Biscuit lens assembly

Abstract

This invention provides a cookie lens assembly comprising a partial reflector, a reflective polarizer, a quarter-wave plate, a polarization-dependent optical element, and at least one polarization controller. When a light beam is introduced into the cookie lens assembly along an optical axis in the Z direction and passes through the polarization controller in a first state, the polarization direction of the light beam is reversed by the polarization controller. When the light beam is introduced into the cookie lens assembly along the optical axis and passes through the polarization controller in a second state, the polarization direction of the light beam is prevented from being reversed by the polarization controller. This alleviates visual fatigue and discomfort caused by visual convergence-accommodation conflict (VAC) in the user's eyes.

Description

Technical Field

[0001] This invention relates to an optical system, and more particularly to an optical system having an adjustable focal length. Background Technology

[0002] Near-eye displays (e.g., head-mounted displays) are used in systems such as Virtual Reality (VR) and Augmented Reality (AR) to create virtual images within the user's field of view (FOV). However, when using such near-eye displays, the phenomenon of vergence-accommodation conflict (VAC) prevents the user from simultaneously performing convergence and accommodation movements with both eyes when estimating the relative distance of objects, leading to visual fatigue and eye strain.

[0003] Furthermore, to provide users with a better field of view, the distance between the near-eye display and each eye is typically maintained within the range of 15mm to 25mm. However, when the user wears glasses, the distance between the user's eyes and the near-eye display cannot be maintained at the aforementioned appropriate distance, which will adversely affect the field of view. Providing additional glasses positioned between the user and the near-eye display for viewing images would cause inconvenience in use. Summary of the Invention

[0004] The purpose of this invention is to provide a cookie lens assembly that can be used to alleviate the visual convergence-accommodation conflict (VAC) caused by a near-eye display and / or can be used to correct vision.

[0005] The biscuit lens assembly of the present invention includes a partial reflector, a reflective polarizer, a quarter-wave plate, a polarization-dependent optical element, and at least one polarization controller.

[0006] The reflected polarizer is positioned behind the partial reflector.

[0007] The quarter-wave plate is positioned between the partial reflector and the reflective polarizer.

[0008] The polarization-dependent optical element is disposed between the quarter-wave plate and the reflective polarizer.

[0009] The at least one polarization controller is located in front of the quarter-wave plate and the polarization-dependent optical element, or behind the polarization-dependent optical element and the reflective polarizer, and the at least one polarization controller can be switched from a first state to a second state via electric drive.

[0010] Specifically, when a light beam is introduced into the biscuit lens assembly along an optical axis located in a Z direction and passes through the polarization controller in the first state, the polarization direction of the light beam is changed by the polarization controller. When the light beam is introduced into the biscuit lens assembly along the optical axis and passes through the polarization controller in the second state, the polarization direction of the light beam is prevented from being changed by the polarization controller.

[0011] Preferably, in the biscuit lens assembly of the present invention, the polarization-dependent optical element is a transmissive liquid crystal element.

[0012] Preferably, in the biscuit lens assembly of the present invention, the polarization-dependent optical element is selected from a fixed-focus liquid crystal lens, an electrically adjustable liquid crystal lens, a liquid crystal grating, a liquid crystal prism, a liquid crystal wavefront corrector, an ultra-lens, and at least one combination thereof.

[0013] Preferably, in the biscuit lens assembly of the present invention, the polarization controller is selected from twisted nematic liquid crystal elements, liquid crystal waveplates, and combinations thereof.

[0014] Preferably, in the biscuit lens assembly of the present invention, the polarization-dependent optical element comprises a plurality of liquid crystal molecules, the long axis of the liquid crystal molecules being parallel to one of the XZ plane or the YZ plane, and the XZ plane being defined by the X direction and the Z direction, the YZ plane being defined by the Y direction and the Z direction, and the X direction, the Y direction and the Z direction being orthogonal to each other.

[0015] Preferably, in the biscuit lens assembly of the present invention, when the light beam is introduced into the biscuit lens assembly along the optical axis located in the Z direction and passes through the polarization controller in the first state, a straight light path is formed that passes through the polarization-dependent optical element only once.

[0016] Preferably, in the biscuit lens assembly of the present invention, when the light beam is introduced into the biscuit lens assembly and passes through the polarization controller in the second state, a folded light path is formed between the partial reflector and the reflective polarizer, and passes through the polarization-dependent optical element three times.

[0017] Preferably, in the biscuit lens assembly of the present invention, the folded light path has three transmission path segments that pass through the polarization-dependent optical element respectively. When the light beam is X-polarized light polarized in the X direction, the light beam travels along two of the transmission path segments and passes through the polarization-dependent optical element. When the light beam is Y-polarized light polarized in the Y direction, the light beam travels along the remaining transmission path segment and passes through the polarization-dependent optical element.

[0018] Preferably, the biscuit lens assembly of the present invention includes two polarization controllers located at the front position and the rear position, respectively.

[0019] Preferably, in the biscuit lens assembly of the present invention, when one of the polarization controllers is in the first state and the other polarization controller is in the second state, the light beam introduced into the biscuit lens assembly forms a straight light path that passes through the polarization-dependent optical element only once.

[0020] Preferably, in the biscuit lens assembly of the present invention, when the light beam is introduced into the biscuit lens assembly and the polarization controller is in either the first state or the second state, a folded light path is formed between the partial reflector and the reflective polarizer, and passes through the polarization-dependent optical element three times.

[0021] Preferably, in the biscuit lens assembly of the present invention, the polarization controllers are all in the first state, and the folded light path has three transmission path segments that pass through the polarization-dependent optical element respectively. When the light beam is Y-polarized light polarized in the Y direction, the light beam travels along two of the transmission path segments and passes through the polarization-dependent optical element. When the light beam is X-polarized light polarized in the X direction, the light beam travels along the remaining transmission path segment and passes through the polarization-dependent optical element.

[0022] Preferably, in the biscuit lens assembly of the present invention, the polarization controllers are all in the second state, and the folded light path has three transmission path segments that pass through the polarization-dependent optical element respectively. When the light beam is X-polarized light polarized in the X direction, the light beam travels along two of the transmission path segments and passes through the polarization-dependent optical element. When the light beam is Y-polarized light polarized in the Y direction, the light beam travels along the remaining transmission path segment and passes through the polarization-dependent optical element.

[0023] Preferably, in the biscuit lens assembly of the present invention, the partial reflector allows partial transmission of the first circularly polarized light and reflects a portion of the first circularly polarized light to convert it into second circularly polarized light, wherein the circular polarization direction of the second circularly polarized light is different from that of the first circularly polarized light.

[0024] Preferably, in the biscuit lens assembly of the present invention, the quarter-wave plate can convert the first circularly polarized light into a first linearly polarized light, convert the first linearly polarized light into the first circularly polarized light, convert the second circularly polarized light into a second linearly polarized light, or convert the second linearly polarized light into the second circularly polarized light, and the linear polarization direction of the second linearly polarized light is different from the linear polarization direction of the first linearly polarized light.

[0025] Preferably, in the biscuit lens assembly of the present invention, the polarization controller in the first state converts the first linearly polarized light into the second linearly polarized light and the second linearly polarized light into the first linearly polarized light.

[0026] Preferably, in the biscuit lens assembly of the present invention, the reflective polarizer is used to reflect the first linearly polarized light and allow the second linearly polarized light to pass through.

[0027] Preferably, in the biscuit lens assembly of the present invention, the first circularly polarized light is left-circularly polarized light, the second circularly polarized light is right-circularly polarized light, the first linearly polarized light is X-polarized light polarized in the X direction, and the second linearly polarized light is Y-polarized light polarized in the Y direction.

[0028] The beneficial effects of the present invention are as follows: by using at least one polarization controller disposed between the quarter-wave plate and the polarization-dependent optical element and / or disposed between the polarization-dependent optical element and the reflective polarizer, and by switching the at least one polarization controller as needed to make it in the first state or the second state, the biscuit lens assembly can have a variety of different optical powers. Therefore, when the biscuit lens assembly is disposed between the display and the user's eyes, by adjusting the optical power of the biscuit lens assembly itself, visual fatigue and discomfort of the user's eyes caused by visual convergence-accommodation conflict (VAC) can be alleviated. Attached Figure Description

[0029] Figure 1 This is an exploded view illustrating an embodiment of the biscuit lens assembly of the present invention, wherein the polarization controller of the biscuit lens assembly is disposed in the front position and is in a first state;

[0030] Figure 2 It is similar to Figure 1The exploded view illustrates that the polarization controller of the embodiment is in a second state;

[0031] Figure 3 This is a schematic diagram illustrating a polarization-dependent optical element (liquid crystal lens element) with a thickness gradient in the embodiment described above, indicating that the polarization direction of linearly polarized light is parallel to a plane parallel to the long axis L of the liquid crystal molecules of the polarization-dependent optical element.

[0032] Figure 4 It is similar to Figure 3 The schematic diagram illustrates that the polarization direction of linearly polarized light is perpendicular to the plane.

[0033] Figure 5 and Figure 6 It is similar to Figure 3 The schematic diagram illustrates that the polarization-dependent optical element (liquid crystal lens) has a refractive index gradient;

[0034] Figure 7 It is similar to Figure 1 The exploded view shows the polarization controller positioned at the rear.

[0035] Figure 8 It is similar to Figure 7 The diagram shows an exploded view, but the polarization controller is in the second state;

[0036] Figure 9 It is similar to Figure 1 The exploded view shows that, however, the embodiment is configured with two polarization controllers respectively located at the front and rear positions, and respectively in the second state and the first state;

[0037] Figure 10 It is similar to Figure 9 The diagram shows an exploded view, but the polarization controller located at the front position is in the first state, and the polarization controller located at the rear position is in the second state.

[0038] Figure 11 It is similar to Figure 9 The exploded diagram shows that all polarization controllers are in the first state; and

[0039] Figure 12 It is similar to Figure 9 The diagram shows an exploded view, but all polarization controllers are in the second state. Detailed Implementation

[0040] Before the present invention is described in detail, it should be noted that similar elements are represented by the same numbers in the following description. The relevant technical content, features, and effects of the present invention will be clearly presented in the following detailed description of embodiments with reference to the accompanying drawings. Furthermore, it should be noted that the drawings of the present invention are only for illustrating the structural and / or positional relationships between elements and are not related to the actual dimensions of each element. The directional terms used in the description and scope of the application (e.g., front, back, left, right, top, bottom, etc.) are intended only to help describe the content and should not be considered as limitations of the present invention in any way.

[0041] See Figure 1 and Figure 2 This invention describes a biscuit-style optical component comprising a partial reflector 10, a reflective polarizer 20, a quarter-wave plate 30, a polarization-dependent optical element 40, and a polarization controller 50. Figure 1 , Figure 2 The X, Y, and Z directions indicated are orthogonal to each other. In this embodiment, the partial reflector 10, the quarter-wave plate 30, the polarization controller 50, the polarization-dependent optical element 40, and the reflective polarizer 20 are sequentially combined with each other along the optical axis A located in the Z direction.

[0042] The partial reflector 10 can be disposed behind a display (not shown, e.g., a near-eye display, or a head-mounted display), and can be selected from a 50 / 50 reflector, reflecting approximately 50% of the light beam emitted from the display, while approximately 50% of the light beam is transmitted. In some embodiments, the partial reflector 10 can partially transmit and partially reflect the first circularly polarized light emitted from the display, converting it into second circularly polarized light, wherein the circular polarization direction of the second circularly polarized light is different from that of the first circularly polarized light. In this embodiment, the example is given where the first circularly polarized light is left-circularly polarized (L-circularly) and the second circularly polarized light is right-circularly polarized (R-circularly).

[0043] The reflective polarizer 20 is disposed behind the partial reflector 10, reflecting the first linearly polarized light and allowing the second linearly polarized light to pass through, wherein the linear polarization direction of the second linearly polarized light is different from that of the first linearly polarized light. In this embodiment, the linear polarization directions of the first and second linearly polarized lights differ by approximately 90 degrees. This is illustrated by taking the first linearly polarized light as X-polarized light polarized in the X direction and the second linearly polarized light as Y-polarized light polarized in the Y direction as an example.

[0044] The quarter-wave plate 30 is disposed between the partial reflector 10 and the reflective polarizer 20, and can convert the first circularly polarized light into the first linearly polarized light, convert the first linearly polarized light into the first circularly polarized light, convert the second circularly polarized light into the second linearly polarized light, or convert the second linearly polarized light into the second circularly polarized light.

[0045] The polarization-dependent optical element 40 is disposed between the quarter-wave plate 30 and the reflective polarizer 20. In some embodiments, the polarization-dependent optical element 40 is a transmissive liquid crystal element, and can be selected from a fixed-focus liquid crystal lens, an electrically adjustable liquid crystal lens, a liquid crystal grating, a liquid crystal prism, a liquid crystal wavefront corrector, a superlens, and at least one combination thereof. In this embodiment, the polarization-dependent optical element 40 has a plurality of liquid crystal molecules 411 located therein, the major axis L of the liquid crystal molecules 411 (see...) Figure 3 The arrangement direction of the liquid crystal molecules 411 is parallel to either the XZ plane or the YZ plane, wherein the XZ plane is defined by the X direction and the Z direction, and the YZ plane is defined by the Y direction and the Z direction. For example, the major axis L of the liquid crystal molecules 411 can be as follows: Figure 3 and Figure 4 As shown, their arrangement direction is parallel to the YZ plane, or it can be as follows: Figure 5 and Figure 6 As shown, the major axis L of the liquid crystal molecule 411 is parallel to the XZ plane.

[0046] In some embodiments, the polarization-dependent optical element 40 may be selected from a liquid crystal element having a thickness gradient (see...). Figure 3 , Figure 4 ), liquid crystal elements with a reflectivity gradient (see Figure 5 , Figure 6 ), a Pancharatnam-Berryphase liquid crystal element (not shown), or other suitable liquid crystal elements.

[0047] In some embodiments, such as Figure 3 , Figure 4 As shown, the polarization-dependent optical element 40 includes a liquid crystal unit 41 having the liquid crystal molecules 411, and an optical lens 42. The optical lens 42 can be selected from a solid lens, a concave lens, a plano-concave lens, a freeform optical lens, or other suitable optical lenses. In some embodiments, such as Figure 5 , Figure 6 As shown, the polarization-dependent optical element 40 has a radial gradient refractive index due to the arrangement of the liquid crystal molecules 411 inside the polarization-dependent optical element 40.

[0048] See Figure 3 and Figure 5 When the polarization directions A1 and A3 of the linearly polarized light are parallel to a plane parallel to the alignment direction of the major axis L of the liquid crystal molecules 411 (i.e., as shown in the figure) Figure 3 The YZ plane shown, or as... Figure 5 As shown in the XZ plane, the linearly polarized light is considered an extraordinary ray, allowing the polarization-dependent optical element 40 to have optical power (Pe). Therefore, the optical power changes as the alignment direction of the liquid crystal molecules 411 changes.

[0049] See Figure 4 and Figure 6 When the polarization directions A2 and A4 of the linearly polarized light are perpendicular to a plane parallel to the alignment direction of the major axis L of the liquid crystal molecules 411 (i.e., as shown in the image) Figure 3 The YZ plane shown, or as... Figure 5 In the XZ plane shown, the linearly polarized light is treated as ordinary ray, allowing the polarization-dependent optical element 40 to have optical power (Po). Therefore, the optical power remains unchanged when the alignment direction of the liquid crystal molecules 411 changes.

[0050] The polarization controller 50 is disposed in either a front position or a rear position. The front position is located between the quarter-wave plate 30 and the polarization-dependent optical element 40, and the rear position is located between the polarization-dependent optical element 40 and the reflective polarizer 20. In some embodiments, such as... Figure 1 and Figure 2 As shown, the polarization controller 50 is positioned at the front and can be switched from a first state to a second state via an electrically driven method. When a light beam from the display is guided into the biscuit lens assembly and passes through the polarization controller 50 in the first state (see...), Figure 1 The polarization direction of the light beam is converted by the polarization controller 50. In this embodiment, the first linearly polarized light is converted into the second linearly polarized light by the polarization controller 50 in the first state, and similarly, the second linearly polarized light can be converted into the first linearly polarized light by the polarization controller 50 in the first state.

[0051] When the light beam is introduced into the biscuit lens assembly and passes through the polarization controller 50 in the second state (see...), Figure 2 This prevents the polarization direction of the light beam from being changed by the polarization controller 50.

[0052] In some embodiments, the polarization controller 50 may be selected from a twisted nematic (TN) liquid crystal element, a liquid crystal waveplate, or a combination thereof. In this embodiment, the polarization controller 50 is a twisted nematic liquid crystal element, and can switch between the first state (off state) and the second state (on state) in a very short time. When no electric field is applied to the twisted nematic liquid crystal element (i.e., the twisted nematic liquid crystal element is in the off state), the polarization direction of the light beam is converted by approximately 90 degrees by the twisted nematic liquid crystal element. When an electric field is applied to the twisted nematic liquid crystal element (i.e., the twisted nematic liquid crystal element is in the on state), the polarization direction of the light beam is not substantially converted.

[0053] See Figure 1 When the light beam is introduced into the biscuit lens assembly and passes through the partial reflector 10, and the polarization controller 50 is in the first state, a straight light path SP is formed that passes through the polarization-dependent optical element 40 only once. The polarization conversion of the light beam in the biscuit lens assembly will be as follows: Figure 1 As shown and explained below, left circularly polarized light 101 from the display passes through the partial reflector 10, then travels along the straight light path SP and is guided by the quarter-wave plate 30. The quarter-wave plate 30 converts the left circularly polarized light 101 into X-polarized light 102. Subsequently, the polarization controller 50, in the first state, converts the X-polarized light 102 into Y-polarized light 103. Finally, the Y-polarized light 103 passes through the polarization-dependent optical element 40 and the reflective polarizer 20, reaching the user's eyes (not shown).

[0054] Therefore, as Figure 1 As shown, under the conditions that (i) the polarization controller 50 is in the first state and (ii) the Y-polarized light 103 passes through the polarization-dependent optical element 40, when the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see...), Figure 3 When the biscuit lens assembly has an optical power (Pe), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 6 When the biscuit lens assembly is used, it has an optical power (Po).

[0055] See Figure 2When the light beam is introduced into the biscuit lens assembly and the polarization controller 50 is in the second state, a folded light path FP is formed between the partial reflector 10 and the reflective polarizer 20, passing through the polarization-dependent optical element 40 three times. The folded light path FP has three transmission path segments P1, P2, and P3, each passing through the polarization-dependent optical element 40. When the light beam travels along two of these transmission path segments P1 and P2 and passes through the polarization-dependent optical element 40, it will be polarized in the X direction. When the light beam travels along the remaining transmission path segment P3 and passes through the polarization-dependent optical element 40, it will be polarized in the Y direction. The polarization conversion of the light beam in the biscuit lens assembly is as follows: Figure 2 As shown, and will be explained below.

[0056] Left circularly polarized light 101 from the display passes through the partial reflector 10 and then travels along one of the transmission path segments P1 to the quarter-wave plate 30, which converts the left circularly polarized light 101 into X-polarized light 102. The X-polarized light 102 passes through the polarization controller 50 without being converted. Then, the X-polarized light 102 continues to travel along one of the transmission path segments P1 and passes through the polarization-dependent optical element 40 for the first time, and is reflected by the reflective polarizer 20 to form X-polarized light 104.

[0057] Subsequently, the reflected X-polarized light 104 travels along another transmission path segment P2 and passes through the polarization-dependent optical element 40 for the second time. It then passes through the polarization controller 50 without being converted. The X-polarized light continues to travel along the transmission path segment P2 to the quarter-wave plate 30, which converts the X-polarized light 104 into left circularly polarized light 105. The partial reflector 10 reflects the left circular plate polarized light 105 and converts it into right circularly polarized light 106.

[0058] Next, the quarter-wave plate 30 converts the right circularly polarized light 106 into Y-polarized light 107, which travels along another transmission path segment P3. The Y-polarized light 107 passes through the polarization controller 50 without being converted. Then, the Y-polarized light 107 continues to travel along the transmission path segment P3 and passes through the polarization-dependent optical element 40 for the third time. It then passes through the reflective polarizer 20 and reaches the user's eyes (not shown).

[0059] Therefore, as Figure 2As shown, under the conditions that (i) the polarization controller 50 is in the second state, (ii) the X-polarized light 102 and 104 pass through the polarization-dependent optical element 40 twice, and (iii) the Y-polarized light 107 passes through the polarization-dependent optical element 40 once, the polarization conversion of the light beam in the biscuit lens assembly is similar to that under the condition that the biscuit lens assembly is not equipped with the polarization controller 50. That is, when the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see... Figure 3 and Figure 4 When the biscuit lens assembly has an optical power of (2Po+Pe), the major axes L of the liquid crystal molecules 411 are all aligned along the x-direction and / or parallel to the XZ plane (see...). Figure 5 and Figure 6 When the biscuit lens assembly has an optical power of (Po+2Pe), the biscuit lens assembly has an optical power of (Po+2Pe).

[0060] It should be noted that, Figure 1 and Figure 2 The polarization states presented are for illustrative purposes only and can vary depending on the polarization pattern of the light beam from the display and the properties of the reflective polarizer 20. For example, when the light beam from the display is right-circularly polarized, or when the reflective polarizer 20 is used to reflect Y-polarized light and transmit X-polarized light, the polarization state of the light beam in the optical path will change accordingly.

[0061] Furthermore, in the diagram, the components such as the partial reflector 10, the quarter-wave plate 30, the polarization controller 50, the polarization-dependent optical element 40, and the reflective polarizer 20 are shown separately from each other. However, in actual implementation, the components are joined together, and there are no gaps between them.

[0062] See Figure 7 and Figure 8 This describes another embodiment of the biscuit lens assembly, the structure of which is similar to... Figure 1 , 2 The difference between the biscuit lens assembly disclosed herein and the one described above is that the polarization controller 50 of the other embodiment is located at the rear position.

[0063] When the light beam is introduced into the biscuit lens assembly and the polarization controller 50 is in the first state, a straight light path SP is formed that passes through the polarization-dependent optical element 40 only once. The polarization conversion of the light beam in the biscuit lens assembly is as follows: Figure 7 As shown, and with Figure 1 The polarization conversion is similar, the main difference being that the polarization direction of the beam passing through the polarization-dependent optical element 40 is different. Figure 1 Thus, the Y-polarized light 103 passes through the polarization-dependent optical element 40, while... Figure 7 In this case, the X-polarized light 102 passes through the polarization-dependent optical element 40. Therefore, as... Figure 7 As shown, under the conditions that (i) the polarization controller 50 is in the first state and (ii) the X-polarized light 102 passes through the polarization-dependent optical element 40, when the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see... Figure 4 When the biscuit lens assembly has an optical power (Po), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 5 When the biscuit lens assembly has optical power (Pe), the biscuit lens assembly has optical power (Pe).

[0064] See Figure 8 When the light beam is introduced into the biscuit lens assembly and the polarization controller 50 is in the second state, a folded light path FP is formed between the partial reflector 10 and the reflective polarizer 20, and passes through the polarization-dependent optical element 40 three times. In this case, the polarization conversion of the light beam in the biscuit lens assembly is similar to that of a biscuit lens assembly without the polarization controller 50, or as... Figure 2 The polarization conversion of the biscuit lens assembly is shown. That is, when the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see...). Figure 3 and Figure 4 When the biscuit lens assembly has an optical power of (2Po+Pe), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 5 and Figure 6 When the biscuit lens assembly has an optical power of (Po+2Pe), the biscuit lens assembly has an optical power of (Po+2Pe).

[0065] See Figures 9 to 12 This describes another embodiment of the biscuit lens assembly, which is similar to... Figure 1 , 2 The structures of the biscuit lens assemblies shown are similar, the difference being that... Figures 9 to 12 The biscuit lens assembly shown is configured with two polarization controllers 50 located at the front and rear positions, respectively. In the following description, the polarization controller 50 located at the front position will be referred to as the front polarization controller 50, and the other polarization controller 50 located at the rear position will be referred to as the rear polarization controller 50.

[0066] See Figure 9 , Figure 10When the light beam is introduced into the biscuit lens assembly, and one polarization controller 50 is in the first state while the other polarization controller 50 is in the second state, a straight light path SP is formed that passes through the polarization-dependent optical element 40 only once.

[0067] exist Figure 9 In this configuration, the front polarization controller 50 is in the second state, and the rear polarization controller 50 is in the first state. The polarization conversion of the light beam in the biscuit lens assembly is similar to that of a biscuit lens assembly equipped only with the rear polarization controller 50 (e.g., ...). Figure 7 (As shown). That is, when the X-polarized light passes through the polarization-dependent optical element 40, and the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see... Figure 4 When the biscuit lens assembly has an optical power (Po), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 5 When the biscuit lens assembly has optical power (Pe), the biscuit lens assembly has optical power (Pe).

[0068] exist Figure 10 In this configuration, the front polarization controller 50 is in the first state, and the rear polarization controller 50 is in the second state. The polarization conversion of the light beam in the biscuit lens assembly is similar to that of a biscuit lens assembly equipped with only one front polarization controller 50 (e.g., ...). Figure 1 (As shown). That is, when the Y-polarized light passes through the polarization-dependent optical element 40, and the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see... Figure 3 When the biscuit lens assembly has an optical power (Pe), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 6 When the biscuit lens assembly is used, it has an optical power (Po).

[0069] See Figure 11 , Figure 12 When the light beam is introduced into the biscuit lens assembly, and both polarization controllers 50 are simultaneously in the first state or the second state, a folded light path FP is formed between the partial reflector 10 and the reflective polarizer 20, and passes through the polarization-dependent optical element 40 three times.

[0070] The beam is then directed as follows Figure 11 The polarization conversion situation in the biscuit lens assembly shown is described below, and both polarization controllers 50 of the biscuit lens assembly are in the first state.

[0071] Left circularly polarized light 201 from the display passes through the partial reflector 10 and travels along one of the transmission path segments P1 to the quarter-wave plate 30. The quarter-wave plate 30 converts the left circularly polarized light 201 into X-polarized light 202. The polarization controller 50, which is in the first state, converts the X-polarized light 202 into Y-polarized light 203. The Y-polarized light 203 continues to travel along the transmission path segment P1 and passes through the polarization-dependent optical element 40 for the first time. The polarization controller 50, which is in the first state, converts the Y-polarized light 203 into X-polarized light 204. The X-polarized light 204 is then reflected by the reflective polarizer 20 to form X-polarized light 205.

[0072] The reflected X-polarized light 205 travels along another transmission path segment P2 and is converted into Y-polarized light 206 by the rear polarization controller 50 in the first state. The Y-polarized light 206 continues to travel along the transmission path segment P2 and passes through the polarization-dependent optical element 40 for the second time. Then, the rear polarization controller 50 in the first state converts the Y-polarized light 206 into X-polarized light 207. Then, the quarter-wave plate 30 converts the X-polarized light 207 into left circularly polarized light 208.

[0073] The partial reflector 10 reflects the left circularly polarized light 208 and converts it into right circularly polarized light 209 that travels along another transmission path segment P3. Next, the quarter-wave plate 30 converts the right circularly polarized light 209 into Y-polarized light 210, and the Y-polarized light 210 is converted into X-polarized light 211 by the polarization controller 50 in the first state. The X-polarized light 211 travels along the transmission path segment P3 and passes through the polarization-dependent optical element 40 for the third time. Thereafter, the X-polarized light 211 is converted into Y-polarized light 212 by the polarization controller 50 in the first state. Finally, the Y-polarized light 212 passes through the reflective polarizer 20 and then reaches the user's eyes (not shown).

[0074] Therefore, as Figure 11 As shown in the following conditions, under the following circumstances: (i) the two polarization controllers 50 are in the first state, (ii) the Y-polarized light 210, 212 pass through the polarization-dependent optical element 40 twice, and (iii) the X-polarized light 211 passes through the polarization-dependent optical element 40 once, when the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see... Figure 3 , 4When the biscuit lens assembly has an optical power of (Po+2Pe), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 5 , 6 When the biscuit lens assembly has an optical power of (2Po+Pe), the biscuit lens assembly has an optical power of (2Po+Pe).

[0075] exist Figure 12 In this case, both polarization controllers 50 are in the second state, and the polarization conversion of the light beam in the biscuit lens assembly is similar to that of a biscuit lens assembly without the polarization controllers 50, or as... Figure 2 or Figure 8 The biscuit lens assembly shown. That is, when the major axes L of the liquid crystal molecules 411 are all aligned along the Y direction and / or parallel to the YZ plane (see... Figure 3 , 4 When the biscuit lens assembly has an optical power of (2Po+Pe), the major axes L of the liquid crystal molecules 411 are all aligned along the X direction and / or parallel to the XZ plane (see...). Figure 5 , 6 When the biscuit lens assembly has an optical power of (Po+2Pe), the biscuit lens assembly has an optical power of (Po+2Pe).

[0076] When the biscuit lens assembly is equipped with the front and rear polarization controllers 50, regardless of whether the major axis L of the liquid crystal molecules 411 is parallel to the YZ plane or aligned with the XZ plane, the biscuit lens assembly will have four optical powers (Pe, Po, 2Po+Pe, Po+2Pe). Assuming the diopter of the optical power (Po) is 0 diopter (0D) and the optical power (Pe) is 1 diopter (1D), the optical power of the biscuit lens assembly can be switched between three different diopter values ​​(0D, 1D, 2D). Furthermore, when the polarization-dependent optical element 40 is selected from an electrically controllable focusing liquid crystal lens, the biscuit lens assembly can have a wider range of diopter adjustability.

[0077] In some embodiments, when a user wears a head-mounted display (not shown) with two pancake lens assemblies respectively positioned in front of the user's eyes, the pancake lens assemblies can adjust their respective optical powers to allow for convergence accommodation. Therefore, visual fatigue and eye discomfort caused by visual-accommodative conflict (VAC) can be alleviated when viewing images using the head-mounted display. In this case, a camera (not shown) can also be used to monitor and track the user's eyes, which helps adjust the optical power of the pancake lens assemblies for the eyes.

[0078] Furthermore, the biscuit lens assembly is positioned in front of the user's eyes and can also be used to correct the user's poor vision. Therefore, the user can view images directly from the head-mounted display without wearing glasses or needing vision correction.

[0079] Furthermore, the biscuit lens assembly of the present invention can also be used as at least part of a corrective lens suitable for everyday vision correction.

[0080] In summary, the biscuit lens assembly of the present invention utilizes a polarization controller 50 disposed between the quarter-wave plate 30 and the polarization-dependent optical element 40 and / or between the polarization-dependent optical element 40 and the reflective polarizer 20, and switches the polarization controller 50 as needed to the first state or the second state, thereby allowing the biscuit lens assembly to have multiple different optical powers. Therefore, when the biscuit lens assembly is disposed between the display and the user's eyes, by adjusting its own optical power, the user's eyes can alleviate visual fatigue and eye discomfort caused by visual-accommodative conflict (VAC) during convergence accommodation, thus effectively achieving the purpose of the present invention.

[0081] The above description is only a preferred embodiment of the present invention, but it is not intended to limit the scope of the present invention. Any person skilled in the art can make further improvements and changes on this basis without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims of this application.

Claims

1. A cookie lens assembly, comprising: Comprising: a partial mirror; a reflective polarizer disposed behind the partial mirror; a quarter wave plate disposed between the partial mirror and the reflective polarizer; a polarization dependent optical element disposed between the quarter wave plate and the reflective polarizer; and at least one polarization controller located at a position in front of the quarter wave plate and the polarization dependent optical element or behind the polarization dependent optical element and the reflective polarizer, the at least one polarization controller being capable of switching from a first state to a second state via electrical driving, wherein when a light beam is introduced into the pancake lens assembly along an optical axis in a Z direction and passes through the polarization controller in the first state, a polarization direction of the light beam is switched by the polarization controller, and when the light beam is introduced into the pancake lens assembly along the optical axis and passes through the polarization controller in the second state, the polarization direction of the light beam is prevented from being switched by the polarization controller, when the polarization controller is in one of the first state and the second state, the light beam introduced into the pancake lens assembly along the optical axis forms a straight light path passing through the polarization dependent optical element only once, and when the polarization controller is in the other of the first state and the second state, the light beam introduced into the pancake lens assembly along the optical axis forms a folded light path between the partial mirror and the reflective polarizer and passing through the polarization dependent optical element three times. The polarization dependent optical element is a transmissive liquid crystal element.

2. The cookie lens assembly of claim 1, wherein, The polarization dependent optical element is selected from a group consisting of a fixed-focus liquid crystal lens, an electrically controlled variable-focus liquid crystal lens, a liquid crystal grating, a liquid crystal prism, a liquid crystal wavefront corrector, an ultrathin lens, and at least one combination thereof.

3. The cookie lens assembly of claim 1, wherein, The polarization controller is selected from a group consisting of a twisted nematic liquid crystal element, a liquid crystal wave plate, and at least one combination thereof.

4. The cookie lens assembly of claim 1, wherein, The polarization dependent optical element includes a plurality of liquid crystal molecules, long axes of the liquid crystal molecules being parallel to one of an XZ plane or a YZ plane, the XZ plane being defined by an X direction and the Z direction, the YZ plane being defined by a Y direction and the Z direction, and the X direction, the Y direction, and the Z direction being orthogonal to each other.

5. The cookie lens assembly of claim 1, wherein, When the light beam is introduced into the pancake lens assembly along the optical axis in the Z direction and passes through the polarization controller in the first state, the straight light path passing through the polarization dependent optical element only once is formed.

6. The cookie lens assembly of claim 5, wherein, When the light beam is introduced into the pancake lens assembly and passes through the polarization controller in the second state, the folded light path between the partial mirror and the reflective polarizer and passing through the polarization dependent optical element three times is formed.

7. The cookie lens assembly of claim 5, wherein, ​ 8. The cookie lens assembly of claim 7, wherein, The folded light path has three transmission path segments through the polarization dependent optical elements, when the light beam is X-polarized light polarized in the X direction, the light beam travels along two of the transmission path segments and passes through the polarization dependent optical elements, and when the light beam is Y-polarized light polarized in the Y direction, the light beam travels along the remaining one of the transmission path segments and passes through the polarization dependent optical elements.

9. The cookie lens assembly of claim 5, wherein, The polarization controllers include two polarization controllers at the front position and the rear position respectively.

10. The cookie lens assembly of claim 9, wherein, When one of the polarization controllers is in the first state and the other polarization controller is in the second state, the light beam introduced into the biscuit lens assembly forms a straight light path passing through the polarization dependent optical element only once.

11. The cookie lens assembly of claim 9, wherein, When the light beam is introduced into the biscuit lens assembly and the polarization controllers are both in one of the first state and the second state, a folded light path is formed between the partial mirror and the reflective polarizer and passes through the polarization dependent optical element three times.

12. The cookie lens assembly of claim 11, wherein, The polarization controllers are both in the first state, the folded light path has three transmission path segments through the polarization dependent optical elements, when the light beam is Y-polarized light polarized in the Y direction, the light beam travels along two of the transmission path segments and passes through the polarization dependent optical elements, and when the light beam is X-polarized light polarized in the X direction, the light beam travels along the remaining one of the transmission path segments and passes through the polarization dependent optical elements.

13. The cookie lens assembly of claim 11, wherein, The polarization controllers are both in the second state, the folded light path has three transmission path segments through the polarization dependent optical elements, when the light beam is X-polarized light polarized in the X direction, the light beam travels along two of the transmission path segments and passes through the polarization dependent optical elements, and when the light beam is Y-polarized light polarized in the Y direction, the light beam travels along the remaining one of the transmission path segments and passes through the polarization dependent optical elements.

14. The cookie lens assembly of claim 5, wherein, The partial mirror partially transmits first circularly polarized light and reflects part of the first circularly polarized light to convert into second circularly polarized light, the circular polarization direction of the second circularly polarized light being different from the circular polarization direction of the first circularly polarized light.

15. The pancake lens assembly of claim 14, wherein, The quarter-wave plate is capable of converting the first circularly polarized light into first linearly polarized light, converting the first linearly polarized light into the first circularly polarized light, converting the second circularly polarized light into second linearly polarized light, or converting the second linearly polarized light into the second circularly polarized light, the linear polarization direction of the second linearly polarized light being different from the linear polarization direction of the first linearly polarized light.

16. The cookie lens assembly of claim 15, wherein, The polarization controller in the first state converts the first linearly polarized light into the second linearly polarized light and converts the second linearly polarized light into the first linearly polarized light.

17. The pancake lens assembly of claim 16, wherein, The reflective polarizer is used to reflect the first linearly polarized light and transmit the second linearly polarized light.

18. The pancake lens assembly of claim 17, wherein, The first circularly polarized light is left circularly polarized light, the second circularly polarized light is right circularly polarized light, the first linearly polarized light is X polarized light polarized in the X direction, and the second linearly polarized light is Y polarized light polarized in the Y direction. The first circularly polarized light is left circularly polarized light, the second circularly polarized light is right circularly polarized light, the first linearly polarized light is X polarized light polarized in the X direction, and the second linearly polarized light is Y polarized light polarized in the Y direction. The first circularly

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