I have some experience with Optech CMS, and the MDL Void Scanner.
In the past we were using the MDL product - the old version of the Void Scanner. I think it was VS-150, and honestly I am not impresed with it. We had serious problems, couple of repairs for an year not because it was hited or something. Plus a lot of incorect models because of the dust in our stopes. I don't know much about the new model of MDL, I know that it is faster, and hope it is stronger.MDL have a good postprocesing software that alows you to filter the data.
After our experience with MDL, now we have two Optech V400 Scanners. I think they are pretty reliable. The models are looking good, the scans are fast - about 7mins for full scan with 1 degree step. One of the scanners was hit by a rock falling from about 30 meters and the result was broken first boom some scratches on the scanner, but it is still working and giving us good results.
I haven't seen Geosight Minei, but have heard good opinions about it.
And as Tim said it is important what do you want to do with the data, and in which software you will process it. And also the onsite demonstration from the diferent companies is the best way to decide what exactly do you need.
Void scanners have come a long way since Optech owned the market for nearly 15 years. The three brands you mention all have their advantages and disadvantages.
The main issues I've always had to consider with void scanners have been
1) The end product from the scanner. Typically all scanners spit out a wireframe but how does the end mine planning software deal with it. As an example, the previous generation raw Optech was easily and quickly imported into Surpac to create a closed and validated solid. I once tested an MDL (this is a few years ago so things perhaps have changed) that required considerable solids editing in Surpac before a closed and validated solid was created. You don't want to be wasting time in the office when you don't have to. If you're getting a demonstration, do a scan and process it in whatever software package you used to see how easily a closed and validated solid is obtained. Further to this, if the scanner is set up incorrectly, how easy is it to manipulate in post processing so that the solid's alignment and position are correct relative to existing mine workings.
2) How robust is the scanner? Scanners fail due to knocks, water ingress, poor wiring etc. If it does fail, what is the turnaround time getting it fixed? How expensive are repairs? Most importantly, can you get a loan scanner for the duration of repairs? Void scanners are great when they work and have no issues but can become an extreme nightmare when they fail and you don't have a backup unit. Some mines might do a couple of void scans a month, some do many scans each and every day.
My recommendations is to get a demonstration from any or all void scanner companies, test the unit and ask lots of questions
Im interested in any feedback, comments and suggestions anyone can pass on regarding the latest CMS Void Scanners that are available. There looks to be 3 main players at the moment, Optech, MDL and Geosight Minei. Any information from people that have used them and have opinion one way or another would be great. Cheers.