An image acquisition device includes an imager including a light receiver, a light shield, a light condenser, and a light emitter. The light shield includes a light transmitting substrate, a light shielding layer, and an opening in the light shielding layer. A light transmitting layer having a refractive index smaller than that of the substrate is between the light condenser and the light shield. When a diameter of a light receiving surface of the light reception element is d, a diameter of the opening is a, a pitch of the light reception elements is p, a refractive index of the light transmitting layer is n1, a refractive index of the substrate is n2, and a distance between the light reception element and the light shielding layer is h, Arctan((p-a/2-d/2)/h)≧Arcsin(n1/n2).