Abstract: There is provided a technique capable of reducing the weight of a counterweight for a lens unit driven by a voice coil motor. An observation apparatus includes a main frame, the lens unit, an image-forming lens, a driving mechanism, and an urging mechanism. The driving mechanism moves the lens unit by means of the driving force of the voice coil motor. The urging mechanism includes a lever portion, the counterweight, and a wire. The lever portion is supported rotatably about a shaft axis extending in an X direction with respect to the frame. The counterweight applies a force to an effort position in the lever portion, the effort position being spaced apart from a fulcrum position supported by the main frame. The wire connects the lens unit to a load position in the lever portion, the load position being closer to the fulcrum position than the effort position.

Abstract: A tubular metal body includes a tubular part having an opening at one end in an axis direction; and a bottom part disposed at another end of the tubular part in the axis direction. The ratio (Rz1/Rz2) of a surface roughness Rz1 of an outer peripheral surface of the bottom part to a surface roughness Rz2 of an outer peripheral surface of a center portion of the tubular part in the axis direction is in a range of 2 or more and 4000 or less. A Vickers hardness HV1 of the outer peripheral surface of the bottom part is 5 HV or more and 27 HV or less smaller than a Vickers hardness HV2 of the outer peripheral surface of the center portion of the tubular part in the axis direction.

Abstract: A tubular metal body includes a tubular part having an opening at one end in an axis direction; and a bottom part disposed at another end of the tubular part in the axis direction. The ratio (Rz1/Rz2) of a surface roughness Rz1 of an outer peripheral surface of the bottom part to a surface roughness Rz2 of an outer peripheral surface of a center portion of the tubular part in the axis direction is in a range of 2 or more and 4000 or less. A Vickers hardness HV1 of the outer peripheral surface of the bottom part is 5 HV or more and 27 HV or less smaller than a Vickers hardness HV2 of the outer peripheral surface of the center portion of the tubular part in the axis direction.