Zoom projection lens, projection system and use method

Abstract

The invention relates to the technical field of projection imaging, and discloses a zoom projection lens, a projection system and a use method, the zoom projection lens comprises a plurality of lens groups which are coaxially arranged, and the lens groups at least comprise first to sixth groups along the direction from the image side to the object side; the equivalent focal lengths of the lens groups from the image side to the object side are F1 to F6 in sequence, and each equivalent focal length meets a specific range; the second group at least comprises a triplet lens, and the triplet lens sequentially comprises a first lens to a third lens along the direction from the image side to the object side; the first lens, the second lens and the third lens have negative focal power, positive focal power and negative focal power respectively; the fifth group at least comprises a doublet lens, and the doublet lens sequentially comprises a fourth lens and a fifth lens along the direction from the image side to the object side; the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens. The method has the advantages that secondary focusing is avoided for compensation, and the use complexity is reduced.

Description

Technical Field

[0001] The present invention relates to the field of projection imaging technology, and in particular to a zoom projection lens, a projection system and a use method thereof. Background Art

[0002] At present, projection display has been gradually applied to various fields such as education, family, military, transportation, office, etc. The products currently on the market require secondary focusing to achieve clear imaging when zooming is required, and the imaging effect is poor. In addition, there is a large distortion problem during the imaging process, and the image cannot be restored well.

[0003] In addition, the projection display market is vast, but as one of the core technologies in projection display, the lens is difficult to design and process, especially taking into account both cost and miniaturization while ensuring image quality, which is a major difficulty in lens design. In order to further improve product performance, such as product resolution, designing a lens that provides clear images during zoom imaging has become a major difficulty in further improving product performance.

[0004] Therefore, it is urgent to develop a zoom projection lens to solve the above problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a zoom projection lens, a projection system and a use method, which avoids secondary focusing compensation and reduces the complexity of use.

[0006] In a first aspect, the present invention provides a zoom projection lens, comprising: A plurality of lens groups arranged coaxially, wherein the lens groups include at least a first group, a second group, a third group, a fourth group, a fifth group and a sixth group along a direction from an image side to an object side; The equivalent focal length of the first group is F1, the equivalent focal length of the second group is F2, the equivalent focal length of the third group is F3, the equivalent focal length of the fourth group is F4, the equivalent focal length of the fifth group is F5, the equivalent focal length of the sixth group is F6, and the equivalent focal length of the projection lens is F; wherein, 3.5<|F1 / F|<6; 10<|F2 / F|<20; 1<|F3 / F|<4; 2<|F4 / F|<10; 1<|F5 / F|<4; 0<|F6 / F|<2; The second group includes at least three cemented lenses, and the three cemented lenses include a first lens, a second lens and a third lens in sequence from the image side to the object side; the first lens has a negative optical power, the second lens has a positive optical power, and the third lens has a negative optical power; The fifth group includes at least a doublet lens, and the doublet lens includes a fourth lens and a fifth lens in sequence from the image side to the object side; the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens.

[0007] Furthermore, the second group further includes an aspheric lens, and the aspheric lens is located on the image side of the triplet lens. A stop is fixed on the image side of the third group.

[0008] Furthermore, the sixth group includes two plastic aspherical lenses, and the positions of the two plastic aspherical lenses are fixed or movable.

[0009] Furthermore, the Abbe numbers of the first lens and the third lens are both smaller than the Abbe number of the second lens.

[0010] Furthermore, the refractive indexes of the first lens and the third lens are both greater than the refractive index of the second lens.

[0011] Furthermore, the center thickness of the first lens and the third lens ranges from 0.5 mm to 2 mm.

[0012] Furthermore, the dispersion coefficient of the fourth lens is less than 50, and the dispersion coefficient of the fifth lens is greater than 50.

[0013] In a second aspect, the present invention provides a zoom projection system, comprising: a zoom projection lens as described in the first aspect; and an image polarizer, a prism and a light valve arranged in sequence on the image side of the zoom projection lens.

[0014] Furthermore, the distance between the vertex of the surface of the image side lens of the projection lens farthest from the light valve and the light valve is BFL, and the farthest distance between the vertex of the image side lens surface and the vertex of the object side lens surface of the projection lens is L; wherein 0<BFL / L<0.5.

[0015] In a third aspect, the present invention provides a method for using a zoom projection system, comprising the following contents: S1, placing the projection system, and adjusting the positions of the lens groups in the projection system so that the lens groups are relatively displaced from each other; S2. When the resolution of the projection image meets the requirement, the positions of the first group and the sixth group are fixed; S3, adjusting the positions of the second group, the third group, the fourth group and the fifth group so that when the projection size meets the requirements, the positions of the lens groups are fixed.

[0016] The embodiments of the present invention have the following technical effects: The present application sets at least six lens groups. First, by setting the equivalent focal length of each group, the purpose of zooming can be achieved. By setting the Abbe number, focal length, refractive index, etc. of the doublet and triplet lenses, the imaging resolution can be adjusted by adjusting the position of each lens group. By controlling the displacement of the second to fifth groups, the magnification can be changed. The image clarity is high in the whole process, and secondary focusing compensation is avoided, which reduces the complexity of use. This application utilizes the advantages of each aspherical lens to ensure that the aspherical surface can solve the problem of unclear imaging caused by focal plane offset during zooming to the greatest extent, and effectively reduces the offset of the optimal focal plane; this application uses 3 aspherical lenses, reduces the use of aspherical lenses, reduces production costs, reduces the overall complexity of the system, and improves the performance of the zoom projection lens The present application ensures that the total optical length is within a relatively small range and reduces the volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a schematic structural diagram of a zoom projection system provided by an embodiment of the present invention; Figure 2 : is a schematic diagram of TV distortion provided by an embodiment of the present invention. In the left coordinate system, the horizontal coordinate represents the magnitude of field curvature, in units of mm, and the vertical coordinate represents the normalized image height; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion, in units of %, and the vertical coordinate represents the normalized image height; Figure 3 is a diagram of light spots under different field of view conditions on an imaging screen provided by an embodiment of the present invention; Figure 4 It is a light fan diagram provided by an embodiment of the present invention; 11 pairs of graphs respectively represent 11 normalized fields of view, and the two graphs in each field of view respectively represent the aberrations in the x-axis direction and the y-axis direction symmetrical with the optical axis as the center of the optical system; the horizontal axis direction in each graph is the pupil height position under the field of view condition, and the vertical axis direction is the error between the light of each wavelength and the main light.

[0019] In the figure, 1 is the first group; 2 is the second group; 3 is the third group; 4 is the fourth group; 5 is the fifth group; 6 is the sixth group; 7 is the aperture; 8 is the image polarizer; 9 is the prism; 10 is the light valve; L1 is the first lens; L2 is the second lens; L3 is the third lens; L4 is the fourth lens; L5 is the fifth lens; L6 is the sixth lens; L7 is the seventh lens; L8 is the eighth lens; L9 is the ninth lens; L10 is the tenth lens; L11 is the eleventh lens; L12 is the twelfth lens; L13 is the thirteenth lens. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. 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 belong to the scope of protection of the present invention. Example 1

[0021] The embodiment of the present invention provides a zoom projection lens, see Figure 1 ,include: A plurality of lens groups arranged coaxially, wherein the lens groups include at least a first group 1, a second group 2, a third group 3, a fourth group 4, a fifth group 5 and a sixth group 6 along a direction from an image side to an object side; An aperture 7 is fixed on the image side of the third group 3; the aperture 7 is fixed on the image side of the third group 3 and moves with the movement of the third group 3, which can improve the coma problem of the system; The equivalent focal length of the first group 1 is F1, the equivalent focal length of the second group 2 is F2, the equivalent focal length of the third group 3 is F3, the equivalent focal length of the fourth group 4 is F4, the equivalent focal length of the fifth group 5 is F5, and the equivalent focal length of the sixth group 6 is F6. The equivalent focal length of the projection lens is F; wherein, 3.5<|F1 / F|<6; 10<|F2 / F|<20; 1<|F3 / F|<4; 2<|F4 / F|<10; 1<|F5 / F|<4; 0<|F6 / F|<2; the present application does not make specific settings for the first group 1, the third group 3, the fourth group 4 and the sixth group 6, and each lens group can meet the corresponding equivalent focal length range. The focal length is limited, and different focal lengths are matched with different distances between lenses in actual use to achieve the purpose of zooming.

[0022] The first group 1, the third group 3, the fourth group 4, and the sixth group 6 are described as follows: Exemplarily, the first group 1 includes a glass lens for preliminarily deflecting incident light to prevent the light from being subsequently transmitted at an excessively large angle, thereby affecting the projection effect.

[0023] The third group 3 and the fourth group 4 are used to adjust the focal length, and only one lens may be provided for each group, so as to reduce the length of the optical system to the greatest extent, and at the same time reduce the cost and the production complexity.

[0024] The sixth group 6 includes two plastic aspheric lenses, and the position between the two plastic aspheric lenses is fixed or movable. The sixth group 6 is used to correct distortion. If the position between the two plastic aspheric lenses is fixed, the system structure can be simplified; if the distance between the two plastic spherical lenses is adjustable, the distortion compensation can be effectively achieved. After such a setting, the plastic aspheric lenses far away from the fifth group 5 can be regarded as the seventh group alone.

[0025] The second group 2 and the fifth group 5 are described in detail below: The second group 2 includes at least three cemented lenses, and the three cemented lenses include a first lens L1, a second lens L2 and a third lens L3 in order from the image side to the object side; the first lens L1 has a negative optical power, the second lens L2 has a positive optical power, and the third lens L3 has a negative optical power; the Abbe numbers of the first lens L1 and the third lens L3 are greater than the Abbe number of the second lens L2; The triplet lens is one of the core components of the projection lens of this application. Its main function is to perform aberration correction and achieve an effective balance between aberration, temperature drift and processability. The specific settings are as follows: The triplet lens is used to correct chromatic aberration and balance the system temperature, so the materials with large differences in Abbe numbers should be selected for each lens. The Abbe numbers of the first lens L1 and the third lens L3 are both smaller than the Abbe number of the second lens L2. For example, the Abbe number of the second lens L2 ranges from 60 to 90, such as 60 or 70 or 90, and the Abbe numbers of the first lens L1 and the third lens L3 range from 15 to 50, such as 15 or 30 or 50. This arrangement can effectively reduce the influence of thermal shrinkage and expansion of the material on the temperature drift of the system and improve the resolution of the lens.

[0026] The refractive indexes of the first lens L1 and the third lens L3 are both greater than the refractive index of the second lens L2, and the negative optical power of the first lens L1 and the third lens L3 is allocated, so that the low refractive index and positive optical power of the second lens L2 located in the middle are neutralized, thereby reducing aberrations such as spherical aberration, coma, and astigmatism of the overall lens.

[0027] Generally, the higher the refractive index is, the stronger the absorption of blue light is, and the lower the light transmittance is. Therefore, the center thickness of the first lens L1 and the third lens L3 needs to be set to avoid the reduction of transmittance as much as possible. Exemplarily, the center thickness of the first lens L1 and the third lens L3 ranges from 0.5 mm to 2 mm.

[0028] In addition, the second group 2 also includes an aspheric lens, which is located on the image side of the triplet lens. The arrangement of the aspheric lens is conducive to improving resolution and correcting image quality. It should be noted that the use of aspheric lenses should be minimized to reduce production costs and reduce the overall complexity of the system, thereby improving the performance of the zoom projection lens.

[0029] The fifth group 5 includes a doublet lens, and the doublet lens includes a fourth lens L4 and a fifth lens L5 in sequence from the image side to the object side; the fourth lens L4 is a biconcave lens, and the fifth lens L5 is a biconvex lens.

[0030] The double-cemented lens is also used to correct aberrations. The fourth lens L4 and the fifth lens L5 are set to be double concave and double convex respectively. During the zoom movement, no additional chromatic aberration will be generated to affect the performance of the overall system.

[0031] After the chromatic aberration is corrected by the three-cemented lens, when it reaches the fifth group 5, the chromatic aberration that needs to be corrected is smaller. Therefore, the doublet lens can be set with materials with relatively close Abbe numbers. Exemplarily, the dispersion coefficient of the fourth lens L4 is less than 50, and the dispersion coefficient of the fifth lens L5 is greater than 50. For example, the dispersion coefficients of the fourth lens L4 and the fifth lens L5 are 37.99 and 60.38 respectively.

[0032] In summary, doublet and triplet lenses play a key role in correcting the color aberration of the system during the zooming process, mainly correcting the axial chromatic aberration and vertical chromatic aberration of the optical lens.

[0033] In the present application, each lens group can be moved or fixed as required during zooming. Each lens group is designed with different displacement distances according to actual needs. For example, when the first group 1 moves 1mm, the second group 2 moves 1.5mm accordingly, and the third group 3 moves 0.5mm accordingly... The lens groups move relative to each other.

[0034] During specific use, the first group 1 and the sixth group 6 can be controlled to move or fix according to actual conditions; since the positions of the first group 1 and the sixth group 6 will affect the resolution of the imaging picture, the positions of the lens groups are adjusted at the same time to keep the resolution of the projection picture in a good state. At this time, the positions of the first group 1 and the sixth group 6 are fixed, and the size of the projection picture can be adjusted by adjusting the second group 2 to the fifth group 5, that is, a zoom operation is performed, and high-quality imaging can be achieved without secondary focusing, thereby reducing the complexity of the operation.

[0035] Based on the above technical solution, the present application sets at least six lens groups, sets the equivalent focal length of each group, and sets the Abbe number, refractive index, etc. of the double-cemented lens and the triple-cemented lens, so that the imaging resolution can be adjusted by adjusting the position of each lens group, and the magnification can be changed by controlling the displacement of the second to fifth groups. The image clarity is high in the whole process, and secondary focusing compensation is avoided, which reduces the complexity of use. This application utilizes the advantages of aspheric lenses, and guarantees to the greatest extent that the aspheric surface can solve the problem of unclear imaging caused by focal plane offset during zooming, and effectively reduces the offset of the optimal focal plane; this application uses three aspheric lenses, which reduces the use of aspheric lenses, reduces production costs, reduces the overall complexity of the system, and improves the performance of zoom projection lenses Example 2

[0036] Based on the content of Example 1, the present application provides a zoom projection system, including: A zoom projection lens in Example 1 and an image polarizer 8, a prism 9 and a light valve 10 are sequentially arranged on the image side of the zoom projection lens. The image polarizer 8, the prism 9 and the light valve 10 are all prior arts and will not be described in detail in this application.

[0037] In addition, to ensure that the total length of the optical system is short, the following settings are made: The distance between the vertex of the surface of the image side lens of the projection lens farthest from the light valve and the light valve is BFL, and the farthest distance between the vertex of the image side lens surface and the vertex of the object side lens surface of the projection lens is L; wherein 0<BFL / L<0.5.

[0038] For other contents, please refer to Example 1, and this application will not go into details. Example 3

[0039] Based on the contents of the foregoing embodiments, the present application provides a method for using a zoom projection system, comprising the following steps: S1, placing the projection system, and adjusting the positions of the lens groups in the projection system so that the lens groups are relatively displaced from each other; S2. When the resolution of the projection image meets the requirement, the positions of the first group 1 and the sixth group 6 are fixed; S3, adjusting the positions of the second group 2, the third group 3, the fourth group 4 and the fifth group 5 so that the projection size meets the requirements, and then fixing the positions of the lens groups. Example 4

[0040] Based on the above embodiments, this application provides a specific embodiment, see Figure 1 , there are 13 lenses in total, the first group 1 includes the sixth lens L6; The second group 2 includes a first lens L1, a second lens L2, a third lens L3, a seventh lens L7 and an eighth lens L8; wherein the first lens L1, the second lens L2 and the third lens L3 form a triplet lens; the eighth lens L8 is an aspherical lens; The third group 3 includes a ninth lens L9, and the positions of the aperture 7 and the ninth lens L9 are fixed; The fourth group 4 includes a tenth lens L10; The fifth group 5 includes a fourth lens L4, a fifth lens L5 and an eleventh lens L11; the fourth lens L4 and the fifth lens L5 form a doublet lens; The sixth group 6 includes a twelfth lens L12 and a thirteenth lens L13. Both the twelfth lens L12 and the thirteenth lens L13 are plastic aspherical lenses.

[0041] From the image side to the object side, the optical power of the 13 lenses is positive, positive, positive, negative, positive, negative, positive, negative, positive, positive, negative, negative, negative, and the overall optical power of the system is positive. The aberration is further corrected by matching the optical power design.

[0042] For other parameter settings, see Example 1.

[0043] Three representative light beams with different wavelengths were set, namely 0.455um, 0.530um, and 0.647um, and green light was selected as the main wavelength. The three wavelengths of light were passed through the above projection system and relevant verification was performed, and the following results were obtained: Figures 2 to 4 , and conduct relevant analysis on the projection effect according to the graphic content: See also Figure 2 The left coordinate system shows that the difference between the image quality in the center and the periphery is small during imaging, while the right coordinate system shows that the imaging distortion is small, meeting the requirement of low distortion.

[0044] See also Figure 3, shows the schematic diagram of point spot imaging of three wavelengths of light on the screen under normalized different field of view conditions, where IMA represents the image plane and OBJ represents the object plane; Figure 3 It shows that under different wavelength conditions, the convergence effect of the light spot is good.

[0045] See also Figure 4 , indicating the aberration value between the x-axis and the y-axis. The aberration under different wavelengths of light is very small.

[0046] In summary, the projection system of the present application has high-quality imaging effects.

[0047] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0048] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A zoom projection lens, characterized in that: include: A plurality of lens groups arranged coaxially, wherein the lens groups include at least a first group (1), a second group (2), a third group (3), a fourth group (4), a fifth group (5) and a sixth group (6) along the direction from the image side to the object side; The equivalent focal length of the first group (1) is F1, the equivalent focal length of the second group (2) is F2, the equivalent focal length of the third group (3) is F3, the equivalent focal length of the fourth group (4) is F4, the equivalent focal length of the fifth group (5) is F5, the equivalent focal length of the sixth group (6) is F6, and the equivalent focal length of the projection lens is F; wherein, 3.5<|F1 / F|<6; 10<|F2 / F|<20; 1<|F3 / F|<4; 2<|F4 / F|<10; 1<|F5 / F|<4; 0<|F6 / F|<2; The second group (2) comprises at least three cemented lenses, wherein the three cemented lenses sequentially comprise a first lens (L1), a second lens (L2) and a third lens (L3) along the direction from the image side to the object side; the first lens (L1) has a negative optical power, the second lens (L2) has a positive optical power, and the third lens (L3) has a negative optical power; The fifth group (5) comprises at least a doublet lens, wherein the doublet lens comprises a fourth lens (L4) and a fifth lens (L5) in sequence from the image side to the object side; the fourth lens (L4) is a biconcave lens, and the fifth lens (L5) is a biconvex lens.

2. The zoom projection lens according to claim 1, characterized in that: The second group (2) further comprises an aspheric lens, wherein the aspheric lens is located on the image side of the triplet lens; and a stop (7) is fixed on the image side of the third group (3).

3. The zoom projection lens according to claim 1, characterized in that: The sixth group (6) includes two plastic aspherical lenses.

4. The zoom projection lens according to claim 1, characterized in that: The Abbe numbers of the first lens (L1) and the third lens (L3) are both smaller than the Abbe number of the second lens (L2).

5. The zoom projection lens according to claim 1, characterized in that: The refractive indexes of the first lens (L1) and the third lens (L3) are both greater than the refractive index of the second lens (L2).

6. The zoom projection lens according to claim 1, characterized in that: The center thickness of the first lens (L1) and the third lens (L3) ranges from 0.5 mm to 2 mm.

7. The zoom projection lens according to claim 1, characterized in that: The dispersion coefficient of the fourth lens (L4) is less than 50, and the dispersion coefficient of the fifth lens (L5) is greater than 50.

8. A zoom projection system, characterized in that: include: A zoom projection lens as claimed in any one of claims 1 to 7; and an image polarizer (8), a prism (9) and a light valve (10) arranged in sequence on the image side of the zoom projection lens.

9. The zoom projection system according to claim 8, characterized in that: The distance between the vertex of the surface of the image side end lens of the projection lens farthest from the light valve (10) and the light valve (10) is BFL, and the farthest distance between the vertex of the image side end lens surface and the vertex of the object side end lens surface of the projection lens is L; wherein 0<BFL / L<0.

5.

10. A method for using a zoom projection system, based on the zoom projection system according to claim 9, characterized in that: The following steps are involved: S1, placing the projection system, and adjusting the positions of the lens groups in the projection system so that the lens groups are relatively displaced from each other; S2. When the resolution of the projection image meets the requirement, the positions of the first group (1) and the sixth group (6) are fixed; S3, adjusting the positions of the second group (2), the third group (3), the fourth group (4) and the fifth group (5) so that when the projection size meets the requirements, the positions of the lens groups are fixed.

Images