JPH0457035A - Camera - Google Patents

Abstract

PURPOSE:To always execute the photometry of an appropriate range by varying a photometric area in accordance with zooming of its photographing area without generating evil effects such as a drop of the light quantity in a finder and a drop of the photodetecting quantity by a photometric element, etc. CONSTITUTION:A photometric circuit 15 of a photographing optical system 2 detects a defocus amount, based on an output of a photometric element, and to an aperture blade 9, an exposure control circuit 13 for driving it is connected, and to a photographic lens 8, a lens control circuit 14 for executing lens driving such as zooming and focusing, etc., varying a focal distance and outputting the lens driving quantity is connected, and the circuits 15, 13 and 14 are connected to a microcomputer 7, respectively. A photometric optical system 1 is provided with a photometric zoom lens 4 and a photometric element 5, a center part 5b and a peripheral part 5a of this element are connected to a photometric circuit 6, which outputs of the center part and the peripheral part are processed separately and inputted to the microcomputer. A finder optical system 3 is provided with a finder zoom lens 18 and a warning light emission diode 19, and the microcomputer is connected to a flash 16. Accordingly, the microcomputer controls the circuit 13, the circuit 14 and the circuit 17, based on information of the circuit 16, the circuit 15 and the circuit 14.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a camera that has a photometric optical system separate from a zoomable photographic optical system, and that changes the photometric area in response to changes in the photographic area due to zooming of the photographic optical system.

[Conventional technology]

Conventionally, the area to be photographed has been divided into multiple photometry areas, for example, to prevent the person from appearing too dark when photographing a person using the camera's automatic exposure when backlit. 2. Description of the Related Art A camera configured to more accurately determine the brightness of a main subject, such as a person, has been provided. By the way, when a zoom lens is used as a photographing lens for such a camera, TTL (Through The Ien) is used for photometry like an eye reflex camera.
If the SE) method is adopted, the metering area changes as the shooting area changes due to zooming, so the metering can always be done according to the shooting area, but like a compact camera, the metering is done using external light. Therefore, if the photometric optical system is provided separately from the photographic optical system, when the photographic lens is zoomed, a shift will occur between the photographic area and the photometric area. For example, when the photographing lens is zoomed to the telephoto end, the ratio of each of the divided photometry areas to the photographing area 72 changes, and the photometry ends up outside the photographing area. Therefore, an example of a camera of this type in which the photometry area is changed in conjunction with the photographing area is the camera disclosed in Japanese Patent Laid-Open No. 2-10335. In this camera, the viewfinder optical system is configured to change magnification in response to zooming of the photographic lens, and the light from the objective lens of the viewfinder optical system is divided into two, and one of the lights is sent to the eyepiece. By configuring the camera to guide the other light to the photometric element, in other words, by incorporating the photometric optical system into the finder optical system, it is possible to perform photometry in accordance with changes in the photographic area caused by zooming of the photographic lens. ing.

[Problem to be solved by the invention]

However, with this camera, the light from the objective lens is split into two, and each split light is guided to the objective lens and the photometric element, so the image in the viewfinder that the photographer can see becomes very dark. At the same time, the amount of light received by the photometric element decreases, reducing its efficiency. Therefore, the technical problem to be solved by the present invention is that in a camera that has a photometric optical system separate from a photographic optical system configured to allow zooming, the amount of light in the viewfinder decreases and the amount of light received by the photometric element decreases. The object of the present invention is to change the photometry area according to zooming of the photographing area without causing such problems as to always perform photometry in an appropriate range.

[Means for Solving the Problems and Operations/Effects] In order to solve the above technical problems, the camera according to the present invention has a photographic optical system configured to be capable of zooming, and a separate photometry system separate from the photographic optical system. The photometric optical system guides light from the subject into the camera, and includes a photometric zoom lens that zooms in conjunction with the zooming of the photographic optical system; It is composed of a photometric element that receives light from a subject. If the camera is configured in this way, the photometric zoom lens is zoomed in conjunction with the zooming of the photographic lens, so the photometric area changes in response to changes in the photographic area. Therefore, the ratio of the photometry area divided into a plurality of areas to the photographing area does not always change. Furthermore, since the light to the photometric element is not divided, the amount of light received does not decrease. In addition, in the above configuration, the zoom lens constituting the photometric optical system is composed of a negative lens whose position is fixed and a positive lens that is movable in the optical axis direction, and the power of the negative lens is ψ1, and the photometric optical system is When the combined power with the optical system set to 7 telephoto ends is ψt, 12 ψ1/ψt
It is preferable to provide means for moving the positive lens on the optical axis of the photometric optical system while satisfying the relationship <2.4. The reason why the relationship between the power of the negative lens and the combined power at the telephoto end is regulated in this way is as follows. That is, k: Zoom lens zoom ratio ψ1: Negative lens power ψ, : Positive lens power ψt: Combined power in telephoto state ψW: Combined power in wide-angle state Et: Distance between each lens Ew in telephoto state :Assuming the distance between each lens in the wide-angle state, when the variable power ratio of the positive lens becomes 1/-/ii+~, the image planes of the lenses at the telephoto end and the wide end match,
The amount of movement of the image plane along the way is reduced. Here, t/
J' and A are as follows. 1, /JTC-(ψ, (1-E+rψ, ))/(ψw(
1-Ew・ψ1))吾-(ψ, (1-Et・ψ,))/
(ψt(1-Et·ψ1)) The closer the distance Et between the lenses in the telephoto state is to 0, the shorter the total length of the lenses becomes, which is preferable. Therefore, by substituting Et=0 into equation 4 above, Q-ψ, /ψ can be considered to be set to about 14 to 6 times as the zoom lens zoom ratio in the case of a general compact camera. Substituting these values for k, we get 12 ψI/ψt<
The relationship 2.4 is obtained. As described above, under this relationship, the position of the imaging plane of the photometric optical system can be made to match at the telephoto end and the wide end,
Moreover, since its position only moves slightly between the telephoto end and the wide end, divisional photometry can always be carried out almost accurately within the photographic area.

【Example】

Below, a first example of a camera according to an embodiment of the present invention will be described.
This will be explained in detail with reference to FIGS. FIG. 1 is a circuit diagram of this camera. As shown in the figure, this camera includes a photometric optical system I for performing external light metering, a photographic optical system 2 configured to be capable of zooming,
It includes a finder optical system 3 that zooms in response to the zooming of the photographic optical system 2. The photographic optical system 2 includes a photographic lens 8 configured as a zoom lens from a plurality of lenses, an aperture blade 9 that is incorporated into the photographic lens 8 and operates during exposure, and a distance measuring element included in a distance measuring circuit 15 in the figure. It is composed of an autofocus mirror 10 that guides light to the camera, and a light shielding film 11 located just in front of the film 12. In the distance measuring circuit I5, the amount of defocus is detected based on the output of the distance measuring element. Further, an exposure control circuit 13 is connected to the diaphragm blade 9 to drive the diaphragm blade 9 to control exposure. A lens control circuit 14 is connected to the lens control circuit 14, which outputs a change in focal length and a lens driving amount necessary for focusing as data. The distance measuring circuit 15, exposure control circuit 13, and lens control circuit 14 described above are each connected to a microcomputer 7 that controls the overall operation of the camera. The photometric optical system 1 includes a photometric zoom lens 4 which is composed of a plurality of lenses so as to operate in accordance with the zooming of the photographic lens 8, and two parts 5a corresponding to the central part of the photographing area and its peripheral parts. It is composed of a photometric element 5 divided into 5b. The photometric element 5 has a central part 5b and a peripheral part 5a connected to a photometric circuit 6, where the output of the central part 5b and the peripheral part 5a of the photometric element are separately processed and sent to the microcomputer 7. is input. The finder optical system 3 includes a finder zoom lens 18 and a microcomputer 7 for issuing a warning to the photographer.
and a warning light emitting diode 19 connected to the warning light emitting diode 19. Further, the microcomputer 7 is connected to the flash L12 via the flash control circuit 17. With the circuit configuration as described above, the microcomputer 7 has a photometry circuit 6, a distance measurement circuit 1,
5 and the lens control circuit 14, the exposure control circuit I3, the lens control circuit 14, and the flash control circuit 17 are controlled. Next, with reference to FIGS. 2 and 3, the drive systems of the photographing lens 8 and the photometric lens 4, which are each configured as a zoom lens, will be explained. FIG. 2 is a sectional view showing the driving parts of the photographing optical system 2 and the photometric optical system 1, and FIG. 3 is a plan view of the lens barrel of the photographing lens. As shown in the figure, the photographing lens 8 is composed of a first lens group 8a and a second lens group 8b. Each lens group 8a, 8b
are housed in the lens barrel in a state where they are each held for 20.2 days by the holding member 20.2. The lens barrel is composed of a fixed barrel 22 and a cam barrel 23. The fixed barrel 22 has straight grooves 22a, 22b, and the cam barrel 23 has diagonal cam grooves 23a, 23b. has been done. The pin 20a provided on the holding member 20 of the second lens group 8a is fitted into the straight-advance groove 11122a and the cam groove 23a, and the second lens group 8 is fitted into the straight-advance groove 22b and the cam groove 23b.
A pin 21a provided on the holding member 21 of b is fitted. Further, a gear portion 23d is formed at the rear end of the outer peripheral surface of the cam lens barrel 23, and the cam lens barrel is rotated by the meshing of the gear 24 attached to the motor 25 and this gear portion 23d. The lens 8 is configured to perform zooming. On the other hand, the zoom lens 4 of the photometric optical system l includes a negative lens 4a whose position is fixed, and a positive lens 4 which is movable in the optical axis direction.
It is composed of b. A drive cam 23c is provided on the outer peripheral surface of the cam barrel 23, and the positive lens 4b is moved in the optical axis direction by the action of this cam 23c, and the photometric lens 4 is zoomed. In addition, each lens 4
Each of a and 4b may be constructed from a plurality of lenses as a lens group, similarly to the photographing lens. Here, the movement of this zoom lens 4 will be explained using FIG. 4. FIG. 4(a) is a schematic diagram showing the arrangement of a photometric optical system 1 consisting of a negative lens 4a, a positive lens 4b, and a photometric element 5. FIGS. 4(b) and 4(c) show changes in the positions of the lenses 4a and 4b when they are moved from the wide-angle end to the telephoto end (shown in the left-right direction in the figure); and the corresponding image plane (indicated by a dashed line)
For example, the fourth
As shown in figure (b), if the negative lens is moved once toward the photometric element side and then moved in the opposite direction to its original position, and at the same time the positive lens 4b is moved toward the negative lens 4a side, the image is shown as a. By focusing the image on a fixed position, it is possible to always obtain a focused image on the photometric element. However, in order to do this, a means for moving both the negative lens 4a and the positive lens 4b is required, which makes the configuration complicated. In addition, in the case of photometry, as long as the approximate brightness can be obtained in the center and periphery depending on the shooting area, the image forming surface does not require strict positional accuracy, so the image forming surface is relative to the light receiving surface. Slight movement is acceptable. However, it is undesirable to form images at different positions at the wide end and telephoto end, and to place the light-receiving surface biased toward either of the image-forming positions, as shown in Figure 4 (C). By fixing the position of the negative lens 4a and moving only the positive lens 4b linearly, the position of the image plane is the same at the telephoto end and the wide end, as shown by b in the figure, and The movement of the image forming surface relative to the light receiving surface is said to be the least when the amount of movement of the image forming surface is maximized exactly in the middle of the wide end, and the light receiving surface C is placed approximately in the middle of that amount of movement. This is preferable in this respect. In order to do this, as mentioned above, 1.2〈ψ
, /ψt<24, the position of the image plane will be the same at the telephoto end and the wide end, and the amount of movement thereof will be reduced. By the way, when the photometric lens 4 is configured to allow zooming as explained above, due to the difference in zoom configuration between the photographing lens 8 and the photometric lens 4, the brightness of the lens (opening A deviation occurs in the aperture value). In this embodiment, the error is set to zero when each lens is in the wide-angle state. Therefore, Fig. 5 is a graph in which the horizontal axis shows the zooming ratio R (the ratio of the focal length at any zoom position to the focal length at the wide end), and the vertical axis shows the change in the number of aperture steps. As shown, the error Δ in the change in the aperture value of the photometric lens, represented by the broken line, with respect to the change in the aperture value of the photographing lens, represented by the solid line.
Ev increases as the lens is zoomed toward the telephoto side and the variable power ratio R increases. If such an error occurs, accurate photometric values cannot be obtained, so it becomes necessary to correct the aperture value. To do this, first, the reference error is that the magnification ratio R is 1.
．． It is sufficient to read the error ΔE v (R) of the change in the aperture for each setting of 5.2.2.5, and perform correction calculations based on that value. Specifically, since each error ΔEv was as shown in the table below,
Proportional calculations are performed based on this value. The amount of correction is determined by the following formula.・If 1≦R<1.5, ΔEv(R)-〇, 09x(R-1)10.5・1.5
If ≦R<2, ΔEv(R)=0.09+0.1X(R-1,5)10
．． 5・If l≦R<1.5, ΔEv(R)−0,19+0.21. X (R-1)1
0.5 The correction amount is obtained in this way, and the operation of the camera when actually performing this calculation to correct the photometric value will be explained using the flowchart shown in FIG. First, in step #l, the output Evs' at the center of the photometric element is
and its peripheral output E va' are input to the microcomputer, and in step #2, the focal length f is input as the zoom information of the photographic lens, and in step #3, based on the variable magnification ratio R, as described above, An aperture correction value ΔEv is calculated. Then, in step #4, this correction value is added to the output E vs' at the center and the output E va' at the periphery of the photometric element, and the photometric values for the center and periphery of the imaging area are determined. Then, in step #5, it is determined whether the difference between the photometric value Evs at the center and the photometric value Eva at the periphery is greater than a preset value C, and if it is, it is determined that there is backlighting, and step #6 Exposure control is performed with flash emission. Further, if it is determined in step #5 that the difference between the photometric value Evs in the center and the photometric value Eva in the peripheral area is smaller than a predetermined value C, in step #7, the center of the photometric area is set to a predetermined value. It is determined whether the image is brighter or darker than the actual value, and if it is dark, the process goes to step #6, an exposure control routine for flash emission, and if it is bright, the process goes to step #8, an exposure control routine for flash non-emission. In this way, light metering is always performed in response to changes in the shooting area due to zooming, and the deviation in lens brightness (open aperture value) between the metering lens and the shooting lens that occurs during zooming is corrected. , it is possible to always perform proper exposure under the proper aperture. In addition, in the method explained above, correction was performed by calculation based on data at three points, but it is possible to subdivide the zoom ratio R and store each correction amount ΔE v (R) in advance in the camera's memory. It is also possible to read this directly and take action accordingly.

[Brief explanation of drawings]

1 to 6 show a camera according to Embodiment I of the present invention, FIG. 1 is a circuit configuration diagram of this camera, and FIG. 2 is a sectional view showing the drive section of the photographing optical system and the photometry optical system. Figure 3 is a plan view of the photographic lens barrel, Figure 4 is a schematic diagram showing the operating states of the lenses that make up the finder optical system, and Figure 5 is a diagram showing the various aperture values of the photographic and metering optical systems during zooming. A graph showing the changes, and FIG. 6 is a flowchart showing the operation of this camera. DESCRIPTION OF SYMBOLS 1...Photometric optical system, 2...Photographing optical system, 3...Finder optical system, 4...Zoom lens for photometry, 4a.
...Negative lens, 4b...Positive lens, 5...Photometering element, 5a...Periphery, 5b...Center, 6...Photometering circuit, 7...Microcomputer, and...Photographing lens , 8a...
2nd lens group, 8b, 2nd lens group, 9, aperture blade, 10
... Autofocus mirror, II... Light-shielding film,
12... Film, 13... Exposure control circuit, 14...
Lens control circuit, 15...Distance measurement circuit, 16...Flash, 17...Flash emission control circuit, 18.Finder lens, 19...Warning light emitting diode, 20
... 1st lune group holding member, 20a... pin, 21.
...Second lens group holding member, 21a...pin, 22.
...Fixed lens barrel, 22a, 22b...straight groove, 23...
・Cam lens barrel, 23a, 23b...cam groove, 23c...
・Drive cam, 23d... Gear part, 24... Gear, 2
5...Motor patent applicant Minolta Camera Co., Ltd. Agent
Patent attorney Maeda Ao (and 1 other person) FJ L~
To V CUC%J Figure 4 Figure 5

Claims (1)

[Scope of Claims] (1) In a camera in which a photographing optical system (2) is configured to be capable of zooming and is provided with a photometric optical system (1) of a split metering method separately from the photographic optical system (2). The photometric optical system (1) includes a photometric zoom lens (4) that guides light from a subject into the camera and is zoomed in conjunction with the zooming of the photographic optical system (2); A camera characterized in that it has a photometric element (5) that receives light from a subject at the rear of (4). (2) The zoom lens (4) constituting the photometric optical system (1) has a negative lens (4a) whose position is fixed and a positive lens (4b) which is movable in the optical axis direction, Let the power of the negative lens (4a) be ψ_1, and the combined power with the photometric optical system (1) set at the telephoto end is ψt
When the relationship 1.2<ψ_1/ψt<2.4 is satisfied, means (20a, 21a, 22a,
22b). The camera according to claim 1, further comprising: 22b).