Imaging Array Pixel Architecture for Fast Frame Capture
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Solution Overview
Problem
Conventional digital radiography image sensing arrays face challenges with long read-out times and disappointing signal-to-noise ratios due to dark current noise, which affects the quality and speed of image capture, particularly in applications requiring high resolution and immobility of subjects during imaging.
Innovation Solution
Incorporating a low-noise image storage element in each pixel, with separate charge storage and switching elements to isolate and read out the signal, reducing dark current noise and enabling faster image acquisition and improved signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional image sensing arrays are used for digital radiography, then image capture can be performed, but read-out time is long (one second or longer) and signal-to-noise ratio is disappointing due to dark current noise
Solution Approach 1:
The patent segments the image capture process into multiple frames, with each frame captured on a separate pixel site within the same pixel. This allows parallel processing of multiple frames simultaneously, reducing the total read-out time from one second or longer to much faster speeds while maintaining signal quality through selective frame combination.
Solution Approach 2:
The patent adds a temporal dimension to the spatial pixel structure by incorporating multiple frame storage capabilities within each pixel. This multi-frame architecture enables simultaneous capture and storage of multiple time-points, allowing rapid sequential imaging without the sequential read-out bottleneck of conventional single-frame systems.
2Productivity
If multiple frames are captured sequentially in conventional arrays, then multiple images can be obtained, but the process is slow and requires the subject to remain immobile for several seconds
Solution Approach 1:
The patent divides the imaging task across multiple pixel sites, with each pixel capable of storing multiple frames independently. This segmentation enables simultaneous capture of multiple frames across the entire array rather than sequential frame-by-frame capture, achieving video-rate imaging where subjects can move naturally without requiring several seconds of immobility.
Solution Approach 2:
The patent enables continuous image capture at video rates by maintaining active sensor elements throughout the exposure period. Multiple frames are accumulated continuously in parallel across the array, eliminating the idle time between frames that occurs in sequential capture systems, thereby allowing natural subject movement during the imaging process.
3Reliability
If dark current noise is present in conventional arrays, then thermal generation of charge carriers occurs, but this creates offset and noise that degrades image quality
Solution Approach 1:
The patent extracts the dark current noise problem from the signal accumulation process by capturing multiple short-duration frames and combining them selectively. Since dark current accumulates over time, dividing the total exposure into multiple brief frames reduces the dark current contribution in each frame, and the signal can be recovered through frame combination while suppressing the noise.
Solution Approach 2:
The patent employs periodic frame capture with multiple short exposure intervals rather than one long continuous exposure. This periodic action allows the system to sample the image at multiple time-points, reducing the impact of thermally generated dark current that accumulates continuously, while maintaining signal integrity through temporal sampling and frame combination.
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 allows for faster image capture with improved signal-to-noise ratio, enabling multiple exposures at video rates and reduced radiation dosage by minimizing dark current noise and read-out time, thus enhancing the overall quality and efficiency of digital radiography.
Implementation Method 1
a scintillator screen 16 for converting the energy from ionized radiation into light radiation having a different frequency, typically within the visible spectrum
Implementation Method 2
each pixel having a photo-activated image sensing element... in which an intermediate scintillator element converts the X-rays to visible-light photons which are then sensed by a light-sensitive image-sensing element
Data Source
AI summary
An imaging array has a plurality of pixel sites (22), each having a photosensing element (24) providing a variable signal in response to incident radiation. A first frame storage circuit (46a) is electrically coupled to the photosensing element and has a first charge storage element for storing a first photosensing element signal and a first switching element (26) to switch the photosensing element to the first frame storage circuit. A second switching element (26) switches the first charge storage element (32) for reading the signal stored. A second frame storage circuit (46b) is electrically coupled to the photosensing element and has a second charge storage element for storing a second signal. A third switching element (26) switches the photosensing element to the second frame storage circuit. A fourth switching element (26) switches the second charge storage element for reading the signal stored.