Focusing and alignment methods for tool microscopes
When using a tool microscope, accurate focusing and aiming usually results in an error of 1-2 micrometers for the same measured object. Therefore, only correct focusing and aiming can ensure the accuracy of the measurement results. The correct focusing and alignment (line pressing) methods are introduced as follows:
1、 Focusing method
1. Firstly, adjust the visibility of the eyepiece, which means that a clear line image can be observed in the eyepiece field of view. If the measurer cannot obtain a clear line image in the eyepiece field of view, the eyepiece visibility circle should be adjusted to match the measurer's vision, so that a clear meter line can be obtained.
2. Move the central microscope through the focusing handwheel to obtain a clear image of the object's contour in the field of view of the eyepiece, and then move the vertical and horizontal workbench for alignment. If the observer's eyes move up and down, left and right in the field of view, and no object image moves relative to the meter line, it indicates that the measured object is correctly imaged on the meter line reticle, and measurement can be carried out at this time. If there is relative movement between the object image and the meter line, it indicates that the microscope has not been properly focused, and further careful focusing is needed to make the object image and the meter line reticle on the same plane.
2、 Line alignment (pressing) method
Line alignment (pressing) refers to the use of a meter shaped line and the edge of the measured object's image contour overlapping each other, which is also known as aiming. For a specific tool microscope, the accuracy of the instrument is certain. To ensure high and reliable measurement accuracy, it largely depends on the correct alignment method. There are two alignment methods: gap alignment method and overlap alignment method.
1. Gap to line method, which is suitable for angle measurement. When measuring angles, when any dotted line of the meter line is placed against one side of the measured angle in the field of view, a narrow gap is maintained between the dotted line of the meter line and the edge of the measured angle. The measurer uses the uniformity of the gap size to determine the degree of alignment between the dotted line of the meter line and the edge of the measured object's image. If the alignment method mentioned above is not used and the method that overlaps with the image edge is directly used, it will not only make it difficult for the measurer to align, but also increase the measurement error. At this point, the image of the measured object's contour in the field of view is not a thin line, but a light and dark contour, and the reticle of the meter line has a certain width. If they are overlapped for measurement, significant alignment errors will inevitably occur, especially when the edges of the measured angle are relatively short, which is even more serious. So the gap alignment method should be used for angle measurement.
2. Overlap alignment method. If the above gap alignment method is still used in length measurement, it will increase the length measurement error. The reason is that the gap cannot be measured and is included in the measured length measurement. Therefore, the overlapping alignment method is used for length measurement. It is to overlap the dashed line of the rice line with the edge of the contour image, so that half of the dashed line is inside the contour image and the other half is outside the image. When aligning, the center of the dotted line on the meter shaped line should be taken as the reference, and the extended part should be used as a reference to obtain accurate measurement results.
