为了填补我国学术界和产业界在压贴三棱镜的国产化设计、制作以及测试等方面工作的空白, 研究了压贴三棱镜镜片结构设计理论, 并推导了压贴三棱镜镜片透过率以及畸变的计算公式, 数值模拟了不同材料、不同棱镜度数的压贴三棱镜的透过率以及压贴三棱镜的畸变情况.数值模拟结果表明: 与现有PVC材料相比, PMMA材料具有更大的阿贝系数和更小的材料吸收率, 是一种制作低成本压贴三棱镜的理想材料.利用金刚石切割工艺制作出精密的压贴三棱镜模版, 模版的表面光洁度达到14级, 并采用热压工艺, 在温度为180 ℃压力为130 kg/cm2的工艺参数下制作出不同棱镜度数的压贴三棱镜样片, 验证了以PMMA材料为基材、采用热压工艺制作压贴三棱镜的可行性.为了测试压贴三棱镜样片的实际棱镜度(Δ), 自主设计并搭建了压贴三棱镜棱镜度测量系统.实验结果表明: 对低(10Δ)、中(20Δ)、高(30Δ)三组压贴三棱镜样片的棱镜度测试结果与理论值的偏差分别为0.01Δ、0.04Δ和0.02Δ.所有样品的棱镜度偏差均符合国家医用棱镜的标准.因此, 所制作的压贴三棱镜样片具有较高的光线偏折精度, 为治疗儿童斜视疾病提供了一种高质量、低成本的产品方案.

In this paper, we present our design of a rigid Fresnel prism and derive the calculations of its transmittance and distortion. The transmittance of prisms made of different kinds of polymers and their distortion were numerically simulated. Simulation results showed that polymethyl methacrylate (PMMA) had a larger Abbe coefficient and a lower material absorption rate than polyvinyl chloride (PVC). Then, on the basis of the simulation, stamps for the prisms were machined using the diamond-cutting method; the surface roughness of the stamps reached class 14. We verified that low-cost prisms can be fabricated from PMMA using the thermopressing method under the conditions of 180 ℃ and 130 kg/cm2. A system was constructed to test the prism diopter (PD) values of the samples. Experimental results showed that the deviations between the calculated and actual PD values for 10Δ (low PD), 20Δ (medium PD), and 30Δ (high PD) prisms were 0.01Δ, 0.04Δ, and 0.02Δ, respectively. The PD deviations of the sample prisms all agreed with the Chinese tolerance standard for a medical prism. Hence, we verified that the rigid prisms fabricated in this study are sufficiently precise to reflect light and are a high-quality, low-cost solution for the treatment of strabismus in children.