Imaging Device Clip Circuit for Horizontal Stripe Noise
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Solution Overview
Problem
Imaging devices face challenges in suppressing horizontal stripe noise during high luminance conditions, which deteriorates image quality by introducing two types of horizontal stripes when synthesizing images processed at different amplification factors, limiting the dynamic range and image quality.
Innovation Solution
The imaging device incorporates a clip circuit that limits signal levels on output lines to predetermined clip levels, and an amplifier unit that amplifies pixel signals at different amplification factors, ensuring the signal levels remain within operable ranges even under high luminance conditions, thereby suppressing horizontal stripe noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single clip level is applied to the output line, then the circuit structure is simple, but horizontal stripe noise occurs under high luminance conditions
Solution Approach 1:
The patent applies dynamics by switching between different clip levels based on the amplification factor being used. The clip level is not fixed but changes dynamically: a first clip level is applied during first amplification factor processing, and a second clip level is applied during second amplification factor processing. This dynamic adjustment prevents horizontal stripe noise while maintaining signal integrity across different processing modes.
Solution Approach 2:
The patent changes the parameter of clip level according to the amplification factor. When the amplification factor changes between first and second values, the clip level相应ly switches between first and second clip levels. This parameter adaptation ensures that the output signal remains within the optimal range for the ADC converter regardless of which amplification factor is active, thereby eliminating horizontal stripe noise.
2Adaptability or versatility
If images are synthesized at different amplification factors to achieve high dynamic range, then the dynamic range is improved, but horizontal stripe noise appears at high luminance conditions
Solution Approach 1:
The patent applies local quality by setting different clip levels for different amplification factor processing paths. Instead of using a uniform clip level for all processing, the system tailors the clip level to each specific amplification factor context. This localized optimization ensures that each processing path operates within its optimal signal range, preventing horizontal stripe noise while maintaining the ability to synthesize high dynamic range images.
3Reliability
If the output signal range is limited to prevent saturation, then signal integrity is maintained, but the dynamic range is reduced
Solution Approach 1:
The patent resolves this contradiction through dynamic clip level switching. During high luminance conditions with first amplification factor, a first clip level prevents saturation and maintains signal integrity. During other conditions with second amplification factor, a second clip level allows broader signal range for extended dynamic range. This dynamic adaptation maintains signal integrity when needed while preserving dynamic range capability when appropriate.
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 effectively reduces horizontal stripe noise and maintains high image quality with a high dynamic range by ensuring signal levels remain within operational limits, even under high luminance conditions, resulting in a high-quality synthesis image with minimal image shift.
Implementation Method 1
a plurality of pixels each including a photoelectric converter that generates charge by photoelectric conversion
Data Source
AI summary
An imaging device includes: pixels each including a photoelectric converter, and an output unit that outputs a pixel signal based on charge in a holding portion; an output line to which signals from the pixels are output; a clip circuit that limits a signal level of the output line to a range whose upper or lower limit is a predetermined clip level; and an amplifier unit that amplifies a signal of the output line. The amplifier unit outputs first and second signals amplified at first and second amplification factors, respectively, for the same pixel signal. The clip circuit limits a signal level of the output line to a first clip level in a first period in which the pixel signal is amplified at a first amplification factor and to a second clip level in a second period in which the pixel signal is amplified at a second amplification factor.