Projector lens

[David Williams 'Chips']

I use an Optoma projector with my Golf simulator setup. I've had it for 3 years now and over that time, the lens has been hit with the ball a few times, but has never caused a problem, until yesterday. I now have a slightly blurry image. It's still very useable but I'm a bit gutted, it's not as clear as it was. Any suggestions on how I can protect the lens during use, to avoid it being hit by the ball?
Thanks and Happy Christmas 🎄
Dave