A rail-carrying plate lies on an upper surface of a base. Furthermore, the fuel injection valve has plural sets each of which comprises one of the stepped recesses and the relevant orifice, the orifices incline to each other, and a step on a downstream side in each of the stepped recesses has a larger diameter than a step on an upstream side thereof. An FPA implemented with such unit cells may be used, for example, in an imaging system capable of detecting a plurality of two dimensional image frames and providing a three dimensional image using the detected two dimensional image frames. An evaluation value is calculated that corresponds to the degree of eye fatigue on the basis of the amount of variation, the variation time, and the number of times of the variation.