Controlling irradiation direction of lamp

The control of the irradiation direction of the lamp is not affected significantly by a variation in a supply voltage or current supplied to a stepping motor 6 directing the irradiation direction of the lamp 5 to a desired direction. When detection means 9 detects a change in a supply voltage or a current supplied to the stepping motor 6, the detection means 9 informs control means 3 of the change so that the control means 3 restricts the allowable range of the rotational speed of the stepping motor 6. For example, the control means 3 defines the allowable range of the rotational speed of the stepping motor 6 in a stepwise fashion or continuously in accordance with a reduction in the supply voltage or the current. When it is detected that the supply voltage or the current comes off a predetermined range, the control means 3 stops controlling the stepping motor 6. Another embodiment limits the rotational speed of the stepping motor in response to rotational status of the motor which may be coil current, position, speed or the like.