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<title>Glass code</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Glass code</span></span>

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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p>A <b>glass code</b> is a method of classifying <a href="Glass" title="Glass">glasses</a> for <a href="Optics" title="Optics">optical</a> use, such as the manufacture of <a href="Lens_(optics)" class="mw-redirect" title="Lens (optics)">lenses</a> and <a href="Prism_(optics)" title="Prism (optics)">prisms</a>. There are many different types of glass with different compositions and optical properties, and a glass code is used to distinguish between them.

</p><p>There are several different glass classification schemes in use, most based on the catalogue systems used by glass manufacturers such as <a href="Pilkington" title="Pilkington">Pilkington</a> and <a href="Schott_Glass" class="mw-redirect" title="Schott Glass">Schott Glass</a>. These tend to be based on the material composition, for example <i>BK7</i> is the Schott Glass classification of a common <a href="Borosilicate_glass" title="Borosilicate glass">borosilicate</a> <a href="Crown_glass_(optics)" title="Crown glass (optics)">crown glass</a>.

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<div class="mw-heading mw-heading2"><h2 id="Technical_definition">Technical definition</h2></div>

<p>The <b>international glass code</b> is based on <a href="U.S._military_standard" class="mw-redirect" title="U.S. military standard">U.S. military standard</a> MIL-G-174, and is a six-digit number specifying the glass according to its <a href="Refractive_index" title="Refractive index">refractive index</a> <span class="texhtml mvar" style="font-style:italic;">n</span><sub>d</sub> at the <a href="Fraunhofer_line" class="mw-redirect" title="Fraunhofer line">Fraunhofer</a> d- (or D<sub>3</sub>-) line, 587.5618 nm, and its <a href="Abbe_number" title="Abbe number">Abbe number</a> <span class="texhtml mvar" style="font-style:italic;">V</span><sub>d</sub> also taken at that line. The resulting glass code is the value of <span class="nowrap"> <span class="texhtml mvar" style="font-style:italic;">n</span><sub>d</sub> − 1 </span> rounded to three digits, followed by <span class="texhtml mvar" style="font-style:italic;">V</span><sub>d</sub> rounded to three digits, with all decimal points ignored. For example, BK7 has <span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">n</span><sub>d</sub> = 1.5168</span> and <span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">V</span><sub>d</sub> = 64.17,</span> giving a six-digit glass code of 517642.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>Consequently, a linear approximation for the refractive index dispersion close that wavelength is given by:

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<annotation encoding="application/x-tex">{\displaystyle n(\lambda )={\frac {1-n_{\mathsf {d}}}{170.2V_{\mathsf {d}}}}(\lambda -589.3)+n_{\mathsf {d}}\ ,}</annotation>

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</math></span><img src="./d0485bfa8ee7e9ed6ab5fb94dc4e669e71c4b0fb.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:34.074ex; height:5.676ex;" alt="{\displaystyle n(\lambda )={\frac {1-n_{\mathsf {d}}}{170.2V_{\mathsf {d}}}}(\lambda -589.3)+n_{\mathsf {d}}\ ,}" loading="lazy"></span></dd></dl></dd></dl>

<p>where <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \lambda }">

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<annotation encoding="application/x-tex">{\displaystyle \lambda }</annotation>

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</math></span><img src="./b43d0ea3c9c025af1be9128e62a18fa74bedda2a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.355ex; height:2.176ex;" alt="{\displaystyle \lambda }" loading="lazy"></span> is the wavelength in nanometers.

</p><p>The following table shows some example glasses and their glass code. Note that the glass properties can vary slightly between different manufacturer types.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

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<th rowspan="2">Glass

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<th rowspan="2">Glass<br>code

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<th colspan="4">Manufacturer name

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<th>Schott</th>

<th>Pilkington</th>

<th>Ohara

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<td><a href="Borosilicate_glass" title="Borosilicate glass">Borosilicate crown</a></td>

<td>64.17

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<td>S-BSL7

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<td><a href="Barium_oxide" title="Barium oxide">Barium crown</a></td>

<td>56.05

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<td>S-BAL14

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<td><a href="Crown_glass_(optics)" title="Crown glass (optics)">Dense crown</a></td>

<td>60.32

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<td>S-BSM16

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<td><a href="Lanthanum_oxide" title="Lanthanum oxide">Lanthanum flint</a></td>

<td>44.85

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<td>S-LAM2

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<td><a href="Flint_glass" title="Flint glass">Dense flint</a></td>

<td>25.76

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<td>S-TIH11

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<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.newportglass.com/GeneCd.htm">"How the generic optical glass code works"</a>. <i>newportglass.com</i>.</cite></span>

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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite class="citation report cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20111008041651/http://www.oharacorp.com/pdf/cross-ref-2010.pdf">Cross reference</a> <span class="cs1-format">(PDF)</span>. <i>OharaCorp.com</i> (Report). 2010. Archived from <a rel="nofollow" class="external text" href="http://www.oharacorp.com/pdf/cross-ref-2010.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2011-10-08<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-11-30</span></span>.</cite></span>

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This article is issued from <a class="external text" title="Last edited on 2025-08-02" href="https://en.wikipedia.org/wiki/?title=Glass_code&oldid=1303906406">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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