DE2836184A1 - OPTICAL DEVICE FOR REPLAYING A PICTURE IMAGE IN INFINITE - Google Patents

Description

Dipl.-Ing.

Rolf Charrier

Patent attorney

Rehlingenstralk 8 P.O. Box 260

D-8 ') 00 Augsburg 31
Telephone 08 21/36015 + 36016

Telex 533275 - 3 -

P>:> vhLVkkrnit) 'Munich No. 154? W style

7681 / ol / Ch / gn. . , _1rt , "

^a Augsburg, lo. August 1978

Farrand Optical Co., Inc.

117 Wall Street
Valhalla, New York Io595 US A,

Optical device for reproducing a depicted image at infinity

The invention relates to an optical system for reproducing an image displayed on a display screen at infinity, wherein between the imaging screen and the viewer are arranged a spherical beam-splitting mirror with a optical axis and a double refractive package, consisting of a first quarter-wave plate, that of the concave side of the mirror is facing, a plane beam-splitting mirror behind the first plate, a second quarter-wave plate behind the plane mirror and a polarizer behind the second platelet, with the axes of the platelets

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are arranged to each other by an integral multiple of 90 ° and the polarizer is arranged to the axis of the second plate with its plane by an odd multiple of 45 °.

In US-PS R 27356 an optical device of the aforementioned type is described with which it is possible to see the image of an object in the Infinite to represent. It is also possible to optically superimpose several images. The device has a large exit pupil and a broad angular field of vision. This device uses a spherical beam-splitting mirror, i.e. a semitransparent mirror Mirror used. There is also a first quarter-wave plate provided, i.e. a lambda 4 plate facing the concave side of the spherical mirror. Behind this Lambda 4 plate there is a second semi-transparent, but flat mirror. This is followed by a second quarter-wave plate at. In addition, a polarizer is provided following the second plate. The axes of the two Lambda 4 plates are arranged to each other by an integral multiple of 90 °. The polarization plane of the polarizer is odd by one Multiples of 45 ° to the axis of the second lambda 4 plate, usually a second polarizer is used, which is arranged between the imaging screen and the spherical semitransparent mirror. The planes of polarization of the two polarizers are arranged in relation to one another by an integral multiple of 90 °. The aforementioned two integer multiples of 90 ° are either even or both odd.

The manufacture of a holographic analog of the aforementioned system is described in US Pat. No. 3,940,203.

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As described in the aforementioned U.S. patents, an image from a display screen will be linearly polarized may or may not be projected in the direction of the viewer, through the first planar polarizer, through the spherically curved one semitransparent, i.e. beam-splitting mirror, and then through the sandwich-like package, which is double refractive, and which consists of a lambda 4 plate, a flat semi-transparent mirror, a second lambda 4 plate and a polarizer. The linearly polarized image that passes through the semi-transparent mirror is from the first lambda 4 plate first circularly polarized, then reflected by the flat semi-transparent mirror back to the spherical mirror, which aligns it, whereby the image then arrives at the second lambda 4 plate, which reverses the circular polarization, after which the aligned image wanders through the last polarizer so that the viewer sees the image practically in infinity. The part of the image going from the flat semi-transparent mirror back to the spherical mirror is not seen by the viewer. It should prevent any part of the picture reaches the viewer directly through the device.

The semi-transparent mirror is either one actual mirror or a holographic analogue thereof. The components of the optical device can be manufactured as a compact layered unit. The unit of polarizer Lambda 4 plates and semi-transparent mirrors are often referred to as-double 1-refractive System because the lambda + plates cause the polarized light to circulate in its plane of polarization. This package can form a compact structural unit together with the spherical mirror.

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This known optical device has some shortcomings. These inadequacies are the ability to see a direct image and the creation of ghost images.

There is therefore the task of creating an optical device of the type mentioned at the beginning Art to be trained in such a way that direct images and ghost images are avoided.

Solved " ¹ ^ ' ''_se problem with the features of claim 1. Pre-embodiments can be found in the subclaims.

An exemplary embodiment is explained in more detail below with reference to the drawings explained. Show it:

Fig. 1 a A known optical device for illustration

a first inadequacy occurring there;

1 b shows the same system for explaining a second shortcoming;

1c shows the same system for illustrating a third shortcoming;

2 shows a schematic representation of a preferred exemplary embodiment of the optical device according to the invention, and FIG
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3a, b and c representations of how those occurring in the prior art in the device according to the invention Deficiencies are avoided.

According to Fig. La a spherical beam-splitting, i.e. semi-permeable Mirror combined with a double refractive, beam-splitting package. These two components essentially make up that Device according to US-PS R 27 356. The double refractive beam splitting Package Ho is composed of a first lambda 4 plate 111, a flat, semitransparent mirror 112, and a second lambda 4 plate 113 and a polarizer 114. The axes of the two lambda 4 plates are, as mentioned above, arranged in relation to one another. Another Polarizer 115 is arranged between mirror loo and imaging screen 12o. The planes of polarization of the two polarizers As mentioned above, 114 and 115 are aligned with one another. One or more superimposed Pictures shown. The viewer 122 is located on the opposite side of the package Ho from the screen. consisting of the components, loo, Ho and 115 gives the viewer the illusion that the image shown on the screen 12o is itself is at infinity or near infinity.

The light emanating from the display screen 12o travels through the polarizer 115 and the beam-splitting mirror loo and is then reflected by the beam-splitting mirror 112, so that the apparent Position of the display screen 12o is determined by the focus of the spherical beam-splitting mirror loo, that is, by the mirror loo is projected into infinity. Unwanted direct light and other possible unwanted images are generated by the polarizers 114 and 115 strongly damped. However, the polarizers are not one hundred percent at eliminating these unwanted images

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The Fig. La shows the case where a bright, high-contrast object viewed by the system on a black background. This is the case, for example, when a bright star is against the dark sky is viewed. The bright image point is labeled 125. This bright pixel 125 on the imaging screen is seen directly by the viewer 122, i.e. the ray 124 runs unbroken from the image point 125 to the viewer 122 as a result of the inadequate Polarizers 114 and 115. For the viewer 122, this bright image point 125 is not at infinity, but rather at it visible on the screen 12o. This unwanted direct image has about 1/75 the brightness of the desired one imaged at infinity Image on.

Fig. Ib shows a further shortcoming in the known System. A bright object imaged on the imaging screen 134 128 is with its passage through the polarizer 135, the mirror 13o and the double refractive package 132 with respect to its Rays directed parallel. The package 132 is here identical to the package Ho na Fig. La. The rays are with 136 to 138 and denoted 136 'to 138'. The image appears to the observer 14o through the parallel aligned rays 138 and 138 ' on the display screen 134 at infinity. As a result of inadequacy However, the polarizer in package 132 can cause the reflection of the pixel 128 from the mirror in the package 132 and its remapping through the spherical mirror 13o result in a ghost image at point. This ghost image, which is visible to the viewer, is referred to as R-2 ghost image and it is formed at a distance from the spherical mirror 13o glc: h its focal length.

The creation of another family of unwanted images is illustrated in Figure Ic. A bright pixel 15o on the screen 156 becomes with respect to its rays, as they pass through the polarizer 158, the mirror 16o and the package 162 are directed parallel so that

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the observer 17o sees the object 15o practically in infinity. The double refractive package 162 is identical to that according to Fig. la. As described in connection with Fig. Ib, At point 172, an R-2 ghost image may form due to the reflection of the image point 15o on the mirror in the package 162 and its tfiederabbild through the spherical mirror 16o. Here, a further ghost image of point 15o can be formed, which is known as the so-called R-3 Is referred to as ghosting. This further ghost occurs at point 174 as a result of the reflection of the R-2 ghost from the mirror of the double refractive package 162 and its re-imaging by the spherical mirror 16o. uas R-3 ghosting between the R-2 ghost and mirror 16o, usually near the flat mirror in package 162.

In order to reduce and / or eliminate these disadvantages, an arrangement according to FIG. 2 is preferably proposed. A spherical, beam-splitting mirror 2oo is shown there, its The focal point is denoted by 2o2, the viewer 2o5 being close to the center of curvature 21o of the spherical mirror 2oo is located. The focal point 2o2 and the crayon center point form 2io an optical axis 215. The imaging screen 22o is located on the other side of the mirror 2oo. Between the mirror 2oo and a polarizer 235 is arranged on the imaging screen 22o. There is again between the mirror 2oo and the viewer 2o5 the double refractive package 23o. This double refractive package 23o is constructed identically to the package * Hq according to FIG. La. However, the planes of package 23o and plane polarizer i 235 are inclined to the normal of the optical axis 215 by a dark θ. In the exemplary embodiment shown, the angle between these planes and a normal to the optical axis 215 is approximately 14. It However, other angles can also be used depending on the focal length of the mirror and the distance between the mirror 2oo and the loading

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Trachter 2o5 can be chosen.

This inclined arrangement avoids the aforementioned disadvantages, as will be explained below with reference to FIGS. 3a, 3b and 3c. According to FIG. 3a, the direct undesired image of the point 3o5 is imaged on the screen 3oo along the beam path 31o, this being The beam path 31o runs at an angle to the optical axis 345, so that this direct image is outside the field of view of the viewer 33o. The direct ray path 31o passes through the inclined polarizer 315, the spherical beam splitting mirror 32o and the inclined double Tf: '- * ".i beam splitting packet 325. The viewer 33o befinuet is in the optical axis 345 of the mirror 32o. The center of curvature of the mirror 32o is denoted by 34o.

Referring to Figure 3b, the R-2 ghost is also out of view of the viewer 43o, who is located near the center of curvature 44o of the mirror 42o along the optical axis. The beam path 41o of this image runs from the image point 4o5 on the screen 4oo through the inclined polarizer 415 through the spherical mirror 42o to the package 425, from where the rays are reflected back onto the spherical mirror 42o and then run outside the optical axis.

3c, the R-3 ghost image is transmitted from the imaging screen 5oo at point 5o5 along the beam path 51o through the inclined polarizer 515, the spherical beam splitting mirror 52o and the inclined double refractive beam splitting packet 525 to form the deflected ghost image R-2 _S where this R-2 ghost image is then reflected from the planar semi-transparent mirror in the package 525 back to the spherical mirror 52o, which aligns the R-3 ghost image along the beam path 512 which runs outside the field of view of the viewer 53o, the latter being in the vicinity of the The center of curvature 54o of the spherical mirror 52o is located.

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BATH ORIGINAL

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The curved mirror can have a cross-section equivalent to a conical one Have section and the optical axis of the mirror can be defined by the center of curvature of the mirror.

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Claims (5)

Dipl.-Ing. Rolf Charrier Patent attorney Rehlingenstrasse 8 P.O. Box 260 D-8900 Augsburg 31 Phone 08 21/3 6015 +3 6016 Telex 53 3 275 Pi. ^ Iicxk; n; "Mün.h.-n \ r. ^ - T-W-M) I Farrand Optical Co., Inc. 7681/01 / Ch / Gr Augsburg, August 10, 1978 Expectations ΐ. .Optical device for reproducing an image on a display screen imaged image at infinity, being between the imaging screen and the viewer arranged are a spherical beam-splitting mirror with an optical axis and a double refractive package, consisting of a first Lambda 4 plate, which faces the concave side of the mirror, splitting a plane beam on Mirror behind the first plate, a second Lambda 4 plate behind the flat mirror and a polarizer behind the second platelet, the axes of the platelets to each other by an integer Multiples of 90 ° are arranged and the polarizer to the axis of the second plate with its plane by an odd multiple of 45 ° is arranged, characterized in that the double refractive package is inclined to a Plane perpendicular to the optical axis z 'is the spherical Mirror and the viewer. 2. Optical device with a further arranged between the imaging screen and the spherical mirror Polarizer, the plane of polarization being the two polarizers to each other by an integer 909810 / 0758- 7681/01 / Ch / Gr - 2 - August 10, 1978 Multiples of 90 ° are arranged, thereby g e k e η n-2 e i c h η e t that the plane of the further polarizer is arranged inclined to the plane perpendicular to the optical axis. 3. Optical device according to claim 1 and 2, characterized g e k e η η ζ e i c h η e t that the levels of the package and the further polarizer run parallel to one another. 4. Optical device according to claim 1, characterized geke η η ζ eich η et that the spherical mirror is formed by its ^h1 ~ aphical analog. 5. Optical device according to one of claims 1 to 4, characterized characterized in that the inclination to the plane perpendicular to the optical axis is approximately 14 . 9 ü 9 8 1 Π / 0 7 5 8