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Array detection method is widely used for measuring the far field laser centroids. The influence of array detector's aperture and dynamic range on the far field laser power was analyzed on the basis of the measurement method and measurement process for the laser spot centroid. The effect of array detector's spatial resolution and spatial duty ratio on the far field laser spot centroid was simulated, and the results were verified by performing experiments, enabling the determination of the technology requirements for the array detector. The expression for the laser spot centroid uncertainty was deduced on the basis of the uncertainty theory and laser spot centroid expression, and the sources of uncertainty were analyzed. The results will be of great importance for measuring the far field laser spot centroids and designing array detectors.

Rammed earth construction is an ancient technique which has recently attracted renewed interest throughout the world. Although rammed earth is currently regarded as a promising material in the construction industry in the context of sustainable development, it is difficult to quantify its bearing capacity, mechanical performance, as well as retrofitting approach, which discourages people from large-scale application in architectural engineering. This paper is devoted to the study of these problems based on rammed earth wall model experimentation. Three different models are studied considering different material components as well as structural configurations. By measuring the strain and deformation of the rammed earth wall models subjected to uniformly-distributed vertical loading, their ultimate bearing capacities are tested based on experimental investigation. Then the method of cement mortar-steel fiber reinforcement (CMSF) is carried out to study the ultimate bearing capacity enhancement of the wall models. Results show that the method of cement mortar-steel fiber reinforcement can increase the ultimate bearing capacity of the rammed earth wall models significantly, which is of relevant engineering significance in practical application.

On the basis of the Lamberts cosine law, the light intensity of a point on the receiving screen behind the diffuse transmission glass screen was theoretically deduced. Combining the application of the diffuse transmission glass screen in the power monitor, the influence of both single-layer glass and multi-layer glasses on the intensity distribution of the incident laser was summarized through numerical simulation. The numerical results show that when the ratio of the radius of the incident laser to the distance from the diffuse transmission screen to the receiving screen is no more than 0.3, the intensity distribution and the caliber of the incident laser couldnt influence the normalized light intensity distribution on the receiving screen. And the normalized light intensity distribution on the receiving screen mainly depends on the distance, which indicates that the arrangement of the glasses or the number of the layers almost have nothing to do with the distribution. This conclusion was proved by the experiment.

In order to improve the ability and accuracy of measuring the temporal-spatial distribution of the intensity of a large-size, high-energy laser beam, a novel array detecting method based on diffuse transmission sampling is proposed. The measurement principle and the design of the sampling and attenuating unit are presented. High-temperature-resistant diffuse transmission material is used to sample and attenuate a high energy laser beam. Pure copper, whose surface is first sand-blasted and then gold-plated, is applied to scatter the incident high-energy laser beam. The formula for the attenuation ratio was derived in detail. We developed two large-aperture array detectors with spatial resolution of 5 mm, spatial duty ratio of 20%, and useable angle range of ±30° without varying the responsivity, the non-uniformity in the laser profile measurement is below 1%, and the repeatability error in the laser power measurement is approximately 1%. The maximal energy density that the array detector can endure is more than 10 kJ/cm(2).

We designed a measurement system to measure large size laser beam intensity distribution based on CCD diffuse transmission imaging. The measurement principle is presented. The configuration of the system is introduced. An emphasis is placed on the design of diffuse transmission target. The methods of spot geometry distortion correction and intensity distortion correction are described in detail. After laser spot correction, we can get the real laser beam intensity profile. The test results are given, which validate the correctness of the method. The paper provides a new way to measure quantitatively the profile of large size laser beam with high accuracy.

The intensity distribution of a laser beam (laser beam profile) is one of its most important characteristics because it yields information on the non-uniformity, centroid, centroid jitter and beam quality. A novel measurement method for obtaining a large laser beam intensity distribution based on CCD diffuse transmission imaging is proposed. The measurement principle is presented. The measurement components of the system have been designed. The layout of the system and the design of a diffuse transmission sampling target are emphasized. The methods of correcting geometric and intensity distortion of the spot are described in detail. The method to calibrate the power coefficient is also given. After the laser spot correction, we can obtain the precise laser beam intensity profile as well as the laser power. The presented test results validate the method. In the measurement field of large laser beams, the method can measure the profile with a non-uniformity of less than 1%, and laser power within 2% error compared with the calibration power meter. The measurement system can be used as a standard measurement instrument after being calibrated when manufactured.