Laser epilation.

[Pauline Aston]

Hello All,

First let me confess a dreadful secret: I'm a long term cross-dresser but
also a competent and experienced electronics design engineer. Unbelievable
but true! Over the years I've spent several thousand pounds on laser hair
removal (ugh I hear you say whereas I usually say ouch).

For those who don't know about this, the laser light resonates with the
melanin molecules in dark hair to produce local heating which kills the
root. Other tissue is ignored. Sadly it only works when the hair follicle
is in a growing phase which most are not at any given time. The net effect
is that many treatments are necessary and there are always some hairs left.

The laser companies cope with this by 'spotting'. That is instead of
charging to scan a whole area (for those interested it's a bee sting every
250mS as the head is moved) they go after individual hairs or clusters at
one and a half dollars
a shot, with an active head of about 9mm square! Count the hairs
on the back of your hand and see what that adds up to!

Now to the crux of my post: The light nowadays comes from semiconductor
lasers. I am a power supply designer and can produce controlled power
pulses at whatever level may be necessary to drive an appropriate laser
diode to produce an appropriate pulse. Because I'm after individual hairs,
not much more than a point source is necessary. I know what fluence,
duration
and wavelength is needed but I don't know anything about high power laser
diodes. Is there anyone who has any special knowledge? Is anything
possible for say a couple of hundred dollars?

Should anyone be reluctant to comment for safety reasons, be aware that I
value my own skin more than most and I'm technically competent.

I look forward to any replies.

Regards,

Pauline Aston.

PS. So many engineers are cross-dressers, MIT has it's own support club for
them!

 

[LesioQ]

Wavelength 800 to 900nm.

AFAIK the wavelength range is way broader than this.
Ruby 694nm lasers are (were) very popular and effective.
Also 1064nm YAGs are being used in epilation.

Look here:
http://www.lasertraining.com/med-33.htm
http://solarls.infonet.by/photoepilation_1_en.htm

LesioQ

 

[Mark Johnson]

I had electrolysis on my eyebrows every week for about 6 months,
and
boy, did it hurt! And now, 6 years later, there are still loads of
unwanted hairs growing.

Electrolysis is a nightmare. Laser epilation around the eye orbit is
apparentl possible providing there is bone for the laser head to be pressed
against. It's only done by a doctor and I for one wouldn't risk it!

Thanks for your interest.

Pauline Aston.

If this could be done with relative safety, myself and my wife, and no
doubt countless others would be interested in this project. I
investigated electrolysis in the past, as I get infected facial hairs
(for a long time just had a full beard). The woman who did (this was
a free sample trial of her service) it removed quite a bit from below
the corner of my mouth, but alas, it ALL returned . Did I mention the
full beard? I grew it back after the trial.

Maybe this is one that Sam oughta get involved with, and put it on his
Laser FAQ? My wife, like most women, struggle with unwanted hairs
here and there, and again, if this was fairly safe and relatively
inexpensive ($100-$150?), would be great "useful" project.

I'll keep looking here for more interest.

 

[Pauline Aston]

"Fleetie" <fleetie@fleetie.demon.co.uk> wrote in message
news:wmDOa.5264$ju6.94882@newsfep4-glfd.server.ntli.net...

Ok, let's do some sums:

I'll assume t=10ms, and intensity (per cm^2) E = 20J.cm^-2.
Wavelength need not concern us for the moment.

During the pulse, the intensity (power per cm^2) is obviously E/t,
so it's 2000 W/cm^2. That's some power!

Ok, now the cheapest CW high-power diode you're likely to find is say,
a 1W or 2W 808nm pump diode. Clearly 1W != 2000W, so you're going to
have to focus it down to a _lot_ less than 1cm^2. Let's see. To make
things easier, I'll assume it's a 2W diode.

We need a spot ((2W/2000W) * 1cm^2) in area to achieve the 2000W/cm^2
target. Assume it's a circular spot. The radius of 1cm^2 dot is
sqrt(1/pi) = 5.6mm, so we have a spot about 11.3mm in diameter.
So the diameter we need is (1/sqrt(1000)) times this, so the spot
must be about 0.36mm in diameter for us to get 2000W/cm^2.

It's do-able, and of course, you _will_ need to build a driver
circuit to make sure you get the same 10ms (or whatever) pulses
as with the real epilator, cos you sure don't want that kind of
power CW on your skin! Frazzling and smells of burning flesh aren't
what you need!

It may be possible to do, but working with a 0.3mm spot is going
to make it damn near useless. It'd be such fine work; you'd be
lucky to zap one follicle at a time. You're back to a situation
similar to that with electrolysis, where you've got to get them
one by one. Ok, you wouldn't have to worry about getting the needle
down inside the follicle, but aiming that beam would be just
a nightmare.

It's not worth it with a 2W laser diode.

You might be better off with something like one of those SSY1 YAG
flashlamp-pumped units, where you get the power from the shortness
of the pulse, and not from focussing down a low-power CW source to a
tiny spot.

Hello Martin,

Like I said I'm not up with laser diodes but just a couple of thoughts: The
first is they must have a transient thermal impedance which allows short
term high applied power. Second, how is their output related to overdrive.
Do they stop lasing or just become monumentally inefficient? How is life
against overdrive.

In terms of beam size, I'm not sure how fluence is related to dispersion by
the time it's penetrated say 5mm to the hair root. Pulse width required
seems to be related to the thermal time constant of the follicle (cooling
time). The pulse gets it hot quickly then the energy has to 'bleed' into
the root cells. Too long a pulse and substantial tissue damage occurs.

I look forward to more replies.

Pauline Aston.

 

[Fleetie]

Hello Martin,

Like I said I'm not up with laser diodes but just a couple of thoughts: The
first is they must have a transient thermal impedance which allows short
term high applied power. Second, how is their output related to overdrive.
Do they stop lasing or just become monumentally inefficient? How is life
against overdrive.

I don't think you can "buy" much power like that. Apparently
(and this is somewhat borne out by my limited experience of
killing LDs), laser diodes are far more sensitive to overcurrent
than normal LEDs, though I don't know by what mechanism. I see
what you're trying to do, but I still think you're onto a loser
with (say) a 2W nominal laser diode where the 2W is the heatsinked
CW rating. If you could make that trade-off to any significant extent,
people would be doing it all the time to turn their 2W CW pump
diodes into 20W pulsed diodes, and I haven't heard much here about
people doing that. But I may be wrong.

I still think a laser designed to be pulsed (e.g. flashlamp-pumped)
is likely to be more successful. You can (or used to be able to) get
flashlamp-pumped YAG units from Meredith Instruments. These would
emit at about 1064nm, but someone else did say that YAG is being
used for epilation. The spot would be invisible, but the effect on
the skin and hair would not, I suspect!

In terms of beam size, I'm not sure how fluence is related to dispersion by
the time it's penetrated say 5mm to the hair root.

5mm?! I'd have thought more like 2 or 3mm. When I feel my chin, I'm sure
there's not even 5mm between the outside of the skin and the bone. On
the legs there may be more. But I suppose the point about the attenuation
by the intervening skin (however thick) remains valid.

Pulse width required
seems to be related to the thermal time constant of the follicle (cooling
time). The pulse gets it hot quickly then the energy has to 'bleed' into
the root cells. Too long a pulse and substantial tissue damage occurs.

I'm not sure this is true. It may be. But on the other hand, you can
ablate material with pico- or nanosecond pulses. I'm not sure how
"thermal time constant" fits in in that scenario. But I would say that
the gap _between_ pulses needs to be sufficient to allow the skin to
cool. <Shudder/>

Perhaps someone brave with a pump diode feels like trying it out
on the back of their hand! (I wouldn't!) And perhaps someone with
an SSY1 or equivalent would try it too! (AFTER doing some calculations
to ensure that something more dangerous would not occur!) I seem
to remember that those SSY1s emit pulses in the NANOsecond range,
not milliseconds. So the power is MUCH higher for a given flash
energy. Not sure what difference that would make. Probably more
ablation and I guess the damage might be confined more to the
surface of the skin, rather than penetrating deeper. I've no doubt
it'd vapourise the hair above the surface of the skin, but don't
know what would happen to that below it.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

 

[Rich Grise]

"Pauline Aston" <Pauline@tel07768165734.fsnet.co.uk> wrote in message news:<be53l5$463$1@newsg3.svr.pol.co.uk>...

Hello All,

.... Over the years I've spent several thousand pounds on laser hair
removal (ugh I hear you say whereas I usually say ouch).

Regards,

Pauline Aston.

Not to change the subject out from under you, but what about that
goop they advertise on late-night TV that seems to work like
Zip-Strip? You slather a handful on where you want hair gone,
and according to the ad, you wipe it off after some undisclosed
amount of time, and all the hair just wipes off as if it
wasn't even connected. Maybe it's camera tricks (like maybe
that hair all over that arm was just lying there loose?)

Good Luck!
Rich

 

[Pauline Aston]

"Rich Grise" <richardgrise@yahoo.com> wrote in message .

Not to change the subject out from under you, but what about that
goop they advertise on late-night TV that seems to work like
Zip-Strip? You slather a handful on where you want hair gone,
and according to the ad, you wipe it off after some undisclosed
amount of time, and all the hair just wipes off as if it
wasn't even connected. Maybe it's camera tricks (like maybe
that hair all over that arm was just lying there loose?)

With a healthy male androgen supply, if you dissolve the top off hairs,
they're back sometimes the same day like stubble. Works with real girls for
fluff removal but anything else - forget it! You should see the rash from
sensitive skin areas too.

Back to lasers.......

Regards,

Pauline Aston

 

[Mark Johnson]

"Pauline Aston" <Pauline@tel07768165734.fsnet.co.uk> wrote in message news:<behihc$j7$1@newsg3.svr.pol.co.uk>...

"Rich Grise" <richardgrise@yahoo.com> wrote in message .

Not to change the subject out from under you, but what about that
goop they advertise on late-night TV that seems to work like
Zip-Strip? You slather a handful on where you want hair gone,
and according to the ad, you wipe it off after some undisclosed
amount of time, and all the hair just wipes off as if it
wasn't even connected. Maybe it's camera tricks (like maybe
that hair all over that arm was just lying there loose?)


With a healthy male androgen supply, if you dissolve the top off hairs,
they're back sometimes the same day like stubble. Works with real girls for
fluff removal but anything else - forget it! You should see the rash from
sensitive skin areas too.

Back to lasers.......

Regards,

Pauline Aston

Out of curiosity, is this type of device effective for those with
black or brown skin, or is the light pulse absorbed more by darker
(more pigmented) skin? Not that it's really an issue to me, but my
skin is normally a lighter brown, from a heritage consisting partly of
native american indian.

I hope someone comes up with some kind of solution to this. I keep
thinking of possibilities...like permanent hair removal
around...ummmm...shall we say, a woman's "bikini" area? Is this
process safe for use in these, errrr, "sensitive" regions?

Ummm, yes...let's get back to lasers...

Seems, though, that if this were going to be fairly inexpensive and
safe, there would probably be some coompany already producing a home
version, like those worthless du-it-yerself home hair removal
contraptions.

 

[Fleetie]

Seems, though, that if this were going to be fairly inexpensive and
safe, there would probably be some coompany already producing a home
version, like those worthless du-it-yerself home hair removal
contraptions.

Well, yes, but...

.... even if it were possible to produce a laser-based product
cheapish, that were powerful enough to epilate to any useful extent,
the function would necessitate that the form of the device be
such that the beam would emerge from the end from an aperture,
which would normally be held against the skin to be treated.

What if someone held the thing up to their eye, or someone else's,
and pressed the button?

Blindness, that's what.

I think that's got to be a large part (if not all) of the reason
such products are (I assume) not available. Litigation. Even if the
product could get legal clearance to be sold in the first place, which
also seems unlikely.

You can get laser-based skin-puncturing products for diabetics to make
small holes in their fingers for obtaining blood samples (I think), but
with those products, the shape of the device can be such that only a
finger can be inserted, and the beam does not make it into "free space"
because if no finger were present, it would hit an "end stop".


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

 

[Pauline Aston]

"Mark Johnson" <mark.johnson2@jacobs.com> wrote in message > >

Out of curiosity, is this type of device effective for those with
black or brown skin, or is the light pulse absorbed more by darker
(more pigmented) skin? Not that it's really an issue to me, but my
skin is normally a lighter brown, from a heritage consisting partly of
native american indian.

I hope someone comes up with some kind of solution to this. I keep
thinking of possibilities...like permanent hair removal
around...ummmm...shall we say, a woman's "bikini" area? Is this
process safe for use in these, errrr, "sensitive" regions?

Sadly, the darker the skin, the more melanin, so the more energy is
dissipated in the skin putting a limit on who can be treated. There is some
consideration related to wavelength, which is why I limited my bandwidth
below the possible resonance range earlier, but even a small amount of sun
tan is significant. There are several papers about on wavelength, fluence
and time variation to treat different skins.

The more intimate areas are ok because they never see the sun (well
usually).

Pauline Aston.

 

[Sam Goldwasser]

Christoph Bollig <laserpower@gmx.net> writes:

I don't think you can "buy" much power like that. Apparently
(and this is somewhat borne out by my limited experience of
killing LDs), laser diodes are far more sensitive to overcurrent
than normal LEDs, though I don't know by what mechanism.

I am not 100% sure, but I think the problem is optical damage, not
thermal. Apperently, the mirrors coated to the semiconductor are not
able to handle much more than the rated cw power. If you have too much
power, even for very short times like a few ns, the mirrors can
damage. That will turn the laser diode into an LED. This also seems to
be the reason, why they are so sensitive to electrical spikes (Sam
will certainly know more).

Yes, it's called "Catastrophic Optical Damage" or COD. The field strength
at the mirror is sufficient to cause it to self destruct and it is vitually
intantaneous.

Osram/Infineon has a good application note. They allow to overdrive by
a factor of 3.5 at 1 mu-s (will not help you). At 1 ms, they do not
allow to overdrive at all.

Depends on the specific diode as well. Some have a COD threshold just
above their maximum ratings. Others will tolerate more.

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