Optical system

Abstract

To provide an optical system regarding a field of an optical lens.SOLUTION: An optical system has an imaging surface, a first lens, and a diaphragm in order from a front side to a rear side, a circular polarizer for emitting light to a rear side of the imaging surface is stuck, a partial reflection element is provided on a front surface of the first lens, a composite film is provided on a rear-side surface, the composite film has a reflection-type polarizing film and a 1 / 4-wavelength plate, the reflection type polarizing film is provided in a rear side of the 1 / 4-wavelength plate, the diaphragm is positioned in a rear side of the optical system, a maximum visible diameter of the optical system is VD, a maximum effective radius of each lens in the optical system is SDmax, an on-axis distance from a front surface of the first lens to the imaging surface is d4, an on-axis distance from a rear surface of the first lens to the imaging surface is TTL, and relational expressions of VD≥6 mm, SDmax≤21.2 mm, and 0.71≤d4 / TTL≤0.85 can be satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of near-eye display technology, and in particular to optical systems. [Background technology]

[0002] In recent years, with the rapid development of technology related to smart head-mounted devices, the applications of electronic devices equipped with optical lenses have become more widespread, and the requirements for optical lenses have become more diversified. Applications in fields such as virtual reality, augmented reality, and mixed reality have grown rapidly, and from the perspective of user experience, there is a very urgent demand for optical systems that combine small size and excellent imaging methods. Summary of the Invention [Problem to be solved by the invention]

[0003] In view of the above problems, an object of the present invention is to provide an optical system that has excellent optical performance and satisfies the design requirements for being small and lightweight. [Means for solving the problem]

[0004] In order to solve the above technical problems, the optical system of the present invention provides an optical system comprising, in order from front to rear, an image plane, a first lens, and an aperture, a circular polarizer for emitting light attached to the rear side of the image plane, a partially reflecting element provided on the front surface of the first lens, and a composite film provided on the rear surface thereof, the composite film comprising a reflective polarizing film and a quarter wave plate, the reflective polarizing film being provided on the rear side of the quarter wave plate, the aperture being located on the rear side of the optical system, a maximum visible diameter of the optical system is VD, a maximum effective radius of each lens in the optical system is SDmax, an axial distance from the front surface of the first lens to the image plane is d4, and an axial distance from the rear surface of the first lens to the image plane is TTL, and the optical system satisfies the following relations: VD≧6 mm, SDmax≦21.2 mm, and 0.71≦d4 / TTL≦0.85.

[0005] Preferably, the front surface of the first lens is aspheric.

[0006] Preferably, the rear surface of the first lens is flat.

[0007] Preferably, the angle of view of the optical system is the FOV, which satisfies 90°≦FOV≦110°.

[0008] Preferably, the partially reflective element is a semi-transmissive semi-reflective film, the transmittance and reflectance of which are both 40% to 60%.

[0009] Preferably, the reflectance of the reflective polarizing film is 95% or more.

[0010] Preferably, the total optical length of the optical system is TTL and satisfies TTL≦24 mm.

[0011] Preferably, the total optical length of the optical system is TTL, the focal length of the optical system is f, and TTL / f≦1.00 is satisfied.

[0012] Preferably, the optical distortion of the optical system is DIST, and DIST≦35% is satisfied.

[0013] Preferably, the chromatic aberration of the optical system is LC, and satisfies LC≦120 μm.

[0014] Preferably, the image surface is a display and has a size of 2.0 to 2.3 inches. Effect of the Invention

[0015] The beneficial effects of the present invention are that a partially reflective element is provided on the front surface of the first lens, and a composite film including a reflective polarizing film and a quarter-wave plate is provided on the rear surface of the first lens, thereby realizing a light path folding structure, controlling the lens radius, and reducing the volume of the optical system; and the maximum visible diameter is 6 mm or more, so that the user can obtain an optimal display effect without having to make complicated adjustments, thereby achieving both compact size and high imaging performance. [Brief description of the drawings]

[0016] In order to more clearly describe the technical ideas in the embodiments of the present invention, the drawings necessary for the description of the embodiments are briefly described below. Obviously, the following description of the drawings is only for describing some embodiments of the present invention, and those skilled in the art can obtain other drawings from these drawings without creative efforts. [Figure 1] FIG. 1 is a diagram showing the structure of an optical system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a spot diagram of the optical system shown in FIG. [Diagram 3] FIG. 3 is a diagram showing chromatic aberration of magnification of the optical system shown in FIG. [Figure 4] FIG. 4 is a diagram showing the field curvature and distortion of the optical system shown in FIG. [Diagram 5] FIG. 5 is a diagram showing the structure of an optical system including the film layers shown in FIG. [Figure 6] FIG. 5 is a diagram showing the structure of an optical system according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a spot diagram of the optical system shown in FIG. [Figure 8] FIG. 8 is a diagram showing chromatic aberration of magnification of the optical system shown in FIG. [Figure 9] FIG. 9 is a diagram showing the field curvature and distortion of the optical system shown in FIG. [Figure 10] FIG. 10 is a diagram showing the structure of an optical system including the film layers shown in FIG. [Figure 11] FIG. 11 is a diagram showing the structure of an optical system according to a third embodiment of the present invention. [Figure 12] FIG. 12 is a spot diagram of the optical system shown in FIG. [Figure 13] FIG. 13 is a diagram showing chromatic aberration of magnification of the optical system shown in FIG. [Figure 14] FIG. 14 is a diagram showing the field curvature and distortion of the optical system shown in FIG. [Figure 15]FIG. 15 is a diagram showing the structure of an optical system including the film layers shown in FIG. [Figure 16] FIG. 16 is a diagram showing the structure of an optical system according to a fourth embodiment of the present invention. [Figure 17] FIG. 17 is a spot diagram of the optical system shown in FIG. [Figure 18] FIG. 18 is a diagram showing chromatic aberration of magnification of the optical system shown in FIG. [Figure 19] FIG. 19 is a diagram showing the field curvature and distortion of the optical system shown in FIG. [Figure 20] FIG. 20 is a diagram showing the structure of an optical system including the film layers shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In order to clarify the objectives, technical solutions and advantages of the present invention, the following detailed description of the embodiments of the present invention will be given with reference to the drawings. Although many technical details are described in the embodiments of the present invention for the purpose of facilitating understanding of the present invention, it is obvious to those skilled in the art that the technical solutions protected by the present invention can be realized without these technical details and various changes and modifications based on the following embodiments.

[0018] (First embodiment)

[0019] As shown in FIG. 1, an optical system 100 is provided that includes, from front to rear, an image plane 11, a circular polarizer 12, a partially reflecting element 13, a first lens 14, a quarter-wave plate 15, a reflective polarizing film 16, and an aperture 18, in that order.

[0020] The image surface 11 emits light. The image surface 11 has a circular polarizer 12 attached to the rear side of the image surface 11, in this embodiment, the image surface 11 is a display and has a size of 2.1 inches, and after the light emitted from the display passes through the circular polarizer 12, it forms a left-handed circularly polarized LCP.

[0021] The front surface 141 of the first lens 14 is provided with a partially reflective element 13, so that some of the light is reflected and some of the light is incident on the first lens 14, in this case the light is left-handed circularly polarised LCP.

[0022] A composite film is provided on the rear surface 142 of the first lens 14, the composite film including a reflective polarizing film 16 and a quarter-wave plate 15, the reflective polarizing film 16 is farther from the rear surface 142 of the first lens 14 than the quarter-wave plate 15, the left-handed circularly polarized light LCP passes through the quarter-wave plate 15 for the first time, is converted into linearly polarized S light, and is reflected by the reflective polarizing film 16, the reflected light in this case is still linearly polarized S light, passes through the quarter-wave plate 15 for the second time, is converted into left-handed circularly polarized LCP, enters the first lens 14 for the second time, is partially reflected by the partial reflection element 13, the reflected light is converted into right-handed circularly polarized RCP, and enters the first lens 14 for the third time, the right-handed circularly polarized RCP is emitted from the first lens 14, enters the quarter-wave plate 15, passes through the quarter-wave plate 15, is converted into linearly polarized P light, and enters the reflective polarizing film 16. The reflective polarizing film 16 has the property of reflecting linearly polarized S light and transmitting linearly polarized P light, so the linearly polarized P light enters the aperture 18 after being transmitted therethrough.

[0023] The position of the diaphragm 18 is a position simulating the surface of the human eye, the diameter of the diaphragm 18 is 6 mm, and the maximum visible diameter of the optical system 100 is defined as VD, which is 6 mm and satisfies VD≧6 mm. That is, the human eye can see a clear image when the diameter moves within a range of at least 6 mm.

[0024] The effective radius of the first lens 14 is 20.3 mm, and the maximum effective radius of the lens in the optical system 100 is defined as SDmax, which satisfies SDmax≦21.2 mm. This contributes to the miniaturization of the optical system.

[0025] In this embodiment, the rear surface 142 of the first lens 14 is flat, which helps to increase the bonding yield of the composite film, and the front surface 141 of the first lens 14 is aspheric, which can reduce chromatic aberration and distortion of the optical system and improve the imaging quality by adjusting the focus position of the displayed image through the aspheric design. In other alternative embodiments, the front surface 141 of the first lens 14 can be a free-form surface.

[0026] In this embodiment, the front surface 141 of the first lens 14 is convex.

[0027] In this embodiment, the field of view of the optical system 100 is defined as FOV, and the FOV is 100.00°, which satisfies 90°≦FOV≦110°. This provides a better user experience with a wide field of view. Preferably, the field of view satisfies 95°≦FOV≦105°.

[0028] In this embodiment, the partially reflective element is a semi-transmissive semi-reflective film, and its transmittance and reflectance are both 50%. In other alternative embodiments, the reflectance and transmittance of the partially reflective element can be adjusted according to specific design requirements, and may be 40:60, 55:45, 60:40, etc.

[0029] In this embodiment, the reflectance of the reflective polarizing film 16 is 95% or more. A higher reflectance can increase the light efficiency of the optical system 100 and increase the display brightness.

[0030] The axial distance from the image plane 11 to the rear surface 172 of the first lens 17, i.e., the total optical length of the optical system, is defined as TTL, and in this embodiment, TTL is 23.534, which satisfies TTL≦24 mm, which helps to reduce the volume of the optical system.

[0031] The axial distance from the front surface of the first lens 14 to the image plane 11 is defined as d4, and in this embodiment, d4 is 14.347, d4 / TTL is 0.737, and satisfies 0.71≦d4 / TTL≦0.85, which helps reduce the volume of the optical system.

[0032] The focal length of the optical system 100 is defined as f, and in this embodiment, f is 24.59, TTL / f is 0.957, and TTL / f≦1.00 is satisfied, which is helpful in reducing the volume of the optical system.

[0033] The optical distortion of the optical system is defined as DIST, and in this embodiment, DIST≦35% is satisfied. This reduces distortion, making it possible to provide a more realistic VR environment to the user.

[0034] The chromatic aberration of the optical system is defined as LC, and in this embodiment, LC≦120 μm is satisfied. This reduces the chromatic aberration, and a more realistic VR environment can be provided to the user.

[0035] The optical system 100 according to the present invention will be described below using examples. The symbols used in each example are as follows. The units of the focal length, axial distance, central radius of curvature, axial thickness, inflection point position, and stationary point position are mm.

[0036] Tables 1 and 2 show setting data for the optical system 100 according to the first embodiment of the present invention.

[0037] [Table 1]

[0038] Here, the meanings of the symbols are as follows: R: Radius of curvature at the center of the optical surface R1: central radius of curvature of the rear surface of the first lens 14 R2: central radius of curvature of the front surface of the first lens 14 d: Axial thickness of the lens, axial distance between lenses. To make the optical path easier to understand, light propagating from the rear to the front is considered a positive value, and light propagating from the front to the rear is considered a negative value. d0: The axial distance from the aperture stop S18 to the object-side surface 142 of the first lens L14 d1: Axial thickness of the first lens L14 d2: Negative value of the axial thickness of the first lens L14 d3: Axial thickness of the first lens L14 d4: the axial distance from the front surface 141 of the first lens 14 to the image plane 11 nd: Refractive index of d line (d line is green light with a wavelength of 550 nm) nd1: Refractive index of the d line of the first lens L14 vd: Abbe number v1: Abbe number of the first lens L14

[0039] Table 2 shows data on the aspheric surfaces of the lenses in the optical system 100 according to the first embodiment of the present invention.

[0040] [Table 2]

[0041] For convenience, the aspheric surface of each lens surface is expressed by the above formula (1), but the present invention is not limited to the aspheric polynomial of this formula (1).

[0042] z=(cr 2 ) / {1+[1-(k+1)(c 2 r 2 )] 1 / 2}+A4r 4 +A6r 6 +A8r 8 +A10r 10 +A12r 12 +A14r 14 +A16r 16 +A18r 18 +A20r 20 +A22r 22 +A24r 24 +A26r 26 (1)

[0043] where k is the conic coefficient, A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26 are aspheric coefficients, c is the central curvature of the optical surface, r is the perpendicular distance between a point on the aspheric curve and the optical axis, and z is the aspheric depth (the perpendicular distance between a point on the aspheric surface that is a distance r away from the optical axis and the tangent plane that is tangent to the vertex on the aspheric optical axis).

[0044] Fig. 2 and Fig. 3 are diagrams showing spot diagrams and lateral chromatic aberrations of light having wavelengths of 450 nm, 540 nm, and 630 nm, respectively, after passing through the optical system 100 according to the first embodiment. Fig. 4 is a diagram showing field curvature and distortion aberrations of light having a wavelength of 540 nm after passing through the optical system 100 according to the first embodiment, where the field curvature S in Fig. 4 is the field curvature in the sagittal direction, and T is the field curvature in the meridional direction.

[0045] In this embodiment, the entrance pupil diameter ENPD of the optical system 100 is 6 mm, TTL is 23.526 mm, d4 / TTL is 0.737, focal length f is 24.59 mm, TTL / f is 0.957, image height IH of the entire field of view is 19.970 mm, and angle of view FOV in the diagonal direction is 100.00°. As a result, the optical system 100 can meet the design requirements of a small volume and a maximum visible diameter of 6 mm or more, and its on-axis and off-axis chromatic aberrations are sufficiently corrected, resulting in excellent optical characteristics.

[0046] Second embodiment

[0047] The second embodiment is almost the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0048] Shown in FIG. 6 is an optical system 200 according to a second embodiment of the present invention.

[0049] Tables 3 and 4 show setting data for the optical system 200 according to the second embodiment of the present invention.

[0050] [Table 3]

[0051] Table 4 shows data on the aspheric surfaces of the lenses in the optical system 200 according to the second embodiment of the present invention.

[0052] [Table 4]

[0053] Fig. 7 and Fig. 8 are diagrams showing spot diagrams and lateral chromatic aberrations of light having wavelengths of 450 nm, 540 nm, and 630 nm, respectively, after passing through the optical system 200 according to the second embodiment. Fig. 9 is a diagram showing field curvature and distortion aberrations of light having a wavelength of 540 nm after passing through the optical system 200 according to the second embodiment, where the field curvature S in Fig. 9 is the field curvature in the sagittal direction, and T is the field curvature in the meridional direction.

[0054] In this embodiment, the entrance pupil diameter ENPD of the optical system 200 is 6 mm, TTL is 22.528 mm, d4 / TTL is 0.711, the maximum effective radius of the lens in the optical system is SDmax 19.5 mm, the focal length f is 23.956 mm, TTL / f is 0.94, the image height IH of the entire field of view is 19.200 mm, and the diagonal field angle FOV is 103.89°. As a result, the optical system 200 can meet the design requirements of a small volume and a maximum visible diameter of 6 mm or more, and its on-axis and off-axis chromatic aberrations are sufficiently corrected, resulting in excellent optical characteristics.

[0055] Third embodiment

[0056] The third embodiment is almost the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0057] Shown in FIG. 11 is an optical system 300 according to a third embodiment of the present invention.

[0058] Tables 5 and 6 show setting data for the optical system 300 according to the third embodiment of the present invention.

[0059] [Table 5]

[0060] Table 6 shows data on the aspheric surfaces of the lenses in the optical system 300 according to the third embodiment of the present invention.

[0061] [Table 6]

[0062] Fig. 12 and Fig. 13 are diagrams showing spot diagrams and lateral chromatic aberrations of light having wavelengths of 450 nm, 540 nm, and 630 nm, respectively, after passing through the optical system 300 according to the third embodiment. Fig. 14 is a diagram showing field curvature and distortion aberrations of light having a wavelength of 540 nm after passing through the optical system 300 according to the third embodiment, where the field curvature S in Fig. 14 is the field curvature in the sagittal direction and T is the field curvature in the meridional direction.

[0063] In this embodiment, the entrance pupil diameter ENPD of the optical system 300 is 6 mm, TTL is 23.530 mm, d4 / TTL is 0.798, the maximum effective radius of the lens in the optical system is SDmax 21.2 mm, the focal length f is 24.643 mm, TTL / f is 0.955, the image height IH of the entire field of view is 19.200 mm, and the diagonal field angle FOV is 96.29°. As a result, the optical system 300 can meet the design requirements of a small volume and a maximum visible diameter of 6 mm or more, and its axial and off-axial chromatic aberrations are sufficiently corrected to provide excellent optical characteristics.

[0064] (Fourth embodiment)

[0065] The fourth embodiment is almost the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0066] Shown in FIG. 16 is an optical system 400 according to a fourth embodiment of the present invention.

[0067] Tables 7 and 8 show setting data for the optical system 400 according to the fourth embodiment of the present invention.

[0068] [Table 7]

[0069] Table 8 shows data on the aspheric surfaces of the lenses in the optical system 400 according to the third embodiment of the present invention.

[0070] [Table 8]

[0071] Fig. 17 and Fig. 18 are diagrams showing spot diagrams and lateral chromatic aberrations after light of wavelengths 450 nm, 540 nm, and 630 nm has passed through the optical system 400 according to the fourth embodiment, respectively. Fig. 19 is a diagram showing field curvature and distortion aberration after light of wavelength 540 nm has passed through the optical system 400 according to the fourth embodiment, where the field curvature S in Fig. 19 is the field curvature in the sagittal direction and T is the field curvature in the meridional direction.

[0072] In this embodiment, the entrance pupil diameter ENPD of the optical system 400 is 6 mm, TTL is 23.664 mm, d4 / TTL is 0.843, the maximum effective radius of the lens in the optical system is SDmax 20.3 mm, the focal length f is 24.617 mm, TTL / f is 0.961, the image height IH of the entire field of view is 19.200 mm, and the diagonal field angle FOV is 96.58°. As a result, the optical system 400 can meet the design requirements of a small volume and a maximum visible diameter of 6 mm or more, and its axial and off-axial chromatic aberrations are sufficiently corrected, resulting in excellent optical characteristics.

[0073] Although the above-mentioned embodiments are specific embodiments for realizing the present invention, it should be understood by those skilled in the art that in practical applications, various changes in form and details can be made without departing from the spirit and scope of the present invention.

Claims

1. an optical system including, in order from the front side to the rear side, an image plane, a first lens, and an aperture; A circular polarizer is attached to the rear side of the image surface, and the image surface is used to emit light; the first lens has a partially reflective element on its front surface and a composite film on its rear surface, the composite film comprising a reflective polarizing film and a quarter-wave plate, the reflective polarizing film being disposed on the rear side of the quarter-wave plate; The diaphragm is located behind the optical system, When a maximum visible diameter of the optical system is defined as VD, a maximum effective radius of each lens in the optical system is defined as SDmax, an axial distance from a front surface of the first lens to the image plane is defined as d4, and an axial distance from a rear surface of the first lens to the image plane is defined as TTL, the following relations are satisfied: VD≧6 mm, SDmax≦21.2 mm, and 0.71≦d4 / TTL≦0.

85. An optical system characterized by:

2. 2. The optical system of claim 1, wherein the front surface of the first lens is aspheric.

3. 2. The optical system of claim 1, wherein the rear surface of the first lens is flat.

4. 2. The optical system according to claim 1, wherein, when the angle of view of the optical system is defined as FOV, the following relation is satisfied: 90[deg.]≦FOV≦110[deg.].

5. 2. The optical system according to claim 1, wherein the partially reflecting element is a semi-transmissive semi-reflective film, the transmittance and reflectance of which are both in the range of 40% to 60%.

6. 2. The optical system according to claim 1, wherein the reflectance of the reflective polarizing film is 95% or more.

7. 2. The optical system according to claim 1, wherein when a total optical length of the optical system is defined as TTL, a relational expression of TTL≦24 mm is satisfied.

8. 2. The optical system according to claim 1, wherein when a total optical length of the optical system is defined as TTL and a focal length of the optical system is defined as f, the optical system satisfies the relation TTL / f≦1.

00.

9. 2. The optical system according to claim 1, wherein, when an optical distortion of the optical system is defined as DIST, a relational expression of DIST≦35% is satisfied.

10. 2. The optical system according to claim 1, wherein, when chromatic aberration of the optical system is defined as LC, a relational expression of LC≦120 μm is satisfied.

11. 2. The optical system according to claim 1, wherein the image surface is a display and has a size of 2.0 to 2.3 inches.

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