Miniature double-prism double-image-source polarization projection optical system

Abstract

According to the polarization projection optical system with the miniature double prisms and the double image sources, the two prisms and the two image sources use polarization light rays in two states, the lighting effect of the projection optical system can be improved, the size of a light machine can be reduced, and therefore compact and high-lighting-effect display is achieved; compared with a previous projection optical system, the lighting effect can be improved by about 100%.

Description

Technical Field

[0001] The present invention belongs to the technical field of near-eye display, and particularly relates to a polarization projection optical system of a micro double prism and double image sources. Background Art

[0002] Since the concepts of virtual reality (VR) and augmented reality (AR) were proposed, the market of near-eye display devices based on VR or AR modes has achieved remarkable development. Among the many hardware implementation methods of applying AR or VR technologies, the near-eye display (NED) is the most effective and can bring the best experience to users. Because the near-eye display needs to be worn on the human head, its light weight, small size and good display effect are particularly important.

[0003] The waveguide system is a representative of the thin and light type in the current near-eye display solutions. The thickness of the waveguide is relatively thin and light, generally within 3 mm. The waveguide needs to be used in combination with a projection system. Due to the low light efficiency of the waveguide, high brightness requirements are imposed on the light engine. However, for the LCOS projection system, in order to realize the optical path of polarized light, there will be a 50% light efficiency loss in such an optical path. In order to avoid such light efficiency loss, two display screens are introduced, but the optical path volume of the two display screens is relatively large. Therefore, there is an urgent need for a compact and efficient projection optical system. Summary of the Invention

[0004] To solve the above problems, the present invention provides a polarization projection optical system of a micro double prism and double image sources, which can improve the light efficiency of the projection optical system and reduce the volume of the light engine.

[0005] A polarization projection optical system of a micro double prism and double image sources includes an illumination light source, a first image source, a second image source, and a first prism and a second prism sharing a transmission surface; wherein, the optical surface shared by the two prisms is denoted as S3;

[0006] The first prism includes a first transmission surface S1, a second transmission surface S2, and a shared transmission surface S3; the second prism includes a shared optical surface S3, a fourth transmission surface S4, a fifth transmission surface S5, and a sixth transmission surface S6;

[0007] The illumination light containing two mutually perpendicular polarization states emitted by the illumination light source enters the second prism from S6, and then is reflected from S4 to S3; wherein, the first polarized light in the illumination light is reflected from S3 to S5 and exits from S5 to the second image source; the second polarized light in the illumination light is transmitted from S3 into the first prism and exits from S2 to the first image source;

[0008] The second polarized light formed after the first polarized light is reflected by the second image source is transmitted to the external waveguide through S5, S3, and S1 in sequence; the first polarized light formed after the second polarized light is reflected by the first image source is transmitted from S2 to S3, then reflected from S3 to S1, and finally transmitted from S1 to the external waveguide, forming a projection of the dual image source at the external waveguide.

[0009] Furthermore, it also includes a TIR lens and a light homogenizer;

[0010] The illumination light is collimated by the TIR lens and homogenized by the light homogenizer in sequence, and then enters the interior of the second prism from S6.

[0011] Furthermore, it also includes a first lens located between the fifth transmission surface S5 and the second image source, and the first lens is used for focusing light.

[0012] Furthermore, it also includes a second lens located between the second transmission surface S2 and the first image source, and the second lens is used for focusing light.

[0013] Furthermore, it also includes a third lens located between the first transmission surface S1 and the exit pupil position, and the third lens is used for focusing light.

[0014] Furthermore, the surface of the fourth transmission surface S4 is a free-form surface with a radius of 25.676, and the free-form surface parameter z satisfies the following equation:

[0015]

[0016] where c is the reciprocal of the radius of curvature, r is the radial distance of any point on the free-form surface, k is the conic constant, C j is the polynomial coefficient, and m, n are auxiliary variables.

[0017] Furthermore, the first image source and the second image source are non-self-luminous display screens based on liquid crystal on silicon display technology.

[0018] Furthermore, a PBS thin film is attached or coated on the surface of the shared transmission surface S3 to reflect the first polarized light and transmit the second polarized light.

[0019] Beneficial effects:

[0020] The present invention provides a polarization projection optical system for a micro dual-prism dual image source. By using two prisms and two image sources for two states of polarized light, the light efficiency of the projection optical system can be improved and the volume of the optical engine can be reduced, thereby achieving a compact and high-light-efficiency display. Compared with the previous projection optical system, the light efficiency can be increased by about 100%. Description of the Drawings

[0021] Figure 1Three-dimensional sectional view of a polarization projection optical system of a micro double prism double image source provided by the present invention;

[0022] Figure 2 Schematic diagram of the polarization optical path of a polarization projection optical system of a micro double prism double image source provided by the present invention;

[0023] Figure 3 Schematic diagram of the optical surface of a polarization projection optical system of a micro double prism double image source provided by the present invention. Detailed implementation manners

[0024] In order to enable those skilled in the art to better understand the solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application.

[0025] The present invention discloses a micro projection system, and also discloses a near-eye display device using the micro projection system and a waveguide system. Among them, the micro projection system includes an image source, an illumination source, and an exit pupil position. The imaging part is that the image source outputs image light to the exit pupil position, and the illumination part is that the illumination source outputs illumination light to the image source position.

[0026] As Figure 1 and Figure 2 shown, a polarization projection optical system of a micro double prism double image source includes an illumination light source 109, a first image source 110, a second image source 111, and a first prism 103 and a second prism 104 sharing a transmission surface; among them, the optical surface shared by the two prisms is denoted as S3; the image source is a passive light-emitting reflective image source and needs to be used in cooperation with the illumination light source.

[0027] The first prism 103 includes a first transmission surface S1, a second transmission surface S2, and a shared optical surface S3; the second prism includes a shared optical surface S3, a fourth transmission surface S4, a fifth transmission surface S5, and a sixth transmission surface S6;

[0028] The illumination light containing two mutually perpendicular polarization states emitted by the illumination light source enters the second prism 104 from S6, and then is reflected from S4 to S3; among them, the first polarized light in the illumination light is reflected from S3 to S5 and exits from S5 to the second image source 111; the second polarized light in the illumination light is transmitted from S3 into the first prism 103 and exits from S2 to the first image source 110;

[0029] The second polarized light formed after the first polarized light is reflected by the second image source 111 is transmitted to the external waveguide through S5, S3, and S1 in sequence; the first polarized light formed after the second polarized light is reflected by the first image source 110 is transmitted from S2 to S3, then reflected from S3 to S1, and finally transmitted from S1 to the external waveguide, forming a projection of the dual image source at the external waveguide. Optionally, the external waveguide can be a waveguide in a near-eye display device.

[0030] Specifically, the first image source 110 and the second image source 111 are non-self-luminous display screens such as Liquid Crystal on Silicon (LCOS), and can change the polarization direction of linearly polarized light while reflecting light.

[0031] The overall optical parameters are shown in Table 1:

[0032] Table 1

[0033] Parameter Value Remarks Field of view 32° Diagonal field of view Focal length 10.62 mm Distortion <1％ Optical distortion MTF >0.4 @ 120 lp / mm Full field of view Exit pupil diameter 4 mm Exit pupil distance 1.5 mm Three-dimensional volume parameter 20 mm * 14 mm * 9.2 mm

[0034] Furthermore, the polarization projection optical system of the micro double prism dual image source of the present invention further includes a TIR lens 108, a light homogenizer 107, a first lens 105, a second lens 106, and a third lens 102; as Figure 3 shown in the polarization light path diagram of the overall system. During the actual imaging process, light is emitted from the LED light source 109. At this time, the light is natural light, collimated by the TIR lens 108, and homogenized by the light homogenizer 107, enters the second prism through the S6 surface, and then is incident on the S3 surface after being reflected by the S4 surface of the second prism. The S3 surface is a functional surface that can reflect the first polarized light and transmit the second polarized light. The first polarized light and the second polarized light are two types of linearly polarized light with perpendicular polarization states of light. Such a functional surface can be realized by attaching or plating a PBS film on the S3 surface. At this time, the light path can be divided into two light paths:

[0035] Light path 1:

[0036] The light reflected by the S3 surface enters the second prism again, then exits from the S5 surface of the second prism, then passes through the lens 105 and is incident on the second image source 111. After being reflected by the second image source 111, the polarization of the light is converted from the first polarization state to the second polarization state. The light passes through the lens 105 again after being reflected by the second image source, enters the S5 of the second prism and is incident on the S3 surface. At this time, since the light is in the second polarization state, the light can pass through, enter the first prism, and exit from the S1 of the first prism, and reach the exit pupil position 101 through the lens 102.

[0037] Light path 2:

[0038] The light transmitted through the S3 surface enters the first prism, then exits from the S2 surface of the first prism, then enters the first image source 110 through the lens 106. After being reflected by the first image source, the polarization state of the light is converted from the second polarization state to the first polarization state. After being reflected by the first image source, the light passes through the lens 106 again and the S2 surface of the first prism. At this time, since the light is in the first polarization state, the light will be reflected and enter the first prism again, and exit from the S1 of the first prism, and reach the exit pupil position 101 through the lens 102.

[0039] For light, there is no polarization loss in the overall optical path. The first polarization state and the second polarization state light are separated and combined in energy through two optical paths. At the same time, two micro prism systems are designed, and the volume of the optical path is compressed.

[0040] As Figure 3 shown is the schematic diagram of the surface of the optical path optical system. In the optical path design, the optically effective surfaces are the S1, S2, and S3 surfaces of the first prism 103, the S3, S4, S5, and S6 surfaces of the second prism 104, the 102_S1 and 102_S2 surfaces of the third lens 102, the 105_S1 and 105_S2 surfaces of the first lens 105, and the 106_S1 and 106_S2 surfaces of the second lens 106.

[0041] The relevant parameters are shown in Table 2:

[0042]

[0043]

[0044] Among them, the S4 surface of the second prism 104 is a free-form surface with a spherical radius of 25.676, and the free-form surface parameters satisfy the following equation.

[0045]

[0046] Among them, c is the reciprocal of the radius of curvature, r is the radial distance of any point on the free-form surface, k is the conic constant, C j is the polynomial coefficient, and m and n are auxiliary variables.

[0047] The Y radius of the S2 surface is 146.1665, k is 0, C j The polynomial coefficients are shown in the following table.

[0048]

[0049]

[0050] In summary, the present invention relates to a micro dual-prism dual-image-source projection optical system. The micro dual-prism projection optical system includes: an illumination light source, a first image source, a second image source, a first prism, and a second prism. The first prism and the second prism share an optical surface, and this surface has a film layer that can reflect the first polarized light and transmit the second polarized light. The illumination light source emits illumination light into the second prism, and the light is polarization beam split into two polarized light beams on the optical surface shared by the first prism and the second prism. One light beam enters the first prism and is displayed through the first image source, and the other light beam is reflected into the second prism and is displayed through the second image source.

[0051] In the present invention, by using two prisms and two image sources for two states of polarized light, the light efficiency of the projection optical system can be improved and the volume of the optical engine can be reduced.

[0052] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can certainly make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A polarization projection optical system with a miniature dual-prism and dual-image source, characterized in that: It includes an illumination light source, a first image source, a second image source, and a first prism and a second prism that share a transmission surface; wherein the optical surface shared by the two prisms is denoted as S3; The first prism includes a first transmission surface S1, a second transmission surface S2, and a common transmission surface S3; the second prism includes a common optical surface S3, a fourth transmission surface S4, a fifth transmission surface S5, and a sixth transmission surface S6; The illumination light source emits two mutually perpendicular polarization states, which are incident from S6 into the second prism, and then reflected from S4 to S3; wherein the first polarized light in the illumination light is reflected from S3 to S5, and emitted from S5 to the second image source; the second polarized light in the illumination light is transmitted from S3 into the first prism, and emitted from S2 to the first image source; The second polarized light generated by the first polarized light reflected by the second image source is transmitted to the external waveguide via S5, S3, and S1 in sequence; the first polarized light generated by the second polarized light reflected by the first image source is transmitted from S2 to S3, then reflected from S3 to S1, and finally transmitted from S1 to the external waveguide, forming a projection of the dual image source at the external waveguide.

2. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: It also includes TIR lenses and light diffusers; The illumination light is collimated by the TIR lens and homogenized by the homogenizer, and then enters the second prism from S6.

3. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: The device further comprises a first lens located between the fifth transmission surface S5 and the second image source, and the first lens is used for focusing light.

4. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: The device further includes a second lens located between the second transmission surface S2 and the first image source, and the second lens is used for focusing light.

5. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: The device further includes a third lens located between the first transmission surface S1 and the exit pupil position, and the third lens is used for focusing light.

6. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: The surface of the fourth transmission surface S4 is a free-form surface with a radius of 25.676, and the free-form surface parameter z satisfies the following equation: Where c is the inverse of the radius of curvature, r is the radial distance of any point on the free-form surface, k is the quadratic constant, and C j are polynomial coefficients, and m and n are auxiliary variables.

7. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: The first image source and the second image source are non-self-luminous display screens based on liquid crystal on silicon display technology.

8. The polarization projection optical system with a micro dual-prism and dual-image source as claimed in claim 1, characterized in that: A PBS film is attached or plated on the surface of the common transmission surface S3 to reflect the first polarized light and transmit the second polarized light.

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