Moeller-Wedel Optical International is a German manufacturer of high precision optical test equipment. The company is a member of the international Hagg-Streit group.
Moeller-Wedel products are generally not intended for focus testing but instead designed for use in industry and scientific applications, mostly for setting precise alignments over a distance and measuring small angles.
The Moeller-Wedel is perhaps best known in the professional cinematography industry for their Camera Testing Instrument III (CTI 3).
The CTI 3 seems, from Moeller-Wedel documentation, to have been initially intended for manufacturers of still cameras (hence the name). It has found widespread acceptance for focus testing of lenses. Unlike the AKR, the CTI 3 was specifically designed for testing focus, and forms the basis of many autocollimator systems for the cine industry, such as the Chrosziel and Gecko-Cam systems.
The CTI 3 uses a unique measurement method developed by Moeller-Wedel. Rather than judging the sharpness of the image, the user sees a reticle with a central bar located between two outer bars. When the inner bar is centered between the outer bars, focus is correct. This method is intended to reduce the variability between multiple users.
The CTI 3 has a fixed dual-tube collimator objective, and the beamsplitter is position in front of the collimator objective, resulting in the unique “L” shape of the CTI 3. The unit is relatively large and heavy compared to their simpler AKR collimators. Production of this instrument is limited and the cost is very high.
Moeller-Wedel also manufacture high quality reflex autocollimators (AKR) with are usually fitted with crosshairs for alignment testing. Configured this way they cannot be used for focus testing.
By replacing the reticle of an AKR with a Siemens star target reticle, the Moeller-Wedel AKR becomes a superb instrument for focus testing.
Although the interpretation of a star target image takes more training that the vertical bar image of the CTI 3, an experienced user can be just as accurate and deal more easily with unusual focus situations.
Unusual focus characteristics of vintage and anamorphic lenses can be deal with most effectively by an experienced user interpreting a star target image.
For example, star targets show astigmatism readily. Dealing with astigmatism is one of the more challenging aspects of calibrating focus on anamorphic lenses.
I have owned and worked with Moeller-Wedel autocollimators for 15 years. I purchased my first M-W AKR unit from ARRI USA when they purchased a new Gecko-Cam collimator system to replace it.
After years of working on a daily basis with the Camera Testing Instrument III (on a Chrosziel system) and the Zeiss K8 and K9 MTF testing systems, I thought of ways that the M-W components could be upgraded to make them even more effective for optical testing.
CinemaTechnic now upgrades M-W AKR collimators for use in testing cine lenses. We have developed our own illumination and video relay systems.
If you would like more information on Moeller-Wedel AKR autocollimators, illumination systems, high definition video relays and custom autocollimator benches, please contact us via email:
©2020 Jorge Diaz-Amador, all rights reserved
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Updated 2020-04-08