Abstract
On the process of alignment for pupil off-axis telescope system, the determination of decentering and tilt misalignments is a key step. In this paper, we proposed a new method which adopts the fully connected neural network (FCNN) as a fitting tool to establish the nonlinear mapping relation between misalignments of different fields of view (FOVs) and Zernike coefficients. Firstly, we establish a pupil off-axis reflection telescope model, then decentering and tilt misalignments are introduced to acquire corresponding aberrations that represented by Zernike coefficients. We use aberrations as the inputs of FCNN; misalignments and FOV as outputs. FCNN is trained by the combination of inputs and outputs as a dataset, and we use a new dataset to test the accuracy and effectiveness of the trained FCNN. The results show that the mean absolute error (MAE) of the X-axis decentering error, V-axis tilt error and angle of view are 0.0506 mm, 0.0204° and 0.0124°, respectively. These results demonstrate that the proposed method is effective and feasible to calculate the misalignments.
Highlights
The imaging ability of transmission telescope cannot meet the requirements of modern astronomical observation
Connected neural network is utilized as complex nonlinear mapping relation fitting tool to establish an input-output mapping between misalignments and Zernike coefficients
Trained with 1600 datasets and iterates many times, the whole process costs less than three hours, the fully connected neural network (FCNN) can directly outputs misalignments in a good precision by using these Zernike coefficients
Summary
The imaging ability of transmission telescope cannot meet the requirements of modern astronomical observation (light collection ability, resolution and the range of FOV). Reflective telescope system includes: off-axis reflective telescope and axisymmetric reflective system. It is more challenging to determine the misalignments quickly and accurately on the process of alignment for the off-axis reflective telescope than axisymmetric reflective system. In off-axis reflective telescopes, the design, manufacturing and the alignment accuracy affect their imaging quality of the optical system [2]–[5]. The accurate alignment depends on the precise determination of the lens’ relative location errors in the optical system. These errors can be divided into two parts: decentering errors and tilt errors.
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