JP2006166336A - Imaging apparatus and electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove a chromatic aberration generated due to an imaging lens while holding down a manufacturing cost. <P>SOLUTION: An imaging apparatus has the imaging lens 10, a beam splitter 11 spectrally diffracting an imaging light projected through the imaging lens 10, and three CCDs 16R, 16G and 16B receiving the light spectrally diffracted by the beam splitter 11 and converting the light into electric signals. The imaging device further has lens groups 15R, 15G and 15B for a correction being disposed among each CCD 16R, 16G and 16B and the beam splitter 11 and removing the chromatic aberration resulting from the imaging lens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus and an electronic camera, and more particularly to an imaging apparatus and an electronic camera including a correction lens group that removes chromatic aberration caused by an imaging lens.

  2. Description of the Related Art Conventionally, video cameras and electronic cameras are provided with an imaging device 100 that converts captured images into electrical signals. As shown in FIG. 6, the imaging apparatus 100 includes an imaging lens 101 that images a subject, and a beam splitter that separates the three primary colors of red (R), green (G), and blue (B) of the imaging light for each primary color. 102 and imaging elements 103R, 103G, and 103B that convert the light after the separation into an electric signal.

  The above-described imaging device is a so-called three-plate type imaging device that assigns one imaging element to monochromatic light composed of one primary color after spectroscopy, and a single-plate type imaging device that splits the three primary colors with one imaging element. Compared with, it is possible to faithfully reproduce the subtle hues from the primary color to the intermediate color, and even in the converted image, a high resolution with a three-dimensional effect and a sense of depth is exhibited. .

However, as shown in FIG. 6, since an air layer is formed between the beam splitter 102 and the image sensors 103R, 103G, and 103B, incident light is reflected on the surfaces of the image sensors 103R, 103G, and 103B. The problem that it ends up has arisen. For this reason, a method of joining the image sensors 103R, 103G, and 103B to the beam splitter 102 and a method of forming an antireflection film for preventing reflection on each of the image sensors 103R, 103G, and 103B have been studied.
However, in the former case, a sufficient effect cannot be obtained, and in the latter case, since the optimal antireflection film thickness corresponding to each monochromatic light after the spectroscopy differs for each primary color, In order to obtain an optimum configuration with respect to the wavelength, a multilayer film is required and high dimensional accuracy is required, which causes a problem that it cannot be a practical method.

Therefore, as a three-plate camera capable of improving sensitivity, a three-plate camera has been developed in which three solid-state imaging devices are optimally designed for the refractive index and thickness dimension of the antireflection film for each color. (For example, refer to Patent Document 1).
JP 2002-309858 A

  However, in the case of the above-described three-plate camera, reflection of incident light on the surface of the image sensor, which has been a problem, can be prevented, but the three primary colors are spectrally separated for each primary color by the beam splitter 102 disposed behind the image pickup lens 101. Since the monochromatic light that has been dispersed is received by the three image pickup devices 103R, 103G, and 103B, the chromatic aberration caused by the image pickup lens 101 is not removed on the surfaces of the image pickup devices 103R, 103G, and 103B. The image formation causes a problem that chromatic aberration of the same level as that of the single-plate imaging device remains.

  In order to remove chromatic aberration of three colors, a lens designed by a lens having a high refractive index such as fluorite, that is, a so-called apochromat lens is required. However, a lens necessary for designing the apochromat lens is expensive. There is also a problem that the manufacturing cost increases.

  The present invention has been made in view of the above-described points, and an object thereof is to provide an imaging apparatus and an electronic camera that can eliminate chromatic aberration caused by an imaging lens and can reduce the manufacturing cost. And

In order to solve the above problems, an imaging apparatus according to the invention described in claim 1
An imaging lens for imaging a subject;
A spectroscopic member that separates imaging light incident through the imaging lens;
A plurality of image sensors that receive light dispersed by the spectral member and convert the light into electrical signals;
A plurality of correction lens groups are provided between each of the imaging elements and the spectral member and remove chromatic aberration caused by the imaging lens.

  The image pickup apparatus according to a second aspect of the invention is characterized in that the spectral member performs spectral separation for each monochromatic light composed of one primary color.

  The imaging apparatus according to a third aspect of the invention is characterized in that the spectral member splits into monochromatic light composed of one primary color and mixed light composed of another primary color.

  In the imaging device according to a fourth aspect of the present invention, the plurality of correction lens groups are such that one correction lens group is an achromatic lens, and the chromatic aberration of the mixed light is removed by the achromatic lens. And

  The image pickup apparatus according to a fifth aspect of the invention is characterized in that the plurality of correction lens groups have a lens movement amount in a zoom operation controlled for each correction lens group.

  An electronic camera according to a sixth aspect of the present invention includes the imaging device according to any one of the first to fifth aspects.

  According to the present invention, an imaging lens that captures an image of a subject, a spectral member that splits imaging light that is incident through the imaging lens, and a plurality of imaging elements that receive light dispersed by the spectral member and convert the light into electrical signals. And a plurality of correction lens groups that are disposed between each imaging element and the spectral member and remove chromatic aberration caused by the imaging lens, so that a lens design suitable for the color of the light after the spectroscopy is performed. As a result, the number of lenses constituting the correction lens group can be reduced, thereby eliminating the chromatic aberration and simplifying the design and suppressing the manufacturing cost.

The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.
The imaging apparatus 1 and the electronic camera 2 in the first embodiment will be described with reference to FIGS.
As shown in FIG. 1, the electronic camera 2 in the present embodiment includes a substantially rectangular parallelepiped casing 3, and the upper surface side of the casing 3 is configured by a pushable button switch. In the shooting mode, a shutter button 4 for instructing a shooting operation by a push operation is provided.

  Further, as shown in FIG. 2, the rear side of the housing 3 is configured by an LCD (Liquid Crystal Display) or the like, and in the shooting mode, the electronic viewfinder serves as a subject, various shooting information such as shooting conditions or setting information. A mode switching unit configured to display various information screens or instruction screens or a selected image in a playback mode and to be switched to various modes by a slide operation. 6 and a cross key that can be pushed in the cross direction, and an operation unit 7 for selecting commands on various guidance or instruction screens by a push operation, and various information such as the composition of an image to be captured and a focal length. An optical finder 8 to be displayed is provided.

  On the other hand, on the front side of the housing 3, as shown in FIG. 3, the imaging device 1, a flash discharge tube (not shown), etc. are provided, and simultaneously with the photographing operation by the pressing operation of the shutter button 4 described above. A flash light emitting device 9 for emitting flash light is provided.

  Among these, as shown in FIG. 4, which is a component part of the imaging device 1 and is provided on the front side of the housing 3, an imaging lens 10 formed of a single lens is provided so that a subject can be imaged. . On the back side of the imaging lens 10, a beam splitter 11 that splits imaging light incident through the imaging lens 10 is provided.

  The beam splitter 11 includes a substantially cuboid dichroic prism in which four prism blocks 12, 12, 12, 12 are joined. The dichroic prism used is a three-color separation type prism, and the imaging light is separated for each primary color of red (R), green (G), and blue (B). Dichroic multilayer films 13 and 14 are formed on the boundary surfaces of the prism blocks 12, 12, 12, and 12 of such a beam splitter 11. One dichroic multilayer film 13 reflects red light, The other dichroic multilayer film 14 reflects blue light.

Correction lens groups 15R, 15G, and 15B for correcting chromatic aberration caused by the imaging lens 10 on the opposite side of the imaging lens 10 across the beam splitter 11 and both sides in the direction orthogonal to the optical axis L of the imaging light. Are arranged respectively. Therefore, these correction lens groups 15R, 15G, and 15B are arranged so as to be U-shaped when viewed from the front.
Each of the correction lens groups 15R, 15G, and 15B is composed of a plurality of lenses such as a doublet in which a plurality of lenses are combined or a single lens, and each lens is optimal for removing chromatic aberration generated in monochromatic light after spectroscopy. Designed for various conditions. The correction lens groups 15R, 15G, and 15B are zoomed by a drive mechanism (not shown) to control the lens movement amount.

  A total of three CCDs (Charge Coupled Devices) 16R, 16G, and 16B molded in a flat plate shape are disposed on the opposite side of the beam splitter 11 across the correction lens groups 15R, 15G, and 15B. These CCDs 16R , 16G, and 16B convert an input image incident as imaging light into an electrical signal. Further, an antireflection film (not shown) suitable for the wavelength of the incident monochromatic light is formed on one surface of each CCD 16R, 16G, 16B, and the monochromatic light is formed on the surface of each CCD 16R, 16G, 16B. It is designed to prevent reflection.

Next, operations of the imaging device 1 and the electronic camera 2 in the present embodiment will be described.
First, as a preparation before shooting, by operating the mode switching unit 6 to switch to the “setting mode”, for example, the flash condition is any one of “forced flash”, “flash prohibited”, or “auto flash”. Various shooting conditions are set, such as selecting an image.

  Next, after operating the mode switching unit 6 again to switch to the “shooting mode”, the viewpoint is adjusted by moving the housing 3 based on the through image displayed on the optical viewfinder 8 and the display unit 5. Let Then, at the moment when a desired image is displayed on the optical viewfinder 8 or the display unit 5, the shutter button 4 is pushed by the user, so that the image data captured by the imaging device 1 is sent to a control unit (not shown). And is stored in a built-in storage unit or an attached removable recording medium (both not shown), and a series of photographing operations is completed.

At this time, in the imaging apparatus 1, the shutter button 4 is pushed, and at the same time, a shutter (not shown) is opened, and imaging light is incident on the imaging apparatus 1 via the imaging lens 10. The incident imaging light is incident on the beam splitter 11, and then split by the dichroic multilayer films 13 and 14 of the beam splitter 11 for each primary color of RGB. Lower and, among the monochromatic light split every primary color, the optical axis L _R of the red light, is bent upward by dichroic multilayer film 13, the optical axis L _B of the blue light by the dichroic multilayer film 14 is bent in the optical axis L _G of the green light goes straight without being affected by the dichroic multilayer films 13 and 14.
Thereafter, each monochromatic light is respectively incident on the correction lens groups 15R, 15G, and 15B, and chromatic aberration is removed through a plurality of lenses, and the focal length is corrected. Finally, the image is formed on one surface of each of the CCDs 16R, 16G, and 16B, and then converted into an electrical signal, and a series of imaging operations is completed.
That is, since the correction lens groups 15R, 15G, and 15B are disposed between the beam splitter 11 and the CCDs 16R, 16G, and 16B, respectively, by designing a lens suitable for the color of the light after the spectrum. The number of lenses constituting the correction lens groups 15R, 15G, and 15B can be reduced.

  Further, since the beam splitter 11 splits the captured image into monochromatic light composed of RGB primary colors, by removing chromatic aberration from the monochromatic light, an achromatic lens that is a lens that removes chromatic aberration of two colors, A lens that removes chromatic aberration of one color, which is easy to design, can be used without using an apochromatic lens that removes chromatic aberration of three colors.

  Further, since the correction lens groups 15R, 15G, and 15B control the lens movement amount in the zoom operation for each correction lens group, even when performing the zoom operation for changing the focal length, The focal length can be adjusted for each monochromatic light.

  As described above, according to the imaging apparatus of the present embodiment, the correction lens groups 15R, 15G, and 15B are respectively disposed between the beam splitter 11 and the CCDs 16R, 16G, and 16B. By designing a lens suitable for each color, it is possible to reduce the number of lenses constituting the correction lens groups 15R, 15G, and 15B, thereby eliminating chromatic aberration and simplifying the design. Can do.

  In addition, the beam splitter 11 splits the captured image into monochromatic light composed of RGB primary colors. Therefore, the achromat is a lens that removes chromatic aberration of two colors by removing chromatic aberration from the monochromatic light after the splitting. It is possible to use a lens that removes one-color chromatic aberration, which is easy to design, without using a lens or an apochromat lens that removes three-color chromatic aberration, thereby reducing manufacturing costs.

  Furthermore, since the lens movement amounts of the correction lens groups 15R, 15G, and 15B are controlled for each correction lens group during the zoom operation, even when the zoom operation for changing the focal length is performed, the spectral movement is performed. It becomes possible to adjust the focal length for each subsequent monochromatic light, whereby the chromatic aberration of each monochromatic light can be removed.

Next, a second embodiment will be described.
In the present embodiment, as shown in FIG. 5, the incident imaging light is split into one primary color and another primary color by the beam splitter 20, and the monochromatic light and the mixed color light after the spectrum are divided into two CCDs 16 </ b> G, Light is received at 16 RBs.
Hereinafter, the second embodiment will be described with reference to FIG. However, the present embodiment differs from the first embodiment described above in the configurations of the beam splitter 20 and the correction lens groups 21 and 22, and the other components are the same as those in the first embodiment. . Therefore, in the present embodiment, description will be made centering on the configuration of the beam splitter 20 and the correction lens groups 21 and 22, and the same components as those in the first embodiment will be denoted by the same reference numerals and detailed descriptions thereof. Description is omitted.

  As shown in FIG. 5, the imaging apparatus 1 according to the present embodiment is provided with a beam splitter 20 on one surface side of the imaging lens 10 provided, as in the first embodiment. The beam splitter 20 is composed of a substantially rectangular parallelepiped half prism composed of two prism blocks 23 and 24. A dielectric multilayer film 25 that transmits a specific color is formed on the boundary surface between the prism blocks 23 and 24 of the beam splitter 20, and reflects red and blue light of incident imaging light. It is supposed to be.

Correction lens groups 21 and 22 are disposed on the opposite side of the imaging lens 10 across the beam splitter 11 and on one side in the direction orthogonal to the optical axis L of the imaging light. These correction lens groups 21 and 22 are configured such that the amount of lens movement during the zoom operation is controlled for each correction lens group by a control mechanism (not shown).
Each of the correction lens groups 21 and 22 includes a plurality of lenses such as a doublet in which a plurality of lenses are combined and a single lens. These lenses are designed under optimum conditions for removing chromatic aberration generated in the light after spectroscopy.

  Of these, one correction lens group 21 is designed to remove chromatic aberration of monochromatic light, as in the first embodiment. On the other hand, the other correction lens group 22 is designed to constitute a so-called achromat lens that removes the chromatic aberration of the mixed light of the two colors.

Next, the operation in this embodiment will be described.
The captured image passes through the imaging lens 10 as imaging light and enters the beam splitter 11. The incident imaging light is split into green monochromatic light and blue and red mixed light by the derivative multilayer film 25 of the beam splitter 11. Then, the optical axis L _RB of the blue and red of the mixed light, the derivative multilayer film 25, is bent downward, the optical axis L _G of the green monochromatic light, travels straight without being affected by the derivative multilayer film 25 .
Thereafter, the monochromatic light and the mixed color light are respectively incident on the correction lens groups 21 and 22, and the chromatic aberration is removed and the focal length is corrected through the plurality of lenses. Finally, the image is formed on one surface of each of the CCDs 16G and 16RB, and then converted into an electric signal to complete a series of imaging operations.

  At this time, since the incident picked-up image is split into green monochromatic light and blue and red mixed light by the beam splitter 20, without using an expensive apochromatic lens, the correction lens group 21, The number of installed 22 can be reduced.

  As described above, according to the imaging apparatus 1 in the present embodiment, the incident captured image is split into the green monochromatic light and the mixed light of blue and red by the beam splitter 20, so one correction lens group By designing an achromat lens, it becomes unnecessary to use an expensive apochromat lens, and the number of correction lens groups 21 and 22 can be reduced. Simplification and manufacturing cost reduction can be achieved.

It is a perspective view which shows the electronic camera in 1st Embodiment. It is a rear view which shows the electronic camera in 1st Embodiment. It is a front view which shows the electronic camera in 1st Embodiment. It is the schematic which shows the structure of the principal part of the imaging device in 1st Embodiment. It is the schematic which shows the structure of the principal part of the imaging device in 2nd Embodiment. It is the schematic which shows the structure of the principal part of the conventional imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Electronic camera 10 Imaging lens 11, 20 Beam splitter 15R, 15G, 15B, 21, 22 Correction lens group 16R, 16G, 16B, 16RB CCD

Claims (6)

An imaging lens for imaging a subject;
A spectroscopic member that separates imaging light incident through the imaging lens;
A plurality of image sensors that receive light dispersed by the spectral member and convert the light into electrical signals;
An imaging apparatus comprising: a plurality of correction lens groups that are disposed between the imaging elements and the spectral member and remove chromatic aberration caused by the imaging lens.   The imaging device according to claim 1, wherein the spectral member splits each monochromatic light composed of one primary color.   The imaging device according to claim 1, wherein the spectral member splits into monochromatic light composed of one primary color and mixed light composed of another primary color.   The imaging apparatus according to claim 3, wherein one of the plurality of correction lens groups is an achromat lens, and chromatic aberration of the mixed light is removed by the achromat lens.   5. The imaging apparatus according to claim 1, wherein the plurality of correction lens groups are controlled by a lens movement amount in a zoom operation for each correction lens group.   An electronic camera comprising the imaging device according to any one of claims 1 to 5.

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