How does 3D Time-of-Flight (TOF) camera work? This is my first post in this forum! So Point me if anything is not clear!

I want to know how TOF camera works? So I've done Google &amp; read some nice explanation about How Phase difference between Transmitted &amp; Received signals can be used to calculate the Depth of an Object from Camera with good example. 

What i did understand:


Depth Can be measured by Calculating the Phase change of the Transmitted signal.
How a light source(IR) can be modulated &amp; demodulated ? Answer
How to filter the reflected IR signal having the same modulation frequency? Answer


What i cannot understand:


How phase change of a continuous square wave signal can be used to Measure the depth? 


Update: Here is a Nice Explanation about this.

Note: I'm talking about TI &amp; Mesa Kind of TOF Camera's using IR Led
The (unwrapped) phase between two constant same frequency signals is linearly related to any delay between the two signals.

Measuring phase of a fixed frequency periodic signal over many periods is sometimes more accurate than trying to detect delay locally (by zero crossing, etc.)