CMOS Image Sensor Ramp Reference Circuit for Pixel Value Accuracy
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Solution Overview
Problem
The dispersion of ramp signals in CMOS image sensors leads to degraded pixel values and subsequent picture quality in image pickup devices.
Innovation Solution
An image pickup device with a reference signal generation unit that includes selectable current sources, terminating resistors, and switches to manage current supply, allowing for precise comparison and AD conversion of electric signals, thereby preventing picture quality degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a slope type AD conversion circuit is used for AD conversion of pixel signals, then the AD conversion can be performed efficiently with a column AD conversion circuit arrayed for each pixel column, but the reference signal (ramp signal) disperses causing pixel value dispersion and picture quality degradation
Solution Approach 1:
The patent changes the parameter of the reference signal generation by introducing multiple current sources with different current values and selectively connecting them to the output terminal through switches. This allows dynamic adjustment of the reference signal characteristics to compensate for dispersion and maintain measurement precision while preserving AD conversion efficiency.
Solution Approach 2:
The patent makes the reference signal generation dynamic by enabling selective connection of different current sources based on switching signals. This dynamic configuration allows the system to adapt to varying conditions and maintain accurate pixel values without sacrificing the efficiency of the column-parallel AD conversion architecture.
2Measurement precision
If multiple current sources are selectively connected to the output terminal to generate the reference signal, then the reference signal accuracy is improved preventing picture quality degradation, but the device complexity increases with multiple switches and terminating resistors
Solution Approach 1:
The patent makes the switching circuit multi-functional by designing it to perform both reference signal generation and current selection functions. The same switches that select current sources also control the connection to terminating resistors, reducing the need for separate control circuits and minimizing overall device complexity while maintaining reference signal accuracy.
Solution Approach 2:
The patent combines multiple current sources, switches, and terminating resistors into an integrated reference signal generation unit. This merging of components allows the circuit to achieve accurate reference signal generation through selective current paths while reducing the overall structural complexity compared to having separate independent circuits for each function.
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 effectively prevents picture quality degradation by ensuring accurate AD conversion and maintaining the integrity of pixel values, enhancing image quality.
Implementation Method 1
a pixel having a photoelectric conversion device that performs photoelectric conversion and configured to output an electric signal
Data Source
AI summary
The present technology relates to an image pickup device and an electronic apparatus capable of preventing degradation of the picture quality. A plurality of current sources can be selectively connected to an output terminal for outputting a reference signal having a level that varies, and a plurality of terminating resistors are connected to the output terminal. The terminating resistors that are to supply current of current sources that are connected to the output terminal are connected by a plurality of switches, and current of current sources that are not connected to the output terminal is supplied to the switches. The present technology can be applied, for example, to image pickup devices that perform AD conversion using a reference signal and so forth.