Zoom projection lens and projection system

Abstract

The application discloses a zoom projection lens, which comprises a first lens group, a second lens group and a third lens group arranged in sequence from the magnifying side to the reducing side, the optical power of each lens group is negative, positive and positive in sequence, the first lens group is used for focusing, the second lens group is used for zooming, and the third lens group is a fixed group, the second lens group comprises a first zoom group, a second zoom group and a third zoom group with positive optical power arranged in sequence from the magnifying side to the reducing side, a diaphragm is arranged between the third zoom group and the second zoom group, the first zoom group, the second zoom group and the third zoom group are moved along the optical axis to zoom, and the diaphragm is synchronously moved with the third zoom group. The application realizes high imaging quality, reduces the diaphragm opening aperture, reduces the overall occupied volume, improves the structural compactness, is light in weight, realizes high-performance continuous zooming, and can support continuous change of picture size at the same projection distance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical lens, in particular to a zoom projection lens and a projection system. BACKGROUND

[0002] With the development of the projection market, users have diversified demand for product presentation, and the use of projection is widely promoted. The demand for using projection in different places and environments is increasing, such as home theater, classroom teaching, conference room, outdoor leisure, etc. This makes the projection with small size, high portability, and better performance deeply favored by the market and the majority of consumers.

[0003] The conventional projection lens in the market is limited by the 100% offset setting of the chip and the demand for high brightness of the projection picture. The FNO is generally F1.7, which makes the lens have a larger aperture, and the system off-axis aberration and distortion greatly affect the performance of the lens, resulting in a large volume, weight, and cost of the projector, inconvenience to move, insufficient MTF performance, and low projection clarity. SUMMARY

[0004] The technical problem to be solved by the present application and the technical task proposed are to improve the prior art and provide a zoom projection lens to solve the problems of large volume, weight, and cost of the projection lens and low projection clarity in the prior art.

[0005] To solve the above technical problems, the technical solution of the present application is:

[0006] A zoom projection lens, comprising a first lens group, a second lens group, and a third lens group arranged in sequence from the magnification side to the reduction side, the optical power of each lens group being negative, positive, and positive in sequence, the first lens group being used for focusing, the second lens group being used for zooming, and the third lens group being a fixed group, the second lens group comprising a first zoom group, a second zoom group, and a third zoom group with positive optical power arranged in sequence from the magnification side to the reduction side, a diaphragm being arranged between the third zoom group and the second zoom group, the first zoom group, the second zoom group, and the third zoom group moving along the optical axis for zooming, and the diaphragm moving synchronously with the third zoom group. The first lens group in the zoom projection lens effectively diverges the light beam to ensure that a large-size image picture is projected, the second lens group adjusts the aperture of the light beam and effectively converges the light rays, compensates for the distortion and spherical aberration generated by the first lens group, realizes high imaging quality, reduces the aperture of the diaphragm, effectively reduces the overall volume occupied by the projection lens, improves the compactness of the structure, is light in weight, realizes continuous zooming with high performance, and supports continuous change of the picture size at the same projection distance.

[0007] Further, the first lens group comprises a first lens, a second lens, a third lens and a fourth lens arranged in sequence from the magnifying side to the reducing side, the first lens and the second lens are both meniscus negative lens convex to the magnifying side, the third lens is double-concave negative lens, and the fourth lens is double-convex positive lens. The first lens and the second lens can jointly converge more light into the optical system, and make the incidence angle of large-angle light gentle, effectively correcting the field curvature.

[0008] Further, the first lens is aspherical negative lens, and the two side surfaces of the first lens are respectively even aspherical surface, effectively correcting the off-axis aberration and distortion mechanical energy.

[0009] Further, the first zoom group comprises a fifth lens, and the fifth lens is meniscus positive lens.

[0010] Further, the second zoom group comprises a sixth lens, and the sixth lens is double-convex positive lens, the number of lenses is small, and the volume of the lens is reduced.

[0011] Further, the absolute value of the curvature radius of the surface close to the reducing side of the sixth lens is greater than 500 mm, and the absolute value of the curvature radius of the surface close to the magnifying side of the fourth lens contained in the first lens group is greater than 500 mm. The surface close to the reducing side of the sixth lens and the surface close to the magnifying side of the fourth lens are approximately plane, the sixth lens and the fourth lens can generate negative distortion, can correct positive distortion, and the sixth lens is located on the magnifying side of the diaphragm, can effectively converge light, reduce the diaphragm opening diameter, and further reduce the overall volume of the lens.

[0012] Further, the third zoom group comprises a three-cemented lens with positive combined focal length arranged adjacent to the diaphragm, and the three-cemented lens comprises three lenses with positive, negative and positive refractive powers connected in sequence from the magnifying side to the reducing side. It can effectively eliminate chromatic aberration and correct system spherical aberration.

[0013] Further, the refractive index of the lens with positive refractive power in the three-cemented lens is lower than that of the lens with negative refractive power, and the Abbe number of the lens with positive refractive power is higher than that of the lens with negative refractive power.

[0014] Further, the two lenses with positive refractive power in the three-cemented lens are respectively made of different low-dispersion materials, and the low-dispersion material is a material with Abbe number greater than 65.

[0015] Further, the third zoom group further comprises a tenth lens and an eleventh lens arranged in sequence on the reducing side of the three-cemented lens, the tenth lens is double-concave negative lens, and the eleventh lens is double-convex aspherical lens, and the two side surfaces of the eleventh lens are respectively even aspherical surface, which can effectively correct system aberration, improve edge field curvature and improve imaging performance.

[0016] Further, the third lens group comprises a twelfth lens, which is a biconvex positive lens, the number of lenses is small, the volume of the lens is reduced, the optical system converges the light into the DMD, and a small telecentric angle is realized.

[0017] Further, in the zooming process from the wide-angle end to the telephoto end, the first zoom group, the second zoom group and the third zoom group are all moved to the magnification side.

[0018] Further, in the zooming process, the positions of the first lens group and the third lens group are unchanged, and the position of the imaging surface is unchanged, the position of the imaging surface can be maintained unchanged during the zooming process, the size of the projection picture can be adjusted under the condition that the position of the imaging surface is unchanged, the projection picture is always clear, and no focusing action is needed.

[0019] Further, the zoom ratio of the zoom projection lens is EFLt / EFLw≥1.5, BFL / EFLw>2.37, the relative aperture Fno≤2.2 at the wide-angle end, the relative aperture Fno≤2.6 at the telephoto end, the total lens length focal ratio TTLw / EFLw≤12.38, the telecentric angle TAw≤1° at the wide-angle end, and the telecentric angle TAt≤1.78° at the telephoto end; wherein EFLt is the effective focal length at the telephoto end, EFLw is the effective focal length at the wide-angle end, and TTLw is the total lens length at the wide-angle end. By optimizing the cooperation between the curvatures, materials, intervals and aspheric coefficients of each lens included in the optical system, a small-aperture high-performance low-distortion zoom projection lens is obtained. Fno is the ratio of the effective focal length of the lens to the aperture diameter. In the case that the effective focal length of the lens remains unchanged, the smaller the aperture diameter, the smaller the overall size of the system, the smaller the volume, the lighter the weight, the lower the cost, the projection lens is in a good state at the spatial limit frequency 93lp / mm, the MTF value of each focal length is good, the distortion is small, the structure is simple, and the imaging quality is good.

[0020] A projection system, characterized in that it comprises the zoom projection lens and a DMD, the DMD is biased to make the outgoing picture biased upward, so that the outgoing light beam is higher than the position of the projection lens, and the projection picture is not blocked by the projection lens.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] The zoom projection lens can reduce the aperture diameter of the diaphragm, the number of lenses is small, the overall occupied volume of the projection lens is effectively reduced, the structure is compact, the weight is light, the cost is low, the chromatic aberration is effectively improved, the distortion is suppressed, the high imaging quality is realized, the continuous zooming of high performance is realized, the continuous change of the picture size can be supported under the same projection distance, the size of the projection picture can be adjusted under the condition that the position of the imaging surface is unchanged, and the projection picture is always clear. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Schematic diagram of the zoom projection lens of the present application at the wide-angle end;

[0024] Figure 2 Schematic diagram of the zoom projection lens of the present application at the telephoto end.

[0025] In the drawings:

[0026] First lens group G1, third lens group G3, first zoom group G21, second zoom group G22, third zoom group G23, first lens L1, second lens L2, third lens L3, fourth lens L4, fifth lens L5, sixth lens L6, seventh lens L7, eighth lens L8, ninth lens L9, tenth lens L10, eleventh lens L11, twelfth lens L12, diaphragm 10, DMD 11, galvanometer 12. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0028] The zoom projection lens disclosed in the embodiments of the present application has small volume, light weight and low cost, can support continuous change of picture size at the same projection distance, and has high projection definition and good picture quality.

[0029] As shown in Figure 1 and Figure 2 A zoom projection lens includes a first lens group G1, a second lens group and a third lens group G3 arranged in sequence from the magnifying side to the reducing side, the optical power of each lens group is negative, positive and positive in sequence, the first lens group G1 is used for focusing, the second lens group is used for zooming, and the third lens group G3 is a fixed group. The second lens group includes a first zoom group G21, a second zoom group G22 and a third zoom group G23 arranged in sequence from the magnifying side to the reducing side, the optical power of each lens group is positive, a diaphragm 10 is arranged between the third zoom group G23 and the second zoom group G22, the first zoom group G21, the second zoom group G22 and the third zoom group G23 move along the optical axis to zoom, and the diaphragm 10 moves synchronously with the third zoom group G23.

[0030] In the embodiment, the first lens group G1 includes first lens L1, second lens L2, third lens L3 and fourth lens L4 arranged in sequence from the magnification side to the reduction side, the first lens L1 and the second lens L2 are both meniscus negative lens convex to the magnification side, the first lens L1 and the second lens L2 effectively correct the field curvature and make the large-angle light incidence angle gentle, and more light is collected, the third lens L3 is double-concave negative lens, the fourth lens L4 is double-convex positive lens, the first lens L1 is plastic aspheric negative lens, and the magnification side surface and the reduction side surface of the first lens L1 are even aspheric surface respectively, and the aspheric lens is used to correct distortion and astigmatism.

[0031] The first zoom group G21 only includes the fifth lens L5, the fifth lens L5 is meniscus positive lens, the number of lenses is small, which is beneficial to reduce the volume of the lens and improve the compactness of the structure.

[0032] The second zoom group G22 only includes the sixth lens L6, the sixth lens L6 is double-convex positive lens, the number of lenses is small, which is beneficial to reduce the volume of the lens; the absolute value of the curvature radius of the surface on the reduction side of the sixth lens L6 is greater than 500 mm, the absolute value of the curvature radius of the surface on the magnification side of the fourth lens L4 included in the first lens group G1 is greater than 500 mm, and the above two surfaces are approximately planar, in other words, the fourth lens L4 and the sixth lens L6 are both approximately plano-convex lens, to generate negative distortion to correct positive distortion, the sixth lens L6 is located on the light-emitting side of the diaphragm 10, effectively converges light, reduces the aperture of the diaphragm 10, and reduces the volume of the lens.

[0033] The third zoom group G23 includes three cemented lenses, tenth lens L10 and eleventh lens L11 arranged in sequence from the magnification side to the reduction side, the three cemented lenses are arranged adjacent to the diaphragm 10, and the synthetic refractive power of the three cemented lenses is positive, the three cemented lenses are composed of three lenses with positive, negative and positive refractive power, specifically, the three cemented lenses include seventh lens L7, eighth lens L8 and ninth lens L9 arranged in sequence from the magnification side to the reduction side, the seventh lens L7 is double-convex positive lens, the eighth lens L8 is double-concave negative lens, and the ninth lens L9 is double-convex positive lens, the refractive index of the seventh lens L7 and the ninth lens L9 is lower than that of the eighth lens L8, the Abbe number of the seventh lens L7 and the ninth lens L9 is higher than that of the eighth lens L8, and the seventh lens L7 and the ninth lens L9 are made of different low-dispersion materials, the low-dispersion material specifically refers to a material with an Abbe number greater than 65, the refractive index, Abbe number and lens shape are optimized according to the application wave band, so that the chromatic aberration and spherical aberration are well corrected, the tenth lens L10 is double-concave negative lens, and the eleventh lens L11 is glass double-convex aspheric lens, the magnification side surface and the reduction side surface of the eleventh lens L11 are even aspheric surface respectively.

[0034] The third lens group G3 only includes a twelfth lens L12, which is a biconvex positive lens. The number of lenses is small, which is conducive to reducing the size of the lens. The eleventh lens L11 and the twelfth lens L12 are both positive focal length lenses, which realizes a small telecentric angle. Since the third lens group G3 is a fixed lens, the back focal length remains unchanged during the entire zooming process.

[0035] During the zooming process from the wide-angle end to the telephoto end, the first zoom group G21, the second zoom group G22 and the third zoom group G23 all move to the magnification side, and the positions of the first lens group G1 and the third lens group G3 remain unchanged during the zooming process, and the position of the imaging surface remains unchanged. In other words, when the user adjusts the zooming, the imaging surface is always fixed and the size of the projected image is adjusted, and the projected image is always clear without adjusting the focusing front group.

[0036] A projection system includes the zooming projection lens and a DMD 11, and the DMD 11 is biased to bias the outgoing image upward, so that the outgoing light beam is higher than the position of the projection lens, and the projected image is not blocked by the projection lens. A galvanometer 12 is further arranged between the DMD 11 and the zooming projection lens. The galvanometer 12 is driven by a driving motor to perform shaking work, so that the projection lens can obtain the resolution inherent to the size of the DMD 11 itself when the galvanometer 12 is stationary and the 4K high resolution when the galvanometer 12 is working. In combination with the 0.47-inch DMD 11, a 254cm (100-inch) image can be projected at a working distance 2215mm. The MTF values of the lens at the spatial limit frequency 93lp / mm are in good condition, the distortion is small, the structure is simple, and the imaging quality is good.

[0037] The zooming projection lens also satisfies the following conditions: the zoom ratio EFLt / EFLw≥1.5, the relative aperture Fno≤2.2 at the wide-angle end, the relative aperture Fno≤2.6 at the telephoto end, the total length focal length ratio TTLw / EFLw≤12.38, BFL / EFLw>2.37, the telecentric angle TAw≤1° at the wide-angle end, and the telecentric angle TAt≤1.78° at the telephoto end; wherein EFLt is the effective focal length at the telephoto end, EFLw is the effective focal length at the wide-angle end, BFL is the optical back focal length, which is the distance from the last surface of the lens to the image plane in the projection lens, and TTLw is the total length at the wide-angle end. The total length of the lens can be defined as the distance from the magnification side vertex of the first lens L1 to the image plane of the DMD 11.

[0038] Specifically, the design parameters of the projection system are shown in Table 1.

[0039] Table 1

[0040]

[0041]

[0042] In the formula, z represents the distance between the vertex of the aspheric surface and the position of the aspheric surface along the optical axis direction at the height r, the parameter c represents the curvature corresponding to the radius, r represents the radial height of the lens, k represents the conic constant, and a1-a8 represent the aspheric coefficients of the second-sixteenth orders, as shown in Table 2.

[0043]

[0044] In the formula, z represents the distance between the vertex of the aspheric surface and the position of the aspheric surface along the optical axis direction at the height r, the parameter c represents the curvature corresponding to the radius, r represents the radial height of the lens, k represents the conic constant, and a1-a8 represent the aspheric coefficients of the second-sixteenth orders, as shown in Table 2.

[0045] Table 2

[0046] K α2 α3 α4 α5 α6 α7 α8 S1 0.0 5.4E-05 -2.4E-07 9.8E-10 -2.8E-12 5.5E-15 -6.4E-18 3.3E-21 S2 0.0 5.0E-05 -1.9E-07 3.6E-10 1.3E-12 -7.8E-15 1.8E-17 1.6E-21 S22 0.0 -1.6E-05 4.0E-07 -1.6E-08 4.5E-10 -6.5E-12 2.4E-14 5.2E-16 S23 0.0 -5.6E-08 -2.0E-07 2.0E-08 -8.6E-10 2.3E-11 -3.6E-13 3.5E-15

[0047] The intervals d1-d4 in Table 1 corresponding to the zoom projection lens in the wide-angle end and the telephoto end of the embodiment are listed in Table 3.

[0048] Table 3

[0049] Spacing (mm) d1 d2 d3 d4 Wide angle end 15.9 15.7 6.3 4.0 Telephoto end 5.0 5.9 15.7 15.3

[0050] The embodiment provides a projection lens with an aperture number F2.2, a distortion less than 0.3%, and a continuous zooming focal length of 10.5-15.8 mm. The lens structure is compact, and the implementation cost is low. At a projection position of 2390 mm, a picture with a diagonal line of 100 inches is formed when the lens is in the wide-angle end, and a picture with a diagonal line of 66 inches is formed when the lens is in the telephoto end. The curvature radius, material, thickness, air gap, and two aspheric lenses of the projection lens are optimized and designed, so that the projection lens has small aperture, small volume, light weight, low cost, small chromatic aberration, small distortion, high imaging performance, high mass production, and is convenient for batch production.

[0051] The above is only the preferred embodiment of the present application, and it should be pointed out that the above preferred embodiment should not be regarded as a limitation of the present application, and the protection scope of the present application should be limited by the scope defined in the claims. For ordinary skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A zoom projection lens characterized by comprising: The lens includes a first lens group, a second lens group and a third lens group arranged in turn from the magnifying side to the reducing side, the optical power of each lens group is negative, positive and positive in turn, the first lens group is used for focusing, the second lens group is used for zooming, and the third lens group is a fixed group, the second lens group includes a first zooming group, a second zooming group and a third zooming group with positive optical power arranged in turn from the magnifying side to the reducing side, a diaphragm is arranged between the third zooming group and the second zooming group, the first zooming group, the second zooming group and the third zooming group move along the optical axis to zoom, and the diaphragm moves synchronously with the third zooming group; The first lens group includes a first lens, a second lens, a third lens and a fourth lens arranged in turn from the magnifying side to the reducing side, the first lens and the second lens are negative lenses respectively, the third lens is a negative lens, and the fourth lens is a positive lens; The first zooming group includes a fifth lens, and the fifth lens is a positive lens; The second zooming group includes a sixth lens, and the sixth lens is a positive lens; The third zooming group includes three lenses with positive, negative and positive refractive powers arranged in turn adjacent to the reducing side of the diaphragm, a tenth lens and an eleventh lens, the tenth lens is a negative lens, and the eleventh lens is a positive lens; The third lens group includes a twelfth lens, and the twelfth lens is a positive lens.

2. The zoom projection lens of claim 1, wherein The first lens and the second lens are meniscus lenses convex to the magnifying side, the third lens is a double-concave lens, and the fourth lens is a double-convex lens.

3. The zoom projection lens of claim 2, wherein The first lens is a negative aspheric lens, and the two side surfaces of the first lens are even aspheric surfaces.

4. The zoom projection lens of claim 1, wherein, The fifth lens is a meniscus lens.

5. The zoom projection lens of claim 1, wherein, The sixth lens is a double-convex lens.

6. The zoom projection lens of claim 5, wherein, The absolute value of the curvature radius of the surface of the sixth lens close to the reducing side is greater than 500 mm, and the absolute value of the curvature radius of the surface of the fourth lens close to the magnifying side included in the first lens group is greater than 500 mm.

7. The zoom projection lens of claim 1, wherein The three lenses with positive, negative and positive refractive powers are three cemented lenses with positive refractive power.

8. The zoom projection lens of claim 1, wherein, The refractive index of the lens with positive refractive power in the three cemented lenses is lower than that of the lens with negative refractive power, and the Abbe number of the lens with positive refractive power is higher than that of the lens with negative refractive power.

9. The zoom projection lens of claim 1, wherein, The two lenses with positive refractive power in the three cemented lenses are made of different low-dispersion materials, and the low-dispersion material is a material with an Abbe number greater than 65.

10. The zoom projection lens of claim 1, wherein, The tenth lens is a double-concave lens, the eleventh lens is a double-convex aspheric lens, and the two side surfaces of the eleventh lens are even aspheric surfaces.

11. The zoom projection lens of claim 1, wherein, The third lens group includes a twelfth lens, and the twelfth lens is a double-convex lens.

12. The zoom projection lens according to any one of claims 1 to 10, characterized in that In the zooming process from the wide-angle end to the telephoto end, the first zooming group, the second zooming group and the third zooming group all move to the magnifying side.

13. The zoom projection lens according to any one of claims 1 to 10, characterized in that In the zooming process, the positions of the first lens group and the third lens group are unchanged, and the position of the imaging surface is unchanged.

14. The zoom projection lens according to any one of claims 1 to 10, characterized in that The zoom projection lens has a zoom ratio of EFLt / EFLw≥1.5, a back focal length to wide angle effective focal length ratio of BFL / EFLw>2.37, a relative aperture Fno≤2.2 at the wide angle end, a relative aperture Fno≤2.6 at the telephoto end, a total track length to wide angle effective focal length ratio of TTLw / EFLw≤12.38, a telecentric angle TAw≤1° at the wide angle end, and a telecentric angle TAt≤1.78° at the telephoto end; wherein EFLt is the effective focal length at the telephoto end, EFLw is the effective focal length at the wide angle end, and TTLw is the total track length at the wide angle end.

15. A projection system, characterized by The zoom projection lens of any one of claims 1 to 14 is combined with a DMD, which is offset placed to offset the exit picture upward.

Images