In the last article, we talked about the the influence of power, frequency and pulse on color marking. This time, we are going to tell the focus length effect on colorful marking.
The story of MOPA color marking
The most direct effect of changing focal length is to change the laser power density. Power density of small focal length is higher, and large focal length will be lower. Because for focal length, the smaller the better ability to focus. Smaller laser spot will lead to high density laser power.
In the field of optics, the relationship between focal spot size and the focal length of F-Theta len is positively correlated with the following figure.
This point is similar to the pressure in physics. When the force of the area is smaller , the greater pressure is. In terms of laser function, with the same laser parameter, different F-Theta lens will lead to different power density on the materials’ surface. In other words, to keep the original energy density still with F-Theta len changing, the most direct way is to change laser power value. To improve the power value, so that we can make sure a basic ratio between F-Theta len and laser power. In this way, we are able to achieve the same color.
Here we have chosen 4 different F-Theta lens: F = 163mm, F = 220mm, F = 254mm, F = 330mm. And the laser source we choose JPT-YDFLP-20W-M6 +, 0.001 fill spacing. In the stainless steel plate, we set pulse width 2ns, 45ns and 80ns . You can see the marking effect in the following pictures:
We have taken 2 articles to describe the frequency, power and focal length on the impact of color marking on stainless steel. In this way, we can find MOPA laser has a clear advantage on color marking.
New article, we will talk some stories of MOPA laser marking machine from our clients. More information, please contact:
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