KR100921147B1 - Lens Module - Google Patents

Abstract

The lens module according to the embodiment includes a first lens group having a negative magnification including a concave lens; A second lens group of positive magnification including a meniscus type lens; A third lens group of positive magnification including a lens having at least one surface aspherical; And a filter for blocking infrared rays.

Lens module

Description

Lens Module

Embodiments relate to a lens module used in a camera module using a high resolution image sensor.

Recently, a camera module for a communication terminal, a digital still camera (DSC, digital still camera), a camcorder, and a PC camera (image pickup device included with a personal computer) have been studied in relation to an image pickup system. In order for the camera module associated with such an image pickup system to obtain an image, the most important component is a lens module for forming an image.

Since the image pickup system requires high performance in resolution and image quality, the configuration of the lens is complicated. However, in the case of constitutional and optical complexity, the size of the image pickup system is increased, making it difficult to miniaturize and thin.

The lens module according to the embodiment includes a first lens group having a negative magnification including a concave lens; A second lens group of positive magnification including a meniscus type lens; A third lens group of positive magnification including a lens having at least one surface aspherical; And a filter for blocking infrared rays.

The lens module according to the embodiment may realize miniaturization of the lens module using only five lenses including an infrared cut filter.

In addition, spherical aberration, coma, and astigmatism can be corrected using an aspherical lens, and the first, second, third, and fourth lenses 10, 20, 30, and 40 are all meniscus-type lenses. Using it, it can be seen that a high resolution lens module can be implemented.

The lens module according to the embodiment includes a first lens group having a negative magnification including a concave lens; A second lens group of positive magnification including a meniscus type lens; A third lens group of positive magnification including a lens having at least one surface aspherical; And a filter for blocking infrared rays.

Hereinafter, a lens module according to an embodiment will be described in detail with reference to the accompanying drawings.

1 is a side cross-sectional view schematically showing an internal structure of a lens module according to an embodiment.

As shown in FIG. 1, the lens module according to the embodiment may include a first lens group 100, a second lens group 200, a third lens group 300, a filter 400, and a light receiving element 500. It is made to include.

In order to obtain a subject image, light corresponding to the image information of the subject passes through the first lens group 100, the second lens group 200, the third lens group 300, and the filter 400. Incident on 500.

The first lens group 100 is fixed, and by moving the second lens group 200 and the third lens group 300 in the optical axis direction, the second lens group 200 has a zooming function. The third lens group 300 may implement a zoom and compensator function.

The first lens group 100 having a negative magnification includes the first lens 10 having a negative refractive index.

In this case, the first lens 10 may be an aspherical lens having at least one surface aspherical and may be formed of an FCD1_HOYA lens which is a glass lens of a meniscus type.

The second lens group 200 having a positive magnification includes an aperture 15, a second lens 20 having a refractive index of positive power, and a third lens 30 having a negative refractive index. Adjust the zoom ratio of the lens module.

In this case, at least one surface of the second lens 20 and the third lens 30 is an aspherical lens, and the second lens 20 is a LAK8 lens which is a meniscus type glass lens. The third lens 30 may be formed of an EFDS1_HOYA lens which is a meniscus type glass lens.

The aperture 15 is disposed between the first lens 10 and the second lens 20, and adjusts a focal length by selectively converging the light incident from the first lens 10. Perform the function.

In addition, the diaphragm 15 is disposed between the first lens 10 and the second lens 20, thereby adjusting the CRA (Chief Ray Angle) to reduce the distortion aberration and to increase the ambient light ratio. .

In addition, vignetting may be performed on the R2 surface of the first lens 10 and the diaphragm 15 to control the light rays reaching the light receiving element 500, and to adjust the amount of light.

The third lens group 300 having a positive magnification is composed of a fourth lens 40 having a positive refractive index, and performs a zoom ratio adjustment and correction function of the lens module.

At least one surface of the fourth lens 40 may be an aspherical lens, and may be formed of a VC81 lens, which is a meniscus type glass lens.

The filter 400 may be an infrared cut filter.

The infrared cut filter functions to block radiant heat emitted from external light from being transmitted to the light receiving element 500.

That is, the infrared cut filter has a structure that transmits visible light and reflects infrared light to flow out.

The filter 400 may be formed of a BSC7_HOYA lens which is a glass lens.

The light receiving device 500 may be an image sensor that converts an optical signal corresponding to an object image into an electrical signal, and the image sensor may be a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor. have.

That is, since the filter 400 is composed of a total of five lenses, the overall length (height) of the lens module may be shortened, thereby miniaturizing the lens module.

In addition, since at least one surface of the first, second, third, and fourth lenses 10, 20, 30, and 40 is made of an aspherical surface, spherical aberration, comatic aberration, and astigmatism (astigmatism) can be corrected.

Because of this structure, the lens module can be formed without breaking the optical path by using a reflective material such as a prism or a mirror.

In addition, since the 2.7x zoom optical system can be implemented with a small number of lenses, the lens module can be miniaturized while maintaining the zoom performance.

In addition, by forming the first lens group 100 into one of the first lens 10 having a negative refractive index, it is possible to reduce the diameter of the lens and also reduce the lens diameter of the second lens group 200.

The lens module according to the embodiment has the optical characteristics as shown in Table 1 below.

Lens surface Surface type Bending Radius (mm) Thickness (mm) Remarks R1 Aspheric surface 11.5228 0.5 FCD1_HOYA R2 Aspheric surface 3.5011 5.2699 R3 Spherical ∞ 0.25 iris R4 Aspheric surface 1.7695 1.2207 LAK8 R5 Aspheric surface 6.5029 0.4 R6 Aspheric surface 9.8086 0.5105 EFDS1_HOYA R7 Aspheric surface 2.50 0.7235 R8 Aspheric surface -15.1426 1.2519 VC81 R9 Aspheric surface -3.80 1.2244 R10 Spherical ∞ 0.3 Filter (BSC7_HOYA) R11 Spherical ∞ 1.1522 filter R12 Spherical ∞ 0.0143 sensor

Table 2 below is aspherical coefficient values for the aspherical lens of the embodiment.

Lens surface K A B C D E R1 7.877 -2.639 × 10 ^-2 0.544 × 10 ^-2 -0.651 × 10 ^-3 0.391 × 10 ^-4 -0.842 × 10 ^-6 R2 -0.009 -0.031 0.595 × 10 ^-2 -0.541 × 10 ^-3 -0.142 × 10 ^-4 0.401 × 10 ^-5 R4 0.016 0.159 × 10 ^-2 0.630 × 10 ^-2 -0.560 × 10 ^-2 -0.399 × 10 ^-2 -0.708 × 10 ^-3 R5 -8.768 0.222 × 10 ^-1 1.791 × 10 ^-2 -0.265 × 10 ^-2 1.697 × 10 ^-2 -0.538 × 10 ^-2 R6 -464.277 0.066 × 10 ^-1 -0.087 × 10 ^-1 0.517 × 10 ^-1 -0.451 × 10 ^-1 0 R7 -12.172 0.780 × 10 ^-1 -0.554 × 10 ^-1 0.731 × 10 ^-2 0.640 × 10 ^-2 0 R8 -168.198 -0.100 × 10 ^-1 0.611 × 10 ^-3 0.106 × 10 ^-3 -0.235 × 10 ^-5 -0.479 × 10 ^-6 R9 -12.654 -0.272 × 10 ^-1 0.519 × 10 ^-2 -0.842 × 10 ^-3 0.939 × 10 ^-4 -0.404 × 10 ^-5

The aspherical coefficient values of Table 2 for the aspherical lens of the embodiment can be obtained from Equation 1 below.

Z = cY ² / [1+ {1- (K + 1) c ² Y ² } ^1/2 ] + A ₁ Y ⁴ + A ₂ Y ⁶ + A ₃ Y ⁸ + A ₄ Y ¹⁰ +.

Z: Distance from the vertex of the lens to the optical axis direction

c: basic curvature of the lens

Y: distance in the direction perpendicular to the optical axis

r: radius of curvature at the vertex of the lens

K: Conic constant

A1, A2, A3, A4: Aspheric constant

That is, spherical aberration, coma and astigmatism can be corrected by using the first, second, third and fourth lenses 10, 20, 30 and 40 having the above aspherical coefficient values.

Table 3 below shows the focus length FL for each lens of the embodiment.

lens Lens surface Focal Length (FL) First lens R1-R2 -10.30 mm (FL1) Second lens R4-R5 3.06 mm (FL2) Third lens R6 ~ R7 -3.72 mm (FL3) Fourth lens R8 ~ R9 6.42 mm (FL4) filter R10 ~ R11 ∞

The focal length of the lens according to the embodiment is not limited to Table 2, and may satisfy the following conditional expression. (Full focal length (FL) is the focal length at wide zoom.)

-3.0 <FL1 / FL <-2.5 [first lens]

1.0 <FL2 / FL <1.5 [second lens]

-1.2 <FL3 / FL <-0.7 [third lens]

1.5 <FL1 / FL <2.0 [the fourth lens]

2 to 4 show a zoom operation according to an embodiment.

FIG. 2 shows a wide zoom, FIG. 3 shows a middle zoom, and FIG. 4 shows positions and optical paths of respective lens groups when tele zooming is performed.

Table 4 below shows the distance between the first lens group 100, the second lens group 200, and the third lens group 300 when wide zoom, middle zoom, and tele zoom are performed.

Lens surface Wide zoom Middle zoom Tele zoom R2 ~ R3 5.27 (mm) 3.52 (mm) 0.66 (mm) R7-R8 0.72 (mm) 3.39 (mm) 6.07 (mm) R9 to R10 1.22 (mm) 0.29 (mm) 0.47 (mm)

In the zoom operation according to the embodiment, when the lens module is zoomed wide, the effective focal length (EFL) is 3.9 mm, the back focal length (BFL) is 1.152 mm, and the front focal length ( The front focal length is 1.727 mm, the F-number is 3.25, the height H is 2.4 mm, and the half angle is 32.2458 degrees.

When the lens module is middle zoomed, the effective focal length (EFL) is 6.07 mm, the rear focal length (BFL) is 1.144 mm, the front focal length is 1.9422 mm, the F number is 4.44, and the image height (H) is 2.4. mm, half view angle is 21.3438 degrees.

When the lens module is tele zoomed, the effective focal length (EFL) is 10.5 mm, the rear focal length (BFL) is 1.094 mm, the front focal length is 4.6155 mm, the F number is 6.11, and the image height (H) is 2.4. mm, half view angle is 13.0715 degrees.

That is, in the embodiment, the lens module may be applied to a sensor having a 1/4 inch size with a height H of 2.4 mm.

In addition, since the effective focal length is 3.9 mm in wide zoom and 10.5 mm in tele zoom, the lens module according to the embodiment may have 2.7 zoom.

5 to 13 are graphs illustrating aberration characteristics and MTF (Modulation Transfer Function) characteristics of the lens module according to the embodiment.

5 is an aberration characteristic when performing a wide zoom function, and FIGS. 6 and 7 are MTF characteristics when a wide zoom is performed.

8 is aberration characteristics when performing the middle zoom function, and FIGS. 9 and 10 are MTF characteristics when middle zoom is performed.

11 is aberration characteristics when performing the tele zoom function, and FIGS. 12 and 13 are MTF characteristics when the tele zoom is performed.

The aberration characteristics are shown in graphs of measuring Longitudinal Spherical Aber., Astigmatic Field Curves, and Distortion. As shown in FIGS. Since the values of the images appear adjacent to the axis in all the fields, it can be seen that the lens module according to the embodiment has excellent aberration characteristics.

6, 7, 9, 10, 12, and 13 show graphs of measuring MTF characteristics depending on a change in spatial frequencies (cycles / mm) of cycles per millimeter. It was.

The MTF is a ratio calculated by calculating the difference between the light from the original subject surface and the image formed after passing through the lens. The MTF is ideally '1', and the resolution decreases as the MTF value decreases.

6, 7, 9, 10, 12, and 13, since the MTF value is high, it can be seen that the lens module according to the embodiment has excellent optical performance.

14 to 19 show aberration characteristics due to tangential field curvature and sagittal field curvature according to each field band on the optical axis in the lens module according to the embodiment.

14 and 15 show a wide zoom function, FIGS. 16 and 17 show a middle zoom function, and FIGS. 18 and 19 show a meridion curve and a curved image curve when performing a tele zoom function. Is a graph showing aberration characteristics.

In the case of this embodiment, by using an aspherical lens and a meniscus type lens, as shown in Figs.

The lens module according to the above embodiment may realize miniaturization of the lens module using only five lenses including an infrared cut filter.

In addition, spherical aberration, coma, and astigmatism can be corrected using an aspherical lens, and the first, second, third, and fourth lenses 10, 20, 30, and 40 are all meniscus-type lenses. Using it, it can be seen that a high resolution lens module can be implemented.

Although the above description has been made based on the embodiments, these are merely examples and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains may not have been exemplified above without departing from the essential characteristics of the present embodiments. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 is a side cross-sectional view schematically showing an internal structure of a lens module according to an embodiment.

2 to 4 show a zoom operation according to an embodiment.

5 to 13 are graphs illustrating aberration characteristics and MTF (Modulation Transfer Function) characteristics of the lens module according to the embodiment.

14 to 19 are graphs illustrating aberration characteristics of tangential field curvature and sagittal field curvature in the lens module according to the embodiment.

Claims (7)

A first lens group having a negative magnification including the first lens as the concave lens; A second lens group of positive magnification including an aperture, a second lens, and a third lens, and including a meniscus type lens; A third lens group of positive magnification including a fourth lens having at least one surface aspherical; And A filter for blocking infrared rays, The first lens and the third lens have a negative refractive index, the second lens and the fourth lens have a positive power refractive index, In wide zoom, the focal length of the first lens relative to the total focal length (FL) -3.0 <focal length of first lens / FL <-2.5 [first lens] Lens module that satisfies the conditional formula. delete The method of claim 1, The second lens group and the third lens group move in an optical axis direction, and the second lens group performs a zooming function, and the third lens group performs a zooming function and a compensator function. Lens module. The method of claim 1, And at least one surface of the first, second, third and fourth lenses is aspheric. The method of claim 1, And the first, second, third and fourth lenses are made of a meniscus type lens. The method of claim 1, Wherein the first lens is an FCD1_HOYA lens, the second lens is an LAK8 lens, the third lens is an EFDS1_HOYA lens, and the fourth lens is a VC81 lens. The method of claim 1, Lens module for which the focal length of each lens with respect to the total focal length (FL) in the case of wide zoom meets the following conditional expression. 1.0 <focal length of second lens / FL <1.5 [second lens] -1.2 <focal length of third lens / FL <-0.7 [third lens] 1.5 <focal length of fourth lens / FL <2.0 [fourth lens]

Images