JP3340636B2 - Single-lens reflex camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-lens reflex camera using a Porro prism as an erecting optical system.

[0002]

2. Description of the Related Art Conventionally, as a photometry system of a single-lens reflex camera, since the photometry reflecting the angle of view of a photographing lens and a filter effect is possible, the luminance of a subject is measured based on the light passing through the photographing lens. So-called TTL (Through Th)
e Lens) method is the mainstream. This TTL method further includes:
Depending on the location of the photometric sensor, a method of installing the photometric sensor on the bottom of the mirror box (hereinafter referred to as "in-body photometric system"), or offset from the finder optical axis immediately after the erecting optical system in the finder optical system To measure the image of the subject on the focus plate by installing a photometric sensor at the specified position (hereinafter referred to as "finder photometric system")
It is roughly divided. However, in recent years, since a mechanism such as a distance measuring optical system and a motor drive for autofocusing needs to be installed below the mirror box, the photometric system in the body is not often used, and the finder photometric system is mainly employed. I have.

[0003] Even when a finder photometry system is employed, if the erecting optical system is a general pentaprism, it is possible to secure a place for installing the photometry sensor without increasing the size of the camera. That is, in the case of the pentaprism, the exit surface is inevitably pentagonal due to the formation of the roof surface. Therefore, even if a fine loupe having a circular or rectangular outer periphery is arranged behind the exit surface, a substantially triangular area near the vertex remains as a useless area that does not face the fine loupe. Therefore, if the photometric sensor is arranged so as to face this substantially triangular area, without changing the shape of pentaperism,
A photometric sensor can be arranged.

[0004]

However, depending on the shape of the imaging medium and the design of the entire camera, it is more appropriate to use a Porro prism composed of a plurality of right angle prisms than to use a penta prism as an erecting optical system. In some cases. In this case, since the shape of the exit surface of the Porro prism is rectangular, by arranging a fine loupe with an appropriate diameter behind the exit surface, light emitted from the entire area of the exit surface is efficiently condensed by the fine loupe. can do. That is, in the case of the Porro prism, there is no space that is originally wasted unlike the penta prism. Therefore, in order to dispose the photometric optical system above the fine loupe (the side farther from the quick return mirror) as in the case of a pentaprism, the entire Porro prism must be thickened. Accordingly, as the size of the entire Porro prism increases, the size of the entire camera also increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a single-lens reflex camera in which a photometric sensor can be arranged behind the exit surface of a Porro prism while suppressing an increase in the size of the Porro prism as an erecting optical system. It is.

[0006]

The present invention has the following features to attain the object mentioned above. That is, claim 1
The described invention is a single-lens reflex camera including a finder for projecting a subject image formed by an imaging optical system onto a focus surface equivalent to an imaging surface and observing the subject image projected on the focus surface with a loupe. A porro prism having a plurality of reflecting surfaces for bending the optical axis of the loupe to allow the subject image projected on the focus surface to be observed as an erect image, and entering the loupe at the exit surface of the porro prism. A light-measuring sensor disposed behind a region that is located on the side in the traveling direction of the incident light on the reflection surface immediately before the light exit surface with respect to the light passage region.

According to this structure, the exit surface of the Porro prism is slightly enlarged in the traveling direction of the light incident on the reflection surface located immediately before the exit surface from the region through which the light incident on the loupe passes. By doing so, an area for disposing the photometric sensor can be secured. Therefore, the expansion of the Porro prism requires only a minimum expansion of such an extent that the exit surface is enlarged. Therefore, the size of the entire prism or the entire camera is not increased. In addition, if the photometric sensor is arranged in a region on the exit surface of the Porro prism on the side opposite to the present invention with a region through which light entering the loupe is interposed, the optical path itself of light entering the loupe must be shifted. Therefore, the size of the entire Porro prism increases, and the size of the entire camera increases.

According to a second aspect of the present invention, in the first aspect, a condensing lens for converging the light emitted from the emission surface of the Porro prism on the photometric sensor is further provided. It is.

According to a third aspect of the present invention, the optical axis of the condenser lens of the second aspect is inclined with respect to the optical axis of the loupe such that the optical axis of the condensing lens moves away from the optical axis of the loupe as approaching the photometric sensor. That is what was specified.

According to a fourth aspect of the present invention, the optical axis of the condenser lens of the third aspect is specified by intersecting with the optical axis of the loupe on the focus surface. Claim 5
According to the invention described in the first aspect, the Porro prism according to the first aspect includes an incident surface on which light emitted from the focus surface is incident, a first reflecting surface for reflecting light transmitted through the incident surface to the object side by 90 degrees, and a first reflecting surface. A second reflecting surface for reflecting the light reflected by the reflecting surface by 90 degrees in a direction orthogonal to the traveling direction of the light incident on the first reflecting surface; This is specified by having a third reflection surface that reflects 90 degrees in a direction parallel to the optical axis of the system, and an emission surface that emits light reflected by the third reflection surface.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (Imaging Device) First, an imaging device used in each embodiment will be described with reference to FIGS.

FIG. 10 is a longitudinal sectional view showing the internal structure of the image pickup device 200. As shown in FIG. 10, the image pickup device 200 includes an electrostatic information recording medium 210 and a charge holding medium 2.
11 is provided. The electrostatic information recording medium 210 is
13, the electrode layer 214, the inorganic oxide layer 215, and the photoconductive layer 216, and the photoconductive layer 216 is
17 and the charge transport layer 218 are polymerized. The charge holding medium 211 includes a liquid crystal support 219 and a liquid crystal electrode layer 22.
The liquid crystal 221 is sealed between the two. The charge transport layer 218 of the electrostatic information recording medium 210 and the charge holding medium 21
The first liquid crystal support 219 is opposed with a small gap.

Between the electrode layer 214 and the liquid crystal electrode layer 220, when the image pickup device 200 is mounted on the camera main body 100 (see FIG. 2), a control power supply 212 on the camera main body 100 side selectively causes the power supply. Voltage is applied. And
When the electrostatic information recording medium 210 is exposed while a voltage is applied between the electrode layer 214 and the liquid crystal electrode layer 220,
Electric charges corresponding to the image are generated in the electrostatic information recording medium 210. As a result, according to the distribution of the charges, the liquid crystal 221
Of the liquid crystal 221 changes. Therefore, when an image is projected on the electrostatic information recording medium 210, the orientation of the molecules of the liquid crystal 221 changes according to the shape of the image.

Since the liquid crystal 221 is a memory type liquid crystal made of smectic liquid crystal, when the voltage of the control power supply 212 is removed after the direction of the molecule is changed according to the shape of the image, the state of the molecule is changed. The image is recorded as it is. Therefore, when the liquid crystal 221 is irradiated with illumination light by a known method, the recorded image can be read out visually. The liquid crystal 22
The image recorded in 1 is erased by heating the liquid crystal 221 to a predetermined temperature using a heating device (not shown), in which case the same recording medium can be reused.

As shown in FIG. 2, the planar shape of the image pickup device 200 is a rectangular shape, and the first
To third recording areas 201, 202, and 203 are sectioned. Each of these recording areas 201, 202, and 203 is set to have a wide shape with its short side directed in the long axis direction of the image sensor 200. (Still Video Camera) The configuration of the still video camera according to the first embodiment that performs color imaging using the above-described imaging device 200 will be described below.

FIG. 1 is a perspective view of the still video camera as viewed obliquely from the upper front, and FIG. 2 is a perspective view of the still video camera viewed obliquely from the lower rear. As shown in FIG. 1, this still video camera includes a camera body 100.
And an interchangeable lens 130.

At the approximate center of the front surface of the camera body 100, a lens mount 101 for mounting an interchangeable lens 130 is formed. This lens mount 101
Is provided on the side of the lens mount 10 to be pressed when the interchangeable lens 130 is removed.
A window 103 for white balance adjustment is disposed at the upper left of the window 1. A flash shoe 104 for mounting a flash is provided substantially at the center of the upper surface of the camera body 100. A release button 105 is provided on the side of the flash shoe 104. A communication connector 106 for transmitting image data to an external computer or the like is provided on a side surface of the camera body 100.

A finder window 110 is provided at an upper portion on the back of the camera body 100. This finder window 1
Below 10, a mode setting switch 111, a drive switch 112, an AV / TV switch 113, an EF switch 114, and a white balance switch 115 are arranged in a vertical (short axis direction of a captured image) direction. . The mode setting switch 111 is connected to the camera body 10
A switch for setting a shooting mode of 0. The drive switch 112 is, for example, a switch for activating a self-timer. The AV / TV switch 113 is a switch that is pressed when selecting one of the aperture priority mode and the shutter speed priority mode. The EF switch 114 is a switch that is pressed when correcting the Ev value. The white balance switch 115 is a switch operated when performing white balance adjustment.

A liquid crystal display section 116 for displaying the operation mode of the camera is provided on the back of the camera body 100 and beside the switches 111 to 115. A mode indicator 1 is provided below the liquid crystal display unit 116.
17 and a scan start button 118 are arranged substantially horizontally. This mode indicator 1
Reference numeral 17 denotes a light emitting unit that lights in different colors according to the operation mode of the camera. Also, the scan start button 11
A switch 8 is pressed in a scan mode for reading an image recorded on the image sensor 200. Below the scan start button 118, a power switch 119 as a slide switch is provided. The power is switched from off to on in accordance with the slide position of the power switch 119, and the operation mode of the camera is switched between the photographing mode and the scan mode by further sliding.

In the center of the lower surface of the camera body 100, a slot 120 for inserting the image pickup device 200 into the camera body 100 is formed. Further, between the slot on the front side of the lower surface of the camera body 100 and the slot 120,
A dial 121 for loading the imaging device 200 into the camera body 100 is provided. This dial 121
An eject button 122 for ejecting the image sensor 200 from the slot 120 is provided beside the.
A screw hole 123 for fixing the camera body 100 to a tripod (not shown) and a lid 124 for opening and closing a battery housing section for housing a battery (not shown) are provided on the rear side of the lower surface of the camera body 100. , Respectively.

Next, the camera body 100 and the interchangeable lens 1
The internal structure of 30 will be described with reference to FIG. FIG.
FIG. 3 is a block diagram showing an internal structure of the interchangeable lens 130 when the interchangeable lens 130 is mounted on a lens mount 101 of the camera body 100.

The system control circuit 3 in FIG.
Reference numeral 00 denotes a microcomputer, which controls the entire camera body 100. The system control circuit 300 includes an exposure control circuit 332 and a light source 34.
0, element moving circuit 353, imaging element driving circuit 333, element reading circuit 354, filter moving circuit 350, amplifier 355, A / D conversion circuit 356, interface circuit 3
58, the image processing circuit 357, the operation unit 360, and the display unit 116 are connected. The exposure control circuit 332 is connected to a photometric sensor 324, a mirror drive circuit 330, and a shutter drive circuit 331. The element reading circuit 354 is also connected to the line sensor 346, the above-described element moving circuit 353, and the amplifier 355. The amplifier 355 also has the above-described A / D conversion circuit 35.
6 are connected. The A / D conversion circuit 356 includes:
Further, the above-described image processing circuit 357 is connected. The interface circuit 358 is connected to the image processing circuit 357.

On the other hand, inside the interchangeable lens 130, a photographing optical system 301 composed of a plurality of lens groups and a diaphragm 302 for restricting a photographing light beam transmitted through the imaging optical system 301 are built in. I have. In the position behind the image pickup optical system 301 (image side) inside the camera body 100, the image pickup light beam is allowed to pass through at the retracted position indicated by the dotted line in FIG. 3 and the descending position indicated by the solid line in FIG. , A quick return mirror 320 is provided as a reflecting optical member for reflecting the photographing light beam upward at a right angle. Behind the quick return mirror 320, there is provided a shutter 321 that allows the photographing light flux to pass by releasing the photographing light for a predetermined time during photographing.
Is provided. The shape of the opening (aperture) when the shutter 321 is released is a horizontal direction (a direction perpendicular to the paper surface of FIG. 3) as compared with a vertical direction (a vertical direction in FIG. 3).
Is a long and wide rectangular shape.

The quick return mirror 320 is driven by a mirror driving circuit 330, and the shutter 321 is driven by a shutter driving circuit 331. The mirror driving circuit 330 and the shutter driving circuit 331
Each is controlled by the exposure control circuit 332. That is, the exposure control circuit 332 is
, An appropriate shutter speed for performing appropriate exposure is calculated based on the light amount signal (reflecting the subject brightness and the aperture value) input from the light receiving element 324, and then the mirror driving circuit The quick return mirror 320 is moved from the lowered position to the retracted position with respect to 330,
Next, the shutter 321 is supplied to the shutter drive circuit 331.
Is opened and closed three times according to the appropriate shutter speed,
Next, the quick return mirror 320 is returned from the retracted position to the lowered position with respect to the mirror driving circuit 330.

The image sensor 200 inserted from the slot 120 is disposed behind the shutter 321 with the color filter 310 interposed therebetween. The image sensor 200 is movable in the vertical direction with its long axis direction oriented in the vertical direction of the camera body 100. This image sensor 20
An elevating mechanism for moving 0 in the vertical direction will be described with reference to FIGS. FIG. 4 is a side view showing a state in which this elevating mechanism is viewed from the same direction as FIG. 3, and FIG.
FIG. 5 is a top view showing a state in which the lifting mechanism is viewed from above. 4 and 5, the color filters 3
The illustration of 10 is omitted.

In FIG. 4, a mounting mechanism 600 provided near the bottom of the camera body 100 mounts the image sensor 200 inserted from the slot 120 on the image sensor holding member 401 or mounts the image sensor 200 on the recording member holding member 401. Is a mechanism for ejecting the recording member 200 to the slot 120. The dial 121 or the eject button 122
It is composed of a member that operates according to the above operation.

The image sensor holding member 401 is a vertically long rectangular transparent member, and the image sensor 200 is mounted on the surface thereof.
The imaging device holding member 401 includes a pair of shafts 40.
3,404 penetrates parallel to the surface. These shafts 403 and 404 are vertically extended inside the camera body 100 such that the surface of the imaging element holding member 401 is orthogonal to the optical axis of the imaging optical system 301 (imaging optical axis l ₁ ). . As a result, the image sensor holding member 401
Is a shaft 40 inside the camera body 100.
It can move up and down along 3,404.

Behind the shafts 403 and 404, a vertically long master plate 402 is provided in parallel with the shafts 403 and 404.
Is provided. Further, a transfer screw 405 is provided further rearward of the master plate 402 so as to extend in parallel with the shafts 403 and 404. The transfer screw 405 is connected to a support member 4 provided at the upper end of the master plate 402.
08 and the first support plate 4 fixed substantially at the center of the main plate 402.
The support member 11 is rotatably supported around an axis. On the other hand, a vertically long slit 402 a parallel to the transfer screw 405 is formed in the master plate 402 so as to face the transfer screw 405. On the back surface of the image pickup device holding member 401, an engaging member 413 that passes through the slit 402a and is screwed to the transfer screw 405 is fixed. Therefore, the elevation position of the imaging element holding member 401 is regulated by the engagement between the transfer screw 405 and the engagement member 413.

Below the first support plate 411 on the back of the master plate 402, a second support plate 412 is fixed in parallel with the first support plate 411. A DC motor 351 whose rotation is controlled by an element moving circuit 353 is attached to the lower surface of the second support plate 412. The drive shaft of the DC motor 351 is the second support plate 412
, And a pinion gear 422 is coaxially fixed to the end thereof. On the other hand, a transfer gear 421 meshing with the pinion gear 422 is coaxially fixed to a portion of the transfer screw 405 protruding through the first support plate 411. Therefore, when the DC motor 351 rotates, the imaging element holding member 401 moves up and down along the shafts 403 and 404 via the engaging member 413. as a result,
The image sensor 200 moves up and down in the camera body 100 in the vertical direction. That is, at the time of shooting, the image sensor 200
Is the recording areas 201, 202 and 203 of the center photographing optical axis l ₁ above in order (i.e., behind the shutter 321) so as to be located, is controlled by the element moving circuit 353 (at this time, the exposure control circuit 332 is each recording area 201,
Each time the 202 and 203 are arranged on the photographing optical axis l _1, to open and close the shutter 321 described above. ). At the time of reading, the image pickup device 200 is connected to a first mirror 3 described later.
The element is moved by the element moving circuit 353 so as to pass between the second mirror 42 and the third mirror 344.

On the other hand, the color filter 310 has a planar shape substantially equal in size to the image sensor 200, and has the same structure as the lifting mechanism (FIGS. 4 and 5) for the image sensor 200 (not shown). The elevating mechanism can move in parallel with the image sensor 200. Specifically, the color filter 310 can overlap with the image sensor 200 without displacement and move integrally with the image sensor 200, or can move independently of the image sensor 200 independently. The color filter 310 covers the first storage area 201 when the color filter 310 overlaps the image sensor 200 without displacement.
G covering the filter element 311 and the second storage area 202
From the (green) filter element 312 and the B (blue) filter element 313 covering the third storage area 203,
Be composed. The movement of the color filter 310 is controlled by a filter moving circuit 350. That is, at the time of photographing, the color filter 310
And are integrally transferred. Therefore, as long as the subject is immobile, the first recording area 201 of the image sensor 200
In the second recording area 202, an image based on the green light component of the light from the subject is recorded, and in the third recording area 203, an image based on the red light component of the light from the subject is recorded.
An image is recorded by the blue light component in the light from the subject.
At the time of reading, the color filter 310
The position where the B filter element 313 overlaps behind the shutter 321 remains retracted. Therefore, the first mirror 34
Only the image sensor 200 passes between the second and third mirrors 344.

The above-described image pickup device driving circuit 333 corresponds to FIG.
The control power supply 212 is connected between the electrode layer 214 of the image sensor 200 and the liquid crystal electrode layer 220 at the time of photographing, and when the photographing is completed, the control power supply 212 is connected to the image sensor. Remove from 200. Note that the image sensor driving circuit 333 operates according to a command signal output from the system control circuit 300.

Below the quick return mirror 320, a first mirror 342 is fixed in parallel with the quick return mirror 320 at the lowered position. Below the first mirror 342, a collimating lens 341 and a light source 3 including a light emitting element (LED) are arranged in order from above.
40 are arranged. Since the optical axis of the collimating lens 341 is oriented in the vertical direction, the first mirror 342
The optical axis after the reflection by is orthogonal to the surface direction of the image sensor 200. A third mirror 344 for bending the optical axis downward is fixed at a position where the optical axis after the reflection crosses the movement path of the image sensor 200. This third mirror 34
The scanner optical system 345 and the line sensor 346 are fixed in order on the optical axis turned back by 4. The line sensor 346 is, for example, a CCD one-dimensional sensor having 2000 pixels. The second mirror 343 is located above the first mirror 342 and on the near side in FIG.
Are fixed in a more upright state than the first mirror 342. Therefore, the light emitted from the light source 340 is
The light passes through the collimator lens 341, passes through the side of the first mirror 342, and is guided to the second mirror 343, where it is reflected and guided to the image sensor 200. The light emitted from the light source 340 is reflected by the first mirror 342 and the third mirror 344, respectively, and guided to the line sensor 346 through the scanner optical system 345.

For this reason, at the time of photographing, the light reflected by the second mirror 343 causes the image to be recorded in the recording areas 201, 202, 203 near the recording areas 201, 202, 203 of the image sensor 200. An alignment index indicating the relative positional relationship is optically formed.

At the time of reading, the illumination light emitted from the light source 340 is reflected by the first mirror 342,
The light passes through the image sensor 200 located between the first mirror 342 and the third mirror 344, is reflected by the third mirror 344, and is guided to the line sensor 346. At this time, the imaging device 200 is
By one horizontal scanning line. Therefore, each recording area 201, 202, 20 of the image sensor 200
3 moves between the first mirror 342 and the third mirror 344,
It moves in a direction orthogonal to the optical path of the illumination light. Therefore, the components on each horizontal scanning line constituting the image recorded on the image sensor 200 are illuminated by the light source 340 and formed on the light receiving surface of the line sensor 346.

The on / off control of the light source 340 is performed by the system control circuit 300 and the line sensor 3
The reading operation of the pixel signal generated at 46 is performed by the element reading circuit 3.
54. Further, the element moving circuit 353 includes:
The DC motor 351 is controlled while receiving a synchronization signal from the element reading circuit 354. The element moving circuit 353 and the element reading circuit 354 are controlled by the system control circuit 300.

The pixel signal read from the line sensor 346 is amplified by the amplifier 355, and is amplified by the A / D converter 3.
It is converted by 56 into a digital pixel signal. The digital pixel signal is subjected to processing such as shading correction and gamma correction in the image processing circuit 357 under the control of the system control circuit 300. And
The pixel signal after this processing is supplied to the interface circuit 358.
Is subjected to predetermined processing such as format conversion,
The data is output to an external computer (not shown) or the like via the communication connector 106 (see FIG. 2). The interface circuit 358 and the image processing device 357 operate according to a command signal from the system control circuit 300.

An operation unit 360 including a switch such as a release button 105 provided on the camera body 100 is connected to the system control circuit 300. The system control circuit 300 performs a shooting operation, an image signal reading operation, and the like according to the operation of the operation unit 360. Further, a liquid crystal display unit 116 (see FIG. 2) for displaying various setting states of the camera body 100 is connected to the system control circuit 300.

Next, the configuration of the finder optical system in the camera body 100 will be described in detail with reference to FIGS. 6 and 7, which are optical configuration diagrams in which only the optical system is extracted from FIGS.

[0039] When the quick return mirror 320 is in the lowered position, the surface of the quick mirror 320 intersect at an angle of 45 degrees with respect to the photographing optical axis l _1. Therefore, the photographing optical axis l ₁ is turned upward by 90 degrees by the surface of the quick return mirror 320.
The optical axis after it has been folded in this manner is hereinafter referred finder optical axis l _2.

[0040] On the surface optically equivalent position of the imaging device 200 in the finder optical axis 1 on _2, (upper surface in FIG. 6, the same below) the upper surface of the focusing screen 326 which serves as a focal plane is arranged I have. Therefore, when the quick return mirror 320 is at the lowered position, an object image is formed on the upper surface of the focus plate 326 by the imaging optical system 301. As shown in FIG. 5, the planar shape of the focus plate 326 is a substantially rectangular shape corresponding to the shape of the image captured by the image sensor 200 (the shape of the aperture of the shutter 321).

From the upper surface of the focus plate 326, the finder optical axis l
_At a position separated by 1.60 mm along ₂ , a plano-convex lens-shaped condenser lens 327 having a flat lower surface (the lower surface in FIG. 6, the same applies hereinafter) is disposed. The condenser lens 327 is made of a glass material having a refractive index of 1.80518. And this condenser lens 327
The radius of curvature of the top surface is 78.0mm, the thickness of the finder optical axis l ₂ is 3.50 mm.

At a position 0.10 mm away from the upper surface of the condenser lens 327 along the finder optical axis l ₂ , a Porro prism 322 as an erecting optical system is
They are arranged in a state of being perpendicular to a the finder optical axis l _2. FIG. 8 is a perspective view of the Porro prism 322. The Porro prism 322 has a refractive index of 1.77250.
As is clear from FIGS. 6 to 8, a first reflecting surface 322b for vertically reversing the image together with the quick return mirror 320, and a second reflecting surface 322 for reversing the image horizontally.
It has a reflection surface 322c and a third reflection surface 322d.

[0043] To describe in more detail the shape of the Porro prism 322, the first reflecting surface 322b is, as to collimate the finder optical axis l ₂ with respect to the imaging optical axis l ₁ is folded 90 degrees toward the object side, the center intersect inclined 45 degrees with respect to the finder optical axis l ₂ in. Distance from the incident surface 322a of the finder optical axis l on ₂ to the first reflecting surface 322b is 22.0 mm. Therefore, the incident surface 322a protrudes from the lower surface 322g in another part of the Porro prism 322.

The second reflecting surface 322c is connected to the finder optical axis l.
₂ as folded 90 degrees to the left as viewed from the imaging element 200 side with respect to the finder optical axis l ₂ at its center 45
They are inclined at an angle. Distance from the first reflecting surface 322b in the finder optical axis l on ₂ to the second reflecting surface 322c is 23.5 mm.

The third reflecting surface 322d is connected to the finder optical axis l.
₂ so as to parallel to the photographing optical axis l ₁ is folded 90 degrees to the imaging element 200 side, intersects inclined 45 degrees with respect to the finder optical axis l ₂ at its center. Distance from the second reflecting surface 322c of the finder optical axis l on ₂ to the third reflecting surface 322d is 27.5 mm.

[0046] In addition, the exit surface 322e is intersected at right angles to the finder optical axis l _2. Third reflective surface 322d
The distance from to the emission surface 332e is 27.0 mm. Therefore, the exit surface 322e is connected to the image pickup device 2 on the entrance surface 322a.
They are displaced parallel to 8.5mm only on the object side from the 00 side edge to the photographing optical axis l _1. The third reflection surface 322d and the emission surface 322e of the Porro prism 322 cross each other at an angle of 45 degrees to form a wedge-shaped edge 322f. The distance to the exit surface 322e from the incident surface 322a of the Porro prism 322 along the finder optical axis l ₂ is a total of 1
00 mm.

When the air conversion distance s from the upper surface (focusing surface) of the focusing plate 326 to the emission surface 322e of the Porro prism 322 is calculated based on the various data described above, the following expression (1) is obtained.

S = 1.6 + 3.5 / 1.80518 + 0.1 + 100 / 1.77250 = 60.06 [mm] (1) A position 0.10 mm away from the emission surface 322e of the Porro prism 322 along the viewfinder optical axis l _2. the first finder magnifier system 323 consisting of a positive lens system is disposed finder optical axis l ₂ coaxially. The focal length of the first Fine-Dollow ぺ system 323 is 63.11 mm. Further, the first finder loupe system 323 thickness along the whole of the finder optical axis l ₂ is 6.5 mm. Therefore, the exit surface of the _first fine loupe system 323 is connected to the image pickup device 2 on the entrance surface 322a in a direction parallel to the photographing optical axis l1.
It exists on the object side of the 00 side edge. Therefore, the imaging device 200, the imaging device holding member 401, and the shaft 403
Does not interfere with the first fine loupe system 323.

At a position 21.91 mm away from the exit surface of the first fine loupe system 323 along the finder optical axis l ₂ , an equal magnification for displacing the eye point in a direction away from the first fine loupe system 323. A relay optical system 325 is provided. Therefore, this relay optical system 3
25, in the direction of the finder optical axis l _2, the image pickup device 200, image pickup element holding member 401, and the shaft 403
Is located behind. Further, between the first finder loupe system 329 and relay optical system 325, the finder optical axis l ₂ is passed through the side of the imaging element 200.

At a position 1.00 mm away from the emission surface of the relay optical system 325 along the finder optical axis l ₂ , the image formed by the first finder loupe system 323 and the relay optical system 325 is inverted left and right and up and down. An erecting prism 328 is provided for the purpose.

[0051] at a position separated 1.02mm along the finder optical axis l ₂ from the exit surface of the erecting prism 328, a second finder magnifier system for the observed enlarged real image which is inverted by the erecting prism 328 329 Is arranged.

[0052] above-described finder optical system specific lens data (optical ranging from focal plane along the finder optical axis l ₂ on the exit surface of the second finder loupe system 329 system) are shown below. In the following, the surface No. is the number of each surface counted from the focus surface as a starting point. Specifically, No. 1 is the focusing surface, No. 2 to 3 are condenser lenses 3
No. 27 entrance and exit surfaces, Nos. 4 and 5 are Porro prisms 3
No. 22 entrance surface and exit surface (each reflection surface is omitted), No. 6 ~
8 is each surface of the first fine loupe system 323, No. 9 to 1
5 is each surface of the relay optical system 325, No. 16 to 19 are each surface of the erecting prism 328 (including each reflection surface), No. 20 to
Reference numeral 26 denotes each surface of the second fine loupe system 329. R is the radius of curvature of each surface. D is the distance on the optical axis to the next surface. Further, n is the refractive index of the material up to the next surface with respect to the d-line (air is omitted). Ν is its Abbe number. Surface No.rdn ν 1 ∞ 1.60 2 ∞ 3.50 1.80518 24.5 3 -78.00 0.10 4 ∞ 100.00 1.77250 49.6 5 ∞ 0.10 6 38.13 5.70 1.74400 44.8 7 -43.00 0.80 1.80518 25.4 8 320.00 21.91 9 -7.60 1.20 1.80518 24.5 10 21.27 7.10 1.55963 61.2 11 -14.79 0.58 12 -39.01 3.02 1.78590 44.2 13 -18.00 0.24 14 59.20 2.80 1.71700 47.9 15 -30.39 1.00 16 ∞ 49.71 1.51633 64.1 17 ∞ 0.90 18 ∞ 29.72 1.56883 56.3 19 ∞ 1.02 20 94.43 3.20 1.80610 40.9 21 -52.20 22 27.00 3.65 1.74400 44.8 23 1430.84 0.24 24 21.95 3.89 1.62280 57.0 25 54.40 1.20 1.80518 25.4 26 20.14 Next, the configuration of the photometric system disposed behind the emission surface 322e of the porro prism 322 will be described. As shown in FIGS. 6 and 7, a photometric optical system including a condenser lens 330 and a photometric sensor 324 is disposed on the emission surface 322 e of the Porro prism 322 on the side of the first fine loupe system 323.

As shown in FIG. 6, the optical axis of the condenser lens 330, that is, the photometric optical axis l ₃ passes through the plane including the finder optical axis l ₂ after being turned back at the first reflecting surface.
As shown in FIG. 7, the edge 3 is larger than the finder optical axis l _2.
It intersects with the exit surface 322e at a position offset by D = 18.40 mm to the 22f side. The angle θ formed by the photometric optical axis l ₃ with respect to the normal to the emission surface 322e (see FIG. 9).
Is required to intersect this photometric optical axis l ₃ with the finder optical axis l ₂ (center of the focus plane) on the focus plane, so that based on s = 60.06 mm and D = 18.40 mm,
It is calculated as in the following equation (2).

Θ = tan ⁻¹ (D / s) = tan ⁻¹ (18.40 / 60.06) ≒ 17.03 [degree] (2) However, in actuality, photometric light is taken into consideration in consideration of the power of the condenser lens 327. angle which the axis l ₃ with respect to the normal line of the exit surface 322e theta is set to 17.4 degrees. Therefore,
Photometric optical axis l ₃ (the optical axis of the condenser lens 330), the finder optical axis toward the photometry sensor 324 (optical axis of the first finder loupe system 323) as away from the l _2, in the finder optical axis l ₂ Leaning against.

[0055] The manner in photometric optical axis l ₃ intersecting the finder optical axis l ₂ at the center of the focal plane by more satisfying, shown in FIG. FIG. 9A shows the viewfinder optical axis l from the entrance surface 322a to the exit surface 322e with reference to the state of the Porro prism 322 viewed from the direction of FIG.
FIG. 4 is an optical path diagram in which a Porro prism 322 is developed to show ₂ as a straight line. Similarly, FIG. 9B shows the Porro prism 3
22 as viewed from the direction of FIG.
FIG. 13 is an optical path diagram in which a Porro prism 322 is developed so as to show a finder optical axis l ₂ extending from 22 a to an emission surface 322 e as a straight line. Along this photometric optical axis l ₃ , a Porro prism 32
A plano-convex lens-shaped condenser lens 330 is coaxially arranged at a position 2.290 mm away from the second exit surface 322e, with the convex surface facing the Porro prism 322 side. The condenser lens 330 is a lens for converging light emitted from the emission surface 322 e of the Porro prism 322 on the photometric sensor 324. The convex surface (incident surface) of this condenser lens has an aspherical shape represented by the following equation (3). X = C · r ² / (1+ (1- (K + 1) · C ² · Y ² ) ^1/2 ) + A4 · Y ⁴ + A6 · Y ⁶ + A8 · Y ⁸ …… (3) , X: sag amount from the tangent plane C: curvature of the aspherical surface Y: height of the aspherical surface from the optical axis K = −0.47: conical coefficient A4 = −5.9 × 10 ⁻⁴ : aspherical coefficient A6 = 1.06 × 10 ^-5: aspheric coefficient A8 = -7.6 × 10 ^-7: the aspherical coefficients, thickness along the photometry optical axis l ₃ of the condenser lens 330 is 2.500Mm.

At a position 4.910 mm away from the plane (outgoing surface) of the condenser lens 330 along the photometric optical axis l ₃ ,
A photometric sensor 324 for receiving the light converged by the condenser lens 330 and detecting the brightness of the focus plate 326
Is arranged. That is, the third reflection surface 322d (the emission surface 3) is smaller than the area of the emission surface 322e of the Porro prism 322 where the light incident on the first fine loupe system 323 passes.
The photometric sensor 324 is disposed in a region on the side of the traveling direction of the incident light to the (reflection surface immediately before 22e).
The photometric sensor 324 has a light receiving surface (condensing lens 33).
0 side) is covered with a cover glass made of parallel flat glass. And the photometric sensor 324
A photocurrent corresponding to the amount of light received on the light receiving surface is input to the exposure control circuit 332.

The photometric optical system described above (photometric optical axis l ₃₎
The specific lens data of the optical system (from the exit surface 322e of the Porro prism 322 to the light-receiving surface of the photometric sensor 324) along the line is shown below. In the following, the surface numbers are the numbers of the respective surfaces counted in order with the emission surface 322e of the Porro prism 322 as No. 100. Specifically, No. 100
Denotes a focus surface, and Nos. 101 to 102 denote an incident surface and an outgoing surface of the condenser lens 330 (a light receiving surface of the photometric sensor 324). R is the radius of curvature of each surface. D is the distance on the optical axis to the next surface. Further, n is the refractive index of the material up to the next surface with respect to the d-line (air is omitted). (Operation of Embodiment) Next, the operation of the still video camera according to the present embodiment configured as described above will be described.

The image sensor 200 includes an image sensor holding member 40.
When 1 is at the lowermost position of the shafts 403 and 404,
The mounting mechanism 600 can be mounted on the imaging element holding member 401. That is, when the imaging device 200 is in the slot 1
When the dial 121 is rotated by being inserted from the
A rubber roller (not shown) in the mounting mechanism 600 rotates to mount the image sensor 200 at a predetermined position on the image sensor holding member 401.

When the image sensor 200 is mounted on the image sensor holding member 401 in this manner, the system control circuit 300 controls the element moving circuit 353 and the filter moving circuit 350, and the first recording area 2 of the image sensor 200 is controlled.
01 and the R filter element 311 of the color filter 310 are positioned in the photographing optical axis ₁₁ (behind the shutter 321). At this time, the shutter 321 remains closed, and the quick return mirror 320 is at the lowered position. Therefore,
Light passing through the imaging optical system 301 is reflected by the quick return mirror 320 and guided to the focus plate 326. Accordingly, in a focus state corresponding to the focus adjustment state of the imaging optical system 301, the subject image is focused on the focus plane (the focus plate 32).
6).

Light diverging from any position in the focus plane enters the entrance surface 322a of the Porro prism 322 via the condenser lens 327. Some of these diverging light in the Porro prism 322, along the finder optical axis l _2, is reflected toward the object side by the first reflecting surface 322b, as viewed from the photographer side by the second reflective surface 322c left The light is reflected by the third reflection surface 322d to the photographer side, and is emitted from the emission surface 322e. Then, the light enters the first finder loupe system 323 along the finder optical axis l ₂ . The first fine loupe system 323 forms a virtual image of a real image of the subject image on the focus plate 326 on the object side. This virtual image is relayed by the relay optical system 325 and is inverted right and left and up and down by the erecting prism 328, and then the second fine loupe system 3
It is magnified by 29 and observed by the photographer.

[0061] Another part of the divergent light, as shown in FIG. 9, in the Porro prism 322, travels along the photometry optical axis l _3, the first finder loupe system 323 at the exit surface 322e The light is emitted from the side (a position offset toward the edge 322f). The emitted light is incident on the condenser lens 330 along the photometric optical axis l ₃ ,
The condenser lens 330 converges on the photometry sensor 324. Therefore, a photocurrent corresponding to the luminance (center-weighted) of the entire area of the focus surface flows through the photometric sensor 324.

Here, when the photographer presses the release button 105 of the operation unit 360, the photographing operation by the system control circuit 300 is started. That is, the exposure control circuit 332 calculates an appropriate shutter speed based on the photocurrent input from the photometric sensor 324. Then, under the control of the exposure control circuit 332, the quick return mirror 32
0 moves to the retreat position, the shutter 321 opens and closes according to an appropriate shutter speed, and an image of a red light component is recorded in the first recording area 201. After the shutter 321 is closed, the element moving circuit 353 and the filter moving circuit 350
Image sensor 200 and color filter 310 under the control of
Rises, the second recording area 202 and the G filter element 3
Reference numeral 12 is positioned in the photographing optical axis ₁₁ (behind the shutter 321). Then, the shutter 321 opens and closes again, and an image based on the green light component is recorded in the second recording area 202.
Similarly, after the shutter 321 is closed, the third recording area 203 and the B filter element 313 are positioned in the photographing optical axis ₁₁ (behind the shutter 321), and the shutter 3
21 is opened and closed, and an image based on the blue light component is recorded in the third recording area 203.

When the shutter 321 is closed and the recording of the image by the blue light component is completed, under the control of the element moving circuit 353 and the filter moving circuit 350, the imaging element holding member 4
01 and the image sensor 200 are lowered to the initial position, and the quick return mirror 320 is returned to the lowered position under the control of the exposure control circuit 332. Thus, the subject image can be observed again by the photographer via the finder optical system.

As described above, the porro prism 322 of the present embodiment has an exit surface which is smaller than that of a normally used porro prism (a porro prism whose shape near the exit surface is prismatic with the finder optical axis at the center). only the reflection surface of the immediately preceding (third reflection surface 322d) and the exit surface (322e) is slightly extended to the side away from the finder optical axis l _2, the side of the light path incident on the viewfinder loupe (first finder magnifier 323) in a square (third traveling direction of the incident light on the reflecting surfaces 322d), it is ensured a space for passing the finder optical axis l _3. Therefore, the photometric optical system (the condensing lens 330 and the photometric sensor 324) is arranged on the side of the fine loupe (first fine loupe 323) by only partially expanding the Porro prism 322 without increasing the size of the entire Porro prism 322. You can do it.

In the above embodiment, the offset amount D of the photometric optical axis l ₃ with respect to the finder optical axis l _{2 is} set to 1
Although 8.40 mm, the offset amount D can be arbitrarily set, preferably within a range of 10 <D <25 [mm]. If the offset amount D is smaller than 10 mm, the condenser lens 330 and the photometric sensor 324 may hit the first fine loupe system 323 or interfere with the optical path of light passing through the first fine loupe system 323. There is. Also, the offset amount D is 25 mm
If it is larger, the condenser lens 330 and the photometric sensor 32
4 is too far from the finder optical axis l ₂ , and the whole Porro prism 322 becomes large.

[0066] Note that when the D = 10, according to the equation (2), the photometry optical axis l ₃ is the angle θ which makes with the normal line of the exit surface 322e, shall be about 10 degrees. Also, D
= If set to 25, according to the equation (2), the photometry optical axis l ₃ is the angle θ which makes with the normal line of the exit surface 322e, shall be about 23 degrees. Therefore, a preferable value range of θ is 10 <θ <23 [degree]. However, if not the photometry and center-weighted, as long as the photometry optical axis l ₃ intersects the focal plane, can be a θ an arbitrary value.

[0067]

According to the single-lens reflex camera of the present invention constructed as described above, even when a porro prism is used as an erecting optical system, the photometric sensor can be polished while suppressing the porro prism from increasing in size. It can be located behind the exit surface of the prism.

[Brief description of the drawings]

FIG. 1 is a perspective view of a still video camera according to a first embodiment of the present invention as viewed from the front upper side.

FIG. 2 is a perspective view of the still video camera and the image sensor of FIG.

FIG. 3 is a block diagram showing an internal configuration of the still video camera of FIG. 1;

FIG. 4 is a side view of a mechanism for elevating and lowering an image sensor in a camera body and its vicinity.

FIG. 5 is a top view of a mechanism for elevating and lowering an image sensor in a camera body and its vicinity

FIG. 6 is an optical configuration diagram in which only an optical system is extracted from FIG.

FIG. 7 is an optical configuration diagram in which only an optical system is extracted from FIG.

FIG. 8 is a perspective view of a pro prism.

FIG. 9 is an exploded view of the Porro prism along the viewfinder optical axis.

FIG. 10 is a longitudinal sectional view showing a configuration of an image sensor.

[Explanation of symbols]

 200 Image sensor 320 Quick return mirror 322 Porro prism 322a Incident surface 322b First reflective surface 322c Second reflective surface 322d Third reflective surface 322e Emission surface 323 First fine loupe system 324 Photometric sensor 326 Focus plate 330 Condenser lens

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Abe 2-36-9 Maenocho, Itabashi-ku, Tokyo Inside Asahiko Gaku Kogyo Co., Ltd. (72) Inventor Takayuki Izumi 2-36-9 Maenocho, Itabashi-ku, Tokyo No. Asahi Kogaku Kogyo Co., Ltd. (56) References JP-A-1-200241 (JP, A) JP-A-60-80428 (JP, U) JP-A-54-27629 (JP, U) (58) Investigated Field (Int.Cl. ⁷ , DB name) G03B 13/26 G03B 13/06

Claims (5)

(57) [Claims] A single-lens reflex camera provided with a finder for projecting a subject image formed by an imaging optical system onto a focus surface equivalent to an imaging surface and observing the subject image projected on the focus surface with a loupe. A porro prism having a plurality of reflection surfaces that bends the optical axis of the loupe so as to observe the subject image projected on the focus surface as an erect image, and enters the loupe at an exit surface of the porro prism. A single-lens reflex camera, comprising: a photometric sensor disposed behind a region located on the side in the traveling direction of the incident light on the reflection surface immediately before the light exit surface with respect to the light passage region. 2. The single-lens reflex camera according to claim 1, further comprising a condenser lens for converging light emitted from an emission surface of said Porro prism on said photometric sensor. 3. An optical axis of said loupe, wherein an optical axis of said condensing lens is inclined with respect to an optical axis of said loupe so as to move away from an optical axis of said loupe as approaching said photometric sensor. Single-lens reflex camera. 4. The single-lens reflex camera according to claim 3, wherein an optical axis of said condenser lens intersects with an optical axis of said loupe on said focus plane. 5. A porro prism comprising: an incident surface on which light emitted from the focus surface is incident; a first reflecting surface for reflecting light transmitted through the incident surface to the object side by 90 degrees; and a first reflecting surface. A second reflecting surface for reflecting the reflected light by 90 degrees in a direction orthogonal to the traveling direction of the light incident on the first reflecting surface, and transmitting the light reflected by the second reflecting surface to the light of the imaging optical system. The single-lens reflex camera according to claim 1, further comprising: a third reflecting surface that reflects 90 degrees in a direction parallel to the axis; and an emitting surface that emits light reflected by the third reflecting surface.