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| I want to measure the specimen size under the microscope. Should I use an Ocular Micrometer ? or a Stage Micrometer ? |
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Simply put.. | |||
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| How to Use an Ocular Micrometer |
| The magnified specimen image is projected onto the ocular micrometer, allowing simultaneous viewing of both the micrometer scale and the sample through the eyepiece. The specimen size is measured by determining the single pitch width on the micrometer scale, which varies depending on the objective lens magnification and can be calculated as follows. |
| Single pitch width of an ocular micrometer under the microscope = [Actual width of a single pitch] ÷ [Objective lens magnification] |
| Example Measurement: |
| The figure below demonstrates measuring the size of a kidney glomerulus:
1. Ocular micrometer: XY11 (10mm / 100 divisions / 1 pitch = 100μm) 2. Objective lens: 20x magnification Using the formula: Single pitch width = 100μm ÷ 20 = 5.0μm Since the glomerulus spans 23 horizontal pitches and 22 vertical pitches, its dimensions can be calculated as: Width: 23 × 5μm = 115μm Length: 22 × 5μm = 110μm |
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| 100 μm (1 pitch) ÷ 20 (objective) = 5 μm X : 40 to 63 : 23 pitch x 5 μm = 115 μm Y : 40 to 62 : 22 pitch x 5 μm = 110 μm |
| How to Use an Ocular & Stage Micrometer for Calibration |
| Objective lenses may have slight magnification errors. The stage micrometer
is used to measure these errors in advance, ensuring more precise measurements. |
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| Example of Magnification Error Measurement for Objective Lenses : |
| ● | Position the micrometers so that the ocular and stage micrometer scales
appear parallel when viewed through the eyepiece. This allows for precise magnification error calculation. |
| ● | The figure below shows an example using a stage micrometer NOB1 (1mm / 100 div / pitch = 10μm) and an ocular micrometer S11 (10mm / 100 div / pitch = 100μm) under a 20x objective lens. |
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| 【Expected Measurement】 If the magnification is accurate, 10 pitches on the stage micrometer should match 20 pitches on the ocular micrometer: 2000 μm = 10 μm (1 pitch of stage micrometer) × 10 pitches × 20x objective 【Observed Measurement】 However, as seen in this example, if the ocular micrometer reads 22 pitches instead of 20, the actual magnification is slightly higher than 20x, indicating a magnification error. 【Correcting Measurement Values】 To obtain more accurate measurements, multiply the ocular micrometer's reading by the error correction factor: 0.91 (= 20 ÷ 22) Thus, the actual measurement value = ocular micrometer reading × 0.91, ensuring more precise results. |
| How to Install an Ocular Micrometer |
| An ocular micrometer is printed in chrome on a glass surface (with the printed side considered the front). Insert it into the eyepiece with the printed side facing the microscope (as shown in the image at the bottom). |
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| Each eyepiece model has a different fitting diameter, and compatible micrometer
sizes vary depending on the eyepiece manufacturer and model number. micrometer sizes vary depending on the eyepiece's manufacturer and model number. Nikon and Olympus Eyepiece & Ocular Micrometer Compatibility List |
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| How to Identify the Front and Back of an Ocular Micrometer |
| The scale of the ocular micrometer is printed in chrome on the glass. Once the printed side is identified, place it on the mounting bracket with the printed side facing the objective lens (downward). *refer to the installation instructions above for details. This section explains how to distinguish the front (printed side) and back side of the micrometer. |
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