JP3146386U - Two lens piece optical image acquisition lens - Google Patents

Abstract

An optical image acquisition lens including two lens pieces is provided.
An aperture stop S is arranged in order from the object side to the image side along the optical axis, and a biconvex aspherical lens. These lenses have a positive refractive index in which at least one optical surface is a spherical surface. A first lens 12 having a convex shape and a spherical surface or an aspherical surface, and an image side surface (concave surface) within the optically effective region from the lens center to the lens edge. And a second lens having a positive refractive index having at least one inflection point, and gradually changing the second lens from a positive refractive index to a negative refractive index.
[Selection] Figure 1

Description

The present invention relates to two lens-piece optical image acquisition lenses, in particular, a lens using an image sensor such as a CCD or CMOS for a small camera or a mobile phone, and is a wide angle composed of two lenses and has a total length. The present invention relates to an optical image acquisition lens that is short and low in cost.

  In accordance with the advancement of science and technology, electronic products are constantly evolving toward light, thin, small and multi-functional, and among electronic products, for example, digital cameras, PC cameras, network cameras, mobile phones, etc. already have image acquisition devices (lens In addition, there is a demand for an apparatus such as a PDA to add an image acquisition apparatus. In order to be convenient to carry and meet the requirements of humanization, the image acquisition device not only needs to have good imaging quality, but also needs to be small volume and low cost. When the image is taken with a narrow field angle, the image width becomes small. However, an image acquisition lens with a large viewing angle can improve the photographing quality of the electronic product and meet the user's request.

Conventionally, image acquisition lenses applied to small electronic products have different structures, such as two lens pieces, three lens pieces, four lens pieces, and five lens pieces, but considering the cost. The number of lenses used by the two lens pieces is small, which is advantageous in terms of cost. Conventional two lens piece optical image acquisition lenses have a variety of different structural designs, the differences between which are determined by changes or combinations of the following various elements: for example, shapes combined between the two lenses Difference in the direction of each convex / concave surface, positive / negative difference in refractive index (refractive power), or difference in conditions satisfying related optical data. As can be seen from the above, the prior art is created by applying different structures or combinations for various different optical purposes when designing an optical image acquisition lens of two lens pieces.
JP 2007-256929 A JP 2007-226033 A

  In recent years, it has been applied to products such as small cameras, mobile phones with cameras, PDAs, etc., and its image acquisition lens requires miniaturization, shortening of focal length, and good aberration adjustment, and two image acquisition lens designs with various miniaturizations Medium, positive refractive index first lens, positive refractive index second lens or any other combination of designs to achieve miniaturization requirements, for example US2005 / 0073753, US2004 / 0160680, US7,110,190, US7,088,528 , US2004 / 0160680; EP1793252, EP1302801; JP2007-156031, JP2006-154517, JP2006-189586; TWM320680, TWI232325; CN101046544, and the like. However, the total length of the lenses described in the above patent documents still needs to be further reduced. For large viewing angle designs required by users, for example, US2008 / 0030875 uses a combination of positive and negative refractive indices, and JP08-334684 and JP2005-107368 have positive or negative-positive refractive indices. Combinations can be used to expand the viewing angle. For example, JP2004-177976, EP1793252 and EP1793254, US6,876,500, US2004 / 0160680, US7,088,528, TWI266074, etc. use a combination of positive and positive refractive indexes to reduce the lens length. Therefore, a design having a large viewing angle and reducing the total length of the lens has a strong demand for users.

An object of the present invention is an aperture stop arranged in order from the object side to the image side along the optical axis, a biconvex aspheric lens, and positive refraction in which at least one optical surface is a spherical surface. A first lens having a refractive index and a new moon type lens, the object side surface is convex and spherical or aspherical, and the image side surface (concave surface) is an optical effective area from the lens center to the lens edge ( two lenses comprising a second lens having a positive refractive index having at least one inflection point within an effective diameter range) and gradually changing the second lens from a positive refractive index to a negative refractive index. It is to provide an optical image acquisition lens composed of one piece. The optical acquisition lens then satisfies the following conditions:
Where bf is the back focal length of the main image acquisition lens system, TL is the distance from the aperture stop on the optical axis to the imaging plane, 2ω is the maximum field angle, and H ₊ Is the length of the perpendicular line from the inflection point on the image side surface of the second lens to the optical axis, H _t is the length of the perpendicular line from the maximum optical effective point on the image side surface of the second lens to the optical axis, d ₂ is the distance from the image side surface of the first lens on the optical axis to the object side surface of the second lens, f _s is the effective focal length of the optical image acquisition lens, and f ₁ is the first lens. F ₂ is the focal length of the second lens.

In addition, the first lens and the second lens of the optical acquisition lens of the two lens pieces are each composed of two aspheric surfaces, and the first lens and the second lens are manufactured from glass or plastic. The

Thereby, this invention can achieve the wide-angle effect and can enlarge the image acquisition angle of a small camera and a mobile phone. Also, the combination of the two lens pieces enables a short back focal length and further reduces the length of the lens, thereby improving the applicability of the image acquisition lens.

  In FIG. 1, an aperture stop S, a first lens 11 and a second lens 12 are arranged in order from the object side to the image side along the optical axis Z of the optical image acquisition lens 1 of the present invention. And an infrared filter (IR cut-off filter) 13 and an image sensing chip 14. At the time of image acquisition, the light beam of the object first passes through the first lens L1 and the second lens L2, and then forms an image on the image sensor 14 through the infrared filter 13.

The first lens 11 is a biconvex lens having a positive refractive index and is made of a glass or plastic material having a refractive index (N _d ) of 1.5 or more, and its object side surface R1 and image side surface R2 are at least 1. The surface is aspheric or both surfaces are aspheric.

The second lens 12 is a new moon lens having a positive refractive index, the object side surface R3 is a convex surface, the image side surface R4 is a concave surface, and the refractive index (N _d ) is larger than 1.5. Alternatively, it is made of a plastic material, and the object side R3 is a spherical surface or an aspherical surface, and the image side surface R4 is an aspherical surface that is entirely concave, and is within the optical effective region from the lens center to the lens edge. Is provided with at least one inflection point, and the second lens 12 is gradually changed from a positive refractive index to a negative refractive index, and its cross section (see FIG. 2) has a concave center and both sides protrude. Forming a mold, that is, the convex surface (or concave surface) of the central region on the wavy object side surface R4 gradually changes the arcuateness (curvature) outward and changes to the concave surface (convex surface) in the outer peripheral region. , Therefore, forming an inflection point while the concavo-convex arc surface changes . An arbitrary cutting line passes through the inflection point and intersects the optical axis perpendicularly, the distance from the inflection point to the optical axis is the height of the lens in the positive refractive index range, and is described as H ₊ That is, the length of the perpendicular from the inflection point to the optical axis. The length of the perpendicular line from the maximum optical effective point of the second lens 12 to the optical axis is described as H _t, and the size of the range in which the ratio of H ₊ and H _t is converted from a positive refractive index to a negative refractive index In order to have a good imaging effect, this range is preferably greater than 50%, and when trying to achieve a wide-angle effect, the range is preferably greater than 75%, ie Satisfy (3).

The aperture stop S belongs to the front photosphere and is stuck on the object side surface R1 of the first lens 11. The infrared filter 13 is a thin film having an infrared function formed by a lens piece or a plating film technique. The image sensor 14 is a CCD or a CMOS.

The optical image acquisition lens 1 of the two lens pieces of the present invention has optical surface curvature radii, aspherical curved surfaces, lens thicknesses (d1 and d3) and intervals (d2 and d4) of the first lens 11 and the second lens 12. Can be combined to make the viewing angle larger than 70 °, that is, the expression (1) is satisfied. The aspherical equation (Aspherical Surface Formula) is the following equation (6).
Here, c is the curvature, h is the height of the lens piece, K is the conic constant, and A _{4 to} A ₁₆ are _{4th to 16th} aspherical surfaces (Nth Order). Aspherical Coefficient).

With the above structure, the back focal length of the optical image acquisition lens 1 of the present invention can be effectively reduced, the length of the lens is reduced, that is, the expression (2) or the expression (4) is satisfied, and the aberration is further reduced. Is effectively corrected and the chief ray angle is reduced, that is, the expression (5) is satisfied.

The preferred embodiments will be described below respectively. Here, in one table of each example, the optical surfaces Surf 1, Surf2, Surf3, and Surf4 are the object side surface R1, the image side surface R2, and the object side surface R3 of the second lens 12 and the image in order, respectively. Side R4. R (unit: mm) is the radius of curvature of each optical surface on the optical axis. d (unit: mm) is the distance between the surfaces on the optical axis (the on-axis surface spacing), N _d is the refractive index of each lens, and ν _d is the Abbe's number of each lens. ). Annotated * is an aspheric optical surface, Fno is the focal length ratio (f number) of the optical image acquisition lens 1, fs is the effective focal length of the image acquisition lens, and 2ω is optical This is the viewing angle of the image acquisition lens 1. In the other table, each term coefficient of the aspherical expression (6) of each optical surface is listed.

<First Embodiment> As shown in FIGS.

In this embodiment, the first lens 11 is made of a glass material having N _d1 of 1.731 and ν _d1 of 40.5. The second lens 12 is made of a glass material having N _d2 of 1.566 and ν _d2 of 24.7. The infrared filter 13 is made of a glass material of BSC7.

In this example, fs is 1.1386 mm, f ₁ is 1.7332 mm, f ₂ is 2.1951 mm, H _t is 0.7395 mm, H ₊ is 0.5903 mm, and TL is 1.5270 mm. That is,
Expressions (1) to (5) are satisfied.

<Second Embodiment> As shown in FIGS. 5 and 6,

In this embodiment, the first lens 11 is made of a glass material having N _d1 of 1.566 and ν _d1 of 24.7. The second lens 12 is made of a plastic material having N _d2 of 1.583 and ν _d2 of 59.5. The infrared filter 13 is made of a glass material of BSC7.

In this example, fs is 1.124 mm, f ₁ is 2.2323 mm, f ₂ is 1.7104 mm, H _t is 0.6620 mm, H ₊ is 0.5276 mm, and TL is 1.7183 mm. That is,
Expressions (1) to (5) are satisfied.

<Third Embodiment> As shown in FIGS.

In this embodiment, the first lens 11 is made of a glass material having N _d1 of 1.537 and ν _d1 of 63.5. The second lens 12 is made of a glass material having N _d2 of 1.731 and ν _d2 of 40.5. The infrared filter 13 is made of a glass material of BSC7.

In this example, fs is 1.20 mm, f ₁ is 1.5836 mm, f ₂ is 3.1876 mm, the R4 optical surface has no inflection point, and TL is 1.7028 mm. That is,
Expressions (1), (2), (4), and (5) are satisfied.

<Fourth Embodiment> As shown in FIGS.

In this embodiment, the first lens 11 is made of a glass material having N _d1 of 1.566 and ν _d1 of 24.7. The second lens 12 is made of a glass material having N _d2 of 1.731 and ν _d2 of 40.5. The infrared filter 13 is made of a glass material of BSC7.

In this example, fs is 1.0663 mm, f ₁ is 2.5387 mm, f ₂ is 1.597 mm, H _t is 0.490 mm, H ₊ is 0.4338 mm, and TL is 1.5275 mm. That is,

Expressions (1) to (5) are satisfied.

<Fifth Embodiment> As shown in FIGS.

In this embodiment, the first lens 11 is made of a glass material having N _d1 of 1.613 and ν _d1 of 26.3. The second lens 12 is made of a glass material having N _d2 of 1.566 and ν _d2 of 24.7. The infrared filter 13 is made of a glass material of BSC7.

In this example, fs is 1.1231 mm, f ₁ is 2.2367 mm, f ₂ is 1.7097 mm, H _t is 0.6654 mm, H ₊ is 0.5456 mm, and TL is 1.7153 mm. That is,

Expressions (1) to (5) are satisfied.

It is an optical structure figure of this invention. It is an image side view of the 2nd lens of this invention. It is an optical path structure figure of 1st Example of this invention. FIG. 4 is a diagram illustrating spherical aberration, field curvature, and distortion of an image according to the first embodiment of the present invention. It is an optical path structure figure of 2nd Example of this invention. It is a spherical aberration of an image formation, a field curvature, and a distortion figure of 2nd Example of this invention. It is an optical path structure figure of 3rd Example of this invention. It is a spherical aberration of an image formation, field curvature, and a distortion figure of 3rd Example of this invention. It is an optical path structure figure of 4th Example of this invention. It is a spherical aberration of an image formation, a field curvature, and a distortion figure of 4th Example of this invention. It is an optical path structure figure of 5th Example of this invention. It is a spherical aberration of an image formation, a field curvature, and a distortion figure of 5th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical image acquisition lens 11 1st lens R1 (1st lens) Object side surface R2 (1st lens) Image side surface S Aperture stop 12 Second lens R3 (2nd lens) Object side surface R4 (2nd lens) Image side surface 13 Infrared rays Filter R5 (Infrared filter) Object side surface R6 (Infrared filter) Image side surface 14 Image sensor d1 Distance from the first lens object side surface to the image side surface on the optical axis d2 Object of the second lens from the first lens image side surface on the optical axis Distance d3 from the second lens object side surface on the optical axis to the image side surface d4 Distance from the second lens image side surface on the optical axis to the object side surface of the infrared filter d5 Image from the infrared filter object side surface on the optical axis Distance to the side d6 Distance from the side of the infrared filter image on the optical axis to the image sensor

Claims (9)

Arranged in order from the object side to the image side along the optical axis,
An aperture stop,
A first lens having a positive refractive index, which is a biconvex aspheric lens and at least one optical surface is a spherical surface;
A new moon type lens whose object side surface is convex and whose image side surface is aspherical concave surface.


Where bf is the back focal length of the image acquisition lens system, TL is the distance from the aperture stop to the imaging surface, and 2ω is the optical image acquisition comprising two lens pieces with the maximum viewing angle. lens. The optical image acquisition lens comprising two lens pieces according to claim 1, wherein both the biconvex surface and the concave surface of the first lens are aspheric optical surfaces. The optical image acquisition lens comprising two lens pieces according to claim 1, wherein both the convex surface and the concave surface of the second lens are aspherical optical surfaces. The second lens has at least one inflection point in an optical effective region from the lens center on the image side surface to the lens edge, and the second lens is gradually changed from a positive refractive index to a negative refractive index. , The position of the inflection point is

H ₊ is the length of the perpendicular from the inflection point on the image side surface of the second lens to the optical axis, and H _t is the length of the perpendicular from the maximum optical effective point on the image side of the second lens to the optical axis. The optical image acquisition lens which consists of two lens pieces of Claim 1 which is length. The image acquisition lens has a short focal length, and the following conditions

Wherein d ₂ is the distance from the image side surface of the first lens to the object side surface of the second lens on the optical axis, and f _s is the effective focal length of the optical image acquisition lens. An optical image acquisition lens comprising two lens pieces according to 2 or 3. The following conditions

4. The optical image acquisition lens comprising two lens pieces according to claim 2, wherein f ₁ is a focal length of the first lens and f ₂ is a focal length of the second lens. The optical image acquisition lens comprising two lens pieces according to claim 1, wherein both the first lens and the second lens are made of a glass material. The optical image acquisition lens comprising two lens pieces according to claim 1, wherein the first lens is made of a glass material and the second lens is made of a plastic material. The optical image acquisition lens comprising two lens pieces according to claim 1, wherein the first lens is made of a plastic material and the second lens is made of a glass material.

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