Annular Spot Research Articles

Beam shaping for two-dimensional laser array by a computational model

The application of two-dimensional array laser source is more and more popular. Currently, many methods have been proposed for the collimation of laser beams; however, there is still a lack of research for the collimation of array laser sources so far. This paper presents a collimating method for array laser source. Through the calculation of the lens surfaces, the shape of the illumination spot on the target can be directly controlled, and the diameter of the lens can be directly constrained by setting the initial point coordinates. In this method, the edge-ray principle is used to simplify the extended light source model. The size and intensity distribution of the light spot irradiated by the light source to the target position were simulated by establishing a ray tracing model. The whole process was calculated using MATLAB software. The corresponding lens model can be obtained by fitting discrete coordinate points using Solid Works. Finally, the optical design software ZEMAX is used for simulation test. After shaping the laser light source with a luminous diameter of 1 mm, a circular and uniform spot is obtained at 100 m. For the point light source model, the divergence angle of 0.28° is achieved. Furthermore, an annular spot is also realized by setting the laser irradiation range, which provide a new solution for customized laser lighting.

Precise autofocus method based on an annular DOE and a cylindrical lens

With the wide application of lithography technology in the field of large-scale microstructure processing, it is necessary to achieve nano-scale autofocus in the range of hundreds of micrometers, which poses a new challenge to the autofocus method. Therefore, a precise autofocus method based on an annular optical diffractive element (DOE) and a cylindrical lens is proposed in this paper. Different from the traditional centroid method, this method uses an annular DOE and a cylindrical lens to modulate the beam section, so that the shape changes of the spot in the horizontal and vertical directions are inconsistent, that is, an elliptical annular spot is formed. Only one detector is used to detect the long axis and short axis of the spot respectively, and then the coarse focus position and the fine focus position can be calculated respectively. Combining these two results, we can perform autofocus with nanometer precision over a large range. In addition, our autofocus system is simple in structure. The feasibility and practicability of the method are verified by simulation and experiment.

Research progress on heteromorphic structure parts fabricated by additive manufacturing based on inside-laser coaxial powder feeding

Inside-laser material feeding laser cladding deposition (IMF-LCD) is a directed energy deposition technology featuring “hollow beam, annular spot, centered powder, and coaxial powder feeding.” IMF-LCD offers distinct advantages over traditional outside laser material feeding laser cladding deposition (OMF-LCD), such as a good laser-powder coupling effect, high powder utilization, high forming flexibility, uniform thermal field distribution in molten pools, and excellent forming surface quality. IMF-LCD would significantly improve forming efficiency and surface quality while it was applied to rapid direct manufacturing and repair of complex metallic parts compared to OMF-LCD. In this manuscript, the working principle of IMF-LCD technology is briefly introduced. Mostly, the research progress on heteromorphic structure parts fabricated by IMF-LCD was summarized, focusing on layered design, posture change, forming strategy optimization, and process parameter adjustment. The heteromorphic structure included a twisted thin-walled structure, variant height/width structure, overhanging structure, and closed structure. Based on the excellent characteristics of this technology, the exploration of high forming quality heteromorphic structural parts is carried out by changing the process parameters and forming processes such as the variable attitude stacking method, the conformal discrete layering method and the normal layering method, and the surface roughness is as low as 1.323 μm, the dimensional accuracy is as high as 1.6%. Simultaneously, the powder utilization rate of IMF-LCD reached 60%–80% on average, in accordance with the advantages of the laser-powder coupling effect. Finally, the remarkable research and application of IMF-LCD technology in high flexibility, high precision, high surface quality, and high material utilization would further promote the development of additive manufacturing with higher performance, higher quality, and lower cost in the future.

Optical design of LED high mast lamp based on TIR freeform lens for annular lighting

The traditional square spot of street lamp is not suitable for the lighting requirements of the annular road lighting. In this paper, a lens design method for producing annular spot of high mast lamp is proposed. The method mainly contains three optical surfaces, in which the inner surface collimates the energy of the centre part of the light source, the total internal reflection surface collimates the light with large angle and low energy and the outer surface refracts all the collimated light to realise the annular illumination distribution on the target surface. In this design, we can change the diameter of the lighting spot through the variation of the inclination angle of the outer surface from 14° to 19° and the diameter of the spot changes from 10.2 m to 12.3 m at the distance of 30 m. The lighting requirements of high mast lighting are realised based on the TIR lens array, in which the average illuminance is more than 20 lx, the illuminance uniformity is more than 0.7 and the light optical utilisation factor is more than 90%.

Descripción de síntomas de mancha anular en el híbrido interespecífico de palma aceitera OxG (Elaeis oleifera x Elaeis guineensis)

Se describen los síntomas que presentan las palmas del híbrido interespecífico OxG (Elaeis oleifera x Elaeis guineensis) al ser afectadas por la enfermedad viral de la mancha anular (MA) asociada al virus AOPRV (African Oil Palm Ring Spot Virus) y establecidas en las etapas de vivero y siembra comercial en campo en las condiciones agroecológicas de Tumaco, Departamento de Nariño, Colombia. La presencia del virus AOPRV, asociado con la enfermedad, se confirmó mediante pruebas moleculares RT-PCR.

Glass apparatus for annular spot testing

Glass apparatus for annular spot testing