TWI504923B - Optical system - Google Patents

Description

Optical system

This invention relates to an optical system and, more particularly, to an optical system having six lenses.

In general, mobile communication devices such as mobile communication terminals, personal digital assistants, and smart phones have a variety of additional functions in addition to basic communication functions and increased use of diverse services provided by communication technologies.

In particular, the photographic module of the device in the mobile communication device has a constant demand for use as a plurality of focusing devices such as a high-definition video capturing device, an automatic focus adjusting device, and a QR code identifying device, except that a single focus is simply used for photography. increase.

In addition, as manufacturers gradually introduce smaller camera modules, mobile communication devices must have higher resolutions at the same time as price reduction, and the manufacturing cost of camera modules should be gradually reduced.

In order to reduce the unit price of the photographic module, it is preferable to reduce the manufacturing cost of the lens group constituting the optical system embedded in the photographic module. But, in order In order to satisfy the above conditions for improving the resolution, a glass lens having a high degree of optical efficiency should be used to constitute an optical system, but it is impossible to reduce the manufacturing cost of a photographic module composed of a plurality of expensive glass lenses.

Moreover, when using multiple glass lenses to overcome the problem of resolution, it is not easy to reduce the weight of the optical system.

In addition, Korean Patent Application Publication No. 2011-24872 is hereby incorporated by reference.

In view of this, the present invention has been made in order to overcome the disadvantages and problems caused by the aforementioned motion photography optical system. Accordingly, it is an object of the present invention to provide an optical system that achieves high resolution and reduces manufacturing costs by installing an optical system using six aspherical plastic lenses.

According to an aspect of the invention for achieving the object, an optical system is provided which sequentially includes, from an object side, a first lens having a positive refractive power and a convex side a second side lens having a negative refractive power; a third lens having a negative refractive power; a fourth lens having a positive refractive power; and a fifth lens having a fifth lens having a negative refractive power; a negative refractive power and an image side surface convex toward the image side; and a sixth lens having a negative refractive power and an image side surface of the concave image side.

Further, this optical system satisfies the following conditional expression for the condition of chromatic aberration correction: |V3-V2|<41 (Conditional 1)

Among them, V3 is the Abbe number of the third lens, and V2 is the Abbe number of the second lens.

In addition, this optical system satisfies the following conditional formula for the design conditions of this optical system: TTL/F<1.5 (Conditional 2)

Among them, TTL is the distance from the first lens to an image plane, and F is the focal length of the optical system as a whole.

Further, this optical system satisfies the following conditional expression regarding the miniaturization condition according to the focal length ratio of this optical system: 1<|F6/F|<6 (Conditional Formula 3)

Among them, F6 is the focal length of the sixth lens, and F is the focal length of the optical system as a whole.

Further, this optical system satisfies the following conditional expression regarding the miniaturization condition of the radius of curvature of the lens according to this optical system: 0 < (R7 + R10) / (R7 - R10) < 1.3 (Condition 4)

Wherein R7 is the radius of curvature of the object side of the fourth lens, and R10 is the radius of curvature of an upper surface of the fifth lens.

Further, this optical system satisfies the following conditional expression for the aberration correction condition of the optical system: |R7/F|<5 (Conditional Formula 5)

Where R7 is the radius of curvature of the object side of the fourth lens, F is light Learn the overall focal length of the system.

Further, this optical system satisfies the following conditional expression for the condition of chromatic aberration correction: |Nd2-Nd5|<0.11 (Conditional expression 6)

Among them, Nd2 is the refractive index of the second lens for the wavelength of the d line (587.6 nm), and Nd5 is the refractive index of the fifth lens for the wavelength of the d line (587.6 nm).

Further, this optical system satisfies the following conditional expression for the condition of spherical chromatic aberration correction of the optical system: F3/F<-5 (Conditional expression 7)

Among them, F3 is the focal length of the third lens, and F is the focal length of the optical system as a whole.

Further, the first to sixth lenses are, for example, plastic lenses, and the lenses of the first to sixth lenses are, for example, aspherical.

Furthermore, an optical filter may be further disposed between the sixth lens and the image plane, and the optical filter is formed by a cover glass plated with an infrared filter for excessively introducing light from the outside. Infrared blocking.

In order to better understand the above and other aspects of the present invention, the preferred embodiments are described below, and in conjunction with the drawings, the detailed description is as follows:

1-14‧‧‧The surface of the lens

L1-L6‧‧‧first to sixth lenses

OF‧‧‧Optical filter

15‧‧‧Image plane

Figure 1 is a lens arrangement of an optical system in accordance with a first embodiment of the present invention Configuration diagram.

Fig. 2 is a modulation conversion function (MTF) diagram of the optical system shown in Fig. 1.

Fig. 3 is an aberration diagram of the optical system shown in Table 1 and Fig. 1.

Fig. 4 is a configuration diagram of a lens arrangement of an optical system in accordance with a second embodiment of the present invention.

Fig. 5 is a modulation conversion function diagram of the optical system shown in Fig. 4.

Fig. 6 is an aberration diagram of the optical system shown in Tables 3 and 4.

Figure 7 is a configuration diagram of a lens arrangement of an optical system in accordance with a third embodiment of the present invention.

Fig. 8 is a diagram showing a modulation conversion function of the optical system shown in Fig. 7.

Fig. 9 is an aberration diagram of the optical system shown in Tables 5 and 7.

Figure 10 is a configuration diagram of a lens arrangement of an optical system in accordance with a third embodiment of the present invention.

Fig. 11 is a diagram showing a modulation conversion function of the optical system shown in Fig. 10.

Fig. 12 is an aberration diagram of the optical system shown in Tables 7 and 10.

A clear understanding of the operational effects will be apparent from the following detailed description and with reference to the accompanying drawings of the preferred embodiments. This operational effect includes a technical arrangement for achieving one of the optical systems in accordance with the present invention.

However, in the lens configuration diagrams of the following embodiments, the thickness, size and shape of the lens may be expanded for the sake of detailed explanation. In particular, the spherical or aspherical shape shown in the lens configuration diagram is for example only, and It is not intended to limit its implementation.

First, Fig. 1 is a configuration diagram of a lens arrangement of an optical system in accordance with a first embodiment of the present invention. As shown, the optical system of the present embodiment includes a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, a third lens L3 having a negative refractive power, and a positive refractive power. A fourth lens L4, a fifth lens L5 having a negative refractive power, and a sixth lens L6 having a negative refractive power.

In addition, the first lens L1 may have a shape having an object side surface convex toward the object side; the fifth lens L5 may also have a shape having an image side surface convex toward the image side; The sixth lens L6 may also have a shape having an image side surface on the concave image side.

In addition, an optical filter (OF) may be disposed between the sixth lens L6 and an image plane 15, and the optical filter OF is formed by a cover glass plated with an infrared filter for external use. Excessive infrared ray blocking in the introduced light.

Furthermore, in the optical system of the present invention, the first lens L1 to the sixth lens L6 may each be a plastic lens, and one or both sides of each of the first lens L1 to the sixth lens L6 may be aspherical.

At least one side of the constituent lenses of the optical system according to the present invention is aspherical, and the reason for making it aspherical is to improve the degree of freedom in design for facilitating aberration correction and mitigating manufacturing tolerances, and aberration correction includes Chromatic aberration correction. In addition, the reason why the first lens L1 to the sixth lens L6 are formed by the plastic lens is to configure an optical system that can be used for a mobile device, and even if the optical system includes a plurality of lenses, the weight can be made lighter; Compared to glass lenses, this optical system has aspherical manufacturing convenience and is mainly installed in mobile equipment. Set characteristics.

Meanwhile, as described above, the optical system of the present invention can perform aberration correction and achieve miniaturization by using a plurality of lenses, by the following conditional expressions 1 and 2. The conditional and operational effects will be described below.

|V3-V2|<41 (Conditional 1)

Among them, V3 is the Abbe number of the third lens L3 (Abbe number), and V2 is the Abbe number of the second lens L2.

Conditional Formula 1 is a condition for the chromatic aberration correction of this optical system. The chromatic aberration correction can be promoted by maintaining the difference in the Abbe number of the third lens L3 and the second lens L2 as small as a predetermined value. Here, when Conditional Formula 1 is satisfied, chromatic aberration can be reduced, and when it deviates from an upper limit of Conditional Formula 1, chromatic aberration may occur.

TTL/F<1.5 (Condition 2)

Among them, TTL is the distance from the first lens L1 to an image plane 15, and F is the focal length of the optical system as a whole.

The conditional expression 2 is a condition regarding the miniaturization according to the focal length ratio of the optical system, and the conditional expression 2 is a conditional expression of the ratio of the distance from the first lens L1 to the upper surface and the focal length of the entire optical system. Here, when it deviates from an upper limit of the conditional expression 2, it becomes difficult to manufacture a compact optical system and to satisfy a predetermined viewing angle required for the mobile device.

1<|F6/F|<6 (Conditional 3)

Among them, F6 is the focal length of the sixth lens L6, F is the optical system The focal length of the body.

The conditional expression 3 is a condition regarding miniaturization according to the focal length ratio of the optical system, and the conditional expression 3 is a conditional expression relating to the ratio of the focal length of the sixth lens L6 to the focal length of the entire optical system. Here, when it deviates from an upper limit of the conditional expression 3, it is difficult to satisfy the condition of the miniaturization because the refractive power of the integral optical system is reduced; when it deviates from a lower limit of the conditional expression 3, it is deviated from the telecentric (telecentric) It is difficult to correct distortion.

0<(R7+R10)/(R7-R10)<1.3 (Condition 4)

Among them, R7 is the radius of curvature of the object side surface of the fourth lens L4, and R10 is the radius of curvature of an upper surface of the fifth lens L5.

The conditional expression 4 is a condition for miniaturization of the radius of curvature of the lens of the optical system, and the conditional expression 4 is a conditional expression relating to the ratio of the sum of the curvature radii of the fourth lens L4 and the fifth lens L5 to the difference. Here, when it deviates from an upper limit of the conditional expression 4, it is difficult to achieve miniaturization, and since the effective diameter of the lens is large, the sensitivity of the lens also changes; when it deviates from a lower limit of the conditional expression 4, it is difficult The optical system is highly resolved.

|R7/F|<5 (Condition 5)

Among them, R7 is the radius of curvature of the object side surface of the fourth lens L4, and F is the focal length of the entire optical system.

The conditional expression 5 is a condition for aberration correction of the optical system, and the conditional expression 5 is a conditional expression relating to the ratio of the radius of curvature of the object side surface of the fourth lens L4 to the focal length of the entire optical system. Here, when it deviates from an upper limit of conditional expression 5, then High resolution is difficult to achieve because of the difficulty in aberration correction of the optical system.

|Nd2-Nd5|<0.11 (Condition 6)

Among them, Nd2 is the refractive index of the second lens L2 for the wavelength of the d line (587.6 nm), and Nd5 is the refractive index of the fifth lens L5 for the wavelength of the d line (587.6 nm).

The conditional expression 6 is a condition for chromatic aberration correction of the optical system, and the conditional expression 6 is a conditional expression relating to the difference in refractive index of the wavelength (587.6 nm) of the d-line of the second lens L2 and the fifth lens L5. Here, when Conditional Formula 6 is satisfied, high resolution of the optical system and chromatic aberration can be minimized.

F3/F<-5 (Condition 7)

Among them, F3 is the focal length of the third lens L3, and F is the focal length of the entire optical system.

The conditional expression 7 is a condition for the aspherical aberration correction of the optical system, and the conditional expression 7 is a conditional expression relating to the ratio of the focal length of the third lens L3 to the focal length of the entire optical system. Here, when it deviates from an upper limit of the conditional expression 5, it is difficult to achieve high resolution of the optical system because of the difficulty in correcting the aspherical aberration.

A compact, wide-angle optical system in accordance with the present invention will now be described in detail with reference to various embodiments.

As described above, the following first to fourth embodiments each include: a first lens L1 having a positive refractive power and an object side surface convex toward the object side; and a second lens L2 having a negative refractive power; a third lens L3 having a negative refractive power; a fourth lens L4 having a positive refractive power; and a fifth lens L5 having a fifth lens a negative refractive power and a convex side image side surface; and a sixth lens L6 having a negative refractive power and a concave image side image side surface; and an optical filter OF disposed on the sixth lens L6 Between an image plane 15 and an optical filter OF is formed by a cover glass plated with an infrared filter.

Furthermore, the first lens L1 to the sixth lens L6 are both formed by a plastic lens, and both sides of the lens are aspherical.

At this time, the aspheric surfaces used in the following respective examples were obtained in accordance with the known formula 1. The values of the conic constant K and the aspheric coefficients A, B, C, D, E, and F are expressed as a power of 10 followed by a value of E, for example, E+02 represents 10 ² , E-02 Represents 10 ^-2 .

Where Z is the distance from the end of the lens in the direction of the optical axis; Y is the distance perpendicular to the direction of the optical axis; c is the reciprocal of the radius of curvature at the end of the lens; K is the conic constant; and A, B, C , D, E, F are aspherical coefficients.

First embodiment

Table 1 below is a numerical example according to the first embodiment of the present invention. Fig. 1 is a configuration diagram of a lens arrangement of an optical system in accordance with a first embodiment of the present invention. Fig. 2 is a modulation transfer function (MTF) diagram of the optical system shown in Fig. 1. Fig. 3 is an aberration diagram of the optical system shown in Table 1 and Fig. 1.

In the first embodiment, the effective focal length F of the optical system as a whole is 4.09 mm. The distance TTL from the first lens L1 to the image plane is 5.0 mm. Further, the first to sixth lenses L1 to L6 are aspherical lenses.

Further, in the first embodiment, the focal length F6 of the sixth lens L6 is -5.98 mm, the refractive index of the second lens L2 for the wavelength of the d line (587.6 nm) is 1.6322, and the wavelength of the fifth lens L5 for the d line ( The refractive index of 587.6 nm) is 1.6349, and the focal length F3 of the third lens L3 is -100 mm.

In Table 1, the symbol * before the number of the surface indicates that it is aspherical. In the first embodiment, the lenses of the first lens L1 to the sixth lens L6 are aspherical on both sides.

Further, the numerical values of the aspherical coefficients according to the first embodiment of Formula 1 are listed in Table 2.

Second embodiment

Table 3 below lists numerical examples in accordance with the second embodiment of the present invention.

Further, Fig. 4 is a configuration diagram of a lens arrangement of an optical system in accordance with a second embodiment of the present invention. Fig. 5 is a modulation conversion function diagram of the optical system shown in Fig. 4. Fig. 6 is an aberration diagram of the optical system shown in Tables 3 and 4.

In the second embodiment, the focal length F of the entire optical system is 4.08 mm, and the distance TTL from the first lens L1 to the image plane 15 is 5.0 mm. Further, the first lens L1 to the sixth lens L6 are all aspherical plastic lenses.

Further, in the second embodiment, the focal length F6 of the sixth lens L6 is -4.45 mm, the refractive index of the second lens L2 for the wavelength of the d line (587.6 nm) is 1.6322, and the wavelength of the fifth lens L5 for the d line ( The refractive index of 587.6 nm) is 1.6349, and the focal length F3 of the third lens L3 is -100 mm.

In Table 3, the symbol * before the number of the surface indicates that it is aspherical. In the second embodiment, the lenses of the first lens L1 to the sixth lens L6 are aspherical on both sides.

Further, the numerical values of the aspherical coefficients according to the second embodiment of Formula 1 are as follows as shown in Table 4.

Third embodiment

Table 5 below lists numerical examples in accordance with the third embodiment of the present invention.

In the third embodiment, the focal length F of the optical system as a whole is 4.25 mm, and the distance TTL from the first lens L1 to the image plane is 5.15 mm. Further, the first lens L1 to the sixth lens L6 are all aspherical plastic lenses.

Further, in the third embodiment, the focal length F6 of the sixth lens L6 is -4.80 mm, the refractive index of the second lens L2 for the wavelength of the d line (587.6 nm) is 1.6322, and the wavelength of the fifth lens L5 for the d line ( The refractive index of 587.6 nm) is 1.5255, and the focal length F3 of the third lens L3 is -100 mm.

In Table 5, the symbol * before the number of the surface indicates that it is aspherical. In the first embodiment, the lenses of the first lens L1 to the sixth lens L6 are aspherical on both sides.

Further, the numerical values of the aspherical coefficients according to the third embodiment of Formula 1 are listed in Table 6.

Fourth embodiment

Table 7 below lists numerical examples in accordance with the fourth embodiment of the present invention.

In addition, FIG. 10 is an optical system according to a third embodiment of the present invention. Configuration diagram of the lens arrangement. Fig. 11 is a diagram showing a modulation conversion function of the optical system shown in Fig. 10. Fig. 12 is an aberration diagram of the optical system shown in Tables 7 and 10.

In the fourth embodiment, the focal length F of the entire optical system is 4.07 mm, and the distance TTL from the first lens L1 to the image plane 15 is 5.01 mm. Further, the first lens L1 to the sixth lens L6 are all aspherical plastic lenses.

Further, in the fourth embodiment, the focal length F6 of the sixth lens L6 is -23.26 mm, the refractive index of the second lens L2 for the wavelength of the d line (587.6 nm) is 1.6322, and the wavelength of the fifth lens L5 for the d line ( The refractive index of 587.6 nm) is 1.6349, and the focal length F3 of the third lens L3 is -24.42 mm.

In Table 7, the symbol * before the number of the surface indicates that it is aspherical. In the fourth embodiment, the lenses of the first lens L1 to the sixth lens L6 are aspherical on both sides.

Further, the numerical values of the aspherical coefficients according to the fourth embodiment of Formula 1 are as follows as shown in Table 8.

Meanwhile, the numerical series of the conditional expressions of the first to fourth embodiments are shown in Table 9.

As described above, the optical system according to the present invention is transmitted through an aspherical plastic lens. The six lenses formed can improve the efficiency of aberration correction and reduce the manufacturing cost, and can achieve high resolution requirements by minimizing chromatic aberration.

In addition, the present invention can also reduce the aberration by configuring the first and fourth lenses of the six lenses constituting the optical system to have a positive refractive power each to produce a high-resolution optical system. .

In conclusion, the present invention has been disclosed in the above preferred embodiments, and is not intended to limit the present invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

1-14‧‧‧The surface of the lens

L1-L6‧‧‧first to sixth lenses

OF‧‧‧Optical filter

15‧‧‧Image plane

Claims (11)

An optical system comprising, in order from an object side, a first lens having a positive refractive power and an object side surface, the object side surface protruding toward the object side; and a second lens having a negative refractive power; a third lens having a negative refractive power; a fourth lens having a positive refractive power; a fifth lens having a negative refractive power and an image side surface, the image side surface being convex toward an image side; A sixth lens having a negative refractive power and an image side surface, the image side surface of the sixth lens being concave toward the image side. The optical system of claim 1, wherein the optical system satisfies the following conditional formula for chromatic aberration correction conditions: |V3-V2|<41; wherein V3 is an Abbe number of the third lens (Abbe number), and V2 is the Abbe number of one of the second lenses. The optical system of claim 1, wherein the optical system satisfies the following conditional formula for the design condition of the optical system: TTL/F<1.5; wherein the TTL is from the first lens to an image plane Distance, F is the focal length of the optical system as a whole. The optical system of claim 1, wherein the optical system The following conditional expression regarding the miniaturization condition according to the focal length ratio of the optical system is satisfied: 1<|F6/F|<6; wherein F6 is the focal length of the sixth lens, and F is the focal length of the entire optical system. The optical system according to claim 1, wherein the optical system satisfies the following conditional formula regarding the miniaturization condition according to the radius of curvature of the lens of the optical system: 0 < (R7 + R10) / (R7 - R10) <1.3; wherein R7 is a radius of curvature of an object side surface of the fourth lens, and R10 is a radius of curvature of an upper surface of the fifth lens. The optical system of claim 1, wherein the optical system satisfies the following conditional condition for the aberration correction condition of the optical system: |R7/F|<5; wherein R7 is the object side of the fourth lens The radius of curvature, F is the focal length of the optical system as a whole. The optical system of claim 1, wherein the optical system satisfies the following conditional formula for chromatic aberration correction conditions: |Nd2-Nd5|<0.11; wherein Nd2 is the wavelength of the second lens for the d line The refractive index (587.6 nm), and Nd5 is the refractive index (587.6 nm) of the fifth lens for the wavelength of the d line. The optical system of claim 1, wherein the optical system The following conditional expression is satisfied for the condition of the spherical chromatic aberration correction of the optical system: F3/F<-5; wherein F3 is the focal length of the third lens, and F is the focal length of the entire optical system. The optical system of claim 1, wherein the first to sixth lenses are plastic lenses. The optical system of claim 1, wherein both sides of the first lens to both sides of the sixth lens are aspherical. The optical system of claim 1, further comprising: an optical filter disposed between the sixth lens and an image plane, wherein the optical filter is plated with an infrared filter. A cover glass is formed to block excessive infrared rays from the externally introduced light.