Leaves bumps

[Jos DC]

Hi. I got these bumps on my orchid leaves before, mostly on cattleya but not this much of them on the same leaf. I noticed these bumps won’t harm my orchid, just looks ugly, or the damage is too little too see. But this time the one lead has too much bumps it makes me wonder what they really are or what causes these in the first place. Any suggestions please let me know. Thank you.
By the way, it’s not scale. I had scale on my orchid before, such a pain in the ***.