发光二极管(Light Emitting Diode,LED)作为一种场致发光光源,已经获得广泛的应用,但在影像测量中的下照明领域还处于起步和探索阶段.影像测量中,光照不均匀或者光强不适,都会影响所拍摄图像的质量.为获得高质量的图像,设计一种基于PWM数字可调的均匀光源系统,用于下照明的影像测量.系统通过正交实验法获得环形的LED阵列、灯的倾角、LED灯的数量、LED的环形直径等,搭建光源系统,使得LED环形阵列在视场2 cm内获得均匀的光强,结合LED发光特性设计PWM脉冲发生电路,通过上位机的软件让均匀光源强度256级可调,适合各种不同的场合,增强实用性.实验数据表明,利用光学显微影像测量系统,在最小放大倍率07倍以及最大放大倍率45倍两种极端情况下,检测4个级别的光强均匀性都超过了83%.该系统完全能够在影像测量中达到要求.

LED (Light Emitting Diode,LED) source is a field luminescence source light.Video lighting measurement is still in the initial exploration stage although it has gained a wide application.Illumination uneven and light intensity discomfort will affect the quality of images.A digital adjustable even lighter system is designed based on PWM to obtain the high quality images for image measurement of under illumination.This digital adjustable even lighter system can obtain annular LED array,light angle,the number of LED lights,light ring diameter with the orthogonal experiment method.We also build a light source system to gain even lighter among 2 cm view field in the LED circular array.A circuit of PWM pulse generation is designed according to the LED light features to gain an even light of 256 adjustable intensity through the PC software on a variety of different occasion.Four different levels of intensity uniformity is tested in the experiment,and experimental data shows that the intensity uniformity reaches up to 83% at the field at 07X and 45X using an optical microscopic image,which meets the requirements of the image measurement.