JP2011107594A - Imaging optical system and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a more inexpensive imaging optical system which can obtain a wider angle of view while holding a sharp image and compact form, and can securely and also easily achieve focusing. <P>SOLUTION: The imaging optical system includes: a refraction type optical element group 2 having negative refractive power; and a reflection type optical element group 3 having positive refractive power. The refraction type optical element group 2 is arranged on the side of a subject and is supported movably along a rotationally symmetric axis S1, and the reflection type optical element group 3 is arranged in such a manner that an optical axis S is reflected in a folded way. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging optical system used for an imaging device for imaging a subject such as a cellular phone, a vehicle, a monitoring device, and an industrial device, and an imaging device using the imaging optical system.

  Imaging devices such as CCDs and CMOSs are widely used for mobile phones, in-vehicle use, monitoring use, industrial use, and the like. An optical system combined with each of these uses is required to have a clear image, a small size, and a low price. In terms of obtaining a clear image, it is preferable to employ a reflecting surface that is low-noise light and does not generate chromatic aberration. Moreover, also about the point made small, the whole optical system can be made compact compared with refractive optical systems, such as a lens, by arrange | positioning a some reflective surface so that an optical axis may be folded.

  As prior art document information related to an imaging optical system having an advantage of a reflecting surface, for example, there are the following Patent Documents 1 and 2.

Japanese Patent No. 3043583 Japanese Patent Laid-Open No. 2005-62803

  Patent Documents 1 and 2 disclose an imaging device of a reflective optical system using a plurality of reflecting surfaces. Such an image pickup apparatus uses a reflecting surface that is low noise light (low flare, low ghost) and does not generate chromatic aberration, and thus can obtain a clear image. Furthermore, since the plurality of reflecting surfaces are arranged so as to fold the optical axis, the entire imaging apparatus can be made compact compared to a refractive optical system such as a lens.

  However, the reflection type optical systems as disclosed in Patent Documents 1 and 2 have a problem that the angle of view is narrow while the entire imaging apparatus can be made compact. One way to obtain a wide angle of view is to widen the entrance. However, the range in which the entrance can be expanded is a range in which the entrance and the reflecting surface do not overlap in the incident direction of the light beam. That is, if the entrance and the reflecting surface overlap in the incident direction of the light beam, the light beam incident on the overlapping reflecting surface hits and a shadow of a portion that hits the formed image is generated. Further, in this case, the occurrence of shadows can be prevented by shifting in the radial direction so as to correspond to the entrance where the reflecting surface is expanded, but the imaging apparatus becomes larger by this shifted distance. That is, in view of the downsizing of the image pickup apparatus, there is a limit to means for widening the entrance and obtaining a wide angle of view.

  In addition, Patent Documents 1 and 2 do not disclose a focus adjustment structure, but a reflection surface that is generally used as a focus adjustment structure of such a reflective optical system is moved back and forth. When the entire operation method for adjusting the focus is used, the image pickup apparatus becomes large and heavy due to the feeding mechanism. Further, it is conceivable to adjust the focus by moving the reflecting surface alone, but in this case, an image shift occurs during reflection, and it is difficult to correct the shift.

  This invention makes it an example of a subject to cope with such a problem. That is, it is an object of the present invention to obtain a wider angle of view while maintaining a clear image and a compact form, and to reliably and easily perform focus adjustment.

  In order to achieve such an object, the switchgear and the reference position correction method for the switchgear according to the present invention include at least the following configurations.

  An imaging optical system according to the present invention includes a refractive optical element group having a negative refractive power and a reflective optical element group having a positive refractive power, and the refractive optical element group is disposed on the subject side. Has been.

  The above-described reflective optical element group is composed of a plurality of reflecting mirror members, and the plurality of reflecting mirror members are arranged so as to fold the optical axis.

  The above-described refractive optical element group is a plurality of lens members having different Abbe numbers.

  The plurality of lens members described above are bonded to each other.

  The above-described refractive optical element group has a common rotational symmetry axis and is supported so as to be movable along this rotational symmetry axis.

  The imaging apparatus includes the imaging optical system described above, and includes an imaging device on which an optical image of a subject is formed by the imaging optical system.

  According to the present invention, a clear image and a compact form can be maintained, a wider angle of view can be obtained, and focus adjustment can be performed reliably and easily.

1 is a cross-sectional view of an imaging apparatus using an imaging optical system according to a first embodiment of the present invention. The schematic diagram (side view) which shows the cross-section optical path of the imaging optical system of FIG. The schematic diagram (plan view) which shows the cross-section optical path of the imaging optical system of FIG. Specifications of the imaging optical system according to the first embodiment. Same as above, configuration data of the imaging optical system. Same as above, lateral aberration of imaging optical system. FIG. 6 is a schematic diagram (side view) showing a cross-sectional optical path of an imaging optical system according to a second embodiment. FIG. 2 is a schematic diagram (plan view) showing a cross-sectional optical path of the imaging optical system. Specifications of the imaging optical system according to the second embodiment. Same as above, configuration data of the imaging optical system. Same as above, lateral aberration of imaging optical system.

  Hereinafter, embodiments of an imaging optical system and an imaging apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a first embodiment of an image pickup apparatus using an image pickup optical system according to the present invention, and FIGS. 2 and 3 are schematic views showing a cross-sectional optical path of the image pickup optical system of FIG. 2 shows an optical path in a side view, and FIG. 3 shows an optical path in a plan view.

  The imaging apparatus A includes an imaging optical system B in which a refracting optical element group 2 having negative refracting power and a reflecting optical element group 3 having positive refracting power are built in a housing 1. A built-in image pickup device 4 for forming an optical image of a subject by the image pickup optical system B is provided.

  The housing 1 supports the refractive optical element group 2 and has an entrance 10 for taking the light R into the imaging optical system B, and an optical path secured until the light R entering from the entrance 10 reaches the image sensor 4. A space 11 is formed. The opening direction of the entrance 10 is a direction in which the axis is coaxial with the optical axis S of the central light ray R.

  In addition, the housing 1 has an antireflection process (not shown) on the inner surface of the optical path space 11 and at least the inner surface that affects the reflection component to the image sensor 4. By this antireflection treatment, flare is reduced by absorbing the reflection component and preventing it from reaching the image sensor 4.

  In the optical path space 11, a light source 12 for irradiating the subject with infrared rays or visible rays is provided. The light source 12 is arranged so that a light beam (not shown) from the light source 12 is directed to the refractive optical element group 2, and this light beam passes through the refractive optical element group 2 and is a subject (not shown). To be irradiated. Since the optical axis (not shown) of the light beam passing through the refractive optical element group 2 is diffused in the direction of spreading due to the negative refractive power of the refractive optical element group 2, the object is irradiated over a wide range. ing.

  The refractive optical element group 2 is an element group composed of two lens members 20 and 21 that are joined. The lens member 20 is a plano-convex lens disposed on the subject side, and the lens member 21 is a plano-concave lens disposed on the imaging element 4 side, and has a negative refractive power by overlapping and joining each other's flat surfaces. The refraction type optical element group 2 having That is, the incident optical axis S can be refracted in the converging direction by the negative refractive power of the refractive optical element group 2 (see FIGS. 2 and 3).

  In addition, since the number of air interfaces is reduced by joining the lens members 20 and 21, the surface reflection of the lens members 20 and 21 is reduced, light loss due to the surface reflection is suppressed, and a clear image can be formed. it can.

  Further, the refractive optical element group 2 uses lens members 20 and 21 having different Abbe numbers that are appropriately selected in order to correct chromatic aberration due to refraction, respectively. 21 corrects the chromatic aberration to obtain a good image over a wide wavelength range from infrared rays to visible rays.

  Further, the refractive optical element group 2 has the rotational symmetry axis S1 of the lens members 20 and 21 in common, and is supported so as to be movable along the rotational symmetry axis S1, and by movement along the rotational symmetry axis S1. Focus adjustment is performed.

  The focus adjustment structure of the refractive optical element group 2 will be specifically described. The refractive optical element group 2 is fitted and supported in a lens barrel 5 that is screwed to the incident port 10 of the housing 1 so as to be coaxial with the axis of the incident port 10. The refractive optical element group 2 is arranged such that the rotationally symmetric axis S1 is coaxial with the axis of the lens barrel 5, and a lens holding ring 50 that is screwed onto the inner periphery of the lens barrel 5 on the subject side. It is fixed by. The lens barrel 5 is screwed to the inner circumference of the entrance 10 and is fixed by a barrel fixing ring 51 screwed to the outer circumference of the lens barrel 5.

  According to such a focus adjustment structure, when the lens barrel fixing ring 51 is tightened and screwed, the lens barrel 5 is fixed to the entrance 10. By rotating the lens barrel fixing ring 51 from this fixed state in the direction of loosening (the direction of unscrewing), the lens barrel 5 can be screwed. Then, the focus of the lens barrel 5 is adjusted by rotating the lens barrel 5 by adjusting the feed amount of the lens barrel 5. After the focus adjustment, the lens barrel 5 is fixed to the entrance 10 by rotating the barrel fixing ring 51 again in the tightening direction and tightening and screwing.

  In this embodiment, a helicoid screw is used for screwing the entrance 10 and the lens barrel 5 and between the lens barrel 5 and the barrel fixing ring 51. The helicoid screw has a smooth feeding force and a strong force. On the other hand, there is no “play” when returning from feeding, so it is suitable for structures that require precise movements such as focusing.

  In addition, this invention is not restricted to the helicoid screw illustrated in the structure which performs a focus adjustment, The focus adjustment by structures other than a helicoid screw is included.

  In the present embodiment, the entrance 10 is closed with the refractive optical element group 2 fixed to the lens barrel 5, thereby preventing dust and the like from entering the optical path space 11. With this configuration, the surface of the lens member 21 facing the optical path space 11, the reflective optical element group 3, the image pickup element 4, the light source 12, and the like are prevented from being stained, and an unclear image due to this stain is not generated.

  The refractive optical element group 2 is not limited to the configuration in which the lens members 20 and 21 are joined, and includes a configuration in which the lens members 20 and 21 are separated. In this case, it is preferable to suppress light loss due to surface reflection (not shown) by applying a multilayer coating on the surfaces of the lens members 20 and 21 to suppress surface reflection. The multilayer coating described above may be performed in a configuration in which the lens members 20 and 21 are joined to each other (not shown).

  The reflective optical element group 3 is an element group composed of four reflecting mirror members: a first reflecting mirror member 30, a second reflecting mirror member 31, a third reflecting mirror member 32, and a fourth reflecting mirror member 33. . Each reflecting mirror member reflects the optical axis S incident from the entrance 10 so that the optical axis S is sequentially folded to the first reflecting mirror member 30 to the fourth reflecting mirror member 33 and reaches the image sensor 4. The reflecting surfaces 30A, 31A, 32A, and 33A of the mirror member are arranged so that the reflecting surface centers (surfaces on which the optical axis S of the central light ray R is reflected) are aligned. Each reflecting mirror member is fixedly held by the holding portion 13 formed in the housing 1 so as to ensure the accuracy of the reflecting surface centers of the reflecting surfaces 30A, 31A, 32A, and 33A.

  In the present embodiment, a part of the second reflecting mirror member 31 closest to the entrance 10 is arranged so as to overlap with the entrance 10 in the incident direction of the light beam R, thereby contributing to the downsizing of the imaging device A. ing. Normally, the incident light ray R hits a part of the second reflecting mirror member 31, but in the imaging optical system B of the present embodiment, the optical axis S is focused by the negative refractive power of the refractive optical element group 2. The second reflecting mirror member 31 is refracted in the direction so as to avoid a part of the second reflecting mirror member 31 and reach the first reflecting mirror member 30 (see FIG. 2). Accordingly, even if a part of the second reflecting mirror member 31 is arranged so as to overlap the incident port 10 in the incident direction of the light ray R, no shadow is generated in the formed image.

  In the present embodiment, the reflecting surfaces 30A, 31A, and 33A of the first reflecting member 30, the second reflecting member 31, and the fourth reflecting member 33 are anamorphic aspheric surfaces, and the reflecting surfaces of the third reflecting member 32 are used. 32A is a spherical surface. Further, the reflecting surface 32A of the third reflecting mirror member 32 also serves as a diaphragm surface, and this diaphragm surface improves the contrast performance.

  The image sensor 4 of the present embodiment is a photosensitive element such as a CCD or CMOS that converts a light beam that has reached the image sensor 4 through the imaging optical system B into an electrical signal. The converted electrical signal is variously processed by the electrical board 14 provided in the housing 1 and transmitted to a display device (not shown) to be displayed as an image.

  The anamorphic aspheric surfaces of the first reflector member 30, the second reflector member 31, and the fourth reflector member 33 of the present embodiment are defined by the following formula 1.

However, each coefficient in Formula 1 is as follows.

Rx: radius of curvature in the X direction at the center of the plane Kx: conic coefficient in the X direction Ry: radius of curvature in the Y direction at the center of the plane Ky: conic coefficient in the Y direction

Ay: Fourth-order aspheric coefficient of rotationally symmetric component Ax: Fourth-order aspherical coefficient of non-rotational symmetric component By: Sixth-order aspherical coefficient of rotationally symmetric component Bx: Sixth-order aspherical coefficient of non-rotational symmetric component Cy: Rotational symmetry 8th-order aspheric coefficient of component Cx: 8th-order aspheric coefficient of non-rotation symmetric component Dy: 10th-order aspheric coefficient of rotation-symmetric component Dx: 10th-order aspheric coefficient of non-rotation symmetric component

  4 shows specifications of the imaging optical system B, FIG. 5 shows configuration data of the imaging optical system B, and FIG. 6 shows lateral aberrations of the imaging optical system B.

  According to the imaging apparatus A and the imaging optical system B of the present embodiment, a clear image and a compact form can be maintained, and a wider angle of view can be obtained, and focus adjustment can be performed reliably and easily. it can.

  That is, a wide angle of view can be obtained by the refractive optical element group 2 having negative refractive power arranged on the entrance 10 side, and reflective optical having positive refractive power arranged on the optical path space 11 side. The element group 3 can fold the optical axis S into a compact form and can form a clear image with low noise light. Further, since the focus adjustment is performed by the movement of the refractive optical element group 2 along the rotational symmetry axis S1, and the movement is performed by screw rotation, the focus adjustment can be reliably performed with a simple structure. In addition, it is possible to prevent the imaging apparatus A from becoming large or heavy as in the overall operation method. Further, by appropriately selecting the Abbe number in the lens members 20 and 21, and by coating the lens surface with a multilayer film, it is possible to minimize the correction of chromatic aberration due to the refractive surface and the occurrence of flare.

  7 to 11 show a second embodiment of the imaging optical system according to the present invention. 7 and 8 are schematic views showing a cross-sectional optical path of the imaging optical system C of the present embodiment (FIG. 7 is a side view and FIG. 8 is a plan view). 9 shows specifications of the imaging optical system C, FIG. 10 shows configuration data of the imaging optical system C, and FIG. 11 shows lateral aberrations of the imaging optical system C.

  The imaging optical system C is smaller than the above-described imaging optical system B in that the external dimensions of the refractive optical element group 2, the reflective optical element group 3, and the imaging element 4 are reduced to a more compact form. Since the structures of the refractive optical element group 2, the reflective optical element group 3, and the imaging element 4 are the same as those of the imaging optical system B of the first embodiment, the description thereof is omitted by attaching the same reference numerals.

  According to the imaging optical system C of the present embodiment, the same effect as the imaging optical system B of the first embodiment can be obtained, and a more compact form can be achieved. And it can apply to the same structure as the imaging device A of 1st Embodiment, and a smaller imaging device (not shown).

  The imaging optical system of the present invention is not limited to use in an imaging apparatus such as a camera as illustrated, but can be used in a projection apparatus such as a projector. Further, the image pickup device is not limited to a CCD or a CMOS, and other photosensitive devices can be used. In addition, the imaging apparatus and the imaging optical system are not limited to the illustrated embodiment, and can be implemented with a configuration in a range that does not deviate from the contents described in the claims.

A: Imaging device B: Imaging optical system C: Imaging optical system 2: Refraction type optical element group 3: Reflection type optical element group 30-33: Reflective mirror member 20, 21: Lens member 4: Imaging element S: Optical axis S1 : Axis of rotation

Claims (6)

A refractive optical element group having negative refractive power;
A reflective optical element group having positive refractive power;
With
The refractive optical element group is an imaging optical system arranged on the subject side.   The imaging optical system according to claim 1, wherein the reflective optical element group includes a plurality of reflecting mirror members, and the plurality of reflecting mirror members are arranged to fold an optical axis.   The imaging optical system according to claim 1, wherein the refractive optical element group is a plurality of lens members having different Abbe numbers.   The imaging optical system according to claim 3, wherein the plurality of lens members are bonded to each other.   5. The imaging optical system according to claim 1, wherein the refractive optical element group has a common rotational symmetry axis and is movably supported along the rotational symmetry axis. 6.   6. An image pickup apparatus comprising the image pickup optical system according to claim 1, further comprising an image pickup element on which an optical image of a subject is formed by the image pickup optical system.

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