An image sensor and well structure associated with and extending away from the surface of the image sensor are provided in various apparatuses, methods, and systems for determining the position of a light emitter located in object space. An exemplary method includes (i) providing the image sensor and structure associated therewith, the structure defining a field of view for each pixel within the array of pixels; (ii) determining a light intensity value for photoactivated pixels receiving light from the light emitter; (iii) identifying a first photoactivated pixel having a local maximum of light intensity; (iv) calculating a perpendicular distance between the first photoactivated pixel and the light emitter; and (v) constructing the position of the light emitter based on a position of the first photoactivated pixel in the array of pixels and the perpendicular distance between the first photoactivated pixel and the light emitter.