Speaker 1: Welcome to Text Stuff, a production from I Heart Radio.
Speaker 1: Hey there, and welcome to Text Stuff. I'm your host,
Speaker 1: Jonathan Strickland. I'm an executive producer with I Heart Radio,
Speaker 1: and I love all things tech. And you know, there
Speaker 1: are times when I sit down to choose a topic
Speaker 1: for Text Stuff and I just come up empty. Either
Speaker 1: I'll only come across stuff that I've already covered in
Speaker 1: the past, or I'll see stuff that just doesn't really
Speaker 1: ignite my curiosity. And honestly, that just makes researching and
Speaker 1: writing and recording these episodes that much more difficult. I
Speaker 1: feel like if I'm jazzed about it, it just comes
Speaker 1: more easily. But once in a while, I'll see either
Speaker 1: an interesting article or a video, or sometimes just a headline,
Speaker 1: and that makes me think I should probably cover that technology.
Speaker 1: And that's what happened to me on the morning of
Speaker 1: April six, twenty twenty, which is the morning that I
Speaker 1: wrote this sentence right here. Now, um, I'm recording this
Speaker 1: on April, so there's a lot of time shifting going
Speaker 1: on here. But the headline I saw was on tech
Speaker 1: Crunch and it read Chinese startup ro kid pitches COVID
Speaker 1: nineteen detection glasses in US, and I know we've had
Speaker 1: a lot of talk about COVID nineteen, but that's not
Speaker 1: what this episode is really going to be about. See,
Speaker 1: those detection glasses don't magically pick up that someone has
Speaker 1: been infected by the coronavirus. It's not like they see
Speaker 1: the coronavirus crawling on the person or anything that would
Speaker 1: really be a trick. No, these are thermal imaging glasses
Speaker 1: with some added bells and whistles, like the ability to
Speaker 1: take photos or record video. That's not necessarily part of
Speaker 1: thermal imaging cameras or sensors. But really, these glasses don't
Speaker 1: tell you if someone has COVID nineteen. They might tell
Speaker 1: you if someone has an elevated body temperature. Now, keeping
Speaker 1: in mind that some folks might be contagious with COVID
Speaker 1: nineteen and not have any symptoms, that means these glasses
Speaker 1: are helpful but not a perfect way to screen people.
Speaker 1: The glasses wouldn't indicate that an asymptomatic person is a threat,
Speaker 1: for example, and other people might have an elevated body temperature.
Speaker 1: You know, people with immuno compromise systems frequently have this problem,
Speaker 1: but they may not necessarily have COVID nineteen. So what
Speaker 1: I'm saying is that critical thinking and a broad spectrum
Speaker 1: approach to taking precautions is necessary, and that putting all
Speaker 1: our eggs in one basket is always a bad idea,
Speaker 1: And I would usually save that stuff for the end,
Speaker 1: but times being what they are, I felt it was
Speaker 1: important to address that first. Anytime anyone claims that they
Speaker 1: have a solution that solves a really complicated problem, it's
Speaker 1: good to take a closer look. But I want to
Speaker 1: talk about thermal imaging technology in general because it does work,
Speaker 1: it's incredibly precise, and it's super awesome stuff. Now, in
Speaker 1: a past episode, I covered how night vision works, and
Speaker 1: that can include normal imaging, but we typically think of
Speaker 1: a different kind of approach with night vision. You know,
Speaker 1: all the television shows and movies tend to show that
Speaker 1: kind of green vision, that green video where stuff is
Speaker 1: super bright. Well, that's really called image enhancement, and that
Speaker 1: method takes all available light that's in an environment and
Speaker 1: then amplifies the signal from that light to create a
Speaker 1: video with an intensity that is easier for us to perceive.
Speaker 1: Thermal imaging is different from that, So thermal imaging has
Speaker 1: to do with infrared light, which in turn, we cannot
Speaker 1: see with our eyeballs. It is invisible to us, but
Speaker 1: we can still sense it because it's heat. All objects
Speaker 1: in the universe omit some level of infrared radiation as
Speaker 1: long as those objects are above absolute zero. Some of
Speaker 1: them do it a lot more than others, you know,
Speaker 1: like stars and stuff. They emit way more infrared radiation.
Speaker 1: But we emit infrared radiation too. We humans were kind
Speaker 1: of like infrared light bulbs. I mean, granted, so is
Speaker 1: a light bulb and every other object to some extent.
Speaker 1: The visible spectrum of light, you know, the stuff that
Speaker 1: we can perceive with our eyes is bordered on either
Speaker 1: side of the electro magnetic spectrum by bands of light
Speaker 1: that are beyond our ability to see. At frequencies higher
Speaker 1: than visible light. So that means the wavelengths of these
Speaker 1: light waves are shorter. That would be ultra violet light
Speaker 1: or UV. At frequencies lower than visible light, or longer
Speaker 1: wavelengths of light, you get infrared. Now there's other stuff
Speaker 1: that goes beyond those bands as well. For example, if
Speaker 1: you keep going to higher frequencies and shorter wavelengths, you
Speaker 1: run into X rays and gamma rays, and if you
Speaker 1: keep going toward the longer wavelengths and lower frequencies, you'll
Speaker 1: hit microwaves and radio waves. The first recorded discovery of
Speaker 1: infrared light comes to us courtesy of smarty pants extraordinaire,
Speaker 1: Sir William Herschel. This guy is what you would call
Speaker 1: of von der Kind. First of all, he was born
Speaker 1: in Germany, so the word I use is linguistically appropriate. Secondly,
Speaker 1: he was a composer, he was an astronomer and just
Speaker 1: generally a scientifically minded guy. And he's the guy who
Speaker 1: discovered uranus the planet. And yes, I'm going to pronounce
Speaker 1: it that way, because to do it the other way
Speaker 1: makes it sound juvenile. He was also the grandfather of
Speaker 1: another William Herschel, who would go on to establish fingerprints
Speaker 1: as a means of authenticating documentation, but I've covered that
Speaker 1: in a different episode. So Billy Herschel the first was
Speaker 1: pontificating about the nature of light, and it was obvious
Speaker 1: that light carried heat with it. When you step out
Speaker 1: of the shade into the sunlight, you feel it. So
Speaker 1: Herschel was working with different types of colored glass. He
Speaker 1: was experimenting with different telescopes that he might be able
Speaker 1: to use to observe the Sun, because the Sun's rays
Speaker 1: are far too bright to stare at without the risk
Speaker 1: of injury. We all know this. You don't stare at
Speaker 1: the sun. So by using glass of different colors, he
Speaker 1: was hoping to reduce the amount of light coming in
Speaker 1: through the telescope so that he could still take a
Speaker 1: closer look at the Sun and make observations safely. But
Speaker 1: you discovered that some colors of glass seemed to reduce
Speaker 1: the amount of heat that was passing through his telescope,
Speaker 1: and others seemed to allow a great deal of heat
Speaker 1: to come through, including enough heat to potentially cause an injury,
Speaker 1: but this time due to heat rather than to the
Speaker 1: intensity of light damaging his eye. And he knew about
Speaker 1: how light could pass through a prism and would break
Speaker 1: apart into the different colors of light, and collectively those
Speaker 1: colors make up white light. What he wondered was if
Speaker 1: those colors carried different amounts of heat. So he set
Speaker 1: up an experiment and he used a prism to break
Speaker 1: light into the different bands of colors, and then he
Speaker 1: used a thermometer with the bulb end blackened by ink,
Speaker 1: and he used that to measure the temperature within each
Speaker 1: band of color. And he noticed as he measured the
Speaker 1: violet end of the spectrum, the temperature readings were lower,
Speaker 1: and towards the red end they were higher, and he
Speaker 1: decided to also test the area just beyond the red end.
Speaker 1: There was no visible light at that section, but he
Speaker 1: observed that it was at that area where the thermometer
Speaker 1: was registering the highest temperature. And this is the earliest
Speaker 1: recording of someone figuring out that there was something beyond
Speaker 1: the rainbow, so to speak. And yeah, I know, I
Speaker 1: misquoted a song just to make that reference. Herschel referred
Speaker 1: to this area beyond visible light as the thermometric spectrum.
Speaker 1: In early days, some would refer to it as dark
Speaker 1: heat or invisible rays. The term infrared wouldn't really come
Speaker 1: around until the other end of the nineteenth century, and
Speaker 1: there are no reliable records that indicate who actually coined
Speaker 1: the term, but whomever was responsible, it became the standard
Speaker 1: way to refer to this specific band of radiation. So
Speaker 1: I've used the term thermal imaging in this episode, and
Speaker 1: the reason I have is that it implies when we
Speaker 1: use these technologies that were not somehow magically seeing infrared radiation. Right,
Speaker 1: We're not able to suddenly see infrared light through this tech. Instead,
Speaker 1: what we're doing is we're using technology to detect infrared
Speaker 1: radiation or heat, and then using some sort of process
Speaker 1: to convert that data into a visual representation. For example,
Speaker 1: with thermal glasses, we'd see different colors that different intensities
Speaker 1: to indicate varying degrees of heat between objects. Typically we
Speaker 1: use colors like bright yellows, oranges, and reds to indicate
Speaker 1: hot surfaces, and greens and blues to indicate cooler surfaces,
Speaker 1: which is nice because that also corresponds to how much
Speaker 1: heat energy those bands of light carry. Not in a
Speaker 1: one to one scale, mind you, but the general principle remains,
Speaker 1: and we kind of grasp it, right, We say, Okay,
Speaker 1: this red thing is definitely hotter than that blue thing.
Speaker 1: But to be able to do all this, we first
Speaker 1: have to be able to detect and measure the heat
Speaker 1: coming from an object in a reliable way in the
Speaker 1: first place. Right. So, one of the cool things about
Speaker 1: physics is how seemingly unrelated factors are actually tied together.
Speaker 1: From the macro scale. That being the world that you
Speaker 1: and I live in most of the time. Anyway, some
Speaker 1: of you may have been having Honey I Shrunk the
Speaker 1: Kid's Adventures, and I'm all for it. But on the
Speaker 1: rand scale, it's not necessarily intuitive. But temperature can have
Speaker 1: a big impact on other stuff, such as electrical properties
Speaker 1: like conductivity and resistance. So just a reminder, conductivity describes
Speaker 1: a material's ability to act as a conduit for an
Speaker 1: electric charge, to allow an electric charge to pass through it.
Speaker 1: Resistance is the flip side of that coin. It's a
Speaker 1: material's tendency to resist an electrical charge. We can think
Speaker 1: of it kind of in terms of friction. If you
Speaker 1: have a very smooth floor that's been recently waxed, there's
Speaker 1: very little friction there, and you might slide all over it,
Speaker 1: perhaps without even intending to do so. But if you're
Speaker 1: on something like a rough concrete surface, there's a lot
Speaker 1: of friction and your attempts to slide would be met
Speaker 1: with a lot of resistance. Well, the electrical world, that's
Speaker 1: kind of analogous to conductivity and electrical resistance. Heat can
Speaker 1: change these properties. For example, even a good conductor has
Speaker 1: saw electrical resistance just like we can't entirely negate friction,
Speaker 1: even with our smoothest materials. But if you cool that
Speaker 1: conductor down, like way down, like colder than the depths
Speaker 1: of space, you can reduce its resistance, and depending on
Speaker 1: the material, you can reduce it all the way down
Speaker 1: to nothing. At that point you've got what's called a
Speaker 1: super conductor. Likewise, a conductive material will increase in resistance
Speaker 1: as it heats up, so temperature and electrical resistance have
Speaker 1: this kind of relationship. Now, the whole reason I went
Speaker 1: down that apparent bunny trail is that it brings us
Speaker 1: to an important component that would play a huge role
Speaker 1: in thermal sensors, and that's the bolometer. Now, when I
Speaker 1: first read this word, which is spelled b O l
Speaker 1: O m e t e R, I had not heard
Speaker 1: anyone pronounce it, and as many of us know, sometimes
Speaker 1: that means in our heads we have a very different pronunciation.
Speaker 1: So when I first read it, I thought it might
Speaker 1: be a bolo meter, and then I immediately second guess
Speaker 1: myself because I'm pretty sure a bolometer would be a
Speaker 1: device for measuring Texas neckties. So no, it's a bolometer. Now,
Speaker 1: to understand a bolometer. It helps if we also understand
Speaker 1: what a wheat Stone bridge is, and it's not an
Speaker 1: architectural thing. This is a type of circuit and its
Speaker 1: purpose is to measure the unknown electrical resistance of a material.
Speaker 1: It was first implemented in eighteen thirty three by Samuel
Speaker 1: Hunter Christie and later refined by Sir Charles Wheatstone in
Speaker 1: the eighteen forties. This is a little tricky to describe
Speaker 1: without the use of visual aids, but I'm going to
Speaker 1: give it a shot. All right, Imagine you have a
Speaker 1: perfect square. Now turn that perfect square forty five degrees
Speaker 1: so that it's a Diamond's got a top, left, right,
Speaker 1: and bottom point. And those four corners of this diamond
Speaker 1: present points of electric potential. And let's let's name the
Speaker 1: top point is A, the bottom point is B, so
Speaker 1: they're opposite each other. The left point is C, the
Speaker 1: right point is D, so they're opposite each other. Now,
Speaker 1: let's also imagine that C and D connect to each
Speaker 1: other with a horizontal line that cuts right through the
Speaker 1: middle of this diamond. So you've got a path going
Speaker 1: from C to D, as well as the uh the
Speaker 1: straight lines of the diamond from A to c A
Speaker 1: to D and then C two B and D two
Speaker 1: B the sides of the diamond. Those lines that I
Speaker 1: just mentioned connecting the points represent resistors. And here's the
Speaker 1: key when using a wheat stone bridge. You know the
Speaker 1: electrical resistance for three of those resistors. Those are ones
Speaker 1: that you have put in place. So you've got three
Speaker 1: resistors where you know the electrical resistance. The fourth resistor
Speaker 1: represents the material you're actually testing. You don't know its
Speaker 1: electrical resistance. So in our little amount engineering wheat stone bridge,
Speaker 1: let's say that the line between point D, which is
Speaker 1: the one that's on the right side of the diamond,
Speaker 1: and point B, which is on the bottom side of
Speaker 1: the diamond, that represents the resistor we're interested in. We're
Speaker 1: trying to figure out what is its electrical resistance. Now,
Speaker 1: another important point is that on the opposite side of
Speaker 1: the circuit, the line that's representing C the point on
Speaker 1: the left, and B on the bottom. So the other
Speaker 1: bottom leg that one is a resistor that we can
Speaker 1: actually adjust the electrical resistance. We can fine tune it.
Speaker 1: It's like a radio dial. You can just fine tune
Speaker 1: that electrical resistance by applying a difference of voltage between
Speaker 1: A at the top and BE at the bottom. We
Speaker 1: allow current to flow through this circuit, and if current
Speaker 1: can flow from point C on the left to point
Speaker 1: D on the right, or vice versa, it means the
Speaker 1: bridge is unbalanced. That means there's more resistance on one
Speaker 1: side of the circuit than the other. So we slowly
Speaker 1: start to find t that one leg that C B resistor,
Speaker 1: and we continue to fine tune it until no current
Speaker 1: is passing between points C and D. That would mean
Speaker 1: that the wheat stone bridge is in balance. It also
Speaker 1: means the ratio of resistance represented by the left side
Speaker 1: of the circuit has to be equal to the ratio
Speaker 1: of resistance on the right side. And we know the
Speaker 1: electrical resistance of three of those four resistors. So by
Speaker 1: knowing the ratio on one side and knowing half of
Speaker 1: the ratio on the other side, we can figure out
Speaker 1: the variable. Right. It's just a simple algebra problem. So
Speaker 1: you just solve for X and boom, you found the
Speaker 1: electrical resistance of that material you were testing. Why is
Speaker 1: all of that important, Well, it's because the bolometer is
Speaker 1: built upon the premise of the wheat stone bridge. In
Speaker 1: Pokemon terms. It would be an evolution. I'll explain in
Speaker 1: just a moment, but first let's take a quick break.
Speaker 1: Before the break, I described the wheat stone bridge circuit
Speaker 1: and how it allows researchers to determine the electrical resistance
Speaker 1: of a material. Now it's time to talk about bolometers
Speaker 1: and Samuel Pierre Pont Langley what a name. It's sp
Speaker 1: Langley's how he was typically referred to, Professor S. P. Langley.
Speaker 1: Langley was a lot of things. He wasn't just a professor.
Speaker 1: He was almost the inventor of the airplane. A couple
Speaker 1: of upstarts called the Right Brothers beat him to it.
Speaker 1: He was also an astronomer, and like Sir William Herschel
Speaker 1: nearly a century earlier, he wanted to find ways to
Speaker 1: study the solar energy that made it from the Sun
Speaker 1: to the Earth, And in eight seventy eight he invented
Speaker 1: an apparatus that could be used to measure the amount
Speaker 1: of infrared energy hitting a specific point. And this was
Speaker 1: the bolometer. So remember the wheat stone bridge I described earlier, Well,
Speaker 1: now imagine you've got the same sort of layout, except
Speaker 1: this time you know the electrical resistance of every leg
Speaker 1: in this circuit, so you're not you're not trying to
Speaker 1: figure out the electrical resistance You already know what it's
Speaker 1: supposed to be for all parts of this wheat stone
Speaker 1: bridge style circuit. However, the material you're using is very
Speaker 1: sensitive to changes in heat, which in turn changes the
Speaker 1: electrical resistance of those resistors like super super sensitive, even
Speaker 1: the shift of just one thousand of a degree celsius
Speaker 1: will make a change in its electrical resistance, So the
Speaker 1: electrical resistance of the materials changes. So rather than tuning
Speaker 1: in to find a specific electrical resistance as you would
Speaker 1: with a traditional wheat stone bridge, a volometer monitors the
Speaker 1: electrical resistance of a circuit, and the changes in resistance
Speaker 1: indicate a change in temperature. A bigger change in electrical
Speaker 1: resistance indicates a higher intensive of infrared radiation, meaning a
Speaker 1: bigger change in temperature. Langley invented an incredibly sensitive thermal detector.
Speaker 1: It was able to pick up incredibly small changes in
Speaker 1: heat from an enormous distance. Reportedly, with one of his
Speaker 1: refined thermal sensors using a bolometer, he could detect the
Speaker 1: body heat of a cow from four hundred meters away.
Speaker 1: The bolometer was that sensitive and would pick up the
Speaker 1: infrared energy coming off that cow, indicating that there was
Speaker 1: something in that spot that was generating more heat than
Speaker 1: the surrounding objects in that environment. So by measuring the
Speaker 1: changes in electrical resistance, you could work back to understand
Speaker 1: the intensity of the infrared radiation hitting that sensor. And
Speaker 1: this was really good for detecting differences in temperature, right,
Speaker 1: not necessarily getting an exact read out of the temperature
Speaker 1: of an object, but rather getting the difference between one
Speaker 1: object and say it's environment or another object, and hotter
Speaker 1: things give off more intense infra red radiation, so you
Speaker 1: can build up your knowledge base this way. There's a
Speaker 1: bit more to it than that. When we talk about
Speaker 1: modern bolometers, those get pretty complicated, and honestly, it gets
Speaker 1: to a point where I don't think I can really
Speaker 1: tackle an explanation that will mean anything without the use
Speaker 1: of visual aids. But the basic principle measuring infrared radiation
Speaker 1: through monitoring electrical changes remains the same. So again, this
Speaker 1: was sort of an indirect way to detect heat, right.
Speaker 1: I mean, the changes in temperature would affect the electrical
Speaker 1: resistance in the bolometer, and that's what we were actually measuring.
Speaker 1: We're not measuring heat, We're measuring electrical resistance that changes
Speaker 1: as a result of infrared radiation or heat, and then
Speaker 1: a meter measuring that resistance would indicate what was going on.
Speaker 1: But this meant researchers had to spend time to refine
Speaker 1: what that actually meant. They had to match the changes
Speaker 1: in electrical resistance to the differences in temperature. And this
Speaker 1: is a part of science and engineering that just blows
Speaker 1: my mind, not just that super smart people had to
Speaker 1: take some known phenomena and then make use of it,
Speaker 1: but then later refine that so that the use is
Speaker 1: more practical. We'd see a lot of further steps build
Speaker 1: upon this foundation. Bilometers could indicate changes in temperature, but
Speaker 1: it would take a lot more work and technology to
Speaker 1: use that data and then convert it again into something
Speaker 1: that could be presented visually as a thermal image or
Speaker 1: thermographic display. So with a bolometer based thermal imager, you've
Speaker 1: got infrared radiation which hits a thermal sensor, which changes
Speaker 1: its electrical resistance as a result, which a meter detects,
Speaker 1: which sends this metric to a processor which interprets that
Speaker 1: data and then converts it into a different type of
Speaker 1: information that can be displayed on a screen. This is
Speaker 1: what amazes me. So the bolometer would become a really
Speaker 1: important tool for astronomers, but it would take a bit
Speaker 1: longer to play a role in thermal imagers, though not
Speaker 1: too much longer. According to multiple sources, the first person
Speaker 1: to create a thermal television camera was the Hungarian born
Speaker 1: Kalman to Hanji in nineteen nine. He built it for
Speaker 1: Britain to use as part of their anti aircraft technologies
Speaker 1: after World War One. I wish I could tell you
Speaker 1: more about the technology of his device, but honestly, there's
Speaker 1: not much information I could find about how it actually worked.
Speaker 1: There's a general agreement that this is the first thermal
Speaker 1: imaging camera, though all of that could ultimately be pulling
Speaker 1: the information from a single source, which makes it less reliable.
Speaker 1: But I couldn't find much information on what the actual
Speaker 1: implementation to Hanyi used in his invention, and in a
Speaker 1: few sources, I found his device confused with a later
Speaker 1: thermographic camera that would be reportedly based off his invention,
Speaker 1: but was its own distinct thing. So while it appears
Speaker 1: The first thermal imaging camera dates to nine nine, and
Speaker 1: it was all about live images. I can't tell you
Speaker 1: a whole lot about it, and I'm sure there are
Speaker 1: patents out there for it, but my patent searches were
Speaker 1: not terribly fruitful. I couldn't find anything all the way
Speaker 1: back at nine that match the description. However, one thing
Speaker 1: I can say is that for the first few decades
Speaker 1: of thermal imaging, almost all the research and development for
Speaker 1: that technology fell to militaries around the world. Thermal detection
Speaker 1: in general was a big area of research, and engineers
Speaker 1: were trying to incorporate thermal sensors and stuff like missiles
Speaker 1: and torpedoes, and later on in rifle scopes and headsets,
Speaker 1: the idea being that this could be part of a
Speaker 1: guidance system to help an explosive projectile lock into a target.
Speaker 1: I mean a lot of military targets are also sources
Speaker 1: of considerable amounts of heat, such as warships, submarines, tanks,
Speaker 1: or aircraft. So a missile or torpedo that has a
Speaker 1: thermal sensor on it would be able to hone in
Speaker 1: on the heat source pretty easily. But by the nineteen fifties,
Speaker 1: other disciplines were also interested in making use of this technology,
Speaker 1: such as in medicine. There were some doctors who were
Speaker 1: hoping to use thermal imaging to help them do stuff
Speaker 1: like identify potentially cancerous tumors. The idea being that a
Speaker 1: cancerous tumor would likely consist of cells replicating at a
Speaker 1: faster rate than normal cells. Thus they would have a
Speaker 1: higher metabolic rate, and you would think that that would
Speaker 1: mean they would be generating more heat than healthy tissue.
Speaker 1: A device sensitive to minute differences in temperature and capable
Speaker 1: of displaying that information on a screen, particularly if you
Speaker 1: could do it in real time, would be handy if
Speaker 1: that hypothesis were to hold true. Now, I want to
Speaker 1: add that this particular approach isn't proven to be the
Speaker 1: most effective means for detecting a tumor, and that other
Speaker 1: methods such as mammograms are far moral liable and likely
Speaker 1: to catch cancer at earlier stages. But at the time
Speaker 1: there were doctors hoping that it might be a helpful technology. However,
Speaker 1: for most part, thermal imaging remained in the domain of
Speaker 1: the military around this time. So we're going to skip
Speaker 1: forward a bit to the development of a different kind
Speaker 1: of heat sensor. This one is based off pyroelectric materials.
Speaker 1: Pyro Electricity refers to a certain set of crystals that
Speaker 1: have large electric fields and that generate a voltage when
Speaker 1: they undergo changes in temperatures. This is similar to, but
Speaker 1: distinct from piezo electricity or piezo electricity if you prefer.
Speaker 1: Those are crystals that accumulate an electric charge after those
Speaker 1: crystals have been subjected to a mechanical stress. They also
Speaker 1: will vibrate if they are subjected to an electric charge.
Speaker 1: So the quartz crystal in a you know, classic watch
Speaker 1: is a piezoelectric crystal. Pyro electric is slightly different. This
Speaker 1: is in changes in temperature. That's where you get the voltage.
Speaker 1: Pyro Electric crystals generate voltages upon those temperature changes, but
Speaker 1: after a while, if the temperature remains constant, the voltage
Speaker 1: will decrease and eventually disappear. These aren't typically used in
Speaker 1: thermal sensors for cameras. They can be, but they're not
Speaker 1: typically used that way. They're commonly found in stuff like
Speaker 1: light switches that automate lights when they detect someone's in
Speaker 1: the area. We often think of these as motion sensors
Speaker 1: and I'm sure some of you out there have stories
Speaker 1: of being in, say I don't know, a bathroom when
Speaker 1: the lights automatically go out, and then you have to
Speaker 1: find creative ways to get the sensors to pick up
Speaker 1: on the fact that you're still in there and you're
Speaker 1: still attending to your dark business. Typically these aren't motion sensors.
Speaker 1: They can be, but they're not always. They often are
Speaker 1: heat sensors. So moving around isn't getting picked up by
Speaker 1: some sort of optical element, at least not in the
Speaker 1: visible spectrum, but rather you are generating a lot more
Speaker 1: infrared radiation as you're moving around, getting head up, and
Speaker 1: thus the sensor picks up this infrared radiation says, whoops,
Speaker 1: somebody's still in here, and then the light cell come
Speaker 1: on so that that warm body inside that bathroom can
Speaker 1: get down to business. Then there are thermo couples. Breaking
Speaker 1: down the name, we can figure out this has something
Speaker 1: to do with heat and it has to something or others, right,
Speaker 1: a couple. So in this case, the couple the something
Speaker 1: or others are strips of two different types of metal.
Speaker 1: The metals have to be specific types that will generate
Speaker 1: a voltage when the temperature of the two metals doesn't match,
Speaker 1: so the temperature of one metal is higher than the
Speaker 1: temperature of the other metal. So when infrared energy hits
Speaker 1: the strips of metal, the strip one of them is
Speaker 1: painted black that one will absorb more energy it heats
Speaker 1: up faster. The change in temperature causes a voltage to
Speaker 1: apply across the circuit and current flows. Typically you create
Speaker 1: a big collection of thermo couples into what is called
Speaker 1: a thermopile to do anything useful with it. All of
Speaker 1: these approaches rely on physical materials generating some sort of
Speaker 1: detectable and measurable response to changes in temperature, and over
Speaker 1: the decades, these sort of components would play a part
Speaker 1: in sensors in general and thermal imaging in particular. In
Speaker 1: nineteen sixty three, an engineer at the company Texas Instruments
Speaker 1: named Kirby Taylor invented a technology called forward looking Infrared
Speaker 1: or f l I R. FLEAR. Okay, so before f
Speaker 1: l I R, most thermal imaging systems used a single
Speaker 1: line of sensors. So just think of a line of
Speaker 1: these things, a vertical line or a horizontal line, and
Speaker 1: you would sweep that line of sensors across an area
Speaker 1: to pick up differences of temperatures, you would physically move
Speaker 1: the sensors across this area. The military would use these
Speaker 1: kind of sensors mounted on planes to do this. The
Speaker 1: planes could fly over an area and scan the area below.
Speaker 1: The line of sensors were perpendicular to the planes travel,
Speaker 1: so the planes flying forward, the line is perpendicular to
Speaker 1: that forward uh direction, and this allowed it to scan
Speaker 1: across the ground underneath. This approach was incapable of producing
Speaker 1: real time two dimensional images. You were getting slices essentially,
Speaker 1: and it would be useful for reconnaissance, such as if
Speaker 1: you wanted to identify, I don't know, a possible Soviet
Speaker 1: missile silo in Siberia or something, but you weren't getting
Speaker 1: a real time image of a heat map. Taylor worked
Speaker 1: on creating a forward looking thermal sensor, one that would
Speaker 1: use a scanning mirror to steer the sensors. So technically,
Speaker 1: what this mirror was doing was sweeping back and forth
Speaker 1: across the sensors, directing the infrared radiation coming in through
Speaker 1: the camera and in a coordinated way so that the
Speaker 1: processor on the other side of this could take the
Speaker 1: information and make a two dimensional image from it. The
Speaker 1: scanning mirror achieved the same effect as moving a line
Speaker 1: of sensors across an area, but you didn't have to
Speaker 1: move the sensors because the mirror was doing the moving
Speaker 1: for them. Now, there are two branching forms of thermal
Speaker 1: imaging sensors that I should mention from this point. There
Speaker 1: are uncooled detectors which can operate at normal temperatures. They
Speaker 1: don't require any special conditions apart from you know, the
Speaker 1: typical stuff like a source of power like a battery.
Speaker 1: Then there are cooled systems which require special cooling systems
Speaker 1: no big shock there to keep the sensors at a
Speaker 1: very low temperature. And these systems work with different types
Speaker 1: of infrared radiation. See, just like the visible light spectrum,
Speaker 1: infrared itself is a spectrum, but it's not just one
Speaker 1: band of frequencies. Right, You've got near infrared on one side.
Speaker 1: That's the side of the band that's best buds of
Speaker 1: the visible spectrum. Right, you've got red light. The red
Speaker 1: light then gradually gives way to near infrared, which is
Speaker 1: invisible to us, but it is much closer to the
Speaker 1: wavelength of red light. Then on the other end of
Speaker 1: the infrared spectrum is what's called long wave infrared, in
Speaker 1: between his midwave infrared. In general, uncooled detectors tend to
Speaker 1: work on the long wave infrared spectrum, while cooled detectors
Speaker 1: focus har har harror on the midwave spectrum. One thing
Speaker 1: that helped bring thermal imaging cameras out of the realm
Speaker 1: of the military, meaning it helped bring the cost down,
Speaker 1: was the development of micro bolometers. Now, a camera could
Speaker 1: have an array of micro bolometers acting like the pixels
Speaker 1: in a digital camera. The camera would bring in infrared
Speaker 1: light just as it would light in a visible spectrum,
Speaker 1: and it would aim that light to an array of
Speaker 1: micro bilometers, just like it would an image sensor in
Speaker 1: a digital camera, and the microprocessor would take the information
Speaker 1: coming from these micro bolometers and interpret it as differences
Speaker 1: in temperature, which in turn could be communicated to the
Speaker 1: user as different colors and levels of brightness to indicate
Speaker 1: which parts of an image were the warmest or coolest.
Speaker 1: I'll talk a bit more about cooled thermal detectors after
Speaker 1: the break. Cooled thermal cameras work on a different principle
Speaker 1: from the micro bilometers. Remember a bolometer describes the technology
Speaker 1: in which a component changes its electrical resistance in response
Speaker 1: to a change in temperature. Measuring that change in electrical
Speaker 1: resistance tells you how much infrared radiation the sensor has encountered.
Speaker 1: Cooled thermal sensors respond to individual photons of infrared light. Yeah,
Speaker 1: just because we can't see it doesn't mean that the
Speaker 1: photons aren't there. So these sensors are sometimes referred to
Speaker 1: as photon counters. These are incredibly precise sensors that can
Speaker 1: detect single photons colliding with them. They might then generate
Speaker 1: what's called a t t L pulse. T t L
Speaker 1: stands for transistor to transistor logic. You can think of
Speaker 1: it as a little digit counter clicker. The sensor picks
Speaker 1: up on a photon collision. There's a clique. It has
Speaker 1: a register to hit. In other words, if it registers
Speaker 1: many hits in a short amount of time, that can
Speaker 1: relate back to intensity, meaning you've found something pretty hot.
Speaker 1: It's super nifty stuff. Others might take a photon and
Speaker 1: generate an electron As a result, that electron would get
Speaker 1: stored in a capacitor and it honestly gets super duper
Speaker 1: technical and also gets beyond my level of familiarity pretty quickly.
Speaker 1: Suffice it to say that this approach is not quite
Speaker 1: the same thing as using a bolometer. There are photon
Speaker 1: counters for all sorts of frequencies of light, not just
Speaker 1: the infrared spectrum, but obviously I are or infrared, that's
Speaker 1: what we're interested in for our topic, So let's get
Speaker 1: back to these cooled thermal sensors. Cameras using the photon
Speaker 1: counting methodology have very short response times, which in turn
Speaker 1: allows for faster frame rates of video, so you get
Speaker 1: better video output than you would with an uncooled system.
Speaker 1: These cameras also have a greater level of sensitivity and
Speaker 1: can be more easily used to detect small differences in
Speaker 1: temperature within the field of view. They're also better at
Speaker 1: detecting thermal output from small objects and depicting those small
Speaker 1: shapes on camera in an accurate way, as opposed to
Speaker 1: an uncooled system, where if it's a small object that's
Speaker 1: giving out heat, chances are you're just going to see
Speaker 1: an unidentifiable blob of color representing that smaller object. You
Speaker 1: wouldn't be able to see what the thing was. You
Speaker 1: would have a rough idea of how warm or cold
Speaker 1: it was with respect to the other things in the environment.
Speaker 1: But that's about it. The cooled cameras come with some
Speaker 1: this advantages. First of all, they tend to be more
Speaker 1: expensive than uncooled systems, so that's a downside. And also
Speaker 1: that has to do partly with the fact that you've
Speaker 1: got a sensor that has to remain cryogenically cooled, and
Speaker 1: that in term requires special considerations and often a good
Speaker 1: deal of energy. It makes the cooled systems unsuitable for
Speaker 1: certain use cases like normal glasses, because I don't know
Speaker 1: about you, but I'm not too eager to put on
Speaker 1: a cryogenically cooled headset anytime soon. In a little film
Speaker 1: called Predator came out and it taught us that I
Speaker 1: don't got time to bleed, Okay. In that movie, a
Speaker 1: group of mercenaries, including the iconic Arnold Schwarzenegger, although I
Speaker 1: just I just quoted the equally iconic Jesse the body Ventura. Anyway,
Speaker 1: they end up becoming the targets of a planet trotting
Speaker 1: big game hunter alien, the titular Predator, and we get
Speaker 1: treat did to Predator vision a few times where we
Speaker 1: see the world from the perspective of this alien, and
Speaker 1: that includes heat vision. Schwarzenegger helps avoid the predator at
Speaker 1: one point by coating himself in mud to disguise his
Speaker 1: heat signature. That would only work for a short while
Speaker 1: because the thermal sensors initially would just pick up on
Speaker 1: the temperature of the mud, not the person under it,
Speaker 1: but your body heat would gradually raise the temperature of
Speaker 1: the mud to your own temperature, so soon you would
Speaker 1: just be a muddy, warm mess, and then shortly after
Speaker 1: that you'd become predator trophy material. Thermal cameras can see
Speaker 1: through stuff like smoke pretty effectively, and firefighters have used
Speaker 1: thermal cameras when entering smoke filled areas to help rescue
Speaker 1: people from dangerous situations. Uh, thermal cameras don't work so
Speaker 1: well in fog and rain because water droplets can scatter
Speaker 1: infrared radiation makes it harder to get a clear image.
Speaker 1: That being said, in certain rainy can sans they can
Speaker 1: be more effective than visible light sensors, so while it's
Speaker 1: not ideal, it's still an improvement over other methods in
Speaker 1: several cases. On top of that, you've got glass. Glass
Speaker 1: is highly reflective for light in the infrared range. Visible
Speaker 1: light can pass through transparent glass no problem, so you
Speaker 1: can see on the other side of a transparent pane
Speaker 1: of glass, but infrared light bounces off that glass like
Speaker 1: it's a mirror. So if you take a thermal image
Speaker 1: of someone who's wearing glasses, you'll see that the lenses
Speaker 1: are just these solid shapes of color. You can't see
Speaker 1: through them. You will be able to see the person's
Speaker 1: eyes because of that reflectivity. Highly reflective surfaces in general
Speaker 1: are a problem. Shiny metal can reflect infrared radiation, which
Speaker 1: means it can be hard to use thermal sensors if
Speaker 1: you want to monitor, say, machinery for signs of overheating.
Speaker 1: One cool thing you can do, and there are great
Speaker 1: photos of people doing this online, is take a photo
Speaker 1: of something warm, like I don't know, your foot inside
Speaker 1: an opaque plastic bag, I mean still attached to you.
Speaker 1: Don't don't remove your foot, but like put a plastic
Speaker 1: bag like a garbage bag or a bin liner, as
Speaker 1: my buddies across the pond would say, around your foot.
Speaker 1: So this is opaque. You cannot see through it, as
Speaker 1: long as that plastic isn't too thick. However, the infrared
Speaker 1: light will pass right through. Visible light gets blocked so
Speaker 1: you can't see your foot, but that infrared radiation passes
Speaker 1: straight through the bag, and a thermal imaging camera can
Speaker 1: still see your foot just fine. Inside of it. You
Speaker 1: also get this kind of nifty halo effect too. The
Speaker 1: Predator film helped bring thermal imaging cameras into the mainstream consciousness,
Speaker 1: but the equipment was still pretty expensive, so you weren't
Speaker 1: likely to find it outside of some limited commercial uses,
Speaker 1: and in the military, firefighters were using it. Heavy industry
Speaker 1: was starting to use it. It would take a while
Speaker 1: for the price to come down enough for inspectors to
Speaker 1: be able to use it, for example. But these days
Speaker 1: thermal cameras and smartphone thermal camera accessories are far more
Speaker 1: accessible than the early days of thermal imaging. It's still
Speaker 1: a relatively expensive technology. You're typically looking at a few
Speaker 1: hundred dollars for a basic thermal imaging camera, probably more
Speaker 1: than a thousand for something of really decent quality, and
Speaker 1: far more than that if you want something of professional quality.
Speaker 1: But that's still an incredible step down in price from
Speaker 1: what it used to be, and when you think about
Speaker 1: everything that has to happen to make thermal imaging possible,
Speaker 1: from detecting heat to measuring intensity to translating that into
Speaker 1: something we can see, all in real time. It's a
Speaker 1: heck of a thing. One thing I wanted to close
Speaker 1: this with is the concept of active I R sensors.
Speaker 1: I've really been talking about passive I R sensors, which detect, measure,
Speaker 1: and display thermal information from the environment. It's coming from
Speaker 1: the environment itself, but there are also active thermal sensors
Speaker 1: which both detect and project infrared radiation. So why do
Speaker 1: they do that? Well, think of it kind of like
Speaker 1: using a flashlight, except the light you're giving off is
Speaker 1: in the infrared spectrum, so we humans can't see that
Speaker 1: light unaided. So you might use something like this and say,
Speaker 1: I don't know, a nighttime military operation, so that no
Speaker 1: one would be the wiser, and you have people snooping
Speaker 1: around using these infrared flashlights and infrared sensors to be
Speaker 1: able to look at their environments in the dark. You
Speaker 1: would have the thermal sensor system, perhaps mounted in a
Speaker 1: head display. Inside that system would be the projector that
Speaker 1: sends out those infrared rays, and then the detector that
Speaker 1: picks up the reflected incoming infrared rays. It's just like
Speaker 1: visible light. When the infrared rays come out of the projector,
Speaker 1: when they hit something, they reflect off and then the
Speaker 1: sensor can pick up that reflection and then you get
Speaker 1: the redoubt in your display or the visualization in your display. Uh.
Speaker 1: That would work pretty well unless the person you're snooping
Speaker 1: around also happens to have thermal imaging sensors, because then
Speaker 1: they would see that beam coming out from your system
Speaker 1: as if it were a flashlight beam. They would be
Speaker 1: picked up. Active i R systems are used in lots
Speaker 1: of applications, such as in robotics. Many robots have active
Speaker 1: i R sensors in them as a way to avoid
Speaker 1: hitting obstacles. The projector sends out an infrared ray, and
Speaker 1: the sensor is looking out for infrared radiation in that
Speaker 1: same frequency band and above some sort of threshold. So
Speaker 1: not just like a tiny indicator has to hit above
Speaker 1: that for the robot to think, oh, there's something in
Speaker 1: my way. So when the sensor detects radiation at or
Speaker 1: above that threshold, it sends a signal that then gets
Speaker 1: acted upon in some way by the robot. An easy
Speaker 1: example This is a robotic vacuum cleaner that starts to
Speaker 1: approach a wall, and then when it gets to a
Speaker 1: certain distance, it's close enough where the infrared radiation coming
Speaker 1: from its projector bounces off the wall and gets picked
Speaker 1: back up by the sensor that tells the robot to
Speaker 1: stop moving forward, to turn and move in a different direction.
Speaker 1: Tuning stuff to a particular infrared frequency helps avoid interference,
Speaker 1: so not just like any infrared ray, but rather within
Speaker 1: this narrow band that's what it's looking for, so it's
Speaker 1: not likely to uh to misidentify another infrared source as
Speaker 1: being a problem. The Microsoft Connect Xbox per referral also
Speaker 1: uses a similar implementation of infrared active sensors to sense depth.
Speaker 1: This sensor includes a near infrared projector, so it's near
Speaker 1: infrared beams. Those are the beams that are still invisible
Speaker 1: to us but are closer to the red side of
Speaker 1: the visible light spectrum, and they can be detected by
Speaker 1: standard digital camera sensors. So the projector and sensors work
Speaker 1: together to measure the time of flight. That it's the
Speaker 1: moment the light leaves the projector to the moment when
Speaker 1: a sensor picks it up and then working backward by
Speaker 1: knowing how long it took the light to go out
Speaker 1: and come back. You know how far things are because
Speaker 1: you know about the constant of the speed of light.
Speaker 1: So the Microsoft system could determine how far away an
Speaker 1: object is, like the player from from the sensor. So
Speaker 1: this gives developers the option to include depth as a
Speaker 1: factor in games and applications that use the connect. So
Speaker 1: you wouldn't just have stuff that relies on movement within
Speaker 1: the two dimensional plane of up and down and left
Speaker 1: and right. It would also take in the third dimension
Speaker 1: of closer to or further from the connect. Now, I
Speaker 1: want you guys to know there's a lot of super
Speaker 1: technical stuff that I skipped over in this episode. There
Speaker 1: are things we could talk about with focal plane arrays
Speaker 1: and various materials used over the years, and thermal sensors,
Speaker 1: but I felt the important part was to get the
Speaker 1: basic understanding down. I think that's pretty cool or hot.
Speaker 1: I'm not sure which. I've misplaced my thermal glasses. And
Speaker 1: as for using them to screen people, as I said,
Speaker 1: it could be useful as a quick first pass for
Speaker 1: anyone who happens to have an elevated body temperature, but
Speaker 1: again that doesn't necessarily indicate a COVID nineteen infection. It's
Speaker 1: not enough of a precautionary measure all on its own.
Speaker 1: And that's not the fall of the technology. That tech
Speaker 1: can be incredibly precise. It's rather that the risks go
Speaker 1: beyond those who may just have a fever and like
Speaker 1: that might not be someone with COVID nineteen, or you
Speaker 1: might be overlooking people who do have COVID nineteen because
Speaker 1: they don't actually have a fever. Yet that as long
Speaker 1: as you overlook these possible vectors, infection will continue, which
Speaker 1: is why we should never consider any one approach to
Speaker 1: be sufficient. We have to take a combination of approaches
Speaker 1: if we want to put protective measures in place. As always,
Speaker 1: make sure you exercise critical thinking, give it a healthy
Speaker 1: dose of compassion, because without compassion, critical thinking is just
Speaker 1: cold and heartless. You gotta have both, and if you're
Speaker 1: able to apply both of them, then I think things
Speaker 1: will be okay. If you guys have suggestions for future
Speaker 1: episodes of tech stuff, whether it's a technology, a company,
Speaker 1: a trend in tech, anything like that, let me know.
Speaker 1: Reach out to me. You can get in touch with
Speaker 1: me on Twitter or Facebook to handle for both is
Speaker 1: tech Stuff h s W and I'll talk to You
Speaker 1: again really soon. Tex Stuff is an I Heart Radio production.
Speaker 1: For more podcasts from My Heart Radio, visit the i
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Speaker 1: your favorite shows.