This paper developed an optical design approach to combine the auto-focusing and image sensing in the 2D inspection
system. The focusing principle here employed the chromatic confocal microscopy due to the one-shot focusing capability.
The system held a special issue that the chromatic confocal microscopy has the higher optical dispersion characteristic
than the 2D image sensor which captures a clear image for the optical inspection. Hence, the system here must be
designed to be characterized with both the higher and lower optical dispersion, which was called as the common path
optical design in this study. That is, an optical approach must be developed to divide and switch the above totally
different dispersion conditions. Accordingly, the higher dispersion device, the chromatic confocal sensor, examined the
object surface height to vertically vary the focused position of the 2D inspection system. Furthermore, the lower
dispersion device, the 2D image sensor, can be adjusted to focus onto the object surface so that a clearly focusing image
can be acquired. The experimental results were also provided to ensure this approach can automatically focus the object
surface and then the clear image can be captured to perform optical inspection to obtain the position, dimension or area.