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利用光来测定物体移动速度的方法有各式各样。这里介绍的是利用一种光栅滤光片对目标物体的象进行测速的方法。这种方法又称之为空间滤频法。图1为光栅滤光片式速度计的原理图,如图所示,将被照明的物体的象呈在光栅滤光片G上,通过光栅滤光片,最后由光电探测器PD所接收。这样,即可在光电探测器的输出端获得与被测物体移动速度成比例的包含着频率成份的电信号。这里,如果把被测物体以微粒形式来考虑,借助于光栅滤光片对被测物体进行观测时,根据光强随时间而变化,可进行直
There are various ways to measure the speed of moving objects using light. Described here is the use of a grating filter on the image of the target speed method. This method is also called spatial filter method. Figure 1 is a schematic diagram of a grating filter type speedometer. As shown, the image of the object to be illuminated is on the grating filter G, passes through the grating filter, and finally is received by the photodetector PD. In this way, it is possible to obtain at the output of the photodetector an electrical signal containing the frequency component in proportion to the speed of movement of the object under test. Here, if the object to be measured in the form of particles to consider, by means of grating filter to observe the measured object, depending on the light intensity over time, can be straight