Apparatus and method for exposure or relief precursors

A method for exposing a relief precursor comprising at least one photosensitive layer, said method comprising the following steps:

• providing a relief precursor,
• optionally performing a pre-exposure with an additional light source,
• performing a first relative movement between a light source and the relief precursor whilst exposing a first side of the relief precursor,
• moving the light source from a first position facing the first side to a second position facing a second side of the relief precursor;
• and
• performing a second relative movement between the light source and the relief precursor whilst exposing the second side of the relief precursor,
• wherein at least one of the first and the second relative movement is a reciprocating movement;
• and
• controlling the performing of the first relative movement so that at least one first reciprocating movement is performed to expose the first side of the relief precursor, wherein the at least one first reciprocating movement comprises a first exposing step comprising exposing during one or more exposure passes the relief precursor according to a first intensity profile and a first speed profile and a second exposing step comprising exposing during one or more exposure passes the relief precursor according to a second intensity profile different from the first intensity profile and/or a second speed profile different from the first speed profile.

An apparatus for exposure of a relief precursor comprising at least one photosensitive layer, said relief precursor having a first side and an opposite second side, said apparatus comprising:

• a light source configured to expose the relief precursor during relative movement between the light source and the relief precursor;
• a moving means configured:
• to cause a first relative movement between the light source and the relief precursor to expose the first side of the relief precursor,
• to cause a second relative movement between the light source and the relief precursor to expose the second side of the relief precursor, and
• to move the light source between a first position and a second position, said first and second positions being on opposite sides of a plane of the relief precursor;
• wherein at least one of the first and the second relative movement is a reciprocating movement;
• a control means configured to control the movement means and/or the light source;
• wherein the at least one first reciprocating movement comprises one or more front exposure steps during one or more front exposure periods, and the at least one second reciprocating movement comprises one or more back exposure steps during one or more back exposure periods, wherein the apparatus comprises an operator interface configured to receive at least one front characteristic representative for the one or more front exposure periods and/or at least one back characteristic representative for the one or more back exposure periods;
• and wherein the control means is configured for determining a sequence of operation for the light source based on the at least one front and/or back characteristic.