Abstract
We introduce a scalable temporally modulated long-wave infrared source design. The design makes use of an array of resistive blackbody heating elements which radiate into a custom aluminum integrating cavity. The output of the box is a rectangular slit, built to match the traditional tungsten ribbon profile for an infrared deflectometry source. Temporal modulation allows for signal isolation and improved resilience to background fluctuations in an infrared deflectometry source. Infrared deflectometry measurements using the new source design and a traditional tungsten ribbon, both with similar radiant flux, were compared for a ground glass surface, an aluminum blank, and an aluminum blank under thermal load (150 °C). Signal-to-noise ratio was ∼4 times higher for the new design and demonstrated improved source temporal stability and geometry. Further, the new design successfully measured the previously untestable hot aluminum flat. The new design improves infrared deflectometry and allows for high contrast thermal deflectometry measurements of optics under thermal load.
Highlights
As manufacturing methods continue to improve, a wider range of materials are being shaped into custom freeform surfaces for new optical applications
Interferometry is a null metrology method, which requires using a null optic as a reference measurement to the unit under test (UUT)
The key limiting factors in a deflectometry test for what is measurable are defined by the source size, the camera field of view (FOV), and whether the tested UUT surface can reflect the light emitted from the source
Summary
As manufacturing methods continue to improve, a wider range of materials are being shaped into custom freeform surfaces for new optical applications. The load will be too great for the ribbon to handle, leading to a failure in the source These comments are not meant to diminish the impact the tungsten ribbon design had on infrared deflectometry and metrology generally. Without the introduction of the tungsten ribbon source, high accuracy, rapid and efficient in-situ testing of diffuse optics was challenging, time consuming, and extremely expensive. Instead, these known limitations to the tungsten ribbon lay out a clear framework of considerations that must be addressed to produce an improved infrared deflectometry system at the source level. An aluminum flat under high thermal load, which has historically been unmeasurable using a traditional source due to the low contrast signal for infrared deflectometry and fluctuating background noise, was successfully measured to demonstrate and confirm the high contrast thermal deflectometry performance when utilizing the LITMIS source
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
