Image Sensor Scanning Circuit Using Periodic Clock Signals
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Solution Overview
Problem
Existing image sensors for X-ray imaging face challenges with high power consumption and noise generation due to continuous current flow in TFTs, leading to reduced signal-to-noise ratio and increased fixed pattern noise, especially when using scanning circuits with a single conductivity type.
Innovation Solution
An image sensor design incorporating a scanning unit that performs serial selection processing on pixel rows with short-cycle control signals, including two clock signals with cycles shorter than a frame period, to minimize continuous current flow and noise, using TFTs of either n-type or oxide semiconductor materials for low power consumption and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a scanning circuit with ratio-type inverter and transmission gate is used, then the image sensor can be configured with only TFTs of a single conductivity type, but electric current flows continuously between voltage sources causing high power consumption
Solution Approach 1:
The patent employs periodic clock signals (CLK1 and CLK2) to control the scanning circuit operation. The TFTs are switched on and off periodically according to the clock cycles, enabling signal transmission only during specific time windows. This periodic operation eliminates continuous current flow while maintaining the scanning function, thereby reducing power consumption significantly.
2Ease of manufacture
If a scanning circuit with ratio-type inverter is used, then the image sensor can be configured with only TFTs of a single conductivity type, but electric current flows continuously generating noise and reducing S/N ratio
Solution Approach 1:
By using periodic clock signals to control TFT switching, the patent ensures that current flows only during necessary signal transmission periods. This periodic operation minimizes continuous current flow and associated noise generation, thereby improving the signal-to-noise ratio of the image sensor.
3Use of energy by moving object
If short-cycle control signals are used for serial selection processing, then power consumption and noise are reduced, but the cycle is shorter than the frame period requiring multiple cycles per frame
Solution Approach 1:
The patent segments the frame period into multiple shorter control signal cycles. By dividing the overall frame processing into sequential segments (odd frames and even frames processed differently), the system achieves lower power consumption within each segment while completing the full frame processing through multiple segments. This segmentation allows efficient use of short-cycle signals without compromising complete frame coverage.
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
The solution achieves low power consumption and significantly reduces noise, enhancing the signal-to-noise ratio and dynamic range, allowing for cost-effective manufacturing of high-resolution image sensors with reduced fixed pattern noise, applicable to both visible light and X-ray imaging.
Implementation Method 1
pixels including a photoelectric conversion element and a switching element connected to the photoelectric conversion element
Data Source
AI summary
An image sensor: includes a pixel matrix in which pixels are disposed in a matrix, each pixel including a photoelectric conversion element and a switching element connected to the photoelectric conversion element; performs selection processing, on each pixel row of the pixel matrix, including selecting a pixel row and outputting a signal to the selected pixel row to make switching elements conductive; performs detection processing of detecting signals from the photoelectric conversion elements in the selected pixel row; and performs the selection processing based on received control signals, wherein the control signals include first control signals having a cycle shorter than a first period in which the selection processing and the detection processing are performed on all pixel rows, and wherein the cycle is equal to or shorter than a second period in which the selection processing and the detection processing are performed on one pixel row.