Optical Filter with Resin Absorber for Angle-Dependent Noise

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Solution Overview

Problem

Conventional near-infrared cut filters used in solid-state image pickup devices suffer from significant signal noise ratio deterioration and adverse effects on camera image quality and color reproducibility when obliquely incident rays are involved, due to their large dependence on incident angle, especially in the visible light passband and near-infrared selective passband.

Innovation Solution

An optical filter with a transparent resin layer containing a compound having an absorption maximum in the 600 to 850 nm range, combined with a dielectric multilayer film, which selectively transmits visible and near-infrared rays, ensuring high transmittance in the visible region and controlled transmittance in the near-infrared region, thereby reducing incident angle dependence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional near-infrared cut filter is used to selectively transmit visible rays and near-infrared rays, then the sensing function for near-infrared rays is enabled, but the signal noise ratio deteriorates and image quality is adversely affected when rays are obliquely incident on the filter

Engineering Contradiction:

Improvenear-infrared sensing functionVSAvoidsignal noise ratio

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent combines a transparent resin layer containing a near-infrared absorbing agent with a dielectric multilayer film to create a composite optical filter. The transparent resin layer selectively absorbs near-infrared rays while maintaining visible light transmission, and the dielectric multilayer film provides additional wavelength-selective filtering. This composite structure enables near-infrared sensing functionality while maintaining high signal-to-noise ratio and image quality even when rays are obliquely incident on the filter.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If a dielectric multilayer film is used to selectively transmit visible and near-infrared rays, then the spectral selectivity is improved, but the transmittance varies greatly when rays are obliquely incident on the filter

Engineering Contradiction:

Improvespectral selectivityVSAvoidtransmittance stability

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent applies different functional layers with specific local properties: the transparent resin layer is designed to absorb near-infrared rays while being transparent to visible light, and the dielectric multilayer film is engineered with specific refractive indices and thicknesses to provide wavelength-selective transmission. By optimizing the local properties of each layer, the filter achieves high spectral selectivity while maintaining stable transmittance characteristics for both perpendicular and oblique incident rays.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If the dependence on incident angle is reduced, then the signal noise ratio and image quality are improved, but the spectral selectivity for near-infrared rays may be compromised

Engineering Contradiction:

Improvesignal noise ratioVSAvoidspectral selectivity

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent merges the functions of near-infrared absorption (transparent resin layer) and wavelength-selective filtering (dielectric multilayer film) into a single integrated optical filter structure. The transparent resin layer containing the near-infrared absorbing agent provides broad near-infrared rejection, while the dielectric multilayer film fine-tunes the spectral transmission characteristics. This merged structure achieves both low incident angle dependence and high spectral selectivity simultaneously.

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 achieves excellent transmission properties for visible and near-infrared rays with reduced incident angle dependence, enhancing imaging sensitivity and color reproducibility while maintaining high near-infrared sensing performance.

Implementation Method 1

a transparent resin layer containing a compound (Z) having an absorption maximum in the wavelength region of from 600 to 850 nm

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

a dielectric multilayer film provided on at least one surface of the base material (i)

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS9606275B2Optical filter, solid-state image pickup device and camera module

Publication Date: 2017.03.28 JSR CORPORATION

AI summary

An optical filter comprises a base material (i) which comprises a transparent resin layer comprising a compound (Z) having an absorption maximum in the wavelength region of from 600 to 850 nm; and a dielectric multilayer film provided on at least one surface of the base material (i). The optical filter selectively transmits visible rays and a part of near-infrared rays, and the optical filter satisfies specific requirements.