  Orthogonal optical coding is widely used in classical multiuser communication
networks. Using the phase conjugation property of stimulated parametric
down-conversion, we extend the current orthogonal optical coding scheme to the
spatial domain to encode and decode image information. In this process, the
idler beam inherits the complex conjugate of the field information encoded in
the seed beam. An encoding phase mask introduced to the input seed beam blurs
the image transferred to the idler. The original image is restored by passing
the coded transferred image through a corrective phase mask placed in the
momentum space of the idler beam. We expect that this scheme can also inspire
new techniques in aberration cancellation and frequency conversion imaging.
