Touch screens have become so commonplace, we barely notice them anymore yet pretty much every single mobile phone in the pocket of every single person around you has one and it's worth remembering that not so long ago touch screen technology was beyond even the wildest dreams of science fiction. You only have to watch the original series of Star Trek to see what's quite humdrum for us today wasn't even imaginable, hardly a generation ago and as if touch screens weren't incredible enough, the resolution and vibrancy of colors that modern screens are able to reproduce is genuine scientific marvel.
So today we're going to examine what actually makes both these incredible technical feats possible and ask the question, How do phone screens work?
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The job of a modern touch screen is to enable delicate precise manipulation of objects represented on a visual interface. In the past for example on your Dad's PC that job was done using a mouse pointer that you drag around and click but when personal computing migrated from dad's hulking home office beast to your much smaller cell phone screen that sort of interface quickly became clunky and awkward to work and be useful.
The modern phone touch screen has to be able to pinpoint with some accuracy where exactly on the display your finger is touching, how does it do this part of the answer lies in the curious electrical properties that lie within each and every one of us.
How Does the LCD Touchscreen work?
Human bodies have what physicists like to call capacitance, that means our bodies are able to conduct electrical current and even store electrical charge. You can see this for yourself whenever you touch one of those plasma ball ornaments in the gadget shop at the mall, all those strange little bolts of lightning are leaping out to zap your fingertips because your body is a conductor.
Now underneath the toughened glass of your phone screen is a tight grid of essentially tiny wires, each thinner than a human hair.
These hairs are made from conductive metal usually Indium Tin Oxide which usefully is also transparent. Some of these tiny wires go horizontally from side to side while others run up and down your screen vertically from top to bottom.
Each wire is shot through with electrical charge and when your finger touches or in fact goes anywhere near this grid its charge is disturbed just like on the plasma ball. This is where the really clever stuff happens deep inside the brain of your phone.
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The disturbance and current created by your finger is identified and tracked down to the precise location you touched. How? because your phone knows precisely which horizontal and vertical wires were disturbed and by how much it's a bit like using a map reading the x and y axes to find a particular city or country but in reverse.
So how about the picture itself until a couple of years ago the industry standard for phone displays was LCD or liquid crystal display.
This clever technology uses a backlight the size of the whole screen.
The light from this is filtered through twin polarizing layers which filter out some or all of the light waves as they pass through between these polarizing layers is a thin layer of liquid crystal organized into tiny cells commonly known as pixels.
Each pixel is assigned one of three colors, Red, Green or Blue by the manufacturer.
An electric signal tells each LCD pixel on an individual basis whether or not it should permit the glow of the backlight to pass through it.
The combination of millions of these tiny Red, Green and Blue pixels switching on or off creates the picture you're looking at right now.
How does the LED or OLED Touchscreen work?
More up-to-date models instead use OLED or Organic Light Emitting Diodes. These are a bit more complicated but suffice it to say they don't need a backlight as each pixel generates its own light source using organic chemistry from simple carbon compounds. What this means for you is that the blacks you see on an OLED screen are blacker because there's no ubiquitous backlight to filter out and your phone runs a little more efficiently which is great for battery life.
So in very simple terms your phone touch screen reads and interprets disturbances on a smart electric grid to figure out exactly where your finger itself a conductor is jabbing and the picture itself is just a load of tiny chemical cells flashing on and off in three different colours to make pretty pictures.
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Other types of screen technology exist but they're not very common in modern photos maybe in another post we'll touch on those. If you liked this short but informative post, do share it with your friends and family.
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