	Optical Micrometers

Hints on Correct Use

Accuracy (Scanning method)

Thrubeam measuring instruments that use the scanning method produce errors equivalent to the vibration amplitude as shown below when the target vibrates in the scanning direction.

If measured values fluctuate due to target vibration, install guide rails or the like to minimize target vibration or increase the number of averaging measurements.

Measuring distance and accuracy (CCD/photodiode method)

The VG Series uses a CCD image sensor as the light receiving element. Therefore, accuracy varies depending on the transmitter-to-receiver distance and the target-to-receiver distance. Accuracy can vary due to the following: As distances become longer, the edge of the shadow produced by the target interrupting the beam becomes vaguer because of stray light or other factors.
Since the transmitter-to-receiver distance and the target-to- receiver distance affects accuracy, as shown below, minimize the transmitter-to-receiver distance and the target-to-receiver distance.

Diagram of accuracy with a short detecting distance

When the transmitter-to-receiver distance and the target-to-receiver distance are short

The edges of the shadow produced by the target are sharp.

Diagram of accuracy with a long detecting distance

When the transmitter-to-receiver distance and the target-to-receiver distance are long

The edges of the shadow produced by the target are vague.

Light intensity correction function (CCD method)

If the distribution of the light intensity emitted from the semiconductor laser diode or the distribution of the sensitivity of the CCD image sensor is not uniform, the accuracy may not be stable. The VG Series is equipped with a light intensity correction function (Auto-gain function) to evenly spread the distribution of light intensity and sensitivity. Before starting detection, be sure to correct light intensity using this function to obtain a stable accuracy.

Measurement of transparent target

When a target interrupts the light beam, a shadow forms in proportion to the target size. The VG Series measures the size and position of this shadow using a 5,000-bit CCD image sensor. However, when the target is transparent, most of the laser beam passes through the target, creating vague edges on the CCD image sensor.
In this case, place the transparent target as close to the transmitter as possible, as shown below. This prevents vague edges from being created, allowing the outer diameter of a transparent target to be measured.

Position of a transparent target affects measurement

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