A short-throw projection lens and projection imaging system

Abstract

The present invention discloses a short-focus projection lens and a projection imaging system, the short-focus projection lens comprising: a lens assembly, the lens assembly comprising a plurality of spherical lenses arranged on the same optical axis, for projecting an external input light beam; the spherical lens comprises a first meniscus lens, a first biconvex lens, a biconcave lens, a second biconvex lens and a second meniscus lens arranged in sequence. The short-focus projection lens provided by the embodiment of the present invention can project an external input light beam by selecting a plurality of coaxially arranged lenses, and the plurality of lenses are all spherical lenses, which can avoid the use of aspherical lenses, and solve the technical problem of the difficulty and high cost of processing the aspherical lenses used in the prior art. In addition, the short-focus projection lens provided by the embodiment of the present invention can use only five lenses, which reduces the number of lenses compared to the lenses in the prior art, and reduces the difficulty of the production and assembly process.

Description

Technical Field

[0001] The present invention relates to the field of projection technology, and particularly to a short-focus projection lens and a projection imaging system. Background Art

[0002] As a core component in a projection device, after the light in the projection device passes through a reflective or transmissive light modulation device, it needs to be projected onto a projection screen through a projection lens to form an image. As projection devices play an increasingly important role in life, they are applied in more and more fields. More devices need to be embedded with projection devices, which places higher requirements on projection lenses, such as smaller size, more compact structure, better imaging effect, lower cost, etc.

[0003] In current projection devices, in order to obtain good display image quality, projection lenses usually have a complex structure, and the number of lenses generally exceeds 7; and projection lenses usually use aspherical lenses. Since aspherical lenses are expensive, the processing and assembly processes are complex, and the yield is not easy to control, the existing high-quality image projection lenses are expensive. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a short-focus projection lens and a projection imaging system to solve the technical problems in the prior art that the number of lenses in a projection lens is large and high-quality lenses are expensive.

[0005] The technical solutions proposed by the present invention are as follows:

[0006] In a first aspect of an embodiment of the present invention, a short-focus projection lens is provided. The short-focus projection lens includes: a lens assembly, the lens assembly includes a plurality of spherical lenses arranged coaxially for projecting and imaging an externally input light beam; the spherical lenses include a first meniscus lens, a first biconvex lens, a biconcave lens, a second biconvex lens, and a second meniscus lens arranged in sequence.

[0007] Optionally, the short-focus projection lens further includes: a diaphragm, the diaphragm is arranged between the biconcave lens and the second biconvex lens.

[0008] Optionally, the focal length f1 of the first meniscus lens satisfies the conditional formula: -250mm < f1 < -350mm; the focal length f2 of the first biconvex lens satisfies the conditional formula: 5mm < f2 < 50mm; the focal length f3 of the biconcave lens satisfies the conditional formula: -5mm < f3 < -50mm; the focal length f4 of the second biconvex lens satisfies the conditional formula: 10mm < f4 < 100mm; the focal length f5 of the second meniscus lens satisfies the conditional formula: -10mm < f5 < -100mm.

[0009] Optionally, the refractive index n1 of the first meniscus lens satisfies the conditional formula: 1.65 < n1 < 1.75; the refractive index n2 of the first biconvex lens satisfies the conditional formula: 1.75 < n2 < 1.85; the refractive index n3 of the biconcave lens satisfies the conditional formula: 1.65 < n3 < 1.75; the refractive index n4 of the second biconvex lens satisfies the conditional formula: 1.70 < n4 < 1.80; the refractive index n5 of the second meniscus lens satisfies the conditional formula: 1.5 < n5 < 1.6.

[0010] In a second aspect of the embodiments of the present invention, a projection imaging system is provided. The projection imaging system includes: a display device, a beam splitting device, and a short-focus projection lens as described in the first aspect and any one of the first aspects of the embodiments of the present invention, which are arranged in sequence; the light beam output by the display device is projected onto a display screen after passing through the beam splitting device and the short-focus projection lens in sequence.

[0011] Optionally, the display device includes: a digital micromirror chip, and the digital micromirror chip is arranged perpendicular to the optical axis of the lens assembly.

[0012] Optionally, the size of the digital micromirror chip is 0.45 inches, and the resolution is 1140×912.

[0013] Optionally, the half field of view angle of the projection imaging system satisfies 10° ≤ FOV ≤ 15°.

[0014] Optionally, the focal length of the projection imaging system satisfies 15mm ≤ f ≤ 25mm.

[0015] Optionally, the numerical aperture of the object side of the projection imaging system satisfies 0.01 ≤ NA ≤ 0.05.

[0016] The technical solution of the present invention has the following advantages:

[0017] The short-focus projection lens provided by the embodiments of the present invention can project and image the externally input light beam by selecting multiple coaxially arranged lenses. All of these lenses are spherical lenses. By reasonably setting parameters such as the focal length of the lens assembly and the distance between each lens, the marginal aberration and spherical aberration of the lens can be effectively reduced, so that the function of an aspherical mirror can be achieved. Therefore, the short-focus projection lens provided by the embodiments of the present invention can avoid the use of an aspherical mirror, and solve the technical problems of difficult processing and high cost of the aspherical lens in the prior art. Moreover, through the reasonable configuration of the optical angles of the spherical lenses in the lens assembly, the short-focus projection lens provided by the embodiments of the present invention can use only five lenses, reducing the number of lenses compared with the lenses in the prior art and reducing the difficulty of production and assembly processes. Therefore, this lens has the advantages of small size, compact structure, few lenses, and low cost.

[0018] The projection imaging system provided in the embodiment of the present invention can set the parameters of each component in the projection imaging system so that the aperture number of the projection imaging system is 2.8 and the distortion is less than 0.1%, thereby achieving low sensitivity and high-quality imaging of the projection imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 Schematic diagram of the structure of a short-throw projection lens in an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the optical path transmission structure of the projection imaging system in an embodiment of the present invention;

[0022] Figure 3 is a point diagram of a projection imaging system in an embodiment of the present invention;

[0023] Figure 4 A modulation transfer function diagram of a projection imaging system according to an embodiment of the present invention;

[0024] Figure 5 Graph showing field curvature and distortion of a projection imaging system in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] The embodiment of the present invention provides a short-throw projection lens, such as Figure 1 As shown, the short-focus projection lens includes: a lens assembly, the lens assembly includes a plurality of spherical lenses arranged with the same optical axis, which are used to project and image the external input light beam; the spherical lens includes a first meniscus lens L1, a first biconvex lens L2, a biconcave lens L3, a second biconvex lens L4 and a second meniscus lens L5 which are arranged in sequence from the object side to the image side.

[0030] like Figure 1 As shown, the second meniscus lens L5 has a first surface 1 convex to the image side and a second surface 2 concave to the object side; the second biconvex lens L4 has a third surface 3 convex to the image side and a fourth surface 4 convex to the object side; the biconcave lens L3 has a sixth surface 6 concave to the image side and a seventh surface 7 concave to the object side; the first biconvex lens L2 has an eighth surface 8 convex to the image side and a ninth surface convex to the object side; the first meniscus lens L1 has a tenth surface convex to the image side and an eleventh surface 11 concave to the object side.

[0031] The short-focus projection lens provided by the embodiment of the present invention can project and image the external input light beam by selecting multiple coaxially arranged lenses. The multiple lenses are all spherical lenses. By reasonably setting the focal length of the lens assembly and the spacing between the lenses and other parameters, the edge aberration and spherical aberration of the lens can be effectively reduced, so that it can play the role of an aspherical mirror. Therefore, the short-focus projection lens provided by the embodiment of the present invention can avoid the use of aspherical mirrors, and solve the technical problems of the difficulty and high cost of processing the lens using aspherical lenses in the prior art. In addition, the short-focus projection lens provided by the embodiment of the present invention can use only five lenses through the reasonable configuration of the light angles of each spherical lens in the lens assembly, which reduces the number of lenses compared to the lens in the prior art and reduces the difficulty of the production and assembly process. Therefore, the lens has the advantages of small size, compact structure, fewer lenses and low cost.

[0032] As an optional implementation of the embodiment of the present invention, Figure 1 As shown, the short-focus projection lens further includes: a diaphragm 30, which is disposed between the biconcave lens L3 and the second biconvex lens L4. The diaphragm 30 can serve as the fourth surface 4 of the short-focus projection lens. By providing the diaphragm 30 in the short-focus projection lens, the passage of light from the biconcave lens L3 to the second biconvex lens L4 can be controlled, the light flux passing through the short-focus projection lens can be adjusted, and at the same time, the interference of stray light generated by reflection of other lenses can be reduced.

[0033] Optionally, in the short-focus projection lens, the first meniscus lens L1 can be made of a glass material, and its refractive index n1 satisfies the conditional formula: 1.65 < n1 < 1.75, and the focal length f1 of the first meniscus lens L1 satisfies the conditional formula: -250 mm < f1 < -350 mm; the first biconvex lens L2 can be made of a glass material, and its refractive index n2 satisfies the conditional formula: 1.75 < n2 < 1.85, and the focal length f2 of the first biconvex lens L2 satisfies the conditional formula: 5 mm < f2 < 50 mm; the biconcave lens L3 can be made of a glass material, and its refractive index n3 satisfies the conditional formula: 1.65 < n3 < 1.75, and the focal length f3 of the biconcave lens L3 satisfies the conditional formula: -5 mm < f3 < -50 mm; the second biconvex lens L4 can be made of a glass material, and its refractive index n4 satisfies the conditional formula: 1.70 < n4 < 1.80, and the focal length f4 of the second biconvex lens L4 satisfies the conditional formula: 10 mm < f4 < 100 mm; the second meniscus lens L5 can be made of a glass material, and its refractive index n5 satisfies the conditional formula: 1.5 < n5 < 1.6, and the focal length f5 of the second meniscus lens L5 satisfies the conditional formula: -10 mm < f5 < -100 mm.

[0034] For the short-focus projection lens provided by the embodiment of the present invention, by setting parameters such as the refractive index and focal length of each lens in the lens assembly and optimizing the distance between the lenses, the marginal aberration of the lens can be effectively reduced, and the imaging quality of the projection lens can be improved. The effect of correcting aberration by multiple spherical lenses is effectively achieved, which is beneficial to realizing the low cost and miniaturization of the short-focus projection lens.

[0035] The embodiment of the present invention also provides a projection imaging system, as Figure 2 shown, the projection imaging system includes: a display device 10, a beam splitter device 20, and the short-focus projection lens as described in the above embodiment, which are arranged in sequence; the light beam output by the display device 10 is projected onto the display screen 50 after passing through the beam splitter device 20 and the short-focus projection lens in sequence.

[0036] For the projection imaging system provided by the embodiment of the present invention, as Figure 2As shown, the light beam output by the display device 10 passes through the spectrometer 20, the first meniscus lens L1, the first biconvex lens L2, the biconcave lens L3, the second biconvex lens L4 and the first surface 1 of the second meniscus lens L5 in sequence and is emitted from the short-focus projection lens. The light can be offset after passing through the short-focus projection lens. After the light enters the projection lens from one side of the optical axis of the projection lens, it is emitted from the projection lens along the other side of the optical axis of the projection lens, so that the projection picture can be projected on one side of the optical axis of the projection lens, avoiding the problem that the projection lens cannot be projected, resulting in cumbersome operation and inconvenient use of the projection imaging system.

[0037] Optionally, the display device 10 includes: a digital micro-mirror device (DMD), which is arranged perpendicular to the optical axis of the lens assembly. In addition, the display device 10 can also use other display elements or display devices that can be used to emit light, such as a liquid crystal on silicon chip (LCOS) instead of the digital micro-mirror chip.

[0038] As an optional implementation of the embodiment of the present invention, the digital micromirror chip size can be selected to be 0.45 inches and the resolution can be 1140×912 in the projection imaging system. After setting the parameters of each component in the projection imaging system, the half field of view FOV. of the projection imaging system can satisfy 10°≤FOV.≤15°; the focal length f of the projection imaging system satisfies 15mm≤f≤25mm; and the object side numerical aperture NA of the projection imaging system satisfies 0.01≤NA≤0.05.

[0039] The projection imaging system provided in the embodiment of the present invention can set the parameters of each component in the projection imaging system so that the aperture number of the projection imaging system is 2.8 and the distortion is less than 0.1%, thereby achieving low sensitivity and high-quality imaging of the projection imaging system.

[0040] In order to achieve the above purpose and improve the optical performance of the short-throw projection lens, the specific parameters of the short-throw projection lens can be shown in Table 1; the parameters include type, radius, thickness, diameter and quadratic surface factor, etc.

[0041] Table 1

[0042]

[0043] Among them, OBJ represents the object plane, IMA represents the image plane, and STO represents the aperture plane. Figure 1 As shown in Table 1, other numbers represent the surfaces of each lens in the lens assembly and the two surfaces 12 and 13 of the light splitting device 20. By setting each element in the projection imaging system according to the parameters in Table 1, the following can be obtained: Figures 3 to 5The schematic diagram showing the imaging effect of the projection imaging system is shown.

[0044] like Figure 3 The figure shows the spot diagram of the projection imaging system. The spot diagram refers to the fact that many light rays emitted from a point, after passing through the light system, are no longer concentrated at the same point due to aberration, but form a diffuse pattern scattered in a certain range. Therefore, the spot diagram can be used to evaluate the imaging quality of the projection imaging system. The figure shows the diffuse spots under different fields of view. Due to spherical aberration, the point imaging is not a point, but a circular spot. The smaller the radius of the circular spot, the smaller the spherical aberration. Figure 3 It can be seen that the spherical aberration of the projection imaging system is small.

[0045] like Figure 4 The figure shows the modulation transfer function of the projection imaging system, where the modulation transfer function (MTF) refers to the relationship between the modulation and the number of line pairs per millimeter in the image, and is used to evaluate the ability to restore the details of the scene. The modulation is the ratio of the difference between the maximum intensity and the minimum intensity to the sum of the maximum intensity and the minimum intensity. MTF is the ratio of the modulation of the image to the modulation of the object, which is a function of the spatial frequency, which is usually expressed in the form of 1p / mm. The modulation transfer function can be used to represent the characteristics of the optical system. The larger the MTF, the better the imaging quality of the system. As can be seen from the figure, it can reach above 0.5 at the horizontal axis of 46lp / mm, indicating that the modulation effect of the projection imaging system is relatively high.

[0046] like Figure 5 As shown, Figure 5 middle Figure 5 (a) represents the field curvature of the projection lens in the projection imaging system, Figure 5 middle Figure 5 (b) indicates the distortion of the projection lens, where field curvature refers to the bending of the field, which is mainly used to indicate the degree of non-coincidence between the intersection of the entire light beam and the ideal image point in the optical system; distortion refers to the aberration of different magnifications of different parts of the object when the object is imaged through the optical system, and distortion will cause the similarity of the object image to deteriorate. Therefore. By setting the parameters of each component in the projection imaging system, the field curvature can be controlled within 0.2, and the distortion can be controlled within 0.1%.

[0047] Although the exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and modifications to these embodiments without departing from the spirit of the present invention and the scope of protection defined by the appended claims, and such modifications and variations all fall within the scope defined by the appended claims. For other examples, those of ordinary skill in the art should readily understand that the order of the process steps may be changed while maintaining the scope of protection of the present invention.

[0048] In addition, the scope of application of the present invention is not limited to the processes, mechanisms, manufactures, material compositions, means, methods and steps of the specific embodiments described in the specification. From the disclosure of the present invention, it will be easily understood by those skilled in the art that the processes, mechanisms, manufactures, material compositions, means, methods or steps that currently exist or will be developed in the future, which perform substantially the same functions as the corresponding embodiments described in the present invention or obtain substantially the same results, can be applied according to the present invention. Therefore, the claims attached to the present invention are intended to include these processes, mechanisms, manufactures, material compositions, means, methods or steps within their scope of protection.

Claims

1. A short-throw projection lens, characterized in that: include: A lens assembly, wherein the lens assembly includes a plurality of spherical lenses arranged on the same optical axis and is used for projecting an image of an external input light beam; The lens assembly is composed of a first meniscus lens, a first biconvex lens, a biconcave lens, a second biconvex lens and a second meniscus lens, which are arranged in sequence from the object side to the image side; The second meniscus lens has a first surface convex to the image side and a second surface concave to the object side; the second biconvex lens has a third surface convex to the image side and a fourth surface convex to the object side; the biconcave lens has a sixth surface concave to the image side and a seventh surface concave to the object side; the first biconvex lens has an eighth surface convex to the image side and a ninth surface convex to the object side; the first meniscus lens has a tenth surface convex to the image side and an eleventh surface concave to the object side; The focal length f1 of the first meniscus lens satisfies the condition: -250 mm <f1<-350mm; The focal length f2 of the first biconvex lens satisfies the condition: 5 mm <f2<50mm; The focal length f3 of the biconcave lens satisfies the condition: -5 mm <f3<-50mm; The focal length f4 of the second biconvex lens satisfies the condition: 10 mm <f4<100mm; The focal length f5 of the second meniscus lens satisfies the condition: -10 mm <f5<-100mm; The refractive index n1 of the first meniscus lens satisfies the conditional formula: 1.65 <n1<1.75; The refractive index n2 of the first biconvex lens satisfies the conditional formula: 1.75 <n2<1.85; The refractive index n3 of the biconcave lens satisfies the conditional formula: 1.65 <n3<1.75; The refractive index n4 of the second biconvex lens satisfies the conditional formula: 1.70 <n4<1.80; The refractive index n5 of the second meniscus lens satisfies the conditional formula: 1.5 <n5<1.6。 2. The short-throw projection lens according to claim 1, characterized in that: Also includes: An aperture is arranged between the biconcave lens and the second biconvex lens.

3. A projection imaging system, characterized in that: include: A display device, a light splitting device and a short-focus projection lens as claimed in claim 1 or 2, which are arranged in sequence; The light beam output by the display device passes through the light splitting device and the short-focus projection lens in sequence and is then projected onto the display screen.

4. The projection imaging system according to claim 3, characterized in that: The display device comprises: a digital micromirror chip, and the digital micromirror chip is arranged perpendicular to the optical axis of the lens assembly.

5. The projection imaging system according to claim 4, characterized in that: The digital micromirror chip has a size of 0.45 inches and a resolution of 1140×912.

6. The projection imaging system according to claim 3, characterized in that: The half field of view angle of the projection imaging system is 10°≤HFOV≤15°.

7. The projection imaging system according to claim 3, characterized in that: The focal length of the projection imaging system is 15mm≤f≤25mm.

8. The projection imaging system according to claim 3, characterized in that: The object-side numerical aperture of the projection imaging system is 0.01≤NA≤0.05.

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