FSBUS NG: Optical encoders from PC mice

Hello.I have noticed, that any PC mouse have at least 1 pair of UV-LED and a coupled phototransistor. If you also add a plastic wheel, you'll get a thing similar to optical encoder (like Grayhill's).There is a possibility to connect Grayhill encoders to FSBUG (with extra hardware). So, I think there must be a possibility to connect self-made optical encoders from old or dead PC mice too.The problem is that phototransistors in Grayhill encoders have common cathode (or common -, or common emitter), but phototransistors from mouse have common anode (or common +, or common collector) - see pic in attachment.As I'm not specialist in this area, I want to ask for advice. Could anybody draw a circuit of hardware to attach to mouse optical encoder so that device could be attached to FSBUS (if there is such possibility ;) )? I think it is possible and is not more complex as an extra hardware for grayhill's encoders, but, please, help.Thanks!