There is no way in android to access to the standard Android camera from a password protected device. However this little application allows to access to a simple camera with a triple press on the power button even when the device is PASSWORD locked...
https://play.google.com/store/apps/details?id=com.aeropic.CameraUnlockFree
try it and if you like keep it and if you really like rate it!
Alain
PS : a more advanced version will be issued soon ...