IL182705A - Compact imaging lens - Google Patents

Description

COMPACT IMAGING LENS Field of the Invention The present invention relates to compact collimating optical systems, and in particular, to optical systems which include an arrangement of reflecting optical elements, retardation plates and reflecting surfaces carried by a common light-transmissive substrate. Such a system is also referred to as a light-guide collimating element (LCE).

The invention can be implemented to advantage in a large number of imaging applications, such as head-mounted and head-up displays, cellular phones, compact displays, 3-D displays, compact beam expanders as well as non-imaging applications such as flat-panel indicators, compact illuminators and scanners.

Background of the Invention One of the important applications for compact optical elements is in head-mounted displays wherein an optical module serves both as a reflecting optical element and a combiner, in which a two-dimensional display is imaged to infinity and reflected into the eye of an observer. The display can be obtained directly from either a spatial light modulator (SLM) such as a cathode ray tube (CRT), a liquid crystal display (LCD), an organic light emitting diode array (OLED), a scanning source or similar devices, or indirectly, by means of a relay lens or an optical fiber bundle. The display comprises an array of elements (pixels) imaged to infinity by a collimating lens and transmitted into the eye of the viewer by means of a reflecting or partially reflecting surface acting as a combiner for non-see-through and see-through applications, respectively. Typically, a conventional, free-space optical module is used for these purposes. As the desired field-of-view (FOV) of the system increases, such a conventional optical module becomes larger, heavier, bulkier, and therefore, even for a moderate performance device, is impractical. This is a major drawback for all kinds of displays but especially in head-mounted applications, wherein the system must necessarily be as light and as compact as possible.

The strive for compactness has led to several different complex optical solutions, all of which, on the one hand, are still not sufficiently compact for most practical applications, and, on the other hand, suffer major drawbacks in terms of manufacturability. Furthermore, the eye-motion-box (EMB) of the optical viewing angles resulting from these designs is usually very small -typically less than 6 mm. Hence, the performance of the optical system is very sensitive, even to small movements of the optical system relative to the eye of the viewer, and does not allow sufficient pupil motion for comfortable reading of text from such displays.

The teachings included in the publication WO 01/95027, WO 2006/013565, WO 2006/085309, WO 2006/085310 and PCT/IL2004/001278 in the name of Applicant, are herein incorporated by references.

Disclosure of the Invention The present invention facilitates the design and fabrication of very compact imaging device for, amongst other applications, head-mounted displays (HMDs). The invention allows relatively wide FOVs together with relatively large EMB values. The resulting optical system offers a large, high-quality image, which also accommodates large movements of the eye. The optical system offered by the present invention is particularly advantageous because it is substantially more compact than state-of-the-art implementations and yet it can be readily incorporated, even into optical systems having specialized configurations.

The invention also enables the construction of improved head-up displays (HUDs). Since the inception of such displays more than three decades ago, there has been significant progress in the field. HUDs have indeed become popular and they now play an important role, not only in most modern combat aircraft, but also in civilian aircraft, in which HUD systems have become a key component for low-visibility landing operation. Furthermore, there have recently been numerous proposals and designs for HUDs in automotive applications where they can potentially assist the driver in driving and navigation tasks. Nevertheless, state-of-the-art HUDs suffer several significant drawbacks. All HUDs of the current designs require a display light source that must be offset a significant distance from the combiner to ensure that the source illuminates the entire combiner's surface. As a result, the combiner-projector HUD system is necessarily bulky, large and requires considerable installation space, which makes it inconvenient for installation and at times even unsafe to use. The large optical aperture of conventional HUDs also poses a significant challenge for the optical design, either rendering the HUDs with compromising the performance, or leading to high cost wherever high-performance is required. The chromatic dispersion of high-quality holographic HUDs is of particular concern.

A broad object of the present invention is therefore to alleviate the drawbacks of state-of-the-art compact optical display devices and to provide other optical components and systems having improved performance, according to specific requirements.

A further object of the present invention relates to its implementation in a compact HUD, alleviating the aforementioned drawbacks. In the HUD design of the current invention, the combiner is illuminated with a compact display light source that can be attached to the substrate. Hence, the overall system is very compact and can be readily installed in a variety of configurations for a wide range of applications. In addition, the chromatic dispersion of the display is negligible and, as such, can operate with wide spectral sources, including a conventional white-light source. In addition, the present invention expands the image so that the active area of the combiner can be much larger than the area that is actually illuminated by the light source.

A still further object of the present invention is to provide a compact display with a wide FOV for mobile, hand-held application such as cellular phones and personal display modules. In today's wireless internet-access market; a sufficient bandwidth is available for full video transmission. The limiting factor remains the quality of the display within the device of the end-user. The mobility requirement restricts the physical size of the displays, and the result is a direct-display with poor image viewing quality. The present invention enables a physically very compact display with a very large virtual image. This is a key feature in mobile communications, and especially for mobile internet access, solving one of the main limitations for its practical implementation. Thereby, the present invention enables the viewing of a digital content of a full format internet page within a small, hand-held device, such as a cellular phone.

In accordance with the invention, there is therefore provided an optical system, comprising a substrate having at least four major surfaces and edges, at least two reflecting surface carried by said substrate, and at least two retardation plates, wherein each of said retardation plate is located between one of said major surfaces of the substrate and one of said reflecting optical elements, characterized by at least one partially reflecting optical element embedded in said substarte .

Brief Description of the Drawings The invention is described in connection with certain preferred embodiments, with reference to the following illustrative figures so that it may be more fully understood.

With specific reference to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description taken with the drawings are to serve as direction to those skilled in the art as to how the several forms of the invention may be embodied in practice.

In the drawings: Fig. 1 is a diagram illustrating an optical system for collimating input light waves from a display light source, in accordance with the present invention; Fig. 2 is a diagram illustrating a method for collimating and coupling-in input waves from a display light source into a light-guide optical element (LOE), in accordance with the present invention; Fig. 3 is a diagram illustrating another method for collimating and coupling-in input waves from a display light source into an LOE, wherein the collimating module is cemented to the LOE, in accordance with the present invention; Figs. 4 and 5 are graphs illustrating the reflectance curves as a function of incident angle, for an exemplary angular sensitive coating for s- and p-polarized light waves respectively; Fig 6 is a diagram illustrating yet another embodiment for collimating and coupling-in input waves from a display light source into an LOE utilizing angular sensitive coating in accordance with the present invention; Fig 7 is a diagram illustrating still a further embodiment for collimating and coupling-in input waves from a display light source into an LOE utilizing a half-wavelength retardation plate in accordance with the present invention; Fig. 8 is a diagram illustrating an optical system for collimating input light waves from a display light source utilizing a blank plate, in accordance with the present invention; Fig. 9 is a diagram illustrating a method for collimating input light waves from a display light source by utilizing two lenses and blank plate, in accordance with the present invention; Fig. 10 is a diagram illustrating a method for collimating input light waves from a display light source by utilizing two lenses, in accordance with the present invention; Fig. 1 1 is a diagram illustrating a method for collimating input light waves from a liquid crystals on silicon (LCOS) display light source, in accordance with the present invention; Fig. 12 is a diagram illustrating another method for collimating input light waves from a liquid crystals on silicon (LCOS) display light source, in accordance with the present invention; Fig. 13 is a three-dimensional diagram illustrating yet another method for collimating input light waves from a liquid crystals on silicon (LCOS) display light source, in accordance with the present invention; Fig. 14 is a diagram illustrating a method for collimating input light waves and coupling-in input waves from a liquid crystals on silicon (LCOS) display light source into an LOE, in accordance with the present invention; Fig. 15 is a diagram illustrating another method for collimating input light waves and coupling-in input waves from a liquid crystals on silicon (LCOS) display light source into an LOE, in accordance with the present invention; Fig. 16 is a diagram illustrating an optical system for collimating input light waves from a display light source utilizing a folding prism, in accordance with the present invention; Fig. 17 is a diagram illustrating an optical system for collimating input light waves from a liquid crystals on silicon (LCOS) display light source utilizing a folding prism, in accordance with the present invention; Fig. 18 illustrates a span of optical rays which are coupled into a light-guide optical element; Fig. 19 is a diagram illustrating a method for coupling light into a light-guide optical element in accordance with the present invention; Fig. 20 is a diagram illustrating a method for coupling light into a light-guide optical element utilizing a coupling prism in accordance with the present invention; Fig 21 illustrates an optical system for collimating and coupling-in input waves from a single display light source into two separate LOEs, in accordance with the present invention; Fig. 22 illustrates a front view of an embodiment of an optical system for collimating and coupling-in input waves from a single display light source into two separate LOEs, in accordance with the present invention; Fig 23 illustrates an optical system for collimating and coupling-in input waves from two display light sources into two separate LOEs, in accordance with the present invention; Fig 24 illustrates another optical system for collimating and coupling-in input waves from two display light sources into two separate LOEs, utilizing an optical beamsplitter in accordance with the present invention; Fig 25 illustrates an optical system for collimating and coupling-in input waves from a single display light source into two separate LOEs, utilizing a polarizing beamsplitter and a dynamic half-wavelength retardation plate in accordance with the present invention; Fig. 26 is a diagram illustrating an optical system for collimating input light waves from a display light source, wherein a ghost image appears in the output image; Fig. 27 is a diagram illustrating an optical system for collimating input light waves from a display light source, utilizing two polarizing beamsplitters and a linear polarizer, in accordance with the present invention; Fig. 28 is a diagram illustrating an optical system for collimating input light waves from a display light source, wherein the output waves are rotated compared to the input waves, in accordance with the present invention; Fig. 29 is a diagram illustrating another optical system for collimating input light waves from a display light source, wherein the output waves are rotated compared to the input waves, in accordance with the present invention; Fig. 30 is a diagram illustrating an optical system for collimating input light waves from a liquid crystals on silicon (LCOS) display light source, wherein the output waves are rotated compared to the input waves, in accordance with the present invention; Fig. 31 is a diagram illustrating an optical system for collimating and coupling-in input waves from a display light source into an LOE, wherein the output waves are rotated compared to the input waves, in accordance with the present invention; Fig. 32 is a diagram illustrating another optical system for collimating and coupling-in input waves from a display light source into an LOE, wherein the output waves are rotated compared to the input waves, in accordance with the present invention; Fig 33 illustrates an optical system having a focusing lens, in accordance with the present invention, and Fig 34 illustrates an optical system having a unity magnification telescope, in accordance with the present invention.

Detailed Description of Preferred Embodiments A superior method of designing lenses that are more compact than the prior art lenses having the required shape according to the preferred outline of the entire optical system while still maintaining the desired optical properties of the system according to the present invention, will now be described.

This method, which achieves these two seemingly contradictory requirements, and which exploits the fact that in most microdisplay light sources, like LCDs or LCOS, the light is linearly polarized, is illustrated in Fig. 1. As illustrated, the s-polarized input light waves 2 from the display light source 4 are coupled into the substrate 6 through the lower surface 8.. Following reflection off the polarizing beamsplitter 10, the waves are coupled out of the substrate through the right surface 12 of the substrate. The waves then pass through a quarter-wavelength retardation plate 14, reflected by a reflecting optical element 16, returned to pass through the retardation plate 14 again, and re-enter the substrate 6 through the right surface 12. The now p-polarized light waves pass through the polarizing beamsplitter 10 and are coupled out of the substrate through the left surface 18 of the substrate. The waves then pass through a second quarter-wavelength retardation plate 20, collimated by a lens 22 at its reflecting surface 24, returned to pass through the retardation plate 20 again, and re-enter the substrate 6 through the left surface 18. The now s-polarized light waves reflected off the polarizing beamsplitter 10 and exit the substrate through the upper surface 26.

Fig. 2 illustrates how the LCE 28 can be combined with a light-guide optical element (LOE) 30 to form the required optical system. Such an LOE typically includes at least two major surfaces 32 and 34 and edges, at least one partially reflecting surface 36 and an optical element 38 for coupling light thereinto. The output waves 40 from the LCE 28 enter the LOE 30 through its lower surface 32. The incoming waves (vis-a-vis the LOE) are reflected from the surface 38 and trapped in the LOE in the same manner as that illustrated in Fig. 2. Now, the LCE 28, comprising the display light source 4, the folding prisms 42 and 44, the polarizing beamspliiter 10, the retardation plates 14 and 20 and the reflecting optical elements 16 and 22 can easily be integrated into a single mechanical module which can be assembled independently of the LOE, with fairly relaxed mechanical tolerances. In addition, the retardation plates 14 and 20 and the reflecting optical elements 16 and 22 could be cemented together respectively to form single elements. Alternatively, other methods could be used to combine these into a single element, such as laminating a quarter-wavelength film onto the front surface of the reflecting optical elements 16 and 22. Furthermore, all the optical elements of the LCE, apart from the display source 4, could be cemented together to form a single optical module. Regarding the display source, it is usually required to keep an air gap between the LCE and the display source in order to enable focusing mechanism. However, there are systems wherein the required focal distance of the LCE is known. For instance, for optical systems wherein the image waves are coupled into an LOE, the optical waves should be collimated by the LCE to infinity. If in addition the focal depth of the collimating lens is large enough to accommodate the various fabrication and assembly tolerances of the LCE, then it is possible to locate the display source 4 in regard to the LCE 28 at a predefined distance. In that case the display source could be cemented to the LCE utilizing an intermediate transparent plate 46 having a thickness according to the required focal distance of the LCE, as illustrated in Fig. 3.

Apparently, it would be advantageous to cement all the various components of the LCE to the LOE 30, to form a single compact element with a much simpler mechanical module. Fig. 3 illustrates a module wherein the upper surface 26 of the substrate 28 is cemented, at the interface plane 48, to the lower surface 32 of the LOE 30. The main problem of the proposed configuration is that the cementing procedure cancels the previously existing air gap 50 (illustrated in Fig. 2) between the LOE 30 and the LCE 28. This air gap is essential for the trapping of the input waves 40 inside the LOE 30. As illustrated in Fig. 3, the trapped light waves 40 should be reflected at the points 52 and 54 from the interface plane 48. Therefore, a proper reflecting coating should be applied at this plane, either at the major surface 32 of the LOE 20 or at the upper surface 26 of the LCE 28. However, a simple reflecting coating cannot be easily applied, since these surfaces should also be transparent to the light waves that enter and exit the LOE 30 at the exemplary points 56. The light waves should pass through the plane 48 at small incident angles, and reflect at higher incident angles. In the example illustrated, the passing incident angles are between 0° and 15° and the reflecting incident angles are between 47° and 80°.

Figs. 4 and 5 illustrate, for s and p-polarization respectively, the reflectance curves as functions of the incident angles for three representative wavelengths in the photopic region: 460 nm, 550 nm and 640 nm. As illustrated in Fig. 4, it is possible to achieve the required behavior of high reflectance (above 95%) at large incident angles and low reflectance (below 5%) at small incident angles, for s-polarized light waves. For p-polarized light however, as illustrated in Fig. 5, it is impossible to achieve high reflectance at incident angles between 50° and 70° due to the proximity to the Brewster angle.

In the system illustrated in Fig. 3 the light waves from the display light source as well as the reflected waves of the coupling mirror 38 which impinge on the points 52 and 54 are s-polarized and the required reflectance could be achieved. There are situations however wherein the light waves from the display light source are linearly p-polarized and the major axis of the grid is rotated by 90° compared to that of Figs. 1 and 2. That is, the polarizing beamsplitter is oriented here to reflect the p-polarization and transmit the s-polarization. Fig. 6 illustrates a method wherein a half-wavelength retardation plate 58 is inserted between the upper surface 26 of the LCE 28 and the lower surface 32 of the LOE 30. Here, when passing through the plate 58 the polarization of the light wave is rotated and the now s-polarized light waves are coupled into the LOE.

A difficulty still existing in the configurations illustrated in Figs. 3 and 6 is that the LOE, as well as the LCE, are assembled from several different components. Since the fabrication process usually involves cementing optical elements, and since the required angular-sensitive reflecting coating is applied to the substrate surface only after the bodies of the LOE 30 and the LCE 28 are complete, it is not possible to utilize the conventional hot-coating procedures that may damage the cemented areas. Novel thin-film technologies, as well as ion-assisted coating procedures, can also be used for cold processing. Eliminating the need to heat parts allows cemented parts to be coated safely. An alternative method is illustrated in Fig. 7. Here, transparent plate 60 is placed at the interface plane48. Now, the required coating can simply be applied to the upper surface of this substrate, which is adjacent to the LOE, utilizing conventional hot-coating procedures and then cementing it at the proper place. .

In the systems illustrated in Figs. 1 to 3 and 6 to 7, it is assumed that the optical path inside the LCE from the display source 4 to the reflecting surface 24 of the lens 22 is the required focal length of the collimating lens. Usually, this can be achieved by controlling the lateral dimensions of the LCE. However, there are systems, particularly for eyeglasses systems, wherein it is desired to minimize the lateral dimension between the right 12 and the left 18 surfaces of the LCE. That is, to reduce the width of the LCE on the expense of expanding the distance between the display source and the LOE. The lateral dimensions of the folding prism could be reduced, as long as the entire FOV of the image can be coupled into the LCE with no vignetting. In that case however, the optical path between the display source 4 and the collimating lens 22 is reduced and therefore the output waves from the LCE are not collimated anymore. As illustrated in Fig. 8, in order to compensate for this defocusing, a blank plate 62 is inserted between the display source 4 and the lower prism 42 of the LCE 28. Preferably, in order to simplify the final assembly of the system, as explained above in reference to Figs. 6-7, the plate 62 is optically cemented to the lower prism 42 at the interface plane 64. As illustrated, even though the lateral dimension of the LCE has been reduced, the marginal waves 66 and 68 are collimated by the LCE to the exit pupil 70 without any obstruction.

In the systems illustrated hitherto only a single spherical converging lens is utilized. For some optical schemes that may be sufficient. However, for other systems with wide FOVs and large input apertures,a better optical quality may be required. One approach to improve the optical properties of the system is to exploit either aspheric or even aspheric-diffractive lenses. Another approach is to utilize more than one reflecting optical element. In the optical system illustrated in Fig. 9, the planar reflecting surface 16 is replaced by a second converging lens 72. Now, the waves that pass through the quarter-wavelength retardation plate 14 are partially collimated by the lens 72 at its reflecting surface 74. The partially collimated waves returned to pass through the retardation plate 14 again, and re-enter the substrate 6 through the right surface 12. The now p-polarized light waves pass through the polarizing beamsplitter 10 and coupled out of the substrate through the left surface 18 of the substrate. The waves then pass through the second quarter-wavelength retardation plate 20, and completely collimated by a lens 22 at its reflecting surface 24. Another benefit of utilizing two lenses in the LCE is that the required focal length can be achieved with a shorter optical path between the display source and the output surface of the LCE, by exploiting an appropriate telephoto design. Figure 10 illustrates an optical system with two converging lenses 22 and 72 wherein it is not necessary to utilize the blank plate 62. This system is shorter than the one illustrated in Fig. 8 as well as narrower than the one which illustrated in Fig. 1.

Another advantage of the proposed imaging method illustrated here manifests itself when utilizing an LCOS device as the display light source. Like LCD panels, LCOS panels contain two-dimensional array of cells filled with liquid crystals that twist and align in response to control voltages. With the LCOS, however, the liquid crystal elements are grafted directly onto a reflective silicon chip. As the liquid crystals twist, the polarization of the light is either changed or unchanged following reflection of the mirrored surface below. This, together with a polarizing beam- splitter, causes modulation of the light and creates the image. In addition, the reflective technology means the illumination and imaging light beams share the same space. Both of these factors necessitate the addition of a special beam-splitting element to the optical module to in order to enable the simultaneous operations of the illuminating as well as the imaging functions. The addition of such an element would normally complicate the optical module and, when using an LCOS as the display light source, some modules using a frontal coupling-in element or a folding prism would become even larger. For the imaging method illustrated in Figs. 8-10, however, it is readily possible to add the illuminating unit to the optical module without significantly increasing the volume of the system.

As illustrated in Fig. 1 1, a cubic polarizing beamsplitter 80 is inserted instead of a simple blank plate between the display source and the LCE. Here, the p-polarized light waves 82, emanating from a light source 84, reflect off the polarizing beamsplitter 86 and illuminate the front surface of the LCOS 88. The polarization of the reflected light from the "light" pixels is rotated to the s-polarization and the light waves are then passed through the beamsplitter 86 and enter the prism 42 through the lower surface 8. The light waves are then collimated as described above in reference to Fig. 1. If the light source 84 is unpolarized, it is possible to add a polarizer 90, which transmits only the desired polarization. Evidently, the LCE 28 remains compact and it retains its narrow form.

A modified version of Fig. 11, wherein a longer optical pathway inside the LCE is required, is illustrated in Fig. 12. Here, the p-polarized light waves 82, emanating from a light source 84, pass through the polarizing beamsplitter 86 and illuminate the front surface of the LCOS 88. The polarization of the reflected light from the "light" pixels is rotated to the s-polarization state. Following reflection off the polarizing beamsplitter 86, the waves are coupled out of the substrate 80 through the lower surface 92 of the substrate. The waves then pass through a quarter-wavelength retardation plate 94, reflected by a reflecting optical element 96, returned to pass through the retardation plate 94 again, and re-enter the substrate 80 through the lower surface 92. The now p-polarized light waves pass through the polarizing beamsplitter 86, and enter the upper prism 42 through the lower surface 8. The light waves are then collimated as described above in reference to Fig. 1. If it is required that the coupled light 82 into the prism 42 will be s-polarized as before, it is possible to add a half-wavelength retardation plate 98 between prisms 80 and 42, which rotates the light into the desired polarization. Apparently, the reflecting surfaces 16 and 96 could be replaced by converging lenses as explained above in reference to Fig. 9 according to the required performance and overall size of the optical system.

In the optical systems illustrated in Figs. 11-12 the folding of the optical path is performed around the y axis, that is, in the x-z plane. Usually, it is preferred to fold the optical system in the plane wherein the dimensions of the system are minimal. Assuming eyeglasses configuration, the x and y axes are referred to the horizontal and vertical axes of the image. For most of the LOE-based eyeglasses configurations the vertical dimension of the input aperture of the LOE, vis-a-vis the vertical output aperture of the LCE, is considerably larger than horizontal dimension of the aperture. Hence, it is preferred to fold the optical pathway in prism 42, which is adjacent to LOE, around the axis, as is illustrated indeed in Figs. 1 1-12. Regarding the display source however, the situation is usually the opposite. That is, the horizontal dimension is larger than the vertical one in a ratio of 4:3 for VGA format and in a ratio of 16:9 for HDTV format. Therefore, it is preferred to fold the optical pathway in the prism 80, which is adjacent to the display source, around the x axis. A modified version of Fig. 1 1, wherein the folding of the optical pathway is performed in two different planes is illustrated in Fig. 13. Here the folding in prism 80 is performed in the y-z plane while in prism 42 it is performed in the x-z plane. As before, if it is required that the coupled light 82 into the prism 42 will be s-polarized compared to the folding beamsplitter 10, it is possible to add a half-wavelength retardation plate 98 between prisms 80 and 42, which rotates the light into the desired polarization.

For eyeglasses configurations it is usually required that the longer dimension of the LCE will be oriented along the handle of the eyeglasses. That is, normal to the major surfaces of the LOE, as illustrated in the preceding figures. For other configurations however, such as hand-held displays, it is required that the longer dimension of the LCE will be oriented parallel to the major surfaces of the LOE. As illustrated in Fig. 14, the s-polarized light waves 82, emanating from a light source 84, are reflected off the first polarizing beamsplitter 86 and illuminate the front surface of the LCOS 88. The polarization of the reflected light from the "light" pixels is rotated to the p-polarization state. Following a passage through the polarizing beamsplitter 86, the waves are coupled out of the prism 100 through the lower surface 92 of the prism. The waves then pass through a quarter-wavelength retardation plate 94, reflected by a reflecting optical element 96, returned to pass through the retardation plate 94 again, and re-enter the prism 100 through the lower surface 92. Following a reflection off the first polarizing beamsplitter 86 and the second beamsplitter 102, the now s-polarized light waves coupled out of the prism 100 through the lower surface 92 of the prism. The waves then pass through a second quarter- wavelength retardation plate 104, collimated by a lens 106 at its reflecting surface 108, returned to pass through the retardation plate 104 again, and re-enter the prism 100 through the surface 92. The now p-polarized light waves pass through the polarizing beamsplitter 102 and exit the substrate through the upper surface 1 10 to enter the LOE 30. A modified version of Fig. 14, wherein the two beamsplitters are oriented parallel to each other is illustrated in Fig. 15. Here, instead of a right-angle prism 100, a parallelepiped 112 connects the two beamsplitters 86 and 102. As a result, the LCOS 88 is not located on the same side of the LCE as the LOE 30 but on the other side. This modification is required for systems wherein it is not allowed to locate the PCB of the LCOS near the LOE due to assembly considerations.

In all the eyeglasses configurations illustrated above the display source plane is oriented parallel to the major surfaces of the LOE. There are systems however, mainly with display sources having PCB with large area, wherein it is required that the display source plane will be oriented normal to the major surfaces of the LOE. Fig. 16 illustrates a modified substrate 114 containing two embedded polarizing beamsplitters 1 16 and 118, two quarter- wavelength retardation plates 120 and 122, two reflecting surfaces 124 and 126 and a converging lens 128. As illustrated, the s-polarized input light wave 130 from the display source 132 reflects off the first reflecting surface 124. Then, following total internal reflection off the left surface 134 of the substrate, the waves are reflected off the first beamsplitter 1 16 and coupled out of the substrate. It is then reflected and changed to p-polarized light by the retardation plate 120 and the second reflecting surface 126. Following a passage through the polarizing beamsplitters 1 16 and 118 the waves are reflected, collimated and changed back to s-polarized light by the retardation plate 122 and the converging lens 128. The waves then reflected off the second polarizing beamsplitter 1 18 and exit the substrate through the upper surface 136. The incoming wave (vis-a-vis the LOE) could now be trapped into the LOE in the same manner as that illustrated in Fig. 2. As illustrated in Fig. 17, in the event where the display light source is an LCOS device, the illumination method will be changed by adding a complementary prism 138 with an embedded polarizing beamsplitter 139, instead of the reflecting surface 124 in fig. 16, and a front light module 140.

For all the optical configurations which were illustrated hitherto, the coupling-in of the light waves into the LOE was performed utilizing a reflecting surface 38 which was embedded inside the LOE substrate. Unfortunately, this coupling-in method suffers from a few major drawbacks. Firstly, since the reflecting surface 38 and the partially reflecting surfaces 36 are oriented at different angles, the fabrication process of an LOE having an internally embedded reflecting mirror 38 is fairly complicated. In addition, the distance / between the input and the output apertures of the LOE, which are set by the couple-in mirror 38 and the couple-out surfaces 36 respectively, is determined by the fabrication process of the LOE. Therefore, it is not possible to control the distance / for a given LOE. Unfortunately, for many applications it is required to keep as a flexible parameter. For example, in an eyeglasses configuration the distance / depends strongly on the size and the shape of the viewer's head and on the particular model of the eyeglasses frame. Therefore, it is advantageous to have the ability to set / during the assembly process. Otherwise, it is required to manufacture the LOEs with a large variety of sizes in order to accommodate all the required possibilities. As a result, it is apparent that a simpler coupling-in configuration is preferred upon that which is illustrated hitherto.

The objective is to find an alternative coupling-in mechanism which will replace the input mirror 38. Figure 18 illustrates a span of rays that have to be coupled into the LOE with a minimal required input aperture. In order to avoid an image with gaps or stripes, the points on the boundary line 146 between the edge of input aperture 148 and the lower surface 150 of the substrate 30 should be illuminated for each one of the input waves by two different rays that enter the substrate from two different locations: One ray 152a that illuminates the boundary line 146 directly, and another ray 152b, which is first reflected by the upper surface 154 before illuminating the boundary line. The size of the input aperture is usually determined by two marginal rays: the rightmost ray 156b of the highest angle of the FOV and the leftmost ray 158a of the lowest angle of the FOV.

The simplest way to couple these rays into the LOE is illustrated in Fig. 19. Here, the principle axis 160 of the LCE 28 is oriented at the required off-axis angle a compared to the major plane of the LOE. A relay prism 162 is located between the LCE 28 and the LOE 30 and is optically cemented to the lower surface 32 of the LOE such that the light from the display source is trapped inside the substrate by total internal reflection. Apparently, the overall shape and size of this module conforms to most of the relevant applications.

In the optical collimating module illustrated in Fig. 19 the off-axis angles of the span of the rays that have to be coupled into the LOE, are set by rotating the LCE module. However, there are cases where it is required to utilize a collimated light waves that impinges the LOE, normal to the substrate plane. In these cases an alternative coupling-in mechanism should replace the input mirror 38. As illustrated in Fig. 20, the lower surface 168 of a coupling-in prism 170 is optically cemented to the LOE 30 at the upper surface 154 of the substrate. The collimated light waves from the display source (not shown) pass through the LOE 30 and the prism 170 and then are reflected from the reflecting surface 172. After passing again through the prism 170 the light waves are coupled into the LOE by total internal reflection. Similarly to what is illustrated above in Fig. 18, in order to avoid an image with gaps or stripes, the points on the boundary line 176 between the lower surface 168 of the prism 170 and the upper surface 154 of the LOE 20 should be illuminated for each one of the input waves by two different rays that enter the substrate from two different locations: One ray 152a first passes through prism 170 and is reflected by the reflecting surface 172, from there it illuminates the boundary line 176. Another ray 152b, is first reflected by the reflecting surface 172 and then by the lower surface 150 of the LOE 30 before illuminating the boundary line. To avoid undesired reflections from the left surface 174 it can be coated by an opaque obstructive layer.

There are some alternatives as to the precise way in which an LOE can utilize the embodiments of the eyeglasses configuration. The simplest option is to use a single element for one eye. Another option is to use an element and a display source for each eye, projecting the same image, wherein the preferred place for the LCEs modules is next to the temples. A similar option is to project the same image for both eyes but utilizing only one LCE which is located between the two glasses, whereby its output is split between the two LOEs. Alternatively, it is possible to project two different parts of the same image, with some overlap between the two eyes, enabling a wider FOV. Yet another possibility is to project two different scenes, one to each eye, in order to create a stereoscopic image. With this alternative, attractive implementations are possible, including 3-dimensional movies, advanced virtual reality, training systems and etc.

A version of a double-image arrangement, containing a single display source 180, two LCEs 182R and 182L, two coupling-in prisms 184R and 184L and two LOEs 30R and 30L is illustrated in Fig. 21. The collimating of the right light waves by the LCE 182R and the coupling in by the prism 184R into the LOE 30R is similar to what is illustrated above in reference to Figs. 2 and 20 respectively. The main difference in the LCE 182R is that instead of utilizing a simple reflecting mirror, a half-reflecting beamsplitter 186 is localized between the LCEs 182R and 182L. As illustrated, the light waves which partially pass through the beamsplitter 186 changed to p-polarized light by passing through two quarter wave retardation plates 188R and 188L which are positioned between the beamsplitter 186 and LCEs 182R and 182L respectively. The p-polarized light passes through the polarizing beamsplitter 190L. The waves are then reflected, collimated and changed back to s-polarized light by the retardation plate 192L and the converging lens 194L. Following a reflection off the polarizing beamsplitter 190L the waves are reflected and changed back to p-polarized light by the retardation plate 196 and the reflecting surface 198. The waves then pass through the polarizing beamsplitter 190L and exit the substrate through the upper surface 200L. The incoming wave (vis-a-vis the LOE) could now be trapped into the LOE in the same manner as that illustrated in Fig. 20.

As illustrated, the polarizations of images 202L and 202R which are created by the LCEs 182L and 182R are p and s respectively. This might be a shortcoming for systems wherein a similar polarization is required from both images. As illustrated, a half-wavelength retardation plate 204 is inserted between the left LCE 182L and the left LOE 30L to create two identical linearly s-polarized images, 206L and 206R, which are projected into the viewer's eyes 208L and 208R respectively. In order to create a proper binocular image, it is essential that the images 206L and 206R will be identical. Therefore, the optical pathways between the display source 180 and the reflecting surfaces of the converging lenses 194L and 194R, as well as the focal lengths of these lenses should be identical. In addition, the parity of the number of reflections in the two LCEs 182L and 182R should be equal. As illustrated in Fig. 21, the number of reflections is 4 and 2 in the LCEs 182L and 182R respectively, and the required identical parity is achieved.

Evidently, this optical arrangement could be assembled inside a spectacles frame, to create an optical device wherein the same image is projected for both eyes 208L and 208R by utilizing only one display light source 180, which is located between the two glasses. Usually, the nose-bridge of a conventional spectacles frame is located a few millimeters above the eyes.

Fig. 22 illustrates a method to insert the images into the eyes of the user properly. Here, the center of the display light source 180 is located above the centers of the eyes 208L and 208R. In addition, the coupling-in prisms 184L and 184R are rotated to a geometry wherein the reflecting mirrors of the prisms 184L and 184R are oriented parallel to the partially reflecting surfaces 36L and 36R respectively. As a result, the projections of the central waves 210L and 21 OR on the LOEs planes are parallel to the major axes of the LOEs 212L and 212R respectively and the image waves are coupled into the LOE wherein the major axes of the images is inclined a few degrees above the horizon. The partially reflecting surfaces 36L and 36R reflect the coupled image back to their original directions and the central image waves are again parallel to the horizon. Evidently, the optical module, which can be added to any conventional frame, could be very compact and lightweight, with no disturbance to the user.

In the configuration illustrated in Figs. 21 and 22 a single display source is utilized. As a result, only a system having identical images for both eyes can be materialized using this configuration. An alternative method, utilizing two different display sources 214L and 214R is illustrate in Fig. 23. Here, the light waves from the display sources 214L and 214R are coupled into the intermediate prism 216 through the surfaces 218L and 218R respectively. The waves are then collimated by the LCEs 220R and 220L and are then trapped inside the LOEs 30R and 30L respectively in a similar manner to the method described above with reference to Fig. 20. a similar geometry is illustrated in Fig. 24 wherein the light waves which are coupled into the prism 216 are reflected off the mirror 222. Here, the light waves from the display sources 214L and 214R are coupled into the LOEs 30L and 30R respectively. Unlike the previous configuration which is illustrated in Figs. 2 land 22, here the display sources are located at the same level as the viewer's eyes wherein the space 224 between the LCEs 220L and 220R is preserved for the upper part of the nose.

The configurations illustrated in Figs. 23and 24 have the capability to project stereoscopic image as well as wider FOV by utilizing two different display sources. However, the necessity to use two different display sources increases the volume, the power consumption as well as the fabrication costs of the optical system. An alternative method, utilizing only a single display source while still preserving the advantages of the configurations of Figs. 23 and 24 is described in fig.25. Here, only a single display source is located next to surface 218L and a beamsplitter 226 is inserted inside the intermediate prism 216. Apparently, a naive method wherein conventional display source 216 and beamsplitter 226 are utilized is not possible. Since the parity of the two images is different, that is, the left image is reflected 5 times while the right image is reflected 4 times before being coupled into the LOEs, the images will be the mirror images of each other. Therefore, to enable the projection of a proper imagery into the eyes, a dynamic half-wavelength retardation plate 228 is inserted between the display source 214 and the surface 218L and a polarizing beamsplitter 226 is inserted inside the prism 216. Here, the display source 214 which is synchronized with the retardation plate 228 is operating at a double rate than usual. At the first stage of each double-cycle an image which is designated to the left eye is emanated from the display source. At the same time, the dynamic retardation plate is switched to the off position and the s-polarized light waves are reflected off the polarizing beamsplitter 226, collimated by the LCE 220L and coupled into the left LOE 30L. At the second stage of each double-cycle an image which is designated to the right eye is emanated from the display source. At the same time, the dynamic retardation plate is switched to the on position, the polarization of the light waves is rotated to the p-state and now the p-polarized light waves pass through the polarizing beamsplitter 226, collimated by the LCE 220R and coupled into the right LOE 30R. The images which are projected into the viewer's eyes can be now either identical, stereoscopic, two different parts of the same image with some overlap between the two eyes or any desired combination.

Hitherto it was assumed that the polarizing beamsplitters totally reflect one polarization and totally transmit the other one. Unfortunately, the operation of the beamsplitter cannot be perfect and there is a cross-talk between the two states. As a result, a small fraction of the s-polarized light waves pass through the beamsplitter and a small fraction of the p-polarized light waves are reflected off the beamsplitter. As illustrated in Fig. 26, a part 230 of the original s-polarized light waves 2 which is emanated from the display source 4 pass through the beamsplitter 10 and is coupled-out of the LCE 28 at a similar direction to that of the collimated light wave 232. Therefore, they cannot be laterally separated. In addition, since these two waves are s-polarized they cannot be separated utilizing a polarizing sensitive element. As a result, the undesired waves 230 will be projected into the viewer's eye and a ghost image that will interfere with the original image will be created.

A possible method to overcome this problem is illustrated in Fig. 27. Here, instead of utilizing a single polarizing beamsplitter 10, two different polarizing beamsplitters, 234 and 236, and a linear polarizer 238 which is oriented to block s-polarized light are inserted into the LCE 28. Now, the s-polarized light waves 240 which pass through the first polarizing beamsplitter 234 are blocked by the polarizer 238. On the other hand, the light waves which are reflected as intended by the first polarizing beamsplitter are reflected and changed to p-polarized light by the retardation plate 14 and the reflecting surface 16. Following a passage through the first beamsplitter 234, the polarizer 236 and the second polarizing beamsplitter 238 the waves are then reflected, collimated and changed back to s-polarized light by the retardation plate 20 and the converging lens 22. Following a reflection off the second polarizing beamsplitter 236 the waves exit the substrate properly collimated through the upper surface 26. Evidently, the configuration illustrated in Fig. 27 solves the ghost image problem. However, the necessity to embed two different polarizing beamsplitters and a linear polarizer inside the LCE complicates the fabrication process of the optical module.

Hitherto, we have assumed that the polarizing beamsplitter is oriented at an angle of 45° in relation to the major surfaces of the LCE. An alternative method to separate between the real and the ghost images by utilizing a different angle is illustrated in Fig. 28. Here, the angle between the lower surface 8 of the LCE and the beamsplitter 10 is set to be 45°+a wherein a positive angular rotation is defined to be counterclockwise. As a result, the central ray 242 from the wave 2 is rotated by the beamsplitter 10 to the angle 90°+2 and is reflected to the angle 270°-2a by the reflecting surface 16. In order to minimize field aberrations, the main axis of the collimating lens 22 is oriented collinear with the incoming central ray 244. Hence, the ray is reflected back by the lens to the angle 90°-2a . The second reflection off the beamsplitter 10 yields the final direction of the central ray to be 4a. Therefore, the real and the ghost images can be angularly separated now. A slightly modified version is illustrated in Fig. 29 wherein, in addition to the rotation of the beamsplitter 10, the reflecting surface 16 is rotated at an angle of β compared to its original orientation. As a result, the direction of the output central ray from the LCE is now 4α+2β. Another example, which is related to the configuration described above in Fig. 15, is illustrated in Fig. 30. Here, the angle between the incoming surface 246 and the first polarizing beamsplitter is 45°+a and the angle between the reflecting surface 250 and the output surface 252 is a. As a result, the angle between the ghost and the real images is 2a.

Another advantage of the configurations illustrated in Figs 29-30 is that it is now possible to differentiate between the mechanical orientation of the LCE and the direction of the output wave. There are cases wherein it is required to rotate the mechanical axis of the LCE while still retaining the on-axis impinging angle on the LOE. As illustrated in Fig. 31, the angle between the lower surface 8 and the beamsplitter 10 is set to -45°-a. As a result, the angle between the input and the output waves of the LCE is -4a. As a result the mechanical angle between the major axis of the LCE and the normal to the LOE, is -4a while the central output wave from the LCE vis-a-vis the central input wave of the LOE impinges normal to the major surface of the LOE as requested. Fig. 32 illustrated another example based on the configuration which is described above in reference to Fig. 19. Here, the angle between surface 8 and the beamsplitter 10 is 52.5°. Therefore, while the mechanical axis of the LCE is oriented at an angle of 30° to the normal of the major surfaces of the LOE, the central incoming wave is oriented at the required off-axis angle of 60°.

In all the optical systems which were described above in relation to Figs. 1 to 32, the LCE operates as a collimator. That is, a real image from a display light source is focused to infinity. In addition, the main purpose for materializing the LCE was to create collimated light waves as the input for an LOE based optical system. Clearly, an LCE device could be utilized for different optical operations and many other applications. That is, the LCE can focus an image to a different distance than infinity and can be inserted in other systems wherein it is desired to achieve good performances and retain a compact and light-weight system.

Fig. 33 illustrates an optical system wherein the LCE serves as a focusing lens for a camera. Here the p-polarized component of the input wave 254 from an external scene passes through the upper surface 256 of the LCE 258 and through the polarizing beamsplitter 260. It is then reflected, converged and changed to s-polarized light by the retardation plate 262 and a focusing lens 264 having a reflective back surface 266. Following a reflection off the polarizing beamsplitter 260 It is then reflected and changed to p-polarized light by the retardation plate 267 and a reflecting surface 268. Following a passage through the beamsplitter 260 the converging light waves exit the LCE through the left surface 270 and is then focused onto the detector plane 272. A focus mechanism might be added to this device by enabling a lateral translation of the camera or of the focusing lens along the z-axis in relation to the lower plane 272.

Another potential application is illustrated in Fig. 34. Here, a converging LCE 276 and a collimating LCE 278 are combined together to form a unity magnification telescope. An optical filter 280 can be inserted to the Fourier plane in order to perform any required image processing. In addition, an energy-sensitive filter can be inserted to block high-intensity signals. Apparently, different LCEs can be combined together to materialize a magnifying or de-magnifying systems. In addition, the telescope can be combined with an LOE in order to project a processed or a magnified image from the external view to a viewer's eye.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (107)

WHAT IS CLAIMED IS:

1. An optical system, comprising: a light transmitting substrate having an entrance surface, an exit surface and at least two other external surfaces and edges; at least one reflecting surface carried by said substrate, and at least two retardation plates, characterized by at least two reflecting optical elements, wherein said retardation plates are located between at least a portion of said two external surfaces of the substrate and said two reflecting optical elements respectively.

2. The optical system according to claim 1, wherein said reflecting surface is not parallel to any of the edges of said substrate.

3. The optical system according to claim 1, wherein said two external surfaces are parallel.

4. The optical system according to claim 1, wherein said two external surfaces are oriented at an angle of 90° to each other.

5. The optical system according to claim 1, further comprising a display light source.

6. The optical system according to claim 5, wherein said display light source produces image light waves which are coupled through said entrance surface into said substrate .

7. The optical system according to claim 6, wherein said light waves are linearly polarized.

8. The optical system according to claim 6, wherein said light waves are unpolarized.

9. The optical system according to claim 5, wherein said display light source is positioned adjacent to the entrance surface of said substrate.

10. The optical system according to claim 6, wherein said light waves are coupled by said reflecting surface out of said substrate.

11. The optical system according to claim 1, wherein at least one of said retardation plates is a quarter-wavelength plate.

12. The optical system according to claim 1, wherein at least one of said reflecting optical elements is an imaging lens.

13. The optical system according to claim 12, wherein said reflecting optical element includes two surfaces, a first of said surfaces is transparent and a second is coated with a reflecting material.

14. The optical system according to claim 13, wherein said retardation plate is positioned between said first transparent surface and one of the external surfaces of said substrate.

15. The optical system according to claim 1, further comprising a blank plate.

16. The optical system according to claim 1, wherein said blank plate is optically attached to one of the surfaces of said substrate.

17. The optical system according to claim 5, wherein said display light source is optically attached to one of the surfaces of said substrate.

18. The optical system according to claim 5, wherein said display light source is an LCD.

19. The optical system according to claim 5, wherein said display light source is an LCOS.

20. The optical system according to claim 1, wherein said reflecting surface carried by said substrate is a polarizing beamsplitter.

21. The optical system according to claim 20, wherein said reflecting surface carried by said substrate is a wire-grid polarizing beamsplitter.

22. The optical system according to claim 20, wherein said reflecting surface carried by said substrate reflects s-polarized light and transmits p-polarized light.

23. The optical system according to claim 20, wherein said reflecting surface carried by said substrate reflects p-polarized light and transmits s-polarized light.

24. The optical system according to claim 1, wherein at least one of said reflecting optical elements is optically attached to one of said quarter-wave retardation device.

25. The optical system according to claim 1, wherein at least one of said quarter-wave retardation device is optically attached to one of said external surfaces of the substrate.

26. The optical system according to claim 1, wherein at least one of said reflecting optical elements is a plano-convex lens.

27. The optical system according to claim 1, wherein at least one of said reflecting optical elements is a plano-concave lens.

28. The optical system according to claim 1, wherein at least one of said reflecting optical elements is a collimating lens.

29. The optical system according to claim 1 , wherein at least one surface of said reflecting optical element is an aspheric surface.

30. The optical system according to claim 1, wherein at least one surface of said reflecting optical element is a diffractive surface.

31. The optical system according to claim 5, wherein said display light source is an OLED.

32. The optical system according to claim 5, further comprising a light source.

33. The optical system according to claim 32, wherein said light source is positioned adjacent to one of the external surfaces of said substrate.

34. The optical system according to claim 32, wherein said light source and said display light source are positioned adjacent to the said entrance surface.

35. The optical system according to claim 32, wherein said light source and said display light source are positioned adjacent to two opposite surfaces.

36. The optical system according to claim 1, further comprising a second reflecting surface carried by said substrate.

37. The optical system according to claim 36, wherein said second reflecting surface is parallel to said first reflecting surface.

38. The optical system according to claim 36, wherein said second reflecting surface is oriented normal to said first reflecting surface.

39. The optical system according to claim 36, wherein said second reflecting surface intersects with said first reflecting surface at one of the edges of said substrate.

40. The optical system according to claim 36, wherein said two reflecting surfaces are rotated compared to said entrance surface of the substrate around two different axes.

41. The optical system according to claim 1, wherein at least one half-wavelength retardation plate is embedded inside said substrate.

42. The optical system according to claim 38, further comprising a third reflecting optical element.

43. The optical system according to claim 42, wherein said third reflecting optical element is positioned adjacent to one of the external surfaces of the substrate.

44. The optical system according to claim 42, wherein a retardation plate is positioned between said third reflecting optical element and said external surface of the substrate.

45. The optical system according to claim 1, further comprising: a second light-transmitting substrate having at least two major surfaces parallel to each other and two edges; an optical element for coupling light into said substrate by internal reflection, and at least one partially reflecting surface located in said substrate, which surface is non-parallel to the major surfaces of said second substrate, wherein said second substrate is positioned adjacent to the exit surface said first substrate.

46. The optical system according to claim 45, wherein optical waves which are coupled out of said first substrate are coupled by said optical element for coupling light into said second substrate by total internal reflection.

47. The optical system according to claim 45, wherein said optical element for coupling light is embedded inside said light-transmitting substrate.

48. The optical system according to claim 45, wherein said optical element for coupling light is a reflecting surface.

49. The optical system according to claim 45, wherein said optical element for coupling light is a light-transmitting prism.

50. The optical system according to claim 49, wherein said at least one surface of said prism is a reflecting surface.

51. The optical system according to claim 49, wherein said second substrate is positioned between said first substrate and said prism.

52. The optical system according to claim 49, wherein said prism is positioned between said first substrate and said second substrate

53. The optical system according to claim 49, wherein optical waves which are coupled out of said first substrate are coupled directly into said second substrate by total internal reflection.

54. The optical system according to claim 45, wherein a half-wavelength retardation plate is positioned between said first and second substrates.

55. The optical system according to claim 53, further comprising a second reflecting optical element which is positioned next to one of the major surfaces of said second substrate.

56. The optical system according to claim 46, wherein said optical waves which are coupled out of said first substrate and coupled into said second substrate by total internal reflection are s-polarized.

57. The optical system according to claim 46, wherein said optical waves which are coupled out of said first substrate and coupled into said second substrate by total internal reflection are p-polarized.

58. The optical system according to claim 1, wherein said retardation plate is optically attached to said substrate.

59. The optical system according to claim 45, wherein said two substrates are optically attached.

60. The optical system according to claim 59, wherein an angular sensitive coating is applied to the exit surface of said substrate.

61. The optical system according to claim 59, further comprising a transparent plate positioned between said two cemented substrates.

62. The optical system according to claim 61, wherein said transparent plate is coated with an angular sensitive coating.

63. The optical system according to claim 62, wherein said angular sensitive coating is applied to the surface of said plate which is cemented to said second light-transmitting substrate.

64. The optical system as claimed in claims 60 and 62, wherein said angular sensitive transmits light waves with low incident angles and reflects s-polarized light with high incident angles.

65. The optical system according to claim 6, further comprising at least one beamsplitter embedded inside said substrates.

66. The optical system according to claim 65, wherein said image light waves are split, by said beamsplitter, into two separated images.

67. The optical system according to claim 5, further comprising a second display light source.

68. The optical system according to claim 67, wherein said substrate further comprising a second entrance surface.

69. The optical system according to claim 68, wherein said second display light source produces image light waves which are coupled through said second entrance surface into said substrate

70. The optical system according to claim 69, wherein said two display sources produce two separated images.

71. The optical system according to claim 5, further comprising a dynamic half-wavelength retardation plate.

72. The optical system according to claim 71, wherein said dynamic half-wavelength retardation plate is poisoned between said display source and the entrance surface of said substrate.

73. The optical system according to claim 71, wherein said dynamic half-wavelength retardation plate is electronically synchronized with said display source.

74. The optical system according to claim 71, wherein said display source is operating at a double rate than usual.

75. The optical system according to claim 71, wherein said display source produces two different interlaced images.

76. The optical system according to claim 75, further comprising a polarizing beamsplitter embedded inside said substrate.

77. The optical system according to claim 76, wherein said image light waves are split, by said polarizing beamsplitter, into two separated images.

78. The optical system claimed in claims 66, 70 or 77, wherein said two images are coupled out of said substrate.

79. The optical system according to claim 78, wherein said two images are identical.

80. The optical system according to claim 78, wherein said two images are two different parts of the same image with some overlap between them.

81. The optical system according to claim 78, wherein said two images produces a stereoscopic image.

82. The optical system according to claim 78, wherein said two images have the same linear polarization.

83. The optical system according to claim 45, wherein said substrate further comprising a second exit surface.

84. The optical system according to claim 83, further comprising; a third light-transmitting substrate having at least two major surfaces parallel to each other and two edges; second optical element for coupling light into said substrate by internal reflection, and at least one partially reflecting surface located in said substrate, which surface is non-parallel to the major surfaces of said third substrate, wherein said third substrate is positioned adjacent to the second exit surface of said first substrate.

85. The optical device as claimed in claims 78 and 84, wherein the image waves which are coupled out of the first substrate are coupled into said second and third substrates by total internal reflection.

86. The optical system according to claim 1, wherein said system is embedded in a spectacle frame.

87. The optical system according to claim 1, wherein said system is embedded in a cellular phone.

88. The optical system according to claim 1, wherein said system is embedded in an entertainment device.

89. The optical system according to claim 1, wherein said system is a collimating lens.

90. The optical system according to claim 1, wherein said system is a focusing lens.

91. The optical system according to claim 90, wherein said system is embedded in a camera.

92. The optical system according to claim 1, wherein said system is a telescope.

93. The optical system according to claim 91, wherein said telescope is unity magnification telescope.

94. The optical system according to claim 91, further comprising an optical filter embedded inside said substrate.

95. The optical system according to claim 93, wherein said optical filter is positioned at the Fourier plane of said telescope.

96. The optical system according to claim 93, wherein said optical filter is an energy-sensitive filter to block high-intensity signals.

97. The optical system according to claim 1 , wherein the surfaces of the substrate form a parallelepiped.

98. The optical system according to claim 1, wherein said reflecting surface is oriented at an angle of 45° in relation to the entrance surface of the substrate.

99. The optical system according to claim 1, wherein at least two opposite surfaces of said substrate are not parallel to each other.

100. The optical system according to claim 1, wherein said reflecting surface is oriented at an angle other than 45° in relation to the entrance surface of the substrate.

101. The optical system according to claim 1, wherein the exit surface is parallel to the entrance surface of said substrate.

102. The optical system according to claim 1, wherein the exit surface is oriented at an angle of 90° in relation to the entrance surface of said substrate.

103. The optical system according to claim 1, wherein the exit surface is neither parallel nor oriented at an angle of 90° in relation to the entrance surface of said substrate.

104. The optical system according to claim 46, wherein the central output wave from the first substrate impinges normal to the major surface of the second surface.

105. The optical system according to claim 104, wherein angle between the entrance surface of the first substrate and the major surface of the second surface is different than zero.

106. The optical system according to claim 104, wherein the axis normal to the entrance surface of the first substrate and the central incoming wave to the second substrate are oriented at different angles to the major surfaces of the second substrate.

107. An optical device according to claim 1, substantially as hereinbefore and with reference to the accompanying drawings. Dr. Yaakov Amitai