Differential Noise Detection Circuit for Optical Print Recognition
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Solution Overview
Problem
Existing print recognition apparatuses, including capacitive, ultrasonic, and optical sensors, face limitations such as short sensing distances and noise interference, which hinder their application in mobile terminal products, particularly due to weak signal-to-noise ratios and various noise sources like electromagnetic waves and internal circuit interference.
Innovation Solution
A noise detection circuit comprising a differential amplifier, analog-to-digital converter, control circuit, and switch circuits that analyze digital signals to determine noise sources, allowing for noise identification and removal, thereby enhancing the performance of optical print recognition systems by distinguishing between external and internal noise sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical sensor is made very small to achieve high resolution, then measurement precision is improved, but the signal becomes weaker and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent combines multiple sensors into a sensor array, where each sensor element remains small for high resolution but the collective array provides sufficient signal strength. The differential amplifier merges signals from multiple sensors to improve signal-to-noise ratio while maintaining the small size of individual sensing elements.
Solution Approach 2:
The patent introduces a differential amplifier as an intermediary component between the optical sensor and the signal processing circuit. This intermediary amplifies the weak signal from the small optical sensor while rejecting common-mode noise, thereby improving signal-to-noise ratio without changing the sensor size.
2Power
If a differential amplifier is used to amplify the signal, then signal strength is improved, but noise from the amplifier itself is introduced
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the output signal and adjusts the amplification gain to optimize signal strength while minimizing noise. The control circuit analyzes the digital signal to determine noise sources and adjusts amplifier parameters accordingly.
Solution Approach 2:
The patent dynamically changes the amplification parameters of the differential amplifier based on the detected signal conditions. By adjusting gain and bandwidth parameters, the system maximizes signal amplification while minimizing the introduction of amplifier noise.
3Adaptability or versatility
If the sensing distance is extended, then applicability to mobile terminals is improved, but signal-to-noise ratio deteriorates due to weaker signals
Solution Approach 1:
The patent uses periodic scanning of multiple sensor elements in the array, activating sensors in sequence rather than simultaneously. This periodic action allows the system to maintain high signal-to-noise ratio by processing signals from individual sensors while achieving extended sensing coverage through the array configuration.
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 noise detection circuit effectively identifies and mitigates noise interference, improving the accuracy and reliability of print recognition in optical systems by differentiating between external and internal noise sources, thus extending their applicability to mobile terminal products.
Implementation Method 1
a differential amplifier, an analog-to-digital converter, a control circuit, and a first switch circuit... an output terminal of the differential amplifier is connected with an input terminal of the analog-to-digital converter
Implementation Method 2
the analog-to-digital converter is configured to convert a signal output by the differential amplifier into a digital signal, and to transmit the digital signal to the control circuit
Data Source
AI summary
Disclosed are a noise detection circuit, a noise detection method, and a print recognition apparatus. The noise detection circuit includes a differential amplifier, an analog-to-digital converter, a control circuit, and a first switch circuit; the control circuit is configured to control the first switch circuit to make the first input signal terminal connected with the reference signal terminal or grounded, and to make the second input signal terminal connected with the reference signal terminal or grounded, and when the first input signal terminal is connected with the reference signal terminal or grounded, and the second input signal terminal is connected with the reference signal terminal or grounded, to analyze the digital signal output by the analog-to-digital converter to determine a source of noise of the print recognition apparatus.