JP2563809Y2 - Imaging equipment - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention is an imaging device, more specifically, one surface is a reflection surface,
The present invention relates to an imaging device having a thin plate glass used as a half mirror having the other surface as a transmission surface.

2. Description of the Related Art Thin plate glass used for a half mirror of a camera or the like requires a very high degree of flatness on its surface in terms of optical performance. Conventionally, in order to satisfy the accuracy, the accuracy of the flatness was maintained by polishing the front and back surfaces.

[Problems to be Solved by the Invention] However, as described above, it is very disadvantageous in terms of manufacturing cost to perform a long-time polishing treatment on both the front and back surfaces of the thin plate glass material. On the other hand, for the application of the thin plate glass to the half mirror of the camera,
There has been a demand for a thin plate glass that has a quality that can sufficiently satisfy the performance required for the thin plate glass and that is inexpensive compared to the conventional half mirror.

An object of the present invention is to provide an imaging apparatus having a low-cost thin plate glass capable of satisfying the performance required by performing a minimum necessary finishing process in order to solve the above-mentioned problems.

[Means and Actions for Solving the Problems] A photographing apparatus according to the present invention includes a photographing lens for forming incident light from a subject on an image plane, and an optical axis in an incident optical path from the photographing lens. It is fixed at a predetermined angle, guides the reflected light to the finder side, and guides the transmitted light to converge on the photographing surface side. A reflection surface for reflecting the light at a reflection angle corresponding to the incident angle, and the other surface is subjected to anti-reflection processing on the surface, and a transmission for transmitting another part of the incident light from the surface to emit the light. A thin plate glass having a surface, the thin plate glass material being subjected to polishing on one surface to be made the reflection surface, and a plane of the other surface to be made the transmission surface. The degree of flatness is relatively higher than the degree And a thin plate glass.

[Embodiment] Before describing an embodiment of the present invention, an outline of the present invention will be briefly described.

The thin plate glass used in the photographing apparatus according to the present invention has one surface as a reflection surface that reflects a part of the incident light, and the other surface as a transmission surface that transmits another part of the incident light. Things. The reflection surface is provided with a reflection coating, and the transmission surface is provided with an antireflection coating. Then, when the thin plate glass is used for a half mirror of a camera, the reflected light beam on the reflecting surface forms an image on a screen mat for a finder,
The transmitted light flux on the transmitting surface forms an image on the light receiving surface of the image sensor. Therefore, when the accuracy of the flatness of the reflecting surface is poor, an image formed by the reflected light beam is represented as an image largely deformed according to the flatness of the reflecting surface. On the other hand, if the thickness of the transmission surface is within a predetermined thickness, the accuracy of the flatness hardly affects the imaging accuracy.

Therefore, as a material of the thin plate glass, for example, if a commercially available transmission glass microscope cover glass that is a thin plate having a thickness of about 0.2 mm is used, as described above, the influence of flatness is large. A material that can be polished only on the reflection surface side to have a predetermined flatness, for example, about 1 μm, or about several lines using a Newton ring, and that the transmission surface side can be provided to a thin plate glass without processing. It is thought that it is possible. FIG. 1 shows an enlarged cross section of the material and the polished surface. That is, reference numeral 2 denotes a thin plate glass, surfaces 2b and 2g indicate material surfaces of the cover glass, and a polished surface is 2a. Then, the surface 2a is provided with a reflective coating to be used as a reflective surface, and the surface 2b is used as a transmissive surface.
It is possible to provide a low-cost thin plate glass that sufficiently functions as a thin plate glass.

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

FIGS. 2, 3, and 4 show the configuration of an imaging optical system of a single-lens reflex camera using a thin plate mirror (hereinafter, referred to as a mirror) which is a thin plate glass according to one embodiment of the present invention. .

The configuration of the image forming optical system of the camera includes a mirror 2, an L block 1 which is a support member for fixing and supporting the mirror 2 by pressing the mirror pressing plate 3 via cushion members 23a, 23b and 23c, and a taking lens. 29 , CCD imaging optical system 27 ,
A finder optical system 28 is provided. The CCD imaging optical system 27 is connected to the C block 4 fixed to the L block 1, the CCD case 6, which is supported by the CCD adjustment cam 5 in a tensioned state by the CCD spring 10, and the CCD case 6. A CCD 8 of an image sensor whose imaging surface is arranged to face the optical axis O via an optical filter 7 and the CCD 8
It is constituted by a CCD holding plate 9 to be attached to the case 6.

In addition, the finder optical system 28 is
A mat receiver 11 attached by a pin screw 14 via a mat spring 15, a screen mat 12 having an image forming surface for a finder, a mat retainer 13, and an F fixed to the L block 1 with the screen mat 12 interposed therebetween. A block 17, a second mirror 18 held by a mirror spring 18 on an F block 17 in a state of being obliquely mounted on a finder optical axis A passing through the screen mat 12, and a finder section supported on the F block 17 in a state orthogonal to the optical axis A An S block 21 is fixed to the F block 17, and a photometric sensor 22 is disposed on the S block 21 with its light receiving surface facing the finder optical axis A. The position and inclination of the mat receiver 11 are adjusted by mat receiving adjustment pins 16 screwed to the mat receiver 11. The image forming surface of the screen mat 12 is set so that the relative position from the reflecting surface of the mirror 2 is equivalent to the image forming position on the CCD 8.

Further, the taking lens 29 is composed of four groups of lenses. As shown in FIG. 3, the lens frame 30 fixed to the L block 1 (see FIG. 2) and the following lens groups are slidably provided. A front cover 31 supported by the lens frame 30 via supporting guide shafts 32a and 32b, and a focusing lens 33 (first group lens), which is one of lens groups sequentially arranged along the optical axis O. And focusing lens 33
(Automatic focusing) drive unit 34, a variator lens 35 (second group lens) and a compensator lens 36 (third group lens) slidably disposed, and a variator lens 35 and a compensator A zoom drive unit 37 for extending the lens 36 in accordance with a zooming instruction, an aperture unit 38,
It is constituted by a relay lens 39 (fourth group lens).

The mirror 2 is a thin plate (about 0.2 mm thick).
A surface for reflection and branching is applied to the surface 2a polished to the predetermined flatness, and an antireflection coating is applied to the back surface 2b. And L of mirror 2
Explaining the mounting structure to the block 1, as shown in FIG. 4, the opening 1a has upper and lower mirror support surfaces 1d and 1e inclined at 45 ° with respect to the optical axis O, and Presser plate mounting surfaces 1f, 1g formed with predetermined steps
Is arranged. Then, the reflection coating surface 2a side of the mirror 2 is brought into contact with the mirror support surfaces 1d and 1e. The mirror holding plate 3 is disposed at a predetermined position on the side, a screw (not shown) is passed through the holes 3a, 3b, 3c, and the mirror 2 is fixed by screwing with screw materials 1h, 1i, 1j. In this manner, the mirror 2 is supported obliquely at an angle of 45 ° with respect to the optical axis O.

The operating state of the light beam of the imaging optical system will be described. First, the incident light from the taking lens 29 passes through the mirror 2 attached to the L block 1 and is partially emitted from its own side. The light is emitted to the first optical path of the optical axis O 'substantially coaxial with the axis O, and the other part of the incident light is orthogonal to the incident optical axis O with a reflection angle corresponding to the incident angle on the reflection surface 2a of the mirror 2. Optical axis A which is the direction
Is reflected on the second optical path and is branched. Then, the light beam emitted to the first optical path O ′ passes through the optical filter 7
It is projected on the imaging surface of CCD8. On the other hand, the light beam reflected in the second optical path direction (optical axis A) is
a Image is formed on a (see FIG. 5). The imaging light flux passes through the screen mat 12 and is reflected by the second mirror 18 obliquely provided on the optical axis in the direction of the finder section 20 and a part of the transmitted light reaches the photometric sensor 22.

Next, the influence of the flatness accuracy of the reflection surface 2a of the mirror 2 on the image formation and the method of supporting the mirror 2 will be described. FIG. 5 shows that an arbitrary incident light E is incident on the L block 1 with respect to the optical axis O.
When the light is reflected by the mirror 2 which is supported at an angle, it indicates a shift of the image forming position on the screen mat 12 due to the surface accuracy of the reflection. Now, let θ be the angle between the incident light E and the optical axis O, and F be the reflection direction at the reflection point 2c on the mirror 2 when the reflection surface 2a is an ideal plane. Is 12b. At the reflection point 2c, if the inclination of the plane changes by an angle ε (not shown) with respect to the ideal plane, the reflection direction is G, and its imaging point is 12c. The direction F of the reflected light forms an angle θ with an axis D orthogonal to the optical axis O, and the direction G of the reflected light is reflected in a direction shifted by an angle 2ε from the direction F which is the direction of reflection by the ideal surface. You.

The distance l 'from the reflection point 2c in the direction F to the ideal imaging point 12b is l' = l / cosθ (1) The deviation amount (inconsistency) Δx between the imaging points 12b and 12c is Δx = 2ε · l '/ cosθ in the above equation is (1) by substituting the equation ^{Δx = 2ε · l / cos 2} θ ...... (2). Here, l is a distance from the reflection point 2c to the screen mat 12
Shows the distance to the imaging plane 12a.

Therefore, the shift amount Δx of the imaging point due to the change ε of the inclination angle of the flatness of the reflection surface 2a of the mirror 2 becomes large in the image corresponding to the portion having the long distance l from the equation (2), and the portion having the short distance l is obtained from the formula (2). Are smaller. Therefore, L of mirror 2
Screen mat imaging surface for support to block 1
The screen mat 12a is supported by the mirror 12a so that the mirror 2 at a far site is as flat as possible with high accuracy and the mirror 2 at a closer site is maintained with a loose accuracy. It is possible to form an image more effectively and accurately.

On the other hand, with respect to the portion of the mirror 2 that can be supported, the distance between the taking lens 29 and the CCD 8, that is, the lens back distance is restricted by the optical design, so that the direction of the optical axis O needs to be as short as possible. Can be obtained as follows.

First, FIG. 7 (A) shows a part of the incident light of the taking lens 29 by the mirror 2 and the CCD 8 for the finder system.
3 shows the positional relationship between the mirror 2 and the screen mat 12 when reflecting the finder light beam in the same direction A as the horizontal scanning direction Y.

The mirror 2 is disposed at an angle of 45 ° with respect to the optical axis O (see FIG. 5), but is disposed on both sides of the mirror 2 on the side intersecting the virtual rotation center axis H that generates the above-mentioned inclined surface. An area, that is, an appropriate position on the upper side 2i and the lower side 2j of the mirror 2 is defined by the supporting surfaces 1e and 1d.
(See Fig. 4)
The width J direction of the mirror 2 can be used without waste without providing an area for fixing. In addition, the opening for the mirror in FIG. 4 has both ends 1a and 1b open to the wall. If the CCD 8 is, for example, 1/2 inch, a passing area of an effective light beam corresponding to an effective imaging surface of 4.8 mm × 6.4 mm can be secured by an effective area J × K (2h portion) of the mirror 2. .

On the other hand, the support surfaces 1e, 1 of the L block 1 supporting the mirror 2
It is assumed that d has at least a higher degree of flatness than the mirror 2 and has such an accuracy that does not hinder the image formation on the screen mat 12. As described above, in order to maintain high-precision flatness for a portion farther from the screen mat 12, the farther site point 2k, of the support surface 2i, 2j.
2l 2 points on the high-precision support surfaces 1e, 1d cushion material 23a, 23b
Press with. And on the screen mat 12 of the support surface 2j,
The point 2m of the closer part is pressed against the support surface 1e with the cushion material 23c, and the mirror 2 is held by three points of points 2k, 2l, and 2m. In this state, the mirror 2 is supported in a state where the portion far from the screen mat 12 is held with higher precision, and the finder image formed on the screen mat 12 can be obtained with less deviation. Become.

FIG. 6 is a sectional view showing a state in which the mirror 2 is pressed and supported by the mirror pressing plate 3 via the cushion members 23a, 23b, and 23c in the above-described manner. In the above example, three cushion members are used for support, but it is also possible to press and support two elongated cushion members corresponding to the two portions of the support portions 2i and 2j. Further, as the material of the cushion members 23a to 23c and the like, for example, malt plane which is a foamed resin material which is an elastic material, urethane foam or the like can be applied.

Next, FIG. 7B shows a case where a part of the light beam of the taking lens 29 reflects the light beam for the finder in the direction A 'perpendicular to the horizontal scanning direction Y of the CCD 8, and the reflected light from the mirror 2'. Is imaged by a screen mat 12 'located above the image, and further reaches a finder section 20' by a half mirror 18 '. In this case, the virtual rotation center axis for the tilt angle of the mirror 2 'is H', and the sides 2i 'and 2j' of the mirror 2 'which intersect with the axial direction H' are used as support parts. Is set.

Further, three points to be pressed by the three cushion members are 2k 'and 2l' at a portion far from the surface of the screen mat 12, and 2m 'at a portion near the surface. The effective area of the mirror 2 'is J'.times.K' (2h 'portion).

Also in this case, the desired function can be obtained even if the two portions of the side portions 2i 'and 2j' are pressed and supported by the elongated cushion material, respectively.

In the supporting method of the above-described embodiment, the mirror 2 supports the portion far from the screen mat 12 at two points and supports the close portion at one point. A method is proposed in which a portion near the screen mat of the mirror 2 is supported at two points, and a portion far from the screen mat is supported and fixed at one point. This method uses two points 2n on the mirror 2 with respect to a portion close to the screen mat 12 when the reflection direction of the finder light beam is the same as the horizontal scanning direction Y of the CCD 8 as shown in FIG. , 2 m, and a portion far from the screen mat 12 supports and fixes one point 2 k or 2 l.

On the other hand, as shown in FIG. 7 (B), when the finder light beam is reflected by the mirror 2 'in a direction A' orthogonal to the horizontal scanning direction Y of the CCD 8, the light beam is similarly placed on a portion close to the screen mat 12 '. 2 points on mirror 2 '
The portion supporting n 'and 2m' and far from the screen mat 12 'supports and fixes one point 2k' or 2l '. Depending on the flatness accuracy of the support surfaces 1e and 1d of the L block 1, or depending on the shape of the support surface, by supporting the mirror 2 'in this manner, the flatness accuracy of a portion farther from the screen mat 12' can be improved. In some cases, high accuracy can be maintained.

As described above, the mirror 2 which is a thin plate-shaped optical member has 23a to 2a.
The support material is pressed against the support surface via an elastic cushion material such as 3c, and the cushion material is previously applied to the pressed portion on the mirror 2 with a pressure-sensitive adhesive (double-sided adhesive) as shown in FIG. If they are adhered with each other, the direction of the front and back sides can be identified at the time of assembly, handling with tweezers or the like becomes easy, and assembly becomes very easy. In the sectional view of FIG.
Reference numerals 23d and 23e indicate the bonding portions. In addition, when bonding these cushioning materials, an index is attached to the bonding place by printing or coating at the time of manufacturing the mirror 2 or by concave forming if it is formed, and the bonding position of the cushioning material is mistaken. No, it can be assembled. In addition, a specific example of the index by the above coating is shown in a plan view of the mirror 2 in FIG. By masking the portions of the antireflection coating surface 2b where the cushions are arranged 2e, 2d, and 2f and performing the antireflection coating, an index as shown in the figure can be given. Further, the same effect can be obtained even if an index is provided by masking a similar place on the reflective coating surface 2a at the time of coating.

[Effects of the Invention] As described above, according to the present invention, aberrations caused by the light that reaches the imaging surface from the imaging lens incident on the glass sheet disposed so as to have a predetermined angle with the optical axis can be reduced. Using a glass as much as possible, even when using fragile thin glass, a good image is obtained by improving the surface accuracy of the thin glass surface on the finder side, and double reflection due to reflection from the back side is provided on the finder side. Since the image is hardly visible, the image is easy to see, and the imaging precision is hardly affected on the photographing surface, and the thin glass that is easily broken can be processed at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a thin plate glass in a photographing apparatus according to the present invention, and FIG. 2 is an image forming optical system in a photographing apparatus showing one embodiment of the present invention using the thin plate mirror of FIG. L of the system
FIG. 3 is an exploded perspective view of a block portion, an imaging optical system and a finder optical system, FIG. 3 is an exploded perspective view of a taking lens unit of an imaging optical system using the thin plate mirror of FIG. 1, and FIG. FIG. 5 is a perspective view of the mirror support portion of the L block of the imaging optical system of FIG. 2, and FIG. 5 is a mirror for explaining a shift of an imaging position on a screen mat in the imaging optical system of FIG. FIG. 6 is a cross-sectional view of a main part of the screen mat part, FIG. 6 is a cross-sectional view of a main part of the mirror support part of the imaging optical system of FIG. 2, and FIGS. FIG. 7 is a perspective view of a main part of the image forming optical system shown in FIG. 2 for explaining a supporting position of the mirror. FIG. 7 (A) shows that the reflection direction for the finder light beam is horizontal to the image sensor. FIG. 7 (B) is a perspective view when the scanning direction coincides with the scanning direction. FIG. 8 is a perspective view of the imaging optical system of FIG. 2 when the cushion material is bonded to the mirror, and FIG. 9 is a perspective view of the mirror of the imaging optical system of FIG. It is a top view which shows a coating state. 2 Thin plate glass 2a Reflective surface, 2b Transmissive surface

Claims (1)

(57) [Scope of request for utility model registration] 1. A photographing lens for forming an incident light from a subject on an image plane, and a light beam incident from the photographing lens is fixed at a predetermined angle to an optical axis in an optical path of the photographing lens. A reflection that guides light to the viewfinder side and guides transmitted light to converge on the shooting surface side. One of the surfaces reflects some of the light incident on that surface at a reflection angle corresponding to the incident angle. A thin plate glass which is formed as a surface, and the other surface is subjected to anti-reflection processing on that surface, and from the surface as a transmission surface for transmitting the above-mentioned incident light through another part and emitting it, A thin plate for polishing a glass material on one surface to be formed as the reflection surface and having a relatively higher flatness than that of the other surface to be formed as the transmission surface. Characterized by having glass and Shadow devices.