Abstract

A 27.5-m-diameter, 210° spherical mirror was housed in one of the pavilions at Expo 70, Osaka, Japan. The mirror was constructed by G. T. Schejdahl on the same principle as the Echo and PAGEOS satellites and made of 12.5-μ Melinex. It was held in place by a negative pressure behind the mirror. This was the first time a number of optical effects could be seen inside a mirror of this size. These are photographically shown and discussed. In addition to the simple first-order real images, higher order image rings were observed. The photographs also indicate the nonparaxial distortion which occurs.

© 1971 Optical Society of America

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References

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  1. F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957).
  2. The Pepsi-Cola Pavilion was designed by a group of contemporary American and Japanese artists and engineers (Pavilion, published by E. P. Dutton & Co., January1972). Robert Whitman is responsible for the concept of the mirror environment and the use of large-scale optics in a theatrical space.
  3. Melinex is an oriented polyester film and a trade name of Imperial Chemical Industries, Ltd.
  4. G. T. Schjedahl Co., “Design and Fabrication of Inflatable and Rigidizing Passive Communications Satellites, Echo I and II,” Papers from the Aerospace Expandable Structures Conference, October 22–24, 1963, AFAPL-AFFDL, p. 576.J. P. Talentino, “Development of the Fabrication and Packaging Techniques for the Echo II Satellite,” NASA TM-X-55764, GSFC, December1966.S. J. Stenlund, “PAGEOS Fabrications, Accuracy and Reliability,” Papers from the Third Aerospace Expandable and Modular Structures Conference, Langley Research Center, May16–18, 1967; AFAPLTR-68-17, p. 181.Lewis A. Teichman, “Fabrication, and Testing of PAGEOS I,” NASA TN-D-4596, Langley Research Center, June1968.
  5. E. Garmire, Appl. Opt. 10, 2759 (1971).
    [CrossRef]

1971

E. Garmire, Appl. Opt. 10, 2759 (1971).
[CrossRef]

Garmire, E.

E. Garmire, Appl. Opt. 10, 2759 (1971).
[CrossRef]

Jenkins, F. A.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957).

White, H. E.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957).

Appl. Opt.

E. Garmire, Appl. Opt. 10, 2759 (1971).
[CrossRef]

Other

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957).

The Pepsi-Cola Pavilion was designed by a group of contemporary American and Japanese artists and engineers (Pavilion, published by E. P. Dutton & Co., January1972). Robert Whitman is responsible for the concept of the mirror environment and the use of large-scale optics in a theatrical space.

Melinex is an oriented polyester film and a trade name of Imperial Chemical Industries, Ltd.

G. T. Schjedahl Co., “Design and Fabrication of Inflatable and Rigidizing Passive Communications Satellites, Echo I and II,” Papers from the Aerospace Expandable Structures Conference, October 22–24, 1963, AFAPL-AFFDL, p. 576.J. P. Talentino, “Development of the Fabrication and Packaging Techniques for the Echo II Satellite,” NASA TM-X-55764, GSFC, December1966.S. J. Stenlund, “PAGEOS Fabrications, Accuracy and Reliability,” Papers from the Third Aerospace Expandable and Modular Structures Conference, Langley Research Center, May16–18, 1967; AFAPLTR-68-17, p. 181.Lewis A. Teichman, “Fabrication, and Testing of PAGEOS I,” NASA TN-D-4596, Langley Research Center, June1968.

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Figures (9)

Fig. 1
Fig. 1

Here the appearance of the first-order real image with many people on the floor is shown. An indication of the spherical accuracy of the mirror is given by the image of the edge of the octagonally shaped center section, which appears straight across several adjacent gores on the Melinex balloon.

Fig. 2
Fig. 2

The woman wearing a large hat and her real image are indicated by the arrows.

Fig. 3
Fig. 3

This photograph shows real images under paraxial conditions and was taken 1.8 m from the center of the floor area with the camera pointed toward the center of the sphere. It shows in detail the distortions resulting from the seals between the gore patterns. (Photograph is printed upside down.)

Fig. 4
Fig. 4

When the viewer walks from the center of the floor toward the periphery and looks up at the mirror, the first-order real image tilts behind him. When he reaches a distance from the mirror of approximately one-half the radius of the floor, a second-order real image appears in front of him of the area of the floor diametrically opposite. This is the real image of the virtual image of S reflecting from the mirror opposite V. As shown in this photograph, the viewer V faces the second-order real image (S2) of a person S who is actually standing behind with his back to the viewer. The photograph, which is taken from a point 1.5–2 m closer to the center than V, also shows the first-order real image (S1) of S.

Fig. 5
Fig. 5

This photograph shows the second-order real-image effect from a point closer to the mirror in which the viewer V is waving at the second-order real images of the group of people standing behind him, an effect that recalls the children’s rhyme, “back to back they faced each other ….”

Fig. 6
Fig. 6

When the viewer stands only a few feet from the mirror looking directly into it, he sees a virtual image of himself, the floor area, and the first order real image of the floor area, i.e., he sees the virtual image of a real image.

Fig. 7
Fig. 7

When the viewer stands close to the edge of the floor with his back to the mirror and looks up to the left or right of him, the higher-order real images appear as rings.4 In this photograph, the first-order real image of a person standing in a tiled section of the floor area is shown on the left of the picture. The two-reflection real-image ring to the right has a symmetrical character. Two images of the same person appear facing each other, and there is a symmetrical reflection of the tiled floor area from the edge of the floor at the mirror to a point a few feet beyond the person. In this photograph, this symmetry, however, is not exact: a larger area of the floor appears to the left than to the right, which can be checked by counting the tile plates (thirty vs fifteen). (Note: photograph printed upside down.)

Fig. 8
Fig. 8

This photograph shows the successive rings of higher-order real images. The first-order real-image ring appears at the extreme left and four more rings can be seen. The photograph was taken from the stairway leading to the mirror dome floor, the photographer standing below floor level close to the mirror (black area at the bottom of the photograph is a guard rail). Each successive ring occupies a smaller angle of vision and hence reflects a smaller section of the tiled area.

Fig. 9
Fig. 9

This photograph was taken with the camera pointing beyond the center of the floor facing the far opposite side of the mirror. The images of the subjects are not inverted upside-down, left-to-right, or back-to-front. This type of second-order real image results from two real-image reflections, i.e., the subject produces a real image which in turn produces another real image. Similar images are seen in Figs. 1 and 2 in the mirror near the horizon. The images do not appear to be located in space as real images should, but rather behind the mirror surface as a virtual image would. A possible explanation of this effect is that the mirror has a cylinder or cone-shaped distortion, producing a series of virtual images. Reflections in two plane mirrors facing each other would give rise to virtual images like those shown in the photograph. No observations of real images in space close to the subject were made, presumably because of the competing illumination of the subject and the surrounding floor area.

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