document: Researchers at St Andrews University said a method using a small circular hole could have wide implications for 3D technology.
  The study, published in Psychological Science, also has implications for people who have just one eye or difficulties with double-eye vision.
  The method was said to create 3D similar to effects used in film-making.
  Researchers said that current thinking was based on the need for two visual images - one from each eye - to be combined in the visual cortex, creating a sense of depth.
  But Dr Dhanraj Vishwanath, a psychologist at the university, believes both eyes are not necessary for this "3D experience".
  Dr Vishwanath said: "We have demonstrated experimentally, for the first time, that the same 'special way' in which depth is experienced in 3D movies can also be experienced by looking at a normal picture with one eye viewing through a small aperture (circular hole).
  "While this effect has been known for a long time, it is usually dismissed.
  "Now we have shown that it is in fact real, and the perceptual results are exactly like stereoscopic 3D, the kind seen in 3D movies.
  "Based on this finding, we have provided a new hypothesis of what the actual cause of the 3D experience might be."
  The university said the 1838 invention of the stereoscope - the technology behind 3D film-making - brought with it the assumption two eyes were necessary for 3D vision.
  Dr Vishwanath said: "This work has significant implications for people who don't have normal binocular vision.
  "First it could help them experience what it means to see in 3D. Second, it could encourage them to seek therapy to try to regain two-eye 3D vision (which produces the strongest 3D effect in everyday life) once they can see first-hand what 'seeing in 3D' is really like."
  Dr Vishwanath and his colleagues are now testing the method with a large group of strabismics, people with misaligned eyes.
  He said that nearly 15% of the population, including Hollywood actor Johnny Depp, may have some form of misalignment.
  The psychologist also believes his theory suggests a 3D experience could be induced simply by increasing resolution, using ultra-high definition (4K) televisions.
  Seeing in 3D with just one eye: Stereopsis without binocular vision is published by Psychological Science. Further research is due to be published later this year.
summary: The effect of "vivid 3D vision" can be experienced with just one eye, a study has suggested.