Optical arrangement of infrared camera

Object of the present invention is to provide an optical arrangement of an infrared camera having both an improved imaging accuracy and a reduced size of the apparatus. To achieve the object, an optical arrangement of the infrared camera comprising a lens unit in which a lens is supported by a frame body, an infrared detector module in which an infrared detector for detecting amount of an infrared ray transmitted through the lens as a heat and converting the infrared rays to an image signal is sealed in a housing having a window portion, and a shutter provided between the lens and the infrared detector module, wherein a detector surface of the infrared detector, the window portion, the shutter, and the lens are arranged such that an inclination angle of a virtual straight line which connects each corner portion of the detector surface of the infrared detector, the window portion and a maximum aperture of the shutter, and edge portion of an effective lens area of a lens closest to the shutter against to an optical axis is 25° to 35° is adopted.