Do we have any specific location for VCSEL with respect to the CCD sensor or the lens. If so what is the max allowable distance between the VCSEL and lens optical center? Also will the location of VCSEL impact on the calibration of the device?
There is no specific guideline where to place the VCSEL relative to the lens, ideally the closer the better to overlap the lens FOV with the VCSEL's field of illumination. But, depending on the actual design you must also consider any shading effects, so most important is for the VCSEL to be at the lens top level on the vertical axis, or, if lower than the lens top level place it far enough to not get any shading.
The calibration of the device will change depending on what types of lenses and VCSELs are being used. The relative position of the VCSEL to the lens will also have a certain degree of impact on the calibration since it determines the illumination pattern but it's not expected to be very high.