After using various laser diodes and various lenses for research, repeated comparisons, and combined with our company’s existing products. A conclusion is drawn that the shape of the light spot is mainly determined by the laser divergence angle of the laser diode and the light spot of the laser diode. It has little to do with the lens.
The function of the lens is to map the image of the laser diode to the back of the lens, so it is basically an excitation What is the shape of the light spot of the diode,what will the light spot of the laser after being focused.
Let’s mainly explored two typical color laser diodes：
Red laser diode, the spot of red laser diode is usually relatively divergent.
In this way, the image formed by the red laser diode after focusing.
It will be a circle where the energy converges in the middle and the energy on both sides diverges. The reason why is a round spot is that the spot of the red laser diode is very divergent and the divergence angle is large. The clear aperture of the laser module is a circle, and the spot can cover The entire clear aperture, so that the final spot will be circular.
Let’s have a look at the blue laser diode then:
We will see that the divergence angle of the blue laser diode on the X axis is relatively large, but the divergence angle on the Y axis is relatively small, and the energy is more concentrated.
After passing through the lens, it is found that the light spot becomes a kind of rectangular-like light spot. By observing the two sides of the light spot, it is found that the two sides of the light spot are still arc-shaped, so it is still a circular clear aperture, but the organ diode has a divergence angle on the X axis. Relatively small, so the spot is square.
We tried a lot of lasers, blue, purple, and green, basically in line with this rule. Therefore, the shape of the laser spot mainly depends on the divergence angle of the laser diode and the spot of the laser diode. Not very much related to the lens.