Abstract: Coded cylindrical drums mounted on the pointers of dials of a meter are provided with parallel axially aligned rows of data elements constituted by opaque and transparent areas. Each of the drums is provided with a transparent centrally located ring parallel to the rows. Light is transmitted diametrally through the drums thereby intersecting the same at two places. So that the light will scan the rows as they are brought into position and so that the light can escape through the transparent ring, the light is converged at two spaced and orthogonally related lines for each drum. This is accomplished by passing the light through a positive aspherical or a spherical lens and cylindrical lens in series. The light is thereby converged at two orthogonally related lines respectively located at a shortened focal length due to the added power of the cylindrical lens and at the positive lens' normal focal length. The difference of the two focal lengths corresponds to the cylindrical drum diameter.