any open source digital-measuring tape?

[DiTBho]

I need to build one with the resolution of 1mm, the tape I need should measure things within 2m.

Let me know 

[Doctorandus_P]

[ledtester]

There's also this idea:

[Doctorandus_P]

Such a mouse has a tiny camera in it.
If you use a regular tape measure and a webcam fixed to it, you can use image recognition software to analyse the position of the measure tape.
If you also look at the numbers on the tape measure, you can even make it an absolute encoder.

Camera modules can be quite small and cheap these days. The bigger problem would be a brainbox with enough brain power to run the image recognition algorithms, and small battery drain power for a decent lifetime (If it's battery powered).

[EPAIII]

I was also thinking about a 2 meter tape measure. But you don't need any fancy image recognition, just a few optical readers (photocells focused on the scale). And a mark on the back or a small hole drilled in the tape can serve as the zero reference. A few logic chips or a processor like Arduino or just a plain PIC could easily handle the logic.

Such a mouse has a tiny camera in it.
If you use a regular tape measure and a webcam fixed to it, you can use image recognition software to analyse the position of the measure tape.
If you also look at the numbers on the tape measure, you can even make it an absolute encoder.

Camera modules can be quite small and cheap these days. The bigger problem would be a brainbox with enough brain power to run the image recognition algorithms, and small battery drain power for a decent lifetime (If it's battery powered).

[ebclr]

As a reference a product ready to do that

https://www.aliexpress.com/item/4000289371852.html?spm=a2g0o.productlist.0.0.6f0e3c9fFaDSHE&aem_p4p_detail=202107202248572800956441060960005714073

[DiTBho]

I was also thinking about a 2 meter tape measure. But you don't need any fancy image recognition, just a few optical readers (photocells focused on the scale). And a mark on the back or a small hole drilled in the tape can serve as the zero reference. A few logic chips or a processor like Arduino or just a plain PIC could easily handle the logic.

A friend located in Estonia sent me a very unique "soviet ultrasonic sensor", and I made a contact-less measuring unit under the precision of 50mm, with a range of 300...900mm. It requires a very precise 16bit timer able to operate with a scale of 10usec. Nice piece of semi-vintage technology (I think the ultrasonic parts were made in 2010) but in original soviet color and shape. It's big and heavy, and looks like something bade during the cold war, but I like it.

Then I bought a couple of industrial meter-tape units, and I attached an optical-flow on the top, this way the optical sensor is able to read the marks on the tape. It works with the precision of 2mm, with a range of 10..1200mm. It requires a 50Kbit/sec SPI line and 2Kbyte of ram of the pattern-image.