开云体育

Alberto

Polarized light filters are available at some surplus optics company or from theater lighting filters.

You can use the light from a LCD monitor and a pair of polarized? ?sunglasses

The light going thru clouds is often polarized, hold the glass up and turn it while wearing polarized? ?sunglasses.

Ive heard that if you stack up 5 or 6 layers of window glass it will act as a polarized filter.

As you know when you cross polarized filters they block much of the light.

Stress areas in the glass will rotate the polarized light differently than other areas

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Set up the glass so the polarized light is going thru it. Look at this thru the other filter (sun glasses) Rotate until it darkens and look for light and dark patterns.

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Try this with tempered glass first so you can see what really bad stress looks like.

If your CRT tubes are not tempered they are probably properly annealed (stress relieved)

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Please use the same units when giving specs mixing inches and MM confuses this old brain of mine. 21 inch (530MM) diagonal size with a 4 (120 MM) Radius of curvature are impossible numbers?I think your 120MM number refers to somthing?diffrent.

Radius of curvature-- is the center point of a sphere, the point that a light point will focus back on itself.

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Focal length ---is the point that light from something far away comes to focus this equals the radius of curvature.

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Sagia is the distance a curve deviates from flat. Hold a straight edge to the concave glass, measure from the center of the straight edge to the glass.

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Because the of the thickness of the glass you will not be changing the curve much

So the first step is finding the focal length. You can use the sagia to calculate it easiest, measure the distance from the glass to the focus point of the sun, or of the distance a light bulb focuses on itself.

Divide the focal length by 4 the result is the largest mirror diameter that will work with this curve. (F4) This is a very fast mirror and very difficult to accurately shape.

Dividing the focal length by 9 (F9) will give you a slow mirror that is very easy to shape (figure).

A quick guess holding a piece of paper to my 18 monitor face looks like 1000MM focal length, small 14 TV = 300MM focal length, 27 TV = 600MM focal length

Sounds to me that you can use a CRT front glass to make a mirror 12MM thick glass is a bit thin but because its curved it should be no harder to work with than flat glass, using epoxy auto body filler to make a holder for the glass should work well just dont glue the glass to the holder and put somthing soft between the glass and holder. if you only grind with mirror on top you will not need a holder. Glue a block to the back of the glass ?for a hand hold to keep the heat from your hand away from the glass. Using pitch for glue works good.

Im probably giving you way more info than you need or want. I hope some of this is usable.

If you have any other questions Ill be glad to help please regard all information as my opinion and not as hard fact.

Good luck

Ron

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