BACKGROUND

Technical Field

The present disclosure relates to a photographing lens assembly, an image capturing unit and an electronic device, more particularly to a photographing lens assembly and an image capturing unit applicable to an electronic device.

Description of Related Art

In recent years, with the popularity of electronic devices having camera functionalities, the demand for miniaturized optical systems has been increasing. As advanced semiconductor manufacturing technologies have reduced the pixel size of image sensors, and compact optical systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical systems featuring better image quality.

With the development of the miniaturized optical systems, electronic devices equipped with the optical systems, such as smartphones, driving recorders, image recognition systems, video game consoles and smart home devices, are the trend of future technologies. Also, in order to obtain user experiences in a broader range of applications, smart electronic devices equipped with one, two, even three lenses, which have different fields of view, have become the mainstream on the market. Accordingly, imaging lenses with different features are provided for various applications; in addition, the need for optical systems with large angle of view is now higher than ever, and the product specifications are becoming more demanding as well.

However, a first lens element (i.e., the lens element closest to the imaged object) in a conventional lens assembly with a wide view angle configuration usually has negative refractive power, an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof. Therefore, it is favorable for light from large angle of view projecting onto an image surface. However, a shape design of the first lens element usually has a big influence on the dimension and size of a photographing module. For example, the center part of the first lens element may protrude out of the photographing module, and thus the photographing module is inapplicable to a compact portable electronic device. Accordingly, there is a need for a photographing lens assembly having a first lens element with a proper shape on the object-side surface thereof for meeting the requirements of compact size and a wide view angle.

SUMMARY

According to one aspect of the present disclosure, a photographing lens assembly includes six lens elements. The six lens elements are, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. The first lens element with negative refractive power has an object-side surface being concave in a paraxial region thereof, wherein the object-side surface of the first lens element has at least one convex critical point in an off-axis region thereof. The third lens element has an image-side surface being convex in a paraxial region thereof. The fourth lens element has positive refractive power. The fifth lens element with negative refractive power has an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof. The sixth lens element has an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the sixth lens element has at least one convex critical point in an off-axis region thereof, and an object-side surface and the image-side surface of the sixth lens element are both aspheric. When a curvature radius of the object-side surface of the first lens element is R1, a curvature radius of an image-side surface of the first lens element is R2, a central thickness of the sixth lens element is CT6, and an axial distance between the fifth lens element and the sixth lens element is T56, the following conditions are satisfied:
|R1/R2|<5.0; and
1.60<CT6/T56<100.

According to another aspect of the present disclosure, a photographing lens assembly includes six lens elements. The six lens elements are, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. The first lens element with negative refractive power has an object-side surface being concave in a paraxial region thereof, wherein the object-side surface of the first lens element has at least one convex critical point in an off-axis region thereof. The third lens element has an image-side surface being convex in a paraxial region thereof. The fourth lens element has positive refractive power. The fifth lens element with negative refractive power has an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof. The sixth lens element has an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the sixth lens element has at least one convex critical point in an off-axis region thereof, and an object-side surface and the image-side surface of the sixth lens element are both aspheric. When a curvature radius of the object-side surface of the first lens element is R1, a curvature radius of an image-side surface of the first lens element is R2, an axial distance between the first lens element and the second lens element is T12, an axial distance between the second lens element and the third lens element is T23, 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, and an axial distance between the fifth lens element and the sixth lens element is T56, the following conditions are satisfied:
|R1/R2|≤3.0; and
0<(T12+T56)/(T23+T34+T45)<3.0.

According to still another aspect of the present disclosure, an image capturing unit includes one of the aforementioned photographing lens assemblies and an image sensor, wherein the image sensor is disposed on an image surface of the photographing lens assembly.

According to yet another aspect of the present disclosure, an electronic device includes the aforementioned image capturing unit.

