Love Lenses? Here’s Your Ultimate Guide To Optical Flats
Do you enjoy studying metal? Optical flats are what you use to test metal or glass surfaces.
Did you know that in 2017, there were 110 thousand tonnes of metal created with reserves of 7,100 kt? In this article, explore all about optical flats, what they are and how to use them. Read on and explore just how beneficial they are, and see glass and metal in their truest form today.
What’s an Optical Flat?
Flat optical lenses are what’s used as test plates to determine the flatness of an unknown surface. It’s used to test glass or metal surfaces such as optical mirrors and windows.
A double-sided optical flat has a precision polish on both sides and can be used as an optical window. A single-sided optical flat only has a polish on one side. The other side is normally left clear.
How It Works?
Optical flats are used with a monochromatic light source. You can read more here about optical flats.
Optical flats are on top of the work to be tested underneath a monochromatic light of wavelength. It normally goes under the wavelength of He-Ne.
When this occurs, dark bands and a pattern of light are formed. This is due to the gap that’s between the optical flat and work surface.
When there’s a change in thickness of the wedge or air gap, it shows the shape and direction of the interference bands. The distance and curvature shows how flat the work surface is when it’s compared to the known surface.
The Accuracy That You Use
This depends on what you’re testing. If it’s flatter than λ/4, then you’ll need a precise flat to see any changes in the patterns.
It’ll show straight parallel lines. If you instead choose 20 or 10 flats, it’ll show enough to measure the surface as well.
You can use a reflection stand to allow you to see the interference fringe pattern of a surface. This needs to be used when you’re measuring a component that’ll be forced and stressed from its original shape.
When using large carbon graphite components with cross-section profiles, they’re known to be unstable. These are what need optical stands.
A reflection stand has an angle-adjustable glass-viewing mirror and a fabricated polypropylene plastic house. The top and front surface of the case are made from acrylic plastic.
It first supports an optical flat above a mirror. The mirror is angled toward the clear acrylic front of the unit. Next, you’ll want to place the size of the monochromatic light unit on a step integral.
This step integral is located within the reflection stand with the diffusing lens over the clear acrylic top surface. A component that requires measuring is put on top of the optical flat with a polished surface.
The only stress that occurs is from the component’s own weight. The fringe pattern reflects down to the mirror and then you view it through the clear front panel.
Cleaning Optical Flats
Cleaning optical flats are vital since dust can lead to inaccuracy in the results. Even if you have a fingerprint on the surface, it can impact the width of the gap. Same with any other imperfections as well.
Many use acetone to clean it and dissolve any oils. Use a scratch-free and lint-free tissue that’s wetted and that you can use across the surface. Make sure that you pull any impurities.
This technique is used numerous times in order to ensure that there are no impurities on the optical flat. In order to prevent recontaminating the flat, use a new tissue.
Choose a dust-free or clean-room in order to clean and perform the test. You’ll want to ensure that dust stays out of the assembly and cleaning of the optical flat.
Choose a temperature-controlled room to prevent any disruptions to the glass. It needs to be on a stable work-surface.
There are 2 types of interference fringes, destructive and constructive. Destructive is where the path length is equal to the multiple halves of a wavelength.
Constructive interference is where the 2 rays are equal to an odd multiple of half a wavelength. The waves will add to light intensity. You can see bright areas with this interference.
All About Optical Flats
Now that you’ve explored more about optical flats, you should be able to choose the right one for you and use it with ease. Would you like to read more technological content? For everything from business to technology, check out our other articles on our site today.