Design for Manufacturing: Silicon and Germanium Windows

The Challenge

During the design of silicon and germanium windows, many optical designers will specify the flatness of the individual surfaces instead of the transmitted wavefront through the optic. 

This causes designers to have tighter surface flatness requirements to ensure that the estimated wavefront through the optic functions in the final system as required.  Infrared windows used in aerial reconnaissance, such as in drone turrets.

The Solution

Design for Manufacturing (DFM) Value-Added Services Using a Zygo 3.39µm Interferometer for Accurate and Cost-Effective IR Window Production

When reviewing this IR window opportunity during our daily DFM meeting, we evaluated it against our current capabilities and saw an opportunity to provide additional information that will enhance the product specification and shared this with our customer. 

In the case of silicon or germanium windows, if a customer has specified surface flatness, we will often recommend a transmitted wavefront specification since we own a Zygo 3.39µm interferometer that can evaluate optics up to 14 inches or 350mm in diameter or diagonal.

This style of interferometer is not common due to its cost of ownership since these systems are 5-6 times more expensive than standard HeNe systems.

By specifying a transmitted wavefront requirement, this enables Sydor Optics to measure the optic as it would be used in the final application. Our engineers worked directly with our customer’s optical design engineers to agree on a specification that will reflect how the optic needs to function in the field.  In addition, we utilized our double-sided lapping and polishing expertise to produce the IR windows that meet our customer’s need for cost-effective optics with a predictable delivery schedule.