Open camera from a button

Hello All,

I have been spending some time learning more about augmented reality and have made some sample applications using Vuforia and Unity. All of my sample applications Open the camera at run time. My next challenge is to build an Android Studio app with simple navigational buttons with one of the buttons being a "Open Camera" button. This button would call a method that would open the AR camera. 

Does anyone know how to achieve this or perhaps point me in the direction of some resources showing how it is done. 

Thanks in advance for any and all responses.