RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number 107142271, filed on Nov. 27, 2018, which is incorporated by reference herein in its entirety.

BACKGROUND

Technical Field

The present disclosure relates to a lens system and a projection apparatus, and more particularly, to a lens system, a projection apparatus and a detecting module applicable to electronic devices.

Description of Related Art

With increasing applications of photographic modules, lens specifications by popular demand are becoming more diverse. A lens unit capable of collecting 3-dimensional information can add depth of field information to two-dimensional images, providing better user experiences with higher accuracy and reality. Further, with appropriate optics and imaging technologies, speed and resolutions of 3-dimensional detection are improved, and such lens units are applicable to 3-dimensional imaging such as augmented realities, face recognitions, iris recognitions, gesture recognitions and 3-dimensional modeling.

In the past, the development of human-computer interaction or imaging devices on the market was mostly limited in two-dimensional space. However, a significant gap still exists between the two-dimensional images and the real images seen by naked eyes. In order to provide a higher level of immersion in electronic devices, or to enhance the convenience of life, the technology for capturing and applying the 3-dimensional information becomes an important part in the technological developments of the future. With light which projects specific patterns onto an detected object, retrieving the light reflected from different depth positions on the detected object by another lens unit, and calculating the changes in properties of the reflected light, a distance between the lens units and the positions of interest on the detected object can be obtained as well as the 3-dimensional structure of the detected object or the motion signals of the detected object can be identified thereby for completing further specific operations or instructions. Currently, various applications on retrieving and interacting with the 3-dimensional image information are available on the market, including face recognition systems, somatosensory game consoles, augmented reality devices, driving assistance systems, various smart electronics, multi-lens devices, wearable devices, digital cameras, recognition systems, entertainment devices, sport devices, smart home systems and other electronics.

SUMMARY

According to one aspect of the present disclosure, an electronic device includes a lens system, the lens system including three lens elements, which are, in order from an outer side to an inner side: a first lens element, a second lens element and a third lens element,

wherein the first lens element with positive refractive power has an outer-side surface being convex in a paraxial region thereof, the second lens element has negative refractive power, the third lens element has positive refractive power, a curvature radius of the outer-side surface of the first lens element is R1, a curvature radius of an inner-side surface of the third lens element is R6, an axial distance between the inner-side surface of the third lens element and an inner-side conjugate surface of the lens system is BL, an axial distance between the outer-side surface of the first lens element and the inner-side surface of the third lens element is TD, a minimum among Abbe numbers of the three lens elements is Vdmin, a maximum among refractive indices of the three lens elements is Nmax, a focal length of the lens system is f, a focal length of the first lens element is f1, a focal length of the second lens element is f2, a focal length of the third lens element is f3, and the following conditions are satisfied:
−2.80<(R1+R6)/(R1−R6)<7.50;
0<BL/TD<1.0;
5.0<Vdmin<25.0;
1.50<Nmax<1.73; and
4.50<|f/f1|+|f/f2|+|f/f3|<12.0.

According to another aspect of the present disclosure, an electronic device includes a projection apparatus, the projection apparatus including a lens system and at least one light source, the lens system including three lens elements, which are, in order from an outer side to an inner side: a first lens element, a second lens element and a third lens element,

wherein the first lens element has an outer-side surface being convex in a paraxial region thereof, the second lens element has an inner-side surface being concave in a paraxial region thereof, there is an air gap between each of adjacent lens elements of the lens system, a curvature radius of the outer-side surface of the first lens element is R1, a curvature radius of an inner-side surface of the third lens element is R6, an axial distance between the inner-side surface of the third lens element and an inner-side conjugate surface of the lens system is BL, an axial distance between the outer-side surface of the first lens element and the inner-side surface of the third lens element is TD, a minimum among Abbe numbers of the three lens elements is Vdmin, a maximum among refractive indices of the three lens elements is Nmax, a focal length of the lens system is f, a focal length of the second lens element is f2, a focal length of the third lens element is f3, and the following conditions are satisfied:
−2.80<(R1+R6)/(R1−R6)<7.50;
0<BL/TD<1.0;
5.0<Vdmin<25.0;
1.50<Nmax<1.73;
2.50<|f/f2|+|f/f3|<10.0; and
−0.80<f/f3<5.0.

According to another aspect of the present disclosure, an electronic device includes a projection apparatus, the projection apparatus including a lens system and at least one light source, the lens system including three lens elements, which are, in order from an outer side to an inner side: a first lens element, a second lens element and a third lens element,

wherein the first lens element with positive refractive power has an outer-side surface being convex in a paraxial region thereof, the third lens element with positive refractive power has an inner-side surface being convex in a paraxial region thereof, a curvature radius of the outer-side surface of the first lens element is R1, a curvature radius of the inner-side surface of the third lens element is R6, an axial distance between the inner-side surface of the third lens element and an inner-side conjugate surface of the lens system is BL, an axial distance between the outer-side surface of the first lens element and the inner-side surface of the third lens element is TD, a minimum among Abbe numbers of the three lens elements is Vdmin, a maximum among refractive indices of the three lens elements is Nmax, a curvature radius of an outer-side surface of the third lens element is R5, and the following conditions are satisfied:
−1.0<(R1+R6)/(R1−R6)<1.0;
0<BL/TD<1.0;
5.0<Vdmin<25.0;
1.50<Nmax<1.73; and
0<(R5+R6)/(R5−R6)<5.0.

