The following assumes that the camera frame rate is 50fps as an example for calculation. In the height range of 50um, 200 frames are collected, theoretically 20ms, and 1 frame corresponds to 0.25um; but in fact, Windows is not a real-time operating system, and the camera image period T0 and grating scale readings are collected. The delay D0 is not a constant value at a constant speed, and there will be fluctuation t1 and delay d1 respectively.
The specific values of t1 and d1 are related to the computing intensity of all applications currently running on Windows, the single-core main frequency of the CPU, and the total number of cores. We measured and inquired about a variety of C++ parallel computing data and concluded that the timing accuracy of Windows 10 is within 1ms. Further, it is assumed that when the M800 is running on Windows 10, the delay fluctuations t1 and d1 are both less than 20ms.
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Because the camera continuously captures images, it can be assumed that the effective sampling frequency is 25fps; that is, 40ms, and 2 frames correspond to a height range of 0.5um
Measured resolution calculation, 1280×1024, RGB24, time-consuming < 20ms. Test PC configuration, see attached table below. Therefore, the definition calculation process will not delay the effective sampling frame rate. As long as the movement speed of the control Z motor is low enough, it can be ensured that 0.5um corresponds to 1 frame of valid image.
Z mechanical transmission, using C3 precision HIWIN-2005 ball screw, 6400 drive subdivision. The measured empty distance is less than 20um, and it can support the continuous and near-uniform movement of the Z axis.
The 3D imaging of the ring sample shows that the surface of the ring flatness and parallelism evaluation is the surface of the concave and convex annual ring sample, and the surface processing accuracy has been within 20um. We recommend using 5x, 10x as the main objective lens to photograph the sample surface; the best comprehensive effect of improving imaging clarity: the single field of view is neither too small, the depth of field is large enough to ensure the acquisition of Z, and it is insensitive to bump growth rings , thus ensuring the final measurement accuracy.
For safe consideration, we suggest that higher-precision measurement equipment can be arranged to inter-calibrate with our equipment to further ensure that the total cost of the project is foolproof.
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