Micrometer ruler

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The micrometer is divided into an eyepiece micrometer and an objective micrometer (mirror micrometer). Eyepiece micrometer: measures the length of an object in the field of view; Objective micrometer: It is a standard length used to calibrate the objective micrometer.

Eyepiece micrometer: It is a circular glass slide with a precise scale engraved in the center, usually dividing 5mm into 50 grids, and each grid is actually equal to 100 μ M. The size of the scale varies with the magnification of the eyepiece and objective used, and must be calibrated using an objective micrometer before use.

Objective micrometer: A specially made glass slide with a small circle in the center. The circle is engraved with divisions, dividing a 1mm long straight line into 100 small grids, with each grid equal to 10 μ M.

Calibration method

1. Remove the eyepiece, unscrew the eyepiece lens from the eyepiece, place the eyepiece micrometer on the middle partition of the eyepiece, with the graduated side facing downwards, then screw on the eyepiece lens and insert it into the lens barrel.

2. Place the objective micrometer on the stage of the microscope, with the graduated side facing upwards, just like observing the specimen, with the graduated small circle located in the center of the field of view.

3. First, observe with a low magnification lens, align with the focal length, and after seeing the scale of the objective micrometer clearly, rotate the eyepiece so that the scale of the objective micrometer is parallel to the scale of the objective micrometer, and make the first line on the left of the two rulers coincide. Then, search for the other overlapping line on the right side of the two rulers.

4. Record the number of grids of the eyepiece micrometer and the objective micrometer between two overlapping lines.

Calculation method

1. The length of each grid of the eyepiece micrometer is equal to the number of objective micrometer grids between two overlapping scales x 10/the number of objective micrometer grids between two overlapping scales.

2. Using the same method, measure the actual length of each grid on the micrometer under different magnification lenses.

3. The scale of the eyepiece micrometer after such measurement is only applicable to the magnification of the eyepiece and objective of the microscope used for measurement. If the objective is replaced, the magnification of the eyepiece must be calibrated again.

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