Solid-State Image Pickup Device Dynamic Range Optimization
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Solution Overview
Problem
In back-side illuminated solid-state image pickup devices, increasing the number of capacitors to enhance dynamic range leads to reduced capacitance and deteriorated image quality due to size constraints, as smaller capacitors result in higher leak currents and noise, affecting image quality.
Innovation Solution
A solid-state image pickup device design that includes separate optoelectronic conversion units for long-time and short-time exposures, with a combining unit that only merges signals when the noise in the long-time exposure signal is equal to or greater than the noise in the short-time exposure signal, utilizing capacitors and floating diffusions to accumulate and process optical signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of capacitors is increased to enhance dynamic range, then the dynamic range is improved, but the capacitance of each capacitor is reduced and image quality deteriorates
Solution Approach 1:
The patent segments the optical signal accumulation into two distinct time periods: a first period for accumulating a first optical signal and a second period for accumulating a second optical signal. This segmentation allows the system to capture both bright and dark scene details without requiring multiple capacitors per pixel, thereby maintaining image quality while expanding dynamic range.
Solution Approach 2:
The patent implements periodic action by conducting optical signal accumulation in sequential time periods rather than simultaneously. The first optical signal is accumulated during a first period, then the second optical signal is accumulated during a second period. This temporal separation allows single capacitors to serve multiple purposes across different time intervals, avoiding the need to increase capacitor count while preserving capacitance values for optimal image quality.
2Quantity of substance
If the area for one capacitor is reduced to accommodate more capacitors, then the number of capacitors increases, but the capacitance is reduced and leak current increases
Solution Approach 1:
The patent segments the accumulation function across time periods rather than requiring spatial multiplication of capacitors. By dividing the accumulation process into a first period and a second period, the system achieves enhanced dynamic range capability without increasing the physical number of capacitors, thereby maintaining adequate capacitance values and controlling leak current levels.
Solution Approach 2:
The patent introduces dynamic temporal control to the accumulation process, where the same capacitor can be reused across different time periods for different accumulation tasks. This dynamic approach replaces the static requirement for multiple simultaneous capacitors, optimizing the use of existing capacitor resources while maintaining sufficient capacitance to minimize leak current effects.
3Adaptability or versatility
If optical signals are combined from long-time and short-time exposures, then dynamic range is enhanced, but noise in the combined signal increases
Solution Approach 1:
The patent implements feedback control through a combining unit that selectively combines the first optical signal and the second optical signal based on noise considerations. The combining unit evaluates the accumulated signals and determines the optimal combination strategy, thereby enhancing dynamic range while controlling noise levels in the final output image.
Solution Approach 2:
The patent changes the temporal parameter of signal accumulation by using different accumulation periods (first period and second period) to capture signals under different conditions. This parameter variation allows the system to obtain complementary information from the same pixel over time, expanding dynamic range while the selective combining process manages noise through intelligent signal processing rather than simple addition.
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 increased dynamic range without deteriorating image quality by optimizing the use of capacitors and noise management, preventing noise-induced image quality degradation and maintaining image fidelity.
Implementation Method 1
an optoelectronic conversion unit that performs an optoelectronic conversion
Data Source
AI summary
A solid-state image pickup device includes an optoelectronic conversion unit, a first optical signal accumulation unit, a second optical signal accumulation unit, and a combining unit, in which the first optical signal accumulation unit accumulates a first optical signal obtained by the optoelectronic conversion by the optoelectronic conversion unit in a first period, the second optical signal accumulation unit accumulates a second optical signal obtained by the optoelectronic conversion by the optoelectronic conversion unit in a second period, the second period being shorter than the first period, and the combining unit combines the second optical signal with the first optical signal when a noise in the first optical signal is equal to or larger than a noise in the second optical signal.