ToF VL6180x not able to give show shapes

Referring to the figure is what my experiment setup is all about, i want to scan an object as where the output is going to be a square shape. But as the tof sensor moves towards the object, it slowly increase the slope until it reaches the height of the object. I want to know why is this happening instead of showing a 90degree shape. Kindly advise on this.

From the data sheet, "Angle of divergent laser emission is 25° +/- 5°."
The laser light is in the shape of a wide angle cone rather than a narrow beam therefore you get poor lateral resolution.