Light field imaging is a method of imaging by acquiring light field information and refocusing on a specific plane. With the limitation of the light field camera structure, the detector is generally modified to achieve coupling of the microlens array and the detector. It is not applicable to infrared light field cameras. To this end, a novel structure of a micro field lens array combined with a relay lens was proposed. This new structure utilized a relay lens to image the intermediate image plane at a 1:1 ratio and eliminated the vignetting of the relay lens through the micro field lens array. The modulation transfer function curve of the system was calculated by the slanted edge method. The image quality of direct coupling, relay lens coupling and new structure coupling were compared. According to different refocus planes, the curve value of the new coupling structure at Nyquist frequency was increased by 5%-240% compared with that of the relay lens coupling structure. It was close to the curve value of the direct coupling structure. The new structure can realize coupling and avoid the sharp decrease of system image quality. It plays an important role in the infrared field camera.