Aligning Optical Axis of 2 Lens Assemblies

[0207]

i have two optical lens assemblies performing separate functions individually. Now I want to allign their optical axis .. how do i achieve the alignment?

(actually i want to allign them back to back and ensure that their optical axes are concordant, if not overlaping ,then atleast parallel )

 

[Andy Resnick]

Optical alignment techniques are not taught as much as they should be. First, each element has at least 4 degrees of freedom: if the propagation direction is 'z', each element can translate in 'x' and 'y', and in addition pitch and yaw rotations. If the assembly is nonaxisymmetric (off-axis parabola, for example) then there is also roll rotation. 'z' translation is not usually considered a degree of freedom, but it can be in some cases.

So the first step is to mount each assembly in a mount that allows independent control of the different degrees of freedom: 2 translation stages and 2 rotation stages. Putting the mount on a rail allows control over the 'z' axis as well. I cannot emphasize enough that taking time and effort to assemble a good mounting rig, with micrometer screws and minimal backlash, will make your life infinitely easier.

Once that is done, alignment is fairly straightforward. If the source is a laser, the easiest is to simply look at the backreflected spot- when the elements are aligned, the backreflection lies centered on the output window of the laser.

In general, the idea is to first establish an optical axis - the source is shooting stright down the mechanical axis of a rail, for example, and any folding mirrors maintain the proper propagation axis. Typically this is done with a pair of pinholes. Then insert each element, starting with the element closest to the source, and align it to maintain the optical axis, again using the pinholes.

Hope this helps.

 

[astrokreng]

Aligning the optical axis of two lens assemblies is an important step in ensuring the proper functioning of your optical system. To achieve this alignment, you will need to follow a few key steps.

1. Identify the optical axis of each lens assembly: The optical axis is an imaginary line that runs through the center of the lens and is perpendicular to the surface of the lens. To align the lenses, you will need to know the exact location of the optical axis for each lens assembly.

2. Use a reference point: Choose a reference point on one of the lens assemblies that will serve as a guide for aligning the other lens assembly. This could be a mark on the lens or a specific point on the lens housing.

3. Adjust the position of the lens assemblies: Using the reference point, adjust the position of the lens assemblies until they are back to back and parallel to each other. This may require making small adjustments to the position of one or both lens assemblies.

4. Use a laser or collimator: A laser or collimator can be used to check the alignment of the optical axes. By shining a laser or collimated light through one lens assembly and observing the output on the other lens assembly, you can determine if the axes are aligned. If the output is not aligned, make further adjustments to the position of the lens assemblies until the output is parallel.

5. Check for overlapping: If your goal is to have the optical axes overlap, continue making small adjustments until the output from both lens assemblies is perfectly aligned.

6. Use locking mechanisms: Once the alignment is achieved, it is important to secure the position of the lens assemblies using locking mechanisms such as screws or clamps. This will prevent any movement that could disrupt the alignment.

It is important to note that achieving perfect alignment of the optical axes may not always be possible due to manufacturing tolerances and limitations. In such cases, it is important to aim for parallel alignment to ensure the best performance of your optical system. Regular checks and adjustments may also be necessary to maintain the alignment over time.