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Passive athermalization has become a key-technology for automotive and other outdoor applications using modern uncooled 25 and 17 micron bolometer arrays. For high volume applications, passive athermalized optical designs with only two lenses reduce costs. A two lens solution requires a careful choice of lens and housing materials. A first order approach to thermal drift uses the RAYLEIGH criteria for depth of focus. It can be seen that narrow field of view lenses are the most sensitive to defocus with temperature. The different methods used to achieve stable performance over the required Temperature Range can be compared, namely passive optical athermalization and passive mechanical athermalization. GASIR ® possesses inherent properties enabling optical passive athermalization. High resolution, two element designs for different field angles are presented. Each lens category is present: Super Wide Angle, Wide Angle, Standard, Tele and Super Tele. All examples are designed for 17micron VGA-detectors. These designs use aspheres and diffractive structures. The impact of temperature on all these parameters can only be determined by ray tracing. The proposed metric is the average of the tangential and sagittal MTF versus image height at Nyquist frequency. A very nonlinear impact of temperature on MTFA at different image heights is clearly visible. Examples are shown. An MTF based criteria for judging athermalization is proposed. It contains two values: the admissible MTF-drop ΔMTF in % and the resulting Temperature Range ΔT in Kelvin. The procedure to get these values is demonstrated. Values of 9 lens assemblies are listed. A comparison with results of first order approach shows limitations of this approach. A general quantification of athermalization is proposed. The pair of values (ΔMTF, ΔT) is independent of other lens indexes. The limitations of this method are discussed. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2015 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 8353 835325-2 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2015 Terms of Use: http://spiedl.org/terms

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The practical application of Fresnel lenses in imaging systems is very much disputed. However, in large field, object side, telecentric lenses conditions are such, that the advantages of lightness, cheap production and short construction length dominate the disadvantages. These disadvantages concern the reduced image quality. Starting from any paraxial relations, we present analytic equations which are useful in estimating the changes in the aberration balance, when a well compensated glass lens front group is replaced by a Fresnel lens singlet. The comparison of a pair oftelecentric lenses with the same basic parameters, built with a glass lens front group and with a Fresnel singlet front group, confirms these equations. The reduced image quality, using a Fresnel singlet as front group in an object side telecentric lens, is caused by noncompensated lateral chromatic aberration, increased distortion values, higher stray light levels and reduced resolving power. For inspection purposes, the distortion is often not so important. Ifthe work pieces are illuminated with monochromatic light, then chromatic aberrations become unimportant. Therefore, for machine vision inspection purposes, the object side telecentric ray path can be straightforwardly achieved using a Fresnel lens front group. This is an alternative to the well known, but expensive, glass front lens solutions.

Die 2‐D‐Messtechnik mit elektronischen Bildaufnehmern hat sich zu einer Schlüsseltechnologie der Automatisierung entwickelt. Dabei hat die Frage nach der erreichbaren Genauigkeit oberste Priorität. Sie entscheidet über die Wahl der Kamera, der Abbildungsoptik und der Beleuchtung.