Internal lens elements in the objectives are made with optical-grade plastic that has been molded and cut to the proper dimensions necessary to produce magnified images of specimens placed on the microscope stage. Laws of geometrical optics assume that light travels along rays that are straight in a homogeneous medium, and are refracted by lenses before proceeding to form an image of the object being examined. Ray trace paths of light passing through each of the QX3 objectives are illustrated in Figure 1. These paths are based on calculations of the objective working distances and the approximate location of the rear focal planes. The QX3 takes advantage of plastic lens technology to produce magnified images and project image data onto the surface of the CMOS active pixel sensor integrated circuit.
Plastic optics have a number of advantages over glass.
They have a much lower cost, a higher impact resistance, are of lighter weight, and have more configuration possibilities for simplifying system design and assembly. Modern plastic lenses have a light transmittance value that is comparable to high-grade crown glasses. These factors make plastic an ideal material for high volume optical instruments such as toy microscopes. There are some disadvantages to plastic optical components. Primarily, plastic optics have a low tolerance to severe temperature fluctuations and they also have a low resistance to scratching.