The document discusses superresolution technology that can improve the resolution of infrared camera images. It begins by explaining the basic problem that small objects may be invisible or measured incorrectly in infrared images due to pixel size limitations. It then describes how superresolution works by using multiple images and deconvolution algorithms to effectively decrease pixel pitch by 1.6x and increase usable resolution also by 1.6x compared to normal images. Experimental results show that superresolution detects spatial frequencies about 50% higher than the camera's detector cutoff and improves temperature measurement accuracy compared to interpolation. The technology will be available as a software update for all current Testo infrared cameras.

1. The SuperResolution
Technology
Welcome to our Webconference:
16.11.2012 Dr. Martin Stratmann/Stefan Wenz/Jennifer Just

2. SuperResolution with
Deconvolution in Detail
What is the Problem?
How can we solve it?

3. 3/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Basic Problem: The Pixels
• Well known Problem:
Small objects are invisible in the image.
Even if visible, measured values are not correct.
• Obvious Solutions:
getting closer, (not always possible)
use tele lens, (have one?)
more pixels, (just a matter of money)
hot object
IR-Camera
long distance

4. 4/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Pushing the Limit
• No Solution: Interpolation
Increasing image size with interpolation does not help.
No new information gained.
• Our Solution: SuperResolution
Use multiple images and some mathematics.
Really get more information from multi-sampling.
• Result: Increase usable resolution by 1.6
Decrease effective pixel pitch by 1.6

5. 5/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Signal Chain of an IR-Camera
IR-lens & Aperture
T
x
60°C
Point Spread Funcion (PSF)
Modulation Transf. Fct (MTF)
Integration and
Sampling
Object IR-detector Electronics & Display Observer
Colormapping
Radiometric Computation

6. 6/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Sensitivity
x
Limitations of Detectors and Basic Superresolution
Area of one Bolometer (pixel pitch ²)
Typical pixel pitch: 25µm
cut-off frequency: 20 [lp/mm] (Nyquist)
Super-Sampling: Take two images, slightly shifted, and combine them
x
Sensitivity
Sensitive Area (only ~75%)

7. 7/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Naive Superresolution by Super-Sampling
• In Theory:
Take 4 images shifted by 1/2pixel pitch in x- and y-direction (super-sampling)
Combine them in a larger image.
• Problems:
How to shift images by exactly 12.5µm? (with a hand-held camera)
What about the Point Spread Function?

8. 8/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Point-Spread-Function
• PSF: How the camera blurres all points
• Lens: chromatic aberration, …
• Aperture: Diffraction, (Airy-Disc)
• For t875: f/# 1.0 -> Airy-Disc = 29 µm
Pixel size of t875 is 25µm
• Energy is distributed over several pixels
T
Airy function Airy disk
Input Output

9. 9/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Convolution and Deconvolution
• Blurring of images: Convolution with Gaussian distribution curve.
• Convolution:
Sending an input signal through a system result in an output signal.
The system applies its transfer function: So = T * Si
The transfer function can be specified as point-spread-function
• Inverting the process of convolution:
Try to reconstruct the signal which has been sent into a system by only
knowing the output signal.
For a given So and T, find Si such that So = T * Si holds.
Deconvolution of images: De-blurring / sharpening
De-blurring: refocus energy from region
Can not reconstruct lost information.
*
T
Si
So
=

10. 10/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Put it all together
• Deconvolution can reduce the blur
• Super-Sampling can reconstruct details
• Solution:
Combine super-sampling with deconvolution.
• Even better:
Use natural motion and compute image shifts
• Required:
Some arbitrary motion, ← Provided by the user.
A smart algorithm. ← Provided by Testo.

11. 11/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Steps from Science to Customer
• Developed algorithm together with a partner
• Main issue: Computational time required for 5 images of 160x120:
Start of optimisation: 30 s
Now: 100 ms
• Super-Resolution will be available for all current testo cameras
No hardware required, just software.
User can update its own cameras.

12. Results
-
Is it really better then
Interpolation?

13. 13/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Interpolation vs. Super-Resolution
Sensor resolution: 160 x 120 (original) / 320 x 240 (superresolved)
Is it really better then Interpolation? Yes it is!

14. 14/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Experimental Evidence
• MTF: Standard way to specify quality of optical systems
Measured in [line pairs / millimeter]
ISO 12233: slanted edge (problematic for processed images)
Here: Variable Frequency Target
• IFOVmeas: That is what really matters for thermal imaging
Setup with black body at reference temp
Vary aperture in front
Observe maximum
Similiar to CNPP Test

15. 15/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Variable Frequency Bar-Target Analysis
Cubic Interpolation Super-Resolution
- Analyse Modulation Transfer Function by observing the bar target.
- Measuring contrast and frequency

16. 16/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Signal Modulation
Normal Image
false temperature
Superresolution
aliasing

17. 17/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Detectable Spatial Frequencies
Cubic Interpolation
0
5
10
15
20
25
30
0 5 10 15 20 25 30 35
Frequency from bar target [lp/mm]
Frequencyfromimage[lp/mm]
Superresolution
0
5
10
15
20
25
30
0 5 10 15 20 25 30 35
Frequency from bar target [lp/mm]
Frequencyfromimage[lp/mm]
no frequencies above detector cut-off
detectable
frequencies approx. 50% above detector cut-off
detectable

18. 18/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Modulation Transfer Function
0,00%
20,00%
40,00%
60,00%
80,00%
100,00%
0 5 10 15 20 25
Spatial Resolution [lp/mm]
Super-Resolution
Normal
Diffraction Limit
Testo 881, 160x120, pixel pitch 25µm, F0,84
x1.6

19. 19/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Variable Aperture
• Setup: Black Body at 60°C,
variable aperture ( d = 2-32mm), camera at 1.6m distance
60°C
160cm
d = 32mm d = 6mm
Evaluating temperature of the hottest spot (Max-on-area)

20. 20/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Temperature Measurement of Variable Aperture
59,4 58,8
57,5
56,1
52,7
40,8
60,9
59,9
61,9
60,7
62,5
43,2
30
35
40
45
50
55
60
65
32 16 8 6 4 2
aperture diameter [mm]
T[°C]
Normal
Superresolution
320x240 pixel, 25µm pixel pitch, 32°-Lens, Distance = 160cm
False Positive
IFOVmeas/1.6 = 4.8mmIFOVmeas =7.8mm
False Negative

21. 21/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Image Comparison
testo 875i Normal
testo 875i Superresolution
testo 882 Normal
testo 882 Superresolution
For 640x480 Sensor:
SuperResolution: 1280x960

22. 22/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Close-ups
testo 875i Normal
testo 875i Superresolution
esto 882 Normal
testo 882 Superresolution

23. 23/24Testo AG, SuperResolution - Webconference (1.0), 1000len-juj, 15.11.2012, Confidentiality 2
Conclusions
• Superresolution + Deconvolution:
Combine several images
Reduce blurring
Use natural motion
• Result:
Increase spatial resolution by 1.6
Decrease effective pixel pitch by 1.6
• Available as software-update for all
current Testo-IR-Cameras
Even for already sold cameras.

24. Testo SuperResolution:
Get the most out of Your Pixels.
Thank you for your attention!
Any questions?