GB2386699A

GB2386699A - Head Mounted Display with Prism and Cut Waveguide

Info

Publication number: GB2386699A
Application number: GB0309953A
Authority: GB
Inventors: Young-Ran Song
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2001-04-30
Filing date: 2002-04-11
Publication date: 2003-09-24
Anticipated expiration: 2022-04-11
Also published as: GB2386700A; GB2386698B; GB2386699B; GB2386697B; GB2386700B; GB2386698A; GB2386697A

Abstract

A wearable display device having a display panel 1300 includes a waveguide 1320 for transmitting a signal. A prism 1310 is attached to an end of the waveguide 1320 in order to emit a signal transmitted via the waveguide 1320. The waveguide 1320 end on which the signal is incident from the display panel 1300 being cut at a predetermined angle. The predetermined angle may be equal to the angle of total internal reflection. An optical device 1330 may also be placed on the prism in order to magnify the transmitted signal.

Description

- 1 - 2386699

Wearable Display Device Description

The present invention relates to a wearable display device.

Conventional optical display systems used in the military, in medicine and for personal entertainment, which are generally known as head (or helmet) mounted display (HMD) systems, have been designed for users to see video signals magnified via eyeglass-type, goggle-type or helmet-type wearable devices. This personal 10 display system allows users to receive video information while moving from place to place. Figure 1 shows one example of an HMD. Referring to Figure 1, the HMD comprises conventional eyeglasses 100 and an image-driving unit 110 that is 15 attached at the centre of the eyeglasses 100. Because of the image-driving unit 110, the HMD is bulky, heavy and inelegant. The large volume and heaviness of the image-driving unit 110 is due to the number of optical elements constituting the unit. 20 Figure 2 shows the structure of a conventional HMD. Referring to Figure 2, the HMD includes an image-driving unit 200, a display panel 210 such as a liquid crystal display (LCD) panel and an optical system 220. The image-driving unit 200 stores an image signal received from exterior sources such as a personal computer or video device (not shown), processes the received signal and displays it on the display 2s panel 210. The optical system 220 generates a virtual image of the image displayed on the display panel 210 at a comfortable distance. The HMD may further include any wearable devices or cable for receiving image signals from an external source.

Figure 3 shows the general structure of the optical system 220 of the HMD of 30 Figure 2. Referring to Figure 3, a conventional optical system is composed of a collimating lens 300, an X prism 310, focusing lenses 320, fold mirrors 330 and ocular lenses (or magnifying lenses) 340. The collimating lens 300 collimates and propagates light (an image signal) emitted from the display panel or the lilies The X

- 2 prism 310 redirects the light received from the collimating lens 300 to both the right and the left. The focusing lenses 320 are separately placed on the right and left of the X prism 310 so that collimated light passing through the X prism 310 is focused.

The fold mirrors 330 change the direction of incident light so that the light focused s by the focusing lenses 320 travels toward the eyes of a user. The ocular lenses (or magnifying lenses) 340 allow small image signals passing through the above-

described optical elements to appear to the eyes of the user. At this time, if an image signal transmitted through the ocular lenses 340 has colour, lenses for removing chromatic aberration must be used as the ocular lenses 340.

In a conventional HMD system, an optical system employs several optical elements to meet demanding design specifications. The optical elements include collimating

lenses, an X prism, focusing lenses, folder mirrors, ocular lenses and the like as described above. For this reason, it is difficult to manufacture the conventional 5 HMD systems. Even if the lenses and elements are designed precisely, additional difficulties in aligning the lenses and devices may occur. In addition, the conventional optical system is bulky and heavy due to the use of a plurality of optical devices, so that it is inconvenient for a person to wear the HMD and expensive to manufacture the HMD.

To solve the above problem, it is an aim of the present invention to provide a wearable display system that is simple to manufacture using a minimum number of optical devices.

25 According to the present invention, there is provided a wearable display apparatus comprising a prism, a source of modulated light positioned for directing light into the prism and an image magnifying element, which may be reflective or transmissive, positioned to receive light from the source of modulated light, wherein the prism, the source of modulated light and the image 30 magnifying element are configured such that light from the source of modulated light is subject to internal reflection in the prism en route to the image magnifying element.

- 3 Preferably, the source of modulated light comprises a light modulator, e.g. a liquid crystal display panel, for modulating a beam of light. More preferably, the light modulator is mounted to a face of the prism. Conveniently, a reflector may be included for directing light from an external light source through the light s modulator. Preferably, the prism comprises a rod-shaped element having an oblique face at one end and the light modulator is mounted at the oblique face. The image magnifying element may be mounted at a side face of the prism or at a further 10 oblique end face of the prism. More preferably, an oblique end face, at which the light modulator or the image magnifying element is mounted, is located on a projection from said rod-shaped element., O The light propagating from the source of modulated light to the image magnifying.

15 element may be subject to internal reflection in the prism a plurality of times.

The image magnifying element may comprise a holographic element.

l. U.. A binocular wearable display device may include two monocular display devices 20 according to the present invention and, preferably, the same prism is employed in each monocular display device.

Embodiments of the present invention, will now be described, by way of example with reference to Figures 4 to 13 of the accompanying drawings, in which: 2s Figure 1 is an exterior view of a conventional head mounted display (HMD); Figure 2 is a schematic diagram of a conventional HMD; Figure 3 is a schematic diagram of the optical system of the HMD of Figure 2; Figures 4A and 4B are views of the exterior of a wearable display system according to the present invention; 30 Figure 5 illustrates a first wearable display system according to the present invention; Figure 6 illustrates a second wearable display system according to the present invention:

- 4 - Figure 7 is a diagram for explaining parameters of a magnifying optical system which are needed in determining the size of a display panel, the size and position of a screen, an eye relief, a field of view (FOV) and the focus and size of a lens;

Figure SA and BB are views illustrating the requirements of a wearable display panel 5 according to the present invention; Figure 9 shows a first wearable display system according to the present invention; Figure 10 shows a second wearable display system according to the present invention; Figure 11 shows a third wearable display system according to the present invention; 10 Figure 12 shows a fourth wearable display system according to the present invention; and Figure 13 shows a fifth wearable display system according to the present invention.

Referring to Figures 4A and 4B, a wearable display system has a simple structure in 15 which a lens 400 and a display panel 410 are combined with each other. The wearable display system according to the present invention is thinner, lighter and smaller than conventional systems due to the use of a grating and a magnifying lens.

Thus, a wearable display system according to the present invention is easy and convenient to wear, like eyeglasses, and unlike existing bulky and heavy helmet-type 20 HMDs. Furthermore, the present invention provides a module-type wearable display system in which a module is capable of being attached to and detached from conventional eyeglasses. The exterior of the wearable display system illustrated in Figures 4A and 4B is just an example and a variety of thin, light and small wearable display systems having different exteriors can be realized.

A wearable display system according to the present invention can be manufactured in both binocular and monocular forms. A binocular type is designed for a user to look at a display image using both of his or her eyes, whereas a monocular type allows a user to look a display image using only one of his or her eyes.

First, a monocular-type wearable display system will be described.

r - D Referring to Figure 5, a wearable display system includes a display panel 500 which displays a signal processed in a predetermined way, a prism waveguide 510 and a magnifying lens 520. When a signal is incident on the waveguide 510 from the display panel 500, it enters and propagates through the waveguide 510. One end of 5 the waveguide 510, at which the display panel is located, is cut obliquely so that light from the display is totally internally reflected at an adjacent face of the waveguide 510 towards the magnifying lens 520 at the opposite face of the waveguide 510. The magnifying lens 520 produces a magnified image for the user.

lo Referring to Figure 6, another wearable display system further includes a reflector 600 in addition to the components shown in Figure 5. With the reflector 600, it is possible to easily control the position of an light source which emits light so that it is incident on the inclined end of the waveguide 510. In the wearable display system shown in Figure 6, light output from the light source is reflected from the reflector 15 600 and is transmitted through the inclined end of the waveguide 510 such that it is incident on the inner side of the waveguide 510 at a total internal reflection angle. --

If the light source is placed to one side of the user, it is possible to realize an eyeglass type display system having light sources on the arms of its frame...v,-

20 To realize the wearable display systems shown in Figures 5 and 6, the size of the magnifying lens 520, the number of times a signal undergoes total internal reflection in the waveguide 510, and the length and width of the waveguide 510 must be determined. 25 Figure 7 is a diagram for explaining the parameters of a magnifying optical field

which are needed for determining the size of the display panel, the size and location of the screen, the eye relief, the field of view (FOV), the focus and size of a lens

and so on. Referring to Figure 7, F denotes the focal length of a lens 700 corresponding to the magnifying lens 520 shown in [Figure 5 and D denotes the 30 diameter of the lens 700. Yo denotes the size of an object 710 that corresponds to the display panel 500 shown in Figure 5. So denotes a distance between the object 710 and the lens 700, which corresponds to the distance between the display panel 500 and the magnifying lens 520. So must be shorter than the focal distance Fof

- 6 the lens 700 so that an image of the object 710 is magnified for the eye of the user.

According to this optical principle, the path of a signal, which is incident upon and propagates in the waveguide 510, is designed to be shorter than the focal distance of the magnifying lens 520 in Figure 5. Yi denotes the size of a virtual image of the 5 object 710 to be seen by a user's eye 720 and Exis the size of the exit pupil of the user's eye 720. Le denotes the distance between the eye of the user 720 and the lens 700, i.e. eye relief, L' denotes a distance between the user's eye 720 and the virtual image Yi, and 8/2 denotes half of a field of view (FOV) defined below.

0 Sidenotes a distance between the virtual image and the lens 710 and the lens 700.

Hereinafter, we will explain a process of obtaining parameters for a magnifying lens using the above-described optical parameters. To determine the type of lens and the position of an object in Figure 7, the size Yo of an object' the size Woof a 15 virtual image, a distance L, between the virtual image and the eye of a user, the eye relief Le and the exit pupil Fix of the eye of a user must first be determined. Using these optical parameters, a magnification Mis obtained by the following expression (1) 20 M= Yi = Si (1) Yo So The distance So between the lens 700 and the object 710 can be measured by applying the obtained M value to the following expression (2): 25 So =-. . (2) Next, the focal distance fof the lens 700 is calculated using So and Si as follows: 1 - 1 = 1... (3)

So Si f

- 7 Then, the held of view (FOV) is calculated as follows: FO V,, = 2 tan 2L'.. (4) s The calibre D of the lens 700 is measured as follows: D tan 2 = 2L (5) Expression (5) is related to only a light signal that is incident upon the centre of the exit pupil, and therefore, the real diameters D of the lens 700 must be measured 0 considering the size of the exit pupil as follows: A, Hi,:. is? D = 2Le tan-+ Ex... (6) As described above, the particulars of a magnifying lens can be determined using 15 the above expressions.

Figures 8A and 8B are diagrams for explaining the design specifications of a

wearable display system according to the present invention. Referring to Figure 8B, an angle of incidence must be larger than a critical angle of total internal 20 reflection tic, and the length d/sin by of the inclined end of a waveguide must be greater than the length of the display panel. These conditions are expressed as follows: 6'> t) = sin'... (7) c n(wavegzlide) 25 where n (waveguide) denotes the refractive index of the waveguide 810. For instance, when the refractive index of the waveguide 810 is 1.49, the critical angle of total internal reflection is 42.2 degrees and thus, the angle of incidence must be greater than 42.2 degrees.

- 8 Figute 9 is a view of a binocular wearable display system according to the present invention. The binocular wearable display system includes a waveguide 900, a first display panel 910, a second display panel 920, a first magnifying lens 930 and a second magnifying lens 940. The principles and specifications of the wearable

5 monocular type display systems described above can be applied to the binocular wearable display system shown in Figure 9. Furthermore, two monocular-type wearable display systems, as shown in Figure 5, can be combined with each other to form a binocular wearable display system such as that shown in Figure 9. The waveguide 900 receives signals from the first and second display panels 910 and 10 920. Both ends of the waveguide 900 are diagonally cut at the same angle as the angle of total internal reflection so that the signals which are transmitted through both ends are reflected at the angle of total internal reflection once inside the waveguide. Display signals are perpendicularly incident on the inclined ends of the waveguide 900, reflected at the angle of total internal reflection in the waveguide 15 900 and propagate towards the centre of the waveguide 900. The first display panel 910 is attached to the left inclined end of the waveguide 900 to be incident on the inner wall thereof, and transmits a signal into the waveguide 900 at the angle of total internal reflection. The first magnifying lens 930 magnifies a signal which is reflected more than one time in the waveguide 900 and reaches the first magnifying 20 lens 930, to be seen by the left eye of a user. The second display panel 920 is attached to the right inclined end of the waveguide 900 and transmits a signal into the waveguide 900 at the angle of total reflection. The second magnifying lens 940 magnifies a signal which is reflected more than one time in the waveguide 900, to be seen by the right eye of a user. The first and second magnifying lenses 930, 940 25 may be hologram lenses that transmit a signal incident thereon at a predetermined angle (which is the predetermined angle of total internal reflection in this embodiment) in a direction which has recorded as a pattern on the hologram lens.

Figure 10 is a view of another binocular wearable display system according to the 30 present invention. The binocular wearable display system shown in Figure 10 has the same structure and function as the binocular wearable display system shown in Figure 9, but further includes first and second reflection plates 1010, 1020. The first and second reflection plates 1010 and 1020 extend from both ends of a

waveguide 1000 and reflect light from light sources at predetermined right and left directions of a user toward the inclined ends of the waveguide 1000, respectively.

The first and second reflection plates 1010,1020 reflect light from light sources placed so that the light is to be incident on the inclined ends of the waveguide 1000 s as collimating light. As shown in Figure 10, since light sources can be placed at either side of a user with the first and second reflection plates 1010 and 1020, it is possible to realize an eyeglass-type wearable display system having light sources at its frame arms.

10 Figure 11 is a view of a monocular-type wearable display system according to a third embodiment of the present invention. The wearable display system includes a display panel 1100 to display a signal processed in a predetermined way, a waveguide 1110 and an optical device 1120.. -

15 The waveguide 1110 for guiding the propagation of the light from the display panel 1100 has two ends that are diagonally cut at a predetermined angle that makes the incident signal be reflected at the angle of total internal reflection from an inner.

wall of the waveguide 1110; one end on which a signal is incident and another end:; through which the signal is emitted. The signal is incident from the display panel 20 1100 attached to an end of the waveguide 1110 which is inclined at the angle of total internal reflection, transmitted into the waveguide 1110 and repeatedly -.

reflected at the angle of total reflection to propagate through the waveguide 1110.

The optical device 1120 is a diffractive optical element or a holographic optical element and magnifies a signal it receives after transmission through the waveguide 25 1110 to form a magnified image in the eye of a user who is positioned within a predetermined focal distance. Here, the optical device 1120 is illustrated as a reflection type, but it may be a transmittance type that forms an image of a signal at the opposite side of the waveguide 1110 illustrated in Figure 11.

30 When signals emitted from the display panel propagates through the waveguide 1110 and are output through the optical device 1120, propagation distances of the incident signals may be different from each other, thus generating aberration. To prevent the aberration, the end of the waveguide 1110 on which a signal is incident

must have the same inclination angle as the end of the waveguide 1110 from which a signal is emitted, so that the propagation distances of the incident signals are the same. s The basic principles of the magnifying optical system explained with reference to Figure 7 are applied in deterr. uning the specifications of the waveguide 1 1 ID, i.e.,

the angle of its inclined ends, the number of times a signal propagating through undergoes total internal reflection, the length and width of the waveguide, the diameter of the optical device 1120, the focal length of the optical device 1120 and 10 so on.

Figure 12 is a view of a monocular-type wearable display system according to the present invention. The wearable display system includes a display panel 1200 for emitting a signal, a prism 1210, a waveguide 1220 and an optical device 1230.

The prism 1210 is attached to one side of the waveguide 1220 and has the display panel 1200 on its surface. A signal output from the display panel is transmitted through the prism 1210 into the waveguide 1220 at a predetermined angle of total internal reflection.

The signal enters the waveguide 1220 via the prism to be repeatedly reflected from the inner surface of the waveguide 1220 at the angle of total internal reflection and propagates through the waveguide 1220. The surface of the waveguide 1220 from which the signal is output is cut at a predetermined angle so that the propagation 2s distance of incident signals through the prism 1210 can be the same, thereby preventing aberration due to a difference in propagation distance between signals.

Here, the inclination angles of both ends of the waveguide 1220 are the same as the incident angle, i.e. the angle of total internal reflection.

30 The optical device 1230 is a diffractive optical element or a holographic optical element and magnifies a signal that is transmitted via the waveguide 1220 to be formed as an image in the eye of user. The optical device 1230 is illustrated as a

reflection type in Figure 12, but may be a transmission type that forms an image of a signal at the opposite side of the focal distance shown in Figure 12.

The basic principles of the magnifying optical system are also applied in 5 determining the specifications of the waveguide 1220, i.e., the angle of the inclined

ends of the waveguide, the number of times the signal undergoes total internal reflection therein, the length and width of the waveguide, the diameter of the optical device 1230 and the distance at which a signal is focused to form an image.

0 Figure 13 is a view of a monocular-type wearable display system according to the present invention. In the wearable display system shown in Figure 13, a waveguide 1320 has the same structure and constitutional elements as the waveguide 1220 shown in Figure 12. However, the location of a display panel 1300 and the;.^.

propagation direction of a signal are opposite to those of the wearable display 15 system shown in Figure 12. The display panel 1300 is attached to the end of the waveguide where the optical device 1230 shown in Figure 12 is positioned and a.

magnifying lens 1330 is attached to the end where the display panel 1200 shown in '.! Figure 12 is positioned. In Figure 13, a signal incident on the display panel 1300 is transmitted out of the waveguide 1320 via a prism 1310 and is magnified by the 20 magnifying lens 1330 attached to the prism 1310 to be seen by the eye of a user.

As described above, a wearable display system according to the present invention includes a waveguide having an end or ends that are diagonally cut so that a signal can be reflected within the waveguide, thus not requiring any elements for reflecting 25 a signal at an angle of total internal reflection. Further, light sources can be freely positioned as desired using a reflection plate.

Claims

- 12 Claims

1. A wearable display system having a display panel which displays a signal processed in a predetermined way, the system comprising: s a waveguide for transmitting a signal; and a Paris.,. attached to an end of the waveguide rot emitting a signal transmitted via the waveguide, wherein an end of the waveguide on which a signal is incident from the display panel is cut at a predetermined angle.

2. The system of claim 1, wherein the predetermined angle is equal to the angle of total internal reflection.

3. The system of claim 1 further comprising an optical device placed on the t' prism for magnifying a signal transmitted through the prism.

4. A wearable display apparatus comprising: a prism; a source of modulated light positioned for directing light into the prism; 20 and an image magnifying element positioned to receive light from the source of modulated light, wherein the prism, the source of modulated light and the image magnifying element are configured such that light from the source of modulated 25 light is subject to internal reflection in the prism en route to the image magnifying element.

5. A wearable display device according to claim 4, wherein the source of modulated light comprises a light modulator for modulating a beam of light.

6. A wearable display device according to claim 5, wherein the light modulator comprises a liquid crystal display panel.

- 13 7. A wearable display device according to claim S or 6, wherein the light modulator is mounted to a face of the prism.

8. A wearable display device according to claim 5, 6 or 7, including a s reflector for directing light from an external light source through the light modulator. 9. A wearable display device according to any one of claims 4 to 8, wherein the prism comprises a rod-shaped element having an oblique face at one end and 0 the light modulator is mounted at the oblique face.

10. A wearable display device according to claim 9, wherein the image magnifying element is mounted at a side face of the prism.

Is 11. A wearable display device according to claim 9, wherein the image magnifying element is mounted at a further oblique end face of the prism.

12. A wearable display device according to claim 9, 10 or 11, wherein an oblique end face, at which the light modulator or the image magnifying element is w:-

20 mounted, is located on a projection from said rod-shaped element.

13. A wearable display device according to any one of claims 4 to 12, wherein light propagating from the source of modulated light to the image magnifying element is subject to internal reflection in the prism a plurality of times.

2s 14. A wearable display device according to any one of claims 4 to 13, wherein the image magnifying element comprises a holographic element.

15. A binocular wearable display device including two monocular display 30 devices according to any one of claims 4 to 14.

16. A binocular wearable display device according to claim 15, wherein the same prism is employed in each monocular display device.

- 14 17. A wearable display system having at least one display panel for displaying a signal processed in a predetermined way, the system comprising: a waveguide for transmitting a signal that is incident thereon from the s display panel; and At least one magnifying lens attached to an end of the waveguide for magnifying the signal transmitted via the waveguide, wherein at least one end of the waveguide is diagonally cut at a predetermined angle so that the signal output from the display panel is totally 10 reflected inside the waveguide.

18. The system of claim 17 further comprising at least one reflection plate for reflecting the signal input from the display panel such that the signal is transmitted into the waveguide through an end thereof and undergoes total internal reflection 75 therein. 19. A binocular wearable display system comprising: a waveguide for transmitting a signal emitted from display panels, and positioned at both ends of the waveguide, and 20 magnifying lenses attached to the waveguide for magnifying the signal transmitted via the waveguide, wherein the both ends of the waveguide are diagonally cut at a predetermined angle so that a signal generated from the display panel is totally reflected in the waveguide.

2s 20. The system of claim 19 further comprising reflection plates extending from both ends of the waveguide for reflecting the signal output from the display panel such that the signal is transmitted into the waveguide through the ends thereof and undergoes total reflection therein.

21. A wearable display system having a display panel for displaying a signal processed in a predetermined way, the system comprising:

- 15 a waveguide for transmitting a signal incident thereon from the display panel; and an optical device attached to a surface of the waveguide, the optical device for magnifying a signal transmitted via the waveguide, s wherein the both ends of the waveguide are diagonally cut at predetermined angles. 22. The system of claim 21, wherein the display panel is attached to an end of the waveguide inclined at a first predetermined angle, and the optical device is 10 attached to the other end inclined at a second predetermined angle.

23. The system of claim 22, wherein the first predetermined angle is equal to the angle of total internal reflection for light entering the end of the waveguide.; 15 24. The system of claim 23, wherein the second predetermined angle is the same as the first predetermined angle.

25. The system of claim 21, wherein the optical device is a reflection type. i, 20 26. The system of claim 21, wherein the optical device is a transmission type.

27. A wearable display system having a display panel which displays a signal processed in a predetermined way, the system comprising: a waveguide for transmitting a signal; 25 a prism attached to an end of the waveguide, the prism for transmitting a signal output from the display panel into the waveguide at an angle such that the signal undergoes total internal reflection inside the waveguide; and an optical device for magnifying a signal transmitted via the waveguide, wherein an end of the waveguide which is opposite to where the prism is 30 attached is cut at a predetermined angle.

28. The system of claim 27, wherein the optical device is a reflection type.

- 16 29. The system of claim 27, wherein the optical device is a transmission type.

30. The system of claim 27, wherein the predetermined angle is equal to the angle of total internal reflection.