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What are periscope lenses on a smartphone?

You might have recently noticed the Samsung S20 adverts that talked about 100X “Space Zoom”. While this sounds impressive you need to look further to understand exactly what this means.

In camera technology there are two types of Zoom available – optical and digital. Optical requires multiple lenses that can be moved to adjust the focal length of the configuration to zoom in and out, whilst digital zooming is carried out by the software, usually cropping and magnifying part of a very detailed image to produce the effect of zoom.

In the Samsung Galaxy S20 Ultra, this has in fact a 4X optical zoom and the rest is achieved digitally. It is the 4X optical zoom that is the thing to get excited about, as 2X has been pretty much the limit up to recently.

Can’t attach a zoom lens to a smartphone

Optical zooming has been limited by the thinness of smartphones. If you think of a zoom lens on a camera, say the ones the paparazzi use to get long range shots of their unsuspecting victims, they are very long and, there is no way they can be utilised in a smartphone. So, if you want to get increased optical zoom in a smartphone you need to look at doing it differently.

This is where a periscope lens comes in. First introduced by Huawei in its 2019 P30 Pro, they are now starting to appear in more flagship models and over time, like all technology, will filter its way down to cheaper handsets.

Periscope lenses an old idea reused

So, how does it work. Well, the clue is in the name – like a periscope! A periscope is effectively a bent tube with mirrors, lenses and prisms that allows you to see round corners by reflecting the light. If this setup is used in a smartphone it means you can get bigger zoom lenses that do not stick out of the back of the phone, but lie flat in the body, only the lens receiving the light is visible on the surface.

Once the light hits this surface lens, rather than being immediately absorbed by the sensor behind (as in a normal lens), it is reflected with a mirror from the vertical to being horizontal to the frame. It can then be passed through another lens (or series of movable lenses) to adjust the zoom setting, before it eventually hits the sensor.

That’s it, like with most great ideas pretty simple.

Will smartphones become bigger?

There is one problem with this approach though, and that is the physical amount of space in the phone’s frame that the periscope assembly takes up. With the battery (getting larger each iteration) and all the other technology already crammed inside, there is very little space. So, something has got to give, either smartphones will become bigger (on the plus side you will get a bigger screen) or something will have to be left out, to accommodate the periscope lens.

It will be interesting to see which way things go. Either way, the increasing ubiquitous nature of the periscope lens is good news for anyone who wants to take some serious pictures with their smartphone.



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