投影仪光学部分的双螺纹透镜又称菲涅尔透镜，它是光学部分的重要元件之一，是由进口双层有机玻璃上精刻螺纹制成，价格昂贵。它的作用是进一步会聚光线，使光线均匀地照射在投影片上。双螺纹透镜的作用相当于一块平凸透镜，但如果投影仪中采用普通光学玻璃制成的平凸透镜聚光 The double-threaded lens of the optical part of the projector, also known as the Fresnel lens, is one of the important components of the optical part. It is made of imported double-layer plexiglass with finely-trimmed thread and is expensive. Its role is to further converge the light, so that the light evenly shines on the slide. The double-threaded lens acts as a plano-convex lens, but if the projector is used in the ordinary optical glass made of plano-convex lens spotlight