TWI614527B - Compact head-mounted display system having uniform image - Google Patents

Abstract

An optical device includes an optical transmission substrate having an input aperture, an output aperture, at least two major surfaces, and an edge, and an optical component for coupling light waves into the substrate with total internal reflection, at least a portion of the reflective surface Located between the two major surfaces of the light transmitting substrate to partially reflect light waves out of the substrate, a first transparent plate having at least two major surfaces, one of the major surfaces of the transparent plate being optically attached a main surface of the light transmitting substrate to define an interface plane, and a light-shielding layer disposed on the interface plane between the substrate and the transparent plate, wherein the light wave system coupled to the interior of the light transmitting substrate is The interface plane partially reflects and partially passes through the interface plane.

Description

Small head-mounted display system with consistent image

The present invention relates to a substrate-oriented optical device, and more particularly to a device comprising a plurality of reflective surfaces carried by a common light-conducting substrate, also referred to as a light-guide optical element (LOE). .

The invention can be implemented in a variety of imaging applications, such as head-mounted displays and heads-up displays, mobile phones, small displays, stereo (3-D) displays, small beam expanders, and non-image applications such as flat panel indicators, small lighting And scanner.

An important application for small optical components is a head-mounted display, in which an optical module is used as an image mirror and a connector, in which a two-dimensional display is imaged at infinity and reflected to a viewing. The eyes of the person. The display can be directly obtained from a spatial light modulator (SLM), such as a cathode ray tube (CRT), a liquid crystal display (LCD), an organic light emitting diode. An organic light emitting diode array (OLED) or a scanning source and the like are indirectly obtained by a relay lens or a fiber bundle. The display includes an array of elements (pixels) imaged at infinity by a collimating mirror and transmitted into the viewer's eye by a reflective or partially reflective surface, the reflective or partially reflective surface being either non-perspective or The connector of the application can be seen through. A conventional free-space optical module is usually used to achieve the above object. However, when the field-of-view (FOV) of the system increases, such conventional optical modules have become Large and too heavy, so even a moderately priced device can't. This is a major drawback of all types of displays, especially in head-mounted applications where the system must be as lightweight and compact as possible.

Efforts to miniaturize have resulted in a number of different complex optical solutions, all of which, on the one hand, are still not small enough for most practical applications, and on the other hand have to bear major obstacles in terms of manufacturability. In addition, the eye-motion-box (EMB) of the optical viewing angles obtained from these designs is typically very small, typically less than 8 mm. Thus, even if the optical system is only slightly moving relative to the viewer's eye, the performance of the optical system is extremely sensitive and does not allow for sufficient pupil movement for reading text conveniently from the display.

Included in PCT Patent Publication No. WO01/95027, WO03/081320, WO2005/024485, WO2005/024491, WO2005/024969, WO2005/124427, WO2006/013565, WO2006/085309, WO2006/085310, WO2006/087709, WO2007/054928, The teachings of WO2007/093983, WO2008/023367, WO2008/129539, WO2008/149339, WO2013/175465, and Israel Patent Publication Nos. IL 232197, IL 235642, IL 236490, and IL 236491 are all in the name of the applicant and Quoted in this case.

The present invention facilitates the construction and fabrication of very small lightguide optical elements, particularly for head mounted displays, among other applications. The present invention achieves a relatively wide field of view and a relatively large eye movement box value. The resulting optical system provides a large, high-quality image and also allows for large movements of the eye. The optical system provided by the present invention is particularly advantageous because it is substantially smaller than the prior art solutions, and it can even be easily incorporated into a specially configured optical system.

Further applications of the present invention are provided for mobile handheld devices, such as mobile phones Wide field of vision. In today's wireless internet-access market, there is enough bandwidth for full video transmission. The limiting factor still lies in the display quality in the end user device. The need for mobility limits the physical size of the display, and the result is a direct display with poor image viewing quality. The present invention implements a display that has a very large virtual image but is physically very small. This is a key feature in mobile communications, especially for mobile Internet access, one of the main limitations of its practical implementation. Thus, the present invention enables digital content viewing of web pages of all formatted Internet sites in small handheld devices, such as mobile phones.

Accordingly, a primary object of the present invention is to alleviate the shortcomings of prior art small optical display devices and to provide other optical components and systems with improved performance in accordance with specific needs.

To this end, in accordance with the present invention, there is provided an optical device comprising a light transmitting substrate having an input aperture, an output aperture, at least two major surfaces and an edge, an optical component for coupling light waves into the base with total internal reflection a material, at least a portion of the reflective surface being located between the two major surfaces of the light transmitting substrate to reflect a portion of the light wave out of the substrate, a first transparent plate having at least two major surfaces, one of the major surfaces of the transparent plate Optically attached to a major surface of the light-transmitting substrate to define an interface plane, and a light-spreading layer disposed on the interface between the substrate and the transparent plate, wherein the light-transmitting substrate is coupled The internal light wave is partially reflected by the interface plane and partially passes through the interface plane.

〔this invention〕

16‧‧‧First reflective surface

18‧‧‧ Collimation display

20‧‧‧ planar substrate

20'‧‧‧Substrate

22‧‧‧Partial reflective surface

22a‧‧‧Partial reflective surface

22b‧‧‧Partial reflective surface

22c‧‧‧Partial reflective surface

22n‧‧‧reflective surface

24‧‧‧ eyes

25‧‧‧瞳孔

26‧‧‧ Lower surface

27‧‧‧ upper surface

28‧‧‧ Direction

30‧‧‧ Direction

80‧‧‧Light

82‧‧‧ points

84‧‧ points

86‧‧‧ points

88‧‧‧Light

90‧‧‧Reflection

100‧‧‧ line

102‧‧‧ points

104‧‧‧Light

106‧‧‧ points

108‧‧‧Light

110‧‧‧ points

112‧‧‧ single plane light waves

114‧‧‧Special perspective

120‧‧‧Transparent board

120’‧‧‧Transparent insert

122‧‧‧Light

124‧‧‧Light

126‧‧ points

128‧‧‧ points

132‧‧‧ points

134‧‧ points

136‧‧‧Light

140‧‧‧Light

142‧‧‧Light

144‧‧‧Reflected light

146‧‧‧reflected light

148‧‧ points

150‧‧ points

152‧‧‧ rays

154‧‧‧Light

156‧‧‧ plane wave

158‧‧ ‧ boundary line

160‧‧‧Out of light

162‧‧‧Out of the light

164‧‧‧Light

165‧‧‧Light

166‧‧‧Spectral coating

167‧‧‧Intersection plane

168‧‧‧Light

170‧‧‧Light

172‧‧ points

174‧‧ points

176‧‧‧Out of the light

178‧‧‧Out of the light

180‧‧ ‧ junction point

182‧‧ ‧ junction point

184‧‧‧reflecting light

186‧‧‧ Reflected light

188‧‧‧Light

190‧‧‧Light

192‧‧ points

194‧‧ points

196‧‧ points

198‧‧ points

200‧‧‧Light

202‧‧‧Light

204‧‧‧Light

206‧‧‧Light

208‧‧‧Transparent board

210‧‧‧Intersection plane

212‧‧‧Light

214‧‧‧Light

215‧‧ points

216‧‧ points

217‧‧ points

218‧‧‧reflecting light

220‧‧‧reflected light

222a‧‧‧Partial reflective surface

222b‧‧‧Partial reflective surface

230‧‧‧diffractive components

232‧‧‧Diffractive components

234‧‧‧Light

236‧‧‧Light

238‧‧‧Substrate

240‧‧‧Right edge

242‧‧‧Transparent board

244‧‧‧ upper surface

246‧‧‧ Junction surface

In _in ‧‧‧ falls into the corner

D _n ‧‧‧ bright hole

T‧‧‧ thickness

The present invention has been described in connection with the preferred embodiments of the invention, and the description

For the detailed description of the specific reference figures, it should be noted that the details are shown by way of example only and for the purpose of the illustrative discussion of the preferred embodiments of the invention, instruction of. In this regard, the structural details of the present invention are not intended to be exhaustive. The description made in conjunction with the figures is intended to be a guide for those skilled in the art to understand how the several forms of the invention are actually implemented. lead.

In the drawings: FIG. 1 is a side view of an exemplary prior art light guiding optical element; FIGS. 2A and 2B are detailed cross-sectional views of an exemplary array of selective reflective surfaces; FIG. 3: Dimorphism according to the present invention A simplified cross-sectional view of a reflective surface that illuminates the light; FIG. 4 is a cross-sectional view of an exemplary array of selective reflective surfaces attached to the edge of the substrate; FIG. 5 is a simplified cross-sectional view of the reflective surface in accordance with the present invention Showing the actual effective aperture of the surface; Figure 6: showing the effective aperture size of the reflective surface as a function of the angle of illumination for an exemplary lightguide optical element; Figure 7: depicting one from three different viewing angles A detailed cross-sectional view of the reflectivity of an exemplary array of reflective surfaces is selected; FIG. 8 is a diagram showing the required distance between two adjacent reflective surfaces as a function of the angle of illumination for an exemplary lightguide optical element; Figure 9: Another simplified cross-sectional view of a reflective surface of the invention having diffracted illumination; FIG. 10: a cross-sectional view of an exemplary array of selective reflective surfaces having an interposed transparent plate attached to the edge of the substrate Figure 11 is another schematic cross-sectional view of a reflective surface having dichromatic illumination rays in accordance with the present invention, wherein the two illuminations are reflected by a two-part reflective surface; Figure 12: Dichoelectric illumination according to the present invention A further simplified cross-sectional view of the reflective surface of the light, wherein the two light rays are remotely coupled into the light guiding optical element and coupled to the light guiding optical element at close distances; 13A and 13B are schematic cross-sectional views of a spectroscopic surface embedded in a light guiding optical element; Fig. 14 is a graph showing the reflectance of a spectroscopic surface as a function of incident angle for a representative angle sensitive coating and S polarized light waves. Figure 15: Another reflectivity plot for a representative angle sensitive coating and S-polarized light, a split surface as a function of angle of incidence; Figure 16: Two-phase split-beam surface embedded in a light-guide optical element BRIEF DESCRIPTION OF THE DRAWINGS FIG. 17 is another schematic cross-sectional view of a light splitting surface embedded in a light guiding optical element, wherein a partially reflective surface is formed inside the transparent attaching plate; and FIGS. 18A and 18B are embedded in a Yet another simplified cross-sectional view of an embodiment of a light splitting surface within a light directing optical element, wherein the coupling into and the coupling emitting element is a diffractive optical element.

Figure 1 is a cross-sectional view showing a light guiding optical element (LOE) of the present invention. The first reflective surface 16 is illuminated by a collimated display 18 from a light source (not shown) that is located behind the device. The reflective surface 16 reflects incident light from the source such that the light falls into a planar substrate 20 with total internal reflection. After several reflections of the surfaces 26, 27 of the substrate, the falling light waves reach an array of partially reflective surfaces 22 that couple light from the substrate into a viewer having a bore 25. Eye 24. Here, the input surface of the light guiding optical element will be defined as the surface into which the input light wave enters, and the output surface of the light guiding optical element will be defined as the surface from which the falling light wave exits the light guiding optical element. In addition, the input aperture of the light guiding optical element to be mentioned is the portion through which the input light wave actually passes through the input surface when entering the light guiding optical element, and the output aperture of the optical guiding optical element mentioned is referred to as the output. Light waves are passed through the portion of the output surface as they exit the lightguide optical element. In the embodiment of the light guiding optical element illustrated in FIG. 1, the input and output surfaces both overlap the lower surface 26, but the input and imaging light waves are located on opposite sides of the substrate or at the edge of the light guiding optical element. One of the other configurations can also be understood. If the central light wave of the light source is coupled out of the substrate 20 in a direction perpendicular to the surface 26 of the substrate, the partially reflective surface 22 is planar, and the off-axis angle of the coupled light wave within the substrate 20 ) is α _in , then the angle between the reflective surface and the normal to the substrate plate is:

As shown in Fig. 1, the falling light reaches the reflecting surface by two distinct directions 28,30. In this embodiment, the falling light reaches the partially reflective surface 22 after an even number of reflections from the substrate surface 26, 27 along one of the directions 28, wherein the falling light and the reflective surface The incident angle β _ref between the normals is:

The falling light reaches the reflective surface after the odd-numbered reflections from the substrate surface 26, 27 in the second direction 30, wherein the off-axis angle is α' _in = 180° -α _in and is between The angle of incidence between the incoming light and the normal to the reflective surface is: The negative sign indicates that the falling light is incident on the back surface of the partially reflective surface 22.

As shown in the first figure, for each reflective surface, each ray first reaches the surface in that direction 30, some of which illuminate the surface again in direction 28. In order to avoid unwanted reflections and ghosting, it is important to ignore the reflectance of the light that illuminates the surface along the second direction 28.

The actual effective area of each reflective surface is an important issue that must be considered. The potential inconsistency in imaging may occur due to the different reflection order of the distinct rays reaching each of the selective reflecting surfaces: some rays do not reach the pre-positional interaction with the selective reflecting surface; other rays pass through one or Arrived after multiple partial reflections. This effect is shown in Figure 2A. For example, assuming α _in = 50°, the ray 80 intersects the first partially reflective surface 22 at point 82. The angle of incidence of the light is 25° and a portion of the energy of the light is coupled out of the substrate. The ray then intersects the same selected partial reflective surface at an incident angle of 75° at point 84 with no significant reflection, and thereafter intersects again at point 86 at an angle of incidence of 25°, at which point the other portion of the energy of the ray The substrate is coupled out. Conversely, the ray 88 depicted in FIG. 2B will only undergo a single reflection 90 on the same surface. Further multiple reflections occur on other partially reflective surfaces.

Figure 3 illustrates this non-uniformity in a detailed cross-sectional view of the partially reflective surface 22 that couples light that exits the substrate and enters a viewer's eye 24. As can be seen, the ray 80 is reflected by the upper surface 27 adjacent the line 100, which line 100 is the intersection of the reflective surface 22 and the upper surface 27. Since the light does not illuminate the reflective surface 22, its brightness remains the same, and it is incident on the surface 22 for the first time after the two outer surfaces have been reflected twice. At this point, the lightwave is partially reflected and the light 104 is coupled out of the substrate 20. With respect to other light rays, such as light 88 (which is just below light 80), it is first incident on surface 22 at point 106 before reaching the upper surface 27, wherein the light wave is partially reflected at point 106 and the light 108 is coupled out of the substrate. Thus, when it is again reflected by the outer surface 26, 27 after secondary reflection at the point 110 of the surface 22, the brightness of the coupled exit light is lower than the adjacent light 104. Thus, all rays that have the same coupling angle of incidence as the ray 80, i.e., to the left of the point 102 when the surface 22 is reached, have a lower brightness. Thus, for this particular coupled incident angle, the reflectivity from surface 22 is indeed darker at the left side of point 102.

The above differences in multipath crossover effects are difficult to fully compensate, however, in fact, the human eye will allow significant changes in brightness and thus remain undetected. For near-eye display, the eye combines light from a single perspective and focuses it on a point on the retina. Since the response curve of the eye is a logarithmic curve, any small changes in the brightness of the display will not be noticed. Therefore, even if the brightness is not uniform in the display, the human eye will feel a high quality image. The medium non-coherent situation required is already The components shown in Figure 1 are obtained. For systems with large fields of view and requiring large eye movement boxes, a relatively large amount of partially reflective surface is required to achieve the desired output aperture. Therefore, the non-uniformity of the multi-way intersection due to the large number of partially reflective surfaces becomes more pronounced, especially at a distance from the eye (e.g., head-up display) such that the inconsistency is unacceptable. In these cases, a more systematic approach is needed to overcome this inconsistency.

Since the "dark" portion of the partially reflective surface 22 has less contribution to coupling the falling light waves out of the substrate, its effect on the optical properties of the light guiding optical element can only be negative, ie, the system The output hole will have a darker portion and dark lines will appear in the image. However, each of the reflective surfaces does not coincide with the transparency of the light waves from the external picture. Thus, if an overlap is provided between the reflective surfaces to compensate for the darker portions of the output aperture, the light passing through the overlapping regions of the output image will experience twice the attenuation and the dark lines will appear in the external image. This phenomenon significantly reduces the effect of not only the display that is at a distance from the eye (for example, the head-up display) but also the effect of the near-eye display, so that it cannot be used.

Fig. 4 is a diagram showing an embodiment for solving this problem. Only the "bright" portions of the partially reflective surfaces 22a, 22b, and 22c are embedded in the substrate, that is, the reflective surfaces 22a, 22b, and 22c no longer intersect the lower major surface 26, but are not at the surface. That is to terminate. Since the ends of the reflective surface are adjacent one after another in the length of the light guiding optical element, there will be no gap in the projected image, and since the surface does not overlap, there will be no gap in the external view. . There are several methods for constructing the light guiding optical element. A transparent plate 120 having a thickness T is preferably attached to the effective area of the substrate by optical cementing. In order to utilize only the effective area of the reflective surface 22 in the correct manner, it is important to calculate the actual effective area of each partially reflective surface and the desired thickness T of the plate 120.

As shown in FIG. 5, in the plane of the reflecting surface 22n of the outer surface 26 of light holes in the D _n (in angle α _in the coupled into the function shown) as:

Since the fall angle α _in can be varied as a function of the field of view, it is important to correlate which angle each reflective surface 22n is associated with in order to calculate its effective aperture.

Figure 6 shows the effective hole as a function of the field angle under the following system parameters: substrate thickness d = 2 mm, substrate refractive index v = 1.51 and partial reflection surface angle α _sur = 64°. In the case of considering the viewing angle, it should be noted that the different portions of the image are derived from the distinct portions of the partially reflective surface.

Figure 7 illustrates this effect as a cross-sectional view of a miniature lightguide optical element display system based on the proposed structure. Here, a single planar light wave 112 representing a particular viewing angle 114 illuminates only portions of all of the arrays formed by the partially reflective surfaces 22a, 22b, and 22c. Thus, a nominal viewing angle is defined for each point on the partially reflective surface, and the effective area required for the reflective surface is calculated from this angle. The precise detailed design of the effective area of each of the partially reflective surfaces is performed as follows: for each particular surface, a ray is divided by the left edge of the surface to the indicated eye pupil 25 (due to Snell's law, Take the refraction into consideration). The calculated direction is set to the nominal incident direction, and the particular effective area is calculated from this direction.

As shown in Fig. 5, the exact value of the effective area of the reflective surface can be used to determine the different distances T between the bright portions of each reflective surface 22n and the lower surface 26. A larger effective area requires a smaller inter-surface distance. This distance represents the thickness of the plate 120 (Fig. 7) that should be attached to the lower surface of the light guiding optical element. As shown in Fig. 5, the distance T as a function of the coupling entry angle α _in is: T = d - D _n . Cot( α _sur ) (5)

Figure 8 illustrates the desired thickness T of the panel 120 as a function of the angle of illumination under the same parameters set forth in reference to Figure 6. Set the thickness T to the maximum calculated value to confirm It is worthwhile to protect the image to avoid the effect of dark lines. Setting the plate 120 that is too thick will result in the opposite effect, namely the appearance of bright lines in the image.

As shown in FIG. 9, the two rays 122, 124 are coupled inside the substrate 20. The two rays are partially reflected from points 126, 128 of surface 22a, respectively. However, only the ray 122 illuminates the point 130 of the second surface 22b and is partially reflected there, while the ray 124 sweeps across the surface 22b without any reflectivity. Thus, the brightness of the light 124 that illuminates the point 134 of the surface 22c is higher than the brightness of the light 122 at the point 132. Therefore, the brightness of the coupled ray 138 from point 138 is higher than the brightness of ray 136 that is coupled by point 132, and the sizing appears in the image. Therefore, the thickness T should be selected to an exact value to avoid dark lines and bright lines in the image.

As shown in Fig. 10, a possible embodiment for obtaining the desired structure is to construct an interposed substrate 20' wherein the thickness T of the plate 120 is based on the viewing angle and the two main substrates are not parallel. A complementary transparent insertion plate 120' is preferably attached to the substrate by optical glue in such a manner that the bonded substrate forms a complete rectangular parallelepiped, for example, the two outer major surfaces of the final light guiding optical element are mutually parallel. However, this method has some drawbacks. First, the manufacturing procedure of the inserted light guiding optical element is more complicated and difficult to handle than the manufacturing procedure of the parallel light guiding optical element. Moreover, this solution is effective for systems with small eye movement boxes that have a commensurate match between the viewing angle and the side positions on the substrate sheet. However, for systems with large eye sports boxes (i.e., the eye can move significantly along the side axis), there will be no good adjustment between the viewing angle and the actual thickness of the plate 120'. Therefore, it is possible to detect dark lines or bright lines in the image.

This occurrence of dark lines or bright lines is caused by the fact that the partially reflective surface in the light guiding optical element is not limited to the surface forming this effect. Referring to Figure 3, the brightness of the coupled ray 88 reflected twice by the surface 22a at point 110 is lower than the brightness of the ray 80 reflected only once by the surface 22a at point 102. Therefore, the brightness of the reflected wave 112 is lower than the brightness of the adjacent light ray 104. However, as shown in Fig. 11, not only the brightness of the reflected wave from the surface 22a is different, but also the brightness of the transmitted light rays 140 and 142 is different. Therefore, the reflected light from the surface 22b The brightness at 144 and 146 at points 148 and 150, respectively, will appear different in the same manner, and a dark line will also appear in this region of the image. Naturally, this difference between the rays will continue to extend into the next partially reflective surface of the lightguide optical element. Therefore, since each of the partially reflective surfaces produces respective dark lines and bright lines according to a precise incident angle, a large amount of dark lines and bright lines will accumulate in the light guiding optical element for a light guiding optical element having a large number of partially reflecting surfaces. The distal edge of the aperture is output, and thus the image quality will be severely degraded.

The source of non-uniformity of the image may be a non-uniformity of image waves coupled into the lightguide optical element. Generally, when there are slight differences in intensity on both sides of a light source, it will be difficult for the viewer to notice. The situation is completely different for images that are coupled into a substrate (ie, as in the lightguide optical element) and are gradually coupled out. As shown in Fig. 12, two rays 152 and 154 are located at the edge of the plane wave 156, which originates from the same point in the display source (not shown). Assuming that the ray 152 is less bright than the ray 154 due to an imperfect imaging system, this lack of quality will be difficult to detect by directly viewing the plane wave 156 due to the distance between the rays. However, this condition changes after being coupled into the light guiding optical element 20. When the ray 154 illuminates a reflective surface 16 that is just to the right of the boundary 156 between the reflective surface 16 and the lower major surface 26, the right ray 152 is reflected from the surface 16 and is totally reflected by the upper surface 27, and subsequently The lower surface 26 is located just to the left of the boundary line 158. Therefore, the light rays 152 and 154 conducted in the light guiding optical element 20 are adjacent. The two outgoing rays 160 and 162, which are derived from rays 152 and 154, respectively, and are reflected by surface 22a, thus have distinct brightness. However, unlike the input light wave 156, the two distinct light rays are adjacent, and the difference is perceived as dark lines in the image. The two rays 164, 165 will continue to conduct in the lightguide optical element alongside each other and will form a dark line at each of the locations where they will be coupled together. Naturally, the best way to avoid this inconsistency is to ensure that all light waves coupled into the lightguide optical element have consistent brightness throughout the input aperture of the entire field of view. This requirement can be extremely difficult to perform for systems with large fields of view and wide input holes.

As shown in Figures 13A and 13B, as previously described with reference to Figure 4, this non-uniform problem may be solved by attaching a transparent plate to one of the major surfaces of the lightguide optical element. However, in this embodiment, a beam splitting coating 166 is disposed on the interface plane 167 between the light guiding optical element 20 and the transparent plate 120. As shown in FIG. 13A, two rays 168 and 170 are coupled within the substrate 20. Only light 168 illuminates the point 172 of the first partially reflective surface 22a and is partially reflected there, and the ray 170 sweeps across the surface 22a without any reflectivity. Thus, assuming that the two rays have the same brightness when coupled into the lightguide optical element, the light 170 that is reflected upward by the lower major surface 26 has a higher brightness than the light 168 that is reflected downward by the upper surface 27. The two ray rays intersect at a point 174 at the interface plane 167. Each of the two intersecting light rays is partially reflected and partially passes through the cladding layer due to the spectral coating disposed thereon. Subsequently, the two rays exchange energy, and the exit rays 176 and 178 from the intersection 174 have similar brightness, which is substantially the average brightness of the two incident rays 168 and 170. In addition, the light is exchanged at two junctions 180 and 182 with two other rays (not shown). Due to this energy exchange, the two reflected rays 184 and 186 from surface 22b will have substantially similar brightness and the brightening effect will be significantly improved.

Similarly, as shown in FIG. 13B, two rays 188 and 190 are coupled to the interior of the substrate 20. However, only light 188 illuminates the point 192 of the first partially reflective surface 22a and is partially reflected there before being reflected by the upper surface 27. Thus, assuming that the two rays have the same brightness when coupled into the lightguide optical element, the light 190 reflected downward by the upper major surface 27 has a higher brightness than the light 188. However, the two rays intersect at a point 194 at the interface plane 167 where energy is exchanged. In addition, the two rays intersect at other points 196 and 198 at the beam splitting surface 167 with other rays. Thus, the rays 200 and 202 reflected from the surface 22a and the rays 204 and 206 reflected to the surface 22b will have substantially the same brightness, and thus the shading effect will be significantly reduced. This brightness uniformity improvement effect can also be achieved for dark lines and bright lines caused by non-uniform illumination of the input aperture of the light guiding optical element. Therefore, falling on the light guide The brightness distribution of the light waves inside the optical element is substantially more uniform at the output aperture of the light guiding optical element than at the input aperture.

As shown in Fig. 13A, the light rays 184, 186 reflected by the surface 22a intersect the beam splitting surface 167 before being coupled out of the light guiding optical element. Therefore, since the surface 167 must be transparent to the light leaving the substrate 20, and for light waves from the external picture in perspective (i.e., light waves that are partially reflected at a small angle of incidence through the plane 167 and at a higher angle of incidence) It is transparent, so a simple reflective coating cannot be easily applied to this surface. Typically, the passing incident angle is between 0° and 15°, and the partially reflected incident angle is between 40° and 65°. In addition, the absorption of the coating should be ignored as the light passes through the interface surface 167 multiple times as it travels inside the lightguide optical element. Therefore, a simple metal coating cannot be used, and a dielectric thin-film coating having high transparency must be used.

Figure 14 depicts the S-polarization reflectance curves as a function of the angle of incidence for three representative wavelengths in the bright-field region: 470 nm, 550 nm, and 630 nm. As shown, for S-polarized light waves, the required partial reflectance (between 45% and 55%) and small incident angle low reflectance (less than 5%) at 40 and 65 are obtained. It is possible. For P-polarized light waves, it is impossible to obtain substantial reflectance at incident angles of 40 and 65 due to the proximity angle (Brewster angle). Since the polarization of an image system based on a light-guide optical element is often S-polarized, the required beam splitter can be easily implemented. However, for a light wave from an external picture that is irradiated to the interface surface at a low incident angle and substantially unpolarized, since the spectral coating must be substantially transparent, the coating should also have a small incident angle and low reflection for the P-polarized light wave. Rate (less than 5%).

The combination of several different component components of the lightguide optical element 20 still poses a problem. Since the manufacturing process generally involves a bonded optical component, and the required angle sensitive reflective coating is disposed on the surface of the lightguide only after the body of the lightguide optical component 20 is completed, it is impossible to use a habit that may damage the bonded region. Know the thermal coating process. New thin film technology and ion assisted coating The (ion-assisted coating) procedure can also be used for cold processes. Eliminating the need for heating components allows the cemented components to be safely routed. Another option is to simply lay the desired coating on the transparent substrate 120 adjacent the lightguide optical element 20 using a conventional thermal coating procedure and then adhere it to the appropriate location. Obviously, this other method is only applicable when the transparent substrate 120 is not too thin, otherwise it may be deformed during the coating process.

When designing a splitting mechanism as described above, some issues should be considered:

a. since the light falling within the light-guide optical element is not only completely reflected by the major surfaces 26 and 27 but also by the internal partial reflection interface plane 167, all three planes will be parallel to each other to ensure The coupled light will maintain its original coupling entry direction inside the lightguide optical element.

b. As shown in Figures 13A and 13B, the transparent plate 120 is thinner than the original light guiding optical element 20. Unlike the uncoated panels in Figures 7 through 10 (where the thickness of the panel 120 is important for consistency optimization), the thickness of the panel can be based on other considerations. select. On the one hand, thicker panels are easier to manufacture, lay and adhere. On the other hand, with a thinner plate, the effective volume of the light wave that the light guiding optical element 20 actually couples to emit the substrate will be higher for a given substrate thickness. Moreover, the ratio between the thickness of the plate 120 and the lightguide optical element 20 may affect the energy exchange process within the substrate.

c. Generally, for a spectroscope designed for full color images, the reflectance curve for the entire brightfield region should be as uniform as possible to eliminate chromatic effects. However, in the structure illustrated in the present invention, since various rays intersect multiple times before being coupled out of the light guiding optical element 20, this need is no longer necessary. Naturally, the spectroscopic coating should take into account the entire wavelength spectrum of the coupled image, but the chromatic flatness of the partially reflective curve can be accommodated in accordance with various parameters of the system.

d. The reflectance-transmittance ratio of the spectral coating layer is not necessarily 50% to 50%. Other ratios can be used to achieve the energy exchange required between the darker and brighter rays. Furthermore, as shown in Fig. 15, a simpler spectral coating can be used, wherein the reflectance is increased from 40% incident angle of 35% to 65° incident angle of 60%.

e. The number of splitting surfaces added to the light guiding optical element is not limited to one. As shown in FIG. 16, another transparent plate 208 can be adhered to the upper surface of the light guiding optical element, wherein a similar spectral coating is disposed on the interface plane 210 between the light guiding optical element 20 and the upper plate 208. Upper to form an optical device having a dichroic surface. Here, the two unequal rays 212 and 214 intersect at a point 215 of the disposed interface plane 210, along with other intersections with other rays at points 216 and 217. This is outside the intersection on the lower beam splitting plane 167. Therefore, it is expected that the uniformity of the reflected rays 218 and 220 will be even better than those of Figures 13A and 13B. Naturally, the manufacturing method of a light guiding optical element having a dichroic interface plane is more complicated than having only a single plane. Therefore, it is only necessary to consider the system where the non-conformity problem is very serious. As previously mentioned, all four reflective surfaces and planes 26, 27, 167 and 210 should be parallel to each other.

f. The transparent plate 120 need not be fabricated using the same optical material as the lightguide optical element 20. In addition, the light-guiding optical element can be made of a tannic acid material for the purpose of eye safety, and the transparent layer can be made of a polymer material. Naturally, special care must be taken to ensure the optical quality of the outer surface and to avoid deformation of the transparent sheet.

g. At this point it is assumed that the transparent plate is completely empty. However, as shown in Fig. 17, partially reflective surfaces 222a and 222b can be fabricated inside the panel 120 to increase the available volume of the lightguide optical element. These surfaces should be completely parallel to the exit surfaces 22a and 22b and indeed face the same direction.

All the different variables of the above embodiment (for example, the thickness and optical material of the plate 120) The exact nature of the spectroscopic coating, the number of spectroscopic surfaces, and the location of the partially reflective surface within the lightguide optical element can have many different possible values. The exact values of these variables are determined by the different parameters of the optical system, as well as the particular requirements of optical quality and manufacturing cost.

Thus far, it is assumed that the light wave is coupled out from the substrate by being oriented at an oblique angle with respect to the major surface and generally covering the partially reflective surface of a dielectric coating. However, as shown in Fig. 18A, a system uses diffractive elements 230 and 232 to couple into and out of the substrate, respectively. The same issue of consistency discussed earlier should also be relevant to this structure. As illustrated, the two rays 234 and 236 from the same point of the display source are coupled into the substrate 238 away from the two edges of the coupling entry element 230. The light rays are coupled out of each other by the coupling injection elements 232. Therefore, any difference between the rays will be easily perceived in the coupled exit wave. In addition, in order to obtain a consistent coupled emission image, the diffraction effect of the coupling ejection element 232 is gradually increased. Thus, distinct rays from the same point element may pass through the distinct locations of the element 232 before coupling out of the element, and thus will have different brightness in the image. Another source of non-uniformity can be caused by the ray 234 being partially circulated out of the substrate at the right edge 240 of the grid 232, and the ray 236 is incident on the lower surface just to the left of the grid. The fact of this diffraction. Thus, for all of the coupled exit locations within the grid 232 of the two adjacent rays 234 and 236, the ray 236 will have a higher brightness and the difference will be readily detectable.

Figure 18B depicts a similar approach to solving these issues. As shown, a transparent plate 242 is adhered to the upper surface 244 of the substrate 238, wherein the interface surface 246 covers a beam splitting layer similar to the coating described above.

18‧‧‧ Collimation display

20‧‧‧ planar substrate

22a‧‧‧Partial reflective surface

22b‧‧‧Partial reflective surface

22c‧‧‧Partial reflective surface

26‧‧‧ Lower surface

120‧‧‧Transparent board

T‧‧‧ thickness

Claims (25)

An optical device comprising: an optical transmission substrate having an input aperture, an output aperture, at least two major surfaces and an edge; an optical component for coupling light waves into the substrate with total internal reflection; at least a portion of the reflection a surface between the two major surfaces of the light transmitting substrate to reflect light waves out of the substrate; a first transparent plate having at least two major surfaces, one of the major surfaces of the transparent plate being optical Attached to a major surface of the light-transmitting substrate to define an interface plane; and a light-distributing layer disposed on the interface between the substrate and the transparent plate, wherein the light-transmitting substrate is coupled An internal light wave is partially reflected by the interface plane and partially passes through the interface plane; wherein the light wave coupled to the substrate by the partially reflective surface passes through the interface surface substantially without any significant reflectivity. The optical device of claim 1, wherein the major surface of the light transmitting substrate is parallel to the major surface of the first transparent plate. The optical device of claim 1, wherein the spectral coating has a substantial reflectance at a large incident angle and a low reflectance at a small incident angle. The optical device of claim 3, wherein the spectral coating has a low reflectance at an incident angle between 0° and 15° and a substantial reflectance at an incident angle greater than 40°. The optical device of claim 3, wherein the spectral coating has a reflectivity higher than 35% at an incident angle higher than 40° and less than 10% at an incident angle lower than 15°. Reflectivity. The optical device of claim 1, wherein the spectral coating is disposed on a major surface of the light transmitting substrate. The optical device of claim 6, wherein the spectral coating is disposed using a cold coating process. The optical device of claim 1, wherein the spectroscopic coating is disposed on one of the surfaces of the first transparent plate. The optical device of claim 3, wherein the reflectance of the spectroscopic coating is substantially constant at an incident angle of more than 40° and less than 60°. The optical device of claim 3, wherein the reflectance of the spectral coating is substantially non-determined at an incident angle greater than 40°. The optical device of claim 10, wherein the reflectance of the spectral coating increases by a function at an incident angle greater than 40°. The optical device of claim 3, wherein the reflectance of the spectroscopic coating is substantially uniform at a large incident angle for the entire bright-view region. The optical device of claim 1, wherein the transparent plate is thinner than the light transmitting substrate. The optical device of claim 1, further comprising a second transparent plate optically attached to the other major surface of the light transmitting substrate to define a second interface plane. The optical device of claim 14, wherein a light-splitting layer is disposed on the second interface plane. The optical device of claim 15, wherein the spectral coating has a substantial reflectance at a large incident angle and a low reflectance at a small incident angle. The optical device of claim 1, wherein the light transmitting substrate and the transparent plate are made of the same optical material. The optical device of claim 1, wherein the light transmitting substrate and the transparent plate are made of two different optical materials. The optical device of claim 1, wherein the transparent plate is made of a tannic acid material. production. The optical device of claim 1, wherein the optical component for coupling light waves into the substrate is a diffractive component. The optical device of claim 1, wherein at least a portion of the reflective surface between the two major surfaces of the light transmitting substrate is a diffractive element. The optical device of claim 1, wherein at least a portion of the reflective surface between the two major surfaces of the light transmitting substrate is oriented at an oblique angle relative to the major surface. The optical device of claim 22, wherein the at least a portion of the reflective surface is covered by a dielectric coating. The optical device of claim 1, comprising a plurality of partially reflective surfaces between the two major surfaces of the light transmitting substrate, wherein the partially reflective surfaces are parallel to each other. The optical device of claim 1, wherein the light distribution of the light wave coupled to the interior of the substrate is uniform at the output aperture of the substrate than the input aperture.