Infrared Imaging Device Voltage Drop Uniformity
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Solution Overview
Problem
Existing thermal infrared solid-state imaging devices face issues with voltage drop distribution due to resistances in vertical power supply and signal lines, leading to saturation of amplifying circuits and uneven output distribution.
Innovation Solution
The device divides the integration time into two periods, alternating the energization path between the vertical power supply line and current source, and positions the current source at the opposite end of the vertical signal line to integrate voltage drops, reducing positional dependence and preventing circuit saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If voltage is supplied through vertical power supply lines to pixel rows sequentially, then power consumption is reduced and circuit operation is simplified, but voltage drop distribution occurs due to line resistance causing output non-uniformity and amplifier saturation
Solution Approach 1:
The pixel array is divided into multiple banks (e.g., 4 banks), and within each bank, pixels are further segmented into groups that share common vertical signal lines. This segmentation allows for more granular control of voltage supply paths, reducing the number of pixels simultaneously drawing current from a single vertical line, thereby minimizing voltage drop distribution while maintaining sequential row-by-row power consumption efficiency.
Solution Approach 2:
Buffer circuits are introduced as intermediary elements between the vertical signal lines and the pixel groups. These buffers act as voltage regulators that compensate for voltage drops caused by line resistance, ensuring uniform voltage delivery to all pixels within a bank regardless of their position. The buffer circuits receive voltage from vertical power supply lines and provide stabilized voltage to pixel groups, eliminating output non-uniformity while preserving the low-power sequential operation mode.
2Measurement precision
If amplification factor is increased to compensate for small pixel voltage changes, then detection sensitivity is improved, but circuit saturation occurs due to voltage drop distribution in power supply and signal lines
Solution Approach 1:
Buffer circuits are positioned as intermediaries between the vertical signal lines and the readout amplifiers. These buffers provide voltage stabilization and isolation, preventing voltage drop distribution from propagating to the amplification stage. By placing buffers at strategic points in the signal path, the system can maintain high amplification factors for improved detection sensitivity without risking saturation caused by power supply voltage variations.
Solution Approach 2:
The circuit design creates equipotential regions by using buffers to maintain equal voltage levels across all pixel groups within a bank. This equipotential approach ensures that voltage drops in vertical signal lines do not create potential differences that would lead to amplifier saturation. The buffers actively regulate voltage to maintain equipotential conditions, allowing high gain operation while preventing saturation.
3Device complexity
If vertical signal lines are used to connect pixel cathodes to integrating circuits, then circuit complexity is reduced, but voltage distribution occurs causing saturation and loss of amplification capability
Solution Approach 1:
The pixel array is segmented into multiple banks with each bank containing pixel groups that share common vertical signal lines. This segmentation reduces the total number of vertical signal lines required compared to a fully individual connection scheme, maintaining relatively low circuit complexity. Within each bank, the segmented structure ensures that voltage drops are localized and can be managed by buffer circuits, preventing harmful voltage distribution while preserving amplification capability.
Solution Approach 2:
Buffer circuits are introduced as intermediary voltage regulation stages between the vertical signal lines and the integrating circuits. These buffers compensate for voltage drops caused by line resistance, eliminating the harmful voltage distribution effect. The buffers maintain stable voltage levels throughout the signal path, allowing the use of simple vertical signal line connections without suffering from saturation or loss of amplification capability.
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 ensures uniform voltage drop distribution across rows, maintaining necessary amplification factors and enhancing output uniformity without causing circuit saturation, regardless of pixel number or wiring layout.
Implementation Method 1
A plurality of diodes 801 each having a thermally insulating structure serving as infrared detector
Implementation Method 2
A circuit of an infrared solid-state imaging device making use of a temperature depending characteristic of a forward voltage of a diode driven at a constant current
Implementation Method 3
The voltage across the constant current source 808 is integrated and amplified in an integrating circuit 809
Data Source
AI summary
A thermal infrared solid-state imaging device includes a pixel array having pixels diodes, a vertical power supply line connected to horizontal drive lines and commonly connecting the horizontal drive lines, integrating circuits for integrating voltages at the ends of the vertical signal lines for a predetermined integration time, and current sources connected to the vertical signal lines at an opposite end to the end of the vertical signal line which is connected to the integrating circuit. The integration time is equally divided substantially into two periods, and during one divided period of the integration time, energization is performed between one end of the vertical power supply line and the current source, and during the other divided period of the integration time, the energization is performed between other end of the vertical power supply line and the current source.