Apparatus and methods are disclosed for implanting a prosthetic nucleus in a chamber of an intervertebral disc after removal of at least a portion of a damaged or degenerated nucleus from the chamber. The light source unit supplies light to the LCD panel. The first component and the second component are distinct. Typically, the ejector extends through the filter housing and axially ejects the filter element from the housing. A background score is estimated based on the first recognition score.