Abstract: A cover portion (300) includes a transmission portion (310) and a heater portion (320). At least a portion of the heater portion (320) is disposed on a lower side (negative side of a sixth direction (V)) of the transmission portion (310) and on one of opposite lateral sides (positive side of a fifth direction (L)) of the transmission portion (310). An amount of heat generated per unit length of the heater portion (320) in a direction along an outer periphery of the transmission portion (310) on the lower side (negative side of the sixth direction (V)) of the transmission portion (310) is higher than an amount of heat generated per unit length of the heater portion (320) in a direction along the outer periphery of the transmission portion (310) on the one of the opposite lateral sides (positive side of the fifth direction (L)) of the transmission portion (310).

Abstract: An outer surface of a casing (100) is provided with a first shape portion (152) and a second shape portion (154). The first shape portion (152) and the second shape portion (154) are engageable with other shape portions located outside the casing (100). The first shape portion (152) and the second shape portion (154) are aligned on the same straight line as a virtual straight line passing through the center of a field of view when viewed from a direction perpendicular to a direction in which the field of view expands. Alternatively, the first shape portion (152) and the second shape portion (154) may be aligned along a direction parallel to this straight line when viewed from the direction perpendicular to the direction in which the field of view expands.

Abstract: A first portion (110) and a second portion (120) of a casing (100) are separable obliquely from a second surface (122) side (upper side, that is, a positive direction side of a third direction (Z)) toward a first surface (112) side (lower side, that is, a negative direction side of the third direction (Z)) of the casing (100) with respect to the first surface (112) or the second surface (122) of the casing (100) from a first side surface (114) (window portion (130)) side (front side, that is, a positive direction side of a first direction (X)) toward an opposite side (fourth side surface 124 side) (rear side, that is, a negative direction side of the first direction (X)) to the first side surface (114) (window portion (130)).