Focusing a laser to a very small dot

[secondLaser]

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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[Unown (WILD)]

What project is this going to be?

 

[secondLaser]

What project is this going to be?

Hi, I need to use the laser to detect small movement(like 0.5mm).

 

[CurtisOliver]

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.

 

[Unown (WILD)]

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

 

[secondLaser]

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

oh no. I am not, I joined the form today . This is related to my school project

 

[Unown (WILD)]

Got it https://laserpointerforums.com/threads/safe-ir-laser-for-trip-wire-set-up.108554/#post-1604481

 

[Unown (WILD)]

oh no. I am not, I joined the form today . This is related to my school project

How old are you?

 

[secondLaser]

How old are you?

24 ...... why

 

[Unown (WILD)]

You said for school. I assumed it was for high school or less. What class in college?

 

[secondLaser]

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.

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!

 

[secondLaser]

You said for school. I assumed it was for high school or less. What class in college?

Hi it is for a capstone project

 

[Unown (WILD)]

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

 

[secondLaser]

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

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.

 

[CurtisOliver]

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!

Single mode diodes are available and they are very light. Weight will be dependent on the diode, module, driver and power supply.

 

[Mattronium]

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=

Gaussian Beam Optics

www.newport.com

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