TW201823794A - Fixed Lens - Google Patents

Abstract

A fixed 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 a magnifying end to a minifying end. 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. The first lens and the seventh lens are aspheric lenses. The fixed lens has advantages of compact size and good imaging quality.

Description

Fixed focus lens

The invention relates to an imaging lens, and in particular to a fixed focus lens.

The projector is used to form an image on the screen. The main working principle is to convert the illumination beam provided by the light source into an image beam through a display element, and project the image beam onto the screen through a projection lens to form an image on the screen.

At present, the trend of the projector market is to develop miniaturization and light weight, especially for micro-projection devices. Therefore, lens manufacturers are focusing on designing suitable lens architectures to reduce the weight and volume of projection lenses. However, while achieving the above advantages, it is often easy to sacrifice the imaging quality of the projection lens. Therefore, how to design a projection lens with good imaging quality under the consideration of size, weight and other factors is a major problem for lens manufacturers.

This "prior art" paragraph is only used to help understand the content of the present invention, so the content disclosed in the "prior art" may include some conventional technologies that do not constitute the ordinary knowledge of those skilled in the art. In addition, the content disclosed in the "prior art" does not represent the content or the problem to be solved by one or more embodiments of the present invention, nor does it mean that prior to the application of the present invention, it has been used by those with ordinary knowledge in the technical field to which it belongs. Know or know.

The invention provides a fixed focus lens, which has 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 by the present invention.

In order to achieve one or some or all of the above or other objectives, the fixed focus lens provided by the present invention includes a first lens, a second lens, a third lens, a fourth lens, The fifth lens, the sixth lens, and the seventh lens, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens have a refractive power or a dioptre, respectively. Are negative, negative, positive, positive, negative, positive, and positive, and the first lens and the seventh lens are aspherical lenses.

The fixed focus lens of the present invention adopts the structure of seven lenses, so it has the advantages of smaller size (shorter total length) and lighter weight. In addition, by using the respective diopters of the seven lenses and using an aspheric lens with the first lens and the seventh lens, the fixed focus lens of the present invention has the advantage of good imaging quality.

In an embodiment of the present invention, the first lens, the second lens, the third lens, and the fourth lens constitute a first lens group, the fifth lens, the sixth lens, and the seventh lens constitute a second lens group. The diopter of one lens group is negative, the diopter of the second lens group is positive, and the fixed-focus lens further includes an aperture light bar, which is arranged between the fourth lens and the fifth lens.

In an embodiment of the present invention, the second lens and the third lens constitute a cemented lens, and the fifth lens and the sixth lens constitute another cemented lens.

In an embodiment of the present invention, the fourth lens is an aspheric lens.

In an embodiment of the present invention, 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.

In an embodiment of the present invention, the first lens group and the second lens group are both used for movement for focusing, and the aperture light bar is linked with the second lens group.

In an embodiment of the present invention, the fixed-focus lens satisfies a relational formula: 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.

In an embodiment of the present invention, 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.

In an embodiment of the present invention, the fixed-focus lens further includes 稜鏡, which is disposed on a side of the seventh lens away from the sixth lens, and the fixed-focus lens satisfies a relational formula: 1.5 <D45 / D7P <> 4.8, D45 Is the distance between the fourth lens and the fifth lens, and D7P is the distance between the seventh lens and 稜鏡.

In an embodiment of the present invention, 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.

In an embodiment of the present invention, the fixed-focus lens satisfies the relationship: 8 <TTL / EFL <18, TTL is the total length of the fixed-focus lens, and EFL is the effective focal length of the fixed-focus lens.

In an embodiment of the present invention, the fixed-focus lens further includes 稜鏡, which is disposed on a side of the seventh lens away from the sixth lens, and the fixed-focus lens satisfies a relational expression: 1 <D45 / D7P <3, D45 is The distance between the fourth lens and the fifth lens, D7P is the distance between the seventh lens and 稜鏡.

In an embodiment of the present invention, 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.

In an embodiment of the present invention, the first lens, the second lens, and the third lens constitute a first lens group, the fourth lens, the fifth lens, the sixth lens, and the seventh lens constitute a second lens group, and the first lens group The refractive power of the lens group is negative, the refractive power of the second lens group is positive, and the fixed-focus lens further includes an aperture light bar, which is disposed between the third lens and the fourth lens.

In an embodiment of the present invention, the fifth lens and the sixth lens constitute a cemented lens.

In an embodiment of the present invention, the material of the first lens is plastic, and the material of the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens is glass.

In an embodiment of the present invention, the first lens group and the second lens group are both used for movement for focusing, and the aperture light bar is linked with the second lens group.

In an embodiment of the present invention, 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.

In an embodiment of the present invention, the fixed-focus lens satisfies the relationship: 8 <TTL / EFL <18, TTL is the total length of the fixed-focus lens, and EFL is the effective focal length of the fixed-focus lens.

In an embodiment of the present invention, the second lens and the third lens of the first lens group are used to move for focusing, and the first lens, the second lens group, and the aperture light barrier of the first lens group are used for focusing. Fixed at all times.

The fixed focus lens of the present invention adopts the structure of seven lenses, so it has the advantages of smaller size (shorter total length) and lighter weight. In addition, by using the respective diopters of the seven lenses and using an aspheric lens with the first lens and the seventh lens, the fixed focus lens of the present invention has the advantage of good imaging quality.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, preferred embodiments are described below in detail with reference to the accompanying drawings, as follows.

The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as: up, down, left, right, front, or rear, are only directions referring to the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

FIG. 1 is a schematic diagram of a fixed focus lens according to an embodiment of the present invention. Referring to FIG. 1, the fixed-focus lens 100 of this embodiment is applied to, for example, a projection device, but can also be applied to an image capture device (not shown). When the fixed-focus lens 100 is applied to a projection device, a light valve P of the projection device is provided at a reduced end of the fixed-focus lens 100, and the fixed-focus lens 100 is used to project an image light beam from the light valve P to On the magnifying screen (not shown). When the fixed-focus lens 100 is applied to an image capturing device, the image sensing element of the image capturing device is disposed at the reduction end, and the fixed-focus lens 100 is used to image an object at the magnified end on the image sensing element.

The fixed-focus lens 100 of this embodiment includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a first lens L1, Six lenses L6 and seventh lens L7, 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 have negative refractive powers, Negative, positive, positive, negative, positive, and positive, and the first lens L1 and the seventh lens L7 are aspherical lenses.

In this 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, and the fifth lens L5, the sixth lens L6, and the seventh lens L7 constitute, for example, Second lens group 120. The refractive power of the first lens group 110 is, for example, negative, and the refractive power of the second lens group 120 is, for example, positive. In addition, the fixed-focus lens 100 further includes, for example, an aperture light barrier 130 disposed between the fourth lens L4 and the fifth lens L5.

In this embodiment, the first lens L1 is, for example, a convex-concave lens having a convex surface facing the magnifying end, the second lens L2 is, for example, a biconcave lens, the third lens L3 is, for example, a biconvex lens, and the fourth lens L4 is, for example, a meniscus lens having a convex surface facing the magnifying end, 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, for example, biconvex lenses. In addition, the second lens L2 and the third lens L3 constitute, for example, a compound lens, and the compound lens is, for example, a double cemented lens configured by colloidally bonding the second lens L2 and the third lens L3. The fifth lens L5 and the sixth lens L6 constitute another compound lens. This compound lens is, for example, a double cemented lens formed by colloidally bonding the fifth lens L5 and the sixth lens L6.

In this embodiment, the fourth lens L4 is, for example, an aspheric lens, but it may also 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 may be selected. Aspheric lens. In addition, the material of the first lens L1 and the fourth lens L4 is, for example, plastic, and the materials of the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are glass, for example.

When applied to a projection device, the fixed-focus lens 100 may further include a lens 140, which is disposed on a side of the seventh lens L7 away from the sixth lens L6, and is located between the seventh lens L7 and the light valve P. This 稜鏡 140 is, for example, a total internal reflection prism (TIR prism) commonly used in projection devices. In addition, the first lens group 110 and the second lens group 120 in this embodiment are both adapted to move along the optical axis OA for focusing, and the aperture light bar 130 is linked with the second lens group 120. Specifically, when the distance between the screen and the fixed-focus lens 100 changes and the image screen projected on the screen becomes blurred, the distance between the first lens group 110 and the aperture light column 130 can be adjusted and the first The distance between the two lens groups 120 and the light valve P is used for focusing, so as to make the image screen clear.

The fixed-focus lens 100 of this embodiment adopts a seven-lens structure. Because the number of lenses is small, it has the advantages of smaller size (shorter overall length) and lighter weight. Moreover, the second lens L2 and the third lens L3 may be designed as a double cemented lens, and the fifth lens L5 and the sixth lens L6 may be designed as another double cemented lens, so as to further shorten the total length of the fixed focus lens 100. In addition, by using the respective diopters of the seven lenses and using the aspheric lens with the first lens L1 and the seventh lens L7, the fixed focus lens 100 has the advantage of good imaging quality. In addition, the refractive index changes due to the temperature change of the lens, which affects the refractive power, and lenses of different materials will have different refractive index changes. In order to avoid blurring of the image caused by such changes, the first lens L1 and the fourth lens L4 in this embodiment are plastic lenses, and the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6, and the seventh lens are used. The lens L7 is a glass lens. This combination of materials can compensate for changes in refractive index of each lens due to temperature changes, making the fixed focus lens 100 less likely to cause image blur due to temperature changes during operation.

In an embodiment, in order to allow enough space between the seventh lens L7 and the light valve P to set 稜鏡 140, the fixed focus lens 100 can satisfy the relationship: BFL / EFL> 1.5, where 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 an embodiment, in order to further shorten the total length of the fixed-focus lens 100 and take into account the viewing angle, the fixed-focus lens 100 can satisfy the relationship: 5.4 <TTL / EFL <15, where TTL (total track length) is the fixed-focus lens 100 The total length, 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 magnifying end to the surface of the seventh lens L7 facing the reducing end.

In an embodiment, for example, the fixed focus lens 100 satisfies 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 seventh lens L7 and 稜鏡 140. the distance between. In this way, when the first lens group 110 and the second lens group 120 perform focusing, there is a wide range of movement range, and it is easy to perform focusing.

In one embodiment, for example, the fixed focus lens 100 satisfies the relationship: 2.5 <| f4 / f1 | <4, where f4 is the focal length of the fourth lens L4, and f1 is the focal length of the first lens L1. In this way, the first lens L1 and the fourth lens L4 can be used to compensate the problem of image enlargement or reduction caused by the high and low temperature difference when the fixed focus lens 100 is in operation, and improve the imaging quality.

Table 1 will give an example of the parameters of the fixed focus lens 100. It should be noted that the data listed in Table 1 are not intended to limit the present invention. Any person with ordinary knowledge in the technical field can refer to the present invention and make appropriate changes to its parameters or settings, but they should still It belongs to the scope of the present invention.

Table I

The distance indicated in Table 1 is the linear distance between two adjacent surfaces on the optical axis OA of the fixed focus lens 100. For example, the distance between the surface S1 is the straight line distance between the surface S1 and the surface S2 on the optical axis OA, and the distance between the surface S13 is the straight line distance between the surface S13 and 稜鏡 140 on the optical axis OA. A surface with a positive radius of curvature indicates that the surface is curved toward the enlarged end, and a surface with a negative 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 all aspheric lenses, for example, the surface S1, the surface S2, the surface S6, the surface S7, the surface S12, and the surface S13 are aspheric, and can be expressed by the following equations:

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

FIG. 2A is a lateral chromatic aberration diagram of an embodiment of the fixed-focus lens of FIG. 1, FIG. 2B is a field curvature diagram of an embodiment of the fixed-focus lens of FIG. 1, and FIG. 2C is an embodiment of the fixed-focus lens of FIG. 1. 2D is a transverse ray fan diagram of an embodiment of the fixed-focus lens of FIG. 1, and FIG. 2E is a modulation transfer function diagram of the entire color focus of the embodiment of the fixed-focus lens of FIG. 1. As shown in FIG. 2A to FIG. 2E, the fixed-focus lens 100 of this embodiment can have good imaging quality under the conditions of both size and weight. In addition, FIG. 2F and FIG. 2G are modulation transfer function diagrams of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 1 at different ambient temperatures, where the ambient temperature of FIG. 2F is 0 degree Celsius and the ambient temperature of FIG. 2G It is 40 degrees Celsius. As can be seen from FIG. 2F and FIG. 2G, the fixed focus lens 100 of this embodiment can reduce the influence of the temperature change on the imaging quality.

FIG. 3 is a schematic diagram of a fixed focus lens according to another embodiment of the present invention. Referring to FIG. 3, the composition structure of the fixed-focus lens 100a of this embodiment is substantially similar to the fixed-focus lens 100 described above. The first lens group 110a of the fixed-focus lens 100a also includes a 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 also includes a fifth lens L5, The sixth lens L6 and the seventh lens L7. The diopters 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 respectively negative, negative, positive, positive, negative, positive, Positive, and the first lens L1 and the seventh lens L7 are aspherical lenses. In addition, the fixed-focus lens 100a may also include an aperture light barrier 130 disposed between the fourth lens L4 and the fifth lens L5.

In the above-mentioned fixed-focus lens 100a, 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 above-mentioned fixed-focus lens 100, and The four lenses L4 are, for example, a convex plano lens or a biconvex lens having a convex surface facing the magnifying end.

In this embodiment, the fixed focus lens 100a can satisfy at least one of the following relations according to design requirements: (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), if BFL / EFL <1.5, the fixed focus lens 100a is likely to interfere with other elements of the projection apparatus. Regarding relational expression (2), if TTL / EFL> 18, the total length of the fixed-focus lens 100a is long, and it is difficult to achieve the advantages of miniaturization. If TTL / EFL <8, the fixed-focus lens 100a cannot easily achieve both miniaturization and wide angle The advantages. Regarding relational expression (3), if D45 / D7P> 3, the distance between the fourth lens L4 and the fifth lens L5 is too large, and it is difficult to effectively correct TV distortion. If D45 / D7P <1, the first The distance between the four lenses L4 and the fifth lens L5 is too small, and mechanical interference is liable to occur. Regarding the relational expression (4), if | f4 / f1 |> 7, although the phenomenon of thermal drift of the fixed focus lens 100a can be improved, the resolution is not good. If | f4 / f1 | <2.5, although fixed focus The lens 100a has better resolution, but the phenomenon of thermal drift is more serious. In addition, in order to further improve the thermal drift phenomenon caused by the thermal expansion of the lens, at least one of the fifth lens L5, the sixth lens L6, and the seventh lens L7 in the second lens group 110a may be made of a material with a negative dn / dt value. In order to improve the thermal drift phenomenon by adjusting the diopter, dn represents the refractive index change, and dt represents the temperature change. In an embodiment, the seventh lens L7 is made of a material with a negative value of dn / dt, for example.

Table 3 will give an example of the parameters of the fixed focus lens 100a. It should be noted that the data and materials listed in Table 3 are not intended to limit the present invention. Any person with ordinary knowledge in the technical field may refer to the present invention to make appropriate changes to its parameters or settings, but they should still It belongs to the scope of the present invention.

Table three

The first lens L1, the fourth lens L4, and the seventh lens L7 are all aspheric lenses, for example, the surfaces S1, S2, S6, S7, S12, and S13 are aspheric. The parameters of the above aspheric surfaces are shown in Table 4: Table 4 .

FIG. 4A is a lateral chromatic aberration diagram of an embodiment of the fixed-focus lens of FIG. 3, FIG. 4B is a field curvature diagram of an embodiment of the fixed-focus lens of FIG. 3, and FIG. 4C is an embodiment of the fixed-focus lens of FIG. FIG. 4D is a transverse ray fan diagram of the embodiment of the fixed-focus lens of FIG. 3, and FIG. 4E is a modulation transfer function diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 3. As shown in FIG. 4A to FIG. 4E, the fixed focus lens 100 a of this embodiment can have good imaging quality under the conditions of both size and weight. In addition, FIG. 4F and FIG. 4G are modulation transfer function diagrams of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 3 at different ambient temperatures, where the ambient temperature of FIG. 4F is 0 degrees Celsius and the ambient temperature of FIG. It is 40 degrees Celsius. As can be seen from FIG. 4F and FIG. 4G, the fixed focus lens 100a of this embodiment can reduce the influence of the temperature change on the imaging quality.

FIG. 5 is a schematic diagram of a fixed focus lens according to another embodiment of the present invention. Please refer to FIG. 5. Similar to the fixed-focus lens 100 of FIG. 1, the fixed-focus lens 200 of this embodiment also includes a first lens L1, a second lens L2, and a lens lens L2, which are sequentially arranged along the optical axis OA from an enlarged end to a reduced end. The third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7, wherein the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 The diopters of the sixth lens L6 and the seventh lens L7 are respectively negative, negative, positive, positive, negative, positive, and positive, and the first lens L1 and the seventh lens L7 are aspherical lenses.

In this embodiment, the first lens L1, the second lens L2, and the third lens L3 constitute a first lens group 210, and the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 constitute a second lens group 210. Lens group 220. 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 light bar 230 disposed between the third lens L3 and the fourth lens L4.

The first lens L1 is, for example, a convex-concave lens with a convex surface facing the magnifying end, the second lens L2 is, for example, a biconcave lens, the third lens L3 and the fourth lens L4 are, for example, biconvex lenses, the fifth lens L5 is, for example, a biconcave lens, and the sixth lens L6. The seventh lens L7 is, for example, a lenticular lens. The fifth lens L5 and the sixth lens L6 constitute, for example, a double cemented lens.

In this 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 other embodiments, any 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. In addition, 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 glass, for example.

When applied to a projection device, the fixed-focus lens 200 may further include 稜鏡 240, which is disposed on a side of the seventh lens L7 away from the sixth lens L6, and is located between the seventh lens L7 and the light valve P. This chirp 240 is, for example, an internal total reflection chirp commonly used in projection devices. In addition, the first lens group 210 and the second lens group 220 in this embodiment are both adapted to move along the optical axis OA for focusing, and the aperture light bar 230 is linked with the second lens group 220. Specifically, when the distance between the screen and the fixed-focus lens 200 changes and the image screen projected on the screen becomes blurred, the distance between the first lens group 210 and the aperture light bar 230 and the first The distance between the two lens groups 220 and the light valve P is used for focusing, so as to make the image screen clear.

The fixed-focus lens 200 of this embodiment adopts a seven-lens structure. Because the number of lenses is small, it has the advantages of smaller size (shorter overall length) and lighter weight. Moreover, the fifth lens L5 and the sixth lens L6 can be designed as a double cemented lens to further shorten the total length of the fixed-focus lens 200. In addition, by using the respective diopters of the seven lenses and using the aspheric lens with the first lens L1 and the seventh lens L7, the fixed-focus lens 200 has the advantage of good imaging quality. In addition, the first lens L1 is a plastic lens, and 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 glass lenses. This makes the fixed focus lens 200 less prone to blurring of the image due to temperature changes during operation.

In an embodiment, in order to allow enough space between the seventh lens L7 and the light valve P to set 稜鏡 240, the fixed-focus lens 200 can satisfy the relationship: BFL / EFL> 1.5, where BFL is a fixed-focus lens The back focal length of 200 is the effective focal length of the fixed-focus lens 200.

In an embodiment, in order to further shorten the total length of the fixed-focus lens 200, the fixed-focus lens 200 can be made to satisfy the relationship: 5.4 <TTL / EFL <15, where TTL (total track length) is the total length of the fixed-focus lens 200 , 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 magnifying end to the surface of the seventh lens L7 facing the reducing end.

Table 5 lists an example of the parameters of the fixed-focus lens 200. It should be noted that the data and materials listed in Table 5 are not intended to limit the present invention. Any person with ordinary knowledge in the technical field may refer to the present invention to make appropriate changes to its parameters or settings, but they should still It belongs to the scope of the present invention.

Table five

Both the first lens L1 and the seventh lens L7 are aspheric lenses. The surface S1, the surface S2, the surface S13, and the surface S14 are aspheric. The parameters of each aspheric surface are shown in Table 6: Table 6

FIG. 6A is a lateral chromatic aberration diagram of an embodiment of the fixed-focus lens of FIG. 5, FIG. 6B is a field curvature diagram of an embodiment of the fixed-focus lens of FIG. 5, and FIG. 6C is an embodiment of the fixed-focus lens of FIG. 5. FIG. 6D is a transverse ray fan diagram of the embodiment of the fixed-focus lens of FIG. 5, and FIG. 6E is a modulation transfer function diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 5. As shown in FIG. 6A to FIG. 6E, the fixed-focus lens 200 of this embodiment can have good imaging quality under the conditions of both size and weight.

FIG. 7 is a schematic diagram of a fixed focus lens according to another embodiment of the present invention. Referring to FIG. 7, the composition structure of the fixed-focus lens 200 a of this embodiment is substantially similar to the fixed-focus lens 200 described above. The first lens group 210a of the fixed-focus lens 200a also includes a first lens L1, the second lens L2, and the third lens L3, and the second lens group 220a of the fixed-focus lens 200a also includes a fourth lens L4, a fifth lens L5, The sixth lens L6 and the seventh lens L7. The diopters 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 respectively negative, negative, positive, positive, negative, positive, Positive, and the first lens L1 and the seventh lens L7 are aspherical lenses. In addition, the fixed-focus lens 200a may also include an aperture light barrier 230 disposed between the third lens L3 and the fourth lens L4.

In the above-mentioned fixed-focus lens 200 a, the types of the first lens L1 to the seventh lens L7 are the same as those of the above-mentioned fixed-focus lens 200. In addition, in the fixed focus lens 200a, the second lens L2 and the third lens L3 of the first lens group 210a are adapted to move along the optical axis OA for focusing, and the first lens L1, the first lens L1 of the first lens group 210a The two lens groups 220a and the aperture light barrier 230 are fixed, for example, during focusing.

In this embodiment, the fixed-focus lens 200 a may satisfy at least one of the following relations according to design requirements: (1) BFL / EFL> 1.5; (2) 8 <TTL / EFL <18.

Table 7 will give an example of the parameters of the fixed-focus lens 200a. It should be noted that the data and materials listed in Table 7 are not intended to limit the present invention. Any person with ordinary knowledge in the technical field can refer to the present invention and make appropriate changes to its parameters or settings, but they should still It belongs to the scope of the present invention.

Table seven

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

FIG. 8A is a lateral chromatic aberration diagram of an embodiment of the fixed-focus lens of FIG. 7, FIG. 8B is a field curvature diagram of an embodiment of the fixed-focus lens of FIG. 7, and FIG. 8C is an embodiment of the fixed-focus lens of FIG. 7. FIG. 8D is a transverse ray fan diagram of the embodiment of the fixed-focus lens of FIG. 7, and FIG. 8E is a modulation transfer function diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 7. As shown in FIGS. 8A to 8E, the fixed-focus lens 200 a of this embodiment can have good imaging quality under the conditions of both size and weight.

FIG. 9 is a block diagram of a projection device according to an embodiment of the invention. Referring to FIG. 9, the projection apparatus 300 in this embodiment includes an illumination system 310, a light valve 320, and a projection lens 330. The illumination system 310 is used to provide an illumination beam 312 to a light valve 320. The light valve 320 is used to convert the illumination beam 312 into an image beam 312a, and the projection lens 330 is used to project the image beam 312a onto a screen to form an image on the screen . The lighting system 310 may use a high-intensity discharge (HID) 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, wherein the transmissive light valve may be a liquid crystal display panel, and the reflective light valve may be a digital micro-mirror device ) Or liquid crystal on silicon panel. The projection lens 330 can be selected from the fixed focus lenses of the above embodiments, such as the fixed focus lens 100, 100a, 200, or 200a, so that the size of the projection device 300 can be reduced, the weight can be reduced, and the imaging quality is good.

In summary, the fixed-focus lens of the present invention uses a seven-lens lens structure, so it has the advantages of smaller size (shorter overall length) and lighter weight. In addition, by using the respective diopters of the seven lenses and using an aspheric lens with the first lens and the seventh lens, the fixed focus lens of the present invention has the advantage of good imaging quality.

However, the above are only the preferred embodiments of the present invention. When the scope of implementation of the present invention cannot be limited by this, that is, the simple equivalent changes and modifications made according to the scope of the patent application and the description of the invention, All are still within the scope of the invention patent. In addition, any embodiment of the present invention or the scope of patent application does not need to achieve all the purposes or advantages or features disclosed by the invention. In addition, the abstract and the title are only used to assist the search of patent documents, and are not intended to limit the scope of rights of the present invention. In addition, the terms "first" and "second" mentioned in this specification or the scope of the patent application are only used to name the element or to distinguish between different embodiments or ranges, not to limit the number of elements. Upper or lower limit.

100, 100a, 200, 200a‧‧‧ fixed focus lens

110, 110a, 210, 210a ‧‧‧ first lens group

120, 120a, 220, 220a‧‧‧Second lens group

130, 230‧‧‧ Aperture Light Bar

140, 240‧‧‧ 稜鏡

300‧‧‧ projection device

310‧‧‧Lighting System

312‧‧‧illuminating beam

312a‧‧‧Image Beam

320‧‧‧light valve

330‧‧‧ projection lens

L1‧‧‧First lens

L2‧‧‧Second lens

L3‧‧‧ Third lens

L4‧‧‧Fourth lens

L5‧‧‧Fifth lens

L6‧‧‧ sixth lens

L7‧‧‧ seventh lens

OA‧‧‧Optical axis

P‧‧‧Light valve

S1 ～ S14‧‧‧ surface

FIG. 1 is a schematic diagram of a fixed focus lens according to an embodiment of the present invention. FIG. 2A is a lateral color diagram of an embodiment of the prime lens of FIG. 1. FIG. FIG. 2B is a field curvature diagram of an embodiment of the fixed-focus lens of FIG. 1. FIG. 2C is a distortion diagram of an embodiment of the fixed focus lens of FIG. 1. FIG. FIG. 2D is a transverse ray fan plot of the embodiment of the fixed-focus lens of FIG. 1. FIG. FIG. 2E is a polychromatic diffraction through focus MTF diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 1. 2F and 2G are modulation transfer function diagrams of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 1 at different ambient temperatures. FIG. 3 is a schematic diagram of a fixed focus lens according to another embodiment of the present invention. 4A is a lateral chromatic aberration diagram of an embodiment of the fixed-focus lens of FIG. 3. FIG. 4B is a field curvature diagram of an embodiment of the fixed focus lens of FIG. 3. 4C is a distortion diagram of an embodiment of the fixed focus lens of FIG. 3. 4D is a transverse ray fan diagram of an embodiment of the fixed-focus lens of FIG. 3. FIG. 4E is a modulation transfer function diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 3. 4F and 4G are modulation transfer function diagrams of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 3 at different ambient temperatures. FIG. 5 is a schematic diagram of a fixed focus lens according to another embodiment of the present invention. 6A is a lateral chromatic aberration diagram of an embodiment of the fixed-focus lens of FIG. 5. FIG. 6B is a field curvature diagram of an embodiment of the fixed focus lens of FIG. 5. 6C is a distortion diagram of an embodiment of the fixed focus lens of FIG. 5. 6D is a transverse ray fan diagram of the embodiment of the fixed-focus lens of FIG. 5. FIG. 6E is a modulation transfer function diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 5. FIG. 7 is a schematic diagram of a fixed focus lens according to another embodiment of the present invention. FIG. 8A is a lateral chromatic aberration diagram of an embodiment of the prime lens of FIG. 7. FIG. FIG. 8B is a field curvature diagram of an embodiment of the fixed focus lens of FIG. 7. FIG. 8C is a distortion diagram of an embodiment of the prime lens of FIG. 7. FIG. 8D is a transverse ray fan diagram of the embodiment of the fixed-focus lens of FIG. 7. FIG. FIG. 8E is a modulation transfer function diagram of the entire focus of the color diffraction of the embodiment of the fixed-focus lens of FIG. 7. FIG. 9 is a block diagram of a projection device according to an embodiment of the invention.

Claims (20)

A 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, which are sequentially arranged from the magnifying end to the reducing end. Where the diopters 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, and the first lens and the seventh lens are aspherical lenses. The fixed-focus lens according to item 1 of the scope of the patent application, wherein the first lens, the second lens, the third lens, and the fourth lens constitute a first lens group, the fifth lens, and the sixth lens The seventh lens and the seventh lens constitute a second lens group, the first lens group has a negative diopter, the second lens group has a positive diopter, and the fixed-focus lens further includes an aperture light bar arranged on the fourth lens. And the fifth lens. The fixed-focus lens according to item 2 of the scope of the patent application, wherein the second lens and the third lens constitute a cemented lens, and the fifth lens and the sixth lens constitute another cemented lens. The fixed-focus lens according to item 2 of the scope of patent application, wherein the fourth lens is an aspheric lens. The fixed-focus lens according to item 4 of the scope of patent application, wherein the material of the first lens and the fourth lens is plastic, the second lens, the third lens, the fifth lens, the sixth lens, the The seventh lens is made of glass. The fixed-focus lens according to item 2 of the scope of the patent application, wherein the first lens group and the second lens group are both used for movement for focusing, and the aperture light bar is linked with the second lens group. The fixed-focus lens described in item 1 of the patent application scope, wherein the fixed-focus lens satisfies the relationship: BFL / EFL> 1.5, BFL is the back focal length of the fixed-focus lens, and EFL is the effective focal length of the fixed-focus lens. The fixed focus lens described in item 2 of the scope of patent application, wherein the fixed focus lens satisfies the relationship: 5.4 <TTL / EFL <15, TTL is the total length of the fixed focus lens, and EFL is the effective focal length of the fixed focus lens . The fixed-focus lens according to item 8 in the scope of the patent application, wherein the fixed-focus lens further includes a stack disposed on a side of the seventh lens away from the sixth lens, and the fixed-focus lens satisfies a relational formula: 1.5 <D45 / D7P <> 4.8, D45 is the distance between the fourth lens and the fifth lens, and D7P is the distance between the seventh lens and the lens. The fixed-focus lens according to item 8 of the application, wherein the fixed-focus lens satisfies the relationship: 2.5 <| f4 / f1 | <4, f4 is the focal length of the fourth lens, and f1 is the focal length of the first lens. The fixed focus lens described in item 2 of the patent application scope, wherein the fixed focus lens satisfies the relationship: 8 <TTL / EFL <18, TTL is the total length of the fixed focus lens, and EFL is the effective focal length of the fixed focus lens . The fixed-focus lens according to item 11 in the scope of the patent application, wherein the fixed-focus lens further includes a stack disposed on a side of the seventh lens away from the sixth lens, and the fixed-focus lens satisfies a relational formula: 1 <D45 / D7P <3, D45 is the distance between the fourth lens and the fifth lens, and D7P is the distance between the seventh lens and the lens. The fixed-focus lens according to item 11 of the scope of patent application, wherein the fixed-focus lens satisfies the relationship: 2.5 <| f4 / f1 | <7, f4 is the focal length of the fourth lens, and f1 is the focal length of the first lens. . The fixed-focus lens according to item 1 of the scope of patent application, wherein the first lens, the second lens, and the third lens constitute a first lens group, the fourth lens, the fifth lens, and the sixth lens And the seventh lens constitutes a second lens group, the first lens group has a negative diopter, the second lens group has a positive diopter, and the fixed-focus lens further includes an aperture light bar arranged on the third lens. And the fourth lens. The fixed-focus lens according to item 14 of the scope of the patent application, wherein the fifth lens and the sixth lens constitute a cemented lens. The fixed-focus lens according to item 14 of the scope of patent application, wherein the material of the first lens is plastic, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the The seventh lens is made of glass. The fixed-focus lens according to item 14 of the scope of the patent application, wherein the first lens group and the second lens group are both used for movement for focusing, and the aperture light bar is linked with the second lens group. The fixed-focus lens according to item 14 of the scope of the patent application, wherein the fixed-focus lens satisfies the relationship: 5.4 <TTL / EFL <15, TTL is the total length of the fixed-focus lens, and EFL is the effective focal length of the fixed-focus lens . The fixed-focus lens described in item 14 of the scope of the patent application, wherein the fixed-focus lens satisfies the relationship: 8 <TTL / EFL <18, TTL is the total length of the fixed-focus lens, and EFL is the effective focal length of the fixed-focus lens. The fixed-focus lens according to item 19 of the scope of the patent application, wherein the second lens and the third lens of the first lens group are used for movement for focusing, and the first lens, the first lens group, The two lens groups and the aperture light barrier are fixed during focusing.