The recommended approach would be to use a function called Disparity Shift to reduce the minimum distance, or MinZ, of the camera so it can better analyze objects at very close range.
If you go to the first link listed in the page below, pages 15 and 16 of the camera tuning guide at this link describe how Disparity Shift affects the camera's vision over distance.
Alternatively, just reducing depth resolution will also reduce MinZ.
The post below on depth scale may also be of use.
MinZ and MaxZ primarily affect depth analysis.
If you need to focus the camera's attention on a certain area of the image instead of everything in the FOV, defining a Region of Interest (where the camera averages the intensity of the pixels in a defined area) may be worth investigating. Page 10 of the tuning guide talks about it.