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Focusing a laser to a very small dot

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secondLaser

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Feb 20, 2022
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Hi all, I am new to lasers and optics in general.

I am currently working on a project and I need to focus a laser to a very small dot(around .1mm, smaller is better). the focal length should be around 100 mm(min) to 300mm (max).

I am willing to spend around 50 - 200 bucks.

Also, I wonder what sensors are commonly used in detecting lasers.

Thanks
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Use any single mode laser and focus it. You’ll get smaller than 0.1mm no problem. I use a 10600nm CO2 with a 50.8mm FL lens at work and we can achieve <0.125mm. Visible lasers have much smaller wavelengths therefore will have much smaller focal spots.
 
This exact question was asked before by another member. I'm trying to search for it because this might be a returning banned member but I can't find it
 
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Unown (WILD) said:
This exact question was asked before by another member. I'm trying to search for it because this might be a returning banned member but I can't find it
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oh no. I am not, I joined the form today :). This is related to my school project
 
You said for school. I assumed it was for high school or less. What class in college?
 
CurtisOliver said:
Use any single mode laser and focus it. You’ll get smaller than 0.1mm no problem. I use a 10600nm CO2 with a 50.8mm FL lens at work and we can achieve <0.125mm. Visible lasers have much smaller wavelengths therefore will have much smaller focal spots.
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Weight is quite important for my project so I hope the whole device can be very light. Do you know which stores sell this kind of device and I don't need to select the optics myself?

Thanks!
 
If it's a capstone project then shouldn't you already know how to do it? I mean it's supposed to be a project based on what you've already learned
 
Unown (WILD) said:
If it's a capstone project then shouldn't you already know how to do it? I mean it's supposed to be a project based on what you've already learned
Click to expand...
this is just a very small part of my project. I would consider it is a good-to-have feature. I know what I want but I just dont know where to get the right items.
 
secondLaser said:
Weight is quite important for my project so I hope the whole device can be very light. Do you know which stores sell this kind of device and I don't need to select the optics myself?

Thanks!
Click to expand...
Single mode diodes are available and they are very light. Weight will be dependent on the diode, module, driver and power supply.
 
It might be a little easier to answer if you said what the laser would be used for. How precise or fast does the measurements need to be? For focus, any single mode laser diode will get you <0.1mm beam diameter when focused to a point <1m maybe. For safety reasons you'll want to keep power under 5mW.
Beam waist=Capture1.PNG

Gaussian Beam Optics

www.newport.com www.newport.com
OR: minimum beam diameter = (4*wavelength*focal length)/(pi*beam diameter at aperture)
 
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