The SLAC National Accelerator Laboratory video Vera C. Rubin Observatory LSST Camera (caution! annoyingly loud music, lower volume before playing) shows a Romanesco broccoli (which I'd assumed was a 3D printed mathematical surface of that name until I checked and found out that this is the name of an actual vegetable i.e. Brassica oleracea) as the object of a pinhole camera projecting its image on to the astoundingly large CCD array.

There are likely several advantages to using the pinhole rather than a well-corrected projection lens, is it possible to say what they are?

Is it also possible to elaborate on the choice of object for the camera?

See also:

Caution! annoyingly loud music, lower volume before playing:


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    $\begingroup$ Broccoli is fractal. No, really, it's a decent physical object with repetitive, high-detail structures. Lots of stuff to try to resolve in the image. $\endgroup$ – Carl Witthoft Sep 9 '20 at 15:38

From the first article you linked:

Taking the first 3,200-megapixel images of a variety of objects, including a head of Romanesco – a type of broccoli – that was chosen for its very detailed surface structure, was one of these tests. To do so without a fully assembled camera, the SLAC team used a 150-micron pinhole to project images onto the focal plane.

Which implies:

  • the advantage of using a pinhole is that it allows the sensors to be tested without requiring the full camera to be assembled yet.
  • the Romanesco was chosen to test the sensors' ability to image an object with detailed structure.
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    $\begingroup$ I think that the circa 200 wavelength wide pinhole also offers the advantages over a projection lens of being very easy to model unambiguously with basic optics (MTF, scattered light, etc) not require any focus or introduce any errors if focus isn't correct, and automatically produces a fairly low light flux which might be suitable for the array, but those aren't mentioned in the linked articles. $\endgroup$ – uhoh Sep 9 '20 at 7:11
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    $\begingroup$ @uhoh - you can speculate all you want but I'm going with the reason the people involved actually stated for why they used a pinhole. $\endgroup$ – user24157 Sep 9 '20 at 7:13
  • $\begingroup$ Ya I know. There may be additional sources about this test beyond those I'd included in the original post, and maybe this is a technique tried before on other cameras, or maybe it's totally unique. I suppose the "broccoli" will turn out to be unique for sure. Let's see what else turns up $\endgroup$ – uhoh Sep 9 '20 at 9:38

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