AND THERMAL IMAGING
Combining LightPath’s high-
volume molding technology
with ISP’s high-value diamond
turning, coatings and polishing
capabilities to create a global
paramount solutions provider.
DESIGNED PRODUCED DELIVERED
Lateral position (mm)
Height (mm) b)
50 45 40 35 30 25 20 15 10 5 0
A variable asym-
is present that ex-
ceeds 2% in some
rings introduced by
a diamond turning
fabrication step ac-
tually make it rel-
atively easy to ob-
serve the distortion
on this part. The
rings should be ax-isymmetric (corre-
sponding to the
diamond tool’s cutting path), and thus
be located the same distance away from
the axis in either the X or Y axis. They
actually vary by up to a millimeter in
some locations (see Fig. 5).
While 3D profilometry/CMM techniques can test a variety of freeform
shapes, interferometry is preferred for
some optical requirements. A CGH null
test has typically been employed in such
cases, but the need for a custom dedicated null restricts design and prototyping flexibility.
The ASI(Q) stitching system provides
flexibility for plano, sphere, and asphere
testing, with now-demonstrated flexibil-
ity for freeform surfaces. We show nano-
meter-level agreement with a CGH test
on a sample freeform, and achieve even
better lateral resolution. Subaperture
stitching lacks the ghosting and oth-
er diffraction artifacts in a CGH that
can corrupt mid-spatial frequency es-
timates. It also simplifies treatment of
the oft-forgotten alignment and distor-
tion correction steps that can bedevil
ASI(Q) is a trademark of QED Technologies.
1. K. P. Thompson, P. Benítez, and J. P. Rolland,
Optics & Photonics News, 23, 9, 32–37 (2012).
2. T. Köhler, C. Schindler, and E. Roth, “Mastering
the art of freeform optics manufacturing,”
OptoNet Ultra Precision Manufacturing
of Aspheres & Freeforms Workshop, Jena,
Germany (Sept. 21, 2016).
3. G. W. Forbes, Opt. Express, 20, 3, 2483–2499
4. G. Derst and V. Giggel, “Fabrication
technologies for large optical components
at Carl Zeiss Jena GmbH,” Proc. SPIE, 7739
5. M. Beier et al., “Fabrication of high
precision metallic freeform mirrors with
magnetorheological finishing (MRF),” Proc.
SPIE, 8884 (2013).
6. T. Blalock, K. Medicus, and J. DeGroote Nelson,
“Fabrication of freeform optics,” Proc. SPIE,
7. P. Murphy, J. Fleig, G. Forbes, D.
Miladinovic,and G. DeVries, “Subaperture
stitching interferometry for testing mild
aspheres,” Proc. SPIE, 6293 (2006).
Chris Supranowitz is a senior applications
engineer and Paul Murphy is a senior optical
engineer, both at QED Technologies, Rochester,
NY; e-mail: email@example.com; www.
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FIGURE 5. Negative X and negative
Y slices for CGH measurement, where
the arrows in the map indicate the
location of the slices (a); the arrows in
the plots indicate three sets of peaks
that are not at consistent locations in
the X and Y slices (b).
lacks the ghosting and
other diffraction artifacts
in a computer-generated
hologram that can corrupt