An embodiment of this application discloses a handheld infrared imager that includes a cell (1) and a batter cover (7). The cell (1) is provided with a circumferential positioning hole (11), a circumferential positioning protrusion (71) is correspondingly provided at an end of the battery cover (7), and the circumferential positioning protrusion and the circumferential positioning hole are engaged with each other to implement relative circumferential positioning. A longitudinal positioning protrusion (12) is provided on an outer peripheral side wall of the cell (1), a longitudinal positioning groove (72) is correspondingly provided on a sidewall of the battery cover (7), and the longitudinal positioning protrusion and the longitudinal positioning groove are engaged with each other to implement relative longitudinal positioning. In embodiments of the present application, in the assembly of the cell and the battery cover, a positioning method with the fixed buckling of the sidewalls of the cell and protrusion-groove engagement of the bottom of the cell is used, so that the assembly is extremely simple.