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I'm used to seeing webcam lenses that look a bit like this:

"Old-style" webcam

But recently, I noticed that there are several webcams (especially Microsoft ones) that have some sort of "concentric recesses" around the camera lens, like in these images:

Example recess 1 Example recess 2 Example recess 3

I don't know the technical name for this (if there is one), so I cannot find much information about it.

I believe it's related to lighting, but I wonder why I don't see this kind of "construction" in other kinds of cameras.

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    A recessed lens probably collects less dust, and is also then more shaded from light sources outside its direct view angle. – Olin Lathrop Jul 13 '13 at 11:14
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This "construction" is very similar to a lens hood and you see it very often.

In normal uses it serves two purposes:

  • Protection from glare. This happens when a light source just outside the visible image area, reaches the lens and is internally reflected. This causes a reduction in contrast and other sorts of visible artifacts.

  • Protection from scratches, bumps etc. Essentially the chance of hitting the front element of the lens to an object are reduced because the lens hood is in the way.

In this case the second purpose is not very relevant because people tend to keep their webcam firmly mounted to their screen. However, it does protect against dust as Olin Lanthrop noted.

It is not just Microsoft Cameras that have this. My Logitech C910 has also a recessed lens but there is also a level glass surface above the whole construction.

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  • Indeed it has some similarities with lens hoods, but what intrigues me is that lens hood are somewhat "continuous" curves, while these webcams are "discrete-like", with several steps. I wonder if there's some sort of Fresnel-like effect, and if so, why I don't see it on other kinds of cameras, like security cameras, which are also kind of stationary (or maybe they do, but I don't see it since they are hidden?). – anol Jul 13 '13 at 15:19
  • Maybe change your question to reflect the steps in the surface. – Unapiedra Jul 14 '13 at 6:45
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There are two advantages to having a recessed lens in a camera designed to be stationary for long periods of time:

  1. Less dust accumulation. By recessing the lens, less dust in the air will wind up on the surface of the lens. The "concentric rings" you note may assist with trapping air currents and the dust they carry.
  2. Less stray light interference. As conditions around a stationary camera change, the lens is protected from light sources outside the field of view causing reflections and flare.

Beyond that, the sellers may feel that creating products that cosmetically resemble much more expensive items such as high end video cameras use in commercial production makes their offerings more attractive to consumers.

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