Is the shutter important?

[Johan]

How important is the shutter?
Can I use a FLIR Lepton camera without shutter to detect people indefinitely?
Do I need to do a manual calibration after a while on a camera without shutter?

[Luke Van Horn]

I just researched this as my shutter recently fell apart. It's used for flat-field correction (FFC).  This can be done manually and may not be necessary for scenes that change frequently (hand-held vs mounted).   

See page 20 of the datasheet for details:  

http://www.flir.com/uploadedFiles/OEM/Products/LWIR-Cameras/Lepton/Lepton-3-Engineering-Datasheet.pdf

[Luke Van Horn]

I should also mention I'm having issues with the image quality since the shutter/auto FFC stopped working.  So, I'd recommend keeping it.

[TomH]

Hello. All,

I say using the shutter would be recommended.

Besides, I notice the shutter does not close whenever I send an FFC command. (though it worked before for a while).

 

I'm finding out whether my raspberry Pi zero and 3 provide enough current for activating the shutter solenoid. I measure its DC resistance: 12 Ohms. Its voltage supply sources from the camera's dedicated GPIO2 pin's VDIO 2.8 to 3.1V. That said, the solenoid current supply must be >= (3V/12), or 250mA.

Since I use the 3.3V supply pin from raspberry Pi, it could be that the Pi does not have enough current for everything the camera needs. Lepton datasheet shows that the camera's typical required current is 235mA during FFC. I will post my finding later.

Tom

[Johan]

The 50° FOV FLIR Lepton has a shutter and it automatically execute FFC. It is annoying that FCC freezes the video feed 1 .. 5 sec.
I also have FLIR Lepton 25° FOV that does not have a shutter and does not execute FFC and I have never experienced any pixel fault with that camera.
I am thinking about turning off FCC of FLIR Lepton 50° FOV.
The FLIR Lepton 25° FOV does not have a shutter, so why would a 50° FOV need a shutter?

On Wednesday, August 30, 2017 at 4:54:54 PM UTC+2, Johan wrote:

[Ben Kluwe]

Hi Johan,

A couple of things:

1. You probably don't want to get rid of the shutter, it allows the camera to correct for drifts over time. Almost all infrared cameras make use of a shutter to get a uniform, 'known' temperature reading. In the world of infrared, this is a very much necessary feature to obtain accurate temperature readings (+-1 degree is considered very good!). Depending on the application it can become strictly necessary.
2. Pixels do not become faulty when no FFC is executed, they merely change their temperature reading over time. This is usually do to some sort of temporal noise filtering/integration/differentiation to get a better signal out of the camera.
3. You can set the shutter mode to manual, so it won't automatically do the FFC, thus you get to choose when the video freezes, but doing it every once in a while is recommended (see 1.)

Hope this helps,

Ben

[Johan]

What about the FLIR Lepton 25° FOV that does not have a shutter, will it drift forever?

[Ben Kluwe]

Every bolometer IR camera will drift. To answer your question, yes, if you don't do an FFC, it will drift indefinetly. The parameters of the drift will be different for every camera.

The shutter is there to provide a uniform background for the camera to measure its readings against a known temperature source and thus apply corrections.

If you want to see the effect of the FFC, you can use the non-shuttered version to do an FFC while imaging an object that has a different temperature to the background (obviously, both must be in the FOV). When the FFC is done, move the object away and you will see an effect called ghosting. The object will appear to be there, but actually isn't due to the temperature correction. Likewise, just after the FFC is done, the object will disappear.

Ben

[Johan]

I think the FLIR Lepton 25° FOV is supposed to have a external shutter.

Reading the datasheet page 59 from
http://www.flir.com/uploadedFiles/OEM/Products/LWIR-Cameras/Lepton/FLIR-Lepton-Software-Interface-Description-Document.pdf

The FLIR Lepton shutted 50° FOV is set to LEP_SYS_FFC_SHUTTER_MODE_AUTO.
The FLIR Lepton non shuttered 25° FOV is set to LEP_SYS_FFC_SHUTTER_MODE_EXTERNAL.