Solid-State Imaging Device Small Pixel Groups HDR
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid-state imaging devices face challenges in capturing images with high dynamic range due to pixel saturation issues, leading to reduced resolution and increased power consumption, especially when trying to balance brightness and low-light conditions.
Innovation Solution
The implementation of a pixel array with small pixel groups having different optical sensitivities, where signal charges are read out simultaneously using multiple AD converting units, allowing for high-speed signal processing and HDR synthesis without the need for frame memory, thus reducing circuit size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of pixels is increased and pixel size is miniaturized, then the resolution is improved, but the dynamic range is narrowed and output saturation occurs more easily
Solution Approach 1:
Each pixel is divided into multiple small pixels (e.g., 2x2=4 small pixels per pixel), where each small pixel has different optical sensitivity. This segmentation allows the system to select appropriate small pixels for different brightness conditions, thereby expanding the effective dynamic range while maintaining the original pixel resolution.
Solution Approach 2:
Different small pixels within the same pixel group are assigned different optical sensitivities (e.g., different microlens structures or photodiode characteristics). This local quality differentiation enables each small pixel to be optimized for specific brightness ranges, allowing the system to capture both high-brightness and low-brightness regions effectively without sacrificing overall resolution.
2Adaptability or versatility
If HDR synthesis is performed by differently setting charge accumulation time and output gain for each horizontal line, then the dynamic range is expanded, but the vertical resolution is decreased by half
Solution Approach 1:
Instead of processing entire horizontal lines with different exposure settings, the patent segments each pixel into multiple small pixels that can be independently controlled. This allows HDR synthesis to be performed at the pixel level rather than line level, maintaining full vertical resolution while achieving expanded dynamic range.
Solution Approach 2:
The patent changes the approach from varying charge accumulation time and output gain at the line level to varying optical sensitivity at the small pixel level within each pixel. This parameter change enables simultaneous capture of multiple brightness ranges without reducing resolution.
3Adaptability or versatility
If two or more images with different charge accumulation times and output gains are synthesized, then the dynamic range is expanded, but the frame rate is delayed and motion blur occurs
Solution Approach 1:
The patent performs HDR synthesis by selecting and combining signals from different small pixels within the same pixel group that have different optical sensitivities. Since all small pixels are exposed simultaneously during a single frame period, the synthesis is accomplished without delaying the frame rate or causing motion blur.
Solution Approach 2:
The patent maintains continuous frame rate operation by performing HDR synthesis within the same exposure period using multiple small pixels with different sensitivities. This eliminates the need for multiple separate exposure cycles, thereby maintaining uninterrupted image capture at the original frame rate.
4Adaptability or versatility
If a frame memory is added to synchronize frame timing for multiple images, then the dynamic range is expanded, but the circuit size and power consumption are increased
Solution Approach 1:
The patent eliminates the need for frame memory by segmenting each pixel into multiple small pixels with different optical sensitivities. The HDR synthesis is performed directly from the simultaneous outputs of these small pixels within the same pixel group, removing the requirement for storing multiple separate frame buffers.
Solution Approach 2:
The patent merges the HDR synthesis function into the pixel array structure itself by incorporating multiple small pixels with different sensitivities within each pixel. This integration eliminates the need for separate frame memory and synchronization circuits, thereby reducing overall circuit size and power consumption.
5Adaptability or versatility
If small pixel groups with different optical sensitivities are used and signal processing is performed to select the optimal pixel, then the dynamic range is expanded, but the amount of signals to be read out is increased and readout speed is reduced
Solution Approach 1:
The patent extracts only the necessary signal information from the small pixel groups. Instead of reading out all signals from all small pixels for processing, the system selectively reads out signals from the optimal small pixel based on brightness conditions, thereby reducing the total amount of data to be read out while maintaining expanded dynamic range capability.
Solution Approach 2:
The patent changes the signal processing approach by using the different optical sensitivities of small pixels as a preprocessing mechanism. The system determines the appropriate brightness range and selects the corresponding small pixel before readout, changing the parameter selection from post-readout processing to pre-readout selection based on sensitivity characteristics.
6Object-affected harmful factors
If reduction of output gain or charge accumulation time is performed, then output saturation in high brightness portions is reduced, but optimal output in low brightness portions cannot be obtained
Solution Approach 1:
The patent applies local quality by assigning different optical sensitivities to different small pixels within the same pixel group. Some small pixels are optimized for high brightness (with lower sensitivity) while others are optimized for low brightness (with higher sensitivity). This allows the system to select the appropriate small pixel for each local brightness condition, preventing saturation in high brightness areas while maintaining optimal output in low brightness areas.
Solution Approach 2:
The patent changes the optical sensitivity parameter of small pixels rather than uniformly reducing output gain or charge accumulation time for the entire pixel array. By varying the sensitivity parameter at the small pixel level, the system can prevent saturation in high brightness regions without compromising the signal quality in low brightness regions.
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 capture of high-quality images with wide dynamic range, maintaining resolution and reducing motion blur, while minimizing power consumption and circuit size.
Implementation Method 1
A pixel array includes a plurality of pixels which are arranged in a horizontal direction and a vertical direction. The pixel array generates signal charges in accordance with an amount of incident light onto each of the pixels.
Data Source
AI summary
According to one embodiment, a solid-state imaging device includes a pixel array and AD converting unit. In the AD converting unit, a plurality of AD converts are arranged in a horizontal direction. The pixel is configured by a small pixel group. The small pixel group is formed of a plurality of small pixels. The plurality of small pixels read out the signal charges. The small pixel group includes two or more small pixels having different optical sensitivities. The solid-state imaging device includes N AD converting units. N is the number of small pixel groups which are arranged in a vertical direction at every small pixel. N is an integer of 2 or higher.