The structural composition and optical principle characteristics of the image measuring instrument

The structural composition and optical principle characteristics of the image measuring instrument. An image measuring instrument usually consists of six parts: machinery, lighting, length measurement, image acquisition, computer and measurement software. The optical principle of the image measuring instrument is very similar to that of an ordinary projector. The difference is that the contour image of the measurement part of the former image is received by the CCD sensor, and the image is collected and processed by the computer, and the latter projects the image directly onto the projection observation screen. The contour is completed by the naked eye of the operator, which results in measurement accuracy and There is a big difference between the degree of automation, and the image measuring instrument usually has a larger measurement range. Usually equipped with 0.7x~4.5x zoom objective lens. In addition to the common bottom and top lighting, the lighting source also has ring lighting, which is suitable for the bottom lighting and the bottom lighting without the error source of the image measuring instrument. The measurement on the image measuring instrument is single-axis or two-dimensional plane coordinates measuring. When measuring, first focus, then align, then read and count, and then calculate and process. The reading comes from the ruler, that is, the grating system. Focusing and alignment depend on the optical microscope and an illumination source will directly affect the measurement effect and accuracy, because if the measuring instrument is based on the image method, if the measured object cannot be illuminated effectively and correctly, the measurement result will obviously deviate from its true size, except In addition to the above factors, environmental conditions are also a non-negligible factor that limits the measurement accuracy. In actual measurement, when the lighting conditions of the light source change, it will directly affect the lighting effect and image quality of the measured workpiece. The main reason is the image measuring instrument. The image is received by the CCD. Although the CCD has the function of automatically adjusting the gain, when the brightness is too high, the adjustment function will be lost. As a result, the image of the measured workpiece is shrinking. If the brightness is too low, the image of the workpiece will become larger. When the image measuring instrument measures the distance between repeated graphic structures, the effect can be ignored as long as the illumination. During the whole measurement process, the conditions remain unchanged. Since each repeated graphic structure becomes larger or smaller at the same time, the distance The measurement and calculation directly eliminate the influence of image distortion, such as measuring the distance between the glass ruler and the grid plate. In addition to this special case, such as measuring the diameter of a circle, the length and width of the workpiece, it will also bring obvious The error.