Ultra-short-throw optical systems and projection equipment

Abstract

The present invention discloses an ultra-short-focus optical system and projection equipment. The ultra-short-focus optical system comprises, arranged in sequence from the object side to the image side, a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, a ninth lens with positive optical power, a tenth lens with positive optical power, an equivalent prism, and a photosensitive chip. The total length of the ultra-short-focus optical system is controlled within 51 mm, and the throw ratio reaches 0.55. Because the first, second, third, and ninth lenses are all plastic lenses, costs are greatly reduced. Furthermore, because the ten lenses adopt a refractive optical path rather than a refractive and reflective optical structure, assembly is simplified and manufacturing costs are reduced, thereby providing a low-cost ultra-short-focus optical system with a small size and a small number of lenses.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to an ultra-short-focus optical system and projection equipment. Background Art

[0002] The characteristic of ultra-short-throw projectors is that they can project a large image at a short distance, which provides convenience for viewing and installation, especially for emerging desktop projections, which require smaller size and closer projection distance.

[0003] The lenses used in most ultra-short-throw projectors on the market are of a refractive and reflective optical structure, which is difficult to manufacture and has high costs. There are also refractive ultra-short-throw structures, which require a large number of lenses and a large size to correct distortion, resulting in high costs. Summary of the Invention

[0004] The main purpose of the present invention is to propose an ultra-short-focus optical system and projection equipment, aiming to provide a low-cost ultra-short-focus optical system with a small volume and a small number of lenses.

[0005] To achieve the above objectives, the present invention provides an ultra-short-focus optical system, which has an object side and an image side arranged opposite to each other along the optical axis. The ultra-short-focus optical system includes a first lens with negative optical focal length, a second lens with negative optical focal length, a third lens with negative optical focal length, a fourth lens with negative optical focal length, a fifth lens with positive optical focal length, a sixth lens with positive optical focal length, a seventh lens with positive optical focal length, an eighth lens with negative optical focal length, a ninth lens with positive optical focal length, a tenth lens with positive optical focal power, an equivalent prism and a photosensitive chip, wherein the first lens, the second lens, the third lens and the ninth lens are all plastic lenses. The total optical length TTL of the ultra-short-focus optical system is ≤51 mm, and the transmittance can reach 0.55.

[0006] Optionally, the first lens, the second lens, the third lens, the fourth lens, and the ninth lens are aspherical lenses;

[0007] The fifth lens, the sixth lens, the seventh lens, the eighth lens and the tenth lens are all spherical lenses.

[0008] Optionally, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens and the tenth lens are all glass lenses.

[0009] Optionally, the ultra-short focus optical system further meets the following conditions:

[0010] and and and and and and

[0011] in, is the optical power of the first lens, is the optical power of the second lens, is the focal power of the third lens, is the optical power of the fourth lens, is the optical power of the fifth lens, is the focal power of the sixth lens, is the focal power of the seventh lens, is the focal power of the eighth lens, is the focal power of the ninth lens, is the optical power of the tenth lens.

[0012] Optionally, the ultra-short focus optical system further meets the following conditions:

[0013] in, is the optical power of the first lens, is the optical power of the second lens, is the focal power of the third lens, is the focal power of the ninth lens.

[0014] Optionally, the seventh lens and the eighth lens are cemented together to form a cemented lens.

[0015] Optionally, the ultra-short focus optical system further satisfies the following condition: 4<T1 / T2<5;

[0016] Among them, T1 is the center distance between the first lens and the tenth lens in the direction of the optical axis, and T2 is the center distance between the tenth lens and the photosensitive chip in the direction of the optical axis.

[0017] Optionally, the ultra-short focus optical system further includes a stop, and the stop is arranged between the sixth lens and the seventh lens.

[0018] Optionally, the ultra-short focus optical system further includes a protective glass, which is arranged between the equivalent prism and the photosensitive chip.

[0019] The present invention also provides a projection device, which includes the above-mentioned ultra-short-focus optical system.

[0020] In the technical solution provided by the present invention, a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, a ninth lens with positive optical power, a tenth lens with positive optical power, an equivalent prism and a photosensitive chip are provided. The first lens, the second lens, the third lens and the ninth lens are all plastic lenses. The first lens is configured as a meniscus lens with its image side bent toward the photosensitive chip to reduce the angle of light entering the rear lens and correct the distortion of large-angle light. The second lens is also configured as a meniscus lens with its image side bent toward the photosensitive chip to further reduce the angle of light entering the rear lens and correct the distortion of large-angle light. The third lens is also configured as a meniscus lens with its image side bent toward the photosensitive chip to correct the residual distortion value. The first lens, the second lens and the third lens can enable the ultra-short focus optical system to obtain a smaller projection ratio value. The fourth lens has a negative optical power, bends the light, increases the height of the light entering the rear lens, and achieves a larger aperture. The fifth lens and the sixth lens correct pupil aberration. The seventh lens and the eighth lens correct the chromatic aberration of the system. The ninth lens increases the height of the light. The tenth lens further converges the light so that the outgoing light can be incident on the prism at a smaller angle and then enter the photosensitive chip, so that the ultra-short focus optical system has a higher resolution. By arranging the above ten lenses in sequence from the projection surface to the photosensitive chip in the order of negative, negative, negative, positive, positive, positive, positive and positive optical power, a smaller total length can be achieved, so that the distance between the first lens and the photosensitive chip is controlled within 51 mm, and the projection ratio can reach 0.55, so as to provide a low-cost ultra-short focus optical system with a small volume and a small number of lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] Figure 1 A schematic structural diagram of the ultra-short focus optical system provided by the present invention;

[0023] Figure 2 for Figure 1 Schematic diagram of MTF of ultra-short focus optical system at room temperature;

[0024] Figure 3 for Figure 1Schematic diagram of MTF of ultra-short focus optical system at high temperature;

[0025] Figure 4 for Figure 1 Schematic diagram of field distortion / field curvature of the ultra-short focus optical system.

[0026] Description of Figure Numbers:

[0027]

[0028]

[0029] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] 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 various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0032] 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 suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text 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.

[0033] Ultra-short-throw projectors are characterized by their ability to project a large image from a short distance, making them convenient for viewing and installation. This is particularly true for emerging desktop projection applications, which require smaller size and closer projection distances. Most ultra-short-throw projectors on the market use lenses that combine refractive and reflective optics, which are difficult and expensive to manufacture. Some ultra-short-throw projectors also use refractive lenses, but to correct for distortion, they require a large number of lenses and are bulky, resulting in high costs.

[0034] In order to solve the above problems, the present invention provides an ultra-short focus optical system. Figures 1 to 4 This is a specific embodiment of the ultra-short focus optical system provided by the present invention.

[0035] See also Figure 1 The ultra-short-focus optical system has an object side and an image side that are relatively arranged along the optical axis. The ultra-short-focus optical system has an object side and an image side that are relatively arranged along the optical axis. The ultra-short-focus optical system includes a first lens 1 with negative optical focal power, a second lens 2 with negative optical focal power, a third lens 3 with negative optical focal power, a fourth lens 4 with negative optical focal power, a fifth lens 5 with positive optical focal power, a sixth lens 6 with positive optical focal power, a seventh lens 7 with positive optical focal power, an eighth lens 8 with negative optical focal power, a ninth lens 9 with positive optical focal power, a tenth lens 10 with positive optical focal power, an equivalent prism 11 and a photosensitive chip 12. The first lens 1, the second lens 2, the third lens 3, and the ninth lens 9 are all plastic lenses. The total optical length TTL of the ultra-short-focus optical system is ≤51 mm, and the throw ratio can reach 0.55.

[0036] In the technical solution provided by the present invention, a first lens 1 with negative optical power, a second lens 2 with negative optical power, a third lens 3 with negative optical power, a fourth lens 4 with negative optical power, a fifth lens 5 with positive optical power, a sixth lens 6 with positive optical power, a seventh lens 7 with positive optical power, an eighth lens 8 with negative optical power, a ninth lens 9 with positive optical power, a tenth lens 10 with positive optical power, an equivalent prism 11 and a photosensitive chip 12 are provided. The first lens 1, the second lens 2, the third lens 3 and the ninth lens 9 are all plastic lenses. The first lens 1 is configured as a meniscus lens, and its image side is bent toward the photosensitive chip 12, thereby reducing the angle of light entering the rear lens and correcting the distortion of large-angle light. The second lens 2 is also configured as a meniscus lens, and its image side is bent toward the photosensitive chip 12, further reducing the angle of light entering the rear lens and correcting the distortion of large-angle light. The third lens 3 is also configured as a meniscus lens, and its image side is bent toward the photosensitive chip 12, thereby correcting residual distortion. The first lens 1, the second lens 2, and the third lens 3 enable the ultra-short-focus optical system to obtain a smaller throw ratio value. The fourth lens 4 has a negative focal power, bends light, increases the height of the light entering the subsequent lens, and achieves a larger aperture. The fifth lens 5 and the sixth lens 6 correct pupil aberration. The seventh lens 7 and the eighth lens 8 correct system chromatic aberration. The ninth lens 9 increases the height of the light. The tenth lens 10 further converges the light, so that the outgoing light can be incident on the prism at a smaller angle and then enter the photosensitive chip 12, so that the ultra-short-focus optical system has a higher resolution. By arranging the above ten lenses in the order of negative, negative, negative, positive, positive, positive, positive, negative, positive, from the projection plane to the photosensitive chip 12, a shorter total length can be achieved, so that the distance between the first lens 1 and the photosensitive chip 12 is controlled within 51 mm, and the throw ratio can reach 0.55, thereby providing a low-cost ultra-short-focus optical system with a small volume and a small number of lenses.

[0037] It should be noted that plastic lenses have strong impact resistance, are light in weight, and have low cost. In the invention, four plastic materials are provided, namely the first lens 1, the second lens 2, the third lens 3, and the ninth lens 9, so that the cost can be greatly reduced.

[0038] It should also be noted that the lenses in the ultra-short-focus optical system are arranged in sequence and adopt a refractive optical path, which makes assembly simple and reduces manufacturing costs.

[0039] Specifically, the characteristic of an aspherical lens is that the curvature changes continuously from the center of the lens to the periphery. Unlike a spherical lens with a constant curvature from the center of the lens to the periphery, an aspherical lens has a better curvature radius characteristic and has the advantages of improving distortion aberration and improving astigmatism aberration. Therefore, in this embodiment, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the ninth lens 9 are aspherical lenses. 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.

[0040] In this embodiment, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, and the tenth lens 10 are all spherical lenses. This reduces costs, reduces assembly sensitivity, and improves product yield while ensuring image quality and reliability. The simultaneous use of spherical and aspherical surfaces controls costs while significantly reducing the size of the lens.

[0041] Specifically, because the chemical properties of plastic materials are relatively unstable when affected by ambient temperature, their refractive index is weaker than that of all-glass lenses, resulting in poorer image reproduction than all-glass lenses. In order to ensure the stability of the ultra-short-focus optical system under temperature changes, in this embodiment, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, and the tenth lens 10 are all glass lenses. Because glass lenses are not easily affected by thermal expansion and contraction and cause focus deviation, glass lenses can effectively resist the problem of lens deformation caused by heat and maintain the high precision of the lens for a long time. The ultra-short-focus optical system uses a glass-plastic hybrid material, which not only saves costs and has strong impact resistance, but also ensures the stability of the system and its applicability to high and low temperatures.

[0042] Specifically, in this embodiment, the ultra-short focus optical system further satisfies the following conditions: and and and and and and in, is the optical power of the first lens 1, is the focal length of the second lens 2, is the focal length of the third lens 3, is the focal length of the fourth lens 4, is the optical power of the fifth lens 5, is the focal length of the sixth lens 6, is the focal power of the seventh lens 7, is the focal power of the eighth lens 8, is the focal length of the ninth lens 9, is the focal power of the tenth lens 10. The focal power is equal to the difference between the image-side and object-side beam convergences, and represents a lens's ability to deflect light. By properly setting constraints on the ratios of the focal powers of the ten lenses, the light beam can be projected in the desired direction, allowing the spherical aberration, coma, and astigmatism of each lens element to compensate for each other, achieving clear imaging.

[0043] Specifically, the ultra-short focus optical system also satisfies the following condition: 4<T1 / T2<5; wherein T1 is the center distance between the first lens 1 and the tenth lens 10 in the optical axis direction, and T2 is the center distance between the tenth lens 10 and the photosensitive chip 12 in the optical axis direction.

[0044] By limiting the ratio of the optical focal length of each lens, as well as the ratio between the first lens 1, the tenth lens 10 and the photosensitive chip 12, the total optical length is controlled within 51 mm, which can achieve a smaller total length and greatly reduce the volume of the system.

[0045] Specifically, in this embodiment, the first lens 1, the second lens 2, the third lens 3 and the ultra-short focus optical system further satisfy the following conditions: in, is the optical power of the first lens 1, is the focal length of the second lens 2, is the focal length of the third lens 3, is the focal length of the ninth lens 9. The ultra-short-throw optical system can work without losing focus when the ambient temperature is 35°C by matching this focal length.

[0046] Specifically, in order to allow optical components to improve the image quality of the ultra-short-focus optical system, reduce light energy loss, increase imaging clarity, protect the scale surface, and further optimize the processing flow to meet design requirements, in this embodiment, the seventh lens 7 and the eighth lens 8 are cemented together to form a cemented lens. By rationally using the cemented components and appropriately distributing the optical power, combined with the thermal parameters of the glass material, aberrations are well corrected and the high and low temperature athermal effect is achieved, while also achieving a clear effect.

[0047] Furthermore, in this embodiment, the ultra-short-throw optical system further includes an aperture 13, which is disposed between the sixth lens 6 and the seventh lens 7. The aperture 13 limits the aperture of the on-axis light beam and blocks some light during the zooming process, thereby reducing light spots, increasing image contrast, and helping to improve image quality.

[0048] Furthermore, in this embodiment, the ultra-short-focus optical system further includes a protective glass disposed between the equivalent prism 11 and the photosensitive chip 12. The protective glass can provide effective protection for the photosensitive chip 12IMAGE and can be configured as a filter. The filter can effectively filter out stray light in non-operating bands to reduce optical noise, thereby easing difficulties in subsequent photoelectric module processing and improving imaging quality.

[0049] Specifically, the surface of the photosensitive chip 12 facing the object side is the imaging surface, that is, it can be the surface of a camera element such as a CCD or CMOS. It can be understood that the light carrying information of the object can pass through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, the tenth lens 10 and the equivalent prism 11 in sequence, and finally form an image on the imaging surface.

[0050] Specifically, the following case shows the actual design parameters of a projection lens with an optical total length of 51mm and a throw ratio of 0.55 for an ultra-short-throw optical system. The material refractive index, curvature radius, and thickness interval of the lens are shown in Table 1 below:

[0051] Table 1

[0052]

[0053]

[0054] Furthermore, in this embodiment, the aspheric surface shape of the aspheric lens satisfies the following conditions:

[0055]

[0056] 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 (when the k coefficient is less than -1, the surface curve is a hyperbola, when the k coefficient is equal to -1, it is a parabola, when the k coefficient is between -1 and 0, it is an ellipse, when the k coefficient is equal to 0, it is a circle, and when the k coefficient is greater than 0, it is an oblate circle, and a1 to a8 represent the coefficients corresponding to each radial coordinate.) Please refer to Tables 2 to 9 below. The above parameters can be used to set the shape and dimensions of the lens object side and image side aspheric surfaces.

[0057] Table 2 Conic coefficients and aspheric coefficients corresponding to the surface of the first lens S1:

[0058]

[0059]

[0060] Table 3 Conic coefficients and aspheric coefficients corresponding to the surface of the first lens S2:

[0061] S2 k -0.9139382 a1 0 a2 -0.00034099915 a3 5.021952e-006 a4 -7.2348642e-008 a5 3.4398043e-010 a6 2.0384992e-012 a7 -2.8138341e-014 a8 8.4269835e-017

[0062] Table 4 Conic coefficients and aspheric coefficients corresponding to the surface of the second lens S3:

[0063] S3 k -0.9311752 a1 0 a2 -0.0001552319 a3 3.5026444e-005 a4 -1.3386331e-006 a5 2.2736863e-008 a6 -1.9956869e-010 a7 8.8440302e-013 a8 -1.553883e-015

[0064] Table 5 Conic coefficients and aspheric coefficients corresponding to the surface of the second lens S4:

[0065]

[0066]

[0067] Table 6 Conic coefficients and aspheric coefficients corresponding to the surface of the third lens S5:

[0068] S5 k -0.9980686 a1 0 a2 0.0012419735 a3 1.1893081e-005 a4 1.2167983e-006 a5 -1.8950758e-007 a6 6.3423128e-009 a7 -8.7135145e-011 a8 4.6523548e-013

[0069] Table 7 Conic coefficients and aspheric coefficients corresponding to the surface of the third lens S6:

[0070] S6 k -1.163029 a1 0 a2 0.0012419735 a3 1.1893081e-005 a4 1.2167983e-006 a5 -1.8950758e-007 a6 6.3423128e-009 a7 -8.7135145e-011 a8 4.6523548e-013

[0071] Table 8 Conic coefficients and aspheric coefficients corresponding to the surface of the ninth lens S17:

[0072]

[0073]

[0074] Table 9 Conic coefficients and aspheric coefficients corresponding to the surface of the ninth lens S18:

[0075]

[0076] Figure 2 The MTF curve of the ultra-short focus optical system at room temperature of 25°C is shown. Figure 3 The MTF curve of the ultra-short focus optical system at a high temperature of 80°C is shown. Figure 4 The distortion diagram and field curvature diagram of the ultra-short focus optical system are displayed.

[0077] As can be seen from the above figures, the spherical aberration, field curvature and distortion of the ultra-short focus optical system in this embodiment can all be well corrected.

[0078] In summary, the total optical length of the ultra-short-focus optical system is controlled within 51 mm, the volume is small, and the projection ratio can reach 0.55.

[0079] The present invention also provides a projection device, which includes the ultra-short-focus optical system described in the above technical solution. The specific structure of the ultra-short-focus optical system refers to the above embodiment. Since the ultra-short-focus optical system of this ultra-short-focus optical system 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, which will not be repeated here.

[0080] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive 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. An ultra-short focus optical system, characterized in that: The ultra-short-focus optical system has an object side and an image side arranged opposite to each other along the optical axis. The ultra-short-focus optical system includes a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, a ninth lens with positive optical power, a tenth lens with positive optical power, an equivalent prism, and a photosensitive chip. The first lens, the second lens, the third lens, and the ninth lens are all plastic lenses. The total optical length TTL of the ultra-short-focus optical system is ≤51 mm, and the throw ratio can reach 0.

55. The first lens, the second lens, the third lens, the fourth lens, and the ninth lens are aspherical lenses; The fifth lens, the sixth lens, the seventh lens, the eighth lens and the tenth lens are all spherical lenses; The ultra-short focus optical system also meets the following conditions: 0.06<|φ1|<0.08, and 0.02<|φ2|<0.03, and 0.03<|φ3|<0.04, and 0.08<|φ4|<0.09, 0.09<φ5<0.1, and 0.09<φ6<0.1, and -0.09<φ7+φ8<-0.08, and 0.03<φ9<0.05, 0.09<φ10<0.1; Among them, φ1 is the optical focal power of the first lens, φ2 is the optical focal power of the second lens, φ3 is the optical focal power of the third lens, φ4 is the optical focal power of the fourth lens, φ5 is the optical focal power of the fifth lens, φ6 is the optical focal power of the sixth lens, φ7 is the optical focal power of the seventh lens, φ8 is the optical focal power of the eighth lens, φ9 is the optical focal power of the ninth lens, and φ10 is the optical focal power of the tenth lens.

2. The ultra-short focus optical system according to claim 1, wherein: The fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the tenth lens are all glass lenses.

3. The ultra-short focus optical system according to claim 1, wherein: The ultra-short focus optical system also satisfies the following conditions: 3<|(φ1+φ2+φ3) / φ9|<4; Wherein, φ1 is the optical power of the first lens, φ2 is the optical power of the second lens, φ3 is the optical power of the third lens, and φ9 is the optical power of the ninth lens.

4. The ultra-short focus optical system according to claim 1, wherein: The seventh lens and the eighth lens are cemented together to form a cemented lens.

5. The ultra-short focus optical system according to claim 1, wherein: The ultra-short focus optical system also satisfies the following conditions: 4<T1 / T2<5; Among them, T1 is the center distance between the first lens and the tenth lens in the direction of the optical axis, and T2 is the center distance between the tenth lens and the photosensitive chip in the direction of the optical axis.

6. The ultra-short focus optical system according to claim 1, wherein: The ultra-short focus optical system further includes a stop, which is disposed between the sixth lens and the seventh lens.

7. The ultra-short focus optical system according to claim 1, wherein: The ultra-short focus optical system further includes a protective glass, which is arranged between the equivalent prism and the photosensitive chip.

8. A projection device, characterized in that: The ultra-short focus optical system according to any one of claims 1 to 7.

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