Intraoral X-ray Sensor with Central Detection Column
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Solution Overview
Problem
Current dental radiology systems face challenges in synchronizing the start and end of X-ray image integration with X-ray flashes while minimizing X-ray exposure, particularly in avoiding wired connections and accommodating varying dark current levels due to temperature changes, which complicates the detection of X-ray flashes.
Innovation Solution
Incorporating a series of photodiodes connected in parallel and aligned along a central column or row within the matrix, these detection photodiodes are connected to a detection conductor and a detection circuit that triggers image capture when the current exceeds a threshold, optimizing the detection of X-ray flashes and minimizing interference with the main pixel array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wired connection is used between the sensor and X-ray source to trigger integration, then synchronization of image capture with X-ray flash is achieved, but device complexity and ease of operation deteriorate due to required common protocol and connection infrastructure
Solution Approach 1:
The patent extracts the X-ray flash detection function from the main pixel array by dedicating a specific central column or row of pixels solely to detection purposes. These detection pixels are electrically isolated from the normal readout circuitry, allowing autonomous detection of X-ray flashes without requiring external wired connections or communication protocols between the sensor and X-ray source.
Solution Approach 2:
The sensor performs self-detection of X-ray flashes using its own pixel array, eliminating the need for external triggering mechanisms. The detection pixels autonomously sense the X-ray flash and generate internal trigger signals, making the system self-sufficient and removing dependence on wired connections or external control infrastructure.
2Measurement precision
If additional X-ray detector components are added beside the image sensor, then X-ray flash detection capability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent makes the pixel array multi-functional by using the same photosensitive elements for both imaging and X-ray flash detection. The detection pixels are structurally identical to the imaging pixels but are electrically isolated and dedicated to detection, allowing a single component to serve dual purposes without requiring separate detector devices or complex assembly processes.
Solution Approach 2:
The patent merges the X-ray detection function with the existing pixel array structure, combining imaging and detection capabilities into a single integrated sensor. This eliminates the need for separate detector components and their associated mounting, alignment, and connection infrastructure, significantly simplifying manufacturing.
3Measurement precision
If the central charge transfer register is made light-sensitive to detect X-ray flashes, then detection capability is improved, but image quality deteriorates due to light interference during charge transfer
Solution Approach 1:
The patent segments the pixel array into distinct functional regions: imaging pixels for capturing the image and detection pixels for detecting X-ray flashes. The detection pixels are electrically isolated from the charge transfer register and readout circuitry, preventing any light interference or charge contamination that would occur if the register itself were used for detection.
Solution Approach 2:
The patent extracts the detection function from the charge transfer register and places it in dedicated detection pixels that are electrically isolated from the imaging signal path. This separation ensures that detection activities do not interfere with the sensitive charge transfer and readout processes that generate the final image.
4Measurement precision
If reference pixels are used to detect X-ray flashes by monitoring charge levels, then detection function is added, but device complexity increases due to specific addressing requirements
Solution Approach 1:
The detection pixels are activated in a periodic manner synchronized with the expected X-ray flash timing. The sensor controller periodically enables the detection pixels to monitor for X-ray flashes during the integration period, using simple temporal gating rather than complex spatial addressing schemes to identify and respond to flashes.
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 solution allows for precise and rapid detection of X-ray flashes, reducing X-ray exposure and minimizing the impact on the final image quality, while maintaining a compact sensor design and easy manufacturing process.
Implementation Method 1
Incorporating a series of photodiodes connected in parallel and aligned along a central column or row within the matrix, these detection photodiodes are connected to a detection conductor and a detection circuit that triggers image capture when the current exceeds a threshold
Implementation Method 2
Modern dental radiology systems use image sensors employing silicon-based MOS technology, covered with a layer of scintillator material that converts X-rays to visible light within a wavelength spectrum to which silicon is sensitive
Data Source
AI summary
The invention relates to medical imaging and, more specifically, to intraoral dental radiology. The sensor according to the invention includes a series (SPHx) of detection photodiodes for detecting the arrival of an X-ray flash. The series of photodiodes occupies the location of a central column of the matrix of pixels. The signal of the missing pixel in each row can be reconstructed by interpolating the signals provided by the adjacent pixels of the row. The detection photodiodes are identical to the photodiodes of the active CMOS pixels. They are all electrically connected on one side to a reference potential and on the other side to a detection conductor (CD) extending along the series of photodiodes. This detection conductor is connected to a detection circuit (DX) delivering a signal for triggering the capture of an image when the detected current or the variation in this current exceeds a threshold showing that an X-ray flash has been initiated.