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Here's an image of a flashlight that produces light in a "square" shape:

enter image description here

What is the purpose of this square light pattern, and why was it designed as a square as opposed to the traditional circular light beam typically emitted by flashlights? You'd normally expect a flashlight to emit light in a circle shape, not a square one as shown in the image below:

enter image description here

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    \$\begingroup\$ A square LED is going to make a square beam when focussed by the lens. \$\endgroup\$
    – Finbarr
    Commented Jan 26, 2023 at 16:34
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    \$\begingroup\$ If LEDs are made on a wafer, they are singulated by sawing them into dice, so the square shape is a natural consequence of that. Sawing them into rounds could maybe be done with a laser saw but it would be expensive and wasteful. \$\endgroup\$
    – John D
    Commented Jan 26, 2023 at 16:37
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    \$\begingroup\$ This is an optics question, not an electricity question \$\endgroup\$ Commented Jan 26, 2023 at 17:12
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    \$\begingroup\$ No special purpose, just an optical effect. At some lens position, then the LED at lens focus, you get image of LED \$\endgroup\$
    – user263983
    Commented Jan 26, 2023 at 17:45
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    \$\begingroup\$ The traditional circular light beam was from filament bulbs but not from a LED. \$\endgroup\$
    – Uwe
    Commented Jan 26, 2023 at 17:45

2 Answers 2

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The light source in this flashlight (an LED) is square, so the lens projects a square beam. Depending on the lens's focus and quality, a more-or-less sharp image of the LED chip is projected.

This is not "by design" in the sense that somebody thought it would be a great idea to have a square light beam; it is because making round LED chips is much more expensive (not impossible, though). Compensating for the square light source would also add extra costs.

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    \$\begingroup\$ One could also make an adapted lens, but that is expensive as well. Basically this is just a cheap flashlight with low-end functional design. \$\endgroup\$
    – datenheim
    Commented Jan 26, 2023 at 17:53
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    \$\begingroup\$ yes, this is definitely a cheap flashlight, I bought it for $2 just wondered how would it emit light, lol \$\endgroup\$
    – grandsirr
    Commented Jan 27, 2023 at 0:57
  • \$\begingroup\$ This effect is much less pronounced (and sometimes unnoticeable) in flashlights that use multiple smaller LEDs. The individual squares overlap, blur together, and approximate the round pattern we expect. \$\endgroup\$
    – bta
    Commented Jan 27, 2023 at 1:46
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I have a LED flash light which can change the focus of the lens so it can light a small spot or a wide area.

When changing to the smaller spot the lighted area gets more and more square. I can't change it to a sharp edged spot, but I suspect your flashlight has the LED in the focus of the lens and so emits a clear image of the LED area. Normally an unwanted effect.

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