Has Superman always been able to do this?

[Rainzo]

Has superman always been able to do this? Emit microwaves?

[Rainzo]

Dang, I don't know why the picture is so small

[randle-el]

I think that's just his "heat" vision. They are likely going with the angle that Superman's eyes can give off directed radiation at various wavelengths. So shorter wavelength radiation results in x-rays which let him see through objects, longer wavelength radiation results in microwaves that produce heat in whatever objects they come in contact with.

[Mat001]

Most likely that's the case. Note that Clark had a different name for telescopic vision when talking to General Lane, before going off to fight Brainiac.