The success of many advanced technologies increasingly depends on the precision of the optical
lenses used. Therefore the demand for high precision optical elements in more common devices and
instruments is increasing as well. Concurrently the need to make devices smaller and lighter weight
is also driving the demand for precision optical elements. Therefore, the use of aspherical glass
lenses is growing tremendously and has become the standard for many applications.
So far most methods for manufacturing aspherical glass surfaces use grinding and polishing. Very
sophisticated methods such as Ion Beam Figuring have not been used for common precision optics.
The reasons for this might be perceptions of high costs, doubt about the ablation rate and limited
knowledge about the technique within the optical industry.
Now Asphericon has set up its first ion beam correction system for precision aspherical optics (asphericon
ION-Finish). This presentation will show how the ion beam technology has matured and
become affordable enough for common precision applications. In some examples we will show how
ion beam systems are used to correct aspheres to precisions of better than lambda/60 rms (10nm).
Together with a flexible measurement technique, the manufacturing of aspherical glass lenses becomes
very fast and cost-efficient. Furthermore, advantages and disadvantages will be discussed. In
connection with that the required quality of the pre-polishing will be addressed too. Finally it will be
shown how fast the correction process can be and how flexibly the size of the tool can be changed.
Recently and upcoming optical applications depend more and more on the precision of the optical elements used. The
last is especially driven by shorter wavelength, higher flux densities and imaging close to the diffraction limit. Therefore
a dramatically increasing demand on high precision and high quality optical components in leading edge equipment as
well as common devices and instruments is observed.
So far a few methods have been introduced to provide an adequate manufacturing performance using mechanical grinding
and polishing techniques. Up to now the very sophisticated ion beam figuring (IBF) has not been used for common
optics. The reasons for this might be the perception of higher costs and less knowledge about the technique in the industry.
Now an affordable ion beam figuring technique has been developed to address precision aspherical optics applications.
This paper introduces ion beam figuring technology based on equipment which is widely used in semiconductor mass
production for ultra precise film thickness trimming.
Ion beam figuring works by raster-scanning a focused broad ion beam across an optical surface with variable velocity
and dwell time in order to precisely and locally trim away surface contour errors.
As a new and cost effective approach the ion beam figuring system used in this presentation applies a 3 axis movement
system only (compared to expensive 5-axis movements in other applications). X-and y-axes are used for the areal scan,
and the z-axis is used for focus adjustment due to the surface contour of the optical element. The system was intentionally
designed without the 2 additional tilt axes for incident angle adjustment and cleverly reduces the complexity and size
of the system.
It is shown that curved spherical or aspherical surfaces can be corrected down to λ/50 or better by using the state of the
art 3-axes trimming system. Even with high spatial frequency parts final processing qualities better than λ/10 are