非接触测量距试件表面几十毫米处的距离或位移时，激光是主要的检测手段。然而，当检测容易吸光的黑色橡胶、表面反射很弱的透明材料以及表面反射和底面反射重合在一起的半透明材料时，激光检测方法就无能为力了。非接触空气耦合式超声无损检测技术很好地弥补了激光检测技术的不足。利用空气耦合超声表面发射法，只需测量试件的表面反射波即可测量任何材料试件的距离或位移。使用表面反射法，选用2 MHz的空气耦合点聚焦探头，在空气中对试件位移进行了实时测量，试验结果表明，温度变化在0.1℃范围内时，检测精度能达到0.01 mm。

For non-contact measuring the distance or displacement in the air a few millimeters apart from the test surface, the laser is the main means of detection. However, the easy-to-absorb black rubber, the transparent material with weak surface reflection, and the translucent material with superficial reflection and bottom reflection being overlapped, the laser detection method cannot do anything. Air-coupled ultrasonic nondestructive testing technology can make up for the lack of laser detection technology. The use of air-coupled ultrasonic surface emission method, simply measuring the surface reflection of the specimen can measure the distance or displacement of any material specimen. In this paper, the real-time measurement of the air-to-specimen displacement was performed by the surface emission method through using 2 MHz air coupling point focus probe, and the experimental results show that when the temperature changes in the range of 0.1℃, the detection accuracy is of 0.01 mm.