Retrace error is rarely specified for an interferometer, often ignored and can cause good parts to fail. Knowing how to minimize this issue, decreases scrap, saves time, and lowers manufacturing cost. Transmitted Wavefront Measurements Recently an Äpre upgrade customer using a 6X zoom interferometer noticed unexplained user-to-user variations. The setup was a window within a Transmission Flat … Continue reading
Precise alignment of the transmission flat (TF) or transmission sphere (TS) is critical for obtaining accurate measurements. A misaligned TF/TS, that is any non-orthogonal tilt relative to the optical axis, will cause the returning beams to pass through the interferometer off axis. Off‐axis beams pick up retrace errors lowering measurement accuracy. This is especially important … Continue reading
Previously difficult measurements of right angle prisms are now possible with the spectrally controlled source (SCI). With the narrow coherence and easy setup even micro-prism measurement is possible. Measuring right angle prisms is complicated by back reflections from the multiple faces of the prism. Äpre SCI technology separates the faces, enabling easy measurement of all … Continue reading
In the semiconductor industry, extremely small surface defects and particles are a major concern that reduces yield and also costs producers time and money. It is therefore critical to inspect the surface of semiconductor wafers for defects and contamination, a challenge many of Holo/Or’s customers in the semiconductor metrology industry face. One of the faster … Continue reading
Easily measure optical wedges using the REVEAL metrology software from Äpre Instruments. Through transmission or reflection, you can accurately determine wedge angle, tilt, magnitude, and more to get the job done right. An Application Note from Äpre teaches how to measure an optical wedge or a group of optical wedges by transmission or reflection. This … Continue reading
Äpre Instruments has released a short paper, entitled “Mid Spatial Frequencies in Optical Surfaces Based on Interferometric Measurements.” The abstract of this paper states: Modern optical polishing introduces mid-spatial frequency errors. Few standards exist to specify and measure mid-spatial frequencies. We propose Fizeau interferometry’s application characterized by power spectral density due to its flexibility and … Continue reading