Bruker Corp.’s third-quarter net income doubled, helped by easy comparisons to a prior-year period weighed down by charges. The Billerica company, which makes scientific instruments, boosted its full-year guidance to 75 to 79 cents per share. Net income was $39.7 million, or 24 cents per share, vs. $19.8 million, or 12 cents, a year ago. Also, Bruker received more than $3 million in orders from a leading provider of consumer displays for its self-calibrating 3-D optical microscopes.