Laser Interference Measurement Research Articles

A temperature measurement system with high resolution and low noise

Due to the temperature fluctuation, both the self-gravity disturbance level of the gravitational wave detection vehicle and the laser interference measurement system are affected, which brings great noise to the gravitational wave measurement, and the temperature field fluctuation has become one of the most important noise sources of the inertial sensor. In order to ensure the noise level of the inertial sensor to meet the needs of detection, this paper uses the AC bridge to reduce the self-noise of the temperature measurement system, improve the resolution of the temperature measurement system, and realize a high-resolution and low-noise temperature measurement system. The experimental results show that the effective value of self-noise of the temperature measurement system is about 3.65 × 10[Formula: see text], and the long-period noise is less than 1 × 10[Formula: see text]. It can be used in the space gravitational wave detection test and control system.

Contactless nondestructive method for determination of the carrier diffusion length in semiconductors and dielectrics

We propose the contactless nondestructive method for determination of the carrier diffusion length in semiconductors and dielectrics. The method is based on optical generation of non-equilibrium carriers at one point of the studied sample and the laser interference measurement of their concentration at another point. When changing the distance between these points, a decrease in the carrier concentration is observed. It depends on the carrier diffusion length, which is determined by comparing the experimental and theoretical dependences of the probe signal on the divergence of the injector and probe beams. We have studied silicon samples protected by an insulator layer and without any covering. The method can be used in scientific research and the electronics industry.

Laser Confocal Interference Multi-Parameter Measurement Method for Spherical Lens

This letter proposes a new, comprehensive laser confocal interference multi-parameter measurement method (CIMPM) to improve the measurement accuracy and efficiency for the multiple parameters of a spherical lens. By integrating laser confocal and sphere interference measurement techniques, the proposed CIMPM uses the laser confocal focusing technique to measure the radius, thickness, and refractivity of a spherical lens, and uses laser interference measurement technique to measure the surface figure. So, this technique achieves high accuracy comprehensive multi-parameter measurements of a spherical lens on a single instrument. Experiments indicate that the proposed CIMPM can achieve a measurement accuracy of 9 ppm for the radius, 3.2.×10 -4 for the thickness, 1.6.×10 -4 for the refractivity, and a peak to valley of λ/20 for the surface figure.

Laser differential confocal interference multi-parameter comprehensive measurement method and its system for spherical lens.

Different measurement methods have been used to achieve different parameter measurements of a spherical lens, and multi-parameter measurements of a spherical lens have low measurement accuracy and efficiency. This paper proposes a new, laser differential confocal interference multi-parameter measurement (DCIMPM) method for spherical lens. Based on this proposed DCIMPM, a multi-parameter comprehensive measurement system is developed for spherical lens, which uses the laser differential confocal parameter measurement technique to measure the radius of curvature, thickness, and refractivity of spherical lens, and uses the laser interference measurement technique to measure the surface figure of a spherical lens. Therefore, the DCIMPM system, for the first time, achieves high-accuracy multi-parameter comprehensive measurements of a spherical lens on a single instrument. Experiments indicate that the developed DCIMPM system can achieve a measurement accuracy of 5 × 10-6 for the lens radius, 2.5 × 10-4 for the lens thickness, 2.2 × 10-4 for the lens refractivity, and a peak to valley of λ/20 for the surface figure of the lens. The proposed DCIMPM principle and developed system provide a new approach to achieve multi-parameter comprehensive measurements for spherical lens.

The Image Processing Algorithm of Surface Topography Based on Laser Interference Measurement

In the measurement methods of microcosmic surface topography, laser interference microscopy with high precision and non-contact advantages, has been widely used. Based on the current processing algorithms of interference image, this paper studies principally the processing algorithms of single-wavelength laser interferometry and analyses the image processing algorithm of two-wavelength laser interferometry. On the basis of the original measurement precision, the two-wavelength measurement method can extend the depth measurement range and restore effectively the tested surface topography.

A novel method to enhance the sensitivity for two-degrees-of-freedom straightness measurement

A low cost and high precision system which can measure two-degrees-of-freedom straightness simultaneously is proposed based on a laser collimator. In the system, a miniature fiber coupled diode laser generates a collimating beam. The sensitivity of the straightness error measurement is magnified by a factor of 4 compared with the lateral movement of the retro-reflector itself after the multi-reflections. A Renishaw ML10 laser interference measurement system was used to verify the developed system in a series of experiments in the laboratory environment. Experimental results agree with the expected results. The two-dimensional straightness error measurement had linear correlativity close to 1 and the standard one-to-one deviation error was better than 0.32 µm obtained over a travel range of 600 µm.

レーザ干渉計の二相正弦波信号による内挿位置の不確かさ低減手法に関する研究

In laser interference measurement, if an amplitude error, a phase error and an offset error are in the two phases sine wave signals which is the output of a laser interferometer, the uncertainty of the position which interpolated below the laser wavelength interval increases.This paper describes the technique of reducing the uncertainty of the interpolated position by presuming the position below a wavelength interval from two phases sine wave signals which compensated the amplitude error, the phase error and the offset error. Furthermore, it was shown that the uncertainty of the calibration below a wavelength interval can be presumed based on two phases sine wave signals.

Temperature measurement of end gas under knocking condition in a spark-igniyion engine by laser interferometry

Knocking is one of the most significant problems that limits the efficiency of an internal combustion engine. It is caused by autoignition of the unburned gas ahead of the flame. In order to understand the knock phenomenon, it is important to measure the temperature of the unburned gas. In this study, with polarization preserving fibers, the laser interference measurement of the unburned gas temperature was performed in a constant-volume and a specially designed engine which could be ignited only once. The engine was fueled with n- butane , oxygen and argon, and was operated under knocking conditions. When the density of the gas changes, the change of the optical path length of the test beam corresponds to the change of the refractive index. The temperature history of the unburned gas was determined by measuring the pressure and the change of interference signal. The optical fiber interference system had the advantage of resisting mechanical vibration because the test and reference beams were transmitted in the same optical fiber and were separated only in the test section.

Temperature Measurement of End Gas under Knocking Condition in a S. I. Engine by Laser Interferometry.

Knock is one of the most significant problems that limit the efficiency of an internal combustion engine. It is caused by autoignition of the unburned gas ahead of the flame. In order to understand the knock phenomenon, it is important to measure the temperature of unberned gas. In this study, with polarization maintaining optical fibers, the laser interference measurement of unburned gas temprature was performed in a constant volume vessel and a specially designed engine which could be ingited only once. The engine fueled with n-butane, oxygen and argon, was operated under knocking conditions. When the density of the gas changes, the change of the optical path length of test beam corresponds to the change of refractive index. The temperature history of the unburned gas was determined by measuring the pressure and the change of interference signal. The optical fiber interference system had the advantage of resisting mechanical vibration because test and reference beams were transmitted in the same optical fiber and were seperated only in the test section.