1. 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

2. 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

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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

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

14. Theory Final design concept
Introduction Theory Validation Conclusion Questions

15. 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

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

17. 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

18. 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

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

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

21. 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

22. 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

23. 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

24. Questions ?
Introduction Theory Validation Conclusion Questions

25. 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