CMOS Image Sensor Subpixels for HDR and LED Flicker Mitigation

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Solution Overview

Problem

Image sensors struggle to capture high dynamic range images without motion artifacts and LED flicker issues, which can lead to dangerous situations in applications like car viewing systems and affect the performance of automated driver assistance systems.

Innovation Solution

A CMOS image sensor with pixels subdivided into subpixels, each with individually adjustable light sensitivity through color filters of varying strengths, allowing for improved dynamic range capture and mitigation of LED flicker.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If multiple images are captured using different exposure times to achieve high dynamic range, then the dynamic range of the captured image is improved, but motion artifacts occur due to changes in the scene between captures

Engineering Contradiction:

Improvedynamic rangeVSAvoidmotion artifacts

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

Each pixel is divided into multiple subpixels with different color filters and sensitivity characteristics. This segmentation allows simultaneous capture of multiple sensitivity responses within a single exposure, achieving HDR效果 without multiple captures and avoiding motion artifacts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from temporal dimension (multiple exposures at different times) to spectral dimension (multiple sensitivities within same exposure). By utilizing wavelength-selective color filters, the system captures multiple sensitivity responses simultaneously in the spectral domain, eliminating motion artifacts while achieving HDR.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Illumination intensity

If shorter exposure time is used to capture bright parts of the image, then the dynamic range is improved, but LED flicker occurs because the camera exposure may miss the LED pulse

Engineering Contradiction:

Improvedynamic rangeVSAvoidLED flicker

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

Different subpixels within the same pixel have different color filters and sensitivity characteristics. This local quality differentiation allows certain subpixels to capture LED light effectively while others capture ambient light, enabling the system to mitigate LED flicker through post-processing combination of subpixel responses.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the sensitivity parameter of subpixels through wavelength-selective color filters. By adjusting the spectral sensitivity of different subpixels, the system can optimize capture of LED light at specific wavelengths while maintaining overall HDR performance and reducing LED flicker effects.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If pixels are subdivided into subpixels with different color filters, then the high dynamic range capture capability is improved, but the device complexity increases

Engineering Contradiction:

Improvedynamic rangeVSAvoidpixel structure

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The subpixel structure serves multiple functions simultaneously: wavelength-selective filtering for HDR capture, LED flicker mitigation through differential sensitivity, and color information capture. This multi-functionality reduces the need for separate components and justifies the increased structural complexity within each pixel.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements a nested structure where multiple subpixels with different color filters are contained within a single pixel boundary. This nesting allows the system to maintain the pixel array structure while incorporating complex multi-sensitivity functionality, managing device complexity through hierarchical organization.

Inventive Principle:

Principle #7Nested doll (Nesting)

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

Enables the capture of high dynamic range images in a single exposure, reducing motion artifacts and LED flicker issues, while maintaining an acceptable signal-to-noise ratio.

Implementation Method 1

The pixel array includes a plurality of photodiodes arranged in rows and columns

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

Each pixel may include multiple subpixels, each having one or more color filters with individually adjustable light sensitivity

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS12310133B2CMOS image sensor with multiple sensitivities for high dynamic range imaging and led flicker mitigation

Publication Date: 2025.05.20 OMNIVISION TECHNOLOGIES INC

AI summary

CMOS image sensor with multiple sensitivities for high dynamic range imaging and LED flicker mitigation. In one embodiment, an image sensor includes a plurality of pixels arranged in rows and columns of a pixel array that is disposed in a semiconductor substrate. Each pixel includes a plurality of cells. A plurality of color filters is disposed over corresponding plurality of cells. The plurality of color filters corresponding to the plurality of cells of an individual pixel have more than one filtering strength for each color of the plurality of color filters.