An image reading apparatus equipped with an illuminating device having little tint variation. The active material based segments include an active material such that activation of the active material by an activation device can allow folding of the panel, can effect self-folding of the panel, or can serve to lock the panel into a fixed position when not activated. Furthermore, the outer wall is produced from a material having a density of at least 1. The vertical polarized beam passes the polarizing beam splitter, deviates from the light path of the outgoing linearly polarized light beam and reaches the absorber.