The limitations of infrared optical systems are mainly attributed to the performance of current practical detectors, which results in a typically narrow imaging field of view. However, employing a scanning imaging system with cascaded micro-lens arrays can extend the imaging field of view. Diffraction effects, beam crosstalk, and dynamic aberration generated during scanning are the principal factors affecting the image quality of the scanning imaging system with cascaded micro-lens arrays. Dynamic aberration is the aberration value of the system with various scanning stages. Our purpose is to study the dynamic aberration characteristics of the system. Building an appropriate theoretical model to describe dynamic aberrations is essential for the system design. Aberration can be applied to guide the system alignment due to the increasingly strict requirements for the alignment of cascaded micro-lens arrays. The distribution control of aberrations on individual optical surfaces is efficient in reducing the system tolerance. The tolerance range can be presented by calculating the aberrations with various scanning stages. Therefore, our study has theoretical and engineering significance in guiding the design optimization and alignment test of scanning imaging systems with cascaded micro-lens arrays.

As the cascaded micro-lens arrays are displaced relative to each other during the scanning, the sub-unit of the scanning system becomes non-rotationally symmetric. The nodal wavefront aberration theory is adopted to describe the aberrations of such systems. Based on this theory, we build a dynamic wavefront aberration model for scanning imaging systems with cascaded micro-lens arrays and propose a method for calculating the wavefront aberrations of the systems. We then apply this model and calculation method to analyze a two-piece micro-lens arrays scanning model. We first examine the primary aberrations under multiple scanning fields of view and discuss how these primary aberrations vary with the scanning fields of view. Then, we calculate the root mean square(RMS) wavefront error of the system and analyze the relationship between the RMS wavefront error and the scanning field of view. When there is decentration on the system surface, the wavefront aberration coefficient of the rotationally symmetric system cannot effectively reflect the actual wavefront aberration contribution of the surface. Therefore, we provide the distribution of primary wavefront aberration values on the optical surface under different scanning fields of view.

First, the variation of five primary wavefront aberrations with normalized fields of view is calculated (Fig. 5). Spherical aberration is not affected by the field of view to result in the same value for each scanning field of view. The relationship between the coma and the field of view is linear, with the coma slope of the coma being negative under the negative field of view. Astigmatism and field curvature are both the quadratic power functions of the field of view, and then their curved shapes are part of the parabola. Distortion is a cubic power function of the field of view, giving rise to its shape being that of a cubic function. The primary wavefront aberrations, except for spherical aberration, increase with the scanning fields of view. Subsequently, the sum of the primary wavefront aberrations and the RMS wavefront error of the system are calculated and analyzed (Fig. 6). It is evident that the sum of primary wavefront aberrations and RMS wavefront error rises with the scanning fields of view. The range of gaze field of view in different scanning fields overlaps, which reflects the aberration correction of the system for larger scanning fields of view. The deviation between the calculated value of RMS wavefront error and the soft simulation results is discussed, along with the deviation causes. Finally, the primary wavefront aberration values of different surfaces of each scanning field of view are given (Fig. 7). It is observed that with the rising scanning fields of view, spherical aberration remains unchanged, while the other four types of aberrations increase gradually. Based on the quantitative relations of various types of aberrations, the system can achieve aberration correction by balancing spherical aberrations of each surface.

The imaging quality of a system can be affected by dynamic aberrations of cascaded micro-lens arrays during the scanning. Therefore, studying the dynamic aberrations of the system is critical to high resolution and a large field of view in infrared imaging systems. We present an applicable method for calculating the wavefront aberration of scanning imaging systems with cascaded micro-lens arrays based on the nodal wavefront aberration theory of non-rotationally symmetric optical systems. We employ this method to calculate the wavefront aberrations of a cascaded micro-lens array scanning system, which effectively reflects the variability of primary aberrations with the scanning fields of view. The proposed method allows for quantitative aberration evaluation in a cascade micro-lens array scanning system. However, since only primary aberrations are considered in our paper, some high-order aberrations may be imported into the system with high-order aspheric surfaces. Thus, further research is essential.