I have been searching for a way to use my android's camera as a webcam. I found a free application DroidCam that performs this action. I have used my HTC 626s Desire as a webcam for many of my YouTube videos.
You can use Droidcam one of two ways. You can connect your android to your computer via a USB cable. Also, you can use a wireless feature.
You must install a free DroidCam application onto your android. Also, you must install a free application on your Microsoft Windows or Linux based operating system. DroidCam is available on the Google play store.
Once you have both pieces of software installed you then must start DroidCam on both your android and computer. You can connect to your android either via wifi or USB. You click on a "Start" button on either a WiFi or USB tab.
Once connected you can obviously see your android camera in action. You can use DroidCam with applications like OBS studio as a webcam. You can broadcast both audio and video.
This free version has limitations. A pro version has other options like 720P, zoom, color adjustments, etc. DroidCam will work with Google plus, Skype, and other programs.