Michael Bechtold

A non-contact surface measurement system for freeform and conformal optics

OptiPro Systems has been developing the UltraSurf, a non-contact measuring system using state of the art, precision motion control. The goal is to precisely scan standard optical shapes such as concave and convex spherical surfaces, as well as the complex geometries of aspheric, ogive, and freeform shapes without the limitations associated with other measurement methods. Common optical measurement methods have limitations with surface roughness, slope error, and deviation from best-fit sphere. Optipro designed the UltraSurf to further the manufacturing capabilities of companies generating complex precision optics. The UltraSurf measures with sub-micrometer non-contact point sensors to collect surface information. Various sensors are commercially available from multiple companies, each with their own distinct optical measuring technology. One optical sensor uses white light confocal chromatic imaging to measure individual optical surfaces. Another optical sensor uses low-coherence interferometry with a near infrared laser, and is able to measure the inside, outside, and thickness of optical materials at a single point. The UltraSurf scans the optical sensors over the surface of the part under test, keeping it normal to the surface. The single point measuring method coupled with computer-controlled motion gives the UltraSurf flexibility to measure greatly varied geometries. Ultimately, a point cloud of the measured surface is generated. The cloud can be used to calculate deviation from the desired shape, as well as various surface parameters. Applications, definitions, and measurement results of freeform and conformal shapes using UltraSurf will be presented.

Ultrasonic grinding of optical materials

Hard ceramic optical materials such as sapphire, ALON, Spinel, PCA, or Silicon Carbide can present a significant challenge in manufacturing precision optical components due to their tough mechanical properties. These are also the same mechanical properties that make them desirable materials when used in harsh environments. Slow processing speeds, premature tool wear, and poor surface quality are common results of the tough mechanical properties of these materials. Often, as a preparatory stage for polishing, the finish of the ground surface greatly influences the polishing process and the resulting finished product. To overcome these challenges, OptiPro Systems has developed an ultrasonic assisted grinding technology, OptiSonic, which has been designed for the precision optics and ceramics industry. OptiSonic utilizes a custom tool holder designed to produce oscillations, in microns of amplitude, in line with the rotating spindle. A software package, IntelliSonic, is integral to the function of this platform. IntelliSonic can automatically characterize tooling during setup to identify and select the ideal resonant peak which to operate at. Then, while grinding, IntelliSonic continuously adjusts the output frequency for optimal grinding efficiency while in contact with the part. This helps maintain a highly consistent process under changing load conditions for a more precise surface. Utilizing a variety of instruments, tests have proven to show a reduction in force between tool and part by up to 50%, while increasing the surface quality and reducing tool wear. This paper will present the challenges associated with these materials and solutions created to overcome them.

Ultrasonic precision optical grinding technology

As optical geometries become more precise and complex and a wider range of materials are used, the processes used for manufacturing become more critical. As the preparatory stage for polishing, this is especially true for grinding. Slow processing speeds, accelerated tool wear, and poor surface quality are often detriments in manufacturing glass and hard ceramics. The quality of the ground surface greatly influences the polishing process and the resulting finished product. Through extensive research and development, OptiPro Systems has introduced an ultrasonic assisted grinding technology, OptiSonic, which has numerous advantages over traditional grinding processes. OptiSonic utilizes a custom tool holder designed to produce oscillations in line with the rotating spindle. A newly developed software package called IntelliSonic is integral to this platform. IntelliSonic automatically characterizes the tool and continuously optimizes the output frequency for optimal cutting while in contact with the part. This helps maintain a highly consistent process under changing load conditions for a more accurate surface. Utilizing a wide variety of instruments, test have proven to show a reduction in tool wear and increase in surface quality while allowing processing speeds to be increased. OptiSonic has proven to be an enabling technology to overcome the difficulties seen in grinding of glass and hard optical ceramics. OptiSonic has demonstrated numerous advantages over the standard CNC grinding process. Advantages are evident in reduced tool wear, better surface quality, and reduced cycle times due to increased feed rates. These benefits can be seen over numerous applications within the precision optics industry.

Grinding, Polishing, and Metrology of Freeform Optics

Currently the design and utilization of freeform shapes are costly due to the difficulties introduced with fabrication and metrology of these parts. OptiPro is developing freeform manufacturing solutions though computer controlled multi-axis optical generating, polishing, and metrology machines

Finishing of Deep Concave, Aspheric, and Plano Surfaces Utilizing the UltraForm 5-Axis Computer Controlled System

UltraForm Finishing is a precision polishing machine capable of finishing a large variety of surfaces. An explanation of the process flow is presented as well as the results from a figure corrected asphere.

Finishing of Optical Materials with Bound and Loose Abrasives Utilizing the Ultraform 5-Axis Computer Controlled System

Finishing using bound and loose abrasives, requires consistent static environmental conditions and deterministic control over the dynamic variables. Experimental analysis of these variables is used to determine their influence on resultant surface form and finish.