JP2000221404A5 - Imaging optical system, optical system using the same, optical apparatus - Google Patents

Description

[0001]
Field of the Invention
The present invention relates to an imaging optical system, an optical system using the same, and an optical apparatus, and in particular, for an optical apparatus using a small imaging device such as a video camera, a digital still camera, a film scanner, or an endoscope. The present invention relates to a decentered optical system having a power on a reflecting surface.

  The present invention has been made in view of such problems in the prior art, and its object is to provide a high-performance, low-cost imaging optical system with a small number of optical elements, an optical system using the same, and an optical system It is providing a device.

  In addition, another object of the present invention is to provide a high-performance imaging optical system miniaturized by folding an optical path using a reflection surface with a small number of reflections, and an optical system and an optical apparatus using the same. It is.

  Another object of the present invention is to arrange a phase type low pass filter in the vicinity of a stop, and to make each prism an appropriate power arrangement, to thereby form a compact and higher performance imaging optical system and an optical system using the same. An optical device is provided.

Claims (27)

A first prism and a second prism are provided across the stop, and the first prism is a first surface for entering a light flux into the prism, and a second surface and a third surface for reflecting the light flux inside the prism, It has a fourth surface for emitting the light flux out of the prism, and at least one of the second and third reflecting surfaces has a rotationally asymmetric surface shape with power, and the second prism has at least three. Having three optical element surfaces, at least one of which has a rotationally asymmetric surface shape with power, and the reflection angle of the axial chief ray at the third surface of the first prism is as follows: An imaging optical system characterized by satisfying the condition, making an angle between an axial chief ray emitted from the final surface of the optical system and an off-axis chief ray small and not forming an intermediate image.
22 ° <| θs3 | <45 ° (1)
Here, θs3 is the reflection angle of the axial chief ray at the third surface of the first prism, assuming that the ray passing through the center of the object point and passing through the center of the aperture to reach the image plane center is the axial chief ray. That is, it is the angle between the normal of the decentered direction of the reflecting surface and the axial chief ray at the intersection of the axial chief ray and the third surface of the first prism. A first prism and a second prism are provided across the stop, and the first prism is a first surface for entering a light flux into the prism, and a second surface and a third surface for reflecting the light flux inside the prism, It has a fourth surface for emitting the light flux out of the prism, and at least one of the second and third reflecting surfaces has a rotationally asymmetric surface shape with power, and the second prism has at least three. Having two optical element surfaces, at least one of which has a rotationally asymmetric surface shape with power, and an axial main surface from the optical surface at the most image side of the second prism to the image surface An imaging optical system characterized in that the distance between light rays satisfies the following condition, the angle between the axial chief ray emitted from the final surface of the optical system and the off-axis chief ray is small, and an intermediate image is not formed.
0.6 f <FB <2.0 f (2)
Here, when the light passing through the center of the object point and passing through the center of the stop and reaching the center of the image plane is the axial chief ray, the optical action surface located closest to the image side of the second prism to the image plane Represents the length along the axial chief ray up to the point where the refractive index of the medium is 1.0 (air), and f is the total focal length of the imaging optical system.   A first prism and a second prism are provided across the stop, and the first prism is a first surface for entering a light flux into the prism, and a second surface and a third surface for reflecting the light flux inside the prism, It has a fourth surface for emitting the light flux out of the prism, and the four surfaces are each composed of independent surfaces, and at least one of the second and third reflective surfaces is rotationally asymmetric with power. The second prism has a reflecting surface that reflects a light beam in the prism, and the reflecting surface has a rotationally asymmetric surface shape with power, the first prism and the second prism An imaging optical system characterized in that a phase type low pass filter is disposed between the two, and an intermediate image is not formed. 3. The image forming optical system according to claim 2, wherein a distance of an axial chief ray from an optical action surface closest to the object side of the second prism to an image plane satisfies the following condition.
2.5f <DR <5.5f (3)
Here, DR denotes an optical action surface located on the most object side of the second prism when a ray passing through the object center and passing through the aperture center and reaching the image plane center is the on-axis chief ray. Shows the length along the axial chief ray up to the point where the refractive index of the medium is 1.0 (air).   The first prism arranges the first surface and the fourth surface so as to face each other across the medium, and arranges the two faces and the third surface so as to face each other via the medium The imaging optical system according to any one of claims 1 to 4, wherein the imaging optical system is configured to form a Z-shaped optical path.   The second surface of the reflective surface or the reflective surface between the first surface that allows the light flux to enter the prism and the fourth surface that emits the light flux out of the prism are not disposed adjacent to each other. The imaging optical system according to any one of claims 1 to 4, wherein the imaging optical system is arranged in a positional relationship in which the third surface is sandwiched.   Both the second surface and the third surface of the first prism are configured to provide a power to the light beam and to have a rotationally asymmetric surface shape that corrects an aberration generated due to decentration. Item 7. The imaging optical system according to any one of Items 1 to 6.   The rotationally asymmetric surface shape of at least one of the second surface and the third surface of the first prism is configured as a plane-symmetry free-form surface shape having only one plane of symmetry. An imaging optical system according to any one of items 1 to 6.   The rotationally asymmetric surface shape of both the second surface and the third surface of the first prism is configured as a plane-symmetry free-form surface shape having only one plane of symmetry. Imaging optical system as described.   The sole symmetry plane of the plane-symmetry free-form surface of the second surface of the first prism and the sole symmetry plane of the plane-symmetry free-form surface of the third surface of the first prism are formed in the same plane The imaging optical system according to claim 9, wherein the first prism is configured.   At least one surface of the first surface or the fourth surface of the first prism is configured to have a rotationally asymmetric surface shape that applies power to the light beam and corrects an aberration generated due to decentration. The imaging optical system according to any one of claims 1 to 10, characterized in that:   The rotationally asymmetric surface shape of at least one of the first surface or the fourth surface of the first prism is configured as a plane-symmetry free-form surface shape having only one plane of symmetry. 11. The imaging optical system as described in 11.   13. The rotationally asymmetric surface shape disposed in the second prism is configured as a plane-symmetry free-form surface shape having only one plane of symmetry, as one surface symmetry. An imaging optical system according to the item.   14. A plane-symmetry free-form surface according to claim 13, wherein at least one plane of symmetry of said first prism and said second prism is arranged on the same plane. Imaging optics.   The image forming optical system according to any one of claims 1 to 14, wherein the second prism is configured to have two or more curved surface-shaped reflecting surfaces for giving a power to a light beam.   The optical action surface of the second prism is composed of three optical action surfaces: an incident surface that doubles as a reflective surface and a transmissive surface, a reflective surface, and an exit surface. An imaging optical system according to any one of the above.   The second prism according to any one of claims 1 to 14, wherein the second prism comprises two reflecting surfaces for giving power to a light beam, an incident surface, and four optically acting surfaces of an emitting surface. Imaging optics.   The second prism according to claim 1, wherein the second prism comprises three optical action surfaces: an incident surface, an exit surface serving both as a reflecting surface and a transmitting surface, and a reflecting surface for applying power to a light beam. 14. The imaging optical system according to any one of 14.   The image forming optical system according to any one of claims 1 to 18, wherein a second reflection surface which is a third surface of the first prism is configured by a rotationally asymmetric surface having positive power.   The first reflecting surface which is the second surface of the first prism is a rotationally asymmetric surface having a negative power, and the second reflecting surface which is a third surface is a rotationally asymmetric surface having a positive power. The imaging optical system according to any one of claims 1 to 18, characterized in that:   The imaging optical system according to any one of claims 1 to 18, wherein a third surface of the second prism is a second reflecting surface, and the second reflecting surface is a rotationally asymmetric surface having positive power. .   22. An image erecting optical system in which the imaging optical system according to any one of claims 1 to 21 is disposed as a finder objective optical system, and further, an object image formed by the finder objective optical system is erected positive. A finder optical system comprising an eyepiece optical system.   A camera apparatus comprising: the finder optical system according to claim 22; and an objective optical system for photographing which is juxtaposed to the finder optical system.   An imaging system comprising: the imaging optical system according to any one of claims 1 to 21; and an imaging device disposed on an image plane formed by the imaging optical system. Optical system.   The imaging optical system according to any one of claims 1 to 21 is disposed as an objective optical system for imaging, and is divided from an optical path different from the optical system for imaging or an optical path of the objective optical system for imaging. A camera apparatus comprising: a finder optical system disposed in any of the optical paths.   22. The imaging optical system according to any one of claims 1 to 21, an imaging element disposed on an image plane formed by the imaging optical system, and image information received by the imaging element. What is claimed is: 1. An electronic camera device comprising: a recording medium; and an image display element that receives image information from the recording medium or the imaging device to form an observation image.   22. An observation system comprising: the imaging optical system according to any one of claims 1 to 21; an image transmission member for transmitting an image formed by the imaging optical system along the long axis direction; An endoscope apparatus comprising: an illumination system having an illumination light transmission member for transmitting illumination light from the illumination light source along the long axis direction.