I want to build a sensor similar to the image below. I am only using this image to help represent the concept.

Imagine a second 'curtain assembly' place in front of the first and rotated 90 degrees.



My objective is to determine the position of a part approx 1/4" sphere as it falls through the two assembly's.

I realize a simple light curtain can not do this for me as it views the light beams as one single beam.

I am wanting to be able to determine which of the light streams on each the x and y plane have been broken by the object. This should let me calculate the position of the part.

I would estimate the distance of each side of the two sensors to be under 5 feet and possibly under 3 feet. I am wondering if I could use low cost UV photo diodes or phototransistors  and uv led's as the light source to accomplish this?

I would like to keep costs down if possible, also the parts are moving quite fast so I need it to have a fast response time also.

I'd appreciate any input or if anyone knows a better solution please chime in.

I think a laser sensor would work but would be expensive. I am also wondering if a machine vision system could accomplish this but the parts are moving very fast and these are also very expensive.

Basically I am wanting to know if this would be feasible.

I thank anyone who can help.