Photon-Counting Image Sensor Exposure Control via Partial Readout
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Solution Overview
Problem
Conventional photon counting type image sensors using avalanche photodiodes face challenges in accurately controlling exposure time due to increased pixel readout intervals, which reduces the accuracy of exposure time control and degrades image quality.
Innovation Solution
An image capturing device with a control unit that manages the readout of count information from counters at predetermined timings during exposure, allowing for precise exposure period control by determining whether the readout count information satisfies predetermined conditions, implemented using processors or circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel readout is performed during exposure to maintain S/N ratio, then image quality is maintained, but pixel readout interval increases and exposure time control accuracy deteriorates
Solution Approach 1:
The pixel array is divided into multiple regions (first region and second region) that can be read out at different timings. This segmentation allows partial readout during exposure without requiring complete readout of all pixels, thereby reducing the impact on exposure time control accuracy while maintaining image quality through selective readout of critical regions.
2Loss of information
If pixel readout information amount is large to capture complete image data, then image completeness is improved, but pixel readout interval increases and exposure control accuracy is reduced
Solution Approach 1:
A determination is made during exposure whether to perform readout based on predetermined conditions (such as subject brightness or exposure requirements). This preliminary determination allows the system to plan readout operations in advance, reducing unnecessary readout operations and their impact on exposure timing while ensuring complete data capture is performed when needed.
Solution Approach 2:
Instead of reading out all pixel data during exposure, only necessary portions are read out based on determination results. This partial action approach reduces readout interval impact on exposure control while capturing sufficient image data to maintain quality, avoiding the need to read out excessive data that would further increase readout intervals.
3Measurement precision
If readout frequency is increased to improve exposure control accuracy, then exposure time control accuracy is improved, but data communication load increases
Solution Approach 1:
The determination of whether to perform readout is extracted as a separate function performed during exposure, independent of the actual readout operation. This extraction allows the system to make readout decisions based on minimal data communication (only determination results), reducing the overall data communication load while maintaining exposure control accuracy through timely determination and selective readout.
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 enables accurate and efficient exposure time control, reducing data communication with the image sensor and shortening the interval for exposure end determination processing, thereby maintaining image quality and improving exposure accuracy.
Implementation Method 1
a current of observable level is produced by the avalanche phenomenon when a single photon enters the APD, for example. By converting the current into a pulse signal and counting the number of pulse signals, the number of incoming photons can be measured directly
Data Source
AI summary
An image capturing device comprising: an image sensing element having a plurality of pixels each including a sensor that outputs a pulse signal in response to incident of a photon, and a counter that counts a number of the pulse signals; a readout unit that reads out count information from the counters; a control unit that controls the readout unit so as to read out the count information from the counters of at least a part of the plurality of the pixels at a predetermined timing during exposure of the pixels; and a determination unit that determines whether the read out count information satisfies a predetermined condition, wherein, in a case where the predetermined condition is satisfied, counting by the counters is stopped.