Ultra-short-focus high-image-quality projection lens and projector using same

Abstract

The invention discloses an ultra-short-focus high-image-quality projection lens and a projector using the same, and belongs to the technical field of image display, and the projection lens sequentially comprises a first lens group and a second lens group from an object side to an image side. The first lens group is composed of three negative-focal-power lenses and a positive-focal-power lens which are sequentially arranged from the object side to the image side. The second lens group is composed of a set of positive-focal-power balsaming lens, a positive-focal-power lens, a set of negative-focal-power balsaming lens and a set of positive-focal-power balsaming lens which are sequentially arranged from the object side to the image side. At least one aspherical lens is used in the first lens group and the second lens group. The combination of the materials and the focal power of the two lens groups meets certain conditions, various aberrations can be effectively controlled, and good optical performance can be obtained. The projection lens is small in lens number, simple in structure and easy to manufacture, and the cost of the projection lens is reduced. And the transmittance is high and the aperture is large, so that the purpose of high-brightness projection is achieved.

Description

Technical Field

[0001] The present invention relates to the field of image display technology, and in particular to an ultra-short-throw high-image-quality projection lens and a projector using the same. Background Art

[0002] As a necessary projection equipment in various places of life such as teaching and cinema, the projection lens is the last link in the projector's optical path and is also an extremely important link. The design of the projection lens not only affects the performance of the projector, but also determines the quality of the projection effect.

[0003] Currently, the common digital projection display technology mainly uses DMD (Digital Micromirror Device) or LCOS (Liquid Crystal On Silicon) as the display device, and uses polarization spectrometers or total reflection spectrometers as lighting or imaging spectrometers. By designing a reasonable projection lens optical path, the image reflected on the display device is focused onto the projection screen.

[0004] The investigation found that the existing 0.65"DMD projection lens on the market has poor image quality, and because the projection lens uses more lenses or more plastic lenses, the transmittance of the entire lens is low, resulting in low brightness of the final projection. Summary of the invention

[0005] The object of the present invention is to provide an ultra-short-throw high-image-quality projection lens and a projector, which can at least solve one of the above problems.

[0006] According to one aspect of the present invention, there is provided an ultra-short-throw high-image-quality projection lens, comprising a first lens group with negative optical power and a second lens group with positive optical power, which are arranged in sequence from the object side to the image side;

[0007] The first lens group and the second lens group are configured to satisfy the following conditional expressions:

[0008] 0.4<|f1 / f2︱<0.7;

[0009] TTL / EFFL<16;

[0010] TTL / BFL<5;

[0011] Wherein: f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, TTL is the distance from the first surface of the first lens of the first lens group to the image plane, EFFL is the focal length of the projection lens, and BFL is the distance from the second surface of the last lens of the second lens group to the image plane.

[0012] In some embodiments, the first lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the object side to the image side;

[0013] The first lens is a meniscus lens, the first surface and the second surface of the first lens are both curved toward the image side, and at least one of the first surface and the second surface is an aspherical surface;

[0014] The second lens is a meniscus lens, wherein the first surface and the second surface are both curved toward the image side;

[0015] The third lens is a biconcave lens;

[0016] The fourth lens is a biconvex lens.

[0017] In some embodiments, the first lens group satisfies at least the following conditional formula:

[0018] Vd41<30;

[0019] Wherein, Vd41 is the dispersion coefficient of the fourth lens.

[0020] In some embodiments, the second lens group includes a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a tenth lens, and an eleventh lens arranged sequentially from the object side to the image side;

[0021] The fifth lens and the sixth lens are combined into a first cemented lens, wherein the fifth lens is a biconvex lens and the sixth lens is a negative power lens;

[0022] The seventh lens is a biconvex lens, and at least one surface of the seventh lens is an aspherical surface;

[0023] The eighth lens and the ninth lens are combined into a second cemented lens, wherein the eighth lens is a negative power lens and the ninth lens is a positive power lens;

[0024] The tenth lens and the eleventh lens are combined into a third cemented lens, wherein the tenth lens is a negative power lens, and the eleventh lens is a positive power lens.

[0025] In some embodiments, the second lens group satisfies at least the following conditional formula:

[0026] Vd21<25;

[0027] Vd22<21;

[0028] (Vd21-Vd22)<5;

[0029] Vd23>60;

[0030] Vd27>80;

[0031] 0.6 <f23 / f2<0.7;

[0032] Among them, Vd21 is the dispersion coefficient of the fifth lens, Vd22 is the dispersion coefficient of the sixth lens, Vd23 is the dispersion coefficient of the seventh lens, Vd27 is the dispersion coefficient of the eleventh lens, f23 is the focal length of the seventh lens, and f2 is the focal length of the second lens group.

[0033] In some embodiments, the ultra-short-throw high-image-quality projection lens further includes an aperture, which is one and is located in the middle of the second lens group. Thus, the aperture is used to limit the light flux of the light passing through the first lens group entering the second lens group, and to make the light cone after passing through the first lens group more symmetrical, so that the coma of the projection lens can be corrected.

[0034] In some embodiments, the ultra-short-throw high-image-quality projection lens system further includes a stop, which is disposed in the second lens group and between the seventh lens and the eighth lens.

[0035] In some embodiments, the position of the aperture is fixed.

[0036] In some implementations, there are only 2 groups of projection lenses.

[0037] According to another aspect of the present invention, a projector is provided, including a housing and the above-mentioned ultra-short-throw high-image-quality projection lens, wherein the projection lens is arranged in the housing.

[0038] Beneficial effects of the present invention:

[0039] After testing, the MTF curve (MTF, English spelling is Modulation Transfer Function, Chinese name is Modulation Transfer Function) of the projection lens of the present invention is excellent, with small distortion and small vertical axis chromatic aberration, and the aperture can reach F2.7;

[0040] The number of lenses in the entire projection lens is small, making the entire lens have high transmittance;

[0041] The projection lens of the present invention not only has good resolution capability, but also can better utilize light effects, thereby improving the brightness of the projected image when used on a projector. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a simplified optical structure diagram of a projection lens involved in Embodiments 1 and 2 of the present invention;

[0043] Figure 2 yes Figure 1 Schematic diagram of the projection structure of the projection lens shown;

[0044] Figure 3 is the MTF curve of the projection lens involved in Example 1 of the present invention;

[0045] Figure 4 is a distortion diagram of the projection lens involved in Embodiment 1 of the present invention;

[0046] Figure 5 is a chromatic aberration diagram of the projection lens involved in Embodiment 1 of the present invention;

[0047] Figure 6 is the MTF curve of the projection lens involved in Example 2 of the present invention;

[0048] Figure 7 is a distortion diagram of the projection lens involved in Embodiment 2 of the present invention;

[0049] Figure 8 : is a chromatic aberration diagram of the projection lens involved in Example 2 of the present invention.

[0050] Figure 1 The figure marks in the figure are: 10-first lens group; 20-second lens group; 30-aperture; 40-DMD protection glass; 50-image plane; 100-projection lens; 101-first lens; 102-second lens; 103-third lens; 104-fourth lens; 201-fifth lens; 202-sixth lens; 203-seventh lens; 204-eighth lens; 205-ninth lens; 206-tenth lens; 207-eleventh lens. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0052] Figures 1 to 8 The ultra-short-throw high-image-quality projection lens according to the present invention is schematically shown.

[0053] like Figure 1-8 As shown, the projection lens 100 of this embodiment includes a first lens group 10 with negative optical focal power and a second lens group 20 with positive optical focal power, which are arranged in sequence from the object side to the image side, and the ratio of the focal length of the first lens group 10 of the projection lens 100 to the focal length of the second lens group 20 is within a preset value range, the ratio of the total length TTL of the projection lens 100 to the effective focal length EFFL is less than a preset value, and the ratio of the total length TTL of the projection lens to the back focal length BFL is less than a preset value.

[0054] Specifically, the first lens group 10 and the second lens group 20 are configured to satisfy the following conditional expressions (1), (2), and (3):

[0055] 0.4<|f1 / f2︱<0.7---------------(1)

[0056] TTL / EFFL<16---------------(2)

[0057] TTL / BFL<5---------------(3)

[0058] Wherein: f1 is the focal length of the first lens group 10, f2 is the focal length of the second lens group 20, TTL is the distance between the first surface of the first lens of the first lens group 10 and the image plane 50, EFFL is the focal length of the projection lens 100, and BFL is the distance between the second surface of the last lens of the second lens group 20 and the image plane 50.

[0059] The projection lens 100 further includes an aperture 30. The aperture 30 is located in the middle of the second lens group 20 to limit the light flux of the light passing through the first lens group 10 entering the second lens group 20, and to make the light cone after passing through the first lens group 10 more symmetrical, so that the coma of the projection lens 100 can be corrected. To facilitate the design of the mechanism, the position of the aperture 30 is set to a fixed position.

[0060] In this embodiment, the first lens group 10 includes a first lens 101, a second lens 102, a third lens 103 and a fourth lens 104 arranged in sequence from the object side to the image side;

[0061] The first lens 101 is a meniscus lens, the first surface and the second surface of the first lens 101 are both curved toward the image side, and at least one of the first surface and the second surface is an aspherical surface;

[0062] The second lens 102 is a meniscus lens, wherein the first surface and the second surface are both curved toward the image side;

[0063] The third lens 103 is a biconcave lens;

[0064] The fourth lens 104 is a biconvex lens.

[0065] The first lens group 10 at least satisfies the following conditional formula (4):

[0066] Vd41<30---------------(4);

[0067] Wherein, Vd41 is the dispersion coefficient of the fourth lens.

[0068] The second lens group 20 includes a fifth lens 201, a sixth lens 202, a seventh lens 203, an eighth lens 204, a ninth lens 205, a tenth lens 206 and an eleventh lens 207, which are arranged in sequence from the object side to the image side;

[0069] The fifth lens 201 and the sixth lens 202 are combined into a first cemented lens, wherein the fifth lens 201 is a biconvex lens and the sixth lens 202 is a negative power lens;

[0070] The seventh lens 203 is a biconvex lens, and at least one surface of the seventh lens 203 is an aspherical surface;

[0071] The eighth lens 204 and the ninth lens 205 are combined into a second cemented lens, wherein the eighth lens 204 is a negative power lens, and the ninth lens 205 is a positive power lens;

[0072] The tenth lens 206 and the eleventh lens 207 are combined into a third cemented lens, wherein the tenth lens 206 is a negative power lens, and the eleventh lens 207 is a positive power lens.

[0073] The second lens group 20 of the present embodiment is configured to satisfy the following conditional expressions (5), (6), (7), (8), (9), and (10):

[0074] Vd21<25---------------(5)

[0075] Vd22<21---------------(6)

[0076] (Vd21-Vd22)<5---------------(7)

[0077] Vd23>60--------------(8)

[0078] Vd27>80--------------(9)

[0079] 0.6 <f23 / f2<0.7--------------(10)

[0080] Wherein, Vd21 is the dispersion coefficient of the fifth lens 201, Vd22 is the dispersion coefficient of the sixth lens 202, Vd23 is the dispersion coefficient of the seventh lens 203, Vd27 is the dispersion coefficient of the eleventh lens 207, f23 is the focal length of the seventh lens 203, and f2 is the focal length of the second lens group 20.

[0081] Next, the operation and effects of the projection lens configured as described above will be described.

[0082] Conditions (1) to (3) define the geometric dimensions of the projection lens 100, which ensure that the length of the lens is reduced as much as possible while ensuring that the BFL is large enough. This way, the back focus has enough space to meet the functional requirements. At the same time, the shortened lens length can reduce the outer diameter of the lens, thereby achieving the purpose of reducing costs.

[0083] Conditional expression (4) specifies the dispersion of the key lens element of the first lens group 10. Satisfying this conditional expression can effectively correct the system chromatic aberration.

[0084] Conditional expressions (5) to (9) define the dispersion of the key lenses of the second lens group 20. Satisfying the conditional expressions can effectively correct the system chromatic aberration.

[0085] Next, specific embodiments of the projection lens according to the present invention will be described.

[0086] There are many possible implementations of the projection lens provided by the present invention. The projection lens is specifically described below using Embodiment 1 and Embodiment 2 as examples. The structures and parameters in Embodiment 1 and Embodiment 2 are merely examples of implementations of the projection lens and are not intended to limit such settings.

[0087] Example 1

[0088] As shown in the following Table 1, it shows the parameters of all lenses of the projection lens of this embodiment.

[0089] Table 1: Statistical table of mirror parameters of all lenses in Example 1

[0090]

[0091] In the column of surface number Si, it is indicated that the surface of the structural element closest to the object side is the first surface, and the surface numbers gradually increase along the image direction;

[0092] In the column of curvature radius Ri, the value of the curvature radius corresponding to the Si number is shown;

[0093] In the column of surface spacing Di, the lens thickness or the spacing value between lenses corresponding to the Si number is shown;

[0094] The units of the curvature radius Ri and the surface spacing Di are millimeters (mm).

[0095] The columns of refractive index Ndj and Abbe number vdj respectively show the refractive index and Abbe number of the jth (j=1 to 9) optical component from the object side with respect to d-light (wavelength 587.6 nm).

[0096] As shown in Table 2 below, it discloses a statistical table of aspheric coefficients corresponding to the aspheric mirror surface in Table 1.

[0097] Table 2: Statistical table of aspheric coefficients corresponding to the aspheric mirror surfaces in Table 1

[0098] K b c d e f g h S1 0.0E+00 1.7E-05 -1.4E-08 4.8E-12 2.6E-15 -1.4E-18 -1.0E-21 7.1E-25 S2 -5.8E-01 9.4E-06 5.5E-08 -1.3E-10 1.3E-14 8.4E-17 4.2E-20 -7.6E-23 S12 -1.4E+00 -3.0E-06 -1.1E-06 1.5E-08 -3.8E-10 -8.0E-14 6.5E-16 1.1E-16 S13 -4.4E-01 1.7E-05 -3.5E-07 -3.5E-08 4.1E-10 4.8E-13 -2.0E-16 3.5E-16

[0099] The symbol "E" indicates that the data immediately following it is a "power exponent" with a base of 10, which means that the value represented by the exponential function with a base of 10 is multiplied by the value before "E". For example, if it is "1.0E-02", it means "1.0×10 -2 ”.

[0100] The aspheric coefficients in Table 2 are based on the center of the lens surface as the origin, the optical axis as the x-axis, and the aspheric surface type expression of the lens surface satisfies the following formula (A):

[0101]

[0102] The specific meanings of the relevant parameters in the above formula (A) are as follows:

[0103] X is the depth of the aspheric surface (mm);

[0104] Y is the distance (height) from the optical axis to the lens surface (mm);

[0105] C is the radius of curvature of the lens, C = 1 / R;

[0106] K is the cone constant;

[0107] b, c, d, e, f, g, and h are aspherical lens coefficients.

[0108] As shown in Table 3 below, three parameters of the projection lens are disclosed.

[0109] Table 3: Statistics of the three parameters of projection lens: focal length, aperture and viewing angle

[0110] f FNO. 2ω 7.42 2.7 114°

[0111] Where: f is the paraxial focal length of the entire system, in mm, FNO. is the aperture, and 2ω is the viewing angle (ω: half viewing angle).

[0112] Example 2

[0113] The number and structure of the lenses of the projection lens of this embodiment are basically the same as those of Embodiment 1, and the only difference is that the parameters of the lenses are different. As shown in Table 4 below, it shows the parameters of all the lenses of the projection lens of this embodiment.

[0114] Table 4: Parameter statistics of the mirror surfaces of all lenses in Example 2

[0115]

[0116] As shown in Table 5 below, it discloses a statistical table of aspheric coefficients corresponding to the aspheric mirror surface in Table 4.

[0117] Table 5: Statistical table of aspheric coefficients corresponding to the aspheric mirror surfaces in Table 4

[0118] K b c d e f g h S3 0.0E+00 1.7E-05 -1.4E-08 4.9E-12 2.4E-15 -1.3E-18 -1.1E-21 7.5E-25 S4 -4.6E-01 8.1E-06 5.0E-08 -1.3E-10 1.6E-14 8.1E-17 4.7E-20 -7.9E-23 S16 -1.5E+00 -1.6E-05 -1.3E-06 1.9E-08 -4.6E-10 -1.0E-12 -4.8E-15 6.7E-16 S17 8.0E-02 7.7E-06 6.9E-08 -5.9E-08 8.9E-10 3.7E-12 1.3E-13 -9.7E-15

[0119] As shown in Table 6 below, three parameters of the projection lens of this embodiment are disclosed.

[0120] Table 6: Statistics of the three parameters of projection lens: focal length, aperture and viewing angle

[0121] f FNO. 2ω 7.45 2.7 113.6°

[0122] Furthermore, as shown in Table 7 below, conditional expressions and specific numerical values ​​of Examples 1 and 2 of the present invention are described.

[0123] Table 7: Statistical table of conditional expressions and specific values ​​of Examples 1 and 2

[0124]

[0125] The following is a further description of the specific data of the above embodiments in conjunction with the accompanying drawings:

[0126] from Figure 3 , Figure 6 From the MTF curve, we can see that the optical transfer function MTF>55% at a spatial frequency of 67lp / mm for the full field of view.

[0127] from Figure 4 , Figure 7 It can be seen from the distortion diagram that the maximum distortion of the entire field of view is less than 1%.

[0128] from Figure 5 , Figure 8 From the chromatic aberration diagram, we can see that the maximum vertical chromatic aberration in the entire field of view is about 4μm.

[0129] From the imaging results and parameters of the projection lens obtained in the above Examples 1 and 2, it can be seen that the projection lens of the present invention has excellent MTF performance, small distortion, small vertical axis chromatic aberration, and the aperture can reach F2.7. In addition, due to the small number of lenses, the transmittance of the entire lens is high. Such a lens can not only have a good resolution ability, but also make better use of light effects, thereby improving the brightness of the projected image when used on a projector.

[0130] In summary, the present invention is a two-group projection lens 100 with large aperture, high image quality, low cost and compact structure. It includes, from the object side to the image side, a first lens group 10 with negative optical power and a second lens group 20 with positive optical power. The first lens group 10 is composed of three negative optical power lenses and one positive optical power lens arranged in sequence from the object side to the image side. The second lens group 20 is composed of a set of positive optical power cemented lenses, a positive optical power lens, a set of negative optical power cemented lenses and a positive optical power cemented lens arranged in sequence from the object side to the image side. In the first lens group 10 and the second lens group 20, at least one aspherical lens is used. The combination of materials and optical power of the two lens groups meets certain conditions, which can effectively control various aberrations and obtain good optical performance. The projection lens 100 has a small number of lenses, a simple structure, and is easy to manufacture, so that the cost of the projection lens 100 is reduced. The small number of lenses of the entire lens makes the transmittance of the entire lens high, and the large aperture achieves the purpose of high brightness projection.

[0131] In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, the values ​​of the radius of curvature, surface spacing, and refractive index of each lens component are not limited to the values ​​shown in the above-mentioned numerical embodiments, and other values ​​may be used. These changes made according to the spirit of the present invention are all included in the protection scope required by the present invention.

[0132] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An ultra-short-throw high-image-quality projection lens, characterized in that: It comprises a first lens group (10) with negative optical power and a second lens group (20) with positive optical power, which are arranged in sequence from the object side to the image side; The first lens group (10) and the second lens group (20) are constructed in a manner that satisfies the following conditional expression: 0.4<|f1 / f2︱<0.7; TTL / EFFL<16; TTL / BFL<5; Wherein: f1 is the focal length of the first lens group (10), f2 is the focal length of the second lens group (20), TTL is the distance between the first surface of the first lens of the first lens group (10) and the image plane (50), EFFL is the focal length of the projection lens (100), and BFL is the distance between the second surface of the last lens of the second lens group (20) and the image plane (50).

2. The ultra-short-throw high-image-quality projection lens according to claim 1, characterized in that: The first lens group (10) comprises a first lens (101), a second lens (102), a third lens (103) and a fourth lens (104) which are arranged in sequence from the object side to the image side; The first lens (101) is a meniscus lens, the first surface and the second surface of the first lens (101) are both curved toward the image side, and at least one of the first surface and the second surface is an aspherical surface; The second lens (102) is a meniscus lens, wherein the first surface and the second surface are both curved toward the image side; The third lens (103) is a biconcave lens; The fourth lens (104) is a biconvex lens.

3. The ultra-short-throw high-image-quality projection lens according to claim 2, characterized in that: The first lens group (10) at least satisfies the following conditional formula: Vd41<30; Wherein, Vd41 is the dispersion coefficient of the fourth lens.

4. The ultra-short-throw high-image-quality projection lens according to claim 1, characterized in that: The second lens group (20) comprises a fifth lens (201), a sixth lens (202), a seventh lens (203), an eighth lens (204), a ninth lens (205), a tenth lens (206) and an eleventh lens (207) which are arranged in sequence from the object side to the image side; The fifth lens (201) and the sixth lens (202) are combined into a first cemented lens, wherein the fifth lens (201) is a biconvex lens, and the sixth lens (202) is a negative power lens; The seventh lens (203) is a biconvex lens, and at least one surface of the seventh lens (203) is an aspherical surface; The eighth lens (204) and the ninth lens (205) are combined into a second cemented lens, wherein the eighth lens (204) is a negative power lens, and the ninth lens (205) is a positive power lens; The tenth lens (206) and the eleventh lens (207) are combined into a third cemented lens, wherein the tenth lens (206) is a negative power lens, and the eleventh lens (207) is a positive power lens.

5. The ultra-short-throw high-image-quality projection lens according to claim 4, characterized in that: The second lens group (20) at least satisfies the following conditional formula: Vd21<25; Vd22<21; (Vd21-Vd22)<5; Vd23>60; Vd27>80; 0.6 <f23 / f2<0.7; Wherein, Vd21 is the dispersion coefficient of the fifth lens (201), Vd22 is the dispersion coefficient of the sixth lens (202), Vd23 is the dispersion coefficient of the seventh lens (203), Vd27 is the dispersion coefficient of the eleventh lens (207), f23 is the focal length of the seventh lens (203), and f2 is the focal length of the second lens group (20).

6. The ultra-short-throw high-image-quality projection lens according to claim 1, characterized in that: It also includes an aperture (30), which is one and is located in the middle of the second lens group (20).

7. The ultra-short-throw high-image-quality projection lens according to claim 5, characterized in that: It also includes a stop (30), which is arranged in the second lens group (20) and located between the seventh lens (203) and the eighth lens (204).

8. The ultra-short-throw high-image-quality projection lens according to claim 6 or 7, characterized in that: The position of the aperture (30) remains fixed.

9. The ultra-short-throw high-image-quality projection lens according to any one of claims 1 to 7, characterized in that: The projection lens (100) has only two groups.

10. A projector, comprising a housing, characterized in that: It also comprises an ultra-short-throw high-image-quality projection lens (100) as claimed in any one of claims 1 to 9, wherein the projection lens (100) is arranged on the housing.

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