I have my set up in trial mode (i.e. nothing stuck together yet!)
Originally i positioned all my optics at the distances I beleieved they should be based on the 160/305 fresnel pair I have.
I set the light source up, then the end of the first fresnel at 160 from the middle of the light bulb and then the start of the second fresnel at 285mm from the objective lens, which is a varifocal of 285mm to 320mm.
I tried it out and got the image focused brilliantly on my wall (impling the 2nd fresnel to object, but the corners were very dim.
At first i though this may have been the condensor so i took this out and gave it another go; same problem.
Next i reduced the distance betweeen my fresnel pair (i havn't split it yet) and the LCD from appox 10mm to approx 2 mm. The prblem did not change.
I then adjusted the distance of the light to the first fresnel and moved it closer. I got a brilliant bright screen and all the corners were bright BUT the middle of the light source itself was only 140mm from the back fresnel. Thinking this was wierd I measured 160mm away (the focal point of the fresnel) and this coincided exactly with the back of my spherical reflector!
Can anyone suggest why this may have happened? I am, of course, happy that everything is working well but equally confused as to what the issue (if any) may be. Also, at 140mm for the light source I am going to have to put a pretty big fan in to keep it cool.
By the way my light source is 250W
Any ideas on why i got the results i did would be great!
Thanks,
Matt
Originally i positioned all my optics at the distances I beleieved they should be based on the 160/305 fresnel pair I have.
I set the light source up, then the end of the first fresnel at 160 from the middle of the light bulb and then the start of the second fresnel at 285mm from the objective lens, which is a varifocal of 285mm to 320mm.
I tried it out and got the image focused brilliantly on my wall (impling the 2nd fresnel to object, but the corners were very dim.
At first i though this may have been the condensor so i took this out and gave it another go; same problem.
Next i reduced the distance betweeen my fresnel pair (i havn't split it yet) and the LCD from appox 10mm to approx 2 mm. The prblem did not change.
I then adjusted the distance of the light to the first fresnel and moved it closer. I got a brilliant bright screen and all the corners were bright BUT the middle of the light source itself was only 140mm from the back fresnel. Thinking this was wierd I measured 160mm away (the focal point of the fresnel) and this coincided exactly with the back of my spherical reflector!
Can anyone suggest why this may have happened? I am, of course, happy that everything is working well but equally confused as to what the issue (if any) may be. Also, at 140mm for the light source I am going to have to put a pretty big fan in to keep it cool.
By the way my light source is 250W
Any ideas on why i got the results i did would be great!
Thanks,
Matt
Ok, so no ideas why i got those results BUT i did find out why my distances didn;t seem to add up - I had the Fresnel in the wrong way around so the 305 was towards the light and the 160 towards the lens. Now i have them the correct way ity all looks damned good.
No idea as i tyoe why i got any results at all BUT I might put my physicis to good use and find it out, even though it has been almost 6 yrs since i did my degree and I cant really remember any of it
Cheers,
Matt
No idea as i tyoe why i got any results at all BUT I might put my physicis to good use and find it out, even though it has been almost 6 yrs since i did my degree and I cant really remember any of it
Cheers,
Matt
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