A method for treating a hinge holder includes the following steps: polishing a surface of the hinge holder; degreasing the hinge holder; cleaning the hinge holder; baking the hinge holder; cooling the hinge holder; screen-printing a part of the surface of the hinge holder; and plating the other part of the surface of the hinge holder with chromium or a chromium-containing compound. The transient recovery circuit operates independently of a regular feedback circuit. The added optical signal is input in a direction parallel to a column in the optical switch matrix. The turntable can move along a guide section to a first position on a rear side and a second position on a front side with respect to the base member. The mat can be used on a patient support surface\u2014such as a bed, cot, stretcher, recliner, operating table, etc. A reference value is calculated by subtracting the candidate pixel value and the median value.