Time Behaviour + Geometry of IR Cameras - Page 1
Forum section: electronics / projects

author: lucidlenn
author_rank: Newbie
timestamp: November 07, 2016, 06:28:50 pm
content: Hi!I'm a currently a student, sitting in Germany. I have to write my bachelor thesis to finish my studies...my task is to test and compare different Infrared Cameras...I'm seeing results but part of my task is to test the cameras on "time behaviour" and "geometry" (i was told to find out where the camera looks).I don't fully understand what time behaviour and geometry means in the context of infrared cameras. Unfortunately my prof just went on vacation - thats why im asking here :-)Does time behaviour refer to the ability of the camera how many pictures it can take for a given amount of time? Or how fast the camera responds to a change of temperature?If it refers to the time the camera needs to identify the change of temperature - how can I test this? I thought about letting the camera view an object of which the temperature changes very quickly and timestamp the temperature change and the time of the camera when it receives the change. The problem here is: I dont know how to synchronize this?Also I am not sure how to test the "geoemtry" of a camera? Any advices?Any advices are welcome!Please excuse my broken english.Cheers!PS: All I get out of the cameras is a series of pictures + timestamps of the pictures + the temperature.

author: LaserSteve
author_rank: Super Contributor
timestamp: November 07, 2016, 08:44:53 pm
content: I'm not a big fan of professors who assign tasks without details. For those students often end up knocking on my door, for clarification.Make sure you have downloaded the data sheets and manuals for the cameras , interface electronics, and the lenses. Then try to understand them on your own. Ask questions if need be, ie Grad students, Lab technicians, Other Professors, etc.The USAF 1951 Resolution TEST Chart at varying distances would be a start. Measuring the field of view across a range of lens zooms, iris settings, and focal distances would be a start. Getting a rough idea of the Mean Transfer Function or # of Line pairs at unit distance is always a good idea.Time behavior (Too Many Definitions to count) May involve flashing a source of heat in the field of view for one frame time and see how long any afterimages stay around. How short a pulse can it see? How long? How does it handle intense heat sources? Caution, borrow a silicon wafer from another lab as a attenuator before exposing expensive thermal cameras to hot sources such as soldering irons, ovens, and flames. Excessively hot or bright sources can be focused down well enough to damage a sensor plane. I did have a grad student burn/damage pixels on my bolometer camera evaluating a hot lab oven for uniformity.Camera shutters of the mechanical leaf kind may be found in your lab, or from a place that has used cameras. Syncing them may not be as needed as you think. Your question may really involve estimations based on frame rate and shutter speed from the data sheet, and not require a measurement.I could go on for hours.I'm a University Research Technician. I'll be honest. At this point, most professors would prefer you email them and ask for brief assistance. Grad student and undergraduate student time is expensive in Western countries. MOST professors do not appreciate when you do some thing off the wall or if you do not use the assistance of equipment that may be on campus that you do not know about.Of course there is the odd professor whom would test you to see what you can come up with, and prefer you not email. Those are the good ones...But they are rare.Ask the more senior student or Postdocs, this may be a common exercise for first years. I suspect your being tested on how YOU behave on your own. You may be being evaluated for admission to further educational opportunities.I'd urge you to draft a brief email to your Prof : Asking what He/She/ wants you to do, and with some of your own suggestions for approval. You need to establish a relationship with your supervisor that is not stressful, or Employment or Grad school will be Hell on Earth.CUE up user Fraiser, who is our resident thermal camera expert. If he does not appear in this thread, go to the Thermal Imaging subforum and find him.Ask him if there are standard tests for IR imaging.Steve

author: lucidlenn
author_rank: Newbie
timestamp: November 08, 2016, 08:47:33 am
content: Hi Steve!That was more than what I was hoping for!I will do my research on your suggestions.Many thanks!LennartPS.: I should've added that I do have Access to a laboratory with a blackbody.

author: lucidlenn
author_rank: Newbie
timestamp: December 02, 2016, 11:29:19 am
content: Hi,so I looked up your suggestions and talked to my prof.What's supposed to be measured is the thermal time constant of the cameras using chopped infrared radiation. I do get the principle.The frequency of the chopping is increased step-by-step and measured by the camera until the camera's responsivity decreases / stays constant.Usual thermal time constants vary between 5 ms and 15 ms.My cameras only get pictures every 120 ms...So how can I calculate the time constant using my series of images?As far as I understand my cameras should stop processing the correct radiation below 120 ms. That doesn't seem right, does it?Thanks in advance for any advice...CheersLennart