Optical system

Abstract

The present invention relates to an optical system, comprising: a first lens (L1) with negative optical power, a second lens (L2) with negative optical power, a third lens (L3) with positive optical power or negative optical power, a fourth lens (L4) with positive optical power, a fifth lens (L5) with negative optical power, and a sixth lens (L6) with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis. The optical system of the present invention can achieve large angle, large aperture, high resolution, and day and night confocality.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging, and in particular to an optical system. Background Art

[0002] With the improvement of living standards and the enhancement of safety awareness, people have higher requirements for home security. Large angle, large aperture and high resolution are the characteristics of smart home monitoring lenses, but the cost of lenses that can meet these requirements is often high, which is contrary to the affordable price of smart monitoring products. Therefore, a large number of optical lenses with low cost but high imaging performance are urgently needed. Summary of the invention

[0003] The object of the present invention is to provide an optical system with higher imaging performance.

[0004] To achieve the above-mentioned object of the invention, the present invention provides an optical system, comprising: arranged in sequence from the object side to the image side along the optical axis: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power or negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power and a sixth lens with positive optical power.

[0005] According to one aspect of the present invention, a stop is further included between the second lens and the third lens or between the third lens and the fourth lens.

[0006] According to one aspect of the present invention, the first lens is a convex-concave spherical or aspherical lens, the second lens is an aspherical lens with a concave object side surface, the third lens is an aspherical lens with a convex object side surface, the fourth lens is a biconvex spherical lens, the fifth lens is an aspherical lens with a concave image side surface, and the sixth lens is a biconvex aspherical lens.

[0007] According to one aspect of the present invention, the first lens is a plastic lens or a glass lens, the fourth lens is a glass lens, and the second lens, the third lens, the fifth lens and the sixth lens are plastic lenses.

[0008] According to one aspect of the present invention, the Abbe number Vd of at least one of the first lens, the second lens and the fourth lens is ≥50.

[0009] According to one aspect of the present invention, the focal length f1 of the first lens, the focal length f3 of the third lens, the focal length f4 of the fourth lens, the focal length f5 of the fifth lens, the focal length f6 of the sixth lens and the effective focal length f of the optical system respectively satisfy the following relationship:

[0010] -2≤f1 / f≤-1.5;

[0011] 3.0≤|f3 / f|≤152;

[0012] 1.8≤f4 / f≤2.4;

[0013] -3.3≤f5 / f≤-2;

[0014] 1.5≤f6 / f≤2.3.

[0015] According to one aspect of the present invention, the Abbe number Vd3 of the third lens is ≤30, and the Abbe number Vd4 of the fourth lens is ≥70.

[0016] According to one aspect of the present invention, the distance BFL from the image-side optical axis center of the sixth lens to the image plane and the effective focal length f of the optical system respectively satisfy the following relationship with the total length TTL of the optical system: 0.23≤BFL / TTL≤0.33; 6.6≤TTL / f≤7.5.

[0017] According to one aspect of the present invention, the air gap G12 between the first lens and the second lens and the air gap G45 between the fourth lens and the fifth lens satisfy the following relationship: 20≤G12 / G45≤45.

[0018] According to one aspect of the present invention, a curvature radius R9 of the image-side surface of the fourth lens and a curvature radius R10 of the object-side surface of the fifth lens satisfy the following relationship: 1.5≤|R10 / R9|≤65.

[0019] According to the solution of the present invention, by reasonably setting the glass-plastic material, convexity and optical focal length of each lens in the optical system, the visible light and infrared light can be confocal, effectively reducing the cost of the optical system. Moreover, it can achieve non-defocusing in the temperature range of -40°C to 80°C, and can be applied to different environments. It can also achieve a maximum aperture of FNO1.6, a resolution of 8 million pixels, and an imaging target surface of 1 / 2.5". The chief ray angle CRA of the maximum field of view of the optical system is ≤15°, and it can be adapted to a variety of sensors, with broad application prospects and improved market competitiveness. It can also achieve image capture with an object field angle of 150°. As a result, the optical system of the present invention has the advantages of large angle, large aperture, high resolution, and day and night confocality.

[0020] According to one solution of the present invention, by selecting different aperture positions, different light blocking positions and adjustments of the incident angle of the main light can be achieved, so that the light passes through the optical system smoothly and the tolerance sensitivity of the entire optical system is reduced.

[0021] According to one embodiment of the present invention, the Abbe number of at least one of the first lens, the second lens and the fourth lens is set to be greater than 50, thereby achieving better chromatic aberration correction by using low-dispersion materials.

[0022] According to one solution of the present invention, by reasonably setting the relationship between the focal lengths of the first lens, the third lens, the fourth lens, the fifth lens and the sixth lens and the effective focal length of the optical system, effective correction of aberrations can be achieved, so that the optical system can meet the characteristics of high resolution while meeting the requirements of day and night confocality and no out-of-focus at high and low temperatures.

[0023] According to one solution of the present invention, the Abbe number of the third lens is less than 30, and the Abbe number of the fourth lens is greater than 70. Thus, by using ultra-low dispersion glass materials, purple fringing and near-infrared aberrations can be effectively balanced.

[0024] According to one solution of the present invention, by reasonably setting the distance BFL from the image center of the sixth lens to the image plane and the relationship between the effective focal length f of the optical system and the total length TTL of the optical system, the size requirements of mainstream cameras can be met and the miniaturization characteristics of the optical system can be met.

[0025] According to one solution of the present invention, the optical system structure can be made more compact by reasonably setting the air intervals between the first lens, the second lens, the fourth lens and the fifth lens.

[0026] According to one solution of the present invention, by reasonably setting the relationship between the curvature radius of the fourth lens and the curvature radius of the fifth lens, not only can the optical system structure be made more compact, but also the light can pass through the two lenses smoothly, thereby reducing the tolerance sensitivity of the optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram showing the structure of an optical system according to a first embodiment of the present invention;

[0028] Figure 2 Schematically showing an MTF diagram of an optical system according to a first embodiment of the present invention;

[0029] Figure 3 Schematically showing a Through-Focus-MTF diagram of an optical system of a first embodiment of the present invention at a frequency of 200 lp / mm;

[0030] Figure 4 Schematically showing the Through-Focus-MTF diagram of the optical system of the first embodiment of the present invention at a low temperature of -40°C and a frequency of 120 lp / mm;

[0031] Figure 5 Schematically showing a Through-Focus-MTF diagram of the optical system of the first embodiment of the present invention at a high temperature of 80°C and a frequency of 120 lp / mm;

[0032] Figure 6A schematic diagram showing the structure of an optical system according to a second embodiment of the present invention;

[0033] Figure 7 Schematically showing an MTF diagram of an optical system according to a second embodiment of the present invention;

[0034] Figure 8 Schematically showing a Through-Focus-MTF diagram of an optical system of a second embodiment of the present invention at a frequency of 200 lp / mm;

[0035] Fig. 9 Schematically showing the Through-Focus-MTF diagram of the optical system at low temperature of -40°C and a frequency of 120 lp / mm according to the second embodiment of the present invention;

[0036] Fig.10 Schematically showing a Through-Focus-MTF diagram of an optical system at a high temperature of 80°C and a frequency of 120 lp / mm according to a second embodiment of the present invention;

[0037] Fig.11 A schematic diagram showing the structure of an optical system according to a third embodiment of the present invention;

[0038] Fig.12 Schematically showing an MTF diagram of an optical system according to a third embodiment of the present invention;

[0039] Fig.13 Schematically showing a Through-Focus-MTF diagram of an optical system of a third embodiment of the present invention at a frequency of 200 lp / mm;

[0040] Fig.14 Schematically showing a Through-Focus-MTF diagram of an optical system at a low temperature of -40°C and a frequency of 120 lp / mm according to a third embodiment of the present invention;

[0041] Fig.15 Schematically showing a Through-Focus-MTF diagram of an optical system at a high temperature of 80°C and a frequency of 120 lp / mm according to a third embodiment of the present invention;

[0042] Fig.16 A schematic diagram showing the structure of an optical system according to a fourth embodiment of the present invention;

[0043] Fig.17 Schematically showing an MTF diagram of an optical system according to a fourth embodiment of the present invention;

[0044] Fig.18A Through-Focus-MTF diagram schematically showing a frequency of 200 lp / mm for an optical system according to a fourth embodiment of the present invention;

[0045] Fig.19 Schematically showing a Through-Focus-MTF diagram of an optical system at a low temperature of -40°C and a frequency of 120 lp / mm according to a fourth embodiment of the present invention;

[0046] Fig. 20 The Through-Focus-MTF diagram of the optical system according to the fourth embodiment of the present invention at a high temperature of 80° C. and a frequency of 120 lp / mm is schematically shown. DETAILED DESCRIPTION

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0049] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0050] See also Figure 1The optical system of the present invention includes: a first lens L1 with negative focal power, a second lens L2 with negative focal power, a third lens L3 with positive or negative focal power, a fourth lens L4 with positive focal power, a fifth lens L5 with negative focal power, and a sixth lens L6 with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis. It also includes an aperture STO, which can be located between the second lens L2 and the third lens L3 or between the third lens L3 and the fourth lens L4. Different aperture positions can achieve different light blocking positions and adjustments of the incident angle of the main light, so that the light passes through the optical system smoothly and reduces the tolerance sensitivity of the entire optical system. The first lens L1 is a convex-concave spherical or aspherical lens, the second lens L2 is an aspherical lens with a concave surface on the object side, the third lens L3 is an aspherical lens with a convex surface on the object side, the fourth lens L4 is a biconvex spherical lens, the fifth lens L5 is an aspherical lens with a concave surface on the image side, and the sixth lens L6 is a biconvex aspherical lens. The first lens L1 is a plastic lens or a glass lens, the fourth lens L2 is a glass lens, and the second lens L2, the third lens L3, the fifth lens L5 and the sixth lens L6 are plastic lenses.

[0051] In the present invention, the Abbe number Vd of at least one of the first lens L1, the second lens L2 and the fourth lens L4 is ≥50. In this way, by using the above-mentioned low-dispersion material, chromatic aberration correction can be better achieved. The focal length f1 of the first lens L1, the focal length f3 of the third lens L3, the focal length f4 of the fourth lens L4, the focal length f5 of the fifth lens L5, the focal length f6 of the sixth lens L6 and the effective focal length f of the optical system respectively satisfy the following relationships: -2≤f1 / f≤-1.5; 3.0≤|f3 / f|≤152; 1.8≤f4 / f≤2.4; -3.3≤f5 / f≤-2; 1.5≤f6 / f≤2.3. In this way, by combining these focal length segments, effective correction of aberrations can be achieved, so that the optical system meets the characteristics of high resolution, while meeting the day and night confocality and high and low temperature non-false focus. The Abbe number Vd3 of the third lens L3 is ≤30, and the Abbe number Vd4 of the fourth lens L4 is ≥70. It can be seen that the present invention uses an ultra-low dispersion glass material (fourth lens), which can effectively balance the purple fringing and near-infrared aberrations. The distance BFL from the center of the optical axis of the image side of the sixth lens L6 to the image plane and the effective focal length f of the optical system respectively satisfy the following relationships with the total length TTL of the optical system: 0.23≤BFL / TTL≤0.33; 6.6≤TTL / f≤7.5. According to this setting, the size requirements of mainstream cameras can be met, and the characteristics of miniaturization of the optical system can be met. The air gap G12 between the first lens L1 and the second lens L2, and the air gap G45 between the fourth lens L4 and the fifth lens L5 satisfy the following relationship: 20≤G12 / G45≤45. This interval setting can make the optical system structure more compact. The curvature radius R9 of the image side surface of the fourth lens L4 and the curvature radius R10 of the object side surface of the fifth lens L5 satisfy the following relationship: 1.5≤|R10 / R9|≤65. Satisfying this relationship can make the optical system structure more compact, and make the light pass through the two lenses smoothly, reducing the tolerance sensitivity of the optical system.

[0052] In this way, the optical system of the present invention adopts a mixed use of glass lenses and plastic lenses, and reasonably configures the optical focal length and concavity of each lens, which can achieve confocality of visible light and infrared light, effectively reducing the cost of the optical system. In addition, it can achieve non-defocusing in the temperature range of -40°C to 80°C, and can be applied to different environments. It can also achieve a maximum aperture of FNO1.6, a resolution of 8 million pixels, and an imaging target surface of 1 / 2.5". The chief ray angle CRA of the maximum field of view of the optical system is ≤15°, which can be adapted to a variety of sensors, has broad application prospects, and enhances market competitiveness. It can also achieve image capture with an object field angle of 150°.

[0053] The optical system of the present invention is specifically described in four groups of implementations. In the following implementations, S0, S2, ..., Sn represent various surfaces in the optical system, the object surface may also be recorded as OBJ, the aperture surface may also be recorded as STO, and the image surface may also be recorded as IMA. The parameter settings of each implementation that specifically meets the above conditional formula are shown in Table 1 below:

[0054]

[0055] Table 1 The aspheric surface of the optical system of the present invention satisfies the following formula:

[0056]

[0057] Where z is the axial distance from the surface to the vertex at a height h perpendicular to the optical axis along the optical axis; c represents the curvature at the vertex of the aspheric surface; k is the cone coefficient; A4, A6, A8, A 10 , A 12 , A 14 , A 16 ···represent the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, sixteenth-order···aspheric coefficients respectively.

[0058] The first implementation method:

[0059] See also Figure 1 In this embodiment, the aperture STO is located between the third lens L3 and the fourth lens L4, and the third lens L3 has positive focal power. The parameters of the optical system of this embodiment are: F#: 1.75; total length of the optical system: 22.4 mm; field angle: 135°.

[0060] The relevant parameters of each lens of the optical system of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 2 below:

[0061] Surface number Surface type R-Value thickness Refractive Index Abbe number S0(OBJ) Spherical Infinity Infinity S1 Spherical 12.373 1.53 1.73 51.5 S2 Spherical 3.136 2.28 S3 Aspheric -3.479 0.79 1.54 55.7 S4 Aspheric -50.565 0.08 S5 Aspheric 11.339 4.72 1.64 23.1 S6 Aspheric -14.08 0.36 S7(STO) Spherical Infinity -0.21 S8 Spherical 6.221 3 1.46 90.2 S9 Spherical -6.221 0.09 S10 Aspheric -382.751 0.7 1.64 23.1 S11 Aspheric 4.697 0.19 S12 Aspheric 4.326 2.03 1.54 55.7 S13 Aspheric -7.02 1.62 S14 Spherical Infinity 0.8 1.52 64.2 S15 Spherical Infinity 4.42 S16(IMA) Spherical Infinity - - -

[0062] Table 2

[0063] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 3 below:

[0064]

[0065]

[0066] Table 3

[0067] Among them, K is the quadratic surface constant of the surface, and A, B, C, D, and E are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0068] Combination Figures 2 to 5 The optical system of this embodiment can achieve co-focusing of visible light and infrared light, effectively reducing the cost of the optical system. In addition, it can achieve non-defocusing in the temperature range of -40℃ to 80℃, and can be applied to different environments. It can also achieve a maximum aperture of FNO1.6, and the resolution can reach 8 million pixels.

[0069] The second implementation method:

[0070] See also Figure 6 In this embodiment, the aperture STO is located between the third lens L3 and the fourth lens L4, and the third lens L3 has a negative optical power. The parameters of the optical system of this embodiment are: F#: 1.6; total length of the optical system: 22.46 mm; field angle: 135°.

[0071] The relevant parameters of each lens of the optical system of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 4 below:

[0072]

[0073]

[0074] Table 4

[0075] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 5 below:

[0076]

[0077] Table 5

[0078] Among them, K is the quadratic surface constant of the surface, and A, B, C, D, and E are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0079] Combination Figures 7 to 10 The optical system of this embodiment can achieve co-focusing of visible light and infrared light, effectively reducing the cost of the optical system. In addition, it can achieve non-defocusing in the temperature range of -40℃ to 80℃, and can be applied to different environments. It can also achieve a maximum aperture of FNO1.6, and the resolution can reach 8 million pixels.

[0080] The third implementation method:

[0081] See also Fig.11 In this embodiment, the aperture STO is located between the third lens L3 and the fourth lens L4, and the third lens L3 has a negative optical power. The optical system parameters of this embodiment are: F#: 1.6; total length of the optical system: 22.46 mm; field angle: 140°.

[0082] The relevant parameters of each lens of the optical system of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 6 below:

[0083] Surface number Surface type R-Value thickness Refractive Index Abbe number S0(OBJ) Spherical Infinity Infinity S1 Spherical 19.879 0.65 1.69 55.5 S2 Spherical 3.151 2.76 S3 Aspheric -3.741 3.09 1.54 55.9 S4 Aspheric -4.985 0.08 S5 Aspheric 6.576 3.5 1.64 23.1 S6 Aspheric 5.093 0.59 S7(STO) Spherical Infinity -0.45 S8 Spherical 4.911 3.75 1.46 90.2 S9 Spherical -4.911 0.08 S10 Aspheric 8.801 0.65 1.61 25.6 S11 Aspheric 3.443 0.12 S12 Aspheric 4.611 2.09 1.54 55.9 S13 Aspheric -10.639 1.62 S14 Spherical Infinity 0.8 1.52 64.2 S15 Spherical Infinity 3.13 S16(IMA) Spherical Infinity - - -

[0084] Table 6

[0085] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 7 below:

[0086]

[0087]

[0088] Table 7

[0089] Among them, K is the quadratic surface constant of the surface, and A, B, C, D, and E are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0090] Combination Figures 12 to 15 The optical system of this embodiment can achieve co-focusing of visible light and infrared light, effectively reducing the cost of the optical system. In addition, it can achieve non-defocusing in the temperature range of -40℃ to 80℃, and can be applied to different environments. It can also achieve a maximum aperture of FNO1.6, and the resolution can reach 8 million pixels.

[0091] The fourth implementation method:

[0092] See also Fig.16 In this embodiment, the stop STO is located between the second lens L2 and the third lens L3, and the third lens L3 has negative focal power. The parameters of the optical system of this embodiment are: F#: 1.6; total length of the optical system: 22.35 mm; field angle: 150°.

[0093] The relevant parameters of each lens of the optical system of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 8 below:

[0094]

[0095]

[0096] Table 8

[0097] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 9 below:

[0098]

[0099] Table 9

[0100] Among them, K is the quadratic surface constant of the surface, and A, B, C, D, and E are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0101] Combination Figures 17 to 20 The optical system of this embodiment can achieve co-focusing of visible light and infrared light, effectively reducing the cost of the optical system. In addition, it can achieve non-defocusing in the temperature range of -40℃ to 80℃, and can be applied to different environments. It can also achieve a maximum aperture of FNO1.6, and the resolution can reach 8 million pixels.

[0102] The above is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical system, characterized in that: The invention comprises six lenses arranged in sequence from the object side to the image side along the optical axis: a first lens (L1) with negative optical power, a second lens (L2) with negative optical power, a third lens (L3) with positive optical power or negative optical power, a fourth lens (L4) with positive optical power, a fifth lens (L5) with negative optical power and a sixth lens (L6) with positive optical power; The effective focal length f of the optical system and the total length TTL of the optical system respectively satisfy the following relationship: 6.6≤TTL / f≤7.

5.

2. The optical system according to claim 1, characterized in that: It also includes an aperture stop (STO) located between the second lens (L2) and the third lens (L3) or between the third lens (L3) and the fourth lens (L4).

3. The optical system according to claim 1, characterized in that The first lens (L1) is a convex-concave spherical or aspherical lens, the second lens (L2) is an aspherical lens with a concave object side surface, the third lens (L3) is an aspherical lens with a convex object side surface, the fourth lens (L4) is a biconvex spherical lens, the fifth lens (L5) is an aspherical lens with a concave image side surface, and the sixth lens (L6) is a biconvex aspherical lens.

4. The optical system according to claim 1, characterized in that The first lens (L1) is a plastic lens or a glass lens, the fourth lens (L1) is a glass lens, and the second lens (L2), the third lens (L3), the fifth lens (L5) and the sixth lens (L6) are plastic lenses.

5. The optical system according to any one of claims 1 to 4, characterized in that: The Abbe number Vd of at least one of the first lens (L1), the second lens (L2) and the fourth lens (L4) is ≥50.

6. The optical system according to any one of claims 1 to 4, characterized in that: The focal length f1 of the first lens (L1), the focal length f3 of the third lens (L3), the focal length f4 of the fourth lens (L4), the focal length f5 of the fifth lens (L5), the focal length f6 of the sixth lens (L6) and the effective focal length f of the optical system respectively satisfy the following relationship: -2≤f1 / f≤-1.5; 3.0≤|f3 / f|≤152; 1.8≤f4 / f≤2.4; -3.3≤f5 / f≤-2; 1.5≤f6 / f≤2.

3.

7. The optical system according to any one of claims 1 to 4, characterized in that: The Abbe number Vd3 of the third lens (L3) is ≤30, and the Abbe number Vd4 of the fourth lens (L4) is ≥70.

8. The optical system according to any one of claims 1 to 4, characterized in that: The distance BFL from the center of the image-side optical axis of the sixth lens (L6) to the image plane and the total length TTL of the optical system satisfy the following relationship: 0.23≤BFL / TTL≤0.

33.

9. The optical system according to any one of claims 1 to 4, characterized in that: An air gap G12 between the first lens (L1) and the second lens (L2), and an air gap G45 between the fourth lens (L4) and the fifth lens (L5) satisfy the following relationship: 20≤G12 / G45≤45.

10. The optical system according to any one of claims 1 to 4, characterized in that: The curvature radius R9 of the image side surface of the fourth lens (L4) and the curvature radius R10 of the object side surface of the fifth lens (L5) satisfy the following relationship: 1.5≤|R10 / R9|≤65.

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