JP2008185627A - Wide converter and method for widening angle of lens by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch a wide angle region into/from an original focal-length region, without having to remove a wide converter. <P>SOLUTION: The wide converter 30 has a function to displace the focal length to a wide-angle side, and a liquid lens is used as one or more lenses 12 and 22 out of lenses constituting the wide converter 30. Either surfaces 3 and 6 of the liquid lenses 12 and 22 are constituted of a deformed film having light transmittance, and liquid inside the liquid lens is made variable so that the focal length may be varied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wide converter that is attached in front of an imaging apparatus or the like and displaces the focal length of the entire optical system to the wide angle side, and a lens widening method using the wide converter.

  Front mounting system that is mounted on the object side of the photographic lens, that is, in front of an imaging device such as a still camera or video camera, and changes the focal length of the entire photographic system to the wide-angle side while maintaining the focal plane of the entire system at a fixed position. Various wide converters have been proposed. In general, this wide converter consists of a lens group having a negative refractive power on the object side and a lens group having a positive refractive power on the image side with a predetermined principal point interval, thereby forming an afocal system as a whole. (For example, refer to Patent Document 1).

JP 2006-276220 A

When conventional wide converters including those disclosed in Patent Document 1 are used, in order to switch between the focal length range (wide angle) when mounted on an imaging device or the like and the focal length range of the original photographing lens, a wide range is required. The converter itself must be installed and removed.
Therefore, once the wide converter is attached, the wide angle state and the original state cannot be switched without removing the wide converter. For this reason, it is desired to enable such switching by a simpler method.

  In view of the above problems, an object of the present invention is to enable switching between a wide-angle region and an original focal length region without removing a wide converter.

In order to solve the above problems, the present invention is a wide converter having a function of displacing a focal length to the wide angle side, and among the lenses constituting the wide converter, at least one lens is configured as a liquid lens.
According to the present invention, in the above-described wide converter, one surface of the liquid lens is configured by a light-transmitting deformable film, and the liquid lens is provided with a liquid moving unit that allows the liquid inside to enter and exit. .

  Furthermore, according to the present invention, in the above-described wide converter, the first lens group and the second lens group are arranged in this order from the object side, and the first lens group is a first lens made of a solid lens. And a second lens having a first deformation film on the image side. The second lens group includes a third lens made of a solid lens and a fourth lens made of a liquid lens having a second deformable film on the image side.

  The present invention is also a method for widening a lens that displaces the focal length to the wide-angle side, and using a liquid lens having a deformation film, the liquid volume of the liquid lens is changed to change the shape of the deformation film. Thus, the first and second states having different focal lengths are switched.

As described above, the wide converter and the lens widening method of the present invention use a liquid lens. As the liquid lens, for example, by using a liquid lens having a light-transmitting deformable film that is deformed elastically on one surface, for example, the focal length of the lens can be made variable with an easy configuration.
Therefore, according to the present invention, once attached to the front of the imaging device or the like, it is possible to easily switch between the wide angle state and the original state without removing.

  In particular, one surface of the liquid lens is formed of a light-transmitting deformable film, and the liquid lens is provided with a movable portion that can move the liquid inside, so that the volume can be changed by the movement of the liquid. The shape of the deformable film can be made variable, whereby the focal length can be adjusted and switched with a simple mechanism.

  Still further, in the wide converter of the present invention, the first lens group and the second lens group are arranged in this order from the object side, and the first lens group is composed of a first lens made of a solid lens, and an image. And a second lens having a first deformation film on the side. In addition, as described later, the second lens group includes a third lens made of a solid lens and a fourth lens made of a liquid lens having a second deformation film on the image side, as will be described later. A wide converter having a large amount of aberration can be easily provided.

  According to the wide converter and the lens widening method of the present invention, it is possible to switch between the wide angle region and the original focal length region without removing the wide converter.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
First Embodiment FIGS. 1A and 1B are schematic cross-sectional configuration diagrams of an example of a wide converter according to a first embodiment of the present invention in a first state and a second state.
The wide converter 30 according to the first embodiment of the present invention includes four lenses in two groups, and as shown in FIGS. 1A and 1B, the first lens group 10 and the first lens group from the object side (left side in the figure). Two lens groups 20 are arranged. The first lens group 10 includes a first lens 11 made of a solid lens and a second lens 12 made of a liquid lens having a deformation film on the image side (right side in the figure). The second lens group 20 includes a third lens 21 made of a solid lens and a fourth lens 22 made of a liquid lens having a deformation film on the image side.

Here, the first lens of the first lens group 10 is a concave lens, and the third lens 21 of the second lens group 20 is a convex lens.
In the first state, as shown in FIG. 1A, both the first and second lenses 11 and 12 are concave lenses, and the first lens group 10 is a lens group having concave lens power. Further, the third and fourth lenses 21 and 22 are both convex lenses, and the second lens group 20 is a lens group having convex lens power. At this time, the entire system has an afocal magnification smaller than 1.

  On the other hand, in the second state, as shown in FIG. 1B, the first lens 11 is a concave lens and the second lens 12 is a convex lens, so that the first lens group 10 has an afocal magnification smaller than 1. Let it be a lens group. Further, the third lens 21 is a convex lens and the fourth lens 22 is a concave lens, so that the second lens group 20 is a lens group having an afocal magnification greater than 1. In this case, the afocal magnification is 1 in the entire system.

  As described above, the lens power is changed between the first state and the second state so that the second lens 12 is in a concave lens and a convex lens, and the fourth lens 22 is in a convex lens and a concave lens. Then, a wide converter capable of switching the afocal magnification between the first and second states can be provided.

  FIG. 2 shows a schematic cross-sectional configuration diagram of an example of the liquid lens constituting the wide converter. As shown in FIG. 2, in this case, an example of a junction type doublet lens shape in which a solid lens is combined and integrated on the object side is shown. That is, the object-side surface is a solid lens 101 made of a material such as light-transmitting glass, and the other surface has a deformation film 107. The solid lens 101, the deformation film 107, and the frame bodies 103 to 105 A liquid lens 102 is configured by enclosing a light transmissive liquid 110 therebetween. The periphery of the liquid lens 102 is liquid-tightly held by, for example, ring-shaped frames 103 to 105. In the example shown in the drawing, a liquid moving unit 106 such as a tube is provided in a part of the frame body 104 so that the liquid 110 inside can be taken in and out. The volume of the liquid 110 inside the liquid lens 102 is changed by driving an external pump mechanism or the like (not shown). As a result, the deformable film 107 is deformed, and the liquid lens 102 can be switched to be a convex lens or a concave lens.

Here, as the liquid in the liquid lens 102, it is desirable to use a material having optical transparency such as silicon oil and having an appropriate refractive index. In addition, the material of the deformation film 107 is a deformable material having appropriate elasticity such as silicon rubber, and preferably has a required light transmittance, and may have a shape such as a deformable thin film. desirable.
With such a configuration, the lens power can be easily changed with a mechanism that changes the volume of the liquid 110, that is, a relatively simple mechanism such as suction or injection of the liquid 110, as described above. A change in afocal magnification can be realized. Further, as in the example described with reference to FIG. 2, by combining two doublet lenses integrated with a solid lens, a wide converter capable of switching between the first and second states described above can be realized with a simpler configuration. It becomes.

Next, a numerical example of a specific lens structure applicable in the first embodiment will be described. In the following example, when it is used as a wide converter attached in front of the imaging device, when the focal length of the master lens of the imaging device is f, the F number is Fno, and the field angle is 2ω (ω is a half field angle),
f = 6.3mm
Fno = 2.2
2ω = 59.32 °
It is.

  As shown in FIG. 1, the entrance and exit surfaces of the first to fourth lenses 11 and 12, 21 and 22 are first to sixth surfaces 1 to 6 from the object side, respectively. Table 1 below shows the radius of curvature of the surface, the surface spacing on the optical axis (surface spacing with the next surface), the refractive index of d-line (wavelength 587.56 nm) in the medium between the surfaces, and the d-line Abbe number. Shown in The radius of curvature of the first surface 1 is infinite, that is, a plane.

  Further, when the afocal magnification is 0.7 in the first state shown in FIG. 1A and the afocal magnification is 1.0 in the second state shown in FIG. 1B, R3 and R6 in Table 1 in each state are shown. Table 2 below shows numerical examples of D2, D3, and D5.

  FIGS. 3A to 3C and FIGS. 4A to 4C show spherical aberration, astigmatism, and distortion in the first state and the second state in the case of such a lens configuration. 3A and 4A, the vertical axis indicates the numerical value obtained by standardizing the pupil radius, the solid line a indicates the value for the d-line having a wavelength of 587.5600 nm, and the broken line b indicates the value for light having a wavelength of 435.8400 nm. Note that the spherical aberration at the d-line indicated by the solid line a in both FIGS. 3A and 4A is substantially zero. 3B and 4B, the alternate long and short dash line T and the solid line S indicate astigmatism on the meridional surface (meridion surface) and the sagittal surface (spherical surface), respectively. From the results of FIGS. 3 and 4, it can be seen that such a lens configuration is in a range applicable as a wide converter.

(2) Second Embodiment Next, a wide converter according to a second embodiment of the present invention will be described. 5A and 5B are schematic sectional views of a wide converter according to the second embodiment. 5A and 5B, parts corresponding to those in FIGS. 1A and 1B are denoted by the same reference numerals, and redundant description is omitted. In this example, only the first surface 1 on the object side of the first lens 11 is an aspherical surface, and the other surfaces are spherical surfaces.

  Also in this embodiment, the second lens 12 of the first lens group 10 and the fourth lens 22 of the second lens group 20 are constituted by liquid lenses. As in the example shown in FIG. 2, the liquid lens may have a doublet lens shape, or may be a separate lens from the first and third lenses 11 and 21 made of a solid lens. In the case of the doublet shape, the wide converter 30 capable of switching between the first state shown in FIG. 5A and the second state shown in FIG. 5B can be realized with a simpler configuration. The material and configuration of the liquid lens can be selected in the same manner as in the first embodiment.

Numerical examples of lens structures applicable to the second embodiment are shown below. In this example as well, the focal length f, F number Fno, and angle of view 2ω of the master lens of the imaging device are the same as those in the numerical example in the first embodiment when used as a wide converter attached in front of the imaging device.
Table 3 below shows the radii of curvature of the first to sixth surfaces 1 to 6, the surface spacing on the optical axis, the refractive index of the d-line in the medium between the surfaces, and the Abbe number of the d-line.

  When the afocal magnification is 0.7 in the first state shown in FIG. 5A and the afocal magnification is 1.0 in the second state shown in FIG. 5B, R3 and R6 in Table 3 in each state are shown. Table 4 below shows numerical examples of D2, D3, and D5.

  In addition, Table 5 below shows the aspheric coefficients on the first surface 1 of the first lens 11 when the aspheric expression is expressed by the following formula 1. In Equation 1, Z is the distance in the optical axis direction from the lens surface when the light traveling direction is positive, h is the height in the direction perpendicular to the optical axis, R is the radius of curvature, k is the conic constant, A, B, C, and D represent aspheric coefficients, respectively.

  6A to 6C and FIGS. 7A to 7C show spherical aberration, astigmatism, and distortion aberration in the first state and the second state in the case of such a lens configuration. 6A and 7A, the vertical axis indicates the numerical value obtained by standardizing the pupil radius, the solid line a indicates the value for the d-line having a wavelength of 587.5600 nm, and the broken line b indicates the value for light having a wavelength of 435.8400 nm. In both FIGS. 6A and 7A, the spherical aberration at the d-line indicated by the solid line a is substantially zero. 6B and 7B, the alternate long and short dash line T and the solid line S indicate astigmatism on the meridional surface and the sagittal surface, respectively. From the results of FIG. 6 and FIG. 7, it can be seen that even when the lens configuration of the second embodiment is used, the range is applicable as a wide converter.

(3) Third Embodiment Next, a wide converter according to a third embodiment of the present invention will be described. 8A and 8B are schematic cross-sectional configuration diagrams of the wide converter according to the second embodiment. 8A and 8B, parts corresponding to those in FIGS. 1A and 1B are denoted by the same reference numerals, and redundant description is omitted. In this example, the first surface 1 on the object side of the first lens 11 and the fourth surface 4 of the second lens 21 are aspherical and the other surfaces are spherical.

  Also in this embodiment, the second lens 12 of the first lens group 10 and the fourth lens 22 of the second lens group 20 are constituted by liquid lenses. Similar to the example shown in FIG. 2, the liquid lens may have a doublet lens shape, or may be a separate lens from the first and third lenses 11 and 21 made of a solid lens. In the case of a doublet shape, it is possible to realize a wide converter 30 that can be switched between the first state shown in FIG. 8A and the second state shown in FIG. 8B with a simpler configuration. The material and configuration of the liquid lens can be selected in the same manner as in the first and second embodiments.

Numerical examples of lens structures applicable to the third embodiment are shown below. In this example as well, the focal length f, F number Fno, and angle of view 2ω of the master lens of the imaging device are the same as those in the numerical example in the first embodiment when used as a wide converter attached in front of the imaging device.
Table 6 below shows the curvature radii of the first to sixth surfaces 1 to 6, the surface spacing on the optical axis, the refractive index of the d-line in the medium between the surfaces, and the Abbe number of the d-line.

  When the afocal magnification is 0.7 in the first state shown in FIG. 8A and the afocal magnification is 1.0 in the second state shown in FIG. 8B, R3 and R6 in Table 6 in each state are shown. Table 7 below shows numerical examples of D2, D3, and D5.

  In addition, Table 8 below shows the aspheric coefficient on the first surface 1 of the first lens 11 when the aspherical expression is set to the above equation (1).

  FIGS. 9A to 9C and FIGS. 10A to 10C show spherical aberration, astigmatism, and distortion aberration in the first state and the second state in the case of such a lens configuration. 9A and 10A, the vertical axis indicates the numerical value obtained by standardizing the pupil radius, the solid line a indicates the value for the d-line having a wavelength of 587.5600 nm, and the broken line b indicates the value for light having a wavelength of 435.8400 nm. In both FIGS. 9A and 10A, the spherical aberration at the d-line indicated by the solid line a is substantially zero. 9B and 10B, the alternate long and short dash line T and the solid line S indicate astigmatism on the meridional surface and the sagittal surface, respectively. From the results of FIG. 9 and FIG. 10, it can be seen that even when the lens configuration of the third embodiment is used, the range is applicable as a wide converter.

  As described above, according to the wide converter of the present invention and the lens widening method using the wide converter, the afocal magnification of the wide converter can be easily switched without requiring a complicated mechanism. It is possible to easily switch between the wide-angle range and the original focal length range without removing itself.

(4) Fourth Embodiment Next, as an embodiment of a lens widening method according to the present invention, an example of a lens widening method when a wide converter according to the present invention is attached to an imaging apparatus will be described. 11A and 11B are schematic configuration diagrams when the wide converter is set to the first state and the second state, respectively, in this imaging apparatus. As shown in FIGS. 11A and 11B, the imaging apparatus 60 includes a master lens 40 and a wide converter 30 that can be removed, for example, in front of the object, that is, on the object side, and an optical image formed by the wide converter 30 and the master lens 40. Has an imaging unit 51 for converting the signal into an electrical signal. As the imaging unit 51, for example, a device using a photoelectric conversion element such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) can be applied. As the wide converter 30, the wide converter lens of the present invention configuration including the wide converter according to the first to third embodiments described above can be applied. 11, the lens unit of the wide converter 30 according to the first embodiment shown in FIG.

  As shown in FIGS. 11A and 11B, the electrical signal formed by the imaging unit 51 is sent to the control unit 53 by the signal processing unit 52 having a video separation circuit, for example, and the video signal is It is processed into a form suitable for the subsequent processing, outputted to the outside as indicated by an arrow Sc, and used for various processing such as display by a display device, recording on a recording medium, and transfer by a communication means.

For example, an operation signal from the outside such as an operation of a zoom button or a wide button is input to the control unit 53, and various processes are performed according to the operation signal. Then, when a wide angle command by a wide button or the like is input as indicated by an arrow Sw, the drive units 56 and 57 are connected via the driver circuits 54 and 55 of the wide converter lens 30 so that a focal length state based on the command is obtained. Is operated to drive, for example, a pump device that moves the liquid of the second lens 12 and the fourth lens 22. Thereby, the deformation films of the second and fourth lenses 12 and 22 are deformed into a predetermined shape, that is, from the first state to the second state or vice versa. The control unit 53 checks the focus state based on the signal sent from the signal processing unit 52, and drives the zoom lens group of the master lens via the driver circuit so as to obtain an optimum focus state (not shown). The position of the drive unit is controlled.
By adopting such a configuration, it is possible to provide an imaging device capable of switching between the wide angle state and the original state by an extremely simple operation of only the operation of the wide button once the wide converter 30 is attached. Become.

  The above-described imaging device 60 can take various forms as a specific product. For example, the present invention can be widely applied as a camera unit of a digital input / output device such as a digital still camera, a digital video camera, a mobile phone incorporating a camera, and a PDA (Personal Digital Assistant) incorporating a camera.

  It should be noted that the specific shapes and numerical examples of the respective parts shown in the above embodiments and numerical examples are merely examples that can be applied when carrying out the present invention. For example, for numerical values of the lens shape, It can be changed as long as it is applicable as a wide converter. For example, when an aberration correction element is used in combination with the wide converter of the present invention, the allowable range of numerical values of each lens shape can be expanded. Furthermore, the state in which the liquid lens can be adopted is not limited to the two states of the first and second states exemplified in the above-described embodiment, and may be configured to take three or more states or continuously. It is also possible to change the deformation film of the liquid lens. In addition, it goes without saying that the material, shape and configuration of each lens used in the wide converter and the lens widening method of the present invention can be variously modified and changed without departing from the configuration of the present invention.

1A is a schematic cross-sectional configuration diagram in a first state of a wide converter according to a first embodiment of the present invention. FIG. B is a schematic cross-sectional configuration diagram of the wide converter according to the first embodiment of the present invention in a second state. FIG. It is a schematic sectional block diagram of the principal part of the wide converter which concerns on the 1st Embodiment of this invention. FIGS. 8A to 8C are diagrams showing aspheric aberration, astigmatism, and distortion in the first state of the wide converter according to the first embodiment of the present invention. FIGS. FIGS. 8A to 8C are diagrams showing aspheric aberration, astigmatism, and distortion in the second state of the wide converter according to the first embodiment of the present invention. FIGS. FIG. 3A is a schematic cross-sectional configuration diagram in a first state of a wide converter according to a second embodiment of the present invention. B is a schematic cross-sectional configuration diagram of a wide converter according to a second embodiment of the present invention in a second state. FIG. FIGS. 7A to 7C are diagrams showing aspheric aberration, astigmatism, and distortion in the first state of the wide converter according to the second embodiment of the present invention. FIGS. FIGS. 8A to 8C are diagrams showing aspheric aberration, astigmatism, and distortion in the second state of the wide converter according to the second embodiment of the present invention. FIGS. FIG. 7A is a schematic cross-sectional configuration diagram of a wide converter according to a third embodiment of the present invention in a first state. FIG. 7B is a schematic cross-sectional configuration diagram in a second state of the wide converter according to the third exemplary embodiment of the present invention. FIGS. 8A to 8C are diagrams showing aspheric aberration, astigmatism, and distortion in the first state of the wide converter according to the third embodiment of the present invention. FIGS. FIGS. 8A to 8C are diagrams showing aspheric aberration, astigmatism, and distortion in the second state of the wide converter according to the third embodiment of the present invention. FIGS. A and B are schematic configuration diagrams of an example of an imaging apparatus according to an embodiment of a lens widening method according to the present invention.

Explanation of symbols

  1. First surface, 2. Second surface, 3. Third surface, 4. Fourth surface, 5. 5. Fifth aspect Sixth surface, 10. 10. First lens group First lens, 12. Second lens, 20. Second lens group, 21. Third lens, 22. Fourth lens, 30. Wide converter, 40. Master lens, 51. Imaging unit, 52. Signal processing unit, 53. Control unit, 54. Driver circuit, 55. Driver circuit, 56. Drive unit, 57. Drive unit, 60. Imaging apparatus, 101. Solid lens, 102. Liquid lens, 103-105. Frame, 106. Liquid moving part, 107. Deformation membrane, 110. liquid

Claims (6)

A wide converter having a function of shifting the focal length to the wide angle side,
Among the lenses constituting the wide converter, one or more lenses are liquid lenses. One surface of the liquid lens is formed of a deformable film having light permeability,
The wide converter according to claim 1, wherein the liquid lens is provided with a liquid moving portion that allows an internal liquid to enter and exit. In the wide converter, the first lens group and the second lens group are arranged in this order from the object side,
The first lens group includes a first lens made of a solid lens, and a second lens made of a liquid lens having a first deformation film on the image side,
2. The second lens group includes a third lens made of a solid lens and a fourth lens made of a liquid lens having a second deformation film on the image side. Wide converter. The first lens of the first lens group is a concave lens;
4. The wide converter according to claim 3, wherein the third lens of the second lens group is a convex lens. A lens widening method that displaces the focal length to the wide-angle side,
Using a liquid lens having a deformation film on the image side, changing the liquid volume of the liquid lens to change the shape of each deformation film, thereby switching between the first and second states having different focal lengths. A method for widening the angle of a lens. The first state is a state where the afocal magnification is smaller than 1.
The lens widening method according to claim 5, wherein the second state is a state where the afocal magnification is 1.

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