automatic object detection and extraction

Hello everyone,

I have a bunch of images like the attached images. I want to automatically extract the tray from the seen. I already tested color thr. but it doesn't work well as the illuminations of images are vary. I also tried to used fft to extract the tray based on its pattern but it failed as well. Template matching was my last try which filed as well.

Do you have any suggestion?

Thanks in advance.