One of the eye-popping techno wonders from the latest Batman installment involves the use of cellphones to “see” inside of buildings. When Lucius Fox plants a cellphone in Lau’s office building, the modified phone somehow creates a map of the buildings interior by using a “high frequency pulse” to create an image. Fox tells Bruce that it works just like sonar. Well to be more accurate he should have called it radar because that’s what it is. Sonar is when you reflect sound waves off of objects to determine their location. Radar is when you use electromagnetic radiation usually at microwave frequencies to do the same thing. Since cellphones emit and receive e-m radiation in the radio wave/microwave frequency range (for cellphones the frequencies are usually between about 800 and 2000 MHz) if you tried to use them as imaging devices then that’s radar.
There are many different types of radar designed for different purposes including military defense, meteorological applications (the Doppler radar they use to image precipitation), police radar, geologic applications (ground penetrating radar); the list goes on. But, not surprisingly, none is capable of coming close to the level of 3-D resolution and the depth of penetration that Fox’s is able to achieve. The more layers the radiation penetrates the more it is absorbed and scattered. This makes resolving and interpreting the reflected signals extremely challenging. Nevertheless it’s an interesting idea extrapolated from existing technology and maybe with some stunningly sophisticated futuristic signal processing algorithm we can make Fox’s dream a reality.