Go to the content (press return)

Strategy to include the induced GRIN profile in plastic lenses done the inyection process in the optical systems design stages

Type of activity
Competitive project
Funding entity
Funding entity code
31.590,00 €
Start date
End date
Any Optical design process must include the specification of its own elements and the environment. During this last decade the injected thermoplastic lenses had achieved the quality standards to be used as a part of the optical systems with high performances, however this thermoplastic lenses (whether of PMMA and PC) presents a change of the refractive index linked at the volume (GRIN behavior) that must be taken in account for this applications. The thermoplastic lenses manufacturing process starts with the material was in liquid phase and is injected in the cast, when the lens is made in thermoplastic material the cooling process is very fast (direct linked with the volume and process) and the lens don’t reach the solid state at the same time, the solidification begins from the skin to the center of the volume. The effect of non-equal solidification time it’s impossible to avoid, also in the best molded lenses, the refractive index changes from the skin to the center; to do this process more difficult to simulate also changes in the surface shape are introduced during the solidification stage. However thermoplastis show two limitations compared to glass: temperature dependence of optics features and refraction index variation depending on lens geometry and molding process parameters. Small changes on process settings affect the shrinkage and therefore the level of internal stress achived by the part during the molding process. As a consequence plastic molded lenses show a volumetric variation of refraction index (called GRIN phenomenom) with a significant impact on its optical performance If we introduce all this phenomena in the optical design process is possible to increase the quality of the lenses. This project want to introduce strategies to describe the material properties measurement strategy and surface shapes during the design stage in order to find better thermoplastic injected lenses with predetermined GRIN profile. To reach our objective we have structured this report around three specific objectives, this objectives are complemented with two extra generic objectives, one devoted to the knowledge transfer and another so select the practical cases where we want to check the accuracy of our strategy To reach our objetivo we proposed three specific objectives that are combined with four specific objectives devoted to the manufacture of samples; modeling, methodology and data and parameter adquisition, the manufacture specific objectives are delevolpe along all the proyect: Specific Objective 1: Measure of the distribution of the refractive index in thermoplastic lenses As we have said the thermoplastic material supplier only offer information of the third digit of the refractive index as a direct consequence of the manufacturing process; in our job we want do an adaptation of the existing technology (CT and QPM) to measure the GRIN profiles in thermoplastic lenses to reduce the acquisition time with an equivalent accuracy. This objective has the great risk but, at the same time, we hope that the great scientific contributions can arrive. Specific Objective 2: Measurement modeling and introduction in the simulation software (own and commercial) Taking as start point the measurements done in the previous specific objective we want adjust analytical models to be incorporated in the optical software design. We want to try using solutions that goes from polynomial expressions to custom models that include the “distance to the skin” as a key value. The models that we will find can be scientifically interesting because they can be used to calculate the real aberration in thermoplastic lenses. Specific Objective 3: Experimental checking of the models Once we have the volumetric distribution of the refractive index for a collection of selected lenses and with the models proposed in the previous objective we will use this models to predict, in a new set of lenses, the aberrations of those lenses. The selection process of the set of lenses used to check the models will be done as an objective itself because we want that this set of lenses covers the most usual cases. The aberration will be measured using a standard setup. In orden to obtain valid samples the last generic objetive are be distruited along all the project, this specific objectives will be carry out by ASCAMM A1.- To develop a model able to predict optical behaviour of a selected group of lenses typologies according to part geometry, thermoplastic type and process settings A2.- To determine a methodology for the optical characterization (GRIN measuring) coordinated with the geometric definition and molding process parametrization A3.- Experimental data acquisition according to a DoE that will allow to refine the model A4.- Validation via real cases
Diseño, GRIN, Lentes, Metrologia, Optica, inyección, plástico
Adm. Estat
Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica 2008-2011
Resoluton year
Funcding program
Diseño y Producción Industrial
Funding subprogram
Diseño y Producción Industrial
Funding call
Proyectos de investigación y acciones complementarias
Grant institution
Gobierno De España. Ministerio De Economía Y Competitividad, Mineco