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Blooming and Smearing in Your Beam Profile? Why It Happens and How to Fix It

When measuring your laser beam profile, you expect the measurement to be accurate, so it can be frustrating to see artifacts that are clearly not right. Before discussing how to fix it, or even when and why it happens, let’s explain what exactly bloom and smear are.

What do blooming and smearing look like?

Bloom is when the image expands somewhat in all directions. Smearing on the other hand, can be identified by a vertical line of higher exposure in one direction only, as shown here:

Why does it happen?

CCD cameras work by transferring incident light into charge in the CCD. When the charge is able to leak into other pixels, this creates undesirable effects such as blooming and smearing. In the case of blooming, charge in a pixel spreads to the surrounding pixels. Smearing is the result of charge spreading along a vertical shift register, which leads to the “long line in one direction” effect.

Because of the nature of how charge builds up and spreads in a CCD camera, this effect is most prevalent with short exposure, NIR-wavelength lasers.

How to avoid smearing or blooming

Since exposure time is a factor when it comes to blooming and smearing, one method to fix this is to simply adjust the exposure time and add attenuation if necessary. However, this is not always advisable or possible. Ophir offers an alternative with its BeamGage Smearing Correction feature. Simply press this button and the proprietary mathematical algorithm will do the rest:

At Ophir, we combine state-of-the-art cameras with very high level software algorithms to provide the highest possible accuracy in beam profile measurement. Contact us to learn more.



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