Compact head mounted display system

Abstract

The present application relates to a compact head-mounted display system. An optical system is provided, comprising: a light-transmitting substrate (20) having at least two major surfaces (26) and an edge; an optical prism (54) having at least a first (58), a second (56) and a third (60) surface for coupling light waves having a given field of view into the substrate by total internal reflection; at least one partially reflective surface located in the substrate, the partially reflective surface being oriented non-parallel to the major surfaces of the substrate, for coupling light waves out of the substrate; at least one of the edges (50) of the substrate being inclined at an inclined angle relative to the major surfaces; a second surface of the prism being positioned adjacent to the inclined edge of the substrate; and a portion of the substrate positioned adjacent to the inclined edge being substantially transparent, wherein light waves enter the prism through the first surface of the prism, traverse the prism without any reflection, and enter the substrate through the inclined edge.

Description

[0001] This application is a divisional application of the Chinese patent application filed on November 25, 2016, with application number 201580028030.6 and invention name “Compact head mounted display system”. The international filing date of the parent application is April 21, 2015, and the international application number is PCT / IL2015 / 050422. Technical Field

[0002] The present invention relates to substrate-guided optical devices and, more particularly, to devices (also referred to as light guide elements) comprising a plurality of reflective surfaces carried by a conventional light-transmitting substrate.

[0003] The present invention may be implemented to benefit a wide variety of imaging applications, such as portable DVDs, mobile phones, mobile television receivers, video games, portable media players, or any other mobile display device. Background Art

[0004] One application of compact optical components involves head mounted displays (HMDs) where the optical module acts as an imaging lens and combiner where a two-dimensional image source is imaged to infinity and reflected into the eyes of a viewer. The display source may be derived directly from 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 light source, or the like, or indirectly by means of a relay lens, fiber bundle, or similar device. The display source comprises an array of elements (pixels) imaged to infinity by a collimating lens and transmitted to the eyes of a viewer by a reflective or partially reflective surface (acting as a combiner for non-see-through and see-through applications). Typically, conventional free space optical modules are used for these purposes. As the desired field of view (FOV) of the system increases, however, such conventional optical modules become larger, heavier, and more cumbersome, and are therefore impractical even for moderate performance devices. This is a major disadvantage for all types of displays, especially in head mounted applications where the system needs to be as light and compact as possible.

[0005] The efforts made for compactness have led to a number of different complex optical solutions, all of which, on the one hand, are still not compact enough for most practical applications and, on the other hand, encounter major drawbacks regarding manufacturability. Furthermore, the eye-motion-box (EMB) of the optical viewing angle resulting from these designs is usually very small, typically less than 8 mm. As a result, the performance of the optical system is very sensitive to even small movements of the optical system relative to the viewer's eye and does not allow sufficient movement of the pupil to comfortably read text from such a display.

[0006] The teachings contained in publication numbers WO01 / 95027, WO03 / 081320, WO2005 / 024485, WO2005 / 024491, WO2005 / 024969, WO2005 / 124427, WO2006 / 013565, WO2006 / 085309, WO2006 / 085310, WO2006 / 087709, WO2007 / 054928, WO2007 / 093983, WO2008 / 023367, WO2008 / 129539, WO2008 / 149339 and WO2013 / 175465, all filed in the name of the present applicant, are incorporated herein by reference. Summary of the invention

[0007] The present invention facilitates very compact light guide optical elements (LOEs) for use in HMDs and other applications. The present invention allows for relatively wide FOVs and relatively large EMB values. The resulting optical system provides a large, high quality image, which also allows for large eye movements. The disclosed optical system is particularly advantageous because it is substantially more compact than prior art embodiments, and thus it can be easily incorporated into optical systems even of special construction.

[0008] It is therefore a broad object of the present invention to alleviate the disadvantages of prior art compact optical display devices and to provide other optical assemblies and systems with improved performance according to specific needs.

[0009] According to the present invention, an optical system is provided, comprising: a light-transmitting substrate having at least two main surfaces and an edge; an optical prism having at least a first, a second and a third surface for coupling light waves having a given field of view into the substrate by total internal reflection; at least one partially reflective surface located in the substrate, the partially reflective surface being oriented non-parallel to the main surfaces of the substrate, for coupling light waves out of the substrate; at least one of the edges of the substrate being inclined at an inclined angle relative to the main surfaces; a second surface of the prism being positioned adjacent to the inclined edge of the substrate; and a portion of the substrate positioned adjacent to the inclined edge being substantially transparent, characterized in that light waves enter the prism through the first surface of the prism, traverse the prism without any reflection and enter the substrate through the inclined edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be described in conjunction with certain preferred embodiments with reference to the accompanying drawings shown below in order to provide a more complete understanding of the present invention.

[0011] With respect to the drawings specifically referenced in detail, it should be emphasized that the drawings specifically drawn are by way of example and are intended only for the purpose of illustrating a schematic discussion of the preferred embodiments of the present invention, and provide what is considered to be the most useful content and description for easy understanding of the principles and concepts of the present invention. In this regard, no attempt is made to show the structural details of the present invention in more detail than is necessary for a basic understanding of the present invention. The description made in conjunction with the drawings serves to guide those skilled in the art to understand how several forms of the present invention may be practically implemented.

[0012] In the attached picture:

[0013] Figure 1 shows the span of light coupled into the LOE according to the present invention;

[0014] Figure 2 shows the span of the rays illuminating the entrance aperture of the LOE;

[0015] FIG3 shows a side view of a prior art exemplary coupling-in mechanism including a prism optically attached to one of the major surfaces of a LOE;

[0016] FIG4 is another schematic diagram showing a side view of a prior art exemplary coupling-in mechanism including a prism optically attached to one of the major surfaces of a LOE;

[0017] Figure 5 shows the span of light rays illuminating an entrance aperture of a LOE, wherein one of the edges of the LOE is tilted at an oblique angle relative to the major surface;

[0018] Figure 6 is a schematic diagram showing another system having a span of light rays illuminating an entrance aperture of a LOE, wherein one of the edges of the LOE is tilted at an oblique angle relative to a major surface;

[0019] Figure 7 is a schematic diagram showing an embodiment of an optical system according to the present invention, which couples an input light wave from a display light source into a substrate, with an intermediate prism attached to the inclined edge of the LOE;

[0020] Figure 8 shows an optical system according to another embodiment of an optical system for coupling incident light waves from a display light source into a substrate, with an intermediate prism attached to the inclined edge of the LOE;

[0021] Fig. 9 is a schematic diagram showing an apparatus for collimating input light waves from a display light source by using a polarization beam splitter according to the present invention;

[0022] Fig.10is a schematic diagram showing an apparatus for collimating input light waves from a liquid crystal on silicon (LCOS) light source according to the present invention; and

[0023] Fig.11A and Fig. 11B are two embodiments showing top views of spectacles according to the invention. DETAILED DESCRIPTION

[0024] The present invention relates to substrate-guided optical devices, in particular compact HMD optical systems. Typically, a collimated image with a limited FOV is coupled into the substrate. Figure 1 As shown, the LOE or image in the substrate 20 in the following contains a span of a plane wave having an intermediate wave 14 and edge waves 16 and 18. The angle between the intermediate wave 14 of the image and the normal to the plane of the major surfaces 26, 32 is α in The FOV within the substrate 20 is defined as 2·Δα. Therefore, the angles between the edge waves 16 and 18 of the image and the normal to the plane of the main surface are α and in +Δα and α in After several reflections from surfaces 26, 32 of substrate 20, the captured wave reaches the array of selectively reflecting surfaces 22, which couples the light wave out of the substrate into the viewer's eye 24. For simplicity, only the light of the intermediate wave 14 is plotted as coupled out of the substrate.

[0025] The object of the present invention is to find a light wave coupling-in mechanism which is different from the coupling-in mechanism of the prior art and has a more compact size. Figure 2 In FIG. 1 , the span of rays that must be coupled into the substrate 20 with the minimum required entrance aperture 21 is shown. To avoid gaps or fringes on the image, points on the borderline 25 between the edge of the entrance aperture 21 and the lower surface 26 of the substrate 20 should be illuminated by two different rays entering the substrate from two different locations for each input light wave: one ray 30 that directly illuminates the borderline 25, and another ray 31 that illuminates the borderline 25 after first being reflected by the upper surface 32 of the substrate. The size of the entrance aperture 21 is usually determined by two edge rays: the rightmost ray 34 at the largest angle of the FOV, and the leftmost ray 36 at the smallest angle of the FOV.

[0026] One possible embodiment for coupling edge light into substrate 20 is shown in FIG3 . Here, an input lightwave source 38 and a collimating module 40 (e.g., a collimating lens) are oriented at a desired off-axis angle relative to major surfaces 26, 32 of substrate 20. A relay prism 44 is located between collimating module 40 and substrate 20 and is optically bonded to lower surface 26 of substrate 20 such that light from display source 38 impinges on major surface 26 at an angle greater than the critical angle for total internal reflection to occur within the substrate. Thus, all optical lightwaves of the image are captured within the substrate by total internal reflection from major surfaces 26 and 32. Although the optical system shown here is simple, this is still not the most compact coupling-in mechanism. It is important for the optical system to be consistent with the external shape of eyeglasses and handheld or other display devices.

[0027] In order to minimize the size of the collimation module 40, the input surface 46 aperture D coupled into the prism 44 T Therefore, the size of the coupling-in prism should also be minimized accordingly, and the coupling light of the entire FOV will pass through the coupling-in prism 44.

[0028] As shown in FIG. 4 , in order to allow the rightmost light 34 of the largest angle of FOV to pass through the prism 44, the aperture D of the output surface 21 of the prism 44 is L The relationship must be satisfied:

[0029] D L ≥2d·tan(α in +Δα) (1)

[0030] Here, d is the thickness of the substrate 20 .

[0031] In addition, in order to allow the leftmost light ray 36 of the smallest angle of FOV to pass through the prism 44, the angle α between the left surface 48 of the prism 44 and the normal to the major surface 26 of the substrate 20 is sur1 The relationship must be satisfied:

[0032] α sur1 ≤α in -Δα (2)

[0033] In order to minimize chromatic aberration of light waves passing through prism 44, it is advantageous to orient input surface 46 coupled into prism 44 substantially orthogonal to image intermediate wave 14. Thus, angle α between input surface 46 of prism 44 and the normal to major surface 26 of substrate 20 is sur2 yes:

[0034] α sur2 =90°-α in (3)

[0035] In order to minimize the size of prism 44, taking the inequality of equation 2 as the limit value, the following internal angle of the prism is obtained: the angle between surfaces 46 and 21 is α in ; The angle between surfaces 48 and 21 is 90°-α in +Δα. Accordingly, the angle between surfaces 46 and 48 is 90°-Δα. Using these values ​​we obtain:

[0036]

[0037] Taking the limiting value of the inequality in equation 1 and inserting it into equation 4, we get:

[0038]

[0039] Although the optical system shown in Figures 3 and 4 appears simple, it is still not the most compact coupling-in mechanism, as it is important for such an optical system to conform to the outer shape of a display (eg, glasses or a handheld display).

[0040] Figure 5 An alternative embodiment of coupling light waves into the substrate through one edge of the substrate is shown. Here, the light wave transmitting substrate 20 has two main parallel surfaces 26 and 32 and edges, wherein at least one edge 50 is oriented at an oblique angle relative to the main surface, and wherein α sur3 is the angle between edge 50 and the normal to the major surface of the substrate. Typically, the incident collimated light wave is coupled directly from air, or alternatively, a collimating module 40 (FIG. 3) may be attached to substrate 20. Therefore, it is advantageous to couple the intermediate wave 14 orthogonal to the inclined surface 50 to minimize chromatic aberration. Unfortunately, coupling light directly through surface 50 does not satisfy this condition. Typically, even for coupled images with modest FOVs, the angle α between the intermediate wave 14 of the image and the normal to the plane of the major surface is in (Figure 3) Condition α must be met in ≥50°. Therefore, if the intermediate wave 14 is indeed orthogonal to the inclined surface 50, the relationship α must be satisfied. sur3 ≤40°. Thus, the result is that the relationship α will be satisfied in the system sur3 <α in , and, for a relatively wide FOV, even the relation α sur3 <<α in +Δα.

[0041] Figure 6A complex situation is shown, where the maximum angle between the captured light and the major surfaces 26, 32 is greater than the angle between the input surface 50 and the major surfaces. As shown, the point on the boundary line 25 between the edge of the input aperture 50 and the lower surface 26 of the substrate 20 is illuminated only by the leftmost light ray 35 of the light wave that directly illuminates the boundary line 25. Another edge light ray 34 incident on the edge 51 of the input surface 50 is first reflected by the upper surface 32 before illuminating the lower surface at a different line 52 located at a distance Δx from the boundary line 25. As shown, the gap Δx is not illuminated at all by the captured light of the edge light wave 34. As a result, black fringes will appear, and the coupled-out light waves and image quality will be significantly degraded.

[0042] This situation is achieved through Figure 7 The illustrated embodiment solves this problem. An intermediate prism 54 is inserted between the collimating module 40 ( FIG. 3 ) and the inclined edge 50 of the substrate. One of the surfaces 56 of the prism is positioned adjacent to the inclined edge 50 of the substrate 20. In most cases, the refractive index of the intermediate prism should be similar to the refractive index of the substrate 20. However, there are also cases where a different refractive index can be selected for the prism to compensate for chromatic aberration in the system. The incident light wave is coupled directly from the air, or alternatively, the collimating module 40 can be attached to the intermediate prism 54. In many cases, the refractive index of the collimating module 40 is substantially different from the refractive index of the substrate 20, and therefore, different from the refractive index of the prism 54. Thus, in order to minimize chromatic aberration, the input surface 58 of the prism 54 should be oriented substantially orthogonal to the intermediate light wave of the incident light. In addition, the leftmost light of the smallest angle of the FOV should pass through the prism 54. Therefore, Figure 7 The structure of should also satisfy the conditions of equations (2) and (3). Figure 6 The phenomenon of undesirable dark streaks is described by the relation:

[0043] α sur3 ≥α in +Δα (6)

[0044] must be satisfied, that is, the angle between the inclined edge of the substrate and the normal to the major surface of the substrate is greater than the maximum angle of the FOV. Therefore, the aperture D of the output surface 56 of the prism 54 is S The relationship must be satisfied:

[0045]

[0046] Obviously, since the light wave enters the prism 54 through the entrance surface 58 of the prism, passes directly through the prism without any reflection, and enters the substrate through the inclined edge 50, the effective area D of the incident surface 58 is P The aperture D relative to the exit surface 56 sIn addition, as described above, in order to allow the leftmost light ray 36 (FIG. 4) of the minimum angle of FOV to pass through the prism 54, the angle α between the left surface 60 of the prism 54 and the normal of the main surface 26 of the substrate is sur1 The relationship of equation (2) must also be satisfied, that is, the angle between the surface 60 of the prism 54 and the normal to the major surface of the substrate is less than the minimum angle of the FOV. Thus, when the relationships of equations (2), (6) and (7) are satisfied, the coupled-in light waves from the entire FOV will completely cover the major surface of the substrate without any stripes or gaps.

[0047] like Figure 8 As shown, by taking the limiting values ​​of the inequalities of equations (2), (6) and (7), the internal angle of prism 54 is: the angle between surfaces 56 and 58 is 2α in -90°+Δα, while the angle between surfaces 56 and 60 is 180°-2α in Therefore, the angle between surfaces 58 and 60 is 90°-Δα. Using these values ​​we have:

[0048]

[0049] Where D P is the effective area of ​​the incident surface 58 of the intermediate prism 54 .

[0050] Thus, by comparing equations (5) and (8), the respective effective areas D of the input surfaces of prisms 54 and 44 of the prior art system of FIG. 4 are P and D T The relationship between them is:

[0051]

[0052] Obviously, for a narrow FOV, that is, Δα<<α in , the improvement is negligible. However, for a relatively wide FOV, the effective area D of the prism 54 P and the effective area D of the prism 44 T For example, for Δα = 12° and α in =52°, the reduction ratio of formula (9) has D P / D T ≈0.7 effective value.

[0053] In the embodiment shown in FIG3 , the collimating module 40 is shown as a simple transmission lens, however, a more compact structure using a reflection lens, a polarization beam splitter and a delay plate may be adopted. In this structure, there are the following facts: Fig. 9As shown, in most microdisplay light sources (such as LCD or LCOS light sources), linearly polarized light is used by optical component 61. As shown, an s-polarized input light wave 62 from a display light source 64 is coupled into a light guide 66 through a lower surface 68 of the light guide 66, which is typically composed of a light wave transmitting material. After reflecting from a polarizing beam splitter 70, the light wave is coupled out of the substrate through a surface 72 of the light guide 66. The light wave then passes through a quarter-wave retarder 74, is reflected by a reflective optical element 76 (e.g., a plane mirror), returns to pass through the retarder 74 again, and re-enters the light guide 66 through surface 72. The now p-polarized light wave passes through the polarizing beam splitter 70 and is coupled out of the light guide through a surface 78 of the light guide 66. The light wave then passes through a second quarter-wave retarder 80, is collimated by a component 82 (e.g., a lens) at its reflective surface 84, returns to pass through the retarder 80 again, and re-enters the light guide 66 through surface 78. The now s-polarized light wave reflects from the polarizing beam splitter 70 and exits the light guide through an exit surface 86 attached to the intermediate prism 54. The reflective surfaces 76 and 84 may be realized by a coating of a metal or a dielectric.

[0054] exist Fig. 9 In the illustrated embodiment, the display source may be an LCD panel, however, there are optical systems, especially those where high brightness imaging properties are required, where an LCOS light source device is preferably used as the display light source. Similar to an LCD panel, an LCOS light source panel comprises a two-dimensional array of cells filled with liquid crystals that are twisted and oriented in response to a control voltage. However, using an LCOS light source, the cells are directly grafted onto a reflective silicon chip. When the liquid crystal is twisted, the polarization of the light is changed or not changed after reflection from the mirror surface below. This, together with the polarization beam splitter, causes modulation of the light waves and produces an image. Reflection technology means that the illumination and imaging beams share the same space. These two factors require the addition of special beam splitting optical elements to the module in order to enable simultaneous operation of the illumination and imaging functions. Adding such elements typically complicates the module, and some modules that use front coupling entry elements or folding prisms will become larger when an LCOS light source is used as a display light source. For example, Fig. 9 The embodiment of can be modified to accommodate an LCOS light source by inserting another beam splitter between the display source 64 and the beam splitter 66. However, this modified version may be problematic for systems with a relatively wide FOV where the focal length of the collimating module is shorter than the optical path of the light passing through the dual beam splitter structure.

[0055] To solve this problem, Fig.10As shown, a modified optical device 90 is provided in which only one reflective surface 84 is positioned adjacent to the surface 78 of the light guide 66. Therefore, the optical path through this light guide 66 is greatly shortened. As shown, an s-polarized light wave 92 emitted from the light source 94 enters the prism 96, reflects from the polarizing beam splitter 98 and illuminates the front surface of the LCOS light source 100. The polarization of the reflected light wave from the "bright" pixel is rotated to p-polarization, and the light wave then passes through the beam splitter 98, and therefore, passes through the polarizer 102 located between the prisms 96 and 66, and the polarizer 102 blocks the s-polarized light reflected from the "dark" pixel of the LCOS light source 100. The light wave then enters the prism 66 and passes through the second beam splitter 70, is coupled out of the prism through the surface 78 of the prism 66, passes through the quarter-wave retarder 80, is collimated by the collimating lens 82 at its reflective surface 84, returns to pass through the retarder 80 again, and passes through the surface 78 to enter the prism 66 again. The now s-polarized light wave reflects from polarizing beam splitter 70 and exits prism 66 through exit surface 86 attached to intermediate prism 54 .

[0056] Now back to Fig. 9 , wherein the viewer's eye 24 is located on the same side of the inclined edge 50 as the optical prism 66, and the size of the optical prism 66 extends mainly on the lower major surface 26 of the substrate 20 and only slightly on the upper surface 32. This slight extension can be achieved by appropriate design (for example, by slightly increasing the angle α of the inclined edge 50). sur3 ) can be completely eliminated.

[0057] However, for Fig.10 In the illustrated embodiment, the optical element 90 extends primarily over the lower surface 26 and the upper surface 32 of the substrate 20 .

[0058] like Fig.11A As shown, the collimation module is composed of Fig.10 This unique structure may be preferred for an optical system consisting of an optical assembly 90 having prisms 66 and 96. The optical assembly 90 is mounted between the eyeglass frame 104 and the base 20. In this case, the viewer's eye 24 is located on the opposite side of the inclined edge 50 of the base 20. The light wave is coupled into the base 20 toward the major surface 32 through the inclined edge 50, bounces from the surface 32 toward the partially reflective surface 22, and exits the base from the partially reflective surface 22 through the major surface 32 toward the viewer's eye 24. Although there is a forward extension 106 of the optical assembly 90 toward the front of the eyeglasses, the rearward extension 108 of the prism 96 is minimal, and the entire optical assembly 90 can be easily integrated into the frame 104 of the eyeglasses.

[0059] Fig. 11B Shown is based on Fig. 9A modification of the optical assembly is shown in which the viewer's eye 24 is located on the same side of the beveled edge 50 of the substrate 20. Light waves emitted from the optical assembly 90 are coupled into the substrate 20 through the beveled edge 50, enter the substrate 20 toward the major surface 26, bounce off the surface 26 toward the major surface 32, and continue from the major surface 32 toward the partially reflective surface 22, and exit the substrate through the major surface 32 toward the viewer's eye 24.

[0060] It is obvious to those skilled in the art that the present invention is not limited to the details of the embodiments listed above, and the present invention can be implemented in other specific forms without departing from the spirit or essential attributes of the present invention. Therefore, the embodiments herein are considered to be illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the appended claims rather than the foregoing description, and therefore all changes within the meaning and scope of the equivalents belonging to the claims are included in the claims.

[0061] Regarding the implementation methods including the above embodiments, the following technical solutions are also disclosed:

[0062] Item 1. An optical system comprising:

[0063] a light-transmitting substrate having at least two major surfaces and an edge;

[0064] an optical prism having at least a first surface, a second surface and a third surface for coupling a light wave having a given field of view into a substrate by total internal reflection;

[0065] at least one partially reflective surface in a substrate, the partially reflective surface being oriented non-parallel with respect to a major surface of said substrate for coupling light waves out of said substrate;

[0066] At least one of the edges of the substrate is inclined at an oblique angle relative to the major surface;

[0067] The second surface of the prism is positioned adjacent to the inclined edge of the substrate, and

[0068] The portion of the substrate located immediately adjacent to the inclined edge is substantially transparent,

[0069] Characterized in that a light wave enters the prism through a first surface of the prism, traverses the prism without any reflection, and enters the substrate through an inclined edge.

[0070] Item 2. An optical system according to Item 1, wherein the field of view is defined by a minimum angle and a maximum angle of light waves coupled into the substrate.

[0071] Item 3. An optical system according to Item 2, wherein the angle between the inclined edge of the substrate and the normal to the major surface of the substrate is greater than the maximum angle of the field of view.

[0072] Item 4. An optical system according to Item 2, wherein the angle between the third surface of the prism and the normal to the main surface of the substrate is less than the minimum angle of the field of view.

[0073] Item 5. An optical system according to Item 1, wherein the first surface of the prism is substantially orthogonal to the intermediate wave of the light waves.

[0074] Item 6. An optical system according to Item 1, wherein the light waves coupled in from the field of view substantially cover the entire major surface of the substrate without forming any stripes or gaps.

[0075] Item 7. The optical system according to Item 1 further includes a collimation module.

[0076] Item 8. An optical system according to Item 7, wherein the collimation module is composed of a light wave transmitting material and has at least one light wave entry surface, at least one light wave exit surface, and multiple external surfaces.

[0077] Item 9. The optical system of Item 8, wherein the first surface of the prism is positioned adjacent to an exit surface of the collimating module.

[0078] Item 10. The optical system of Item 8, wherein the collimation module comprises:

[0079] at least one light wave reflecting surface carried by the optical device and located at one of said outer surfaces;

[0080] at least one retarder carried by the optical device and located on at least a portion of the outer surface;

[0081] at least one lightwave collimating component covering at least a portion of at least one of the retarders, and

[0082] At least one light wave polarization beam splitter is disposed at an angle to at least one of the light wave entrance or exit surfaces.

[0083] Item 11. The optical system according to Item 7 further comprises a display light source.

[0084] Item 12. The optical system of Item 11, wherein light waves emitted from the display source are collimated by a collimation module and coupled into the substrate through a prism.

[0085] Item 13. An optical system according to Item 1, wherein the refractive index of the prism is similar to the refractive index of the substrate.

[0086] Item 14. An optical system as described in Item 1, wherein the refractive index of the prism is different from the refractive index of the substrate.

[0087] Item 15. The optical system of Item 1, wherein a refractive index of the prism is substantially different from a refractive index of the collimating module.

[0088] Item 16. An optical system as described in Item 1, wherein the light waves are coupled out of the substrate through at least one partially reflecting surface and enter the viewer's eye.

[0089] Item 17. An optical system according to Item 16, wherein the viewer's eyes are located on the same side of the inclined edge of the substrate.

[0090] Item 18. An optical system according to Item 16, wherein the viewer's eye is located on the opposite side of the inclined edge of the substrate.

[0091] Item 19. The optical system of Item 16, wherein the collimation module extends substantially beyond both major surfaces of the substrate.

Claims

1. An optical system, comprising: a light-transmitting substrate having at least two parallel major surfaces and an edge; At least one of the edges of the substrate is inclined at an inclination angle relative to the major surface, an optical prism having at least a first surface, a second surface and a third surface for coupling light waves having a given field of view into the substrate, wherein the first surface and the second surface form a narrow portion of the optical prism; an optical arrangement for coupling light waves out of said substrate; The second surface of the prism is positioned adjacent to the inclined edge of the substrate, and wherein the narrow portion of the optical prism is positioned adjacent to the narrow portion of the inclined edge, and the light wave enters the prism through a first surface of the prism, traverses the prism without any reflection, and thus passes through the inclined edge into the substrate, wherein the field of view is defined by a minimum angle and a maximum angle of the light wave coupled into the substrate relative to a normal to the main surface, wherein the angle between the inclined edge of the substrate and the normal to the main surface of the substrate is greater than or equal to the maximum angle of the field of view, and the angle between the third surface of the prism and the normal to the main surface of the substrate is less than or equal to the minimum angle of the field of view, The size of the second surface of the prism directly contacting the inclined edge of the substrate satisfies the following relationship: The angle between the intermediate wave of the image in the substrate and the normal to the plane of the main surface is α in , the deviation of the maximum angular field of view within the substrate from the intermediate wave field of view is defined as Δα, and d is the thickness of the substrate, and Wherein, the first surface extends beyond the thickness of the substrate.

2. The optical system according to claim 1, wherein: The first surface of the prism is substantially orthogonal to the intermediate wave of the light waves.

3. The optical system according to claim 1, wherein: The light waves coupled in from the field of view cover substantially the entire major surface of the substrate without forming any stripes or gaps. The optical system according to claim 1 , further comprising a collimation module.

5. The optical system according to claim 4, wherein: The collimating module is composed of a light wave transmission material and has at least one light wave incident surface, at least one light wave exit surface and a plurality of outer surfaces.

6. The optical system according to claim 5, wherein: The first surface of the prism is positioned adjacent to the exit surface of the collimating module.

7. The optical system according to claim 5, wherein: The collimation module comprises: at least one light wave reflecting surface carried by the optical device and located at one of said outer surfaces; at least one retarder carried by the optical device and located on at least a portion of the outer surface; at least one lightwave collimating component covering at least a portion of at least one of said retarders, and At least one light wave polarization beam splitter is disposed at an angle to at least one of the light wave incident surface or the light wave exit surface.

8. The optical system of claim 4, further comprising a display light source.

9. The optical system according to claim 8, wherein: The light waves emitted from the display source are collimated by the collimating module and coupled into the substrate through the prism.

10. The optical system according to claim 1, wherein: The refractive index of the prisms is similar to the refractive index of the substrate.

11. The optical system according to claim 1, wherein: The refractive index of the prism is different from the refractive index of the substrate.

12. The optical system according to claim 1, wherein: The prism has a refractive index that is substantially different from a refractive index of the collimating module.

13. The optical system according to claim 1, wherein: The substrate comprises at least one partially reflective surface, and the light waves are coupled out of the substrate through the at least one partially reflective surface and into the eye of a viewer.

14. The optical system according to claim 13, wherein: The viewer's eyes are located on the same side of the sloped edge of the substrate.

15. The optical system according to claim 13, wherein: The viewer's eyes are located on the opposite side of the sloped edge of the substrate.

16. The optical system according to claim 13, wherein: The collimation module extends substantially beyond both major surfaces of the substrate.

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