WEBVTT - TechStuff Gets in Touch with Touch Screens 0:00:04.240 --> 0:00:07.240 Welcome to tech Stuff, a production of I Heart Radios, 0:00:07.320 --> 0:00:13.880 How Stuff Works. Hey there, and welcome to tech Stuff. 0:00:14.000 --> 0:00:17.079 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:17.120 --> 0:00:19.279 How Stuff Works and I Heart Radio and I love 0:00:19.320 --> 0:00:23.520 all things tech and listener Robert Casey pinned me on 0:00:23.560 --> 0:00:26.640 Twitter with a request that I do an episode about 0:00:26.720 --> 0:00:31.639 touch screens and stylus is or STYLI Now. My original 0:00:31.720 --> 0:00:35.600 co host, Chris Palette, and I covered this topic on 0:00:35.720 --> 0:00:39.680 an ancient episode of tech Stuff that published all the 0:00:39.680 --> 0:00:45.360 way back on October nineteen, two thousand nine, Holy Cow, 0:00:45.880 --> 0:00:49.159 ten years ago. But I think it's past time to 0:00:49.320 --> 0:00:53.000 revisit this topic and give it the full modern day 0:00:53.080 --> 0:00:56.560 tech stuff treatment. Now, there are a few interesting things 0:00:56.680 --> 0:00:59.319 about touch screens in general that I'd like to get 0:00:59.360 --> 0:01:03.360 all the way. One is that it's pretty ubiquitous today. 0:01:03.520 --> 0:01:06.400 It's it's it's a user interface that you find everywhere 0:01:06.440 --> 0:01:11.200 for everything from mobile or mobile devices to lots of 0:01:11.240 --> 0:01:15.720 different laptop and desktop displays. Now, granted, I've never owned 0:01:15.959 --> 0:01:19.800 a laptop or desktop display that had touch screen technology 0:01:19.800 --> 0:01:23.080 incorporated in it, largely because I didn't see a lot 0:01:23.160 --> 0:01:25.760 of use in that Based on how I tend to 0:01:25.800 --> 0:01:28.039 interact with computers, Not to say that there's no use 0:01:28.080 --> 0:01:30.360 for it, just that the way I use computers, it 0:01:30.360 --> 0:01:32.920 wouldn't make sense for me. Usually I don't have the 0:01:32.959 --> 0:01:35.720 display so close that reaching out and touching it would 0:01:35.720 --> 0:01:38.720 be terribly easy or comfortable, And most of what I 0:01:38.800 --> 0:01:42.880 use computers for requires lots of typing, which isn't great 0:01:42.959 --> 0:01:46.480 on most touch screen implementations. I guess you could pare 0:01:46.520 --> 0:01:49.320 it with voice recognition and get more use out of it, 0:01:49.800 --> 0:01:52.080 But I am curious if any of you guys use 0:01:52.160 --> 0:01:56.559 computers with touch displays and what do you use them for? 0:01:56.800 --> 0:01:59.400 As I'm sure there are plenty of use cases where 0:01:59.440 --> 0:02:03.400 it is incredibly handy so to speak. Oh and there 0:02:03.400 --> 0:02:07.000 will probably be a lot of unintentional puns in this episode, 0:02:07.440 --> 0:02:11.480 and maybe a couple of intended ones will be but 0:02:11.639 --> 0:02:15.840 a touch away, so to speak. Anyway, touch screens are everywhere, 0:02:16.120 --> 0:02:19.680 but their history is fairly recent. Another thing I find 0:02:19.720 --> 0:02:22.040 really interesting about them is that there are a lot 0:02:22.040 --> 0:02:24.680 of different ways to go about it, and the end 0:02:24.760 --> 0:02:27.960 result aims to be the same, but there are several 0:02:28.000 --> 0:02:32.120 approaches to implementing touch screens, and each implementation has its 0:02:32.160 --> 0:02:36.080 advantages and disadvantages, so we'll cover those in this episode. 0:02:36.520 --> 0:02:39.880 And yet, one more thing I think is interesting is 0:02:39.919 --> 0:02:43.359 really just how innovative touch screen devices have been. If 0:02:43.360 --> 0:02:46.600 you look back at the science fiction films and TV 0:02:46.760 --> 0:02:50.200 series from the nineteen fifties and even into the nineteen sixties, 0:02:50.360 --> 0:02:54.320 when touch screen technology was first being described, you'll rarely 0:02:54.360 --> 0:02:58.000 see examples of that idea. Touch Screens were such a 0:02:58.080 --> 0:03:03.320 leap forward that spec lative fiction writers weren't really imagining 0:03:03.360 --> 0:03:06.880 it as a user interface. That's why in series like 0:03:06.960 --> 0:03:10.960 Star Trek, the original series, you'll see characters interacting with 0:03:11.080 --> 0:03:16.000 physical dials and knobs and levers that are the controls 0:03:16.040 --> 0:03:19.400 of a twenty third century spaceship. You know, you look 0:03:19.400 --> 0:03:22.079 at those controls today and you think, oh, that looks antiquated. 0:03:22.680 --> 0:03:24.959 Unlike a lot of technologies we've seen over the last 0:03:25.000 --> 0:03:29.600 several decades, touch screens weren't heavily predicted in fiction. And 0:03:29.639 --> 0:03:31.640 I think I'll have to do an episode dedicated to 0:03:31.760 --> 0:03:34.840 tech that writers described years before it became a reality. 0:03:34.920 --> 0:03:37.600 That's an interesting subject of its own, Like the types 0:03:37.640 --> 0:03:41.280 of technology that science fiction writers predicted before it happened. 0:03:41.600 --> 0:03:44.720 You know, things like you know, geosynchronous satellites, but that's 0:03:44.720 --> 0:03:49.120 for another episode. Okay, so we're ready for our history lesson, 0:03:49.200 --> 0:03:51.920 which is you longtime listeners know is sort of a 0:03:51.960 --> 0:03:55.320 requirement in every tech stuff episode. Before I dive in, 0:03:55.400 --> 0:03:58.040 I want to give a shout out to Florence Ion's 0:03:58.200 --> 0:04:02.000 article from Touch to Plays to the Surface, A brief 0:04:02.040 --> 0:04:05.840 history of touch screen technology in Ours Technica. It's a 0:04:05.840 --> 0:04:09.400 fantastic summary of the evolution of the technology, and if 0:04:09.440 --> 0:04:12.080 you want to learn more about the history of touch screens, 0:04:12.080 --> 0:04:14.160 I urge you to seek it out. It was not 0:04:14.280 --> 0:04:17.559 the only source I used when getting all the history stuff, 0:04:17.600 --> 0:04:21.680 but it was a great resource. Also. I normally break 0:04:21.760 --> 0:04:24.760 up the history and the description of how technology works 0:04:24.800 --> 0:04:28.479 into different parts of episodes typically, but in this case, 0:04:28.920 --> 0:04:32.080 I think it works better to describe how each version 0:04:32.160 --> 0:04:35.120 of the technology works as we get to them, and 0:04:35.200 --> 0:04:37.400 as a peak behind the curtain. I came to that 0:04:37.480 --> 0:04:39.880 decision after I was about a third of the way 0:04:39.960 --> 0:04:43.400 done typing out all of my notes, so I actually 0:04:43.440 --> 0:04:45.719 went back and revised my notes quite a bit and 0:04:45.800 --> 0:04:48.080 rearranged things because I did not like the way the 0:04:48.120 --> 0:04:52.719 episode flowed in its original form. So all that being said, 0:04:53.000 --> 0:04:55.800 where did the idea for the touch screen interface come 0:04:55.880 --> 0:04:59.599 from well before there were touch screens that could interpret 0:04:59.680 --> 0:05:02.919 the touch of a finger or stylus, there was the 0:05:03.040 --> 0:05:05.520 light pen. The first light pen was part of a 0:05:05.560 --> 0:05:09.279 system that IBM design called Whirlwind, which the company built 0:05:09.279 --> 0:05:12.919 for Norad. But the way touch screens work is different 0:05:13.080 --> 0:05:16.120 from the way light pens work. With touch screens, the 0:05:16.160 --> 0:05:19.800 technology for detecting a point of contact is generally built 0:05:20.000 --> 0:05:24.240 into or behind or sometimes in front of the screen itself. 0:05:24.920 --> 0:05:27.960 With a light pen, the detector is actually in the 0:05:28.040 --> 0:05:31.560 pen side of the interface, not on the screen side, 0:05:31.839 --> 0:05:34.760 so the screen is a nert. It's the pen that's active. 0:05:35.279 --> 0:05:38.840 Light pens have a photoelectric cell built into them, in 0:05:38.839 --> 0:05:43.440 other words, a sensor that detects light, and typically light 0:05:43.480 --> 0:05:46.839 pen is tethered to the computer system it's connected to. 0:05:46.960 --> 0:05:50.400 It's actually physically connected with a cable. Holding a light 0:05:50.440 --> 0:05:53.120 pen up to a screen would allow the light pen 0:05:53.240 --> 0:05:57.880 to register when the monitors electron beams scanned across that point, 0:05:58.440 --> 0:06:01.080 because monitors in those days were based off the old 0:06:01.160 --> 0:06:06.279 cathode ray tube technology, which uses an electron gun that 0:06:06.480 --> 0:06:10.599 shoots a beam of electrons in row after row after row, 0:06:10.839 --> 0:06:14.200 so it goes it scans across the screen and then 0:06:14.320 --> 0:06:17.880 down the screen. So it goes one line across, then 0:06:17.960 --> 0:06:21.279 moves down the line, goes across, moves down the line, etcetera, etcetera. 0:06:21.960 --> 0:06:25.640 And these electrons then hit against phost four points on 0:06:25.680 --> 0:06:28.640 the back side of the screen and it generates light. Now, 0:06:28.680 --> 0:06:31.919 because the light pins were tethered to the computer system, 0:06:31.960 --> 0:06:35.440 the computer would pick up precisely where on the screen 0:06:35.480 --> 0:06:38.360 the light pin was sitting, and it did this by 0:06:38.400 --> 0:06:42.640 cross referencing the time of contact with the position of 0:06:42.680 --> 0:06:46.080 the electron beam at that moment. So the light pin 0:06:46.120 --> 0:06:50.360 would detect this electron beam, and that message would be 0:06:50.400 --> 0:06:52.640 sent to the computer, and the computer knew where the 0:06:52.680 --> 0:06:56.160 electron beam was at that precise instant, and that way 0:06:56.200 --> 0:06:58.760 it knew where the point of contact was. Now, this 0:06:58.839 --> 0:07:01.960 is largely an outlier of the touchscreen topic, but it's 0:07:02.000 --> 0:07:04.720 kind of a predecessor, so I thought it would include it. Now, 0:07:04.839 --> 0:07:07.960 unlike a lot of other technologies, which tend to get 0:07:08.000 --> 0:07:10.920 pretty muddy when you start asking questions like where did 0:07:10.920 --> 0:07:14.480 this idea come from? We can be reasonably certain that 0:07:14.760 --> 0:07:18.760 Eric Arthur Johnson or E. A. Johnson proposed the first 0:07:18.880 --> 0:07:24.080 technological solution to creating a touch screen computer interface. Johnson 0:07:24.120 --> 0:07:26.920 was an engineer at what was at that point the 0:07:27.160 --> 0:07:32.000 Royal Radar Establishment, which was a research facility in Malvern, England, 0:07:32.320 --> 0:07:35.760 and as the name suggests, this facility was chiefly focused 0:07:35.760 --> 0:07:39.560 on developing new radar technologies, and it wasn't It was 0:07:39.600 --> 0:07:43.000 operating as a research organization that worked closely with British 0:07:43.120 --> 0:07:46.880 Armed Forces. It would later become the Defense Evaluation and 0:07:46.960 --> 0:07:51.000 Research Agency after merging with a few other organizations, and 0:07:51.120 --> 0:07:54.880 later still it would become part of a defense contractor 0:07:54.920 --> 0:07:59.880 in England called Kinetic spelled with a que. Johnson was 0:08:00.120 --> 0:08:04.720 working on improving the user interface for air traffic control staff. 0:08:04.760 --> 0:08:08.200 He wrote an article and had the title touch Display 0:08:08.360 --> 0:08:12.480 a novel input output device for computers. It was published 0:08:12.480 --> 0:08:16.760 in the journal Electronics Letters on October uh in nineteen. 0:08:17.680 --> 0:08:20.640 I said on October, I should say in October nine, 0:08:21.360 --> 0:08:24.080 because I don't have the precise date of when in 0:08:24.120 --> 0:08:26.600 October it came out. But in nineteen sixty seven he 0:08:26.640 --> 0:08:30.760 published a follow up piece titled touch Displays a Programmed 0:08:30.840 --> 0:08:34.880 Man Machine Interface that further developed this concept and fleshed 0:08:34.920 --> 0:08:37.560 it out, and he was describing what would become the 0:08:37.600 --> 0:08:42.079 capacitive touch screen interface. And I also find this interesting 0:08:42.400 --> 0:08:45.840 because for many years, it seemed the majority of consumer 0:08:45.880 --> 0:08:50.080 products that had touch screens used an alternative to the 0:08:50.120 --> 0:08:54.480 capacity of approach, known as resistive touch screens, and those 0:08:54.520 --> 0:08:57.679 two technologies make up the majority of the touch screens 0:08:57.760 --> 0:09:01.440 we tend to encounter. I'll explain the differences between them 0:09:01.559 --> 0:09:05.080 when we get to each, but first before I get 0:09:05.120 --> 0:09:08.480 into the differences, what our capacity of touch screens and 0:09:08.520 --> 0:09:12.560 how do they register touch? Well, they only register a 0:09:12.640 --> 0:09:17.839 touch if the substance touching the screen can hold an 0:09:17.840 --> 0:09:21.959 electrical charge, So stuff like our skin. Our skin can 0:09:22.000 --> 0:09:25.360 hold an electrical charge. It's electrically conductive. So if you've 0:09:25.400 --> 0:09:29.400 ever used a touch screen while wearing gloves and nothing happened, 0:09:29.800 --> 0:09:33.560 it's probably because the capacity of touch screen was not 0:09:33.760 --> 0:09:37.640 able to detect any sort of electrical connection. The gloves 0:09:37.640 --> 0:09:42.480 were acting like insulators. They inhibit electrical charge. That's why 0:09:42.520 --> 0:09:44.520 there are companies out there that sell gloves that have 0:09:44.720 --> 0:09:48.679 conductive wire or conductive pads at the fingertips. And it's 0:09:48.720 --> 0:09:51.840 also why you can't use something like an inert plastic 0:09:51.960 --> 0:09:55.560 stylus on a capacity of screen. You can use a 0:09:55.640 --> 0:10:00.720 stylus that has a conductive surface at the hip, that 0:10:00.760 --> 0:10:05.000 would work. But if it's just a plastic stick, for example, 0:10:05.320 --> 0:10:08.439 it wouldn't activate the screen. But you could use something 0:10:08.440 --> 0:10:11.920 else like um, you know, like a hot dog, which 0:10:11.960 --> 0:10:14.120 is I understand it used to be a thing in 0:10:14.160 --> 0:10:17.839 South Korea. People would use hot dogs to activate their 0:10:17.840 --> 0:10:20.120 capacitive touch screens when it was too cold for them 0:10:20.160 --> 0:10:23.360 to not wear gloves, which tells me you could probably 0:10:23.400 --> 0:10:27.200 make a killing in soul by selling screen cleaners dedicated 0:10:27.200 --> 0:10:32.320 to eradicating weener grease from your screens. But how do 0:10:32.559 --> 0:10:36.240 the capacity of screens actually detect touch. There's a couple 0:10:36.280 --> 0:10:39.360 of different approaches, but the general idea is to create 0:10:39.360 --> 0:10:43.240 a surface that holds an electrical charge, and in many 0:10:43.320 --> 0:10:46.640 implementations this is done with a grid of very fine 0:10:46.880 --> 0:10:51.000 conductive wires running in rows and columns on an x 0:10:51.160 --> 0:10:55.360 y grid. In other words, so like a net, sensors 0:10:55.559 --> 0:10:58.640 pick up changes in this electrical charge when they happen. 0:10:58.920 --> 0:11:02.720 So if an object act that conducts electricity makes contact 0:11:02.720 --> 0:11:06.360 with the screen, so for example, your finger, there's a 0:11:06.480 --> 0:11:09.680 change in that electrical charge. Technically the change is a 0:11:09.800 --> 0:11:13.800 drop in voltage. So by detecting where that change happens 0:11:13.840 --> 0:11:17.880 along those x y coordinates, A microprocessor can interpret the 0:11:17.920 --> 0:11:22.760 touch and associate it with whatever command you wanted to execute. So, 0:11:22.920 --> 0:11:26.040 in the example of activating an icon on a screen, 0:11:26.520 --> 0:11:31.120 the icon represents the execution of a particular app or program. 0:11:31.160 --> 0:11:35.440 When the microprocessor or touch sensor detects a contact at 0:11:35.480 --> 0:11:38.720 the location of such an icon, it interprets that touch 0:11:38.920 --> 0:11:43.439 to mean execute the program associated with the image at 0:11:43.520 --> 0:11:47.200 these coordinates on the display, and then it will launch 0:11:47.240 --> 0:11:50.880 the app. A similar thing happens with gesture controls like 0:11:50.960 --> 0:11:55.280 swiping or pinching. Engineers and programmers have to build in 0:11:55.320 --> 0:11:58.680 this capability so that the system can interpret the meaning 0:11:58.800 --> 0:12:02.760 behind the gestures and thus produced the appropriate result, But 0:12:02.800 --> 0:12:06.280 the actual detection of a touch all comes down to 0:12:06.400 --> 0:12:10.640 that change and voltage. Early capacity of screens could really 0:12:10.679 --> 0:12:14.360 only detect one point of contact, so if you tried 0:12:14.440 --> 0:12:17.680 touching the screen with more than one finger, typically the 0:12:17.720 --> 0:12:21.800 screen would only register that first touch. This is because 0:12:21.840 --> 0:12:26.160 the sensing technology was limited. Early sensors would estimate the 0:12:26.280 --> 0:12:31.079 point of contact. It wasn't incredibly precise. It was precise 0:12:31.200 --> 0:12:35.080 enough for general use, but you couldn't really get fine 0:12:35.160 --> 0:12:39.480 tuning with it. Later implementations would incorporate better sensors, and 0:12:39.480 --> 0:12:42.800 eventually you'd find capacity of screens in which each row 0:12:43.120 --> 0:12:47.000 or column of wires had its own associated sensors, which 0:12:47.040 --> 0:12:49.960 increased their accuracy, and it opened up the possibility of 0:12:49.960 --> 0:12:54.160 a capacity of screen with multi touch capability. Johnson would 0:12:54.200 --> 0:12:57.520 receive a U S patent for his invention in nineteen 0:12:57.679 --> 0:13:02.040 sixty nine. So if you'd like an engineer's explanation of 0:13:02.080 --> 0:13:05.200 the basic technology behind these capacity of touch screens, you 0:13:05.360 --> 0:13:08.840 two can search for u S Patent three million, four 0:13:08.920 --> 0:13:13.320 hundred eighty two thousand, two hundred forty one. The patent 0:13:13.440 --> 0:13:17.200 includes circuit diagrams and a flow chart that are helpful 0:13:17.200 --> 0:13:20.240 to understand how it works as well. The capacity of 0:13:20.280 --> 0:13:24.040 screen was a great innovation, but it saw little adoption 0:13:24.320 --> 0:13:28.160 over the following few years. An alternative approach would get 0:13:28.160 --> 0:13:31.199 a bit more traction. In the short term. You could 0:13:31.240 --> 0:13:35.240 say the tech world couldn't resist it. I'll explain more 0:13:35.640 --> 0:13:47.440 after this break in nineteen seventy, Dr George Samuel Hurst 0:13:47.600 --> 0:13:51.320 invented the first resistive touch screen. In the late nineteen 0:13:51.320 --> 0:13:53.880 forties through the nineteen fifties, he had worked at the 0:13:53.920 --> 0:13:57.520 oak Ridge National Laboratory and R and D facility that 0:13:57.640 --> 0:14:00.559 is funded by the U. S Department of Energy. Herst 0:14:00.600 --> 0:14:03.720 has been working in the field of atomic physics, developing 0:14:03.760 --> 0:14:08.600 stuff like radiation detectors at nuclear testing sites. In nineteen 0:14:08.720 --> 0:14:12.440 sixty six, he accepted a job as professor of physics 0:14:12.480 --> 0:14:15.760 at the University of Kentucky. While in that role, he 0:14:15.800 --> 0:14:19.720 continued doing research into atomic physics, but his team was 0:14:19.800 --> 0:14:23.120 running into some obstacles, particularly in the use of a 0:14:23.200 --> 0:14:27.640 vander graphic accelerator, which is an electro static generator that 0:14:27.760 --> 0:14:31.640 can be used as a particle accelerator. To quote the Minerals, 0:14:31.680 --> 0:14:36.600 Metals and Materials Society, which has a PDF about these devices, quote, 0:14:37.120 --> 0:14:40.520 a high potential difference is built up and maintained on 0:14:40.560 --> 0:14:44.920 a smooth conducting surface by the continuous transfer of positive 0:14:44.920 --> 0:14:48.840 static charges from a moving belt to the surface. When 0:14:48.960 --> 0:14:52.720 used as a particle accelerator, and ion source is located 0:14:52.800 --> 0:14:56.960 inside the high voltage terminal. Ions are accelerated from the 0:14:57.000 --> 0:15:00.440 source to the target by the electric voltage between the 0:15:00.520 --> 0:15:06.040 high voltage supply and ground. Now that sounds complicated, but 0:15:06.320 --> 0:15:10.840 it's essentially a vandergraph generator and you've probably seen one 0:15:10.880 --> 0:15:13.440 of these, maybe non in person, but probably at least 0:15:13.480 --> 0:15:16.880 in a picture or video. They typically look like silver 0:15:17.160 --> 0:15:21.360 orbs that can give off a spectacular spark when they operate. 0:15:21.400 --> 0:15:25.000 There's typically a large silver orb on a pedestal, and 0:15:25.040 --> 0:15:28.440 then there's a smaller silver orb that's located a certain 0:15:28.480 --> 0:15:31.480 distance away from the large one, and when you turn 0:15:31.520 --> 0:15:36.440 it on, inside that pedestal, there is a belt that's 0:15:36.520 --> 0:15:39.200 running in a loop, and the belt is essentially building 0:15:39.280 --> 0:15:44.640 up a positive charge inside that large silver orb, and 0:15:44.680 --> 0:15:48.120 when the the voltage difference is enough between the large 0:15:48.120 --> 0:15:51.720 silver orb and the small silver orb, it will create 0:15:51.760 --> 0:15:55.560 a spark between the two. It can be really really spectacular. 0:15:55.720 --> 0:15:57.480 Now I'll have to do a full episode on those 0:15:57.520 --> 0:15:59.840 in the future. Let's get back to touch screens. So 0:16:00.000 --> 0:16:02.280 Hearst was working with others on his team to come 0:16:02.360 --> 0:16:06.200 up with what they called an electrically conductive paper in 0:16:06.320 --> 0:16:09.440 order to work with these vander Graph accelerators and to 0:16:10.000 --> 0:16:14.360 make their notes more um efficient. The paper would be 0:16:14.360 --> 0:16:17.720 able to pinpoint contact, and when mapped to an x 0:16:17.840 --> 0:16:21.200 Y coordinate system, could be used to specify a particular 0:16:21.240 --> 0:16:26.400 location of contact. So Herst thought, wait a minute, this 0:16:26.440 --> 0:16:29.080 could be used as an interface for computers, not just 0:16:29.120 --> 0:16:32.400 for registering a specific point in space for the purposes 0:16:32.440 --> 0:16:35.400 of research. So Heirst returned to work for the oak 0:16:35.480 --> 0:16:39.520 Ridge National Laboratory in ninety and he refined his idea. 0:16:39.720 --> 0:16:42.720 He worked with nine other Eggheads to create the first 0:16:42.800 --> 0:16:48.680 resistive touch screen. Okay, so, a resistive touch screen has 0:16:48.760 --> 0:16:52.320 a couple of layers, one of which is conductive and 0:16:52.360 --> 0:16:55.560 the other of which is resistive, meaning it resists the 0:16:55.600 --> 0:16:58.920 flow of electrons through the material, and separating those two 0:16:59.040 --> 0:17:03.720 layers are small spacers. Spacers are essentially little blocks of 0:17:03.880 --> 0:17:07.000 non conductive material. They act as as support structure. They 0:17:07.080 --> 0:17:10.040 keep the two layers from being in contact with one another, 0:17:10.560 --> 0:17:13.480 and there's also usually a scratch resistant layer on top 0:17:13.600 --> 0:17:17.320 of the surface that faces the user. Because using a 0:17:17.359 --> 0:17:20.960 resistive screen touch screen means that you're actually having to 0:17:21.000 --> 0:17:23.800 apply pressure on the touch screen. You're not just touching it, 0:17:23.800 --> 0:17:28.200 you're actually pressing it. So when you press a resistive screen, 0:17:28.440 --> 0:17:31.919 you apply that little bit of pressure. The conductive and 0:17:31.960 --> 0:17:36.760 resistive layers move closer together, they're flexible, and eventually they 0:17:36.800 --> 0:17:40.320 touch each other. Now both layers have an electrical current 0:17:40.400 --> 0:17:44.080 running through them, and when they make contact, the electrical 0:17:44.119 --> 0:17:49.080 field changes, and sensors and a microprocessor detect and analyze 0:17:49.119 --> 0:17:51.879 that point of contact and register it so that the 0:17:51.920 --> 0:17:54.880 device does whatever it is you wanted to do, from 0:17:54.880 --> 0:17:59.080 allowing you to make a digital signature to executing a command. Now, 0:17:59.160 --> 0:18:03.080 unlike a capac poet of screen, resistive screens don't require 0:18:03.119 --> 0:18:06.800 the point of contact to come from an electrically conductive material. 0:18:07.200 --> 0:18:10.679 A resistive screen doesn't care if the thing touching the 0:18:10.720 --> 0:18:13.679 screen is your finger, or it's a hot dog wiener, 0:18:14.280 --> 0:18:18.399 or a plastic stylus or a rock or whatever it 0:18:18.560 --> 0:18:22.399 is that's applying the pressure. All the electrical activity is 0:18:22.440 --> 0:18:26.320 contained within those layers that make up the outer part 0:18:26.359 --> 0:18:29.159 of the screen. So you can operate a device with 0:18:29.200 --> 0:18:33.200 a resistive touch screen even if you're wearing non conductive gloves. 0:18:33.520 --> 0:18:36.200 And if the screen were to get a little wet, 0:18:36.560 --> 0:18:38.680 you never want your electronics to really get wet. But 0:18:38.720 --> 0:18:40.800 let's say a little water gets on it, it wouldn't 0:18:40.800 --> 0:18:44.359 affect the performance. That's different from a capacitive screen. If 0:18:44.400 --> 0:18:46.919 you've ever had a smartphone get a little bit of 0:18:46.920 --> 0:18:48.920 water on it. Let's say it's a very light rain 0:18:49.119 --> 0:18:50.919 and you're trying to use your smartphone, you might have 0:18:50.960 --> 0:18:54.280 encountered some problems with it. Well. Capacitive touch screens don't 0:18:54.280 --> 0:18:56.400 work so well when they get a little water on them. 0:18:56.800 --> 0:19:01.639 It messes with this ability to detect the actual point 0:19:01.680 --> 0:19:07.240 of contact with a conductive surface. So resistive screens don't 0:19:07.280 --> 0:19:09.760 have that issue, although you still shouldn't really operate them 0:19:09.760 --> 0:19:13.040 in the rain. Now that being said, resistive touch screens 0:19:13.240 --> 0:19:16.400 tend to be harder to read and to see what's 0:19:16.440 --> 0:19:19.240 on the screen. They require more layers than a capacity 0:19:19.240 --> 0:19:21.880 of screen does, and they tend to reflect a lot 0:19:21.880 --> 0:19:25.800 more ambient light than capacitive screens. Plus, while they are 0:19:25.960 --> 0:19:30.359 pretty hardy, they do rely on detecting pressure, and depending 0:19:30.400 --> 0:19:32.480 on how hard people are pushing while they're trying to 0:19:32.560 --> 0:19:36.080 use these things, it can cause some wear and tear 0:19:36.240 --> 0:19:39.560 on the device. If the spacers that separate those two 0:19:39.680 --> 0:19:42.600 screens get damaged, then the screen can end up having 0:19:42.760 --> 0:19:46.440 points of contact before you've even touched it, which sends 0:19:46.560 --> 0:19:49.479 erroneous signals to the microprocess or it doesn't actually know 0:19:49.560 --> 0:19:53.720 where you're trying to touch it because it's getting conflicting information. Also, 0:19:54.160 --> 0:19:57.400 they were limited to detecting a single point of contact 0:19:57.600 --> 0:20:01.119 which eliminated the possibility for a multi touch Still, because 0:20:01.119 --> 0:20:03.600 they could stand up to a lot of punishment and 0:20:03.640 --> 0:20:06.240 they could work in different environments, they found a lot 0:20:06.240 --> 0:20:11.400 of applications in different technologies, particularly in stuff like military tech. Now, 0:20:11.440 --> 0:20:15.240 just one year after Hurst's resistive touch screen approach made 0:20:15.280 --> 0:20:20.560 the news, the University of Illinois introduced the PLATO for system. 0:20:20.560 --> 0:20:26.840 PLATO stands for Programmed Logic for Automatic Teaching Operations. One 0:20:26.840 --> 0:20:30.040 of the components of this system was an orange plasma 0:20:30.119 --> 0:20:36.040 display with touch screen capability, But unlike the previous inventions, 0:20:36.440 --> 0:20:41.240 this approach relied upon an infrared touch panel. All right, well, then, 0:20:41.280 --> 0:20:45.080 how does an infrared touch panel work. Well, imagine that 0:20:45.160 --> 0:20:47.399 you have an array of l e ED s that 0:20:47.480 --> 0:20:51.160 emit light in the infrared spectrum, so they're like tiny 0:20:51.280 --> 0:20:56.080 little infrared flashlights. Infrared is outside the visible spectrum of light. 0:20:56.160 --> 0:20:58.280 So to us it would seem as if an LED 0:20:58.440 --> 0:21:01.000 light was off because we can't see that light. But 0:21:01.080 --> 0:21:04.280 in fact, it would be beaming this infrared light across 0:21:04.440 --> 0:21:07.760 the surface of a screen, and on the other side 0:21:07.840 --> 0:21:10.480 of the beam would be a photo cell. So, in 0:21:10.520 --> 0:21:12.919 other words, a light sensor, and it's a sensor at 0:21:13.000 --> 0:21:17.240 tuned specifically to detecting that frequency of infrared light that 0:21:17.359 --> 0:21:21.359 it was paired with. So if you could see these lights, 0:21:21.600 --> 0:21:24.680 it would look like a laser grid, kind of like 0:21:24.720 --> 0:21:28.719 admission impossible or Tom Cruise is coming down from the ceiling. 0:21:29.000 --> 0:21:33.320 It's pretty awesome scene. But that's what infrared touch screen 0:21:33.359 --> 0:21:36.159 would look like if you could see those infrared beams. Now, 0:21:36.200 --> 0:21:39.160 if the beam remains unbroken, then it's clear there's no 0:21:39.200 --> 0:21:42.359 contact with the screen. If the sensors keep on picking 0:21:42.440 --> 0:21:45.359 up the light, they just say, all right, nothing's touching. 0:21:45.880 --> 0:21:50.120 But if something that blocks the light that's between the 0:21:50.240 --> 0:21:52.520 l e ED that's emitting the light and the photo cell, 0:21:52.960 --> 0:21:56.359 that interruption would indicate that something has touched the screen. 0:21:56.960 --> 0:21:59.119 And by arranging the l e d s and the 0:21:59.160 --> 0:22:02.800 photo cells and having them paired up in columns and 0:22:02.880 --> 0:22:06.480 in rows as a grid system, then you have a 0:22:06.520 --> 0:22:09.320 whole net of those invisible beams. Touching a point on 0:22:09.359 --> 0:22:13.200 the screen would interrupt both horizontal and vertical beams along 0:22:13.240 --> 0:22:18.080 the surface, So a microprocessor could detect which photo cells 0:22:18.080 --> 0:22:21.840 had registered the interruption and then plot the point where 0:22:21.880 --> 0:22:25.480 that happened. So it's very similar to plotting a point 0:22:25.560 --> 0:22:29.200 on a grid in math class. Like the resist of screens, 0:22:29.680 --> 0:22:33.040 this approach had the benefit of working with any light 0:22:33.080 --> 0:22:36.040 blocking material. It did not have to be electrically conductive, 0:22:36.680 --> 0:22:39.359 so a plastic stylus works just as well as a 0:22:39.400 --> 0:22:42.879 finger if the technology is implemented properly. Also, there's no 0:22:42.960 --> 0:22:46.680 need to work in thin metallic wires in the screen itself, 0:22:46.720 --> 0:22:50.200 because the screen is not what's detecting the touch. It's 0:22:50.280 --> 0:22:54.000 this laser grid essentially not really lasers, but this led 0:22:54.160 --> 0:22:58.480 grid with the photo cells, so the screen wouldn't have 0:22:58.520 --> 0:23:01.600 any wires in it. It would be brighter and provide 0:23:01.600 --> 0:23:05.399 more clarity than early capacity and resist of versions could. 0:23:05.920 --> 0:23:09.400 That was a big advantage. The infrared approach would see 0:23:09.520 --> 0:23:13.000 use in the nineteen eighties in the HP one fifty. 0:23:13.240 --> 0:23:16.040 That was a computer system from well then Hewlett Packard 0:23:16.400 --> 0:23:21.000 before they became just HP and it costs the princely 0:23:21.240 --> 0:23:25.760 sum of two thousand, seven hundred ninety five dollars in 0:23:25.880 --> 0:23:29.320 ninety three, but if we have adjust that for inflation, 0:23:30.000 --> 0:23:33.120 that means in today's money it would cost about seven thousand, 0:23:33.160 --> 0:23:37.040 two hundred dollars. Yikes. The HP one fifty version, or 0:23:37.119 --> 0:23:39.880 portly had some issues that that made it less practical. 0:23:39.960 --> 0:23:43.560 So I imagine that, uh, the fact that it wasn't 0:23:43.600 --> 0:23:46.359 working perfectly and that the price tag was so high 0:23:46.560 --> 0:23:48.560 meant it didn't get a whole lot of traction in 0:23:48.560 --> 0:23:52.080 the market. Later on, devices like the Sony E reader 0:23:52.240 --> 0:23:56.040 would actually adopt this technology. Now around the same time 0:23:56.080 --> 0:23:58.920 that the infrared system debuted in the mid nineteen seventies, 0:23:59.320 --> 0:24:03.879 g why Zapp Finel and Chris Herold of the Architecture 0:24:03.960 --> 0:24:05.879 Machine Group at M I T. And I know I 0:24:05.960 --> 0:24:09.480 butchered their names. I apologize anyway, they created a touch 0:24:09.520 --> 0:24:13.680 screen interface that could detect not just touch but also pressure. 0:24:14.119 --> 0:24:16.920 I mean it wasn't like a resistive screen in that sense. 0:24:17.160 --> 0:24:20.160 It could actually detect how much pressure you were applying 0:24:20.320 --> 0:24:23.119 to the screen. In fact, the system could detect up 0:24:23.119 --> 0:24:27.560 to eight different signals from a single touch point, including torque, 0:24:28.040 --> 0:24:30.080 which meant you could push your finger on the screen 0:24:30.640 --> 0:24:33.320 and you add some pressure to it and then twist 0:24:33.520 --> 0:24:36.760 your finger, and the interface could detect that you were 0:24:36.760 --> 0:24:41.800