Optical assembly with backlight monitoring

The invention provides an optical assembly with backlight monitoring. The assembly comprises a transmission substrate and at least one set of optical transmission units. A first interface, a second interface, a third interface, and a fourth interface are arranged on the transmission substrate; the first interface and the second interface are total-reflection interfaces; the third interface and thefourth interface serve as parallel interfaces for each other; and an air gap is formed between the third interface and the fourth interface. The optical transmission units include VCSEL chips, MPD chips, incident collimating lenses, first focusing lenses and second focusing lenses. The first interface, the third interface and the fourth interface cooperate with each other to form a first opticalpath; the second interface and the third interface cooperate with each other to form a second optical path; and the first optical path and the second optical path are used for front light transmissionand backlight monitoring.