Technically interesting, but I'll add to photoptimist's point about dimness, the view will be tiny AND dim. 1/1.7" sensor is twice as small as 110 film in linear dimension. Of course you can optically magnify by a factor of 2 but then your view will be dimmer by a factor of 4. Joy of photography and tinier dimmer VF don't seem to go together.
Originally posted by photoptimist The 9.2 mm flange focal distance probably does have enough space for a 4.6mm mirror although the space is pretty tight. One concept that might help is a left-right (or up/down) sliding mirror rather than a flipping mirror (there would be plenty of room inside the camera for such a tiny mirror assembly).
Sounds cool but that won't work for 1/1.7" sensor.
Lens' end of the bayonet mechanism sticks into the camera by about 4mm. Rear elements are recessed from the bottom of the lens but not that much (let's say 2mm maximum). So we're NOT talking about 9.2mm space, we're talking about 5.2mm from the sensor to the lens' bottom, and 7.2mm or smaller from the sensor to the rear element.
OTOH 1/1.7" sensor is 5.7mm high which also defines the absolute minima for the depth of the mirror box. 5.7mm>5.2mm, so the bottom edge of the mirror will hit the lens' bayonet flange when the mirror moves to the side.
Conventional flip mechanism won't work either. The mirror height should be at least a factor of sqrt(2) larger than that of the sensor, i.e. 8mm. The resting place for the mirror during exposure needs to be at least 8mm deep. But 8mm>7.2mm, there's no space deep enough above or below the sensor.
So OVF=new mount and larger body.