How to get the depth values of the camera view?

Hi, I'm a beginner of Unity. For some reason, I have to get the depth values of every pixel in the camera view.

Thanks to the website (http://williamchyr.com/2013/11/unity-shaders-depth-and-normal-textures/ ), I can get the depth image of the camera view.

However, I need more precise depth values (not 0~255) in c# and export the values as a .txt file.

How can I get the values? I had stuck in this problem for few days. Please help me. Thank you very much!