Imaging Sensor ADC With Band-Limited Preamplifier for Noise Reduction
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Solution Overview
Problem
Current imaging elements with successive approximation resistor type analog-digital converters face challenges in reducing noise during analog-digital conversion, which can lead to determination errors in comparators due to circuit noise.
Innovation Solution
Incorporating a preamplifier with a band limiting function and a digital-analog converter that uses capacitance elements for re-AD conversion, where additional capacitance elements are used for lower bits, and selectively applying reference voltages for re-AD conversion, to reduce noise and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a successive approximation resistor type analog-digital converter is used for high-speed conversion, then conversion speed is improved, but circuit noise increases causing determination errors
Solution Approach 1:
The patent applies preliminary action by performing a first analog-digital conversion before the second conversion, and by pre-charging capacitance elements with reference voltages before the final determination. This preliminary conversion and charging process prepares the system in advance, allowing the comparator to make more accurate comparisons while reducing the impact of noise during the critical determination phase.
Solution Approach 2:
The patent implements feedback by using the result of the first analog-digital conversion to guide the second conversion process. The digital-analog converter uses the digitally converted value to generate a comparison reference voltage, which is then fed back to the comparator for a second comparison. This feedback mechanism allows the system to refine its measurement and overcome noise-induced errors by comparing the input signal against a dynamically generated reference.
2Device complexity
If standard analog-digital conversion is performed once, then device complexity is reduced, but measurement precision deteriorates due to noise
Solution Approach 1:
The patent applies segmentation by dividing the analog-digital conversion process into two distinct stages: a first conversion that provides an initial digital value, and a second conversion that refines the result using feedback from the first stage. This segmentation allows each conversion stage to focus on specific aspects of the signal, with the first stage handling coarse conversion and the second stage handling fine-tuned conversion with noise rejection, thereby improving overall precision without requiring a completely different converter architecture.
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 configuration reduces circuit noise, enhances the accuracy of analog-digital conversion, and minimizes determination errors, resulting in a more reliable digital signal output.
Implementation Method 1
a pixel array part including a plurality of pixels performing photoelectric conversion in units of pixel columns
Implementation Method 2
the successive approximation resistor type analog-digital converter has a preamplifier having a band limiting function
Implementation Method 3
a digital-analog converter that uses a capacitance element to convert a digital value after analog-digital conversion to an analog value
Data Source
AI summary
An imaging element according to a first aspect includes: a successive approximation resistor type analog-digital converter that converts an analog signal output from a pixel including a photoelectric conversion part into a digital signal, in which the successive approximation resistor type analog-digital converter has a preamplifier having a band limiting function. An imaging element according to a second aspect includes a DAC in which the successive approximation resistor type analog-digital converter uses a capacitance element to convert a digital value after AD conversion to an analog value, and sets the analog value to a comparison reference for comparison with an analog input voltage. Then, the DAC includes one of lower-bit capacitance elements including a plurality of capacitance elements, and after performing AD conversion for all bits, each of the plurality of capacitance elements is selectively applied with at least a first reference voltage to a fourth reference voltage, so that re-AD conversion is performed for lower bits.