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

Abstract

The present invention discloses an ultra-short-focus, high-image-quality projection lens and a projector using the same, belonging to the field of image display technology. The projection lens includes a first lens group and a second lens group, sequentially from the object side to the image side. The first lens group consists of three negative-power lenses and one positive-power lens, sequentially arranged from the object side to the image side. The second lens group consists of a set of positive-power cemented lenses, a positive-power lens, a set of negative-power cemented lenses, and a set of positive-power cemented lenses, 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 material and optical power combination of the two lens groups meets certain conditions, which can effectively control various aberrations and obtain good optical performance. The projection lens has a small number of lenses, a simple structure, and is easy to manufacture, which reduces the cost of the projection lens. In addition, the transmittance is high and the aperture is large, thereby achieving the purpose of high-brightness projection.

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] Projectors are essential projection equipment in various places of life, such as teaching and cinemas. 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 common digital projection display technologies mainly use DMD (Digital Micromirror Device) or LCOS (Liquid Crystal On Silicon) as display devices, and use polarization splitter elements or total reflection splitter elements as lighting or imaging splitter elements. By designing a reasonable projection lens optical path, the image reflected from the display device is focused onto the projection screen.

[0004] An investigation revealed that the existing 0.65" DMD projection lenses on the market have poor image quality. Furthermore, because these projection lenses use more lenses or more plastic lenses, the overall lens transmittance is low, resulting in low projected brightness. 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-mentioned 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 having negative optical power and a second lens group having positive optical power, arranged sequentially from the object side to the image side;

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

[0008] 0.4<|f1 / f2︱<0.7;

[0009] TTL / EFFL<16;

[0010] TTL / BFL<5;

[0011] Where: 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, wherein both the first surface and the second surface of the first lens are curved toward the image side, and at least one of the first surface and the second surface is aspherical;

[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, which are arranged in sequence from the object side to the image side;

[0021] The fifth lens and the sixth lens are combined to form 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 aspherical;

[0023] The eighth lens and the ninth lens are combined to form 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 to form 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] Wherein, Vd21 is the chromatic aberration coefficient of the fifth lens, Vd22 is the chromatic aberration coefficient of the sixth lens, Vd23 is the chromatic aberration coefficient of the seventh lens, Vd27 is the chromatic aberration 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 a single aperture located in the middle of the second lens group. The aperture limits the amount of light passing through the first lens group that enters the second lens group, making the light cone after passing through the first lens group more symmetrical and correcting coma aberration in the projection lens.

[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 located between the seventh lens and the eighth lens.

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

[0036] In some embodiments, there are only two groups of projection lenses.

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

[0038] Beneficial effects of the present invention:

[0039] Tests have shown that the projection lens of the present invention exhibits excellent MTF (Modulation Transfer Function) curves, with minimal distortion and vertical chromatic aberration, and an aperture of up to F2.7.

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

[0041] The projection lens of the present invention not only has a 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 the projection lens involved in Examples 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 Example 1 of the present invention;

[0046] Figure 5 is a chromatic aberration diagram of the projection lens involved in Example 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 Example 2 of the present invention;

[0049] Figure 8 2 is a chromatic aberration diagram of the projection lens according to Example 2 of the present invention.

[0050] Figure 1 Reference numerals in the figure: 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 with reference to 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 power and a second lens group 20 with positive optical 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] Projection lens 100 also includes an aperture 30. Located in the middle of second lens group 20, aperture 30 limits the amount of light entering second lens group 20 after passing through first lens group 10. This also makes the light cone after passing through first lens group 10 more symmetrical, thereby correcting coma aberration in projection lens 100. To facilitate mechanical design, aperture 30 is fixed.

[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, wherein both the first surface and the second surface of the first lens 101 are curved toward the image side, and at least one of the first surface and the second surface is aspherical;

[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 satisfies at least 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 order 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 aspheric 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 this 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 projection lens 100, minimizing the lens length while ensuring a sufficiently large BFL. This ensures sufficient back focus to meet functional requirements. Furthermore, a shorter lens length reduces the outer diameter of the lens, thereby 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 systematic chromatic aberration.

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

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

[0086] The projection lens provided by the present invention has multiple possible implementations. The following specifically describes the projection lens using Embodiments 1 and 2 as examples. The structures and parameters in Embodiments 1 and 2 are merely examples of implementations of the projection lens and are not intended to limit such configurations.

[0087] Example 1

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

[0089] Table 1: Parameter statistics of all lenses in Example 1

[0090]

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

[0092] In the column of curvature radius Ri, the value of curvature radius corresponding to 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 distance 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 j-th (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: Statistics 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 and the optical axis as the x-axis. The aspheric surface 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, it discloses three parameters of the projection lens.

[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 the 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 Example 1, with the only difference being 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 all lenses in Example 2

[0115]

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

[0117] Table 5: Statistics 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, it discloses three parameters of the projection lens of this embodiment.

[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 embodiment with reference to the accompanying drawings:

[0126] from Figure 3 、 Figure 6 From the MTF curve, we can see that the optical transfer function MTF is greater than 55% at a spatial frequency of 67lp / mm across the entire 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 As can be seen from the chromatic aberration diagram, the maximum vertical chromatic aberration in the entire field of view is about 4μm.

[0129] The imaging results and parameters of the projection lens obtained in Examples 1 and 2 above demonstrate that the projection lens of the present invention exhibits excellent MTF performance, minimal distortion, and low vertical chromatic aberration, with an aperture of up to F2.7. Furthermore, due to its small number of lens elements, the overall lens transmittance is high. This lens not only provides excellent resolution but also allows for better utilization of light, thereby enhancing the brightness of the projected image when used on a projector.

[0130] In summary, the present invention provides a two-group projection lens 100 with a large aperture, high image quality, low cost, and a compact structure. From the object side to the image side, it comprises: a first lens group 10 with negative power and a second lens group 20 with positive power. The first lens group 10 consists of three negative power lenses and one positive power lens, arranged sequentially from the object side to the image side. The second lens group 20 consists of a set of positive power cemented lenses, one positive power lens, a set of negative power cemented lenses, and one positive power cemented lens, arranged sequentially from the object side to the image side. At least one aspherical lens is used in both the first lens group 10 and the second lens group 20. The material and power combination of the two lens groups meets certain requirements, effectively controlling various aberrations and achieving excellent optical performance. The projection lens 100 has a small number of lenses, a simple structure, and is easy to manufacture, reducing the cost of the projection lens 100. The small number of lenses in the entire lens group results in high transmittance, which, combined with the large aperture, achieves high-brightness projection.

[0131] Furthermore, the present invention is not limited to the above-described embodiments and is susceptible to various modifications. For example, the values ​​of the curvature radius, interplanar spacing, and refractive index of each lens component are not limited to those shown in the above numerical examples; other values ​​may be employed. Such modifications, made in accordance with the spirit of the present invention, are encompassed within the scope of protection claimed 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 inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. An ultra-short-throw, high-image-quality projection lens, characterized in that: The optical system is composed of a first lens group (10) having negative refractive power and a second lens group (20) having positive refractive power 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 formula: 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); The first lens group (10) consists of a first lens (101), a second lens (102), a third lens (103) and a fourth lens (104) 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 aspheric 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; The first lens (101) and the second lens (102) are negative power lenses; The second lens group (20) consists of 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) 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 aspheric 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.

2. The ultra-short-throw, high-image-quality projection lens according to claim 1, wherein: The first lens group (10) satisfies at least the following conditional formula: Vd41<30; Wherein, Vd41 is the dispersion coefficient of the fourth lens.

3. The ultra-short-throw, high-image-quality projection lens according to claim 1, wherein: The second lens group (20) satisfies at least 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).

4. The ultra-short-throw, high-image-quality projection lens according to claim 1, wherein: It also includes a stop (30), which is one and located in the middle of the second lens group (20).

5. The ultra-short-throw, high-image-quality projection lens according to claim 3, wherein: The invention also includes a stop (30), wherein the stop (30) is arranged in the second lens group (20) and is located between the seventh lens (203) and the eighth lens (204).

6. The ultra-short-throw, high-image-quality projection lens according to claim 4 or 5, wherein: The position of the aperture (30) is fixed.

7. The ultra-short-throw, high-image-quality projection lens according to any one of claims 1 to 6, wherein: The projection lens (100) has only two groups.

8. A projector, comprising a housing, characterized in that: It also includes an ultra-short-throw, high-image-quality projection lens (100) according to any one of claims 1 to 7, wherein the projection lens (100) is arranged on the housing.

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