Some people at delta bot google group tried to use optical approach and they failed. The angles to achieve total reflexion are too low. Problems with varying optical properties of bed over the area. It does not mean it is not possilbe. But it probably will not be that easy.
For capacitive aproach you need a conductive bed but it does not need to be optically uniform. It needs to be rather clean, but heatbed needs to be already clean for filament to stick. Well maybe it will not work well for people who use glue sticks or abs juice.
As for as uniformly conductive layer in the bed, maybe a mirror would do. Though not sure how to make a reliable electrical connection to the aluminium layer of the mirror. If the aluminium layer is too thin then its resistance may be a problem too.
I think it is worth a try but I'm not expert in the area of capacitive displacement sensors. I do not know about anybody who already tried this.
Other than that, I do not really see why people consider (non-removable) z-probes so usefull. I have one too but it is removable. I used it for the intial calibration. And I used it once more for calibration when the diagonalRods/carriages/platform were changed. Otherwise there was no need for it.
For capacitive aproach you need a conductive bed but it does not need to be optically uniform. It needs to be rather clean, but heatbed needs to be already clean for filament to stick. Well maybe it will not work well for people who use glue sticks or abs juice.
As for as uniformly conductive layer in the bed, maybe a mirror would do. Though not sure how to make a reliable electrical connection to the aluminium layer of the mirror. If the aluminium layer is too thin then its resistance may be a problem too.
I think it is worth a try but I'm not expert in the area of capacitive displacement sensors. I do not know about anybody who already tried this.
Other than that, I do not really see why people consider (non-removable) z-probes so usefull. I have one too but it is removable. I used it for the intial calibration. And I used it once more for calibration when the diagonalRods/carriages/platform were changed. Otherwise there was no need for it.