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Transmission Spheres

At Torrent Photonics, we produce a high-quality extended-range line of transmission spheres (t-spheres). This line includes many standard F/# 633nm builds as well as custom F/# and custom wavelength t-spheres available upon request. T-spheres are a necessary part of Fizeau interferometry and are used to measure the transmitted wavefront of optical systems and the reflected wavefront of optical surfaces.

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Transmission-Sphere-scaled

Applications and Benefits

As an example, when using an SLR camera, the camera body cannot take a picture without a camera lens attached. Similarly, an interferometer body cannot measure without a transmission sphere or transmission flat. F/# is the ratio between focal length and entrance pupil diameter where different F/#‘s are required to measure different radius optics. F/# can be simply thought of as the ratio between the radius of curvature and visible aperture for reflected wavefront measurements. A “faster” (smaller number) F/# can measure a larger area for a given radius, but the focal length is shortened, limiting the radius of curvatures you can measure with it.

The key to the accuracy of a t-sphere is the final surface of the assembly, known as the reference surface. When light from the interferometer passes through the reference, the resulting wavefront interferes with the surface(s) under test. In general, the reference surface is assumed to be perfect, and all the interference that is measured by the interferometer is assumed to be from the part under test. Torrent Photonics high precision, pitch polished reference surfaces for smooth, low irregularity wavefronts. This level of optical workmanship allows us to offer all our t-spheres (including our F/0.56) at λ/20 quality (at λ = 632.8nm) and most at λ/40 level.

Advantages

  • Proprietary Kreischer extended range designs for measurement of longer convex radius of curvatures than comparable F/# t-spheres
  • Unique optical design to reduce the effects of lateral (tilt) retrace error
  • More catalog standard F/#‘s than found from other sources, which fill in the gaps in metrology.

4-Inch TS Series

f/No. R D WD OD L EFL
f/0.56 22.7 40.7 8.1 147.8 132.3 55.8
f/0.65 39.0 60.0 22.0 133.4 101.8 65.6
f/0.75 50.0 66.7 32.5 133.4 101.8 76.1
f/1.0 90.0 90.0 72.2 133.4 96.3 100.3
f/1.5 142.7 96.4 130.0 133.4 83.4 150.4
f/2.4 264.5 110.2 255.0 133.4 96.3 244.4
f/3.3 344.7 104.2 336.0 133.4 71.1 339.3
f/4.9 540.1 110.2 532.0 133.4 71.1 500.2
f/6.0 633.3 104.7 626.0 133.4 71.1 615.3
f/7.1 800.1 112.7 794.0 133.4 71.1 723.5
f/10.7 1201.4 112.3 1195.0 133.4 71.1 1087.8
f/12.0 diverger 1,201 cx 104.0 n/a 134.2 20.4 -1185.0
f/12.5 converger 1,258.0 cc 101.0 1253.0 134.2 20.4 1286.0
f/14.3 converger 1,431.9 cc 99.9 1425.0 134.2 20.4 1462.3
f/16.5 converger 1,654.4 cc 100.1 1648.0 134.2 20.4 1683.2
f/20.0 diverger 2,043 cx 102.7 n/a 134.2 20.4 -2026.4

6-Inch TS Series 

f/No. R D WD OD L EFL
f/0.75 72.1 96.0 47.0 180.1 149.9 107.5
f/1.1 130.7 120.9 109.0 180.1 110.1 160.8
f/1.6 220.3 136.5 199.0 180.1 110.1 243.0
f/2.4 346.7 146.9 333.0 180.1 89.9 361.5
f/3.5 518.3 148.1 507.0 180.1 89.9 532.6
f/5.0 739.8 150.4 730.0 180.1 89.9 749.8
f/7.4 1128.0 152.4 1120.0 180.1 89.9 1127.4
f/15.5 converger 2342.3 cc 150.9 2314.7 177.7 47.5 2373.6

 

R  Radius of the reference surface
D  Diameter of the reference surface
WD  Working distance from focal point to cell
OD  Outer diameter of the lens cell
L  Length the cell extends beyond the interferometer
EFL  Effective focal length

OEM Customization Options

Torrent Photonics provides original equipment manufacturer (OEM) customization services, creating application-specific multispectral engines for easy integration into handheld instrumentation and optical devices. We can also customize your filters, optimizing spectral bands and imaging for your application.

Whether you need customization for proof of concept or high-volume production, we have the expertise and operational capabilities to provide solutions.

OEM Customization Options