Multi-focus display system combining liquid crystal variable delay and polarization beam splitter

Abstract

The present invention provides a multi-focal plane display system that combines a liquid crystal variable retarder and a polarization beam splitter element. By controlling the switches of two liquid crystal variable retarders (LCVRs) respectively, the on and off states of the first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 are changed, so that the optical path of light transmitted in the multi-focal plane display system is different. In turn, the direction and time of light emission from the polarization beam splitter prism (PBS prism) are different. The four different on and off states achieved by the two liquid crystal variable retarders produce four different focal plane images, and can achieve rapid switching of the images of the four focal planes. At the same time, the human eye can observe the real world through the half-reflecting half-mirror lens.

Description

Technical Field

[0001] The present invention belongs to the technical field of augmented reality (AR) and virtual reality (VR), and in particular relates to a multi-focal plane display system combining a liquid crystal variable delay device and a polarization beam splitting element. Background Art

[0002] Augmented reality (AR) and virtual reality (VR) technologies, as crucial bridges connecting the digital and physical worlds, have developed rapidly in recent years, with their application scenarios continuously expanding. From entertainment and gaming to education and training, from remote collaboration to medical surgery simulation, AR / VR technologies, with their immersive and interactive features, have revolutionized various industries. In the VR field, the current mainstream solution is the pancake system. In the AR field, there are more options, such as waveguides, freeform prisms, freeform mirrors, and birdbaths. However, while these technologies provide an immersive experience, they also face the problem of vergence-accommodation conflict (VAC). In natural vision, the human eye adjusts the curvature of the lens to change focus (accommodation) and changes the point of convergence of the line of sight (vergence) by adducting or abducting the eyeball. In traditional AR / VR systems, because virtual images are typically displayed on a screen at a fixed distance, this leads to a mismatch between accommodation and vergence, causing VAC. This not only affects the user's depth perception but can also cause discomfort such as visual fatigue and vertigo.

[0003] To address the VAC problem, researchers have proposed various solutions, including varifocal display technology, light field display, holographic display, and Maxwell view. Varifocal display technology simulates real-world depth perception by providing multiple image focal planes or rapidly switching focal planes based on the viewer's current focus. This may involve complex optical systems to achieve focal length changes, increasing the size and cost of the device. Another approach is light field display technology, which displays light from all directions in the optical scene to provide more physiological visual information than traditional 2D displays. However, it is limited by the balance between angular resolution and viewpoint resolution, making it difficult to achieve high-resolution displays. Holographic display technology, based on the principle of light diffraction, can recreate light waves equivalent to real 3D objects and support user freedom of focus. However, holographic displays are limited by the performance and computing power of the spatial light modulator (SLM), and the images suffer from issues such as insufficient viewing angle and low resolution due to speckle effects. Furthermore, researchers have proposed using Maxwellian-view display to eliminate accommodation cues and mitigate the effects of VAC. But Maxwell view display systems are typically limited to a finite eyebox size, and even the slightest deviation in the user's pupil position can cause the image to disappear completely. Summary of the Invention

[0004] To solve the above problems, the present invention provides a multi-focal plane display system that combines a liquid crystal variable retarder and a polarization beam splitter. By controlling the switches of two liquid crystal variable retarders LCVR respectively, fast switching of images of four focal planes can be achieved.

[0005] A multi-focal display system combining a liquid crystal variable retarder and a polarization beam splitter element includes a polarizer LP, a first quarter-wave plate QWP1, a first liquid crystal variable retarder LCVR1, a transflective film BS, a first glass sheet Glass1, a second quarter-wave plate QWP2, a polarization beam splitting film PBS, a second liquid crystal variable retarder LCVR2, a polarization beam splitting prism PBS prism, and a third quarter-wave plate QWP3 and a first total reflection film RF1 sequentially arranged on the reflective light path of the polarization beam splitting prism PBS prism; and a second glass sheet Glass2, a fourth quarter-wave plate QWP4, and a second total reflection film RF2 sequentially arranged on the transmitted light path of the polarization beam splitting prism PBS prism.

[0006] Light emitted from the screen Display passes through the polarizer LP, the first quarter-wave plate QWP1, the first liquid crystal variable retarder LCVR1, the transflective film BS, the first glass Glass1, the second quarter-wave plate QWP2, the polarization beam splitting film PBS, and the second liquid crystal variable retarder LCVR2 before entering the polarization beam splitting prism PBS prism. The first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 have different on and off states, resulting in different optical path lengths for the light in the multi-focal plane display system. Consequently, the light exits the polarization beam splitting prism PBS prism in different directions and at different times. The four different on and off states achieved by the two liquid crystal variable retarders result in four different focal plane images.

[0007] Furthermore, when the first liquid crystal variable retarder LCVR1 is off and the second liquid crystal variable retarder LCVR2 is on, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at 45 degrees relative to the polarizer LP, becoming right-handed circularly polarized light. When the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the off state, the polarization state does not change. The right-handed circularly polarized light exiting the first liquid crystal variable retarder LCVR1 then passes through the semi-transmissive and semi-reflective film BS to obtain right-handed circularly polarized light with half the light energy lost. The right-handed circularly polarized light with half the light energy lost passes through the first glass plate Glass1 and the second quarter-wave plate QWP2 in sequence to become P light. The P light directly passes through the polarization beam splitter film PBS and enters the second liquid crystal variable retarder LCVR2 in the on state, whereupon the polarization state of the P light changes by 90 degrees to become S light. The S light enters the interior of the polarization beam splitter prism PBS prism and is reflected by the polarization beam splitter prism PBS. The light is reflected in the prism and enters the third quarter-wave plate QWP3 on the reflection light path, becoming left-hand circularly polarized light. The left-hand circularly polarized light is then reflected by the first total reflection film RF1 and becomes right-hand circularly polarized light. The right-hand circularly polarized light reflected back by the first total reflection film RF1 passes through the third quarter-wave plate QWP3 again and becomes P light again. The finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

[0008] Furthermore, when the first liquid crystal variable retarder LCVR1 is turned on and the second liquid crystal variable retarder LCVR2 is turned off, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at a 45-degree angle relative to the polarizer LP, and becomes right-handed circularly polarized light; the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the turned-on state, and becomes left-handed polarized light; the left-handed circularly polarized light emitted from the first liquid crystal variable retarder LCVR1 then passes through the semi-transparent and semi-reflective film BS to obtain left-handed circularly polarized light with half the light energy lost; the left-handed circularly polarized light with half the light energy lost passes through the first glass sheet Gla in sequence. ss1, the second quarter-wave plate QWP2 turns into S light; the S light is reflected on the polarization beam splitter film PBS, and passes through the second quarter-wave plate QWP2 again to become right-handed circularly polarized light. The regenerated right-handed circularly polarized light is reflected a second time on the semi-transparent and semi-reflective film BS and turns into left-handed circularly polarized light again. The left-handed circularly polarized light generated at this time passes through the second quarter-wave plate QWP2 for the third time to become P light; the P light is directly transmitted from the polarization beam splitter film PBS into the second liquid crystal variable retarder LCVR2 in the closed state, and the polarization state does not change; the P light from the second liquid crystal variable retarder LCVR2 enters the polarization beam splitter prism PBS The light passes through the interior of the polarization beam splitter prism PBS prism and is transmitted through the second glass piece Glass2 and the fourth quarter-wave plate QWP4 in the transmission light path, becoming right-handed circularly polarized light. The right-handed circularly polarized light is then reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected back by the second total reflection film RF2 is again converted into S light by the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

[0009] Furthermore, when the first liquid crystal variable retarder LCVR1 is closed and the second liquid crystal variable retarder LCVR2 is closed, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 arranged at 45 degrees relative to the polarizer LP, becoming right-handed circularly polarized light. When the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the closed state, the polarization state does not change. The right-handed circularly polarized light exiting the first liquid crystal variable retarder LCVR1 then passes through the semi-transmissive and semi-reflective film BS to obtain right-handed circularly polarized light with half the light energy lost. The right-handed circularly polarized light with half the light energy lost passes through the first glass plate Glass1 and the second quarter-wave plate QWP2 in sequence to become P light. The P light directly transmits through the polarization beam splitting film PBS and enters the second liquid crystal variable retarder LCVR2 in the closed state without changing its polarization state. The P light exiting the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism and is reflected by the polarization beam splitting prism PBS. The light is transmitted through the prism and enters the second glass piece Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path, becoming right-handed circularly polarized light. The right-handed circularly polarized light is then reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected back by the second total reflection film RF2 is again converted into S light by the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBSprism.

[0010] Furthermore, when the first liquid crystal variable retarder LCVR1 is turned on and the second liquid crystal variable retarder LCVR2 is turned on, the light emitted from the screen Display first passes through the polarizer LP and the first quarter wave plate QWP1 placed at 45 degrees relative to the polarizer LP, and becomes right-handed circularly polarized light; when the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the turned-on state, it becomes left-handed polarized light; the left-handed circularly polarized light from the first liquid crystal variable retarder LCVR1 then passes through the semi-transparent and semi-reflective film BS to obtain left-handed circularly polarized light with half of the light energy lost; the left-handed circularly polarized light with half of the light energy lost passes through the first glass The S light is reflected on the polarization beam splitter film PBS and passes through the second quarter-wave plate QWP2 to become right-hand circularly polarized light. The regenerated right-hand circularly polarized light is reflected for the second time on the semi-transparent and semi-reflective film BS and becomes left-hand circularly polarized light. The left-hand circularly polarized light generated at this time passes through the second quarter-wave plate QWP2 for the third time to become P light. The P light is directly transmitted from the polarization beam splitter film PBS into the second liquid crystal variable retarder LCVR2 in the turned-on state, and the polarization state of the P light changes by 90° to become S light. The S light enters the polarization beam splitter prism PBS The light passes through the third quarter-wave plate QWP3 on the reflection light path and becomes left-hand circularly polarized light. The left-hand circularly polarized light then passes through the first total reflection film RF1 and becomes right-hand circularly polarized light. The right-hand circularly polarized light reflected by the first total reflection film RF1 passes through the third quarter-wave plate QWP3 again and becomes P light again. The finally generated P light transmits through the polarization beam splitter prism PBS prism.

[0011] Furthermore, a multi-focal plane display system combining a liquid crystal variable delay device and a polarization beam splitter element further includes a relay lens assembly;

[0012] The light from the first liquid crystal variable retarder LCVR1 is shaped by the relay lens group and then enters the semi-transparent and semi-reflective film BS.

[0013] Furthermore, a multi-focal display system combining a liquid crystal variable retarder and a polarization beam splitter element further includes a free-form prism;

[0014] The light from the polarization beam splitter prism PBS prism is refracted and reflected inside the free-form surface prism before entering the human eye.

[0015] Furthermore, a multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter element further includes a free-form surface reflector;

[0016] The light is reflected from the polarization beam splitter prism PBS prism on the free-form surface mirror and then enters the human eye.

[0017] Furthermore, the structure of any liquid crystal variable retarder LCVR is, from top to bottom, an upper quarter wave plate, an upper glass substrate, an upper indium tin oxide layer, an upper alignment layer, a twisted nematic liquid crystal layer, a lower alignment layer, a lower indium tin oxide layer, a lower glass substrate, and a lower quarter wave plate;

[0018] When no voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder (LCVR) is in the off state. The polarization state of light will change by 90° after passing through the twisted nematic liquid crystal layer. However, the polarization state of light will not change after passing through the upper quarter-wave plate, upper glass substrate, upper indium tin oxide layer, upper alignment layer, twisted nematic liquid crystal layer, lower alignment layer, lower indium tin oxide layer, lower glass substrate, and lower quarter-wave plate in sequence.

[0019] When voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder LCVR is in the on state. The polarization state of light does not change after passing through the twisted nematic liquid crystal layer. However, after the light passes through the upper quarter-wave plate, upper glass substrate, upper indium tin oxide layer, upper alignment layer, twisted nematic liquid crystal layer, lower alignment layer, lower indium tin oxide layer, lower glass substrate, and lower quarter-wave plate in sequence, the polarization state will change by 90°.

[0020] Beneficial effects:

[0021] The present invention provides a multi-focal plane display system that combines a liquid crystal variable retarder and a polarization beam splitter element. By controlling the switches of two liquid crystal variable retarders (LCVRs) respectively, the on and off states of the first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 are changed, so that the optical path of light transmitted in the multi-focal plane display system is different. In turn, the direction and time of light emission from the polarization beam splitter prism (PBS prism) are different. The four different on and off states achieved by the two liquid crystal variable retarders produce four different focal plane images, and can achieve rapid switching of the images of the four focal planes. At the same time, the human eye can observe the real world through the half-reflecting half-mirror lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the four-focal-plane optical paths of the PBS prism and dual-focal-plane module provided by the present invention; (a) illustrates two light paths when the second LCVR is in the on state; (b) illustrates two light paths when the second LCVR is in the off state;

[0023] Figure 2 The working principle of the LCVR provided by the present invention; wherein (a) shows the change in the arrangement state of the liquid crystal and the polarization state of light when the power is off; (b) shows the change in the arrangement state of the liquid crystal and the polarization state of light when the power is on;

[0024] Figure 3Optical path diagram of the multi-focal augmented reality display system provided by the present invention that combines the LCVR-PBS display module with the off-axis free-form prism system;

[0025] Figure 4 Optical path diagram of the multi-focal augmented reality display system provided by the present invention that combines the LCVR-PBS display module with the off-axis free-form surface reflection system;

[0026] Figure 5 Schematic diagram of the MTF comparison of the system at different diopters when the exit pupil size is 4mm; among them, (a) is the MTF at 0.2D; (b) is the MTF at 1.8D; (c) is the MTF at 3.4D; (d) is the MTF at 5D. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0028] This paper designs a novel optical NED system. By integrating a liquid crystal variable retarder and a PBS prism, combined with freeform surface elements, an augmented reality near-eye display system is designed. This system can provide four virtual image planes of varying depths while simultaneously viewing the real environment. It achieves four focal planes ranging from 0.2D to 5D, covering the human eye's observation range from near to far. The paper details the optical design principles of this multi-focal plane NED system and derives a mathematical model to describe the relationship between virtual image distance and the system. Finally, by building a prototype, the paper demonstrates the system's excellent performance and broad application potential.

[0029] Specifically, such as Figure 1 As shown, a multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter element includes a polarizer LP, a first quarter-wave plate QWP1, a first liquid crystal variable retarder LCVR1, a semi-transmissive semi-reflective film BS, a first glass sheet Glass1, a second quarter-wave plate QWP2, a polarization beam splitting film PBS, a second liquid crystal variable retarder LCVR2, a polarization beam splitting prism PBS prism, and a third quarter-wave plate QWP3 and a first total reflection film RF1 sequentially arranged on the reflection light path of the polarization beam splitting prism PBS prism, and a second glass sheet Glass2, a fourth quarter-wave plate QWP4, and a second total reflection film RF2 sequentially arranged on the transmission light path of the polarization beam splitting prism PBS prism.

[0030] Light emitted from the screen Display passes through the polarizer LP, the first quarter-wave plate QWP1, the first liquid crystal variable retarder LCVR1, the transflective film BS, the first glass Glass1, the second quarter-wave plate QWP2, the polarization beam splitting film PBS, and the second liquid crystal variable retarder LCVR2 before entering the polarization beam splitting prism PBS prism. The first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 have different on and off states, resulting in different optical path lengths for the light in the multi-focal plane display system. Consequently, the light exits the polarization beam splitting prism PBS prism in different directions and at different times. The four different on and off states achieved by the two liquid crystal variable retarders result in four different focal plane images.

[0031] It should be noted that a liquid crystal variable retarder (LCVR) is a device that uses the optical properties of liquid crystal materials to adjust the phase delay of light wavefront. Figure 2 As shown, the structure of any liquid crystal variable retarder LCVR is, from top to bottom, an upper quarter wave plate, an upper glass substrate, an upper indium tin oxide layer, an upper alignment layer, a twisted nematic liquid crystal layer, a lower alignment layer, a lower indium tin oxide layer, a lower glass substrate, and a lower quarter wave plate; Figure 2 As shown in (a) in the figure, in the absence of an external electric field, the orientation of the liquid crystal molecules from top to bottom gradually rotates from the x direction to the z direction. The z-polarized light incident on the LC layer is converted into x-polarized light. Figure 2As shown in (b) of Figure 1, when the voltage (V) significantly exceeds the threshold voltage (Vth), the LC molecules reorient along the y-direction, and the polarization state of light polarized in the z-direction remains unchanged when passing through the LC. The changes in light passing through the LC can be precisely controlled by adjusting the intensity of the electric field. When no voltage is applied to the LC, the LC is in the OFF state, and the corresponding phase retardation of the LC is π; light passing through it undergoes a 90° polarization change. When a voltage is applied to the LC, the LC is in the ON state, and the corresponding phase retardation of the LC is 0; light passing through it does not undergo a polarization change. The polarization switching time can be controlled within 5ms. In this way, we can achieve a phase retardation transition from 0 to π by applying and releasing voltage, making the LVCR a switchable half-wave plate. However, it differs from a traditional half-wave plate in that twisted nematic liquid crystal can deflect any polarization of light by 90°. A half-wave plate, on the other hand, has a fixed fast and slow axis orientation and can only deflect light polarized in a specific direction by 90°. Therefore, to achieve conversion between left-handed and right-handed circularly polarized light by switching voltage, quarter-wave plates (QWPs) with the same optical axis above and below the LCVR are required. When power is applied to the LC, the LC has no effect on the polarization state. The stacked QWP layer can be considered an electrically switchable half-wave plate, known as an LCVR. Right-handed circularly polarized light passes through the LCVR to become left-handed circularly polarized light. When the LC discharges, the LC shifts the polarization state by 90°, leaving the circularly polarized light unchanged after passing through the LCVR.

[0032] That is, when no voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder (LCVR) is in the off state. The polarization state of light will change by 90° after passing through the twisted nematic liquid crystal layer. However, the polarization state of light will not change after passing through the upper quarter-wave plate, upper glass substrate, upper indium tin oxide layer, upper alignment layer, twisted nematic liquid crystal layer, lower alignment layer, lower indium tin oxide layer, lower glass substrate, and lower quarter-wave plate in sequence.

[0033] When voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder LCVR is in the on state. The polarization state of light does not change after passing through the twisted nematic liquid crystal layer. However, after the light passes through the upper quarter-wave plate, upper glass substrate, upper indium tin oxide layer, upper alignment layer, twisted nematic liquid crystal layer, lower alignment layer, lower indium tin oxide layer, lower glass substrate, and lower quarter-wave plate in sequence, the polarization state will change by 90°.

[0034] The following describes in detail the working process of the multi-focus display system in four on and off states corresponding to the two liquid crystal variable retarders LCVR.

[0035] In the first aspect, when the first liquid crystal variable retarder LCVR1 is turned off and the second liquid crystal variable retarder LCVR2 is turned on, the corresponding Figure 3The light emitted by the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at 45 degrees relative to the polarizer LP, and becomes right-handed circularly polarized light; when the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the closed state, the polarization state does not change; the right-handed circularly polarized light coming out of the first liquid crystal variable retarder LCVR1 passes through the semi-transparent and semi-reflective film BS to obtain right-handed circularly polarized light with half of the light energy lost; the right-handed circularly polarized light with half of the light energy lost passes through the first glass plate Glass1 and the second quarter-wave plate QWP2 in sequence to become P light; the P light directly passes through the polarization beam splitting film PBS and enters the second liquid crystal variable retarder LCVR2 in the open state, and the polarization state of the P light changes by 90 degrees to become S light; the S light enters the interior of the polarization beam splitting prism PBS prism and is reflected by the polarization beam splitting prism PBS. The light is reflected in the prism and enters the third quarter-wave plate QWP3 on the reflection light path, becoming left-hand circularly polarized light. The left-hand circularly polarized light is then reflected by the first total reflection film RF1 and becomes right-hand circularly polarized light. The right-hand circularly polarized light reflected back by the first total reflection film RF1 passes through the third quarter-wave plate QWP3 again and becomes P light again. The finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

[0036] Secondly, when the first liquid crystal variable retarder LCVR1 is turned on and the second liquid crystal variable retarder LCVR2 is turned off, the corresponding Figure 3The light emitted by the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at 45 degrees relative to the polarizer LP, and becomes right-handed circularly polarized light; when the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the turned-on state, it becomes left-handed polarized light; the left-handed circularly polarized light coming out of the first liquid crystal variable retarder LCVR1 passes through the semi-transparent and semi-reflective film BS again to obtain left-handed circularly polarized light with half of the light energy lost; the left-handed circularly polarized light with half of the light energy lost passes through the first glass piece Glass1, the second quarter-wave plate QWP2, and the second quarter-wave plate QWP3 in sequence. The S light is reflected by the polarization beam splitting film PBS and becomes right-handed circularly polarized light after passing through the second quarter-wave plate QWP2. The regenerated right-handed circularly polarized light is then reflected a second time by the semi-transmissive and semi-reflective film BS and becomes left-handed circularly polarized light. The left-handed circularly polarized light then passes through the second quarter-wave plate QWP2 for a third time and becomes P light. The P light directly transmits through the polarization beam splitting film PBS and enters the second liquid crystal variable retarder LCVR2, which is in the closed state, without changing its polarization state. The P light exiting the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism and transmits through the polarization beam splitting prism PBS prism. It then enters the second glass plate Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path and becomes right-handed circularly polarized light. The right-handed circularly polarized light is then reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected by the second total reflection film RF2 passes through the third quarter-wave plate QWP3 and becomes S light again. The resulting S light is then reflected and passes through the polarization beam splitting prism PBS prism.

[0037] In the third aspect, when the first liquid crystal variable retarder LCVR1 is turned off and the second liquid crystal variable retarder LCVR2 is turned off, the corresponding Figure 3The light emitted by the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at 45 degrees relative to the polarizer LP, and becomes right-handed circularly polarized light; when the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the closed state, the polarization state does not change; the right-handed circularly polarized light exiting the first liquid crystal variable retarder LCVR1 passes through the semi-transmissive and semi-reflective film BS to obtain right-handed circularly polarized light with half of the light energy lost; the right-handed circularly polarized light with half of the light energy lost passes through the first glass plate Glass1 and the second quarter-wave plate QWP2 in sequence to become P light; the P light directly transmits through the polarization beam splitting film PBS and enters the second liquid crystal variable retarder LCVR2 in the closed state, and the polarization state does not change; the P light exiting the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism and is reflected by the polarization beam splitting prism PBS. The light is transmitted through the prism and enters the second glass piece Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path, becoming right-handed circularly polarized light. The right-handed circularly polarized light is then reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected back by the second total reflection film RF2 is again converted into S light by the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

[0038] In the fourth aspect, when the first liquid crystal variable retarder LCVR1 is turned on and the second liquid crystal variable retarder LCVR2 is turned on, the corresponding Figure 3The light emitted by the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at 45 degrees relative to the polarizer LP, and becomes right-handed circularly polarized light; when the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1 in the turned-on state, it becomes left-handed polarized light; the left-handed circularly polarized light from the first liquid crystal variable retarder LCVR1 passes through the semi-transparent and semi-reflective film BS to obtain left-handed circularly polarized light with half the light energy lost; the left-handed circularly polarized light with half the light energy lost passes through the first glass piece Glass1, the second quarter-wave plate Q WP2 is converted into S light; the S light is reflected by the polarization beam splitter film PBS and passes through the second quarter-wave plate QWP2 again to become right-handed circularly polarized light. The regenerated right-handed circularly polarized light is then reflected a second time by the semi-transmissive and semi-reflective film BS and becomes left-handed circularly polarized light. The left-handed circularly polarized light generated at this time passes through the second quarter-wave plate QWP2 for the third time to become P light; the P light is directly transmitted from the polarization beam splitter film PBS into the second liquid crystal variable retarder LCVR2 in the turned-on state, where the polarization state of the P light changes 90° and becomes S light; the S light enters the interior of the polarization beam splitter prism PBS prism and is reflected in the polarization beam splitter prism PBS prism, entering the third quarter-wave plate QWP3 on the reflection light path and becoming left-handed circularly polarized light. The left-handed circularly polarized light is then reflected by the first total reflection film RF1 and becomes right-handed circularly polarized light; the right-handed circularly polarized light reflected back from the first total reflection film RF1 passes through the third quarter-wave plate QWP3 again and becomes P light again. The finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

[0039] Furthermore, combining the four working states of the two liquid crystal variable retarders LCVR, it can be seen that Figure 1 As shown in (a) of the figure, the dotted box represents the dual-focal-plane display module. When the first liquid crystal variable retarder LCVR1 is discharged, that is, in the off state, the polarization state of light in the first liquid crystal variable retarder LCVR1 does not change. When the first liquid crystal variable retarder LCVR1 is energized, that is, in the on state, the phase delay of light in the first liquid crystal variable retarder LCVR1 is π. In other words, when the state of the second liquid crystal variable retarder LCVR2 remains unchanged, the optical path length of light transmitted through the multi-focal-plane display system is different when the first liquid crystal variable retarder LCVR1 is in the on state and the off state, thus achieving dual-focal-plane display functionality.

[0040] like Figure 1As shown in Figure (b), by multiplexing the dual-focal-plane display module described above and then changing the on and off states of the second liquid crystal variable retarder LCVR2, the optical path of light transmitted throughout the multi-focal-plane display system can be further varied. In other words, the present invention can achieve optical path variations by controlling the distances between the QWP and the polarization beam splitter prism PBS prism, located in both the reflected and transmitted light paths. Ultimately, by rapidly switching the power on and off of the two LVCRs, a time-division multiplexed four-focal-plane display system can be realized. Due to the LCVR's high refresh rate, the human eye's persistence of vision allows for simultaneous viewing of images at different depths.

[0041] Furthermore, the multi-focal display system of the present invention further includes a relay lens assembly and a free-form surface prism; Figure 3 As shown, light emitted from the screen first passes through the polarizer LP and the first quarter-wave plate QWP1 to become circularly polarized light, then passes through the first liquid crystal variable retarder LCVR1. The light then passes through the relay lens assembly and reaches the LCVR-PBS display module. By controlling the on / off switch of the first liquid crystal variable retarder LCVR1, the left-hand circular polarization and right-hand circular polarization can be switched. This allows the light to either directly transmit through the polarization beam splitter film PBS or be reflected from the polarization beam splitter film PBS and then bend back between the second quarter-wave plate QWP2 and the first glass plate Glass1, thereby creating a difference in the optical path between the two light paths. When the second liquid crystal variable retarder LCVR2 is off, the light is not reflected within the polarization beam splitter prism PBS prism. When the second liquid crystal variable retarder LCVR2 is on, the light is reflected within the polarization beam splitter prism PBS prism. To achieve light reflection and polarization state conversion, the QWP and total reflection film RF are attached to the upper side (reflection light path) and right side (transmission light path) of the polarization beam splitter prism PBS prism, respectively. The difference between the two sides lies in the addition of a second glass sheet, Glass2, on the right side to achieve a difference in the optical path lengths of the two light beams. All four light beams then propagate beneath the polarizing beam splitter prism (PBS prism), forming an intermediate image plane. The light then continues downward to the freeform prism, where it is refracted and reflected before entering the eye. By independently controlling the on / off switches of the two liquid crystal variable retarders (LCVRs), the images of the four focal planes can be rapidly switched. Simultaneously, the human eye can observe the real world through the freeform prism.

[0042] In addition, the free-form surface prism part can also be replaced with a free-form surface reflector without changing its function. Figure 4As shown, light emitted from the screen first passes through the polarizer LP and the first quarter-wave plate QWP1 to become circularly polarized light, then passes through the first liquid crystal variable retarder LCVR1. The light then passes through the relay lens assembly and reaches the LCVR-PBS display module. Controlling the on / off switch of the first liquid crystal variable retarder LCVR1 allows switching between left-handed and right-handed circular polarization. This allows the light to either directly transmit through the polarization beam splitter film PBS or be reflected off the polarization beam splitter film PBS and then bend back between the second quarter-wave plate QWP2 and the first glass sheet Glass1, thereby creating a difference in the optical path length between the two light paths. When the second liquid crystal variable retarder LCVR2 is off, the light is not reflected within the PBS prism. When the second liquid crystal variable retarder LCVR2 is on, the light is reflected within the polarization beam splitter prism PBS prism. To achieve light reflection and polarization conversion, QWP and total reflection films are attached to the top and left sides of the polarization beam splitter prism PBS prism, respectively. The difference between the two sides is the addition of a second glass sheet Glass2 on the left side to achieve the difference in the optical path length between the two light paths. All four light beams then propagate downward through the polarizing beam splitter prism (PBS), forming an intermediate image plane. The light then continues downward to the free-form semi-reflective mirror, where it is reflected into the human eye. By independently controlling the on / off switches of the two liquid crystal variable retarders (LCVRs), the images of the four focal planes can be rapidly switched. Simultaneously, the human eye can observe the real world through the semi-reflective mirror.

[0043] like Figure 5 As shown in the figure, it is a schematic diagram of the MTF comparison of the system at different diopters with a 4mm exit pupil size. It can be seen that 4 focal planes with a refractive power range of 0.2D to 5D are realized, covering the human eye's observation range from far to near.

[0044] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may of course make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A multi-focal display system combining a liquid crystal variable retarder and a polarization beam splitter, characterized in that: The optical system includes a polarizer LP, a first quarter-wave plate QWP1, a first liquid crystal variable retarder LCVR1, a semi-transmissive and semi-reflective film BS, a first glass piece Glass1, a second quarter-wave plate QWP2, a polarization beam splitting film PBS, a second liquid crystal variable retarder LCVR2, a polarization beam splitting prism PBS prism, and a third quarter-wave plate QWP3 and a first total reflection film RF1 sequentially arranged on the reflected light path of the polarization beam splitting prism PBS prism, and a second glass piece Glass2, a fourth quarter-wave plate QWP4, and a second total reflection film RF2 sequentially arranged on the transmitted light path of the polarization beam splitting prism PBS prism. Light emitted from the screen Display passes through the polarizer LP, the first quarter-wave plate QWP1, the first liquid crystal variable retarder LCVR1, the transflective film BS, the first glass Glass1, the second quarter-wave plate QWP2, the polarization beam splitting film PBS, and the second liquid crystal variable retarder LCVR2 before entering the polarization beam splitting prism PBS prism. The first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 have different on and off states, resulting in different optical path lengths for the light in the multi-focal plane display system. Consequently, the light exits the polarization beam splitting prism PBS prism in different directions and at different times. The four different on and off states achieved by the two liquid crystal variable retarders result in four different focal plane images.

2. The multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to claim 1, wherein: When the first liquid crystal variable retarder LCVR1 is closed and the second liquid crystal variable retarder LCVR2 is opened, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at a 45-degree angle relative to the polarizer LP, becoming right-handed circularly polarized light. When the right-handed circularly polarized light passes through the closed first liquid crystal variable retarder LCVR1, the polarization state does not change. The right-handed circularly polarized light exiting the first liquid crystal variable retarder LCVR1 then passes through the semi-transmissive and semi-reflective film BS, obtaining right-handed circularly polarized light with half the light energy lost. The right-handed circularly polarized light with half the light energy lost passes through the first glass plate Glass1 and the second quarter-wave plate QWP2 in sequence, becoming P light. The P light directly passes through the polarization beam splitter film PBS and enters the opened second liquid crystal variable retarder LCVR2, where the polarization state of the P light changes by 90 degrees to become S light. The S light enters the interior of the polarization beam splitter prism PBSprism and is reflected by the polarization beam splitter prism PBS. The light is reflected in the prism and enters the third quarter-wave plate QWP3 on the reflection light path, becoming left-hand circularly polarized light. The left-hand circularly polarized light is then reflected by the first total reflection film RF1 and becomes right-hand circularly polarized light. The right-hand circularly polarized light reflected back by the first total reflection film RF1 passes through the third quarter-wave plate QWP3 again and becomes P light again. The finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

3. The multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to claim 1, wherein: When the first liquid crystal variable retarder LCVR1 is turned on and the second liquid crystal variable retarder LCVR2 is turned off, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at 45 degrees relative to the polarizer LP, becoming right-handed circularly polarized light. The right-handed circularly polarized light then passes through the first liquid crystal variable retarder LCVR1 in the turned-on state, becoming left-handed polarized light. The left-handed circularly polarized light from the first liquid crystal variable retarder LCVR1 then passes through the semi-transparent and semi-reflective film BS, obtaining left-handed circularly polarized light with half the light energy lost. The left-handed circularly polarized light then passes through the first glass sheet Glass in sequence.

1. The second quarter-wave plate QWP2 turns into S light; the S light is reflected on the polarization beam splitter film PBS and passes through the second quarter-wave plate QWP2 again to become right-handed circularly polarized light. The regenerated right-handed circularly polarized light is reflected a second time on the semi-transparent and semi-reflective film BS and becomes left-handed circularly polarized light again. The left-handed circularly polarized light generated at this time passes through the second quarter-wave plate QWP2 for the third time to become P light; the P light is directly transmitted from the polarization beam splitter film PBS into the second liquid crystal variable retarder LCVR2 in the closed state, and the polarization state does not change; the P light from the second liquid crystal variable retarder LCVR2 enters the polarization beam splitter prism PBS The light passes through the interior of the polarization beam splitter prism PBS prism and is transmitted through the second glass piece Glass2 and the fourth quarter-wave plate QWP4 in the transmission light path, becoming right-handed circularly polarized light. The right-handed circularly polarized light is then reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected back by the second total reflection film RF2 is again converted into S light by the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

4. The multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to claim 1, wherein: When the first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 are closed, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 arranged at a 45-degree angle relative to the polarizer LP, becoming right-handed circularly polarized light. When the right-handed circularly polarized light passes through the first liquid crystal variable retarder LCVR1, which is in the closed state, the polarization state does not change. The right-handed circularly polarized light exiting the first liquid crystal variable retarder LCVR1 then passes through the semi-transmissive and semi-reflective film BS, resulting in right-handed circularly polarized light with half the light energy lost. The right-handed circularly polarized light with half the light energy lost passes through the first glass plate Glass1 and the second quarter-wave plate QWP2 in sequence, becoming P light. The P light directly transmits through the polarization beam splitter film PBS and enters the second liquid crystal variable retarder LCVR2, which is in the closed state, without changing its polarization state. The P light exiting the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitter prism PBS and is reflected by the polarization beam splitter prism PBS. The light is transmitted through the prism and enters the second glass piece Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path, becoming right-handed circularly polarized light. The right-handed circularly polarized light is then reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected back by the second total reflection film RF2 is again converted into S light by the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

5. The multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to claim 1, wherein: When the first liquid crystal variable retarder LCVR1 is turned on and the second liquid crystal variable retarder LCVR2 is turned on, the light emitted from the screen Display first passes through the polarizer LP and the first quarter-wave plate QWP1 placed at a 45-degree angle relative to the polarizer LP, becoming right-handed circularly polarized light. The right-handed circularly polarized light then passes through the first liquid crystal variable retarder LCVR1 in the turned-on state, becoming left-handed polarized light. The left-handed circularly polarized light from the first liquid crystal variable retarder LCVR1 then passes through the semi-transparent and semi-reflective film BS to obtain left-handed circularly polarized light with half the light energy lost. The left-handed circularly polarized light with half the light energy lost passes through the first glass plate G in sequence. The S light is reflected by the polarization beam splitter film PBS and becomes right-handed circularly polarized light after passing through the second quarter-wave plate QWP2 again. The regenerated right-handed circularly polarized light is then reflected a second time by the semi-transmissive and semi-reflective film BS and becomes left-handed circularly polarized light again. The left-handed circularly polarized light generated at this time passes through the second quarter-wave plate QWP2 for the third time and becomes P light. The P light is directly transmitted from the polarization beam splitter film PBS into the second liquid crystal variable retarder LCVR2 in the turned-on state, where the polarization state of the P light changes by 90° and becomes S light. The S light enters the interior of the polarization beam splitter prism PBS prism and is reflected in the polarization beam splitter prism PBS prism. It enters the third quarter-wave plate QWP3 on the reflection light path and becomes left-handed circularly polarized light. The left-handed circularly polarized light is then reflected by the first total reflection film RF1 and becomes right-handed circularly polarized light. The right-handed circularly polarized light reflected back by the first total reflection film RF1 passes through the third quarter-wave plate QWP3 and becomes P light again. The finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

6. A multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to any one of claims 1 to 5, characterized in that: Also includes relay lens set; The light from the first liquid crystal variable retarder LCVR1 is shaped by the relay lens group and then enters the semi-transparent and semi-reflective film BS.

7. A multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to any one of claims 1 to 5, characterized in that: Also included are free-form prisms; The light from the polarization beam splitter prism PBS prism is refracted and reflected inside the free-form surface prism before entering the human eye.

8. A multi-focal plane display system combining a liquid crystal variable retarder and a polarization beam splitter according to any one of claims 1 to 5, characterized in that: Also included are freeform mirrors; The light is reflected from the polarization beam splitter prism PBS prism on the free-form surface mirror and then enters the human eye.

9. A multi-focal display system combining a liquid crystal variable retarder and a polarization beam splitter according to any one of claims 1 to 5, characterized in that: The structure of any liquid crystal variable retarder LCVR is, from top to bottom, an upper quarter wave plate, an upper glass substrate, an upper indium tin oxide layer, an upper alignment layer, a twisted nematic liquid crystal layer, a lower alignment layer, a lower indium tin oxide layer, a lower glass substrate, and a lower quarter wave plate. When no voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder (LCVR) is in the off state. The polarization state of light will change by 90° after passing through the twisted nematic liquid crystal layer. However, the polarization state of light will not change after passing through the upper quarter-wave plate, upper glass substrate, upper indium tin oxide layer, upper alignment layer, twisted nematic liquid crystal layer, lower alignment layer, lower indium tin oxide layer, lower glass substrate, and lower quarter-wave plate in sequence. When voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder LCVR is in the on state. The polarization state of light does not change after passing through the twisted nematic liquid crystal layer. However, after the light passes through the upper quarter-wave plate, upper glass substrate, upper indium tin oxide layer, upper alignment layer, twisted nematic liquid crystal layer, lower alignment layer, lower indium tin oxide layer, lower glass substrate, and lower quarter-wave plate in sequence, the polarization state will change by 90°.

Images