1. Optical Performance Requirements

  The design of molds for optical instrument lenses must account for the specific optical performance goals. This includes factors like focal length, aberration correction, and light transmission. Advanced optical design software is used to model the lens geometry and predict its optical behavior. For example, in the design of a camera lens mold, the curvature of the surfaces needs to be precisely calculated to achieve the desired focal length and image quality. The thickness distribution of the lens is also carefully designed to minimize aberrations such as spherical and chromatic aberration. The position and shape of the gate and runner system in the mold are crucial as they can affect the flow of molten glass and the quality of the final lens. If the flow is not uniform, it can lead to inhomogeneities in the refractive index and optical distortion.

2. Dimensional Accuracy and Tolerances

  Tight dimensional tolerances are essential in mold manufacturing for optical lenses. Tolerances in the sub-micron range are common for critical dimensions such as the radius of curvature and lens thickness. The mold must be designed to account for the shrinkage of the glass during cooling. Simulation software is used to predict the shrinkage behavior and adjust the mold design accordingly. Any deviation from the correct dimensions can result in a significant degradation of the optical performance. For instance, a slight change in the curvature of a telescope lens can lead to inaccurate focusing and a blurred image. The mold also needs to have precise parting lines to ensure clean separation of the lens from the mold without leaving any marks or defects on the surface.