Intro to Thermal Imaging

Introduction

The goal of this lab was to get a better understanding of thermal cameras, how they work, and what they can and cannot do. The thermal camera used to capture the images was a FLIR E series. 

Methods

The methods for testing the thermal camera involved using it capture images, to gather data on their thermal values. Some of the things that had to be considered while capturing the images were the use of false color, and the use of overlaying thermal over electro optical (EO) images .  

Their were 2 color palates that were used in the lab, Ironbow, which is yellow hot and purple for cold, and a black and white scale. The benefits of the Ironbow palate was that it was easier to identify which part is cold and which is hot as this is how one would normally expect as people have associated blue with cold and red for hot. A drawback of using the iron coloration is that some detail is lost in the process of adding the color. The benefits of using the black and white scale is that it represents the true data that comes out of the thermal imagery, and it has more detail than the iron scale. A downside to the black and white scale is that they are not as intuitive as both white hot and black hot are used, even if white hot is more common, it could create some confusion if the scale is lost. 

Figure 1. An EO image of the air conditioning duct 

Figure 2. An IR image of the air conditioning duct, with the
Ironbow color palate

Figure 3. An IR image of the air conditioning duct, with the
White Hot color palate

Results

Temperature Scales:

 The images taken with the IR camera have a temperature scale, which shows the color values for the hottest and coldest objects in the image. The temperature scale adjust for the range of the image, in the image of the Air conditioning vent, (Figure 2 & Figure 3) the scale's highest temperature is 71.0 & 71.1 degrees Fahrenheit and the scales lowest temperature is 56.2 & 55.7. When their is a different high temperature and low temperature the camera adjust the scale and the color grading accordingly, like in the picture of the bus, with its exhaust being a temperature of higher than 266 degrees Fahrenheit, and the coldest object outside in the image being the light post at 64.6 degrees Fahrenheit. 

Figure 4. An IR image of a bus using the White Hot palate

Figure 5. An EO image of the back of a bus and the
parking lot around it. 

Another thing that was tested during the lab was the effects of glass being in between the object you want to sense and the thermal camera. Their were two trials that were tested and the glass behaved slightly differently each time. In figure and figure the glass door is in front of the person in the image, and the thermal does not show the persons heat value, but instead shows the heat values of the people taking the image. The glass acts like a mirror to the thermal sensor. 

Figure 6. An EO image of a person standing outside a glass
door of the NISW building 

Figure 7. An IR image, using the ironbow color palate, of
a person standing outside a glass door

In the second test the person put their hand on the glass which can be seen by the thermal camera as the heat transfers through the glass, but the rest of him cannot be seen with the thermal camera as the glass acts like a mirror. 

Figure 8. An EO image of a person pressing their hand
against a glass door

Figure 9. An IR image, using the ironbow color palate, of
a person pressing their hand against a glass door

Next to be tested was how a thermal cameras temperatures changes as the hot and cold objects move further away from the camera, this was tested by having a person who's known temperature was around 98.6 move about 20 feet away from the IR camera and stand below a tree. The Camera sensed his temperature to be around 89.5 degrees Fahrenheit which is about 9 degrees lower than it should be. 

Figure 10. An EO image of a person standing next to a tree
20+ feet away from the camera. 

Figure 11. An IR image digitally zoomed, using the
white hot palate, of a person standing 20+ feet away

Discussion

The lab helped introduce the IR camera settings for handheld IR cameras and showed some of their applications and drawbacks. IR cameras have many applications, such as monitoring pipelines, and looking for hot spots on them which could show problems, or looking at roof to spot inefficiencies with the insulation. Their are some drawbacks for IR cameras that affect UAS operations with them, one being that the temperatures get less accurate with distance, which is a problem for UAS as most are further than 20 feet away from the objects that they are taking images of. Another drawback of IR is the inability of getting a temperature of glass, and images of glass can skew the data as they show reflected thermal images.
Conclusion
In conclusion, IR is another sensor that can be used to help Identify problems and inefficiencies that the human eye and electo optical cameras cannot see.