The prototyping process of miniaturized plastic imaging lens is described. The sequence is divided into five phases: specification, optics design, optomechanical design, manufacturing and characterization. During specification, the optical and mechanical requirements of the lens are defined. In the optical design phase, the lens is optimized, and a tolerance analysis is carried out. Simulation tools, especially, an image quality simulator, can be used to visualize and verify the performance of the design. Mechanical design is performed considering the geometrical specifications and optical tolerances of the system. In addition, stray light analysis is carried out to verify the optical performance of the optomechanics. Plastic optics are particularly vulnerable to stray light due to the integrated mountings, which provide additional paths for unwanted light. If the prototype is used for preliminary performance evaluation of a future product, the differences between prototype and mass manufacturing methods need to be considered carefully. After the lenses are manufactured they are characterized, and the experimental results are compared with the original specifications and estimations obtained from the previous design verification simulations. New error analysis simulations can be performed in order to pinpoint faults in manufactured modules. If the performance of the prototype is not sufficient, a new prototyping iteration circle is needed. The whole process is described and analyzed using a miniature, plastic imaging lens as an example, but it can also be applied to other optical prototyping tasks.