Image Pickup Device Variable Gain Control Wide Dynamic Range
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Solution Overview
Problem
Image pickup devices face challenges in achieving a wide dynamic range due to pixel signals reaching saturation or falling below noise levels, particularly when luminance changes significantly, leading to inadequate gradation levels in bright or dark portions.
Innovation Solution
The implementation of an image pickup device with a control unit that applies multiple gains to pixel signals based on signal values, using different exposure periods and thresholds to optimize signal amplification and conversion, allowing for variable gain control in analog-to-digital conversion units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single gain is applied to pixel signals, then the device complexity is low, but the dynamic range is limited and gradation levels are insufficient in bright or dark portions
Solution Approach 1:
The patent applies variable gain control where the gain value dynamically changes based on the signal level of pixel data. The gain control unit selects different gain values (first gain for higher signal levels, second gain for lower signal levels) to adapt to different luminance conditions, thereby expanding the dynamic range without requiring multiple fixed gain circuits
Solution Approach 2:
The patent changes the gain parameter based on signal level thresholds. By comparing the signal value of pixel data with a threshold and selectively applying different gain values, the system achieves wide dynamic range coverage while maintaining relatively simple circuit architecture through parameter variation rather than structural complexity
2Measurement precision
If multiple gains are applied to pixel signals, then the dynamic range and gradation levels improve, but the device complexity and control difficulty increase
Solution Approach 1:
The patent segments the signal range into different levels (higher than threshold, lower than threshold) and applies different gain values to each segment. This segmentation approach allows precise gradation control in different luminance regions while keeping the control logic simple through clear threshold-based classification
Solution Approach 2:
The gain control unit uses feedback from the signal value comparison to automatically select appropriate gain values. By continuously monitoring pixel data signal levels and adjusting gain accordingly, the system achieves high measurement precision without complex manual control mechanisms
3Reliability
If variable gain control is implemented, then noise is reduced and image quality improves, but the analog-to-digital conversion complexity increases
Solution Approach 1:
The patent performs gain control on pixel signals before analog-to-digital conversion. By pre-amplifying or attenuating signals to optimal levels prior to conversion, the system improves signal-to-noise ratio and image quality while simplifying the AD conversion process itself, as the signals are already conditioned for conversion
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 achievement of a wide dynamic range by effectively managing signal amplification and conversion, improving gradation levels across varying luminance conditions and reducing noise, thereby enhancing image quality.
Implementation Method 1
a plurality of pixels 100 each having a photoelectric conversion unit that produces electric charges in accordance with light
Data Source
AI summary
An image pickup device according to an embodiment includes pixels each configured to output an analog signal based on electric charges produced in a photoelectric conversion unit and a control unit configured to control a gain applied to the analog signal to be at least a first gain and a second gain greater than the first gain in accordance with a signal value of the analog signal. Each of the pixels outputs, as the analog signal, a first signal and a second signal based on electric charges produced in the photoelectric conversion unit in a first exposure period and a second exposure period shorter than the first exposure period. The control unit controls the gain applied to the analog signal by selecting one from the first gain and the second gain in accordance with the signal value, for at least one of the first signal and the second signal.