JP2010039320A - Focusing plate for single-lens reflex camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focusing plate for a single-lens reflex camera in which a fine line whose light transmittance is different from that of a mat surface having a diffusing function for confirming a focusing state is drawn on the mat surface, wherein it is easy to observe the fine line even when an object is dark, and which is easy to manufacture. <P>SOLUTION: In the focusing plate for the single lens reflex camera, the fine line is drawn by a plane whose light transmittance is higher than that of the mat surface and which is observed as being more bright than the mat surface by an observer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a focus plate for a single-lens reflex camera.

In general, a single-lens reflex camera focusing plate is a thin line (engraved) having a light transmittance different from that of the mat surface in order to display a distance measuring area and a photometric area on a mat surface having a diffusion function for confirming a focus state. Line). Conventionally, this fine wire has consisted of a groove or protrusion having a V-shaped cross section formed on the mat surface (ground glass surface).
JP 2005-338862 A

  The thin line consisting of grooves or protrusions with a V-shaped cross section has a lower light transmittance than the mat part (because the light scatters at the same thin line part and the amount of light reaching the observer's eyes decreases). Visible as a black line. However, a fine line visually recognized as a black line is difficult to visually recognize when the subject is dark.

  Further, this focus plate is usually composed of a molded product of a synthetic resin material, and the mold is generally formed by Ni electroforming. The protrusion or groove for forming the groove or protrusion having the V-shaped cross section needs to be post-processed on the Ni electroforming mold. However, the Ni electric mold is a material that is extremely difficult to cut, and has a molding problem.

  An object of the present invention is to obtain a focusing plate for a single-lens reflex camera that is easy to visually recognize and is easy to manufacture even when the subject is dark, based on the above-mentioned problem awareness of the focusing plate for a single-lens reflex camera. .

  The conventional thin line of the focus plate was based on the idea that the light transmittance is lower than that of the matte surface and the black line appears black. The present inventor has completed the present invention by reversing this idea and making light transmission of fine lines higher than that of the mat surface to draw a bright line that is visible brightly in the mat surface.

  The present invention provides a focusing screen for a single-lens reflex camera in which a thin line having a light transmission rate different from that of the mat surface is formed on a mat surface having a diffusion function for confirming a focus state. It is characterized by being drawn by a flat surface that has high transmittance and is visible to an observer brighter than the mat surface.

  More specifically, the planar roughness Ra (l) of the planar thin wire is smaller than the planar roughness Ra (m) of the mat surface (Ra (l) <Ra (m)).

  More specifically, the planar roughness Ra (l) of the planar thin wire is 0.1 μm or less, and the planar roughness Ra (m) of the mat surface is 0.1 μm to 1 μm.

  It is practical to make the plane thin line parallel to the focus plate plane.

  Further, the line width of the thin planar wire is preferably 50 μm to 500 μm.

  The focus plate is preferably formed from a molded product of a synthetic resin material.

  The focusing plate for a single-lens reflex camera of the present invention is provided with a flat surface that allows an observer to visually recognize the thin line provided on the mat surface as a bright line, so that the thin line is easy to see even when the subject is dark. Further, when forming from a molded product of a resin material, it is only necessary to form a narrow groove corresponding to the plane thin wire and having a flat surface smoother than the mat surface on the bottom surface. Can be formed.

  1 and 2 show an embodiment of a focus plate 10 for a single-lens reflex camera according to the present invention. As is well known, the single-lens reflex camera focusing plate 10 is placed at a position optically equivalent to the imaging surface of the single-lens reflex camera, and a subject image is formed by the photographing lens, and the subject image is an eyepiece ( It is observed by an observer (photographer) with an eyepiece.

  The single-lens reflex camera focusing plate 10 of the present embodiment is entirely composed of a mat surface 11 and has a thin flat line 12 indicating a distance measuring area and a photometric area therein. The mat surface 11 has a surface roughness enough to have a diffusion function for confirming the focus state. Various patterns are known, and the surface roughness is, for example, about 0.5 μm in Ra. Of course, the numerical value of this surface roughness is an example, and it is not limited to this as long as it is a mat surface that can be used for the purpose of confirming the focus state.

  As shown in FIG. 2, the thin planar wire 12 that is a feature of the present embodiment is a plane (mirror surface) parallel to the plate thickness plane of the single-lens reflex camera focus plate 10. As described above, the mat surface is defined as a surface having a diffusion function for confirming the focus state, whereas the plane (mirror surface) of the present embodiment has a higher light transmittance than the mat surface, and the observer Is defined as a surface that can be viewed brighter than the mat surface. Specifically, the surface roughness is about 0.01 μm or less in terms of Ra. Of course, the numerical value of this surface roughness is an example, and it is not limited to this as long as the object of being visually recognized as a brighter line in the mat surface than the mat surface can be achieved. The line width of the planar thin wire 12 is preferably about 50 μm to 500 μm. This is wider than the line width of the conventional V-shaped thin line of 30 μm to 50 μm, whereas the conventional thin line is recognized as black (dark), whereas the planar thin line 12 of the present embodiment. Is recognized brightly, and widening the width makes it easy to see.

  FIG. 3 schematically shows a light beam passing situation of the focusing plate 10 for the single-lens reflex camera of the present embodiment. Light rays incident on the focus plate 10 from the direction orthogonal to the plate surface diffuse on the mat surface 11 portion, but go straight on the plane thin wire 12 portion (the light transmittance on the plane thin wire 12 is the light on the mat surface 11). It is higher than the transmittance), and the observer observes the plane fine wire 12 portion brighter than the mat surface 11 portion. The plane thin wire 12 does not need to be strictly parallel to the plate thickness plane of the single-lens reflex camera focus plate 10, but if the angle is too much, the above effect cannot be obtained.

  The focusing plate 10 for a single-lens reflex camera of the present embodiment can be formed by post-processing the thin flat wire 12 with respect to the focusing plate 10 having the mat surface 11 as a whole. However, in consideration of mass productivity, it is preferable that the resin material is formed from a molded product.

  FIG. 4 shows an example of a method for manufacturing a mold using a photolithography technique and an electroforming technique. First, a positive (or negative) photoresist 21 is applied on the substrate 20 by spin coating, and the surface of the photoresist 21 is made as flat as possible (FIG. 1A). Next, the photoresist 21 is irradiated with ultraviolet rays using a light mask 22 having a diffusion mask 11X corresponding to the mat surface 11 and a light transmission line (or light blocking line) 12X corresponding to the planar thin line 12 (see FIG. (B)). When the photoresist 21 is developed, as shown in FIG. 6C, the light transmission line (or light blocking line) 12X portion is formed with the transfer plane fine line 12P formed by leaving the plane of the photoresist 21 as it is, and the diffusion mask 11X. A transfer mat surface 11P having irregularities corresponding to the mat surface is formed in the portion. When the Ni electroformed layer 23 is formed on the photoresist 21 having the transfer mat surface 11P and the transfer plane thin wire 12P formed in this manner by a known method, the Ni electroformed layer 23 is used for a single-lens reflex camera. A mold for forming the focus plate 10 is formed (FIG. 4D).

  That is, the Ni electroforming mold 23 is formed with a fine wire plane forming portion 12M to which the transfer flat fine wire 12P is transferred, and a mat surface intermediate portion 11M to which the transfer mat surface 11P is transferred. Therefore, according to this Ni electroforming mold 23, the focus plate 10 of the present embodiment can be formed of a resin material.

  According to the method for manufacturing a mold for focusing on a single-lens reflex camera, it is not necessary to perform post-processing such as conventional V-groove processing, and a mold can be easily created.

It is a top view which shows one Embodiment of the focus board for single-lens reflex cameras by this invention. It is sectional drawing which follows the II-II line of FIG. It is a figure which shows typically the permeation | transmission state of the light by the focus board for single-lens reflex cameras by this invention. It is process drawing which shows an example of the manufacturing method of the shaping | molding die of the focus board for single-lens reflex cameras by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Focus board for single-lens reflex cameras 11 Mat surface 12 Planar thin wire 20 Substrate 21 Photoresist 11P Transfer mat surface 12P Transfer flat wire 22 Optical mask 23 Ni electroformed layer (molding die)

Claims (6)

In the focus plate for a single-lens reflex camera in which a thin line having a light transmittance different from that of the mat surface is drawn on the mat surface having a diffusion function for confirming the focus state,
A focusing plate for a single-lens reflex camera, characterized in that the thin line is a flat surface that has a light transmittance higher than that of the mat surface and is visible to an observer brighter than the mat surface. 2. A focusing plate for a single-lens reflex camera according to claim 1, wherein the planar roughness Ra (l) of the planar thin wire is smaller than the planar roughness Ra (m) of the mat surface (Ra (l) <Ra (m)). Focus plate for reflex camera. 3. A focusing plate for a single-lens reflex camera according to claim 1 or 2, wherein the planar thin line has a surface roughness Ra (l) of 0.1 [mu] m or less, and a mat surface has a surface roughness Ra (m) of 0.1 [mu] m. A focusing plate for a single-lens reflex camera having a size of ˜1 μm. 4. The single-lens reflex camera focus plate according to claim 1, wherein the thin flat line is parallel to the focus plate plane. 5. 5. The single-lens reflex camera focus plate according to claim 1, wherein the line width of the planar thin line is 50 μm to 500 μm. 6. 6. A single-lens reflex camera focus plate according to claim 1, wherein the single-lens reflex camera focus plate is a molded product of a synthetic resin material.

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