Head mounted display

A head mounted display includes first and second light source modules, a light reversely turning module, an image output module, first and second eyepiece modules, and a beam splitting mirror. The first and second light source modules are respectively configured to emit first and second lights. The image output module is configured to receive the first and second lights, generating first and second image lights with corresponding image information respectively. The light reversely turning module is optically coupled between the first light source module (or the second light source module) and the image output module, making a propagating direction of the first light (or the second light) in reverse to that of the first image light (or the second light). The beam splitting mirror is optically coupled between the image output module and the first/second eyepiece module, guiding the first/second image light into the first/second eyepiece module.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number 105116194, filed May 25, 2016, which is herein incorporated by reference.

BACKGROUND

Technical Field

The present disclosure relates to a head mounted display. More particularly, the present disclosure relates to a stereo head mounted display.

Description of Related Art

In recent years, with the increasing development of virtual reality technology, an optical product which can show a stereoscopic image has become a focal point in the consumer market. Conventionally, a head mounted display can respectively provide different images to two eyes of an observer, and the eyes of the observer can respectively receive different image information, so that the observer can perceive a stereoscopic image by exploiting the binocular parallax of typical human sight. However, a conventional head mounted display has a complex structure, a huge size and a heavy weight, which may affect wearing convenience and comfort of the observer.

SUMMARY

The disclosure provides a head mounted display, which can reduce a horizontal area of the head mounted display, and can improve a convenience and a comfort of wearing the head mounted display.

In accordance with some embodiments of the present disclosure, a head mounted display includes a first light source module, a second light source module, a light reversely turning module, an image output module, a first eyepiece module, a second eyepiece module and a beam splitting mirror. The first light source is configured to emit a first light. The second light source module is configured to emit a second light. The image output module is configured to receive the first light and the second light, and to respectively generate a first image light and a second image light with corresponding image information. The light reversely turning module is optically coupled between the first light source module and the image output module, making a propagating direction of the first light in reverse to a propagating direction of the first image light. Similarly, the light reversely turning module is optically coupled between the second light source module and the image output module, making a propagating direction of the second light L2reverse to a propagating direction of the second image light. The first eyepiece module is configured to make the first image light image to a first target position. Similarly, the second eyepiece module is configured to make the second image light image to a second target position. The beam splitting mirror is optically coupled between the image output module and the first eyepiece module, and the beam splitting mirror is configured to guide the first image light into the first eyepiece module. Similarly, the beam splitting mirror is optically coupled between the image output module and the second eyepiece module, and the beam splitting mirror is configured to guide the second image light into the second eyepiece module.

In one or more embodiments of this disclosure, since a configuration of the first light source module, the second light source module and the beam splitting mirror, the head mounted display can respectively provide two eyes of an observer with the different image information (that is, the first image light and the second image light), and then the different image information received by the two eyes of the observer may be combined in a brain of the observer, so that the observer can perceive a stereoscopic image. Furthermore, the light reversely turning module may make the propagating direction of the first light in reverse to the propagating direction of the first image light, so the first light source module and the image output module may be located on different level heights. Similarly, the light reversely turning module may make the propagating direction of the second light in reverse to the propagating direction of the second image light, so the second light source module and the image output module may be located on different level heights. Therefore, the horizontal area of the head mounted display may be reduced, benefiting to minimize the size of the head mounted display.

DETAILED DESCRIPTION

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. Furthermore, the term “device A is optically coupled to device B” indicates a light from or through the device A can directly propagate into the device B, and if a light from or through the device A can propagate into the device B, the other optical devices can be interposed between the device A and the device B. Similarly, the term “device A is optically coupled between device B and device C” indicates a light can propagate into the device A, device B and device C, and other optical devices can be interposed between the device A, device B and the device C.

FIG. 1is a perspective view of a head mounted display in accordance with some embodiments of the present disclosure. As shown inFIG. 1, a head mounted display10includes a first light source module100, a second light source module200, a light reversely turning module300, an image output module400, a first eyepiece module500, a second eyepiece module600and a beam splitting mirror700. The first light source100is configured to emit a first light L1. The second light source module200is configured to emit a second light L2. The image output module400is configured to receive the first light L1and the second light L2, and to respectively generate a first image light I1and a second image light I2with corresponding image information. The light reversely turning module300is optically coupled between the first light source module100and the image output module400, for making a propagating direction of the first image light I1in reverse to a propagating direction of the first light L1. Similarly, the light reversely turning module300is optically coupled between the second light source module200and the image output module400, for making a propagating direction of the second image light I2in reverse to a propagating direction of the second light L2. The first eyepiece module500is configured to make the first image light I1image to a first target position P1. Similarly, the second eyepiece module600is configured to make the second image light I2image to a second target position P2. The beam splitting mirror700is optically coupled between the image output module400and the first eyepiece module500, and the beam splitting mirror700is configured to guide the first image light I1into the first eyepiece module500. Similarly, the beam splitting mirror700is optically coupled between the image output module400and the second eyepiece module600, and the beam splitting mirror700is configured to guide the second image light I2into the second eyepiece module600. By such a configuration, the head mounted display10can respectively provide two eyes of an observer with the different image information (that is, the first image light I1and the second image light I2), and then the different image information received by the two eyes of the observer may be combined in a brain of the observer, so that the observer can perceive a stereoscopic image.

More particularly, in some embodiments, as shown inFIG. 1, when the first light source module100emits the first light L1, the first light L1may propagate along a first direction D1(that is, propagating from the left to the right as shown in the figure). When the first light L1arrives at the light reversely turning module300, the propagating direction of the first light L1may be changed by the light reversely turning module300for making the first light L1redirected to the image output module400. Then, the image output module400receives the first light L1and generates the first image light I1propagating along a second direction D2(that is, propagating from the right to the left as shown in the figure). In other words, the light reversely turning module300can change an optical path of the first light L1for making the first light L1emitted by the first light source module100redirected and arrive at the image output module400. More particularly, in some embodiments, as shown inFIG. 1, the propagating direction of the first light L1may be changed from the first direction D1(from the left to the right) into a third direction D3(from the bottom to the top), and then changed into the first direction D1(from the left to the right) for going into the image output module400. Similarly, when the second light source module200emits the second light L2, the second light L2may propagate along the first direction D1(that is, propagating from the left to the right as shown in the figure). When the second light L2arrives at the light reversely turning module300, the propagating direction of the second light L2may be changed by the light reversely turning module300for making the second light L2redirected to the image output module400. Then, the image output module400receives the second light L2and generates the second image light I2propagating along a second direction D2(that is, propagating from the right to the left as shown in the figure). In other words, the light reversely turning module300can change an optical path of the second light L2for making the second light L2emitted by the second light source module200redirected and arrive at the image output module400. Accordingly, the optical path of the first light L1may be changed by the light reversely turning module300, so the first light source module100and the image output module400may be located on different level heights. Similarly, the optical path of the second light L2may be changed by the light reversely turning module300, so the second light source module200and the image output module400may be located on different level heights. Therefore, a horizontal area of the head mounted display10may be reduced, benefiting to minimize the head mounted display10.

For example, as shown inFIG. 1, the first light source module100is located on a level height h1, and the second light source module200is located on a level height h2, and the image output module400is located on a level height h3, in which the level height h3is larger than the level height h2, and the level height h3is larger than the level height h1. In other words, the first light source module100and the second light source module200is located below the image output module400(as shown inFIG. 1, the first light source module100and the second light source module200may be located on a lower left of the image output module400), which may benefit to minimize the horizontal area of the head mounted display10. For example, in some embodiments, as shown inFIG. 1, the first light source module100and the second light source module200may be underlying the first eyepiece module500and the second eyepiece module600, so as to minimize the he horizontal area of the head mounted display10. In some embodiments, the level height h1where the first light source module100is located is substantially equal to the level height h2where the second light source module200is located. In other words, the first light source module100and the second light source module200are located on the substantially equal level height, thereby benefiting to minimize a thickness of the head mounted display10.

More particularly, in some embodiments, as shown inFIG. 1, the first light source module100may include a solid-state light source array110. Similarly, the second light source module200may include a solid-state light source array210. The solid-state light source arrays110and210may include at least one solid-state light source, but is not limited to be, such as a red light source, a green light source or a blue light source, and it may be a light emitting diode or an organic light emitting diode. The first light L1emitted by the solid-state light source array110of the first light source module100is substantially a collimated light, that is, a divergence angle of the first light L1is close to zero. Therefore, after the image output module400receives the first light L1, the image output module400may generate the substantially collimated first image light I1, so the first image light I1may be precisely guided into the first target position P1through the first eyepiece module500avoiding the first image light I1shifting from the first target position P1to the second target position P2. Similarly, the second light L2emitted by the solid-state light source array210of the second light source module200is substantially a collimated light, that is, a divergence angle of the second light L2is close to zero. Therefore, after the image output module400receives the second light L2, the image output module400may generate the substantially collimated second image light I2, so the second image light I2may be precisely guided into the second target position P2through the second eyepiece module600avoiding the second image light I2shifting from the second target position P2to the first target position P1. Furthermore, in some embodiments, as shown inFIG. 1, the first light source module100and the second light source module200may also include tapered rods120and220, and may include ball lenses130and230configured to adjust the intensity and the uniformity of lights, thereby improving an image quality of the head mounted display10.

In some embodiments, as shown inFIG. 1, the light reversely turning module has a first light-redirecting unit310and a second light-redirecting unit320, the first light-redirecting unit310is configured to reflect and redirect the first light L1from the first light source module100and the second light L2from the second light source module200to the second light-redirecting unit320, and the second light-redirecting unit320is configured to reflect and redirect the first light L1and the second light L2from the first light-redirecting unit310into the image output module400. More particularly, in some embodiments, as shown inFIG. 1, the first light-redirecting unit310has a reflective surface312. A distance between the reflective surface312and the first light source module100(such as the ball lens130of the first light source module100) is increasing along a direction towards the second light-redirecting unit320, thereby benefiting to reflect and redirect the first light L1to the second light-redirecting unit320. In other words, the reflective surface312has a normal vector N1being towards the top left of the figure. Accordingly, when the first light L1propagates along the first direction D1and arrives at the reflective surface312of the first light-redirecting unit310, the first light L1may be reflected by the reflective surface312and propagate towards the second light-redirecting unit320along the third direction D3. Then, when the first light L1propagates along the third direction D3and goes into the second light-redirecting unit320, the first light L1can be reflected and redirected by a certain surface of the second light-redirecting unit320for propagating towards the image output module400along the first direction D1, so the first light L1can arrive at the image output module400. Similarly, a distance between the reflective surface312and the second light source module200(such as the ball lens230of the second light source module200) is increasing along a direction towards the second light-redirecting unit320, thereby benefiting to reflect and redirect the second light L2to the second light-redirecting unit320. Accordingly, when the second light L2propagates along the first direction D1and arrives at the reflective surface312of the first light-redirecting unit310, the second light L2may be reflected by the reflective surface312and propagate towards the second light-redirecting unit320along the third direction D3. Then, when the second light L2propagates along the third direction D3and goes into the second light-redirecting unit320, the second light L2can be reflected and redirected by the certain surface of the second light-redirecting unit320for propagating towards the image output module400along the first direction D1, so the second light L2can arrive at the image output module400.

As a result, by the first light-redirecting unit310and the second light-redirecting unit320, the first light L1from the first light source module100and the second light L2from the second light source module200arriving at the image output module400may be redirected at least two times, so the image output module400can be disposed on the level height being different from the level height where the first light source module100and the second light source200are disposed (for example, the image output module400is disposed on the top right inFIG. 1), thereby minimizing the horizontal area of the head mounted display10. In some embodiments, for example, the first light-redirecting unit310may be a reflected mirror, which may be, but is not limited to be, a reflected mirror with an aluminum coating, a reflected mirror with a metal coating, a reflected mirror with a high reflectivity material, so as to redirect the first light L1and the second light L2to the second light-redirecting unit320more effectively.

FIG. 2is an enlarged cross-section view of a local area R of theFIG. 1.

In some embodiments, as shown inFIG. 1andFIG. 2, the second light-redirecting unit320has a redirecting surface322, the redirecting surface322is configured to reflect and redirect the first light L1and the second light L2from the first light-redirecting unit310to the image output module400, and the first image light I1and the second image light I2generated by the image output module400may propagate into the redirecting surface322, and an incident angle of the first image light L1and an incident angle of the second image light L2at the redirecting surface322is less than a critical angle of the redirecting surface. The critical angle is a least angle of incidence arriving at the redirecting surface322of the second light-redirecting unit320above which the total internal reflection occurs. In other words, when the first light L1arrives at the redirecting surface322of the second light-redirecting unit320, the first light L1can be reflected and redirected to the image output module400. Then, the image output module400receives the first light L1and generates the first image light I1with the image information, since the incident angle of the first image light I1at the redirecting surface322is design to being less than the critical angle, the first image light I1may not be totally reflected, and the first image light I1may penetrate the second light-redirecting unit320, thereby benefiting to guide the first image light I1into the beam splitting mirror700. Similarly, when the second light L2arrives at the redirecting surface322of the second light-redirecting unit320, the second light L2can be reflected and redirected to the image output module400. Then, the image output module400receives the second light L2and generates the second image light I2with the image information, since the incident angle of the second image light I2at the redirecting surface322is design to being less than the critical angle, the second image light I2may not be totally reflected, and the second image light I2may penetrate the second light-redirecting unit320, thereby benefiting to guide the second image light I2into the beam splitting mirror700. As a result, by the second light-redirecting unit320, the optical path of the lights from the first light-redirecting unit310may be controlled, and the optical path of the lights from the image output module400may also be controlled. For example, in some embodiments, the second light-redirecting unit320may be, but is not limited to be, a totally internal reflection prism, so as to separate the first light L1and the first image light I1more effectively, and also to separate the second light L2and the second image light I2more effectively. For example, in some embodiments, by designs of the incident angles of the first light L1and the second light L2arriving at the image output module400, or designs of the emitting angles of the first image light I1and the second image light I2generated by the image output module400, so the incident angles of the first image light I1and the second image light I2at the redirecting surface322is less than the critical angle of the redirecting surface322, but it is not limited.

In some embodiments, as shown inFIG. 1andFIG. 2, the light reversely turning module300further includes a penetrate assist unit330. The penetrate assist unit330is abutted against the redirecting surface322of the second light-redirecting unit320, and the penetrate assist unit330and the second light-redirecting unit320may have different refractive indexes to make the first light L1and the second light L2propagating at the redirecting surface322reflected totally, and make at least one part of the first image light I1and the second image light I2penetrate the redirecting surface322. More particularly, in some embodiments, as shown inFIG. 2, the penetrate assist unit330may include a connect surface332, the connect surface332is connected to the redirecting surface322of the second light-redirecting unit320, and a refractive index n1of the penetrate assist unit330is less than a refractive index n2of the second light-redirecting unit320. Accordingly, when the first light L1(or the second light L2) from the first light-redirecting unit310is transmitted to the redirecting surface322of the second light-redirecting unit320, since the refractive index n1of the penetrate assist unit330is less than the refractive index n2of the second light-redirecting unit320, and the incident angle of the first light L1(or the second light I2) is designed to be larger than the critical angle(arcsin(n/n2)), the first light L1(or the second light L2) may be totally reflected at the redirecting surface322. In other words, the first light L1(or the second light L2) may not penetrate the second light-redirecting unit320, that is, the first light L1(or the second light I2) may be totally reflected to the image output module400. For example, in some embodiments, by designs of the position of the first light source module100relative to the image output module400, the position of the second light source module200relative to the image output module400, the position of the first light-redirecting unit310relative to the image output module400, an angle formed between the normal vector N1of the first light-redirecting unit310and the first light L1or the second light L2, or an arranged location of the second light-redirecting unit320, so the incident angle of the first light L1(or the second light L2) at the redirecting surface322may be larger than the critical angle of the redirecting surface322.

In some embodiments, as shown inFIG. 2, the emitting angle of the first image light I1is designed to make the incident angle of the first image light I1arriving at the redirecting surface322be less than the critical angle(arcsin(n1/n2)), so the first image light I1may penetrate the redirecting surface322. Similarly, the emitting angle of the second image light I2is designed to make the incident angle of the second image light I2arriving at the redirecting surface322be less than the critical angle(arcsin(n1/n2)), so the second image light I2may penetrate the redirecting surface322. It is noted that, in some embodiments, the incident angle of the first light L1arriving at the image output module400can be different from the incident angle of the second light L2arriving at the image output module400, so the emitting angle of the first image light I1generated by the image output module400can be different from the emitting angle of the second image light I2generated by the image output module400, thereby benefiting to guide the first image light I1into the first target position P1and benefiting to guide the second image light I2into the second target position P2.

For example, in some embodiments, another devices can be applied to separate the optical path of the first light L1and the optical path of the first image light I1generated by the image output module400, and to separate the optical path of the second light L2and the optical path of the second image light I2generated by the image output module400. For example, when the image output module400includes a silicon-based liquid crystal cell, the first light L1and the second light L2may be converted into the first image light I1and the second image light I2with different polarization, and the second light-redirecting unit320may include a polarized beam splitter and a quarter-wave plate, so as to separate the optical paths of the first image light I1and the second image light I2.

In some embodiments, the image output module400is a digital micro-mirror device configured to reflect and make the first light L1from the second light-redirecting unit320become the first image light I1with the image information, and to reflect and make the second light L2from the second light-redirecting unit320become the second image light I2with the image information. More particularly, the digital micro-mirror device may include a plurality of micro reflected mirrors, so the reflected direction of the light received by each micro reflected mirror can be controlled. Each micro reflected mirror represents an image pixel, and each micro reflected mirror can be driven by a control device, so the micro reflected mirror can be rotated to a corresponding angle, thereby benefiting to reflect a light to a predetermined position.

For example, when the first light L1is redirected to the digital micro-mirror device by the second light-redirecting unit320, some of the micro reflected mirrors can be rotated to a first group angle, so as to receive the first light L1and to reflect the first light L1to become the first image light I1with the image information. Similarly, when the second light L2is redirected to the digital micro-mirror device by the second light-redirecting unit320, some of the micro reflected mirrors can be rotated to a second group angle, so as to receive the second light L2and to reflect the second light L2to become the second image light I2with the image information. It is noted that the first group angle may be different from the second group angle, so the digital micro-mirror device may generate the different emitting angles for the first image light I1and the second image light I2in a reflecting manner. That is, the digital micro-mirror device may generate different optical paths of the first image light I1and the second image light I2, which may benefit to precisely transmit the first image light I1to the first eyepiece module500by the beam splitting mirror700, and benefit to precisely transmit the second image light I2to the second eyepiece module600by the beam splitting mirror700. In other words, when the image output module400is the digital micro-mirror device, it may separate the optical paths of the first image light I1and the second image light I2more effectively, avoiding the first image light I1and the second image light I2from interfering with each other and reflecting the first image light I1and the second image light I2to the first eyepiece module500and the second eyepiece module600more precisely. For example, in some embodiments, the image output module400may be a tilt and roll pixel digital micro-mirror device, so as to separate the optical paths of the first image light I1and the second image light I2more effectively.

More particularly, in some embodiments, as shown inFIG. 1, the first light L1emitted by the first light source module100propagate along the first direction D1, and the second light L2emitted by the second light source module200propagate along the first direction D1. After the first light L1and the second light L2are redirected to the image output module400by the light reversely turning module300, the image output module400reflects the first image light I1and the second image light I2with the corresponding image information. It is noted that the image output module400is designed to reflect and generate the first image light I1(or the second image light I2) propagating along the second direction D2, in which the first direction D1is reverse to the second direction D2. In other words, a difference between the propagating direction of the first light L1(or the second light L2) and the propagating direction of the first image light I1(or the second image light I2) is 180 degrees.

Reference is made toFIG. 3, which is a top view of the head mounted display in accordance with some embodiments of the present disclosure. More particularly, in some embodiments, as shown inFIG. 3, the beam splitting mirror700may include a first beam splitting unit710and a second beam splitting unit720, and the first beam splitting unit710is abutted against the second beam splitting unit720. The first beam splitting unit710has a first beam splitting surface712and a first rear surface714opposite to each other, and the second beam splitting unit720has a second beam splitting surface722and a second rear surface724opposite to each other, and the first rear surface714and the second rear surface724are facing to each other and form an acute angle. The first beam splitting surface712is farther away from the first target position P1than the first rear surface714being, and the second beam splitting surface722is farther away from the second target position P2than the second rear surface724being. As shown inFIG. 3, the first beam splitting surface712is located on the optical path of the first image light I1, so as to redirect the first image light I1to the first eyepiece module500. Similarly, the second beam splitting surface722is located on the optical path of the second image light I2, so as to redirect the second image light I2to the second eyepiece module600. As a result, the first image light I1and the second image light I2may be respectively redirected to the first eyepiece module500and the second eyepiece module600by the beam splitting mirror700.

In some embodiments, as shown inFIG. 3, the head mounted display10may further include a lens group420, the lens group420is optically coupled between the image output module400and the beam splitting mirror700, and the lens group420is configured to adjust qualities of images of the first image light I1and the second image light I2. For example, a refractive power or another optical parameters of each lens of the lens group420may be designed to eliminate a distortion of the first image light I1and the second image light I2generated by the image output module400, which may assist to improve the quality of the first image light I1imaging to the first target position P1and to improve the quality of the second image light I2imaging to the second target position P2.

In some embodiments, as shown inFIG. 3, the first eyepiece module500may include a partially light reflective unit510and an image-reflected mirror520. The partially light reflective unit510is optically coupled between the first beam splitting unit710of the beam splitting mirror700and the image-reflected mirror520. For example, when the first image light I1arrives at the first beam splitting surface712of the first beam splitting unit710, the first image light I1may be redirected and guided into the partially light reflective unit510in a reflecting manner, and then the partially light reflective unit510may redirect a part of the first image light I1to the image-reflected mirror520in a reflecting manner thereby forming a first intermediate image, and the first intermediate image is projected to the first target position P1by a first eyepiece530. Similarly, in some embodiments, the second eyepiece module600may include a partially light reflective unit610and an image-reflected mirror620. The partially light reflective unit610is optically coupled between the second beam splitting unit720of the beam splitting mirror700and the image-reflected mirror620. For example, when the second image light I2arrives at the second beam splitting surface722of the second beam splitting unit720, the second image light I2may be redirected and guided into the partially light reflective unit610in a reflecting manner, and then the partially light reflective unit610may redirect a part of the second image light I2to the image-reflected mirror620in a reflecting manner thereby forming a second intermediate image, and the second intermediate image is projected to the second target position P2by a second eyepiece630. For example, in some embodiments, the partially light reflective units510and610may be, but is not limited to be, beam-splitters or totally internal reflection prisms to redirect the first image light I1(or the second image light I2) to the image-reflected mirror520(or the image-reflected mirror620). Alternatively, in some embodiments, another devices can be applied to redirect the first image light I1from the beam splitting mirror700to the first eyepiece530, and redirect the second image light I2from the beam splitting mirror700to the second eyepiece630. For example, when the first image light I1and the second image light I2are two different polarized lights, the partially light reflective units510and610may include a polarized beam splitter and a quarter-wave plate.

More particularly, in some embodiments, as shown inFIG. 3, the first beam splitting surface712and the second beam splitting surface722may intersect at a ridge R. There is an imaginary plane730on which the ridge R lies and perpendicular to an arrange direction of the image output module400and the beam splitting mirror700. The imaginary plane730may include a first imaginary plane732and a second imaginary plane734that intersect at the ridge R. The first imaginary plane732and the first beam splitting surface712respectively have peripheries7322and7122distal to the ridge R. The peripheries7322and7122are aligned in a line perpendicular to the imaginary plane730. Similarly, the second imaginary plane734and the second beam splitting surface722respectively have peripheries7342and7222distal to the ridge R. The peripheries7342and7222are aligned in a line perpendicular to the imaginary plane730. The first image light I1may be propagated to the first beam splitting surface712through a center of the first imaginary plane732. Similarly, the second image light I2may be propagated to the second beam splitting surface722through a center of the second imaginary plane734. In other words, the first image lights I1may converge at the center of the first imaginary plane732, and the second image lights I2may converge at the center of the second imaginary plane734.

In some embodiments, the first light source module100and the second light source module200emit lights in a time sequence. In other words, the first light source module100and the second light source module200alternately emit lights according to the time sequence. Reference is made toFIG. 4, which is a schematic diagram showing an optical path of the head mounted display10at a first time point in accordance with some embodiments of the present disclosure. For example, as shown inFIG. 1andFIG. 4, at a first time point, the first light source module100emits the first light L1, the first light L1is redirected to the image output module400by the light reversely turning module300for generating the first image light I1, and the first image light I1is guided into the first target position P1(such as a left eye of an observer) by the beam splitting mirror700and the first eyepiece module500. Reference is made toFIG. 5, which is a schematic diagram showing an optical path of the head mounted display10at a second time point in accordance with some embodiments of the present disclosure. For example, as shown inFIG. 1andFIG. 5, at a second time point, the second light source module200emits the second light L2, the second light L2is redirected to the image output module400by the light reversely turning module300for generating the second image light I2, and the second image light I2is guided into the second target position P2(such as a right eye of the observer) by the beam splitting mirror700and the second eyepiece module600. As a result, by fast switching the first light source module100and the second light source module200in the time sequence, the corresponding first image light I1and the second image light I2may be respectively imaged to the first target position P1and the second target position P2in the time sequence, so as to achieve a stereoscopic display of the head mounted display10. In other words, the head mounted display10of the present disclosure uses a time-multiplex way to switch the first light source module100and the second light source module200in the time sequence, so the head mounted display10can provide a stereoscopic image.

In some embodiments, the image output module400provides a plurality of reflected patterns in the time sequence, and the first light source module100and the second light source module200switched substantially synchronizes with the reflected patterns switched. More particularly, in some embodiments, the reflected patterns can be classified as a first group of reflected patterns and a second group of reflected patterns, and the first group of reflected patterns and the second group of reflected patterns are switched in the time sequence, that is, the image output module400alternately provides the first group of reflected patterns and the second group of reflected patterns according to the time sequence. For example, at the first time point, the first light source emits the first light L1to the image output module400, and the image output module400substantially provides the first group of reflected patterns in synchronization, so the image output module400receives the first light L1and generates the first image light I1with the image information of the first group of reflected patterns. Then, at the second time point, the second light source emits the second light L2to the image output module400, and the image output module400substantially provides the second group of reflected patterns in synchronization, so the image output module400receives the second light L2and generates the second image light I2with the image information of the second group of reflected patterns. In other words, at a first time t1, the first light source module100may be controlled to emit light, and the second light source module200may be controlled to not emit light, and the image output module400may be controlled to provide the first group of reflected patterns. Then, at a second time t2, the first light source module100may be controlled to not emit light, and the second light source module200may be controlled to emit light, and the image output module400may be controlled to provide the second group of reflected patterns. Accordingly, the first light L1generated by the first light source module100substantially synchronizes with the first group of reflected patterns generated by the image output module400, so as to generate the first image light I1with the corresponding correct image information, which may benefit to image the first image light I1to the first target position P1. Similarly, the second light L2generated by the second light source module200substantially synchronizes with the second group of reflected patterns generated by the image output module400, so as to generate the second image light I2with the corresponding correct image information, which may benefit to image the second image light I2to the second target position P1.

In accordance with some embodiments of the present disclosure, since the first light source module100and the second light source module200switch in a time sequence and the configuration of the beam splitting mirror700, the head mounted display10may respectively provide the first image light I1and the second image light I2to a left eye and a right eye of an observer in the time sequence, so as to generate a stereoscopic image. Furthermore, the light reversely turning module300may make the propagating direction of the first light L1in reverse to the propagating direction of the first image light I1, so the first light source module100and the image output module400may be located on different level heights. Similarly, the light reversely turning module300may make the propagating direction of the second light L2in reverse to the propagating direction of the second image light I2, so the second light source module200and the image output module400may be located on different level heights. Therefore, the horizontal area of the head mounted display10may be reduced, benefiting to minimize the size of the head mounted display10.