work in -20 degree

hello everyone. in our project we need to use analog laser distance sensors and laser field scanner in -20 even -30 degree on moving crane. sensors working in -20 degree are very expensive and field scanner which we found works in min. -10 degree. What do you suggest how we can give a warm that all devices work normally? Thanks for your helps.

Maybe an acrylic (or other transparent material) dome with a heater inside?

That will work but you will want to make sure it is vacuum sealed and the inside is moister free. Otherwise you can get condensation in the dome.

well a heated dome, with a small bag of silicagel. no need for vacuum though.
or old fashioned mechanical device.