2.1 F Number:

The F number is the ratio of the focal length (f) to the aperture (A). This is a common way of specifying the aperture of the lens.

The pixel light collection power scales as a second power of the F number. It is important to have a very low F number to get the largest aperture possible.

The low F number has other side effects to account for. Low F number lenses have a very narrow depth-of-field owing to the large aperture sizes. Depth-of-field is the range of distances over which the camera appears to be in focus. The lens depth-of-field must be carefully designed considering the application for the camera. The limits of lens depth-of-field should match or exceed the minimum and maximum distance requirements of the final cameras that the lens would be used in. Depth-of-field increases as the pixel size increases. TI's 3D ToF sensors have pixel sizes larger than usual RGB camera sensors. Owing to the larger pixel size, the OPT8241 will have a very wide depth-of-field compared to a typical RGB camera for the same lens.