I am currently writing a background section on lidar sensing for part of my dissertation. I have either confused myself or not thought on the topic enough and I am attempting to gain a clearer understanding of how, and the form of, data from a lidar camera is produced.
At surface level or in terse summaries of lidar sensing you may frequently see something akin to "lidar sensors produce point cloud data". Though through my research I don't necessarily directly see how this is achieved. For example, in Paul McManamon's work "Field Guide to Lidar" he provides a high level categorical description of lidar sensors
Range-only lidar, or 1D lidar, measures only one dimension: range. 2D lidar is similar to passive imaging in that it measures both azimuth and elevation but does not measure range. A common type of lidar is the 3D lidar, measuring angle/angle/range. A 3D image can be only 3D, with no grayscale, or can measure grayscale. Polarization and color(wavelength) are other dimensions that can be measured.
Based on my experience, and McManamon's description of 3D lidar, I have seen two distinct forms of lidar imagery. The first is a point cloud, a set/bag of points in 3D space with no regular structure, grid, or ordering. The second may be described as a "2D depth image". Here the $X, Y$ values fall on a regular grid or structure and have some ordering (almost directly analogous to an RGB image $X, Y$ values) and the $Z$ values are naturally understood and viewed as greyscale pixel values where the grey intensity relates to depth or range from the viewing location.
Thus from my understanding lidar cameras do not directly capture and produce point cloud data, they capture "2D depth images". These images are then translated to some global coordinate space and co-registered. After this process the regular structure, grid, or ordering disappears as the single collections, specifically pixels, are mixed into a true point cloud.
Is this the correct understanding of how lidar sensors produce point cloud data, or is there some form of sensor which natively produces a point cloud from a single image collection?
Hopefully this is a good forum for this question, other sister sites such as Digital Signal Processing and Electrical Engineering seem to specific for this question.