Build Instructions: Filter Selector Assembly

A project log for ramanPi - Raman Spectrometer

The open source 3D Printable Raman Spectrometer using a RaspberryPi and easy to find off the shelf components..

fl@C@fl@C@ 09/25/2014 at 23:598 Comments

Note: This log entry is a living document. I'll be updating this post to reflect the current configuration as time goes on.. There will also be a log at the end of the post noting modifications to the log, etc..

UPDATED-----> 09.25.2014

This log entry will instruct you on building the Objective Lens Mount..

Tools Required:

Components Required:


1. Print and clean up the plastic parts. Be sure to use the 3D printed part guidelines. All spurs and supports need to be cleaned as much as possible.

2. Gather the 550nmLP filter, the 522nmSP filter, the filter wheel, the filter wheel back, 8 of the M2 4mm screws, the 522nm mount cover, and the 550nm mount cover..


3. Take the 550nm Long Pass FIlter, notice around the edge there is an arrow.. That arrow goes toward the back of the filter wheel.. You are looking at the front of the wheel here...Place the filter in the 550nm Long Pass Filter Mounting Hole..

4. Gently place the 550NM mount cover over the filter, and insert screws..

NOTE: You can remove the cotton gloves, but I recommend keeping the nitrile gloves on. 

5. Gently tighten the screws..Do not over-tighten.

6. Gather the 522NM Short Pass Filter, four M2 4mm screws, the 522nm mount and the filter wheel with the 550nm Long Pass Filter installed.


7. Notice the arrow on the 522NM Short Pass Filter.. This arrow also points to the back of the filter wheel.

8. Gently place the 522NM Short Pass Filter into the filter wheel mount. (Arrow points back!)

NOTE: You can remove the cotton gloves, but I'd still recommend keeping the nitrile gloves on.. 

9. Gently place the 522NM mount over the 522NM Short Pass FIlter, and gently screw it in place.

10. Gather the Filter Selector Assembly Back, the stepper motor and its pinion gear.

11. Attach the pinion gear to the stepper motor.

12. Insert the stepper motor into the Filter Selector Assembly Back.. 

13. Make sure it is seated properly..

14. Grab the two 608Z bearings, the Filter Selector Assembly Front and the back you just finished.

15. Gently insert the bearings into the bearing mounts..

16. Take the Filter Selector Assembly back with the stepper, pinion and bearing...and the filter wheel with the filters..

17. Place the filter wheel into the assembly.. The filters should be facing the front..  Don't worry about alignment at this point, we will cover that in a later configuration section.

18. Take the back of the assembly, the front and the M4 16mm screws..

19. Place the front onto the back of the assembly very carefully, and screw it together....

That completes this section! Congratulations!!

Set aside and move to next build!

You can close this tab or return to the build instructions here!


09.23.2014 - New Entry


lilzzman71 wrote 03/01/2015 at 19:11 point

  Hi, Here's 532nm narrow band filter, it should save your 2 filters and mechanic turning.

  Are you sure? yes | no

fl@C@ wrote 03/03/2015 at 12:15 point

Hi... That's a bandpass filter...   It's the opposite of a notch filter.  The bandpass filter would be what you'd want to use in front of the laser to only allow the 532nm light to pass from the laser into the system..  The page you supplied says "Narrow band filter is a major role in light of a specific wavelength through, let the other wavelengths of the light reflection ( or attenuation)of optical components" ...  Where he says 'light of a specific wavelength through' would mean that it only lets that light through...  Which is the opposite of a notch filter....the function the two edge filters replicate...  =)  

  Are you sure? yes | no

lilzzman71 wrote 02/26/2015 at 19:45 point

So your assembly really depends on the shape of the filter. The short pass one is long skinny rectangular shape and long pass is circular in shape.    What if both of my filters are circular and different diameters?  I think circular ones are more common?

  Are you sure? yes | no

fl@C@ wrote 02/27/2015 at 01:03 point

The point of the design is mainly so that anyone can customize it to their needs.  With parts sourced from eBay or wherever...  I am working toward refining the design so I can produce kits that will have a standardized bom..  If your filters are circular and different diameters, the .scad files are located in the github repository and can be modified to suit your needs..

Try emailing me here and I'll answer your questions.. It's getting a little confusing with multiple questions in multiple places.. :)

  Are you sure? yes | no

lilzzman71 wrote 02/25/2015 at 02:12 point

Again, no instruction to instruct newbie why need a 532nm filter.  This is receiving end from the laser source right?   Shouldn't you need a 532nm interference filter to block out the laser source and pass the scattered light through?  You need to block the 532nm light right?

  Are you sure? yes | no

fl@C@ wrote 02/25/2015 at 08:06 point

Hi...  Please take a look at ...  The two edge filters act as a notch filter to remove the 532nm light...  

  Are you sure? yes | no

lilzzman71 wrote 02/25/2015 at 19:48 point

great thanks, any idea how much a notch filter worth versus edge filter? what kind of ball park are we talking about?    Are we sure no chemical would shift the frequency between 522 to 550nm band?

  Are you sure? yes | no

fl@C@ wrote 02/26/2015 at 04:48 point

Notch filters vary, depending on what you're looking for... ( )  But expect anywhere from $350 to about $1000 each..

The desire is to create a very narrow band between the two edge filters something closer to 530 to 534 would be great if you could match a pair and find them cheap enough..  In the real world, you're probably going to have to do the best you can, its one of the give and takes of reducing a hundred thousand dollar piece of gear down to about a thousand...  I am putting considerable effort into sourcing parts for the kits that will come with as closely matched pair as I can find...  Hopefully soon...

  Are you sure? yes | no