Retroreflective Light Source Device for FMCW Distance Measurement
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Solution Overview
Problem
Existing distance measurement devices using light sources face challenges in achieving sufficient frequency shift without compromising the quality of the light source, such as wavelength width or intensity waveform, in frequency modulated continuous wave (FMCW) schemes.
Innovation Solution
A light source device that includes a laser source, a retroreflective material, and an optical system with a modulation unit that changes the optical path length between the laser source and the retroreflective material over time, utilizing the Doppler effect to modulate the wavelength of the light, thereby achieving a sufficient frequency shift without affecting the light source's quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wavelength swept light source is used to change wavelength with time, then frequency shift is obtained, but the quality of light source such as wavelength width or intensity waveform deteriorates
Solution Approach 1:
The invention separates the frequency modulation function from the light source itself. The light source generates stable continuous light, while a separate modulation unit (scanning mirror or rotation body) performs the frequency modulation by changing the optical path length. This segmentation allows the light source quality to be maintained while achieving the required frequency shift for FMCW operation.
Solution Approach 2:
The invention introduces an intermediary element (retroreflective material on a scanning mirror or rotation body) that mediates between the stable light source and the requirement for frequency modulation. By placing the retroreflective material on a moving component, the system achieves frequency shift through the Doppler effect without directly modulating the light source, thus preserving light quality.
2Productivity
If optical path length is changed rapidly to achieve sufficient frequency shift, then measurement capability is improved, but maintaining light source quality becomes more difficult
Solution Approach 1:
The invention makes the optical path length dynamic by placing the retroreflective material on a moving component (scanning mirror or rotation body). This allows rapid change in optical path length at a rate of tens of thousands of wavelengths per second, achieving the required frequency shift for high-speed distance measurement while the light source itself remains stable and maintains its quality.
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 allows for a significant frequency shift in the measurement light, enabling accurate and high-resolution distance calculations without degrading the light source's quality, as demonstrated by the ability to change the optical path length by tens of thousands of wavelengths per second, resulting in a frequency shift up to 8 times the repetition frequency.
Implementation Method 1
change a wavelength of the light with time using a Doppler effect
Data Source
AI summary
A light source device includes a light source that generates continuous light, a retroreflective material that retroreflects a light beam from the light source, an optical system that guides the light beam from the light source to the retroreflective material and output the light beam retroreflected from the retroreflective material to the outside, and a modulation unit that is disposed in the optical system, changes an optical path length between the light source and the retroreflective material with time, and changes a wavelength of the light beam with time using a Doppler effect.