CN101726830B - Small short rear focus two-element optical imaging lens - Google Patents

Abstract

A compact short back focal length image capturing lens, in order from an object side to an image side, comprises: an aperture diaphragm; a first lens with a meniscus aspheric surface with positive diopter, wherein the convex surface faces the object side and the concave surface faces the image side; a meniscus-shaped aspheric second lens with negative diopter, wherein the convex surface faces the image side and the concave surface faces the object side; and an infrared filter; the optical image capturing lens meets the following conditions:

wherein f is₁Is the focal length of the first lens, f₂The focal length of the second lens element is long, bf is the back focal length of the image capturing lens system, and TL (total length) is the distance from the aperture diaphragm to the imaging surface; therefore, the invention can achieve the effect of short back focus, effectively shorten the length of the optical image taking lens and be applied to the use requirements of thinner small cameras and mobile phones.

Description

Small short rear focus two-element optical imaging lens

technical field

The invention relates to a small-sized short-back-focus two-lens optical imaging lens, especially an image sensor using CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) for small cameras or mobile phones. The lens provides a short back focus, short overall length and low-cost optical imaging lens composed of positive diopter and negative diopter lenses.

Background technique

In electronic products such as: digital camera (Digital Still Camera), computer camera (PC camera), network camera (Network camera), mobile phone (mobile phone), personal digital assistant (PDA) and other devices often have imaging lenses; and In order to be easy to carry and meet the needs of humanization, the imaging lens not only needs to have good image quality, but also needs to have a smaller volume (or total length) and lower cost to meet the needs of users.

There are currently two-lens, three-lens, four-lens, and five-lens types of imaging lenses used in small electronic products. However, considering the cost, the two-lens type uses fewer lenses, and the cost more advantageous. The existing two-element optical imaging lens has many different structural designs, but the differences or technical features between them are determined by the changes or combinations of the following factors: the shape design of the corresponding fit between the two lenses Different, such as the first and second lenses are meniscus shape lenses, bi-convex and bi-concave respectively; or the corresponding convex/concave directions of the two lenses are different; Or the diopters (refractive power) corresponding to the two lenses are different in positive and negative; or the relevant optical data between the two lens groups/lenses such as f _s (effective focal length of the imaging lens system), di (the Distance between i), Ri (radius of curvature of each optical surface i) etc. satisfies different conditions; as can be seen from the above, in terms of the design of the optical imaging lens of the two mirror formula, the prior art is in the technical field of designing the optical imaging lens , which produce different changes or combinations for the application of various optical purposes, and because of the different shapes, combinations, functions or functions of the lenses used, it can be regarded as novelty and innovative step ).

In recent years, in order to be used in small cameras, camera phones, PDAs and other products, the imaging lens requires miniaturization, short focal length, and good aberration adjustment. In the design of various miniaturized two-lens imaging lenses, the first diopter of positive A lens, a second lens with positive diopter or other combined designs are most likely to meet the needs of miniaturization, such as US2005/0073753, US2004/0160680, US7,110,190, US7,088,528, US2004/0160680; European patent EP1793252, EP1302801; Japanese patents JP2007-156031, JP2006-154517, JP2006-189586; Taiwan patents TWM320680, TWI232325; Chinese patent CN101046544, etc. However, the total length of the optical imaging lens disclosed in these patents should be further reduced; for the short back focus design required by users, such as US Patent US2006/0221467, Japanese Patent JP2005121685, and JP2006154517 use positive-negative diopters combination; U.S. Patent US20030/0197956 uses a combination of negative-positive diopters; U.S. Patent US5,835,288 uses a combination of biconcave and biconvex lenses; Japanese Patent JP20040281830 uses a combination of positive or negative-positive diopters; or as Japanese Patent Publication No. JP2003215446, JP2004-177976, European patents EP1793252 and EP1793254, US patents US6,876,500, US2004/0160680, US7,088,528, Taiwan patent TWI266074, etc. use a combination of positive and positive diopters to reduce the total length of the lens. Among the various designs for shortening the total length of the lens, the short back focus is still the most direct and effective, but directly shortening the back focus will result in difficulty in focusing. For this reason, the present invention proposes a more practical design. While shortening the back focal length, the air space between lenses is shortened to make up for the difficulty of focusing and reduce imaging distortion, so that it can be easily applied to electronic products such as small cameras and camera phones.

Contents of the invention

The main purpose of the present invention is to provide a small-sized short back focus two-element optical imaging lens. While shortening the back focal length, the air space between the lenses is shortened to make up for the difficulty of focusing and reduce imaging distortion, so that it can be easily applied to small cameras, On electronic products such as camera phones.

The small-sized short back focus two-element optical imaging lens of the present invention is arranged along the optical axis from the object side (objectside) to the image side (image side) and includes: an aperture stop (aperture stop); a positive diopter The first lens (a first lens of positive refractive power) is a crescent lens and the object side is convex, and the two optical surfaces are aspheric; a second lens with negative refractive power (a second lens of negative refractive power) It is a crescent-shaped lens with a convex image side, and both optical surfaces are aspherical; an infrared filter and an image sensor; and the optical imaging lens meets the following conditions:

$\mathrm{<span\; class="notranslate">\; 0.25</span>}<span\; class="notranslate">\; \&le;</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.4</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; 0.25</span>}<span\; class="notranslate">\; \&le;</span>\frac{\mathrm{<span\; class="notranslate">\; b\; f</span>}}{\mathrm{<span\; class="notranslate">\; TL</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.4</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.3</span>}<span\; class="notranslate">\; \&le;</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.01</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4.0</span>}<span\; class="notranslate">\; \&le;</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1.5</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Among them, f _s is the effective focal length of the optical imaging lens, f ₁ is the focal length of the first lens, f ₂ is the focal length of the second lens, bf is the rear focal length of the imaging lens system, and TL is The distance from the aperture stop to the imaging surface on the optical axis, _d2 is the distance from the image side of the first lens to the object side of the second lens on the optical axis, _d4 is the distance from the image side of the second lens to the object side of the infrared filter on the optical axis d ₆ is the distance from the image side of the infrared filter on the optical axis to the imaging surface of the image sensor, R ₂ is the radius of curvature of the image side of the first lens on the paraxial axis, and R ₃ is the object side of the second lens The paraxial radius of curvature.

Furthermore, the first lens and the second lens of the short back focus two-element optical imaging lens can be made of glass or plastic.

Therefore, the combination of the two lenses can achieve a short rear focal length, further reducing the length of the lens, and can be made of the same material to reduce the production cost, so as to improve the applicability of the imaging lens.

Description of drawings

Fig. 1 is a schematic view of the optical structure of the present invention;

Fig. 2 is a schematic view of the optical path structure of the present invention;

Fig. 3 is the field curvature (field curvature) diagram of the first embodiment of the present invention;

Fig. 4 is an imaging distortion (distortion) diagram of the first embodiment of the present invention;

Fig. 5 is the longitudinal aberration diagram of the first embodiment of the present invention (when the radius is 0.6086mm);

Fig. 6 is a field curvature diagram of the second embodiment of the present invention;

Fig. 7 is an imaging distortion diagram of the second embodiment of the present invention;

Fig. 8 is a longitudinal aberration diagram of the second embodiment of the present invention (when the radius is 0.5588mm);

Fig. 9 is a field curvature diagram of the third embodiment of the present invention;

Fig. 10 is an imaging distortion diagram of the third embodiment of the present invention;

Fig. 11 is a longitudinal aberration diagram of the third embodiment of the present invention (at a radius of 0.4996 mm).

Explanation of reference signs:

1-optical imaging lens; 11-the first lens; R1-(the first lens) object side; R2-(the first lens) image side; S-aperture stop; 12-the second lens; R3-(the second Lens) object side; R4-(second lens) as the side; 13-infrared filter; 14-image sensor; d1-the distance from the first lens object side to the image side on the optical axis; d2-on the optical axis The distance from the first lens image side to the second lens object side; the distance from the second lens object side to the image side on the d3-optical axis; the distance from the second lens image side to the infrared filter object side on the d4-optical axis; d5- the distance from the object side of the infrared filter on the optical axis to the image side; d6- the distance from the image side of the infrared filter on the optical axis to the image sensor.

Detailed ways

In order to make the present invention more definite and detailed, hereby enumerate preferred embodiment and coordinate following figure, the structure and technical characteristic of the present invention are described in detail as follows:

With reference to shown in Fig. 1, it is a schematic structural view of a two-lens optical imaging lens 1 of the present invention, which is arranged along the optical axis Z from the object side (object side) to the image side (image side) and includes: an aperture stop S, a first lens 11, a second lens 12, an infrared filter (IR cut-off filter) 13 and an image sensor (image sensing chip) 14; The light rays pass through the first lens 11 and the second lens 12 first, and then pass through the infrared filter 13 to be imaged on the imaging surface (image) of the image sensor 14 .

The first lens 11 is a crescent lens, the object side R1 is convex and the image side R2 is concave, has a positive diopter, and can be made of glass or plastic material, and its object side R1 and image side R2 are non-linear. sphere.

The second lens 12 is a crescent lens, the object side R3 is concave and the image side R4 is convex, has a negative diopter, can be made of glass or plastic material, and its object side R3 and image side R4 are both non-refractive. sphere.

The aperture stop (aperture stop) S belongs to a pre-diaphragm, which is attached to the object side R1 of the first lens 11; the infrared filter (IR cut-off filter) 13 can be a lens, Or use coating technology to form a thin film with infrared filter function; the image sensor (image sensing chip) 14 includes CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor).

In addition, the two-element optical imaging lens 1 of the present invention has the radius of curvature of the optical surface of the first lens 11 and the second lens 12, the aspherical surface, the lens thickness (d1 and d3) and the air distance ( _d2 , _d4 and _d6 ) After the optical combination, the formed lens has a short back focal length, which can further shorten the total length of the lens and the back focal length within a smaller range, which satisfies formula (2). The optical surfaces of the first lens 11 and the second lens 12 are aspherical surfaces, and the equation (Aspherical Surface Formula) of the aspherical surfaces is formula (5)

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{<span\; class="notranslate">\; (</span>\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">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; h</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">\; h</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">\; h</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">\; h</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="h"\; filenames="H2008101674561E00011.png"\; state="\{\{state\}\}">h</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Where c is the curvature, h is the lens height, K is the cone factor (Conic Constant), A ₄ , A ₆ , A ₈ , A ₁₀ , A ₁₂ , A ₁₄ are four, six, eight, ten, twelve, fourteen respectively Nth Order Aspherical Coefficient.

With the above-mentioned structure, the rear focal length of the two-element optical imaging lens 1 of the present invention can be effectively reduced to reduce the length of the lens, which satisfies formulas (1) to (4).

Hereby enumerate preferred embodiment, and explain as follows respectively:

<First embodiment>

Please refer to Fig. 2, 3, 4, and 5, which are respectively the optical path structure schematic diagram of the first embodiment of the optical imaging lens 1 of the present invention and field curvature, imaging distortion (distortion) and radius (radius) Vertical aberration diagram at 0.6086mm.

The following table (1) lists the optical surface number (surface number) numbered sequentially from the object side to the image side, and the radius of curvature R (unit: mm) of each optical surface on the optical axis (the radius of curvature R) , the distance d (unit: mm) between each surface on the optical axis (the on-axis surface spacing), the refractive index (N _d ) of each lens and the Abbe's number (Abbe's number) v _d of each lens.

Table I)

^* aspherical surface

In Table (1), the optical surfaces marked with * are aspherical optical surfaces, Surf1 and Surf2 represent the object side R1 and image side R2 of the first lens 11 respectively, and Surf3 and Surf4 respectively represent the surface of the second lens 12 Object side R3 and image side R4, f _s is the effective focal length of the imaging lens. The following table (2) lists the various coefficients of the aspheric surface formula (5) of each optical surface:

Table II)

In this embodiment, the first lens 11 and the second lens 12 are made of the same glass material, the refractive index N _d is 1.587, and the Abbe number v _d is 60.0 _; It is made of glass material whose Abbe number v _d is 1.517 and 64.17.

The effective focal length f _s of the optical imaging lens 1 of the present embodiment is 3.408mm, the focal length f ₁ of the first lens 11 is 2.7879mm, and the focal length f ₂ of the second lens 12 is -15.418mm; The distance TL (total length) from the object side R1 of the lens 11 to the imaging surface of the image sensor 15 is 3.763 mm; that is,

$\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.3811</span>}<span\; class="notranslate">\; ;</span>$ $\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.1808</span>}<span\; class="notranslate">\; ;</span>$ $\frac{\mathrm{<span\; class="notranslate">\; b\; f</span>}}{\mathrm{<span\; class="notranslate">\; TL</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.350</span>}<span\; class="notranslate">\; ;</span>$ $\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3.6101</span>}$

Conditional expressions (1) to (4) can be satisfied.

As shown in the above table (1), table (2) and the field curvature, imaging distortion (distortion) and vertical aberration (vertical aberration) at a radius of 0.6086 mm in Figures 3 to 5, It can be proved that the two-element optical imaging lens of the present invention can effectively correct aberrations, make the optical imaging lens 1 have high resolution and short back focus effect, can effectively reduce the length of the lens, and improve the applicability of the present invention.

In the field curvature curves shown in Figures 3, 6, and 9, the abscissa represents the focal length in millimeters; the ordinate represents the image height, and the curves T and S correspond to the tangential and radial directions respectively. It can be seen from the figure that for different focal lengths Under the offset, the field curvature changes caused by different image heights of the optical axis.

In the imaging distortion curves shown in Figures 4, 7, and 10, the abscissa represents the percentage of the distortion rate; the ordinate represents the different image heights of the optical axis. It can be seen from the figure that the distortion rate changes for different image heights. situation.

In the aberration curves shown in Figs. 5, 8, and 11, the ordinate is the longitudinal aberration, and the abscissa is the focal length, and the unit is millimeter. It can be seen from the figure that the spherical aberration changes under different focal length offsets.

<Second Embodiment>

Please refer to Figures 2, 6, 7, and 8, which are the optical path structure schematic diagram of the second embodiment of the optical imaging lens 1 of the present invention and the field curvature, imaging distortion, and longitudinal aberration diagrams at a radius of 0.5588 mm.

The following table (3) lists the number of optical surfaces sequentially numbered from the object side to the image side, the radius of curvature R of each optical surface on the optical axis, the distance d between each surface on the optical axis, and the refractive index of each lens ( N _d ) and the Abbe number v _d of each lens.

Table (3)

^* aspherical surface

The following table (four) lists the various coefficients of the aspheric surface formula (5) of each optical surface:

Table (4)

In this embodiment, the first lens 11 and the second lens 12 are made of the same glass material, their refractive index N _d is 1.587, and Abbe's number v _d is 60.0; the infrared filter 13 is made of its refractive index N Made of glass material with _d being 1.517 and Abbe number v _d being 64.17.

The effective focal length f _s of the optical imaging lens 1 of this embodiment is 3.129mm, and the focal length f ₁ of the first lens 11 is 2.7719mm, and the focal length f ₂ of the second lens 12 is -130.8mm; The distance TL (total length) from the object side R1 of a lens 11 to the imaging surface of the image sensor 15 is 3.5959 mm; that is,

$\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.3155</span>}<span\; class="notranslate">\; ;</span>$ $\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 0212</span>}<span\; class="notranslate">\; ;</span>$ $\frac{\mathrm{<span\; class="notranslate">\; b\; f</span>}}{\mathrm{<span\; class="notranslate">\; TL</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.3946</span>}<span\; class="notranslate">\; ;</span>$ $\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 6480</span>}$

Conditional expressions (1) to (4) can be satisfied.

As shown in Table (3) and Table (4) above and the field curvature, imaging distortion and longitudinal aberration diagrams of Figs. The optical imaging lens 1 has high resolution and short back focus effect, can effectively reduce the length of the lens, and improve the applicability of the present invention.

<Third embodiment>

Please refer to FIGS. 2, 9, 10, and 11, which are the optical path structure schematic diagram of the third embodiment of the optical imaging lens 1 of the present invention and the field curvature, imaging distortion, and longitudinal aberration diagrams at a radius of 0.4996 mm.

The following table (5) lists the number of optical surfaces sequentially numbered from the object side to the image side, the radius of curvature R of each optical surface on the optical axis, the distance d between each surface on the optical axis, and the refractive index of each lens ( N _d ), the Abbe number v _d of each lens.

Table (5)

^* aspherical surface

The following table (6) lists the various coefficients of the aspheric surface formula (5) of each optical surface:

Table (6)

In this embodiment, the first lens 11 and the second lens 12 are made of the same glass material, their refractive index N _d is 1.580, and Abbe's number v _d is 58.9; the infrared filter 13 is made of its refractive index N Made of glass material with _d being 1.517 and Abbe number v _d being 64.17.

The effective focal length _fs of the optical imaging lens 1 of the present embodiment is 2.878mm, and the focal length _f1 of the first lens 11 is 2.4924mm, and the focal length _f2 of the second lens 12 is -11.1504mm; The distance TL from the object side R1 of a lens 11 to the imaging surface of the image sensor 15 is 3.3509 mm; that is,

$\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.2898</span>}<span\; class="notranslate">\; ;</span>$ $\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 2235</span>}<span\; class="notranslate">\; ;</span>$ $\frac{\mathrm{<span\; class="notranslate">\; b\; f</span>}}{\mathrm{<span\; class="notranslate">\; TL</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.3551</span>}<span\; class="notranslate">\; ;</span>$ $\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 9593</span>}$

Conditional expressions (1) to (4) can be satisfied.

As shown in Table (5) and Table (6) above and the field curvature, imaging distortion and longitudinal aberration diagrams of Figs. The optical imaging lens 1 has high resolution and short back focus effect, can effectively reduce the length of the lens, and improve the applicability of the present invention.

The above are only preferred embodiments of the present invention, and are only illustrative, not restrictive, of the present invention. Those skilled in the art understand that many changes, modifications, and even equivalent changes can be made within the spirit and scope defined by the claims of the present invention, but all will fall within the scope of the present invention.

Claims (3)

1. A small-sized short-back focus two-lens optical imaging lens, characterized in that it is arranged along the optical axis from the object side to the image side and includes: an aperture stop; A first lens with positive diopter, which is a crescent lens, its convex surface faces the object side, and both optical surfaces are aspherical; A second lens with negative diopter, which is a crescent lens, its convex surface faces the image side, and both optical surfaces are aspherical; an infrared filter; and an image sensor; Wherein, the first lens and the second lens are made of the same glass material; and satisfy the following conditions: $\mathrm{<span\; class="notranslate">\; 0.25</span>}<span\; class="notranslate">\; \&le;</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.4</span>}$ $<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.3</span>}<span\; class="notranslate">\; \&le;</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.01</span>}$ $\mathrm{<span\; class="notranslate">\; 0.25</span>}<span\; class="notranslate">\; \&le;</span>\frac{\mathrm{<span\; class="notranslate">\; b\; f</span>}}{\mathrm{<span\; class="notranslate">\; TL</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.4</span>}$ Among them, f _s is the effective focal length of the optical imaging lens, f ₁ is the focal length of the first lens, f ₂ is the focal length of the second lens, bf is the rear focal length of the imaging lens system, TL is the aperture stop to the imaging surface d ₂ is the distance from the image side of the first lens to the object side of the second lens on the optical axis, d ₄ is the distance from the image side of the second lens to the object side of the infrared filter on the optical axis, d ₆ is the distance on the optical axis The distance from the image side of the infrared filter to the imaging surface of the image sensor. 2. according to claim 1 described small-sized short rear focus two optics optical imaging lens, it is characterized in that, this imaging lens has short back focal length, meets the following conditions: $\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; \&le;</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 0.2</span>}$ Wherein, d ₂ is the distance from the image side of the first lens to the object side of the second lens on the optical axis, and f _s is the effective focal length of the optical imaging lens. 3. according to claim 1 described small-sized short back focal length two lens optical imaging lens, it is characterized in that, satisfy the following conditions: $<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4.0</span>}<span\; class="notranslate">\; \&le;</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1.5</span>}$ Wherein, R2 is the radius of curvature of the paraxial axis of the image side of the first lens, and _R3 is the radius of curvature of the paraxial axis of the object side of the second lens.

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