http://imagej.273.s1.nabble.com/Removing-grill-grate-horizontal-stripes-in-background-tp5009203p5009212.html
My idea was having the light from left&right at a rather glancing angle. With proper shields at the left&right this may prevent illuminating the background objects below the grid.
Concerning the reflections, let us assume that the camera has a viewing angle of +/-20 ° left and right w.r.t. its axis, which I assume perpendicular. Then, the light must be at the sides of the belt such that it is more than 20° from the vertical direction when seen from any position of the grid. This simply follows when assuming specular reflection at the top of the grid.
More glancing (having the lights further down) is better, however, because the grid won't be ideal, it will have imperfections that may still cause specular reflection.
> @Joel :
> Hi Joel,
> Thanks for your response.
> With some other operations with your image as a starting point I got this :
>
> <
http://imagej.1557.x6.nabble.com/file/n5009210/Inverse_FFT_of_Food_processed.jpg>
>
> This kind of result is fine, since I can get the coverage of the food on the
> belt from an histogram.
> However, FFT and inverse FFT seems to take some time, so it maybe not fit a
> live camera feed.
> But it is still a nice first solution for my problem !
>
> How did you choose to use R=34.4 ?
> Since my goal is to make it automatic for every frame of a video, I wonder
> if I can put it as a parameter.
> Does it mean that the filter is cutting small frequencies (ie small edges?)
> ?
> Is it already filtering only horizontal small frequencies ? if not, is there
> any other selection filter (your circle) that I can use to cut only the
> horizontal line ?
>
> Thanks again!
>
> @Michael :
>
> Thanks for your advice.
> /(3) have the same light intensity in all of the image (currently, it gets
> much darker towards the back).
> /
> I will take more precaution with my footage.
> Put the camera directly above the belt. I will probably process only the
> center region of the picture since the shadow in the back is getting the
> region much darker.
> /(2) have the background as dark as possible (block light that would
> illuminate background objects below the grid) /
> I unfortunately can't change the background.
>
> /(1) with light from left and right only, you should be able to eliminate
> the reflections on the grid
> /
> That's interesting ! Is there any particular good way to install the light
> from left/right to avoid reflections ?
>
> Thanks again !
>
>
>
> Regards,
> Kiwa.