Speaker 1: Welcome to Tech Stuff, a production from iHeartRadio.
Speaker 2: Hey there, and.
Speaker 1: Welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm
Speaker 1: an executive producer with iHeart Podcasts and how the tech
Speaker 1: are you? So I'm still on vacation and that means
Speaker 1: that we're going to listen to an episode that originally
Speaker 1: published on May thirty first, twenty twenty three. It is
Speaker 1: titled Getting in Touch with touch Screens. So, yeah, we
Speaker 1: talk all about the touch screen technology and the two
Speaker 1: well there's more than two, but the two major ways
Speaker 1: touch screen technology tends to work.
Speaker 2: Enjoy.
Speaker 1: Let's talk a bit about touch screens. So, in the
Speaker 1: grand scheme of things, they're a fairly recent invention. If
Speaker 1: you look back at the original Star Trek series, you
Speaker 1: can see that they are a recent invention because they
Speaker 1: didn't think about touch screens when they were designing the sets.
Speaker 2: For Star Trek.
Speaker 1: The Enterprise, which is the flagship of the Federation, used
Speaker 1: physical buttons and switches, not touch screens. Now that should
Speaker 1: not come as a surprise. The set designers were taking
Speaker 1: their inspiration from electronic devices and mainframe computers of the
Speaker 1: time and then just saying how can we make that
Speaker 1: look more futury, and you can't blame them for failing
Speaker 1: to predict that in the future people would interact with
Speaker 1: technologies through other means, including voice and touch. By the
Speaker 1: time we get up to Star Trek the next Generation,
Speaker 1: things had changed.
Speaker 2: 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: images from behind the screen onto the screen. And also
Speaker 1: behind the screen, you could have a bunch of near
Speaker 1: infrared cameras, and these near infrared cameras could detect when
Speaker 1: a fingertip or some object makes contact with the surface
Speaker 1: that's on the other side and then map that to
Speaker 1: a program that creates the appropriate response. The original Microsoft Surface,
Speaker 1: which later would be called the Pixel Sense, had something
Speaker 1: like this and used multiple near infrared cameras I think
Speaker 1: five of them behind the screen to detect and track
Speaker 1: objects that make contact with the screen. If you don't recall,
Speaker 1: the pixel Sense had sort of a table form factor.
Speaker 1: It was quite a large display, bigger than what you
Speaker 1: would have with like a tablet.
Speaker 2: But I wanted to.
Speaker 1: Talk about the differences between the two most common touch
Speaker 1: screen technologies that consumers typically encounter. So first up is
Speaker 1: actually capacitive touch. This is really the type of screen
Speaker 1: you're most likely to encounter these days. Most touch screen
Speaker 1: technology falls back on this, and capacitive touch predates the
Speaker 1: other technology that we'll talk about by about five years
Speaker 1: or so. So back in nineteen sixty five, there was
Speaker 1: a British engineer named E. A. Johnson who developed capasitive
Speaker 1: touch technologies while working for the Royal Radar Establishment. He
Speaker 1: wrote up his work in a paper he titled Touch
Speaker 1: Displays a Programmed Man Machine Interface in nineteen sixty seven.
Speaker 1: A capacitive screen consists of several layers, so we're gonna
Speaker 1: work from the bottom up, and by up, I mean
Speaker 1: like at the top layer will be the surface that
Speaker 1: you would interact with. So at the base you have
Speaker 1: your actual display. Right, this is what is generating the
Speaker 1: image that you're gonna see through the other layers. So
Speaker 1: all the layers on top of this need to be
Speaker 1: transparent because otherwise you wouldn't be able to see the
Speaker 1: stuff that's on the display, and you've kind of eliminated
Speaker 1: the purposes of having a touchscreen device. Now. Typically you
Speaker 1: would have a thin glass substrate that would be on
Speaker 1: top of the display, and then the next layer up
Speaker 1: would be a conductive layer. So this is a layer
Speaker 1: that creates an electrostatic field across it. On top of
Speaker 1: that layer is a 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.
Speaker 2: So let's just say it's your finger. Make it easy.
Speaker 1: So you touch your finger to the surface of a screen.
Speaker 1: Your finger is conductive, and once you touch the screen,
Speaker 1: some of the charge on the surface underneath that top
Speaker 1: layer transfers to your finger, and the charge decreases at
Speaker 1: the point of contact. So you've got circuits that are
Speaker 1: built into the edge of the screen, often at the corners,
Speaker 1: and they detect where precisely that charge decrease in the
Speaker 1: capacitive layer happens and registers this as a contact and
Speaker 1: then that translates into an action based on whatever it
Speaker 1: is you're doing.
Speaker 2: So like if you're playing a.
Speaker 1: Game and you move your finger across the screen, it says,
Speaker 1: all right, well, the point of contact started at this position,
Speaker 1: it ended at that position, and that means we need
Speaker 1: to reflect that in moving a character from one point
Speaker 1: to another or whatever it may be. Now, this is
Speaker 1: why if you're wearing non conductive gloves, you can't interact
Speaker 1: with a touch screen, a capacitive touch screen properly unless
Speaker 1: you carry around something like a hot dog around that
Speaker 1: would work. I've actually seen people or pictures of people
Speaker 1: in Japan doing that when the weather was really darn cold.
Speaker 2: Hm hot dog phone.
Speaker 1: But also like anything that has a conductive rather a
Speaker 1: conductive surface would work. It's just that if you're wearing
Speaker 1: gloves that insulate you, then that doesn't work. That's why
Speaker 1: some gloves come with a little conductive mesh at the
Speaker 1: fingertips so that you can still interact with your capacitive
Speaker 1: touch screen device is while wearing the gloves. Now, the
Speaker 1: version that Johnson invented way back in nineteen sixty five
Speaker 1: was understandably limited. It could only detect the presence of
Speaker 1: a touch. It couldn't tell the difference between one finger
Speaker 1: or two fingers or anything like that. I don't think
Speaker 1: it could even detect where on the screen the touch happened,
Speaker 1: just that there was a touch. So, in other words,
Speaker 1: it was kind of an on off or binary system.
Speaker 1: Either something conductive was in contact with the screen or
Speaker 1: it wasn't. But this served as the foundation for the
Speaker 1: capacitive touch screens we use today. The problem is they
Speaker 1: were expensive, so while it was possible, it didn't really
Speaker 1: proliferate because the use cases were fairly limited, and it
Speaker 1: didn't make any sense to try and incorporate that into
Speaker 1: consumer technology because whatever you made would be way too expensive.
Speaker 1: The other common touch screen technology is called resistive touch.
Speaker 1: In nineteen seventy, an inventor named G. Samuel Hurst was
Speaker 1: trying to figure out a way to more efficiently make
Speaker 1: use of a vandograph accelerator, and so he came up
Speaker 1: with the idea of using electrically conductive paper.
Speaker 2: Essentially, these papers.
Speaker 1: Would have like a grid along the you know, 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 way,
Speaker 1: a vandograph generator, you know, a vandograph accelerator is what
Speaker 1: Hearst was referring to. But that's because a vandograph generator
Speaker 1: was used as a very primitive particle accelerator back in
Speaker 1: the day. It is an electrostatic generator. You've probably at
Speaker 1: least seen pictures of these, if not actually seen one
Speaker 1: in use. So typically you're using a belt mounted on
Speaker 1: some rollers that turn very quickly. This makes the belt
Speaker 1: move very quickly, and the moving belt actually typically makes
Speaker 1: contact with another surface, but it generates this electrostatic charge
Speaker 1: and carries that charge to a hollow metal globe. The
Speaker 1: globe itself is also mounted on top of a column
Speaker 1: that's made of some sort of insulator material, so this
Speaker 1: isolates the metal globe. Right, You're building up this electrostatic
Speaker 1: charge in the metal globe and there's nowhere for the
Speaker 1: charge to go because you've isolated the globe, and then
Speaker 1: you can bring something conductive in you know, general proximity
Speaker 1: of the globe, and as you get close enough, the
Speaker 1: 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 science classrooms to help demonstrate the principles of electrostatics.
Speaker 1: But back in the day they were used as particle
Speaker 1: accelerators in physics research. Yes, today it's a toy and
Speaker 1: a science classroom, but back in the day it was
Speaker 1: a particle accelerator. Anyway, Doctor Hurst used the electrically conductive
Speaker 1: paper to plot charges on X and y axis, and
Speaker 1: only a bit later did he realize that what he
Speaker 1: 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: lot of charges. Using a vandograph accelerator, and he thought
Speaker 1: that he could make this into a touch screen interface,
Speaker 1: so this would be a resistive touch screen. They actually
Speaker 1: have more layers than capacitive touch screens. That also means
Speaker 1: they block a little more light than capacitive touchscreens 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.
Speaker 2: They are there to act as a separator.
Speaker 1: They keep the first transparent conductive layer separate from a
Speaker 1: second transparent conductive layer, so they're there to keep space
Speaker 1: between those two layers. So again above these separator dots
Speaker 1: is that second transparent conductive layer. And then on the
Speaker 1: very top you have a flexible transparent film on top.
Speaker 1: This is where you would make contact with the screen.
Speaker 1: So when you push down on the screen, whether it's
Speaker 1: with a conductive surface or not, what you're doing is
Speaker 1: you're deforming the top most transparent layer to push down
Speaker 1: and come into contact with the next transparent conductive layer.
Speaker 1: That creates a circuit. So as long as you're pushing
Speaker 1: down with enough force, you're creating the circuit and it
Speaker 1: will detect that. So typically you've got other circuits in
Speaker 1: the device that detect drops in voltage or changes in voltage,
Speaker 1: and that's how they can detect the precise location where
Speaker 1: the touch happened. So again doesn't matter if it's your finger,
Speaker 1: if you're wearing gloves, if you're using a stylus, it
Speaker 1: doesn't really matter. What matters is that that top transparent
Speaker 1: conductive layer comes into contact with the bottom transparent conductive
Speaker 1: layer and creates a circuit. So the capacitive screen actually
Speaker 1: came first, but the resistive screen was more popular. It
Speaker 1: got more popular, and it did so faster than capacitive.
Speaker 1: So why is that, Well, mostly it comes down to cost. Also,
Speaker 1: like the fact that you didn't have to have a
Speaker 1: conductive material to work with it meant that you could
Speaker 1: actually use it for lots of other stuff, including stuff
Speaker 1: where you might have to do something like wear gloves,
Speaker 1: but you could use a stylus like That's a useful
Speaker 1: part of that technology is the fact that you can
Speaker 1: still work with it even if you aren't able to,
Speaker 1: you know, use your fingers directly on the screen. But
Speaker 1: it was much cheaper, and that was really the big thing.
Speaker 1: So capacitive sort of took a back seat for a while,
Speaker 1: and it would require a lot more innovation in the
Speaker 1: space to make capacitive screens more attractive than resistive screens. However,
Speaker 1: these days, most consumer devices you're going to come into
Speaker 1: 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 that's definitely a positive.
Speaker 2: They tend to.
Speaker 1: Be more durable as well as you can imagine if
Speaker 1: you've got a resistive touch screen, which is it works
Speaker 1: based upon you pushing the screen hard enough to make
Speaker 1: contact between two layers. I mean, you don't have to
Speaker 1: push super hard, but it does have to be enough
Speaker 1: pressure so that the some detects. There's a touch there well.
Speaker 1: As you might imagine, this eventually deforms the upper transparent
Speaker 1: conductive layer, and that you can eventually get to points
Speaker 1: where it's already close to or making contact with the
Speaker 1: lower layer. Just kind of like having a short circuit, right,
Speaker 1: and it makes it more difficult to have an accurate experience.
Speaker 1: Using resistive touch screens doesn't happen overnight, but over time
Speaker 1: it does happen. So that's one of the other benefits
Speaker 1: capacitive touch screens have over resistive. It's also easier to
Speaker 1: use capacitive touch screens for multi touch functions in general,
Speaker 1: not that you couldn't do it with resistive touch screens,
Speaker 1: but it's just it's easier when you're not focusing on
Speaker 1: using pressure to make that point of contact. You will
Speaker 1: still find resistive touch screens, however, in devices that are
Speaker 1: aimed at lower price points, So if you're looking at
Speaker 1: like a Budge tablet, there are a lot of industrial
Speaker 1: uses for resistive touch screens to this day. And keep
Speaker 1: in mind, as I said at the beginning of this episode,
Speaker 1: there are other types of touch screen technologies besides these two.
Speaker 1: There's some that use acoustics, there're some that use infra
Speaker 1: red lasers. Like I said, with the surface, there are
Speaker 1: the kinds that use you know, cameras that are mounted
Speaker 1: behind the screen itself. It's not like these two are
Speaker 1: the only two. There are lots of other technologies. It's
Speaker 1: just those two are the ones you're most likely to
Speaker 1: come into contact with, both figuratively and literally. So I
Speaker 1: hope that this was interesting and informative, a little text
Speaker 1: off tidbits episode, and I'm trying to do more of
Speaker 1: these because it's fun to do these short ones. It's
Speaker 1: just a challenge because you know, I'm a chatty kathy.
Speaker 1: This episode probably could have been eight minutes long and
Speaker 1: instead of going twice as long. So but hey, I
Speaker 1: like your company, hope you like mine, And if you
Speaker 1: have any suggestions for little things that you would like
Speaker 1: explained in the tech space, even.
Speaker 2: If 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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