Object finding using arduino

Hello friends, i've been working on my project and i've arrived to a point where my robot needs to detect ping pong balls and go collect it. Any advice on how to approach on such a thing ? The project is about building a robot that will collect ping pong balls in a open 1.5x1.5 m square. But the question is that instead of just detecting the balls in front of my robot using ultrasonic sensor can i actually tell the robot to find for such a thing ?
Much appreciated.

The Pixy camera is Arduino compatible, and can detect and locate colored blobs.

jremington:
The Pixy camera is Arduino compatible, and can detect and locate colored blobs.

@jremington the pixy camera sadly costs 200 usd in my country and it is perfect for my project. Do you know any other modules that function like the pixy camera ?

Can't you mail order it? USD 70 from Jameco Electronics.

jremington:
Can’t you mail order it? USD 70 from Jameco Electronics.

Sadly, a lot of countries have broken postal systems and ridiculous import duties. I tend to believe posts like this because I’ve been in that situation. Companies like Jameco don’t even ship to a lot of places.

aarg:
Sadly, a lot of countries have broken postal systems and ridiculous import duties. I tend to believe posts like this because I've been in that situation. Companies like Jameco don't even ship to a lot of places.

my country's postal system is broken , and besides i don't have time for online shipping .

Ping-pong balls can be problematic for sonar sensors.