Abstract: An optical reader for reading high density dibit encoded data from a data strip comprises an optical detector (13) and a detector (14,15,DSP) connected to the optical detector (13) and arranged to decode its output. The detector includes a row of photosensitive elements arranged to extend transversely across a row of dibits and to form an image of the row of dibits. The decoder (14,15,DSP) includes a buffer (15) arranged to store the row image. An image transform device detects a skew angle of the strip and transforms the stored image to compensate for the distortion of the image.