coding for portable camera based text reading for blind person

Such devices already exist.

Perhaps this is a very good idea. The difference is: using non-specialized equipment: cheap consumer camera with standard interface, a Web camera, and a usual consumer-level computer, perhaps a tablet computer with a big screen (then the camera might not be needed).

But all you need it just a very usual camera preview and capture software and some convenient zoom control. You can find huge number of code samples everywhere including CodeProject. You did not specify UI library to use or application type, but you can find it for any of them. For example:
http://www.codeproject.com/search.aspx?q=camera+capture+.NET&doctypeid=1[^].

—SA