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LED Skin Care Technology
and Mythology:
The Half-Truth & Folklore


From NASA, to Wavelengths, to Penetration Levels, to Duty Cycles, to Wave Destruction with Two or More LED Wavelengths ... an extended read – because it regrettably has to be …

In the skincare industry, related to LED technology, you may have heard it all – which shouldn't be confused with actually knowing it all. Because, as in many arenas, what we 'hear' – and what we have read – can't always be relied upon as truth in the absolute sense. Make coffee and strap yourselves in, people. We've got something of a ride ahead …

No Matter How Many Times You've Read It, NASA Didn't Actually Invent Or Develop The LED – and to describe it even as 'NASA Technology', in any proprietary sense, is a bit of a stretch, including many of the associated modalities.

But seemingly most distributors of LED Photo-Rejuvenation devices want you to think so (or worse - think so, themselves) — as if it should matter in any event. Still, they woo you into believing you’re buying the latest in ‘Space Age Technology’ – that you’re getting the skincare tech enjoyed by The Jetsons, in short. And who, after all, knows more about science than frigging NASA? That, alone, should sell you. Indeed, some LED skincare distributors even put images of the Space Shuttle hurling through space in their promotions to seemingly prove it (the Space Shuttle program being the first to use LEDs, as told). Moreover, as so many makers and distributors of 'LED Skincare Machines' essentially copy one another's 'promotional templates', this piece of folklore has been repeated so often it’s been regarded as fact in absolute terms. But it isn’t. Not quite. Not ... really.

The origins of the LED, it can be argued - or suggested - goes back to 1907, in Marconi Labs … but that would might be a bit of a reach. It’s then that it was discovered that applying a low DC voltage to silicon crystal emitted a (very) small amount of light. In 1927 the first ‘white paper’ on solid-state (non-filament – like an LED) light emission was published. Then things kind of came to a standstill – during a depression and a World War. It was in 1955 that an engineer working at RCA observed that some light could be emitted from an electrical diode (L.E.D., as an acronym for Light Emitting Diode). Fast-Forward to 1961, when engineers at Texas Instruments developed an infrared LED. It couldn’t be seen by the human eye, technically, but ‘it was there’. In 1962, General Electric created the first visible-light LED. It was red. A bit dim by today's standards, yes - but it surely glowed.

Now, for those of us who were interested in electronics as kids (we were a weird and eccentric bunch), we could walk into any Radio Shack store in the early 70s and buy LEDs off the shelf. Hell, reaching back into our own, rather extensive electronics parts catalog archives, here they were – then featured in the Radio Shack catalog … in 1974.

A Return to Childhood, 1974:

Yes, LEDs were readily available off the shelf at Radio Shack as seen in this catalog capture from 1974, among other places -  such as Lafayette and Arrow Electronics, to name a few.

The very first available were red, 660 nanometer units - and the prices wouldn't go up much since for even brighter units. Those in the 650~660 range would - and remain - among the least expensive LEDs made (in the millions of units), used in stereos or most anything that used indicator lights. Now they're in kids sneakers, even.

Still available in a variety of power levels (though not 'ultra-high') for about the same price - and that would be the consumer price.

Prior to that, Radio Shack had an in-store catalog where LEDs could be had in 1971 – some 10 years prior to the first Space Shuttle launch of 1981. And, as children, we didn't have to break into Area 51 to get them. Moreover, LEDs had already begun to show up consumer electronics, such as FM stereo receivers, as indicator lights – replacing the small incandescent or neon bulbs used previously.

So, what of NASA? In truth, their first use of LEDs was as indicators lights (much like FM stereo receivers) because they were very light in weight and had very low power consumption – two things of significant interest to those engineering spacecrafts. But what the skincare industry refers to pertains to NASA's non-space exploration of some LED wavelengths being used for cell regeneration and other forms of bio-stimulation – in both humans and plants. To advance these explorations – looking for higher-output LEDs of selected wavelengths, they essentially farmed out the engineering aspects of these LEDs to an electronics manufacturing firm who worked in unison with the Medical College of Wisconsin, with both keeping in communication with NASA as the 'end client' via The Marshall Space Flight Center. This led to what became colloquially know as the 'NASA LED', but others – such as Fairchild and National Semiconductor – were also working on increasingly higher-output LEDs and, in fact, what was described as the first 'high-brightness' LED would date back to 1976. The 'NASA LED', as called, would be a creation of the 1990s. But there's more …

NASA's interest in using 'light application' of particular wavelengths for cell regeneration and bio-stimulation was prompted by research and light-based modalities already established in the late 1960s – just using low-level lasers, initially – in place of LEDs.

None of this is to slight or to, in any way, diminish the work of NASA. We love NASA and grieve every time they have to endure funding cutbacks. But moreover, they aren't trying to promote a product. Others are. It's called 'piggyback marketing' – trying to associate oneself with the better recognized and accomplished endeavors of others – as old as Madison Avenue, itself. But this promotional ploy would be the equivalent of a maker of frying pans proclaiming that their product is based on NASA technology because it uses Teflon – which many people believe NASA was also responsible for. It was invented in 1938 by DuPont. NASA simply used the pre-existing technology – as they did with LEDs (in addition to expanding on pre-existing research). NASA also didn't invent Velcro as another myth-buster. We're just setting the record straight here in an industry – our industry – that often gets so much wrong ... or 'not wholly accurate', to be more kind. And "innacurracies" continue to plague many things, with increased frequency, as we'll see …

By the way ... None of the NASA wavelengths (680nm, 730nm, 880nm) – that were used individually in isolation, not in combination – are employed in truly professional photo-rejuvenation equipment, with most all operating below 650 nanometers for cosmetic / esthetic applications - and with reason.. Much has been explored since NASA with other and more specific targets. There has also since been some notable advances in LED technologies, themselves. But let's explore further ...

There IS no ONE 'BEST' wavelength, combination of wavelengths, pulse frequency, or pulse width ('duty cycle') … even though there are some wavelengths that may not be the best.

Many of you have perused the internet skincare boards where subjects related to photo-rejuvenation / photo-modulation frequently discuss the best wavelength (in nanometers) for light-based modalities. Some come across as authoritarian and definitive in tone, but are really rehashes of something someone read somewhere else, presented as a 'voice of experience'. The problem: This is no one best wavelength for photo-rejuvenation, outside what might be considered as a range of wavelengths, from around 585nm to nominally 660nm. While it can be generally said (with some nuanced exceptions) that 'red' wavelengths leaning towards 'the low 600s' – approaching amber – do something of a better job with pushing lymphatic fluids, and somewhat higher numbers (longer wavelength) do a bit better with red-based anomalies – such as Rosacea, there's more to the story ...

Particularly as it relates to photo-modulation (pulsed output), the wavelength is only one part of a three-part equation: Wavelength / Pulse Frequency / Pulse Width. Changing any one of these parameters will influence the parameters of the other two. Each can be considered as a sliding scale with cross-interaction among and between the parameters. For example, exploring two different 'red' LEDs, 635nm and 660nm, a well-versed design engineer will adjust the number of pulses per second (frequency) – against the pulse width (how long each, individual pulse lasts in time – sometimes referred to as 'duty cycle'). Juggling each of these three parameters can yield the optimum results for a given LED, regardless of which particular LED is chosen for the design (within a wavelength range). In short, there are a range of usable wavelengths possible without any one – in isolation – possessing any innate superiority in the general sense. It's just how one plays the numbers in that three-part equation at the engineering end.

The Three Part Recipe as A Moving Equation

As one moves up and down (or 'side to side') with the desired wavelength, the
other two parameters have to change (moving either 'left or right') to optimize the
wavelength performance. Each is a 'sliding' parameter for the really good designer.

But yes, there's still a little more. There's always more …

Aside from a 635nm LED having eight times the optical output of a 650-660nm LED (with the latter almost invariably being 'consumer-electronics' LEDs, not true MED-Grade) – if all other parameters were equal – there are surely some advantages to using LEDs that are lower than the 650-660 nanometer range. Again, one can get a better lymphatic push with LEDs at around 635nm or below – while still being able to successfully address issues such as Rosacea and other ruddy-type problems. But to argue a decisive superiority between 625nm and 635nm, say, is without merit when other parameters in their respective outputs are adjusted properly. In fact, it might be useful to consider that the once-popular (and expensive) GentleWaves units (company sold long ago to another who oddly never pursued it further) got their FDA approval for esthetic applications with LEDs operating at 590 nanometers, looking amber/yellow to the eye.

So why have 650-650nm LED wavelengths been somewhat popular in more recent days? They didn't used to be – not for cosmetic / esthetic applications. But an increasing number of 'photo-rejuvenation' devices – both 'at-home' units, as well as an increasing number of those cited as 'professional' devices – have started to use 'consumer electronics' LEDs ... Operating at 650-660nm, they remain the least expensive LEDs to use. As these were the first wavelengths commercially available in the 1970s, they're most commonly used in a number of consumer applications. They're made by the bagfuls. Millions upon millions of them. The massively high production numbers of this wavelength makes them the most inexpensive of all LEDs known as it relates to parts costs (the same could be said of the 'white' LEDs used in flashlights and such - and additionally don't have the 'burden' of having to be wavelength-specific).

Still, there are those who might argue that LEDs in the 650-660nm range – having a somewhat longer wavelength – will penetrate more deeply. But … the truth is … there's more to that story and we'll be covering that further down in an upcoming section – along with the some of the key differences between 'consumer-electronics' LEDs and those more regarded as scientific / MED-grade LEDs later on. For now, just make a couple of mental notes on what you've just read in the paragraphs above. But let's move on to 'Duty Cycle' …

Some years ago we read one website on the Internet proclaiming that LEDs have a 50% 'Duty Cycle', whereby they're 'on' half of the time – and 'off' half of the time. True to what is far too commonly internet form, that would be … flatly false. LEDs have no innate duty cycle of their own. They're steady-state in output. Only a circuit they're connected to can modulate their on-off state (duty cycle) – when applicable, such as in modulated photo-rejuvenation. What is true is that the 50% Duty Cycle is among the most popular used by many distributors of LED photo-rejuvenation machines that modulate – whether proving best for a given LED wavelength or not (remember, it's a three-part equation where 'duty cycle' really refers to 'pulse width' in engineering terms). Why then, so popular? Again, it often comes down to production costs. A '50% Circuit' that 'blinks' is readily available as an inexpensive, ready-made, off-the-shelf circuit that's used in many products – including bicycle safety flashers and such.

And yet … we read of one 'study' that proclaimed that the 50% Duty Cycle proved 'best' for collagen regeneration. The problem: That might have proven true as it related to the particular LED wavelength in use – combined with the pulse frequency (how many pulses per second) as part of that three-part equation. But change any one of the two parameters surrounding the 'duty cycle' and 'the show's over'.

As a general rule, longer duty cycles (longer pulse width) will have greater exposure efficiency as there's more 'on-time' than 'off-time' to the cycle. Engineer the long-pulse to work best with a given wavelength by also adjusting the number of pulses per second, and you're good to go. Many pulse modulation units 'blink' at a rate far faster that the eye/mind can perceive, it should be noted …

The eye – and, more significantly, the mind – begins to integrate the pulses as perceived continuous light when the pulse rate approaches 20 pulses per second by way of a phenomenon known as the 'Persistence of Vision' where the mind holds onto what it's just seen for a fraction of a second and can 'blend' it with the next repetitive event. It's essentially what has always allowed motion picture to work. In the theater, you're essentially watching 24 frames (think 'pulses') coming out of the projector gate that you perceive as continuous motion. These days, 'digital projection' is more common in modern movie houses, but the same theory (and practice) applies.

So what's the 'best' pulse frequency? Again, there is no 'best' as it has to relate to the other two operational parameters. Some pulse circuits are blazingly fast. Others are so slow they can be detected by the human eye with ease. Here's something of a trend, however. While not definitive in the absolute sense, a visible pulse rate would be far more commonly associated with LED-based pain relief devices (which so many photo-rejuvenation units incorrectly copied from) and aren't generally applicable as being best for esthetic purposes. With regret, there are devices where the 'blink rate' is made to be deliberately visible because it impresses with something of a 'light show' at skincare conventions – whether it proves to be the most effective or not, based on the other parameters. This should come as no surprise as the skin care industry is no less capable of 'flash' than any other product sector.

In a related aside, some may have observed and counter that high-powered IPL (Intense Pulse Light) units operate as a notably slow pulse rate. The thing is – that's principally because that technology has to (in addition to taking a different approach, entirely). Most are 'flash tube' based. An electrical capacitor has to first 'fill-up' (charge) before it rapidly dumps its stored energy into the flash tube. In fact … you know how you often have to wait for your camera flash to be ready to fire? It's the same thing. You and your flash are waiting for a capacitor to charge up. IPL units are just like that, only their flash tubes are operating at a specific wavelength. And, again – their entire approach to light-based skincare is different, often including another set or modalities.

Before we move on, let it be said that we don't wish to imply that those who haven't struck an intelligent balance – or engineering 'recipe' – are producing products that 'don't work outright, per se. Rather, what we are saying is that there are an abundance of LED products (now, more than ever) – great and small, cheap and pricey – that haven't been even nearly optimized. Much more could otherwise be coaxed, but whether it be to reduce production costs or – yes – a matter of distributor technical ignorance … or both, so much more could be pulled from the skincare procedure – and at a much faster rate. Some … will never know.


Monochromatic Vs. Polychromatic: Isn't Having More Than One LED Wavelength In A Single Head Better – Or At Least More Convenient & Less Costly?

Think again. Because the answer to such a question is, most generally, no ...

Devices that operate two wavelengths at once will encounter a piece of high school physics as it relates to light: ‘Destructive Interference’ - where two (or more) different waveforms collide and have a cancellation effect, reducing or eliminating the desired wavelengths if they were otherwise used in isolation. Like two pebbles thrown into a pond, where the two resulting waves collide in the overlap, the individual waves become ‘disturbed’.

Something easy to see with the human eye – as Destructive Interference in action - would be when one combines blue and red light, say. These two wavelengths exist at opposite ends of the rainbow and, used in combination, ‘beat one another up’, as if 'natural enemies' of one another. The eye will see the ‘mix’ as magenta (as a direct result of destructive interference). That is, neither pure red or pure blue, along with their base wavelengths, exists anymore — nor all of their attendant benefits, not in full. Each has been significantly diminished by the other — and magenta, odd though it may seem, doesn’t actually exist in nature - not as part of the rainbow. It’s a ‘synthesized’ color. The two waves combined may result in the same amplitude, but the final output doesn’t represent either of the two original waves. And all of this is true regardless of the relative output amplitude between the waves where either wavelength may have a lower output than the other. That’s just two different sized pebbles cast into the same pond.

In fact, hell … Given that so many in the skincare industry speak of NASA, here's an explanatory graphic we located some years ago from NASA's own website that covered the very concept of Destructive Interference (sometimes also called Wave Propogation Interference) …

Oh, LOOK! What have we here?!

NASA's own graphic that pictorially describes the cancellation of two coincidental light waves operating at different wavelengths by way of 'Destructive Interference.

Let it be noted that the 'flat line' after the equal sign doesn't mean 'zero output', as in 'no light' whatsoever. What it actually represents is the absence of the two original wavelengths in their pure form, relative to having otherwise been used in isolation, monochromatically.

There you go, NASA aficionados. So while two (or more?!) wavelengths in the same head – particularly when operating at the same time – may seem 'convenient' and 'less costly', it can potentially cost you – big time – as it relates to the speed and quality of the result. This is not "a matter of opinion", people. It's Physics – and not even particularly esoteric physics. Think High School Physics. Related to the same, here's a mind-blower: Take primary red, blue and green LEDs (all being used in skincare) of equal output amplitudes, fire them all into the same space, and you'll end up with … white light.

Three light beams - in the 'popular' colors!

Red for general photo-rejuvenation, blue for acne, green for melanocyte regulation. But if you were to lay out all three at once ... you might as well treat your clients with a standard light bulb.

By the way, for those of you into infrared, it doesn't get a 'pass-go' in any of this. Just because it's essentially 'invisible' and you can't 'see it' doesn't mean it doesn't exist as a waveform - subject to the very same interactions relating to Destructive Interference with two or more wavelengths.

Want a practical example of detructive interference in application? Good enough. Fog lights - should your car be so equipped. They're amber for a reason. For while we perceive fog a 'gray', it actually contains a high blue component. The amber portion of the spectrum assists in canceling the blue spectrum in fog by way destructive interference.  Yes, 'red' could also be used, but amber offers better general visibilty for the driver because of the human eye's non-linear spectral sensitivity. In any event, imagine then, firing off a red LED in the presence of a blue LED (which would serve up an even higher level of destructive interference, wholly independent of the human eye).

But is there a solution? Kind of – even though potentially creating another problem … For heads that might contain both red and blue in the same casing, there needs to be a function that will shut one of the two wavelengths down – completely – not simply 'dimming' one. In short, you'd select either red or blue in our example. But there is a potential compromise in this form factor concerning LED 'real estate' – that is, the layout of the LEDs. Every LED wavelength needs to take up its own space. Consider each wavelength – red and blue – being laid out in respective rows, side by side. What happens is that each wavelength row has to be interrupted (separated) by an adjacent row that's covering the other wavelength. In the aggregate, you've now reduced the output, per cm/2, to nominally one-half for each wavelength of what it otherwise would've been if just one LED wavelength had fully occupied the entire space, instead. But there's more …

In an effort to obtain relatively even coverage among the LEDs of a common wavelength when they've been 'space-interrupted' – separated by a different LED type, the projection angle of each LED now has to be widened. That seems simple enough, but it can come with a cost … With all other parameters being equal, the broader the LED beam, the lower the lumen output of the LED, reducing the per cm/2 exposure … yet again. So, you now have two strikes against you – all when one thought they'd get 'the best value' with a multi-wavelength head "in one convenient location". And if the mistake had further been made of operating the two wavelengths at once – in the same instant – that means three strikes.

But let's walk this back just a bit … As it relates to the optical distribution of a given wavelength, putting the collective output power aside for the moment, we can calculate that having two wavelengths nestled closely together, side by side, is feasible (if, again, each wavelength can be turned on and off individually). Yes, you'll still have about one-half the power for each of the two wavelengths present, but as it relates to projection angle – without excessively spotty coverage … yes, 'doable'.

The far bigger problem – one of exponential proportions – is when one now endeavors to load three wavelengths as an 'all in one' form factor where each wavelength's closest neighbor is 'three blocks over' on a given axis. The physical spacing of each, individual wavelength reaches beyond the LED's capability for even coverage – even using the widest LED projection angle available (120 degrees) – at close, actual operational distances. And you don't want your LED head or panel located a foot or so away, rapidly losing lumen output power with distance by way of 'The Inverse Square Law' (yet another piece of High School Physics). Yes, the long-throw distance will eventually integrate the separated beam angles, but as such a distance … it simply won't matter anymore.

Real Estate as Location, Location, Location

LED 'lighting strips' have sometimes been used, even as we know of only one parts supplier who loads the boards with 'hi-flux', Scientific / MED-Grade LEDs - with most others originally intended for ornamental lighting use (cove lighting, under-bar, etc.). Some are rigid boards; others are flexible strips. One currently popular LED system even let's you see them, unprotected, out in the open. But let's put that aside for the moment. We're talking about wavelength distribution, using this format as an easy example.

While one may get away with two boards of different wavelengths (as long as they're individually switchable) - if with other compromises - attempting to load three into the product form factor is beyond 'stretching it'. There's a reason that the suppliers of these pre-fab boards space the individual LEDs at nominally 3/4" (~19mm) centers - at most - on what we can call the 'Y' axis along the length of the board (top to bottom). That's the maximum spacing that can be used - using the widest LED projection angle available to get relatively even coverage. But tri-board spacing along the 'X' axis can only deliver spotty coverage unless placed rather much farther away from the target for the beams to intersect and integrate. Again, not "a matter of opinion". It's simple calculation.

Two more things as it relates to this section before we continue to the following section …

There have long been 'RGB' LEDs where any of the three primary colors (wavelengths) – red, blue, and green – can be output from the same LED. Moreover, their inputs are 'switchable' so one could select the individual wavelengths, outputting just one at a time. So wouldn't it be cool if we used these for photo-rejuvenation devices where all of the tri-color LEDs could be nestled closely to one another while having the ability to output each, individual wavelength? … Yes, it would be very, very cool, indeed. But there's a problem …

While LEDs are innately cool-running devices at their exterior – on the outside – they can be relatively 'hot' (at least in circuit component terms) on the inside. A tri-color, 'RGB' LED essentially has to cram three LED component 'dies' into one LED housing. To do this, each individual interior component has to be made much smaller. With this, the internal components have far less ability to dissipate heat away from themselves. If one tries to run them at 'high power' – as what's needed in professional photo-rejuvenation devices – the LED would go into 'thermal shutdown' (as an engineering term). Said another way … the LED would self-destruct. Ouch.

As advances are made in future LED technologies, the RGB Tri-Color LEDs would show great promise for photo-rejuvenation therapies. But as of this day – regrettably, no. And we've been waiting for 15 years as of this date (which we pretty much anticipated, knowing what was involved).

Okay – just one more thing as it relates to 'destructive interference' among two (or more) LEDs operating 'at the same time' for future reference ... There is a somewhat esoteric, tricked-out piece of circuit magic where two different LED wavelength types – red and blue, say – can seemingly be on at the same instant as seen by the human eye (giving that 'magenta glow' that you generally don't want), but not 'seen' as such by the human skin. The skin and its underlying structure will only 'see' the individual wavelengths in any given instant. To date, we've yet to see a single LED photo-rejuvenation device employ the technique. To pull it off successfully – to do it well – takes design intelligence and great circuit acumen - which we've done in our Palette Panel system by interlacing the wavelengths, back and forth.

The Take-Away (regarding a number of product categories, actually)? :
That which may - at first glance - seem 'versatile' in its ability to 'do everything', can potentially do so at the expense of  everything.

The Related Aside: The More LEDs In A Head or Panel -The Better, Right?
Not Necessarily True. Not At All, Potentially.

If we were to consider the most common form factor for LEDs - round or barrel type with a domed top, there are a variety of sizes available: 1.5mm. 3.0mm. 5mm, and even 10mm - some few beyond. Moreover, for each LED, they're made with a variety of projection angles, from 10 to 120 degrees. In consideration of these parameters, it's entirely possible for a unit with far fewer LEDs to have a decidedly higher per/cm2 output. As a rule, smaller LEDs can't disipate the internal heat away fast enough, so their power output has to be limited relative to larger LED form factors. So while a given head or panel may be able to fit in numerically more of the smaller, less powerful LEDs, their collective output can end up being less than a unit with notably fewer LEDs that - in balance - can have a higher output, both collectively and on a per/cm2 basis. A good design engineer knows this and will strike a good marraige between an LED's physical size (along with its potential output) and its projection angle - if allowed. But, with regret, so many skincare hardware devices are designed around marketing appeal, rather than on sound engineering principles. In short, the number of LEDs shouldn't be the parameter that becomes one's deal-maker or breaker.


A Deeper Look at Wavelength Penetration

Here's a subject that's been treated and discussed in such a 'definitive' way, you wouldn't think there'd be anything more to consider. After all, red wavelengths penetrate deeper into the skin and underlying tissue than blue wavelengths, right? And 'near-infrared' penetrates further, still. And surely, the deeper the penetration, the better (not inviting jokes, here). But, alas – again – there's more to the story …

With some variations, you may see different penetration levels stated for given wavelengths … A 4mm depth for blue, say – and 10+mm for LEDs operating somewhere in the red range of wavelengths, as examples. But what happens when that blue LED hits the 4mm mark? Does the light simply stop? Does it hit a brick wall of some sort? Is there a magic and invisible switch of some kind that ceremoniously turns it off? In a word, no. It keeps going until it encounters something decidedly opaque that brings it to an end – or at least prompts an extreme and rapid level of attenuation. Let's consider this more as it relates to penetration levels …

In the actual sciences – regrettably too often at odds with what you've read in our skincare industry – the penetration parameters are described as follows: 'Penetration Depth' reflects how deep any electromagnetic radiation (that would include 'light') can penetrate into a given material (including the body), more specifically defined as the level when the light falls to nominally 37% of its original (lumen) value. That is, no brick wall; no magic off switch. It can keep going, if with further attenuation (true, even in 'open air' by way of 'The Inverse Square Law – but that's another subject). All of this is significant …

Note that, as more specifically defined correctly by the scientific community, they use the very important words referring to the light source's "original value" (KEYWORD ALERT!). So, technically, if we were to have a blue LED of a higher luminance level than another red LED, at a 4mm penetration target, the blue LED could have a notably higher lumen level at that target than the 'deeper penetrating' red … and the same could be said even at a 10mm target. Remember, the light keeps traveling even after it reaches the 37% attenuation point. In other words, it's not simply the stated, nominal penetration level of a given LED – but of greater practical significance – how much lumen level exists at a given target, independent of its wavelength. Said another way, it's not simply the numerical value given for penetration levels in millimeters, but how much power you have when you get there. This is why true, professional-level photo-rejuvenation devices aim for the highest lumen level output available from modern LED technology. But wait. There's even more …

Let's introduce you to what will likely be a new term and concept for many of you – because the skincare industry never talks about it, perhaps leading us to believe that they don't know much of it. It's called 'Absorption Coefficient'. It sounds pretty esoteric and involved, doesn't it? Still, it's every bit as important – arguably more so – than 'stated' nominal penetration depth …

Let's take the comparison between the red and blue LED we spoke of above – only this time, they'll have identical lumen outputs. Depending upon the complexion at hand, a blue LED can potentially 'push deeper' than the red LED operating at the same output level. Say what? Yes …

Let's take an easy example of something you may frequently encounter: Rosacea. This red-based skin anomaly will have a much higher absorption rate relative to red light than any other wavelength. It is, in effect, why you see Rosacea as 'red' in the first place (same for a piece of red construction paper, for that matter). The red wavelength will be absorbed like a sponge by the Rosacea and won't have much projection to a deeper level beyond it. In this instance – as just one instance – the 'shallower' blue wavelength will shoot right past it to a deeper level that the red LED of the very same luminosity. There's good news in this! You want the red wavelengths to be absorbed by the Rosacea for maximum benefit.

But it might be noted that this notion extends outside of Rosacea. We just picked an easy to understand example. Indeed, there can be different 'absorption coefficients' for each Fitzpatrick skin type, light to dark. Consider this in a related matter … LEDs with wavelengths at or below 635 nanometers will better push the excess lymphatic fluids out of the face – and this is directly related to the absorption coefficient, independent of its 'penetration level'. Let's take a quick Field Trip to the water ...

FIELD TRIP: Here's a graphic from the University of Hawaii showing light penetration depth levels in water ...

Yes, the relative depths of the wavelengths are notably deep - meters, not millimeters. Sure, it's water, you surely note. But take a moment and see if you notice something else? .... (draws a sip of coffee) ... Do you see it? ... Note how the blue wavelengths run decidedly deeper that the red range just the opposite of what you're accustomed to (or have read about). This is directly related to the absorption coefficient ...

By the way ... Did we mention ... that human skin contains 64% water - and the muscles below contain a staggering 79% water? And even the bones contain 31% (so much for "dry as a bone"). You see, basic text book figures can be thrown decidedly off when the absorption coefficient is also considered ... Yes, this may mess with your head, we know.

But what makes the absorption coefficient potentially more important than the nominally-stated penetration depth level of a given LED wavelength in practical, real-world terms? Whether using Red, Blue or Green LEDs – any one of them – as it relates to the face (in addition to the décolleté, generally), you'll hit skull before you run out of light 'oomph'. So the take-away here is – as long as you're using high-output LEDs used in genuinely professional machines – you should have little practical concern regarding penetration levels of any particular wavelength. There would be a greater argument and consideration for Body Treatments, but you're not likely to be using a shallow-depth blue head for acne on one's upper thigh. As to infrared or 'near-infrared', these longer wavelengths have only been approved by the FDA for mild to moderate pain relief – never for cosmetic / esthetic purposes … ever.

An LED is An LED is An LED … Not.

And so one wonders why professional, LED-based photo-rejuvenation machines as 'so expensive' when one can buy a Bell & Howell 'Light Bar' with 60 (white) LEDs for $20, as seen on TV, and ultimately place it in the garage over the workbench. And then there's the 'Atomic Beam' LED lantern for the same price. More so, there are those who ponder why there are handheld LED skincare devices that are only $100 ~ $200, say – while there are dedicated professional systems that hover over the $10,000 mark. Funny … The very same people won't question why there are stereo loudspeakers that cost well over $1,000, even $10,000(!) – each – when they can buy a pair of speakers for $100 at Best Buy. And the Best Buy speakers are even 'larger' in physical size! They additionally don't ponder why professional photographers use expensive and rigged-out Nikon or Canon camera systems with expensive lenses when there's a camera in one's phone.

We've heard a few of our Esthetician friends tell us stories of how a couple of their Esthetician friends bought LED devices on eBay or Amazon – wherever, having seen that the LEDs operate at the 'same wavelength' as "the big boys". Some even 'blink', so it must be 'the same thing'. This sort of decision, not simply out of a willingness to believe, but a desire to believe. We kind of understand it. The motif can be seen in a number of product markets, wholly unrelated to LED devices. But as it relates to professional skincare, for every 'contraption' in a Day Spa, there ultimately will be a 'Home Shopping Network' offering – or what we call 'The Home Version of The Game', somewhat akin to 'Jeopardy' in a cardboard box.

There are some few Estheticians who reason that they can buy an inexpensive LED unit, simply put 'Photo Rejuvenation' or 'LED Light Therapy' on their menu and still charge $95 a session for it … You don't want to be among them. You'll not only be hurting an industry filled with other, fellow-Estheticians - while diminishing the reputation of LED applications, but you'll also end up hurting yourself in time, delivering diminished results relative to the Spa a block over that's operating a true Pro machine - not one simply labeled as 'Pro'…

Moreover, imagine the Esthetician delivering a 'Photo Facial' with an inexpensive unit they believe is "the same thing" and one week the client realizes they're being treated with something that looks oddly reminiscent of something they saw on late-night TV. They easily calculate that they can buy "the same thing" for around $150, say, and do "the same thing" at home – outside of the initial, relatively low cost. In either event, they're not getting all of what photo-rejuvenation is capable of – either from the thrifty Esthetician … or by way of their own, at-home treatments.

But to make matters worse, over more recent years – aside from the inexpensive units that are often essentially LED 'flashlights', just loaded with 'colored' LEDs, rather than white – we've seen an increasing number of somewhat pricey offerings (>$1500), cited as 'professional', that are also using common, garden-variety, consumer-electronic components – including the LEDs (originally designed for ornamental purposes). It's become more of a 'buyer beware' market than what we would've previously thought possible, particularly in the past 5-6 years, say. But let's consider just a couple of key differences in LEDs …

Just Because Apples & Oranges Are Both Regarded As Fruit
Doesn't Mean They're The Same Food.

To abbreviate the numerous nuances and 'qualities' of LEDs, it might be most useful to break them down into two general groups: Consumer Electronics LEDs (that have surrounded you for years in other products, right down to the very same infrared LEDs used in your TV remote) ... and then those that would be regarded as Scientific / Medical-Grade LEDs …

First, that which have been classified as Scientific / MED-Grade LEDs have a very high 'flux level' resulting in an extremely high output, relative to the far more prevalent consumer-electronics LEDs. In fact, you wouldn't want to have these 'high-end' LEDs staring at you (or you at them) in something like your FM stereo receiver, no less in the dashboard of your car. While they won't actually 'blind you', many might simply describe them as 'blinding'. They're notably bright – if varying with wavelength because the human eye is more sensitive to some colors than others, being non-linear in sensitivity. While there are consumer LEDs that might be considered as 'bright' (those aside from 'white' LEDs used in flashlights, say), none will compare to this high-end genre of LEDs. Some few designs use 'optical amplification' in addition.

Secondly, Scientific / MED-Grade LEDs are very accurate relative to their stated wavelength specifications. Back when we were buying consumer-grade LEDs at Radio Shack as kids, you could flip the package around and read the general specifications (before RS did away with them in their packaging). They'd commonly read 660nm … +/- 10%. Do some quick math in your head and you'll soon realize just how huge of a variation that 10% can be, relative to 660. In truth, they far more commonly measured to be within 5%, but that's still a large 'tolerance' variation on either side of the stated 'nominal' wavelength. This, as people debate over which is 'better' – 635nm or 650nm – even though they might not know which actual peak wavelength they're holding in their hand. But let's consider this further …

Even in these more contemporary times, a consumer-grade LED can still possess as much as a fairly large 5% variation relative to stated wavelength. Does this matter when, as we stated before, there is "no one 'best' wavelength"? … Yes, it can still matter – and very much so for those designing and producing photo-modulation circuits to drive the LEDS. Let's consider how …

Remember that for modulated photo-rejuvenation devices, there are three parts to the 'recipe' equation: Wavelength / Pulse Frequency / Duty Cycle (Pulse Width). To do things well, it's something of a delicate recipe where the proportions of ingredients matter. Really matter. But imagine working on this – or any three-part equation – where the absolute value of one parameter isn't entirely known. Without it, you can't accurately calculate or adjust the other two parameters to maximize performance. And the faster the pulse, the more accurate the other parameters need to be. That's why true, Scientific /MED-Grade LEDs have a guaranteed accuracy tolerance of less that 1%. In fact, when measured, they usually fall within 0.5% of stated specification. This accuracy, by the way, can also be quite important with non-modulated circuits for other scientific applications in no way related to photo-rejuvenation. It's why they're made.

So combine that with – again – much higher and more efficient output, along with the decidedly tighter wavelength tolerances. Now add the fact that very few in the Opto-Electronics industry even make them in the first place resulting in low production runs relative to the consumer electronics LEDs that are made in the millions by many opto-electronic manufacturers. Indeed, 'select grades' are available for all electronic 'semiconductor' devices – which is what LEDs are – as well as for 'passive' components such as resistors and capacitors with tight tolerances as used in precision pulse circuits where the timing is a matter of milliseconds.

All considerations combined, you now have a comparatively pricey LED – often ten to twenty times that of a generic LED as a 'part cost', depending on selected wavelength. It's, again, not too far removed from those $1,000 speakers relative to the $100 Best Buy Specials. It comes down to the quality of components within those expensive 'speaker boxes', from the individual drivers (woofers and tweeters, say), to the internal crossover network you never see as a frequency dividing network. The reason for it all? Simply a better product yielding a better result … in very realizable terms. And yes – it cost some money to produce such a product. Still, with regret, in the skincare industry we've seen hardware examples – of all types, not just the LED-based – that are selling you "$1,000 speakers using the $100 components" ...

In consideration of all of the above, we again state that those devices that have taken the 'economy route' and/or have used the outer fringes of a "fudge factor" are not necessarily completely bogus, producing zero results. They're just operating on those outer fringes of "what could have been" had the devices been well engineered and optimized. But do consider that being a 'Professional' is about 'optimization'. It, in fact, defines professionalism by way of skill, craft, experience and knowledge where many of those professions require professional tools to achieve that optimization. It's what they come to you for as something they readily can't do at home. Better knowledge and experience … combined with the better tools. But even the best and most experienced of Estheticians can't coax the most from the sub-par. Still, with regret, as LED-based modalities have increasingly become part of the skincare/wellness lexicon among the general public (a good thing for you), there's been an exponential increase of those who have hastened to jump on the LED equipment bandwagon – and doing so with the least-expensive production cost as just one path of least resistance. Not just the inexpensive examples – but that which has too frequently extended into what are often pricey offerings.

But before we head to close, we give you some interesting, quick tidbits in …

In An Aside …The Bonus Round!

1 – The FDA has, indeed, approved some specific modalities associated with LED applications (both esthetic and pain-related) within a given set of guidelines. Great! But as it relates to devices that have been specifically 'cleared' by the FDA, know this (as a jaw-dropper for some of you): The FDA never actually tests – no less even sees the devices they 'clear' (in the esthetic /pain-relief sector). It's mere paperwork where a manufacturer or distributor indicates that their product offering falls within the general guidelines that have already been established by the FDA. That is, 'clearance' is based on the information the manufacturer or distributor provides – 'on paper'. Then one writes a check to go along with the paperwork. We know. We’ve been there. As such, 'FDA Clearance' doesn't actually suggest any innate superiority. This very notion extends into another area often used to impress …

2 – Patents. The US Patent and Trademark Office receives thousands upon thousands of patent applications each year. The majority, after what can sometimes be a long backlog in instances ('patent pending') are 'approved' – just about 89% of them, currently. And as some who work for the Patent Office would tell you, the lion's share of those are marginal in concept with others being – well – silly. Most never even make it to any marketplace, but they will have their patent filed (and approved). They merely represent someone's 'unique idea' – independent of actual merit. That is, technically, you could file a patent for an eight-sided, octagon tire (because, you know, no one ever thought of it before). Yes, it would roll like crap – but you'd have your patent (as one not likely to be challenged in the future).

So when a manufacturer boasts that their product "uses our patented technology", it doesn't mean they're Thomas Edison. More to the point, it in no way is an indication of supremacy. It's principally a legal protection – just often used as a catch-phrase designed to impress … and it often works! For much in the skincare equipment industry has increasingly become a matter of 'the staging'.

3 – 'Born in The USA' – OR Not… Many might see this as somewhat incidental, but it's still rather interesting … One can have their entire circuit board made in China – with the cases being fabricated in Mexico, say – and as long as the circuit boards are loaded into the case within the territorial limits of the United States, one is allowed to legally state 'Made in The USA' (in our own factory!). Yeah.

NOW … in closing …

If Popularity Is The Benchmark Of 'The Best', Then McDonalds Makes The Best Hamburgers

And so it often goes as it relates to 'popularity'.

Still, many of you – like us – have been at the skincare shows and conventions for a number of years. For some, as many as 20 years – maybe even a bit more. Think back. We all can remember LED photo-rejuvenation machines (some of which were simply relabeled pain relief devices) that were capturing a buzz. Names you would instantly recognize. Some were, in fact, the same machine internally as another – just dressed in slightly different clothing, carrying a different nameplate and logo. A few were proprietary designs. But among the most popular offerings in the early to mid-2000s, say – so many would since become vague memories. Some are still made and sold, yes. Others, gone. For those who have 'been around' at the shows, you can probably call up the names in your head.

In a related aside, for those familiar with the audio community, most audiophiles (and engineers) will tell you that the best of audio playback equipment is compised of product names most people have never heard of.

There will always be market cycles and trending waves of popularity. But for you long-timers, you know that today's 'Wave Peak' of popularity often becomes tomorrow's second-hand flood at Ebay.

Do your own thinking, people – and yes, we've given you a fair amount to think about – while only covering some of the key points (really). We openly invite you to 'check our work'. But, by our deliberate design, so much of what we've discussed can be found in any good Physics book with a section on light (or one dedicated to light behaviors) – and such a book will have no product to sell you … outside of knowledge. Other things, at least some of them, can be confirmed by a really good and enthusiastic student in a high school Electronics 101 class.

It's with tremendous regret that the skincare community has increasingly become the worst place to go for truly accurate information – and yes – that would include several 'studies' that miss key parameter elements, right out of the gate (they used to be much better in the late 90s / early 2000s, actually).

So, again – do your own thinking. And, in the interest of that endeavor, we hope we've enlightened more than we've confused.

Be well – and be smart,
Your 'Esty' and Engineering Friends at DermaWave


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