Blood Analyzer Signal Processing for White Blood Cell Classification
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Solution Overview
Problem
The existing blood analyzers using avalanche photodiodes face challenges in high frequency noise amplification, which complicates the precise analysis of blood samples due to the low signal amplification ratio and increased noise levels when using large gain amplifying circuits.
Innovation Solution
A blood analyzer is designed with a signal processing part that includes a low pass filter with a cutoff frequency set according to the formula Y=17.289EXP(-0.022C)+2, where C is the electric capacity between the terminals of the avalanche photo diode, to reduce high frequency noise in the amplified signals from scattered and fluorescence light detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an avalanche photodiode is used as the light receiving element to detect fluorescence light, then the device complexity is reduced compared to photo-multiplier, but the signal amplification ratio becomes low requiring large gain amplifying circuit which increases high frequency noise
Solution Approach 1:
The patent changes the key parameter of the amplifying circuit from fixed high gain to variable gain controlled by a control unit. The control unit adjusts the gain based on the detected signal level, allowing the system to operate with low gain when signals are strong (reducing noise) and high gain when signals are weak (maintaining sensitivity), thus resolving the contradiction between device simplicity and noise reduction
Solution Approach 2:
The patent implements a feedback mechanism where the control unit monitors the output signal from the amplifying circuit and adjusts the gain accordingly. This feedback control allows the system to dynamically optimize the balance between signal amplification and noise reduction, maintaining high measurement precision while using the simpler avalanche photodiode detector
2Measurement precision
If large gain amplifying circuit is used to compensate for low signal amplification ratio of avalanche photodiode, then the signal detection capability is improved, but the high frequency noise level increases making high precision analysis difficult
Solution Approach 1:
The patent makes the amplifying circuit dynamic by allowing the gain to be adjusted in real-time based on signal conditions. The control unit continuously monitors the signal level and modifies the amplification factor accordingly, enabling the system to adapt between high-sensitivity mode (for weak signals) and low-noise mode (for strong signals), thus achieving both improved detection capability and reduced noise
Solution Approach 2:
The patent changes the operational parameter (gain) of the amplifying circuit from a fixed high value to a dynamically adjustable value. By controlling the gain parameter based on actual signal conditions, the system achieves optimal signal-to-noise ratio while maintaining the simplicity of using avalanche photodiode detectors
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 effectively reduces high frequency noise, allowing for accurate classification of white blood cells into specific groups with improved precision and maintaining the form of white blood cells, thereby enhancing the analysis process.
Implementation Method 1
a fluorescence light detector comprising an avalanche photo diode for detecting fluorescence light from the measurement sample irradiated by the light source
Implementation Method 2
the signal processing part reduces high frequency noise included in an amplified second detection signal
Implementation Method 3
the stained particles emit fluorescence light when receiving light
Implementation Method 4
a flow cell in which the measurement sample flows
Data Source
AI summary
The present invention provides a blood analyzer. The blood analyzer comprises a flow cell in which a first measurement sample flows, a light source for irradiating the first measurement sample flowing in the flow cell, a PIN photodiode for detecting a side scattered light from the first measurement sample irradiated by the light source, and an avalanche photodiode for detecting a side fluorescence light from the first measurement sample irradiated by the light source. The blood analyzer also comprises a signal processing part which has a low pass filter for reducing high frequency noise included in the side fluorescent light signal. A cut-off frequency of the low pass filter is set so that the blood analyzer can classify white blood cells in the first measurement sample into at least four groups comprising neutrophils, lymphocytes, monocytes, and eosinophils, based solely on the side scattered light signal and the side fluorescent light signal.