For the sharpest vision, the image of an object should be focused on the:

The fovea is the region of the retina that is responsible for sharp central vision. It contains a high concentration of cone photoreceptors, which are sensitive to colors and details, allowing for the perception of fine visual acuity. When an image is focused directly on the fovea, it results in the clearest and most detailed representation of the object being observed.

In contrast, the blind spot is an area of the retina where there are no photoreceptors, which means visual information cannot be detected there. The optic chiasm and optic nerve are parts of the visual pathway that relay information from the retina to the brain, but they do not directly contribute to the focusing of an image. Therefore, for optimal visual clarity, focusing on the fovea is essential.