Optical Glass

The impressive range of technical qualities found in optical glass reflects the variety of different applications our extensive portfolio covers. In all cases, SCHOTT’s robust quality control and commitment to using the finest quality materials is assured.

Stringent quality control for consistently reliable performance

Homogenous refractive index

Carefully controlled manufacturing processes ensure glass blanks with highly homogeneous refractive index distribution. SCHOTT achieves refractive index variation below one part per million. Extremely accurate, highly advanced interferometers determine the homogeneity.

Industry-leading transmittance values

SCHOTT’S current portfolio includes 13 HT and HTultra glasses. Several exhibit the very best transmittance values currently available in the optical glass market, including N-BAK4HT, N-BK7HT, F2HT, N-SF57HTultra, and N-SF6HTultra.

Leading metrology

SCHOTT is continuously developing its metrology equipment to remain at the leading edge of measurement. This high sophisticated metrology equipment enables SCHOTT to offer the tightest tolerances on the market.

High quality standards

SCHOTT is both ISO 9001 and 14001 certified, with all optical glass products going through a stringent quality inspection before delivery. The production of optical glass is continuously monitored at all stages of production, in addition to an elaborate final inspection.

Properties of Optical Glass

Tolerances for refractive index and Abbe number (according to ISO 12123)

nd νd
Step 0.5* ± 0.0001 (NP010) ± 0.1% (AN1)
Step 1 ± 0.0002 (NP020) ± 0.2% (AN2)
Step 2 ± 0.0003 (NP030) ± 0.3% (AN3)
Step 3 ± 0.0005 (NP050) ± 0.5% (AN5)
* only for selected glass types


Forms of Supply

We master the entire value chain an offer various supply forms. For specifications and tolerances please view our ‘Optical Glass – Catalog’ in the download section. 

Raw Glass

  • Blocks: Blocks have up to five unworked, as-cast surfaces. Usually, at least one surface has been worked. The edges are rounded. Blocks are fine annealed and thus suitable for cold working.
  • Strips: Strips normally have unworked or ground surfaces and broken or cut ends. Strips are either coarse annealed or fine annealed. Coarse annealed strips are only suitable for reheat pressings
  • Rods: SCHOTT offers the widest range of rods with different geometries, formats and materials.

Cut Blanks

  • Plates: Plates are quadrilateral fabricated parts. All six sides are worked; the edges have protective bevels.
  • Round plates: Round plates are cylindrical parts for which the diameter is larger than the thickness. Round plates are machined on all surfaces.
  • Worked rods: Worked rods are cylindrical parts that are machined on all sides. The length of a rod is always greater than its diameter.
  • Cut prisms: Cut prisms are prisms produced by cutting and can be ground on all sides. Equilateral and non-equilateral prisms can be produced in various forms (ridge, penta, triple prisms …) using different fabrication technologies.


  • Pressed blanks: Pressed blanks are hot formed parts with mainly round cross sections, defined radii and bevels.
  • Pressed prisms: Pressed prisms are hot formed parts with angled, prismatic shapes. Other dimensions are possible upon request

We also offer high-precision optical components made of optical glass.

Optical Glass Specifications
SCHOTT optical glasses are specified according to their optical and internal properties.

Optical Properties:

  • Refractive index with tolerances
  • Abbe value with tolerances
  • Refractive index homogeneity
  • Internal transmission
  • Color code

Internal Properties:

  • Striae
  • Bubbles and inclusions
  • Stress birefringence

Unless specifically requested, SCHOTT optical glass will be delivered in refractive index/Abbe number step 3/3 with a standard test report. The refractive index of all parts of a lot will not deviate by more than ±1 x 10-4 (± 2 x 10-4 for pressing) from the test report.


Quality Assurance

SCHOTT is both ISO 9001 and 14001-certified and can be your trusted partner. Our optical glass goes through a stringent quality inspection before delivery. The production of optical glass is continuously monitored at all stages in addition to an elaborate final inspection.

Delivery lots are tested for refractive index scattering, stress birefringence, striae and bubbles according to DIN ISO 10110. A test certificate in accordance with DIN EN 10204 documents the standard supply quality. Upon request, we can also supply test certificates with increased accuracy. For high homogeneous cut blanks, we confirm homogeneity through interferometry.


Abbe Diagram - nd-vd Picture for OnEx - EN 2020


Properties of High Homogeneity Glass


SCHOTT offers glasses in five levels of homogeneity. Thanks to a carefully controlled manufacturing process, glass pieces in H4 quality have a maximum peak to valley refractive index variation of 2 x10-6, while the quality level H5 achieves a value of 1 x10-6. The maximum variation of refractive index is expressed in peak to valley values in accordance with ISO 12123.


Homogeneity of optical glass

Increased requirements for refractive index homogeneity comprise five classes in accordance with the standard ISO 10110 and ISO 12123.

Homogeneity classes and their maximum variation of refractive index as well as applicability can be found in the ‘Optical Glass Catalog’, available in the download section. (1.4. Refractive Index Homogeneity)

SCHOTT offers a selection of optical glasses as fine annealed cut blanks in high homogeneities from stock. An overview of available glass types, dimensions, and homogeneity levels can be found in our ‘Optical Glass Catalog’, available in the download section. (1.4.1 High Homogeneity Glass available from stock)

Properties of i-Line Glass

Forms of Supply

We offer i-Line glasses up to 300 mm in diameter and thicknesses up to 100 mm. Customized dimensions are possible upon request. 

Customized shapes include:

  • CNC machined
  • Coated
  • Polished
  • Sub-assembled

Refractive Index Homogeneity

The maximum variation of refractive index depends on the glass dimension.

  • Ø 150 mm  with a maximum variation of 0.5 · 10–6
  • Ø 200 mm  with a maximum variation of 1.0 · 10–6 (H5)
  • Ø 250 mm  with a maximum variation of 2.0 · 10–6 (H4)

We also offer high-precision optical components made of i-Line glasses.



Homogeneity, bubbles/inclusions, and dispersion values can be found in the ‘Optical Glass – Catalogue', available in the download section.


Quality Assurance

  • i-Line glass is subject to a 100% control of homogeneity, stress birefringence, striae, bubbles, and inclusions.
  • Refractive index and transmittance are statistically controlled.


Properties of HT and HTultra Glass

HT and HTultra Glass

* Wavelength for transmittance 0.7 and 0.05
** 10 mm thickness, 400 nm wavelength


Overview of High Transmittance***

N-BAK4HT, nd = 1.5883, vd = 55.98

Overview of High Transmittance 


N-BK7HT, nd = 1.51680, vd = 64.17

Overview of High Transmittance 


N-KZFS4HT, nd = 1.61336, vd = 44.49

Overview of High Transmittance 


N-LASF9HT, nd = 1.85025, vd = 32.17

Overview of High Transmittance 


N-LASF45HT, nd = 1.80107, vd = 34.97

Overview of High Transmittance 


N-SF6HTultra, nd = 1.80518, vd = 32.36

Overview of High Transmittance 


N-SF57HTultra, nd = 1.84666, vd = 23.78

Overview of High Transmittance 

***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. Graphics are valid for 25 mm sample thickness.


Forms of Supply

HT and HTultra glasses are available in various supply forms:


  • Polished prisms with dimensions from 10 mm - 200 mm
  • Lenses with dimensions from 3 mm - 200 mm


  • From 5 mm - 320 mm in diameter and center thickness from 2 mm - 100 mm  

Raw Glass

  • Strips with dimensions ≤ 50 mm
  • Blocks with dimensions 190 mm x 180 mm x 140 mm 

Other supply forms and dimensions are possible upon request (depending on glass type). 

We also offer high-precision optical components made of optical glass.


Properties of Low Tg Glass for Precision Molding


Low Tg glasses have a glass transformation temperature suitable for precision molding and a special glass composition to decrease the tendency for devitrification and to reduce the reaction with mold materials within the molding temperature range.


During precision glass molding, a polished or fire-polished preform is shaped into a final geometry, while conserving its surface quality. The typical temperature range for the molding process is between 500-700°C, enabling the extension of the operating lifetime of the mold material and a significant time reduction of the press process.



Abbe Diagram - Low Tg Picture for OnEx - EN 2018




For specifications and tolerances please view our ‘Optical Materials for Precision Molding Datasheet’ in the download section.

Forms of Supply

Low Tg glass for precision molding is available in various supply forms:

Optical glass rods

  • Various shapes with < 1 mm – 7.5 mm in diameter and length up to 1,000 mm
  • Various surface qualities with > 7.5 mm – 12.5 mm in diameter and length up to 140 mm

Ball lenses

  • Different formats with 0.8 mm - 320 mm in diameter

Other supply forms and dimensions are possible upon request. 


Properties of Radiation Resistant Glasses

For use in surroundings with high ionizing radiation

SCHOTT Advanced Optics offers a variety of radiation resistant glass types with different dispersion properties:

  • BK7G18
  • LF5G19
  • LF5G15
  • K5G20
  • LAK9G15
  • F2G12
  • SF6G05

These glass-types are suitable for use in surroundings with high radioactivity. The radiation resistance differs with each glass type, whereas it can be extremely high for some types such as the BK7G18 and LF5G19.

Please note that all radiation resistant glasses except LAK9G15 are usually available in standard bubble quality according to the optical glass catalog. The total allowable cross section of bubbles in LAK9G15 is 0.1 mm2 per 100 ccm for bubbles larger than 0.03 mm in diameter. A large amount of inclusions < 0.03 mm diameter is typical for this type of glass and cannot be avoided by production means.


Forms of Supply

Radiation resistant glasses are available in various supply forms:

  • Cut blanks
  • Pressings
  • Rods 

Customized dimensions are possible upon request. 

We also offer high-precision optical components made of radiation resistant glasses


Quality Assurance

  • Test certificates for refractive index and dispersion and detailed transmittance data upon request.
  • Accurate measurement microscopes and stress measurement setups according to the 'de Senarmont' method for the examination of internal quality and stress birefringence.
  • Interferometer with aperture up to 24 inches in diameter for optical homogeneity inspection.

No. Year Title Authors Published in                 
[48]  2021 From history to future market requirements of optical glass at SCHOTT  R. Jedamzik, U. Petzold, F. Rupp  Proc. SPIE. 11889
[47] 2021 Review of Optical Manufacturing 2000 to 2020 A. Zhang, R. N. Youngworth
Proc. SPIE. Press Book
2021 Optical materials for blue-laser processing
R. Jedamzik, A. Carre, V. Hagemann, L. Bartelmess, S. Leukel, U. Petzold
Proc. SPIE. 11818
Optical glass: Challenges from optical design
U. Fotheringham, M. Letz, U. Petzold, S. Ritter, Y. Menke-Berg
Encyclopedia of materials
[44] 2020 Optical materials for digital projection
R. Jedamzik, V. Hagemann, V. Dietrich, U. Petzold
Proc. SPIE 11262
2020 Optical material for space applications R. Jedamzik, G. Weber, U. Petzold Proc. SPIE 11451
[42] 2019 Optical glass: refractive index homogeneity from small to large parts - an overview R. Jedamzik, U. Petzold Proc. SPIE 10914
[41] 2018 Effects of the EU's Reach and RoHS regulations on optical and filter glass P. Hartmann SPIE Newsroom
[40] 2018 Mechanical strength of optical glasses P. Hartmann Proc. SPIE 10692
[39] 2018 Effects of striae inside optical glasses on optical systems S. Reichel, P. Hartmann, U. Petzold, S. Gärtner, H. Gross Proc. SPIE 10690
[38] 2018 Investigation of striae tolerance in optical system Y. Zhang, Y-N. Chen. H. Gross, P. Hartmann, St. Reichel Proc. SPIE 10690
[37] 2018 From VIS to SWIR: a challenge for optical glass and IR materials R. Jedamzik, U. Petzold, G. Weber Proc. SPIE 10528
[36] 2017 SCHOTT optical glass in space R. Jedamzik, U. Petzold Proc. SPIE 10401
[35] 2017 Introducing the quantum efficiency of fluorescense of SCHOTT optical glass R. Jedamzik, F. Elsmann, A. Engel, U. Petzold, J. Pleitz Proc. SPIE 10375
[34] 2017 Optical Glass: A High-Tech Base Material as Key Enabler for Photonics U. Petzold IntechOpen
[33] 2017 Preliminary results of a new proposal for objective human independent striae maesurement S. Reichel, U. Petzold, C. Lempa Proc. SPIE 10329
[32] 2017 Latest results solarization of optical glasses with pulsed laser radiation R. Jedamzik, U. Petzold Proc. SPIE 10097
[31] 2016 Large optical glass blanks for the ELT generation R. Jedamzik, U. Petzold, V.Dietrich, V.Wittmer, and O. Rexius Proc. SPIE 9912
[30] 2015 Instantaneous Dispersion: A Window into Property Relationships for Optical Glass N. A. Carlie Int. Appl. Glass Sci., Vol. 6, No. 4
[29] 2015 Optical glass: standards – present state and outlook P. Hartmann Adv. Opt. Techn., Vol. 4, No. 5-6
[28] 2015 Optical glass: deviation of relative partial dispersion from the normal line—need for a common definition P. Hartmann Opt. Eng., Vol. 54, No. 10
[27] 2015 The ESA radglass activity: A radiation study of non rad-hard glasses I. Manolis, J.L. Bezy, A. Costantino, R. Vink, A. Deep, M. Ahmad, E. Amorim, M. D. Miranda, and R. Meynart Proc. SPIE 9639
[26] 2015 V-Block refractometer for monitoring the production of optical glasses U. Petzold, R. Jedamzik, P. Hartmann, and S. Reichel Proc. SPIE 9628
[25] 2015 Results of a polishing study for SCHOTT XLD glasses Jedamzik, H. Yadwad, and V. Dietrich Proc. SPIE 9628
[24] 2015 Efficient simulation of autofluorescence effects in microscopic lenses H. Gross, O. Rodenko, M. Esslinger, and A. Tünnermann Proc. SPIE 9626
[23] 2015 Optical lead flint glasses – key material in optics since centuries and in future P. Hartmann Proc. SPIE 9626
[22] 2014 Optical Glass P. Hartmann SPIE Press (Book)
[21] 2014 EU regulations threaten availability of raw materials for optics P. Hartmann SPIE Professional
[20] 2014 Optical glass - refractive index change with wavelength and temperature M. Englert, P. Hartmann and S. Reichel Proc. SPIE 9131
[19] 2014 Optical Glass with tightest refractive index and dispersion tolerances for high-end optical designs R. Jedamzik, S. Reichel and P. Hartmann Proc. SPIE 8982
[18] 2013 Recent Results on Bulk Laser Damage Threshold of Optical Glasses R. Jedamzik and F. Elsmann Proc. SPIE 8603
[17] 2013 Cladding YAG crystal fibers with high-index glasses for reducing the number of guided modes K.-Y. Hsu, M.-H. Yang, D.-Y. Jheng, C.-C. Lai, S.-L. Huang, K. Mennemann, and V. Dietrich Opt. Mat. Express, Vol. 3, No. 6
[16] 2012 110 years BK7 – Optical glass type with long tradition and ongoing progress P. Hartmann Proc. SPIE 8550
[15] 2012 Optical glass: past and future of a key enabling material P. Hartmann Adv. Opt. Techn. 1
[14] 2011 Optical glass and the EU directive RoHS P. Hartmann and U. Hamm Proc. SPIE 8065
[13] 2011 Optical Glass – Dispersion in the Near Infrared P. Hartmann Proc. SPIE 8167
[12] 2011 LED collimation using high index glass R. Biertümpfel and S. Reichel Proc. SPIE 8170
[11] 2010 Optical glass and glass ceramic historical aspects and recent developments: a Schott view P. Hartmann, R. Jedamzik, S. Reichel and B. Schreder Appl. Opt., Vol. 49, No. 16
[10] 2009  Measurement and simulation of striae in optical glass H. Gross, M. Hofmann, R. Jedamzik, P. Hartmann, and S. Sinzinger Proc. SPIE 7389
[9] 2008 Optical glasses and optical elements: comparison of specification standards ISO DIS 12123 and ISO 10110 P. Hartmann, R. Jedamzik Proc. SPIE 7102
[8]  2008 Optical materials for astronomy from SCHOTT: the quality of large components R. Jedamzik, J. Hengst, F. Elsmann, C. Lemke, T. Döhring, and P. Hartmann Proc. SPIE 7018
[7] 2008 Refractive Index Drop Observed After Precision Molding of Optical Elements: A Quantitative Understanding Based on the Tool– Narayanaswamy–Moynihan Model U. Fotheringham, A. Baltes, P. Fischer, P. Hoehn, R. Jedamzik, C. Schenk, C. Stolz, and G. Westenberger J. Am. Ceram. Soc., Vol. 91, No. 3
[6] 2006 Challenges in optics for Extremely Large Telescope Instrumentation P. Spano, F.M. Zerbi, C.J. Norrie, C.R. Cunningham, K.G. Strassmeier, A. Bianco, P.A. Blanche, M. Bougoin, M. Ghigo, P. Hartmann, L. Zago, E. Atad-Ettedgui, B. Delabre, H. Dekker, M. Melozzi, B. Snyders, R. Takke, and D.D. Walker Astron. Nachr. / AN 999, No 88
[5] 2006 Large optical glass lenses for ELTs P. Hartmann and R. Jedamzik Proc. SPIE 6273
[4] 2005 Tailored properties of optical glasses R. Jedamzik, B. Hladik, and P. Hartmann Proc. SPIE 5965
[3] 2004 Removing the mystique of glass selection R. E. Fischer, A. J. Grant, U. Fotheringham, P. Hartmann, and S. Reichel  Proc. SPIE 5524
[2] 2004 Large optical glass blanks for astronomy R. Jedamzik and P. Hartmann Proc. SPIE 5494
[1] 2003 Optical glasses and glass ceramics for large optical systems T. Doehring, P. Hartmann, H. F. Morian, and R. Jedamzik Proc. SPIE 4842

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