Solid State Image Sensor Pulse Thinning for Wide Dynamic Range
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Solution Overview
Problem
Existing solid state image sensors face challenges in achieving a wide dynamic range without increasing signal amount, particularly due to the limitations of bit width in photon counting methods.
Innovation Solution
A solid state image sensor that thins out pulses issued from a sensor unit at a thinning ratio corresponding to the number of pulses, using a frequency divider and counter circuit to count pulses, allowing for dynamic adjustment of counting frequency based on the count value, thereby reducing the bit width of image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the bit width of the counter is increased to achieve a wide dynamic range, then the dynamic range is improved, but the signal amount increases and the number of pixels cannot be increased
Solution Approach 1:
The patent applies dynamics by making the counting frequency variable rather than fixed. The counting frequency is dynamically adjusted based on the brightness of the imaging target, allowing the system to adapt to different lighting conditions. This resolves the contradiction by enabling a wide dynamic range without requiring a fixed high bit width, thus controlling signal amount while maintaining pixel count.
Solution Approach 2:
The patent changes the parameter of counting frequency based on imaging conditions. By adjusting the counting frequency parameter according to target brightness, the system achieves wide dynamic range capability without increasing bit width, thereby controlling signal amount and enabling higher pixel counts.
2Illumination intensity
If the bit width of the counter is increased to achieve a wide dynamic range, then the dynamic range is improved, but the counter scale and readout memory scale increase
Solution Approach 1:
The patent uses dynamic adjustment of counting frequency to replace the need for increased counter bit width. By making the counting frequency adaptive to imaging conditions, the system achieves wide dynamic range with a fixed, smaller counter scale, reducing device complexity.
Solution Approach 2:
The patent changes the operating parameter (counting frequency) rather than increasing hardware scale (bit width). This parameter change approach achieves the same functional effect with reduced hardware complexity, allowing for more compact counter and readout memory designs.
3Measurement precision
If the counting frequency is increased to count more photons, then the measurement precision is improved, but the signal amount increases
Solution Approach 1:
The patent optimizes the counting frequency parameter based on imaging conditions rather than using a fixed high frequency. This parameter optimization achieves sufficient photon counting precision for each condition while controlling the overall signal amount, resolving the contradiction between precision and signal volume.
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 the realization of a wide dynamic range while suppressing the increase in signal amount, allowing for a reduction in the scale of the counter and readout memory, which contributes to an increase in the number of pixels and reduces costs.
Implementation Method 1
a sensor unit that issues pulses at a frequency corresponding to a frequency at which photons are incident
Implementation Method 2
a frequency divider that thins out the pulses issued from the sensor unit at a thinning ratio corresponding to the number of pulses issued from the sensor unit
Data Source
AI summary
The present invention provides a solid state image sensor, an image capturing apparatus, and an image capturing method that can realize a wide dynamic range while suppressing an increase in a signal amount. A solid state image sensor includes a sensor that issues pulses at a frequency corresponding to a frequency at which photons are incident; and a counter circuit that thins out the pulses issued from the sensor at a thinning ratio corresponding to the number of pulses issued from the sensor, and counts the pulses.