Imaging Device Column Amplifier Gain Current Control
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Solution Overview
Problem
Imaging devices face the challenge of smear, a phenomenon where illuminance differences at the boundary of bright portions in an image lead to unwanted vertical or horizontal lines, caused by the operation of readout circuits and charge generation, resulting in image deterioration.
Innovation Solution
The imaging device incorporates a column amplifier circuit with a switchable gain amplifier and a transistor that controls current flow, allowing the control unit to adjust the current supplied based on the amplifier's gain, thereby reducing smear by managing the bias voltage across the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the gain of the column amplifier circuit is increased to improve signal amplification, then the image brightness is improved, but the smear component superimposed on the pixel signal also increases, resulting in image deterioration
Solution Approach 1:
The patent applies dynamics by making the transistor current values changeable according to the amplifier gain setting. The control unit dynamically adjusts the first and second current values based on whether the amplifier is operating at first gain or second gain, allowing the system to adapt to different operating conditions and suppress smear at each gain level
Solution Approach 2:
The patent changes the electrical parameter (current value) of the transistor based on the amplifier gain setting. By switching between different current values (first current value at first gain, second current value at second gain), the system optimizes the balance between signal amplification and smear suppression for each gain condition
2Measurement precision
If the gain of the column amplifier circuit is increased to improve signal amplification, then the image quality is improved, but smear occurs more prominently, causing vertical or horizontal lines in the image
Solution Approach 1:
The patent applies local quality by providing different current values to the transistor depending on the specific gain operating mode. Instead of using a uniform current setting, the system tailors the current characteristics to each gain condition, optimizing local performance for smear suppression while maintaining signal detection accuracy
Solution Approach 2:
The control unit implements feedback by monitoring the amplifier gain setting and automatically adjusting the transistor current values accordingly. This closed-loop control ensures that the optimal current values are applied for each gain level, preventing smear while maintaining measurement precision
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 effectively reduces smear, even at higher gain settings, enabling the acquisition of higher quality images without the darker image issues associated with smear.
Implementation Method 1
each of which includes a photoelectric conversion unit that generates charges by photoelectric conversion
Data Source
AI summary
An imaging device includes pixels arranged to form columns and each including a photoelectric conversion unit that generates charges by photoelectric conversion, column circuits provided to the columns, respectively, and each receiving a signal from a part of the pixels, a first common control line connected to each of the column circuits, and a control unit that controls the column circuits. Each of the column circuits includes an amplifier circuit whose gain is switchable and a first transistor that controls a current flowing in the amplifier circuit, and the control unit controls the column circuit so that the first transistor supplies a current of a first current value when the amplifier circuit is at a first gain and the first transistor supplies a current of a second current value different from the first current value when the amplifier circuit is at a second gain different from the first gain.