Liquid droplets detection

[Michele_R]

I everybody!I have to check the waterproof (and also the gasproof) of can filling valves. The containers can be filled up with different sparkling liquid (sugar water based) and if the valves aren’t ok or damaged, the liquid comes out (usually in form of small drops) on the upper valve side. Looking for some ideas I found a document where the autor said that a way “to see water” could be to use IR illumination and InGaAs vision sensor, because water has an high absorption between 1.35µm and 1.55µm wavelength and so it becomes dark.Does anybody here have tested a solution like this? What do you think?Any help will be greatly appreciated. Thanks MicheleAUROS-Ing.Michele RossiSoftware e Tecnologie per Automazione

[InfiniteNothing]

Could you fill the container with a phosphorecent material and test in a perfectly dark area so that if any light is detected you know there's a leak?

[Sundar...]

HI Michele,

I guess you should the explore properties of the droplets under IR and UV .

That would give you a better idea to extract only your area of interest

from the complete/rest of the image ( In this case the droplets from the background )

Also later the threshold on this image should help you give a better perspective

of what is required for analysis

Sundar.

[Michele_R]

Hi,thank you for your answers. I can give you some information more. I’m speaking about an industrial filling up line, so, I have to do “on-line” tests with the real liquid inside the cans and I can’t use other substances. The containers are inox steel cans. In fact, the waterproof problem is relative to the “O-rings” that are present in the valves and in the can cover because its could be damaged or moved during the filling up and closing phases. The article that I mentioned has been written by Lot-Oriel (see www.lot-oriel.com) and is speaking about the use of  “XenICs” infrared camera (see http://www.xenics.com/content/view/156/364/). I haven’ found this camera in the “NI Camera Advisor” for compatibility with LabView. Interesting for "liquid" appearence an behavior is the following link:  http://www.xenics.com/content/view/209/492/I’ll be waiting for your opinion. Thank you in advance.Best regards 

Michele

[BruceAmmons]

CameraLink interface will most likely work.  It might take generating a camera file, though.  This is probably going to give you the best results, even if it takes a little effort to set it up the first time.

USB will not work as well.  NI has a free USB driver, but it wouldn't necessarily work with the camera.  USB is a weak area in machine vision cameras.

Analog signals (CCIR, RS170) would work with an analog framegrabber card.  Analog signals are not as high of quality as digital signals, though, so I don't recommend analog.  It is a somewhat obsolete format.

Bruce

[Michele_R]

Hi Bruce,

I’m thinking me too that “USB cameras” aren’t the best choice for an industrial application and environment, so, I agree with you about “camera link”, but the question is:

“have someone had some experience in liquid  detection (expecially “water”) with IR camera with InGaAs vision sensor?”. Thank you Michele

[Robert_Eastlund]

For detecting water droplets or moisture, I would suggest using a InGaAs SWIR camera, see attached example video.  Sensors Unlimited sells several SWIR cameras that work with the NI Camera Link frame grabbers, see http://www.sensorsinc.com/cameras.html.  Ideally, the water droplets will appear to be dark in comparison to their background.  Note: the far infrared cameras detect moisture as a change in temperature.  In the SWIR range, the water appears to be contrasted because it is absorbing the light.

-Robert

[Michele_R]

Thank you very much Robert,

this is the information that I was looking for. I'll try to explore in depth in this way.

Have you used also both IR illumination and IR camera?

Do you have an idea (approximately) about the price of this camera type?

Regards

Michele 

[Robert_Eastlund]

You will need to use a lightsource with light output in the 1500nm range, see http://www.illuminationtech.com/products/option_ir.pdf.  Most halogen lightsources w/ out IR cut filters will work fine.  You can also place a narrow bandpass filter in front of the camera.  If I remember correctly, you will want a bandpass filter that passes between 1400 and 1500nm.  The Sensors Unlimited cameras are 20K or more.

-Robert