Interference Measurement Techniques Research Articles

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.

Developments of characterization of the foam shell target for fast ignition realization experiment-I (FIREX-I)

Equipments and techniques have been developed for characterization of the foam shell target for the FIREX-I. An interference measurement technique is planned to use to measure the quantity of fuel in a foam shell. A preliminary experiment of the interference measurement technique was carried out. Experimental results indicate the refractive index of RF foam is near 1.08 and that of vacant RF foam containing liquid H2 is near 1.22. Calculations indicate the refractive index of vacant RF foam is 1.07 and that of RF foam containing H2 is 1.19. Some causes of these differences were discussed.

Recent developments in RF interference

Present trends in the design of transmitters, receivers, and antennas for use in communications and radar are reviewed to assess their impact on interference, interference measurement techniques, shielding and prediction methods. It is shown that transmitter power output and antenna size have increased by a factor of 10 in the last decade and that similar increases are anticipated in the next five to ten years. Transmitter spurious outputs are now frequently greater than the desired outputs of transmitters a few years ago. It is also shown that receiver sensitivity improvement, as a result of new techniques (masers, parametric, amplifiers, etc.), may not be realizable unless antenna side- and backlobes are drastically reduced. It is further shown that the sensitivity and frequency range of field intensity meters must be increased to permit meaningful measurements in the light of these developments. It is suggested that the performance of filters for transmitters must be developed for receivers to reduce interference.