Vanessa Bryant is suing the L.A. County Sheriff and his department, claiming they caused her severe emotional distress ... when deputies allegedly took personal cellphone photos of the bodies of Kobe and Gigi Bryant at the scene of the helicopter crash that took their lives.

According to the lawsuit, obtained by TMZ, "no fewer than 8 sheriff's deputies at the crash site, pulled out their personal cell phones and snapped photos of the dead children, parents and coaches. The deputies took these photos for their own personal gratification."

The lawsuit goes onto allege the photos were the subject of conversation within the sheriff's dept ... with deputies showing their colleagues the pictures that had no investigative purpose.

The lawsuit notes how the photos were exposed ... when a deputy was at a bar and showed the photos to a woman he was trying to impress. The bartender heard the conversation, blew the whistle and called the sheriff's department.

Vanessa says in the suit ... that's when Sheriff Villanueva tried to cover it all up by going to the Sheriff's substation that responded to the crash and telling deputies if they deleted the photos they would not face discipline. The suit claims the purpose of his talk was destruction of evidence.  The lawsuit claims Villanueva did not tell the families about the photos and they only learned of it in the media when the story broke that deputies took the photos.

The lawsuit claims the Sheriff never gave the family straight answers and now Vanessa is in constant fear the photos will leak ... "Ms. Bryant feels ill at the thought of strangers gawking at images of her deceased husband and child, and she lives in fear that she or her children will one day confront horrific images of their loved ones online."

The lawsuit seeks unspecified damages, including punitive damages.

We reached out to the Sheriff's Dept. ... so far, no word back.