Step 4: Projector-Camera Configuration

Picture of Projector-Camera Configuration
We'll use a "portrait" setup for this scan. This means that the projector and camera will be mounted on their sides. Projectors tend to have some internal lens shift: when you place a projector on a table, it projects the image "up" to a screen rather than shooting straight. To compensate for this, make sure the camera's optical axis is tangential to the surface the projector is hitting. In other words, if the projector has been rotated clockwise, keep the camera to the right of the projector.

At this point, the image planes of the camera and projector are approximately rectified: a horizontal line from the projector is a horizontal line on the camera. A white wall is helpful as a backdrop for testing that the camera and projector are aligned (in general, more reflective colors like white are easier to scan than darker colors).

Once aligned, the camera's perspective needs to have a vertical offset from the projector's perspective. Move the camera up: enough so you can see the curve in the cosine pattern being projected. Too much, and you'll be capturing a lot of shadows (areas where the projecting isn't projecting) or missing areas where the projector is projecting.

For mounting, you can use pretty much anything that is suitably stable. I've used everything from spider projector mounts, to desks with tape and cardboard, to music stands. The main goal is making sure that the geometry doesn't change while you're capturing each pattern.