Fixed-focus lens and imaging system

Abstract

The present invention relates to a fixed-focus lens and an imaging system. Along the object side to the image side direction, the fixed-focus lens sequentially includes a first lens group, a diaphragm, and a second lens group with positive optical power. The first lens group includes two negative-power lenses and two positive-power lenses, or includes three negative-power lenses and two positive-power lenses. The fixed-focus lens of the present invention has high resolution and a large aperture, can clearly image in a relatively dark environment, and can work normally and not defocus at -40°C to +80°C.

Description

Technical Field

[0001] The present invention relates to the technical field of optical system and device design, and particularly relates to a fixed-focus lens and an imaging system. Background Art

[0002] With the development of social economy, the high-speed road network is becoming increasingly dense and the traffic is becoming increasingly busy. In order to maintain traffic safety, prevent traffic jams, and achieve orderly traffic conditions under busy traffic, the development of intelligent transportation systems is of practical significance for improving the management level of roads. Video camera technology is a key technology in intelligent transportation systems, and video camera systems are key devices in intelligent transportation systems. However, the existing series of video camera lenses cannot meet the requirements of intelligent transportation systems. Summary of the Invention

[0003] The purpose of the present invention is to solve the above problems and provide a high-pixel, large-aperture fixed-focus lens and an imaging system.

[0004] To achieve the above purpose, the present invention provides a fixed-focus lens, which sequentially includes a first lens group, a diaphragm, and a second lens group with positive optical power along the object side to the image side direction. The first lens group includes two negative-power lenses and two positive-power lenses or includes three negative-power lenses and two positive-power lenses.

[0005] According to one aspect of the present invention, along the object side to the image side direction, the first lens group sequentially includes a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, and a fourth lens with positive optical power.

[0006] According to one aspect of the present invention, along the object side to the image side direction, the first lens group sequentially includes a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, and a ninth lens with negative optical power.

[0007] According to one aspect of the present invention, along the object side to the image side direction, the first lens is a convex-concave lens, the object side surface of the second lens is concave, the third lens is a concave-convex lens, and the object side surface of the fourth lens is convex.

[0008] According to one aspect of the present invention, along the object side to the image side direction, the second lens group sequentially includes a fifth lens with positive or negative optical power, a sixth lens with positive or negative optical power, a seventh lens with positive optical power, and an eighth lens with positive optical power.

[0009] According to one aspect of the present invention, the fifth lens is a double-concave or double-convex lens, the sixth lens is a double-concave or double-convex lens, the image side surface of the seventh lens is convex, and the object side surface of the eighth lens is convex.

[0010] According to one aspect of the present invention, the ninth lens is a convex-concave lens.

[0011] According to one aspect of the present invention, the fifth lens and the sixth lens form a cemented lens group with a negative optical power.

[0012] According to one aspect of the present invention, the refractive index and Abbe number of the fifth lens are n5 and v5 respectively, and the refractive index and Abbe number of the sixth lens are n6 and v6 respectively, satisfying: 0.7 ≤ n5 / n6 ≤ 1.35, 0.25 ≤ v5 / v6 ≤ 3.8.

[0013] According to one aspect of the present invention, the refractive index and Abbe number of the ninth lens are n9 and v9, satisfying the relational expression: 1.75 ≤ n9 ≤ 1.85, 23 ≤ v9 ≤ 31.

[0014] According to one aspect of the present invention, the total optical system length TTL of the fixed-focus lens and the focal length f of the optical system satisfy: TTL / f ≤ 5.43.

[0015] The present invention also provides an imaging system including the above fixed-focus lens. A cylindrical beam splitter is further provided between the second lens group of the fixed-focus lens and the image plane. The cylindrical beam splitter is inclined. Along the object side to the image side direction, the cylindrical beam splitter sequentially includes a plane and a cylindrical surface having an inclination angle of 0-2 degrees with the plane;

[0016] The plane is uniquely provided with a beam splitting film system.

[0017] According to one aspect of the present invention, a compensation device is further provided between the cylindrical beam splitter and the image plane. Along the object side to the image side direction, the compensation device sequentially includes a second plane and an inclined surface having an inclination angle of 0-2 degrees with the second plane;

[0018] The inclined surface is a plane or a curved surface.

[0019] According to one aspect of the present invention, the thickness of the cylindrical beam splitter is less than 3 mm.

[0020] The fixed-focus lens of the present invention, through the reasonable combination of positive and negative optical powers, enables the fixed-focus lens of the present invention to have excellent performance of high pixels and large apertures, and the aperture number F is less than or equal to 1.6. At the same time, the tolerance of the fixed-focus lens is corrected, and the lens assembly yield is high.

[0021] The fixed-focus lens of the present invention, the fifth lens and the sixth lens form a cemented lens group with a positive optical power. The setting of the cemented lens group is beneficial to correcting the chromatic aberration of the optical system and can also compensate for the change in focal length caused by temperature changes, ensuring that the optical system of the fixed-focus lens of the present invention can still image normally when the temperature changes.

[0022] For the fixed-focus lens of the present invention, the refractive index and Abbe number of the fifth lens are n5 and v5 respectively, and the refractive index and Abbe number of the sixth lens are n6 and v6 respectively, satisfying: 0.7 ≤ n5 / n6 ≤ 1.35, 0.25 ≤ v5 / v6 ≤ 3.8. With such a setting, the ability of this cemented lens group to correct chromatic aberration can be fully exerted, and the entire optical system can well correct chromatic aberration by only using one set of cemented lens groups.

[0023] For the fixed-focus lens of the present invention, the refractive index and Abbe number of the ninth lens are n9 and v9, satisfying the relational expression: 1.75 ≤ n9 ≤ 1.85, 23 ≤ v9 ≤ 31. With such a setting, the tolerance of the entire optical system can be further corrected, and the lens assembly yield can be improved.

[0024] For the optical system of the fixed-focus lens of the present invention, the total length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 5.43. With such a setting, while ensuring that the optical system meets certain focal length requirements, the total length of the optical system is the shortest, realizing the advantage of miniaturization. Brief Description of the Drawings

[0025] Figure 1 Schematic diagram showing the structure of the fixed-focus lens according to Embodiment 1 of the present invention;

[0026] Figure 2 Schematic diagram showing the 145 lp / mm - MTF graph of the fixed-focus lens according to Embodiment 1 of the present invention;

[0027] Figure 3 Schematic diagram showing the +20°C 75 lp / mm - Through-Focus-MTF graph of the fixed-focus lens according to Embodiment 1 of the present invention;

[0028] Figure 4 Schematic diagram showing the -40°C 75 lp / mm - Through-Focus-MTF graph of the fixed-focus lens according to Embodiment 1 of the present invention;

[0029] Figure 5 Schematic diagram showing the +80 75 lp / mm - Through-Focus-MTF graph of the fixed-focus lens according to Embodiment 1 of the present invention;

[0030] Figure 6 Schematic diagram showing the structure of the fixed-focus lens according to Embodiment 2 of the present invention;

[0031] Figure 7 Schematic diagram showing the 145 lp / mm - MTF graph of the fixed-focus lens according to Embodiment 2 of the present invention;

[0032] Figure 8 Schematic diagram showing the +20°C 75 lp / mm - Through-Focus-MTF graph of the fixed-focus lens according to Embodiment 2 of the present invention;

[0033] Figure 9 Schematic representation of the through-focus MTF graph of the fixed-focus lens at -40°C and 75 lp / mm according to Embodiment 2 of the present invention;

[0034] Figure 10 Schematic representation of the through-focus MTF graph of the fixed-focus lens at +80 and 75 lp / mm according to Embodiment 2 of the present invention;

[0035] Figure 11 Schematic structural diagram of the fixed-focus lens according to Embodiment 3 of the present invention;

[0036] Figure 12 Schematic representation of the MTF graph of the fixed-focus lens at 145 lp / mm according to Embodiment 1 of the present invention;

[0037] Figure 13 Schematic representation of the through-focus MTF graph of the fixed-focus lens at +20°C and 75 lp / mm according to Embodiment 3 of the present invention;

[0038] Figure 14 Schematic representation of the through-focus MTF graph of the fixed-focus lens at -40°C and 75 lp / mm according to Embodiment 3 of the present invention;

[0039] Figure 15 Schematic representation of the through-focus MTF graph of the fixed-focus lens at +80 and 75 lp / mm according to Embodiment 3 of the present invention;

[0040] Figure 16 Schematic structural diagram of the fixed-focus lens according to Embodiment 4 of the present invention;

[0041] Figure 17 Schematic representation of the MTF graph of the fixed-focus lens at 145 lp / mm according to Embodiment 4 of the present invention;

[0042] Figure 18 Schematic representation of the through-focus MTF graph of the fixed-focus lens at +20°C and 75 lp / mm according to Embodiment 4 of the present invention;

[0043] Figure 19 Schematic representation of the through-focus MTF graph of the fixed-focus lens at -40°C and 75 lp / mm according to Embodiment 4 of the present invention;

[0044] Figure 20 Schematic representation of the through-focus MTF graph of the fixed-focus lens at +80 and 75 lp / mm according to Embodiment 4 of the present invention;

[0045] Figure 21 Schematically showing the structure of the imaging system according to the present invention Figure One ;

[0046] Figure 22 Schematically showing the structure of the imaging system according to the present invention Figure Two 。 Detailed implementation manners

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0048] The present invention will be described in detail below in conjunction with the drawings and specific implementation manners. The implementation manners cannot be enumerated one by one here, but the implementation manners of the present invention are not limited to the following implementation manners.

[0049] As Figure 1 shown, the present invention provides a fixed-focus lens, which sequentially includes a first lens group, a diaphragm, and a second lens group with positive optical power along the object side to the image side direction. The first lens group includes two negative-power lenses and two positive-power lenses or includes three negative-power lenses and two positive-power lenses. According to the concept of the present invention, the first lens group can have positive or negative optical power.

[0050] According to an embodiment of the present invention, along the object side to the image side direction, the first lens group sequentially has a first lens L1 with optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, and a fourth lens L4 with positive optical power.

[0051] According to the second embodiment of the present invention, along the object side to the image side direction, the first lens group sequentially includes a first lens L1 with negative optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, and a ninth lens L9 with negative optical power. Adding a ninth lens L9 with negative optical power in front of the diaphragm can further correct the tolerance of the optical system of the fixed-focus lens of the present invention, which is beneficial to improving the lens assembly yield.

[0052] Combined with Figure 1 shown, the second lens group of the present invention sequentially includes a fifth lens L5 with positive or negative optical power, a sixth lens L6 with positive or negative optical power, a seventh lens L7 with positive optical power, and an eighth lens L8 with positive optical power along the object side to the image side direction.

[0053] That is to say, in the fixed-focus lens of the present invention, the first lens group includes four or five lenses, and the second lens group includes four lenses. In the present invention, the first lens L1 is a convex-concave lens, the object side of the second lens L2 is concave, the third lens L3 is a convex-concave lens, and the object side of the fourth lens L4 is convex. The fifth lens L5 is a double-concave or double-convex lens, the sixth lens L6 is a double-concave or double-convex lens, the image side of the seventh lens L7 is convex, and the object side of the eighth lens L8 is convex. The ninth lens L9 is a convex-concave lens.

[0054] In the fixed-focus lens of the present invention, through the reasonable combination of positive and negative optical powers, the fixed-focus lens of the present invention has excellent performance of high pixels and large apertures, and the aperture number F is less than or equal to 1.6. At the same time, the tolerance of the fixed-focus lens is corrected, and the lens assembly yield is high.

[0055] Combined Figure 1 As shown, in the present invention, the fifth lens L5 and the sixth lens L6 form a cemented lens group with negative optical power. The setting of the cemented lens group is beneficial to correcting the chromatic aberration of the optical system and can also compensate for the change in focal length caused by temperature changes, ensuring that the optical system of the fixed-focus lens of the present invention can still image normally when the temperature changes.

[0056] In the fixed-focus lens of the present invention, the refractive index and Abbe number of the fifth lens L5 are n5 and v5 respectively, and the refractive index and Abbe number of the sixth lens L6 are n6 and v6 respectively, satisfying: 0.7 ≤ n5 / n6 ≤ 1.35, 0.25 ≤ v5 / v6 ≤ 3.8. With such a setting, the ability of this cemented lens group to correct chromatic aberration can be fully exerted, and the entire optical system can well correct chromatic aberration only using one group of cemented lens groups.

[0057] In the fixed-focus lens of the present invention, the refractive index and Abbe number of the ninth lens L9 are n9 and v9, satisfying the relational expression: 1.75 ≤ n9 ≤ 1.85, 23 ≤ v9 ≤ 31. With such a setting, the tolerance of the entire optical system can be further corrected, and the lens assembly yield can be improved.

[0058] The total length TTL of the optical system of the fixed-focus lens of the present invention and the focal length f of the optical system satisfy: TTL / f ≤ 5.43. With such a setting, while ensuring that the optical system meets certain focal length requirements, the total length of the optical system is the shortest, realizing the advantage of miniaturization.

[0059] The following gives four specific embodiments according to the above settings of the present invention to specifically illustrate the imaging lens according to the present invention.

[0060] The data of the four embodiments are as follows in Table 1:

[0061] Conditional Example 1 Example 2 Example 3 Example 4 1.75≤n9≤1.85 - - 1.78 1.85 23≤v9≤31 - - 25.7 30.1 TTL / f ≤ 5.43 4.731 5.175 4.841 5.422 0.7 ≤ n5 / n6 ≤ 1.35 1.187 1.241 0.872 0.829 0.25 ≤ v5 / v6 ≤ 3.8 0.315 0.298 2.766 3.189

[0062] Table 1

[0063] Embodiment 1:

[0064] Figure 1 Schematically shows the structural diagram of the fixed-focus lens according to Embodiment 1 of the present invention. In this embodiment, the first lens group of the fixed-focus lens includes four lenses, namely the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4. The second lens group includes four lenses (L5-L8). In this embodiment, the first lens group has a positive optical power, the TTL of the fixed-focus lens is 77.49 mm, f = 16.38 mm, FOV = 59.14°, and FNO = 1.6.

[0065] The following Table 2 lists the relevant parameters of each lens in this embodiment, including the surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0066]

[0067]

[0068] Table 2

[0069] Figures 2 - 5 Respectively schematically show the 145 lp / mm-MTF graph, +20°C 75 lp / mm-Through-Focus-MTF graph, -40°C 75 lp / mm-Through-Focus-MTF graph, and +80 75 lp / mm-Through-Focus-MTF graph of the fixed-focus lens according to Embodiment 1 of the present invention. Combining with the attached drawings, it can be known that the fixed-focus lens of this embodiment has high resolution and a large aperture, can clearly image in a darker environment, and can work normally and not defocus at -40°C to +80°C.

[0070] Embodiment 2:

[0071] Figure 6 Schematically shows the structural diagram of the fixed-focus lens according to Embodiment 2 of the present invention. In this embodiment, the first lens group of the fixed-focus lens includes four lenses, namely the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4. The second lens group includes four lenses (L5-L8). In this embodiment, the first lens group has a positive optical power, the TTL of the fixed-focus lens is 77.98 mm, f = 15.07 mm, FOV = 64.98°, and FNO = 1.6.

[0072] The following Table 3 lists the relevant parameters of each lens in this embodiment, including the surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0073]

[0074]

[0075] Table 3

[0076] Figures 7 - 10 Schematically show the 145 lp / mm - MTF graph, +20°C 75 lp / mm - Through - Focus - MTF graph, -40°C 75 lp / mm - Through - Focus - MTF graph, and +80 75 lp / mm - Through - Focus - MTF graph of the fixed - focus lens according to Embodiment 2 of the present invention. From the accompanying drawings, it can be known that the fixed - focus lens of this embodiment has high resolution and a large aperture, can clearly image in a relatively dark environment, and can work properly and not defocus at -40°C to +80°C.

[0077] Embodiment 3:

[0078] Figure 11 Schematically show the structural diagram of the fixed - focus lens according to Embodiment 3 of the present invention. In this embodiment, the first lens group of the fixed - focus lens includes five lenses, namely the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the ninth lens L9. The second lens group includes four lenses (L5 - L8). In this embodiment, the first lens group has a negative optical power, the TTL of the fixed - focus lens is 83.94 mm, f = 17.34 mm, FOV = 56.21°, and FNO = 1.6.

[0079] The following Table 4 lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0080]

[0081]

[0082] Table 4

[0083] Figures 12 - 15 Schematically show the 145 lp / mm - MTF graph, +20°C 75 lp / mm - Through - Focus - MTF graph, -40°C 75 lp / mm - Through - Focus - MTF graph, and +80 75 lp / mm - Through - Focus - MTF graph of the fixed - focus lens according to Embodiment 3 of the present invention. From the accompanying drawings, it can be known that the fixed - focus lens of this embodiment has high resolution and a large aperture, can clearly image in a relatively dark environment, and can work properly and not defocus at -40°C to +80°C.

[0084] Embodiment 4:

[0085] Figure 16 Schematic diagram showing the structure of the fixed-focus lens according to Embodiment 4 of the present invention. In this embodiment, the first lens group of the fixed-focus lens includes five lenses, namely the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the ninth lens L9. The second lens group includes four lenses (L5-L8). In this embodiment, the first lens group has a negative optical power, the TTL of the fixed-focus lens is 84.47 mm, f = 15.58 mm, FOV = 61.83°, and FNO = 1.6.

[0086] The following Table 5 lists the relevant parameters of each lens in this embodiment, including the surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0087]

[0088]

[0089] Table 5

[0090] Figures 17 - 20 Respectively schematically show the 145 lp / mm-MTF graph, +20°C 75 lp / mm-Through-Focus-MTF graph, -40°C 75 lp / mm-Through-Focus-MTF graph, and +80 75 lp / mm-Through-Focus-MTF graph of the fixed-focus lens according to Embodiment 4 of the present invention. It can be seen from the accompanying drawings that the fixed-focus lens in this embodiment has high resolution and a large aperture, can clearly image in a relatively dark environment, and can work normally and not defocus at -40°C to +80°C.

[0091] Combined with Figure 21 and Figure 22 As shown, the present invention also provides an imaging system including the above fixed-focus lens. From the object side to the image side, it sequentially includes: a fixed-focus lens 1, a cylindrical beam splitter 2; wherein, the central optical axis of the cylindrical beam splitter is perpendicular to its plane and passes through the center of the plane, and its central optical axis is inclined to the optical axis of the imaging system, and the inclination angle is 30 to 50 degrees. The intersection point of the central optical axis of the cylindrical beam splitter and its plane can coincide with the optical axis of the imaging system or can deviate from the optical axis of the imaging system by 0 to 5 mm (the illustrated example is that the intersection point of the central optical axis of the cylindrical beam splitter and its plane can coincide with the optical axis of the imaging system). According to one implementation manner of the present invention, the thickness of the cylindrical beam splitter is less than 3 mm. The cylindrical beam splitter sequentially includes from the object side to the image side: a plane 21, a cylindrical surface 22 having an inclination angle of 0 to 2 degrees with the plane. According to the concept of the present invention, the cylindrical surface 22 can be a spherical cylindrical surface or an aspherical cylindrical surface. A beam splitting film system is plated on the plane 21 of the cylindrical beam splitter 2 of the present invention.

[0092] In the imaging system of the present invention, a compensation device 3 is further provided between the cylindrical beam splitter 2 and the image plane. The compensation device 3 includes, in sequence from the object side to the image side: a second plane 31, and an inclined plane 32 having an inclination angle of 0 to 2 degrees with respect to the second plane, where the inclined plane 32 can be a plane or a curved surface.

[0093] The working principle of the imaging system of the present invention is as follows: The cylindrical beam splitter 2 is placed obliquely on the image side of the fixed-focus lens optical system. When the outgoing light of the last lens of the original fixed-focus lens 1 passes through the coated plane 21 of the cylindrical beam splitter, the light is divided into two beams of visible light and non-visible light, enabling the optical system to perform visible light and non-visible light imaging simultaneously. The transmitted light can be subjected to aberration correction when passing through the cylindrical surface 22 of the cylindrical beam splitter. Preferably, a compensation device 3 is further provided on the image side to further correct the aberration. Then, after image processing of the imaging pictures on the two imaging planes, a synthetic imaging result with the best reducibility to the object is obtained.

[0094] The above is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that, along the object side to the image side direction, it successively includes a first lens group, a diaphragm, and a second lens group with positive optical power, totaling two lens groups. The first lens group includes two negative-power lenses and two positive-power lenses or includes three negative-power lenses and two positive-power lenses; the total length TTL of the optical system of the fixed-focus lens and the focal length f of the optical system satisfy: 4.731 ≤ TTL / f ≤ 5.43; the first lens group successively includes a first lens (L1) with negative optical power, a second lens (L2) with negative optical power, a third lens (L3) with positive optical power, and a fourth lens (L4) with positive optical power, totaling four lenses; the second lens group successively includes a fifth lens (L5) with negative optical power, a sixth lens (L6) with positive optical power, a seventh lens (L7) with positive optical power, and an eighth lens (L8) with positive optical power, totaling four lenses; or the first lens group successively includes a first lens (L1) with negative optical power, a second lens (L2) with negative optical power, a third lens (L3) with positive optical power, a fourth lens (L4) with positive optical power, and a ninth lens (L9) with negative optical power, totaling five lenses; the second lens group successively includes a fifth lens (L5) with positive optical power, a sixth lens (L6) with negative optical power, a seventh lens (L7) with positive optical power, and an eighth lens (L8) with positive optical power, totaling four lenses.

2. The fixed-focus lens according to claim 1, characterized in that, along the object side to the image side direction, the first lens (L1) is a convex-concave lens, the object side surface of the second lens (L2) is concave, the third lens (L3) is a concave-convex lens, and the object side surface of the fourth lens (L4) is convex.

3. The fixed-focus lens according to claim 1, characterized in that, the fifth lens (L5) is a double-concave or double-convex lens, the sixth lens (L6) is a double-concave or double-convex lens, the image side surface of the seventh lens (L7) is convex, and the object side surface of the eighth lens (L8) is convex.

4. The fixed-focus lens according to claim 1, characterized in that, the ninth lens (L9) is a convex-concave lens.

5. The fixed-focus lens according to claim 2 or 3, characterized in that, the fifth lens (L5) and the sixth lens (L6) form a cemented lens group with negative optical power.

6. The fixed-focus lens according to claim 5, characterized in that, the refractive index and Abbe number of the fifth lens (L5) are n5 and v5 respectively, and the refractive index and Abbe number of the sixth lens (L6) are n6 and v6 respectively, satisfying: 0.7 ≤ n5 / n6 ≤ 1.35, 0.25 ≤ v5 / v6 ≤ 3.

8.

7. The fixed-focus lens according to claim 4, characterized in that, the refractive index and Abbe number of the ninth lens (L9) are n9 and v9, satisfying the relational expression: 1.75 ≤ n9 ≤ 1.85, 23 ≤ v9 ≤ 31.

8. An imaging system comprising the fixed-focus lens according to any one of claims 1-7, characterized in that, a cylindrical beam splitter is further provided between the second lens group of the fixed-focus lens and the image plane, the cylindrical beam splitter is inclined, and along the object side to the image side direction, the cylindrical beam splitter sequentially includes a plane and a cylindrical surface having an inclination angle of 0-2 degrees with the plane; a beam splitting film system is plated on the plane.

9. The imaging system according to claim 8, characterized in that, a compensation device is further provided between the cylindrical beam splitter and the image plane, and along the object side to the image side direction, the compensation device sequentially includes a second plane and an inclined surface having an inclination angle of 0-2 degrees with the second plane; the inclined surface is a plane or a curved surface.

10. The imaging system according to claim 8, characterized in that, the thickness of the cylindrical beam splitter is less than 3 mm.

Images