"HT" & "HTultra" Glass

Product Information

Optical glasses with ultra-high transmittance

As part of its extensive portfolio of optical glasses, SCHOTT has been offering special glass variants that are known for their superior transmittance. These special glass types with significantly improved transmittance are identified with the suffix "HT" or "HTultra". They are especially suitable for digital projection and high-end optical systems.

Our current portfolio includes 13 "HT" and "HTultra" glasses, (e.g. N-BK7HT, N-SK2HT). Several of our glass types exhibit the best transmittance values available in the maket, including:
  • N-BAK4HT
  • N-LASF45HT
  • N-SF57HTultra
  • N-SF6HTultra
"HT" and "HTultra" glasses are provided as raw material, as pressings and in the form of finished components.


  • Improved transmittance especially in the blue-violet spectral range
    → improves color contribution and causes better mesoptic vision
  • Reduced 'thermal lensing effect' due to higher transmittance
    → reduces energy absorption and improves image quality
  • Faster polimerization of UV active glues due to better UV transmittance
    → time savings while processing
  • High product quality due to stringent quality control procedures
  • Excellent application support and expertise
  • Extensive processing capabilities (e.g. CNC machining, coating, polishing, sub-assembly)
  • Product range specifically suited for long-term availability

Supply Forms

"HT" and "HTultra" glasses are available as:
Supply Forms*
  • polished prisms
  • lenses
10 mm - 200 mm
3 mm - 200 mm
Pressings diameter: 5 mm - 320 mm
center thickness: 2 mm - 100 mm
Raw glass
  • strips
  • blocks
≤ 50 mm
190 mm x 180 mm x 140 mm

* Other supply forms and dimensions upon request (depend on glass type). 
   Please contact us.           
We also offer high-precision optical components made of "HT" and "HTultra" glasses.

Technical Information


Color Code
N-BK7HT 1.51680 64.17 0.998 33/29
N-SK2HT 1.60738 56.65 0.996 34/30
N-BAK4HT 1.56883 55.98 0.993 36/32
F2HT 1.62004 36.37 0.996 35/32
N-LASF45HT 1.80107 34.97 0.886 43/35
SF6HT 1.80518 25.43 0.941 41/36
N-SF6HTultra 1.80518 25.36 0.887 43/37*
N-SF6HT 1.80518 25.36 0.877 44/37
SF57HTultra 1.84666 23.83 0.924 39/36*
N-SF57HTultra 1.84666 23.78 0.830 40/37*
N-SF57HT 1.84666 23.78 0.793 41/37*
N-LASF9HT 1.85025 32.17 0.843 40/36*
 additional variants
* wavelength for transmittance 0.7 and 0.05
** 10 mm thickness, 400 nm wavelength
*** Whereas the internal transmittance curves of standard optical glasses in the datasheet comprise median values for the glass types, "HT" and "HTultra" glass internal transmittance curves are guaranteed minimum values for internal transmittance in the visible spectrum. Shown graphics are valid for 25 mm sample thickness.
Advanced Optics

Hattenbergstrasse 10
55122 Mainz
E-Mail to SCHOTT+49 (0) 6131/661812
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