With the advantages of ultrahigh resolution and acquisition rate, line scan cameras are increasingly being deployed for precision measurement. In order to achieve high precision, the intrinsic parameters must be calibrated properly. However, the existing calibration models that only calibrate the principle points and the distortion on one-dimensional direction and ignore the other directions result in limited adaptability and accuracy, which are especially serious for multiline cameras. To conquer this challenge, this paper proposes a precise calibration method which is qualified both for multiline cameras and single-line cameras. Through the analysis of the relative position relationship between pixel array and principle point, a method for calibrating the principle points and the distortion on two-dimensional direction is proposed and a flexible calibration device is designed based on a theodolite. The calibration quality is improved by the novel calibration method which effectively establishes the correspondence relationship between the rays and pixels by recording incident angle of collimated beam and its image respectively. Moreover, a robust optimization algorithm is proposed to enhance the stability of parameter estimation. The proposed method is verified by Monte-Carlo simulation, real experimental data and flight, the results show that the two-dimensional calibration model can improve the calibration accuracy of the multiline cameras by 45 pixels at most and its re-projection measurement uncertainty is as low as 0.1 pixels. The comparative results of the experiments demonstrate that the proposed method has the advantages of high accuracy, low cost, and easy implementation.

The non-linear dynamic behavior of a hybrid air bearing-rotor system is very complicated and requires careful attention when designing to avoid spindle failure, especially under ultra-high speed condition. In this paper, the rotor trajectory of a hybrid air bearing-rotor system is obtained by solving the unsteady Reynolds equation and motion equations simultaneously. The typical non-linear behavior of hybrid air bearing-rotor systems is illustrated with the analysis of the rotor trajectory, the phase angle, time domain vibration and power spectral density. Furthermore, the influences of the rotor mass, external load, rotating speed and unbalanced mass on the non-linear behavior are investigated. Finally, the effect of structure parameters on the rotor trajectory is studied and the phenomenon under ultra-high speed condition is illustrated, which provides some new guidelines on the ultra-high speed air spindle design.

The spiral-grooved structure has been proposed for promoting the load capacity and stiffness of hybrid air journal bearings. In this paper, the dynamic characteristics of spiral-grooved hybrid bearings are first calculated. The stability criteria of the bearings are proposed and analyzed with different groove structure parameters using frequency domain analysis. It is found that the length of the spiral-groove has significant influence on the stability of the spindle system. Finally, the critical speed of the spiral-grooved hybrid bearing and rotor system is analyzed, and an experiment is carried out to validate the proposed model, finding that groove structure can promote the stability of the air bearing systems.

For traditional imaging systems, high imaging quality and system miniaturization are often contradictory. In order to meet the requirements of high imaging quality and system miniaturization, this paper proposes a method to correct the aberration of coherent imaging optical systems. The method is based on the idea of phase recovery and the imaging principle of a coherent imaging system to recover the aberrations at the exit pupil of the system. According to the recovered aberrations, conjugate filters are constructed to correct the image quality in the frequency domain. The imaging quality of the system is improved without changing the original optical path, and the simplicity of the system is guaranteed. To solve the pupil frequency domain aberration more accurately, this paper adopts the dual competition and parallel recombination strategy based on the genetic algorithm and introduces the disaster model. The improved genetic algorithm can effectively restrain the appearance of the “precocity” phenomenon. Finally, the paraxial imaging optical path is simulated and verified by experiments. The results show that, after aberration correction, the image sharpness is improved and the edge information is richer, which verifies the feasibility of the coherent imaging system image quality enhancement method proposed in this paper.