Radiation-Hardened ROIC with TDI for Space Imaging
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Solution Overview
Problem
Conventional optical sensors, particularly those using CCD technology, have low radiation tolerance, making them unsuitable for space environments and requiring shielding, and lack the capability for longer integration times, motion compensation, and detection of faint objects at extreme ranges.
Innovation Solution
A radiation-hardened integrated circuit with time-domain integration (TDI) capability, comprising a read-out integrated circuit (ROIC) layer and a photo-sensitive layer, fabricated using CMOS or GaAs technology, which allows for longer integration times, motion compensation, and detection of faint objects, and is suitable for use in small-aperture optical systems and photon-counting applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CCD technology is used, then imaging capability is achieved, but radiation tolerance is very low
Solution Approach 1:
The patent changes the fundamental parameter of the imaging technology from CCD to CMOS architecture, which inherently provides superior radiation tolerance. This parameter change enables the sensor to withstand space radiation environments without requiring heavy shielding, directly resolving the contradiction between achieving imaging capability and maintaining radiation tolerance.
Solution Approach 2:
The patent replaces the charge transfer mechanism of CCD with the charge-to-voltage conversion mechanism of CMOS pixels. This substitution eliminates the need for complex charge transfer paths that are vulnerable to radiation-induced defects, thereby improving radiation tolerance while maintaining imaging functionality.
2Duration of action of moving object
If conventional sensors are used, then basic imaging is achieved, but integration time is limited
Solution Approach 1:
The patent implements Time-Delayed Integration (TDI) mode where charge is continuously accumulated across multiple stages over an extended period. This continuous integration process allows the sensor to collect photons over longer durations (e.g., 10-100 times longer than conventional sensors), significantly improving signal quality for faint objects while maintaining temporal coherence through the TDI shift register mechanism.
3Measurement precision
If longer integration times are used, then sensitivity to faint objects improves, but motion blur increases
Solution Approach 1:
The patent introduces dynamic motion compensation through the TDI shift register that can be electronically adjusted to match the apparent motion of objects across the field of view. By dynamically shifting the integration window in sync with object motion, the system maintains image stability and prevents motion blur even during long integration times, thereby resolving the contradiction between detection sensitivity and image stability.
4Reliability
If radiation shielding is added to protect CCD sensors, then radiation tolerance improves, but device complexity and weight increase
Solution Approach 1:
The patent replaces mechanical radiation shielding with an intrinsic radiation-hardened CMOS architecture. This substitution eliminates the need for heavy shielding structures by using radiation-tolerant semiconductor physics and circuit design, thereby improving radiation tolerance while reducing device complexity and mass.
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 integrated circuit significantly improves sensitivity and radiation tolerance, enabling effective imaging in space environments without shielding, and enhances the ability to detect faint objects at extreme ranges while compensating for linear and rotational motion.
Implementation Method 1
Each pixel has a photosensing element to produce charge in response to incident photons from an object
Data Source
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AI summary
An integrated circuit for generating image data comprises a focal-plane array of unit cells, a controller, and a memory structure having a plurality of storage locations. Each unit cell may store charge based on detected photons. The controller may read a value based on the stored charge from at least some of the unit cells, and either add the read value to an existing value in the corresponding storage location when operating in frame-sum mode, or add the read value to an existing value in a shifted storage location when operating in time-delay integration (TDI) mode. This may allow faint objects as well as objects moving in the field-of-view of the focal-plane array to be observed. The integrated circuit may be fabricated from radiation-hardened CMOS technology and may be a layer of a sensor chip assembly.