Hvala za pomoč pri iskanju filtra.
A ni ta filter, ki mi ga priporočaš praktično enak temu, ki sem ga naročil?
Pri Stock optics sem naročil ta filter (830nm-25mm-Diameter-x-1mm-Thick-Long-Pass-infrared), dobil pa filter, ki je popolnoma neuporaben in ne blokira čisto nič rdeče svetlobe.
Ko sem se pritožil, da ni uporaben, so mi priznali, da so poslali čisto napačnega in, da bodo čez tri tedne dobili novo pošiljko in mi takrat poslali drugega, lahko pa še izberem katerega točno bi rad.
Priporoča mi tega:
http://www.stockoptics.com/media/datasheets/longpass/RG850.pdf
Mislite, da bi bil tale res pravi?
A ima kaj dosti vpliva debelina filtra imajo med 1 in 3mm debeline.
Cena je nekje med 20 za 1 mm in 50 evri za 3mm-verjetno se bom odločil za srednjega 2mm.
Kaj mu naj odgovorim?
Tole mi je napisal.
Okay, looking at this in greater detail, this is where it can get a bit
complicated. These glass types are called Long Pass which means the
material is absorbing the UV light and the visible light. Visible light is
450-650nm. It will also start to absorb the NIR light and then it starts to
cut on. The confusing part is that generally speaking, once you hit peak
transmission, the thickness of the material doesn't affect the overall
transmission value but it does move the cut on and 50% transmission point.
All long pass filters are designated from their 50% transmission point.
The difficult point is finding a material that allows enough IR light to
pass at the required wavelength, whilst blocking off the visible. Your
light is transmitting at 915nm but, when you place the IR filter in front,
it is still possible for some people to see some small amount of radiation
from the bulb. Because every one's eyes are different, I may see it, you
may not
Have a look at these data sheets from our website and you will get a better
understanding of what I am trying to explain.
http://www.stockoptics.com/long-pass-filter-datasheets
Have a look at the data sheet for RG850 and if you imagine drawing a
vertical line at 915nm, everything to the left of that line is being
transmitted. You can see that the material is starting to transmit at
around 800nm and it gives around 96% peak transmission at 915nm. You will
lose around 8% transmission because the filter has no AR Coating, so the
best you will get is around 88% typically. This is based on a 3mm thick
filter. If the filter is thinner, say 2mm, that whole transmission line
starts to move to the left, so you can now see that more lower NIR light is
starting to be transmitted. Make the filter 1mm thick and even more NIR
light is now creeping through.
I would go for an 850nm filter and 3mm thick. Have a look at the data and
let me know what you think.
Regards