CGH for freeform surfaces

Recent advancements in optical manufacturing techniques have made it possible to create complex Optical Components with exceptional precision. However, Optical Metrology often remains a limiting factor in the fabrication of these intricate surfaces, such as freeform surfaces, off axis parabola, cylindrical surfaces as existing methods for qualification and feedback are frequently not precise, flexible or capable enough. A computer-generated hologram (CGH) addresses many of these surface and Optical System testing challenges, making the qualification of complex optical surfaces feasible while preserving precision, resolution, speed, and other advantages. MG-Optics will make the custom cgh design and fabrication for your freeform optics. The test accuracy achieves 1/100λ. 

Complex Surface Optical Metrology Enabled by custom CGH, CGH nulls convert a collimated wavefront to a freeform surface to match the freeform optics design

Ray Diagram Freeform with CGH show as below:

A CGH transforms the regular wavefront from an interferometer—whether collimated or spherical—into a custom-designed wavefront that conforms to the unique shape of the surface being tested. This results in an interferometric null test when the test optics is properly aligned with the CGH nulls.

To further explain this process, consider how the light rays from the interferometer interact during the test. A CGH is designed to bend the rays across the aperture in a specific manner, ensuring that all rays strike the test optic at normal incidence. Consequently, all rays reflect off the test surface and return through the CGH to the interferometer along the same path they initially took—resulting in a null test!

A CGH null test can be configured for various types of surfaces, including convex, concave, aspherical, off axis and even freeform geometries. While there are some limitations, the vast majority of optical surfaces can be tested effectively using a custom CGH.

If you are interested with our products, Just send us your drawings or specifications, we will begin preparing a quotation for you. 

Contact with our professional technician engineer now!