How much safer does an IR filter make the laser? Also, does an IR filter reduce visible brightness at all, or just the invisible IR light? Where can you get IR filters?
The filters are IN the laser device, you don't see them. The process of producing the beam can generate a LOT of IR, and, its invisible, so you don't SEE it hitting your eye, and, damage occurs deep inside the eye because your lens doesn't reflect it as it does visible wavelengths, etc...and, IR = HEAT.
GOOD lasers include an IR filter as part of a standard assembly. Budget versions may leave it off, as you can't tell by looking if its in there, etc...especially looking at an advertisement.
If the laser's spec is a visible beam, that DOES at least act as a tracer for the invisible beam (The invisible beam is where the visible beam is pointed...), but, the IR part can be "brighter" than the visible part. That can make the visible spot APPEAR to be "ok" to look at (not that bright) but leave you unaware of the IR boring into your eye balls and damaging them. You might not even feel pain or discomfort for a while AFTER the exposure....so a long point at something can lead to quite a lot of exposure.
Laser goggles CAN include multiple wavelength protection, say vis + IR, but, they HAVE TO have gaps in the coverage even in Vis, or they would not be able to see through, etc.
Example:
Notice the coverage described on the lens:
190 - 534 nm + 960 - 1064 nm OD 7+
That means that it has an Optical Density of 7+ for those two bands.
850 - 925 nm OD 5+
The optical density is 5+ for that band.
925 - 1070 nm 6+ for that band, and so forth.
The higher the optical density, the less light gets through the lens, and the more protective it is.
Notice that there's NO protection listed for 534 nm to 850 nm...so that's the light you are SEEING with.
The IR protection is in the higher bands, in this case, from ~ 850 nm upwards. ISO considers near IR to start at 780 nm for example, so these glasses let through the red end of IR. ALL of my lasers have IR filters though.
It ALSO means that these shields give a lot of protection in the UV to Green wavelengths, so blue and green lasers would be appropriate for them for example (445 nm or 532 nm, etc), but that a Yellow laser (~ 580 nm, etc...) or Orange or Red, would NOT be a good choice, and you'd use DIFFERENT goggles with OD designed for THOSE wavelengths.
These also list the % VLT, which is the percent of Visible Light Transmitted, in this case, 35% of the Visible Light Is Transmitted....similar to what gets through a regular pair of sunglasses in practical terms. A higher %VLT means those sunglasses are lighter, so your view is brighter, less is blocked, and so forth.
For example, if the OD is closer to 4, the %VLT might be closer to 50% for some glasses....depending upon how much of the visible is included in the blocking.
