Patent Publication Number: US-9405098-B1

Title: Mobile device and optical imaging lens thereof

Description:
INCORPORATION BY REFERENCE 
     This application claims priority from R.O.C. Patent Application No. 104117217, filed on May 28, 2015, the contents of which are hereby incorporated by reference in their entirety for all purposes. 
     TECHNICAL FIELD 
     The present disclosure relates to a mobile device and an optical imaging lens thereof, and particularly, relates to a mobile device applying an optical imaging lens having four lens elements and an optical imaging lens thereof. 
     BACKGROUND 
     The ever-increasing demand for smaller sized mobile devices, such as cell phones, digital cameras, etc. has triggered a corresponding and growing need for smaller sized photography modules. Such modules may comprise elements such as an optical imaging lens, a module housing unit, and an image sensor, etc., contained therein. Size reductions may be contributed from various aspects of the mobile devices in light of the specification required in the market, such as good optical characteristics, the difficulty to make each component, the nature of the material, the yield, and so on, therefore it is not as simple as just proportionally shrinking the size of each component. 
     Therefore, it may be a challenge to develop optical imaging lens which may be capable to place with four lens elements therein, with a shorter length, while also having good optical characteristics. 
     SUMMARY 
     Aspects of the present disclosure may provide a mobile device and an optical imaging lens thereof. With controlling the convex or concave shape of the surfaces and at least two inequalities, the length of the optical imaging lens may be shortened while good optical characteristics and system functionality may be maintained. 
     In an exemplary embodiment, an optical imaging lens may comprise, sequentially from an object side to an image side along an optical axis, an aperture stop, and first, second, third and fourth lens elements, each of the first, second, third and fourth lens elements may have refracting index, an object-side surface facing toward the object side and an image-side surface facing toward the image side and a central thickness defined along the optical axis. 
     In the specification, parameters used here are: the distance between the aperture stop and the object-side surface of the next lens element along the optical axis, represented by TA (negative sign represents the direction of the distance is from the image side to the object side), the central thickness of the first lens element, represented by T1, an air gap between the first lens element and the second lens element along the optical axis, represented by G12, the central thickness of the second lens element, represented by T2, an air gap between the second lens element and the third lens element along the optical axis, represented by G23, the central thickness of the third lens element, represented by T3, an air gap between the third lens element and the fourth lens element along the optical axis, represented by G34, the central thickness of the fourth lens element, represented by T4, a distance between the image-side surface of the fifth lens element and the object-side surface of a filtering unit along the optical axis, represented by G4F, the central thickness of the filtering unit along the optical axis, represented by TF, a distance between the image-side surface of the filtering unit and an image plane along the optical axis, represented by GFP, the central thickness of an image sensor along the optical axis, represented by TI, a focusing length of the first lens element, represented by f1, a focusing length of the second lens element, represented by f2, a focusing length of the third lens element, represented by f3, a focusing length of the fourth lens element, represented by f4, the refracting index of the first lens element, represented by n1, the refracting index of the second lens element, represented by n2, the refracting index of the third lens element, represented by n3, the refracting index of the fourth lens element, represented by n4, the refracting index of the filtering unit, represented by n6, an abbe number of the first lens element, represented by v1, an abbe number of the second lens element, represented by v2, an abbe number of the third lens element, represented by v3, an abbe number of the fourth lens element, represented by v4, an effective focal length of the optical imaging lens, represented by EFL or f, a distance between the object-side surface of the first lens element and an image plane along the optical axis, represented by TTL, a sum of the central thicknesses of all four lens elements, i.e. a sum of T1, T2, T3 and T4, represented by ALT, a sum of all three air gaps from the first lens element to the fourth lens element along the optical axis, i.e. a sum of G12, G23 and G34, represented by AAG, and a back focal length of the optical imaging lens, which is defined as the distance from the image-side surface of the fifth lens element to the image plane along the optical axis, i.e. a sum of G4F, TF and GFP, and represented by BFL. 
     In an aspect of the present disclosure, in the optical imaging lens, the object-side surface of the first lens element may comprise a convex portion in a vicinity of a periphery of the first lens element, and the image-side surface of the first lens element may comprise a convex portion in a vicinity of the periphery of the first lens element, the second lens element has negative refracting index, and the object-side surface of the second lens element may comprise a concave portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the second lens element, the third lens element has positive refracting index, and the object-side surface of the third lens element may comprise a concave portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the third lens element, and the image-side surface thereof may comprise a convex portion in a vicinity of the periphery of the third lens element, the image-side surface of the fourth lens element may comprise a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the fourth lens element, the optical imaging lens may comprise no other lenses having refracting index beyond the four lens elements, and the central thickness of the second lens element is represented by T2, the central thickness of the fourth lens element is represented by T4, an air gap between the third lens element and the fourth lens element along the optical axis is represented by G34, a sum of the central thicknesses of all four lens elements is represented by ALT, and T2, T4, G34 and ALT satisfy the inequalities:
         ALT/T2≦5.4 Inequality (1); and   (T2+T4)/G34≦4.0 Inequality (2).       

     In another exemplary embodiment, other inequality(s), such as those relating to the ratio among parameters could be taken into consideration. For example:
         AAG/G12≦6.0 Inequality (3);   (G23+G34)/T4≦2.2 Inequality (4);   AAG/T4≦2.7 Inequality (5);   (T1+T2)/G12≦4.8 Inequality (6);   EFL/G23≧7.3 Inequality (7);   ALT/G12≦10.0 Inequality (8);   (T3+T4)/G12≦5.0 Inequality (9);   EFL/T1≧5.5 Inequality (10);   T1/G12≦2.9 Inequality (11);   ALT/G12≦9.2 Inequality (12);   EFL/(G23+G34)≧4.5 Inequality (13); and/or   EFL/(T1+T4)≧3.1 Inequality (14).       

     Aforesaid exemplary embodiments are not limited and could be selectively incorporated in other embodiments described herein. 
     In some exemplary embodiments, more details about the convex or concave surface structure could be incorporated for one specific lens element or broadly for plural lens elements to enhance the control for the system performance and/or resolution, for example, the image-side surface of the second lens element may comprise a convex portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the second lens element. It is noted that the details listed here could be incorporated in example embodiments if no inconsistency occurs. 
     In another exemplary embodiment, a mobile device comprising a housing and a photography module positioned in the housing may be provided. The photography module may comprise any of aforesaid example embodiments of optical imaging lens, a lens barrel, a module housing unit, a substrate and an image sensor. The lens barrel may be suitable for positioning the optical imaging lens, the module housing unit may be suitable for positioning the lens barrel, the substrate may be suitable for positioning the module housing unit and the image sensor may be positioned at the image side of the optical imaging lens. 
     By controlling the convex or concave shape of the surfaces and at lease two inequalities, the mobile device and the optical imaging lens thereof in exemplary embodiments may achieve good optical characteristics and may effectively shorten the length of the optical imaging lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: 
         FIG. 1  is a cross-sectional view of one single lens element according to the present disclosure; 
         FIG. 2  is a cross-sectional view showing the relation between the shape of a portion and the position where a collimated ray meets the optical axis; 
         FIG. 3  is a cross-sectional view showing the relation between the shape of a portion and he effective radius of a first example; 
         FIG. 4  is a cross-sectional view showing the relation between the shape of a portion and he effective radius of a second example; 
         FIG. 5  is a cross-sectional view showing the relation between the shape of a portion and he effective radius of a third example; 
         FIG. 6  is a cross-sectional view of a first embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 7  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a first embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 8  is a table of optical data for each lens element of a first embodiment of an optical imaging lens according to the present disclosure; 
         FIG. 9  is a table of aspherical data of a first embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 10  is a cross-sectional view of a second embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 11  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a second embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 12  is a table of optical data for each lens element of the optical imaging lens of a second embodiment of the present disclosure; 
         FIG. 13  is a table of aspherical data of a second embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 14  is a cross-sectional view of a third embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 15  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a third embodiment of the optical imaging lens according the present disclosure; 
         FIG. 16  is a table of optical data for each lens element of the optical imaging lens of a third embodiment of the present disclosure; 
         FIG. 17  is a table of aspherical data of a third embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 18  is a cross-sectional view of a fourth embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 19  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a fourth embodiment of the optical imaging lens according the present disclosure; 
         FIG. 20  is a table of optical data for each lens element of the optical imaging lens of a fourth embodiment of the present disclosure; 
         FIG. 21  is a table of aspherical data of a fourth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 22  is a cross-sectional view of a fifth embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 23  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a fifth embodiment of the optical imaging lens according the present disclosure; 
         FIG. 24  is a table of optical data for each lens element of the optical imaging lens of a fifth embodiment of the present disclosure; 
         FIG. 25  is a table of aspherical data of a fifth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 26  is a cross-sectional view of a sixth embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 27  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a sixth embodiment of the optical imaging lens according the present disclosure; 
         FIG. 28  is a table of optical data for each lens element of the optical imaging lens of a sixth embodiment of the present disclosure; 
         FIG. 29  is a table of aspherical data of a sixth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 30  is a cross-sectional view of a seventh embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 31  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a seventh embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 32  is a table of optical data for each lens element of a seventh embodiment of an optical imaging lens according to the present disclosure; 
         FIG. 33  is a table of aspherical data of a seventh embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 34  is a cross-sectional view of an eighth embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 35  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of an eighth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 36  is a table of optical data for each lens element of the optical imaging lens of an eighth embodiment of the present disclosure; 
         FIG. 37  is a table of aspherical data of an eighth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 38  is a cross-sectional view of a ninth embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 39  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a ninth embodiment of the optical imaging lens according the present disclosure; 
         FIG. 40  is a table of optical data for each lens element of the optical imaging lens of a ninth embodiment of the present disclosure; 
         FIG. 41  is a table of aspherical data of a ninth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 42  is a cross-sectional view of a tenth embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 43  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of a tenth embodiment of the optical imaging lens according the present disclosure; 
         FIG. 44  is a table of optical data for each lens element of the optical imaging lens of a tenth embodiment of the present disclosure; 
         FIG. 45  is a table of aspherical data of a tenth embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 46  is a cross-sectional view of an eleventh embodiment of an optical imaging lens having four lens elements according to the present disclosure; 
         FIG. 47  is a chart of longitudinal spherical aberration and other kinds of optical aberrations of an eleventh embodiment of the optical imaging lens according the present disclosure; 
         FIG. 48  is a table of optical data for each lens element of the optical imaging lens of an eleventh embodiment of the present disclosure; 
         FIG. 49  is a table of aspherical data of an eleventh embodiment of the optical imaging lens according to the present disclosure; 
         FIG. 50  is a table for the values of parameters of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of all eleven example embodiments; 
         FIG. 51  is a structure of an example embodiment of a mobile device; and 
         FIG. 52  is a partially enlarged view of the structure of another example embodiment of a mobile device. 
     
    
    
     DETAILED DESCRIPTION 
     For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features. Persons having ordinary skill in the art will understand other varieties for implementing example embodiments, including those described herein. The drawings are not limited to specific scale and similar reference numbers are used for representing similar elements. As used in the disclosures and the appended claims, the terms “example embodiment,” “exemplary embodiment,” and “present embodiment” do not necessarily refer to a single embodiment, although it may, and various example embodiments may be readily combined and interchanged, without departing from the scope or spirit of the present disclosure. Furthermore, the terminology as used herein is for the purpose of describing example embodiments only and is not intended to be a limitation of the disclosure. In this respect, as used herein, the term “in” may include “in” and “on”, and the terms “a”, “an” and “the” may include singular and plural references. Furthermore, as used herein, the term “by” may also mean “from”, depending on the context. Furthermore, as used herein, the term “if” may also mean “when” or “upon”, depending on the context. Furthermore, as used herein, the words “and/or” may refer to and encompass any and all possible combinations of one or more of the associated listed items. 
     In the present specification, the description “a lens element having positive refracting index (or negative refracting index)” may mean that the paraxial refracting index of the lens element in Gaussian optics is positive (or negative). The description “An object-side (or image-side) surface of a lens element” may only include a specific region of that surface of the lens element where imaging rays are capable of passing through that region, namely the clear aperture of the surface. The aforementioned imaging rays can be classified into two types, chief ray Lc and marginal ray Lm. Taking a lens element depicted in  FIG. 1  as an example, the lens element may be rotationally symmetric, where the optical axis I may be the axis of symmetry. The region A of the lens element may be defined as “a portion in a vicinity of the optical axis”, and the region C of the lens element may be defined as “a portion in a vicinity of a periphery of the lens element”. Besides, the lens element may also have an extending portion E extended radially and outwardly from the region C, namely the portion outside of the clear aperture of the lens element. The extending portion E may be used for physically assembling the lens element into an optical imaging lens system. Under normal circumstances, the imaging rays may not pass through the extending portion E because those imaging rays only pass through the clear aperture. The structures and shapes of the aforementioned extending portion E are only examples for technical explanation, the structures and shapes of lens elements should not be limited to these examples. Note that the extending portions of the lens element surfaces depicted in the following embodiments are partially omitted. 
     The following criteria are provided for determining the shapes and the portions of lens element surfaces set forth in the present specification. These criteria mainly determine the boundaries of portions under various circumstances including the portion in a vicinity of the optical axis, the portion in a vicinity of a periphery of a lens element surface, and other types of lens element surfaces such as those having multiple portions. 
       FIG. 1  is a radial cross-sectional view of a lens element. Before determining boundaries of those aforesaid portions, two referential points may be defined first, central point and transition point. The central point of a surface of a lens element may be a point of intersection of that surface and the optical axis. The transition point may be a point on a surface of a lens element, where the tangent line of that point may be perpendicular to the optical axis. Additionally, if multiple transition points appear on one single surface, then these transition points may be sequentially named along the radial direction of the surface with numbers starting from the first transition point. For instance, the first transition point (closest one to the optical axis), the second transition point, and the Nth transition point (farthest one to the optical axis within the scope of the clear aperture of the surface). The portion of a surface of the lens element between the central point and the first transition point may be defined as the portion in a vicinity of the optical axis. The portion located radially outside of the Nth transition point (but still within the scope of the clear aperture) may be defined as the portion in a vicinity of a periphery of the lens element. In some embodiments, there are other portions existing between the portion in a vicinity of the optical axis and the portion in a vicinity of a periphery of the lens element; the numbers of portions depend on the numbers of the transition point(s). In addition, the radius of the clear aperture (or a so-called effective radius) of a surface may be defined as the radial distance from the optical axis I to a point of intersection of the marginal ray Lm and the surface of the lens element. 
     Referring to  FIG. 2 , determining the shape of a portion is convex or concave may depend on whether a collimated ray passing through that portion converges or diverges. That is, while applying a collimated ray to a portion to be determined in terms of shape, the collimated ray passing through that portion may be bent and the ray itself or its extension line may eventually meet the optical axis. The shape of that portion may be determined by whether the ray or its extension line meets (intersects) the optical axis (focal point) at the object-side or image-side. For instance, if the ray itself intersects the optical axis at the image side of the lens element after passing through a portion, i.e. the focal point of this ray is at the image side (see point R in  FIG. 2 ), the portion may be determined as having a convex shape. On the contrary, if the ray diverges after passing through a portion, the extension line of the ray intersects the optical axis at the object side of the lens element, i.e. the focal point of the ray is at the object side (see point M in  FIG. 2 ), that portion may be determined as having a concave shape. Therefore, referring to  FIG. 2 , the portion between the central point and the first transition point has a convex shape, the portion located radially outside of the first transition point has a concave shape, and the first transition point is the point where the portion having a convex shape changes to the portion having a concave shape, namely the border of two adjacent portions. Alternatively, there is another way to determine whether a portion in a vicinity of the optical axis has a convex or concave shape by referring to the sign of an “R” value, which is the (paraxial) radius of curvature of a lens surface. The R value may be used in optical design software such as Zemax and CodeV. The R value usually appears in the lens data sheet in the software. For an object-side surface, positive R may mean that the object-side surface is convex, and negative R means that the object-side surface is concave. Conversely, for an image-side surface, positive R may mean that the image-side surface is concave, and negative R may mean that the image-side surface is convex. The result found by using this method should be consistent as by using the other way mentioned above, which may determine surface shapes by referring to whether the focal point of a collimated ray is at the object side or the image side. 
     For none transition point cases, the portion in a vicinity of the optical axis may be defined as the portion between 0-50% of the effective radius (radius of the clear aperture) of the surface, whereas the portion in a vicinity of a periphery of the lens element may be defined as the portion between about 50% to about 100% of effective radius (radius of the clear aperture) of the surface. 
     Referring to the first example depicted in  FIG. 3 , only one transition point, namely a first transition point, may appear within the clear aperture of the image-side surface of the lens element. Portion I may be a portion in a vicinity of the optical axis, and portion II may be a portion in a vicinity of a periphery of the lens element. The portion in a vicinity of the optical axis may be determined as having a concave surface due to the R value at the image-side surface of the lens element is positive. The shape of the portion in a vicinity of a periphery of the lens element may be different from that of the radially inner adjacent portion, i.e. the shape of the portion in a vicinity of a periphery of the lens element may be different from the shape of the portion in a vicinity of the optical axis; the portion in a vicinity of a periphery of the lens element may have a convex shape. 
     Referring to the second example depicted in  FIG. 4 , a first transition point and a second transition point may exist on the object-side surface (within the clear aperture) of a lens element. In which portion I is the portion in a vicinity of the optical axis, and portion III is the portion in a vicinity of a periphery of the lens element. The portion in a vicinity of the optical axis has a convex shape because the R value at the object-side surface of the lens element is positive. The portion in a vicinity of a periphery of the lens element (portion III) has a convex shape. What is more, there may be another portion having a concave shape existing between the first and second transition point (portion II). 
     Referring to a third example depicted in  FIG. 5 , no transition point exists on the object-side surface of the lens element. In this case, the portion between about 0% to about 50% of the effective radius (radius of the clear aperture) may be determined as the portion in a vicinity of the optical axis, and the portion between about 50% to about 100% of the effective radius may be determined as the portion in a vicinity of a periphery of the lens element. The portion in a vicinity of the optical axis of the object-side surface of the lens element may be determined as having a convex shape due to its positive R value, and the portion in a vicinity of a periphery of the lens element may be determined as having a convex shape as well. 
     In the present disclosure, examples of an optical imaging lens which is a prime lens are provided. Example embodiments of an optical imaging lens may comprise an aperture stop, a first lens element, a second lens element, a third lens element and a fourth lens element, each of the lens elements may comprise refracting index, an object-side surface facing toward an object side and an image-side surface facing toward an image side and a central thickness defined along the optical axis. These lens elements may be arranged sequentially from the object side to the image side along an optical axis, and example embodiments of the lens may comprise no other lenses having refracting index beyond the four lens elements. In an example embodiment: the object-side surface of the first lens element may comprise a convex portion in a vicinity of a periphery of the first lens element, and the image-side surface of the first lens element may comprise a convex portion in a vicinity of the periphery of the first lens element, the second lens element has negative refracting index, and the object-side surface of the second lens element may comprise a concave portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the second lens element, the third lens element has positive refracting index, and the object-side surface of the third lens element may comprise a concave portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the third lens element, and the image-side surface thereof may comprise a convex portion in a vicinity of the periphery of the third lens element, the image-side surface of the fourth lens element may comprise a concave portion in a vicinity of the optical axis and a convex portion in a vicinity of a periphery of the fourth lens element, the optical imaging lens may comprise no other lenses having refracting index beyond the four lens elements, and the central thickness of the second lens element is represented by T2, the central thickness of the fourth lens element is represented by T4, an air gap between the third lens element and the fourth lens element along the optical axis is represented by G34, a sum of the central thicknesses of all four lens elements is represented by ALT, and T2, T4, G34 and ALT satisfy the inequalities:
         ALT/T2≦5.4 Inequality (1); and   (T2+T4)/G34≦4.0 Inequality (2).       

     In some embodiments, the lens elements may be designed in light of the optical characteristics and the length of the optical imaging lens. For example, the convex portion in a vicinity of a periphery of the first lens element formed on the object-side surface thereof and the convex portion in a vicinity of a periphery of the first lens element formed on the image-side surface thereof may assist in collecting light, these characters along with the aperture stop positioned before the object-side surface of the first lens element may assist in shortening the length of the optical imaging lens. Together with the negative refracting index of the second lens element, the concave portion in a vicinity of the optical axis and the concave portion in a vicinity of a periphery of the second lens element formed on the object-side surface thereof, the positive refracting index of the third lens element, the concave portion in a vicinity of the optical axis and the concave portion in a vicinity of a periphery of the third lens element formed on the object-side surface thereof, the convex portion in a vicinity of a periphery of the third lens element formed on the image-side surface thereof, the concave portion in a vicinity of the optical axis and the convex portion in a vicinity of a periphery of the fourth lens element formed on the image-side surface thereof, the curvature of field and distortion may be eliminated. Further, together with the convex portion in a vicinity of the optical axis and the convex portion in a vicinity of a periphery of the second lens element formed on the image-side surface thereof may assist in promoting the imaging quality. 
     To shorten the length of the optical imaging lens, the lens elements are required for a shorter thickness; however, considering both the difficulty to assembly the optical imaging lens and imaging quality, the optical imaging lens may be better configured if it satisfies aforesaid Inequalities (1) and (2). Further, the optical imaging lens may be better configured if it satisfies aforesaid Inequalities (4), (6), (8), (9) and/or (11) to carry out great optical characters, short length, as well as feasibility. Preferably, the value of ALT/T2 may be within 3.8˜5.4, the value of (T2+T4)/G34 may be within 2.3˜4.0, the value of (G23+G34)/T4 may be within 1.2˜2.2, the value of (T1+T2)/G12 may be within 3.3˜4.8, the value of ALT/G12 may be within 7.0˜10.0 which may be further less than 9.2 to assist in shortening the length of the optical imaging lens, the value of (T3+T4)/G12 may be within 3.7˜5.0, and the value of T1/G12 may be within 1.7˜2.9. 
     To shorten the length of the optical imaging lens, the air gaps between the lens elements are required for shorter distances, and the optical imaging lens may be better configured if it satisfies: AAG/G12≦6.0 which preferably may be further within 2.8˜6.0, and/or AAG/T4≦2.7 which preferably may be further within 1.8˜2.7. 
     The length of the air gaps and the thickness of the lens elements may be shortened to achieve a short length of the optical imaging lens. However, considering the difficulty of assembling the lens elements and the imaging quality, it may be helpful to satisfy at least one of the limitations with respect to the ratio between a thickness of the lens element, an air gap or a focusing length of the optical imaging lens as follows to configure the optical imaging lens well: EFL/T1≧5.5, EFL/G23≧7.3, EFL/(G23+G34)≧4.5, and/or EFL/(T1+T4)≧3.1. Preferably, the value of EFL/T1 may be further within 5.5˜7.3, the value of EFL/G23 may be further within 7.3˜10.5, the value of EFL/(G23+G34) may be further within 4.5˜6.0, and the value of EFL/(T1+T4) may be further within 3.1˜4.2. 
     In light of the unpredictability in an optical system, in the present disclosure, satisfying these inequality listed above may preferably shortening the length of the optical imaging lens, lowering the f-number, enlarging the shot angle, promoting the imaging quality and/or increasing the yield in the assembly process. 
     When implementing example embodiments, more details about the convex or concave surface could be incorporated for one specific lens element or broadly for plural lens elements to enhance the control for the system performance and/or resolution, for example, the image-side surface of the second lens element may comprise a convex portion in a vicinity of the optical axis and a concave portion in a vicinity of a periphery of the second lens element. It is noted that the details listed here could be incorporated in example embodiments if no inconsistency occurs. 
     Several exemplary embodiments and associated optical data will now be provided for illustrating example embodiments of optical imaging lens with good optical characteristics and a shortened length. Reference is now made to  FIGS. 6-9 .  FIG. 6  illustrates an example cross-sectional view of an optical imaging lens 1 having four lens elements of the optical imaging lens according to a first example embodiment.  FIG. 7  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 1 according to an example embodiment.  FIG. 8  illustrates an example table of optical data of each lens element of the optical imaging lens 1 according to an example embodiment.  FIG. 9  depicts an example table of aspherical data of the optical imaging lens 1 according to an example embodiment. 
     As shown in  FIG. 6 , the optical imaging lens 1 of the present embodiment may comprise, in order from an object side A1 to an image side A2 along an optical axis, an aperture stop  100 , a first lens element  110 , a second lens element  120 , a third lens element  130  and a fourth lens element  140 . A filtering unit  150  and an image plane  160  of an image sensor are positioned at the image side A2 of the optical lens 1. Each of the first, second, third, fourth lens elements  110 ,  120 ,  130 ,  140  and the filtering unit  150  may comprise an object-side surface  111 / 121 / 131 / 141 / 151  facing toward the object side A1 and an image-side surface  112 / 122 / 132 / 142 / 152  facing toward the image side A2. The example embodiment of the filtering unit  150  illustrated may be an IR cut filter (infrared cut filter) positioned between the fourth lens element  140  and an image plane  160 . The filtering unit  150  may selectively absorb light with specific wavelength from the light passing optical imaging lens 1. For example, IR light may be absorbed, and this will prohibit the IR light which is not seen by human eyes from producing an image on the image plane  160 . 
     Please noted that during the normal operation of the optical imaging lens 1, the distance between any two adjacent lens elements of the first, second, third and fourth lens elements  110 ,  120 ,  130 ,  140  may be an unchanged value, i.e. the optical imaging lens 1 may be a prime lens. 
     Exemplary embodiments of each lens element of the optical imaging lens 1 which may be constructed by plastic material will now be described with reference to the drawings. 
     An example embodiment of the first lens element  110  may have a positive refracting index. The object-side surface  111  may be a convex surface comprising a convex portion  1111  in a vicinity of the optical axis and a convex portion  1112  in a vicinity of a periphery of the first lens element  110 . The image-side surface  112  may comprise a concave portion  1121  in a vicinity of the optical axis and a convex portion  1122  in a vicinity of the periphery of the first lens element  110 . 
     An example embodiment of the second lens element  120  may have negative refracting index. The object-side surface  121  may be a concave surface comprising a concave portion  1211  in a vicinity of the optical axis and a concave portion  1212  in a vicinity of a periphery of the second lens element  120 . The image-side surface  122  may be a concave surface comprising a concave portion  1221  in a vicinity of the optical axis and a concave portion  1222  in a vicinity of the periphery of the second lens element  120 . 
     An example embodiment of the third lens element  130  has positive refracting index. The object-side surface  131  may be a concave surface comprising a concave portion  1311  in a vicinity of the optical axis and a concave portion  1312  in a vicinity of a periphery of the third lens element  130 . The image-side surface  132  may be a convex surface comprising a convex portion  1321  in a vicinity of the optical axis and a convex portion  1322  in a vicinity of the periphery of the third lens element  130 . 
     An example embodiment of the fourth lens element  140  may have negative refracting index. The object-side surface  141  may comprise a convex portion  1411  in a vicinity of the optical axis and a concave portion  1412  in a vicinity of a periphery of the fourth lens element  140 . The image-side surface  142  may comprise a concave portion  1421  in a vicinity of the optical axis and a convex portion  1422  in a vicinity of the periphery of the fourth lens element  140 . 
     In example embodiments, air gaps may exist between the lens elements  110 ,  120 ,  130 ,  140 , the filtering unit  150  and the image plane  160  of the image sensor. For example,  FIG. 1  illustrates the air gap d1 existing between the first lens element  110  and the second lens element  120 , the air gap d2 existing between the second lens element  120  and the third lens element  130 , the air gap d3 existing between the third lens element  130  and the fourth lens element  140 , the air gap d4 existing between the fourth lens element  140  and the filtering unit  150  and the air gap d5 existing between the filtering unit  150  and the image plane  160  of the image sensor. However, in other embodiments, any of the aforesaid air gaps may or may not exist. For example, the profiles of opposite surfaces of any two adjacent lens elements may correspond to each other, and in such situation, the air gap may not exist. The air gap d1 is denoted by G12, the air gap d2 is denoted by G23, the air gap d3 is denoted by G34 and the sum of d1, d2 and d3 is denoted by AAG. 
       FIG. 8  depicts the optical characteristics of each lens elements in the optical imaging lens 1 of the present embodiment, and please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  111  of the first lens element  110  to the image plane  160  along the optical axis may be about 4.454 mm, and the image height may be about 2.94 mm. 
     The aspherical surfaces, including the object-side surface  111  and the image-side surface  112  of the first lens element  110 , the object-side surface  121  and the image-side surface  122  of the second lens element  120 , the object-side surface  131  and the image-side surface  132  of the third lens element  130 , the object-side surface  141  and the image-side surface  142  of the fourth lens element  140  are all defined by the following aspherical formula: 
               Z   ⁡     (   Y   )       =           Y   2     R     /     (     1   +       1   -       (     1   +   K     )     ⁢       Y   2       R   2               )       +       ∑     i   =   1     n     ⁢       a     2   ⁢           ⁢   i       ×     Y     2   ⁢           ⁢   i                   
wherein, Y represents the perpendicular distance between the point of the aspherical surface and the optical axis; Z represents the depth of the aspherical surface (the perpendicular distance between the point of the aspherical surface at a distance Y from the optical axis and the tangent plane of the vertex on the optical axis of the aspherical surface); R represents the radius of curvature of the surface of the lens element; K represents a conic constant; and a 2i  represents an aspherical coefficient of 2i th  level. The values of each aspherical parameter are shown in  FIG. 9 .
 
     Please refer to  FIG. 7 , part (a), longitudinal spherical aberration of the optical imaging lens in the present embodiment is shown in the coordinate in which the horizontal axis represents focus and the vertical axis represents field of view, and  FIG. 7 , part (b), astigmatism aberration of the optical imaging lens in the present embodiment in the sagittal direction is shown in the coordinate in which the horizontal axis represents focus and the vertical axis represents image height, and  FIG. 7 , part (c), astigmatism aberration in the tangential direction of the optical imaging lens in the present embodiment is shown in the coordinate in which the horizontal axis represents focus and the vertical axis represents image height, and  FIG. 7 , part (d), distortion aberration of the optical imaging lens in the present embodiment is shown in the coordinate in which the horizontal axis represents percentage and the vertical axis represents image height. The curves of different wavelengths (470 nm, 555 nm, 650 nm) are closed to each other. This represents off-axis light with respect to these wavelengths is focused around an image point. From the vertical deviation of each curve shown therein, the offset of the off-axis light relative to the image point may be within about ±0.05 mm. Therefore, the present embodiment improves the longitudinal spherical aberration with respect to different wavelengths. For astigmatism aberration in the sagittal direction, the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm, for astigmatism aberration in the tangential direction, the focus variation with respect to the three wavelengths in the whole field falls within ±0.08 mm, and the variation of the distortion aberration may be within about ±2.5%. 
     Reference is now made to  FIGS. 10-13 .  FIG. 10  illustrates an example cross-sectional view of an optical imaging lens 2 having four lens elements of the optical imaging lens according to a second example embodiment.  FIG. 11  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 2 according to the second example embodiment.  FIG. 12  shows an example table of optical data of each lens element of the optical imaging lens 2 according to the second example embodiment.  FIG. 13  shows an example table of aspherical data of the optical imaging lens 2 according to the second example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 2, for example, reference number  231  for labeling the object-side surface of the third lens element  230 , reference number  232  for labeling the image-side surface of the third lens element  230 , etc. 
     As shown in  FIG. 10 , the optical imaging lens 2 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  200 , a first lens element  210 , a second lens element  220 , a third lens element  230  and a fourth lens element  240 . 
     The differences between the second embodiment and the first embodiment may include the radius of curvature, thickness of each lens element, the distance of each air gap, aspherical data, related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  241 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  211 ,  221 ,  231  facing to the object side A1 and the image-side surfaces  212 ,  222 ,  232 ,  242  facing to the image side A2, may be similar to those in the first embodiment. Here and all the embodiments below, for clearly showing the drawings of the present embodiment, only the surface shapes which are different from that in the first embodiment are labeled. Specifically, for the configuration of the concave/convex shape of the object-side surface  241 , the difference between the present embodiment and the first embodiment may include a convex portion  2412  in a vicinity of a periphery of the fourth lens element  240  formed on the object-side surface  241  thereof. Please refer to  FIG. 12  for the optical characteristics of each lens elements in the optical imaging lens 2 of the present embodiment, and please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  211  of the first lens element  210  to the image plane  260  along the optical axis may be about 4.327 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 11 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 11 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 11 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 11 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the HFOV of the optical imaging lens 2 may be greater than that in the first embodiment, and the length of the optical imaging lens 2 may be shorter. 
     Reference is now made to  FIGS. 14-17 .  FIG. 14  illustrates an example cross-sectional view of an optical imaging lens 3 having four lens elements of the optical imaging lens according to a third example embodiment.  FIG. 15  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 3 according to the third example embodiment.  FIG. 16  shows an example table of optical data of each lens element of the optical imaging lens 3 according to the third example embodiment.  FIG. 17  shows an example table of aspherical data of the optical imaging lens 3 according to the third example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 3, for example, reference number  331  for labeling the object-side surface of the third lens element  330 , reference number  332  for labeling the image-side surface of the third lens element  330 , etc. 
     As shown in  FIG. 14 , the optical imaging lens 3 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  300 , a first lens element  310 , a second lens element  320 , a third lens element  330  and a fourth lens element  340 . 
     The differences between the third embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  341 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  311 ,  321 ,  331  facing to the object side A1 and the image-side surfaces  312 ,  322 ,  332 ,  342  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the object-side surface  341 , the difference between the present embodiment and the first embodiment may include a convex portion  3412  in a vicinity of a periphery of the fourth lens element  340  formed on the object-side surface  341  thereof. Please refer to  FIG. 16  for the optical characteristics of each lens elements in the optical imaging lens 3 of the present embodiment, and please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  311  of the first lens element  310  to the image plane  360  along the optical axis may be about 4.408 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 15 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 15 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 15 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 15 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 3 may be shorter, and the distortion aberration of the optical imaging lens 3 may be less. 
     Reference is now made to  FIGS. 18-21 .  FIG. 18  illustrates an example cross-sectional view of an optical imaging lens 4 having four lens elements of the optical imaging lens according to a fourth example embodiment.  FIG. 19  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 4 according to the fourth embodiment.  FIG. 20  shows an example table of optical data of each lens element of the optical imaging lens 4 according to the fourth example embodiment.  FIG. 21  shows an example table of aspherical data of the optical imaging lens 4 according to the fourth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 4, for example, reference number  431  for labeling the object-side surface of the third lens element  430 , reference number  432  for labeling the image-side surface of the third lens element  430 , etc. 
     As shown in  FIG. 18 , the optical imaging lens 4 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  400 , a first lens element  410 , a second lens element  420 , a third lens element  430  and a fourth lens element  440 . 
     The differences between the fourth embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  441 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  411 ,  421 ,  431  facing to the object side A1 and the image-side surfaces  412 ,  422 ,  432 ,  442  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the object-side surface  441 , the difference between the present embodiment and the first embodiment may include a convex portion  4412  in a vicinity of a periphery of the fourth lens element  440  formed on the object-side surface  441  thereof. Please refer to  FIG. 20  for the optical characteristics of each lens elements in the optical imaging lens 4 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  411  of the first lens element  410  to the image plane  460  along the optical axis may be about 4.393 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 19 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 19 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.06 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 19 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 19 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 4 may be shorter, and the distortion aberration of the optical imaging lens 4 may be less. 
     Reference is now made to  FIGS. 22-25 .  FIG. 22  illustrates an example cross-sectional view of an optical imaging lens 5 having four lens elements of the optical imaging lens according to a fifth example embodiment.  FIG. 23  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 5 according to the fifth embodiment.  FIG. 24  shows an example table of optical data of each lens element of the optical imaging lens 5 according to the fifth example embodiment.  FIG. 25  shows an example table of aspherical data of the optical imaging lens 5 according to the fifth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 5, for example, reference number  531  for labeling the object-side surface of the third lens element  530 , reference number  532  for labeling the image-side surface of the third lens element  530 , etc. 
     As shown in  FIG. 22 , the optical imaging lens 5 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  500 , a first lens element  510 , a second lens element  520 , a third lens element  530  and a fourth lens element  540 . 
     The differences between the fifth embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  511 ,  521 ,  531 ,  541  facing to the object side A1 and the image-side surfaces  512 ,  522 ,  532 ,  542  facing to the image side A2, may be similar to those in the first embodiment. Please refer to  FIG. 24  for the optical characteristics of each lens elements in the optical imaging lens 5 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  511  of the first lens element  510  to the image plane  560  along the optical axis may be about 4.402 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 23 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 23 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 23 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 23 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 5 may be shorter, the distortion aberration of the optical imaging lens 5 may be less, and the HFOV of the optical imaging lens 5 may be greater. 
     Reference is now made to  FIGS. 26-29 .  FIG. 26  illustrates an example cross-sectional view of an optical imaging lens 6 having four lens elements of the optical imaging lens according to a sixth example embodiment.  FIG. 27  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 6 according to the sixth embodiment.  FIG. 28  shows an example table of optical data of each lens element of the optical imaging lens 6 according to the sixth example embodiment.  FIG. 29  shows an example table of aspherical data of the optical imaging lens 6 according to the sixth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 6, for example, reference number  631  for labeling the object-side surface of the third lens element  630 , reference number  632  for labeling the image-side surface of the third lens element  630 , etc. 
     As shown in  FIG. 26 , the optical imaging lens 6 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  600 , a first lens element  610 , a second lens element  620 , a third lens element  630  and a fourth lens element  640 . 
     The differences between the sixth embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  641 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  611 ,  621 ,  631  facing to the object side A1 and the image-side surfaces  612 ,  622 ,  632 ,  642  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the object-side surface  641 , the difference between the present embodiment and the first embodiment may include a convex portion  6412  in a vicinity of a periphery of the fourth lens element  640  formed on the object-side surface  641  thereof. Please refer to  FIG. 28  for the optical characteristics of each lens elements in the optical imaging lens 6 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  611  of the first lens element  610  to the image plane  660  along the optical axis may be about 4.366 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 27 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 27 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 27 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 27 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 6 may be shorter and the HFOV of the optical imaging lens 6 may be greater. 
     Reference is now made to  FIGS. 30-33 .  FIG. 30  illustrates an example cross-sectional view of an optical imaging lens 7 having four lens elements of the optical imaging lens according to a seventh example embodiment.  FIG. 31  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 7 according to the seventh embodiment.  FIG. 32  shows an example table of optical data of each lens element of the optical imaging lens 7 according to the seventh example embodiment.  FIG. 33  shows an example table of aspherical data of the optical imaging lens 7 according to the seventh example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 7, for example, reference number  731  for labeling the object-side surface of the third lens element  730 , reference number  732  for labeling the image-side surface of the third lens element  730 , etc. 
     As shown in  FIG. 30 , the optical imaging lens 7 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  700 , a first lens element  710 , a second lens element  720 , a third lens element  730  and a fourth lens element  740 . 
     The differences between the seventh embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  741 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  711 ,  721 ,  731  facing to the object side A1 and the image-side surfaces  712 ,  722 ,  732 ,  742  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the object-side surface  741 , the difference between the present embodiment and the first embodiment may include a convex portion  7412  in a vicinity of a periphery of the fourth lens element  740  formed on the object-side surface  741  thereof. Please refer to  FIG. 32  for the optical characteristics of each lens elements in the optical imaging lens 7 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  711  of the first lens element  710  to the image plane  760  along the optical axis may be about 4.453 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 31 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 31 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 31 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 31 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 7 may be shorter. 
     Reference is now made to  FIGS. 34-37 .  FIG. 34  illustrates an example cross-sectional view of an optical imaging lens 8 having four lens elements of the optical imaging lens according to a eighth example embodiment.  FIG. 35  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 8 according to the eighth embodiment.  FIG. 36  shows an example table of optical data of each lens element of the optical imaging lens 8 according to the eighth example embodiment.  FIG. 37  shows an example table of aspherical data of the optical imaging lens 8 according to the eighth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 8, for example, reference number  831  for labeling the object-side surface of the third lens element  830 , reference number  832  for labeling the image-side surface of the third lens element  830 , etc. 
     As shown in  FIG. 34 , the optical imaging lens 8 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  800 , a first lens element  810 , a second lens element  820 , a third lens element  830  and a fourth lens element  840 . 
     The differences between the eighth embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  841 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  811 ,  821 ,  831  facing to the object side A1 and the image-side surfaces  812 ,  822 ,  832 ,  842  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the object-side surface  841 , the difference between the present embodiment and the first embodiment may include a convex portion  8412  in a vicinity of a periphery of the fourth lens element  840  formed on the object-side surface  841  thereof. Please refer to  FIG. 36  for the optical characteristics of each lens elements in the optical imaging lens 8 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  811  of the first lens element  810  to the image plane  860  along the optical axis may be about 4.404 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 35 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 35 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 35 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 35 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 8 may be shorter, and the HFOV of the optical imaging lens 8 may be greater. 
     Reference is now made to  FIGS. 38-41 .  FIG. 38  illustrates an example cross-sectional view of an optical imaging lens 9 having four lens elements of the optical imaging lens according to a ninth example embodiment.  FIG. 39  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 9 according to the ninth embodiment.  FIG. 40  shows an example table of optical data of each lens element of the optical imaging lens 9 according to the ninth example embodiment.  FIG. 41  shows an example table of aspherical data of the optical imaging lens 9 according to the ninth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 9, for example, reference number  931  for labeling the object-side surface of the third lens element  930 , reference number  932  for labeling the image-side surface of the third lens element  930 , etc. 
     As shown in  FIG. 38 , the optical imaging lens 9 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  900 , a first lens element  910 , a second lens element  920 , a third lens element  930  and a fourth lens element  940 . 
     The differences between the ninth embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the image-side surface  922 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  911 ,  921 ,  931 ,  941  facing to the object side A1 and the image-side surfaces  912 ,  932 ,  942  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the image-side surface  922 , the difference between the present embodiment and the first embodiment may include a convex portion  9221  in a vicinity of the optical axis formed on the image-side surface  922  of the second lens element  920 . Please refer to  FIG. 40  for the optical characteristics of each lens elements in the optical imaging lens 9 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  911  of the first lens element  910  to the image plane  960  along the optical axis may be about 4.409 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 39 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 39 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 39 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 39 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 9 may be shorter, and the HFOV of the optical imaging lens 9 may be greater. 
     Reference is now made to  FIGS. 42-45 .  FIG. 42  illustrates an example cross-sectional view of an optical imaging lens 10 having four lens elements of the optical imaging lens according to a tenth example embodiment.  FIG. 43  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 10 according to the tenth embodiment.  FIG. 44  shows an example table of optical data of each lens element of the optical imaging lens 10 according to the tenth example embodiment.  FIG. 45  shows an example table of aspherical data of the optical imaging lens 10 according to the tenth example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 10, for example, reference number  1031  for labeling the object-side surface of the third lens element  1030 , reference number  1032  for labeling the image-side surface of the third lens element  1030 , etc. 
     As shown in  FIG. 42 , the optical imaging lens 10 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  1000 , a first lens element  1010 , a second lens element  1020 , a third lens element  1030  and a fourth lens element  1040 . 
     The differences between the tenth embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  1041  and the image-side surface  1022 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  1011 ,  1021 ,  1031  facing to the object side A1 and the image-side surfaces  1012 ,  1032 ,  1042  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the image-side surface  1022 , the difference between the present embodiment and the first embodiment may include a convex portion  10221  in a vicinity of the optical axis formed on the image-side surface  1022  of the second lens element  1020 ; for the configuration of the concave/convex shape of the object-side surface  1041 , the difference between the present embodiment and the first embodiment may include a convex portion  10412  in a vicinity of a periphery of the fourth lens element  1040  formed on the object-side surface  1041  thereof. Please refer to  FIG. 44  for the optical characteristics of each lens elements in the optical imaging lens 10 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  1011  of the first lens element  1010  to the image plane  1060  along the optical axis may be about 4.404 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 43 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 43 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 43 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 43 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the length of the optical imaging lens 10 may be shorter, and the HFOV of the optical imaging lens 10 may be greater. 
     Reference is now made to  FIGS. 46-49 .  FIG. 46  illustrates an example cross-sectional view of an optical imaging lens 11 having four lens elements of the optical imaging lens according to an eleventh example embodiment.  FIG. 47  shows example charts of longitudinal spherical aberration and other kinds of optical aberrations of the optical imaging lens 11 according to the eleventh embodiment.  FIG. 48  shows an example table of optical data of each lens element of the optical imaging lens 11 according to the eleventh example embodiment.  FIG. 49  shows an example table of aspherical data of the optical imaging lens 11 according to the eleventh example embodiment. The reference numbers labeled in the present embodiment are similar to those in the first embodiment for the similar elements, but here the reference numbers are initialed with 11, for example, reference number  1131  for labeling the object-side surface of the third lens element  1130 , reference number  1132  for labeling the image-side surface of the third lens element  1130 , etc. 
     As shown in  FIG. 46 , the optical imaging lens 11 of the present embodiment, in an order from an object side A1 to an image side A2 along an optical axis, may comprise an aperture stop  1100 , a first lens element  1110 , a second lens element  1120 , a third lens element  1130  and a fourth lens element  1140 . 
     The differences between the eleventh embodiment and the first embodiment may include the radius of curvature and thickness of each lens element, the distance of each air gap, aspherical data and related optical parameters, such as back focal length, and the configuration of the concave/convex shape of the object-side surface  1141 , but the configuration of the concave/convex shape of surfaces, comprising the object-side surfaces  1111 ,  1121 ,  1131 ,  1141  facing to the object side A1 and the image-side surfaces  1112 ,  1122 ,  1132 ,  1142  facing to the image side A2, may be similar to those in the first embodiment. Specifically, for the configuration of the concave/convex shape of the object-side surface  1141 , the difference between the present embodiment and the first embodiment may include a convex portion  11412  in a vicinity of a periphery of the fourth lens element  1140  formed on the object-side surface  1141  thereof. Please refer to  FIG. 48  for the optical characteristics of each lens elements in the optical imaging lens 11 of the present embodiment, please refer to  FIG. 50  for the values of T1, T2, T3, T4, G12, G23, G34, AAG, ALT, EFL, BFL, ALT/T2, (T2+T4)/G34, AAG/G12, (G23+G34)/T4, AAG/T4, (T1+T2)/G12, EFL/G23, ALT/G12, (T3+T4)/G12, EFL/T1, T1/G12, ALT/G12, EFL/(G23+G34) and EFL/(T1+T4) of the present embodiment. 
     The distance from the object-side surface  1111  of the first lens element  1110  to the image plane  1160  along the optical axis may be about 4.459 mm and the image height may be about 2.94 mm. 
     As the longitudinal spherical aberration shown in  FIG. 47 , part (a), the offset of the off-axis light relative to the image point may be within about ±0.05 mm. As the astigmatism aberration in the sagittal direction shown in  FIG. 47 , part (b), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.04 mm. As the astigmatism aberration in the tangential direction shown in  FIG. 47 , part (c), the focus variation with respect to the three wavelengths in the whole field may fall within about ±0.08 mm. As shown in  FIG. 47 , part (d), the variation of the distortion aberration may be within about ±2.5%. 
     Compared with the first embodiment, the optical imaging lens 11 may be easier to make, and the HFOV of the optical imaging lens 11 may be greater. 
     Please refer to  FIG. 50 , which shows the values of parameters of all eleven embodiments. 
     Reference is now made to  FIG. 51 , which illustrates an example structural view of a first embodiment of mobile device  20  applying an aforesaid optical imaging lens. The mobile device  20  may comprise a housing  21  and a photography module  22  positioned in the housing  21 . Examples of the mobile device  20  may be, but are not limited to, a mobile phone, a camera, a tablet computer, a personal digital assistant (PDA), etc. 
     As shown in  FIG. 51 , the photography module  22  may comprise an aforesaid optical imaging lens with four lens elements, which may be a prime lens and for example the optical imaging lens 1 of the first embodiment, a lens barrel  23  for positioning the optical imaging lens 1, a module housing unit  24  may suitable for positioning the lens barrel  23 , a substrate  162  for positioning the module housing unit  24 , and an image sensor  161  which may be positioned on the substrate  162  and at an image side of the optical imaging lens 1. The image plane  160  may be formed on the image sensor  161 . 
     In some other example embodiments, the structure of the filtering unit  150  may be omitted. In some example embodiments, the housing  21 , the lens barrel  23 , and/or the module housing unit  24  may be integrated into a single component or assembled by multiple components. In some example embodiments, the image sensor  161  used in the present embodiment is directly attached to a substrate  162  in the form of a chip on board (COB) package, and such package is different from traditional chip scale packages (CSP) since COB package does not require a cover glass before the image sensor  161  in the optical imaging lens 1. Aforesaid exemplary embodiments are not limited to this package type and could be selectively incorporated in other described embodiments. 
     The four lens elements  110 ,  120 ,  130 ,  140  are positioned in the lens barrel  23  in the way of separated by an air gap between any two adjacent lens elements. 
     The module housing unit  24  may comprise a lens backseat  2401  for positioning the lens barrel  23  and an image sensor base  2406  positioned between the lens backseat  2401  and the image sensor  161 . The lens barrel  23  and the lens backseat  2401  are positioned along a same axis I-I′, and the lens backseat  2401  is close to the outside of the lens barrel  23 . The image sensor base  2406  is exemplarily close to the lens backseat  2401  here. The image sensor base  2406  could be optionally omitted in some other embodiments of the present disclosure. 
     Because the length of the optical imaging lens 1 may be merely about 4.454 mm, the size of the mobile device  20  may be quite small. Therefore, the embodiments described herein meet the market demand for smaller sized product designs. 
     Reference is now made to  FIG. 52 , which shows another structural view of a second embodiment of mobile device  20 ′ applying the aforesaid optical imaging lens 1. One difference between the mobile device  20 ′ and the mobile device  20  may be the lens backseat  2401  comprising a first seat unit  2402 , a second seat unit  2403 , a coil  2404  and a magnetic unit  2405 . The first seat unit  2402  is close to the outside of the lens barrel  23 , and positioned along an axis I-I′, and the second seat unit  2403  is around the outside of the first seat unit  2402  and positioned along with the axis I-I′. The coil  2404  may be positioned between the first seat unit  2402  and the inside of the second seat unit  2403 . The magnetic unit  2405  may be positioned between the outside of the coil  2404  and the inside of the second seat unit  2403 . 
     The lens barrel  23  and the optical imaging lens 1 positioned therein are driven by the first seat unit  2402  for moving along the axis I-I′. The rest structure of the mobile device  20 ′ may be similar to the mobile device  20 . 
     Similarly, because the length of the optical imaging lens 1, 4.454 mm, may be shortened, the mobile device  20 ′ may be designed with a smaller size and meanwhile good optical performance may still provided. Therefore, the present embodiment meets the demand of small sized product design and the request of the market. 
     According to above illustration, the longitudinal spherical aberration, astigmatism aberration both in the sagittal direction and tangential direction and distortion aberration in all embodiments are meet user term of a related product in the market. The off-axis light with respect to three different wavelengths (470 nm, 555 nm, 650 nm) is focused around an image point and the offset of the off-axis light relative to the image point is well controlled with suppression for the longitudinal spherical aberration, astigmatism aberration both in the sagittal direction and tangential direction and distortion aberration. The curves of different wavelengths are closed to each other, and this represents that the focusing for light having different wavelengths is good to suppress chromatic dispersion. In summary, lens elements are designed and matched for achieving good imaging quality. 
     While various embodiments in accordance with the disclosed principles been described above, it should be understood that they are presented by way of example only, and are not limiting. Thus, the breadth and scope of exemplary embodiment(s) should not be limited by any of the above-described embodiments, but should be defined only in accordance with the claims and their equivalents issuing from this disclosure. Furthermore, the above advantages and features are provided in described embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages. 
     Additionally, the section headings herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of such claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings herein.