The invention provides a
flashlight for automatically adjusting brightness with the change of an
irradiation distance, and discloses a
light source for automatically adjusting the brightness with the change of the
irradiation distance. The
flashlight comprises an ultrasonic
distance detection module, a switch, a button, a
flashlight body, a snoot, an
optical filter, an
led lamp, a front fixing ring, a back fixing ring, a circuit board and other parts. The
distance detection module can detect the distance between an irradiated object aligned to the
light source and the
light source in real time and transmit the information to a singlechip through an I / O port, the singlechip receives the
signal, outputs PWM
waves with different duty ratios, controls a driving module to output different voltages and provides different current for the high-power
led lamp through a
resistor, in order to adjust the brightness of the light source and automatically adjust the
light intensity of the light source with the change of the
irradiation distance, so that an illumination effect is guaranteed to be basically unchanged in the case of light source
jitter or distance change. The flashlight provided by the invention automatically changes the illumination brightness according to the distance, and meanwhile, the illumination brightness corresponding to the same irradiation distance can also be changed by the button to realize human-friendly adjustment.