Quetelet rings on LCD displays?

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    Lcd Rings
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Discussion Overview

The discussion revolves around the appearance of interference patterns on LCD displays, specifically resembling Quetelet rings, and the underlying mechanisms that may cause these patterns. Participants explore the nature of the particles or structures responsible for the observed effects, considering both theoretical and practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the appearance of interference patterns on LCD displays when illuminated by a flashlight, questioning whether these patterns can be accurately termed Quetelet rings.
  • Another participant suggests that the interference pattern may be due to a transflector, a component used in certain displays that scatters light.
  • A different viewpoint proposes that the equivalent 'particles' causing the interference might be micro pits etched into the glass surface for a matte finish, rather than dust particles.
  • A participant provides a link to scholarly resources for further exploration of Quetelet rings.

Areas of Agreement / Disagreement

Participants express differing opinions on the nature of the particles responsible for the interference patterns, with no consensus reached on whether they can be classified as Quetelet rings or what specific structures are involved.

Contextual Notes

There is uncertainty regarding the exact mechanisms behind the interference patterns, including the role of the transflector and the nature of the surface features on the LCD displays. The discussion also highlights the challenges in photographing these effects due to the limitations of smartphone cameras.

Who May Find This Useful

This discussion may be of interest to individuals exploring optical phenomena, display technology, or those curious about the interaction of light with surfaces in various contexts.

Orthoceras
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When shining a flashlight at particular LCD displays, an interesting interference pattern appears, consisting of parallel or concentric lines. It closely resembles Quetelet rings seen on dusty mirrors and glass panes. Quetelet rings are formed when light from a dust particle interferes with the light from its mirror image.

For example, when shining a flashlight at a digital whiteboard (brand Prowise), such a pattern appears. When moving the flashlight in circles around your eye or the camera lens, the pattern will rotate, without any preferred direction. If you move the flashlight laterally towards your eye or the camera lens, the distance between the interference maxima increases, as illustrated in this video (link). The digital whiteboard was clean, no dust on the glass, so the necessary condition for Quetelet rings seems to be missing.
Quetelet combi.png

C is the position of the mirror image of the camera lens, Ln is the position of the mirror image of the flashlight. Top - camera and lamp equally remote from the screen: interference pattern consists of straight lines. Bottom - camera closer to monitor than lamp: interference pattern consists of concentric circles.I saw the same interference pattern on two laptops, Asus Vivobook Flip 14 and Lenovo Chromebook Ideapad Flex 5. Here too, any dust had been wiped off the screen, so that Quetelet rings were not to be expected.

In summary, two questions are:
1) is it right to call the interference pattern that appears on these LCD displays Quetelet rings?
2) how does this pattern arise at these screens? Which 'particles' have replaced the conventional dust particles? Google wasn't very helpful.
 
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Science news on Phys.org
Orthoceras said:
Which 'particles' have replaced the conventional dust particles?
You may be seeing the random dust effect from a transflector, used in low-power all-light-readable displays.

The transflector is a part-silvered scatterer, formed by random deposition on a layer of polymer. It is placed in front of the backlighting, at the back of the LCD sandwich.
https://en.wikipedia.org/wiki/Transflective_liquid-crystal_display
 
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You may be right, but I am not sure what the equivalent particles are, and how they could be photographed. For the time being I prefer thinking the equivalent particles are actually etched micro pits into the smooth glass surface, created for a matte appearance. I took the picture below with my smartphone and a tiny macro lens, accidentally at the right focal distance. Recording it was difficult because my smartphone has an autofocus that seems to avoid focussing at this very narrow surface layer depth.

Prowise2.jpg
 
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