Design method of optical imaging lens

Abstract

The invention provides a design method of an optical imaging lens, the optical imaging lens comprises an optical system, the optical system is mainly composed of an optical lens made of a plastic material and an optical lens made of a silica gel material, the sum of the focal power of all the optical lenses made of the plastic material is set as Qp, the sum of the focal power of all the optical lenses made of the silica gel material is set as Qs, and the sum of the focal power of all the optical lenses made of the silica gel material is set as Qp. The sign symbols of Qp and Qs are set to be opposite. According to the method, more design freedom degrees can be realized, the use of glass lenses can be effectively reduced or glass lenses are not used, the mass production cost is lower, athermalization can be realized, and stable optical performance at different temperatures is realized.

Description

Technical Field

[0001] The invention relates to the technical field of optical imaging display, and specifically discloses a design method for an optical imaging lens. Background Art

[0002] The design of optical lenses is generally based on a certain temperature for performance optimization, and the conventional design is based on an ambient temperature of 20 degrees. At other temperatures, indicators such as clarity may decrease, because the optical materials, lens surface, air gap, lens barrel, etc. in the optical lens will change with the ambient temperature, causing optical defocus. This degradation of optical image quality caused by ambient temperature changes is also considered to be an optical aberration, aberration caused by heat, referred to as thermal aberration. For optical products with a large range of final application temperature environments, thermal aberration needs to be eliminated, otherwise the image will be blurred. For example, for automotive products or monitoring products, the ambient temperature may be -40 degrees to +70 degrees for parts, and the ambient temperature changes greatly. Such products generally require thermal aberration of the applied optical lenses.

[0003] At present, optical lenses are made of optical plastics. Optical plastics have many advantages, such as easy manufacturing of complex aspheric surfaces, light materials, high efficiency of mass injection molding, and high cost performance. However, optical plastics are easily affected by the ambient temperature, that is, the optical stability of the material with temperature changes is poor, which is mainly reflected in: 1. The refractive index (refractive index) changes with temperature (dn / dt, also called thermo-optical coefficient) is large, one order of magnitude higher than that of optical glass; 2. The coefficient of thermal expansion (Coefficient of Temperature Expansion, referred to as CTE) is large. At present, lenses made of optical plastics alone cannot eliminate thermal differences, and optical glass lenses need to be added to improve the performance stability of the lens at different temperatures, that is, glass-plastic hybrid lenses. If the thermal requirements are higher, all-glass lenses need to be used. However, the cost of glass lenses is often higher. The cost of ordinary spherical glass is generally 1.5 to 3 times that of plastic lenses of the same size (related to the cost of specific glass materials), and aspherical lenses with stronger optical control capabilities generally need to be made using glass molding, which is more expensive, 3 to 5 times the price of plastic lenses. There are even more restrictions on the processing of glass, and certain surface shapes or structures cannot be achieved. For example, in China Authorization Announcement No. CN 110632744 B, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all glass lenses; in view of this situation, it is urgent to solve it. Summary of the invention

[0004] Based on this, it is necessary to provide a design method for an optical imaging lens in response to the existing technical problems. The method is low-cost, can achieve more design freedom, and can effectively reduce the use of glass lenses or eliminate glass lenses, with lower mass production costs. At the same time, it can eliminate thermal differences and achieve stable optical performance at different temperatures.

[0005] To solve the problems in the prior art, the present invention provides a method for designing an optical imaging lens, including an optical system, wherein the optical system is mainly composed of an optical lens made of a plastic material and an optical lens made of a silicone material, wherein the sum of the focal lengths of all the lenses made of the plastic material is set to Qp, the sum of the focal lengths of all the optical lenses made of the silicone material is set to Qs, and the positive and negative signs of Qp and Qs are set to be opposite.

[0006] Preferably, it meets the conditional formula -2>Qp / Qs>-10.

[0007] Preferably, the optical system also includes a glass optical lens.

[0008] Preferably, the optical lens made of silicone material is formed by silicone injection molding.

[0009] Preferably, the optical lens made of silicone material is molded by silicone compression molding.

[0010] Preferably, the optical lens made of silicone material is integrated with at least one of an optical lens made of plastic material and a glass lens.

[0011] Preferably, the optical lens made of silicone material and the optical lens made of plastic material are manufactured as one body.

[0012] Preferably, the lens made of plastic material is configured as a positive lens, and the optical lens made of silicone material is configured as a negative lens.

[0013] Preferably, the lens made of plastic material is configured as a negative lens, and the optical lens made of silicone material is configured as a positive lens.

[0014] Preferably, the silicone material is replaced with an optical material whose optical stability with temperature change is lower than or equal to that of the silicone material, such as any one of organic silicon PDMS (polydimethylsiloxane), photoresist, optical glue, and epoxy resin. The manufacturing method may be heat curing or UV curing.

[0015] The beneficial effects of the present invention are as follows: the optical lens made of silicone material is used to provide thermal stability of the lens, which can reduce the use of glass lenses, reduce costs, and increase design freedom and design means. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of a conventional optical system.

[0017] Figure 2 It is a structural diagram of embodiment 1 of the present invention.

[0018] Figure 3 It is a structural diagram of embodiment 2 of the present invention.

[0019] Figure 4 This is a schematic diagram of the structure of the third embodiment of the present invention.

[0020] Figure 5 This is a structural diagram of embodiment 4 of the present invention.

[0021] Figure 6 This is a structural diagram of Embodiment 5 of the present invention.

[0022] Figure 7 This is the MTF curve diagram of -20° of Example 5 of the present invention.

[0023] Figure 8 This is the MTF curve diagram of 20° in Example 5 of the present invention.

[0024] Fig. 9 This is the MTF curve diagram of 70° in Example 5 of the present invention.

[0025] Fig.10 This is a structural diagram of embodiment 6 of the present invention.

[0026] Fig.11 This is the MTF curve diagram of -20° of Example 6 of the present invention.

[0027] Fig.12 This is the MTF curve diagram of 20° of Example 6 of the present invention.

[0028] Fig.13 This is the MTF curve diagram of 70° of Example 6 of the present invention.

[0029] The accompanying drawings are marked as: paraxial light 10, an optical lens 12 made of k pieces of plastic material, an optical lens 13 made of n pieces of silicone material, a glass lens 11, a glass lens A14, a plastic lens A15, a silicone lens A16, a plastic lens group A18, a silicone lens B17, a plastic lens group B19, a silicone lens B20, a glass lens B21, a first plastic lens C22, a glass lens C23, a silicone lens C24, a second plastic lens C25, a silicone lens D26, a plastic lens D27, a glass lens D28, a silicone lens F29, and a plastic lens group F30. DETAILED DESCRIPTION

[0030] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0031] refer to Figures 1 to 13 .

[0032] The basic embodiment of the present invention discloses a design method for an optical imaging lens, including an optical system, wherein the optical system is mainly composed of an optical lens made of a plastic material and an optical lens made of a silicone material, wherein the sum of the optical powers of all the lenses made of the plastic material is set to Qp, the sum of the optical powers of all the optical lenses made of the silicone material is set to Qs, and the positive and negative signs of Qp and Qs are set to be opposite, which meets the conditional formula -2>Qp / Qs>-10.

[0033] like Figure 1 Schematic diagram, in an optical system, the paraxial light 10 enters the lens at a height h. Assume that there are k optical lenses 12 made of plastic material and n optical lenses 13 made of silicone material. The heights of the paraxial light 10 at the optical lenses made of plastic material are hp1, hp2,.., hpk, respectively, and the corresponding focal lengths are fp1, fp2,…, fpk. Then the corresponding optical power is the inverse of the corresponding focal length, recorded as Qp1, Qp2,…, Qpk.

[0034] Similarly, for the paraxial light height of the optical lens made of silicone material, hs1, hs2, .., hsn, and the corresponding focal length fs1, fs2, ..., fsn, the corresponding optical power is the reciprocal of the corresponding focal length, recorded as Qs1, Qs2, ..., Qsn.

[0035] The composite optical power of the optical lens made of plastic material is defined as Qpi=(hpi / h)*(1 / fpi), where i is 1, 2, ..., k. Similarly, the composite optical power of the optical lens made of silicone material is defined as Qsi=(hsi / h)*(1 / fsi), where i is 1, 2, ..., n.

[0036] Then the total composite optical power of the optical lens made of plastic material is Qp=ΣQpi, where i is 1, 2, ..., k. Similarly, the total composite optical power of the optical lens made of silicone material is Qs=ΣQpi, where i is 1, 2, ..., n.

[0037] In the optical system, the optical stability of the glass lens 11 with temperature changes is much better than that of the optical lens made of plastic material and the optical lens made of silicone material, so it can be ignored in the initial design.

[0038] We define the thermal property of the lens as heat dissipation r = dQ / dt / Q, where Q is the focal length of the lens, and we can deduce r = dn / dt / (n-1)-CTE. Since the corresponding parameters of r depend on the material's thermo-optic coefficient dn / dt, refractive index n, and thermal expansion coefficient CTE, which are all related quantities of the material itself, the material's heat dissipation r is uniquely determined by the optical material.

[0039] As shown in Table 1, we show the thermal dissipation of common optical materials such as plastic, glass, and silicone. As can be seen from the table, the thermal dissipation of silicone material rs is about 4 times that of plastic material rp. A negative thermal dissipation indicates that for a positive lens, as the temperature rises, the focal length decreases.

[0040] Table 1

[0041]

[0042] In an optical system, we hope that the optical properties do not change with the temperature of the application environment and are stable, so that the focal length of the system remains unchanged, that is, the change in total optical focal length dQ is 0, which can be written as: dQ=0; and dQ=dQg+dQp+dQs, where Qg, Qp, and Qs are the composite optical focal lengths of the corresponding glass, plastic, and silicone, respectively.

[0043] If there is no glass, set dQg = 0; calculate the effect of unit temperature change, find the differential of optical power with respect to temperature t, and set it to 0, then: dQ / dt = dQg / dt + dQp / dt + dQs / dt = 0;

[0044] According to the definition: rg*Qg / dt+rp*Qp / dt+rs*Qs / dt=0;

[0045] Simplify the above formula: Qs = -rg / rs*Qg-rp / rs*Qp; From Table 1, we can see that, in general, rg / rs < 1 / 50; it can be ignored in the preliminary analysis. Then Qs = -rp / rs*Qp, that is, Qp / Qs = -rs / rp;

[0046] From Table 1, we can see that rs / rp≈4, so Qp / Qs≈-4.

[0047] The above reasoning is based on ideal conditions. Considering the actual barrel material, flange design, etc., the application conditions can be relaxed during preliminary calculations, -2>Qp / Qs>-10. Optical software can be used to assist in optimization.

[0048] In actual use, if the distance between the lenses is not large, the ordinary optical power (the inverse of the focal length of the lens) can be used to approximately replace the composite optical power, that is, Q = 1 / f. In this way, the relevant parameters can be estimated more quickly during the preliminary design, and a design framework can be further provided for software optimization. Therefore, for the imaging lens with stable temperature performance of the present invention, the sum of the optical power Qp of all plastic material lenses and the sum of the optical power Qs of the silicone material optical lens have a numerical ratio of -2>Qp / Qs>-10.

[0049] There are many ways to implement this architecture, and the total optical power of the silicone lens can be positive or negative. It only needs to be opposite to that of the plastic lens and the value satisfies the above formula.

[0050] Preferably, the optical lens of silicone material is molded by silicone injection molding.

[0051] Preferably, the optical lens of silicone material is molded by silicone compression molding.

[0052] Preferably, the optical lens made of silicone material and the optical lens made of plastic material are manufactured as one body.

[0053] The first embodiment, as Figure 2 Schematic diagram, application architecture without glass lens. Along the optical axis from the object side to the image side, it includes plastic lens group A18 and silicone lens B17 in sequence. At this time, the total focal length of plastic lens group A18 is positive, and the focal length of silicone lens B17 is negative.

[0054] In a second embodiment, the optical system further comprises a glass optical lens. Figure 3 Schematic diagram of the application architecture with glass lenses. Along the optical axis, from the object side to the image side, it includes glass lens A14, plastic lens A15, and silicone lens A16 in sequence. At this time, plastic lens A15 is negative and silicone lens A16 is positive.

[0055] In a third embodiment, an optical lens made of silicone material is integrated with at least one of an optical lens made of plastic material and a glass lens. Figure 4 Schematic diagram, along the optical axis from the object side to the image side, it includes a plastic lens group B19, a silicone lens B20, and a glass lens B21 in sequence. The silicone lens B20 and the glass lens B21 are set as an integrated structure, which can increase the firmness of the entire silicone lens.

[0056] In a fourth embodiment, an optical lens made of silicone material, an optical lens made of plastic material, and an optical lens made of glass material are made into one piece. Figure 5 Schematic diagram, along the optical axis from the object side to the image side, it includes a first plastic lens C22, a glass lens C23, a silicone lens C24, and a second plastic lens C25 in sequence. The glass lens C23, the silicone lens C24, and the second plastic lens C25 are set as an integrated structure, which can also increase the firmness of the entire lens.

[0057] In a fifth embodiment, the lens made of plastic material is configured as a positive lens, and the optical lens made of silicone material is configured as a negative lens. Figure 6 Schematic diagram, along the optical axis from the object side to the image side, it includes a silicone lens D26, a plastic lens D27, and a glass lens D28 in sequence, wherein the silicone lens D26 has a negative optical power, and the plastic lens D27 has a positive optical power. Figure 7 The MTF of this embodiment at -20°C is shown. Figure 8 The MTF of this embodiment at 20°C is shown. Fig. 9The figure shows the MTF of this embodiment at 70°C. It can be seen that the MTF of this embodiment is very stable at different temperatures from -20°C to 70°C.

[0058] Table 2

[0059]

[0060] Table 3

[0061]

[0062] The expression for aspheric surface is as follows:

[0063]

[0064] Where z is the vector height of the aspheric surface at position r; c is the paraxial curvature of the aspheric surface, c = 1 / R (that is, the paraxial curvature c is the inverse of the surface curvature radius R); k is the cone coefficient; A, B, .., J are high-order coefficients.

[0065] Other system parameters for this design are:

[0066] Table 4

[0067]

[0068] The relationship satisfied is:

[0069] Table 5

[0070] Constraints Design Results Qs and Qp have different signs From the parameter table, we know that -2>Qp / Qs>-10 Qp / Qs=-4.96 Knowing that it is satisfied

[0071] In a sixth embodiment, the optical lens made of silicone material is configured as a negative lens, and the lens made of plastic material is configured as a positive lens. Fig.10 Schematic diagram, along the optical axis from the object side to the image side, it includes a silicone lens F29 and a plastic lens group F30 in sequence, wherein the silicone lens F29 has a negative optical focal length, and the total optical focal length of the plastic lens group F30 is a positive lens. Fig.11 The MTF of this embodiment at -20°C is shown. Fig.12 The MTF of this embodiment at 20°C is shown. Fig.13 The figure shows the MTF of this embodiment at 70°C. It can be seen that the MTF of this embodiment is very stable at different temperatures from -20°C to 70°C.

[0072] Table 6

[0073]

[0074]

[0075] Table 7

[0076]

[0077] The expression for aspheric surface is as follows:

[0078]

[0079] Where z is the vector height of the aspheric surface at position r; c is the paraxial curvature of the aspheric surface, c = 1 / R (that is, the paraxial curvature c is the inverse of the surface curvature radius R); k is the cone coefficient; A, B, .., J are high-order coefficients.

[0080] Other system parameters of this design are

[0081] Table 8

[0082]

[0083] Satisfied relationship

[0084] Table 9

[0085] Constraints Design Results Qs and Qp have different signs From the parameter table, we know that -2>Qp / Qs>-10 Qp / Qs=-4.08 Knowing that it is satisfied

[0086] The present invention utilizes an optical lens made of silicone material to provide thermal stability of the lens, which can reduce the use of glass lenses, reduce costs, and increase design freedom and design means.

[0087] Preferably, the silicone material is replaced with an optical material whose optical stability with temperature change is lower than or equivalent to that of the silicone material, such as any one of organic silicon PDMS (polydimethylsiloxane), photoresist, optical glue, and epoxy resin.

[0088] The above-mentioned embodiments only express six implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for designing an optical imaging lens, comprising an optical system, characterized in that: The optical system is mainly composed of optical lenses made of plastic materials and optical lenses made of silicone materials, wherein the sum of the optical focal lengths of all plastic material lenses is set to Qp, the sum of the optical focal lengths of all silicone material optical lenses is set to Qs, and the positive and negative signs of Qp and Qs are set to be opposite.

2. The method for designing an optical imaging lens according to claim 1, characterized in that: It meets the conditional formula -2>Qp / Qs>-10.

3. The method for designing an optical imaging lens according to claim 1 or 2, characterized in that: The optical system also includes a glass optical lens.

4. The method for designing an optical imaging lens according to claim 3, wherein: The optical lens made of silicone material is molded by silicone injection molding.

5. The method for designing an optical imaging lens according to claim 3, wherein: The optical lens made of silicone material is formed by pressing silicone.

6. The method for designing an optical imaging lens according to claim 3, wherein: The optical lens made of silicone material is integrated with at least one of the optical lens made of plastic material and the glass lens.

7. The method for designing an optical imaging lens according to claim 1, wherein: The optical lens made of silicone material and the optical lens made of plastic material are manufactured as one body.

8. The method for designing an optical imaging lens according to claim 3, wherein: The lens made of plastic material is configured as a positive lens, and the optical lens made of silicone material is configured as a negative lens.

9. The method for designing an optical imaging lens according to claim 3, wherein: The lens made of plastic material is configured as a negative lens, and the optical lens made of silicone material is configured as a positive lens.

10. The method for designing an optical imaging lens according to claim 1, wherein: The silicone material is replaced with an optical material whose optical stability with temperature change is lower than or equal to that of the silicone material, such as any one of organic silicon PDMS (polydimethylsiloxane), photoresist, optical glue, and epoxy resin.

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