Table Color Selection: problems with black

[sebastian]

After reading http://www.liteplacer.com/select-a-table/ I figured that a black table with a matte surface would be best suited for the down looking camera as it would provide best possible contrast for white tapes and any color PCBs.

Unfortunately the chinese cameras make that a very bad choice.
They adjust the brightness automatically (all attempts to find a way to lock or set the parameters manually so far failed) and if they see a black table they think everything is too dark and will push the brightness until they are basically blind.

black-table01.jpg (91.14 KiB) Viewed 2453 times

Adding white elements around the tapes helps:

black-table02.jpg (96.64 KiB) Viewed 2453 times

[mawa]

Yes that problem can also arise when you, like I did,

a) use a black 3d printed tape holder (maltes design)
b) use a black plastic tape (12mm with pockets for WS2812 RGB LED)
c) have relatively large white components (WS2812 RGB LED)

If you place the single LED on a white surface, you can clearly see the circular window an the small controller chip inside. But on a black surface you only get a blurred white square.

Unfortunately not all USBcams support it, but on many cameras you can set camera property manually using AForge, OpenCV or EmguCv.

I experimented a little with it, but you have to save the current settings before you change any of them because you can mess up the camera quite easily.
Due to lack of time I postponed that problem.

Here's a small code sample I found here:

http://stackoverflow.com/questions/2486 ... osure-time

Code: Select all

private IAMCameraControl cameraControls;
...
cameraControls = (IAMCameraControl)source.SourceObject;

cameraControls.Set(CameraControlProperty.Exposure, -11, CameraControlFlags.Manual);

Addendum: I just tried the original cameras and they don't support camera control properties. The Logitec 270 on the other hand does but the reaction is not what I expected.

[sebastian]

I found a workaround solution to trick the bottom vision camera into dimming brightness: attaching a white paper label to the table to partly fill the cameras view with bright white elements

Details (also with bottom vision CV parameters for nozzle tip recognition):
https://wiki.apertus.org/index.php/Lite ... n_Settings