CN101231377B - an optical lens - Google Patents

Abstract

The invention discloses an optical lens, comprising first and second lenses arranged coaxially symmetrically about the optical axis; the first lens has a positive diopter, and includes a first surface and a second surface both of which are convex, and the first surface faces The object plane, the optical effective diameter of the first surface is smaller than the second surface; the second lens has a negative diopter and includes a third surface and a fourth surface, the third surface is a concave surface facing the object surface, and the fourth surface is a convex surface ; The dispersion value of the first lens is greater than that of the second lens, and the refractive index value of the first lens is smaller than that of the second lens. The optical lens of the invention can reduce the cost while ensuring excellent imaging quality.

Description

an optical lens

technical field

The invention relates to optical devices, in particular to an optical lens.

Background technique

Optical lens is an important component of digital imaging equipment. In recent years, low-end mobile phones have been equipped with cameras as standard. How to reduce production costs while ensuring the image quality of the lens has become a hot spot in optical lens design. At the same time, mobile phones are becoming thinner and lighter, which also forces lens design to pursue a shorter total optical length. The needs of mass production in modern industry require optical design not only to pursue better imaging quality, but also to have good processability, adapt to the operability of the later process, and effectively improve the yield rate and reduce production costs. This makes the optical lens to meet the following characteristics as much as possible:

1. Good imaging quality. Especially for medium and low frequencies, it has a good optical transfer function (MTF) graph;

2. Small and light. That is, the total length is required and the number of lenses is small.

3. Large viewing angle. It can be adapted to a variety of sensors (sensors) of various models, and has the universality of multiple models, and the field of view can be ≥ 65°;

4. Low cost. That is to say, try to use cheap materials instead of expensive materials under the premise of ensuring image quality. Adopt easier processing technology;

Contents of the invention

The technical problem to be solved by the invention is to overcome the deficiencies of the prior art and provide an optical lens with excellent imaging quality and low cost.

Technical problem of the present invention is solved by following technical scheme:

An optical lens, comprising first and second lenses arranged coaxially symmetrically with respect to the optical axis; the first lens has a positive diopter and includes a first surface and a second surface both of which are convex, and the first surface faces the object The optical effective diameter of the first surface is smaller than that of the second surface; the second lens has a negative diopter and includes a third surface and a fourth surface, the third surface is a concave surface facing the object plane, and the fourth lens The surface is convex; the dispersion value of the first lens is larger than that of the second lens, and the refractive index value of the first lens is smaller than that of the second lens.

Preferably,

Also included is a fixed diaphragm located in front of the first lens near the object space.

The optical lens satisfies the following relationship:

1.25<f/L<1.55;

0.35<f1/f<0.55;

_LH /L＞0.25;

1<n2/n1<1.2;

1<v1/v2<3;

Wherein: f is the effective focal length value of described optical lens, and f1 is the effective focal length value of the first lens, and L is the distance from the diaphragm of optical lens to the imaging surface, and L _H is the distance from the fourth surface to the imaging surface when L H is the air conversion distance distance, n1 is the refractive index of the first lens, v1 is the dispersion value of the first lens; n2 is the refractive index of the second lens, and v2 is the dispersion value of the second lens.

It also includes a filter between the second lens and the imaging surface, the filter is a flat glass, including a first parallel plate surface adjacent to the second lens and a second parallel plate adjacent to the imaging surface The surface of at least one of the first and second parallel plate surfaces is coated with an infrared cut-off filter film.

At least one surface of the first and second lenses is an aspheric surface, and the coordinate values of each point on the aspheric surface satisfy the following aspheric surface formula:

$\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cr"\; filenames="H2007100730076E00011.png,H2007100730076E00012.png"\; state="\{\{state\}\}">cr</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="H2007100730076E00011.png,H2007100730076E00012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="H2007100730076E00011.png,H2007100730076E00012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="r"\; filenames="H2007100730076E00012.png,H2007100730076E00021.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="r"\; filenames="H2007100730076E00012.png,H2007100730076E00021.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="8"\; label="r"\; filenames="H2007100730076E00041.png,H2007100730076E00071.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="10"\; label="r"\; filenames="H2007100730076E00041.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="12"\; label="r"\; filenames="H2007100730076E00011.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}$

Among them: z is the axial value perpendicular to the optical axis starting from the intersection point of each aspheric surface and the optical axis, k is the quadratic surface coefficient, c is the curvature of the mirror center, r is the height of the mirror center; a2, a4, a6, a8, a10, and a12 are aspherical coefficients.

The value range of the quadratic surface coefficient is: -15<quadratic surface coefficient<15, and the value range of the mirror surface center curvature is: -10<mirror surface center curvature<10.

The material of the first lens and the second lens is plastic or glass.

The parameters of the optical lens are as follows:

Lens parameters:

Aspheric Coefficient:

type k a2 a4 a6 a8 a10 a12 first surface -0.404 0.629 -0.195 0.189 -17.687 153.115 -620.158 second surface -0.254 -0.468 0.243 0.154 -6.836 13.900 -6.259 third surface 9.295 -1.713 2.173 7.837 -77.002 203.807 -175.915 The fourth surface -0.343 -1.276 0.494 3.510 -11.938 15.445 -7.043

The parameters of the optical lens are as follows:

Lens parameters:

Aspherical Coefficient:

type k a2 a4 a6 a8 a10 a12 first surface -1.929 0 -0.915 -72.978 3194.712 -4.861E+004 0 second surface -0.714 0 0.684 -31.631 231.757 -809.043 0 third surface -1.177 0 -2.533 -18.474 412.024 -2179.793 0 The fourth surface 0 0 1.335 4.260 -6.458 37.748 0

The parameters of the optical lens are as follows:

Lens parameters:

Aspherical Coefficient:

type k a2 a4 a6 a8 a10 a12 first surface -2.816 0 -0.755 -30.097 956.209 -1.268E+004 0 second surface -0.807 0 0.561 -23.077 134.704 -445.707 0 third surface -6.890 0 2.890 -0.293 -32.206 644.018 0 The fourth surface 0 0 1.194 2.983 -11.692 29.919 0

The beneficial effect that the present invention compares with prior art is:

The first lens of the optical lens of the present invention has positive refractive power, can gather light effectively, and the material dispersion value that the first lens adopts is big, can effectively reduce chromatic aberration; The surface shape conforms to the surface shape of the second surface of the first lens, so that the light has a smaller incident angle on the third surface, which can effectively control the advanced aberration of the entire optical lens; the fourth surface of the second lens is convex, Slightly undulating trend, can effectively reduce the chief ray exit angle at the edge, and improve the edge illumination of the image plane. However, the present invention only uses two lenses, so that the optical lens of the present invention can reduce the cost while ensuring excellent imaging quality.

The diaphragm of the optical lens of the present invention is placed at the forefront close to the object plane, so that the structure of the optical lens is simple and compact, and the total length is small. The overall length of the optical lens of this lens is short, and it has a large field of view, so that it can be adapted to various sensors such as 1/7, 1/7.5, 1/8, etc., and meets the needs of various mobile phones.

The optical lens of the invention can effectively reduce various aberrations, including spherical aberration, coma, astigmatism, field curvature and distortion, etc., and improves the relative illuminance.

The optical lens of the present invention has a shorter focal length but a longer back focus, which greatly facilitates production, can effectively improve yield, reduce production cost, and is suitable for large-scale industrial production.

The invention controls the incidence angle of light on each surface to be less than 28°, and eliminates the ghost phenomenon to a certain extent.

The lens of the invention can be made of plastic material, thereby greatly reducing the production cost and being suitable for large-scale industrial production.

Description of drawings

Fig. 1 is a schematic structural view of a specific embodiment of the present invention

Fig. 2 is the MTF diagram of Embodiment 1 of the present invention;

Fig. 3 is a schematic diagram of field of view consistency in Embodiment 1 of the present invention;

Fig. 4 is a schematic diagram of horizontal axis chromatic aberration in Embodiment 1 of the present invention;

Fig. 5 is a schematic diagram of the distortion of the optical lens according to Embodiment 1 of the present invention;

Fig. 6 is a schematic structural diagram of a second embodiment of the present invention

FIG. 7 is an MTF diagram of Embodiment 2 of the present invention;

FIG. 8 is a schematic diagram of field of view consistency in Embodiment 2 of the present invention;

Fig. 9 is a schematic diagram of the horizontal axis chromatic aberration of Embodiment 2 of the present invention;

Fig. 10 is a schematic diagram of distortion in Embodiment 2 of the present invention;

Fig. 11 is a schematic structural view of a third embodiment of the present invention

Fig. 12 is an MTF diagram of Embodiment 3 of the present invention;

Fig. 13 is a schematic diagram of field of view consistency in Embodiment 3 of the present invention;

Fig. 14 is a schematic diagram of the horizontal axis chromatic aberration of Embodiment 3 of the present invention;

FIG. 15 is a schematic diagram of distortion in Embodiment 3 of the present invention.

Detailed ways

The optical lens shown in Figures 1, 6, and 11 includes a coaxial first lens 1 and a second lens 2 sequentially from the object side; the first lens 1 and the second lens 2 are respectively symmetrical about the optical axis. The first lens 1 has a positive diopter and includes a first surface 11 and a second surface 12 ; the second lens 2 has a negative diopter and includes a third surface 21 and a fourth surface 22 . Both the first surface 11 and the second surface 12 are convex, and the optical effective diameter of the first surface 11 is smaller than that of the second surface 12 . The third surface 21 is a concave surface facing the object plane, and the fourth surface 22 is a convex surface.

Both the first lens 1 and the second lens 2 have at least one surface as an aspheric surface, and the coordinate values of each point on the aspheric surface satisfy the following aspheric surface formula:

$\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="cr"\; filenames="H2007100730076E00011.png,H2007100730076E00012.png"\; state="\{\{state\}\}">cr</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="H2007100730076E00011.png,H2007100730076E00012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="r"\; filenames="H2007100730076E00011.png,H2007100730076E00012.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="r"\; filenames="H2007100730076E00012.png,H2007100730076E00021.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="6"\; label="r"\; filenames="H2007100730076E00012.png,H2007100730076E00021.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="8"\; label="r"\; filenames="H2007100730076E00041.png,H2007100730076E00071.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="10"\; label="r"\; filenames="H2007100730076E00041.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="12"\; label="r"\; filenames="H2007100730076E00011.png"\; state="\{\{state\}\}">r</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>$

Among them: z is the axial value perpendicular to the optical axis o direction starting from the intersection point of each aspheric surface with the optical axis o, that is, the mirror depth value. Since the selected lens shape is an axisymmetric lens, the aspheric surface formula is taken as Even items. k is the quadratic surface coefficient, that is, the taper of the lens; c is the curvature of the center of the mirror, c=1/R, where R is the radius of curvature of the center of the mirror; r is the height of the center of the mirror; a2, a4, a6, a8, a10, a12 are Aspheric coefficients. The shape of each surface can be determined by the above aspheric formula.

The value range of the quadric surface coefficient k is: -15<k<15, the value range of the mirror surface center curvature c is: -10<c<10, and the aspheric coefficients a2, a4, a6, The value ranges of a8, a10, and a12 can be any value.

The optical lens may further include a fixed diaphragm 4 located in front of the first lens 1 and close to the object side, and the fixed diaphragm 4 has an aperture of a fixed diameter. The optical lens may also include a filter 3 behind the second lens 2 and away from the object. The optical filter 3 is a flat glass, including a first parallel plate surface 31 and a second parallel plate surface 32 . The first parallel plate surface 31 is adjacent to the second lens 2 , and the second parallel plate surface 32 is adjacent to the imaging plane.

The above optical lens meets the following conditions:

1.25<f/L<1.55;

0.35<f1/f<0.55;

_LH /L＞0.25;

1<n2/n1<1.2;

1<v1/v2<3;

Wherein: f is the effective focal length value of the whole optical lens; f1 is the effective focal length value of the first lens 1; L is the total length of the optical lens, i.e. the distance from the diaphragm of the optical lens to the imaging surface; L _H is the back focus value of the lens, namely The distance from the fourth surface of the optical lens to the imaging surface when the air conversion distance is used. The air-converted distance refers to the assumption that there is no glass filter; n1 is the refractive index of the first lens 1, and v1 is the dispersion value of the first lens 1; n2 is the refractive index of the second lens 2, and v2 is the second lens 2 dispersion value.

An optical lens that meets the above conditions can ensure an appropriate back focus on the basis of shortening the total length of the lens, and can also correct various aberrations, especially astigmatism and distortion aberrations, and obtain ideal optical performance.

The first lens 1 is the closest to the aperture, and a material with a high dispersion value should be selected to eliminate the influence of chromatic aberration as much as possible; the second lens 2 controls the direction of light to the imaging surface, and a high refractive index material should be selected to shorten the total length of the optical lens . At the same time, the difference in refractive index and dispersion value between the first lens 1 and the second lens 2 is beneficial to the elimination of other various aberrations. Therefore, the first lens 1 of the above-mentioned optical lens is preferably made of a material with high dispersion and low refractive index, and the second lens 2 is preferably made of a material with high refractive index and low dispersion.

Due to the good structure disclosed in the present invention, optical materials can be selected in a wide range. Specifically, both the first lens 1 and the second lens 2 can use plastic structural materials or glass structural materials.

The optical filter 3 is preferably made of borosilicate glass material made of molten pure raw materials, with a refractive index n4=1.5168 and a dispersion v4=64.17. Preferably, the surface of at least one of the first parallel plate surface 31 and the second parallel plate surface 32 of the optical filter 3 is coated with a layer of infrared cut-off filter film (IR-cutCoating), to filter out the Reflects infrared rays in the light, thereby improving image quality.

Specific Embodiments 1, 2, and 3 provide specific parameter values of the implementations based on the above structures. Among them, the radius of curvature refers to the radius of curvature of the surface intersecting the optical axis; the distance value refers to the distance from the object surface along the optical axis to the imaging surface from a selected surface to the next adjacent surface. The units of these specific parameters are millimeters (mm).

Specific implementation mode one:

The optical lens shown in Fig. 1 is the optical lens of specific embodiment one, and the parameter of this optical lens is as follows:

Lens parameters:

Aspherical Coefficient:

type k a2 a4 a6 a8 a10 a12 first surface -0.404 0.629 -0.195 0.189 -17.687 153.115 -620.158 second surface -0.254 -0.468 0.243 0.154 -6.836 13.900 -6.259

type k a2 a4 a6 a8 a10 a12 third surface 9.295 -1.713 2.173 7.837 -77.002 203.807 -175.915 The fourth surface -0.343 -1.276 0.494 3.510 -11.938 15.445 -7.043

For the optical lens of the specific embodiment 1, its optical performance diagrams are shown in FIGS. 2 , 3 , 4 , and 5 .

Fig. 2 is the lens optics modulation transfer function curve (MTF) of optical lens, and among the figure horizontal axis represents spatial frequency, unit: line pair per millimeter (lp/mm); Vertical axis represents the numerical value of modulation transfer function (MTF), described The value of MTF is used to evaluate the imaging quality of the lens, and the value range is 0-1. The higher and straighter the MTF curve, the better the imaging quality of the lens and the stronger the ability to restore the real image. The diffraction limit (DIFF LIMIT) in Figure 2 represents the imaging condition of the ideal lens for optimal imaging. This is a limit case, and it is impossible to achieve such an effect with the actual lens used. The closer the actual MTF curve is to its DIFF LIMIT curve, the better the image quality. S and T in Figure 2 represent the MTF curves in the sagittal and meridional directions (two mutually perpendicular planes), respectively. DEG is the angle (degree), which represents the value of each field of view. When studying the imaging quality of a lens, several representative fields of view such as 0 field of view, 0.3 field of view, 0.5 field of view, 0.7 field of view, and 1 field of view are usually selected as research objects to evaluate the image of the lens as a whole. Quality, of which 0--0.7 field of view is generally considered to be the most important. For example, if the angle of view of a lens is 60 degrees, then its half angle of view is 30 degrees (because the lenses of the present invention all have symmetrical optical structures along the optical axis, often only the half of the field of view is studied in the analysis software Optical properties, that is, there is a half field of view), the 0.3 field of view is 9 degrees, the 0.5 field of view is 15 degrees, and the 0.7 field of view is 21 degrees. In the specific operation, the set field of view can be adjusted according to the specific situation of the design. As shown in Figure 2, the selected fields of view are 0 degrees, 9.3 degrees, 15.5 degrees, 21.7 degrees, and 25.5 degrees for overall evaluation The image quality of this design. It can be seen that the MTF curves of each field of view in the figure are very close to those in the meridional (T) and sagittal (S) directions. This just reflects that the imaging quality of the lens in this specific embodiment is excellent, and it shows that: the imaging performance of the lens in each field of view, the two directions of the meridian direction (T) and the sagittal direction (S) has good consistency, that is It is said that it can ensure that the lens can image clearly on the entire imaging surface. It will not appear that the middle is clear and the edges are blurred.

Fig. 3 is a schematic diagram of the consistency of the field of view of this specific embodiment, wherein the horizontal axis represents the distance, and 0 is the ideal imaging surface, which is the position of the best imaging surface during design, but in actual manufacturing, it is impossible to achieve no Error, the sensor that is often used to convert it into a digital signal after receiving light is generally placed at the position of the imaging surface (sensor) that is not exactly on the best imaging surface, but has a little deviation. S and T represent the MTF curves in the sagittal and meridional directions (two mutually perpendicular planes), respectively. DEG is the angle (degree), which represents the value of each field of view. It is generally considered that the MTF value above 0.3 is considered acceptable, that is, the limit situation that the human eye can distinguish. Figure 3 reflects a situation where the image plane is defocused. It can be seen from Figure 3 that the MTF curves representing each field of view (direction) have relatively high values, and even if the imaging plane deviates from a certain distance, it can still guarantee >=0.3. . This shows that the focal depth of the lens of this specific embodiment is relatively long, which is suitable for production needs.

Fig. 4 is the horizontal axis chromatic aberration schematic diagram of this specific embodiment, and in Fig. 4, the maximum field of view (MAXIUM FIELD), that is, the half field of view is 34.5 degrees, and the overall field of view is 69 degrees, and the horizontal axis in the figure is the length Size, unit um (1*E-6m), Airy disk (Airy), that is, in the case of the diffraction limit (the best imaging condition of an ideal lens), the smallest spot when the light is focused is the Airy disk. It can be seen from the figure that the chromatic aberration of the horizontal axis is within the size range of the Airy disk, indicating that the chromatic aberration of the lens is corrected well.

FIG. 5 is a schematic diagram of the distortion of the optical lens according to this specific embodiment, wherein the horizontal axis is the percentage, and the vertical axis is the field of view. Distortion is a kind of distortion when the actual lens images the object. It will make the straight line image into a curve, which is unavoidable in actual imaging. The three curves in Figure 5 represent three colors of visible light (used to represent the distortion in the entire range of visible light), and the distortion values in the entire field of view are between -2% and 2%, and within this range The distortion of the human eye is not sensitive, and it will not affect the imaging when it is practical.

Specific implementation mode two:

The optical lens shown in Fig. 6 is the optical lens of specific embodiment two, and the parameter of this optical lens is as follows:

Lens parameters:

type Radius of curvature (R) Distance value (d) Refractive index dispersion value Aperture surface 0 first surface 1.013 0.586 1.53 55.6 second surface -0.336 0.123 third surface -0.213 0.382 1.585 29.5 The fourth surface -0.550 0.400 1st parallel plane 0.300 1.5168 64.17

Aspherical Coefficient:

type k a2 a4 a6 a8 a10 a12 first surface -1.929 0 -0.915 -72.978 3194.712 -4.861E+004 0 second surface -0.714 0 0.684 -31.631 231.757 -809.043 0 third surface -1.177 0 -2.533 -18.474 412.024 -2179.793 0 The fourth surface 0 0 1.335 4.260 -6.458 37.748 0

For the optical lens of the second specific embodiment, its optical performance diagrams are shown in FIGS. 7 , 8 , 9 , and 10 . Fig. 7 is the lens optics modulation transfer function curve (MTF) of optical lens, and each line in the figure represents the MTF of meridional field of view (T) and sagittal field of view (S) in different fields of view and each field of view, from the figure It can be seen that the imaging performance of the lens in each field of view, meridional field of view (T) and sagittal field of view (S) has good consistency, which can ensure that the lens can image clearly on the entire imaging surface. Instead of being clear in the middle and blurry at the edges. It can be seen from Figure 8 that the focal depth of the lens is longer, which is suitable for production needs. From Figure 9, it can be seen that the size of the horizontal axis chromatic aberration is within the size range of the Airy disk, indicating that the chromatic aberration correction of the lens is good. It can be seen from Figure 10 that the distortion value in the entire field of view is between -2% and 2%, and the distortion within this range belongs to the category of insensitivity of the human eye, and it will not affect the imaging when used.

Specific implementation mode three:

The optical lens shown in Fig. 11 is the optical lens of specific embodiment two, and the parameter of this optical lens is as follows:

Lens parameters:

Aspherical Coefficient:

type k a2 a4 a6 a8 a10 a12 first surface -2.816 0 -0.755 -30.097 956.209 -1.268E+004 0 second surface -0.807 0 0.561 -23.077 134.704 -445.707 0 third surface -6.890 0 2.890 -0.293 -32.206 644.018 0 The fourth surface 0 0 1.194 2.983 -11.692 29.919 0

For the optical lens in the third embodiment, its optical performance diagrams are shown in FIGS. 12 , 13 , 14 , and 15 . Fig. 12 is the lens optical modulation transfer function curve (MTF) of optical lens, and each line in the figure represents the MTF of meridional field of view (T) and sagittal field of view (S) in different fields of view and each field of view, from the figure It can be seen that the imaging performance of the lens in each field of view, meridional field of view (T) and sagittal field of view (S) has good consistency, ensuring that the lens can image clearly on the entire imaging surface. Instead of being clear in the middle and blurry at the edges. It can be seen from FIG. 13 that the optical lens of this specific embodiment has a longer focal depth, which is suitable for production needs. It can be seen from Figure 14 that the size of the horizontal axis chromatic aberration is within the size range of the Airy disk, indicating that the chromatic aberration correction of the lens is good. It can be seen from Figure 15 that the distortion value in the entire field of view is between -2% and 2%, and the distortion within this range belongs to the category of insensitivity of the human eye, and it will not affect the imaging when used.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (8)

1. An optical lens, comprising a fixed diaphragm, a first lens and a second lens that are symmetrical about the optical axis and coaxially arranged successively from the object plane to the imaging plane; the first lens has a positive diopter, including a convex surface The first surface and the second surface, the first surface faces the object plane, the optical effective diameter of the first surface is smaller than the second surface; the second lens has a negative diopter, including the third surface and the fourth surface, The third surface is a concave surface facing the object plane, and the fourth surface is a convex surface; the dispersion value of the first lens is greater than that of the second lens, and the refractive index value of the first lens is smaller than that of the second lens, which is characterized in that : The optical lens satisfies the following relationship: 1.25<f/L<1.55; 0.35<f1/f<0.55; _LH /L＞0.25; 1<n2/n1<1.2; 1<v1/v2<3; Wherein: f is the effective focal length value of described optical lens, and f1 is the effective focal length value of the first lens, and L is the distance from the diaphragm of optical lens to the imaging surface, and L _H is the distance from the fourth surface to the imaging surface when L H is the air conversion distance distance, n1 is the refractive index of the first lens, v1 is the dispersion value of the first lens; n2 is the refractive index of the second lens, and v2 is the dispersion value of the second lens. 2. The optical lens according to claim 1, characterized in that: It also includes a filter located between the second lens and the imaging surface, the filter is a flat glass, including a first parallel plate surface adjacent to the second lens and a second parallel plate adjacent to the imaging surface The surface of at least one of the first and second parallel plate surfaces is coated with an infrared cut-off filter film. 3. The optical lens according to claim 1 or 2, characterized in that: Both the first and second lenses have at least one surface as an aspheric surface, and the coordinate values of each point on the aspheric surface satisfy the following aspheric surface formula: $\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; cr</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}$ Among them: z is the starting point of the intersection of each aspheric surface and the optical axis, the axial value perpendicular to the optical axis, k is the coefficient of the quadratic surface, c is the curvature of the center of the mirror, r is the height of the center of the mirror; a2, a4, a6, a8, a10, a12 are aspheric coefficients. 4. The optical lens according to claim 3, characterized in that: The value range of the quadratic surface coefficient is: -15<the quadratic surface coefficient<15, and the value range of the mirror surface center curvature is: -10<mirror surface center curvature<10. 5. The optical lens according to claim 4, characterized in that: The material of the first lens and the second lens is plastic or glass. 6. The optical lens according to claim 5, characterized in that: The parameters of the optical lens are as follows: Lens parameters:

Aspherical Coefficient: type k a2 a4 a6 a8 a10 a12 first surface -0.404 0.629 -0.195 0.189 -17.687 153.115 -620.158 second surface -0.254 -0.468 0.243 0.154 -6.836 13.900 -6.259 third surface 9.295 -1.713 2.173 7.837 -77.002 203.807 -175.915 fourth surface -0.343 -1.276 0.494 3.510 -11.938 15.445 -7.043 . 7. The optical lens according to claim 5, characterized in that: The parameters of the optical lens are as follows: Lens parameters:

Aspherical Coefficient: type k a2 a4 a6 a8 a10 a12 first surface -1.929 0 -0.915 -72.978 3194.712 -4.861E+004 0 second surface -0.714 0 0.684 -31.631 231.757 -809.043 0 third surface -1.177 0 -2.533 -18.474 412.024 -2179.793 0 fourth surface 0 0 1.335 4.260 -6.458 37.748 0 . 8. The optical lens according to claim 5, characterized in that: The parameters of the optical lens are as follows: Lens parameters:

Aspherical Coefficient: type k a2 a4 a6 a8 a10 a12 first surface -2.816 0 -0.755 -30.097 956.209 -1.268E+004 0 second surface -0.807 0 0.561 -23.077 134.704 -445.707 0 third surface -6.890 0 2.890 -0.293 -32.206 644.018 0 fourth surface 0 0 1.194 2.983 -11.692 29.919 0 .

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