An ultralong back working distance retro telephoto lens

Abstract

The application belongs to the technical field of optical imaging, and proposes a super-long back working distance reverse telephoto lens. The lens comprises a first lens group, a diaphragm, a second lens group, a light splitting prism and an image sensor; the lens is suitable for a projection device, has the characteristics of good imaging quality, low distortion, good optical performance consistency and super-long back working distance. The lens contains two three-cemented lenses, which greatly contributes to the correction of chromatic aberration of the lens and greatly benefits the projection imaging.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging technology, specifically relating to an ultra-long back-working distance reverse telephoto lens. Background Technology

[0002] With the rapid development and popularization of projection technology, projectors and related equipment have been widely used in various fields such as homes, education, commerce, medicine, and industry. Projection technology can be divided into several mainstream display technologies, including DLP, LCD, and LCOS. The images from DLP, LCD, and LCOS display chips are ultimately projected into ultra-large and ultra-high-definition images through lenses. Among them, LCD and LCOS technologies require the use of multiple beam-splitting prisms, so the projection lenses used often require a large back working distance. Summary of the Invention

[0003] The main objective of this invention is to propose an ultra-long back-working distance reverse telephoto lens to meet the high requirements of LCD or LCOS projection devices for ultra-long back-working distance.

[0004] To achieve the above objectives, this invention proposes an ultra-long rear working distance reverse telephoto lens. Along the optical axis from object to image, the lens comprises a first lens group, an aperture stop, and a second lens group. The first lens group, from object to image, consists of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The first lens is a meniscus lens with negative optical power and an aspherical surface. The second lens is a biconcave spherical lens with negative optical power, the third lens is a biconvex spherical lens with positive optical power, the fourth lens is a biconcave spherical lens with negative optical power, and the fifth lens is a biconvex spherical lens with positive optical power. The second, third, and fourth lenses are combined in a cemented carbide configuration. The lens group comprises, from object side to image side, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens. The sixth lens is a meniscus lens with positive optical power, the seventh lens is a meniscus lens with negative optical power, the eighth lens is a biconvex spherical lens with positive optical power, the ninth lens is a meniscus lens with negative optical power, and the tenth lens is a biconvex spherical lens with positive optical power. The seventh, eighth, and ninth lenses are combined to form a cemented triplet lens. The aperture stop is located between the fifth and sixth lenses. The lens also includes a beam splitter and an image sensor. The beam splitter is located on the image side of the second lens group, and the image sensor is located on the mirror side of the beam splitter.

[0005] Furthermore, the first lens is a plastic lens.

[0006] Furthermore, the second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth lenses are all glass lenses.

[0007] Furthermore, the equivalent focal length of the lens, the focal length of the first lens group, and the focal length of the second lens group satisfy the following relationship:

[0008] -5 <F1 / F0<-4;

[0009] 3.5 <F2 / F0<4.5;

[0010] Wherein, F0 represents the equivalent focal length of the lens, F1 represents the focal length of the first lens group, and F2 represents the focal length of the second lens group.

[0011] Furthermore, the lens's reverse telephoto factor, i.e., the back working distance, and the lens's equivalent focal length F0 satisfy the following relationship:

[0012] BFL / F0 > 5.0;

[0013] Wherein, F0 represents the equivalent focal length of the lens, and BFL represents the back working distance of the lens.

[0014] This invention creates an ultra-long back-working distance retro-projection lens. The lens comprises a first lens group and a second lens group along the optical axis from the object side to the image side, and also includes a beam splitter and an image sensor. The total number of lenses in this projection lens is ten. The lens employs a combination of lenses with various surface shapes, designed with the optical power, surface shape, and relative position of each lens in mind. This lens is suitable for projection equipment and features high image quality, low distortion, good optical performance consistency, and an ultra-long back-working distance. The lens includes two cemented triplet lenses, which significantly contribute to lens chromatic aberration correction and greatly benefit projection imaging. Attached Figure Description

[0015] To illustrate the embodiments and related technical solutions of the present invention in more detail, the accompanying drawings used in introducing the embodiments and related technical solutions are briefly described below. Obviously, the drawings described below are only embodiments of this specification. Based on this embodiment, other embodiments obtained by those skilled in the art without creative effort should all fall within the protection scope of the present invention.

[0016] Figure 1 This is a schematic diagram of the lens structure provided by the present invention;

[0017] Figure 2 Ray tracing diagram provided by the present invention;

[0018] Figure 3 The lens field curvature curve diagram provided for this invention;

[0019] Figure 4 The distortion curve of the lens provided for this invention;

[0020] Figure 5A pattern of light spots for the lens provided by this invention;

[0021] Figure 6 A relative illumination diagram of the lens provided for this invention;

[0022] Figure 7 The modulation transfer function (MTF) curve of the lens provided for this invention;

[0023] Figure 8 A transverse chromatic aberration diagram of the lens provided by this invention;

[0024] Figure 9 The axial chromatic aberration diagram of the lens provided by this invention.

[0025] Among them, 1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-fifth lens, S-aperture stop, 6-sixth lens, 7-seventh lens, 8-eighth lens, 9-ninth lens, 10-tenth lens, 101-first lens group, 102-second lens group. Detailed Implementation

[0026] The technical solution will now be described in detail with reference to the accompanying drawings.

[0027] Example 1, see Figure 1 , Figure 2 A super-long rear working distance reverse telephoto lens, comprising a first lens group 101, an aperture stop S, and a second lens group 102 along the optical axis from the object side to the image side; the first lens group 101, from the object side to the image side, consists of a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5; the first lens 1 is a meniscus lens with negative optical power and an aspherical surface; the second lens 2 is a biconcave spherical lens with negative optical power; the third lens 3 is a biconvex spherical lens with positive optical power; the fourth lens 4 is a biconcave spherical lens with negative optical power; and the fifth lens 5 is a biconvex spherical lens with positive optical power, wherein the second lens 2, the third lens 3, and the fourth lens 5 are combined to form a cemented triode lens; the second... The lens group 102, from the object side to the image side, consists of a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, and a tenth lens 10. The sixth lens 6 is a meniscus lens with positive optical power, the seventh lens 7 is a meniscus lens with negative optical power, the eighth lens 8 is a biconvex spherical lens with positive optical power, the ninth lens 9 is a meniscus lens with negative optical power, and the tenth lens 10 is a biconvex spherical lens with positive optical power. The seventh lens 7, the eighth lens 8, and the ninth lens 9 are combined to form a cemented triplet lens. The aperture S is located between the fifth lens 5 and the sixth lens 6. The lens also includes a beam splitter prism and an image sensor. The beam splitter prism is located on the image side of the second lens group 102, and the image sensor is located on the image side of the beam splitter prism.

[0028] Example 2, based on Example 1, further includes that the first lens 1 is a plastic lens.

[0029] Example 3, based on Example 1, further includes the following: the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10 are all glass lenses.

[0030] Example 4, based on Example 1, further includes the following relationship: the equivalent focal length of the lens, the focal length of the first lens group, and the focal length of the second lens group satisfy the following relationship:

[0031] -5 <F1 / F0<-4;

[0032] 3.5 <F2 / F0<4.5;

[0033] Wherein, F0 represents the equivalent focal length of the lens, F1 represents the focal length of the first lens group, and F2 represents the focal length of the second lens group.

[0034] Example 5, based on Example 1, further includes the following relationship between the lens's reverse telephoto factor, i.e., the back working distance, and the lens's equivalent focal length F0:

[0035] BFL / F0 > 5.0;

[0036] Wherein, F0 represents the equivalent focal length of the lens, and BFL represents the back working distance of the lens.

[0037] This invention and its embodiments provide an ultra-long rear working distance retroreflective telephoto lens. In the technical solution provided by this invention, a negative optical power aspherical lens is used as the first lens 1 to correct astigmatism and field curvature of large-angle light, resulting in smaller angular and residual aberrations in the light entering the rear group. A cemented triplet lens composed of the second lens 2, third lens 3, and fourth lens 4 uses a combination of high and low Abbe numbers to correct chromatic aberration. A fifth lens 5 increases the light density entering the rear group, giving the system a larger aperture. The aperture stop S limits the beam aperture on the axis. The sixth lens 6 is mainly used to deflect light entering the rear group system, reducing spherical aberration. A cemented triplet lens composed of the seventh lens 7, eighth lens 8, and ninth lens 9 uses a low-high-low Abbe number combination to further correct chromatic aberration, making the system's aberrations adaptable to three-color laser or three-color LED light sources. The tenth lens 10 further corrects system distortion. From the overall design structure of the projection lens, it has a highly symmetrical double-Gaussian structure, providing the possibility for correcting lens astigmatism and chromatic aberration. By rationally setting up ten lenses and conditionally limiting each optical power, an ultra-long back working distance of the lens was achieved, while maintaining high image quality.

[0038] The surface parameters of each optical component within the lens provided by this invention and the spacing between each optical component are shown in Table 1:

[0039]

[0040]

[0041] Furthermore, in this invention, the aspherical surface shape of the aspherical lens satisfies the following conditions:

[0042]

[0043] Where c is the curvature corresponding to the radius, y is the radial coordinate (its unit is the same as the lens length unit), k is the conic section coefficient, and a i For the 2ith order of aspherical coefficients.

[0044] Table 2. Conicity and Asphericity Coefficients for Aspherical Lenses:

[0045]

[0046] In this invention, the projection ratio of the lens can reach 1.0 to 2.0, which can make the distance between the lens and the projection screen smaller, and achieve a larger image display within a shorter projection distance.

[0047] Lens performance data in this invention:

[0048] Figure 3 Field curvature curve of the lens provided for this invention;

[0049] The lens provided by this invention has very small field curvature in both the meridional and sagittal directions, resulting in good performance.

[0050] Figure 4 The distortion curve of the lens provided for this invention;

[0051] The maximum distortion of the lens provided by this invention is ±0.2433%.

[0052] Figure 5 A pattern of light spots for the lens provided by this invention;

[0053] The lens provided by this invention has very small aberrations such as astigmatism, coma, and chromatic aberration.

[0054] Figure 6 A relative illumination diagram of the lens provided for this invention;

[0055] It can be seen that the relative illumination at the edge of the field of view is around 75%.

[0056] Figure 7The modulation transfer function (MTF) curve of the lens provided for this invention;

[0057] As can be seen, the vertical axis value is close to 0.5 and the curve is relatively flat, indicating that the imaging difference between the lens edge and the center is small and the imaging quality is good.

[0058] Figure 8 A transverse chromatic aberration diagram of the lens provided by this invention;

[0059] It can be seen that the vertical chromatic difference is within the Airy disk range, and the color reproduction is high.

[0060] Figure 9 Axial chromatic aberration diagram of the lens provided for this invention;

[0061] It can be seen that the axial color difference is also very small, and the color reproduction is high.

[0062] The above description is only one of the preferred embodiments of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the inventive concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

[0063] It should be noted that all directional indications (such as up, down, left, right, etc.) in the embodiments of this invention are mainly in relation to the accompanying drawings, and the above directional terms are not intended to limit this invention.

[0064] In the embodiments of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as merely indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may indicate or implicitly include at least one of that feature.

[0065] With the rapid development and popularization of projection technology, projectors and related equipment have been widely used in various fields such as homes, education, commerce, medicine, and industry. Projection technology can be divided into several mainstream display technologies, including DLP, LCD, and LCOS. The images from DLP, LCD, and LCOS display chips are ultimately projected into ultra-large and ultra-high-definition images through lenses. Among them, LCD and LCOS technologies require the use of multiple beam-splitting prisms, so the projection lenses used often require a large back working distance.

Claims

1. An ultra-long back working distance retro-telephoto lens characterized by: The lens comprises a first lens group, a diaphragm and a second lens group along the optical axis from the object side to the image side, the first lens group comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens in order from the object side to the image side, the first lens is a meniscus lens with negative focal power, the surface profile of the first lens is aspheric, the second lens is a double-concave spherical lens with negative focal power, the third lens is a double-convex spherical lens with positive focal power, the fourth lens is a double-concave spherical lens with negative focal power, and the fifth lens is a double-convex spherical lens with positive focal power, wherein the second lens, the third lens and the fourth lens are combined into a three-cemented lens, the second lens group comprises a sixth lens, a seventh lens, an eighth lens, a ninth lens and a tenth lens in order from the object side to the image side, the sixth lens is a meniscus lens with positive focal power, the seventh lens is a meniscus lens with negative focal power, the eighth lens is a double-convex spherical lens with positive focal power, the ninth lens is a meniscus lens with negative focal power, and the tenth lens is a double-convex spherical lens with positive focal power, wherein the seventh lens, the eighth lens and the ninth lens are combined into a three-cemented lens, the diaphragm is located between the fifth lens and the sixth lens, the number of lenses with focal power of the lens is ten, the lens further comprises a light splitting prism and an image sensor, the light splitting prism is located on the image side of the second lens group, and the image sensor is located on the image side of the light splitting prism, the first lens is a plastic lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens and the tenth lens are glass lenses, and the following relationships are met by the equivalent focal length of the lens, the focal length of the first lens group and the focal length of the second lens group: -5 < F1 / F0 < -4; 3.5 < F2 / F0 < 4.5; wherein F0 represents the equivalent focal length of the lens, F1 represents the focal length of the first lens group, and F2 represents the focal length of the second lens group.

2. An ultra-long rear working distance reverse telephoto lens as claimed in claim 1, characterized in that: The back focus of the lens, i.e. the back working distance and the equivalent focal length F0 of the lens meet the following relationship: BFL / F0 > 5.0; wherein F0 represents the equivalent focal length of the lens, and BFL represents the back working distance of the lens.

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