CMOS Image Sensor Pixel Array with Unfiltered Pixels

Solution Overview

Problem

CMOS image sensors face reduced light sensitivity and increased noise as pixel areas shrink, particularly in low light conditions, limiting the ability to increase pixel density while maintaining a compact chip footprint.

Innovation Solution

Incorporating unfiltered, light-efficient pixels alongside color-filtered pixels in a CMOS image sensor array, allowing unfiltered pixels to receive light across the full visible spectrum and improve low-light sensitivity and reduce noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If pixel areas are shrunk to increase pixel density, then pixel density is improved, but light sensitivity deteriorates and noise increases

Engineering Contradiction:

Improvepixel densityVSAvoidlight sensitivity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The pixel array is segmented into two distinct types: color-filtered pixels for color information and unfiltered pixels for luminance information. This segmentation allows each pixel type to be optimized for its specific function, with unfiltered pixels capturing more light across the full spectrum to improve sensitivity and reduce noise in low-light conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel array have different optical properties. Color-filtered pixels use spectral filters to capture color information, while unfiltered pixels remain transparent across the visible spectrum to maximize light capture. This local differentiation of optical quality enables simultaneous optimization for both color rendering and light sensitivity.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If pixel areas are shrunk to increase pixel density, then pixel density is improved, but noise increases

Engineering Contradiction:

Improvepixel densityVSAvoidnoise

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The pixel array is segmented into two distinct types: color-filtered pixels for color information and unfiltered pixels for luminance information. This segmentation allows each pixel type to be optimized for its specific function, with unfiltered pixels capturing more light across the full spectrum to improve sensitivity and reduce noise in low-light conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel array have different optical properties. Color-filtered pixels use spectral filters to capture color information, while unfiltered pixels remain transparent across the visible spectrum to maximize light capture. This local differentiation of optical quality enables simultaneous optimization for both color rendering and light sensitivity.

Inventive Principle:

Principle #3Local quality

3Loss of information

If color filters are added to all pixels, then color information is improved, but light sensitivity deteriorates

Engineering Contradiction:

Improvecolor informationVSAvoidlight sensitivity

Core Design Contradiction:

Loss of informationVSReliability

Solution Approach 1:

The pixel array is segmented into two distinct types: color-filtered pixels for color information and unfiltered pixels for luminance information. This segmentation allows each pixel type to be optimized for its specific function, with unfiltered pixels capturing more light across the full spectrum to improve sensitivity and reduce noise in low-light conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The imaging sensor achieves multi-functionality by combining color-filtered pixels and unfiltered pixels within the same array. The color-filtered pixels provide color information while the unfiltered pixels provide luminance information, and together they enable the sensor to function effectively in both well-lit and low-light conditions without requiring separate sensors.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration enhances low-light sensitivity and reduces noise, enabling cleaner image information and improved picture depth resolution without expanding the chip footprint, suitable for high-resolution compact cameras.

Implementation Method 1

Light striking each photodiode changes its current-voltage (I/V) characteristic and the CMOS support senses characteristic changes in each diode

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS7821553B2Pixel array, imaging sensor including the pixel array and digital camera including the imaging sensor

Publication Date: 2010.10.26 GLOBALFOUNDRIES US INC

AI summary

A pixel array in an image sensor, the image sensor and a digital camera including the image sensor. The image sensor includes a pixel array with colored pixels and unfiltered (color filter-free) pixels. Each unfiltered pixel occupies one or more array locations. The colored pixels may be arranged in uninterrupted rows and columns with unfiltered pixels disposed between the uninterrupted rows and columns. The image sensor may in CMOS with the unfiltered pixels reducing low-light noise and improving low-light sensitivity.