x-y axis mapping in rslogix 5000

I'm not quite sure how to use a photo-eye to raise and lower a boom to avoid running into an object as it passes over top and maintain a set distance away from the object. I would have to store this "map of the object" for forward and reverse passes over the object. I will be using vfd's and motors w/encoders. The photo-eye will be on the leading edge of the boom as it moves toward the object. I'm not looking for someone to write the code just suggestions and instructions that I could use to "map the object". Thanks for any help.

Is the object going to me moving at all or just the boom?

Just the boom

The boom arm will move up and down as it passes over the object.

I can picture doing it with two photoeyes, one, called X, oriented in the direction of motion (looking toward the object to be avoided. The other, called Y, looking down to detect the object while the boom is passing over it.
When both photoeyes detect nothing, the boom can move down to its lowered limit.
When X detects the object move up, regardless of the state of Y.
When X detects nothing but Y detects the object, stop upward motion, but do not permit downward motion.
That won't require mapping the object, nor will it maintain a fixed distance between the boom and the object. For that, I think you'll need two analog sensors with a signal proportional to the distance to the object.

Thanks Steve

If you are able to map the area to avoid, you could set up some move's to make sure the boom was always lower than those Y areas while in the X position. think of it as a dip in Y while moving in X.