A make-or-break attitude in every batch of lenses we make

  • Reasons behind the choices Cosina makes

The above photograph shows multiple optical elements neatly arranged and immobilized for polishing. Optical elements can be polished one at a time or in batch. To do this, the optical elements are attached to either a concave or convex polishing plate of a specified curvature. This method is used to polish optical elements of small size and gradual curvature (large radius). The necessary process for batch polishing for small diameter optical elements is, first attach them by water at equal intervals to a large impression plate with the targeted finishing curvature, then transfer to a mold so that the optical elements will be facing upward.

Immobilizing optical elements on plate with molten pitch

At this point, a special thermoplastic pitch is used. Heated to a liquid, the pitch is poured over the impression plate where the are attached and the plate is coupled with the mold. The sink into the soft pitch, which is then cooled to room temperature where it solidifies and thus immobilizes the optical elements. After that, the impression plate and mold are separated by tapping one time with a hammer, revealing the lenses stuck to the mold in the curvature transferred from the impression plate. All steps in this process require dexterous manual work and must be done carefully and intentionally.

Optical elements held in the mold

The small diameter optical elements sit neatly arranged in the mold. In batch polishing, optical elements cannot be repolished if deemed to be of undesirable quality, because it is impossible to rearrange the optical elements in the exact same positions and angles on the impression plate. So, why do we employ such a tediously long process that offers no room for an error? We do that because, we are more than willing to guarantee product precision, though the method may place strict requirement to our production floor. When polishing just one small diameter lens at a time, quirkish results are readily manifested with curved surfaces. No matter how troublesome, precision must never be compromised. So, every batch of lenses we produce carries our resolute stance of providing users with high-end optical devices.