Laser interference and damage can severely disrupt the operation of optoelectronic imaging systems. However, simulating far-field laser effects under laboratory near-field conditions remains challenging owing to differences in wavefront curvature, beam divergence, and atmospheric-induced distortions. Traditional beam-expanding systems fail to replicate both the wavefront curvature and effective beam size of far-field laser propagation. This paper proposes a novel near-field equivalent far-field (NEFF) laser spot design method using symmetric lens arrays to precisely emulate far-field laser characteristics in controlled laboratory environments. This approach addresses the critical need for high-fidelity experimental validation of optoelectronic system vulnerability to laser interference over long ranges.

The proposed method is based on Gaussian beam propagation theory and matrix optics. A four-lens symmetric optical system is designed to match both the wavefront curvature radius (R) and effective beam waist radius (ω) of far-field laser. The ABCD matrix formalism is applied to derive the lens focal length and spacing relationships to achieve parameter equivalence. Establishing the equivalence conditions using Gaussian beam q-parameter analysis. A four-lens system with a co-focal architecture is configured to balance the wavefront curvature and beam divergence (Fig. 1). A 532 nm laser testbed with adjustable lens spacing is implemented to simulate far-field distances (Fig. 3). The near-field simulation and true far-field interference patterns are quantitatively compared using metrics such as mean square error (MSE), peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), and visual geometry group-16 (VGG-16) similarity indices (Table 5).

The proposed NEFF system demonstrates exceptional equivalence in terms of static and dynamic laser characteristics. For a 3-km far-field scenario, the system achieves a wavefront curvature error rate under 10% and beam size accuracy exceeding 99% (Table 2). Near-field simulation laser spots [Figs. 4(a)-(d)] closely replicate the far-field irradiation effects, including diffraction rings and point-array structures [Figs. 4(e)?(h)]. Quantitative analysis reveals that PSNR exceeds 17.28 dB and the VGG-16 similarity exceeds 0.64 across varying irradiance levels (Table 5). By adjusting the lens spacing, the system can simulate far-field distances ranging from 100 m to 10 km (Table 4). ZEMAX simulations confirm that long-focal-length lenses can minimize wavefront distortion (Fig. 5). The error sensitivity analysis (Table 2) reveals that a 10% focal length deviation causes a curvature error of under 6.5% when using 1000-mm lenses.

This study presents a breakthrough in near-field emulation of far-field laser effects through a symmetric lens array design. The NEFF system achieves dual-parameter equivalence with high fidelity, enabling cost-effective laboratory evaluation of optoelectronic systems under realistic long-range laser interference scenarios. The key innovations include the following:

1) A scalable optical architecture capable of simulating far-field distances from 100 m to 10 km with compact physical dimensions.

2) Experimental validation showing >99% beam size accuracy and PSNR of >17 dB compared with true far-field irradiation.

3) Demonstration of robustness to fabrication errors through error sensitivity analysis.

Future work will integrate dynamic phase modulation to simulate atmospheric turbulence effects, further enhancing the applicability of the system in defense and space communication research.