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They seem to be essentially talking about Fresnel lenses or am I misunderstanding something? Why are they calling them diffractive lenses, I always thought that
by danbruc 3y ago
They seem to be essentially talking about Fresnel lenses or am I misunderstanding something? Why are they calling them diffractive lenses, I always thought that Fresnel lenses are also refractive with some unwanted diffraction at the edges of the ridges? Or do those proposed lenses work differently, does diffraction contribute intentionally and significantly because of the finer structure?
- ycui1986 3y agoI am confused at the beginning, but it seems to me the author did not know the difference between diffractive optics and Fresnel lens. That significant reduce the credibility of the author. It is embarrassing for someone in academia to confuse these two different things.
- zalo 3y agoPerhaps they should have started at the Wikipedia entry for “Zone Plate” instead
- nimish 3y ago>It is embarrassing for someone in academia to confuse these two different things. I've been digging through the academic publications for a completely different field and it appears that they have very little or outdated knowledge of parallel fields, almost siloed.
- time0ut 3y agoI believe the author showed up in the comments on the Ars version of the article [0] and touched on some of these ambiguities. [0] https://arstechnica.com/space/2023/07/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb/?comments=1&comments-page=1 https://arstechnica.com/space/2023/07/a-new-thin-lensed-tele...
- kristianp 3y agoOne of the comments (from user Wickwick) explains the difference concisely: > I was going to make a small adjustment to the post on this topic. The lenses Fresnel designed were refractive (and reflective) and not diffractive. In fact, it's the diffraction of the transitions that ruins the image quality of these sorts of lenses.
- venusenvy47 3y agoThis is what I understand is the drawback of a Fresnel lense. The article is written in first person, but I can't find the name of the author anywhere around the article.
- intrasight 3y agoI was expecting an article about negative index of refraction metamaterial lens and then read Fresnel and basically stopped reading.