Cd-Te X-ray Imaging System Pixel Calibration
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Solution Overview
Problem
Current high-energy radiation imaging systems, particularly those using Cd—Te or Cd—Zn—Te based detector substrates, face limitations in frame rate and accuracy due to electrical performance issues like leakage current and material defects, which restrict their ability to operate effectively at high frame rates and achieve high bit depth without signal-to-noise ratio saturation.
Innovation Solution
A high-energy, real-time X-ray imaging system that utilizes Cd—Te or Cd—Zn—Te based detector substrates with a high-density pixelized readout face, enabling frame rates up to 300 fps and achieving bit depths of 14 to 18 bits by applying individual pixel calibration corrections derived from a calibration process, which accounts for offset, gain, and temporal corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge integration time is increased to improve digitization accuracy, then measurement precision improves, but productivity deteriorates due to signal-to-noise ratio saturation limiting integration time to a few seconds
Solution Approach 1:
The patent applies preliminary calibration to each pixel to determine individual correction values for offset, gain, and temporal non-linearities. This pre-characterization of pixel responses enables accurate correction at high frame rates without requiring long integration times, thus resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The system uses feedback from calibration data to dynamically correct pixel values during operation. By continuously applying correction values derived from calibration measurements, the system maintains high accuracy at high frame rates, overcoming the signal-to-noise ratio saturation limitation
2Productivity
If frame rate is increased to improve productivity, then productivity improves, but measurement precision deteriorates due to electrical performance issues like leakage current and material defects
Solution Approach 1:
The patent applies local quality by determining individual correction values for each pixel based on its specific characteristics. This pixel-by-pixel calibration accounts for local variations in electrical performance and material defects, enabling high frame rate operation while maintaining measurement precision through customized correction for each pixel's unique response
Solution Approach 2:
The system changes parameters by applying multiple types of corrections (offset, gain, and temporal) to pixel values based on calibration data. These parameter changes compensate for electrical performance issues and material defects, allowing high frame rate operation without sacrificing image accuracy
3Measurement precision
If individual pixel calibration corrections are applied to achieve high bit depth, then measurement precision improves, but device complexity increases due to calibration and correction processing
Solution Approach 1:
The patent performs preliminary calibration of each pixel before operation to determine correction values for offset, gain, and temporal non-linearities. This one-time pre-characterization enables high bit depth imaging without requiring complex real-time processing during operation, as the correction values are pre-computed and stored for application during normal imaging
Solution Approach 2:
The system uses copying by creating a lookup table or storage structure containing pre-computed correction values for each pixel. Instead of performing complex calculations in real-time, the system copies and applies pre-determined correction values from calibration data, achieving high bit depth while reducing operational complexity
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 system achieves high frame rate and high bit depth imaging without the need for extended charge integration times, thereby reducing noise and improving image accuracy, overcoming the limitations of existing systems by enabling real-time image reconstruction and static image composition from multiple frames.
Implementation Method 1
the impinging radiation is directly converted to electrical charge in the detector material itself
Data Source
AI summary
A calibrated real-time, high energy X-ray imaging system is disclosed which incorporates a direct radiation conversion, X-ray imaging camera and a high speed image processing module. The high energy imaging camera utilizes a Cd—Te or a Cd—Zn—Te direct conversion detector substrate. The image processor includes a software driven calibration module that uses an algorithm to analyze time dependent raw digital pixel data to provide a time related series of correction factors for each pixel in an image frame. Additionally, the image processor includes a high speed image frame processing module capable of generating image frames at frame readout rates of greater than ten frames per second to over 100 frames per second. The image processor can provide normalized image frames in real-time or can accumulate static frame data for substantially very long periods of time without the typical concomitant degradation of the signal-to-noise ratio.