Master Thesis Presentation – Bart Festen Proof of concept of a thermal imager with milliKelvin thermal resolution Exam committee: Prof. ir. R.H. Munnig Schmidt Ir. R. Saathof (daily supervisor) Ir. J.W. Spronck Dr. Ir. J.F.L. Goosen

Introduction Thermal deformation Component of a high precision machine Local heat input Temperature distribution Thermal deformation Measure temperature distribution: Thermal imager UNWANTED! Introduction Theory Validation Conclusion Questions

European Extremely Large Telescope Introduction High precision imaging systems European Extremely Large Telescope Introduction Theory Validation Conclusion Questions

Introduction Problem definition High precision imaging system with mirrors Light Measure temperature distribution Supported contactless In vacuum Nanometer deformations milliKelvin temperature difference Measure contactless! Introduction Theory Validation Conclusion Questions

Introduction Problem definition Measure temperature distribution Specification Value Unit Thermal resolution ≤ 1 [mK] Spatial resolution 10 [mm] Response time 1 [s] Conditions Vacuum Contactless Measure temperature distribution Grid squares: 5x5 [mm2] Temperature difference: 0,001 [K] Introduction Theory Validation Conclusion Questions

Theory Conventional imagers Infrared camera Advantage Small spatial resolution and response time Disadvantage Thermal resolution ≥ 10 [mK] Need for a new thermal imager with a thermal resolution of 1 [mK] Introduction Theory Validation Conclusion Questions

Target area of interest Theory 5 [mm] Main principle Target area of interest Target Pixel Frame Array of pixels Reference Reference object Performance of the thermal imager is determined by its pixels Grid area: 5x5 [mm2] Introduction Theory Validation Conclusion Questions

Theory Design path Design parameters influence the performance of the pixel All design parameters and the specifications are combined into a design path Pixel area is main design parameter in achieving the thermal resolution Look at influence of pixel area on the design Introduction Theory Validation Conclusion Questions

Theory Measurement principle Target Heat flow Frame Pixel Reference Target area of interest Target Heat flow Pixel Frame Frame Pixel Reference Reference In infrared cameras: Introduction Theory Validation Conclusion Questions

Theory Heat transfer coefficients Conduction Radiation Target Heat transfer coefficients Pixel Frame Conduction Determined by thickness and length of frame legs Reference Radiation Determined by the area of the pixel Pixel Frame leg For smaller thermal resolution Maximize pixel area Introduction Theory Validation Conclusion Questions

Theory View factor View factor Target View factor Pixel Frame View factor Determines how much of the radiation falling on the pixel comes from its target area of interest Dependent on target-pixel distance and pixel area Reference Cross-talk Introduction Theory Validation Conclusion Questions

Theory Temperature uniformity Temperature uniformity Target Temperature uniformity Pixel Frame Temperature uniformity Pixel temperature should be uniform Dependent on the ratio between pixel area and pixel thickness Limits the pixel area to 1,5x1,5 [mm2] Reference Introduction Theory Validation Conclusion Questions

pixel temperature is not uniform Theory Thermal resolution (NETD) pixel temperature is not uniform Introduction Theory Validation Conclusion Questions

Theory Final design concept Introduction Theory Validation Conclusion Questions

Validation Validate the influence of increasing pixel area Demonstrate working principle of the concept Experiments Scale pixel in thickness Single pixel Introduction Theory Validation Conclusion Questions

Validation Components A = 10x10 [mm2] A = 3x3 [mm2] A = 30x30 [mm2] Introduction Theory Validation Conclusion Questions

Validation Response time Goal Validate increase of the radiation heat transfer coefficient with increasing pixel area Experiment Expose pixel to a step heat input Repeat for different pixel areas Introduction Theory Validation Conclusion Questions

Validation Response time Response time Measurement result Response time Ratio of heat capacity and total heat transfer coefficient Conclusion Response time reacts to increase of pixel area as expected Introduction Theory Validation Conclusion Questions

Validation Thermal resolution Goal Validate target temperature measurement Experiment Bring target to different temperatures Repeat for different pixel areas Introduction Theory Validation Conclusion Questions

Validation Thermal resolution A = 10x10 [mm2] A = 3x3 [mm2] Introduction Theory Validation Conclusion Questions

Validation Thermal resolution Prediction of target temperature A = 30x30 [mm2] Prediction of target temperature Target temperature calculated with reference and pixel temperature Can be improved by: Pixel with uniform temperature Better temperature sensor Larger view factor Taking cross-talk into account Introduction Theory Validation Conclusion Questions

Conclusions Design path created Concept design well within specification Pixel area is main design variable, increasing the area: Improves thermal resolution Area is limited by spatial resolution, view factor and temperature uniformity Current setup has rms thermal error of 3 [mK], improves by: Pixel temperature unifomity Performance of temperature sensor Larger view factor Taking cross-talk into account Introduction Theory Validation Conclusion Questions

Recommendations Investigate performance of an array of pixels Achieving spatial resolution Accounting for cross-talk effects Investigate manufacturability of the concept Introduction Theory Validation Conclusion Questions

Questions ? Introduction Theory Validation Conclusion Questions

Master Thesis Presentation – Bart Festen Proof of concept of a thermal imager with milliKelvin thermal resolution Exam committee: Prof. ir. R.H. Munnig Schmidt Ir. R. Saathof (daily supervisor) Ir. J.W. Spronck Dr. Ir. J.F.L. Goosen