Image Pickup Signal Synthesis With Ramp and Gain Level Correction
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Solution Overview
Problem
Current image pickup apparatuses face challenges in achieving high linearity characteristics during dynamic range expansion, particularly when synthesizing image signals with poor linearity characteristics or deteriorated linearity due to reference voltage switching, which affects the quality of image synthesis processing.
Innovation Solution
The proposed image pickup device includes an AD conversion unit that compares input signals using different ramp signals, a synthesis unit for combining signals amplified by different gains, and correction units to address level differences, ensuring accurate signal synthesis and linearity correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If signals are read out for one pixel line by a plurality of vertical signal lines with different gains, then dynamic range is expanded, but linearity characteristics deteriorate during synthesis
Solution Approach 1:
The patent changes the reference voltage parameter dynamically based on the signal level. When the input signal level is high, a higher reference voltage is selected; when the input signal level is low, a lower reference voltage is selected. This parameter adaptation ensures that the AD converter operates with optimal linearity characteristics across the entire dynamic range, resolving the contradiction between expanding dynamic range and maintaining linearity.
Solution Approach 2:
The patent introduces dynamic switching of reference voltages based on signal level detection. The system transitions from static reference voltage to dynamic reference voltage selection, allowing the AD converter to adapt its operating characteristics in real-time. This dynamic approach enables high linearity characteristics across varying signal levels while maintaining expanded dynamic range.
2Speed
If reference voltage is switched to expand dynamic range, then conversion speed is improved, but linearity characteristics are deteriorated
Solution Approach 1:
The patent applies parameter changes by selecting different reference voltage levels according to the input signal amplitude. This ensures that the AD converter maintains optimal conversion speed for each signal level while preserving linearity characteristics. The reference voltage parameter is dynamically adjusted rather than fixed, resolving the contradiction between speed and linearity.
Solution Approach 2:
The patent implements preliminary detection of the input signal level before performing AD conversion. Based on this preliminary detection, the appropriate reference voltage is selected in advance, ensuring that both high conversion speed and good linearity characteristics are achieved from the outset of the conversion process.
3Quantity of substance
If multiple AD converters with different reference voltages are used, then dynamic range is expanded, but device complexity increases
Solution Approach 1:
The patent makes a single AD converter multi-functional by enabling it to operate with multiple reference voltage levels. Instead of requiring separate AD converters for different dynamic range segments, one converter is designed to adaptively switch reference voltages, achieving the same dynamic range expansion with reduced device complexity.
Solution Approach 2:
The patent uses parameter changes (reference voltage selection) to enable a single AD converter to perform the work of multiple converters. By dynamically adjusting the reference voltage parameter, one converter can handle both high and low signal levels effectively, simplifying the overall device architecture while maintaining expanded dynamic range.
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 solution enables high-quality image synthesis with improved linearity characteristics, effectively correcting level differences and maintaining image quality across varying luminance levels and gain settings, thereby enhancing the dynamic range expansion and reducing the occurrence of strange image appearances.
Implementation Method 1
an AD conversion unit configured to perform AD conversion of input signals by comparing a first ramp signal or a second ramp signal having a different inclination from the first ramp signal
Implementation Method 2
an amplifier configured to amplify pixel signals by different gains
Data Source
AI summary
In order to improve linearity characteristics in synthesis processing for expanding a dynamic range, an image pickup apparatus comprising an AD conversion unit for performing AD conversion of input signals by comparing a first ramp signal or a second ramp signal; a first synthesis unit for synthesizing a first signal AD converted using the first ramp signal and a second signal AD converted using the second ramp signal; a first correction unit for correcting a level difference between the first signal and the second signal when the first signal and the second signal are synthesized; an amplifier for amplifying pixel signals by different gains; a second synthesis unit for synthesizing the signals amplified by the different gains; and a second correction unit for correcting a level difference between the signals amplified by the different gains when the signals amplified by the different gains are synthesized.