Abstract: In view of the current machine vision detection target illumination uniformity is low and insufficient energy utilization, this paper proposed for the first time using LED free surface reflective cup to replace the ordinary diode array arrangement, and optimize the optimal spacing, realize the compensation of target center illumination, reduce the loss of large angle light source, improve the illumination uniformity and energy utilization rate in the light source array system. The paper first theoretically analyzes the relationship between the optimal spacing between the light sources and the half-light intensity angle and the target surface distance, respectively. Then, the optimal spacing of the free-surface reflective cup array is rectangular, ring and triangular, and the comparative analysis of the corresponding array experiment is conducted using ordinary diode. The results show that, the energy utilization rate of the system is higher than 70%, the illumination uniformity is higher than 89%, and the energy utilization rate is improved by at least 58.6%, and the illumination uniformity is improved by at least 12.8% compared with the ordinary diode array. Among them, the overall light source of the free surface rectangular array light source has the highest illumination, the best energy utilization rate is 74.2%, 61.9% higher compared with the ordinary diode array; the free surface ring array light source, the best illumination uniformity is 94.1%, and 15% higher compared with the traditional diode array. The final experimental results show that the LED free surface reflective cup light source for array combination, so that the overall light source effect is significantly improved.