Image Sensor Waveguide Noise Suppression via Wavelength-Dependent Geometry

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Solution Overview

Problem

Image sensors with waveguide structures face challenges in guiding light due to pixel miniaturization, leading to increased noise components from oblique light incidence and diffraction, which existing techniques fail to effectively suppress.

Innovation Solution

The image sensor design includes a waveguide with a core and opening widths that increase with the wavelength of incident light, along with a light shielding portion to block oblique light and diffracted light, and an anti-reflection film to enhance light condensation, effectively reducing noise components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If pixel size is reduced to increase resolution, then the number of pixels increases, but noise components from oblique light incidence and diffraction increase

Engineering Contradiction:

ImproveresolutionVSAvoidnoise components

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The waveguide core width is set to differ from the opening width of the light shielding portion, creating local structural variations that control light propagation characteristics. This local quality differentiation allows selective suppression of oblique light while maintaining normal light transmission to the light receiving portion

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameters of the waveguide structure by setting the core width to be different from the opening width. This parameter modification optimizes the waveguide's light confinement properties and reduces diffraction effects at the waveguide opening, thereby suppressing noise components

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the waveguide core width is reduced to block oblique light, then noise suppression improves, but light condensing characteristics deteriorate

Engineering Contradiction:

Improvenoise componentsVSAvoidlight condensing characteristics

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The light shielding portion's opening width is set differently from the waveguide core width, creating localized structural characteristics that selectively block oblique light while allowing the waveguide core to maintain optimal dimensions for light condensation and guidance

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If the opening width of light shielding portion is increased to improve light transmission, then sensitivity improves, but oblique light and diffracted light increase causing more noise

Engineering Contradiction:

ImprovesensitivityVSAvoidnoise components

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent creates local structural quality differences by setting the waveguide core width to be different from the light shielding opening width. This allows the opening to be optimized for blocking oblique light while the core maintains dimensions optimized for light guidance and sensitivity

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

By changing the geometric parameters to have different widths for the core and opening, the patent simultaneously optimizes both noise suppression and light transmission characteristics, achieving high sensitivity without excessive noise

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 significantly reduces noise components and maintains sensitivity by optimizing the waveguide core and opening widths based on the wavelength of incident light, improving image quality.

Implementation Method 1

a waveguide configured to guide the incident light from a light incident surface to the light receiving portion

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

noise due to diffraction of light from a waveguide core portion and a light shielding material opening

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10373994B2Image sensor, for suppressing occurrence of noise components

Publication Date: 2019.08.06 SONY SEMICON SOLUTIONS CORP

AI summary

There is provided an image sensor having a plurality of pixels, each pixel including a light receiving portion configured to receive incident light, a waveguide configured to guide the incident light from a light incident surface to the light receiving portion, and a light shielding portion disposed between the light incident surface and the light receiving portion, for blocking the incident light. The light shielding portion has an opening formed near a light emitting surface of the waveguide. The light receiving portion receives the incident light passing through the waveguide and the opening. A width of a core of the waveguide and a width of the opening are set so that the widths increase as a wavelength of the light incident on a pixel becomes longer.