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Hi Steve,
Your logic is correct. Many manufacturers state the output power as per the laser diode they are using. Thus a 5mw Sanyo diode operating at it's required current drive will put out 5mw. However, if you then use collimating or focussing optics, or a line generating optic, there will be some power loss through the optics.
This can be in the order of 25%, thus the available ouput power in this hypothetical case is now 3.75 mw.
Most laser diodes emit an elliptical beam with the vertical axis having a divergency of say 30 degrees and the horizontal axis having a divergence of say 12 degrees.
Thue a manufacturer "spot" size may be stated at 1mm which unless the system has suitable optics to create a circular spot, this "stated" 1mm spot is more likely to be an ellipse shape with the vertical length of the beam being 1mm whilst the horizontal length is 0.4mm.
If a line generator lens is used then the beam could be 5mm x 1mm. Both of these will be at a given distance from the face of the diode.
This is where the problem comes in. As you move further away from the tissue surface, the spot size (unless truly collimated to produce a minimally divergibg beam) then becomes larger the further away from the tissue surface.
Line generators can also suffer this problem, so the further away from the tissue surface, the longer & wider the line.
You still have the original output power, but the Power Density on the tissue surface decreases dramatically the further you move the treatment tip away.
Given the two examples above, the "Spot" of 1mm x 0.4mm with an output power of 3.75mw (after the lens system) has a Power Density of 1.19 Watts/cm2
The "Line" of 5mm x 1mm (at 3.75mw) has a Power Density of 0.075 Watts/cm2. Thus the line version has to be applied 15.86 times longer to deliver the same Power Density.
Thus your point about the higher power Laser diode eg 20mw being used to minimise these factors is valid. More importantly, the manufacturer should state the exact output power at the treatment face ie where the laser is applied to the tissue. You also need to know the duty cycle if the laser is pulsed as again this will affect the "mean average" output power which in turn affects the treatment time for required Dosages.
Trust this helps,
Kerry
Kind Regards
Kerry Tume
M.Ac.F. M.I.L.A. ACONT
NAALT WALT LIA
Kerry Tume
M.Ac.F. M.I.L.A. ACONT
NAALT WALT LIA
----- Original Message -----From: Jennifer RubySent: Wednesday, March 15, 2006 1:34 AMSubject: Re: [Therapeutic-Laser_Therapy] Line vs Dot and power output question..Hi Steve!
I don't know the answer to this question.... Hoping someone with laser
manufacturing wisdom will give some insight to this question.
Health, Hope, Joy & Healing :
May you Prosper, even as your Soul Prospers 3John 2
Jennifer Ruby
Email advice is not a substitute for medical treatment.
http://www.rubysemporium.com
http://groups.yahoo.com/group/SymphonicHealth
http://groups.yahoo.com/group/Therapeutic-Laser_Therapy
http://www.lazrpulsr.com
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----- Original Message -----
From: "esl5552001" <SCL555@...>
To: <Therapeutic-Laser_Therapy@yahoogroups.com>
Sent: Monday, March 13, 2006 1:56 PM
Subject: [Therapeutic-Laser_Therapy] Line vs Dot and power output question..
| I have noticed that some lasers on the market (635nm healing lasers)
| use a dot and some lasers use a line. I have heard it said that if you
| are using a 5mw line then you are losing a significant amount of power.
| For instance the Erchonia is said to only produce .6mw output of power
| at the aperture. Wouldn't it make sense to just use 15-20mw diode (or
| whatever it takes) until you arrive at the desired 5mw output at the
| aperture for a line generated laser? Then you could cover more area in
| less time with greater effect using a true 5mw. Just trying to arrive
| at the bottom line of all this laser tech(pun intended).
|
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