3D modeling with only one sensor and lens?

lili23 wrote:

It seems 3D modeling require at least 2~3 lenses and sensor but I also see some technology to create 3D modeling with just one sensor and lens. I wonder why not using only one sensor and lens instead of dual or triple cameras?

To see depth, i.e. 3D, you need to see two overlapping images. Our front facing and overlapping binocular vision is the reason we see depth over most of our visual fields, the part in front of us. At the outer edges of our vision there is no overlap so our peripheral vision isn't 3D.

Depth perception - Wikipedia

To replicate depth perception photographically you need two images taken with a horizontal separation between the two images, each image viewed by only one eye.

You can take the two required images with two cameras, a dual lens camera, or by moving a single camera from side to side as you take the two images.

Taking the two images with a single camera requires that you move it side to side. There are mechanical devices to do this or you can just move your body side to side, which is called the cha cha method.

Stereo photography techniques - Wikipedia

Stereoscopy.com - The World of 3D-Imaging! (3D Photography / Stereo Photography)

To view the two images in 3D you need an appropriate device to show each image to only one eye, or you need to learn how to do this by your self.

This is one type of viewing device that uses two lenses that show your left and right eyes only the appropriate image so that your brain can combine the two images so that you see the image with depth. This type of device for viewing prints has been around since the 1840's. Virtual reality devices are a variation of this type of viewer.

You can color one image red and the other blue green and view a single image with the two views overlapping. You need red/blue green anaglyph glasses for this.

eBay - Anaglyph Glasses

Anaglyph 3D image

The 3D you see in a movie theater uses polarized lights to project two overlapping images on a screen. The glasses you wear have polarized lenses that let you see only one of the images with each eye.

If you have a 3D TV they swap the two images on the screen and use special glasses synchronized to the screen to show you only one image at a time

With practice you can learn to see only one of the two images when they are shown side by side. Reversing the positions of the two images and viewing them with crossed eyes is generally easier.

Non-cross eyed viewing 3D image

Cross eyed viewing image