Optical Glass Catalogue 2010
90Pages

Description of Properties 2009 Optical Glass

4 Table of Contents Foreword 5 1 Optical Properties . 7 1.1 Refractive index, Abbe number, dispersions, glass designations 7 1.2 Tolerances for refractive index and Abbe number . 8 1.3 Test reports for refractive indices and dispersions . 10 1.4 Refractive index homogeneity 11 1.5 Internal transmittance, color code 13 2 Internal Properties 15 2.1 Striae 15 2.2 Bubbles and inclusions . 16 2.3 Stress birefringence 18 3 Chemical Properties 20 3.1 Climatic resistance 20 3.2 Stain resistance . 21 3.3 Acid resistance 22 3.4 Alkali resistance and phosphate resistance 24 3.5 Identification of...

5 Foreword For more than 125 years SCHOTT offers a large variety of high quality optical glasses. They cover the needs of the broad range of optical applications from consumer products to optical systems at the leading edge of research. With this catalog we present our lead and arsenic free N-glasses and other optical materials addressing special requirements, such as: – Low Tg glass types suited for the precision molding process – Classical glass types with lead oxide as an essential component for outstanding optical properties – Fused silica for optical lithographic applications with...

6 The optical data of the UV-materials fused silica listed in this pocket catalog are meant for the use in optical applications and therefore referenced to air, like all the other optical materials in this catalog. For the use of those materials in lithography for which transmittance data below 250 nm are required we kindly request you to contact us directly in order to discuss technical aspects more in detail. That applies also for i-line glasses, which are used for lithography due to their superb transmittance in the near UV-range and in optical homogeneity. We would be pleased to offer...

7 1.1 Refractive index, Abbe number, dispersions, glass designations The most common identifying features for characterizing an optical glass are the refractive index nd in the middle range of the visible spectrum and the Abbe number nd = (nd – 1)/(nF – nC) as a measure for dispersion. The difference nF – nC is called the principal dispersion. Optical glass can also be designated by a numerical code, often called glass code. SCHOTT uses a ninedigit code. The first six places correspond to the common international glass code. They indicate the optical position of the individual glass. The...

8 1.2 Tolerances for refractive index and Abbe number The tolerances for the refractive index and Abbe number are listed in table 1.2. The standard delivery quality for fine annealed glass is step 3 for nd and step 4 for nd. We will supply material in tighter steps upon demand. All deliveries of fine annealed optical glass and cut blanks are made in lots of single batches. The batch may be a single block or several strips. The delivery lots are identified by a delivery lot number. The delivery lots are formed based on the specified maximum allowed refractive index and Abbe number deviation...

9 All parts of a delivery lot of fine annealed optical glass, cut blanks or pressings meet the normal quality of refractive index variation as given in the following table 1.3. If requested, parts can also be supplied in lots with tighter refractive index variation as indicated in table 1.3. Fine annealed glass, cut blanks Pressings Designation Refractive index variation Designation1) Refractive index variation SN ± 1 x 10 –4 LN ± 2 x 10 –4 S0 ± 5 x 10 –5 LH1 ± 1 x 10 –4 S1 ± 2 x 10–5 LH2 ± 5 x 10 –5 Table 1.3: Tolerance of refractive index variation within a lot of fine annealed glass and...

10 1.3 Test reports for refractive indices and dispersions 1.3.1 Standard test reports We provide standard test reports according to ISO 10474 for all deliveries of fine annealed optical glass. The information they contain based on sampling tests refers to the median position of the optical values of a delivery lot. The value of the individual part may deviate from the reported median value by the tolerance of refractive index variation. The measurements are performed with an accuracy of ± 3 x 10 –5 for refractive index and ± 2 x 10 –5 for dispersion. The numerical data are listed to 5...

11 Upon request, refractive index data can be provided for an expanded spectral range of 185 nm to 2325 nm and the constants of the Sellmeier dispersion formula can be listed for the applicable spectral range. The measurement is done with a prism goniometer. The accuracy is ± 1 x 10–5 for refractive index and ± 3 x 10–6 for dispersion. An accuracy of up to ± 4 x 10–6 for the refractive index and ± 2 x 10–6 for the dispersion measurement, independent of the glass type and measurement wavelength, can be provided on request. The standard measurement temperature is 22 °C. The measurement...

12 measured wave front deviations containing all aberrations. In many cases it is acceptable to subtract certain aberration terms of negligible impact on the application. For example focal aberrations (expressed by the focal term) can often be corrected by adapting the geometry of the final part. This should be specified in advance. Increased requirements for refractive index homogeneity comprises 5 classes in accordance with the standard ISO 10110 Part 4 (see table 1.5). For class 0 of the standard, please refer to the tolerances of refractive index variation in section 1.2. Maximum...

13 1.5 Internal transmittance, color code The internal transmittance, i. e. the light transmittance excluding reflection losses, is closely related to the optical position of the glass type according to general dispersion theory. Using the purest raw materials and sophisticated melting technology it is possible to approach the dispersion limits for internal transmittance in the short wave spectral range. SCHOTT seeks to achieve the best possible internal transmittance within economical reasonable limits. The internal transmittance and the color code given in the data section comprises...