Connecting a supply voltage from linear encoder to camera IO board with a current limiter
If the camera needs 5 volts and takes up to 50 mA then supply it with 5 volts and even if the supply is capable of proviging 140 mA (or more) it doesn't matter because the camera will take only the current it needs to operate. I expect that the 140 mA figure is a maximum rating for the device i.e. it is capable of supplying 5 volts to a load than can take up to 140 mA.

Regards your comment, this contradicts what your main question body appears to say so please provide a link to the camera interface card data sheet so this contradiction can be resolved.