TDI Image Sensor Charge Transport Layer Segmentation
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Solution Overview
Problem
Current image sensors for time delay and integration (TDI) imaging face limitations in signal-to-noise ratio, particularly for wavelengths beyond visible light, due to the use of silicon and digital or voltage domain summation in CMOS technology.
Innovation Solution
An image sensor with an array of photo-sensitive elements featuring a charge transport layer and active layer, where the charge transport layer is divided into portions controlled by separate gates, allowing lateral charge transfer and read-out peripherally, enabling detection of ultraviolet and infrared light with improved signal-to-noise characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If silicon-based CCD is used for TDI imaging, then charge accumulation and transfer can be achieved with high signal-to-noise ratio, but wavelength detection is limited to visible range
Solution Approach 1:
The photo-sensitive device is segmented into distinct functional layers: an active layer for charge generation and a charge transport layer for charge transfer. This segmentation allows each layer to be optimized for its specific function, enabling the use of non-silicon materials in the active layer for extended wavelength detection while maintaining reliable charge transfer through the semiconductor substrate.
Solution Approach 2:
The charge transport layer acts as an intermediary between the active layer and the semiconductor substrate. It receives charges from the active layer and transfers them to the read-out circuitry in the substrate, enabling the coupling of non-silicon photo-sensitive materials with silicon-based processing circuits for TDI imaging.
2Adaptability or versatility
If CMOS technology with digital summation is used for TDI imaging, then various wavelengths can be detected, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent replaces digital/voltage domain summation with physical charge domain accumulation. Charges are physically accumulated in the charge transport layer during the integration period, and this accumulated charge is then transferred as a single unit to the read-out circuitry, avoiding the noise accumulation inherent in digital summation methods.
3Ease of operation
If charges are transferred within semiconductor substrate, then TDI imaging can be performed, but detection is limited to silicon-sensitive wavelengths
Solution Approach 1:
The device is segmented into an active layer for light detection and a charge transport layer for charge transfer. This allows the active layer to be made from materials sensitive to different wavelength ranges (UV, visible, IR) while the charge transport layer and substrate provide the charge transfer and read-out infrastructure.
Solution Approach 2:
The photo-sensitive device uses composite material structure combining non-silicon active layer materials (for extended wavelength detection) with semiconductor charge transport layer and substrate (for charge transfer and circuit integration), achieving both broad wavelength detection and reliable charge transfer.
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 the signal-to-noise ratio by allowing charges to be accumulated and transferred efficiently, reducing noise and enabling high-quality imaging across various light wavelengths, including ultraviolet and infrared.
Implementation Method 1
an active layer configured to generate charges in response to incident light on the active layer
Implementation Method 2
a charge transport layer formed of a semiconductor, wherein the charge transport layer comprises a first portion and a second portion... the first gate is configured to control a potential of the first portion of the charge transport layer and the second gate is configured to control a potential of the second portion of the charge transport layer
Data Source
Figure 1
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AI summary
An image sensor for time delay and integration (TDI) imaging comprises: an array (102) of photo-sensitive elements (110) arranged in rows (104) and columns (106), wherein each photo-sensitive element (110) comprises: an active layer (120) configured to generate charges in response to incident light; a charge transport layer (118) comprising a first portion (118a) and a second portion (118c); and at least a first and a second gate (114a; 114c) configured to control a potential of the first portion (118a) and the second portion (118b), respectively, and wherein the first and the second gates (114a; 114c) are configured for controlling movement of charges from the first portion (118a) to the second portion (118c); wherein the array (102) of photo-sensitive elements (110) is configured to control transfer of charges from the second portion (118c) of a first photo-sensitive element (110a) to the first portion (118a) of a second photo-sensitive element (110b).