DE102005015145A1 - Objective for e.g. digital camera, has lens whose surface is planer in central area and is convexly formed in border area, and admission window arranged before another lens, where infrared-filter is arranged behind former lens - Google Patents

Abstract

The objective has a lens (4) whose surface (12) is turned away from an object side and is aspherically designed. A diaphragm (110) is arranged between two lenses (1, 2). The surface (12) of the lens (4) is planer in a central area (120) and is convexly formed in a border area (121). An admission window is arranged before the lens (1), and an infrared-filter (112) is arranged behind the lens (4).

Description

The The invention relates to an objective in which, from an object side her seen, a first lens of positive power, a second Lens of negative refractive power, a third lens of positive refractive power, and a fourth lens of negative power along a common optical axis are arranged one behind the other, wherein at least an object facing away from the object surface of the fourth lens aspherical and a diaphragm disposed between the first lens and the second lens is.

The The invention further relates to an image pickup device having a Image pickup element and arranged in front of the image pickup element Lens.

The Invention finally relates an electro-optical device.

A lens, an image pickup device and a device of the aforementioned type are known from US 6,747,810 B2 known.

The The present invention generally relates to axially small-sized Lenses and their applications. Especially are lenses for mobile phones and similar electronic equipment addressed, but without the invention to this scope limited is.

lenses for mobile phones have to be compact, lightweight and easy and inexpensive to manufacture. by virtue of the small size of a Mobile phones and the requirement that the display of the mobile phone at the same time can be used as a viewfinder "is the line of sight of the Lens for the mobile phone in the direction of its depth, so the smallest Dimension, fixed. Since mobile phones should be as flat as possible, can the length of the lens consequently only a few mm.

In spite of these already difficult to reconcile guidelines the lenses for Mobile phones in addition also good optical properties, in particular a high imaging quality with the lowest possible Have distortions. The demands on the image quality result also from the very small pixel pitch of example 3 μm im associated image pickup element. Especially in the border area the distortions be low, which is why the so-called TV distortion must be sufficiently corrected. In the border area is also a Good illumination required, because the dynamic range of usual digital imaging elements is smaller than that of conventional Footage.

From the above US 6,747,810 B2 is a four-lens lens of the + - + - known, which is intended for use in digital cameras. Seen from the object side, there is an aperture between the first and the second lens. Both surfaces of the fourth lens are aspherical. The surface facing away from the object side is substantially concave. The lens has only a relatively small opening (light intensity) of 1: 4.8 and a length of 2.27 normalized to the focal length of 6.56 mm, which corresponds in absolute values to a length of 14.88 mm. The length is so relatively large and the opening small.

From the US 4,035,063 are known Dreilinsige lenses, in which also, as seen from the object side, a diaphragm between the first and the second lens is arranged. On the side facing away from the object side of the third lens is a plane-parallel transparent plate, the aspherical in some embodiments on its image-side surface, in other embodiments on its object-side surface in the edge region, and is formed substantially convex. This aspherical design of the plane-parallel plate has the purpose of correcting aberrations far away from the optical axis. For this reason, the respective asphere is located far from the aperture. The lenses also have only a relatively low light intensity tive also have only a relatively low light intensity of 1: 4.5.

Of the Invention is based on the object, an objective of the above to further develop the type mentioned that even better picture quality at even shorter length is reached. Furthermore, an image pickup device and an electro-optical device be provided over the picture quality mentioned at the lowest possible Dimensions have

at an objective of the type mentioned, this object is achieved by the invention solved that the surface the fourth lens in a central region plan and in an edge region is convex.

at an image pickup device of the type mentioned is the Task according to the invention thereby solved, the lens is formed in the aforementioned manner.

at an electro-optical device of the aforementioned type, the object according to the invention solved, that it is with an image pickup device of the above At provided.

The The object underlying the invention is complete in this way solved.

Thereby, that said image side surface of the fourth lens in the mentioned Is formed, a FITS good picture is achieved, in particular in an interaction of the lens with an electronic Image Sensor.

Whose Because sensors have only a limited acceptance angle, so it without the inventive measures In the border area comes to a shading when the light rays fall there relatively flat on the sensors. In conventional Image pickup elements in the edge region of the angle of incidence, i. the angle to the optical axis, not greater than about 25 °. By the special formation of the edge area compensates for this effect, by deflecting the marginal rays of light so that they at an angle of less than 25 ° to the optical axis on the Sensors hit.

For the correction of off-axis aberrations, as in the lens according to the US 4,035,063 be corrected, the formation of the asphere in the lens according to the invention is rather disadvantageous. This correction therefore takes place through the total correction of the lens.

At the according to the invention becomes a high light intensity or opening of 1: 2.9, and with only a very short length, the at 1.25, normalized to the focal length.

at a particularly preferred embodiment The invention are all surfaces aspherical of all four lenses educated.

These measure has the advantage that a particularly short length can be achieved.

Further is preferred if an entrance window is arranged in front of the first lens is.

These measure has the advantage of providing effective dust protection for the lens can be realized.

Further can in embodiments arranged the invention behind the fourth lens an infrared filter be.

These measure has the advantage that on the one hand a dust protection for a possibly shown behind the lens image pickup element On the other hand, interfering infrared light is filtered out by the filter.

at particularly preferred applications of the invention is behind the fourth Lens arranged an image plane of an image pickup element.

These measure has the advantage that the lens is used in electro-optical devices can be, especially in mobile phones, notebooks, PGAs, as well as in digital cameras, surveillance cameras, webcams etc.

For all these and other applications, a particular embodiment is preferred which is designed according to the following values:

• * optional

development constants of the aspheres:

• ASP 3: K: 0.000000 A: 0.510204E-02 B: 0.198736E-03 C: 0.111597E-02 D: 0.000000E + 00
• ASP 4: K: 0.000000 A: 0.631303E-02 B: -.553562E-03 C: 0.177248E-03 D: 0.000000E + 00
• ASP 7: K: 0.000000 A: 0.405755E-01 B: 0.120842E-01 C: 0.224906E-01 D: 0.000000E + 00
• ASP 8: K: 0.000000 A: 0.194218E-01 B: 0.105418E-01 C: = .396063E-02 D: 0.000000E + 00
• ASP 9: K: 0.000000 A: -.141654E-01 B: 0.476600E-02 C: -.101551E-02 D: 0.000000E + 00
• ASP 10: K: 0.000000 A: 0.157624E-01B: 0.314134E-03 C: 0.658900E-04 D: 0.000000E + 00
• ASP 11: K: 0.000000 A: 0.346293E-01 B: -.666398E-02 C: 0.694282E-03 D: 0.000000E + 00
• ASP 12: K: 0.000000 A: 0.311670E-02 B: -.272320E-02 C: 0.133110E-03 D: 0.000000E + 00

at embodiments According to the invention, the lenses are made in a manner known per se Plastic; in particular, the first lens and the third exist Zeonex lens and / or more preferably the second lens and the fourth polycarbonate lens.

As already mentioned, the lens is preferably for a telephone, in particular a mobile phone used, or for an electro-optical Device, in particular a camera equipped with a mobile data processing device or for a camera.

Further Advantages will be apparent from the description and the accompanying drawings.

It it is understood that the above and the following yet to be explained Features not only in the specified combination, but also usable in other combinations or alone are without departing from the scope of the present invention.

embodiments The invention are illustrated in the drawings and in the following description explained. Show it:

1 a schematic side view of an embodiment of an objective according to the invention in a greatly enlarged scale;

2 : Diagrams representing the transverse deviations in the image plane in tangential and in sagittal direction in the objective according to 1 ;

3 : a diagram representing the angle of incidence on the image plane; and

4 : a graph, showing the course of the MTF loss in the image center.

In 1 designated 100 as a whole, an embodiment of an objective according to the invention with an optical axis 102 , The objective 100 is of the type + - + -.

In the presentation of the 1 is located on the left side of the lens 100 an object page 104 and on the right side a picture page 106 , Object side is the lens 100 with an entrance window 108 completed. Behind it are behind the optical axis 102 a first lens I of positive refractive power, a second lens II of negative refractive power, a third lens III of positive refractive power, and a fourth lens IV of negative refractive power. A panel 110 is located between the first lens I and the second lens II. At the image-side end is the lens 100 with an IR filter 112 completed. Behind it is an image plane 114 taken from a picture-taking element 116 is taken.

In 1 are further with the numbers 1 to 16 the usual surfaces or levels drawn.

All surfaces 3 . 4 and 7 - twelve the lenses I-IV are formed aspherical. The from the object side 104 remote surface twelve the fourth lens IV has a central area 120 which is designed substantially planar, as well as a border area 121 which is aspherical and substantially convex.

The structural details of the above and in 1 shown lens 100 can be found in the usual notation from the following information:

development constants of the aspheres:

• ASP 3: K: 0.000000 A: 0.510204E-02 B: 0.198736E-03 C: 0.111597E-02 D: 0.000000E + 00
• ASP 4: K: 0.000000 A: 0.631303E-02 B: -.553562E-03 C: 0.177248E-03 D: 0.000000E + 00
• ASP 7: K: 0.000000 A: 0.405755E-01 B: 0.120842E-01 C: 0.224906E-01 D: 0.000000E + 00
• ASP 8: K: 0.000000 A: 0.194218E-01 B: 0.105418E-01 C: = .396063E-02 D: 0.000000E + 00
• ASP 9: K: 0.000000 A: -.141654E-01 B: 0.476600E-02 C: -.101551E-02 D: 0.000000E + 00
• ASP 10: K: 0.000000 A: 0.157624E-01B: 0.314134E-03 C: 0.658900E-04 D: 0.000000E + 00
• ASP 11: K: 0.000000 A: 0.346293E-01 B: -.666398E-02 C: 0.694282E-03 D: 0.000000E + 00
• ASP 12: K: 0.000000 A: 0.311670E-02 B: -.272320E-02 C: 0.133110E-03 D: 0.000000E + 00

As a result of the formation of the aspheres arises for the lens 100 a very short axial length of only 7 mm. The opening or light intensity is 1: 2.5.

The special shape of the surface twelve As a result, the sensors in the image pickup element 116 Even in the edge area relatively steep (angle of incidence <25 °) are illuminated, so that no brightness decrease and no distortion occur at the edge. The TV distortion is less than 0.8%.

The Lenses I-IV are preferably made of plastic, for example by Spraying or pressing. For the first lens I and the third lens III is preferably the plastic Zeonex used, for the second lens II and the fourth lens IV polycarbonate.

2 shows for the lens 100 in the usual representation, the transverse deviations in the image plane in the tangential and in the sagittal direction. All ten individual diagrams are parameterized according to the five light wavelengths a) to e) given below on the right.

3 shows the course of the angle of incidence over the relative field and you can see there through the asphere of the surface twelve clearly detect compensated edge compensation. The angle of incidence is always below 25 °.

4 Finally, it shows the course of the MTF loss over the relative image height. Because the surface twelve the fourth lens IV in the central area 120 plan, results in a special image quality in this area, unlike convex aspheres, as in the aforementioned US 6,747,810 B2 is specified. In the case of a convex asphere, a turning point in the aspheric function is obtained near the center of the image, which makes the system sensitive to tolerances. The plane design according to the invention, however, leads to an increase in the fall of the MTF with respect to the tolerances by 7.8-15.4% in the middle of the picture, such as 4 shows.

The Lens is preferably used in image pickup devices, as for electro-optical devices be used. Examples include phones, in particular Mobile phones, notebooks, PGAs, digital cameras, surveillance cameras, webcams etc.

Claims (14)

Lens in which, from an object side ( 104 ), a first lens (I) of positive power, a second lens (II) of negative power, a third lens (III) of positive power, and a fourth lens (IV) of negative power along a common optical axis ( 102 ) are arranged one behind the other, wherein at least one of the object side ( 104 ) facing away from the surface ( twelve ) of the fourth lens (IV) formed aspherical and a diaphragm ( 110 ) between the first lens (I) and the second lens (II), characterized in that the surface ( twelve ) of the fourth lens (IV) in a central area ( 120 ) plan and in a border area ( 121 ) is convex. Lens according to claim 1, characterized in that all surfaces ( 3 . 4 . 7 - twelve ) of all four lenses (I-IV) are formed aspherical. Lens according to claim 1 or 2, characterized in that in front of the first lens (I) an entrance window ( 108 ) is arranged. Lens according to one or more of claims 1 to 3, characterized in that behind the fourth lens (IV) an infrared filter ( 112 ) is arranged. Lens according to one or more of claims 1 to 3, characterized in that behind the fourth lens (IV) an image plane ( 114 ) of an image pickup element ( 116 ) is arranged. Lens according to one or more of claims 2 to 5, characterized in that it is formed according to the following values:

* optional aspheric developer constants: ASP 3: K: 0.000000 A: 0.510204E-02 B: 0.198736E-03 C: 0.111597E-02 D: 0.000000E + 00 ASP 4: K: 0.000000 A: 0.631303E-02 B: -.553562E-03 C: 0.177248E-03 D: 0.000000E + 00 ASP 7: K: 0.000000 A: 0.405755E-01 B: 0.120842E-01 C: 0.224906E-01 D: 0.000000E + 00 ASP 8: K: 0.000000 A: 0.194218E-01 B: 0.105418E-01 C: = .396063E-02 D: 0.000000E + 00 ASP 9: K: 0.000000 A: -.141654E-01 B: 0.476600E-02 C: - .101551E-02 D: 0.000000E + 00 ASP 10: K: 0.000000 A: 0.157624E-01 B: 0.314134E-03 C: 0.658900E-04 D: 0.000000E + 00 ASP 11: K: 0.000000 A: 0.346293E -01 B: -.666398E-02 C: 0.694282E-03 D: 0.000000E + 00 ASP 12: K: 0.000000 A: 0.311670E-02 B: -.272320E-02 C: 0.133110E-03 D: 0.000000E +00 Lens according to one or more of claims 1 to 6, characterized in that the lenses (I-IV) are made of plastic. Lens according to claim 7, characterized the first lens (I) and the third lens (III) consist of Zeonex. Lens according to claim 7 or 8, characterized in that the second lens (Ii) and the fourth lens (IV) are made of polycarbonate consist. Image recording device with an image recording element ( 116 ) and one in front of the image pickup element ( 116 ) lens ( 100 ), characterized in that the lens ( 100 ) is designed according to one or more of claims 1 to 9. Electro-optical device with an image pickup device according to claim 10. device according to claim 11, characterized in that it is a telephone, in particular is a mobile phone. device according to claim 11, characterized in that it is a data processing device, in particular is a mobile computing device. device according to claim 11, characterized in that it is a camera.