Lens array with measurement structures

A lens array, comprising:

• a first lens surface and a second lens surface opposite to each other and arranged along a first direction;
• a first structure, a second structure, and a third structure disposed on the first lens surface and outside an optically active area of the first lens surface;
• and
• a fourth structure, a fifth structure, and a sixth structure disposed on the second lens surface and outside an optically active area of the second lens surface;
• wherein the first structure corresponds to the fourth structure along the first direction, the first structure and the fourth structure are configured to have distinguishable measurement edges with respect to the first direction, the second structure corresponds to the fifth structure along the first direction, the second structure and the fifth structure are configured to have distinguishable measurement edges with respect to the first direction, the third structure corresponds to the sixth structure along the first direction, and the third structure and the sixth structure are configured to have distinguishable measurement edges with respect to the first direction.