## Attributes for Laser Measurement

Before getting into the details of non-contact laser sensors, you need to understand their attributes in order to improve the results obtained when using them for measurement. Laser probes are excellent at gathering large amounts of data quickly. They are also good for measuring parts that may otherwise deform under the pressure of a tactile probe.

However, keep in mind that measurements taken with laser sensors are influenced by other factors such as sunlight, surface finish, surface reflectivity, and surface color. In order to compensate for some of these factors, filters can be applied to the data to handle the influence. But you should understand how and why these items affect the results.

Sunlight

Unlike other non-contact systems, laser sensors are not generally affected by standard industrial lighting. Laser sensors will work under varied lighting conditions because the sensor’s frequency is tuned to its own laser. Only light that has the same frequency as the laser itself can affect the measurement. Because sunlight contains all frequencies of light, it is important to keep sunlight in the inspection room at a minimum.

Surface Finish

Because tactile probes are larger than the deviation in most surface finish, a tactile probe acts as an averaging filter. When the tactile probe comes in contact with the surface, it gives an average of the highest points on the surface. When using a laser sensor, the light reflects off the surface of the part. How the light reflects, depends a lot on the roughness of the surface, even if it does not appear rough to the human sight or touch.

Surface Reflectivity

Generally, surfaces with a matte finish work better than those with a glossy finish. A glossy surface finish usually has directional reflection. Depending on the angle of the light, you will get too much or too little light. You might even get a ‘hot spot’ (something that looks like a ‘blob’ in the graphics display area). This blob is actually the image of the light source. The reflection of light might add some extraneous points to the scan line, but the rest of the points will not be affected by the reflection. You can compensate for surface reflectivity by spraying the part with an aerosol powder or paint.

Surface Color

Because the laser is light, the surface color also has potential for impact on measurement. In a similar way that black absorbs heat from the sun, black surfaces will absorb the laser light making measurement of black surfaces difficult. Darker colors have more potential for problems. If your part is too dark, you can apply powder coatings to it to make it easier to sample.

It will take some time and experience working with your particular parts and in your specific environment to determine what settings will work best for you. You should experiment with the capabilities of your specific sensor to improve the results of measurements.

Remember that you are working with a Laser sensor. Consult your probe documentation for safety issues and procedures for a safe work environment.