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Optical filter and optical device

a technology of optical filter and optical device, which is applied in the direction of polarising elements, instruments, television systems, etc., can solve the problems of difficult to implement quality control, reduce the degree of freedom of design, and difficult to provide optical filter plate within limited space, so as to achieve efficient utilization of limited space and low cost

Inactive Publication Date: 2005-01-20
NIKON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] An object of the present invention is to provide an optical filter that can be mounted by efficiently utilizing the limited space at the front surface of a solid image-capturing element or the like at low cost and an optical device provided with the optical filter.

Problems solved by technology

Since a sufficient space for accommodating a holding member is required along the direction of the optical axis to hold such a rectangular parallelepiped optical filter plate, there is a problem in that it is difficult to provide the optical filter plate within the limited space.
For instance, rigorous dimensional restrictions are imposed along the direction of the optical axis if the optical filter is to be placed between an optical lens and the solid image-capturing element or between a mechanical shutter and the solid image-capturing element, which greatly reduces the degree of freedom afforded in design.
In addition, while it is conceivable to use glue to paste the optical filter plate to the protective glass of the solid image-capturing element without employing any holding member, it is difficult to implement quality control to ensure that there is no dust or air bubbles present when the optical filter is being laminated, and there is a problem in that if dust or the like is discovered after the optical filter is glued, the problem cannot be corrected.
In particular, this will result in a serious increase in the production costs when a high-density pixel solid image-capturing element with a high unit price is used.

Method used

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  • Optical filter and optical device
  • Optical filter and optical device
  • Optical filter and optical device

Examples

Experimental program
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first embodiment

[0024]FIG. 1 shows the structure assumed in the first embodiment of the digital camera mounted with the optical filter plate (element) according to the present invention. A taking lens 10 is an optical system that forms an image of a light flux (ray) from a subject (not shown) at the light-receiving surface of a solid image-capturing element 7 or at a focus plate 4 via a quick-return mirror 5. A viewfinder optical system, which includes the focus plate 4 with its upper surface constituting a Fresnel condenser and a condenser lens 3 constituted of a plano-convex lens placed above the focus plate 4, is observed by the photographer with an eyepiece lens 1 through a pentaprism 2. In addition, the viewfinder optical system is exchangeable, and the position of the solid image-capturing element 7 and the position of the focus plate 4 are conjugate with each other relative to the taking lens 10. The taking lens 10 is mounted by engaging a lens-side mount 9 with a camera-side mount 8.

[0025]...

second embodiment

[0044]FIG. 6 illustrates the structure of the second embodiment of the digital still camera mounted with the optical filter plate (element) according to the present invention. This embodiment differs from the first embodiment in that it is not provided with the adapter 12. Since other structural features are identical to those in the first embodiment, their explanation is omitted and only the point concerning the absence of the adapter 12 is explained below.

[0045]FIG. 7, which corresponds to FIG. 3 illustrating the first embodiment, illustrates how the optical filter plate 11 is mounted. The optical filter plate 11 is identical to that shown in FIG. 2. As illustrated in FIGS. 6 and 7, the second embodiment is not provided with the adapter 12 or the wall 16 that regulates the position of the adapter 12.

[0046] Namely, positioning of the optical filter plate 11 is achieved entirely by the opening portion of the holder 13, and this embodiment may be adopted when it is not crucial to a...

third embodiment

[0047]FIG. 8 illustrates the structure of the third embodiment of a digital still camera mounted with the optical filter plate (elements) according to the present invention. While the optical filter plate 11 is provided between the shutter 6 and the solid image-capturing element 7 in the first embodiment, the optical filter plate 11 is provided between the shutter 6 and the quick-return mirror 5 in the third embodiment. Since other structural features are identical to those in the first embodiment, their explanation is omitted and the explanation below will focus on the difference.

[0048] The optical filter plate 11 is structured as illustrated in FIG. 2. The optical filter plate 11 is secured by bonding the surface of the stage perpendicular to the optical axis to the contact surface of the holder 31 with glue. The holder 31, which is secured to a frame 32 of the camera main body, is provided with an opening matching the size of the birefringent plate 101 and the infrared-cutting f...

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PUM

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Abstract

An optical filter that is provided at an optical path between a photoelectric conversion device which converts a subject image formed at a light-receiving surface thereof to an electrical signal and an optical system which forms the subject image with a light flux from the subject at the photoelectric conversion device, to filter the light flux, includes a stage formed at, at least, a portion of an external circumference of the optical filter.

Description

[0001] The disclosure of the following priority application is herein incorporated by reference: [0002] Japanese Patent Application No. 11-47744, filed Feb. 25, 1999 BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to an optical filter (plate) provided at the front surface of a solid image-capturing element (e.g., a CCD) or the like and an optical device mounted with this optical filter. [0005] 2. Description on the Related Art [0006] A CCD employed in a digital camera or the like converts a two-dimensional optical image having specific spatial frequency characteristics to an electrical signal by sampling it in time sequence. If the spatial frequency of the optical image is equal to or less than the Nyquist frequency (a frequency equal to ½ of the sampling clock), alias signal, moire and the like are not generated. For this reason, it is necessary to restrict the spatial frequency of an optical image input to the CCD to be equal to or...

Claims

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Application Information

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IPC IPC(8): G02B5/20G02B5/30G02B7/00G02B27/46H04N5/225H04N5/335H04N5/353H04N5/372
CPCG02B7/006H04N5/2254G02B27/46H04N23/55
Inventor KOUNO, YOUSUKE
Owner NIKON CORP