Dear :

As the author of [books], you are well-known among professionals. Would you be willing to help the young engineers in our company become new explorers of the enormous potential of [new tech, etc.]?

On behalf of [company], I am inviting you to speak at our seminar "." The meeting will be held at [time], [date], at [location].

I'm sure you will get enthusiastic responses if you could speak to our engineers for one hour and then answer questions.

I would be most grateful if you could accept my invitation. Hope to hear from you soon.

Sincerely yours,

[name]

[title]