In Android 4.1, when you set the lock screen security to "slide", you can quickly access the camera by sliding left.
Is there a way to get a similar sliding mechanism, but at the same time require a PIN to access the rest of the phone?
From my experience you will need to use a custom lock screen such as widget locker to do what you want. This can not be done with the stock Android lock screen.
This application lets you start the camera app even from a password locked screen. Full disclosure: I developed the app.