1. Whether the focal length is adjusted properly.
2. Whether there is too much paper soaked in water on the engraved material, or whether there is too much water on the paper.
3. Whether the laser tube is aging.
4. Whether the optical path is correct. (Recorrect)
5. The lens is dirty and the dust is too thick.
6. Broken lens.
7. The laser tube head is contaminated.
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