Transmission Spheres
At Resistance Optics, 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.
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. Resistance Optics' high precision, pitch polished reference surfaces have 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.
Below is our current Standard T-Spher
Current Standard T-Sphere Offerings
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
T-Sphere Applications
Since the 1970’s, Fizeau interferometers have been the industry standard method of ensuring quality of optical components. As such, nearly any optics company that manufactures, tests, or purchases optical components either uses or would like to have an interferometer at their disposal. Any optic that has a curved surface needs a T-Sphere in order for it to be tested with an interferometer. Even if the surface is not spherical, but aspheric, freeform, cylindrical, ect, a T-Sphere can be used as part of the testing with other equipment.
Interested in pricing for one of our T-Sphere models above?
Have questions about custom offerings?