In Windows phone you can “press and hold” the camera button to launch the camera without unlocking the screen. This will launch the camera in locked mode; i.e., you will not be able to access other items other than the camera & pictures shot in the current session. Below is how you enable it.
- Navigate to settings.
- Swipe right to “applications” tab.
- Tap “photos + camera”.
- Check the option “Press and hold camera button to wake up the phone”.