An adapter is provided for adapting an optical instrument, such as a camera (3) or a projector, to capture or display panoramic three-dimensional images. The adapter comprises a plurality of mirrors (1a, 1b, 1c), each of which has a reflective surface which is in the shape of a curved non-circular conic section rotated about an axis of symmetry (15a, 15b, 15c). The reflective surfaces have first foci which are spaced perpendicularly from a longitudinal axis of the adapter and which are angularly spaced around the longitudinal axis. For example, the conic section may be a hyperbola with first foci equidistantly spaced from the longitudinal axis and equiangularly spaced around 15b the longitudinal axis. The axes of symmetry (15a, 15b, 15c) of the mirrors (1a, 1b, 1c) converge to intersect the longitudinal axis at a point which is coincident with the front principal point of, for example, a camera lens (12). Thus, single shot capture of all the image data for the or each panoramic three-dimensional image may be performed.