Solid-State Imaging AD Conversion Dynamic Range Control
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Solution Overview
Problem
Existing solid-state imaging apparatuses face challenges in expanding dynamic range while maintaining good signal-to-noise (S/N) ratio, particularly in MOS image sensors, as they require complex circuitry and additional signal lines for resolution information.
Innovation Solution
A solid-state imaging apparatus with an imaging section, a reference signal supply section, and AD conversion sections that adjust the gradient of a ramp signal based on pixel values to control the dynamic range expansion, eliminating the need for additional signal lines by detecting resolution from specific pixel values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If line memories and combining circuits are added to expand dynamic range, then dynamic range is expanded, but device complexity increases
Solution Approach 1:
The patent changes the parameter of the ramp signal gradient to control AD conversion resolution dynamically. By adjusting the gradient between a first gradient (higher resolution) and a second gradient (lower resolution), the system expands dynamic range without adding line memories or combining circuits, thus resolving the contradiction between dynamic range expansion and circuit complexity
Solution Approach 2:
The patent makes the AD conversion resolution dynamic by switching between different ramp signal gradients based on pixel value thresholds. This dynamic adjustment allows the system to adapt to different luminance conditions, achieving expanded dynamic range while avoiding the need for static additional circuitry
2Adaptability or versatility
If additional signal lines are added for resolution information, then dynamic range expansion is achieved, but device complexity increases
Solution Approach 1:
The patent implements self-service by having the imaging section itself generate and output resolution information through specific pixel values (such as OB pixel values) without requiring external signal lines. The system uses its own pixel data to convey resolution information, eliminating the need for additional dedicated signal lines while achieving dynamic range expansion
3Adaptability or versatility
If AD conversion resolution is reduced to expand dynamic range, then dynamic range is expanded, but measurement precision deteriorates
Solution Approach 1:
The patent dynamically adjusts the ramp signal gradient based on detected pixel values. When pixel values are below a first threshold, the system uses a first gradient for higher precision measurement. When pixel values exceed the threshold, it switches to a second gradient to expand dynamic range. This dynamic switching resolves the contradiction by adapting precision to the actual signal level
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
The solution allows for dynamic range expansion while maintaining good S/N ratio without the need for additional circuitry or signal lines, simplifying the apparatus configuration and improving image processing efficiency.
Implementation Method 1
an imaging section having n×m pixels arranged in a matrix each configured to store a charge corresponding to incident light
Implementation Method 2
each configured to count the time taken until the signal level of the ramp signal from the reference signal supply section reaches the signal level of the pixel signal from the corresponding pixel column, thereby converting the pixel signal to a pixel value
Data Source
AI summary
An imaging section outputs n pixel signals every pixel row of n×m pixels, and n AD conversion sections, corresponding to n pixel columns of the n×m pixels, convert the n pixel signals to n pixel values. A resolution control section controls the n AD conversion sections so that the AD conversion resolution of the n AD conversion sections become a first resolution, or a second resolution rougher than the first resolution, based on the AD conversion resolution of the n AD conversion sections and the n pixel values.