## ALLVAR Alloys for Optics | |

ALLVAR Alloys offer a high magnitude Negative Thermal Expansion (NTE) in the axial direction, and a positive expansion in the radial direction. This NTE can compensate for the natural changes in an optic’s focal length as temperature changes, thus allowing reduced length, weight, and complexity of optical assemblies, like the one shown to the left. | |

## The IR Optic Problems | |

The A particularly challenging issue arises in infrared optics when large changes in refractive index with temperature (𝑑𝑛/𝑑𝑇) create a negative 𝛿 | |

The current solution to the negative 𝛿_{𝑓} problem is the parallel system displayed to the left. The trade off is the increased diameter, length and weight with decreased mechanical stiffness and stability when compared to the simpler series system. | |

## With ALLVAR NTE Metals, you can:*Decrease*thermal compensator*length, diameter,*and*weight**Simplify*design and manufacturing.
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## A Solution by the Numbers | |

The plot below demonstrates how ALLVAR Alloys can simultaneously open the achievable series system design window and decrease the length of commonly used Aluminum and Delrin parallel systems. The term 𝐿_{2}/𝑓 is used to quantify the increase in total thermal compensator length of the parallel system compared to the series system. It represents the increased length required per unit of focal length. | |

Comparing commonly used Aluminum and Delrin to ALLVAR Alloy 30 and Delrin, . Not only does the current theoretical parallel system window the savings are immediately apparentextend down to -30×10, but the ALLVAR-Delrin system can ^{-6} K^{-1}reduce compensator length up to 40%. |

For more info, please refer to the technology page.