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, a fifth lens and a Fresnel lens which are sequentially arranged along an optical axis from an object side to an image side, the first lens, the fourth lens and the fifth lens have positive focal power, and the second lens and the third lens have negative focal power; the second lens is an aspheric 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, larger, heavier, and more expensive, causing inconvenience in actual use. Furthermore, since the imaging lens includes a large number of lenses, a longer overall structure, and a larger volume, it will also affect the overall optical path layout in the projection optical machine used by the imaging 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, a fifth lens and a Fresnel lens arranged in sequence from the object side to the image side along an optical axis; the first lens, the fourth lens and the fifth lens have positive optical power, and the second lens and the third lens have negative optical power; the second lens is an aspherical lens; the projection lens also includes an aperture stop, which is located between the second lens and the third lens.

[0005] In at least one embodiment of the present application, the second lens is an 8th-order even-order aspheric lens.

[0006] In at least one embodiment of the present application, the aperture of the second lens is less than 60 mm.

[0007] In at least one embodiment of the present application, the apertures of the first lens, the fourth lens, and the fifth lens are larger than the apertures of the second lens and the third lens; the first lens, the fourth lens, and the fifth lens are glass lenses; and the second lens and the third lens are plastic lenses.

[0008] In at least one embodiment of the present application, the third lens is a spherical lens or an aspherical lens.

[0009] In at least one embodiment of the present application, the first lens and the second lens are convex lenses, the third lens and the fourth lens are negative meniscus lenses, and the fifth lens is a biconvex lens.

[0010] In at least one embodiment of the present application, the total optical length of the projection lens is less than 90 mm.

[0011] 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%.

[0012] In at least one embodiment of the present application, the focal length of the Fresnel lens is greater than 130 mm.

[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 as described in any of the above items, 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 power, lens surface shape, etc.) of each optical lens in the projection lens (mainly including the first lens, the second lens, the third lens, the fourth lens and the fifth lens), the number of optical lenses in the projection lens can be reduced to 5 (the first lens, the second lens, the third lens, the fourth lens and the fifth lens) on the basis of satisfying the projection optical machine to achieve 4K resolution. It is particularly suitable for 4K LCD projection optical machines above 5.5 inches. The projection lens of this embodiment achieves high-resolution display through 5 lenses. On the basis of 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] Fifth lens 16

[0026] Fresnel lens 17

[0027] LCD 20

[0028] Optical axis L

[0029] Optical surfaces 111, 112, 121, 122, 131, 141, 142, 151, 152, 161, 162

[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 5 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, and includes a first lens 11, a second lens 12, an aperture 13, a third lens 14, a fourth lens 15, a fifth lens 16, and a Fresnel lens 17, which are arranged in sequence from the object side to the image side along the optical axis L. The LCD 20 is located on a side of the Fresnel lens 17 away from the fifth lens 16. That is, the projection image light emitted from the LCD 20 passes through the Fresnel lens 17, the fifth lens 16, the fourth lens 15, the third lens 14, the aperture 13, the second lens 12, and the first lens 11 in sequence and then is emitted from the projection lens 10.

[0034] In this embodiment, the first lens 11, the fourth lens 15 and the fifth lens 16 have positive power, and the second lens 12 and the third lens 14 have negative power. The first lens 11 and the second lens 12 are convex lenses, the third lens 14 and the fourth lens 15 are negative meniscus lenses, and the fifth lens 16 is a double convex lens.

[0035] In this embodiment, the lens diameter of the second lens 12 is less than 60 mm, and the focal length of the Fresnel lens 17 is greater than 130 mm. The working wavelength of the projection lens 10 is between 450 and 610 μm (including the end values), the aperture number F / # is 2.6, the projection ratio is 1.2:1, the total optical length is less than 90 mm, and the distortion is less than 1%.

[0036] In this embodiment, the first lens 11, the fourth lens 15 and the fifth lens 16 are spherical lenses, and the second lens 12 and the third lens 14 are aspherical lenses. Further, the first lens 11, the fourth lens 15 and the fifth lens 16 are glass lenses, and the second lens 12 and the third lens 14 are plastic lenses.

[0037] In this embodiment, the diameters of the first lens 11 , the fourth lens 15 and the fifth lens 16 are larger than the diameters of the second lens 12 and the third lens 14 .

[0038] In other embodiments of the present application, the third lens 14 may also be a spherical lens. When the third lens 14 is an aspherical lens, it has a higher resolution. When the third lens 14 is a spherical lens, it is helpful to reduce the processing difficulty and production cost. In this embodiment, the third lens 14 has a relatively small effect on the modulation effect of the projection image light in the entire projection lens 10. On the basis of making the projection lens 10 meet the basic requirements of 4K display, the third lens 14 can use a spherical lens to save the cost of the projection lens 10. For scenes with higher display requirements, the third lens 14 can use an aspherical lens to improve the overall resolution of the projection lens 10.

[0039] 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 optical surfaces 141 and 142, the fourth lens 15 has optical surfaces 151 and 152, and the fifth lens 16 has optical surfaces 161 and 162. The optical surfaces 111, 112, 121, 122, 131, 141, 142, 151, 152, 161 and 162 are arranged in sequence from the object side to the image side along the optical axis.

[0040] The 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 optical surface.

[0041] Table 1

[0042]

[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 surface curve is 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 2 The 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 Each curve in the figure represents the modulation transfer function curve 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 still greater than 0.4, 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 in the projection lens 10 (mainly including the first lens 11, the second lens 12, the third lens 14, the fourth lens 15 and the fifth lens 16), the number of optical lenses in the projection lens 10 can be reduced to 5 (the first lens 11, the second lens 12, the third lens 14, the fourth lens 15 and the fifth lens 16) 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 above 5.5 inches.

[0053] The projection lens 10 of this embodiment achieves high-resolution display through 5 lenses, which reduces the overall cost, overall manufacturing difficulty and overall weight of the projection lens 10 while maintaining good optical imaging performance. In addition, the outer diameter of the plastic aspheric lens (the second lens 12 and the third lens 14) 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, a fifth 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, the fourth lens and the fifth lens have positive refractive power, and the second lens and the third lens have negative refractive power; The second lens is an aspherical 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 an 8th-order even-order aspheric lens.

3. The projection lens according to claim 2, wherein: The aperture of the second lens is less than 60 mm.

4. The projection lens according to claim 1, wherein: The apertures of the first lens, the fourth lens and the fifth lens are larger than the apertures of the second lens and the third lens; The first lens, the fourth lens and the fifth lens are glass lenses; The second lens and the third lens are plastic lenses.

5. The projection lens according to claim 1, wherein: The third lens is a spherical lens or an aspherical lens.

6. The projection lens according to claim 1, wherein: The first lens and the second lens are convex lenses, the third lens and the fourth lens are negative meniscus lenses, and the fifth lens is a double convex lens.

7. The projection lens according to any one of claims 1 to 6, characterized in that: The total optical length of the projection lens is less than 90 mm.

8. 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%.

9. The projection lens according to claim 1, wherein: The focal length of the Fresnel lens is greater than 130 mm.

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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