Term
| What percent of lenses are AR coated in the U.S.? |
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Definition
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Term
| What is the purpose of AR coating? |
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Definition
1) Increase the amount of light through the lense
2) Reduce unwanted reflections |
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Term
| What happense to the majority of light that strikes a lens surface? |
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Definition
| The majority of light striking a lens surface is refracted |
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Term
| What occurs in AR coating if the path difference is an even number of half wavelengths? |
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Definition
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Term
| What occurs in AR coating if the path difference is an odd number of half wavelengths? |
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Definition
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Term
| What two conditions must be met in order for the two reflecting waves produced by an AR coated lense to cancel each other out? |
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Definition
Amplitude Condition-both wave amplitudes must be equal
Path condition-waves must be 1/2 wavelength out of phase |
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Term
| How does the refractive index of a lens material influence the amount of reflection and glare? |
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Definition
| The higher the lens index, the more reflections and glare |
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Term
| Can you fullfill the path condition for all wavelengths using AR coating? |
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Definition
| No, the path condition will only be met for one wavelength. We usually choose 555 nm because it is the most visible |
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Term
| How do you decrease the reflections further if the path condition only works for one specific wavelength? |
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Definition
| use multiple coating layers |
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Term
| Toward which end of the spectrum do reflections increase? |
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Definition
| the longer red and violet ends of the visible spectrum |
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Term
| What type of lense is heated to 300 degrees and then uses 2500 degree magnesium for AR coating? |
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Definition
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Term
| What material lense is heated to 100 degree and uses sodium dioxide (quartz) for AR coating? |
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Definition
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Term
| What chemical is added to the outer layer of a lense lense to create a hydrophobic coating |
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Definition
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Term
| How many layers are AR coatings usually? |
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Definition
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Term
| order are layers added to no glare coating? |
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Definition
1. Remove all coatings
2. Add primer coating
3. Add hard coating
4. Add 8 layers in a vacuum
5. Add antiparticulate coating
6. Add hydrophobic coating, includes antistatic effect
7. Pad control layer to allow the pad to stick during lens blocking |
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Term
| Name two examples of hydrophobic coating? |
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Definition
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Term
| What does the hydrophobic layer of coating do? |
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Definition
1. causes water and grease to form smaller droplets and therefore be less noticeable
2. increases hardness
3. reduces reflections noticed by observers
4. reduces the "glassiness" of the lens appearance |
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Term
| By what percent do mirrored coatings reduce visible light? |
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Definition
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Term
| What is one precaution to take with scratch resistant coated lenses? |
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Definition
| avoid exposure to excessive heat |
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Term
| Will scratch resistant coating or AR coating change the impact resistance of a lens? |
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Definition
| Yes, either coating will decrease the lenses impact resistance |
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