APD Cytometer Feedback Circuit for Low-Light Sperm Sensing
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Solution Overview
Problem
Flow cytometry systems face challenges in detecting low levels of light emitted by sperm cells stained with fluorescent dyes, requiring sensitive and expensive photomultiplier tubes (PMTs) that need time to warm up and are prone to damage from light exposure.
Innovation Solution
A cytometer using an avalanche photodiode (APD) with a switching power supply, filter, and voltage adjustment circuitry, including a temperature sensor and feedback loop, to adjust voltages and improve sensitivity and efficiency, replacing the need for PMTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photomultiplier tubes (PMTs) are used to detect low-level light emission from sperm cells, then detection sensitivity is improved, but device cost increases and the detector requires warm-up time and is prone to light damage
Solution Approach 1:
The patent changes the operating parameters by using an avalanche photodiode (APD) instead of a photomultiplier tube (PMT), operating the APD in avalanche mode with high reverse bias voltage to achieve sufficient gain for low-level light detection while avoiding the complexities and vulnerabilities of PMTs
Solution Approach 2:
The patent replaces expensive, fragile PMTs with more robust, lower-cost avalanche photodiodes that are less susceptible to damage from light exposure and do not require extensive warm-up periods, making the system more practical for routine use
2Measurement precision
If photomultiplier tubes (PMTs) are used for light detection, then detection capability is improved, but the device requires high voltage power supply and light-shutter mechanisms increasing complexity
Solution Approach 1:
The patent extracts and eliminates the light-shutter mechanism and complex high-voltage power supply requirements by using an avalanche photodiode that can be continuously biased without risk of light damage, removing unnecessary components and simplifying the overall system
Solution Approach 2:
The patent implements a feedback circuit that automatically adjusts the reverse bias voltage applied to the avalanche photodiode based on the detected light signal level, optimizing detection sensitivity while maintaining system simplicity without requiring complex manual control mechanisms
3Measurement precision
If photomultiplier tubes (PMTs) are used to detect fluorescent light from sperm cells, then measurement accuracy is improved, but the system becomes more expensive and requires longer preparation time
Solution Approach 1:
The patent eliminates the warm-up requirement by using an avalanche photodiode that can be immediately activated upon system startup, unlike PMTs that require gradual heating and stabilization of the photocathode and electron multiplication stages, thereby reducing preparation time
Solution Approach 2:
The patent changes the detector type and its operational characteristics to eliminate the warm-up phase entirely, allowing the system to reach full detection capability immediately when powered on, improving operational efficiency
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 APD-based cytometer achieves low-level fluorescence detection with lower costs, no warm-up time, smaller active area, and improved control over detection, enabling accurate differentiation of sperm cells by chromosomal content without the need for expensive PMTs.
Implementation Method 1
The amount of fluorescent light may vary based at least in part on a relative amount of at least one particle differentiation characteristic (for example, the relative amount of chromosomes) present in each of the plurality of particles. The fluorescent light may be received by one or more optical elements that ultimately focus the received light onto a detection component, such as a photomultiplier tube ('PMT'). The detection component may generate an electrical, analog signal in response to the received light.
Implementation Method 2
The switching power supply includes a feedback loop. The filter is electrically connected between the switching power supply and the avalanche photodiode. The voltage adjustment circuitry adjusts a voltage on the feedback loop based at least in part on a voltage measured between the filter and the avalanche photodiode.
Implementation Method 3
The filter is electrically connected between the switching power supply and the avalanche photodiode
Implementation Method 4
A cytometer using an avalanche photodiode (APD) with a switching power supply, filter, and voltage adjustment circuitry, including a temperature sensor and feedback loop, to adjust voltages and improve sensitivity and efficiency
Data Source
AI summary
A cytometer includes an avalanche photodiode, a switching power supply, a filter, and voltage adjustment circuitry. The switching power supply includes a feedback loop. The filter is electrically connected between the switching power supply and the avalanche photodiode. The voltage adjustment circuitry adjusts a voltage on the feedback loop based at least in part on a voltage measured between the filter and the avalanche photodiode.