Critical illumination

<h2 id="optical-principles">Optical principles</h2>

<p>Critical illumination acts to form an image of the light source on the specimen to illuminate it.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> This image is formed by the <a href="/facts/Condenser_(optics)/l4MRBDDK">condenser or collector lens</a>. This illumination is bright but not always even, as any structure in the light source (for example the filament of a <a href="/facts/Light_bulb/v3fb5WBp">light bulb</a>) will be visible in the resulting image. Homogeneous light sources such as a <a href="/facts/Flame/UMNDVEe8">flame</a> or <a href="/facts/Sunlight/WPkJRC7s">sunlight</a> give more even illumination. Alternatively, a <a href="/facts/Ground_glass/dbceXmJo">ground</a> or <a href="/facts/Milk_glass/ayGtH8p3">opal glass</a> diffuser can be used to homogenize the light source, but this will cause a significant amount of light to be scattered away from the sample.
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Optical_microscopy/5700vcna">Optical microscopy</a></li>
<li><a href="/facts/August_K%C3%B6hler/fz0TWs8X">August Köhler</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"The History of Microscope Illumination Methods" Nuhsbaum. Retrieved 2023-09-05. <a href="https://nuhsbaum.com/the-history-of-microscope-illumination-methods/" target="_blank">https://nuhsbaum.com/the-history-of-microscope-illumination-methods/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"Microscope Illumination" Molecular Expressions. Retrieved 2023-09-05. <a href="https://micro.magnet.fsu.edu/primer/anatomy/illumination.html" target="_blank">https://micro.magnet.fsu.edu/primer/anatomy/illumination.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
</ol>

Critical illumination open-in-new

Critical illumination