So how does the mirror work? What is oriented where reflecting what?
Pictures would be helpful.
I would advise against counting on some kind of percieved increase in brightness when you are using the same amount of net power - much has been made of the fact that LEDs can be pulsed at higher power for a fraction of the second, even though the eye is going to average it out to the same amount anyway.
Pictures would be helpful.
I would advise against counting on some kind of percieved increase in brightness when you are using the same amount of net power - much has been made of the fact that LEDs can be pulsed at higher power for a fraction of the second, even though the eye is going to average it out to the same amount anyway.
My guess is, the human eye perceives strobed light as being brighter. Of course the only reference I can find says differently: http://members.misty.com/don/ledp.html . Doesn't 100% convince me though, sorry I can't find a better reference. I'm not sure how the human eye and the solar cell mentioned in the article differ in terms of brightness integration-time.
seoehlke, you mentioned a spinning beam that is perceived at roughly 1/2 the intensity of the actual beam intensity. What is the angular extent of the beam when it's not spinning? Wouldn't the perceived intensity be 360 degrees / beamwidth degrees? Would that intensity be higher in the center of the spinning beam?
I'm not trying to disbelieve your claim, just curious about the basic phenomenon and numbers. I tried to simulate it with my laser level, but failed :-(
seoehlke, you mentioned a spinning beam that is perceived at roughly 1/2 the intensity of the actual beam intensity. What is the angular extent of the beam when it's not spinning? Wouldn't the perceived intensity be 360 degrees / beamwidth degrees? Would that intensity be higher in the center of the spinning beam?
I'm not trying to disbelieve your claim, just curious about the basic phenomenon and numbers. I tried to simulate it with my laser level, but failed :-(
I am still working on the actual shape of the outgoing beam. It appears, at this point, that the beam will be roughly 25 degrees vertically by 5 degrees horizontally giving me a wide line of light that is uniform in intensity from top to bottom.
There is no need for anyone to apolize for anything. Criticism is always good!
I have been doing very basic tests. i purchased a small motor from Radio Shack that revolved at up tp 18,000 RPM and attached a 1/2 inch mirror to the shaft at a 45 degree angle. I than shined a 50W halogen bulb through a 1/2 inch hole and focusing lens onto the mirror.
I took a reading of intensity from the outgoing beam before I spun up the light with a optical sensor that measures in volts. I than spun up the mirror and took another reading. The second reading, in volts was roughly a tenth of the initial reading. This was because the outgoing beam of the halogen was roughly 36 degrees horizontally, so the sensor saw it a tenth of the time every time it rotated while it was black 9/10 of the time.
However, when I ran the signal through a sample and hold circuit and an integrator, attempting to mimic the eye, I indeed seemed to see roughly 1/2 RMS of the total light output. By spinning fast enough for the light to make essentially 3 revolutions for every time the eye takes a sample, it does appear plausible.
Thoughts?
There is no need for anyone to apolize for anything. Criticism is always good!
I have been doing very basic tests. i purchased a small motor from Radio Shack that revolved at up tp 18,000 RPM and attached a 1/2 inch mirror to the shaft at a 45 degree angle. I than shined a 50W halogen bulb through a 1/2 inch hole and focusing lens onto the mirror.
I took a reading of intensity from the outgoing beam before I spun up the light with a optical sensor that measures in volts. I than spun up the mirror and took another reading. The second reading, in volts was roughly a tenth of the initial reading. This was because the outgoing beam of the halogen was roughly 36 degrees horizontally, so the sensor saw it a tenth of the time every time it rotated while it was black 9/10 of the time.
However, when I ran the signal through a sample and hold circuit and an integrator, attempting to mimic the eye, I indeed seemed to see roughly 1/2 RMS of the total light output. By spinning fast enough for the light to make essentially 3 revolutions for every time the eye takes a sample, it does appear plausible.
Thoughts?
There are rods and cones on the retina... I never learned how exactly they work... here's a start:
http://webvision.umh.es/webvision/temporal.html
Apparently the rods are slow (100ms) integrators and the cones are faster (10-15ms).
OK so far, but have searched site and not found what Iam thinking of. the basic problems are of single point light source right? and leds are multiple. Well if you had a cone of glass or plexi, with the sides painted (black/siver/white. whatever) and the top either flat or domed, the light would possibly be a single point as the glass/plexi would be a light transmitter. Would that work?
Attachments
I've been looking at several options for collecting the LED array into a single beam and have read a couple of pieces on optical homegenizers, essentially what you showed. At the moment I am attempting to do this with a modified Newtonian telescope set-up.
LEDs that will dissipate multiple watts of heat are designed to be mounted on heatsinks where required.
Had a eureka moment just then. Suppose you use 50 or 60 10k mcd white leds in a straight row, and point them at a square rod mirror ( a square tube with four mirrors on each side ) and spin the sq rod at high speed, say 3000rpm which would give 12000 mirror reflections per minute or 200 per second. At 30ma per led that would not be too much amperage used. Yes I know that a single light source is best, the scan rate might interfere, the colour of `white` leds is not pure etc, so maybe someone has some input on this one. Also to spread the light more evenly, maybe some sort of diffuser could be implemented. If this would work, just think, a small low voltage decent projector with very little heat could be made. The main concern I have would be the light intensity form top to bottom and scan rate interference with the lcd
Just found this :
http://www.optiled.biz/products/products.html
I'm a total noob in this, but
If I understand the specs sheet correctly - the Commercial Led spotlamp is capable of providing 2881 lumens !?
http://www.optiled.biz/america/downloads/Spot_Lamp_Spec_Sheet.PDF
http://www.optiled.biz/products/products.html
I'm a total noob in this, but
If I understand the specs sheet correctly - the Commercial Led spotlamp is capable of providing 2881 lumens !?
http://www.optiled.biz/america/downloads/Spot_Lamp_Spec_Sheet.PDF
mixing up Lux and Lumens!
Sorry, but 2881 Lux is the light intensity measured in the 9 cm diameter circle. If you look at the lower rows of that table, it shows the Lux dropping as the circle gets bigger. If you made a circle that had an area of one meter squared, then you would get an intensity of just 18.33 Lux. The Lux reading spread over exactly one meter squared is the number of Lumens the lamp is delivering, so the output is actually 18.33 Lumens.
A typical 400 Watt MH lamp puts out about 33000 Lumens, so it would take 1800 of these LED spotlights to deliver the same amount of light. And those 1800 LED spotlights would consume...
4500 WATTS!
Just because one small (ie. 20 ma) LED feels cool, does not mean that LEDs are super-efficient. The very best LEDs now give you about 45 Lumens per Watt. (Compared to >80 Lumens per Watt for MH lamps.) These OptiLed spotlights give you just 7.33 Lumens per Watt, so they are really awful. All of that waste power has to go somewhere if it is not coming out as light: Even the best LEDs will make about twice as much heat, compared to a MH lamp.
Sorry, but 2881 Lux is the light intensity measured in the 9 cm diameter circle. If you look at the lower rows of that table, it shows the Lux dropping as the circle gets bigger. If you made a circle that had an area of one meter squared, then you would get an intensity of just 18.33 Lux. The Lux reading spread over exactly one meter squared is the number of Lumens the lamp is delivering, so the output is actually 18.33 Lumens.
A typical 400 Watt MH lamp puts out about 33000 Lumens, so it would take 1800 of these LED spotlights to deliver the same amount of light. And those 1800 LED spotlights would consume...
4500 WATTS! Just because one small (ie. 20 ma) LED feels cool, does not mean that LEDs are super-efficient. The very best LEDs now give you about 45 Lumens per Watt. (Compared to >80 Lumens per Watt for MH lamps.) These OptiLed spotlights give you just 7.33 Lumens per Watt, so they are really awful. All of that waste power has to go somewhere if it is not coming out as light: Even the best LEDs will make about twice as much heat, compared to a MH lamp.
Wow, thanks for the info Guy.
I'm just little afraid of the MH lamps
I mean.. if this MH lamp leaks/brakes - will I sense anything before
killing all my neighbors 😀 ?
I'm just little afraid of the MH lamps
I mean.. if this MH lamp leaks/brakes - will I sense anything before
killing all my neighbors 😀 ?
MH lamp failure
Since the quartz glass arc chamber can break when the lamp fails, the manufacturers recommend that you use their lamps inside an enclosure. That will contain the glass shards, if the outer glass also breaks.
In a DIY projector, the lamp is completely surrounded by your enclosure, so any lamp pieces will also be contained. The main concern would be that if a lamp explodes, it might damage the LCD. I prefer to use a piece of Lexan polycarbonate to support my condensor fresnel. The Lexan cuts out damaging UV, and it will also protect the fresnels and LCD from anything short of a hand grenade.
Lexan is used to replace glass in windows where you need high security: A thief can beat on a Lexan window pane with a hammer, and it will just put a few small dents in it.
The tiny bit of mercury and chlorine released by breaking a MH lamp would be insignificant. Just don't eat the broken bits. 😀
Since the quartz glass arc chamber can break when the lamp fails, the manufacturers recommend that you use their lamps inside an enclosure. That will contain the glass shards, if the outer glass also breaks.
In a DIY projector, the lamp is completely surrounded by your enclosure, so any lamp pieces will also be contained. The main concern would be that if a lamp explodes, it might damage the LCD. I prefer to use a piece of Lexan polycarbonate to support my condensor fresnel. The Lexan cuts out damaging UV, and it will also protect the fresnels and LCD from anything short of a hand grenade.
Lexan is used to replace glass in windows where you need high security: A thief can beat on a Lexan window pane with a hammer, and it will just put a few small dents in it.
The tiny bit of mercury and chlorine released by breaking a MH lamp would be insignificant. Just don't eat the broken bits. 😀
lexan
Lexan brand of polycarbonate is sold by home improvement stores and window glass repair shops. It is used to replace window glass to make your house much more secure: A thief can beat on it with a hammer, and it will only slightly dent the surface. It is much stronger than acrylic (ie. Plexiglas).
There are many different types of Lexan. You need to get one like XL10 that has a UV blocking coating on at least one side. (Some types have the coating on both sides.) If the type you get has coating only on one side, then you must install it in your projector with that side facing the lamp.
Lexan brand of polycarbonate is sold by home improvement stores and window glass repair shops. It is used to replace window glass to make your house much more secure: A thief can beat on it with a hammer, and it will only slightly dent the surface. It is much stronger than acrylic (ie. Plexiglas).
There are many different types of Lexan. You need to get one like XL10 that has a UV blocking coating on at least one side. (Some types have the coating on both sides.) If the type you get has coating only on one side, then you must install it in your projector with that side facing the lamp.
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