Optical Sensing Pixel Shielding for Higher Signal-to-Noise Ratio

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Solution Overview

Problem

Conventional optical sensing devices face issues with stray light or ambient light affecting the signal-to-noise ratio, leading to poor performance in applications like fingerprint recognition in smartphones and tablets.

Innovation Solution

The design incorporates a light shielding layer with specific openings corresponding to the sensing element, overlapping with the driving circuit, which reduces the influence of stray light and ambient light, improving the signal-to-noise ratio and simplifying the manufacturing process by using organic or metal materials for the shielding layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional light collimating structure is used, then the optical sensor can be integrated into electronic products, but stray light or ambient light affects the operation of the optical sensors, resulting in poor signal-to-noise ratio

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidstray light or ambient light influence

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The light shielding layer is divided into multiple segments: a first light shielding layer with first openings corresponding to the sensing element, and a second light shielding layer with second openings. This segmentation allows precise control of light paths while blocking stray light from different directions, thereby improving signal-to-noise ratio without compromising sensor integration.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The light shielding layer acts as an intermediary structure between the sensing element and the ambient environment. It selectively blocks stray light and ambient light while allowing desired optical signals to pass through the openings, thus mediating the interaction between light and the sensing element to improve measurement precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If additional light shielding structures are added to block stray light, then signal-to-noise ratio improves, but device complexity increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidstructure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The light shielding function is merged with the existing sensor structure by integrating the light shielding layer into the sensor assembly. The first and second light shielding layers are combined with the sensing element and driving circuit in a compact arrangement, achieving stray light blocking without proportionally increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The light shielding layer serves multiple functions: it blocks stray light, defines the optical path through its openings, and can be integrated with the driving circuit layout. This multi-functionality allows a single structure to address multiple requirements, improving signal-to-noise ratio without excessive complexity increase.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-affected harmful factors

If multiple light shielding layers are implemented, then stray light blocking improves, but manufacturing complexity increases

Engineering Contradiction:

Improvestray light blocking capabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The light shielding layers are designed with specific parameter optimizations: the first openings are positioned to correspond with the sensing element, and the second openings are arranged to block stray light from specific directions. These parameter changes allow effective stray light blocking while maintaining compatibility with standard manufacturing 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 solution enhances the signal-to-noise ratio of optical signals, reduces stray capacitance, and improves the sensitivity of the sensing element while simplifying the manufacturing process and increasing the reliability of the optical sensing device.

Implementation Method 1

The first light shielding layer includes at least one first opening corresponding to the sensing element, and the first light shielding layer is overlapped with the driving circuit

Methodology Applied

Scientific EffectLight shielding: Absorption (EM radiation)

Implementation Method 2

The sensing pixel includes a sensing circuit and a sensing element electrically connected to the sensing circuit

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS11953372B2Optical sensing device

Publication Date: 2024.04.09 INNOLUX CORP

AI summary

An optical sensing device is disclosed. The optical sensing device includes a sensing pixel, a driving circuit and a first light shielding layer. The sensing pixel includes a sensing circuit and a sensing element electrically connected to the sensing circuit. The driving circuit is electrically connected to the sensing circuit. The first light shielding layer includes at least one first opening corresponding to the sensing element, and the first light shielding layer is overlapped with the driving circuit in a top-view direction of the optical sensing device.