A stereoscopic image apparatus comprising: a polarizing beam splitter (21, 22) adapted to receive image light from an image surface and to split the incident image light into (a) a transmitted image light having a first state of polarization, and (b) first and second reflected image lights having a second state of polarization, the second state being different from the first state, wherein the polarization beam splitter has two plates (21, 22) joined to each other, and a junction of the two plates is located on a path of the incident image light; first and second reflective members (23, 24) configured to modify paths of the first and the second reflected image lights so that the transmitted image light and the first and the second reflected image lights are projected to form a single image on an image-forming surface, wherein the single image is formed by superimposing a first image from the transmitted image light and a second image from the first and the second reflected image lights at the substantially same area on the image-forming surface, first, second and third polarization modulators (27a, 27b, 27c) capable of selectively switching the polarization states of the transmitted image light and the first and the second reflected image lights between first and second output states of polarization, wherein the first, the second and the third polarization modulators are controlled to selectively switch the polarization states of the transmitted image light and the first and the second reflected image lights to have the same output state of polarization at a given instant, thereby forming a single polarized image on the image-forming surface at the said given instant. a polarizing beam splitter (21, 22) adapted to receive image light from an image surface and to split the incident image light into (a) a transmitted image light having a first state of polarization, and (b) first and second reflected image lights having a second state of polarization, the second state being different from the first state, wherein the polarization beam splitter has two plates (21, 22) joined to each other, and a junction of the two plates is located on a path of the incident image light; first and second reflective members (23, 24) configured to modify paths of the first and the second reflected image lights so that the transmitted image light and the first and the second reflected image lights are projected to form a single image on an image-forming surface, wherein the single image is formed by superimposing a first image from the transmitted image light and a second image from the first and the second reflected image lights at the substantially same area on the image-forming surface, first, second and third polarization modulators (27a, 27b, 27c) capable of selectively switching the polarization states of the transmitted image light and the first and the second reflected image lights between first and second output states of polarization, wherein the first, the second and the third polarization modulators are controlled to selectively switch the polarization states of the transmitted image light and the first and the second reflected image lights to have the same output state of polarization at a given instant, thereby forming a single polarized image on the image-forming surface at the said given instant.