Photoacoustic Measurement Pulse Width Limiting Circuit
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Solution Overview
Problem
Existing photoacoustic measurement apparatuses face issues with excessive laser light output due to failures in pulse generation or pulse width limiting circuits, and are prone to malfunctions from static electricity and electromagnetic compatibility (EMC) influences.
Innovation Solution
A photoacoustic measurement apparatus with a laser light source, an excitation light source power supply unit that includes a capacitor, a switch circuit, a discharge control circuit, and a pulse width limiting circuit formed of a passive element, such as a pulse transformer, to control and limit the pulse width of the driving pulse, preventing excessive laser light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pulse generation circuit and pulse width limiting circuit are used to control the flash lamp, then the lighting time can be limited to ensure safety, but the system becomes vulnerable to failures from static electricity and electromagnetic compatibility influences
Solution Approach 1:
The patent extracts the pulse width limiting function from the complex logic circuit and implements it using a simple RC circuit. This separates the safety-critical timing function from the vulnerable digital logic, making the system more resistant to static electricity and EMC influences while maintaining the lighting time limit for safety.
Solution Approach 2:
The patent uses simple, inexpensive passive components (resistors and capacitors) instead of complex logic circuits for the pulse width limiting function. These passive components are inherently more reliable and resistant to environmental factors like static electricity and electromagnetic interference.
2Manufacturing precision
If logic circuits are used for pulse generation and pulse width limiting, then precise control is achieved, but the circuits are easily affected by static electricity and electromagnetic compatibility issues
Solution Approach 1:
The patent replaces the electronic logic circuit system with an analog RC circuit system for pulse width limiting. This substitution eliminates the vulnerability of digital logic to static electricity and EMC while maintaining precise pulse width control through the natural charging characteristics of the RC circuit.
Solution Approach 2:
The RC circuit acts as an intermediary between the power supply and the flash lamp, providing passive, analog pulse width limiting that is inherently immune to static electricity and electromagnetic compatibility issues that affect digital logic circuits.
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 solution effectively prevents excessive laser light emission and reduces the risk of malfunctions caused by static electricity and EMC, ensuring safer and more reliable photoacoustic measurements.
Implementation Method 1
a capacitor for supplying a charged voltage to the excitation light source
Implementation Method 2
a pulse width limiting circuit for limiting a pulse width of the driving pulse output from the discharge control circuit, the pulse width limiting circuit being formed of a passive element; preferably, the passive element is a pulse transformer
Implementation Method 3
a laser light source that has an excitation light source, which emits excitation light
Implementation Method 4
a laser medium, which emits laser light in response to incidence of the excitation light
Implementation Method 5
photoacoustic imaging for imaging the inside of the living body using the photoacoustic effect. In general, in the photoacoustic imaging, pulsed laser light, such as a laser pulse, is emitted into the living body. In the living body, the living body tissue absorbs the energy of the pulsed laser light, and ultrasound waves (photoacoustic signal) are generated by adiabatic expansion due to the energy
Data Source
AI summary
There is provided a photoacoustic measurement apparatus including a laser light source unit that has a flash lamp for emitting excitation light and a laser rod for emitting laser light in response to incidence of the excitation light, an excitation light source power supply unit that has a capacitor bank for supplying a voltage to the flash lamp, an IGBT for controlling an output of the voltage charged in the capacitor bank to the flash lamp, a discharge control circuit for generating a driving pulse for driving the IGBT, and a pulse width limiting circuit for limiting a pulse width of the driving pulse output from the discharge control circuit, the pulse width limiting circuit being formed of a passive element, and a photoacoustic wave detection unit that detects photoacoustic waves generated inside a subject by emission of light emitted from the laser light source unit to the subject.