Fixed-focus projection optical system and projection equipment

Abstract

The utility model discloses a fixed-focus projection optical system and projection equipment, and relates to the technical field of optics, and the fixed-focus projection optical system is provided with an object side and an image side which are oppositely arranged along the direction of an optical axis. The fixed-focus projection optical system is composed of a first lens, a diaphragm, a second lens, a third lens, a Fresnel lens and a display chip which are sequentially arranged from the object side to the image side. Wherein the focal power of the first lens is positive, the object side surface is a convex surface, and the image side surface is a concave surface; the focal power of the second lens is negative, the object side surface is a concave surface, and the image side surface is a concave surface; the focal power of the third lens is positive, the object side surface is a convex surface, and the image side surface is a convex surface; the fixed-focus projection optical system is high in resolution, small in size, bright in picture and good in projection effect.

Description

Technical Field

[0001] The utility model relates to the technical field of optics, in particular to a fixed-focus projection optical system and projection equipment. Background Art

[0002] With the recent development of projection technology, projectors have become widely used in homes, education, and offices. Most common projection systems on the market are direct projection systems. However, these systems generally suffer from disadvantages such as large size, high cost, and low resolution. Some lenses sacrifice resolution or use plastic aspherical lenses to reduce costs. However, due to the high heat generated by projectors, these lenses are prone to defocusing, affecting performance. Utility Model Content

[0003] The main purpose of the utility model is to provide a fixed-focus projection optical system and projection equipment, aiming to improve resolution, reduce volume and make the picture brighter and the imaging effect better.

[0004] To achieve the above-mentioned object, the present invention proposes a fixed-focus projection optical system, which has an object side and an image side arranged opposite to each other along the optical axis. The fixed-focus projection optical system is composed of a first lens, an aperture, a second lens, a third lens, a Fresnel lens, and a display chip, which are arranged in sequence from the object side to the image side.

[0005] The first lens has a positive optical power, a convex object-side surface, and a concave image-side surface;

[0006] The second lens has a negative optical power, a concave object-side surface, and a concave image-side surface;

[0007] The third lens has positive optical power, a convex object-side surface, and a convex image-side surface.

[0008] In one embodiment, the focal length f1 of the first lens is positive, the focal length f2 of the second lens is negative, and the focal length f3 of the third lens is positive;

[0009] Among them, 200mm<|f1|<250mm, 40mm<|f2|<70mm, and 30mm<|f3|<50mm.

[0010] In one embodiment, the refractive index of the first lens is n1, the refractive index of the second lens is n2, and the refractive index of the third lens is n3. The refractive indices of the first lens, the second lens, and the third lens satisfy the following relationship:

[0011] 1.50≤n1≤1.70, 1.50≤n2≤1.70, 1.65≤n3≤1.80.

[0012] In one embodiment, the Abbe coefficient of the first lens is v1, the Abbe coefficient of the second lens is v2, and the Abbe coefficient of the third lens is v3. The Abbe coefficients of the first lens, the second lens, and the third lens satisfy the following relationship:

[0013] 20.0≤v1≤40.0, 20.0≤v2≤40.0, 30.0≤v3≤55.0.

[0014] In one embodiment, the diameter of the first lens is D1, where D1<36 mm.

[0015] In one embodiment, the light emitting surface diameter of the display chip is IC, wherein IC≤91 mm.

[0016] In one embodiment, the first lens is a plastic aspheric surface, the second lens is a plastic aspheric surface, the third lens is a glass spherical surface, and the image side surface of the Fresnel lens is a plastic aspheric surface.

[0017] In one embodiment, the total optical length of the fixed-focus projection optical system is TTL, wherein TTL≤28.69 mm.

[0018] In one embodiment, the aperture value of the fixed-focus projection optical system is F, wherein 2.5≤F≤3.0.

[0019] The present invention further provides a projection device, comprising a fixed-focus projection optical system, wherein the fixed-focus projection optical system has an object side and an image side arranged opposite to each other along an optical axis, and the fixed-focus projection optical system comprises a first lens, an aperture, a second lens, a third lens, a Fresnel lens, and a display chip, which are arranged in sequence from the object side to the image side.

[0020] The first lens has a positive optical power, a convex object-side surface, and a concave image-side surface;

[0021] The second lens has a negative optical power, a concave object-side surface, and a concave image-side surface;

[0022] The third lens has positive optical power, a convex object-side surface, and a convex image-side surface.

[0023] The technical solution of this utility model, by providing a first lens with positive optical power, helps shorten the projection distance and increase the throw ratio. By comprehensively adjusting the optical power of each lens, the lens can effectively control the light flow, allowing more light to enter while making the structure more compact. The combination of different lenses and the rational distribution of optical power also achieve high resolution, small size, bright images, and better projection effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0025] Figure 1 This is a structural schematic diagram of an embodiment of a fixed-focus projection optical system provided by the present utility model;

[0026] Figure 2 for Figure 1 A schematic diagram of an MTF curve of an embodiment of a medium-fixed-focus projection optical system;

[0027] Figure 3 for Figure 1 A schematic diagram of a SPOT point of an embodiment of a medium-fixed-focus projection optical system.

[0028] Description of Figure Numbers:

[0029] 100. Fixed-focus projection optical system; 1. First lens; 2. Second lens; 3. Third lens; 4. Fresnel lens; 5. Display chip.

[0030] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts shall fall within the scope of protection of the present invention.

[0032] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0033] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0034] Currently, fixed-focus lenses generally have disadvantages such as large size, high cost, and low resolution. In order to reduce costs, a small number of lenses sacrifice some resolution or use plastic aspherical surfaces. However, due to the high heat generated by the projector, these lenses are often prone to out-of-focus due to high temperature, affecting the use effect.

[0035] In order to solve the above problems, the utility model proposes a fixed-focus projection optical system.

[0036] First, it's important to understand that focal power is equal to the difference between the image-side and object-side beam convergences, and it characterizes an optical system's ability to deflect light. The larger the absolute value of the focal power, the greater the light-bending ability; the smaller the absolute value, the weaker the light-bending ability. When the focal power is a positive number, the light is refracted in a convergent manner; when the focal power is a negative number, the light is refracted in a divergent manner. Focal power can be applied to characterize a specific refractive surface of a lens, a single lens, or a system composed of multiple lenses.

[0037] See also Figure 1 In one embodiment of the present invention, the fixed-focus projection optical system has an object side and an image side that are oppositely arranged along the optical axis direction. The fixed-focus projection optical system is composed of a first lens 1, an aperture, a second lens 2, a third lens 3, a Fresnel lens 4 and a display chip 5, which are arranged in sequence from the object side to the image side; wherein, the first lens 1 has a positive optical power, a convex object side surface, and a concave image side surface; the second lens 2 has a negative optical power, a concave object side surface, and a concave image side surface; the third lens 3 has a positive optical power, a convex object side surface, and a convex image side surface.

[0038] The first lens 1 has a positive optical power, a convex object-side surface, and a concave image-side surface, which can introduce more light, shorten the projection distance, and increase the throw ratio, thereby achieving a small size for the fixed-focus projection optical system. The aperture (not shown) is provided between the first lens 1 and the second lens 2, and can adjust the field of view, block far-axis light, and prevent far-axis light from affecting the imaging quality, thereby improving image quality and providing the lens with a large light throughput. The second lens 2 has a concave object-side surface and a concave image-side surface, and the third lens 3 has a convex object-side surface and a convex image-side surface. This arrangement ensures that the concave and convex surfaces of the second lens 2 and the third lens 3 complement each other, better fit, and a more compact structure. In addition, the second lens 2 has a negative optical power and the third lens 3 has a positive optical power, which controls the light trajectory and improves resolution. The Fresnel lens 4 can convert the divergent light beam emitted by the light source in the projection system into parallel light or convergent light. The annular grooves on the lens surface precisely refract the light, making the light more concentrated, thereby improving the clarity and uniformity of the image. In addition, compared with traditional thick lenses, the thin design of the Fresnel lens 4 can reduce the volume and weight of the projection device without sacrificing optical performance, making it more compact and lightweight; the display chip 5 is used to project a visible image.

[0039] In the technical solution of the present invention, the first lens 1 is set to have a positive optical power, a convex object-side surface, and a concave image-side surface, which is beneficial to shortening the projection distance and increasing the projection ratio; by comprehensively setting the optical power and shape coordination relationship of each lens, the light trend can be well controlled, and the structure can be made more compact while introducing more light; by combining different lenses with each other and reasonably allocating the positive and negative optical powers, the fixed-focus projection optical system has high resolution, small size, bright picture, and better projection effect.

[0040] See also Figure 2 In one embodiment of the present invention, it should be understood that the focal length refers to the distance from the rear surface of the lens to the image plane in the optical system. The focal length determines the magnification and viewing angle of the image. The optical power is the reciprocal of the focal length. The focal length f1 of the first lens 1 is positive, the focal length f2 of the second lens 2 is negative, and the focal length f3 of the third lens 3 is positive; wherein, 200mm<|f1|<250mm, 40mm<|f2|<70mm, and 30mm<|f3|<50mm; through the mutual combination of different lenses and the reasonable distribution of optical power, the optical system has a small volume while improving the resolution of the fixed-focus projection optical system.

[0041] In one embodiment of the present invention, the refractive index of the first lens 1 is n1, the refractive index of the second lens 2 is n2, and the refractive index of the third lens 3 is n3. The refractive indices of the first lens 1, the second lens 2, and the third lens 3 satisfy the following relationship: 1.50≤n1≤1.70, 1.50≤n2≤1.70, and 1.65≤n3≤1.80. By adopting the above, the refraction angle and path of light can be more precisely controlled, thereby ensuring that the light converges to the correct position and forms a clear, distortion-free image. This helps to improve the sharpness and color accuracy of the image.

[0042] In one embodiment of the present invention, the dispersion coefficient of the first lens 1 is v1, the dispersion coefficient of the second lens 2 is v2, and the dispersion coefficient of the third lens 3 is v3. The dispersion coefficients of the first lens 1, the second lens 2, and the third lens 3 satisfy the following relationship: 20.0≤v1≤40.0, 20.0≤v2≤40.0, and 30.0≤v3≤55.0. It is understood that different colors of light, due to their different wavelengths, will undergo different degrees of refraction when passing through the lens, resulting in different focus positions, resulting in chromatic aberration, and affecting image clarity and color accuracy. By limiting the dispersion coefficients of the first lens 1, the second lens 2, and the third lens 3, the refractive index differences of light of various wavelengths can be effectively balanced, chromatic aberration can be reduced, and image edges can be made clearer and color transitions more natural.

[0043] In order to facilitate the installation of the fixed-focus projection optical system and reduce the volume of the fixed-focus projection optical system, the first lens 1 should not be too large. In one embodiment of the present invention, the diameter of the first lens 1 is D1, where D1<36mm. By limiting the diameter of the first lens 1, installation is facilitated, the volume of the fixed-focus projection optical system is reduced, and it is adaptable to more scenarios.

[0044] In one embodiment of the present invention, it can be understood that when the light-emitting surface is too large, the lenses cannot collect all the light, which affects the imaging quality. For this reason, the diameter of the light-emitting surface of the display chip 5 is IC, where IC≤91mm, so that the fixed-focus projection optical system can project a complete image and improve the imaging effect.

[0045] See also Figure 1 In one embodiment of the present invention, the first lens 1 is a plastic aspheric surface, the second lens 2 is a plastic aspheric surface, the third lens 3 is a glass spherical surface, and the image side surface of the Fresnel lens 4 is a Fresnel surface.

[0046] It can be understood that the characteristics of aspherical lenses are: the curvature changes continuously from the center of the lens to the periphery of the lens. Unlike spherical lenses with a constant curvature from the center of the lens to the periphery of the lens, aspherical lenses have better curvature radius characteristics and have the advantages of improving distortion and astigmatism. After using aspherical lenses, the aberrations that occur during imaging can be eliminated as much as possible, thereby improving the imaging quality of the lens.

[0047] Specifically, in one embodiment of the present invention, the surface shape of the aspheric lens in the projection optical system should satisfy the following equation:

[0048]

[0049] Where c is the curvature corresponding to the radius; y is the radial coordinate (its unit is the same as the lens length unit); k is the conic coefficient, and A, B, C, D, E, F, G... represent the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, sixteenth-order... aspheric coefficients, respectively.

[0050] More specifically, in one embodiment of the present invention, the even-order coefficients of each aspheric surface are shown in Table 1 below.

[0051] Table 1

[0052]

[0053]

[0054] The above parameters can be used to accurately set the shape and size of the lens's aspherical surface to correct distortion and eliminate aberrations that occur during imaging as much as possible, thereby improving the imaging quality of the lens. They can also be used to correct pupil aberrations caused by large apertures, thereby improving the imaging quality of the system. At the same time, the number of spherical lenses set up can be greatly reduced, reducing the system volume.

[0055] In addition, when the fixed-focus projection optical system is in an actual working environment, the system generates a large amount of heat, and the adjacent first lens is set to a plastic aspheric lens with positive optical focal length, and the second lens is set to a plastic aspheric lens with negative optical focal length, so as to maintain the overall focal length stable and achieve thermal compensation.

[0056] Furthermore, because glass lenses are expensive and difficult to manufacture, in one embodiment of the present invention, the first lens 1 and the second lens 2 are made of plastic spherical surfaces. Plastic spherical surfaces are relatively low in cost and can be easily processed into various complex shapes and sizes through processes such as injection molding and die casting, making it easier to achieve aspheric surface designs, thereby improving optical performance and reducing aberrations. It is understandable that the present invention does not limit the type of plastic. It can be K26R plastic or PC plastic. The K26R plastic has high transparency and excellent heat resistance, its light transmittance is close to that of glass, and it maintains stable performance in high-temperature environments, so that the projector does not defocus in high-brightness working environments; it can also be PC plastic, i.e., optical-grade polycarbonate, which has high transparency and excellent impact resistance, its light transmittance is close to that of glass, and it has good processing performance and low cost, making it easier to manufacture aspheric surface designs.

[0057] The third lens 3 is a glass spherical surface, which reduces various optical aberrations while effectively suppressing the chromatic aberration of the system. At the same time, because glass lenses are not easily affected by thermal expansion and contraction, they can effectively resist the problem of lens deformation caused by heat and maintain the high precision of the lens for a long time. In addition, the aberrations that occur during imaging can be eliminated as much as possible, thereby improving the imaging quality of the lens and reducing the impact of temperature on the optical performance of the lens. The present invention does not limit the specific material of the glass lens; it can be FCD1, H-ZLAF55C, as long as it can meet the imaging requirements. In one embodiment of the present invention, H-LAK7A glass with lanthanide elements added is used, which significantly increases the refractive index of the glass, allowing H-LAK7A to more effectively control light, which is particularly important for optical designs that require high light efficiency or small size. In addition, although H-LAK7A has a high refractive index, through careful material design, H-LAK7A balances dispersion performance, reduces chromatic aberration, and thus improves clarity.

[0058] The image side of the Fresnel lens 4 is a Fresnel surface, which accurately refracts light through the annular grooves on the lens surface, making the light more concentrated, thereby improving the clarity and uniformity of the image.

[0059] Specifically, in one embodiment of the present invention, the focal length of the fixed-focus projection optical system is f=86, the aperture value is F=2.8, and the light-emitting surface diameter is 91 mm. The parameters of the fixed-focus projection optical system are shown in Table 2 below.

[0060] Table 2

[0061]

[0062] Figure 2 The figure shows a schematic diagram of the MTF curve of an embodiment of the present invention. Figure 3The figure shows a schematic diagram of a SPOT point provided by another embodiment of the present invention. Figure 2-3 It can be seen that the fixed-focus lens provided in this embodiment has good imaging capabilities.

[0063] In one embodiment of the present invention, the total optical length of the fixed-focus projection optical system, that is, the distance from the object plane of the first lens 1 to the display chip 5 is TTL, where TTL≤28.69 mm; by limiting the total optical length of the display chip 5, the volume of the fixed-focus lens can be further reduced, which is conducive to the miniaturization of the fixed-focus lens.

[0064] In one embodiment of the present invention, the aperture value of the fixed-focus projection optical system is F, where 2.5mm≤F≤3.0mm; when the aperture value F of the fixed-focus projection optical system is within this range, the resolution and contrast of the lens are optimal, the lens transmits a large amount of light, the picture brightness is high, and the imaging effect is better.

[0065] The present utility model also proposes a projection device, which includes a fixed-focus projection optical system. The specific structure of the fixed-focus projection optical system refers to the above-mentioned embodiment. Since the present projection device adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0066] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A fixed-focus projection optical system, characterized in that: The fixed-focus projection optical system has an object side and an image side that are arranged opposite to each other along the optical axis direction, and the fixed-focus projection optical system is composed of a first lens, an aperture, a second lens, a third lens, a Fresnel lens, and a display chip that are sequentially arranged from the object side to the image side; Wherein, the first lens has a positive optical power, a convex object side surface, and a concave image side surface; The second lens has a negative optical power, a concave object side surface, and a concave image side surface; The third lens has positive optical power, a convex object-side surface, and a convex image-side surface.

2. The fixed-focus projection optical system according to claim 1, characterized in that: The focal length f1 of the first lens is positive, the focal length f2 of the second lens is negative, and the focal length f3 of the third lens is positive; Among them, 200mm<|f1|<250mm, 40mm<|f2|<70mm, and 30mm<|f3|<50mm.

3. The fixed-focus projection optical system according to claim 1, wherein: The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, and the refractive indices of the first lens, the second lens and the third lens satisfy the following relationship: 1.50≤n1≤1.70, 1.50≤n2≤1.70, 1.65≤n3≤1.

80.

4. The fixed-focus projection optical system according to claim 1, wherein: The dispersion coefficient of the first lens is v1, the dispersion coefficient of the second lens is v2, and the dispersion coefficient of the third lens is v3. The dispersion coefficients of the first lens, the second lens, and the third lens satisfy the following relationship: 20.0≤v1≤40.0, 20.0≤v2≤40.0, 30.0≤v3≤55.

0.

5. The fixed-focus projection optical system according to claim 1, wherein: The diameter of the first lens is D1, wherein D1<36 mm.

6. The fixed-focus projection optical system according to claim 1, wherein: The diameter of the light emitting surface of the display chip is IC, wherein IC≤91 mm.

7. The fixed-focus projection optical system according to claim 1, wherein: The first lens is a plastic aspherical lens, the second lens is a plastic aspherical lens, the third lens is a glass spherical lens, and the image side of the Fresnel lens is a Fresnel surface.

8. The fixed-focus projection optical system according to claim 1, wherein: The total optical length of the fixed-focus projection optical system is TTL, wherein TTL≤28.69 mm.

9. The fixed-focus projection optical system according to claim 1, wherein: The aperture value of the fixed-focus projection optical system is F, wherein 2.5≤F≤3.

0.

10. A projection device, characterized in that: Comprising the fixed-focus projection optical system as described in any one of claims 1 to 9.

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