four-color shades) during a change of phase by inclination of the visual. Synchronization of parallelism of the printing to the lenticules The origin of this problem is a fault in the printing and forcibly generates a phase defect. The passage from one visual to another must be simultaneous over the entire format. But when this problem occurs, there is a lag in the effects on the diagonals. At the end of one diagonal of the visual, there is one effect, and at the other end, there is another. Phasing In most cases, the phasing problem comes from imprecise cutting of the material, as explained below. Nevertheless, poor printing and rectification conditions may also be behind it. In theory, for a given angle of observation, one and the same visual must appear, for the entire batch. As a general rule, the angle of vision is around 45°, and this angle must be in agreement with the sequence provided by the master. If the images have a tendency to double perpendicularly (for 3D) or if the images provided for observation to the left appear to the right (top/bottom), then there is a phasing problem. Cutting defects Defects, in the way the lenticular lens has been cut, can lead to phase errors between the lens and the image. Two examples, taken from the same production batch: The first image shows a cut which removed about 150 µm of the first lens, and which shows irregular cutting of the lenticular lenses. The second image shows a cut which removed about 30 µm of the first lens. Defects in cutting such as these lead to a serious phase problem. In the printing press the image being printed is aligned relative to the edges of the sheet of material. If the sheet is not always cut in the same place relative to the first lenticule, a phase error is introduced between the lenses and the image slices. See also Autostereoscopy, any method of displaying stereoscopic images without the use of glasses Integral imaging, a broader concept that includes lenticular printing Lenticular lens, the technology used in lenticular printing and for 3D displays Parallax barrier, another technology for displaying stereoscopic images without the use of glasses References Sources Bordas Encyclopedia: Organic Chemistry (French). Okoshi, Takanori Three-Dimensional Imaging Techniques'' Atara Press (2011), External links Vari-Vue Official Vari-Vue website Patent 2063985: Apparatus for Making a Composite Stereograph filed 24