Photon Counting Pixel Offsets to Prevent Image Degradation
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Solution Overview
Problem
Existing photoelectric conversion apparatuses using avalanche photodiodes experience image degradation due to sudden variations in source voltage caused by simultaneous switching of counter outputs, leading to unevenness and spots in images.
Innovation Solution
The apparatus includes offset adding circuits that set different offset values for each counter circuit, controlling the timing of output level changes to prevent sudden voltage variations and count errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple counters are used to count photons from multiple pixels, then photon counting capability is improved, but source voltage varies causing image degradation
Solution Approach 1:
The patent applies preliminary action by setting different offset values for each counter before the counting operation begins. These offset values are predetermined and stored in offset registers, ensuring that when counting starts, each counter begins from a different initial state. This preliminary differentiation prevents simultaneous switching of counter outputs, thereby avoiding source voltage variations that would degrade image quality while maintaining the multi-pixel photon counting capability
2Productivity
If counters operate simultaneously to improve productivity, then counting speed is improved, but voltage variation causes measurement errors
Solution Approach 1:
The patent applies local quality by giving each counter a unique offset value that is specific to that counter's location or identity in the array. This local differentiation ensures that while all counters operate simultaneously for high productivity, each counter's output switching occurs at slightly different times due to their unique offset values, preventing the simultaneous switching that would cause voltage spikes and count errors
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 stabilizes the source voltage, preventing image degradation and ensuring consistent image quality by varying the timing of counter output switches.
Implementation Method 1
an avalanche photodiode... counting the number of incident photons and outputting the counted number as a digital signal
Implementation Method 2
Utilizing an avalanche phenomenon that occurs when an avalanche photodiode is operated in a Geiger mode
Data Source
AI summary
A photoelectric conversion apparatus includes a first pixel, a second pixel, and an offset adding circuit. The first pixel includes a first avalanche photodiode and a first count circuit. The first count circuit is configured to count a first signal that is based on the number of photons that have entered the first avalanche photodiode. The second pixel includes a second avalanche photodiode and a second count circuit. The second count circuit is configured to count a second signal that is based on the number of photons that have entered the second avalanche photodiode. The offset adding circuit is configured to set an offset value for each of the first count circuit and the second count circuit. The first count circuit starts a first counter operation from a first offset value. The second count circuit starts a second counter operation from a second offset value.