Optical lens assembly for image taking

Abstract

An optical lens assembly for image taking, sequentially from an object side to an image side along an optical axis comprises: the first lens element with refractive power, a bi-convex second lens element with positive refractive power, the third lens element with negative refractive power having a concave object-side surface and a convex image-side surface, the fourth lens element with positive refractive power having a convex object-side surface and a concave image-side surface. All four lenses may be made of plastic with bi-aspherical surfaces. Additionally, the optical lens assembly for image taking satisfies conditions to shorten the total length and reduce the sensitivity in order to achieve the goal of a fine aberration correction and ready for its use in cameras and camera mobile phones.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an optical lens assembly for image taking, and more particularly to an optical lens assembly composed of four lenses and applied to an electronic product, and the optical lens assembly has the features of short total length and low cost.[0003]2. Description of the Related Art[0004]As science and technology advance, the development of electronic products such as digital still cameras, web cameras, and mobile phone cameras comes with an optical lens assembly with a smaller size and a lower cost to meet user requirements, while providing an optical lens assembly with good aberration correction capability, high resolution, and high image quality.[0005]In general, a conventional optical lens assembly for image taking for a mini electronic product has different designs including the two-lens, three-lens, four-lens, and five-or-more lens designs. If the image quality is taken in consideration, ...

AI Technical Summary

Benefits of technology

[0018]With the aforementioned first lens element, second lens element, third lens element and fourth lens element of the present invention installed with an appropriate distance apart from each other on the optical axis, the total length of the optical lens assembly can be reduced effectively and good aberration correction and modulation transfer function (MTF) can be achieved.

[0019]In the optical lens assembly for image taking in accordance with the present invention, the second lens element has positive refractive power to provide the required refractive power for the system and help reducing the total length of the optical lens assembly for image taking; and the third lens element has negative refractive power for effectively compensating the image aberration produced by the first and second lens elements with positive refractive power, and correcting the Petzval sum of the system to make the peripheral image surface flatter and favors the correction of the color difference of the system to improve the resolution of the optical lens assembly for image taking; and the fourth lens element with positive refractive power further improves the refractive power and modulation transfer function (MTF), such that the overall image aberration and distortion of the optical lens assembly for image taking can comply with the high resolution requirement.

[0020]In the optical lens assembly for image taking in accordance with the present invention, the combination of the first and second lens elements can enhance the refractive power effectively to shorten the total length of the optical lens assembly for image taking. The combination of the third lens element with a concave object-side surface and a convex image-side surface and the fourth lens element with a convex object-side surface and a concave image-side surface can correct the astigmatic image. Further, the first lens element, third lens element and fourth lens element are made of plastic, and a simple surface shape favors the manufacture and lower the low cost.

Problems solved by technology

However, the optical lens assemblies disclosed in these patents still required a reduction of the total length of the lens.

Although the total length of the lens is effectively reduced, the drawback is that the aberration correction is difficult to improve or the image distortion is hard to lower down.

On the other hand, the reduction of the total length of the lens can be accomplished by adopting a concave surface (or a convex surface) at the object-side surface of the third lens element or fourth lens element near the optical axis and a convex surface (or a concave surface) while approaching the rim of the lens, such that the curvature has a very large change, but such lens is very difficult to manufacture.

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