KR20090089234A - Image capturing lens system - Google Patents

Abstract

An image capturing lens system is provided to make a post-process simple by dividing a light passed through a phase modulation mask into an X-component and an Y-component. In an image capturing lens system, a pick-up lens group comprises a plurality of lenses. The pick-up lens group is composed of a high power lens(L1), a first meniscus lens(L2), a second meniscus lens(L3), and a correction lens(L4). A convex side of the first meniscus lens is faced to the object side, and the convex side of the second meniscus lens is faced to the image side. The first meniscus lens reduces spherical aberration of lens as a low-powered negative corrector.

Description

Imaging lens system {Image capturing lens system}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging lens system, and more particularly, to an imaging lens system for obtaining a clear image from a short distance to a long distance.

In general, a fixed focus optical system deteriorates the point spread function as the object approaches the camera, so that the focus is not properly established. In order to solve this problem, an optical system that performs an auto focusing function has been proposed. However, such an optical system requires the transfer of a lens or an image sensor for automatic focusing, and a driving device for this is essential. Therefore, the optical apparatus to which the auto focusing optical system is applied has a problem that not only increases the weight but also enlarges the size. Therefore, an apparatus or method for obtaining an image having excellent image quality over a wide focal length through image processing without providing a driving device for automatic focusing has been proposed.

The present invention proposes an imaging lens system which makes the modulation transfer function of light transmitted through the imaging lens system constant.

An imaging lens system according to an aspect of the present invention includes an imaging lens group including a plurality of lenses; A phase located within a group of imaging lenses that satisfies a phase mask function defined for the x- and y-axes to make the MTF (modulation transfer function) constant, regardless of the distance of light incidence, angle of incidence, and wavelength of light. Mask, wherein the phase mask function is Φ (x) = Ax (x / xmax) ^Bx and Φ (y) = Ay (y / ymax) ^By , where x is the position of the x-axis of light passing through the phase mask Where y represents the position of the y-axis of light passing through the phase mask, xmax represents the x-axis maximum position of the light passing through the phase mask, and ymax is the maximum position of the y-axis of light passing through the phase mask.

According to an embodiment of the present invention, in the phase mask function, Ax and Ay may have values of 0.007 to 0.012 mm, and Bx and By may have values of 2.4 to 2.9 mm.

In addition, the imaging lens group has a shooting distance of 0.18 m to infinity, a focal length f 'of 5 mm, a high F number of F / # of 2 or more, and a field of view (Fov). Can be designed to be 46.5deg (± 23.25.deg). The imaging lens group may include a high power lens, a first meniscus lens facing the convex face toward the object side, a second meniscus lens facing the convex face toward the image side, and a correcting lens.

In addition, the imaging lens system according to an embodiment of the present invention further includes an aperture positioned in the imaging lens group, and the aperture may be positioned such that lenses included in the imaging lens group are symmetrically disposed with respect to the surface of the aperture. have.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. In the following description of the present invention, if it is determined that detailed descriptions of related well-known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

1 is a diagram illustrating an imaging lens system according to an exemplary embodiment of the present invention.

The imaging lens system according to an embodiment of the present invention includes a phase mask PM so as to make the MTF constant regardless of the incident distance of the light, the incident angle of the light, and the wavelength of the light. The MTF shows how the resolution chart projected through the lens reproduces the original original compared to the original resolution chart. If the MTF is made constant regardless of the distance of incidence, the angle of incidence, and the wavelength of light, the image captured through the lens can be restored to the original image by a single MTF. Can simplify post-processing.

Referring to FIG. 1, an imaging lens system according to an exemplary embodiment includes an imaging lens group L1, L2, L3, and L4 including a plurality of lenses and a phase mask PM positioned in the lens group. do.

The imaging lens group includes four lenses, that is, a high power lens L1, a first meniscus lens L2 with a convex side facing the object side, a second meniscus lens L3 with a convex side facing the image side, and a correcting lens. (L4) may be included.

The high power lens L1 collects all the light coming from the object, and the first meniscus lens L2 is a low-powered negative corrector that reduces spherical aberration of the reds. It serves to reduce. The aspherical shape of the thick correction lens L4 located in the middle of the iris and the sensor serves to reduce field aberration.

In addition, the four lenses L1, L2, L3, and L4 of the imaging lens group may be designed to generate a high quality image with respect to a midpoint of an operating shooting distance of light. That is, the imaging lens groups L1, L2, L3, and L4 excluding the phase mask PM may be designed to generate a higher quality image by minimizing wave aberration with respect to an intermediate point of the incident distance of light. .

The imaging lenses L1, L2, L3, and L4 according to an embodiment of the present invention have a uniform MTF at a shooting distance of 0.18 m to infinity, a focal length f 'of 5 mm, and an F number. It can be designed so that (F / #) is higher than 2, and Fov is 46.5deg (± 23.25.deg). Where deg is the distance from the center of the lens. For example, 0deg means light passing through the center of the lens, and 23.5deg means light passing through the lens boundary.

The phase mask PM may be designed to satisfy a phase mask function defined for the x-axis and the y-axis in order to keep the MTF constant regardless of the incident distance of the light, the incident angle of the light, and the wavelength of the light.

According to an embodiment of the present invention, the phase mask function may be represented by Equations 1 and 2 below.

[Equation 1]

Φ (x) = Ax (x / xmax) ^Bx

Here, x represents the position of the x-axis of the light passing through the phase mask PM, and xmax represents the maximum position of the x-axis of the light passing through the phase mask PM. Ax represents the amplitude of the function, and Bx represents the power of the function.

[Equation 2]

Φ (y) = Ay (y / ymax) ^By

Here, y represents the position of the y-axis of the light passing through the phase mask PM, and ymax represents the maximum position of the axis of the light passing through the phase mask PM. Ay represents the amplitude of the function, By represents the power of the function.

According to an embodiment of the present invention, Ax and Ay may have values of 0.007 to 0.012 mm as similar values, and Bx and By may have values of 2.4 to 2.9 mm as similar values. That is, the imaging lens system can be optimized so that the MTF is constant in a range where Ay is 0.010 mm and has a positive and negative error value of about 0.002 mm, By is 2.7 mm and a positive and negative error value of about 0.2 mm.

Although not clearly shown in FIG. 1, the display device may further include a stop positioned in the imaging lens group according to the exemplary embodiment. The iris may be positioned such that lenses included in the imaging lens group are symmetrically disposed with respect to the surface of the iris. The aberration reduction design is possible by positioning the aperture within the imaging lens group without placing the aperture between the lens and the object as usual.

FIG. 2 is a table showing a configuration of the imaging lens system shown in FIG. 1.

FIG. 2 shows information about each side shown in FIG. 1.

In FIG. 2, OBJ STANDARD represents an object to be imaged. In FIG. 2, standard represents a spherical surface, Evenasph represents an aspherical surface, and Binary 2 represents a surface for diffraction. Comment is a remarks column, Radius is the curvature of each side, and Thickness is the thickness up to the next side of each side. Glass represents a material. Diameter is the size of each face, and Conic is a constant that represents the shape of each face.

Considering where the thickness is zero, each side corresponds to each side of the imaging lens system including the lens of FIG.

For example, the high power lens L1 has a radius of 1.536499 mm, a thickness of 1.033312 mm, a material of FPL-51, a diameter of 2.76855 mm, and a conic constant of -0.09540922.

3A and 3B are diagrams showing detailed data of the imaging lens system shown in FIG.

3A and 3B show polynomial aspheric coefficients that determine the shape of each face. Polynomial aspherical coefficients exist only in aspherical surfaces. And since the polynomial aspherical surface is rotationally symmetric, only even coefficients exist.

For example, face 1 of the first lens has coeff on r2 of 0, coeff on r4 of 0.00058976302, coeff on r6 of -5.4235834e-005, and coeff on r8 of zero.

As described above, Binary 2 is a curved surface exhibiting diffraction as described above, and each coefficient representing the aspherical surface represents a polynomial aspheric coefficient, and additional information representing variation of diffraction, that is, maximum term, maximum rad ap, term on P to 2, Term on P to 4.

In (7) (SODC_02.DLL) SODC_02 ~ 0.01 ^ 2.5, acx, apx, acy, apy represent a function of the phase modulation mask, acx corresponds to Ax described above, acy corresponds to Ay described above, apx corresponds to Bx, and apy corresponds to By. The table of FIG. 3A shows the case where Ax and Ay are 0.01 mm and Bx and By are 2.5 mm.

According to an embodiment of the present invention, an image signal having a constant MTF may be obtained regardless of a photographing distance of a light source, an angle incident on a lens of light, and a wavelength. Therefore, in the post-processing process of processing an image, an image may be processed by applying a constant MTF, thereby simplifying the post-processing process.

In addition, according to an embodiment of the present invention, a phase mask may be positioned between the lenses to easily correct aberration of the lens. In addition, since light passing through the phase modulation mask of the present invention can be separated into an X-axis component and a Y-axis component, image processing may be performed by performing one-dimensional signal processing twice instead of two-dimensional signal processing in a post-processing process. As a result, the complexity of the post-treatment process can be significantly reduced.

The above description is only one embodiment of the present invention, and those skilled in the art may implement the present invention in a modified form without departing from the essential characteristics of the present invention. Therefore, the scope of the present invention should not be limited to the above-described examples, but should be construed to include various embodiments within the scope equivalent to those described in the claims.

1 is a view showing an imaging lens system according to an embodiment of the present invention,

FIG. 2 is a table showing the configuration of the imaging lens system shown in FIG. 1;

3A and 3B are diagrams showing detailed data of the imaging lens system shown in FIG.

Claims (5)

An imaging lens group including a plurality of lenses; A phase mask positioned within the imaging lens group and satisfying a phase mask function defined for the x-axis and the y-axis to make the MTF constant regardless of the incident distance of the light, the incident angle of the light, and the wavelength of the light, The phase mask function is Φ (x) = Ax (x / xmax) ^Bx and Φ (y) = Ay (y / ymax) ^By , where x represents the position of the x-axis of light passing through the phase mask, y represents the position of the y-axis of the light passing through the phase mask, xmax represents the maximum position of the x-axis of the light passing through the phase mask, ymax is the maximum position of the y-axis of the light passing through the phase mask Imaging lens system. The method of claim 1, In the phase mask function, Ax and Ay have values of 0.007 to 0.012 mm, and Bx and By have values of 2.4 to 2.9 mm. The method of claim 1, The imaging lens group has a shooting distance of 0.18 m to infinity, a focal length f 'of 5 mm, a high F number of F / # of 2 or more, and a Fov of 46.5 deg (± 23.25). .deg). The method of claim 1, The imaging lens group includes a high power lens, a first meniscus lens facing a convex face toward the object side, a second meniscus lens facing a convex face toward the image side, and a correcting lens. The method of claim 1, Further comprising a stop located in the imaging lens group, And the aperture is positioned such that lenses included in the imaging lens group are symmetrically disposed with respect to a surface of the aperture.

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