Speaker 1: Welcome to tech Stuff, a production from iHeartRadio. Hey there,
Speaker 1: and welcome to tech Stuff. I'm your host, Jonathan Strickland.
Speaker 1: I'm an executive producer with iHeartRadio. And how the tech
Speaker 1: are you. Let's talk a bit about touch screens. So
Speaker 1: in the grand scheme of things, they're a fairly recent invention.
Speaker 1: If you look back at the original Star Trek series,
Speaker 1: you can see that they are a recent invention because
Speaker 1: they didn't think about touch screens when they were designing
Speaker 1: the sets for Star Trek. The Enterprise, which is the
Speaker 1: flagship of the Federation, used physical buttons and switches, not
Speaker 1: touch screens. Now, that should not come as a surprise.
Speaker 1: The set designers were taking their inspiration from electronic devices
Speaker 1: and mainframe computers of the time and then just saying,
Speaker 1: how can we make that look more futury? And you
Speaker 1: can't blame them for failing to predict that in the
Speaker 1: future people would interact with technologies through other means, including
Speaker 1: voice and touch. By the time we get up to
Speaker 1: Star Trek the next generation, things had changed quite a bit.
Speaker 1: The controls on the new Enterprise were these sort of
Speaker 1: touch sensitive panels. They had control surfaces that were built
Speaker 1: directly into walls and consoles in such a way that
Speaker 1: I bet it was someone's full time gig on the
Speaker 1: set to just wipe down the surfaces to get rid
Speaker 1: of all the smudges. They also had voice commands built
Speaker 1: into their computer system at that point, so that was
Speaker 1: pretty cool too. They kind of had both of those
Speaker 1: blossoming technologies involved in Star Trek next generation. And there
Speaker 1: are actually several different methods that you could follow to
Speaker 1: create a touch screen or touch surface. So for example,
Speaker 1: you could have a rear projection screen and you're projecting
Speaker 1: image is from behind the screen onto the screen, and
Speaker 1: also behind the screen, you could have a bunch of
Speaker 1: near infrared cameras, and these near infrared cameras could detect
Speaker 1: when a fingertip or some object makes contact with the
Speaker 1: surface that's on the other side and then map that
Speaker 1: to a program that creates the appropriate response. The original
Speaker 1: Microsoft surface, which later would be called the Pixel Sense,
Speaker 1: had something like this and used multiple near infrared cameras
Speaker 1: I think five of them behind the screen to detect
Speaker 1: and track objects that make contact with the screen. If
Speaker 1: you don't recall, the pixel Sense had sort of a
Speaker 1: table form factor. It was quite a large display, bigger
Speaker 1: than what you would have with like a tablet. But
Speaker 1: I wanted to talk about the differences between the two
Speaker 1: most common touchscreen technologies that consumers typically encounter. So first
Speaker 1: up is actually capacitive touch. This is really the type
Speaker 1: of screen you're most likely to encounter these days. Most
Speaker 1: touch screen technology falls back on this, and capacitive touch
Speaker 1: predates the other technology that we'll talk about by about
Speaker 1: five years or so. So back in nineteen sixty five,
Speaker 1: there was a British engineer named E. A. Johnson who
Speaker 1: developed capasitive touch technologies while working for the Royal Radar Establishment.
Speaker 1: He wrote up his work in a paper he titled
Speaker 1: Touch Displays a Programmed Man Machine Interface in nineteen sixty seven.
Speaker 1: A capacitive screen consists of several layers, So we're going
Speaker 1: to work from the bottom up, and by up, I
Speaker 1: mean like at the top layer will be the surface
Speaker 1: that you would interact with. So at the base you
Speaker 1: have your actual display, right, this is what is generating
Speaker 1: the image that you're going to see through the other layers.
Speaker 1: So all the layers on top of this need to
Speaker 1: be transparent, because otherwise you wouldn't be able to see
Speaker 1: the stuff that's on the display, and you've kind of
Speaker 1: eliminated the purposes of having a touchscreen device. Now, typically
Speaker 1: you would have a thin glass substrate that would be
Speaker 1: on top of the display, and then the next layer
Speaker 1: up would be a conductive layer. So this is a
Speaker 1: layer that creates an electrostatic field across it. On top
Speaker 1: of that layer is a thin transparent layer, and this
Speaker 1: is the layer that you could actually touch. So if
Speaker 1: something conductive makes contact with this top layer, then some
Speaker 1: of the electrostatic charge on the layer beneath the top
Speaker 1: layer will transfer to that conductive material. So let's just
Speaker 1: say it's your finger. Make it easy. So you touch
Speaker 1: your finger to the surface of a screen. Your finger
Speaker 1: is conductive, and once you touch the screen, some of
Speaker 1: the charge on the surface underneath that top layer transfers
Speaker 1: to your finger, and the charge decreases at the point
Speaker 1: of contact. So you've got circuits that are built into
Speaker 1: the edge of the screen, often at the corners, and
Speaker 1: they detect where precisely that charge decrease in the capacitive
Speaker 1: layer happens and registers this as a contact and then
Speaker 1: that translates into an action based on whatever it is
Speaker 1: you're doing so. Like if you're playing a game and
Speaker 1: you move your finger across the screen, it says, all right, well,
Speaker 1: the point of contact started at this position, it ended
Speaker 1: at that position, and that means we need to reflect
Speaker 1: that in moving a character from one point to another
Speaker 1: or whatever it may be. Now, this is why if
Speaker 1: you're wearing non conductive gloves, you can't interact with a
Speaker 1: touch screen, a capacitive touch screen properly, unless you, you know,
Speaker 1: carry around something like a hot dog around that would work.
Speaker 1: I've actually seen people or pictures of people in Japan
Speaker 1: doing that when the weather was really darn cold. Hot
Speaker 1: dog phone. But also like anything that hasity, a conductive
Speaker 1: rather a conductive surface would work. It's just that if
Speaker 1: you're wearing gloves that insulate you, then that doesn't work.
Speaker 1: That's why some gloves come with a little conductive mesh
Speaker 1: at the fingertips so that you can still interact with
Speaker 1: your capacitive touch screen devices while wearing the gloves. Now,
Speaker 1: the version that Johnson invented way back in nineteen sixty
Speaker 1: five was understandably limited. It could only detect the presence
Speaker 1: of a touch. It couldn't tell the difference between one
Speaker 1: finger or two fingers or anything like that. I don't
Speaker 1: think it could even detect where on the screen the
Speaker 1: touch happened, just that there was a touch. So in
Speaker 1: other words, it was kind of an on off or
Speaker 1: binary system. Either something conductive was in contact with the
Speaker 1: screen or it wasn't. But this served as the foundation
Speaker 1: for the capacitive touch screens we used today. The problem
Speaker 1: is they were expensive, so while it was possible, it
Speaker 1: didn't really proliferate because the use cases were fairly limited,
Speaker 1: and it didn't make any sense to try and incorporate
Speaker 1: that into consumer technology because whatever you made would be
Speaker 1: way too expensive. The other common touch screen technology is
Speaker 1: called resistive touch. In nineteen seventy, an inventor named G.
Speaker 1: Samuel Hurst was trying to figure out a way to
Speaker 1: more efficiently make use of a vandograph accelerator, and so
Speaker 1: he came up with the idea of using electrically conductive paper. Essentially,
Speaker 1: these papers would have like a grid along the X
Speaker 1: and y axis of the paper, and you could detect
Speaker 1: a change in voltage along those grids, so you could
Speaker 1: you could plot a specific point of contact by the
Speaker 1: way a vandograph generator, you know, a vandograph accelerator is
Speaker 1: what Hearst was referring to, but that's because a vandograph
Speaker 1: generator was used as a very primitive particle accelerator back
Speaker 1: in the day. It is an electrostatic generator. You've probably
Speaker 1: at least seen pictures of these, if not actually seen
Speaker 1: one in use. So typically you're using a belt mounted
Speaker 1: on some rollers that turn very quickly. This makes the
Speaker 1: belt move very quickly, and the moving belt actually typically
Speaker 1: makes contact with another surface, but it generates this electrostatic
Speaker 1: charge and carries that charge to a hollow metal globe.
Speaker 1: The globe itself is also mounted on top of a
Speaker 1: column that's made of some sort of insulator material, so
Speaker 1: this isolates the metal globe. Right, You're building up this
Speaker 1: electrostatic charge in the metal globe and there's nowhere for
Speaker 1: the charge to go because you've isolated the globe. And
Speaker 1: then you can bring something conductive in you know, general
Speaker 1: proximity of the globe, and as you get close enough,
Speaker 1: the difference in electric potentials will cause a spark to form.
Speaker 1: Like you essentially create a circuit very very briefly, and
Speaker 1: then you get this zap of a spark and you've
Speaker 1: probably seen, like I said, one of these, either in
Speaker 1: video or maybe even in person. You're likely to find
Speaker 1: it in like science classrooms to help demonstrate the principles
Speaker 1: of electrostatics. But back in the day they were used
Speaker 1: as particle accelerators in physics research. Yes, today it's a
Speaker 1: toy and a science classroom, but back in the day,
Speaker 1: it was a particle accelerator. Anyway, doctor Hurst used the
Speaker 1: electrically conductive paper to plot charge on X and y axis,
Speaker 1: and only a bit later did he realize that what
Speaker 1: he was doing could potentially have other applications outside the lab.
Speaker 1: I'll explain more, but first let's take a quick break.
Speaker 1: So doctor Hurst and his team figured that they might
Speaker 1: actually have some applications for this conductive paper beyond the
Speaker 1: plotting of charges using a vandograph accelerator. And he thought
Speaker 1: that he could make this into a touchscreen interface. So
Speaker 1: this would be a resistive touch screen. They actually have
Speaker 1: more layers than capacitive touch screens. That also means they
Speaker 1: block a little more light than capacitive touch screens do,
Speaker 1: so resistive screens tend to be dimmer than capacitive ones.
Speaker 1: So let's go through those layers again and again, we're
Speaker 1: going to start from the display side up to the
Speaker 1: surface where you would make contact with the screen. So
Speaker 1: at the very base you've still got your display, just
Speaker 1: like with capacitive. On top of the display, you've got
Speaker 1: a glass substrate. Above that you have a transparent conductive layer,
Speaker 1: so again similar to what you would have with the
Speaker 1: capacitive screen. But next you would have a layer of
Speaker 1: what are called separator dots. So these are our little
Speaker 1: supports that are non conductive. They are there to act
Speaker 1: as a separator. They keep the first transparent conductive layer
Speaker 1: separate from a second transparent conductive layer, so they're there
Speaker 1: to keep space between those two layers. So again above
Speaker 1: these separator dots is that second transparent conductive layer, and
Speaker 1: then on the very top you have a flexible transparent
Speaker 1: film on top. This is where you would make contact
Speaker 1: with the screen. So when you push down on the screen,
Speaker 1: whether it's with a conductive surface or not, what you're
Speaker 1: doing is you're deforming the top most transparent layer to
Speaker 1: push down and come into contact with the next transparent
Speaker 1: conductive layer. That creates a circuit. So as long as
Speaker 1: you're pushing down with enough force, you're creating the circuit
Speaker 1: and it will detect that touch. So typically you've got
Speaker 1: other circuits in the device that detect drops in voltage
Speaker 1: or changes in voltage, and that's how they can detect
Speaker 1: the precise location where the touch happened. So again, doesn't
Speaker 1: matter if it's your finger, if you're wearing gloves, if
Speaker 1: you're using a stylus, it doesn't really matter. What matters
Speaker 1: is that that top transparent conductive layer comes into contact
Speaker 1: with the bottom transparent conductive layer and creates a circuit.
Speaker 1: So the capacitive screen actually came first, but the resistive
Speaker 1: screen was more popular. It got more popular, and it
Speaker 1: did so faster than capacitive. So why is that, Well,
Speaker 1: mostly it comes down to cost. Also, like the fact
Speaker 1: that you didn't have to have a conductive material to
Speaker 1: work with it meant that you could actually use it
Speaker 1: for lots of other stuff, including stuff where you might
Speaker 1: have to do something like wear gloves, but you could
Speaker 1: use a stylus like That's a useful part of that
Speaker 1: technology is the fact that you can still work with
Speaker 1: it even if you aren't able to, you know, use
Speaker 1: your fingers directly on the screen. But it was much
Speaker 1: cheaper and that was really the big thing, so capacitive
Speaker 1: sort of took a back seat for a while, and
Speaker 1: it would require a lot more innovation in the space
Speaker 1: to make capacitive screens more attractive than resistive screens. However,
Speaker 1: these days, most consumer devices you're going to come in
Speaker 1: to contact with use capacitive touch screens, largely because, I mean,
Speaker 1: they're still more expensive than resistive touch screens, but they
Speaker 1: can display brighter images, so that's definitely a positive. They
Speaker 1: tend to be more durable as well as you can
Speaker 1: imagine if you've got a resistive touch screen, which is
Speaker 1: it works based upon you pushing the screen hard enough
Speaker 1: to make contact between two layers. I mean, you don't
Speaker 1: have to push super hard, but it does have to
Speaker 1: be enough pressure so that the system detects there's a
Speaker 1: touch there. Well, as you might imagine, this eventually deforms
Speaker 1: the upper transparent conductive layer, and that you can eventually
Speaker 1: get to points where it's already close to or making
Speaker 1: contact with the lower layer. Just kind of like having
Speaker 1: a short circuit, right, and it makes it more difficult
Speaker 1: to have an accurate experience. Using resistive touch screens. Doesn't
Speaker 1: happen overnight, but over time it does happen, So that's
Speaker 1: one of the other benefits capacitive touch screens have over resistive.
Speaker 1: It's also easier to use capacitive touch screens for multi
Speaker 1: touch functions in general, not that you couldn't do it
Speaker 1: with resistive touch screens, but it's just it's easier when
Speaker 1: you're not focusing on using pressure to make that point
Speaker 1: of contact. You will still find resistive touch screens, however,
Speaker 1: in devices that are aimed at lower price points, So
Speaker 1: if you're looking at like a budget tablet, there are
Speaker 1: a lot of industrial uses for resistive touch screens to
Speaker 1: this day. And keep in mind, as I said at
Speaker 1: the beginning of this episode, there are other types of
Speaker 1: touch screen technologies besides these two. There's some that use acoustics,
Speaker 1: there's some that use infrared lasers. Like I said with
Speaker 1: the surface, there are the kinds that use you know,
Speaker 1: cameras that are mounted behind the screen itself. It's not
Speaker 1: like these two are the only two. There are lots
Speaker 1: of other technologies. It's just those two are the ones
Speaker 1: you're most likely to come into contact with, both figuratively
Speaker 1: and literally. So I hope that this was interesting and informative.
Speaker 1: A little tech Stuff Tidbits episode, and I'm trying to
Speaker 1: do more of these because it's fun to do these
Speaker 1: short ones. It's just a challenge because you know, I'm
Speaker 1: a chatty Kathy. This episode probably could have been eight
Speaker 1: minutes long and instead of going twice as long. So
Speaker 1: but hey, I like your company, hope you like mine,
Speaker 1: And if you have any suggestions for little things that
Speaker 1: you would like explained in the tech space, even if
Speaker 1: it's something like, hey, can you give a quick rundown
Speaker 1: on logic gates and what those do or something along
Speaker 1: those lines, let me know and I'll look into it.
Speaker 1: And I hope you are all well, and I'll talk
Speaker 1: to you again really soon. Tech Stuff is an iHeartRadio production.
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