CN103064175B - Projection lens - Google Patents

Abstract

A projection lens comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from an enlargement side to a reduction side. The diopters of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are respectively negative, positive, negative and positive. The diopter of the fourth lens is larger than the diopter of the first lens and the second lens. The refractive index of the fourth lens is N_dAnd the focal length is f₄. The focal length of the fifth lens is f₅. The projection lens satisfies 0.45 < | f₄/(f₅×N_d) The | is less than 1.2, so as to obtain the advantages of better imaging quality and small volume.

Description

projection lens

technical field

The invention relates to a lens, and in particular to a projection lens.

Background technique

With the advancement of technology, Pico Projection Lens has gradually become one of the mainstream in the market. The main market of micro-projection lenses is positioned in portable personal electronic products, so low price has also become an important factor. In addition, an important feature of the pico projector is that the light source is changed from the traditional high-pressure mercury lamp (UHP) to an environmentally friendly and power-saving light-emitting diode light source. However, it is hoped to maintain high brightness while reducing the size, which means that the lens has a smaller numerical aperture (F number), generally 2.4. In order to obtain higher luminous flux, the numerical aperture must be reduced, and using a large aperture lens is another effective method. However, as the aperture becomes larger, the lens becomes relatively larger, resulting in a sharp increase in aberrations, so the difficulty of optical design is greatly increased. Generally speaking, many patents usually use aspherical lenses to correct aberrations or increase lenses, which will run counter to the goal of cost reduction.

In addition, in addition to the above-mentioned trends of micro-projection lenses, another key point is Short Throw Ratio. This means that a large screen can be projected at a relatively short projection distance. However, a large projection angle will greatly increase the optical aberration, so it will become difficult to correct the aberration in the optical design.

U.S. Patent No. 5933280 discloses a projection lens, which includes five lenses, the first lens is aspheric, the second lens is aspheric, the third lens is biconvex, the fourth lens is aspheric and the fifth lens It is an aspheric surface, wherein the diopter of the third lens is greater than 70% of the diopter of the entire optical system. In addition, low-dispersion high-refractive materials are commonly used for projection lenses for green images, and high-dispersion high-refractive materials are used for red and blue projection lenses.

U.S. Patent No. 7075622 discloses a projection lens, which includes six lenses, which are negative first lens, positive second lens, negative third lens, negative fourth lens, and positive fifth lens. lens and the positive sixth lens, wherein the fourth lens and the fifth lens are cemented lenses 40 . In addition, the first lens and the second lens have the function of eliminating off-axis coma, astigmatism and distortion, and properly arranging the second lens, the third lens and the fourth lens can make the light entering the fourth lens almost parallel to the optical axis The light entering the fourth lens will not have chromatic aberration.

U.S. Patent No. 6124978 discloses a projection lens, which is a Gaussian structure and includes six lenses, wherein these lenses are sequentially a first lens with a positive refractive power, a second lens with a negative refractive power, and a third lens with a negative refractive power. The lenses include a lens with negative refractive power and a lens with positive refractive power, a fourth lens with positive refractive power, and a fifth lens with positive refractive power. In particular, this structure can achieve the purpose of correcting astigmatism, small aperture value and overall length of the optical structure.

US Patent No. 7679832 discloses a projection lens composed of five lenses. These lenses are sequentially a first lens with a negative refractive power, a second lens with a positive refractive power, a third lens with a positive refractive power, and the third lens includes a lens with a positive refractive power and a lens with a negative refractive power. lens, and a fourth lens with a positive refractive power. The projection lens can achieve the advantages of short optical structure, wide viewing angle and high resolution.

Contents of the invention

The invention provides a projection lens, which has the advantages of better imaging quality and small volume.

Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

To achieve one or part or all of the above objectives or other objectives, an embodiment of the present invention provides a projection lens, which is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens. The first lens, the second lens, the third lens, the fourth lens and the fifth lens are arranged in order from the enlargement side to the reduction side. The diopters of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are respectively negative, negative, positive, negative, and positive. The diopter of the fourth lens is greater than the diopter of the first lens and the second lens. In addition, the refractive index of the fourth lens is N _d and the focal length is f ₄ , and the focal length of the fifth lens is f ₅ , wherein the projection lens satisfies 0.45<│f ₄ /(f ₅ ×N _d )│<1.2. The curvature of the surface of the fourth lens close to the reduction side is different from the curvature of the surface of the fifth lens close to the enlargement side, and at least two of the third lens, the fourth lens and the fifth lens are aspherical lenses.

In one embodiment of the present invention, the focal length of the third lens is f ₃ , and the distance between the surface of the fifth lens near the reduction side and the image processing element is d _BF , wherein the projection lens satisfies 0.45<d _BF /f ₃ < 1.3.

In an embodiment of the present invention, at least one surface of the first lens and the second lens is aspherical.

In an embodiment of the present invention, at least two of the third lens, the fourth lens and the fifth lens each have an aspheric surface.

In an embodiment of the present invention, each of the first lens and the second lens is a convex-concave lens with a convex surface facing the magnifying side. The third lens is a biconvex lens, the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens.

In an embodiment of the present invention, each surface of the first lens, the second lens, the third lens and the fourth lens is aspherical.

In one embodiment of the present invention, the first lens is a convex-concave lens with a convex surface facing the magnification side, the second lens is a biconcave lens, the third lens is a biconvex lens, the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens.

In an embodiment of the present invention, each surface of the first lens, the second lens, the fourth lens and the fifth lens is aspheric.

In an embodiment of the present invention, the projection lens further includes an aperture stop, wherein the aperture stop is disposed between the third lens and the fourth lens.

In an embodiment of the invention, the numerical aperture of the projection lens is between 2.2 and 2.0.

Based on the above, the embodiments of the present invention can achieve at least one of the following advantages or effects. The spherical aberration produced by the projection lens at large apertures is corrected by the fourth lens, so that good image projection can be presented at large apertures. In addition, the projection lens can also effectively correct the chromatic aberration generated during projection by satisfying 0.45<│f ₄ /(f ₅ ×N _d )│<1.2 at the same time, thereby providing better quality projection images. In addition, the projection lens can also meet the requirements of 0.45<d _BF /f ₃ <1.3. When the condition exceeds the upper limit, the Back Focal Length (BF) will become relatively large, which cannot meet the compact condition. At the same time, the off-axis aberration Rapid deterioration. When the condition exceeds the lower limit, the BF becomes relatively small, and it is easy to interfere with and collide with the lighting system on the mechanism, and it is easy to cause insufficient peripheral light.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, a number of embodiments will be described below in detail with reference to the accompanying drawings.

Description of drawings

1 is a schematic diagram of a projection lens according to an embodiment of the present invention;

2A to 2D and FIG. 3 are imaging optical simulation data diagrams of the projection lens of FIG. 1;

4 is a schematic diagram of a projection lens according to another embodiment of the present invention;

5A to 5D and FIG. 6 are imaging optical simulation data diagrams of the projection lens of FIG. 4;

Detailed ways

The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed descriptions of multiple embodiments in conjunction with the accompanying drawings. The directional terms mentioned in the following embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only referring to the directions of the drawings. Accordingly, the directional terms are used to illustrate, not to limit, the invention.

FIG. 1 is a schematic diagram of a projection lens according to an embodiment of the present invention. Please refer to FIG. 1 , the projection lens 100 of this embodiment includes a first lens 110 , a second lens 120 , a third lens 130 , a fourth lens 140 and a fifth lens 150 arranged in sequence from the enlargement side to the reduction side. The diopters of the first lens 110 , the second lens 120 , the third lens 130 , the fourth lens 140 and the fifth lens 150 are negative, negative, positive, negative, and positive, respectively. In this embodiment, both the first lens 110 and the second lens 120 are convex-concave lenses with convex surfaces facing the magnification side, the third lens 130 is a biconvex lens, the fourth lens 140 is a biconcave lens, and the fifth lens 150 is a biconvex lens. Figure 1 shows.

In addition, the diopter of the fourth lens 140 is greater than the diopter of the first lens 110 and the second lens 120, so as to correct the spherical aberration phenomenon generated by the projection lens 100 during projection. In this way, when the projection lens 100 performs large-angle image projection, It will be able to present good image projection at short focal length, such as: high-resolution projected image. That is to say, the projection lens 100 of the present embodiment can utilize the property of the fourth lens 140 having greater refractive power to present better optical performance. In addition, in correcting the chromatic aberration generated by the projection lens 100 during projection, the projection lens 100 can effectively correct the chromatic aberration generated during projection by satisfying the following conditional formula (1), thereby providing better quality images. Projected screen.

0.45<│f ₄ /(f ₅ ×N _d4 )│<1.2 …………Conditional expression (1)

The fourth lens 140 has a refractive index N _d4 and a focal length of f ₄ , and the fifth lens 150 has a focal length of f ₅ .

In addition, in order to enable the projection lens 100 to have a larger system aperture, that is, a smaller aperture value (F number), the projection lens 100 of this embodiment can satisfy the above conditional formula (1) and simultaneously satisfy the following conditions Formula (2), so that the numerical aperture of the projection lens 100 can fall between 2.2 and 2.0, or even less than 2.0.

0.45<d _BF /f ₃ <1.3 …………Conditional expression (2)

The focal length of the third lens 130 is f ₃ , and the distance between the surface S10 of the fifth lens 150 near the reducing side and the image processing element 160 is d _BF .

In detail, the distance between the surface S10 of the fifth lens 150 near the reduction side _and the image processing element 160 is _dBF , which will vary due to focusing. Therefore, _dBF can be defined as the projection lens 100 at a reasonable When the projection distance is about 1M to 3M, the back focal length when the focus is clear. In this embodiment, if the projection lens 100 satisfies d _BF /f ₃ >1.3, the d _BF will become relatively large, which cannot satisfy the compact condition, and at the same time, the off-axis aberration will also deteriorate rapidly; if When the projection lens 100 satisfies 0.45>d _BF /f ₃ , it is easy to cause mechanical interference and collision with the lighting system, and it is easy to cause insufficient peripheral light. In other words, the projection lens 100 can effectively improve the quality of the projected picture by properly designing the relationship between the focal length _f3 of the third lens 130 and the distance d _BF between the fifth lens 150 and the image processing device 160. And it can also have the advantage of volume miniaturization.

In addition, in order to further improve the problems of coma, astigmatism or distortion that may be generated by the projection lens 100 during projection, at least one surface of the first lens 110 and the second lens 120 is The aspheric surface. In this embodiment, both surfaces of the first lens 110 and the second lens 120 are designed as aspheric surfaces, as described in the following paragraphs. That is to say, the projection lens of this embodiment can eliminate the aberration outside the optical axis by making at least one surface of the first lens 110 and the second lens 120 each be aspherical. Furthermore, since the projection lens 100 of this embodiment can exhibit a larger projection angle, this embodiment can design at least two surfaces of the third lens 130, the fourth lens 140, and the fifth lens 150 as aspheric surfaces. , to correct the distortion that the projection lens 100 tends to produce when projecting at a short focal length, wherein the present embodiment takes the surfaces of the first lens 110, the second lens 120, the third lens 130 and the fourth lens 140 as aspherical surfaces as an example illustrate.

Generally speaking, the above-mentioned image processing element 160 (Image Processing Device) can be disposed on the reduction side. In this embodiment, the image processing element 160 may be a light valve (LightValve) or a photosensitive element. In addition, a glass cover may also be configured to protect the image processing element 160 . In this embodiment, the projection lens 100 can project the image on the reduction side to the enlargement side for image projection.

In addition, the projection lens 100 may further include an aperture stop 170 , wherein the aperture stop 170 is disposed between the third lens 130 and the fourth lens 140 , as shown in FIG. 1 .

As a supplementary note, when designing the projection lens 100 , it is not limited that the projection lens 100 must satisfy the conditions listed above at the same time, but the conditions listed above may be selectively satisfied depending on the requirements of optical imaging quality.

An embodiment of the projection lens 100 will be described below. It should be noted that the data listed in the following Table 1 is not intended to limit the present invention. After referring to the present invention, any person skilled in the art can make appropriate changes to its parameters or settings by applying the principles of the present invention However, it should still belong to the scope of the present invention.

Table I

f ₃ 18.349 f ₄ -15.173 f ₅ 11.428 _f 16.15 │f ₄ /(f ₅ ×N _d4 )│ 0.72 d _BF /f ₃ 0.88

In Table 1, the spacing refers to the linear distance between two adjacent surfaces on the optical axis A of the projection lens 100, for example, the spacing of the surface S1, that is, the linear distance between the surface S1 and the surface S2 on the optical axis A . For the thickness, refractive index and Abbe number corresponding to each lens in the remarks column, please refer to the values corresponding to each pitch, refractive index and Abbe number in the same column. In addition, in Table 2, the surfaces S1 and S2 are the two surfaces of the first lens 110, and the surfaces S3 and S4 are the two surfaces of the second lens 120, wherein the surface S3 is substantially convex because of the aspherical design, and the surface S5 and S6 are two surfaces of the third lens 130 , surfaces S7 and S8 are two surfaces of the fourth lens 140 , and surfaces S9 and S10 are two surfaces of the fifth lens 150 . Please refer to Table 1 for parameters such as the radius of curvature and spacing of each surface, and will not repeat them here.

In addition, the above-mentioned surfaces S1-S8 are even-order aspheric surfaces, which can be expressed by the following formula:

$\begin{array}{c}\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; cr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}\\ <span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}$

In the formula, Z is the offset (Sag) in the direction of the optical axis A, and c is the reciprocal of the radius of the Osculating Sphere, that is, the radius of curvature near the optical axis A (such as the curvature of S1 and S2 in Table 2 the reciprocal of the radius). k is the quadratic surface coefficient (Conic), r is the height of the aspheric surface, which is the height from the center of the lens to the edge of the lens, and A ₂ , A _{4 ,} A ₆ , A 8 , A ₁₀ , A ₁₂ , A ₁₄ ... is the aspheric coefficient (Aspheric Coefficient), and the coefficient A2 is 0 in this embodiment. Table 2 below lists the aspherical parameter values of surfaces S1-S8.

Table II

Aspheric parameters Quadratic coefficient k Factor A ₄ Coefficient A ₆ Factor A ₈ S1 4.4803 5.1647E-5 -1.1645E-7 2.7073E-10 S2 0.4010 3.9936E-5 -1.3059E-7 -4.8232E-10 S3 -999.7554 2.3672E-4 -1.9173E-5 3.1797E-7 S4 -6.2457 1.9143E-3 -5.7178E-5 8.6673E-7 S5 -1.5451 1.5520E-4 2.8276E-8 -3.3000E-9 S6 -10.6950 -3.6392E-5 3.4163E-6 -4.8183E-8 S7 -30.0000 2.7325E-4 -7.7020E-5 3.9418E-6 S8 -1.7216 3.2808E-4 -5.7597E-5 2.5478E-6

2A to 2D and FIG. 3 are imaging optical simulation data diagrams of the projection lens in FIG. 1 . In detail, FIG. 2A is a simulation graph of spherical aberration (Spherical Aberration), wherein FIG. 2A is simulated by light of two different wavelengths (460nm and 550nm respectively). FIG. 2B is a simulation graph of astigmatism, wherein FIG. 2B is simulated by light of two different wavelengths (460nm and 550nm respectively). FIG. 2C is a simulation graph of distortion (Distortion), wherein FIG. 2C is simulated by light of a wavelength (for example: 680nm). FIG. 2D is a simulation graph of lateral chromatic aberration, and FIG. 2D is simulated by light of a wavelength (eg: 550nm). In addition, Figure 3 is a simulation graph of Ray Fan analysis, in which Figure 3 is simulated by light of three different wavelengths (460nm, 550nm, and 680nm). Since the graphs shown in FIGS. 2A to 2D and FIG. 3 are all within the standard range, it can be verified that the projection lens 100 of this embodiment can indeed have good optical imaging quality.

FIG. 4 is a schematic diagram of a projection lens according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 4 at the same time. The projection lens 200 of this embodiment adopts a similar concept and structure to the aforementioned projection lens 100 . Specifically, the first lens 210 is a convex-concave lens with a convex surface facing the magnification side, the second lens 220 is a convex-concave lens with a convex surface facing the magnification side, the third lens 230 is a biconvex lens, the fourth lens 240 is a biconcave lens, and the fifth lens 250 is a biconvex lens. In this embodiment, the surfaces of the first lens 210, the second lens 220, the fourth lens 240, and the fifth lens 250 are aspheric, that is, the first lens 210, the second lens 220, the fourth lens 240, and the fifth lens The five lenses 250 are aspherical lenses.

In the projection lens 200, since the diopter of the fourth lens 240 is also greater than the diopter of the first lens 210 and the second lens 220, and the projection lens 200 also satisfies the aforementioned conditional formula (1) or conditional formula (2), therefore, in this embodiment The projection lens 200 of this example also has the advantages and functions mentioned above for the projection lens 100 .

Similarly, in order to further improve the problems of coma, astigmatism or distortion that may be generated by the projection lens 200 during projection, the first lens 210 and the second lens 220 each have at least one surface It is an aspheric surface, and in this embodiment, both surfaces of the first lens 210 and the second lens 220 adopt an aspheric design, as described in the following paragraphs. That is to say, the projection lens of this embodiment can eliminate the aberration outside the optical axis by making at least one surface of the first lens 210 and the second lens 220 each be aspherical. Furthermore, since the projection lens 200 of this embodiment can exhibit a larger projection angle, this embodiment can design at least two surfaces of the third lens 230, the fourth lens 240, and the fifth lens 250 as aspherical surfaces, In order to correct the distortion that is likely to occur when the projection lens 200 is projected at a short focal length, this embodiment is illustrated by taking the surfaces of the first lens 210, the second lens 220, the fourth lens 240, and the fifth lens 250 as aspheric surfaces. .

An embodiment of the projection lens 200 will be described below. It should be noted that the data listed in the following Table 3 is not intended to limit the present invention. After referring to the present invention, any person skilled in the art can make appropriate changes to its parameters or settings by applying the principles of the present invention action, it should still belong to the scope of the present invention.

Table three

f ₃ 21.127

f ₄ -13.984 f ₅ 8.913 _f 16.62 │f ₄ /(f ₅ ×N _d4 )│ 0.961 d _BF /f ₃ 0.787

In Table 3, the spacing refers to the linear distance between two adjacent surfaces on the optical axis A of the projection lens 200, for example, the spacing of the surface S1, that is, the linear distance between the surface S1 and the surface S2 on the optical axis A . For the thickness, refractive index and Abbe number corresponding to each lens in the remarks column, please refer to the values corresponding to each pitch, refractive index and Abbe number in the same column. In addition, in Table 3, the surfaces S1 and S2 are the two surfaces of the first lens 210, the surfaces S3 and S4 are the two surfaces of the second lens 220, the surfaces S5 and S6 are the two surfaces of the third lens 230, and the surfaces S7 and S8 are are the two surfaces of the fourth lens 240 , and the surfaces S9 and S10 are the two surfaces of the fifth lens 250 . For parameters such as radius of curvature and spacing of each surface, please refer to Table 4, which will not be repeated here.

In addition, the above-mentioned surfaces S1-S4, S7-S10 are even-order aspheric surfaces, which can be expressed by the following formula:

$\begin{array}{c}\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; cr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}\\ <span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}$

In the formula, Z is the offset (Sag) in the direction of the optical axis A, and c is the reciprocal of the radius of the Osculating Sphere, that is, the radius of curvature near the optical axis A (such as the curvature of S1 and S2 in Table 2 the reciprocal of the radius). k is the quadratic surface coefficient (Conic), r is the height of the aspheric surface, which is the height from the center of the lens to the edge of the lens, and A ₂ , A _{4 ,} A ₆ , A 8 , A ₁₀ , A ₁₂ , A ₁₄ ... is the aspheric coefficient (Aspheric Coefficient), and the coefficient A2 is 0 in this embodiment. Table 2 below lists the aspheric parameter values of surfaces S1-S4, S7-S10.

Table four

5A to 5D and FIG. 6 are imaging optical simulation data diagrams of the projection lens shown in FIG. 4 . In detail, FIG. 5A is a simulation graph of spherical aberration (Spherical Aberration), wherein FIG. 5A is simulated by light of two different wavelengths (460nm and 550nm respectively). FIG. 5B is a simulation graph of astigmatism, wherein FIG. 5B is simulated by light of two different wavelengths (460nm and 550nm respectively). FIG. 5C is a simulation graph of distortion, wherein FIG. 5C is simulated by light of a wavelength (eg, 680nm). FIG. 5D is a simulation graph of lateral chromatic aberration, and FIG. 5D is simulated by light of a wavelength (eg, 550 nm). In addition, Figure 6 is a simulation graph of Ray Fan analysis, in which Figure 3 is simulated by light of three different wavelengths (460nm, 550nm, and 680nm). Since the graphs shown in FIGS. 5A to 5D and FIG. 6 are all within the standard range, it can be verified that the projection lens 200 of this embodiment can indeed have good optical imaging quality.

To sum up, the projection lens of the present invention has at least the following advantages. First, by making the refractive power of the fourth lens larger than that of the first lens and the second lens, it means that the projection lens of this embodiment can use the characteristics of the fourth lens having a larger refractive power to correct the projection. The spherical aberration phenomenon produced by the lens during projection, so that when the projection lens performs large-angle image projection, it will be able to present good image projection at a short focal length. In addition, the projection lens can also effectively correct the chromatic aberration generated during projection by satisfying 0.45<│f ₄ /(f ₅ ×N _d4 )│<1.2 at the same time, thereby providing better quality projection images. In addition, the projection lens can also satisfy 0.45<d _BF /f ₃ <1.3, so as to obtain a larger system aperture, that is, a smaller aperture value (F number). Furthermore, it is also possible to improve the coma aberration that the projection lens may produce during projection by properly selecting at least one of the four surfaces of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens to be aspherical. (Coma), astigmatism (Astigmatism) or distortion (Distortion) problems.

The above are only preferred embodiments of the present invention, and should not limit the scope of the present invention with this, that is, all simple equivalent changes and modifications made according to the claims of the present invention and the contents of the description of the invention still belong to Within the scope covered by the patent of the present invention. In addition, any embodiment or claim of the present invention does not necessarily achieve all the objects or advantages or features disclosed in the present invention. In addition, the abstract and the title are only used to assist in the search of patent documents, and are not used to limit the scope of rights of the present invention. In addition, terms such as first lens, second lens, etc. mentioned in the specification are only used to indicate the names of components, and are not used to limit the upper limit or lower limit of the number of components.

Claims (10)

1. a projection lens, be made up of the first lens, the second lens, the 3rd lens, the 4th lens and the 5th lens, described first lens, described second lens, described 3rd lens, described 4th lens and described 5th lens by Zoom Side to reduced side sequential, and the diopter of described first lens, described second lens, described 3rd lens, described 4th lens and described 5th lens is respectively negative, negative, positive, negative, positive, the diopter of described 4th lens is greater than the diopter of described first lens and described second lens

The refractive index of wherein said 4th lens is N _d4and focal length is f ₄, the focal length of described 5th lens is f ₅, described projection lens meets 0.45< │ f ₄/ (f ₅× N _d4) │ <1.2,

The curvature of wherein said 4th lens near the surface of reduced side is different from the curvature of described 5th lens near the surface of Zoom Side, and described 3rd lens, described 4th lens and described 5th lens at least it two is non-spherical lens.

2. projection lens as claimed in claim 1, the focal length of wherein said 3rd lens is f ₃, the distance of described 5th lens between the surface of described reduced side to image processing elements is d _bF, described projection lens meets 0.45<d _bF/ f ₃<1.3.

3. projection lens as claimed in claim 1, wherein said first lens and described second lens at least respectively have a surface for aspheric surface.

4. projection lens as claimed in claim 1, at least it two respectively has a surface to be aspheric surface for wherein said 3rd lens, described 4th lens and described 5th lens.

5. projection lens as claimed in claim 1, wherein said first lens and described second lens are respectively the meniscus convex surface facing described Zoom Side, described 3rd lens are biconvex lens, and described 4th lens are biconcave lens, and described 5th lens are biconvex lens.

6. projection lens as claimed in claim 5, each surface of wherein said first lens, described second lens, described 3rd lens and described 4th lens is aspheric surface.

7. projection lens as claimed in claim 1, wherein said first lens are the meniscus convex surface facing described Zoom Side, and described second lens are biconcave lens, and described 3rd lens are biconvex lens, described 4th lens are biconcave lens, and described 5th lens are biconvex lens.

8. projection lens as claimed in claim 7, each surface of wherein said first lens, described second lens, described 4th lens and described 5th lens is aspheric surface.

9. projection lens as claimed in claim 1, also comprises:

Aperture diaphragm, is configured between described 3rd lens and the 4th lens.

10. projection lens as claimed in claim 1, the numerical aperture of wherein said projection lens drops between 2.2 and 2.0.