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Transformation of the perceptual world

  In his 1896 paper [12], George Stratton reported on experiments in which he wore eyeglasses that inverted his visual field of view. Stratton argued that since the image upon the retina was inverted, it seemed reasonable to examine the effect of presenting the retina with an ``upright image''.

His ``upside-down'' glasses consisted of two lenses of equal focal length, spaced two focal lengths, so that rays of light entering from the top would emerge from the bottom, and vice-versa. Stratton, upon first wearing the glasses, reported seeing the world upside-down, but, after an adaptation period of several days, was able to function completely normally with the glasses on.

Dolezal [13] (page 19) describes ``various types of optical transformations'', such as the inversion explored by Stratton, as well as displacement, reversal, tilt, magnification, and scrambling. Kohler [14] also discusses ``transformation of the perceptual world''.

Stratton, Dolezal, and Kohler explored the use of optics (lenses, prisms, and the like). Stuart Anstis was the first to explore, in detail, an electronically mediated world.

Anstis [15], using a camcorder that had a ``negation'' switch on the viewfinder, experimented with living in a ``negated'' world. He walked around holding the camcorder up to one eye, looking through it, and observed that he was unable to learn to recognize faces in a negated world. His negation experiment bore a similarity to Stratton's inversion experiment mentioned in Sec 2.1, but the important difference within the context of this paper is that Anstis experienced his mediated visual world through a video signal.

Using a camcorder as a reality mediator has several drawbacks. Firstly, it is awkward (one hand is occupied constantly, and the apparatus protrudes far enough that it gets in the way of most day-to-day activities), and secondly, it makes people feel much more self-conscious (whether they're gambling or otherwise). Thirdly, it is not easy to insert arbitrary computational power between the camera and the viewfinder.

WearCam provides a practical solution to these three problems, by serving as a wearable, tetherless color stereo `reality mediator' made from video cameras and battery-powered display. One realization of WearCam, made from a display having 480 lines of resolution, is depicted in Fig 1.

Figure 1: `Reality mediator' as of late 1994, showing a color stereo head-mounted display (VR4) with two cameras mounted to it. The inter-camera distance and field of view match approximately my interocular distance and field of view with the apparatus removed. The components around my waist comprise communications equipment, and the like. Antennas, etc. are located at the back of the head-mount to balance the weight of the cameras, so that the unit is not front-heavy.

Here, I mounted the cameras the correct interocular distance apart, and used cameras that had the same field of view as the display devices. With the cameras connected directly to the displays, an illusion of transparency [2] will be realized to some degree, at least to the extent that each ray of light entering the apparatus (e.g. absorbed and quantified by the cameras) will appear to emerge at roughly the same angle (by virtue of the display).

Although I had no depth-from-focus capability there was enough depth perception remaining on account of the stereo disparity for me to function somewhat normally with the apparatus.

A first step in using a reality mediator is to wear it for a while to become accustomed to its characteristics. Unlike in typical beam-splitter implementations of augmented reality, transparency, if desired, is synthesized, and therefore only as good as the components used to make the apparatus.

I wore the apparatus in identity map configuration (cameras connected directly to the displays) for several days. I could easily walk around the building, up and down stairs, through doorways, to and from the lab, etc. I did, however, experience difficulties in scenes of high dynamic range, and also in reading fine print (such as a restaurant menu or a department store receipt printed in faint ink when the ribbon was near the end of its useful life).

The unusual appearance of the apparatus was itself a hinderance in my daily activities (for example when I wore it to a formal dinner), but after some time people appeared to become accustomed to seeing me this way.

The attempt to create an illusion of transparency was itself a useful experiment because it established some working knowledge of what can be performed when vision is diminished or degraded to RS170 resolution and field of view is somewhat limited by the apparatus.

next up previous
Next: Video mediation Up: The `Personal Visual Previous: The `Personal Visual

Steve Mann
Wed Feb 14 01:19:59 EST 1996