A man allegedly exposed himself in a doorway near the car park in Marshalls Yard in Gainsborough.
He then ran off towards the end of Marshalls Yard and down an alleyway leading to the main road after the incident, which happened at around 3.30pm on January 13.
Police are appealing for information to help with their investigation into the indecent exposure incident.
The force published an image on Thursday, January 30 of a man they wish to identify, who they believe can assist with their investigation.
Anyone who recognises the man or has information should contact Lincolnshire Police on 101 or via email at force.c[email protected] quoting reference number 20000023977.
It can also be reported through the independent charity Crimestoppers anonymously on 0800 555 111 or online here.