JP2006078937A - Telescope optical system and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telescope optical system and an imaging apparatus capable of facilitating focusing. <P>SOLUTION: In a telescope optical system which is provided with a eyepiece 4 for observing an image 3 formed by an objective lens 1, an aperture diaphragm 11 for closing the diameter of luminous flux at the exit pupil position is arranged between the objective lens 1 and image 3 image forming position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a telescope optical system and an imaging apparatus.

  FIG. 6 is a conceptual diagram showing a cross section of a conventional ground telescope.

  An objective lens 101, an erecting prism 102, and an eyepiece lens 104 are arranged from an observation target (not shown) in a lens barrel 105A of the ground telescope.

  An image 103 is formed in front of the eyepiece 104 by the objective lens 101, and this image 103 is observed through the eyepiece 104. The inverted image is restored by the erecting prism 102.

  For example, natural observation such as birdwatching is performed visually using a ground telescope with a magnification of about 20 to 80 times.

  In recent years, digital cameras have become widespread, and an increasing number of people shoot observation objects such as wild birds by combining digital cameras with ground telescopes.

  By placing a digital camera behind the eyepiece of the terrestrial telescope, it is possible to shoot with super telephoto. The focal length of the photographing optical system at this time is a value obtained by multiplying the focal length of the digital camera by the magnification of the ground telescope.

  In order to shoot without vignetting around the field of view, it is necessary to match the entrance pupil position of the digital camera and the exit pupil position (eye point) of the telescope. In order to shoot without vignetting in the zoom type digital camera, shooting is usually performed on the telephoto side so that the entrance pupil position is as close to the object side of the lens as possible.

  Since the size of the image sensor of a digital camera is very small compared to the size of a 35 mm film, when the focal length of the entire photographic optical system is converted into the focal length of a 35 mm camera lens, the focal length exceeds several thousand mm. Corresponds to a telephoto lens.

  A lens with a long focal length can capture a large observation object, but the depth of field is shallow (when the observation object is close, the depth of field is about several centimeters).

An example of the relationship between the focal length of the photographing optical system and the depth of field is shown below.
Terrestrial telescope magnification 30x Terrestrial telescope objective lens diameter (aperture stop diameter) 80mm
Digital camera focal length 15mm
Imaging optical system focal length 450mm
Digital camera pixel size 3μm
Image height on the image sensor 6μm
Shooting distance 20m
Depth of field ± 6.4cm

  The aperture stop diameter was the diameter of the central beam of the field at the position of the objective lens of the terrestrial telescope.

In the calculation of the depth of field, the image height on the image sensor is a value at an interval when one pixel is sandwiched between two points.
JP-A-4-67115

  By the way, when the depth of field is shallow, since the in-focus range is narrow, it is difficult to focus on an observation object that moves like a wild bird or a deep observation object.

  On the other hand, when the depth of field is increased, the in-focus range is widened, so that it is easy to focus on an observation object that moves like a wild bird or a deep observation object.

  The depth of field can be increased by reducing (squeezing) the diameter of the aperture stop.

  However, since the aperture (effective diameter) of the objective lens functions as an aperture stop in the terrestrial telescope, the diameter of the aperture stop cannot be reduced and the depth of field cannot be controlled.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a telescope optical system and an imaging apparatus that can easily perform focusing.

  In order to solve the above-mentioned problem, an invention according to claim 1 is an object of the present invention to provide an aperture stop for reducing the diameter of a light beam at the exit pupil position in a telescope optical system having an eyepiece for observing an image formed by an objective lens. It is characterized by having.

  According to a second aspect of the present invention, in the telescope optical system according to the first aspect, the aperture stop is disposed between the objective lens and a position where the image is formed.

  According to a third aspect of the present invention, in the telescope optical system according to the first aspect, the aperture stop is disposed on the object side of the objective lens.

  According to a fourth aspect of the present invention, in the telescope optical system according to the third aspect, the aperture stop is detachable from a lens barrel of the objective lens.

  According to a fifth aspect of the present invention, in the telescope optical system according to the first or second aspect of the present invention, the telescopic optical system includes a moving unit that moves the aperture stop along the optical axis of the objective lens.

  According to a sixth aspect of the present invention, in the telescope optical system according to any one of the first to fifth aspects, an erecting prism is disposed between the objective lens and a position where the image is formed. It is characterized by that.

  The invention described in claim 7 is characterized in that an imaging means is disposed behind the eyepiece lens of the telescope optical system according to any one of claims 1 to 6.

  According to the telescope optical system and the imaging apparatus of the present invention, focusing can be easily performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram showing a cross section of the ground telescope according to the first embodiment of the present invention.

  A digital camera (imaging device) 8 is arranged behind the eyepiece 4 of the ground telescope (telescope optical system) 5.

  The terrestrial telescope 5 includes an objective lens 1, an erecting prism 2, an eyepiece lens 4, and an aperture stop 11.

  The digital camera 8 includes an imaging lens system 6 and an image sensor (imaging means) 7.

  The exit pupil position (not shown) of the terrestrial telescope 5 coincides with the entrance pupil position (not shown) of the digital camera 8.

  The effective diameter of the objective lens 1 is φS.

  The aperture stop 11 changes the effective diameter of the objective lens 1 to reduce the diameter of the light beam at the exit pupil position.

  The aperture stop 11 is disposed between the objective lens 1 and the position of the image 3 formed by the objective lens 1.

  A ring member 12 for changing the diameter of the aperture stop 11 is rotatably provided on the outer peripheral surface of the lens barrel 5A.

  The ring member 12 is connected to the aperture stop 11 via the conversion mechanism 13. The conversion mechanism 13 converts the rotation of the ring member 12 into a change in the diameter of the aperture stop 11.

  Instead of the ring member 12, a lever (not shown) that changes the diameter of the aperture stop 11 may be provided on the outer peripheral surface of the lens barrel 5A.

  An image 3 is formed in front of the eyepiece 4 by the objective lens 1 (the inverted image is restored by the erecting prism 2). The light beam emitted from the terrestrial telescope 5 via the eyepiece 4 passes through the exit pupil (incidence pupil) and is re-imaged on the image sensor 7 via the eyepiece 6.

  When photographing using the digital camera 8, the ring member 12 is rotated as necessary.

  When the ring member 12 is rotated, the diameter of the aperture stop 11 is reduced according to the rotation of the ring member 12. As a result, the effective diameter (φS) of the objective lens 1 is reduced (the diameter of the light beam at the exit pupil position of the ground telescope 5 is reduced), and the depth of field is increased.

When the diameter of the aperture stop 11 was changed, the depth of field changed as follows.
Shooting distance: 20m
Aperture aperture diameter 80mm 70mm 60mm
Depth of field ± 6.4 cm ± 7.3 cm ± 8.5 cm

The use of the terrestrial telescope 5 and the digital camera 8 is as follows.
Terrestrial telescope magnification 30x Terrestrial telescope objective lens diameter 80mm
Digital camera focal length 15mm
Imaging optical system focal length 450mm
Digital camera pixel size 3μm

  According to this embodiment, since the depth of field can be increased according to the diameter of the aperture stop 11 and the range in focus can be expanded, focusing can be performed easily.

  FIG. 2 is a plan view showing an example of an aperture stop.

  The aperture stop 11 is configured by combining a plurality (five in FIG. 2) of stop blades 11a to 11e. The area of the opening 11A is changed by rotating the diaphragm blades 11a to 11e around one end. When the area of the opening 11A is the maximum, it is substantially circular as shown in the figure.

  FIG. 3 is a conceptual diagram showing a cross section of a terrestrial telescope according to the second embodiment of the present invention. Portions common to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  This embodiment is different from the first embodiment in that the aperture stop 21 is arranged on the object side of the objective lens 1 (the object side of the lens barrel 15A of the ground telescope (telescope optical system) 15).

  The terrestrial telescope 15 includes an objective lens 1, an erecting prism 2, an eyepiece lens 4, and an aperture stop 21.

  The aperture stop 21 is a combination of a plurality of aperture blades as in the first embodiment.

  A ring member 22 for changing the diameter of the aperture stop 21 is rotatably provided on the outer peripheral surface of the lens barrel 15A.

  The ring member 22 is connected to the aperture stop 21 via the conversion mechanism 23. The conversion mechanism 23 converts the rotation of the ring member 22 into a change in the diameter of the aperture stop 21.

  Instead of the ring member 22, a lever (not shown) that changes the diameter of the aperture stop 21 may be provided on the outer peripheral surface of the lens barrel 15A.

  When photographing using the digital camera 8, the ring member 22 is rotated as necessary.

  According to this embodiment, the same effects as those of the first embodiment can be obtained, and the aperture stop 21 is disposed close to the front surface of the objective lens 1, so that the peripheral luminous flux can be used effectively during photographing. .

  FIG. 4 is a conceptual diagram showing a cross section of a terrestrial telescope according to a third embodiment of the present invention. The parts common to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  This embodiment is different from the first embodiment in that the aperture stop 31 is detachably disposed on the object side of the objective lens 1 (the object side of the lens barrel 25A of the ground telescope (telescope optical system) 25).

  The terrestrial telescope 25 includes an objective lens 1, an erecting prism 2, an eyepiece lens 4, and an aperture stop 31.

  The aperture stop 31 includes a cylindrical portion 31a that can slide with respect to the inner peripheral surface of the lens barrel 25A, and a donut-shaped disc portion 31b that is integrally formed at one end of the cylindrical portion 31a. The effective diameter (φS) of the objective lens 1 (the diameter of the light beam at the exit pupil position of the terrestrial telescope 25) is reduced by the disc portion 31b.

  When photographing using the digital camera 8, an aperture stop 31 is attached to the object side of the objective lens 1 as necessary.

  Although this embodiment does not continuously change the aperture diameter as in the first and second embodiments, a plurality of aperture stops 31 having different aperture diameters (diameters of the opening portions of the disk portion 31b) are prepared in advance. If so, you can shoot without problems in practice.

  According to this embodiment, the same effects as those of the first embodiment can be obtained. In addition, when only visual observation is performed without photographing, the aperture stop 31 can be removed as indicated by the dotted line, so that the ground telescope 25 can be reduced in weight and easily carried. Furthermore, since a mechanism for changing the diameter of the aperture stop 11 or the like is not required, the ground telescope 25 can be provided at a low cost. In addition, since the aperture stop 31 can be attached to a conventional terrestrial telescope that does not have a built-in aperture stop, it is possible to widen the object to be photographed without much cost.

  FIG. 5 is a conceptual diagram showing a cross section of a terrestrial telescope according to a fourth embodiment of the present invention. Portions common to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  This embodiment is different from the first embodiment in that the aperture stop 41 can be moved along the optical axis of the objective lens 1.

  The terrestrial telescope (telescope optical system) 35 includes an objective lens 1, an erecting prism 2, an eyepiece lens 4, and an aperture stop 41.

  The aperture stop 41 is a donut-shaped disk and moves between a position a on the optical axis L and a position b (a position where the light flux is not limited). By moving the aperture stop 41, the diameter of the light beam incident from the objective lens 1 can be reduced.

  A rotating ring 42 for moving the aperture stop 41 is rotatably provided on the outer peripheral surface of the lens barrel 35A. A conversion mechanism 45 that converts the rotational force of the rotary ring 42 into the linear motion of the aperture stop 41 is disposed in the lens barrel 35A.

  The rotating ring 42 and the conversion mechanism 45 constitute the moving means of claim 5. This moving means is the same as the mechanism for moving the focusing lens in the optical system in the optical axis direction using the focus ring (corresponding to the rotating ring 42) of a telescope or binoculars.

  A lever (not shown) may be provided in place of the ring member 42.

  When photographing, the ring member 42 is rotated as necessary.

  According to this embodiment, the same effects as those of the first embodiment can be obtained.

  In the first and fourth embodiments, when the positions of the aperture stops 11 and 41 are close to the image plane 3, the central beam of the field of view that mainly affects the depth of field is not reduced at the time of shooting, and only the peripheral beam of the field of view is reduced. Since there is a risk of reduction, it is preferable to set the position so that it can be reduced from the central beam of the field of view (position where the aperture stops 11 and 41 are far from the image plane 3).

FIG. 1 is a conceptual diagram showing a cross section of the ground telescope according to the first embodiment of the present invention. FIG. 2 is a plan view showing an example of an aperture stop. FIG. 3 is a conceptual diagram showing a cross section of the ground telescope according to the second embodiment of the present invention. FIG. 4 is a conceptual diagram showing a cross section of the ground telescope according to the third embodiment of the present invention. FIG. 5 is a conceptual diagram showing a cross section of a ground telescope according to a fourth embodiment of the present invention. FIG. 6 is a conceptual diagram showing a cross section of a conventional ground telescope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Erect prism 3 Image 4 Eyepiece 5, 15, 25, 35 Terrestrial telescope (telescope optical system)
5A, 15A, 25A, 35A Lens barrel 7 Imaging element (imaging means)
8 Digital camera (imaging device)
11, 21, 31, 41 Aperture stop 12 Ring member (diameter changing means)
42 Rotating ring 45 Conversion mechanism

Claims (7)

  A telescope optical system comprising an eyepiece for observing an image formed by an objective lens, wherein the telescope optical system comprises an aperture stop for reducing the diameter of the light beam at the exit pupil position.   The telescope optical system according to claim 1, wherein the aperture stop is disposed between the objective lens and a position where the image is formed.   The telescope optical system according to claim 1, wherein the aperture stop is disposed on an object side of the objective lens.   4. The telescope optical system according to claim 3, wherein the aperture stop is removable from the lens barrel of the objective lens.   3. The telescope optical system according to claim 1, further comprising a moving unit that moves the aperture stop along the optical axis of the objective lens.   6. The telescope optical system according to claim 1, wherein an erecting prism is disposed between the objective lens and a position where the image is formed.   An imaging apparatus, wherein imaging means is arranged behind the eyepiece of the telescope optical system according to any one of claims 1 to 6.

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