scholarly journals A Method for Expansion of Z-Directional Measurement Range in a Mode-Locked Femtosecond Laser Chromatic Confocal Probe

2019 ◽  
Vol 9 (3) ◽  
pp. 454 ◽  
Author(s):  
Chong Chen ◽  
Ryo Sato ◽  
Yuki Shimizu ◽  
Taku Nakamura ◽  
Hiraku Matsukuma ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Femtosecond Laser ◽  
Intensity Ratio ◽  
Theoretical Calculations ◽  
Expansion Method ◽  
Measurement Range ◽  
Laser Source ◽  
Peak Wavelength ◽  
Dual Detector ◽  
Chromatic Confocal Probe

A method is proposed to expand the Z-directional measurement range of a fiber-based dual-detector chromatic confocal probe with a mode-locked femtosecond laser source. In the dual-detector chromatic confocal probe, the Z-directional displacement of a measurement target is derived from the peak wavelength in the normalized intensity ratio from the two light intensities obtained by the two identical fiber detectors. In this paper, a new method utilizing the main-lobe and side-lobes of axial responses acquired from both the normalized intensity ratio Ia and the invert normalized intensity ratio In, which is the inverse of Ia, is proposed to obtain the seamless relationship between the peak wavelength and the Z-directional displacement of a measurement target. Theoretical calculations and experimental investigation are carried out to demonstrate the feasibility of the proposed measurement range expansion method.

scholarly journals An Off-Axis Differential Method for Improvement of a Femtosecond Laser Differential Chromatic Confocal Probe

2020 ◽  
Vol 10 (20) ◽  
pp. 7235
Author(s):  
Chong Chen ◽  
Yuki Shimizu ◽  
Ryo Sato ◽  
Hiraku Matsukuma ◽  
Wei Gao
Keyword(s):  
Femtosecond Laser ◽  
Focal Plane ◽  
Signal To Noise Ratio ◽  
Single Mode ◽  
Measurement Range ◽  
Single Mode Fiber ◽  
Differential Method ◽  
Laser Source ◽  
Dual Detector ◽  
Chromatic Confocal Probe

This paper presents an off-axis differential method for the improvement of a femtosecond laser differential chromatic confocal probe having a dual-detector configuration. In the proposed off-axis differential method employing a pair of single-mode fiber detectors, a major modification is made to the conventional differential setup in such a way that the fiber detector in the reference detector is located at the focal plane of a collecting lens but with a certain amount of off-axis detector shift, while the fiber detector in the measurement detector is located on the rear focal plane without the off-axis detector shift; this setup is different from the conventional one where the difference between the two confocal detectors is provided by giving a defocus to one of the fiber detectors. The newly proposed off-axis differential method enables the differential chromatic confocal setup to obtain the normalized chromatic confocal output with a better signal-to-noise ratio and approaches a Z-directional measurement range of approximately 46 μm, as well as a measurement resolution of 20 nm, while simplifying the optical alignments in the differential chromatic confocal setup, as well as the signal processing through eliminating the complicated arithmetic operations in the determination of the peak wavelength. Numerical calculations based on a theoretical equation and experiments are carried out to verify the feasibility of the proposed off-axis differential method for the differential chromatic confocal probe with a mode-locked femtosecond laser source.

Profile Measurement by Using a Femtosecond Laser Chromatic Confocal Probe

2020 ◽  
Author(s):  
Ryo Sato ◽  
Yuki Shimizu ◽  
Hiraku Matsukuma ◽  
Wei Gao
Keyword(s):  
Thermal Stability ◽  
Femtosecond Laser ◽  
Surface Profile ◽  
Sample Surface ◽  
Measurement Range ◽  
Laser Source ◽  
Profile Measurement ◽  
Experimental Setup ◽  
Chromatic Confocal Probe ◽  
Surface Profile Measurement

Abstract Confocal probes are widely employed in many industrial fields due to the depth-sectioning effect. The author’s group has also proposed a chromatic confocal probe employing a mode-locked femtosecond laser source which can realize an axial resolution of 30 nm and a measurement range of 40 μm Efforts have also been made to improve the thermal stability of the developed femtosecond laser chromatic confocal probe so that the probe can be applied for long-term displacement measurement or surface profile measurement. Meanwhile, surface profile measurement has not been carried out by using the developed femtosecond laser chromatic confocal probe. For the verification of the performance of developed probe in profile measurement, in this paper, an experimental setup is built and a basic experiment is carried out. By using the probe with further improved thermal stability, the measurement of a sample surface profile is carried out. In this paper, the development of the experimental setup with the femtosecond laser chromatic confocal probe, as well as the results of the surface profile measurements, is presented.

scholarly journals Investigation and Improvement of Thermal Stability of a Chromatic Confocal Probe with a Mode-Locked Femtosecond Laser Source

2019 ◽  
Vol 9 (19) ◽  
pp. 4084 ◽  
Author(s):  
Ryo Sato ◽  
Yuki Shimizu ◽  
Chong Chen ◽  
Hiraku Matsukuma ◽  
Wei Gao
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
Femtosecond Laser ◽  
Thermal Instability ◽  
Theoretical Calculations ◽  
Surface Profile ◽  
Laser Source ◽  
Profile Measurement ◽  
Chromatic Confocal Probe ◽  
Thermal Stability Of

An intentional investigation on the thermal stability of a mode-locked femtosecond laser chromatic confocal probe, which is a critical issue for the probe to be applied for long-term displacement measurement or surface profile measurement requiring long-time scanning, is carried out. At first, the thermal instability of the first prototype measurement setup is evaluated in experiments where the existence of a considerably large thermal instability is confirmed. Then the possible reasons for the thermal instability of the measurement setup are analyzed quantitatively, such as the thermal instability of the refractive index of the confocal lens and the thermal expansion of mechanical jigs employed in the probe. It is verified that most of the thermal instability of the measurement setup is caused by the thermal expansion of mechanical jigs in the probe. For the improvement of the thermal stability of the probe, it is necessary to employ a low thermal expansion material for the mechanical jigs in the measurement setup and to shorten the optical path length of the laser beam. Based on the analysis result, a second prototype probe is newly designed and constructed. The improved thermal stability of the second prototype probe is verified through theoretical calculations and experiments.

A chromatic confocal probe with a mode-locked femtosecond laser source

2018 ◽  
Vol 103 ◽  
pp. 359-366 ◽  
Author(s):  
Xiuguo Chen ◽  
Taku Nakamura ◽  
Yuki Shimizu ◽  
Chong Chen ◽  
Yuan-Liu Chen ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Source ◽  
Chromatic Confocal Probe

scholarly journals Measurement Range Expansion of Chromatic Confocal Probe with Supercontinuum Light Source

2021 ◽  
Vol 15 (4) ◽  
pp. 529-536
Author(s):  
Hiraku Matsukuma ◽  
◽  
Ryo Sato ◽  
Yuki Shimizu ◽  
Wei Gao
Keyword(s):  
Light Source ◽  
Range Expansion ◽  
Wide Spectrum ◽  
Surface Profile ◽  
Measurement Range ◽  
Detection Sensitivity ◽  
Laser Source ◽  
Supercontinuum Light Source ◽  
Chromatic Confocal Probe ◽  
Measurable Range

Confocal probes have been widely adopted in various industries owing to their depth-sectioning effects. A dual-detector differential chromatic confocal probe using a mode-locked femtosecond laser source is proposed herein, and the measurement range expansion of the probe using a supercontinuum light source is discussed. Supercontinuum light has an extremely wide spectrum. A simulation based on wave optics is performed to evaluate the detection sensitivity and measurable range by considering the chromatic aberration of the lens materials. Additionally, an experimental setup is constructed using a supercontinuum light source, and its feasibility is validated. A measurable range of 200 μm is adopted in the experiment, and three-dimensional surface profile measurements are performed. However, the developed confocal probe has not been used for surface topography measurements. Experiments are conducted to verify the performance of the developed probe.

scholarly journals An Optical Frequency Domain Angle Measurement Method Based on Second Harmonic Generation

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 670
Author(s):  
Wijayanti Dwi Astuti ◽  
Hiraku Matsukuma ◽  
Masaru Nakao ◽  
Kuangyi Li ◽  
Yuki Shimizu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic Generation ◽  
Frequency Domain ◽  
Harmonic Generation ◽  
Measurement Method ◽  
Second Harmonic ◽  
Angle Measurement ◽  
Laser Source ◽  
Optical Frequency ◽  
Measurable Range

This paper proposes a new optical angle measurement method in the optical frequency domain based on second harmonic generation with a mode-locked femtosecond laser source by making use of the unique characteristic of the high peak power and wide spectral range of the femtosecond laser pulses. To get a wide measurable range of angle measurement, a theoretical calculation for several nonlinear optical crystals is performed. As a result, LiNbO3 crystal is employed in the proposed method. In the experiment, the validity of the use of a parabolic mirror is also demonstrated, where the chromatic aberration of the focusing beam caused the localization of second harmonic generation in our previous research. Moreover, an experimental demonstration is also carried out for the proposed angle measurement method. The measurable range of 10,000 arc-seconds is achieved.

Research on Hydroforming of Bimetallic Lined Pipe

2010 ◽  
Vol 97-101 ◽  
pp. 4172-4177 ◽  
Author(s):  
Qin Zhu Chen ◽  
Xue Sheng Wang ◽  
Zheng Bian Wang
Keyword(s):  
Experimental Investigation ◽  
Theoretical Analysis ◽  
Industrial Production ◽  
New Technology ◽  
Expansion Method ◽  
Technical Characteristic ◽  
Stress And Strain ◽  
Hydroforming Process ◽  
Outer Pipe

A new kind of hydraulic expansion device for bimetallic CRA-lined pipe has been researched and developed, as well as its operational principal and technical characteristic were introduced. The stress and strain in the liner and outer pipe during the hydroforming process have been analyzed theoretically and the mechanism of hydraulic expansion method is studied, and the final forming pressure formula has been obtained. The theoretical analysis is verified by experimental investigation, the results indicate that the new technology is feasible and can be applied in industrial production.

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