Short-focus lens and LCD projector

Abstract

The utility model relates to a short focus lens and a liquid crystal display (LCD) projector, the short focus lens is composed of four lenses with focal power, and the four lenses are respectively a fourth lens, a third lens, a second lens and a first lens which are sequentially arranged along the light emitting direction; wherein the first lens and the third lens both have negative focal power, and the second lens and the fourth lens both have positive focal power. Under the combined action of the four lenses, the number of lenses used by the short-focus lens can be reduced while a large field angle and a short focal length of the short-focus lens are ensured, so that the whole short-focus lens is small in size and light in weight.

Description

Technical Field

[0001] The utility model relates to the technical field of LCD projection, in particular to a short-focus lens and an LCD projector. Background Art

[0002] As a common consumer electronic product, a projector can project the display content in a display light valve through an imaging projection lens. Among them, the imaging lens plays an important role in the projector. The focal length of the imaging lens determines the size of the projected image of the projector. In the projector industry, the ratio of the projection distance to the width of the projected image is defined as the projection ratio. Currently, the projection ratios of the projection lenses on the market are generally between 1.2 and 1.5. When a 150-inch image needs to be projected, a projection distance of more than 4m is often required, and the application scenarios in ordinary families cannot meet such a long projection distance. Therefore, there is an urgent need to develop a short-focus projection lens with a small projection ratio. Summary of the Utility Model

[0003] Based on this, the purpose of the utility model is to overcome the deficiencies of the prior art and provide a short-focus lens and an LCD projector.

[0004] To achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0005] A short-focus lens, which is composed of four lenses with optical power. The four lenses are the fourth lens, the third lens, the second lens, and the first lens arranged in sequence along the light-emitting direction; among them, both the first lens and the third lens have negative optical power, and both the second lens and the fourth lens have positive optical power;

[0006] The incident surface of the first lens along the optical axis direction is concave, and the exit surface along the optical axis direction is convex;

[0007] The incident surface of the second lens along the optical axis direction is concave, and the exit surface along the optical axis direction is convex;

[0008] The incident surface and the exit surface of the third lens along the optical axis direction are both concave;

[0009] The incident surface and the exit surface of the fourth lens along the optical axis direction are both convex;

[0010] And the short-focus lens satisfies the following relationships:

[0011] -3 ≤ f1 / f ≤ -2.5;

[0012] 1.0 ≤ f2 / f ≤ 1.3;

[0013] -1.1 ≤ f3 / f ≤ -0.8;

[0014] 0.5 ≤ f4 / f ≤ 0.8;

[0015] Wherein, f is the focal length of the short - focus lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

[0016] In a preferred or alternative embodiment, the short - focus lens satisfies the following relationship:

[0017] -2.8 ≤ f1 / f2 ≤ -2.5;

[0018] 2.8 ≤ f1 / f3 ≤ 3.2;

[0019] 1.6 ≤ f2 / f4 ≤ 2.

[0020] In a preferred or alternative embodiment, the short - focus lens satisfies the following relationship:

[0021] 1.61 ≤ Nd1 ≤ 1.63, 1.61 ≤ Nd2 ≤ 1.63, 1.58 ≤ Nd3 ≤ 1.61, 1.61 ≤ Nd4 ≤ 1.63;

[0022] Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, and Nd4 is the refractive index of the fourth lens.

[0023] In a preferred or alternative embodiment, the short - focus lens satisfies the following relationship:

[0024] 3mm ≤ D12 ≤ 5mm, 9mm ≤ D23 ≤ 11mm, 0mm ≤ D34 ≤ 0.5mm;

[0025] Wherein, D12 is the distance between the incident light surface of the first lens and the emergent light surface of the second lens along the optical axis direction, D23 is the distance between the incident light surface of the second lens and the emergent light surface of the third lens along the optical axis direction, and D34 is the distance between the incident light surface of the third lens and the emergent light surface of the fourth lens along the optical axis direction.

[0026] In a preferred or alternative embodiment, the short - focus lens satisfies the following relationship:

[0027] 1.5mm ≤ D1 ≤ 2.0mm, 6mm ≤ D2 ≤ 7mm, 2mm ≤ D3 ≤ 2.5mm, 5.5mm ≤ D4 ≤ 6mm;

[0028] Wherein, D1 is the thickness of the first lens along the optical axis direction, D2 is the thickness of the second lens along the optical axis direction, D3 is the thickness of the third lens along the optical axis direction, and D4 is the thickness of the fourth lens along the optical axis direction.

[0029] In a preferred or alternative embodiment, the short-focus lens satisfies the following relationships:

[0030] 100mm ≤ R1 ≤ 150mm, 45mm ≤ R2 ≤ 55mm;

[0031] 30mm ≤ R3 ≤ 35mm, 230mm ≤ R4 ≤ 250mm;

[0032] -50mm ≤ R5 ≤ -45mm, 85mm ≤ R6 ≤ 90mm;

[0033] 650mm ≤ R7 ≤ 700mm, -25mm ≤ R8 ≤ -20mm;

[0034] Wherein, R1 is the curvature radius of the light-emitting surface of the first lens, R2 is the curvature radius of the light-incident surface of the first lens, R3 is the curvature radius of the light-emitting surface of the second lens, R4 is the curvature radius of the light-incident surface of the second lens, R5 is the curvature radius of the light-emitting surface of the third lens, R6 is the curvature radius of the light-incident surface of the third lens, R7 is the curvature radius of the light-emitting surface of the fourth lens, and R8 is the curvature radius of the light-incident surface of the fourth lens.

[0035] In a preferred or alternative embodiment, the third lens is a plastic lens, and the first lens, the second lens, and the fourth lens are all glass lenses.

[0036] Compared with the prior art, the short-focus lens described in the embodiments of the present application, under the combined action of the four lenses as described above, enables the short-focus lens to have a large field of view angle and a short focal length while reducing the number of lenses used in the short-focus lens, making the entire short-focus lens small in size and light in weight.

[0037] An LCD projector according to the present application includes: the short-focus lens as described above.

[0038] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0039] Figure 1 It is a schematic structural diagram of the short-focus lens according to the embodiment of the present application;

[0040] Figure 2 It is a distortion diagram corresponding to the short-focus lens according to the embodiment of the present application;

[0041] Figure 3 The modulation transfer function curve corresponding to the short-focus lens of the embodiment of the present application;

[0042] Figure 4 The relative illuminance diagram corresponding to the short-focus lens of the embodiment of the present application. Specific embodiments

[0043] To further illustrate the embodiments, the present utility model provides drawings. These drawings are a part of the disclosure of the present utility model, which are mainly used to illustrate the embodiments and can be used to explain the operating principle of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these contents, those of ordinary skill in the art should be able to understand other possible embodiments and the advantages of the present utility model.

[0044] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "left", "right", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present utility model 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 should not be construed as a limitation to the present utility model.

[0045] Please refer to Figures 1 to 3 , this embodiment provides a short-focus lens for an LCD projector, which is composed of four lenses with optical powers. The four lenses are the fourth lens 40, the third lens 30, the second lens 20, and the first lens 10 arranged in sequence along the light exit direction. The short-focus lens described in this embodiment can be applied to an LCD projector. The light emitted from the LCD screen of the LCD projector passes through the fourth lens 40, the third lens 30, the second lens 20, and the first lens 10 and then exits, thereby forming a projection image.

[0046] Among them, both the first lens 10 and the third lens 30 have negative optical powers, and both the second lens 20 and the fourth lens 40 have positive optical powers; the optical power is used to represent the ability of the short-focus lens to deflect light. Among them, a lens with a positive optical power indicates that it has the ability to converge light, and a lens with a negative optical power indicates that it has the ability to diverge light.

[0047] In this embodiment, the third lens is a plastic lens, and the first lens, the second lens, and the fourth lens are all glass lenses, which makes the lens lightweight while ensuring the projection effect.

[0048] The incident surface 11 of the first lens 10 in the optical axis direction is concave, and the exit surface 12 in the optical axis direction is convex; the incident surface 21 of the second lens 20 in the optical axis direction is concave, and the exit surface 22 in the optical axis direction is convex; the incident surface 31 and the exit surface 32 of the third lens 30 in the optical axis direction are both concave; the incident surface 41 and the exit surface 42 of the fourth lens 40 in the optical axis direction are both convex.

[0049] For the short - focus lens described in the embodiments of the present application, under the combined action of the four lenses as described above, the short - focus lens can reduce the focal length while ensuring a large field of view, is suitable for use, and can also reduce the number of lenses used in the short - focus lens, making the entire short - focus lens small in size, light in weight, and low in cost.

[0050] As a preferred embodiment, the short - focus lens satisfies the following relationships:

[0051] -3 ≤ f1 / f ≤ -2.5;

[0052] 1.0 ≤ f2 / f ≤ 1.3;

[0053] -1.1 ≤ f3 / f ≤ -0.8;

[0054] 0.5 ≤ f4 / f ≤ 0.8;

[0055] Among them, f is the focal length of the short - focus lens, f1 is the focal length of the first lens 10, f2 is the focal length of the second lens 20, f3 is the focal length of the third lens 30, and f4 is the focal length of the fourth lens 40. By reasonably allocating the focal lengths of the lenses, it is beneficial to better achieve the field of view of the short - focus lens and improve the overall performance of the short - focus lens.

[0056] As a preferred embodiment, the short - focus lens also satisfies the following relationships:

[0057] -2.8 ≤ f1 / f2 ≤ -2.5;

[0058] 2.8 ≤ f1 / f3 ≤ 3.2;

[0059] 1.6 ≤ f2 / f4 ≤ 2.

[0060] As a preferred embodiment, the short - focus lens also satisfies the following relationships:

[0061] 1.61 ≤ Nd1 ≤ 1.63, 1.61 ≤ Nd2 ≤ 1.63, 1.58 ≤ Nd3 ≤ 1.61, 1.61 ≤ Nd4 ≤ 1.63;

[0062] Wherein, Nd1 is the refractive index of the first lens 10, Nd2 is the refractive index of the second lens 20, Nd3 is the refractive index of the third lens 30, and Nd4 is the refractive index of the fourth lens 40. A reasonable distribution of the refractive indices of the lenses helps to improve the environmental adaptability of the short-focus lens.

[0063] As a preferred embodiment, the short-focus lens further satisfies the following relationships:

[0064] 3mm ≤ D12 ≤ 5mm, 9mm ≤ D23 ≤ 11mm, 0mm ≤ D34 ≤ 0.5mm;

[0065] Wherein, D12 is the distance between the incident surface 11 of the first lens 10 and the exit surface 22 of the second lens 20 along the optical axis direction, D23 is the distance between the incident surface 21 of the second lens 20 and the exit surface 32 of the third lens 30 along the optical axis direction, and D34 is the distance between the incident surface 31 of the third lens 30 and the exit surface 42 of the fourth lens 40 along the optical axis direction. Setting the distances between the lenses in this way helps to improve the image quality of the short-focus lens and shorten the overall length of the short-focus lens.

[0066] As a preferred embodiment, the short-focus lens further satisfies the following relationships:

[0067] 1.5mm ≤ D1 ≤ 2.0mm, 6mm ≤ D2 ≤ 7mm, 2mm ≤ D3 ≤ 2.5mm, 5.5mm ≤ D4 ≤ 6mm;

[0068] Wherein, D1 is the thickness of the first lens 10 along the optical axis direction, D2 is the thickness of the second lens 20 along the optical axis direction, D3 is the thickness of the third lens 30 along the optical axis direction, and D4 is the thickness of the fourth lens 40 along the optical axis direction. Setting the thicknesses of the lenses in this way helps to improve the image quality of the short-focus lens and shorten the overall length of the short-focus lens.

[0069] As a preferred embodiment, the short-focus lens further satisfies the following relationships: 100mm ≤ R1 ≤ 150mm, 45mm ≤ R2 ≤ 55mm; 30mm ≤ R3 ≤ 35mm, 230mm ≤ R4 ≤ 250mm; -50mm ≤ R5 ≤ -45mm, 85mm ≤ R6 ≤ 90mm; 650mm ≤ R7 ≤ 700mm, -25mm ≤ R8 ≤ -20mm;

[0070] Among them, R2 is the radius of curvature of the incident surface 11 of the first lens 10, R1 is the radius of curvature of the exit surface 12 of the first lens 10, R4 is the radius of curvature of the incident surface 21 of the second lens 20, R3 is the radius of curvature of the exit surface 22 of the second lens 20, R6 is the radius of curvature of the incident surface 31 of the third lens 30, R5 is the radius of curvature of the exit surface 32 of the third lens 30, R7 is the radius of curvature of the exit surface 42 of the fourth lens 40, and R8 is the radius of curvature of the incident surface 41 of the fourth lens 40. The radius of curvature of each lens is set in this way, which helps to improve the image quality of the short-focus lens.

[0071] In a preferred embodiment, both the incident surface 31 and the exit surface 32 of the third lens 30 are aspherical surfaces. That is, both surfaces of the third lens 30 are aspherical surface profiles. The aspherical surface profile lens has more degrees of freedom, can better reduce the aberration of the entire projection lens, and improve the imaging quality. At the same time, it is lighter, thinner, and flatter, which is beneficial to the miniaturization of the projection lens. Using the aspherical surface profile lens not only meets the miniaturization of the projection lens but also meets the requirements of high imaging quality.

[0072] The specific design parameters of the short-focus lens in this embodiment are shown in Table 1 below:

[0073] Table 1

[0074]

[0075] Among them, the aspherical surface profile expression of the third lens 30 in this application is:

[0076]

[0077] In the above formula, z is the sag height of the aspherical surface profile, r is the radius of the aspherical surface, k is the conic coefficient, and c is the curvature. The specific parameters are shown in Table 2.

[0078] Table 2

[0079] Surface number K α1 α2 α3 α4 α5 α6 α7 32 -19.2 0 -5.25E-05 1.82E-07 3.67E-09 -2.87E-12 -9.78E-15 0 31 -305 0 -1.43E-05 2.198E-08 4.54E-10 3.5E-13 -1.1E-14 0

[0080] Among them, the parameters to be explained are as follows:

[0081] The focal length f of the short-focus lens is 53 mm;

[0082] The focal length f1 of the first lens 10 is -159 mm;

[0083] The focal length f2 of the second lens 20 is 62.3 mm;

[0084] The focal length f3 of the third lens 30 is 52.6 mm;

[0085] The focal length f4 of the fourth lens 40 is 34.49 mm;

[0086] The lens thickness D1 of the first lens 10 in the optical axis direction is 1.5 mm;

[0087] The lens thickness D2 of the second lens 20 in the optical axis direction is 6.9 mm;

[0088] The lens thickness D3 of the third lens 30 in the optical axis direction is 2.4 mm;

[0089] The lens thickness D4 of the fourth lens 40 in the optical axis direction is 5.7 mm;

[0090] The D12 is 4.3 mm, D23 is 9.5 mm, and D34 is 0.3 mm

[0091] The total length TTL of the short-focus lens is 30.6 mm;

[0092] The field of view angle of the short-focus lens described in this application can reach 88°, RI ≥ 52%, where RI represents the ratio of the marginal illuminance to the central illuminance, the optical distortion < 2%, and MTF ≥ 0.4 @ 11 Ip / mm, which can meet the image quality requirements of 2.69-inch 720P. With the above design parameters of the lens, when the projection distance is 2 m, a 150-inch large screen can be projected, and the projection ratio is 0.6.

[0093] Based on the above Table 1 and various data, the design result analysis of the short-focus lens in the embodiment of the present invention is provided below.

[0094] Please refer to Figure 2 , Figure 2 , which is the distortion diagram corresponding to the short-focus lens of this embodiment. The ordinate of the distortion diagram is the field of view angle, and the abscissa unit of the distortion is a percentage. It can be seen that the distortion of the maximum field of view angle is less than 2%, indicating that the distortion of this short-focus lens is very small.

[0095] Please refer to Figure 3 , Figure 3 , which is the modulation transfer function curve diagram corresponding to the short-focus lens of this embodiment. Among them, the modulation transfer function (MTF) refers to the relationship between the modulation degree 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. At the same spatial frequency, the larger the corresponding MTF value, the better.

[0096] Please refer to Figure 4 , Figure 4 , which is the relative illuminance diagram corresponding to the short-focus lens of this embodiment.

[0097] Figures 2 to 4The design result analysis of the short-focus lens can be used to evaluate the quality of lens design. The short-focus lens described in this embodiment can achieve the effects of a large field of view and a short focal length, and has a small volume, a light weight, and a high resolution, and can efficiently provide clear images.

[0098] The present utility model also provides an LCD projector, which includes the short-focus lens as described above. Since this LCD projector adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated herein one by one.

[0099] The above embodiments only represent several implementation manners of the present utility model, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several deformations and improvements can still be made, and these all belong to the protection scope of the present utility model.

Claims

1. A short-focus lens, characterized in that: The short-focus lens is composed of four lenses with optical power, and the four lenses are respectively a fourth lens, a third lens, a second lens and a first lens arranged in sequence along the light emission direction; wherein the first lens and the third lens both have negative optical power, and the second lens and the fourth lens both have positive optical power; The light incident surface of the first lens along the optical axis is a concave surface, and the light exit surface along the optical axis is a convex surface; The light incident surface of the second lens along the optical axis is a concave surface, and the light exit surface along the optical axis is a convex surface; The light incident surface and the light emitting surface of the third lens along the optical axis are both concave surfaces; The light incident surface and the light exit surface of the fourth lens along the optical axis are both convex surfaces; And the short-focus lens satisfies the following relationship: -3≤f1 / f≤-2.5; 1.0≤f2 / f≤1.3; -1.1≤f3 / f≤-0.8; 0.5≤f4 / f≤0.8; Among them, f is the focal length of the short-focus lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

2. The short-focus lens according to claim 1, characterized in that: The short-focus lens satisfies the following relationship: -2.8≤f1 / f2≤-2.5; 2.8≤f1 / f3≤3.2; 1.6≤f2 / f4≤2.

3. The short-focus lens according to claim 1, characterized in that: The short-focus lens satisfies the following relationship: 1.61≤Nd1≤1.63, 1.61≤Nd2≤1.63, 1.58≤Nd3≤1.61, 1.61≤Nd4≤1.63; Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, and Nd4 is the refractive index of the fourth lens.

4. The short-focus lens according to claim 1, characterized in that: The short-focus lens satisfies the following relationship: 3mm≤D12≤5mm, 9mm≤D23≤11mm, 0mm≤D34≤0.5mm; Among them, D12 is the distance between the light incident surface of the first lens and the light exit surface of the second lens along the optical axis, D23 is the distance between the light incident surface of the second lens and the light exit surface of the third lens along the optical axis, and D34 is the distance between the light incident surface of the third lens and the light exit surface of the fourth lens along the optical axis.

5. The short-focus lens according to claim 4, characterized in that , the short-focus lens satisfies the following relationship: 1.5mm≤D1≤2.0mm, 6mm≤D2≤7mm, 2mm≤D3≤2.5mm, 5.5mm≤D4≤6mm; Wherein, D1 is the thickness of the first lens along the optical axis, D2 is the thickness of the second lens along the optical axis, D3 is the thickness of the third lens along the optical axis, and D4 is the thickness of the fourth lens along the optical axis.

6. The short-focus lens according to any one of claims 1 to 5, characterized in that: The short-focus lens satisfies the following relationship: 100mm≤R1≤150mm, 45mm≤R2≤55mm; 30mm≤R3≤35mm, 230mm≤R4≤250mm; -50mm≤R5≤-45mm, 85mm≤R6≤90mm; 650mm≤R7≤700mm, -25mm≤R8≤-20mm; Among them, R1 is the curvature radius of the light exit surface of the first lens, R2 is the curvature radius of the light incident surface of the first lens, R3 is the curvature radius of the light exit surface of the second lens, R4 is the curvature radius of the light incident surface of the second lens, R5 is the curvature radius of the light exit surface of the third lens, R6 is the curvature radius of the light incident surface of the third lens, R7 is the curvature radius of the light exit surface of the fourth lens, and R8 is the curvature radius of the light incident surface of the fourth lens.

7. The short-focus lens according to claim 6, characterized in that: The short-focus lens satisfies the following relationship: The third lens is a plastic lens, and the first lens, the second lens and the fourth lens are all glass lenses.

8. An LCD projector, characterized in that: include: A short-focus lens as claimed in any one of claims 1 to 7.

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