Everyone wants to hack a laser tape measure for aircraft navigation. It would indeed make a cheap, extremely accurate, reliable altimeter.
Today, it's the DLR130. It outputs at 1cm accuracy at 3Hz. You need 10Hz for flight, so maybe there's a way to speed it up.
It's very well constructed.
The battery contacts must be desoldered.
The keypad must be removed.
A 100uF 16V cap didn't survive the operation. It got hung up on a protrusion on the battery side. The optics & keypad are integrated in the same frame. It's much lighter than the complete package.
The LCD could be removed to make it lighter, but never reattached.
A solenoid shutters the laser every few seconds, for some kind of calibration.
The LCD is held on by double sided tape which must be carefully pried without shattering the LCD.
The emitter & receiver have different filters.
The laser used for aiming it also seems to be the laser used for ranging. The keypad & processing board occupy the same space, so it couldn't be stripped down any further.
The magic is done by the CF325. The internet got nowhere with it. There's obviously a very simple measurement result going to the ATMega169. The entire left half of the circuit board could probably be omitted, but the update rate is probably limited by the CF325 instead of anything programmable.
The reflected light goes into this magic device. Years ago, this used to be a giant tin can. Years before that, this was a 1lb device.