光镊可以非接触、无损伤地操纵尺度位于数纳米到数十微米之间的生物细胞、亚细胞、生物大分子以及胶体粒子，已经成为生命科学和胶体化学领域不可缺少的研究工具。根据几何光学，对基于有限远光学系统显微镜的光镊光路进行了分析计算。这类系统由捕获光源、准直透镜、倒置生物显微镜、大数值孔径物镜、成像系统和CCD相机组成，可以在保持物镜后瞳充满度的情况下调整阱位和刚度，具有捕获力大、被捕获的粒子成像清晰等优点，可以很好地满足科研和教学需求。

Optical tweezers, or single beam gradient force optical traps, are very suitable for micromanipulation with large spectrum of specimens in the diameter range from several nanometers to tens of micrometers. Optical path of optical tweezers based on finite conjugate microscope systems is analysed and calculated. The design of optical tweezers consists of laying out a trapping laser, a collimation lens, an inverted microscope with a high numerical aperture objective and a CCD camera. The optical trains are to maximize the convergence angle and to maintain the trap position while retaining the same degree of overfilling of the microscope entrance aperture. The formulations provide the basis for theoretical analysis of experimental alignment and adjustment.