Update README.md

image path problems.

README.md

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 The aim of this project is to  test the reliability of automatic oscillometric blood pressure measurements by implementing a real-time application in C++. The application automatically measures the user's pulse and blood pressure by using a manual blood pressure cuff equipped with a pressure sensor that is connected to a [USB-DUX-SIGMA](http://www.linux-usb-daq.co.uk/prod2_duxsigma/) converter, connected to a Linux computer.
 
 <p align="center">
-  <img src="https://itsbelinda.github.io/obp/doc/latex/figures/hw_overview.svg" alt="obp hardware overview." width="80%">     
+  <img src="doc/latex/figures/hw_overview.svg" alt="obp hardware overview." width="80%">     
 </p>
 
 If there is no USB-DUX devide connected to the computer, the application will not start up. If the USBDUX-D device is used, a warning will be written into the programs log file, but the application will still run. The USBDUX-D device has only 12-bit instead of 24, like the SIGMA device, which is not enough for the blood pressure detection to work.