JP2018109755A - Fixed-focus lens - Google Patents

Abstract

The present invention provides a fixed focus lens. The fixed focus lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in order from an enlargement end to a reduction end, Among them, the refractive powers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are negative, negative, positive, positive, negative, positive, and positive, respectively. Yes, and the first lens and the seventh lens are aspherical lenses. [Selection diagram] Fig. 1

Description

  The present invention relates to an imaging lens, and more particularly, to a fixed lens.

  The projector is used to form an image screen on the screen, and its main operating principle is that the display assembly converts the illumination beam provided by the light source into an image beam, and the projection lens converts the image beam. Projecting on a screen to form a video screen on the screen.

  At present, the projectors in the market tend to have development goals of miniaturization and weight reduction, and in particular, small projectors are attracting attention. Thus, each lens manufacturer is dedicated to designing an appropriate lens structure so as to reduce the weight and volume of the projection lens. However, at the same time as achieving the above advantages, it is often easy to sacrifice the imaging quality of the projection lens. Therefore, how to design a projection lens having good imaging quality under conditions that consider factors such as size and weight is one of the challenges for lens manufacturers.

  In addition, since this "background art" part is only for helping an understanding to the content of this invention, the content currently disclosed by this "background art" part is not known to those skilled in the art. May include technology. Thus, the content disclosed in this “Background” section is well known to those skilled in the art prior to the filing of the present invention, or the problem to be solved by one or more embodiments of the present invention. Does not mean that

  An object of the present invention is to provide a fixed focus lens having the advantages of small size and good imaging quality.

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

  In order to achieve one or some or all of the above-described objects or other objects, the fixed focus lens according to the present invention includes a first lens, a second lens, and a third lens arranged in order from the enlargement end to the reduction end. , Fourth lens, fifth lens, sixth lens and seventh lens, of which the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens and seventh lens are refracted The forces (also called diopters) are negative, negative, positive, positive, negative, positive and positive, respectively, and the first lens and the seventh lens are aspheric lenses.

  The fixed focus lens according to the present invention adopts a seven-lens structure, and thus has the advantages of relatively small size (relatively short total length) and relatively light weight. Further, by combining the respective refractive powers of the seven lenses and using the aspherical lenses for the first lens and the seventh lens, the fixed focus lens according to the present invention also has an advantage of good imaging quality.

  In order to make the above features and advantages of the present invention more apparent, the following detailed description will be given by way of example and with reference to the accompanying drawings.

It is a figure which shows the fixed focus lens in one Example of this invention. FIG. 2 is a diagram showing lateral color in the embodiment of the fixed focus lens of FIG. FIG. 2 is a diagram showing field curvature in one embodiment of the fixed focus lens of FIG. FIG. 2 is a diagram showing distortion in the embodiment of the fixed focus lens of FIG. FIG. 2 is a diagram showing a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 2 is a diagram illustrating a through-focus multicolor diffraction modulation transfer function (polychromatic diffraction through focus MTF) in the embodiment of the fixed focus lens of FIG. FIG. 2 is a diagram showing a through-focus polychromatic diffraction modulation transfer function under one environmental temperature in the embodiment of the fixed focus lens of FIG. FIG. 2 is a diagram showing a through focus polychromatic diffraction modulation transfer function under another environmental temperature in the embodiment of the fixed focus lens of FIG. It is a figure which shows the fixed focus lens in the other Example of this invention. FIG. 4 is a diagram showing a color difference in the horizontal direction in one embodiment of the fixed focus lens of FIG. FIG. 4 is a diagram showing field curvature in an embodiment of the fixed focus lens of FIG. FIG. 4 is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. FIG. 4 is a diagram showing a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 4 is a diagram showing a through-focus polychromatic diffraction modulation transfer function in the embodiment of the fixed focus lens of FIG. FIG. 4 is a diagram showing a through-focus polychromatic diffraction modulation transfer function under one environmental temperature in the embodiment of the fixed focus lens of FIG. FIG. 4 is a diagram showing a through-focus polychromatic diffraction modulation transfer function under another environmental temperature in the embodiment of the fixed focus lens of FIG. It is a figure which shows the fixed focus lens in the other Example of this invention. FIG. 6 is a diagram showing the color difference in the horizontal direction in one embodiment of the fixed focus lens of FIG. FIG. 6 is a diagram showing field curvature in one embodiment of the fixed focus lens of FIG. FIG. 6 is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. FIG. 6 is a diagram showing a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 6 is a diagram showing a through focus polychromatic diffraction modulation transfer function in the embodiment of the fixed focus lens of FIG. It is a figure which shows the fixed focus lens in the other Example of this invention. FIG. 8 is a diagram showing a lateral color difference in an example of the fixed focus lens of FIG. FIG. 8 is a diagram showing field curvature in an example of the fixed focus lens of FIG. FIG. 8 is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. FIG. 8 is a diagram illustrating a transverse ray fan plot in the embodiment of the fixed focus lens of FIG. FIG. 8 is a diagram showing a through-focus polychromatic diffraction modulation transfer function in one embodiment of the fixed focus lens of FIG. It is a block diagram of the projection apparatus in one Example of this invention.

  The above-described and other technical contents, features, functions, and effects of the present invention will become apparent from the following detailed description of preferred embodiments based on the accompanying drawings. It should be noted that the terms for the directions mentioned in the following examples, such as up, down, left, right, front or back, are only directions of the attached drawings. Accordingly, the directional terminology used is for the purpose of describing the present invention only and is not intended to limit the present invention.

  FIG. 1 is a diagram showing a fixed focus lens in one embodiment of the present invention. As shown in FIG. 1, the fixed focus lens 100 of the present embodiment is used in, for example, a projection apparatus, but may be used in an image acquisition apparatus (not shown). When the fixed focus lens 100 is used in the projection device, the light valve P of the projection device is installed at the reduction end of the fixed focus lens 100, and the fixed focus lens 100 expands the image light flux from the light valve P. Used to project onto a screen (not shown) located at the edge. When the fixed focus lens 100 is used in the image acquisition device, the image sensing assembly of the image acquisition device is installed at the reduction end, and the fixed focus lens 100 is used to image the object at the enlargement end on the image sensing assembly. .

  The fixed focus lens 100 of the present embodiment includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5 arranged in order from the enlargement end to the reduction end along the optical axis OA. , Including the sixth lens L6 and the seventh lens L7, of which the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 The refractive powers are negative, negative, positive, positive, negative, positive and positive, respectively, and the first lens L1 and the seventh lens L7 are aspheric lenses.

  In the present embodiment, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 constitute, for example, the first lens group 110, the fifth lens L5, the sixth lens L6, and the seventh lens. L7 constitutes the second lens group 120, for example. The refractive power of the first lens group 110 is negative, for example, and the refractive power of the second lens group 120 is positive, for example. The fixed focus lens 100 further includes, for example, an aperture 130, which is disposed between the fourth lens L4 and the fifth lens L5.

  In the present embodiment, the first lens L1 is, for example, a convex-concave lens whose convex surface faces the enlargement end, the second lens L2 is, for example, a biconcave lens, and the third lens L3 is, for example, a biconvex lens. The fourth lens L4 is, for example, a concavo-convex lens whose convex surface faces the magnifying end, and the fifth lens L5 is, for example, a convex-concave lens whose convex surface faces the magnifying end, and the sixth lens L6 and the seventh lens L7. Are both biconvex lenses, for example. Also, the second lens L2 and the third lens L3 constitute, for example, one compound lens (Cemented lens), and this compound lens joins, for example, the second lens L2 and the third lens L3 with an adhesive. This is a bi-junction lens constituted by the above. The fifth lens L5 and the sixth lens L6 constitute another compound lens, and this compound lens is, for example, a double-joint formed by joining the fifth lens L5 and the sixth lens L6 with an adhesive. It is a lens.

  In the present embodiment, the fourth lens L4 is, for example, an aspheric lens, but it may be a spherical lens. The second lens L2, the third lens L3, the fifth lens L5, and the sixth lens L6 are, for example, spherical lenses, but any of the second lens L2, the third lens L3, the fifth lens L5, and the sixth lens L6 One of them may select and use an aspheric lens. The material of the first lens L1 and the fourth lens L4 is, for example, plastic, and the material of the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6, and the seventh lens L7 is, for example, , Glass.

  When used in a projection apparatus, the fixed focus lens 100 may further include a prism 140, which is disposed on one side of the seventh lens L7 away from the sixth lens L6, and also the seventh lens L7 and the light valve P. Located between and. This prism 140 is, for example, a common total internal reflection prism (TIR prism) in a projection apparatus. Further, both the first lens group 110 and the second lens group 120 of the present embodiment can move along the optical axis OA so as to perform focusing, and the aperture 130 and the second lens group 120 are Can be linked. Specifically, when the image screen projected on the screen becomes blurred due to a change in the distance between the screen and the fixed focus lens 100, the distance between the first lens group 110 and the aperture 130 is reduced. Focusing is performed by adjusting the distance and the distance between the second lens group 120 and the light valve P, thereby making the video screen clear.

  The fixed focus lens 100 of this embodiment employs a seven-lens structure. Since the number of lenses is relatively small, the size is relatively small (total length is relatively short), and the weight is relatively light. Also, the total length of the fixed focus lens 100 is designed by designing the second lens L2 and the third lens L3 as one bi-junction lens and designing the fifth lens L5 and the sixth lens L6 as another bi-junction lens. Can be further shortened. Further, by combining the respective refractive powers of the seven lenses and using the aspherical lenses for the first lens L1 and the seventh lens L7, the fixed focus lens 100 has an advantage of good image quality. In addition, the refractive index of the lens changes due to a change in temperature, which may affect the refractive power, and lenses made of different materials also have different refractive index changes. In order to avoid blurring of the image screen due to such changes, the first lens L1 and the fourth lens L4 of this embodiment employ plastic lenses, and the second lens L2, the third lens L3, Glass lenses are used for the fifth lens L5, the sixth lens L6, and the seventh lens L7. This combination of materials compensates for changes in the refractive index of each lens due to changes in temperature, so that the image screen is not blurred due to changes in temperature during the operation of the fixed focus lens 100. it can.

  In one embodiment, in order to provide a sufficient space for installing the prism 140 between the seventh lens L7 and the light valve P, the fixed focus lens 100 satisfies the relational expression BFL / EFL> 1.5. Of these, BFL (back focal length) is the back focal length of the fixed focus lens 100, and EFL (effective focal length) is the effective focal length of the fixed focus lens 100.

  In one embodiment, in order to further reduce the total length of the fixed focus lens 100 and consider the viewing angle, the fixed focus lens 100 may satisfy the relational expression 5.4 <TTL / EFL <15, TTL (total track length) is the total length of the fixed focus lens 100, and EFL is the effective focal length of the fixed focus lens 100. The total length here refers to the distance from the surface of the first lens L1 facing the enlargement end to the surface of the seventh lens L7 facing the reduction end.

  In one example, the fixed focus lens 100 satisfies, for example, the relationship 1.5 <D45 / D7P <4.8, where D45 is the distance between the fourth lens L4 and the fifth lens L5, and D7P is , The distance between the seventh lens L7 and the prism 140. In this way, the first lens group 110 and the second lens group 120 have a wide range of movement when focusing, and focusing is easy.

  In one embodiment, the fixed focus lens 100 satisfies, for example, the relational expression 2.5 <| f4 / f1 | <4, where f4 is the focal length of the fourth lens L4, and f1 is the first lens L1. Is the focal length. In this way, the first lens L1 and the fourth lens L4 can compensate for the problem of image enlargement or reduction due to the temperature difference when the fixed focus lens 100 is operated, and can improve the imaging quality.

  Table 1 shows an example of each parameter of the fixed focus lens 100. Note that the data in Table 1 does not limit the present invention. Those skilled in the art can refer to the present invention and appropriately change its parameters or settings, all of which belong to the technical scope of the present invention.

表１中の距離とは、２つの隣接する表面の、固定焦点レンズ100の光軸OA上での直線距離を指す。例えば、表面S1の距離は、表面S1と表面S2との光軸OA上での直線距離であり、表面S13の距離は、表面S13とプリズム140との光軸OA上での直線距離である。曲率半径が正の値である表面は、該表面が拡大端に向かって湾曲することを表し、曲率半径が負の値である表面は、該表面が縮小端に向かって湾曲することを表す。

The distance in Table 1 refers to the linear distance on the optical axis OA of the fixed focus lens 100 between two adjacent surfaces. For example, the distance of the surface S1 is a linear distance on the optical axis OA between the surface S1 and the surface S2, and the distance of the surface S13 is a linear distance on the optical axis OA between the surface S13 and the prism 140. A surface with a positive radius of curvature indicates that the surface is curved toward the enlarged end, and a surface with a negative value of the radius of curvature indicates that the surface is curved toward the reduced end.

  The first lens L1, the fourth lens L4, and the seventh lens L7 are, for example, both aspherical lenses, of which the surface S1, the surface S2, the surface S6, the surface S7, the surface S12, and the surface S13 are aspherical. Yes, it can be expressed by the following formula.

式中で、Zは、光軸方向における座標値であり、B、C、D、E、F、G及びHは、非球面係数であり、Kは、二次曲面定数であり、Rは、曲率半径であり、Yは、光軸方向に直交する座標値であり、また、上方を正方向とする。上述の各非球面のパラメータは、表２に示される。

In the equation, Z is a coordinate value in the optical axis direction, B, C, D, E, F, G and H are aspherical coefficients, K is a quadric surface constant, and R is The radius of curvature, Y is a coordinate value orthogonal to the optical axis direction, and the upward direction is the positive direction. The parameters of each aspheric surface described above are shown in Table 2.

図2Aは、図1の固定焦点レンズの一実施例における横方向色差を示す図である。図2Bは、図1の固定焦点レンズの一実施例における像面湾曲を示す図である。図2Cは、図1の固定焦点レンズの一実施例における歪みを示す図である。図2Dは、図1の固定焦点レンズの一実施例における横方向光線ファンプロットを示す図である。図2Eは、図1の固定焦点レンズの一実施例におけるスルーフォーカス多色回折変調伝達関数を示す図である図。図2A乃至図2Eに示すように、本実施例の固定焦点レンズ100は、サイズ及び重量を考慮した条件下で、良好な結像品質を有する。また、図2F及び図2Gは、図1の固定焦点レンズの一実施例の異なる環境温度下でのスルーフォーカス多色回折変調伝達関数を示す図であり、そのうち、図2Fの環境温度は、摂氏0度であり、図2Gの環境温度は、摂氏40度である。図2F及び図2Gから分かるように、本実施例の固定焦点レンズ100は、温度の変化による結像品質への影響を軽減することができる。

FIG. 2A is a diagram showing a lateral color difference in an embodiment of the fixed focus lens of FIG. FIG. 2B is a diagram showing field curvature in an example of the fixed focus lens of FIG. FIG. 2C is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. FIG. 2D is a diagram showing a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 2E is a diagram showing a through-focus polychromatic diffraction modulation transfer function in one embodiment of the fixed focus lens of FIG. As shown in FIGS. 2A to 2E, the fixed focus lens 100 of the present embodiment has a good imaging quality under conditions that take size and weight into consideration. FIGS. 2F and 2G are diagrams showing through-focus polychromatic diffraction modulation transfer functions at different environmental temperatures of the embodiment of the fixed focus lens of FIG. 1, in which the environmental temperature in FIG. The ambient temperature in FIG. 2G is 40 degrees Celsius. As can be seen from FIGS. 2F and 2G, the fixed focus lens 100 of the present embodiment can reduce the influence on the imaging quality due to a change in temperature.

  FIG. 3 is a diagram showing a fixed focus lens according to another embodiment of the present invention. As shown in FIG. 3, the configuration of the fixed focus lens 100a of the present embodiment is substantially similar to the above-described fixed focus lens 100. The first lens group 110a of the fixed focus lens 100a also includes the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4, and the second lens group 120a of the fixed focus lens 100a is also the fifth lens L5. A sixth lens L6 and a seventh lens L7. The refractive powers of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are negative, negative, positive, positive and negative, respectively. The first lens L1 and the seventh lens L7 are aspherical lenses. The fixed focus lens 100a may also include an aperture 130 disposed between the fourth lens L4 and the fifth lens L5.

  In the fixed focus lens 100a described above, the types of the first lens L1, the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are the same as those of the fixed focus lens 100 described above. However, the fourth lens L4 is, for example, a convex flat lens or a biconvex lens whose convex surface faces the enlargement end.

  In the present embodiment, the fixed focus lens 100a can satisfy at least one of the following relational expressions according to the design needs.

(1) BFL / EFL> 1.5
(2) 8 <TTL / EFL <18
(3) 1 <D45 / D7P <3
(4) 2.5 <| f4 / f1 | <7
Regarding the relational expression (1), when BFL / EFL <1.5, the fixed focus lens 100a is likely to interfere with other elements of the projection apparatus. Regarding the relational expression (2), when the TTL / EFL> 18, the total length of the fixed focus lens 100a is relatively long, and it is difficult to achieve the advantage of downsizing, and when TTL / EFL <8, the fixed focus lens 100a is difficult to achieve the advantages of both miniaturization and wide angle. As for the relational expression (3), when D45 / D7P> 3, the distance between the fourth lens L4 and the fifth lens L5 is too large, and it is difficult to effectively calibrate TV distortion. In the case of / D7P <1, the distance between the fourth lens L4 and the fifth lens L5 is too small, and mechanism interference is likely to occur. Regarding the relational expression (4), when | f4 / f1 |> 7, the phenomenon of thermal drift of the fixed focus lens 100a can be improved, but the resolution is not good, and | f4 / f1 When <2.5, the fixed focus lens 100a has a relatively good resolution, but the phenomenon of thermal drift is relatively severe. In addition, in order to further improve the problem of the thermal drift phenomenon caused by the lens being subjected to thermal expansion, at least one of the fifth lens L5, the sixth lens L6, and the seventh lens L7 in the second lens group 110a. By selecting a material with negative dn / dt and adjusting the refractive power, the phenomenon of thermal drift can be improved, of which dn represents the change in refractive index and dt is Represents temperature change. In one embodiment, for the seventh lens L7, for example, a material having a negative value of dn / dt is selected.

  Table 3 shows an example of each parameter of the fixed focus lens 100a. Note that the data shown in Table 3 does not limit the present invention. Those skilled in the art can refer to the present invention and appropriately change its parameters or settings, all of which belong to the technical scope of the present invention.

第一レンズL1、第四レンズL4及び第七レンズL7は、例えば、ともに、非球面レンズであり、そのうち、表面S1、表面S2、表面S6、表面S7、表面S12、表面S13は、非球面である。上述の各非球面のパラメータは、表4に示されている。

The first lens L1, the fourth lens L4, and the seventh lens L7 are, for example, both aspherical lenses, of which the surface S1, the surface S2, the surface S6, the surface S7, the surface S12, and the surface S13 are aspherical. is there. The parameters of each aspheric surface described above are shown in Table 4.

図4Aは、図3の固定焦点レンズの一実施例における横方向色差を示す図である。図4Bは、図3の固定焦点レンズの一実施例における像面湾曲を示す図である。図4Cは、図3の固定焦点レンズの一実施例における歪みを示す図である。図4Dは、図3の固定焦点レンズの一実施例における横方向光線ファンプロットを示す図である。図4Eは、図3の固定焦点レンズの一実施例におけるスルーフォーカス多色回折変調伝達関数を示す図である。図4A乃至図4Eに示すように，本実施例の固定焦点レンズ100aは、サイズ及び重量の両方を配慮した条件下で、良好の結像品質を有することができる。また、図4F及び図4Gは、図3の固定焦点レンズの一実施例における異なる環境温度下でのスルーフォーカス多色回折変調伝達関数を示す図である。そのうち、図4Fの環境温度は、0℃であり、図4Gの環境温度は、40℃である。図4F及び図4Gから分かるように、本実施例の固定焦点レンズ100aは、温度の変化による結像品質への影響を低減することができる。

FIG. 4A is a diagram showing a lateral color difference in an example of the fixed focus lens of FIG. 4B is a diagram showing field curvature in an example of the fixed focus lens of FIG. FIG. 4C is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. 4D is a diagram illustrating a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 4E is a diagram showing a through-focus polychromatic diffraction modulation transfer function in one embodiment of the fixed focus lens of FIG. As shown in FIGS. 4A to 4E, the fixed focus lens 100a of the present embodiment can have good imaging quality under conditions that consider both size and weight. FIGS. 4F and 4G are diagrams showing through-focus polychromatic diffraction modulation transfer functions under different environmental temperatures in the embodiment of the fixed focus lens of FIG. Among them, the environmental temperature in FIG. 4F is 0 ° C., and the environmental temperature in FIG. 4G is 40 ° C. As can be seen from FIGS. 4F and 4G, the fixed focus lens 100a of the present embodiment can reduce the influence on the imaging quality due to the temperature change.

  FIG. 3 is a diagram showing a fixed focus lens according to another embodiment of the present invention. As shown in FIG. 3, similar to the fixed focus lens 100 of FIG. 1, the fixed focus lens 200 of this embodiment also includes a first lens L1 and a second lens arranged in order from the enlargement end to the reduction end along the optical axis. It includes a lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7, of which the first lens L1, the second lens L2, the third lens L3 and the fourth lens The refractive powers of L4, fifth lens L5, sixth lens L6 and seventh lens L7 are negative, negative, positive, positive, negative, positive and positive, respectively, and the first lens L1 and the seventh lens L7 are It is an aspherical lens.

  In this embodiment, the first lens L1, the second lens L2, and the third lens L3 constitute the first lens group 210, and the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are The second lens group 220 is configured. The refractive power of the first lens group 210 is, for example, negative, and the refractive power of the second lens group 220 is, for example, positive. The fixed focus lens 200 further includes, for example, an aperture 230, which is disposed between the third lens L3 and the fourth lens L4.

  The first lens L1 is, for example, a convex-concave lens whose convex surface faces the enlargement end, the second lens L2 is, for example, a biconcave lens, and the third lens L3 and the fourth lens L4 are, for example, both biconvex lenses. The fifth lens L5 is, for example, a biconcave lens, and the sixth lens L6 and the seventh lens L7 are, for example, biconvex lenses. Further, the fifth lens L5 and the sixth lens L6 constitute, for example, a bi-junction lens.

  In the present embodiment, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are, for example, spherical lenses. In another embodiment, any one of the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 may be an aspheric lens. The material of the first lens L1 is, for example, plastic, and the materials of the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are, for example, , Glass.

  When used in the projection apparatus, the fixed focus lens 200 further includes a prism 240, which is disposed on one side of the seventh lens L7 away from the sixth lens L6, and between the seventh lens L7 and the light valve P. Located between. This prism 240 is, for example, a common internal total reflection prism in a projection apparatus. In addition, both the first lens group 210 and the second lens group 220 of the present embodiment can move along the optical axis so as to perform focusing, and the aperture 230 and the second lens group 220 are Can be linked. More specifically, the distance between the first lens group 210 and the aperture 230 when the image screen projected on the screen becomes blurred due to the change in the distance between the screen and the fixed focus lens 200. Further, by adjusting the distance between the second lens group 220 and the light valve P and performing focusing, the image screen can be made clear.

  The fixed focus lens 200 of this embodiment employs a seven-lens structure. Since the number of lenses is relatively small, the size is relatively small (total length is relatively short), and the weight is relatively light. In addition, the total length of the fixed focus lens 200 can be shortened by designing the fifth lens L5 and the sixth lens L6 as a double-junction lens. Further, by combining the respective refractive powers of the seven lenses and using the aspherical lenses for the first lens L1 and the seventh lens L7, the fixed focus lens 200 has the advantage of good imaging quality. Have. Also, the first lens L1 adopts a plastic lens, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 adopt glass lenses, Such a combination of materials may prevent the image screen from being blurred due to a change in temperature when the fixed focus lens 200 is operated.

  In one embodiment, in order to provide sufficient space for the prism 240 between the seventh lens L7 and the light valve P, the fixed focus lens 200 satisfies the relational expression BFL / EFL> 1.5. Of these, BFL is the back focal length of the fixed focus lens 200, and EFL is the effective focal length of the fixed focus lens 200.

  In one embodiment, in order to further reduce the total length of the fixed focus lens 200, the fixed focus lens 200 may satisfy the relational expression 5.4 <TTL / EFL <15, of which TTL (total track length ) Is the total length of the fixed focus lens 200, and EFL is the effective focal length of the fixed focus lens 200. The total length here refers to the distance from the surface of the first lens L1 facing the enlargement end to the surface of the seventh lens L7 facing the reduction end.

  Table 5 shows an example of each parameter of the fixed focus lens 200. Note that the data in Table 5 does not limit the present invention. Those skilled in the art can refer to the present invention and appropriately change its parameters or settings, all of which belong to the technical scope of the present invention.

第一レンズL1及び第七レンズL7は、ともに、非球面レンズであり、そのうち、表面S1、表面S2、表面S13及び表面S14は、非球面であり、各非球面のパラメータは、表6に示されている。

Both the first lens L1 and the seventh lens L7 are aspherical lenses, of which the surface S1, the surface S2, the surface S13, and the surface S14 are aspherical, and the parameters of each aspherical surface are shown in Table 6. Has been.

図6Aは、図5の固定焦点レンズの一実施例における横方向色差を示す図である。図6Bは、図5の固定焦点レンズの一実施例における像面湾曲を示す図である。図6Cは、図5の固定焦点レンズの一実施例における歪みを示す図である。図6Dは、図5の固定焦点レンズの一実施例における横方向光線ファンプロットを示す図である。図6Eは、図5の固定焦点レンズの一実施例におけるスルーフォーカス多色回折変調伝達関数を示す図である。図6A乃至図6Eに示すように、本実施例の固定焦点レンズ200は、サイズ及び重量を考慮した条件下で、良好な結像品質を有する。

FIG. 6A is a diagram showing a lateral color difference in an example of the fixed focus lens of FIG. FIG. 6B is a diagram showing field curvature in an example of the fixed focus lens of FIG. FIG. 6C is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. 6D is a diagram showing a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 6E is a diagram showing a through-focus polychromatic diffraction modulation transfer function in one embodiment of the fixed focus lens of FIG. As shown in FIGS. 6A to 6E, the fixed focus lens 200 of the present embodiment has good imaging quality under conditions that take size and weight into consideration.

  FIG. 7 is a diagram showing a fixed focus lens according to another embodiment of the present invention. As shown in FIG. 7, the configuration of the fixed focus lens 200a of the present embodiment is substantially similar to the above-described fixed focus lens 200. The first lens group 210a of the fixed focus lens 200a also includes a first lens L1, a second lens L2, and a third lens L3, and the second lens group 220a of the fixed focus lens 200a is also a fourth lens L4 and a fifth lens L5. A sixth lens L6 and a seventh lens L7. The refractive powers of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are negative, negative, positive, positive and negative, respectively. The first lens L1 and the seventh lens L7 are aspherical lenses. The fixed focus lens 200a may also include an aperture 230, which is disposed between the third lens L3 and the fourth lens L4.

  In the fixed focus lens 200a described above, the types of the first lens L1 to the seventh lens L7 are the same as those of the fixed focus lens 200 described above. In the fixed focus lens 200a, the second lens L2 and the third lens L3 of the first lens group 210a can move along the optical axis OA so as to perform focusing, and the first lens group 210a For example, the one lens L1, the second lens group 220a, and the aperture diameter light column 230 are fixed and do not move when focusing.

  In this embodiment, the fixed focus lens 200a can satisfy at least one of the following relational expressions according to the design needs.

(1) BFL / EFL> 1.5
(2) 8 <TTL / EFL <18
Table 7 shows an example of each parameter of the fixed focus lens 200a. Note that the data in Table 7 does not limit the present invention. Those skilled in the art can refer to the present invention and appropriately change its parameters or settings, all of which belong to the technical scope of the present invention.

第一レンズL1及び第七レンズL7は、ともに、非球面レンズであり、そのうち、表面S1、表面S2、表面S13、表面S14は、非球面であり、各非球面のパラメータは、表8に示されている。

Both the first lens L1 and the seventh lens L7 are aspherical lenses, of which the surface S1, the surface S2, the surface S13, and the surface S14 are aspherical, and the parameters of each aspherical surface are shown in Table 8. Has been.

図8Aは、図7の固定焦点レンズの一実施例における横方向色差を示す図である。図8Bは、図7の固定焦点レンズの一実施例における像面湾曲を示す図である。図8Cは、図7の固定焦点レンズの一実施例における歪みを示す図である。図8Dは、図7の固定焦点レンズの一実施例における横方向光線ファンプロットを示す図である。図8Eは、図7の固定焦点レンズの一実施例におけるスルーフォーカス多色回折変調伝達関数を示す図である。図8A乃至図8Eに示すように、本実施例の固定焦点レンズ200aは、サイズ及び重量の両方を配慮した条件下で、良好な結像品質を有する。

FIG. 8A is a diagram showing a lateral color difference in an example of the fixed focus lens of FIG. FIG. 8B is a diagram showing field curvature in one embodiment of the fixed focus lens of FIG. FIG. 8C is a diagram showing distortion in one embodiment of the fixed focus lens of FIG. FIG. 8D is a diagram showing a transverse ray fan plot in one embodiment of the fixed focus lens of FIG. FIG. 8E is a diagram showing a through-focus polychromatic diffraction modulation transfer function in one embodiment of the fixed focus lens of FIG. As shown in FIGS. 8A to 8E, the fixed focus lens 200a of the present embodiment has good imaging quality under conditions that take both size and weight into consideration.

  FIG. 9 is a block diagram of a projection apparatus in an embodiment of the present invention. As shown in FIG. 9, the projection apparatus 300 of this embodiment includes an illumination system 310, a light valve 320, and a projection lens 330. The illumination system 310 is used to provide the illumination beam 312 to the light valve 320, the light valve 320 is used to convert the illumination beam 312 to the image beam 312a, and the projection lens 330 is used to convert the image beam 312a to the screen. Is used to form a video screen on the screen. The illumination system 310 may use a high-intensity discharge (HID) lamp, such as a high-pressure mercury lamp, a light emitting diode light source, or a laser light source. The light valve 320 may be a transmissive light valve or a reflective light valve, of which the transmissive light valve may be a liquid crystal display panel, and the reflective light valve is digital. A micromirror assembly (digital micro-mirror device) or LCOS (liquid crystal on silicon panel) may be used. The projection lens 330 may select and use the fixed focus lens of each of the above-described embodiments, for example, the fixed focus lens 100, 100a, 200 or 200a, thereby reducing the size and weight of the projection apparatus 300. And has good imaging quality.

  In summary, the fixed-focus lens of the present invention employs a seven-lens structure, and thus has the advantages of relatively small size (relatively short total length) and relatively light weight. In addition, by combining the respective refractive powers of the seven lenses and using the aspherical lenses for the first lens and the seventh lens, the fixed focus lens of the present invention also has an advantage of good imaging quality.

  Although the present invention has been disclosed above based on the preferred embodiments described above, the preferred embodiments described above are not intended to limit the present invention, and those skilled in the art will understand the spirit of the present invention. As long as the scope of the present invention is not deviated, minor modifications and color changes can be made to the present invention. Therefore, the protection scope of the present invention is based on what is defined in the appended claims. In addition, any embodiment or claim of the present invention need not achieve all of the objects, advantages or features disclosed in the present invention. Moreover, a part of summary and the title of an invention are only for assisting the search of literature, and do not limit the scope of rights of the present invention. Also, terms such as “first”, “second”, etc. referred to in this specification or in the claims are used to name elements or to distinguish different embodiments or ranges. Are not intended to limit the upper or lower limit on the quantity of elements.

100, 100a, 200, 200a: Fixed focus lens
110, 110a, 210, 210a: First lens group
120, 120a, 220, 220a: Second lens group
130, 230: Aperture
140, 240: Prism
L1: First lens
L2: Second lens
L3: Third lens
L4: Fourth lens
L5: Fifth lens
L6: 6th lens
L7: 7th lens
OA: Optical axis
P: Light valve
S1-S14: Surface

Claims (20)

A fixed focus lens,
The fixed focus lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens that are arranged in order from the enlargement end to the reduction end,
The refractive powers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are negative, negative, positive, positive, negative, respectively. A fixed focus lens that is positive and positive, and wherein the first lens and the seventh lens are aspherical lenses. The fixed focus lens according to claim 1,
The first lens, the second lens, the third lens and the fourth lens constitute a first lens group, and the fifth lens, the sixth lens and the seventh lens comprise a second lens group. Configure
The refractive power of the first lens group is negative, the refractive power of the second lens group is positive, and the fixed focus lens is disposed between the fourth lens and the fifth lens. A fixed focus lens further including an aperture. The fixed focus lens according to claim 2,
The second lens and the third lens constitute one cemented lens, and the fifth lens and the sixth lens constitute another cemented lens. The fixed focus lens according to claim 2,
The fourth lens is a fixed focus lens which is an aspheric lens. The fixed focus lens according to claim 4,
The first lens and the fourth lens are made of plastic, and the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are made of glass. Focus lens. The fixed focus lens according to claim 2,
The first lens group and the second lens group are both moved so as to perform focusing, and the aperture is interlocked with the second lens group. The fixed focus lens according to claim 1,
The fixed focus lens satisfies a relational expression BFL / EFL> 1.5, BFL is a back focal length of the fixed focus lens, and EFL is an effective focal length of the fixed focus lens. The fixed focus lens according to claim 2,
The fixed focus lens satisfies a relational expression 5.4 <TTL / EFL <15, TTL is a total length of the fixed focus lens, and EFL is an effective focal length of the fixed focus lens. The fixed focus lens according to claim 8,
The fixed focus lens further includes a prism arranged on one side of the seventh lens away from the sixth lens,
The fixed focus lens satisfies the relational expression 1.5 <D45 / D7P <4.8, D45 is a distance between the fourth lens and the fifth lens, and D7P is the seventh lens and the prism. Fixed focus lens, which is the distance between. The fixed focus lens according to claim 8,
The fixed focus lens satisfies a relational expression 2.5 <| f4 / f1 | <4, f4 is a focal length of the fourth lens, and f1 is a focal length of the first lens. . The fixed focus lens according to claim 2,
The fixed focus lens satisfies a relational expression 8 <TTL / EFL <18, TTL is a total length of the fixed focus lens, and EFL is an effective focal length of the fixed focus lens. . The fixed focus lens according to claim 11,
The fixed focus lens further includes a prism arranged on one side of the seventh lens away from the sixth lens,
The fixed focus lens satisfies the relational expression 1 <D45 / D7P <3, D45 is a distance between the fourth lens and the fifth lens, and D7P is the seventh lens and the prism. Fixed focus lens, which is the distance between. The fixed focus lens according to claim 11,
The fixed focus lens satisfies a relational expression 2.5 <| f4 / f1 | <7, f4 is a focal length of the fourth lens, and f1 is a focal length of the first lens. . The fixed focus lens according to claim 1,
The first lens, the second lens, and the third lens constitute a first lens group, and the fourth lens, the fifth lens, the sixth lens, and the seventh lens comprise a second lens group. The refractive power of the first lens group is negative, the refractive power of the second lens group is positive, and the fixed focus lens is between the third lens and the fourth lens. A fixed focus lens further comprising a disposed aperture. The fixed focus lens according to claim 14,
The fifth lens and the sixth lens are fixed focus lenses constituting a cemented lens. The fixed focus lens according to claim 14,
The first lens is made of plastic, and the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are made of glass. Focus lens. The fixed focus lens according to claim 14,
The first lens group and the second lens group move so as to perform focusing, and the aperture is interlocked with the second lens group. The fixed focus lens according to claim 14,
The fixed focus lens satisfies a relational expression 5.4 <TTL / EFL <15, TTL is a total length of the fixed focus lens, and EFL is an effective focal length of the fixed focus lens. The fixed focus lens according to claim 14,
The fixed focus lens satisfies 8 <TTL / EFL <18, TTL is a total length of the fixed focus lens, and EFL is an effective focal length of the fixed focus lens. The fixed focus lens according to claim 19,
The second lens and the third lens of the first lens group move so as to perform focusing, and the first lens, the second lens group, and the aperture light column of the first lens group are in focus. A fixed-focus lens that does not move when fixed.

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