Updated: Aug 3, 2020
Luke writes a letter probably to his publisher/financier Theophilus. The form is a historical report as means for a theological communication and intended to be so. This contributes to Luke's emphasis that what he writes is the truth about Jesus as fulfillment of the messianic prophecies of the OT. Luke shows how the Holy Spirit works in and through the Messiah Jesus to offer and realise the peace relationship between God and those that put their trust in Jesus, as well as to lead them into peace relationships. Jesus' ministry is accompanied by signs and wonders, as Isaiah 61 says.
Luke is convinced that this is the truth about Jesus and that the reader can also experience this Jesus (who is being God himself) and experience peace with God and his people by the Holy Spirit if he or she decides to place his trust in him.
Inspiration in this sense would be the conviction of speaking the truth by the Holy Spirit based on sound research guided by the Spirit. It is in the interest of the reader to believe this and to respond positively to it.
The Greek terminology being used corresponds to OT prophetic pneumatology. Luke places himself therefore in line with that stream of literature that Jews in general and Luke specifically believes to be inspired becoming himself part of it.