Photon Counting Image Sensor with Illuminance-Adaptive Pulse Timing
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Solution Overview
Problem
Existing image sensors face challenges in simultaneously achieving high dynamic range (HDR) and high frame rate due to the significant variation in the number of pulses according to illuminance levels, requiring large counters that are difficult to size appropriately.
Innovation Solution
The solution involves modulating the period of the pulse signal in image sensors based on ambient illuminance, dividing frames into sub-frames, and adjusting the pulse signal period to prevent counter overflow, allowing for fixed counter sizes and improved frame rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the counter size is increased to handle high illuminance conditions, then the dynamic range is improved, but the pixel area and frame rate are degraded
Solution Approach 1:
The patent applies dynamics by making the counter capacity adaptive rather than fixed. The counter dynamically adjusts its capacity based on ambient illuminance conditions - using a first (smaller) capacity in low illuminance and a second (larger) capacity in high illuminance. This resolves the contradiction by allowing the system to have sufficient counting capacity only when needed (high illuminance), while maintaining smaller pixel area and higher frame rate in normal conditions.
Solution Approach 2:
The patent changes the parameter of counter capacity based on illuminance conditions. By detecting ambient illuminance and switching between different counter capacities (first counter capacity for low illuminance, second counter capacity for high illuminance), the system optimizes the trade-off between dynamic range and frame rate without requiring a permanently large counter.
2Reliability
If the pixel area is increased to accommodate larger counters, then the dynamic range is improved, but the resolution and frame rate are degraded
Solution Approach 1:
The counter capacity is made dynamic based on illuminance conditions rather than being fixed at a large size. This allows the pixel to maintain small area (for high resolution) while still achieving large dynamic range when needed by temporarily increasing counter capacity only during high illuminance conditions.
Solution Approach 2:
The patent changes the counter capacity parameter according to ambient illuminance, allowing the system to achieve high dynamic range performance only when necessary (in high illuminance conditions) without permanently increasing pixel area, thereby maintaining high resolution.
3Reliability
If a fixed large counter is used to handle all illuminance conditions, then the dynamic range is improved, but the device complexity and power consumption increase
Solution Approach 1:
Instead of using a fixed large counter for all conditions, the system dynamically switches between a first counter (smaller capacity for low illuminance) and a second counter (larger capacity for high illuminance). This reduces average device complexity and power consumption while maintaining the ability to handle high dynamic range conditions when they occur.
Solution Approach 2:
The patent changes the operational parameter of counter capacity based on detected illuminance levels, allowing the system to use minimal resources (smaller counter) during normal operation and only activate the larger counter capacity when high illuminance conditions require it, thereby reducing overall device complexity.
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 enables high dynamic range and high frame rate performance by preventing counter overflow and reducing pixel size while maintaining accurate photon counting, even in varying illuminance conditions.
Implementation Method 1
Image sensors receive light incident thereon from an object and photoelectrically convert the received light into an electrical signal
Data Source
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AI summary
An image sensor including a plurality of pixels, wherein each pixel includes: a photodiode; a pulse generator configured to generate a pulse signal based on an electric signal generated according to a photon incident on the photodiode; and a counter configured to count and output the number of pulse signals, and wherein a period of the pulse signal is increased with increasing ambient illuminance of the image sensor.