Transparent Image Sensor With Non-Local Readout Circuit
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Solution Overview
Problem
Current image sensors face challenges in achieving high photoconductive gain and sensitivity while maintaining low dark current levels, especially in miniaturized pixels, and they struggle to be flexible, stretchable, and transparent, which are essential for emerging applications.
Innovation Solution
The image sensor design incorporates a non-local readout circuit with a photo-active element and a non-photo-active reference element, both made with two-dimensional materials, which allows for balanced biasing and reduced dark current, enabling high photoconductive gain and sensitivity without the need for in-pixel electronics, and can be integrated into flexible and transparent devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If in-pixel readout electronics are used, then pixel functionality and readout capability are improved, but pixel area is reduced and device complexity increases
Solution Approach 1:
The patent extracts the readout electronics from the pixel area and places them in a separate readout circuit located outside the pixel array. This allows the pixels to be read out through a shared readout circuit without requiring individual in-pixel electronics, thereby maintaining full readout capability while preserving maximum pixel area for light collection.
Solution Approach 2:
The readout circuit is designed to serve multiple pixels simultaneously through time-multiplexed readout, allowing a single readout circuit to handle the entire pixel array. This universal approach eliminates the need for dedicated in-pixel electronics in each pixel while maintaining full readout functionality across all pixels.
2Area of stationary object
If pixel size is reduced for miniaturization, then device compactness is improved, but photoconductive gain and sensitivity deteriorate
Solution Approach 1:
The patent changes the material parameter by using two-dimensional materials (such as graphene, MoS2, WS2, WSe2, MoSe2, h-BN, or black phosphorus) for the photodetector layer. These 2D materials exhibit high photoconductive gain even at the nanoscale, enabling miniaturized pixels to maintain high sensitivity and photoconductive gain despite their reduced size.
Solution Approach 2:
The patent employs composite material structures combining 2D photodetector materials with appropriate substrates and contact layers. This composite approach enables the integration of highly sensitive photodetectors into miniaturized pixels while maintaining the necessary electrical and optical properties for high sensitivity detection.
3Ease of manufacture
If conventional image sensor design is used, then manufacturing compatibility with CMOS process is improved, but flexibility and transparency are reduced
Solution Approach 1:
The patent uses thin-film 2D materials that are inherently flexible and can be integrated onto flexible substrates. These 2D materials maintain compatibility with flexible device manufacturing processes while enabling the image sensor to be integrated into wearable devices, flexible displays, and other applications requiring flexibility and transparency.
4Area of stationary object
If back-side illuminated image sensor design is used, then pixel fill factor is improved, but manufacturing complexity and cost increase dramatically
Solution Approach 1:
The patent extracts the readout electronics from the pixel structure entirely and places them in a separate readout circuit outside the pixel array. This eliminates the need for back-side illumination processing and complex in-pixel electronics, achieving high pixel fill factor through simple front-side 2D photodetector integration while maintaining straightforward manufacturing processes.
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 achieves high signal-to-noise ratios and enhanced pixel sensitivity without cooling, while allowing for compact, flexible, and transparent image sensors suitable for various applications, including gaze tracking.
Implementation Method 1
Each pixel includes a photo-active element or photodetector, which is usually a photodiode
Implementation Method 2
The present invention also relates to an optoelectronic device comprising said image sensor, and to a gaze tracking apparatus comprising said optoelectronic device... makes it possible to obtain pixels with high photoconductive gain, i.e. with a built-in photoconductive gain, enhanced responsivity and/or improved sensitivity
Data Source
AI summary
Provided are gaze tracking apparatuses, which in some embodiments can include an optoelectronic device, wherein the optoelectronic device includes an image sensor with non-local readout circuit having a substrate and a plurality of pixels and operatively connected to a control unit, wherein a first area of the substrate is at least partially transparent to visible light and at least the plurality of pixels of the image sensor are arranged on the first area of the substrate to aim to an eye of a user when placed in front of an inner face of the substrate, and wherein the control unit is also adapted to control the image sensor to acquire image information from the user's eye for performing a gaze tracking of the user's eye.