JP5003120B2 - Imaging lens and imaging apparatus - Google Patents

Description

  The present invention relates to a novel imaging lens and imaging apparatus. More specifically, the present invention relates to a compact and high-performance compact imaging lens suitable for a compact imaging device used in a mobile phone, a PC (Personal Computer), and the like, and an imaging apparatus using the imaging lens.

  In recent years, image pickup devices have been rapidly reduced in size and increased in pixel count, and in particular, image forming devices such as information terminal devices such as mobile phones and PCs have high imaging performance, low cost, and downsizing. It has been demanded. In recent years, there is a strong demand for reducing the height of the optical system in the optical axis direction (shortening the total length).

  However, at present, it is difficult to reduce the manufacturing and assembly tolerances in manufacturing. For example, when the optical system is designed to be small as a whole, the distance from the lens back, that is, the image side most protrusion on the final lens surface to the image sensor is maintained while maintaining the effective image circle diameter in consideration of conventional manufacturing tolerances. Ensuring it has emerged as a great demand and challenge. At the same time, the spatial margin allowed for the optical system is reduced, so that it is difficult to design surface shapes that can be used as ghost countermeasures and to install light-shielding components, contrary to the current situation where the degree of design freedom is narrowing. Increasing the height of the lens tends to increase the angle of incidence of light rays on the periphery of the image sensor surface. When using an imaging lens with a low profile in the imaging device, it is important to suppress the deterioration of shading, especially in terms of camera image quality. Has become a major issue.

  As an imaging lens used in such an imaging device, for example, there is one described in Patent Document 1. The configuration consists of a positive first power lens having a convex surface on the object side in order from the object side, a stop, a second positive power lens having a convex surface on the image side, and a negative shape having a concave shape on the image side in the vicinity of the paraxial axis. It consists of a third lens with a power of.

  The imaging lens described in Patent Document 1 can be composed entirely of resin lenses, thereby reducing costs and reducing the size while obtaining high image quality by using aspheric surfaces on each surface. I am trying.

JP 2005-91513 A

  By the way, in the imaging lens described in Patent Document 1, in the third lens, the vicinity of the optical axis of the image side surface has a concave shape, so it is difficult to obtain a long lens back. . The third lens adds positive power as it goes to the periphery, and has a wavy surface shape in which the peripheral portion of the image side surface protrudes to the image side rather than the vicinity of the optical axis. When multiple reflections of light occur between an image sensor represented by Charge-Coupled Device (CMOS) or complementary metal-oxide-semiconductor (CMOS) or an optical component between the lens and the image sensor, the harmful light Has a surface shape that is easily returned to the vicinity of the center of the image sensor, and there is a problem that a ghost attributed to this tends to occur.

  In view of the above-described problems, the present invention provides a small imaging lens that is small in size and high in performance, can be reduced in cost, and is less likely to cause ghosts, and an imaging apparatus using the imaging lens. This is the issue.

An imaging lens according to an embodiment of the present invention includes a first lens, a diaphragm, a second lens, and a third lens arranged from the object side to the image side, and the third lens is negative at the center. The image side surface has a flat surface or a convex shape with respect to the image side , and the first lens has a positive power and a convex surface on the object side. The second lens has a meniscus shape having a convex surface on the image side, and at least one of all the constituent lens surfaces has an aspherical surface. The following conditional expressions (1) to ( Satisfy 3).
(1) -∞ ≤ f3 / f ≤ -0.75
(2) 0.5 ≤ f1 / f ≤ 2.9
(3) | R31 | <| R32 |
However,
f: Focal length on the image side of the entire optical system
f1: Image side focal length of the first lens
f3: Image side focal length of the third lens
R31: Radius of curvature near the optical axis of the object side surface of the third lens
R32: radius of curvature near the optical axis of the image side surface of the third lens
And

The imaging device of the present invention is an imaging device including an imaging lens and an imaging element that converts an optical image formed by the imaging lens into an electrical signal, and the imaging lens is arranged from the object side to the image side. A first lens, a diaphragm, a second lens, and a third lens are arranged, and the third lens has a negative power at the center, a positive power at the periphery, and The image side surface has a flat or convex shape with respect to the image side , the first lens has a meniscus shape having a positive power and a convex surface on the object side, and the second lens has a convex surface on the image side. The lens has a meniscus shape, and at least one of all the constituent lens surfaces is aspherical, and satisfies the following conditional expressions (1) to (3).
(1) -∞ ≤ f3 / f ≤ -0.75
(2) 0.5 ≤ f1 / f ≤ 2.9
(3) | R31 | <| R32 |
However,
f: Focal length on the image side of the entire optical system
f1: Image side focal length of the first lens
f3: Image side focal length of the third lens
R31: Radius of curvature near the optical axis of the object side surface of the third lens
R32: radius of curvature near the optical axis of the image side surface of the third lens
And

  In the present invention, high image quality without shading deterioration and ghosting can be achieved, and a compact configuration can be achieved.

  The best mode for carrying out the imaging lens and the imaging apparatus of the present invention will be described below.

  First, the imaging lens of the present invention will be described.

  The imaging lens of the present invention is configured by arranging a first lens, a diaphragm, a second lens, and a third lens from the object side to the image side, and the third lens has negative power at the center. The peripheral portion has a positive power, and the image side surface has a flat or convex shape with respect to the image side.

  Therefore, the imaging lens of the present invention can achieve high image quality with no shading deterioration and no ghosting, and can be made compact.

  Since the third lens has a negative power at the center and a positive power at the periphery, the incident angle of the light beam on the periphery of the image sensor becomes too large while ensuring an effective image circle diameter. And shading deterioration can be suppressed.

  In addition, the image side surface of the third lens is close to the light receiving surface of the image sensor and is easily affected by multiple reflections from stray light and incident rays within the angle of view, so it is likely to be an indirect light source for ghosts. In the imaging lens of the present invention, the image side surface of the third lens is flat or convex with respect to the image side. That is, since the vicinity of the optical axis is flat or convex and has a shape that does not have an inflection point that protrudes toward the image side as it goes to the periphery, the reflection angle of harmful light that becomes a ghost can be easily directed to the outside of the imaging surface. It becomes a shape, and a ghost can be reduced compared with the conventional thing which made the optical axis vicinity concave shape.

In the imaging lens of the present invention, the first lens has a meniscus shape having a positive power and a convex surface on the object side, and the second lens has a meniscus shape having a convex surface on the image side. At least one of the constituent lens surfaces is aspherical, and satisfies the following conditional expressions (1) to (3).
(1) -∞ ≤ f3 / f ≤ -0.75
(2) 0.5 ≤ f1 / f ≤ 2.9
(3) | R31 | <| R32 |
However,
f: Focal length on the image side of the entire optical system
f1: Image side focal length of the first lens
f3: Image side focal length of the third lens
R31: Radius of curvature near the optical axis of the object side surface of the third lens
R32: The radius of curvature in the vicinity of the optical axis of the image plane side surface of the third lens.

  Conditional expression (1) is a conditional expression that defines the power of the third lens. If it is out of the range defined by conditional expression (1), the field curvature aberration is likely to be deteriorated, the flange back is shortened and the space length required on the image sensor side is easily infringed, and distortion aberration is also caused. Touches in the positive direction.

  Conditional expression (2) is a conditional expression that defines the power of the first lens. The first lens is mainly responsible for correcting spherical aberration. If the upper limit value of conditional expression (2) is exceeded, off-axis spherical aberration will move to the over side and coma will deteriorate at the same time. If the lower limit value of conditional expression (2) is not reached, the spherical aberration will be exposed to the under side, and the field curvature will also be greatly affected to the under side. It becomes difficult.

The problems in downsizing the imaging lens are that the image quality is deteriorated and the design difficulty of the imaging apparatus is increased. The deterioration in image quality mainly includes shading deterioration and ghosting, and at the same time, it becomes difficult to perform optical design that secures a lens back. In order to improve these, it is desirable that the third lens satisfies all of the following configurations a.) To c.) Particularly in the positive / negative aperture configuration.
a.) Satisfy conditional expression (3) b.) On the image side surface, the vicinity of the optical axis has a flat or convex shape and bends toward the object side as it goes to the periphery c.) Light The power in the vicinity of the axis is negative and it has a positive power as it goes to the periphery. A.) When it is assumed that the imaging device is assembled, It is based on the premise that a minimum space is secured, and means an advantageous configuration when the lens back length is relatively long. Here, the “minimum space in the direction of the optical axis necessary on the image sensor device side” means, for example, an interval in the direction of the optical axis composed of an image sensor device or a configuration necessary for maintaining the quality of image quality, Furthermore, it means the length to which adjustment margins necessary for adjusting the focus with the lens component are added.

  When the conditional expression (3) is satisfied, the position of the surface on the image plane side of the third lens is relatively on the object side with respect to the rear principal point of the third lens. Easy to design to be relatively wide. In this specification, the term “lens back” refers to a spatial distance from the point or surface closest to the image sensor to the surface of the image sensor on the final surface of the lens.

  c.) is effective in suppressing the deterioration of shading determined by the correlation between the lens and the image sensor when the imaging device is completed, and the chief ray incident angle to the peripheral image height from the center of the image sensor toward the edge is It has the effect of retaining a relatively sharp angle.

  b.) is a state where the imaging device is completed, and when a strong light beam reaches the cover glass or the imaging device of the imaging device, harmful light reflected by these surfaces reaches the image side surface of the third lens, Furthermore, it is effective as a countermeasure against ghosts that occur when harmful light reflected by the image-side surface of the third lens reaches the image pickup device surface again, and the image-side surface of the third lens is substantially flat to convex. As a result, harmful light from the image sensor side is easily released in the peripheral direction.

  In addition, curvature of field and astigmatism can be well suppressed by positioning the stop in front of the second meniscus lens having a convex shape on the image side.

In the imaging lens according to the embodiment of the present invention, it is desirable to satisfy any or some of the following conditional expressions (4) to (8).
(4) 0.5 ≤ | f2 / f |
(5) -1> R32 or 10 <R32
(6) 0.50 ≤ H / f ≤ 1.3
(7) 0.41 ≤ tanθ ≤ 0.79
(8) 0.17 <R11 / f <0.34
However,
f2: Image side focal length of the second lens
R11: radius of curvature near the optical axis of the object side surface of the first lens H: optical total length θ: a half angle of view at the maximum image height.

  Conditional expression (4) is a conditional expression that defines the power of the second lens. If the condition of the conditional expression (4) is not satisfied, the curvature of field will shift to the over side, and in particular, the chromatic aberration of magnification will increase. As a result, will the total optical length be extended even if correction is performed on other surfaces? Or, the eccentricity sensitivity becomes high and the optical system is difficult to manufacture.

  Conditional expression (5) is a conditional expression that defines the radius of curvature of the image side surface of the third lens. If -1> R32 is not satisfied, the curvature of field and distortion are likely to largely touch in the plus direction, making correction difficult. If 10 <R32 cannot be satisfied, correction of chromatic aberration of magnification becomes difficult, and the peripheral surface tends to protrude toward the image side rather than the vicinity of the optical axis. Reflecting on the image side surface of the lens, it becomes easy to return to the image pickup device again, and a ghost is likely to occur due to this.

  Conditional expression (6) is a conditional expression that defines the ratio between the power and the total length of the entire optical system. If the upper limit value of conditional expression (6) is exceeded, it will be difficult to obtain a sufficient effective image circle diameter in addition to the increase in total length. On the other hand, if the value is below the lower limit, for example, a load is applied to the power distribution of the first lens and the second lens and the eccentricity sensitivity is increased, so that the defect rate at the time of manufacture increases and the lens back is shortened.

  Conditional expression (7) is a conditional expression that defines the half field angle at the maximum image height, that is, the maximum incident angle of the chief ray, and defines the field angle range of this single focus lens.

  Conditional expression (8) is a conditional expression that defines the radius of curvature of the object side surface of the first lens. If the upper limit of conditional expression (8) is exceeded, spherical aberration and curvature of field will touch the underside. If the lower limit is not reached, off-axis spherical aberration moves to the over side, and coma is greatly generated, making correction difficult even with the entire lens system.

  Next, specific embodiments of the imaging lens of the present invention and numerical examples in which specific numerical values are applied to the embodiments will be described with reference to the drawings and tables.

  In each embodiment, an aspherical surface is introduced, and the aspherical shape is defined by the following equation (1).

In equation 1, the distance from the tangent plane of the aspheric vertex of the coordinate point on the aspheric surface where the height from the optical axis is y is X, and the curvature (1 / r) of the aspheric vertex is c. .

  FIG. 1 is a diagram showing the lens configuration of a first embodiment 1 of the imaging lens of the present invention. The imaging lens 1 is composed of a resin material and a meniscus first lens L1 having a convex shape on the object side and having positive power, an aperture S, and a convex shape on the image side. A second lens L2 having power and a third lens L3 made of a resin material and having negative power near the optical axis and having positive power toward the periphery are arranged.

  It is desirable that the object side surface in the vicinity of the optical axis of the third lens L3 has a negative power in order to maintain astigmatism and flange back length. On the other hand, the image-side surface in the vicinity of the optical axis of the third lens L3 is a flat or convex surface in order to prevent reflected light from the surface of the image sensor, which tends to be a ghost secondary light source, from being reflected near the center of the image sensor. Has a shape. Therefore, the surface near the optical axis of the third lens L3 may have a meniscus shape, for example.

  In the imaging lens 1, the stop S is disposed between the first lens L1 and the second lens L2, and the object side surface of the second lens L2 has a concave meniscus shape, so that axial chromatic aberration is reduced. Has a suppressive action.

  As described above, when the first lens L1 to the third lens L3 are all formed of a resin material, it is difficult to achieve both the optical total length and the optical performance because the resin lens tends to have a refractive index smaller than that of the glass lens. . However, it is possible to prevent deterioration of optical performance by performing power distribution so as to satisfy the conditional expressions (1) to (8) and adopting an aspheric shape for each surface.

  By making the first lens L1 to the third lens L3 resin lenses having excellent moldability, manufacturing is easy while adopting an aspheric shape on each surface, which contributes to cost reduction. In particular, the third lens L3 is an aspherical lens made of resin, and the positive power is increased in the peripheral portion as compared with the vicinity of the optical axis, so that the curvature of field is corrected well, and the principal ray to the imaging device is obtained. Can be made close to an angle perpendicular to the light receiving surface. Further, by reducing the shape near the optical axis to a flat or convex shape, it is possible to suppress the reduction of the lens back length.

  Furthermore, since all the lenses can be formed of a resin material, it is easy to adopt an aspheric shape for all lens surfaces, and the thickness of each lens can be reduced. A compact optical system can be obtained while maintaining the imaging performance.

  Note that an optical element OE such as a cover glass, an infrared cut filter, or a low-pass filter formed of resin or glass may be disposed between the third lens L3 and the imaging plane IMG.

  Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the imaging lens 1 according to the first embodiment. In Table 1 and the table showing other lens data, “surface number” indicates the i-th counted from the object side, “R” indicates the paraxial radius of curvature of the i-th surface, and “d” Indicates the axial upper surface distance between the i-th surface and the (i + 1) -th surface, and “n” indicates the refractive index at the d-line (wavelength = 587.56 nm (nanometer)) of the medium having the i-th surface on the object side. , “Νd” indicates the Abbe number at the d-line of the medium having the i-th surface on the object side. Regarding “R”, “0” indicates that the surface is a plane. Also, no data is displayed for the aperture.

All lens surfaces, that is, the first surface to the sixth surface are aspherical surfaces. Therefore, Table 2 shows the aspheric coefficients of the first to sixth surfaces in Numerical Example 1 together with the conic constant K. In Table 2 and the following tables showing aspheric coefficients, “e-i” represents an exponential expression with a base of 10, that is, “10- ⁱ ”. For example, “0.12345e-05” represents “ 0.12345 × 10 ⁻⁵ ”.

  Table 3 shows the focal length, numerical aperture, half angle of view, and total lens length of Numerical Example 1.

  FIG. 2 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, and distortion aberration) of Numerical Example 1. In the spherical aberration diagram, the broken line indicates the spherical aberration with respect to the wavelength = 587.56 nm, the solid line indicates the wavelength = 546.07 nm, the two-dot chain line indicates the spherical aberration with respect to the wavelength = 486.13 nm, and in the astigmatism diagram, the solid line indicates A broken line with respect to the sagittal image plane indicates each aberration with respect to the meridional image plane.

  As is apparent from these aberration diagrams, it can be seen that the imaging lens according to Numerical Example 1 has excellent optical performance in which each aberration is well corrected.

FIG. 3 is a diagram showing a lens configuration of a second embodiment 2 of the imaging lens of the present invention. The imaging lens 2 is composed of a resin material, and a first meniscus lens L1 having a convex shape on the object side and having a positive power, an aperture S, and a convex shape on the image side . A second lens L2 having power and a third lens L3 made of a resin material and having negative power near the optical axis and having positive power toward the periphery are arranged. Note that an optical element OE such as a cover glass, an infrared cut filter, or a low-pass filter formed of resin or glass may be disposed between the third lens L3 and the imaging plane IMG.

  Note that the details of the configuration of each lens are the same as those in the first embodiment, and a description thereof will be omitted.

  Table 4 shows lens data of Numerical Example 2 in which specific numerical values are applied to the imaging lens 2 according to the second embodiment.

  All lens surfaces, that is, the first surface to the sixth surface are aspherical surfaces. Therefore, Table 5 shows the aspheric coefficients of the first to sixth surfaces in Numerical Example 2 together with the conic constant K.

  Table 6 shows the focal length, numerical aperture, half angle of view, and total lens length of Numerical Example 2.

  FIG. 4 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, and distortion) of Numerical Example 2. In the spherical aberration diagram, the broken line indicates the spherical aberration with respect to the wavelength = 587.56 nm, the solid line indicates the wavelength = 546.07 nm, the two-dot chain line indicates the spherical aberration with respect to the wavelength = 486.13 nm, and in the astigmatism diagram, the solid line indicates A broken line with respect to the sagittal image plane indicates each aberration with respect to the meridional image plane.

  As is apparent from these aberration diagrams, the imaging lens according to Numerical Example 2 has excellent optical performance in which each aberration is well corrected.

FIG. 5 is a diagram showing the lens configuration of the third embodiment 3 of the imaging lens of the present invention. The imaging lens 3 is composed of a resin material, and a first meniscus lens L1 having a convex shape on the object side and having a positive power, an aperture S, and a convex shape on the image side . A second lens L2 having power and a third lens L3 made of a resin material and having negative power near the optical axis and having positive power toward the periphery are arranged. Note that an optical element OE such as a cover glass, an infrared cut filter, or a low-pass filter formed of resin or glass may be disposed between the third lens L3 and the imaging plane IMG.

  Note that the details of the configuration of each lens are the same as those in the first embodiment, and a description thereof will be omitted.

  Table 7 shows lens data of Numerical Example 3 in which specific numerical values are applied to the imaging lens 3 according to the third embodiment.

  All lens surfaces, that is, the first surface to the sixth surface are aspherical surfaces. Therefore, Table 8 shows the aspherical coefficients of the first surface to the sixth surface in Numerical Example 3 together with the conic constant K.

  Table 9 shows the focal length, the numerical aperture, the half angle of view, and the total lens length of Numerical Example 3.

  FIG. 6 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, and distortion) of Numerical Example 3. In the spherical aberration diagram, the broken line indicates the spherical aberration with respect to the wavelength = 587.56 nm, the solid line indicates the wavelength = 546.07 nm, the two-dot chain line indicates the spherical aberration with respect to the wavelength = 486.13 nm, and in the astigmatism diagram, the solid line indicates A broken line with respect to the sagittal image plane indicates each aberration with respect to the meridional image plane.

  As is apparent from these aberration diagrams, it can be seen that the imaging lens according to Numerical Example 3 has excellent optical performance in which each aberration is favorably corrected.

Table 10 shows values corresponding to the conditional expressions (1), (2), (4) to (8) in the numerical examples 1 to 3.

Each of the numerical examples 1 to 3 satisfies all the conditional expressions (1), (2), (4) to (8) .

  Next, the imaging apparatus of the present invention will be described.

An imaging apparatus according to the present invention includes an imaging lens and an imaging element that converts an optical image formed by the imaging lens into an electrical signal. The imaging lens includes a first lens and a diaphragm from the object side to the image side. The second lens and the third lens are arranged, and the third lens has a negative power in the central portion, a positive power in the peripheral portion, and the surface on the image side faces the image side. On the other hand, it has a planar or convex shape.
In the imaging apparatus of the present invention, the first lens has a meniscus shape having a positive power and a convex surface on the object side, and the second lens has a meniscus shape having a convex surface on the image side. At least one of the constituent lens surfaces is aspherical, and satisfies the following conditional expressions (1) to (3).
(1) -∞ ≤ f3 / f ≤ -0.75
(2) 0.5 ≤ f1 / f ≤ 2.9
(3) | R31 | <| R32 |
However,
f: Focal length on the image side of the entire optical system
f1: Image side focal length of the first lens
f3: Image side focal length of the third lens
R31: Radius of curvature near the optical axis of the object side surface of the third lens
R32: The radius of curvature in the vicinity of the optical axis of the image plane side surface of the third lens.

  7 to 9 show an embodiment in which the imaging apparatus of the present invention is applied to a camera unit of a mobile phone.

  7 and 8 show the appearance of the mobile phone 10.

  The mobile phone 10 is configured such that the display unit 20 and the main body unit 30 are connected to each other so as to be foldable at a central hinge portion. The mobile phone 10 is folded as shown in FIG. As shown, the display unit 20 and the main body unit 30 are opened.

  An antenna 21 for transmitting / receiving radio waves to / from a base station is provided at a position close to one side on the back side of the display unit 20, and the inner surface of the display unit 20 includes the antenna 21. A liquid crystal display panel 22 having a size that occupies substantially the entire side surface is disposed, and a speaker 23 is disposed above the liquid crystal display panel 22. Further, the display unit 20 is provided with an imaging unit 1A of a digital camera unit, and the imaging lens 1 of the imaging unit 1A faces outward through a facing hole 24 formed on the back surface of the display unit 20. It is out. Here, the term “imaging unit” is used as a configuration including the imaging lens 1 and the imaging element 4. That is, the imaging lens 1 and the imaging device 4 need to be provided in the display unit 20 at the same time, but other parts constituting the digital camera unit, such as a camera control unit and a recording medium, are arranged in the main body unit 30. The concept of the imaging unit was used to clarify that it may be acceptable. In addition, as the said image pick-up element 4, what uses photoelectric conversion elements, such as CCD and CMOS, is applicable, for example. As the imaging lens 1, the imaging lenses 1 to 3 of the present invention described above can be used, and further, the imaging lens of the present invention implemented in a form other than the above-described embodiments can be used.

  An infrared communication unit 25 is disposed at the tip of the display unit 20, and the infrared communication unit 25 includes an infrared light emitting element and an infrared light receiving element (not shown).

  On the inner surface of the main body 30, there are provided operation keys 31, 31,... Such as numeric keys "0" to "9", a calling key, a power key, etc., and the operation keys 31, 31,. A microphone 32 is disposed below the portion where the symbol is disposed. In addition, a memory card slot 33 is provided on the side surface of the main body 30, and the memory card 40 can be inserted into and removed from the main body 30 via the memory card slot 33.

  FIG. 9 is a block diagram showing the configuration of the mobile phone 10.

  The mobile phone 10 includes a CPU (Central Processing Unit) 50, and the CPU 50 controls the overall operation of the mobile phone 10. That is, the CPU 50 develops a control program stored in a ROM (Read Only Memory) 51 in a RAM 52 (Random Access Memory), and controls the operation of the mobile phone 10 via the bus 53.

  The camera control unit 60 controls the image pickup unit 1A including the image pickup lens 1 and the image pickup element 4 to shoot images such as still images and moving images. The obtained image information is compressed into JPEG, MPEG, etc. And then on the bus 53. The image information placed on the bus 53 is temporarily stored in the RAM 52, and is output to the memory card interface 41 as necessary, and stored in the memory card 40 by the memory card interface 41, or the display control unit 54. Is displayed on the liquid crystal display panel 22. In addition, audio information recorded through the microphone 32 at the same time as shooting is also temporarily stored in the RAM 52 together with image information via the audio codec 70, stored in the memory card 40, and displayed on the liquid crystal display panel 22. At the same time, it is output from the speaker 23 via the audio codec 70. Furthermore, the image information and the sound information are output to the infrared interface 55 as necessary, and output to the outside via the infrared communication unit 25 by the infrared interface 55, and a device including a similar infrared communication unit, For example, the information is transmitted to an external information device such as a mobile phone, a personal computer, or a PDA. When displaying a moving image or a still image on the liquid crystal display panel 22 based on the image information stored in the RAM 52 or the memory card 40, the camera control unit 60 decodes the file stored in the RAM 52 or the memory card 40. The image data after decompression is sent to the display control unit 54 via the bus 53.

  The communication control unit 80 transmits and receives radio waves to and from the base station via the antenna 21. In the voice call mode, the received voice information is processed and then output to the speaker 23 via the voice codec 70. The voice collected by the microphone 32 is received via the voice codec 70, subjected to predetermined processing, and transmitted.

  Since the imaging lens 1 described above can be configured to have a short depth, the imaging lens 1 can be easily mounted on a device having a limited thickness such as the mobile phone 10, and an imaging lens for a mobile phone that is a portable information device. It is suitable as.

  In the above embodiment, an example in which the imaging device of the present invention is applied to a mobile phone has been shown. However, the imaging device of the present invention can also be applied to other information devices such as personal computers and PDAs. Of course, it has a great advantage when applied to these information devices.

  It should be noted that the specific structures, shapes, and numerical values shown in the embodiments and numerical examples described above are only examples of the implementations that are carried out in carrying out the present invention, and thus the technology of the present invention. The scope should not be interpreted in a limited way.

It is a figure which shows the lens structure of 1st Embodiment of this invention imaging lens. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration of the numerical example 1 which applied the specific numerical value to 1st Embodiment. It is a figure which shows the lens structure of 2nd Embodiment of this invention imaging lens. It is a figure which shows the spherical aberration, astigmatism, and distortion of Numerical Example 2 which applied the specific numerical value to 2nd Embodiment. It is a figure which shows the lens structure of 3rd Embodiment of this invention imaging lens. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration of Numerical Example 3 which applied the specific numerical value to 3rd Embodiment. 8 and 9 show an embodiment in which the imaging apparatus of the present invention is applied to a camera unit of a mobile phone, and this figure is a perspective view showing a non-use state or a standby state. It is a perspective view which shows a use condition. It is a block diagram which shows an internal structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Imaging lens, 2 ... Imaging lens, 3 ... Imaging lens, L1 ... 1st lens, L2 ... 2nd lens, L3 ... 3rd lens, S ... Diaphragm, 10 ... Mobile phone (imaging device), 4 ... Imaging element

Claims (2)

A first lens, a diaphragm, a second lens, and a third lens are arranged from the object side to the image side.
The third lens has a negative power at the center, a positive power at the periphery, and the image side surface has a flat or convex shape with respect to the image side,
The first lens has a meniscus shape having a positive power and a convex surface on the object side,
The second lens has a meniscus shape having a convex surface on the image side,
At least one of all the constituent lens surfaces is aspheric,
An imaging lens that satisfies the following conditional expressions (1) to (3):
(1) -∞ ≤ f3 / f ≤ -0.75
(2) 0.5 ≤ f1 / f ≤ 2.9
(3) | R31 | <| R32 |
However,
f: Focal length on the image side of the entire optical system
f1: Image side focal length of the first lens
f3: Image side focal length of the third lens
R31: Radius of curvature near the optical axis of the object side surface of the third lens
R32: The radius of curvature in the vicinity of the optical axis of the image plane side surface of the third lens. An imaging device including an imaging lens and an imaging element that converts an optical image formed by the imaging lens into an electrical signal,
The imaging lens is configured by arranging a first lens, a diaphragm, a second lens, and a third lens from the object side to the image side,
The third lens has a negative power at the center, a positive power at the periphery, and the image side surface has a flat or convex shape with respect to the image side,
The first lens has a meniscus shape having a positive power and a convex surface on the object side,
The second lens has a meniscus shape having a convex surface on the image side,
At least one of all the constituent lens surfaces is aspheric,
An imaging device characterized by satisfying the following conditional expressions (1) to (3):
(1) -∞ ≤ f3 / f ≤ -0.75
(2) 0.5 ≤ f1 / f ≤ 2.9
(3) | R31 | <| R32 |
However,
f: Focal length on the image side of the entire optical system
f1: Image side focal length of the first lens
f3: Image side focal length of the third lens
R31: Radius of curvature near the optical axis of the object side surface of the third lens
R32: The radius of curvature in the vicinity of the optical axis of the image plane side surface of the third lens.

Images