Projection lens and projection ray machine

Abstract

The utility model provides a projection lens. The projection lens comprises a first lens, a second lens, a third lens, a fourth lens and a Fresnel lens which are sequentially arranged along an optical axis from an object side to an image side, the first lens and the fourth lens have positive focal power, and the second lens and the third lens have negative focal power; the first lens is a crescent lens, the second lens and the third lens are biconcave lenses, and the fourth lens is a biconvex lens; the projection lens further comprises a diaphragm, and the diaphragm is located between the second lens and the third lens. The projection lens can be applied to an LCD projection light machine with the size of more than 5.5 inches, and the 4K resolution is realized. The utility model further provides a projection ray machine.

Description

Technical Field

[0001] The present application relates to the field of projection display technology, and in particular to a projection lens and a projection optical machine including the projection lens. Background Art

[0002] Optical imaging lenses are widely used in smart phones, projection, automotive, security and other fields. In projection systems, as projection technology continues to mature, the requirements for projection images are also increasing, and the requirements for the imaging quality of imaging lenses in projection systems are also getting higher and higher.

[0003] The current 4K LCD imaging lens, in order to achieve ultra-high resolution, includes more than 6 glass lenses. This makes the overall structure of the imaging lens longer, the lens diameter larger (up to 80mm), the volume larger, the weight heavier, and the cost higher, which causes inconvenience in actual use. Since the imaging lens includes a large number of lenses, the overall structure is longer, and the volume is larger, it will also affect the overall optical path layout in the projection optical machine used by the imaging lens. When the above-mentioned projection lens is used in a projector, it brings huge challenges to the autofocus, motor, reliability testing, etc. of the lens. Utility Model Content

[0004] In a first aspect, the present application provides a projection lens, comprising a first lens, a second lens, a third lens, a fourth lens and a Fresnel lens arranged in sequence from the object side to the image side along an optical axis; the first lens and the fourth lens have positive focal power, and the second lens and the third lens have negative focal power; the first lens is a crescent lens, the second lens and the third lens are biconcave lenses, and the fourth lens is a biconvex lens; the projection lens also includes an aperture stop, and the aperture stop is located between the second lens and the third lens.

[0005] In at least one embodiment of the present application, the second lens is a plastic aspherical lens.

[0006] In at least one embodiment of the present application, the second lens is an 8th-order even-order aspheric lens.

[0007] In at least one embodiment of the present application, the first lens, the third lens, and the fourth lens are all glass spherical lenses.

[0008] In at least one embodiment of the present application, the third lens and the fourth lens form a doublet lens, and the whole lens has positive refractive power.

[0009] In at least one embodiment of the present application, the first lens has a first focal length f1, the second lens has a second focal length f2, the doublet lens has a combined focal length f3, and the projection lens has a system focal length f: 1.2 <f1 / f<1.5,-2.3<f2 / f<-2,1<f3 / f<1.3。

[0010] In at least one embodiment of the present application, a first distance H1 is provided between the first lens and the third lens, and a second distance H2 is provided between the second lens and the third lens: 0.1

[0011] In at least one embodiment of the present application, the first lens has a first refractive index n1, the second lens has a second refractive index n2, the third lens has a third refractive index n3, and the fourth lens has a fourth refractive index n4: n1=1.71, n2=1.59, n3=1.65, n4=1.83.

[0012] In at least one embodiment of the present application, the aperture number of the projection lens is 2.6, the projection ratio is 1.2:1, and the distortion is less than 1%.

[0013] A second aspect of the present application provides a projection optical machine, comprising: a liquid crystal display screen, for emitting projection image light; and a projection lens such as any of the above, located on the optical path of the projection image light, for projecting the projection image light onto an imaging medium.

[0014] The projection optical machine of the embodiment of the present application adopts the above-mentioned projection lens. By reasonably designing the optical parameters (optical focal length, lens surface shape, etc.) of each optical lens (mainly including the first lens, the second lens, the third lens and the fourth lens) in the projection lens, the number of optical lenses in the projection lens can be reduced to 4 (the first lens, the second lens, the third lens and the fourth lens) on the basis of satisfying the 4K resolution of the projection optical machine, which is particularly suitable for 4K LCD projection optical machines above 5.5 inches. The projection lens of this embodiment achieves high-resolution display through 4 lenses, and while maintaining good optical imaging performance, it also reduces the overall cost, overall volume, overall manufacturing difficulty and overall weight of the projection lens. In addition, the reduction in the volume and weight of the projection lens is conducive to the layout of the overall optical path in the projection optical machine including the projection lens. Furthermore, in this embodiment, the aperture is located between the second lens and the third lens, so that the projection image projected by the projection lens has better display quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram of the optical path structure of the projection optical machine according to an embodiment of the present application.

[0016] Figure 2 for​ Figure 1 Figure 2. Plot of the modulation transfer function of the projection lens.

[0017] Main component symbols

[0018] Projection light machine 1

[0019] Projection lens 10

[0020] First lens 11

[0021] The second lens 12

[0022] Aperture 13

[0023] The third lens 14

[0024] The fourth lens 15

[0025] Fresnel lens 16

[0026] LCD 20

[0027] Doublets 101

[0028] Optical surfaces 111, 112, 121, 122, 131, 141, 151, 102

[0029] Optical axis L

[0030] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0031] The embodiment of the present application provides a projection lens and a projection optical machine including the projection lens. By reasonably setting the optical parameters (optical power, lens surface shape, etc.) of the lens in the projection lens, the projection lens can achieve 4K high-definition imaging effects through 4 lenses, and is particularly suitable for projection optical machines for close-range projection of 4K LCDs larger than 5.5 inches.

[0032] See also Figure 1 The projection optical machine 1 of this embodiment includes a projection lens 10 and a liquid crystal display (LCD) 20. The LCD 20 has a light emitting surface facing the projection lens 10, and is used to emit projection image light. The projection lens 10 is located on the optical path of the projection image light, and is used to project the projection image light onto the surface of a display medium (such as a projection cloth, a wall, etc.) outside the projection optical machine 1 to present a corresponding projection image.

[0033] In this embodiment, the projection lens 10 has an optical axis L. The projection lens 10 includes a first lens 11, a second lens 12, a diaphragm 13, a third lens 14, a fourth lens 15, and a Fresnel lens 16 arranged in sequence along the optical axis L from the object side to the image side. The LCD 20 is located on the side of the Fresnel lens 16 away from the fourth lens 15. That is, the projection image light emitted from the LCD 20 passes through the Fresnel lens 16, the fourth lens 15, the third lens 14, the diaphragm 13, the second lens 12, and the first lens 11 in sequence and exits from the projection lens 10.

[0034] In this embodiment, the first lens 11 and the fourth lens 15 have positive optical powers, and the second lens 12 and the third lens 14 have negative optical powers. In this embodiment, the third lens 14 and the fourth lens 15 form a doublet lens 101, and the doublet lens 101 as a whole has a positive optical power. The first lens 11 is a crescent lens, the second lens 12 and the third lens 14 are biconcave lenses, and the fourth lens 15 is a biconvex lens.

[0035] In this embodiment, the first lens 11, the third lens 14, and the fourth lens 15 are glass spherical lenses, and the second lens 12 is a plastic aspherical lens. The outer diameter of the second lens 12 as a plastic aspherical lens is smaller than the outer diameters of the first lens 11, the third lens 14, and the fourth lens 15.

[0036] In this embodiment, the first lens 11 has a first focal length f1, the second lens 12 has a second focal length f2, the doublet lens 101 has a combined focal length f3, and the projection lens 10 has a system focal length f. Then the above focal lengths satisfy the following numerical relationships: 1.2 < f1 / f < 1.5, -2.3 < f2 / f < -2, 1 < f3 / f < 1.3. In this embodiment, by controlling the displacement of the first lens 11, the second lens 12, the diaphragm 13, the third lens 14, and the fourth lens 15 as a whole along the optical axis L, focusing of the projection lens 10 can be achieved.

[0037] In this embodiment, there is a first distance H1 between the first lens 11 and the third lens 14, and a second distance H2 between the second lens 12 and the third lens 14. Then the above distances satisfy the following numerical relationships: 0.1 < H1 / f < 0.25, 0.03 < H2 / f < 0.07.

[0038] In this embodiment, the first lens 11 has a first refractive index Nd1, the second lens 12 has a second refractive index Nd2, the third lens 14 has a third refractive index Nd3, and the fourth lens 15 has a fourth refractive index Nd4. Then the above refractive indices satisfy the following numerical relationships: Nd1 = 1.71, Nd2 = 1.59, Nd3 = 1.65, Nd4 = 1.83.

[0039] In this embodiment, the working wavelength of the projection lens 10 is between 450 and 610 μm (including the end values), the aperture number F / # of the projection lens 10 is 2.6, the projection ratio is 1.2:1, and the distortion is less than 1%.

[0040] In this embodiment, the first lens 11 has optical surfaces 111 and 112, the second lens 12 has optical surfaces 121 and 122, the aperture 13 has an optical surface 131, the third lens 14 has an optical surface 141 facing the second lens 12, the doublet lens 101 has an optical surface 102 between the third lens 14 and the fourth lens 15, and the fourth lens 15 has an optical surface 151 on the side away from the third lens 14. The optical surfaces 111, 112, 121, 122, 131, 141, 102, 151 are arranged in sequence from the object side to the image side along the optical axis.

[0041] Detailed lens design parameters of the projection lens 10 are shown in Table 1 below, where the spacing represents the vertical distance between the current optical surface and the next adjacent optical surface.

[0042] Table 1

[0043]

[0044] In this embodiment, the second lens 12 is an 8th-order even-order aspheric lens, and its object-side surface (i.e., optical surface 121) and image-side surface (i.e., optical surface 122) are both aspheric surfaces. The equation of the aspheric lens surface curve is expressed as follows:

[0045]

[0046] Where: c is the curvature; k is the cone coefficient; r is the radial distance, α is a polynomial coefficient of different orders. The aspheric parameters of the object side of the second lens 12 in this embodiment are shown in Table 2 below:

[0047] Table 2

[0048]

[0049] In this embodiment, the modulation transfer function (MTF) of the projection lens 10 under visible light is as follows: Figure 2 shown.

[0050] The function of modulation degree varying with spatial frequency is called modulation transfer function, which can reflect the ability of the optical system to transfer sinusoidal modulation degrees of various frequencies. Figure 2The horizontal axis represents the spatial frequency, with the unit of line pairs per millimeter (lp / mm); the vertical axis represents the light transfer function modulus, with a value range of 0 to 1. The closer the value of the vertical axis is to 1, the closer the contrast and resolution are to 100%, indicating that the imaging effect of the projection lens is better. Figure 2 The curves in the figure represent the modulation transfer function curves of different fields of view.

[0051] Depend on Figure 2 It can be seen that as the spatial frequency gradually increases, the MTF of different fields of view of the projection lens 10 varies within a relatively high value range. When the spatial frequency is 16lp / mm, the MTF of different fields of view of the projection lens 10 is almost still greater than 0.4 (the MTF of very few fields of view is less than 0.4 but still greater than 0.36), meeting the requirements of 4K picture clarity.

[0052] The projection optical machine 1 of the embodiment of the present application adopts the above-mentioned projection lens 10. By reasonably designing the optical parameters (optical focal length, lens surface shape, etc.) of each optical lens (mainly including the first lens 11, the second lens 12, the third lens 14 and the fourth lens 15) in the projection lens 10, the number of optical lenses in the projection lens 10 can be reduced to 4 (the first lens 11, the second lens 12, the third lens 14 and the fourth lens 15) on the basis of satisfying the 4K resolution of the projection optical machine 1. It is particularly suitable for 4K LCD projection optical machines 1 with a resolution of 5.5 inches or above.

[0053] The projection lens 10 of this embodiment achieves high-resolution display through four lenses, which reduces the overall cost, overall manufacturing difficulty and overall weight of the projection lens 10 while maintaining good optical imaging performance. The outer diameter of the plastic aspheric lens (second lens 12) in the projection lens 10 is small and has high machinability. In addition, the reduction in volume and weight of the projection lens 10 is beneficial to the layout of the overall optical path in the projection optical machine 1 including the projection lens 10. Furthermore, in this embodiment, the aperture 13 is located between the second lens 12 and the third lens 14, so that the projection image projected by the projection lens 10 has better display quality.

[0054] Those skilled in the art should recognize that the above implementation modes are only used to illustrate the present application, and are not used as limitations on the present application. As long as they are within the essential spirit of the present application, appropriate changes and modifications made to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. A projection lens, characterized in that: It includes a first lens, a second lens, a third lens, a fourth lens and a Fresnel lens which are arranged in sequence from the object side to the image side along the optical axis; The first lens and the fourth lens have positive refractive power, and the second lens and the third lens have negative refractive power; The first lens is a crescent lens, the second lens and the third lens are biconcave lenses, and the fourth lens is a biconvex lens; The projection lens further includes an aperture stop, and the aperture stop is located between the second lens and the third lens.

2. The projection lens according to claim 1, wherein: The second lens is a plastic aspherical lens.

3. The projection lens according to claim 2, wherein: The second lens is an 8th-order even-order aspheric lens.

4. The projection lens according to claim 2, wherein: The first lens, the third lens and the fourth lens are all glass spherical lenses.

5. The projection lens according to any one of claims 1 to 4, characterized in that: The third lens and the fourth lens form a doublet lens, and the whole lens has positive power.

6. The projection lens according to claim 5, wherein: The first lens has a first focal length f1, the second lens has a second focal length f2, the doublet lens has a combined focal length f3, and the projection lens has a system focal length f: 1.2 <f1 / f<1.5,-2.3<f2 / f<-2,1<f3 / f<1.3。 7. The projection lens according to claim 6, wherein: There is a first distance H1 between the first lens and the third lens, and there is a second distance H2 between the second lens and the third lens: 0.1 <H1 / f<0.25、0.03<H2 / f<0.07。 8. The projection lens according to any one of claims 1 to 4, characterized in that: The first lens has a first refractive index Nd1, the second lens has a second refractive index Nd2, the third lens has a third refractive index Nd3, and the fourth lens has a fourth refractive index Nd4: Nd1=1.71, Nd2=1.59, Nd3=1.65, Nd4=1.

83.

9. The projection lens according to claim 1, wherein: The projection lens has an aperture number of 2.6, a projection ratio of 1.2:1, and a distortion of less than 1%.

10. A projection optical machine, characterized in that: include: A liquid crystal display screen, used for emitting projection image light; as well as The projection lens according to any one of claims 1 to 9, located on the optical path of the projection image light, and used to project the projection image light onto an imaging medium.

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