High Precision Alignment of Micro Lenses on an Arbor with Four Degrees of Freedom
Particularly in the production of micro lenses, as used in endoscopes, the manufacturing process finishes with the turning of the lens edge to the final diameter. To do so, the lenses are aligned and cemented on an arbor or mandrel which specifies the axis of symmetry and is used as a holding fixture for the processing machine. Two assumptions are made with this process:
- The center point of the ring chuck on which the lens is cemented is on the reference axis of the arbor.
- The bottom lens surface lies in full contact on the ring chuck.
Unfortunately, reality looks somewhat different: Even with the most high quality arbors, the tolerance between the center point of the ring chuck and the arbor axis is at least 1 µm. Furthermore, the quality of the arbor is continually reduced by its use in production, due to the application of the cement, its removal and the subsequent cleaning. But also the cementing process of the lens on the arbor is error-prone as resulting cement wedges lead to a tilt of the lens axis relative to the arbor axis, which has previously remained unconsidered.
With the new Lens Align 4D module for the proven OptiCentric® 100, TRIOPTICS now has an answer to this variety of difficulties. Product developer Christian Wilde explains: "Lens Align 4D enables high precision results to be achieved without being dependent on the quality of the arbor and the adhesive layer. The completely automated and, consequently, user-independent process is also very fast. It takes less than one minute for the measurement, alignment and UV curing."
In order to achieve this, the lens is held by a piezoelectric micro-gripper over the ring chuck on an adhesive drop. The holding pressure of the gripper can be individually adjusted, so that the process also protects the lens. The lens is then aligned to the arbor axis with respect to tilt and shift, in four degrees of freedom, and held at a defined distance over the ring chuck. Consistent accuracies of 1 µm for the shift and 5 arcsec for the tilt can then be realized, independently of the arbor.
In addition to the described application, the Lens Align 4D module can also be used for the alignment of micro lenses in mounts. "In general, it can be said that Lens Align 4D enables the alignment of micro lenses in relation to all mechanical reference axes," summarizes Wilde.
The first presentation of the Lens Align 4D module will be made at OptiFab 2017 in Rochester, NY, USA. The reasons for and information about the requirements in the alignment and cementing process of lenses on an arbor will be explained in a lecture on October 16th, as part of Session 3, "Grinding and Polishing Processes III."
About the lecture:
Event: OptiFab 2017, Rochester, NY, USA
Title: Novel Process for Production of Micro Lenses with Increased Centering Accuracy and Imaging Performance
Author: Christian Wilde
Date: Monday, October 16, 2017, 1:30 PM – 3:30 PM
Meeting room: Highland A/B