Research On Adaptive Focusing Technique Of Non-orthogonal Shaft Laser Theodolite

Based on the traditional three-axis structure of theodolites,the research group breaks through the structure of tri-axis orthogonality,and uses the autofocusing collimator laser to take place of the traditional telescope.In this paper,a new non-orthogonal axis laser theodolite structure and its measurement principle and method are proposed and studied,which can be used for the automatic,precise measurement of large space objects and large size objects.This laser "theodolite" is different from the traditional theodolite.On one hand,the horizontal axis,vertical axis and collimation axis are not required to be strict orthogonal,which greatly reduces the difficulty and cost of designing,processing,assembly,calibration and maintenance;On the other hand,the collimation laser is used to replace the traditional telescope,and the "collimation axis" is identified by the collimated laser beam,which realizes the visualization of the collimation axis.It provides the conditions for basing on the visual measurement technology to realize the automatic tracking and guidance of the laser "theodolite".The laser beam identifies the visual collimation axis,and its directivity and collimation quality at the measurement target directly affect the recognition,tracking and guidance positioning based on the vision measurement technology,thus affecting the measuring accuracy of the system.Therefore,for large-scale measurement applications,the adaptive laser alignment adjustment of the system is particularly important.In this paper,the alignment adjustment of the laser is based on the electrically tunable lens.By a certain control strategy,we could change the shape and size of the liquid chamber to change the focal length.Compared with the traditional zooming method by adjusting the position of the optical lens group,the zooming method based on the electrically tunable lens has obvious advantages such as simple structure and fast zoom speed.But when setting up the laser "theodolite",the electrically tunable lens and laser can't be guaranteed strict alignment,which can't guarantee the ideal coaxial relationship of the laser beam and the electrically tunable lens optical axis.At this time,the outgoing beam of the electrically tunable lens deflects,and when the measuring distance changes,the outgoing beam will be further deflection at the time of laser alignment adjustment.Based on the analysis of the electrically tunable lens optics theory,in this paper we proposed the mathematic model of the focal position changing with the focal length of the electrically tunable lens when the position between the laser and the electrically tunable lens was fixed,and carried on the experimental verification.It provides a theoretical basis for realizing the collimation of the laser and high precision measurement based on the electrically tunable lens which can be used to construct the non-orthogonal axis laser "theodolite" system.The self-adaptability of laser collimation adjustment is the basis for realizing high-precision large-scale automatic measurement.In this paper,we studied the electrically tunable lens auto-focusing technology based on image processing,and constructed a non-orthogonal axis laser "theodolite" closed-loop auto-focusing system,which was composed of a laser,an electrically tunable lens and a high-resolution camera.The system could adjust the collimation of the laser according to position of the collimated spot,and realize the adaptive adjustment of the laser.The system could adapt to the measurement of the large-scale target points,improving the measurement efficiency and meeting the demands of automatic measurement.