Reciprocal Birefringent Filter Rotation for High-Speed Wavelength Switching
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Solution Overview
Problem
Existing laser source units that switch between multiple wavelengths are limited by the rotation speed of birefringent filters, making it difficult to achieve high-speed switching without increasing the angular velocity, which hampers efficient photoacoustic image generation.
Innovation Solution
A laser source unit that includes a birefringent filter reciprocatively rotated within a predetermined range, including a discontinuous point of transmission wavelength change characteristics, and a Q switch controlled to emit pulse laser beams at specific wavelengths, allowing for high-speed switching of multiple wavelengths without increasing the rotation speed of the birefringent filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the birefringent filter is rotated at a predetermined rotation speed to switch between multiple wavelengths, then the wavelength switching function is achieved, but the switching speed is limited and cannot be increased without increasing the angular velocity
Solution Approach 1:
The birefringent filter is rotated reciprocally (back and forth) rather than continuously in one direction, allowing the system to revisit the same wavelength positions multiple times per rotation cycle. This dynamic rotation pattern enables faster effective wavelength switching without increasing the maximum angular velocity of the filter
Solution Approach 2:
The reciprocal rotation creates periodic passes through each wavelength position, with the Q switch triggered at specific periods when the filter reaches desired wavelengths. This periodic action allows multiple wavelength selections within a single rotation cycle, improving switching speed while maintaining manageable rotation speeds
2Productivity
If the Q switch is controlled to emit pulse laser beams at specific wavelengths corresponding to discontinuous points of transmission wavelength change, then high-speed wavelength switching is achieved, but the control timing precision must be extremely high
Solution Approach 1:
The system pre-positions the birefringent filter to specific rotational angles where discontinuous changes in transmission wavelength occur. By preparing the filter at these predetermined positions before Q switch activation, the system achieves precise wavelength selection without requiring extremely high timing precision during the actual emission moment
Solution Approach 2:
The invention exploits the inherent discontinuous parameter changes in the birefringent filter's transmission characteristics at specific rotation angles. By triggering the Q switch at these natural discontinuity points, the system achieves rapid wavelength transitions that are less sensitive to timing variations, reducing the required control precision
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
Enables rapid switching and emission of pulse laser beams at multiple wavelengths, improving the speed and efficiency of photoacoustic image generation by leveraging the greater change in transmission wavelength at discontinuous points, thus enhancing imaging capabilities.
Implementation Method 1
a birefringent filter which is inserted into the optical resonator and changes an oscillation wavelength of the optical resonator in association with rotational displacement of the birefringent filter
Implementation Method 2
a Q switch which is inserted into the optical resonator; an emission control unit that irradiates the laser rod with excitation light from the excitation light source and then turns on the Q switch
Implementation Method 3
a laser rod; an excitation light source that irradiates the laser rod with excitation light
Implementation Method 4
an optical resonator that includes a pair of mirrors facing each other with the laser rod interposed therebetween
Implementation Method 5
a photoacoustic image generation apparatus which irradiates an object with a laser beam having a plurality of wavelengths to detect a photoacoustic signal
Data Source
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AI summary
Using a laser source unit, a plurality of wavelengths are switched at a high speed without increasing a rotation speed of a birefringent-filter. A Q switch and a birefringent filter are inserted into an optical resonator including a pair of mirrors facing each other with a laser rod interposed therebetween. The birefringent-filter changes an oscillation wavelength of the optical resonator in association with rotational displacement. Driving means reciprocatively rotates the birefringent-filter in a predetermined range including a discontinuous point of change characteristics of a transmission wavelength for the rotational displacement. An emission control unit irradiates the laser rod with excitation light from a flash lamp, and then turns on the Q switch at a timing when a rotational displacement position of the birefringent-filter is set to a position corresponding to the wavelength of the pulse laser beam to be emitted, to cause the pulse laser beam to be emitted.