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Image capturing optical lens system

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Image capturing optical lens system


This invention provides an optical lens system comprising: a first lens element with positive refractive power; a second lens element with negative refractive power; a third lens element with negative refractive power having a concave object-side surface and at least one of the object-side surface and the image-side surface thereof being aspheric; a plastic fourth lens element having at least one of the object-side surface and the image-side surface thereof being aspheric; a plastic fifth lens element having a concave image-side surface, at least one of the object-side surface and the image-side surface thereof being aspheric, and at least one inflection point is formed on at least one of the object-side surface and the image-side surface thereof. By such arrangement, photosensitivity and total track length of the system can be reduced, and the aberration and astigmatism of the system can be effectively corrected. Moreover, high image resolution can be obtained.
Related Terms: Astigmatism Photosensitivity

Browse recent Largan Precision Co., Ltd. patents - Taichung, TW
Inventors: Hsiang-Chi Tang, Ming-Ta Chou, Tsung-Han Tsai
USPTO Applicaton #: #20120314302 - Class: 359714 (USPTO) - 12/13/12 - Class 359 


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The Patent Description & Claims data below is from USPTO Patent Application 20120314302, Image capturing optical lens system.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 100120114 filed in Taiwan, R.O.C. on Jun. 9, 2011, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image capturing optical lens system, and more particularly, to a compact image capturing optical lens system used in electronic products.

2. Description of the Prior Art

In recent years, with the popularity of portable electronic products having photographing function, the demand of compact imaging lens system has grown. Generally, the sensor of a general photographing camera is none other than CCD (Charge Coupled Device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, advances in semiconductor manufacturing technology have allowed the pixel size of sensors to be reduced and therefore lead compact imaging lens systems to higher resolution. In the meantime, the demand for better image quality is also increased.

A conventional image capturing lens system equipped on a portable electronic product is in various design of two-lens element, three-lens element, four-lens element or five-lens element, such as the one set forth in U.S. Pat. No. 7,365,920. However, with the popularity of high level portable electronic products, such as smart phone and PDA (Personal Digital Assistant), the demand for the pixel size and image quality of compact imaging lens system increase fast, and the conventional lens system with four lens elements can no longer satisfy the imaging lens systems of even higher level. Moreover, a conventional image capturing lens system having five lens elements usually adopts different assemblies of positive or negative refractive power or has a cemented doublet lens element. This kind of five-lens element lens system frequently has the drawback of excessively long total track length so that is not suitable for compact electronic products

Inasmuch as the foregoing, a need is continuously existed for a lens system with good image quality and moderate total track length and is suitable for compact and portable electronic products.

SUMMARY

OF THE INVENTION

The present invention provides an image capturing optical lens system, in order from an object side to an image side comprising five lens elements with refractive power: a first lens element with positive refractive power; a second lens element with negative refractive power; a third lens element with negative refractive power having a concave object-side surface and at least one of the object-side surface and the image-side surface thereof being aspheric; a fourth lens element having at least one of the object-side surface and the image-side surface thereof being aspheric and made of plastic; and a fifth lens element having a concave image-side surface, at least one of the object-side surface and the image-side surface thereof being aspheric, at least one inflection point is formed on at least one of the object-side surface and the image-side surface thereof and made of plastic; wherein a curvature radius of the object-side surface of the second lens element is R3, a curvature radius of the image-side surface of the second lens element is R4, a curvature radius of the object-side surface of the third lens element is R5, a curvature radius of the image-side surface of the third lens element is R6, a curvature radius of the object-side surface of the fourth lens element is R7, a curvature radius of the image-side surface of the fourth lens element is R8, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, an axial distance between the second lens element and the third lens element is T23, and they satisfy the following relations: −5.0<(R3+R4)/(R3−R4)<−0.75; −5.0<(R5+R6)/(R5−R6)<−0.8; −5.3<R7/R8<6.5; and 0.1<(T34+T45)/T23<1.8.

On the other hand, the present invention provides an image capturing optical lens system, in order from an object side to an image side comprising five lens elements with refractive power: a first lens element with positive refractive power; a second lens element with negative refractive power; a third lens element with negative refractive power having a concave object-side surface and at least one of the object-side surface and the image-side surface thereof being aspheric; a fourth lens element with positive refractive power having at least one of the object-side surface and the image-side surface thereof being aspheric and made of plastic; and a fifth lens element with negative refractive power having a concave image-side surface, at least one of the object-side surface and the image-side surface thereof being aspheric, at least one inflection point is formed on at least one of the object-side surface and the image-side surface thereof and made of plastic; wherein a curvature radius of the object-side surface of the second lens element is R3, a curvature radius of the image-side surface of the second lens element is R4, a curvature radius of the object-side surface of the third lens element is R5, a curvature radius of the image-side surface of the third lens element is R6, the image capturing optical lens system further comprises a stop, an axial distance between the stop and an image plane is SL, an axial distance between the object-side surface of the first lens element and the image plane is TTL, and they satisfy the following relations: −5.0<(R3+R4)/(R3−R4)<−0.75; −5.0<(R5+R6)/(R5−R6)<−0.8; and 0.70<SL/TTL<0.93.

By such arrangement, photosensitivity and total track length of the system can be reduced, and the aberration and astigmatism of the system can be effectively corrected. Moreover, high image resolution can be obtained.

In the aforementioned image capturing optical lens system, the first lens element has positive refractive power and thereby can provide significant positive refractive power needed for the system and is favorable for reducing the total track length thereof. When the second lens element has negative refractive power, the aberration provided by the first lens element can be effectively corrected. Also, the chromatic aberration can be favorably corrected. When the third lens element has negative refractive power, the third lens element can correct the aberration and chromatic aberration and reduce the sensitivity of the system along with the second lens element. When the fourth lens element has positive refractive power and the fifth lens element has negative refractive power, a positive-negative telephoto structure is formed so that the back focal length of the system is favorably reduced as well as the total track length of the system.

In the aforementioned image capturing optical lens system, the second lens element has a concave object-side surface and a convex image-side surface so that the astigmatism of the system can be favorably corrected. When the third lens element has a concave object-side surface, the astigmatism of the system can be favorably corrected. When the fifth lens element has concave image-side surface, the principal point of the system can be positioned away from the image plane so that the total track length thereof can be shortened for keeping the system compact. In addition, when at least one inflection is formed on at least one of the object-side and image-side surfaces of the fifth lens element, the angle at which light projects onto the image sensor from the off-axis field can be effectively reduced so that the sensing efficiency of the image sensor can be improved and the off-axis aberration can be corrected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an image capturing optical lens system in accordance with a first embodiment of the present invention.

FIG. 1B shows the aberration curves of the first embodiment of the present invention.

FIG. 2A shows an image capturing optical lens system in accordance with a second embodiment of the present invention.

FIG. 2B shows the aberration curves of the second embodiment of the present invention.

FIG. 3A shows an image capturing optical lens system in accordance with a third embodiment of the present invention.

FIG. 3B shows the aberration curves of the third embodiment of the present invention.

FIG. 4A shows an image capturing optical lens system in accordance with a fourth embodiment of the present invention.

FIG. 4B shows the aberration curves of the fourth embodiment of the present invention.

FIG. 5A shows an image capturing optical lens system in accordance with a fifth embodiment of the present invention.



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stats Patent Info
Application #
US 20120314302 A1
Publish Date
12/13/2012
Document #
13236886
File Date
09/20/2011
USPTO Class
359714
Other USPTO Classes
International Class
02B13/18
Drawings
15


Astigmatism
Photosensitivity


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