the pressing front end part 41 a of the holding axis 41 is inserted into the opening of the axis core hole 61 a of the cylinder part 61 a portion between the opening of the axis core hole 61 a at an outer end side of the cylinder part 61 and the insertion groove part 62 is held between the pressing front end part 41 a of the holding axis 41 and the second side piece 21 c on the basis of elastic pressure see fig3 a in this way the lens main body b becomes turnable about a horizontal axis l of the supporting arm part a by the lens holding part 2 of the supporting arm part a and the holding unit 4 see fig1 b 1c 2a 5a to 5d etc further by elastic bias force of the elastic member 43 a portion between an outer end in an axial direction of the cylinder part 61 and the insertion groove part 62 is held on the basis of elastic pressure therefore the lens part 5 of the lens main body b can be stopped at an arbitrary position and can maintain a stopped state that is the operator.