Projection lens

Abstract

The utility model provides a projection lens. The projection lens at least comprises a first lens group, a diaphragm and a second lens group from a first side to a second side, the first lens group comprises a first lens with negative focal power and a second lens with positive focal power, and the first lens is a meniscus lens; the second lens group comprises a third lens, a fourth lens and a fifth lens with positive focal power, at least one of the third lens to the fifth lens is an aspheric lens, and at least two adjacent lenses of the third lens to the fifth lens form a doublet lens; the total optical length TTL of the projection lens and the effective focal length Fs of the projection lens meet the condition that TTL / Fs is larger than or equal to 2.5 and smaller than or equal to 14. The projection lens solves the problems of large size and high cost of the projection lens in the prior art.

Description

Technical Field

[0001] The utility model relates to the technical field of optical imaging equipment, in particular to a projection lens. Background Art

[0002] With the continuous updating and optimization of projection lenses, projection lenses have been widely used in various fields. The reasonable distribution of the focal length of each lens in the projection lens and the air gap between the lenses is the design focus. In addition, in order to meet the characteristics of low cost, compact structure and high resolution, it is necessary to reasonably introduce plastic aspheric surfaces, cemented lenses, molded glass aspheric surfaces, etc. to solve these problems.

[0003] Current projection lenses usually require a larger relative aperture, usually satisfying F#<3.0. This poses a great challenge to the design of projection lenses, which often makes the cost difficult to control and are large in size.

[0004] That is to say, the projection lens in the prior art has the problems of large size and high cost. Utility Model Content

[0005] The main purpose of the utility model is to provide a projection lens to solve the problems of large size and high cost of the projection lens in the prior art.

[0006] In order to achieve the above-mentioned purpose, the utility model provides a projection lens, which comprises at least a first lens group, an aperture and a second lens group from a first side to a second side, wherein the first lens group comprises a first lens with negative optical power and a second lens with positive optical power, and the first lens is a meniscus lens; the second lens group comprises a third lens, a fourth lens and a fifth lens with positive optical power, at least one of the third lens to the fifth lens is an aspherical lens, and at least two adjacent lenses of the third lens to the fifth lens form a double cemented lens; the total optical length TTL of the projection lens and the effective focal length Fs of the projection lens satisfy the following relationship: 2.5≤TTL / Fs≤14.

[0007] Furthermore, the first side surface of the first lens is a convex surface, and the second side surface is a concave surface; or the first side surface of the first lens is an "M" shape or a meniscus shape.

[0008] Further, the first lens is an aspherical lens; and / or the second lens is a spherical lens or an aspherical lens.

[0009] Furthermore, the third lens and the fourth lens form a doublet lens, and the total optical power of the doublet lens is positive or negative.

[0010] Further, the third lens and the fourth lens are both glass lenses; and / or the fifth lens is an aspherical lens.

[0011] Furthermore, the Abbe number of at least one of the third lens and the fourth lens is greater than 80; and / or the refractive index of at least one of the third lens and the fourth lens is greater than 1.8.

[0012] Furthermore, the effective focal length F1 of the first lens group and the effective focal length Fs of the projection lens satisfy: -150 < F1 / Fs < -60 or 60 < F1 / Fs < 100; and / or the effective focal length F2 of the second lens group and the effective focal length Fs of the projection lens satisfy: 1.0 < F2 / Fs < 4.0.

[0013] Furthermore, the outer diameter ΦL1 of the first lens and the f-number Fno of the projection lens satisfy: 3.7 ≤ ΦL1 / Fno ≤ 15, and / or the f-number Fno of the projection lens satisfies: 1.5 ≤ Fno ≤ 4.0; and / or the back focal length BF of the projection lens and the effective focal length Fs of the projection lens satisfy: 2.2 ≤ BF / Fs ≤ 3.0.

[0014] Furthermore, the overall optical length TTL of the projection lens satisfies: 20 mm ≤ TTL ≤ 80 mm; and / or the effective focal length Fs of the projection lens and the image plane height H_image of the projection lens satisfy: 1.2 ≤ Fs / H_image ≤ 3.8.

[0015] Furthermore, both the second lens and the fifth lens are biconvex lenses.

[0016] Furthermore, the projection lens further includes a galvanometer, a prism, and a DMD chip located on the second side of the second lens group.

[0017] Applying the technical solution of the present utility model, the projection lens includes at least a first lens group, a diaphragm, and a second lens group from the first side to the second side. The first lens group includes a first lens with negative optical power and a second lens with positive optical power, and the first lens is a meniscus lens; the second lens group includes a third lens, a fourth lens, and a fifth lens with positive optical power. At least one of the third lens to the fifth lens is an aspherical lens, and at least two adjacent lenses among the third lens to the fifth lens form a doublet; the overall optical length TTL of the projection lens and the effective focal length Fs of the projection lens satisfy: 2.5 ≤ TTL / Fs ≤ 14.

[0018] By reasonably allocating the optical power of each lens and reasonably selecting aspheric lenses and double-cemented lenses, distortion and field curvature can be well corrected, and the aperture of the projection lens can be controlled at the same time. The aspheric lens can well control the light aperture, distortion and telecentric angle, and the double-cemented lens can well correct chromatic aberration. By constraining 2.5≤TTL / Fs≤14, the overall size can be constrained to achieve a compact structure. In addition, the projection lens of the present application can effectively improve the chromatic aberration of the system, suppress the occurrence of system distortion, and has the advantages of miniaturization, large aperture, low distortion, low cost, and can ensure high imaging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0020] Figure 1 A schematic structural diagram of a projection lens according to an optional embodiment of the utility model is shown.

[0021] The above drawings include the following reference numerals:

[0022] L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; STOP, aperture; 10, galvanometer; 20, prism; 30, protective glass; 40, DMD chip; 50, projection screen. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present utility model will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0025] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0026] It should be noted that, in the present specification, the expressions first, second, third, etc. are only used to distinguish one feature from another feature, but do not mean any limitation to the features.

[0027] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens close to the first side is called the first side of the lens, and the surface of each lens close to the second side is called the second side of the lens. The judgment of the surface shape in the paraxial region can be based on the judgment method of the general knowledgeable person in this field, and the positive and negative R value (R refers to the radius of curvature of the paraxial region, usually refers to the R value on the lens database (lens data) in the optical software) is used to judge the concave and convex. For the first side, when the R value is positive, it is judged as a convex surface, and when the R value is negative, it is judged as a concave surface; for the second side, when the R value is positive, it is judged as a concave surface, and when the R value is negative, it is judged as a convex surface.

[0028] In the present application, the left side of the projection lens is the first side, and the right side is the second side. In a specific embodiment of the present application, the first side of the projection lens is the projection screen side, and the second side is the DMD chip side. During projection, light from the DMD chip can be imaged on the projection screen side.

[0029] In order to solve the problems of large volume and high cost of projection lenses in the prior art, the utility model provides a projection lens.

[0030] like Figure 1 As shown, the projection lens includes at least a first lens group, an aperture STOP and a second lens group from the first side to the second side, the first lens group includes a first lens L1 with negative optical focal length and a second lens L2 with positive optical focal length, and the first lens L1 is a meniscus lens; the second lens group includes a third lens L3, a fourth lens L4 and a fifth lens L5 with positive optical focal length, at least one of the third lens L3 to the fifth lens L5 is an aspherical lens, and at least two adjacent lenses of the third lens L3 to the fifth lens L5 form a double cemented lens; the total optical length TTL of the projection lens and the effective focal length Fs of the projection lens satisfy the following relationship: 2.5≤TTL / Fs≤14.

[0031] By reasonably allocating the optical power of each lens and reasonably selecting aspheric lenses and double-cemented lenses, distortion and field curvature can be well corrected, and the aperture of the projection lens can be controlled at the same time. The aspheric lens can well control the light aperture, distortion and telecentric angle, and the double-cemented lens can well correct chromatic aberration. By constraining 2.5≤TTL / Fs≤14, the overall size can be constrained to achieve a compact structure. In addition, the projection lens of the present application can effectively improve the chromatic aberration of the system, suppress the occurrence of system distortion, and has the advantages of miniaturization, large aperture, low distortion, low cost, and can ensure high imaging performance.

[0032] In this embodiment, the projection lens further includes a galvanometer 10, a prism 20, a protective glass 30, and a DMD chip 40, which are sequentially arranged on the second side of the second lens group.

[0033] In this embodiment, the first side surface of the first lens L1 is convex, and the second side surface is concave. Such a setting is beneficial to ensuring a relatively large light passing aperture and being able to receive more light; the first lens L1 is an aspherical lens, and the second lens L2 is a spherical lens or an aspherical lens. Such a setting enables the first lens L1 and the second lens L2 to undertake the ability of distortion correction, which is beneficial to increasing the field of view angle of the system, and can well correct off-axis aberrations such as distortion, coma, field curvature, and astigmatism, ensuring that the incident angle of light on the lens surface is relatively gentle, and no large high-order aberrations are generated while ensuring a large field of view; specifically, the first side surface of the first lens L1 is "M"-shaped or meniscus-shaped. In addition, using an aspherical lens can reasonably distribute light to a certain extent, effectively reducing the lens aperture diameter, and is beneficial to reducing the volume of the entire lens.

[0034] In this embodiment, both the third lens L3 and the fourth lens L4 are glass lenses; the optical power of the third lens L3 and the optical power of the fourth lens L4 have opposite signs. That is to say, in an alternative embodiment, the third lens L3 is a glass lens with negative optical power, and the fourth lens L4 is a glass lens with positive optical power; in another alternative embodiment, the third lens L3 is a glass lens with positive optical power, and the fourth lens L4 is a glass lens with negative optical power. At the same time, the third lens L3 and the fourth lens L4 form a doublet lens, and the total optical power of the doublet lens is positive or negative. The fifth lens L5 is an aspherical lens. Such a setting can well correct chromatic aberration, spherical aberration, and control the beam aperture, and at the same time can well control the image-side telecentric angle of the entire projection lens.

[0035] In this embodiment, the relationship between the effective focal length F1 of the first lens group and the effective focal length Fs of the projection lens satisfies: -150 < F1 / Fs < -60 or 60 < F1 / Fs < 100; the relationship between the effective focal length F2 of the second lens group and the effective focal length Fs of the projection lens satisfies: 1.0 < F2 / Fs < 4.0. By reasonably restricting the ratio between the effective focal lengths of the two lens groups and the effective focal length of the entire projection lens, it is beneficial to the reasonable distribution of the focal lengths of the first lens group and the second lens group, ensuring the smooth transition of light.

[0036] In this embodiment, the relationship between the outer diameter ΦL1 of the first lens L1 and the f-number Fno of the projection lens satisfies: 3.7 ≤ ΦL1 / Fno ≤ 15, and the f-number Fno of the projection lens satisfies: 1.5 ≤ Fno ≤ 4.0. Preferably, 1.55 ≤ Fno ≤ 4.0. Such a setting can reasonably restrict the size and aperture of the first lens L1 on the premise of ensuring a large aperture, which is beneficial to ensuring that more light exits from the first lens L1 to the projection screen 50.

[0037] In this embodiment, the back focal length BF of the projection lens and the effective focal length Fs of the projection lens satisfy: 2.2≤BF / Fs≤3.0. Reasonable restriction of the back focal length of the projection lens is conducive to ensuring that there is enough space behind the projection lens.

[0038] In this embodiment, the third lens L3 and the fourth lens L4 are cemented together to correct chromatic aberration, and the Abbe number of at least one of the third lens L3 and the fourth lens L4 is greater than 80; the refractive index of at least one of the third lens L3 and the fourth lens L4 is greater than 1.8.

[0039] In this embodiment, the total optical length TTL of the projection lens satisfies: 20 mm ≤ TTL ≤ 80 mm. By constraining the total optical length to be within the range of 20 mm to 80 mm, it is helpful to ensure a short total optical length and miniaturization.

[0040] In this embodiment, the effective focal length Fs of the projection lens and the image plane height H_image of the projection lens satisfy the following relationship: 1.2≤Fs / H_image≤3.8.

[0041] In this embodiment, the second lens L2 and the fifth lens L5 are both biconvex lenses.

[0042] The projection lens of the present application is composed of five lenses from the first lens L1 to the fifth lens L5, and the total number of lenses is relatively small. By reasonably setting the surface shape of the lens, it is beneficial to ensure that the light aperture is larger, the more light can be received, and the structure of the projection lens is simple and compact, and the aperture is small, which is conducive to achieving low cost. At the same time, due to the small number of lenses, the projection lens of the present application can effectively improve the transmittance within the visible light range of 380nm to 700nm, and the transmittance can be ≥90%; relative to the same design, it can greatly improve the brightness of the projection light machine.

[0043] Table 1 below shows a basic structural parameter table of a projection lens of an optional embodiment of the present application.

[0044]

[0045] Table 1

[0046] Combining Table 1 and Figure 1 It can be seen that the first lens L1 and the fifth lens L5 are both aspherical lenses, and the second lens L2 to the fourth lens L4 are all spherical lenses. The first side surface of the first lens L1 is convex, and the second side surface is concave. The first side surface of the second lens L2 is convex, and the second side surface is convex. The first side surface of the third lens L3 is concave, and the second side surface is convex. The first side surface of the fourth lens L4 is concave, and the second side surface is convex. The first side surface of the fifth lens L5 is convex, and the second side surface is convex.

[0047] In the above embodiment, the first lens L1 and the fifth lens L5 are both aspherical lenses, and the surface shape of each aspherical lens can be defined by but not limited to the following aspherical formula:

[0048]

[0049] Among them, the letter z represents the surface sag; c is the curvature; r is the radial coordinate; k is the quadratic coefficient; α is the aspheric coefficient.

[0050] Table 2 below shows various aspheric coefficients α1 to α8 that can be used for the aspheric lens surfaces S1, S2, S9, and S10 in the above-described embodiment.

[0051] S1 S2 S9 S10 <![CDATA[α1]]> -0.00028 0.000486 -4.50E-05 3.06E-06 <![CDATA[α2]]> 3.50E-06 -1.01E-05 5.41E-08 -8.13E-08 <![CDATA[α3]]> -5.6E-08 2.39E-07 3.01E-13 -8.27E-11 <![CDATA[α4]]> 2.14E-10 -3.83E-09 3.11E-13 4.37E-12 <![CDATA[α5]]> -2.21E-14 -3.98E-14 -4.23E-14 -3.98E-14 <![CDATA[α6]]> 1.7E-15 -4.20E-13 6.14E-16 7.44E-16 <![CDATA[α7]]> -2.19E-18 6.35E-16 -7.88E-18 -6.55E-19 <![CDATA[α8]]> 0 0 0 0

[0052] Table 2

[0053] Obviously, the embodiments described above are only some embodiments of the utility model, not all embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0056] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A projection lens, characterized in that: From the first side to the second side, it includes at least a first lens group, a stop (STOP), and a second lens group. The first lens group includes a first lens (L1) with negative optical power and a second lens (L2) with positive optical power. The first lens (L1) is a meniscus lens. The second lens group includes a third lens (L3), a fourth lens (L4), and a fifth lens (L5) with positive optical power. At least one of the third lens (L3) to the fifth lens (L5) is an aspherical lens, and at least two adjacent lenses among the third lens (L3) to the fifth lens (L5) form a doublet lens. The relationship between the total optical length TTL of the projection lens and the effective focal length Fs of the projection lens satisfies: 2.5 ≤ TTL / Fs ≤ 14.

2. The projection lens according to claim 1, characterized in that: The first side of the first lens (L1) is convex, and the second side is concave; or the first side of the first lens (L1) is "M"-shaped or meniscus-shaped.

3. The projection lens according to claim 1, characterized in that: The first lens (L1) is an aspherical lens; and / or the second lens (L2) is a spherical lens or an aspherical lens.

4. The projection lens according to claim 1, characterized in that: The third lens (L3) and the fourth lens (L4) form a doublet lens, and the total optical power of the doublet lens is positive or negative.

5. The projection lens according to claim 1, wherein: Both the third lens (L3) and the fourth lens (L4) are glass lenses; and / or the fifth lens (L5) is an aspherical lens.

6. The projection lens according to claim 1, wherein: The Abbe number of at least one of the third lens (L3) and the fourth lens (L4) is greater than 80; and / or the refractive index of at least one of the third lens (L3) and the fourth lens (L4) is greater than 1.

8.

7. The projection lens according to any one of claims 1 to 6, characterized in that: The relationship between the effective focal length F1 of the first lens group and the effective focal length Fs of the projection lens satisfies: -150 < F1 / Fs < -60 or 60 < F1 / Fs < 100; and / or The relationship between the effective focal length F2 of the second lens group and the effective focal length Fs of the projection lens satisfies: 1.0 < F2 / Fs < 4.

0.

8. The projection lens according to any one of claims 1 to 6, characterized in that: The relationship between the outer diameter ΦL1 of the first lens (L1) and the f-number Fno of the projection lens satisfies: 3.7 ≤ ΦL1 / Fno ≤ 15, and / or the f-number Fno of the projection lens satisfies: 1.5 ≤ Fno ≤ 4.0; and / or the relationship between the back focal length BF of the projection lens and the effective focal length Fs of the projection lens satisfies: 2.2 ≤ BF / Fs ≤ 3.

0.

9. The projection lens according to any one of claims 1 to 6, characterized in that: The total optical length TTL of the projection lens satisfies: 20 mm ≤ TTL ≤ 80 mm; and / or The relationship between the effective focal length Fs of the projection lens and the image plane height H_image of the projection lens satisfies: 1.2 ≤ Fs / H_image ≤ 3.

8.

10. The projection lens according to any one of claims 1 to 6, characterized in that: Both the second lens (L2) and the fifth lens (L5) are biconvex lenses.

11. The projection lens according to claim 1, wherein: The projection lens further includes a galvanometer (10), a prism (20), and a DMD chip (40) located on the second side of the second lens group.

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