An optical lens with stable imaging

Abstract

The present invention relates to the field of optical lenses, and relates to an optical lens with stable imaging, which comprises, from the object side to the image side, 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 negative optical power, and a fifth lens with positive optical power, and a stop is also provided between the third lens and the fourth lens, wherein: the convex surface of the first lens and the second lens faces the object side, and the concave surface faces the image side; the convex surface of the fourth lens faces the object side, and the concave surface faces the image side; wherein the focal length value F4 of the fourth lens and the focal length value F5 of the fifth lens satisfy |F4 / F5|≤0.92. In this way, the present invention reasonably distributes the optical power of each lens, so that the lens has a small defocus offset under high and low temperature conditions, and the MTF is more uniform, so that the lens can obtain good clarity under high or low temperature environments, and can better adapt to harsh environments.

Description

Technical Field

[0001] The present invention relates to the field of optical lenses, and more particularly to an optical lens with stable imaging. Background Art

[0002] With the rapid development of intelligent driving assistance systems, wide-angle lenses are widely used in side-view lenses and surround-view lenses in vehicle-mounted systems. With the popularization of vehicle-mounted wide-angle lenses, the requirements for their resolution are getting higher and higher. With the complexity of vehicle-mounted systems, the space for lens assembly is greatly limited. Wide-angle lenses need to meet the requirements of miniaturization while having a large field of view. At the same time, drivers have higher requirements for the brightness, clarity, color reproduction, and high and low temperature imaging quality stability of the imaging picture. To meet the above requirements, all-glass lenses can be used, but their cost is too high and the processing cycle is long. If plastic lenses are partially used, the ability of plastic lenses to cope with temperature changes is not as good as that of all-glass lenses. Most optical lenses have poor resolution performance at high and low temperatures, and the defocus value is large at high and low temperatures. In actual applications, the environment in which vehicle-mounted lenses are used outdoors is relatively harsh, and sometimes they are in bad weather such as rain, snow, and dust. In this regard, the stability requirements of the lenses are also higher. Summary of the invention

[0003] The present invention is to overcome the problem that most optical lenses using plastic lenses described in the background art have poor resolution performance at high and low temperatures and large defocus values ​​at high and low temperatures, because the stability of plastic lenses in dealing with temperature changes is not as good as that of all-glass lenses. The present invention provides an optical lens with stable imaging. The present invention also has good resolution performance at high and low temperatures, and has smaller defocus values ​​at high and low temperatures.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: an optical lens with stable imaging, which comprises, from the object side to the image side, 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 negative optical power and a fifth lens with positive optical power, and a stop is further provided between the third lens and the fourth lens, wherein:

[0005] The convex surface of the first lens faces the object side, and the concave surface faces the image side;

[0006] The convex surface of the second lens faces the object side, and the concave surface faces the image side;

[0007] The side of the third lens facing the object side and the side facing the image side are both convex;

[0008] The convex surface of the fourth lens faces the object side, and the concave surface faces the image side;

[0009] The side of the fifth lens facing the object side and the side facing the image side are both convex;

[0010] Among them, the focal length value F4 of the fourth lens and the focal length value F5 of the fifth lens satisfy |F4 / F5| ≤ 0.92. In this way, by reasonably distributing the optical power of each lens, the invention makes the defocus offset of the lens small under high temperature and low temperature conditions, and the MTF is more uniform, so that the lens can obtain good clarity under high temperature or low temperature environments and is more adaptable to harsh environments.

[0011] Preferably, the total optical length TTL of the optical lens and the overall focal length EFL of the optical lens satisfy TTL / EFL ≤ 15.6. In this way, the lens can be made more compact.

[0012] Preferably, the distance d12 between the first lens and the second lens and the total optical length TTL of the optical lens satisfy 0.1 < d12 / TTL < 0.3. In this way, the lens can be made more compact.

[0013] Furthermore, the fourth lens and the fifth lens are cemented to form a doublet lens. In this way, the fourth lens and the fifth lens form a combined cemented lens, and the cemented lens can effectively improve the chromatic aberration of the optical system.

[0014] Preferably, the concave surface of the first lens satisfies:

[0015] 0.25 < ARCTAN(SAG(S2) / D(S2)) - ARCTAN(SAG(S2) / 2 / D(S2) / 2) < 0.45,

[0016] In the formula, S2 represents the second optical surface from the object side to the image side of the optical lens, D(S2) represents the semi-aperture of the maximum clear aperture of the second optical surface corresponding to the maximum field of view angle of the optical lens, and SAG(S2) represents the Sg value corresponding to the second optical surface. In this way, the meniscus shape of the first lens facing the object side can collect light in a larger field of view and enter the optical system to complete large-angle imaging, and at the same time can improve the edge illumination of the lens.

[0017] Preferably, the concave surface of the second lens satisfies:

[0018] 0.25 < ARCTAN(SAG(S4) / D(S4)) - ARCTAN(SAG(S4) / 2 / D(S4) / 2) < 0.55,

[0019] In the formula, S4 represents the fourth optical mirror surface from the object side to the image side of the optical lens, D(S4) represents the semi-aperture of the maximum aperture of the fourth optical mirror surface corresponding to the maximum field angle of the optical lens, and SAG(S4) represents the Sg value corresponding to the fourth optical mirror surface. In this way, the image side surface of the second lens is a large-angle shape, which reduces the deflection angle of the light, is conducive to reducing aberrations while reducing the total length of the lens.

[0020] Preferably, the two optical surfaces of the second lens, the two optical surfaces of the fourth lens, and the two optical surfaces of the fifth lens are all aspherical surfaces, and the two optical surfaces of the third lens are both spherical surfaces.

[0021] Preferably, the total optical length TTL of the optical lens satisfies TTL≤13.2 mm. In this way, the lens can be made more compact.

[0022] Preferably, the first lens satisfies:

[0023] Nd1≥1.7, Vd1≥46;

[0024] Here, Nd1 represents the d-light refractive index of the first lens material, and Vd1 represents the d-light Abbe constant of the first lens material.

[0025] Compared with the prior art, the beneficial effects are:

[0026] 1. The present invention reasonably distributes the optical power of each lens so that the lens has good resolution performance at -40℃~105℃, the high and low temperature defocus is less than 10um, and the MTF is more uniform, so that the lens can obtain good clarity in high or low temperature environments, the imaging stability is higher, and it has better imaging performance in high and low temperature environments, and can better adapt to harsh environments.

[0027] 2. The optimized curved shape of the first lens in the present invention is conducive to reducing the overall peripheral distortion of the system and improving the illumination; the large-angle shape of the second lens expands the light, making the overall uniformity of the light energy better, which is conducive to more uniform picture brightness, and makes the deflection angle of the light in a large field of view smaller, the light trend is more moderate, and the overall length of the system is shortened while reducing the aberration. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the optical lens provided by the present invention.

[0029] Figure 2 It is a modulation transfer function curve diagram of Example 1.

[0030] Figure 3 This is a modulation transfer function graph of Example 2.

[0031] Figure 4 It is a modulation transfer function curve diagram of Example 3.

[0032] Figure 5 It is the high and low temperature defocus curve diagram of Example 1-3 at -40°C.

[0033] Figure 6 It is the high and low temperature defocus curve diagram of Example 1-3 at 20°C.

[0034] Figure 7 It is the high and low temperature defocus curve diagram of Example 1-3 at 105°C. DETAILED DESCRIPTION

[0035] The drawings are only for illustrative purposes and cannot be construed as limiting the present invention. To better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are only for illustrative purposes and cannot be construed as limiting the present invention.

[0036] Examples 1-3

[0037] Embodiments 1-3 all provide an optical lens with stable imaging, such as Figure 1 As shown, from the object side to the image side, the lens system 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 negative optical power, and a fifth lens L5 with positive optical power, and a stop is further provided between the third lens L3 and the fourth lens L4, wherein:

[0038] The convex surface of the first lens L1 faces the object side, and the concave surface faces the image side;

[0039] The second lens L2 has a convex surface facing the object side and a concave surface facing the image side;

[0040] The third lens L3 has a convex surface on both the side facing the object and the side facing the image.

[0041] The fourth lens L4 has a convex surface facing the object side and a concave surface facing the image side;

[0042] The fifth lens L5 has a convex surface on both the side facing the object side and the side facing the image side;

[0043] The fourth lens L4 and the fifth lens L5 are glued together to form a double glued lens; the two optical mirrors of the second lens L2, the two optical mirrors of the fourth lens L4 and the two optical mirrors of the fifth lens L5 are all aspherical lenses, that is, the corresponding optical mirrors S3, S4, S8, S9, S10 in the figure are all aspherical, and the two optical mirrors of the third lens L3 are all spherical, that is, the corresponding optical mirrors S6 and S7 in the figure are all spherical lenses. And the first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5 are all lenses made of plastic, and the third lens L3 is a lens made of glass. In the present invention, only one glass lens is used, and the overall cost and manufacturing price are greatly reduced, and L3 is a glass lens, DN / DT is large, stability is good, and high and low temperature imaging properties are good. In Examples 1-3, the semi-aperture D(S2) of the maximum aperture of the first optical mirror corresponding to the maximum field angle of the optical lens is less than 5.7 mm. In this way, the curvature of the first lens is reasonably distributed, so that the semi-aperture is less than 5.7 mm, which facilitates the miniaturization of the surround view lens and saves assembly space.

[0044] In Examples 1-3, the main functions and effects of each lens are as follows:

[0045] The first lens L1: Its meniscus shape facing the object side can collect light from a larger field of view into the optical system to complete large-angle imaging; and in practical applications, considering the harsh outdoor use environment of the vehicle-mounted lens, which may be in severe weather such as rain, snow, and dust, such a shape is conducive to the sliding of water droplets and prevents dust from accumulating in corners, reducing the impact on imaging.

[0046] The second lens L2 expands the light collected by the first lens L1 to make the light field more uniform, which is beneficial to the improvement of the relative illumination of the lens; and its large-angle shape on the image side reduces the deflection angle of the light, making the light trend smoother, which is beneficial to the reduction of aberrations. At the same time, it can effectively reduce the optical path of the entire system, reduce the overall length of the lens, and facilitate miniaturization.

[0047] The third lens L3, a biconvex positive power lens, is used to balance the spherical aberration introduced by the first two negative power lenses.

[0048] The aperture is placed between L3 and the glued part to converge the front and rear light and shorten the overall length of the optical system.

[0049] The fourth lens L4 and the fifth lens L5 are bonded to form a double bonded lens, which converges the front light, eliminates or balances the chromatic aberration produced by the lens, and reduces the tolerance sensitivity; the fourth lens L4 and the fifth lens L5 are both plastic lenses, which are used to control their focal lengths, thereby controlling the back focus offset of the lens at high and low temperatures.

[0050] Figure 1In the embodiment 1-3, the parameters of the optical lens are different.

[0051] The basic parameters of the optical lens of Example 1 are shown in Table 1 below:

[0052] Surf(Optical Mirror) Radius Thickness Nd(refractive index) Vd (Abbe constant) 1 13.5011 0.8002 1.74 49.60 2 3.0589 2.8940 3 -18.0758 0.6370 1.54 56.11 4 1.3448 1.4825 5 3.5004 2.9224 1.85 23.79 6 -3.3819 -0.0414 STO Infinity 0.1957 8 12.9631 0.5500 1.64 23.53 9 0.6385 1.8702 1.54 56.11 10 -1.5728 0.1093 11 Infinity 0.3162 1.52 64.20 12 Infinity 1.1351 13 Infinity 0.4162 1.52 64.20 14 Infinity 0.3905 IMA Infinity 0.0000

[0053] Table 1. Basic parameters of each optical mirror in Example 1

[0054] The basic parameter settings of each optical mirror surface in the optical lens of Example 2 are shown in Table 2 below:

[0055]

[0056]

[0057] Table 2. Basic parameters of each optical mirror in Example 2

[0058] The basic parameter settings of each optical mirror surface in the optical lens of Example 3 are shown in Table 3 below:

[0059] Surf Radius Thickness Nd Vd 1 11.0000 0.9500 1.80 46.57 2 3.4753 1.5980 3 -50.0000 0.5500 1.54 56.11 4 1.0823 1.4129 5 3.3063 3.0000 1.78 25.72 6 -2.5141 -0.0400 STO Infinity 0.1439 8 8.3265 0.5500 1.64 23.53 9 0.5957 1.8188 1.54 56.11 10 -1.5888 0.1985 11 Infinity 0.3000 1.52 64.20 12 Infinity 0.9194 13 Infinity 0.4000 1.52 64.20 14 Infinity 0.1947 IMA Infinity 0.0000

[0060] Table 3. Basic parameters of each optical mirror in Example 3

[0061] In Table 1-3, STO represents the aperture surface, and IMA represents the imaging surface.

[0062] Since the optical mirrors S3, S4, S8, S9, and S10 are all aspherical surfaces, their corresponding aspherical surface equations are:

[0063]

[0064] Where: Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height h along the principal optical axis; c = 1 / r, c is the curvature of the pole of the aspheric surface, r represents the curvature radius of the mirror surface, k is the cone coefficient, and A, B, C, D, and E are high-order aspheric coefficients.

[0065] The high-order aspheric coefficients of each optical mirror surface in Example 1 are shown in Table 4 below:

[0066] Surf K A B C D E 3 -124.2602 2.1993E-02 -6.3652E-03 9.9029E-04 -8.2120E-05 2.2269E-06 4 -2.1269 1.0218E-01 -3.0337E-03 -2.3823E-03 -3.8095E-04 5.2687E-04 8 -133.3149 -9.0888E-02 1.8287E-01 -5.3962E-01 6.8918E-01 -3.0577E-01 9 -0.9574 -3.3501E-01 1.9786E-01 -1.1185E-01 4.3854E-02 -9.5962E-03 10 -11.2831 -2.3487E-01 2.1710E-01 -1.3613E-01 4.4377E-02 -5.3707E-03

[0067] Table 4

[0068] The high-order aspheric coefficients of each optical mirror surface in Example 2 are shown in Table 5 below:

[0069] Surf K A B C D E 3 -101.2873 2.2246E-02 -6.3246E-03 9.7976E-04 -8.1483E-05 0 4 -2.0387 1.0373E-01 -2.9673E-03 -2.4397E-03 -4.6887E-04 0 8 -89.3705 -8.5276E-02 1.8060E-01 -5.5277E-01 8.0275E-01 -4.4410E-01 9 -0.9568 -3.4704E-01 1.7702E-01 -8.2074E-02 -1.0903E-03 5.4678E-03 10 -11.9044 -2.3481E-01 2.2159E-01 -1.3918E-01 4.6847E-02 -5.7514E-03

[0070] Table 5

[0071] The high-order aspheric coefficients of each optical mirror surface in Example 3 are shown in Table 6 below:

[0072] Surf K A B C D E 3 81.1937 2.3529E-02 -5.9132E-03 8.4908E-04 -6.5444E-05 2.1065E-06 4 -0.4238 2.4394E-02 2.9030E-03 1.7322E-03 -4.0681E-03 7.1902E-04 8 -26.0897 -1.0593E-01 1.1533E-01 -3.8716E-01 6.7136E-01 -4.4410E-01 9 -1.1939 -2.3064E-01 1.9648E-01 -1.0191E-01 1.5067E-02 5.4678E-03 10 -8.0146 -1.9541E-01 1.6128E-01 -1.0495E-01 3.7668E-02 -5.7514E-03

[0073] Table 6

[0074] The corresponding optical parameters in Examples 1-3 are shown in Table 7 below:

[0075] Example 1 Example 2 Example 3 EFFL 0.879233 0.932943 0.938140 F1 -5.481443 -5.343866 -6.662589 F2 -2.294862 -2.248810 -1.957135 F3 2.498991 2.540425 2.335385 F4 -1.058003 -1.093203 -1.021483 F5 1.197292 1.203458 1.134265 F45 3.707401 3.599899 3.670773 d12 2.894003 2.151456 1.598000 d23 1.482471 1.464055 1.412900 TTL 13.678000 13.151200 11.996160 SAG(S2) 2.279273 2.070280 1.692408 SAG(S4) 0.983814 1.188284 1.270279 SAG(S2) / 2 0.381289 0.360664 0.336357 SAG(S4) / 2 0.201886 0.235928 0.222654 D(S2) 2.957891 2.852301 2.983101 D(S4) 1.426047 1.502651 1.332240 D(S2) / 2 1.478946 1.426151 1.491551 D(S4) / 2 0.713024 0.751326 0.666120

[0076] Table 7

[0077] The conditional formulas of the optical parameters in Examples 1-3 are shown in Table 8 below:

[0078] Conditional expression Example 1 Example 2 Example 2 F4 / F5 -0.883663 -0.90838 -0.90057 d12 / TTL 0.2115808 0.163594 0.133209 TTL / EFL 15.556741 14.09647 12.78717 ARCTAN(SAG(S2) / D(S2))-ARCTAN(SAG(S2) / 2 / D(S2) / 2) 0.4042219 0.380151 0.294254 ARCTAN(SAG(S4) / D(S4))-ARCTAN(SAG(S4) / 2 / D(S4) / 2) 0.3279893 0.364835 0.439015

[0079] Table 8

[0080] In Tables 7 and 8, Fn represents the effective focal length of the nth lens; F45 represents the effective focal length of the cemented lens formed by the fourth lens L4 and the fifth lens L5; EFL represents the focal length of the entire optical lens group; the total optical length of the TTL optical lens, that is, the distance from the center of the object side of the first lens L1 to the imaging surface; d12 represents the interval between the first lens L1 and the second lens L2, that is, the distance between the image side of the first lens L1 and the object side of the second lens L2; ​​d23 represents the interval between the second lens L2 and the third lens L3, that is, the distance between the image side of the second lens L2 and the object side of the third lens L3; Sn represents the nth optical mirror surface, as shown in FIG. Figure 1 As shown in ; D(Sn) represents the semi-aperture of the maximum aperture of the optical mirror Sn corresponding to the maximum field angle of the optical lens; SAG(Sn) represents the Sg value corresponding to the optical mirror Sn.

[0081] Optical experiments were carried out on Examples 1, 2 and 3, and the corresponding modulation transfer function curves (MTF) are shown as follows: Figure 2 , 3 , as shown in Figure 4.

[0082] The defocus curves of the optical lenses in Examples 1-3 were obtained by testing at -40°C, 20°C, and 105°C, respectively. The defocus curves of the optical lenses in Examples 1-3 at -40°C were as follows: Figure 5 As shown, the defocus curves at 20°C are Figure 6 As shown, the defocus curves at 105°C are Figure 7As shown in the figure, it can be seen from the high and low temperature defocus curves that by reasonably allocating the optical power of each lens and selecting suitable materials, the lens can also have good resolution performance at -40℃~105℃, and the high and low temperature defocus is less than 10um.

[0083] Combining Table 7 and Table 8, it can be seen that in Examples 1-3, by reasonably allocating the focal length of each lens, the lens has a small defocus offset under high and low temperature conditions, and the MTF is more uniform, so that the lens can obtain good clarity under high or low temperature environments and can better adapt to harsh environments. In addition, the optimized curved shape of the first lens L1 in the present invention is conducive to reducing the overall peripheral distortion of the system and improving the illumination; the large-angle shape of the second lens L2 expands the light beam, making the overall uniformity of the light energy better, which is conducive to more uniform picture brightness, and making the deflection angle of the light in the large field of view smaller, the light trend is more gentle, and the overall length of the system is shortened while reducing aberrations.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An optical lens with stable imaging, the optical lens having five lenses, which include, from the object side to the image side: A first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, and a fifth lens with positive focal power, wherein a stop is provided between the third lens and the fourth lens, characterized in that: The convex surface of the first lens faces the object side, and the concave surface faces the image side; The object side surface of the second lens is concave, and the image side surface is concave; The side of the third lens facing the object side and the side facing the image side are both convex; The convex surface of the fourth lens faces the object side, and the concave surface faces the image side; The side of the fifth lens facing the object side and the side facing the image side are both convex; The focal length F4 of the fourth lens element and the focal length F5 of the fifth lens element satisfy 0.883663≤|F4 / F5|≤0.92; Wherein, the concave surface of the first lens satisfies: 0.25 <ARCTAN(SAG(S2) / D(S2))-ARCTAN(SAG(S2 / 2) / D(S2) / 2)<0.45, Wherein, S2 represents the second optical surface of the optical lens from the object side to the image side, D(S2) represents the semi-aperture of the maximum clear aperture of the second optical surface corresponding to the maximum field angle of the optical lens, SAG(S2) represents the Sg value corresponding to the second optical surface, ARCTAN(SAG(S2) / D(S2)) is the inverse tangent function of the ratio of SAG(S2) to D(S2), ARCTAN(SAG(S2 / 2) / D(S2) / 2) is the inverse tangent function of the ratio of SAG(S2 / 2) to D(S2) / 2, and ARCTAN(SAG(S2) / D(S2)) -ARCTAN(SAG(S2 / 2) / D(S2) / 2) is the difference between the two.

2. The optical lens with stable imaging according to claim 1, characterized in that: The total optical length TTL of the optical lens and the entire focal length EFL of the optical lens satisfy 12.78717≤TTL / EFL≤15.

6.

3. The optical lens with stable imaging according to claim 1, characterized in that: The distance d12 between the first lens and the second lens satisfies 0.1 <d12 / TTL<0.3。 4. The optical lens with stable imaging according to claim 1, characterized in that: The fourth lens and the fifth lens are cemented together to form a double cemented lens.

5. The optical lens with stable imaging according to claim 1, characterized in that: The concave surface of the second lens satisfies: 0.25 <ARCTAN(SAG(S4) / D(S4))-ARCTAN(SAG(S4 / 2) / D(S4) / 2)<0.55, Wherein, S4 represents the fourth optical surface of the optical lens from the object side to the image side, D(S4) represents the semi-aperture of the maximum aperture of the fourth optical surface corresponding to the maximum field angle of the optical lens, SAG(S4) represents the Sg value corresponding to the fourth optical surface, ARCTAN(SAG(S4) / D(S4)) is the inverse tangent function of the ratio of SAG(S4) to D(S4), ARCTAN(SAG(S4 / 2) / D(S4) / 2) is the inverse tangent function of the ratio of SAG(S4 / 2) to D(S4) / 2, and ARCTAN(SAG(S4) / D(S4))-ARCTAN(SAG(S4 / 2) / D(S4) / 2) is the difference between the two.

6. The optical lens with stable imaging according to claim 1, characterized in that: The semi-aperture of the maximum light aperture of the first lens corresponding to the maximum field angle of the optical lens is less than 5.7 mm.

7. The optical lens with stable imaging according to claim 1, characterized in that: The two optical mirror surfaces of the second lens, the two optical mirror surfaces of the fourth lens, and the two optical mirror surfaces of the fifth lens are all aspherical surfaces, and the two optical mirror surfaces of the third lens are both spherical surfaces.

8. The optical lens with stable imaging according to claim 1, characterized in that: The total optical length TTL of the optical lens satisfies 11.99616 mm≤TTL≤13.2 mm.

9. The optical lens with stable imaging according to claim 1, characterized in that: The first lens satisfies: 1.80 ≥Nd1 ≥1.7, 49.60 ≥Vd1 ≥46; Here, Nd1 represents the d-light refractive index of the first lens material, and Vd1 represents the d-light Abbe constant of the first lens material.

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