Barcode Signal Noise Reduction via Synchronous Detection
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Solution Overview
Problem
Bar code readers face interference from ambient light and internal scattering noise, leading to signal misreading and failure in accurately decoding bar codes, especially when low-frequency components overwhelm the system's operating range.
Innovation Solution
A system and method that includes transmitting pulsed light at a selected frequency, filtering and amplifying the electrical signal, removing low-frequency noise components using high-pass filters or differential circuits, and applying Automatic Gain Control to ensure proper binary assignment and data extraction from the bar code signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If synchronous detection is used to remove ambient light interference, then high-frequency ambient light is filtered out, but low-frequency scattered light components remain and overwhelm the signal
Solution Approach 1:
The patent segments the noise filtering process into two distinct stages: first using synchronous detection to remove high-frequency ambient light, then using a separate low-pass filter to remove low-frequency scattered light components. This multi-stage segmentation approach allows each filtering mechanism to target specific frequency ranges without interfering with the other, resolving the contradiction between removing ambient light and preserving signal precision.
Solution Approach 2:
The patent introduces an intermediary low-pass filter between the synchronous detector and the signal processing stages. This intermediary component specifically targets and removes low-frequency scattered light that passes through the synchronous detector, acting as a mediator that protects the final signal from being overwhelmed by internal scattering noise while preserving the bar code signal integrity.
2Measurement precision
If signal amplification is applied to enhance bar code signal, then signal intensity increases, but low-frequency noise components are also amplified causing signal collapse
Solution Approach 1:
The patent extracts and removes the harmful low-frequency noise components from the signal before amplification occurs. By using a low-pass filter to take out the scattered light components that would otherwise be amplified along with the bar code signal, the system can then safely amplify the remaining signal without risking signal collapse from noise dominance.
Solution Approach 2:
The patent performs preliminary noise removal through low-pass filtering before the signal amplification stage. This preliminary action eliminates the low-frequency scattered light components in advance, preventing them from being amplified and causing signal collapse, thereby ensuring reliable signal stability while still achieving the desired signal intensity enhancement.
3Measurement precision
If high power is used to overcome ambient light interference, then signal strength increases, but power consumption increases and may exceed operating range
Solution Approach 1:
The patent converts the harmful ambient light and scattered light into beneficial filtering opportunities. By using synchronous detection tuned to the laser frequency, the system selectively identifies and extracts the bar code signal from the ambient light background. The low-pass filter then converts the scattered light problem into a solvable frequency separation task, allowing the system to achieve adequate signal strength without excessive power consumption.
Solution Approach 2:
The patent changes the frequency parameter of the light source to 2 MHz, which is higher than typical ambient light frequencies. This parameter change allows the synchronous detector to distinguish the bar code signal from ambient light without requiring high power levels, as the frequency differentiation provides natural signal separation that reduces the need for power-intensive amplification.
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 filters out ambient and internal noise, allowing for accurate bar code reading even in environments with significant low-frequency noise, ensuring reliable signal resolution into logical '1' and '0' values.
Implementation Method 1
converting light received at the bar code reader from the bar code into an electrical signal
Data Source
AI summary
A system and method for reading a bar code are disclosed which may include transmitting light pulsed at a selected frequency to illuminate the bar code; converting light received at the bar code reader from the bar code into an electrical signal; transmitting the electrical signal through a signal conditioning circuit to filter and amplify the electrical signal, to thereby provide a conditioned electrical signal; sampling the conditioned electrical signal at the selected frequency; removing energy due to light scattering within a housing of the bar code reader from the sampled, conditioned electrical signal; generating one of a logical “1” and a logical “0” output based on a value of the signal generated by the step of removing; and resolving output from the step of generating into data indicative of information on the bar code.