Assistance in finding correct LIDAR for short-range object detection task [closed]

Question

I am working on a task that involves finding a distance of a moving object going a static linear object, e.g a long pole. After trying some approaches (mostly involving stereo vision), I have come up with the idea of building an array of 1D Lidars set apart in fixed distances from each other and from the static object that could help achieve this task: (array in red, pole is gray, pardon the drawing :) )

1. The moving object goes over the static object, and "cuts" the beams of several of the 1D Lidars in our array.
2. We thus know the object position with a precision of the space between Lidars in our 1D array.

I have searched for various lidars to achieve this purpose, and because of the precision being tied to spacing between sensors, the following constraints arise:

1. Something small is necessary for this purpose - diameter of max 2cm, assuming this is still a circle-shaped sensor.
2. Since it's tracking a moving object, a scanning frequency of, say, >30hz would be good.
3. The range is up to 5 meters.
4. The beam is very directional and focused, so that there is no crosstalk/interference between elements of lidar array.
5. Precision does not matter, I just need to know if there is an object present or not.

The closest candidate that fulfills the requirements by size is actually an ultrasonic sensor, however that has issues with focus and interference, plus needs a receiver on the other side, thus does not fit this task.

I also searched for pre-built lidar arrays, but generally they were either too large or too slow. If anyone knows of a sensor that fulfills this purpose or can guide me to who might offer one, I would appreciate it. Thank you.

EDIT: Clarifications for project:

This is a research project for sports with a flexible budget, so costs are not much of a limit. The area of interest is within a range of 1 to 5 meters, and the tracked object is a human. Our desire is to precisely measure the object with a max disparity of up to 2cm to a height of up to 40cm, but it may be less. The attached pic illustrates our case - an object goes over the virtual "tube" (a region of interest, essentially) center with an unknown distance, which is the distance we would like to measure.

Answer 1

Go back and look at the camera idea again, but this time put the camera at the end of the "tube" (where you sketched the lidar) looking along the tube just like the lidar does. It will see everything the lidar would, except better. Cameras already have a dense, high performance array of sensors (at the image plane).

A simple webcam would meet your criteria of size and precision, and fancier cams can offer a higher frame rate if you need it. Methods of camera calibration, motion detection, and blob tracking are mature and available for free (such as OpenCV).

This might be a solution to the problem, although it doesn't exactly answer the question as phrased. If xen20 likes this, he or she can edit the question and text to admit this answer (and make it not a shopping question). Then I can edit this answer to remove this meta paragraph.