High precision digital control LED spot light source used to calibrate CCD camera

This paper introduces a method that uses a Light Emitting Diode( LED) point light source as the camera calibration light. According to the characteristics of the LED point light source,a constant current source is used to provide the necessary current and a illuminometer is used to measure the luminance of the LED point light source. The constant current source is controlled by an ARM MCU and its data are exchanged with the host computer through the mode of serial communications. The PC is used as the host computer,and it adjusts the current according to the luminance of the LED point light source until the luminance achieves an anticipated value. Experimental analysis shows that the LED point light source with a higher precision can meet the requirements of the calibration light source,and can adaptively control the luminance of LED well.The system is convenient and flexible,and its performance is stable and reliable.