## 3 Results and Discussion
### Optical Imaging Experiment  
An optical imaging experiment was designed to evaluate the focusing and imaging of the microlens array. First, optical simulation software ZEMAX was used to design and simulate a 10 \(\times\) 10 microlens array's light path. Figure 7a shows that a combination of point light sources and single convex lenses is used to form a parallel light source. After the parallel light passes through the microlenses, a 10 \(\times\) 10 array of focused spots is formed on the screen. Figure 7b,c show that the aspheric microlens array has excellent focusing performance for parallel light. As the point light source obtains the parallel light, the imaged light intensity on the screen will fluctuate owing the X coordinate axis change (See Figure 7d).  
Based on the mentioned ZEMAX optical simulation model, a platform for optical imaging experiments was established. Figure 8a shows aspherical-array optical imaging, including A (light source controller), B (parallel light source device), C (aspheric lens array), D (magnifying lens), E (complementary metal oxide semicond (CMOS) camera), and F (screen). The light source controller drives parallel light sources to achieve a constant current control with a high pulse width modulation (PWM) frequency, suppressing the light source flicker and ensuring stable light emission. Through the control software, the light source can realize 256-level brightness adjustment and channel switching. Besides, the parallel light source's beam diameter is 30 mm, and the flatness is less than 0.1. The camera is a CMOS camera with 25,921,944 pixels, a 15 fps frame rate, and black and white pigments. The centering holder can adjust angles and positions. The imaging system includes a target (a screen with a capital letter \"A\") and a PMMA sample on a rotating table. During the measurement, the black capital letter \"A\" is projected through the PMMA microlens array,  
Figure 6: **(a)** 3 \(\times\) 3 MLA characterization of the mold, **(b)** 3 \(\times\) 3 MLA characterization of the sample, **(c)** the original measurement surface, and **(d)** the profile and error of the two radial cross-section surfaces.  
and each microlens can form tiny and clear \"A\" images on the charge coupled device (CCD) camera (See Figure 8b). The produced microlenses have good imaging performance.  
Moreover, the focusing function of the micro lens array was also tested. As shown in Figure 8c, a parallel beam is projected onto the PMMA microlens array, and the focus image is obtained by adjusting the distance. To evaluate the uniformity of light spots, a random line with 10 spots was selected and the light intensity of each spot was calculated. It can be seen that the manufactured PMMA compound eye lens has perfect focusing function and uniform light spot intensity.  
Figure 8: (**a**) The schematic diagram of optical imaging platform, (**b**) focus imaging and intensity data captured by CCD camera of PMMA microlens array, and (**c**) the capital letter “A” focused on the aspheric lens array.  
Figure 7: Simulation of optical imaging. (**a**) Three-dimensional schematic diagram of optical simulation, (**b**) simulated light focusing points on the receiver, (**c**) planar ray tracing simulation, and (**d**) light intensity distribution of the receiver x section.