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Application SolutionsMeasuring Height/Step Height

Finding The Right Solution for Height/Step Measurement

When looking for the best way to measure height or step height, there are a number of important factors to consider, including the shape of the target, the type of measurement system, and the installation environment. Selecting equipment that doesn't adequately meet your needs can lead to insufficient precision and increased man-hours during production, so choosing the right equipment is important. This site is designed to help you discover the best way to perform this measurement with confidence.

Height/Step Height Solutions

  • STEP 1: Look at the methods outlined in each item to find the best measurement method.
  • STEP 2: Download the catalog to learn more about the system.
  • STEP 3: Get in touch with your local measurement expert to have an on-site consultation about your application.
  1. A- Single-point height measurement  B- Muluti-point height (step) measurement
  2. B-A- Two measurement locations near each other  B-B- Two measurement locations far away from each other
  3. B-A-A- Measuring from above  B-A-B- Measuring from the side
  4. Example Applications
    • A- Measurement 1 Height measurement of dispensers
    • B-A-A- Measurement 2 Height measurement of connector terminals
    • B-A-B- Measurement 3 Step measurement of electrode terminals
    • B-B- Measurement 1 Height measurement of  vehicles

Precautions during Height Measurement

About the effect of the tilt of the sensor head

If the optical axis is not perpendicular to the target, a measurement error caused by angle θ occurs in the height value, as shown in figure 1.
If θ is greater than 0.8°, the measurement error is approximately 0.01%, so correct the tilt in advance if you are concerned about its effect.
You can easily correct the tilt by preparing one master workpiece and using the scaling settings.

Figure 1:Optical-axis tilt θ

Transparent objects and objects with mirror finished surfaces

If the target is a transparent object or an object with a mirror finished surface, you have to install the sensor head tilted at an angle that is half the angle of the projected and received light, α, in relation to the target, as shown in figure 2.
(When using the triangulation method.)

Also, if the target is a transparent object, a key point for stable measurement is to have the transparent object be at least as thick as a certain value. If the object is thin, the value measured for the front surface height may be lower than it should be due to the effect of the light reflected from the back surface of the transparent object.
The limit of the thickness to ensure that the measurements are not affected varies depending on factors such as the sensor head type, the transparency of the target, and the reflective status of the back surface, so check with your manufacturer.

a/2

Precautions during Step Measurement

About the effect of the tilt of the sensor head

If the optical axis of the 2D laser displacement sensor is not perpendicular to the target, a measurement error caused by angle θ occurs in the step value, as shown in figure 3.
The larger the distance (X) between the two points being measured for the step, the greater the measurement error.
For example, even if the tilt θ is only 0.1°, the measurement error becomes approximately 50 μm if X = 30 mm.
Therefore, the tilt correction function is generally used when performing step measurements.

Figure 3:Optical-axis tilt θ,True step,Measured value,Distance between two points (X)

Transparent objects and objects with mirror finished surfaces

If at least one of the surfaces being measured in the step measurement is a transparent object or an object with a mirror finished surface, install the sensor head tilted at an angle that is half the angle of the projected and received light, α, in relation to the target, as shown in figure 4.
It is also necessary to prepare a head that is dedicated for use with transparent objects and objects with mirror finished surfaces.

Furthermore, if the target is a transparent object, it must be at least as thick as a certain value in order for the surface height to be measured accurately.
If the object is thin, the value measured for the front surface height may be lower than it should be due to the effect of the light reflected from the back surface of the transparent object.
The limit of the thickness to ensure that the measurements are not affected varies depending on factors such as the sensor head type, the transparency of the target, and the reflective status of the back surface, so check with your manufacturer.

Figure 4:Front,Side,Transparent/mirror finished surface

Which Method Is Better? Contact VS Non-contact

Measuring soft targets

When the probe comes into contact with a soft target, the target is indented, which leads to a corresponding measurement error.
With non-contact measurement, it is possible to measure targets that deform such as soft targets and liquid surfaces.

Measuring light targets

For targets that are thin and light, it is necessary to hold down the target to ensure that it does not float (that there is no gap made of air) in order to accurately measure the surface height.
With contact measurement, the probe presses down on the target surface, which eliminates errors caused by the target floating in the air. For this reason, the contact method is better suited to this type of measurement than the non-contact method.

Measuring indentations

With a non-contact laser displacement sensor, the measurement spot (which ranges from a few micrometers to hundreds of micrometers in size) is generally smaller than the probes used in contact measurement. This makes it possible to accurately measure the base height of more narrow indentations with the non-contact method.

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