A fixed focus lens
Patent Information
- Application Number
- CN202522108138.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-09-29
- Estimated Expiration
- 2035-09-30
AI Technical Summary
目前市场上的定焦镜头相对孔径较小（常用方案为Fno1.4-Fno2.8），亮度不高、弱光下解像力不足（边缘出现暗角、弱光下需增加补光灯实现夜视增强）、体积偏大、高低温性能不稳定、红外共焦补光下色彩缺失、细节不清晰一直是安防镜头领域中较为关注的问题
1）该镜头采用6G4P玻塑混合结构，实现了大视场角、大光圈、大靶面、8M高解像力、无热化、全天候监控一体化设计，通过玻璃球面透镜与塑胶非球面透镜协同校正，在保证视场角≥150°下，实现大光圈F1.0、大靶面1/1.8”、8M高解像力的设计，极限解像力达250lp/mm，同时通过合理分配透镜及透镜组的材料搭配与光焦度，实现系统在-40℃~80℃的工作温度条件下不虚焦；另外通过大通光口径，夜间也可实现微光成像，满足白天夜间及温度差异变化情况下的高清监控需求。
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Figure CN224816586U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of optical system technology, and in particular to a fixed-focus lens. Background Technology
[0002] Driven by the digital information age, the demand for fixed-focus lenses in the security, public safety, and monitoring facilities sectors is increasing, and various intelligent high-definition cameras are widely used in various fields. Currently, fixed-focus lenses on the market have relatively small apertures (commonly Fno1.4-Fno2.8), low brightness, insufficient resolution in low light (resulting in vignetting at the edges and requiring additional lighting for enhanced night vision in low light), large size, unstable performance at high and low temperatures, color loss under infrared confocal illumination, and unclear details – all of which have been major concerns in the security lens field. Therefore, it is imperative to launch a fixed-focus lens with advantages such as a large aperture (Fno1.0), high imaging resolution (8M), low-light full-color imaging, stable imaging performance, large light transmission, and all-weather monitoring capabilities. Utility Model Content
[0003] The purpose of this invention is to address the aforementioned problems by providing a fixed-focus lens with a large aperture, large focal length, wide field of view, 8M high resolution, no calorification, all-weather monitoring, and high environmental stability.
[0004] To achieve the above objectives, this utility model provides a fixed-focus lens, comprising ten lenses arranged sequentially along the optical axis from the object side to the image side: a first convex-concave lens (L1) with negative optical power, a second convex-concave lens (L2) with negative optical power, a third convex-concave lens (L3) with negative optical power, a fourth biconvex lens (L4) with positive optical power, a fifth convex-concave lens (L5) with negative optical power, a sixth biconvex lens (L6) with positive optical power, a seventh convex-concave lens (L7) with negative optical power, an eighth convex-concave lens (L8) with positive optical power, a ninth convex-concave lens (L9) with negative optical power, and a tenth convex-concave lens (L10) with positive optical power. In the fixed-focus lens, the second lens (L2), third lens (L3), ninth lens (L9), and tenth lens (L10) are plastic aspherical lenses, while the remaining lenses are glass spherical lenses. The fixed-focus lens also includes an aperture stop (STO), which is located between the third lens (L3) and the fourth lens (L4), and includes a second surface of the third lens and a first surface of the fourth lens; and between the fourth lens and the fifth lens, and includes a second surface of the fourth lens and a first surface of the fifth lens.
[0005] Preferably, the fixed-focus lens satisfies the following conditions:
[0006] Among them, f1, f2, f3, f4, f6, f7, f8, f9, f 10 These correspond sequentially to the focal lengths of the first lens (L1), the second lens (L2), the third lens (L3), the fourth lens (L4), the sixth lens (L6), the seventh lens (L7), the eighth lens (L8), the ninth lens (L9), and the tenth lens (L10). The sum of the reciprocals of the focal lengths of the above lenses is expressed as C-all.
[0007] Preferably, the total optical length (TTL) of the fixed-focus lens and the focal length (F) of the fixed-focus lens satisfy the following relationship: 7.40 < TTL / F < 9.47; Preferably, the total optical length (TTL) of the fixed-focus lens and the image plane (H) of the fixed-focus lens satisfy the following relationship: 6.73 < TTL / H < 7.15; Preferably, the aperture size FNO of the fixed-focus lens satisfies the relationship: 0.92 < FNO < 1.14; Preferably, the focal length F4 of the fourth lens (L4) of the fixed-focus lens satisfies the relationship F between the focal length F of the system and the focal length F: 3.33 < F4 / F < 3.92.
[0008] Preferably, the combined focal length FB12 of the cemented doublet lens group of the fifth lens (L5), sixth lens (L6), seventh lens (L7), and eighth lens (L8) of the fixed-focus lens satisfies the relationship F with the system focal length: 3.05 < FB12 / F < 3.66.
[0009] Preferably, the combined focal length F910 of the ninth lens (L9) and the tenth lens (L10) of the fixed-focus lens satisfies the relationship F between the focal length F of the system and the combined focal length F: 7.23 < F910 / F < 13.57.
[0010] Preferably, the combined focal length F123 of the fixed-focus lens's first lens (L1), second lens (L2), and third lens (L3) satisfies the relationship dsto between the object side surface and the center of the aperture stop (STO): -0.57 < F123 / dsto < -0.37.
[0011] Compared with the prior art, the beneficial effects of this utility model are as follows: 1) This lens adopts a 6G4P glass-plastic hybrid structure, achieving a large field of view, large aperture, large target surface, 8M high resolution, no pyrolysis, and all-weather monitoring integrated design. Through the coordinated correction of glass spherical lens and plastic aspherical lens, it achieves a large aperture of F1.0, a large target surface of 1 / 1.8”, and 8M high resolution while ensuring a field of view of ≥150°. The ultimate resolution reaches 250lp / mm. At the same time, by rationally allocating the materials and optical power of the lens and lens group, the system can maintain focus under the working temperature conditions of -40℃ to 80℃. In addition, with a large light-transmitting aperture, it can also achieve low-light imaging at night, meeting the high-definition monitoring needs of day and night and temperature difference conditions.
[0012] 2) Compact structure and high environmental stability: By using a hybrid optical architecture of glass and plastic, spherical and aspherical lenses and cemented lens groups, the number of system lenses and the total system length are reduced to <30mm. At the same time, low-light imaging and heat-free design ensure high environmental stability and realize all-weather high-definition monitoring.
[0013] 3) Low cost and high yield manufacturing: By combining glass and plastic lenses (60% glass), the reasonable glass-plastic ratio reduces system color difference and system tolerance sensitivity while taking into account lightweighting, improves yield, and meets the needs of large-scale mass production in the consumer market. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the fixed-focus lens disclosed in Embodiment 1 of this utility model; Figure 2 This is the MTF diagram of the fixed-focus lens disclosed in Embodiment 1 of this utility model; Figure 3 This is a schematic diagram of the fixed-focus lens disclosed in Embodiment 2 of this utility model; Figure 4 This is the MTF diagram of the fixed-focus lens disclosed in Embodiment 2 of this utility model; Figure 5 This is a schematic diagram of the fixed-focus lens disclosed in Embodiment 3 of this utility model; Figure 6 This is the MTF diagram of the fixed-focus lens disclosed in Embodiment 3 of this utility model; Explanation of reference numerals in the attached diagram: L1: First lens; L2: Second lens; L3: Third lens; L4: Fourth lens; L5: Fifth lens; L6: Sixth lens; L7: Seventh lens; L8: Eighth lens; L9: Ninth lens; L10: Tenth lens; STO: Aperture stop; Parallel flat glass; Image plane. Detailed Implementation
[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0016] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application.
[0017] A fixed-focus lens comprises ten lenses arranged sequentially along the optical axis from the object side to the image side: a first concave-convex lens (L1) with negative optical power, a second concave-convex lens (L2) with negative optical power, a third concave-convex lens (L3) with negative optical power, a fourth biconvex lens (L4) with positive optical power, a fifth concave-convex lens (L5) with negative optical power, a sixth biconvex lens (L6) with positive optical power, a seventh concave-convex lens (L7) with negative optical power, an eighth concave-convex lens (L8) with positive optical power, a ninth concave-convex lens (L9) with negative optical power, and a tenth concave-convex lens (L10) with positive optical power. In the fixed-focus lens, the second lens (L2), third lens (L3), ninth lens (L9), and tenth lens (L10) are plastic aspherical lenses, while the remaining lenses are glass spherical lenses. The fixed-focus lens also includes a stop (STO), located between the third lens (L3) and the fourth lens (L4), comprising the second surface of the third lens and the first surface of the fourth lens; and between the fourth lens and the fifth lens, comprising the second surface of the fourth lens and the first surface of the fifth lens. Through the optical architecture formed by the combination of the above ten lenses in terms of optical power and shape, a 150° wide field of view, a maximum aperture of FNO 0.9, a 1 / 1.8” large target surface, 8M high resolution, thermal reduction, low-light imaging, and all-weather monitoring integrated design can be achieved.
[0018] In this embodiment of the invention, the fixed-focus lens meets the following conditions:
[0019] Among them, f1, f2, f3, f4, f6, f7, f8, f9, f 10The focal lengths of the first lens (L1), second lens (L2), third lens (L3), fourth lens (L4), sixth lens (L6), seventh lens (L7), eighth lens (L8), ninth lens (L9), and tenth lens (L10) are respectively represented by C-all. When the above conditions are met, better image quality can be obtained for each focal length. Furthermore, by rationally allocating lens materials and their corresponding optical powers, the lens can maintain focus within a temperature range of -40℃ to 80℃, ensuring high environmental stability.
[0020] In this embodiment of the present invention, the total optical length TTL of the fixed-focus lens and the focal length F of the fixed-focus lens satisfy the following relationship: 7.40 < TTL / F < 9.47; In this embodiment of the present invention, the total optical length TTL of the fixed-focus lens and the image plane H of the fixed-focus lens satisfy the following relationship: 6.73 < TTL / H < 7.15; In this embodiment of the invention, the aperture size FNO of the fixed-focus lens satisfies the relationship: 0.92 < FNO < 1.14; wherein, the maximum aperture can reach FNO 0.9, which enables the lens to form clear images even in low light while miniaturizing the structure.
[0021] In this embodiment of the invention, the focal length F4 of the fourth lens (L4) of the fixed-focus lens satisfies the relationship F with the system focal length F: 3.33 < F4 / F < 3.92. By adjusting the material and optical power of the fourth lens, chromatic aberration and aberration caused by light entering through the aperture can be corrected, which helps to ensure high resolution.
[0022] In this embodiment of the invention, the combined focal length FB12 of the cemented doublet lens group of the fifth (L5), sixth (L6), seventh (L7), and eighth (L8) lenses of the fixed-focus lens satisfies the relationship F with the system focal length: 3.05 < FB12 / F < 3.66. The cemented doublet lens group allows for a more compact structure of the fixed-focus lens, facilitating miniaturization and improving the correction of system aberrations and chromatic aberration.
[0023] In this embodiment of the invention, the combined focal length F910 of the ninth lens (L9) and the tenth lens (L10) of the fixed-focus lens satisfies the relationship F with the system focal length: 7.23 < F910 / F < 13.57. This is beneficial for correcting some field curvature and astigmatism, and also helps to control the principal ray angle CRA of the fixed-focus lens, thereby improving the relative illumination of the fixed-focus lens.
[0024] In this embodiment of the invention, the combined focal length F123 of the first lens (L1), second lens (L2), and third lens (L3) of the fixed-focus lens satisfies the relationship dsto between the object side surface and the center of the aperture stop (STO): -0.57 < F123 / dsto < -0.37. By adjusting the distance between the light entering from the front end and the aperture stop, the light path of the entire fixed-focus lens optical system can be controlled, reducing aberrations caused by large-angle light and improving edge imaging quality.
[0025] The fixed-focus lens of this utility model will be specifically described below with reference to three embodiments, in conjunction with accompanying drawings and tables. In the following embodiments... In this embodiment, the aperture STO is referred to as one side, and the image plane is referred to as one side.
[0026] The parameters for each embodiment that conforms to the above conditions are shown in Tables 1 and 2 below:
[0027] Table 1
[0028] Table 2 In various embodiments of this utility model, the plastic aspherical lens of the fixed-focus lens satisfies the following formula: In the above formula, z is the axial distance from the vertex to the surface at a position perpendicular to the optical axis at a height h; c represents the curvature at the vertex of the aspherical surface; k is the conic coefficient; A4, A6, A8, A10, A12, A14, A16... represent the fourth, sixth, eighth, tenth, twelfth, fourteenth, sixteenth... aspherical coefficients, respectively.
[0029] Example 1 See Figure 1 The parameters of the fixed-focus lens in this embodiment are as follows: Overall lens length: 30.30mm; field of view: 150°; image plane: 4.50mm; focal length: 4.09mm. The aperture stop STO is located between the third and fourth lenses (including the second surface of the third lens and the first surface of the fourth lens).
[0030] The relevant parameters of each lens in the fixed-focus lens of this embodiment include: surface type, radius of curvature R value, thickness, refractive index of the material and Abbe number, as shown in Table 3 below.
[0031]
[0032] Table 3 Specifically, in the above example, the first lens L1 has a first surface and a second surface, the second lens L2 has a third surface and a fourth surface, the third lens L3 has a fifth surface and a sixth surface, the fourth lens L4 has an eighth surface and a ninth surface, the fifth and sixth cemented lenses L5 and L6 have a tenth surface, an eleventh surface and a twelfth surface, the seventh and eighth cemented lenses L7 and L8 have a thirteenth surface, a fourteenth surface and a fifteenth surface, the ninth lens L9 has a sixteenth surface and a seventeenth surface, and the tenth lens L10 has an eighteenth surface and a nineteenth surface. The aperture has a seventh surface, the flat glass has a twentyth surface and a twenty-first surface, and the image plane has a twenty-second surface.
[0033] The aspherical coefficients of each aspherical lens in the fixed-focus lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A10. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 and the sixteenth-order aspherical coefficient A 16 As shown in Table 4 below.
[0034]
[0035] Table 4 Combination Figure 1 As shown in Tables 1 to 4 above, the fixed-focus lens of this embodiment effectively balances the chromatic aberration, aberrations, and high and low temperature performance of the optical system through the synergistic correction of the glass spherical lens and the plastic aspherical lens. This achieves a 150° wide field of view, an aperture of up to Fn0.9, a 1 / 1.8” large aperture, and 8M high resolution. Simultaneously, it maintains stable imaging under high and low temperature conditions, without defocusing within a temperature range of -40℃ to 80℃, and still provides clear imaging in low-light conditions at night. Low-light imaging and a thermal-free design ensure high environmental stability, enabling all-weather high-definition monitoring.
[0036] Example 2 See Figure 3 The parameters of the fixed-focus lens in this embodiment are as follows: Overall lens length: 30.30mm; field of view: 144°; image plane: 4.42mm; focal length: 3.66mm. The aperture stop STO is located between the fourth and fifth lenses (including the second surface of the fourth lens and the first surface of the fifth lens).
[0037] The relevant parameters of each lens in the fixed-focus lens of this embodiment include: surface type, radius of curvature R value, thickness, refractive index of the material and Abbe number, as shown in Table 5 below.
[0038]
[0039] Table 5 Specifically, in the above example, the first lens L1 has a first surface and a second surface, the second lens L2 has a third surface and a fourth surface, the third lens L3 has a fifth surface and a sixth surface, the fourth lens L4 has a seventh surface and an eighth surface, the fifth and sixth cemented lenses L5 and L6 have a tenth surface, an eleventh surface and a twelfth surface, the seventh and eighth cemented lenses L7 and L8 have a thirteenth surface, a fourteenth surface and a fifteenth surface, the ninth lens L9 has a sixteenth surface and a seventeenth surface, and the tenth lens L10 has an eighteenth surface and a nineteenth surface. The aperture plane has a ninth surface, the flat glass has a twentieth surface and a twenty-first surface, and the image plane has a twenty-second surface.
[0040] The aspherical coefficients of each aspherical lens in the fixed-focus lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A10. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 and the sixteenth-order aspherical coefficient A 16 As shown in Table 6 below.
[0041]
[0042] Table 6 Combination Figure 3 As shown in Tables 1, 2, 5, and 6 above, the fixed-focus lens of this embodiment effectively balances the chromatic aberration, aberrations, and high and low temperature performance of the optical system through the synergistic correction of the glass spherical lens and the plastic aspherical lens. This achieves a 150° wide field of view, an aperture of up to Fn0.9, a 1 / 1.8” large aperture, and 8M high resolution. Simultaneously, it maintains stable imaging under high and low temperature conditions, without defocusing within a temperature range of -40℃ to 80℃, and still provides clear imaging in low-light conditions at night. Low-light imaging and a thermal-free design ensure high environmental stability, enabling all-weather high-definition monitoring.
[0043] Example 3 See Figure 5 The parameters of the fixed-focus lens in this embodiment are as follows: Overall lens length: 30.30mm; field of view: 140°; image plane: 4.24mm; focal length: 3.2mm. The aperture stop STO is located between the third and fourth lenses (including the second surface of the third lens and the first surface of the fourth lens).
[0044] The relevant parameters of each lens in the fixed-focus lens of this embodiment include: surface type, radius of curvature R value, thickness, refractive index of the material and Abbe number, as shown in Table 7 below.
[0045]
[0046] Table 7 Specifically, in the above example, the first lens L1 has a first surface and a second surface, the second lens L2 has a third surface and a fourth surface, the third lens L3 has a fifth surface and a sixth surface, the fourth lens L4 has an eighth surface and a ninth surface, the fifth and sixth cemented lenses L5 and L6 have a tenth surface, an eleventh surface and a twelfth surface, the seventh and eighth cemented lenses L7 and L8 have a thirteenth surface, a fourteenth surface and a fifteenth surface, the ninth lens L9 has a sixteenth surface and a seventeenth surface, and the tenth lens L10 has an eighteenth surface and a nineteenth surface. The aperture has a seventh surface, the flat glass has a twentyth surface and a twenty-first surface, and the image plane has a twenty-second surface.
[0047] The aspherical coefficients of each aspherical lens in the fixed-focus lens of this embodiment include: the quadratic surface constant K, the fourth-order aspherical coefficient A4, the sixth-order aspherical coefficient A6, the eighth-order aspherical coefficient A8, and the tenth-order aspherical coefficient A10. 10 12th order aspherical coefficient A 12 Fourteenth-order aspherical coefficient A 14 and the sixteenth-order aspherical coefficient A 16 As shown in Table 8 below.
[0048]
[0049] Table 8 Combination Figure 3 As shown in Tables 1, 2, 7, and 8 above, the fixed-focus lens of this embodiment effectively balances the chromatic aberration, aberrations, and high and low temperature performance of the optical system through the synergistic correction of glass spherical lenses and plastic aspherical lenses. This achieves a 150° wide field of view, an aperture of up to Fn0.9, a 1 / 1.8” large aperture, and 8M high resolution. Simultaneously, it maintains stable imaging under high and low temperature conditions, without defocusing within a temperature range of -40℃ to 80℃, and still provides clear imaging in low-light conditions at night. Low-light imaging and a thermal-free design ensure high environmental stability, enabling all-weather high-definition monitoring.
[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0051] The embodiments described above are merely specific and detailed examples of the present application, and should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A fixed-focus lens, characterized in that: The fixed-focus lens comprises ten lenses arranged sequentially along the optical axis from the object side to the image side: a first lens (L1) with negative optical power, a second lens (L2) with negative optical power, a third lens (L3) with negative optical power, a fourth lens (L4) with positive optical power, a fifth lens (L5) with negative optical power, a sixth lens (L6) with positive optical power, a seventh lens (L7) with negative optical power, an eighth lens (L8) with positive optical power, a ninth lens (L9) with negative optical power, and a tenth lens (L10) with positive optical power.
2. The fixed-focus lens according to claim 1, characterized in that: The fixed-focus lens also meets the following conditions: Among them, f1, f2, f3, f4, f6, f7, f8, f9, f 10 These correspond sequentially to the focal lengths of the first lens (L1), the second lens (L2), the third lens (L3), the fourth lens (L4), the sixth lens (L6), the seventh lens (L7), the eighth lens (L8), the ninth lens (L9), and the tenth lens (L10). The sum of the reciprocals of the focal lengths of the above lenses is expressed as C-all.
3. The fixed-focus lens according to claim 1, characterized in that: The fixed-focus lens also meets the following conditions: The total optical length TTL of the fixed-focus lens and the focal length F of the fixed-focus lens satisfy the following relationship: 7.40 < TTL / F < 9.47; The total optical length TTL of the fixed-focus lens and the image plane H of the fixed-focus lens satisfy the following relationship: 6.73 < TTL / H < 7.15; The aperture size FNO of the fixed-focus lens satisfies the following relationship: 0.92 < FNO < 1.
14.
4. The fixed-focus lens according to claim 1, characterized in that: Along the optical axis from the object side to the image side, the first lens (L1) is a convex-concave lens, the second lens (L2) is a paraxial concave-convex lens, the third lens (L3) is a paraxial concave-convex lens, the fourth lens (L4) is a biconvex lens, the fifth lens (L5) is a convex-concave lens, the sixth lens (L6) is a biconvex lens, the seventh lens (L7) is a convex-concave lens, the eighth lens (L8) is a convex-concave lens, the ninth lens (L9) is a paraxial convex-concave lens, and the tenth lens (L10) is a paraxial convex-concave lens.
5. The fixed-focus lens according to claim 1, characterized in that: The second lens (L2), the third lens (L3), the ninth lens (L9), and the tenth lens (L10) are plastic aspherical lenses, while the first lens (L1), the fourth lens (L4), the fifth lens (L5), the sixth lens (L6), the seventh lens (L7), and the eighth lens (L8) are glass spherical lenses.
6. The fixed-focus lens according to claim 1, characterized in that: The fixed-focus lens also includes an aperture stop (STO) located between the third lens (L3) and the fourth lens (L4), comprising a second surface of the third lens and a first surface of the fourth lens; and between the fourth lens and the fifth lens, comprising a second surface of the fourth lens and a first surface of the fifth lens.
7. The fixed-focus lens according to claim 1, characterized in that, The focal length F4 of the fourth lens (L4) and the focal length F of the system satisfy the following relationship: 3.33 < F4 / F < 3.
92.
8. The fixed-focus lens according to claim 1, characterized in that, The combined focal length FB12 of the cemented doublet lens group consisting of the fifth lens (L5), the sixth lens (L6), the seventh lens (L7), and the eighth lens (L8) satisfies the relationship F between the focal length F of the system and the combined focal length FB12.
9. The fixed-focus lens according to claim 1, characterized in that, The combined focal length F910 of the ninth lens (L9) and the tenth lens (L10) satisfies the following relationship with the system focal length F: 7.23 < F910 / F < 13.
57.
10. The fixed-focus lens according to claim 1, characterized in that, The combined focal length F123 of the first lens (L1), the second lens (L2), and the third lens (L3) satisfies the relationship dsto between the object side surface and the center of the aperture stop (STO): -0.57 < F123 / dsto < -0.37.