization dependence causes unignorable errors in high-precision measurements

Engineering Contradiction:

Improvefilter structureVSAvoidmeasurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Multiple optical function layers are combined into a single filter component. The first optical function layer and second optical function layer are merged such that their polarization dependence effects cancel each other out, achieving high measurement accuracy without requiring multiple separate filters or complex calibration procedures.

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 optical filter design significantly reduces measurement errors by effectively canceling out polarization dependence, ensuring accurate measurements across varying light conditions.

Implementation Method 1

the transmittance of a thin film filter has polarization dependence depending on the incident angle of light to be measured. Theoretically, there is no polarization dependence at vertical incidence. However, latest investigations found out that a thin film filter has a minute level of polarization dependence at vertical incidence.

Methodology Applied

Scientific EffectPolarization dependence: Polarisation

Implementation Method 2

the first optical function layer and the second optical function layer each have a high transmittance axis, the high transmittance axis being determined by a polarization direction in which transmittance of linearly polarized light at vertical incidence is greatest

Methodology Applied

Scientific EffectMalus's law:

Data Source

PatentUS20250271604A1Optical filter, method of manufacturing optical filter, optical filter unit, method of manufacturing optical filter unit, and optical measurement apparatus

Publication Date: 2025.08.28 KONICA MINOLTA INC

AI summary

There is provided an optical filter having a light transmittance characteristic or a light reflectance characteristic for a predetermined wavelength range. The optical filter includes a first optical function layer and a second optical function layer each having a transmittance that varies in a polarization direction of linearly polarized light at vertical incidence. The first optical function layer and the second optical function layer each have a high transmittance axis that is determined by a polarization direction in which transmittance of linearly polarized light at vertical incidence is greatest. The first optical function layer and the second optical function layer are disposed such that an angle formed by the high transmittance axis of the first optical function layer and the high transmittance axis of the second optical function layer is within a range of 90°±30°.