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影像法是目前测量螺纹,丝杠牙形半角的主要方法之一。本文指出了在这种方法中,由于人们把螺旋面上水平含轴截面以外的点所成的像,近似地当作水平含轴截面上点成的像而引入的理论误差、其数值在丝杠牙形半角的测量中是不可忽视的;同时还指出了,这些成像点在显微镜物方的分布是空间的,但是人们观察的是它们在分划板平面上形成的影像,这就引入了第二项理论误差——空间边界点通过显微镜在平面上形成的影像边界所具有的理论误差。这项误差的数值在丝杠牙形半角测量中同样是不可忽视的,同时还通过调焦误差影响着测量结果的稳定性。因此,用影像法测量那些牙形半角小而螺旋升角大的丝杠之牙形半角是不合适的。文中给出了哪些丝杠可以用影像法测量,哪些则不可以的判别方法。
Imaging method is one of the main methods to measure the thread, screw tooth half angle. This paper shows that in this method, the theoretical error introduced by approximating the image of a point on the helical surface beyond the horizontal axial cross-section is approximately the same as the theoretical error introduced in the wire It was pointed out that the distribution of these imaging points on the object side of the microscope is spatial but one observes the images they form on the plane of the reticle, The second theoretical error is the theoretical error posed by the boundary of the image at the boundary of the point where the image is formed on a plane by a microscope. The value of this error in the screw teeth half-width measurement is also not be ignored, but also through the focus error affect the stability of the measurement results. Therefore, the use of imaging method to measure those teeth small half-angle screw lead screw angle tooth half-angle is not appropriate. The paper gives which screw can be measured by video method, which is not the discriminant method.