Compared with the traditional total-internal-reflection (TIR) prism, the right-angle TIR prism is convenient to process. Meanwhile, it decreases 50% in the volume and 43% in the weight, which lowers the cost. Using the theory of optics the right-angle TIR prism is optimized in order to make it easier to process the structure. In the optical software simulation, the system′s efficiency decreases from 53% to 48.3%, while its uniformity can be enhanced from 68% to 91%. It proves that the right-angle TIR prism is reasonable and practicable.