Optical projection system

Abstract

The present application provides an optical projection system configured to make imaging light from a display screen pass through the optical projection system into an eye of an observer to form an image. Wherein a side facing the eye is an eye side and a side facing the display screen is a display side. The optical projection system comprises, in order from the eye side to the display side along an optical axis, a first lens, a second lens, a third lens and a fourth lens, each of the first lens to the fourth lens comprises an eye side surface facing the eye side and passing the imaging light and a display side surface facing the display side and passing the imaging light, the optical projection system further comprises an aperture, a prism module and a protective cover plate. Wherein the optical projection system has only the above four lenses with refractive power, and satisfies the following conditional expression: 12.0 degrees ≤ FOV / 2 ≤ 13.2 degrees, wherein FOV is the field of view angle of the optical projection system.

Description

Technical Field

[0001] This invention relates to an optical system, and more particularly to an optical projection system. Background Technology

[0002] Micro-projection displays, augmented reality (AR) devices, virtual reality (VR) headsets, and various imaging lens modules are all common optical display technologies in recent years. These devices generally include a light source module, imaging components, optical lenses, an optomechanical module, an optical path reflection component, or an optical waveguide to generate images and present them to the user or project them onto an external interface. Micro-projection devices often employ projection modules with integrated optomechanical systems, such as image generators using digital optical processing (DLP), liquid crystal on silicon (LCoS), or micro-LEDs, paired with corresponding projection lens modules to form a visible image. In augmented reality display technology, common solutions include optical waveguides, freeform lenses, combined lenses, or reflective structures to guide the displayed image into the user's field of vision. Virtual reality display technology generally uses near-eye display panels with imaging lenses to form corresponding wide-view images. Furthermore, imaging lens modules are widely used in mobile devices, wearable devices, and micro-optical systems, typically including multiple lenses, an aperture, a fixed or focusing structure, and configured with corresponding optical parameters according to application requirements. Summary of the Invention

[0003] This invention provides an optical projection system with good resolution and a small size that makes it easy to install on wearable or portable devices, making it suitable for use in augmented reality and virtual reality fields.

[0004] This invention provides an optical projection system configured to allow imaging light from a display screen to pass through the optical projection system and enter the observer's eye to form an image. The side facing the eye is the eye side, and the side facing the display screen is the display side. The optical projection system, from the eye side to the display side, sequentially includes a first lens, a second lens, a third lens, and a fourth lens along the optical axis. Each of the first to fourth lenses includes an eye side facing the eye side and allowing imaging light to pass through, and a display side facing the display side and allowing imaging light to pass through. The optical projection system also includes an aperture, a prism module, and a protective cover. The optical projection system has only the above four lenses with diopter, and satisfies the following condition: 12.0 degrees ≤ FOV / 2 ≤ 13.2 degrees, where FOV is the field of view of the optical projection system.

[0005] In one embodiment of the present invention, the diopter of the first lens is positive.

[0006] In one embodiment of the present invention, the eye-side surface of the first lens is convex.

[0007] In an embodiment of the present invention, the dioptric power of the above-mentioned second lens is negative.

[0008] In an embodiment of the present invention, the eye-side surface of the above-mentioned second lens is a concave surface.

[0009] In an embodiment of the present invention, the above-mentioned second lens is the lens with the smallest Abbe number among the first lens to the fourth lens.

[0010] In an embodiment of the present invention, the radius of curvature of the eye-side surface of the above-mentioned second lens is smaller than the radius of curvature of the display-side surface.

[0011] In an embodiment of the present invention, the dioptric power of the above-mentioned third lens is positive.

[0012] In an embodiment of the present invention, the eye-side surface of the above-mentioned third lens is a concave surface, and the display-side surface of the third lens is a convex surface.

[0013] In an embodiment of the present invention, the dioptric power of the above-mentioned fourth lens is positive.

[0014] In an embodiment of the present invention, the eye-side surface of the above-mentioned fourth lens is a convex surface.

[0015] In an embodiment of the present invention, the above-mentioned optical projection system further satisfies the following conditional expression: 8.2 mm ≤ TTL ≤ 8.6 mm, wherein TTL is the system length of the optical projection system.

[0016] In an embodiment of the present invention, the above-mentioned optical projection system further satisfies the following conditional expression: 1.80 ≤ N1 ≤ 2.10, wherein N1 is the refractive index of the first lens.

[0017] In an embodiment of the present invention, the above-mentioned optical projection system further satisfies the following conditional expression: 4.4 mm < T4I < 5.1 mm, wherein T4I is the distance from the display-side surface of the fourth lens to the display screen on the optical axis.

[0018] In an embodiment of the present invention, the above-mentioned optical projection system further satisfies the following conditional expression: 0.65 < ImgH / Rp < 0.80, wherein ImgH is the image height of the optical projection system, and Rp is the radius of the aperture.

[0019] In an embodiment of the present invention, the above-mentioned optical projection system further satisfies the following conditional expression: 3.0 < EFFL / Rp < 3.4, wherein EFFL is the effective focal length of the optical projection system, and Rp is the radius of the aperture.

[0020] In one embodiment of the present invention, the optical projection system further satisfies the following condition: -2.9 < (Fg1 / EFFL) < -2.4, where Fg1 is the equivalent focal length of the combination of the first lens and the second lens, and EFFL is the equivalent focal length of the optical projection system.

[0021] In one embodiment of the present invention, the optical projection system further satisfies the following condition: 0.53 < (Fg2 / EFFL) < 0.63, where Fg2 is the equivalent focal length of the combination of the third lens and the fourth lens, and EFFL is the equivalent focal length of the optical projection system.

[0022] In one embodiment of the present invention, the optical projection system further includes at least one display component for providing a display screen, wherein the number of the at least one display component is one to three.

[0023] In one embodiment of the present invention, when the number of the above-mentioned at least one display component is multiple, the light beams provided by the multiple display components have different wavelengths, or the light beams provided by at least two of the multiple display components have different polarization states.

[0024] Based on the above, in the optical projection system of the present invention, a first lens, a second lens, a third lens, and a fourth lens are sequentially included along the optical axis from the eye side to the display side. The optical projection system has only these four lenses with diopter, and they satisfy the following condition: 12.0 degrees ≤ FOV / 2 ≤ 13.2 degrees, where FOV is the field of view of the optical projection system. Therefore, the optical projection system can be made compact, easily installed on wearable or portable devices for use in augmented reality and virtual reality applications, while maintaining good optical quality. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an optical projection system according to an embodiment of the present invention;

[0026] Figures 2A to 2D for Figure 1 Modulation transfer function curve, lateral chromatic aberration, and various aberration diagrams of the optical projection system in the embodiment;

[0027] Figure 3 This is a schematic diagram of an optical projection system according to another embodiment of the present invention;

[0028] Figures 4A to 4D for Figure 3 Modulation transfer function curve, lateral chromatic aberration, and various aberration diagrams of the optical projection system in the embodiment;

[0029] Figure 5 This is a schematic diagram of an optical projection system according to another embodiment of the present invention;

[0030] Figures 6A to 6D for Figure 5 Modulation transfer function curve, lateral chromatic aberration, and various aberration diagrams of the optical projection system in the embodiment;

[0031] Figure 7 This is a schematic diagram of an optical projection system according to another embodiment of the present invention;

[0032] Figure 8 This is a schematic diagram of an optical projection system according to another embodiment of the present invention;

[0033] Figure 9 This is a schematic diagram of an optical projection system according to another embodiment of the present invention.

[0034] Explanation of icon numbers

[0035] 0: Aperture;

[0036] 1: First lens;

[0037] 2: Second lens;

[0038] 3: Third lens;

[0039] 4: Fourth lens;

[0040] 8: Prism module;

[0041] 8A, 8B, 8C, 8D: Prisms;

[0042] 9: Protective cover plate;

[0043] 10, 10A, 10B: Optical projection system;

[0044] 11, 21, 31, 41, 81, 91: Side view of the eye;

[0045] 12, 22, 32, 42, 82, 92: Show the side view;

[0046] 99, 99A, 99B, 99C: Display screen;

[0047] A1: Lateral view;

[0048] A2: Display side;

[0049] L, LA, LB, LC: Imaging rays. Detailed Implementation

[0050] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same component reference numerals are used in the drawings and description to denote the same or similar parts.

[0051] Figure 1This is a schematic diagram of an optical projection system according to an embodiment of the present invention. Please refer to... Figure 1 This embodiment provides an optical projection system 10, configured to allow imaging light L from a display screen 99 to pass through the optical projection system 10 and enter the observer's eye to form an image. The side facing the eye is designated as the eye side A1, and the side facing the display screen 99 is designated as the display side A2. The optical projection system 10, from the eye side A1 to the display side A2, sequentially includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 along the optical axis I.

[0052] In this embodiment, the optical projection system 10 further includes an aperture 0, a prism module 8, and a protective cover plate 9. The aperture 0 is located between the eye side A1 and the first lens 1, but the invention is not limited thereto. The prism module 8 is located between the fourth lens 4 and the protective cover plate 9, and the protective cover plate 9 is located between the prism module 8 and the display side A2. The prism module 8 is used to transmit the imaging light L from the display side A2 to the lens group, and it includes at least one prism, such as one, two, or four, for configuration in the optical projection system 10 with different numbers of display components, the detailed implementation of which will be described in subsequent paragraphs. The protective cover plate 9 is configured on the display component providing the display image 99 to provide a protective effect. However, in different embodiments, the protective cover plate 9 may be designed to have different types of coatings to provide additional optical effects, such as anti-reflection, light filtering, increased visible light efficiency, etc., and the invention is not limited thereto.

[0053] In this embodiment, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the prism module 8, and the filter 9 of the optical projection system 10 each have eye side surfaces 11, 21, 31, 41, 81, and 91 facing the eye side A1 and allowing the imaging light L to pass through, and display side surfaces 12, 22, 32, 42, 82, and 92 facing the display side A2 and allowing the imaging light L to pass through.

[0054] The first lens 1 has positive refractive power. The eye-side surface 11 of the first lens 1 is convex. The display-side surface 12 of the first lens 1 is convex. In this embodiment, the eye-side surface 11 of the first lens 1 is aspheric and the display-side surface 12 is spherical, but the present invention is not limited thereto.

[0055] The second lens 2 has negative refractive power. The eye-side surface 21 of the second lens 2 is concave. The display-side surface 22 of the second lens 2 is concave. In this embodiment, both the eye-side surface 21 and the display-side surface 22 of the second lens 2 are aspherical, but the present invention is not limited thereto.

[0056] The third lens 3 has positive refractive power. The eye-side surface 31 of the third lens 3 is concave. The display-side surface 32 of the third lens 3 is convex. In this embodiment, the eye-side surface 31 of the third lens 3 is spherical and the display-side surface 32 is aspherical, but the present invention is not limited thereto.

[0057] The fourth lens 4 has positive refractive power. The eye-side surface 41 of the fourth lens 4 is convex. The display-side surface 42 of the fourth lens 4 is convex. In this embodiment, both the eye-side surface 41 and the display-side surface 42 of the fourth lens 4 are aspherical, but the present invention is not limited thereto.

[0058] Therefore, in this embodiment, the refractive power of the first lens 1 to the fourth lens 4 is positive, negative, positive, and positive in that order. Furthermore, the second lens 2 has the lowest Abbe number among the first lens 1 to the fourth lens 4. In this embodiment, the optical projection system 10 contains only the aforementioned four lenses with refractive power. In this embodiment, the effective focal length (EFFL) of the optical projection system 10 is 4.73 mm, the half field of view (HFOV) is 12.25 degrees, the system length is 8.30 mm, the aperture radius is 1.5 mm, and the image height is 1.02 mm. Other detailed optical data for this embodiment are shown in Table 1 below.

[0059] Table 1

[0060]

[0061] Furthermore, in this embodiment, the eye surfaces 11, 21, and 41 of the first lens 1, the second lens 2, and the fourth lens 4, and the display surfaces 22, 32, and 42 of the second lens 2, the third lens 3, and the fourth lens 4, totaling six surfaces, are aspherical. Among them, the eye surfaces 11, 21, and 41 and the display surfaces 22, 32, and 42 are general even-order aspherical surfaces. These aspherical surfaces are defined according to the following formula (1):

[0062]

[0063] in:

[0064] R: Radius of curvature of the lens surface near the optical axis I;

[0065] Z: Depth of the aspherical surface (the perpendicular distance between a point on the aspherical surface at a distance Y from the optical axis I and a tangent plane that is tangent to the vertex on the optical axis I of the aspherical surface).

[0066] Y: The perpendicular distance between a point on the aspherical curve and the optical axis I;

[0067] K: Conic constant;

[0068] a 2i : The second-order aspherical coefficient.

[0069] The aspherical coefficients of the eye surface 11 of the first lens 1 to the display surface 42 of the fourth lens 4 in formula (1) are shown in Table 2 below. In Table 2, field number 21 indicates that it is the aspherical coefficient of the eye surface 21 of the second lens 2, and so on for the other fields. In this embodiment, the second-order aspherical coefficient a2 of each aspherical surface is zero, and therefore is not listed in Table 2.

[0070] Table 2

[0071]

[0072] Figures 2A to 2C for Figure 1 The modulation transfer function curve, lateral chromatic aberration, and various aberration diagrams of the optical projection system in this embodiment are shown below. Please refer to... Figures 2A to 2D . Figure 2A The accompanying drawings illustrate the modulation transfer function (MTF) curves of the optical projection system 10 in this embodiment when the imaging light wavelength L is 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 2B The accompanying drawings illustrate the lateral spherical aberration on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 2C The accompanying drawings illustrate the field curvature aberrations in the sagittal and tangential directions on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 2D The accompanying drawings illustrate the distortion aberration on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm and 656 nm.

[0073] exist Figure 2A In the modulation transfer function curve, regardless of whether it is in the sagittal or meridional direction, the modulus of each wavelength of light at different positions is greater than 0.55, still close to the diffraction limit curve, thus exhibiting good optical imaging quality. Figure 2BIn the lateral color difference diagram, the maximum deviation of the imaging point position between each wavelength on the display screen 99 is shown. The curves formed for each viewing field are very close to the center, and the imaging point deviation is controlled within ±1.2 micrometers. This indicates that, under the same viewing field, the imaging points of each wavelength converging on the imaging surface are not significantly separated. Therefore, this embodiment does indeed significantly improve color difference. Figure 2C In the attached diagram showing field curvature aberrations, the focal length variation for the five representative wavelengths falls within ±0.03 mm across the entire field of view, demonstrating that the optical system of this embodiment can effectively eliminate aberrations. Figure 2D The attached diagram shows that the distortion aberration in this embodiment is maintained within the range of ±0.6%, indicating that the distortion aberration in this embodiment meets the imaging quality requirements of the optical system.

[0074] In addition, the important parameters of the optical projection system 10 in this embodiment can be defined as follows:

[0075] in,

[0076] EFFL is the equivalent focal length of the optical projection system 10;

[0077] FG1 is the equivalent focal length of the combination of the first lens 1 and the second lens 2;

[0078] FG2 is the equivalent focal length of the combination of the third lens 3 and the fourth lens 4;

[0079] FOV is the field of view of the optical projection system 10;

[0080] ImgH is the image height of the optical projection system 10;

[0081] N1 is the refractive index of the first lens 1;

[0082] Rp is the radius of aperture 0;

[0083] T4I is the distance on optical axis I from the display side 42 of the fourth lens 4 to the display screen 99; and

[0084] TTL is the system length of optical projection system 10.

[0085] In addition, in order to make the optical projection system 10 small in size and easy to install on wearable or portable devices for use in augmented reality and virtual reality applications, while maintaining good optical quality, the optical projection system 10 further satisfies the following conditions to achieve a better configuration.

[0086] in,

[0087] The optical projection system 10 satisfies the condition: 12.0 degrees ≤ FOV / 2 ≤ 13.2 degrees;

[0088] The optical projection system 10 satisfies the conditional expression: 8.2 mm ≤ TTL ≤ 8.6 mm;

[0089] The optical projection system 10 satisfies the conditional expression: 1.80 ≤ N1 ≤ 2.10;

[0090] The optical projection system 10 satisfies the conditional expression: 4.4 mm < T5I < 5.1 mm;

[0091] The optical projection system 10 satisfies the conditional expression: 0.65 < ImgH / Rp < 0.80;

[0092] The optical projection system 10 satisfies the conditional expression: 3.0 < EFFL / Rp < 3.4;

[0093] The optical projection system 10 satisfies the conditional expression: -2.9 < (FG1 / EFFL) < -2.4; and

[0094] The optical projection system 10 satisfies the conditional expression: 0.53 < (FG2 / EFFL) < 0.63.

[0095] Figure 3 which is a schematic diagram of an optical projection system according to another embodiment of the present invention. Please refer to Figure 3 . The second embodiment of the optical imaging lens 10 of the present invention is substantially similar to the first embodiment, and the differences between the two are as follows: each optical data, aspheric coefficient and parameters among the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are more or less different. In this embodiment, the eye-side surface 11 of the first lens 1 is a spherical surface, the eye-side surface 31 of the third lens 3 is an aspheric surface, and the display-side surface 42 of the fourth lens 4 is a concave surface.

[0096] In this embodiment, the effective focal length (EFFL) of the optical projection system 10 is 4.62 mm, the half field of view (HFOV) is 12.5 degrees, the system length is 8.50 mm, the aperture radius is 1.5 mm, and the image height is 1.02 mm. Other detailed optical data of this embodiment are shown in Table 3 below.

[0097] Table 3

[0098]

[0099] Each aspheric coefficient in formula (1) for the eye-side surface 11 of the first lens 1 to the display-side surface 42 of the fourth lens 4 is shown in Table 4 below.

[0100] Table 4

[0101]

[0102] Figures 4A to 4D for Figure 3 The modulation transfer function curve, lateral chromatic aberration, and various aberration diagrams of the optical projection system in this embodiment are shown below. Please refer to... Figures 4A to 4D . Figure 4A The accompanying drawings illustrate the modulation transfer function curves of the optical projection system 10 of this embodiment when the wavelength of the imaging light L is 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 4B The accompanying drawings illustrate the lateral color difference on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 4C The accompanying drawings illustrate the field curvature aberrations in the sagittal and meridional directions on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 4D The accompanying drawings illustrate the distortion aberrations on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm and 656 nm.

[0103] exist Figure 4A In the modulation transfer function curve, regardless of whether it is in the sagittal or meridional direction, the modulus of each wavelength of light at different positions is greater than 0.55, still close to the diffraction limit curve, thus exhibiting good optical imaging quality. Figure 4B In the lateral color difference diagram, the maximum deviation of the imaging point position between each wavelength on the display screen 99 is shown. The curves formed for each viewing field are very close to the center, and the imaging point deviation is controlled within ±1.2 micrometers. This indicates that, under the same viewing field, the imaging points of each wavelength converging on the imaging surface are not significantly separated. Therefore, this embodiment does indeed significantly improve color difference. Figure 4C In the attached diagram showing field curvature aberrations, the focal length variation for the five representative wavelengths falls within ±0.04 mm across the entire field of view, demonstrating that the optical system of this embodiment can effectively eliminate aberrations. Figure 4D The attached diagram shows that the distortion aberration in this embodiment is maintained within the range of ±0.6%, indicating that the distortion aberration in this embodiment meets the imaging quality requirements of the optical system.

[0104] Figure 5 This is a schematic diagram of an optical projection system according to another embodiment of the present invention. Please refer to... Figure 5 The third embodiment of the optical imaging lens 10 of the present invention is generally similar to the first embodiment, but the differences are as follows: the optical data, aspherical coefficients, and parameters between the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are more or less different. Specifically, the display side 12 of the first lens 1 is concave, and the display side 42 of the fourth lens 4 is also concave.

[0105] In this embodiment, the optical projection system 10 has an effective focal length (EFFL) of 5.56 mm, a half field of view (HFOV) of 13 degrees, a system length of 8.45 mm, an aperture radius of 1.65 mm, and an image height of 1.27 mm. Other detailed optical data for this embodiment are shown in Table 5 below.

[0106] Table 5

[0107]

[0108] The aspherical coefficients of the eye side 11 of the first lens 1 to the display side 42 of the fourth lens 4 in formula (1) are shown in Table 6 below.

[0109] Table 6

[0110]

[0111] Figures 6A to 6D for Figure 5 The modulation transfer function curve, lateral chromatic aberration, and various aberration diagrams of the optical projection system in this embodiment are shown below. Please refer to... Figures 6A to 6D . Figure 6A The accompanying drawings illustrate the modulation transfer function curves of the optical projection system 10 of this embodiment when the wavelength of the imaging light L is 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 6B The accompanying drawings illustrate the lateral color difference on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 6C The accompanying drawings illustrate the field curvature aberrations in the sagittal and meridional directions on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm. Figure 6D The accompanying drawings illustrate the distortion aberrations on the display screen 99 when the wavelengths are 436 nm, 486 nm, 546 nm, 588 nm and 656 nm.

[0112] exist Figure 6A In the modulation transfer function curve, regardless of whether it is in the sagittal or meridional direction, the modulus of each wavelength of light at different positions is greater than 0.6, still close to the diffraction limit curve, thus exhibiting good optical imaging quality. Figure 6BIn the lateral color difference diagram, the maximum deviation of the imaging point position between each wavelength on the display screen 99 is shown. The curves for each viewing field are very close to the center, and the imaging point deviation is controlled within ±1.6 micrometers. This indicates that, under the same viewing field, the imaging points of each wavelength converging on the imaging surface are not significantly separated. Therefore, this embodiment does indeed significantly improve color difference. Figure 6C In the attached diagram showing field curvature aberrations, the focal length variation for the five representative wavelengths falls within ±0.05 mm across the entire field of view, demonstrating that the optical system of this embodiment can effectively eliminate aberrations. Figure 6D The attached diagram shows that the distortion aberration in this embodiment is maintained within the range of ±1.6%, indicating that the distortion aberration in this embodiment meets the imaging quality requirements of the optical system.

[0113] Figure 7 This is a schematic diagram of an optical projection system according to another embodiment of the present invention. Please refer to... Figure 7 The optical projection system 10 in this embodiment is... Figure 1 The difference between the optical projection system 10 and the optical projection system 10 is that... Figure 7 The optical projection system 10 also displays the imaging ray L near the edge of the optically effective area. In this embodiment, the display component (display screen 99) is a single unit, and the prism module 8 includes only a single prism.

[0114] Figure 8 This is a schematic diagram of an optical projection system according to another embodiment of the present invention. The optical projection system 10A of this embodiment is similar to... Figure 7 The optical projection system 10 shown differs from the traditional one in that, in this embodiment, the optical projection system 10A includes two display components, providing two display screens 99A and 99B respectively. For example, in this embodiment, the light beams provided by the two display components (the two display screens 99A and 99B) have different wavelengths. In another embodiment, the polarization states of the light beams provided by the two display components (the two display screens 99A and 99B) may be designed to be different, but the invention is not limited thereto. On the other hand, in this embodiment, the prism module 8 includes two prisms 8A and 8B. Prism 8A is disposed on the transmission path of the imaging light LA ​​emitted from display screen 99A, and is used to guide the imaging light LA ​​through prism 8B to the fourth lens 4. Prism 8B is disposed on the transmission path of the imaging light LB emitted from display screen 99B, and is used to guide the imaging light LB through reflection by prism 8A to the fourth lens 4. The interface between the two prisms 8A and 8B can be customized with different coating materials based on the differences in the types of the two display screens 99A and 99B, which will not be elaborated further.

[0115] Figure 9 This is a schematic diagram of an optical projection system according to another embodiment of the present invention. The optical projection system 10B of this embodiment is similar to... Figure 7 The optical projection system 10 shown differs from the traditional system in that, in this embodiment, the optical projection system 10B includes three display components, providing three display images 99A, 99B, and 99C respectively. For example, in this embodiment, the light beams provided by the three display components (the three display images 99A, 99B, and 99C) have different wavelengths. In another embodiment, the polarization states of the light beams provided by at least two of the three display components (the three display images 99A, 99B, and 99C) may be different, but the invention is not limited thereto. On the other hand, in this embodiment, the prism module 8 includes four prisms 8A, 8B, 8C, and 8D. Prism 8A is disposed on the transmission path of the imaging light LA ​​emitted from the display image 99A, and is used to guide the imaging light LA ​​through prisms 8B, 8C, and 8D to the fourth lens 4. Prism 8B is positioned in the transmission path of the imaging light LB emitted from display screen 99B. It guides the imaging light LB through reflections by prisms 8A and 8C, then through prism 8D to the fourth lens 4. Prism 8C is positioned in the transmission path of the imaging light LC emitted from display screen 99C. It guides the imaging light LC through reflections by prisms 8A and 8B, then through prism 8D to the fourth lens 4. The interface between the three prisms 8A, 8B, and 8C can be coated with different materials depending on the type of the three display screens 99A, 99B, and 99C; details are omitted here.

[0116] In summary, the optical projection system of the present invention includes, sequentially from the eye side to the display side along the optical axis, a first lens, a second lens, a third lens, and a fourth lens. The optical projection system has only these four lenses with diopter, and they satisfy the following condition: 12.0 degrees ≤ FOV / 2 ≤ 13.2 degrees, where FOV is the field of view of the optical projection system. Therefore, the optical projection system can be compact, easily installed on wearable or portable devices for use in augmented reality and virtual reality applications, while maintaining good optical quality.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical projection system, characterized in that, The optical projection system is configured such that imaging light from a display screen passes through the optical projection system and enters an observer's eye to form an image, wherein the side facing the eye is an eye side and the side facing the display screen is a display side. The optical projection system sequentially comprises a first lens, a second lens, a third lens and a fourth lens along an optical axis from the eye side to the display side. Each of the first lens to the fourth lens comprises an eye side facing the eye and allowing the imaging light to pass through and a display side facing the display side and allowing the imaging light to pass through. The optical projection system further comprises a diaphragm, a prism module and a protective cover plate; wherein, the only lenses having refractive power in the optical projection system are the four lenses described above, and the following conditional expression is satisfied: 12.0 degrees ≤ FOV / 2 ≤ 13.2 degrees, where FOV is the field of view angle of the optical projection system.

2. The optical projection system according to claim 1, characterized in that, The first lens has positive refractive power.

3. The optical projection system according to claim 1, characterized in that, The eye side of the first lens is a convex surface.

4. The optical projection system according to claim 1, characterized in that, The second lens has negative refractive power.

5. The optical projection system according to claim 1, characterized in that, The eye side of the second lens is a concave surface.

6. The optical projection system according to claim 1, characterized in that, The second lens is the lens with the smallest Abbe number among the first lens to the fourth lens.

7. The optical projection system according to claim 1, characterized in that, The radius of curvature of the eye side of the second lens is smaller than the radius of curvature of the display side.

8. The optical projection system according to claim 1, characterized in that, The third lens has positive refractive power.

9. The optical projection system according to claim 1, characterized in that, The eye side of the third lens is a concave surface, and the display side of the third lens is a convex surface.

10. The optical projection system according to claim 1, characterized in that, The fourth lens has positive refractive power.

11. The optical projection system according to claim 1, characterized in that, The eye side of the fourth lens is a convex surface.

12. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: 8.2 mm ≤ TTL ≤ 8.6 mm, where TTL is the system length of the optical projection system.

13. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: 1.80 ≤ N1 ≤ 2.10, where N1 is the refractive index of the first lens.

14. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: 4.4 mm < T4I < 5.1 mm, where T4I is the distance between the display side of the fourth lens and the display screen on the optical axis.

15. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: 0.65 < ImgH / Rp < 0.80, where ImgH is the image height of the optical projection system, and Rp is the radius of the diaphragm.

16. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: 3.0 < EFFL / Rp < 3.4, where EFFL is the effective focal length of the optical projection system, and Rp is the radius of the diaphragm.

17. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: -2.9 < (FG1 / EFFL) < -2.4, where FG1 is the effective focal length of the combination of the first lens and the second lens, and EFFL is the effective focal length of the optical projection system.

18. The optical projection system according to claim 1, characterized in that, The optical projection system further satisfies the following conditional expression: 0.53 < (FG2 / EFFL) < 0.63, where FG2 is the effective focal length of the combination of the third lens and the fourth lens, and EFFL is the effective focal length of the optical projection system.

19. The optical projection system according to claim 1, characterized in that, The optical projection system further includes at least one display component for providing the display image, wherein the number of the at least one display component is one to three.

20. The optical projection system according to claim 19, characterized in that, When the number of the at least one display component is multiple, the light beams provided by the multiple display components have different wavelengths, or the light beams provided by at least two of the multiple display components have different polarization states.

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