How can I resolve depth inversion Issue with augmented reality marker based game?

Hello all,

I am a Unity newbie and I am trying to create a simple game using unity augmented reality marker as a sword. So basically, some objects would be flying towards the sword and the user has to cut it,

The issue here is when I move the marker towards to the laptop camera, the sword becomes bigger, which in the view of the game, looks like I am moving the sword away from the flying objects.

So I just want to reverse the direction of the sword, ie. if i move the sword closer to the camera, I want to sword to become smaller ( instead of getting bigger like in the normal marker detection). Any pointers on how I can do this would be greatly appreciated. Please let know if more details are needed.

Thanks for your time.

Regards, Riswan