Solid-State Imaging Device Voltage Level Detection Circuit
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Solution Overview
Problem
MOS solid-state imaging devices fail to detect high-luminance subjects as saturation signal levels, resulting in unnatural images, particularly when capturing high-speed continuous-exposure images, due to variations in transistor threshold values and the need for high-speed signal processing during limited horizontal blanking periods.
Innovation Solution
Incorporating a correction circuit within the solid-state imaging device that includes a voltage level detection unit and a column signal processing unit to immediately judge and correct pixel output voltages, eliminating the need for external signal processing and accommodating transistor threshold variations, by outputting a predetermined voltage based on logic output voltages and pixel output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external signal processing is used to correct high-luminance detection errors, then detection accuracy is improved, but processing time increases and power consumption rises
Solution Approach 1:
The correction circuit is merged with the solid-state imaging device itself, combining the detection function and correction function into a single integrated system. This eliminates the need for external signal processing, thereby reducing processing time and power consumption while maintaining detection accuracy.
Solution Approach 2:
The correction circuit operates during the horizontal blanking period, performing correction actions in advance before the next image capture cycle begins. This preliminary action ensures that corrections are completed without extending the overall processing time of the imaging device.
2Speed
If correction processing is performed during horizontal blanking period, then processing speed is improved, but available processing time is limited
Solution Approach 1:
The correction circuit is designed to autonomously operate during the horizontal blanking period using the existing timing structure of the imaging device. It self-manages the correction process without requiring additional external control, efficiently utilizing the limited time window available.
3Measurement precision
If transistor threshold variations are compensated externally, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The threshold compensation function is merged into the correction circuit within the imaging device, eliminating the need for separate external compensation systems. This integration reduces overall system complexity while maintaining detection accuracy.
Solution Approach 2:
The correction circuit automatically compensates for transistor threshold variations using internal reference voltages and comparison mechanisms, making the system self-sufficient without requiring external calibration or adjustment.
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
Enables real-time correction of high-luminance image detection as saturation signal levels, preventing black images from being captured instead of white images, even in high-speed continuous-exposure modes, and reduces power consumption by optimizing operation periods.
Implementation Method 1
a photoelectric transducer PD which converts incident light to charges
Data Source
AI summary
In the case where a subject is captured with a high-luminance light, such as sunlight, for a background, a phenomenon that a portion of the high-luminance subject is detected as a no-signal level is prevented. The solid-state imaging device includes: a photoelectric transducer PD which converts incident light to charges; a voltage level detection circuit 50 in which pixel units 10an1 and 10bn1, each having a voltage conversion amplifying transistor Q13a which outputs a voltage by converting the charges accumulated in the photoelectric transducer PD, are arranged one-dimensionally or two-dimensionally, and which detects a pixel output voltage outputted from each of the pixel units to the common column signal line Ln; and a column signal processing circuit 80 which receives a logic output voltage of the voltage level detection circuit 50 and the pixel output voltage and which outputs a voltage to a horizontal output circuit 90. The column signal processing circuit 80 outputs either a voltage identical to the pixel output voltage or a fixed voltage, depending on the logic output voltage.