Aligning flat optical surfaces to precise gap widths
The challenge
Several optical elements with a 20mm diameter are to be aligned on top of each other with a defined gap width and joined using UV-curing adhesives to form optical sub-assemblies. The following tolerances must be achieved:
- Parallelism of the respective surface pairs better than 5µm/20mm
- Concentricity better than 15µm
- Defined air gap between 20µm and 25µm

The concept
To achieve parallelism in the joining partners over the entire surface, the optical element must be precisely handled and positioned with at least five degrees of freedom. Only the rotation around the surface normals is not absolutely necessary in this case.
At the same time, numerous macroscopic movements and interactions are required, for example when applying adhesive, feeding and removing the components and measuring the gripped components.
Building blocks
The alignment and assembly process

Loading the components
The first element is removed from the input magazine, measured on both sides and fixed in the clamping fixture.

Adhesive dispensing
The previously determined amount of adhesive is applied to the edge area of the glass surface in a defined pattern.

Precise pre-alignment
The second element is gripped, measured on both sides and positioned above the first element at double the nominal distance.

Active alignment in position, tip and tilt
The lower element is aligned using a SMARPOD. The position is controlled to the three gap widths, which are detected by the tangential measuring cameras.

Adhesive curing by UV
The adhesive is activated by UV light so that the components are firmly bonded.

Inspection and removal
After adhesive curring the assembly is illuminated and examined to verify that the gap width and the respective positions of the components conforms to the defined tolerances. The inspected end product is then removed from the assembly mount and placed into the output magazine.
Achieve unparalleled precision in parallel alignment of components
SmarAct’s solutions enable fully automated assembly with alignments at micrometer-level accuracy, as demonstrated in our application example. If your project demands similar capabilities or tailored solutions, our sales engineers are ready to assist you — contact us today!