An elongated strap member that is coiled in a box and is bent lengthwise as it is drawn out of the box, providing an economical, light, compact means of connecting multiple structural members without sagging or other disadvantageous deformations between the structural members. The microstructure rows are arranged on the light output surface, and the extending direction thereof is parallel to the extending direction of the first side. The expected value is a weighted average of all the measurements for a variable, in which the weight assigned to the measurement from each sensor is determined according to both its reliability and accuracy. A segment of the imaginary straight line is delimited by the first point and the second point.