A fixed-focus lens

Abstract

The present invention discloses a fixed-focus lens, comprising a first lens to a ninth lens arranged in sequence from the object side to the image side along the optical axis; the first lens, the second lens, the sixth lens and the eighth lens all have negative optical power, and the third lens, the fourth lens, the fifth lens, the seventh lens and the ninth lens all have positive optical power; wherein the fifth lens and the sixth lens constitute a first cemented lens, and the seventh lens, the eighth lens and the ninth lens constitute a second cemented lens; the first lens to the ninth lens are all glass spherical mirrors. Thus, by setting a full glass spherical lens and matching a reasonable optical power, the performance of the lens can reach a resolution of more than 12 million pixels (MP), an aperture FNo2.0, an optical total length TTL27mm, an imaging target surface of 1 / 2.5 inches, day and night confocality, no focus deviation from -40 degrees to +80 degrees, and F-Theta distortion less than 10%.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of optical imaging technology, and in particular to a fixed-focus lens. Background Art

[0002] At present, the mainstream fixed-focus lenses in the security monitoring market are made of glass-plastic hybrid lenses. Plastic aspherical lenses have many advantages, such as being cheaper, easier to correct high and low temperature drift, and more convenient to correct aberrations than spherical lenses. However, plastic also has its disadvantages, such as poor resistance to ultraviolet rays, and its resolution performance will gradually deteriorate with the erosion of high temperature and high humidity climate environments. Summary of the invention

[0003] The present invention provides a fixed-focus lens made of all-glass material, which has good weather resistance, can achieve day and night confocality, and does not degrade image resolution or shift focus at high and low temperatures.

[0004] To achieve the above object, the present invention provides a fixed-focus lens, comprising:

[0005] A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens are arranged in sequence from the object side to the image side along the optical axis;

[0006] The first lens, the second lens, the sixth lens and the eighth lens all have negative optical power, and the third lens, the fourth lens, the fifth lens, the seventh lens and the ninth lens all have positive optical power; wherein, the fifth lens and the sixth lens constitute a first cemented lens, and the seventh lens, the eighth lens and the ninth lens constitute a second cemented lens; the first lens to the ninth lens are all glass spherical mirrors.

[0007] Optionally, a surface of the lens adjacent to the object plane is an object side surface, and a surface of the lens adjacent to the image plane is an image side surface;

[0008] The object side surface of the first lens is convex, and the image side surface is concave; the object side surface of the second lens is convex, and the image side surface is concave; the object side surface of the third lens is convex, and the image side surface is convex; the object side surface of the fourth lens is concave, and the image side surface is convex; the image side surface of the fifth lens is convex; the object side surface of the sixth lens is concave, and the image side surface is convex; the object side surface of the seventh lens is convex, and the image side surface is convex; the object side surface of the eighth lens is concave, and the image side surface is concave; the object side surface of the ninth lens is convex, and the image side surface is convex.

[0009] Optionally, the first lens to the ninth lens and the fixed-focus lens satisfy the following relational expressions: -0.6 < F1 / F < -0.4; -0.45 < F2 / F < -0.3; 0.15 < F4 / F < 0.26; 0.05 < Fa / F < 0.25; 0.1 < Fb / F < 0.23, where F1 is the optical power of the first lens, F2 is the optical power of the second lens, F3 is the optical power of the third lens, F4 is the optical power of the fourth lens, Fa is the optical power of the first cemented lens, Fb is the optical power of the second cemented lens, and F is the optical power of the fixed-focus lens.

[0010] Optionally, the fifth lens to the ninth lens satisfy the following relational expressions: -1.85 < F5 / F6 < -1.1; -0.62 < F7 / F8 < -0.55; -0.62 < F9 / F8 < -0.55, where F5 is the optical power of the fifth lens, F6 is the optical power of the sixth lens, F7 is the optical power of the seventh lens, F8 is the optical power of the eighth lens, and F9 is the optical power of the ninth lens.

[0011] Optionally, the third lens, the fourth lens and the fixed-focus lens satisfy the following relational expression: 0.45 < (F3 + F4) / F < 0.6, where F3 is the optical power of the third lens, F4 is the optical power of the fourth lens, and F is the optical power of the fixed-focus lens.

[0012] Optionally, the distance BFL from the center of the image-side optical axis of the ninth lens to the image plane and the distance TTL from the center of the object-side optical axis of the first lens to the image plane satisfy: BFL / TTL > 0.18; the clear aperture D1 of the first lens and the distance TTL from the center of the optical axis of the first lens to the image plane satisfy: D1 / TTL < 0.42.

[0013] Optionally, the refractive index of the third lens is greater than 1.9 and the Abbe number is less than 30.

[0014] Optionally, the refractive index of the fifth lens is less than 1.65 and the Abbe number is greater than 60.

[0015] Optionally, the refractive index of the seventh lens is less than 1.65 and the Abbe number is greater than 60.

[0016] Optionally, the refractive index of the ninth lens is less than 1.65 and the Abbe number is greater than 60.

[0017] The fixed-focus lens proposed in the embodiment of the present invention, through the setting of a full-glass spherical lens and matching with a reasonable optical focal length, can achieve a resolution of more than 12 megapixels (MP), an aperture FNo2.0, an optical total length TTL27mm, an imaging target surface of 1 / 2.5 inches, day and night confocality, no focus deviation from -40 degrees to +80 degrees, an F-Theta distortion of less than 10%, and a field of view of 130 degrees. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of a fixed-focus lens according to an embodiment of the present invention;

[0019] Figure 2 axial aberration curve of the fixed-focus lens of an embodiment of the present invention at a room temperature of 20 degrees;

[0020] Figure 3 axial aberration curve of the fixed-focus lens of an embodiment of the present invention at a low temperature of -40 degrees;

[0021] Figure 4 axial aberration curve of the fixed-focus lens of an embodiment of the present invention at a high temperature of 80 degrees;

[0022] Figure 5 : is a chromatic aberration curve of the fixed-focus lens of an embodiment of the present invention at a room temperature of 20 degrees;

[0023] Figure 6 The field curvature curve and distortion curve of the fixed-focus lens of the embodiment of the present invention at a room temperature of 20 degrees;

[0024] Figure 7 is a schematic structural diagram of a fixed-focus lens according to an embodiment of the present invention;

[0025] Figure 8 The axial aberration curve of the fixed-focus lens according to one embodiment of the present invention at a room temperature of 20 degrees;

[0026] Fig. 9 The axial aberration curve of the fixed-focus lens of one embodiment of the present invention at a low temperature of -40 degrees;

[0027] Fig.10 The axial aberration curve of the fixed-focus lens according to one embodiment of the present invention at a high temperature of 80 degrees;

[0028] Fig.11 : is a chromatic aberration curve of a fixed-focus lens according to an embodiment of the present invention at a room temperature of 20 degrees;

[0029] Fig.12 The field curvature curve and distortion curve of a fixed-focus lens according to an embodiment of the present invention at a room temperature of 20 degrees;

[0030] Fig.13is a schematic structural diagram of a fixed-focus lens according to another embodiment of the present invention;

[0031] Fig.14 is an axial aberration curve of a fixed-focus lens according to another embodiment of the present invention at a room temperature of 20 degrees;

[0032] Fig.15 The axial aberration curve of the fixed-focus lens of another embodiment of the present invention at a low temperature of -40 degrees;

[0033] Fig.16 An axial aberration curve of a fixed-focus lens according to another embodiment of the present invention at a high temperature of 80 degrees;

[0034] Fig.17 is a chromatic aberration curve of a fixed-focus lens according to another embodiment of the present invention at a room temperature of 20 degrees;

[0035] Fig.18 The field curvature curve and distortion curve of a fixed-focus lens according to another embodiment of the present invention at a room temperature of 20 degrees are shown. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0037] Figure 1 Schematic diagram of the structure of a fixed-focus lens according to an embodiment of the present invention. The present invention proposes a fixed-focus lens, such as Figure 1 As shown, including:

[0038] A first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8 and a ninth lens 9 are arranged in sequence from the object side to the image side along the optical axis;

[0039] The first lens 1, the second lens 2, the sixth lens 6 and the eighth lens 8 all have negative optical power, and the third lens 3, the fourth lens 4, the fifth lens 5, the seventh lens 7 and the ninth lens 9 all have positive optical power; among them, the fifth lens 5 and the sixth lens 6 constitute a first cemented lens, and the seventh lens 7, the eighth lens 8 and the ninth lens 9 constitute a second cemented lens; the first lens 1 to the ninth lens 9 are all glass spherical mirrors.

[0040] It can be understood that the optical power is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, which characterizes the ability of the optical system to deflect light rays. The greater the absolute value of the optical power, the stronger the bending ability of the light rays; the smaller the absolute value of the optical power, the weaker the bending ability of the light rays. When the optical power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light rays is divergent. The optical power can be used to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be used to characterize a certain lens, or can be used to characterize a system formed by multiple lenses together (i.e., a lens group). In this embodiment, each lens can be fixed in a lens barrel ( Figure 1 not shown in the figure), and by reasonably distributing the optical power of the lenses, the imaging effect of the large-aperture fixed-focus lens is better, where the optical power is the reciprocal of the focal length.

[0041] In addition, each of the lenses from the first lens 1 to the ninth lens 9 is indirectly supported by a mylar sheet or a spacer ring. An aperture stop (not shown in the figure) can be arranged between the fourth lens 4 and the fifth lens 5. And a flat glass 10 with a certain thickness is provided on the image side. The entire fixed-focus lens is composed of the flat glass 10, nine spherical lenses, and the aperture stop, which can avoid image degradation and focus shift at high and low temperatures.

[0042] Optionally, the surface of the lens adjacent to the object side is the object side surface, and the surface of the lens adjacent to the image side is the image side surface;

[0043] The object side surface of the first lens 1 is convex, and the image side surface is concave; the object side surface of the second lens 2 is convex, and the image side surface is concave; the object side surface of the third lens 3 is convex, and the image side surface is convex; the object side surface of the fourth lens 4 is concave, and the image side surface is convex; the image side surface of the fifth lens 5 is convex; the object side surface of the sixth lens 6 is concave, and the image side surface is convex; the object side surface of the seventh lens 7 is convex, and the image side surface is convex; the object side surface of the eighth lens 8 is concave, and the image side surface is concave; the object side surface of the ninth lens 9 is convex, and the image side surface is convex.

[0044] It should be noted that the object side surface of the fifth lens 5 can be concave, can be convex, or can be flat, without specific limitation.

[0045] Optionally, the first lens 1 to the ninth lens 9 and the fixed-focus lens satisfy the following relational expressions: -0.6 < F1 / F < -0.4; -0.45 < F2 / F < -0.3; 0.15 < F4 / F < 0.26; 0.05 < Fa / F < 0.25; 0.1 < Fb / F < 0.23, where F1 is the optical power of the first lens 1, F2 is the optical power of the second lens 2, F3 is the optical power of the third lens 3, F4 is the optical power of the fourth lens 4, Fa is the optical power of the first cemented lens, Fb is the optical power of the second cemented lens, and F is the optical power of the fixed-focus lens.

[0046] That is to say, when the optical powers of the first lens 1 to the ninth lens 9 are within the above ranges, spherical aberration, coma, field curvature, astigmatism and other aberrations can be reasonably corrected, so that the visible light image quality meets the requirements.

[0047] Optionally, the fifth lens 5 to the ninth lens 9 satisfy the following relational expressions: -1.85 < F5 / F6 < -1.1; -0.62 < F7 / F8 < -0.55; -0.62 < F9 / F8 < -0.55, where F5 is the optical power of the fifth lens 5, F6 is the optical power of the sixth lens 6, F7 is the optical power of the seventh lens 7, F8 is the optical power of the eighth lens 8, and F9 is the optical power of the ninth lens 9.

[0048] That is to say, when the fifth lens 5 and the sixth lens 6 are cemented, the seventh lens 7, the eighth lens 8 and the ninth lens 9 are cemented, and the optical powers satisfy the above ranges, the longitudinal chromatic aberration and day-night confocal can be better corrected.

[0049] Optionally, the third lens 3, the fourth lens 4 and the fixed-focus lens satisfy the following relational expression: 0.45 < (F3 + F4) / F < 0.6, where F3 is the optical power of the third lens 3, F4 is the optical power of the fourth lens 4, and F is the optical power of the fixed-focus lens.

[0050] That is to say, when the optical powers of the third lens 3 and the fourth lens 4 satisfy the above ranges, defocusing at high and low temperatures can be ensured.

[0051] Optionally, the distance BFL from the image-side optical axis center of the ninth lens 9 to the image plane and the distance TTL from the object-side optical axis center of the first lens to the image plane satisfy: BFL / TTL > 0.18; the clear aperture D1 of the first lens 1 and the distance TTL from the optical axis center of the first lens 1 to the image plane satisfy: D1 / TTL < 0.42, so as to ensure that the fixed-focus lens will not interfere with the base and the housing during installation.

[0052] Optionally, the refractive index of the third lens 3 is greater than 1.9 and the Abbe number is less than 30.

[0053] Optionally, the refractive index of the fifth lens 5 is less than 1.65 and the Abbe number is greater than 60.

[0054] Optionally, the refractive index of the seventh lens 7 is less than 1.65 and the Abbe number is greater than 60.

[0055] Optionally, the refractive index of the ninth lens 9 is less than 1.65 and the Abbe number is greater than 60.

[0056] Therefore, through the setting of the full-glass spherical lens and the matching of reasonable optical focal length, the performance of the fixed-focus lens can reach a resolution of more than 12 million pixels (MP), an aperture FNo2.0, an optical total length TTL27mm, an imaging target surface of 1 / 2.5 inches, day and night confocality, no focus deviation from -40 degrees to +80 degrees, F-Theta distortion less than 10%, and when the image plane diameter IH=3.6, the field of view angle meets 60° <FOV / 2<70°。

[0057] The fixed-focus lens provided by the present invention is described below with reference to several specific embodiments.

[0058] Example 1

[0059] like Figure 1 As shown, the structure of the fixed-focus lens has been described above and will not be repeated here. In addition to the above, the object side surface of the fifth lens 5 is a convex surface, and the fixed-focus lens further includes a flat glass 10.

[0060] Further, the parameters of the first lens 1 to the ninth lens 9 satisfy the following conditions:

[0061] Table 1

[0062] F1 / F F2 / F F4 / F Fa / F Fb / F F5 / F6 F7 / F8 F9 / F8 (F3+F4) / F -0.56 -0.42 0.24 0.08 0.21 -1.25 -0.59 -0.58 0.57

[0063] Among them, assuming that the optical focal power of the entire fixed-focus lens is F, the optical focal powers of the nine lenses are F1, F2, F3, F4, F5, F6, F7, F8, and F9 respectively, the optical focal power of the first cemented lens formed by the fifth lens 5 and the sixth lens 6 is Fa, and the optical focal power of the second cemented lens formed by the seventh lens 7, the eighth lens 8, and the ninth lens 9 is Fb.

[0064] Table 2

[0065] BFL / TTL D1 / TTL FOV / 2 n3 v3 n5 v5 n7 v7 n9 v9 0.28 0.34 62.67° 1.92 20.88 1.59 60.47 1.59 68.62 1.59 68.62

[0066] Among them, the distance from the first lens to the image plane is TTL, the distance from the ninth lens 9 to the image plane is BFL, the maximum clear aperture of the first lens 1 is D1, the object field angle is FOV, the refractive index and Abbe number of the third lens 3 are n3 and v3 respectively, the refractive index and Abbe number of the fifth lens 5 are n5 and v5 respectively, the refractive index and Abbe number of the seventh lens 7 are n7 and v7 respectively, and the refractive index and Abbe number of the ninth lens 9 are n9 and v9 respectively.

[0067] Table 3

[0068] Surface number Face type Curvature radius (mm) R Thickness(mm)D Refractive index n Abbe number v Semi-caliber S1 Spherical 28.663 0.700 1.6968 55.46 4.80 S2 Spherical 3.580 1.567 3.08 S3 Spherical 13.108 0.600 1.7618 26.61 3.00 S4 Spherical 4.037 2.200 2.57 S5 Spherical 12.517 3.000 1.9229 20.88 2.46 S6 Spherical -31.878 1.230 2.10 S7 Spherical -17.230 3.000 1.5250 70.36 2.08 S8 Spherical -5.469 0.633 2.37 S9 Spherical -56.301 1.615 1.5941 60.47 2.35 S10 Spherical -3.940 0.500 1.9007 37.05 2.35 S11 Spherical -8.290 0.069 2.46 S12 Spherical 8.647 1.712 1.5928 68.62 2.40 S13 Spherical -6.495 0.600 1.8830 39.23 2.48 S14 Spherical 7.355 1.913 1.5928 68.62 2.65 S15 Spherical -7.675 6.835 2.83 S16 flat INF 0.7 1.5168 64.21 5.00 S17 flat INF 0.1 5.00

[0069] Among them, the surface numbers in Table 3 are numbered according to the surface order of each lens, where "S1" represents the front surface (object side) of the first lens 1, "S2" represents the back surface (image side) of the first lens 1, and so on; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light, a blank space represents that the current position is air, "INF" represents infinity, and "S9" can be an aperture.

[0070] It can be understood that by setting the above parameters, the following results are obtained, where: Figure 2 axial aberration curve of the fixed-focus lens of an embodiment of the present invention at a room temperature of 20 degrees; Figure 3 axial aberration curve of the fixed-focus lens of an embodiment of the present invention at a low temperature of -40 degrees; Figure 4 axial aberration curve of the fixed-focus lens of an embodiment of the present invention at a high temperature of 80 degrees; Figure 5 : is a chromatic aberration curve of the fixed-focus lens of an embodiment of the present invention at a room temperature of 20 degrees; Figure 6 The field curvature curve and distortion curve of the fixed focus lens of the embodiment of the present invention at a room temperature of 20 degrees are shown; wherein, Figure 2 It can be seen that the axial aberration is well corrected at 0.5 and 1.0 fields of view, and the spherical aberration is also controlled within 10μm. Good image quality can be obtained. Figure 3 It can be seen that the temperature drift is less than 5μm at low temperature. Figure 4 It can be seen that the temperature drift is less than 5μm at high temperature. Figure 5 It can be seen that the focal shift at 850nm is less than 11μm, and the day and night confocal effect is good. Figure 6 It can be seen that the meridian and sagittal field curvature and astigmatism are well corrected, the absolute value of F-theta distortion is less than 10%, and good image quality can be obtained.

[0071] Example 2

[0072] like Figure 7 As shown, the fixed-focus lens comprises: a first lens 21, a second lens 22, a third lens 23, a fourth lens 24, a fifth lens 25, a sixth lens 26, a seventh lens 27, an eighth lens 28 and a ninth lens 29 which are arranged in sequence from the object side to the image side along the optical axis;

[0073] The first lens 21, the second lens 22, the sixth lens 26 and the eighth lens 28 all have negative optical power, and the third lens 23, the fourth lens 24, the fifth lens 25, the seventh lens 27 and the ninth lens 29 all have positive optical power; wherein, the fifth lens 25 and the sixth lens 26 constitute a first cemented lens, and the seventh lens 27, the eighth lens 28 and the ninth lens 29 constitute a second cemented lens; the first lens 21 to the ninth lens 29 are all glass spherical mirrors. The object side surface of the first lens 21 is convex, and the image side surface is concave; the object side surface of the second lens 22 is convex, and the image side surface is concave; the object side surface of the third lens 23 is convex, and the image side surface is convex; the object side surface of the fourth lens 24 is concave, and the image side surface is convex; the object side surface of the fifth lens 25 is convex, and the image side surface is convex; the object side surface of the sixth lens 26 is concave, and the image side surface is convex; the object side surface of the seventh lens 27 is convex, and the image side surface is convex; the object side surface of the eighth lens 28 is concave, and the image side surface is concave; the object side surface of the ninth lens 29 is convex, and the image side surface is convex. The fixed-focus lens also includes a flat glass 20.

[0074] Further, the parameters of the first lens 21 to the ninth lens 29 satisfy the following conditions:

[0075] Table 4

[0076] F1 / F F2 / F F4 / F Fa / F Fb / F F5 / F6 F7 / F8 F9 / F8 (F3+F4) / F -0.47 -0.72 0.18 0.18 0.13 -1.65 -0.58 -0.56 0.50

[0077] Among them, assuming that the optical focal length of the entire fixed-focus lens is F, the optical focal lengths of the nine lenses are F1, F2, F3, F4, F5, F6, F7, F8, and F9 respectively, the optical focal length of the first cemented lens formed by the fifth lens 25 and the sixth lens 26 is Fa, and the optical focal length of the second cemented lens formed by the seventh lens 27, the eighth lens 28, and the ninth lens 29 is Fb.

[0078] Table 5

[0079] BFL / TTL D1 / TTL FOV / 2 n3 v3 n5 v5 n7 v7 n9 v9 0.22 0.38 64.27° 2.00 19.32 1.59 68.62 1.55 75.50 1.59 68.62

[0080] Among them, the distance from the first lens to the image plane is TTL, the distance from the ninth lens 29 to the image plane is BFL, the maximum clear aperture of the first lens 21 is D1, the object field angle is FOV, the refractive index and Abbe number of the third lens 23 are n3 and v3 respectively, the refractive index and Abbe number of the fifth lens 25 are n5 and v5 respectively, the refractive index and Abbe number of the seventh lens 27 are n7 and v7 respectively, and the refractive index and Abbe number of the ninth lens 29 are n9 and v9 respectively.

[0081] Table 6

[0082]

[0083]

[0084] Among them, the surface numbers in Table 6 are numbered according to the surface order of each lens, where "S1" represents the front surface (object side) of the first lens 1, "S2" represents the back surface (image side) of the first lens 1, and so on; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light, and a blank space represents that the current position is air; "INF" represents infinity, and "S9" can be an aperture.

[0085] It can be understood that by setting the above parameters, the following results are obtained, where: Figure 8 The axial aberration curve of the fixed-focus lens according to one embodiment of the present invention at a room temperature of 20 degrees; Fig. 9 The axial aberration curve of the fixed-focus lens of one embodiment of the present invention at a low temperature of -40 degrees; Fig.10 The axial aberration curve of the fixed-focus lens according to one embodiment of the present invention at a high temperature of 80 degrees; Fig.11 : is a chromatic aberration curve of a fixed-focus lens according to an embodiment of the present invention at a room temperature of 20 degrees; Fig.12 The field curvature curve and distortion curve of a fixed-focus lens according to an embodiment of the present invention at a room temperature of 20 degrees are shown; wherein, Figure 8 It can be seen that the axial aberration is well corrected at 0.5 and 1.0 fields of view, and the spherical aberration is also controlled within 10μm. Good image quality can be obtained. Fig. 9 It can be seen that the temperature drift is less than 5μm at low temperature. Fig.10 It can be seen that the temperature drift is less than 5μm at high temperature. Fig.11 It can be seen that the focal shift at 850nm is less than 11μm, and the day and night confocal effect is good. Fig.12 It can be seen that the meridian and sagittal field curvature and astigmatism are well corrected, the absolute value of F-theta distortion is less than 10%, and good image quality can be obtained.

[0086] Example 3

[0087] like Fig.13 As shown, the fixed-focus lens comprises: a first lens 31, a second lens 32, a third lens 33, a fourth lens 34, a fifth lens 35, a sixth lens 36, a seventh lens 37, an eighth lens 38 and a ninth lens 39 which are arranged in sequence from the object side to the image side along the optical axis;

[0088] The first lens 31, the second lens 32, the sixth lens 36 and the eighth lens 38 all have negative optical power, and the third lens 33, the fourth lens 34, the fifth lens 35, the seventh lens 37 and the ninth lens 39 all have positive optical power; wherein, the fifth lens 35 and the sixth lens 36 constitute a first cemented lens, and the seventh lens 37, the eighth lens 38 and the ninth lens 39 constitute a second cemented lens; the first lens 31 to the ninth lens 39 are all glass spherical mirrors. The object side surface of the first lens 31 is convex, and the image side surface is concave; the object side surface of the second lens 32 is convex, and the image side surface is concave; the object side surface of the third lens 33 is convex, and the image side surface is convex; the object side surface of the fourth lens 34 is concave, and the image side surface is convex; the object side surface of the fifth lens 35 is convex, and the image side surface is convex; the object side surface of the sixth lens 36 is concave, and the image side surface is convex; the object side surface of the seventh lens 37 is convex, and the image side surface is convex; the object side surface of the eighth lens 38 is concave, and the image side surface is concave; the object side surface of the ninth lens 39 is convex, and the image side surface is convex. The fixed-focus lens also includes a glass plate 30.

[0089] Further, the parameters of the first lens 31 to the ninth lens 39 satisfy the following conditions:

[0090] Table 7

[0091] F1 / F F2 / F F4 / F Fa / F Fb / F F5 / F6 F7 / F8 F9 / F8 (F3+F4) / F -0.45 -0.34 0.17 0.16 0.15 -1.55 -0.58 -0.57 0.51

[0092] Among them, assuming that the optical focal length of the entire fixed-focus lens is F, the optical focal lengths of the nine lenses are F1, F2, F3, F4, F5, F6, F7, F8, and F9 respectively, the optical focal length of the first cemented lens formed by the fifth lens 35 and the sixth lens 36 is Fa, and the optical focal length of the second cemented lens formed by the seventh lens 37, the eighth lens 38, and the ninth lens 39 is Fb.

[0093] Table 8

[0094] BFL / TTL D1 / TTL FOV / 2 n3 v3 n5 v5 n7 v7 n9 v9 0.21 0.39 64.27° 1.92 20.88 1.59 68.62 1.59 68.62 1.59 68.62

[0095] Among them, the distance from the first lens 31 to the image plane is TTL, the distance from the ninth lens 39 to the image plane is BFL, the maximum clear aperture of the first lens 1 is D1, the object field angle is FOV, the refractive index and Abbe number of the third lens 33 are n3 and v3 respectively, the refractive index and Abbe number of the fifth lens 35 are n5 and v5 respectively, the refractive index and Abbe number of the seventh lens 37 are n7 and v7 respectively, and the refractive index and Abbe number of the ninth lens 39 are n9 and v9 respectively.

[0096] Table 9

[0097] Surface number Face type Curvature radius (mm) R Thickness(mm)D Refractive index n Abbe number v Semi-caliber S1 Spherical 10.986 0.700 1.9212 23.96 5.20 S2 Spherical 3.941 2.050 3.62 S3 Spherical 14.810 1.114 1.5005 66.05 3.41 S4 Spherical 3.431 2.193 2.60 S5 Spherical 16.641 2.500 1.9229 20.88 2.29 S6 Spherical -16.641 0.367 2.03 S7 Spherical -8.709 4.000 1.6511 55.90 1.82 S8 Spherical -5.884 0.824 2.57 S9 Spherical 33.807 2.167 1.5928 68.62 2.64 S10 Spherical -4.190 0.700 1.8340 37.35 3.00 S11 Spherical -9.089 0.070 4.00 S12 Spherical 13.370 2.004 1.5928 68.62 3.20 S13 Spherical -6.555 0.600 1.7283 28.31 3.20 S14 Spherical 6.555 2.004 1.5928 68.62 3.13 S15 Spherical -13.370 4.806 3.25 S16 flat INF 0.7 1.5168 64.21 5.00 S17 flat INF 0.1 5.00

[0098] Among them, the surface numbers in Table 9 are numbered according to the surface order of each lens, where "S1" represents the front surface (object side) of the first lens 1, "S2" represents the back surface (image side) of the first lens 1, and so on; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light, and a blank space represents that the current position is air; "INF" is infinity, and "S9" can be an aperture.

[0099] It can be understood that by setting the above parameters, the following results are obtained, where: Fig.14 is an axial aberration curve of a fixed-focus lens according to another embodiment of the present invention at a room temperature of 20 degrees; Fig.15 The axial aberration curve of the fixed-focus lens of another embodiment of the present invention at a low temperature of -40 degrees; Fig.16 An axial aberration curve of a fixed-focus lens according to another embodiment of the present invention at a high temperature of 80 degrees; Fig.17 is a chromatic aberration curve of a fixed-focus lens according to another embodiment of the present invention at a room temperature of 20 degrees; Fig.18 The field curvature curve and distortion curve of the fixed focus lens of another embodiment of the present invention at a room temperature of 20 degrees are shown; wherein, Fig.14 It can be seen that the axial aberration is well corrected at 0.5 and 1.0 fields of view, and the spherical aberration is also controlled within 10μm. Good image quality can be obtained. Fig.15 It can be seen that the temperature drift is less than 5μm at low temperature. Fig.16 It can be seen that the temperature drift is less than 5μm at high temperature. Fig.17 It can be seen that the focal shift at 850nm is less than 11μm, and the day and night confocal effect is good. Fig.18 It can be seen that the meridian and sagittal field curvature and astigmatism are well corrected, the absolute value of F-theta distortion is less than 10%, and good image quality can be obtained.

[0100] In summary, the fixed-focus lens proposed in the embodiment of the present invention, through the setting of a full-glass spherical lens and matching with a reasonable optical focal length, can achieve a resolution of more than 12 megapixels (MP), an aperture FNo2.0, an optical total length TTL27mm, an imaging target surface of 1 / 2.5 inches, day and night confocality, no focus shift from -40 degrees to +80 degrees, an F-Theta distortion of less than 10%, and no degradation of resolution or focus shift at high and low temperatures.

[0101] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that: Including: A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence from the object side to the image side along the optical axis; The first lens, the second lens, the sixth lens, and the eighth lens all have negative optical powers, and the third lens, the fourth lens, the fifth lens, the seventh lens, and the ninth lens all have positive optical powers; among them, the fifth lens and the sixth lens form a first cemented lens, and the seventh lens, the eighth lens, and the ninth lens form a second cemented lens; the first lens to the ninth lens are all glass spherical mirrors; An aperture stop is arranged between the fourth lens and the fifth lens.

2. The fixed-focus lens according to claim 1, characterized in that: The surface of the lens adjacent to the object side is the object side surface, and the surface of the lens adjacent to the image side is the image side surface; The object side surface of the first lens is convex, and the image side surface is concave; the object side surface of the second lens is convex, and the image side surface is concave; the object side surface of the third lens is convex, and the image side surface is convex; the object side surface of the fourth lens is concave, and the image side surface is convex; the image side surface of the fifth lens is convex; the object side surface of the sixth lens is concave, and the image side surface is convex; the object side surface of the seventh lens is convex, and the image side surface is convex; the object side surface of the eighth lens is concave, and the image side surface is concave; the object side surface of the ninth lens is convex, and the image side surface is convex.

3. The fixed-focus lens according to claim 1 or 2, characterized in that: The first lens to the ninth lens and the fixed-focus lens satisfy the following relationships: -0.6 < F1 / F < -0.4; -0.45 < F2 / F < -0.3; 0.15 < F4 / F < 0.26; 0.05 < Fa / F < 0.25; 0.1 < Fb / F < 0.23, where F1 is the optical power of the first lens, F2 is the optical power of the second lens, F4 is the optical power of the fourth lens, Fa is the optical power of the first cemented lens, Fb is the optical power of the second cemented lens, and F is the optical power of the fixed-focus lens.

4. The fixed-focus lens according to claim 1 or 2, characterized in that: The fifth lens to the ninth lens satisfy the following relationships: -1.85 < F5 / F6 < -1.1; -0.62 < F7 / F8 < -0.55; -0.62 < F9 / F8 < -0.55, where F5 is the optical power of the fifth lens, F6 is the optical power of the sixth lens, F7 is the optical power of the seventh lens, F8 is the optical power of the eighth lens, and F9 is the optical power of the ninth lens.

5. The fixed-focus lens according to claim 1 or 2, characterized in that: The third lens, the fourth lens, and the fixed-focus lens satisfy the following relationship: 0.45 < (F3 + F4) / F < 0.6, where F3 is the optical power of the third lens, F4 is the optical power of the fourth lens, and F is the optical power of the fixed-focus lens.

6. The fixed-focus lens according to claim 1 or 2, characterized in that: The distance BFL from the image side optical axis center to the image plane of the ninth lens and the distance TTL from the object side optical axis center to the image plane of the first lens satisfy: BFL / TTL>0.18; the clear aperture D1 of the first lens and the distance TTL from the optical axis center to the image plane of the first lens satisfy: D1 / TTL<0.

42.

7. The fixed-focus lens according to claim 1, wherein: The refractive index of the third lens is greater than 1.9, and the Abbe number is less than 30.

8. The fixed-focus lens according to claim 1, wherein: The refractive index of the fifth lens is less than 1.65, and the Abbe number is greater than 60.

9. The fixed-focus lens according to claim 1, wherein: The refractive index of the seventh lens element is less than 1.65, and the Abbe number is greater than 60.

10. The fixed-focus lens according to claim 1, wherein: The refractive index of the ninth lens is less than 1.65, and the Abbe number is greater than 60.

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