Multi-focal-plane display system combining liquid crystal variable delayer and polarization beam-splitting element

Abstract

According to the multi-focal-plane display system combining the liquid crystal variable delayers and the polarization beam-splitting element, the on-off states of the first liquid crystal variable delayer LCVR1 and the second liquid crystal variable delayer LCVR2 are changed by controlling the on-off states of the two liquid crystal variable delayers LCVRs respectively, so that the optical paths of light rays transmitted in the multi-focal-plane display system are different, and the transmission efficiency of the light rays in the multi-focal-plane display system is improved. The two liquid crystal variable delayers are arranged on the substrate, so that the emergent directions and the emergent time of light rays from the PBS prism are different, four different opening and closing states are realized through the two liquid crystal variable delayers, four different focal plane pictures are obtained, and quick switching of the pictures of the four focal planes can be realized; meanwhile, human eyes can observe the real world through the semi-reflecting and semi-transmitting mirror.

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 surface display system combining a liquid crystal variable delay device and a polarization beam splitting element. Background Art

[0002] As an important bridge connecting the digital world and the real world, augmented reality (AR) and virtual reality (VR) technologies have developed rapidly in recent years, and their application scenarios have been continuously expanded. From entertainment games to education and training, from remote collaboration to medical surgery simulation, AR / VR technology has brought revolutionary changes to all walks of life with its immersive experience and interactivity. In the field of VR, the current mainstream solution is the pancake system. In the field of AR, there are more options. For example, waveguides, free-form prisms, free-form reflectors, birdbaths, etc. However, while providing an immersive experience, these technologies also face the problem of Vergence-Accommodation Conflict (VAC). In natural vision, the human eye changes the focus (accommodation) by adjusting the curvature of the lens, and changes the intersection of the line of sight (vergence) by adducting or abducting the eyeball. In traditional AR / VR systems, since virtual images are usually displayed on a screen at a fixed distance, the eye's accommodation and convergence do not match, thus causing VAC, which not only affects the user's depth perception, but also may cause visual fatigue, dizziness and other discomfort.

[0003] In order to solve the VAC problem, researchers have proposed a variety of solutions. These include zoom display technology, light field display, holographic display, Maxwell view and other methods. Zoom display technology simulates the depth perception of the real world by providing multiple image focal planes or quickly switching focal planes according to the viewer's current focus. It may introduce a complex optical system to achieve focal length changes, increasing the size and cost of the device. Another method is light field display technology, which provides more physiological visual information than traditional 2D displays by displaying light from all directions in the optical scene. It is subject to the balance between angular resolution and viewpoint resolution, and it is difficult to achieve high-resolution display effects. Holographic display technology is based on the principle of light diffraction, which can restore light waves equivalent to real 3D objects and support users to focus freely. Holographic display is affected by the performance and computing power of the spatial light modulator (SLM), and the image has the defects of insufficient viewing angle and low resolution due to speckle effect. In addition, some researchers have proposed using Maxwellian-view display to eliminate adjustment cues to reduce the impact of VAC. But Maxwell view display systems are typically limited to a finite eyebox size, and a slight 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 combining a liquid crystal variable delay device and a polarization beam splitter element, which can realize fast switching of images of four focal planes by controlling the switches of two liquid crystal variable retarders LCVR respectively.

[0005] A multi-focal display system combining a liquid crystal variable retarder and a polarization beam splitter element, comprising 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 a 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 a transmission light path of the polarization beam splitting prism PBS prism;

[0006] The light emitted by the screen Display passes through the polarizer LP, the first quarter-wave plate QWP1, the first liquid crystal variable retarder LCVR1, the semi-transmissive and semi-reflective 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 in sequence, and then enters the polarization beam splitting prism PBS prism. Among them, the opening and closing states of the first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 are different, so that the optical path of the light transmitted in the multi-focal plane display system is different, and then the direction and time of the light emitted from the polarization beam splitting prism PBS prism are different, and four different focal plane images are obtained through the four different opening and closing states realized by the two liquid crystal variable retarders.

[0007] Further, when the first liquid crystal variable retarder LCVR1 is turned off and the second liquid crystal variable retarder LCVR2 is turned on, the 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-off 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-transmissive and semi-reflective film BS again 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 sheet 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 turned-on 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 The light is reflected in the prism and enters the third quarter-wave plate QWP3 on the reflection light path, 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 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 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 sheet Gla sequentially. ss1, the second quarter wave plate QWP2 turns into S light; the S light is reflected on the polarization beam splitting film PBS, and passes through the second quarter wave plate QWP2 again to become right-handed circularly polarized light, then the regenerated right-handed circularly polarized light is reflected for the second time on the semi-transparent and semi-reflective film BS and turns into left-handed circularly polarized light again, and 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 splitting film PBS into the second liquid crystal variable retarder LCVR2 in the closed state, and the polarization state does not change; the P light coming out of the second liquid crystal variable retarder LCVR2 enters the polarization beam splitting prism PBS prism, and is transmitted in the polarization beam splitter prism PBS prism, entering the second glass piece Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path, and becoming right-handed circularly polarized light. Then the right-handed circularly polarized light is 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 through the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

[0009] Further, when the first liquid crystal variable retarder LCVR1 is turned off and the second liquid crystal variable retarder LCVR2 is turned off, the 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-off 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 again 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 sheet 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 into the second liquid crystal variable retarder LCVR2 in the turned-off state, and the polarization state does not change; the P light coming out of the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism, and is Transmission occurs in 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. Then the right-handed circularly polarized light is 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 passes through the third quarter-wave plate QWP3 again and becomes S light again. 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 to become 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 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 film BS in sequence. The S light is reflected on 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 reflected for the 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 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, and the polarization state of the P light changes by 90° and becomes S light. The S light enters the polarization beam splitter prism PBS prism, and is reflected in the polarization beam splitter prism PBS prism, and enters the third quarter-wave plate QWP3 on the reflection light path, becoming left-handed circularly polarized light, and then the left-handed circularly polarized light is reflected by the first total reflection film RF1 to become right-handed circularly polarized light; the right-handed circularly polarized light reflected back by the first total reflection film RF1 is again converted into P light by the third quarter-wave plate QWP3, and the finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

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

[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] Further, a multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter element also includes a free-form surface 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] Further, a multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter element also 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 before entering the human eye.

[0017] Further, 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] Among them, when no voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder LCVR is in a closed state, and the polarization state of the light will change by 90° after passing through the twisted nematic liquid crystal layer, while the polarization state of the light will not change after passing through the upper quarter wave plate, the upper glass substrate, the upper indium tin oxide layer, the upper alignment layer, the twisted nematic liquid crystal layer, the lower alignment layer, the lower indium tin oxide layer, the lower glass substrate, and the 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, and the polarization state of the light will not change after passing through the twisted nematic liquid crystal layer. However, after the light passes through the upper quarter wave plate, the upper glass substrate, the upper indium tin oxide layer, the upper alignment layer, the twisted nematic liquid crystal layer, the lower alignment layer, the lower indium tin oxide layer, the lower glass substrate, and the 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 combining a liquid crystal variable delay device and a polarization beam splitting element. By respectively controlling the switches of two liquid crystal variable delay devices LCVR, the on and off states of a first liquid crystal variable delay device LCVR1 and a second liquid crystal variable delay device LCVR2 are changed, so that the optical path of light transmitted in the multi-focal plane display system is different, and then the direction and time of light emitted from a polarization beam splitting prism PBS prism are different. Four different on and off states are realized by the two liquid crystal variable delay devices, and four different focal plane images are obtained, and fast switching of images of four focal planes can be realized; at the same time, the human eye can observe the real world through a semi-reflective and semi-transparent lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The schematic diagram of the 4-focal plane optical path of the PBS prism and the dual-focal plane module provided by the present invention; wherein (a) is a schematic diagram of two light paths when the second LCVR is in the on state; (b) is a schematic diagram of 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) is the change of the arrangement state of the liquid crystal and the polarization state of the light when the power is off; (b) is the change of the arrangement state of the liquid crystal and the polarization state of the light when the power is on;

[0024] Figure 3Optical path diagram of a multi-focal augmented reality display system combining an LCVR-PBS display module and an off-axis free-form surface prism system provided by the present invention;

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

[0026] Figure 5 Schematic diagram of the MTF comparison of the system at different diopter 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] The present invention designs a new type of optical NED system. By integrating a liquid crystal variable retarder and a PBS prism, and combining free-form surface elements, an augmented reality near-eye display system is designed. The system can provide four virtual image planes of different depths, and can view the real environment at the same time, realizing four focal planes in the refractive range of 0.2D to 5D, covering the human eye's observation range from far to near. The present invention introduces in detail the optical design principle of this multi-focal plane NED system, and derives relevant mathematical models to describe the relationship between the virtual image distance and the system; finally, by building a principle prototype, the present invention verifies the excellent performance and wide application potential of the system.

[0029] Specifically, Figure 1 As shown, a multi-focal display system combining a liquid crystal variable retarder and a polarization beam splitter element comprises 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 a 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 a transmission light path of the polarization beam splitting prism PBS prism;

[0030] The light emitted by the screen Display passes through the polarizer LP, the first quarter-wave plate QWP1, the first liquid crystal variable retarder LCVR1, the semi-transmissive and semi-reflective 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 in sequence, and then enters the polarization beam splitting prism PBS prism. Among them, the opening and closing states of the first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 are different, so that the optical path of the light transmitted in the multi-focal plane display system is different, and then the direction and time of the light emitted from the polarization beam splitting prism PBS prism are different, and four different focal plane images are obtained through the four different opening and closing states realized by the two liquid crystal variable retarders.

[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 the 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), when the voltage (V) greatly exceeds the threshold voltage (Vth), the LC molecules are redirected along the y direction, and the polarization state of the polarized light in the z direction does not change when passing through the LC. The change of 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 delay of the LC is π; when the light passes through it, a 90° polarization state change occurs. When a voltage is applied to the LC, the LC is in the ON state, and the corresponding phase delay of the LC is 0; when the light passes through it, no polarization state change occurs. The switching time of the polarization state can be controlled within 5ms. In this way, we can achieve the transition from 0 to π in the phase delay by applying voltage and releasing voltage, so that the LVCR can be used as a switchable half-wave plate. However, the difference between it and the traditional half-wave plate is that the twisted nematic liquid crystal can cause any polarized light to be deflected by 90°. The half-wave plate has a fixed fast and slow axis direction, and can only deflect polarized light in a specific direction by 90°. Therefore, in order to achieve the conversion between left-handed and right-handed circularly polarized light by switching voltage, it is necessary to add quarter-wave plates with the same optical axis above and below the LCVR. When the LC is powered on, the LC has no effect on the polarization state. After superimposing two layers of QWP, the whole can be regarded as an electrically controlled switchable half-wave plate, which is called LCVR. The right-handed circularly polarized light becomes left-handed circularly polarized light after passing through the electrically controlled switchable half-wave plate LCVR. When the LC is discharged, the polarization state of the LC changes by 90°, and the direction of rotation of the circularly polarized light does not change after passing through the electrically controlled switchable half-wave plate LCVR.

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

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

[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° 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 again 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 turn 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, then the polarization state of the P light changes by 90° to become S light; the S light enters the interior of the polarization beam splitting prism PBS prism and is The light is reflected in the prism and enters the third quarter-wave plate QWP3 on the reflection light path, 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 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] In the second aspect, 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 plate Glass1, the second quarter wave plate QWP2, and the second quarter wave plate QWP3 in turn. The S light is reflected on the polarization beam splitting 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 reflected for the second time on 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 splitting film PBS into the second liquid crystal variable retarder LCVR2 in the closed state, and the polarization state does not change. The P light coming out of the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism, and is transmitted in the polarization beam splitting prism PBS prism, and enters the second glass sheet Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path and becomes right-handed circularly polarized light. Then the right-handed circularly polarized light is reflected by the second total reflection film RF2 and becomes left-handed circularly polarized light. The left-handed circularly polarized light reflected back from the second total reflection film RF2 passes through the third quarter-wave plate QWP3 and becomes S light again. Finally, the generated S light is 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° 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 loss; the right-handed circularly polarized light with half of the light energy loss passes through the first glass sheet Glass1 and the second quarter-wave plate QWP2 in turn to become P light; the P light is directly transmitted from the polarization beam splitting film PBS into the second liquid crystal variable retarder LCVR2 in the closed state, and the polarization state does not change; the P light coming out of the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism, and is Transmission occurs in 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. Then the right-handed circularly polarized light is 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 passes through the third quarter-wave plate QWP3 again and becomes S light again. 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 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 loss; the left-handed circularly polarized light with half of the light energy loss passes through the first glass plate Glass1, the second quarter-wave plate Q WP2 becomes S light; the S light is reflected on the polarization beam splitting film PBS, and passes through the second quarter wave plate QWP2 again to become right-handed circularly polarized light, then the regenerated right-handed circularly polarized light is reflected for the second time on the semi-transparent and semi-reflective film BS and becomes left-handed circularly polarized light again, and 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 splitting 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 interior of the polarization beam splitting prism PBS prism, and is reflected in the polarization beam splitting prism PBS prism, enters the third quarter wave plate QWP3 on the reflection light path, and becomes left-handed circularly polarized light, and then the left-handed circularly polarized light is reflected by the first total reflection film RF1 to become 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 to become P light, and the finally generated P light is transmitted through the polarization beam splitting 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), the dotted box is a 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 the light in the first liquid crystal variable retarder LCVR1 does not change; when the first liquid crystal variable retarder LCVR1 is powered on, that is, in the on state, the phase delay of the light in the first liquid crystal variable retarder LCVR1 is π; that is, when the state of the second liquid crystal variable retarder LCVR2 remains unchanged, since the first liquid crystal variable retarder LCVR1 is in the on state ON and the off state OFF, the optical path of the light transmitted in the entire multi-focal plane display system is different, and the dual-focal plane display function is obtained.

[0040] like Figure 1As shown in (b), by multiplexing the dual-focal plane display module introduced above and then changing the on and off states of the second liquid crystal variable retarder LCVR2, the optical path of the light transmitted in the entire multi-focal plane display system can be further changed; that is, the present invention can control the different distances between the QWP located on the reflected light path and the transmitted light path of the polarization beam splitter prism PBS prism and the polarization beam splitter prism PBS prism to achieve the difference in optical path. Finally, by quickly switching the power on and off of the two LVCRs, a time-division multiplexed 4-focal plane display system can be realized. Due to the high refresh rate of the LCVR, the visual persistence effect of the human eye can be used to simultaneously see images of 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, the light emitted by the screen first passes through the polarizer LP and the first quarter wave plate QWP1 to become circularly polarized light, and then passes through the first liquid crystal variable retarder LCVR1. Then the light passes through the relay lens group to reach the LCVR-PBS display module. By controlling the switch of the first liquid crystal variable retarder LCVR1, the switching between left-handed circular polarization and right-handed circular polarization can be achieved. Then, the light is directly transmitted through the polarization beam splitter film PBS or reflected on the polarization beam splitter film PBS and then turned back between the second quarter wave plate QWP2 and the first glass sheet Glass1, thereby causing the difference in the optical path of the two paths. When the second liquid crystal variable retarder LCVR2 is in the off state, the light is not reflected inside the polarization beam splitter prism PBS prism. When the second liquid crystal variable retarder LCVR2 is in the on state, the light is reflected inside the polarization beam splitter prism PBS prism. In order to realize the reflection of light and the conversion of polarization state, 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 is that an additional second glass sheet Glass2 is added on the right side to achieve the difference in the optical path of the two light beams. Then the four light beams propagate along the bottom of the polarization beam splitter prism PBS prism to form an intermediate image plane. The light continues to reach the free-form surface prism downward, and enters the human eye after being refracted and reflected inside it. By controlling the switches of the two liquid crystal variable retarders LCVR respectively, the images of the four focal planes can be quickly switched. At the same time, the human eye can observe the real world through the free-form surface prism.

[0042] In addition, the free-form surface prism part can also be replaced by a free-form surface reflector without changing its function. Figure 4As shown, the light emitted by the screen first passes through the polarizer LP and the first quarter wave plate QWP1 to become circularly polarized light, and then passes through the first liquid crystal variable retarder LCVR1. Then the light passes through the relay lens group to reach the LCVR-PBS display module. By controlling the switch of the first liquid crystal variable retarder LCVR1, the switching between left-handed circular polarization and right-handed circular polarization can be achieved. Then, the light is directly transmitted through the polarization beam splitter film PBS or reflected on the polarization beam splitter film PBS and then turned back between the second quarter wave plate QWP2 and the first glass sheet Glass1, thereby causing the difference in the optical path of the two paths of light. When the second liquid crystal variable retarder LCVR2 is in the off state, the light is not reflected inside the PBS prism. When the second liquid crystal variable retarder LCVR2 is in the on state, the light is reflected inside the polarization beam splitter prism PBS prism. In order to realize the reflection of light and the conversion of polarization state, QWP and total reflection film are attached to the upper side and left side of the polarization beam splitter prism PBS prism respectively. The difference between the two sides is that an additional layer of second glass sheet Glass2 is added on the left side to realize the difference in the optical path of the two paths of light. Then the four rays of light propagate along the bottom of the polarization beam splitter prism PBS prism to form an intermediate image plane. The light continues downward to the free-form semi-reflective and semi-mirror lens and is reflected into the human eye. By controlling the switches of the two liquid crystal variable retarders LCVR respectively, the images of the four focal planes can be quickly switched. At the same time, the human eye can observe the real world through the semi-reflective and semi-mirror lens.

[0043] like Figure 5 As shown in the figure, it is a schematic diagram of the MTF comparison of the system under different diopter when the exit pupil size is 4mm; it can be seen that 4 focal planes in the refractive power range of 0.2D to 5D are realized, covering the observation range of the human eye 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 certainly 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 delay device and a polarization beam splitter, characterized in that: It 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 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 which are sequentially arranged along an optical path, and a second glass sheet Glass2, a fourth quarter-wave plate QWP4 and a second total reflection film RF2 which are sequentially arranged on a transmission optical path of the polarization beam splitting prism PBS prism; The light emitted by the screen Display passes through the polarizer LP, the first quarter-wave plate QWP1, the first liquid crystal variable retarder LCVR1, the semi-transmissive and semi-reflective 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 in sequence, and then enters the polarization beam splitting prism PBS prism. Among them, the opening and closing states of the first liquid crystal variable retarder LCVR1 and the second liquid crystal variable retarder LCVR2 are different, so that the optical path of the light transmitted in the multi-focal plane display system is different, and then the direction and time of the light emitted from the polarization beam splitting prism PBS prism are different, and four different focal plane images are obtained through the four different opening and closing states realized by the two liquid crystal variable retarders.

2. A multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in claim 1, characterized in that: When the first liquid crystal variable retarder LCVR1 is turned off and the second liquid crystal variable retarder LCVR2 is turned on, the light emitted by the screen Display first passes through the polarizer LP and the first quarter wave plate QWP1 placed at 45° 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-off 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 again 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 sheet Glass1 and the second quarter wave plate QWP2 in turn 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 turned-on state, then the polarization state of the P light changes by 90° to become S light; the S light enters the interior of the polarization beam splitting prism PBSprism 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-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 again and becomes P light again. The finally generated P light is transmitted through the polarization beam splitter prism PBS prism.

3. A multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in claim 1, characterized in that: 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 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 loss; the left-handed circularly polarized light with half of the light energy loss 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, then the regenerated right-handed circularly polarized light is reflected for the second time on the semi-transparent and semi-reflective film BS and turns into left-handed circularly polarized light again, and 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 coming out of the second liquid crystal variable retarder LCVR2 enters the polarization beam splitter prism PBS prism, and is transmitted in the polarization beam splitter prism PBS prism, entering the second glass piece Glass2 and the fourth quarter-wave plate QWP4 on the transmission light path, and becoming right-handed circularly polarized light. Then the right-handed circularly polarized light is 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 through the third quarter-wave plate QWP3. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

4. A multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in claim 1, characterized in that: When the first liquid crystal variable retarder LCVR1 is turned off and the second liquid crystal variable retarder LCVR2 is turned off, the 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-off 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-transmissive and semi-reflective film BS again to obtain right-handed circularly polarized light with half of the light energy loss; the right-handed circularly polarized light with half of the light energy loss passes through the first glass sheet Glass1 and the second quarter wave plate QWP2 in turn to become P light; the P light directly transmits through the polarization beam splitting film PBS into the second liquid crystal variable retarder LCVR2 in the turned-off state, and the polarization state does not change; the P light coming out of the second liquid crystal variable retarder LCVR2 enters the interior of the polarization beam splitting prism PBS prism and is Transmission occurs in 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. Then the right-handed circularly polarized light is 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 passes through the third quarter-wave plate QWP3 again and becomes S light again. The finally generated S light is reflected and passes through the polarization beam splitter prism PBS prism.

5. A multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in claim 1, characterized in that: 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 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 loss; the left-handed circularly polarized light with half of the light energy loss passes through the first glass plate G in sequence. lass1, the second quarter wave plate QWP2 becomes S light; the S light is reflected on the polarization beam splitting film PBS, and passes through the second quarter wave plate QWP2 again to become right-handed circularly polarized light, then the regenerated right-handed circularly polarized light is reflected for the second time on the semi-transparent and semi-reflective film BS and becomes left-handed circularly polarized light again, and 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 splitting 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 interior of the polarization beam splitting prism PBS prism, and is reflected in the polarization beam splitting prism PBSprism, enters the third quarter wave plate QWP3 on the reflection light path, and becomes left-handed circularly polarized light, and then the left-handed circularly polarized light is reflected by the first total reflection film RF1 to become 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 to become P light, and the finally generated P light is transmitted through the polarization beam splitting prism PBS prism.

6. A multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in 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 display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in 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 display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in any one of claims 1 to 5, characterized in that: Also included are free-form reflectors; The light is reflected from the polarization beam splitter prism PBS prism on the free-form surface mirror before entering the human eye.

9. A multi-focal display system combining a liquid crystal variable delay device and a polarization beam splitter as claimed in 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; Among them, when no voltage is applied to the twisted nematic liquid crystal layer, the liquid crystal variable retarder LCVR is in a closed state, and the polarization state of the light will change by 90° after passing through the twisted nematic liquid crystal layer, while the polarization state of the light will not change after passing through the upper quarter wave plate, the upper glass substrate, the upper indium tin oxide layer, the upper alignment layer, the twisted nematic liquid crystal layer, the lower alignment layer, the lower indium tin oxide layer, the lower glass substrate, and the 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, and the polarization state of the light will not change after passing through the twisted nematic liquid crystal layer. However, after the light passes through the upper quarter wave plate, the upper glass substrate, the upper indium tin oxide layer, the upper alignment layer, the twisted nematic liquid crystal layer, the lower alignment layer, the lower indium tin oxide layer, the lower glass substrate, and the lower quarter wave plate in sequence, the polarization state will change by 90°.

Images