CMOS X-ray Detector Bright Pixel Correction
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Solution Overview
Problem
Conventional dental x-ray systems using film expose patients to high x-ray doses, are costly, and pose disposal challenges, while solid-state sensors reduce dosage but increase thickness and degrade image resolution due to scattering issues.
Innovation Solution
The system employs a controller that measures charge over time to identify and correct x-ray hits in pixel sensors, using distributed ADCs and adaptive thresholding to combine data from multiple frames, reducing the need for thick shielding and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shielding layer is added to block x-rays and reduce bright pixels, then the number of bright pixels is reduced to an acceptable level, but the thickness of the sensor increases significantly
Solution Approach 1:
The patent removes the shielding layer entirely from the sensor structure. Instead of physically blocking x-rays with a thick shielding plate, the system extracts and eliminates the harmful bright pixels through digital image processing algorithms that identify and correct x-ray hit events in the captured images.
Solution Approach 2:
The patent replaces the mechanical/physical shielding approach (using a thick plate to block x-rays) with a computational/software-based solution. The system uses image processing algorithms to detect and correct x-ray hits digitally, substituting physical blocking with electronic/c computational methods.
2Ease of operation
If the sensor thickness is reduced to improve patient comfort, then the sensor becomes more patient-friendly, but the ability to shield x-rays and reduce bright pixels is compromised
Solution Approach 1:
The patent extracts and removes the shielding layer from the sensor design, allowing for a thinner sensor that improves patient comfort. The harmful bright pixels are then extracted and corrected through digital image processing rather than physical blocking.
Solution Approach 2:
The patent substitutes the mechanical shielding function with a computational correction system. The thin sensor allows patient comfort while the software-based bright pixel correction maintains image quality without requiring thick physical shielding.
3Device complexity
If conventional film is used for x-ray detection, then the system is simple and well-established, but the patient is exposed to high x-ray doses and film processing costs increase
Solution Approach 1:
The patent changes the detection parameter from film-based optical detection to solid-state photodetector-based electronic detection. This parameter change enables digital imaging with lower x-ray doses while maintaining system simplicity through the use of standard CMOS technology and digital image processing.
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 approach reduces the thickness of the sensor, enhances image resolution, and minimizes bright pixels, providing a more patient-friendly and cost-effective digital dental imaging solution.
Implementation Method 1
a layer of scintillation material is used to convert the x-rays to visible light
Implementation Method 2
each of said pixel sensors comprises a photodetector that stores a charge in response to said light being received by that photodetector
Implementation Method 3
The optical fibers are doped with a heavy metal that absorbs x-rays that are not converted in the scintillation material
Data Source
AI summary
An image sensor having a two-dimensional array of pixel sensors [201], a layer of scintillation material[206], and a controller[202] is disclosed. The layer of scintillation material is adjacent to the two-dimensional array, the scintillation material emits light in response to x-rays impinging thereon. The pixel sensors detect this light. The controller reads out data stored in the two-dimensional array of pixel sensors and forms an image therefrom. The controller corrects the data for errors resulting from x-rays that generate electrons that are stored in the pixel sensors [41] in the process of forming the image. In one aspect of the invention, the controller forms the image by causing the two-dimensional array to form a plurality of frames, each frame includes a measurement of a charge stored on each photodiode[46] during a preceding time period. The controller selectively combines data from the frames to form the image.