Total internal reflexion on a polymer

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SUMMARY

The discussion centers on solving the problem of total internal reflection in a 6.5mm Acrylic panel when attempting to illuminate an artwork from the front. Ramon Pujals seeks advice on materials to enhance contact between the artwork and the Acrylic to prevent light loss. Recommendations include using pure 100% glycerine, which has a refractive index of 1.475, and optical silicone oil with a refractive index of approximately 1.50. Additionally, an Acrylic Matching Fluid from Cargille is suggested, although it is noted to be expensive.

PREREQUISITES
  • Understanding of refractive indices, specifically for Acrylic (1.4) and glycerine (1.475).
  • Knowledge of total internal reflection principles in optics.
  • Familiarity with materials used in optical applications, such as silicone oil.
  • Experience with applying viscous fluids for optical clarity.
NEXT STEPS
  • Research the properties and applications of glycerine in optical setups.
  • Investigate the use of optical silicone oil for enhancing light transmission.
  • Explore the specifications and uses of Acrylic Matching Fluid from Cargille.
  • Learn about techniques for achieving bubble-free applications in optical bonding.
USEFUL FOR

This discussion is beneficial for optical engineers, artists seeking innovative lighting solutions, and anyone involved in enhancing light transmission in acrylic materials.

ramonpujals
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Dear Everyone

I am facing the following engineering problem. I "inject" light in a flat (6.5mm) Acrylic panel at the edges of it. Due the different refractive index of the Acrylic material (1.4) and air (1) 90% of the "injected light" experiments total internal reflexion. I need to get the light out of the Acrylic panel on one of its planes. Pls., see the attachment.
The purpose of this is to light frontally an artwork as oposed to the standard backlighting.

The main problem am facing is that the contact between the artwork and the botton plane of the Acrylic panel is not tight enough. There is air between and total internal reflexion persists, hence the artwork is not illuminated. Is there any material I can place between the artwork and the bottom plane of the Acrylic panel to enhance the contact between them?

I will be glad if anyone can give me some idea.

Be well

Ramon Pujals
Barcelona
 

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Try using pure 100% glycerine between artwork and acrylic. Its index of refraction is 1.475, close to lucite (1.50). Its vapor pressure is only 1 mm Hg at 125 deg C. I do not know about solubility/interaction with your artwork. Apply blob near center of acrylic(without bubbles) and use ink roller and fingers behind artwork to squeeze excess and bubbles out to perimeter. Use pressure plate behind artwork to maintain pressure on back of artwork.
[Edit] This optical silicone oil, used for hiding scratches in glass etc., might also work. It has an index of refraction about 1.50.
See http://store.pasco.com/pascostore/showdetl.cfm?&DID=9&Product_ID=56874&groupID=156&Detail=1
[Edit #2] Here is an Acrylic Matching Fluid (matches acrylic index of refraction) from Cargylle (but it is not cheap). It has the viscosity of honey.
http://www.cargille.com/AC5032.pdf
 
Last edited:
Dear Bob

THKS a lot. Using a viscose fluid was my first though owin to the need of enhanced contact. But I didnt know glycerine was the appropriate one, big thanks. I have to check the possible interations between the paint of the artwork, as you pointed out.

lets see how it turns out.

THKS
 

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