Measuring Parallelism with a Smart Laser Autocollimator

Laser Autocollimators are useful for measuring flatness and parallelism between two planes.  This is often an easy application, but it can get more complicated if one plane is more reflective than the second, or vice versa. Extra time may need to be spent on adjusting the laser intensity and the shutter speed of the sensor. Fortunately, modern technology has solved this issue. One optical component that can automatically adjust the shutter speed and laser intensity of the sensor to adjust for uneven reflectiveness is a Smart Laser Autocollimator.

Smart Laser Autocollimator

In this example, a parallel mirror with high reflectiveness will be compared to a piece of stainless steel from a hardware store with low reflectiveness to find the parallelism between a hypothetical sample that is more reflective than its reference point.

The stainless steel strip is reflective, but not as reflective as a proper mirror. This is demonstrated by tuning the Smart Laser Autocollimator to read the reflection of the mirror, then moving it out of the way using the stage and attempting to measure the reflection angle of the stainless steel strip. The sensor was previously tuned to the optical mirror, which will be used as a starting point (Figure 1). When the mirror is moved out of the way, the sensor cannot read the reflection of the stainless steel strip, thus showing the difference in reflectiveness (Figure 2).

Figure 1: Suruga Seiki Optical Mirror compared to stainless steel strip. The sensor is tuned to the mirror.
Figure 1: Suruga Seiki Optical Mirror compared to stainless steel strip. The sensor is tuned to the mirror.

The way to remedy this situation on older model Laser Autocollimator units is to manually adjust the shutter speed and intensity of the laser (Figure 3). Doing so can take time, and is not appropriate for production floor activities that need to be done quickly.

This is where the Smart Laser Autocollimator H410 series shows why it’s called the “Smart” Laser Autocollimator. Shutter and laser intensity are adjusted by the processing unit and can be set to process automatically through the LD adjustment settings.

Figure 2: Mirror moved so laser reflects off of stainless steel strip. The readout shows an Error because it is not tuned to read that reflection.

The LD adjustment settings, and all settings, are accessed by pressing the icon on the bottom right-hand corner of the screen (Figure 4). The Settings menu will have a few options to choose from, the LD Adjustment tab is easy to find (Figure 5). The menu shows options for Auto or Manual adjustment, Tuning (for manual adjustment), and selection for the internal or external light source. Setting the LD Adjustment to Auto will allow the Smart Laser Autocollimator to automatically adjust the shutter speed and intensity of the laser as the surface changes. Since the stainless steel strip has an imperfect surface, you might see two dots in the newly tuned reflection (Figure 6), with one sharp dot for the mirror (Figure 7) after moving it back into place. From here, pressing the Run button will bring back the measurement screen so that the offset between the mirror and the stainless steel can be seen in milliradians (Figure 8, Figure 9).

Figure 4: Enter Settings to adjust the sensor.
Figure 5: LD Adjustment menu. Manual and Auto Adjustment and Tuning selections are on top.
Figure 6: Adjustment settings changed to Auto. Two reflections appear within the set tolerance.
Figure 7: The Mirror is moved back into place and the resulting reflection is clear and sharp.
Figure 8: Stainless steel strip off center measurement.
Figure 9: Optical Mirror off-center measurement.

Tolerance verification between two surfaces of different reflectance is now quick and easy thanks to automatic sensor adjustment on the Smart Laser Autocollimator. Integration into machinery and production lines can help make higher quality products in less time. Explore the MISUMI H410 Smart Laser Autocollimator here.

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