Ultra-short-throw projection optical system and projection equipment

Abstract

The present invention discloses an ultra-short-throw projection optical system, comprising a display unit arranged in sequence along a projection direction, a first lens group with positive focal power, a second lens group with positive focal power, a third lens group with negative focal power, and an aspherical reflector, wherein the first lens group comprises a first lens, a second lens, and an aperture arranged in sequence along the projection direction, the first lens is a glass aspherical lens, the second lens is a glass spherical lens, and the first lens and the second lens are respectively bent from their center to their periphery in a direction gradually toward the aperture. The ultra-short-throw projection optical system and projection equipment provided by the present invention can achieve the requirements of a large aperture while having the advantages of high resolution.

Description

Technical Field

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

[0002] With the development of projection technology in recent years, projection equipment has been widely used in home, education, office and other fields. Among them, ultra-short-throw projectors are favored because they can project large images at a short distance and can be better used in compact space environments. As the core component of ultra-short-throw projectors, ultra-short-throw projection optical systems are relatively expensive. In order to reduce costs, the aperture value of existing ultra-short-throw projection optical systems is generally above 2.5, and the aperture is small. Summary of the invention

[0003] The main purpose of the present invention is to provide an ultra-short-throw projection optical system and a projection device, aiming to solve the problem of small aperture of the existing ultra-short-throw projection optical system.

[0004] To achieve the above-mentioned object, the present invention proposes an ultra-short-throw projection optical system, comprising a display unit, a first lens group with positive optical power, a second lens group with positive optical power, a third lens group with negative optical power, and an aspherical reflector, which are sequentially arranged along a projection direction;

[0005] Among them, the first lens group includes a first lens, a second lens and an aperture arranged in sequence along the projection direction, the first lens is a glass aspherical lens, the second lens is a glass spherical lens, and the first lens and the second lens are respectively bent gradually toward the aperture from their center to their periphery.

[0006] Optionally, both the second lens group and the third lens group can be movably arranged to approach and move away from the display unit along the projection direction.

[0007] Optionally, a linkage member is further included, and the linkage member connects the second lens group and the third lens group respectively.

[0008] Optionally, the second lens group includes a third lens, and the third lens is a plastic aspherical lens.

[0009] Optionally, the optical power of the first lens group is set to φ1, 0.04≤φ1≤0.06;

[0010] The optical power of the second lens group is set to φ2, 0≤φ2≤0.01;

[0011] The focal power of the third lens group is set to φ3, -0.04≤φ3≤0;

[0012] The optical power of the aspherical reflector is set to φ4, 0.06≤φ4≤0.09.

[0013] Optionally, the third lens group includes a fourth lens and a fifth lens sequentially arranged along the projection direction, and the fourth lens and the fifth lens are plastic aspherical lenses.

[0014] Optionally, the optical power of the fourth lens is greater than or equal to -0.05 and less than or equal to 0;

[0015] The optical power of the fifth lens is greater than or equal to 0 and less than or equal to 0.04.

[0016] Optionally, an optical axis is formed in the ultra-short-throw projection optical system;

[0017] The display unit includes a digital micromirror device, and the offset between the center of the digital micromirror device and the optical axis is C, 2.6mm≤C≤3mm.

[0018] Optionally, the first lens group further includes a cemented lens, the cemented lens is located on a side of the first lens away from the second lens, and the cemented lens includes a sixth lens and a seventh lens that are cemented together.

[0019] The present invention also provides a projection device, comprising the above-mentioned ultra-short-throw projection optical system, wherein the ultra-short-throw projection optical system comprises a display unit, a first lens group with positive optical power, a second lens group with positive optical power, a third lens group with negative optical power, and an aspherical reflector, which are sequentially arranged along a projection direction;

[0020] Among them, the first lens group includes a first lens, a second lens and an aperture arranged in sequence along the projection direction, the first lens is a glass aspherical lens, the second lens is a glass spherical lens, and the first lens and the second lens are respectively bent gradually toward the aperture from their center to their periphery.

[0021] In the technical solution of the present invention, the projection light is transmitted sequentially through the first lens group with positive focal power, the second lens group with positive focal power, and the third lens group with negative focal power. At the same time, the first lens of the glass aspherical lens is matched with the second lens of the glass spherical lens, and the first lens and the second lens are respectively bent gradually toward the aperture from the center to the periphery, which effectively corrects the spherical aberration and coma generated by the aperture, improves the height of the rear group of light, and has the advantage of high resolution while achieving the requirement of large aperture. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0023] Figure 1 A schematic diagram of an embodiment of an ultra-short-throw projection optical system provided by the present invention;

[0024] Figure 2 for Figure 1 Schematic diagram of the projection light path of the medium and ultra-short-throw projection optical system;

[0025] Figure 3 for Figure 1 Schematic diagram of the mirror surfaces of each lens in the ultra-short-throw projection optical system.

[0026] Description of Figure Numbers:

[0027] Label name Label name 100 Ultra short throw projection optical system 27 Twelfth lens 1 Display unit 3 Second lens group 11 DMD Chip 31 The third lens 12 Equivalent prism 4 The third lens group 2 First lens group 41 The fourth lens 21 First lens 42 Fifth lens 22 Second lens 43 The eighth lens 23 Aperture 44 The ninth lens 24 The sixth lens 45 Tenth lens 25 Seventh lens 5 Aspheric Mirrors 26 Eleventh lens

[0028] 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

[0029] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0030] 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 under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] 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 used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. 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 the field to implement. When the combination of technical solutions is 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.

[0032] With the development of projection technology in recent years, projection equipment has been widely used in home, education, office and other fields. Among them, ultra-short-throw projectors are favored because they can project large images at a short distance and can be better used in compact space environments. As the core component of ultra-short-throw projectors, ultra-short-throw projection optical systems are relatively expensive. In order to reduce costs, the aperture value of existing ultra-short-throw projection optical systems is generally above 2.5, and the aperture is small.

[0033] In view of this, the present invention provides an ultra-short-throw projection optical system. Figures 1 to 3 This is an embodiment of the ultra-short-throw projection optical system provided by the present invention.

[0034] Please refer to Figure 1 and Figure 2 The ultra-short-throw projection optical system 100 includes a display unit 1, a first lens group 2 with positive optical power, a second lens group 3 with positive optical power, a third lens group 4 with negative optical power, and an aspherical reflector 5, which are sequentially arranged along a projection direction, wherein the first lens group 2 includes a first lens 21, a second lens 22, and an aperture 23, which are sequentially arranged along the projection direction, the first lens 21 is a glass aspherical lens, the second lens 22 is a glass spherical lens, and the first lens 21 and the second lens 22 are respectively bent gradually toward the aperture 23 from the center to the periphery.

[0035] In the technical solution of the present invention, the projection light is transmitted sequentially through the first lens group 2 with positive focal power, the second lens group 3 with positive focal power, and the third lens group 4 with negative focal power. At the same time, the first lens 21 of the glass aspherical lens is matched with the second lens 22 of the glass spherical lens, and the first lens 21 and the second lens 22 are respectively bent gradually toward the aperture 23 from the center to the periphery, effectively correcting the spherical aberration and coma generated by the aperture 23, and improving the height of the rear group of light, while achieving the requirement of large aperture and having the advantage of high resolution.

[0036] It should be emphasized that the present invention does not limit the specific curvature of the first lens 21 and the second lens 22, as long as the spherical aberration and coma generated by the aperture 23 can be effectively corrected. Figure 1 In this embodiment, the curvature of the light emitting surface (the side close to the aspheric reflector 5) of the first lens 21 is greater than the curvature of the light incident surface (the side close to the display unit 1), and the curvature of the light incident surface of the second lens 22 is greater than the curvature of the light emitting surface.

[0037] It can be understood that the focal power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, and it characterizes the ability of an optical element to deflect light. When the focal power is a positive number, the refraction of light is convergent; when the focal power is a negative number, the refraction of light is divergent. The focal power can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group).

[0038] Furthermore, the second lens group 3 and the third lens group 4 can be movably arranged to move closer to and away from the display unit 1 along the projection direction. The focusing of the ultra-short-focus projection optical system 100 is achieved through the movement of the second lens group 3 and the third lens group 4, which helps to improve the optical performance of the ultra-short-focus projection optical system 100.

[0039] It should be noted that the present invention does not limit the specific movement mode of the second lens group 3 and the third lens group 4. The second lens group 3 and the third lens group 4 may be moved independently, or the second lens group 3 and the third lens group 4 may be arranged in linkage. Figure 1 In this embodiment, the ultra-short-throw projection optical system 100 further includes a linkage member (not shown in the figure), and the linkage member is respectively connected to the second lens group 3 and the third lens group 4. The second lens group 3 and the third lens group 4 are driven by the linkage member to adjust their positions according to a certain proportional relationship, thereby realizing linkage focusing. The distortion and resolution correction of different pictures of 70 inches to 120 inches can be realized through linkage focusing.

[0040] The present invention does not limit the specific implementation of the linkage member, which may be a screw structure or a gear structure, or other structures that realize the linkage between the second lens group 3 and the third lens group 4, which will not be described one by one here.

[0041] In addition, the second lens group 3 includes a third lens 31, and the third lens 31 is a plastic aspherical lens. The third lens 31 is a plastic aspherical lens. Combined with the third lens group 4, the effect of correcting the distortion and resolution of different screen sizes of 70 inches to 120 inches is further improved.

[0042] Furthermore, the focal power of the first lens group 2 is set to φ1, 0.04≤φ1≤0.06; the focal power of the second lens group 3 is set to φ2, 0≤φ2≤0.01; the focal power of the third lens group 4 is set to φ3, -0.04≤φ3≤0; the focal power of the aspheric reflector 5 is set to φ4, 0.06≤φ4≤0.09. When the lens groups are allocated according to the above focal power, a projection ratio of less than 0.2 can be achieved, and there is no false focus at high temperature. At the same time, the sensitivity of each lens group is greatly reduced, which is convenient for mass production.

[0043] Furthermore, the third lens group 4 includes a fourth lens 41 and a fifth lens 42 sequentially arranged along the projection direction. The fourth lens 41 and the fifth lens 42 are plastic aspherical lenses, so that the incident angle of light can be effectively corrected and the size and cost of the lens can be reduced.

[0044] Furthermore, the optical focal length of the fourth lens 41 is greater than or equal to -0.05 and less than or equal to 0, and the optical focal length of the fifth lens 42 is greater than or equal to 0 and less than or equal to 0.04. By combining the optical focal lengths of the fourth lens 41 and the fifth lens 42, the lens can be automatically balanced under high temperature conditions to achieve non-false focus at high temperatures.

[0045] It should be noted that the third lens group 4 further includes an eighth lens 43, a ninth lens 44 and a tenth lens 45 which are sequentially arranged along the projection direction; the eighth lens 43, the ninth lens 44 and the tenth lens 45 are all located between the fourth lens 41 and the second lens group 3; the eighth lens 43, the ninth lens 44 and the tenth lens 45 are all glass spherical lenses; the optical focal lengths of the eighth lens 43 and the tenth lens 45 are both greater than or equal to 0 and less than or equal to 0.04; and the optical focal length of the ninth lens 44 is greater than or equal to -0.05 and less than or equal to 0.

[0046] An optical axis is formed in the ultra-short-throw projection optical system 100, and the display unit 1 includes a digital micromirror device. The offset between the center of the digital micromirror device and the optical axis is C, and 2.6mm≤C≤3mm. This is conducive to improving the image clarity. For details, please refer to Figure 1 In this embodiment, the digital micromirror device is a DMD (Digital Micromirror Device) chip, the center of the DMD chip 11 is offset from the optical axis by 2.8 mm, the DMD chip 11 is 0.33 inches, its resolution is 1368x768, and it can achieve 1080P through a galvanometer.

[0047] The display unit 1 further includes an equivalent prism 12 , which is disposed between the DMD chip 11 and the first lens group 2 , and can reduce aberrations caused by light refraction and transmission.

[0048] The first lens group 2 also includes a cemented lens, which is located on the side of the first lens 21 away from the second lens 22. The cemented lens includes a sixth lens 24 and a seventh lens 25 that are cemented together, which helps to eliminate chromatic aberration. It can be understood that chromatic aberration will be formed after light passes through the lens, making the image blurry. Therefore, chromatic aberration has become a serious defect of lens imaging. The cemented lens is a lens that is glued together. When light passes through one of the lenses of the cemented lens and is refracted, chromatic aberration will be generated. When the refracted light continues to pass through the other lens, the chromatic aberration generated is exactly the opposite and can offset the chromatic aberration that occurred before, thereby achieving the purpose of eliminating chromatic aberration.

[0049] Specifically, the gluing connection between the sixth lens 24 and the seventh lens 25 is achieved by optical glue, and the optical glue has high light transmittance, which helps to improve the imaging effect of the projected light.

[0050] It should be noted that the first lens group 2 also includes an eleventh lens 26 and a twelfth lens 27 arranged in sequence along the projection direction, the eleventh lens 26 and the twelfth lens 27 are both located between the sixth lens 24 and the display unit 1, the eleventh lens 26 and the twelfth lens 27 are both glass spherical lenses, and the optical focal power of the eleventh lens 26 and the optical focal power of the twelfth lens 27 are both greater than or equal to 0 and less than or equal to 0.04.

[0051] It should be noted that the aspheric surface shapes of the first lens 21, the third lens 31, the fourth lens 41, the fifth lens 42 and the aspheric reflector 5 satisfy the equation:

[0052]

[0053] In the above equation, parameter c is the curvature corresponding to the radius, y is the radial coordinate whose unit is the same as the unit of the lens length, and k is the coefficient of the conic quadratic curve; when the k coefficient is less than -1, the surface curve of the lens is a hyperbola; when the k coefficient is equal to -1, the surface curve of the lens is a parabola; when the k coefficient is between -1 and 0, the surface curve of the lens is an ellipse, when the k coefficient is equal to 0, the surface curve of the lens is a circle, and when the k coefficient is greater than 0, the surface curve of the lens is an oblate circle; a1 to a8 respectively represent the coefficients corresponding to each radial coordinate.

[0054] The following case shows actual design parameters of an ultra-short-throw projection optical system 100 with a F1.8 and a projection ratio of 0.2. Please refer to Table 1 for details.

[0055] Table 1 Parameters of the ultra-short-throw projection optical system 100

[0056]

[0057]

[0058] Among them, OBJ is the object plane, IMA is the image plane, S26 is the light exit surface of the equivalent prism 12, S27 is the light entrance surface of the equivalent prism 12, S1 to S25 are the mirror surfaces of each lens respectively. For the specific reference of S1 to S25 to the mirror surface, please refer to Figure 3 .

[0059] In addition, the S1 coefficient is:

[0060] k: -768;

[0061] a1: 0;

[0062] a20.00011485935;

[0063] a3: -5.3053334e-007;

[0064] a4: 2.126744e-009;

[0065] a5: -5.4787393e-012;

[0066] a6: 8.0470803e-015;

[0067] a7: -4.9662071e-018.

[0068] The S2 coefficient is:

[0069] k: -565.9319;

[0070] a1: 0;

[0071] a2: -4.6842153e-006;

[0072] a3: 1.3583932e-008;

[0073] a4: 2.96366079486753e-012;

[0074] a5: 2.35668648024052e-015;

[0075] a6: -1.7709563837241e-019;

[0076] a7: -6.05918030192083e-022.

[0077] The coefficient of S3 is:

[0078] k: -565.9319;

[0079] a1: 0;

[0080] a2: -4.6842153e-006;

[0081] a3: 1.3583932e-008;

[0082] a4: 2.96366079486753e-012;

[0083] a5: 2.35668648024052e-015;

[0084] a6: -1.7709563837241e-019;

[0085] a7: -6.05918030192083e-022.

[0086] The coefficient of S4 is:

[0087] k: -0.4040741;

[0088] a1: 0;

[0089] a2: 4.90490480030574e-007;

[0090] a3: -2.05760498407608e-010;

[0091] a4: 2.99679825125034e-014;

[0092] a5: 5.55711304020551e-018;

[0093] a6:-2.86845642405709e-021;

[0094] a7: 2.91053534222281e-025.

[0095] The S5 coefficient is:

[0096] k: 90.3686;

[0097] a1: 0;

[0098] a2: 3.37355419190151e-008;

[0099] a3:-1.68426620586378e-010;

[0100] a4:-1.77578855135222e-011;

[0101] a5: 1.31858269908392e-013;

[0102] a6: 1.61679421023673e-016;

[0103] a7:-3.13849187032395e-018.

[0104] The S12 coefficient is:

[0105] k: -1.3840751;

[0106] a1: 0;

[0107] a2:-2.79361010729748e-008;

[0108] a3: -6.6497057344366e-010;

[0109] a4:-2.54430577284334e-013;

[0110] a5:-1.84664483140541e-015;

[0111] a6: 6.46082131490784e-017;

[0112] a7:-1.54392143969012e-019.

[0113] The S13 coefficient is:

[0114] k: -25.2567;

[0115] a1: 0;

[0116] a2: 4.90490480030574e-007;

[0117] a3:-3.94843412007971e-010;

[0118] a4: 3.02112629843759e-013;

[0119] a5: 1.40840432176276e-015;

[0120] a6: 6.90569325719901e-019;

[0121] a7:-6.52550386131808e-021.

[0122] The S18 coefficient is:

[0123] k: -12.457;

[0124] a1: 0;

[0125] a2: 4.904900574e-007;

[0126] a3: -2.05760908e-010;

[0127] a4: 2.99679824e-014;

[0128] a5: -7.4255518e-16;

[0129] a6: 1.3859057e-18;

[0130] a7: 1.8118184e-23.

[0131] The S19 coefficient is:

[0132] k: -1.4040741;

[0133] a1: 0;

[0134] a2: -5.2362612e-06;

[0135] a3: -2.057608e-010;

[0136] a4: 2.9244063e-09;

[0137] a5: 5.5046807e-16;

[0138] a6: 5.5046807e-16;

[0139] a7: 4.8296771e-18.

[0140] The present invention achieves a projection ratio of less than 0.20 and an aperture of 1.8 by adopting three plastic aspheric lenses (a third lens 31, a fourth lens 41 and a fifth lens 42), thereby meeting the requirements of high resolution and high brightness while ensuring low cost. By reasonably allocating the lens focal length, the ultra-short focus projection optical system 100 can balance the focus deviation of each lens under high temperature conditions when three plastic aspheric lenses are adopted, thereby achieving no false focus under high temperature conditions. By reasonably arranging the lens structure, the second lens group 3 and the third lens group 4 can correct the field curvature and distortion under different projection sizes, so that the projection picture can still maintain high resolution between 70 inches and 120 inches.

[0141] The present invention also provides a projection device, including the above-mentioned ultra-short-focus projection optical system 100. The projection device includes all the technical features of the above-mentioned ultra-short-focus projection optical system 100, and therefore also has the technical effects brought by all the above-mentioned technical features, which will not be described one by one here.

[0142] 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 changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An ultra-short-throw projection optical system, characterized in that: The device comprises a display unit, a first lens group with positive optical power, a second lens group with positive optical power, a third lens group with negative optical power and an aspherical reflector which are sequentially arranged along a projection direction; Wherein, the first lens group comprises a first lens, a second lens and an aperture sequentially arranged along the projection direction, the first lens is a glass aspherical lens, the second lens is a glass spherical lens, and the first lens and the second lens are both concave-convex lenses, and the light incident surfaces thereof are convex surfaces, the curvature of the light exiting surface of the first lens is greater than the curvature of the light incident surface, the curvature of the light incident surface of the second lens is greater than the curvature of the light exiting surface, the light incident surface is a side close to the display unit, and the light exiting surface is a side close to the aspherical reflector; The first lens group further includes an eleventh lens, a twelfth lens, a sixth lens and a seventh lens sequentially arranged along the projection direction, the eleventh lens, the twelfth lens, the sixth lens and the seventh lens are all located between the first lens and the display unit, and the optical power of the eleventh lens and the twelfth lens is positive; The second lens group includes a third lens of positive optical power; The third lens group includes an eighth lens, a ninth lens, a tenth lens, a fourth lens and a fifth lens arranged in sequence along the projection direction, the fifth lens, the eighth lens and the tenth lens have positive focal powers, and the fourth lens and the ninth lens have negative focal powers; The second lens group and the third lens group can be movably arranged to approach and move away from the display unit along the projection direction.

2. The ultra-short-throw projection optical system according to claim 1, characterized in that: It also includes linkage parts, which respectively connect the second lens group and the third lens group.

3. The ultra-short-throw projection optical system according to claim 1, wherein: The third lens is a plastic aspherical lens.

4. The ultra-short-throw projection optical system according to claim 1, wherein: The optical power of the first lens group is set to φ1, 0.04≤φ1≤0.06; The optical power of the second lens group is set to φ2, 0<φ2≤0.01; The focal power of the third lens group is set to φ3, -0.04≤φ3<0; The optical power of the aspherical reflector is set to φ4, 0.06≤φ4≤0.

09.

5. The ultra-short-throw projection optical system according to claim 1, wherein: The fourth lens and the fifth lens are plastic aspherical lenses.

6. The ultra-short-throw projection optical system according to claim 1, wherein: The refractive power of the fourth lens is greater than or equal to -0.05 and less than 0; The optical power of the fifth lens is greater than 0 and less than or equal to 0.

04.

7. The ultra-short-throw projection optical system according to claim 1, wherein: An optical axis is formed in the ultra-short-throw projection optical system; The display unit includes a digital micromirror device, and the offset between the center of the digital micromirror device and the optical axis is C, 2.6mm≤C≤3mm.

8. The ultra-short-throw projection optical system according to claim 1, wherein: The sixth lens and the seventh lens are cemented and connected.

9. A projection device, characterized in that: Comprising the ultra-short focus projection optical system as described in any one of claims 1 to 8.

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