Light magnification
- Thread starter Stu
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Mine Explorer
Guest
I don't think it's actually 'magnifying' the light. The lens just concentrates it into a tighter beam, so more of the light generated enters your eye, or illuminates the spot on the wall it's pointing at, and thus appears brighter. The downside to this is the light doesn't cover such a wide area.
If you look at an old oil lamp (the type with a bulls-eye lens). The flame on it's own will generate an even diffused light that goes everywhere. Placing the flame behind the huge bulls-eye lens will concentrate the light into a tighter beam, making it appear very bright to look at, but it's no longer lighting up the whole room, just a small section.
...is this effectively magnifying the light? Yes if the area you want illuminated is less than the area of the beam of light, No if the area you want illuminated is larger than the beam of light.
If you look at an old oil lamp (the type with a bulls-eye lens). The flame on it's own will generate an even diffused light that goes everywhere. Placing the flame behind the huge bulls-eye lens will concentrate the light into a tighter beam, making it appear very bright to look at, but it's no longer lighting up the whole room, just a small section.
...is this effectively magnifying the light? Yes if the area you want illuminated is less than the area of the beam of light, No if the area you want illuminated is larger than the beam of light.
Cave_Troll
Active member
what we're probably talkign about here is focusing.
given that light spreads out in a sphere, focussing that sphere of light to a beam will make a big aparant difference.
you can magnify light using a photo multiplier tube (passive night vission)
light in| PMT | light out
What basically happens is that a light photon hits a screen. that causes an electron to be ejected. this electron is accelerated and hits another screen that emits a number of photons. (roughly speaking)
you end up with monocromatic light. the systyem does not work well with high light levels and its more efficiant to make more light in the first place than try and amplify it.
given that light spreads out in a sphere, focussing that sphere of light to a beam will make a big aparant difference.
you can magnify light using a photo multiplier tube (passive night vission)
Code:
| |
~~> | e> |~~>
| |~~>
| |
~~> | e> |~~>
| |~~>light in| PMT | light out
What basically happens is that a light photon hits a screen. that causes an electron to be ejected. this electron is accelerated and hits another screen that emits a number of photons. (roughly speaking)
you end up with monocromatic light. the systyem does not work well with high light levels and its more efficiant to make more light in the first place than try and amplify it.
Cave_Troll
Active member
3 things affect the aparent brightness of your light
The source (bulb/LED/PL panel)
the reflector
the lense
now my Princeton Tec Impact is a single bright LED with a reflector, but what makes the real difference is the lense which is shaped to focus the beam to a spot.
My PT Attitude has 3 LEDs and a reflector but just a flat lense. thus i get a wider "flood" illumination.
The source (bulb/LED/PL panel)
the reflector
the lense
now my Princeton Tec Impact is a single bright LED with a reflector, but what makes the real difference is the lense which is shaped to focus the beam to a spot.
My PT Attitude has 3 LEDs and a reflector but just a flat lense. thus i get a wider "flood" illumination.
With LEDs, there can be an additional lens effect depending on the LED type.
Old-style 5mm LEDs had an integral lens which gave some kind of beam shape to the emitted light (often in the range 10-40 degrees). That's why arrays of 5mm LEDs withouit any extra optics could give a fairly good forwards throw of light, though generally without a sharply defined edge to the beam.
Placing some kind of reflector round the LED may direct the [fraction of] light emitted vaguely sideways into a beam, but if much of the light is being sent fairly forwards due to the inherent focussing in the LED package, a lens may be a better way of making a beam.
In such lights, if the lens is doing the main focussing, and if the lens has to be some way in front of the LED, I suppose a reflector *might* sometimes be used mainly to make sure that any light that wouldn't otherwise pass through the lens still ended up going out of the front of the light in at least some direction, even though light bouncing off the reflector would not end up being focussed into the actual main beam.
Regular Luxeon emitters give a much wider spread of light than most 5mm LEDs, and do require external optics to give any kind of beam, while the side-emitting Luxeons are specifically designed for fitting in a reflector.
Old-style 5mm LEDs had an integral lens which gave some kind of beam shape to the emitted light (often in the range 10-40 degrees). That's why arrays of 5mm LEDs withouit any extra optics could give a fairly good forwards throw of light, though generally without a sharply defined edge to the beam.
Placing some kind of reflector round the LED
In such lights, if the lens is doing the main focussing, and if the lens has to be some way in front of the LED
Regular Luxeon emitters give a much wider spread of light than most 5mm LEDs, and do require external optics to give any kind of beam, while the side-emitting Luxeons are specifically designed for fitting in a reflector.
