Converting 12VDC to 1.5VDC
Although an LDO or standard regulator can be used, the large voltage difference between input and output will result in significant power dissipation that is purely wasted:

100mA*(12.0-1.5) = 1W

That's a full watt that doesn't do anything but turn to heat (and you need to deal with properly dissipating it).

A DC/DC buck converter will give you what you want. For a ready made solution, Sparkfun has a breakout board for a DC/DC converter that will do what you need.