Highly Dynamic Laser Focusing Mechanism
This technology platform described below is meant for optical applications needing high acceleration, high resolution, high frequencies and very long lifetime. In order to reach a precise relative positioning between two mobile lenses moving on the same axis and a perpendicularity of a few tenth of a degree with the machine interfaces, the stack-up has to be shortest and assembly tricks have to be applied. In the proposed solution, the precision needed in term of concentricity and perpendicularity is performed in only one component, which geometries are machined during the same manufacturing process.
Indeed, the borehole, in which the two lenses are guided, and the flange including the positioning features, are made in the same part. The two linear ball bearings are matched together in order to have an identical inside diameter. They can be based on either a recirculating balls or ball cages with limited strokes. The second solution would be preferred for small strokes and permit to save space to integrate bigger lenses. A cam follower in contact with an eccentric magnetic cam ensures the drive transmission.
This technology can be easily customized to very different sizes and specifications. The geometry tested so far is reaching the following specifications (per lens):
- Stroke ±1.5mm;
- Resolution: 1 µm;
- Frequency : up to 50Hz;
- Acceleration: up to 15g;
Possible technology customization:
- Motor selection related to frequency, speed and acceleration requirements;
- Cam and linear ball bearing type regarding the needed stroke;
- Cost vs resolution, proposing the system in open loop with a homing sensor;
- Dimensions regarding the optical system, size and number of mobile lenses;
- Flanges, to integrate fixed lenses;
- Bellows, if a clean lens chamber is needed;
- Overall size. Our product range of linear ball bearings covers from ID 1.5mm to 6mm for the L steel version, and up to 25mm with the cost effective DBL version.
Actuators for Miniature Lenses
Eye tomography and cataract operations require the focus of the laser beam to be very precise. MPS has developed high-precision miniature lens actuators for a manufacturer of ophthalmic devices.
These actuators consist of a 6 mm micromotor, a pre-loaded screw-nut system and a linear guideway. The system is designed in such a way that it is able to compensate for the imperfection of axes alignment. The most stringent requirement is to find point 0 with a precision of 1 µm between each measurement.
Developed by MPS, the system very precisely actuates a lens on a linear basis with a laser beam passing through it. This actuator consists of a ball screw and two linear bearings and must ensure that the lens is completely perpendicular with its axis during any movement. The linear positioning precision is 1 µm.