This overview reflects the ISO working group activities of ISO/TC 172 Subcommittee 1 during the last years which have resulted in revisions and new ISO standards for optical components. For ISO 10110, ISO 14999 and other standards new surface forms and metrology techniques have been considered, standards about material characteristics have been consolidated, and optical drawings have been updated. Selected examples of new improvements and future work items are given.
The shortcomings of the standard glass 'maps’ that currently appear in optical design programs are discussed. There is a clear benefit in having a glass map that is interactive, i.e. allows the user to change system glasses directly from the map. This has been implemented in the WinLens software, and the work is reviewed in this paper. Most aspects of this 'active’ map can be customized to suit the requirements for any given lens design task. Standard maps, such as n-v-diagrams, may be generated, but for non-standard wavebands. Unusual variable combinations, such as internal transmission versus dispersion, may also be displayed. Finally, glasses in these plots may be color coded to display one or more extra optical, chemical, mechanical or thermal properties. These simple new tools can reveal significant correlations between properties and allow the designer to effectively consider a wider range of properties in his glass selection.
The full optimization process includes definition and maintenance of the merit function, selection of optimization strategy, the actual automatic improvement of the system, designer intervention and review of the final results. Well optimized systems are almost always achieved, not by a single run, but by repeated backtracking and re-optimization. A number of improvements to the whole process are presented, both to the damped lest squares algorithm itself and to the 'handling.' The enhancements include extensions to the classical damped least squares. These enhancements have been implemented in the widely used WinLens software package.
Over the years much time has been dedicated to improving lens optimization routines. Most of the work has been upon the damped least squares (DLS) method. In this paper a number of theoretical and practical enhancements are presented. Some are new, others have already been published but never transposed into commercial software. These enhancements combine to allow the user to make more informed choices at every stage of an optimization, and have now been incorporated into the widely used WinLens software package.
Complicated dielectric coatings consist of a large number of layers and thus have many interfaces, that may contribute to the total absorption of the coatings. We examined this contribution of the interfaces using two different approaches. For the determination of the absorption of the first interface between the substrate and the coatings we varied the thickness of dielectric single layers. For the examination of the influence of the interfaces within a dielectric stack, coatings consisting of (lambda) /2-layers were produced and their absorption was measured.
A new program for the tolerancing of optical designs is presented. This software was developed using a combination of theoretical understanding and practical experience. A comprehensive sensitivity analysis provides insight into the key parameters. Tolerance editors allow the user to define satisfactory tolerances in an interactive process involving parameter and defect variations; a key feature is the statistical prediction of system performance, which provides rapid feedback on the impact of any change. The production of a batch of optical systems under the current tolerances can be modeled in a Monte Carlo simulation; the resultant aberration variations are shown in multiple dynamic graphs.
Caused by several personal wishes for special features in an optical design program, which were not found in commercial software, and caused by the need of an easy documentation and handling of standard optical components from the catalog a new low cost optical analysis software was created. Meanwhile this analysis software grew up to a very useful optical design program. The intention for the development, the state today, and some special features of the software will be discussed.
The measurement of total scatter losses is a major prerequisite for the development, optimization and commercialization of high quality optical components. Especially in laser technology, optical scattering gained of importance in the source of the development of laser system with ever increasing output power and improved beam parameters. Besides its influence on the efficiency of laser systems and the beam steering arrangement, total scattering is an important safety aspect for application of these laser systems in materials processing, medicine and fundamental research. As a consequence of this global trend, working groups of TC 172/SC 9 initialized the development of an International Standard for the measurement of total scattering in optical components.
For comparability and replacability of optical component for lasers and laser system an international standard was developed. In this standard codes for the single components were laid down as well as preferred substrate materials. The most important dimension and dimensional tolerances and the material and surface equality were standardized. In the following paper the contents of the standard will be shown. Besides this some critical notes will be given.
The requirements for optical components and systems which are used for laser applications are different and normally stronger compared to standard applications. First of all, the quality is determined by the optical design of components and systems are used for different applications from DUV to NIR. Furthermore, especially in high power systems the properties of the optical elements limit their general use and their life time. For the industrial fabrication of optics in large quantities special production procedure and additional measurements for the characterization of the quality have to be performed. As is well known, the short term as well as the long term stability is limited by the material, the polishing quality and the coating. Therefore toady new standards for specification and testing of absorption, scattering and laser damage are applied in the industrial fabrication. Standardized laser components and typical data of surface quality and damage threshold will be discussed.
For optical systems special anti-reflection coatings can be designed which reduce the reflectance for a high number of glasses at normal and non-normal incidence (multi- configuration). In that way, all lenses of a lens system can be coated with the same coating design. The results for single wavelength (laser) applications as well as for broadband applications will be discussed. Furthermore, the application of these coatings in several lens designs will be demonstrated. For this, transmissions are calculated in an improved optical lens design program (WinLens). The transmission performance of complex lens systems is listed surface by surface and is graphically displayed for the optical axis and for all chief rays and therefore for all main angles of incidence. Experience about these new coating designs combined with new features in an optical design software provides new aspects about `re-design to cost' for the lens designer.
For laser applications very smooth surfaces are required more frequently. High power systems need components, such as cavity mirrors and lenses for beam forming and focussing, with extremely high laser damage threshold. In low power systems for metrology any light scattering originating from a relatively high surface roughness results in measuring errors. In both cases flat and curved surfaces with very low micro-roughness rms values close to 1 nm or even less have to be produced. This requires the optimization of the polishing process. Minimized surface roughness and light scattering are shown as results of this optimization.
The use of partially transmitting mirrors for high-power laser radiation, especially in laser cavities, requires substrates with very high-quality surfaces to avoid laser damage. The damage can arise from local increase of electro-magnetic field strength and absorption in the thin film coating and in the bounding layer of the substrate material. Therefore, extremely fine polished surfaces are needed. For YAG-laser-application at 1064 nm mostly quartz materials are used which require optimized tooling and techniques for the polishing process. The optimization of this process is achieved by identification and subsequent systematic variation of the main polishing parameters. The resulting surfaces are tested with respect to micro- roughness, light scattering and laser damage threshold both for uncoated and coated substrates. It will be shown that the damage threshold of laser mirrors can be increased by more than 100% compared with conventionally produced surfaces. Extreme threshold values can reach the damage threshold of the pure substrate material.
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