Display Device Photosensor Leakage Current Reduction

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Solution Overview

Problem

Existing display devices face challenges in accurately sensing light due to leakage currents when photosensors are adjacent to light-emitting pixels, which can lead to incorrect fingerprint identification.

Innovation Solution

A display device is designed with light-emitting pixels and photosensors alternately disposed in specific directions, allowing for a sensing mode with distinct frame periods where only certain pixels emit light, thereby minimizing leakage currents and enhancing light sensing accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If photosensors are disposed adjacent to light-emitting pixels to increase sensing coverage, then the sensing area is improved, but leakage current increases and sensing accuracy deteriorates

Engineering Contradiction:

Improvesensing areaVSAvoidsensing accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The display panel is divided into distinct light-emitting pixel regions and photosensor regions that are spatially separated. The photosensors are disposed in non-pixel regions rather than adjacent to light-emitting pixels, segmenting the functional areas to prevent interference between light emission and light sensing operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A light shield or isolation structure is introduced as an intermediary element between light-emitting pixels and photosensors. This intermediary prevents stray light from reaching photosensors, thereby eliminating leakage current while maintaining sensing coverage through proper spatial arrangement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If photosensors are disposed adjacent to light-emitting pixels to reduce device complexity, then the device structure is simplified, but leakage current increases and fingerprint identification accuracy deteriorates

Engineering Contradiction:

Improvedevice structureVSAvoidfingerprint identification accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The device structure is segmented into distinct functional zones: light-emitting pixel regions and photosensor regions. By disposing photosensors in non-pixel regions rather than adjacent to pixels, the structure maintains simplicity while ensuring functional separation to prevent leakage current and maintain fingerprint identification reliability.

Inventive Principle:

Principle #1Segmentation

3Productivity

If all pixels emit light during sensing to improve sensing speed, then the sensing time is reduced, but leakage current increases and causes incorrect fingerprint identification

Engineering Contradiction:

Improvesensing speedVSAvoidfingerprint identification accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The display operates in periodic cycles alternating between light-emitting periods and light-sensing periods. During sensing periods, light emission is suspended while photosensors are activated, and during display periods, photosensors are deactivated while pixels emit light. This periodic operation enables both fast sensing and accurate fingerprint identification by eliminating leakage current interference.

Inventive Principle:

Principle #19Periodic action

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 proposed solution effectively reduces leakage currents, allowing for accurate light sensing and fingerprint measurement by isolating the photosensors from the light-emitting pixels during specific frame periods.

Implementation Method 1

The optical method may authenticate the user's fingerprint by sensing light reflected from the user's fingerprint

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

The optical method may authenticate the user's fingerprint by sensing light reflected from the user's fingerprint

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS20250182705A1Display device

Publication Date: 2025.06.05 SAMSUNG DISPLAY CO LTD

AI summary

A display device includes light emitting pixels that emit light, photosensors each controlling a sensed current according to an incident light, and a read-out circuit that senses the sensed current of each of the photosensors and converts the sensed current into digital sensed data. In a sensing mode including a first frame period and a second frame period, the light emitting pixels include first sensing pixels that emit the light during the first frame period and second sensing pixels that do not emit the light during the first frame period, the photosensors include first photosensors and second photosensors, and a first distance between any one of the first sensing pixels and a first photosensor adjacent to the first sensing pixel among the first photosensors is greater than a second distance between the first sensing pixel and a second photosensor adjacent to the first sensing pixel among the second photosensors.