JPH08278528A - Camera - Google Patents

Abstract

PURPOSE: To aim at a target of ah object after a focus is detected and to output photometric information taking account of the size of the object as well. CONSTITUTION: This camera is provided with luminance detecting means SPDI- SPD4 detecting luminance in each region, after a region is divided into at least a first region including a focus detecting region and a region outside the first region, focusing means 30 and 31 for moving a lens up to a focusing position, based on the result of the detection of the focus, a magnification detecting means 24 obtaining information corresponding to the magnification of the object with a distance up to it and a focal distance and an arithmetic means 24 which executes a photometric calculation for an exposure by using the luminance of each region detected by the luminance detecting means SPD1-SPD4, at the time of moving the lens up to the focusing position by the focusing means 30 and 31 and changes weighing of the luminance of the outside region against the luminance of the first region, based on the information corresponding to the magnification obtained by the magnification detecting means 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a camera having a brightness detecting means for detecting the brightness of a plurality of divided areas.

[0002]

2. Description of the Related Art As a conventional photometry system for a camera, there are a center-weighted photometry, an average photometry, a partial photometry, a spot photometry, and the like, each of which has been put to practical use. However, each photometric method has advantages and disadvantages, and it is difficult and troublesome for a photographer to select a photometric method in a camera that allows the photographer to select the photometric method. Therefore, in recent years, the object scene is divided into a plurality of areas for photometry, and the brightness information such as the maximum brightness value, the minimum brightness value, the difference between the maximum brightness value and the minimum brightness value, and the average brightness value is used as a parameter. By implementing a calculation designated by an algorithm on the above-mentioned photometric information, the exposure value is determined as much as possible to achieve the proper exposure. With the advent of such a camera, it is possible to provide a more appropriate exposure value corresponding to the luminance distribution of the field, as compared with a camera that performs uniform photometry such as average photometry.

[0003]

However, even in such a system, it is not possible to grasp in which part of the subject field the main subject is located, and depending on the position and size of the main subject, shooting may be performed. There were times when the exposure value was different from what the person was aiming for. (Object of the Invention) An object of the present invention is to solve the above-mentioned problems, to provide a camera capable of narrowing down the focus on a subject for which focus detection has been performed and outputting photometric information in consideration of its size. is there.

[0004]

In order to achieve the above object, the present invention is directed to a first area including at least a focus detection area and an outer area outside the first area. Luminance detecting means for detecting the luminance of the object, focus adjusting means for moving the lens to a focusing position based on the focus detection result, and obtaining information corresponding to the photographing magnification of the photographing object based on the distance to the photographing object and the focal length. Magnification detection means;
A photometric calculation for exposure is performed using the brightness of each of the areas detected by the brightness detection means when the lens is moved to the in-focus position by the focus adjustment means. Arithmetic means for changing the weighting of the luminance of the outer area with respect to the luminance of the first area based on the information corresponding to the photographing magnification obtained by the detecting means.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show an embodiment of the present invention. SPD1 to SPD4 are silicon photodiodes constituting a photometric sensor for measuring the field brightness in a divided pattern corresponding to the photographing screen 1 as shown in FIG. 2, 2 to 5 are logarithmic compression diodes, and 6 to 9 are operational amplifiers. 10 to 13 are analog switches which are turned on / off according to a signal from a decoder described later, 14 is an operational amplifier, 1
Reference numeral 5 denotes a diode, which constitutes a circuit for compensating the reverse saturation current of the logarithmic compression diodes 2 to 5 together with the constant current source 16 for flowing the forward current Iref to the diode 15. Reference numeral 17 denotes a resistor having a temperature coefficient for compensating the temperature of the logarithmic compression diodes 2 to 5 and the diode 15 together with an operational amplifier 18 and a resistor 19. Reference numerals 20 and 21 denote resistors fixed to a photographic lens barrel. Reference numeral 22 denotes a photographic lens. A slider that slides on the resistor 20 in conjunction with the rotation of the distance ring. The slider 22 generates a voltage (voltage obtained by dividing the reference voltage Vref) corresponding to the focus position of the photographing lens. I do. 23
Is the resistor 2 linked to the rotation of the zoom ring of the taking lens.
1, the slider 23 has a voltage (reference voltage Vre) corresponding to the zoom position (focal length) at that time.
A voltage obtained by dividing f) is generated.

Reference numeral 24 denotes an arithmetic control circuit having an arithmetic function and various control functions, 25 to 27 analog switches that are turned on and off in accordance with signals from the arithmetic control circuit 24, and 28 analog input through the analog switches 25 to 27. A / D conversion circuit for converting a signal into a digital signal, 2
Reference numeral 9 is a decoder for selecting (turning on) the analog switches 10 to 13 according to a signal from the arithmetic control circuit 24, and 30 is an infrared light emitting diode, a light receiving element for receiving the reflected light of the infrared light from the subject, and the like. An AF control circuit including a distance detection unit including the distance detection unit and a drive control unit that drives the photographing lens to the in-focus position by the motor 31 based on the distance signal obtained by the distance detection unit, and 32 is the first stroke of the release button. Is a switch that is turned on, 33 is a release switch that is turned on by the second stroke of the release button, and 34 is a battery that serves as a power supply for each circuit. Note that E in FIG. 2 indicates a distance measuring area corresponding to the visual field range of a distance measuring sensor (not shown) arranged in the center of the photographing screen 1.

Next, the operation will be described. When the first stroke of the release button is performed and the switch 32 is turned on, the arithmetic control circuit 24 turns on the analog switch 26 and outputs an operation start signal to the AF control circuit 30. Then, the distance detection unit in the AF control circuit 30 starts an operation of obtaining a distance signal to the main subject arranged in the distance measurement area E at the center of the photographing screen 1. On the other hand, the slider 22
A voltage corresponding to the rotational position of the distance ring of the taking lens is generated at the input terminal. This signal is input to the A / D conversion circuit 28 via the analog switch 26, converted into a digital signal, and then arithmetically controlled. AF control circuit 30 via circuit 24
To the drive control unit in the. When the distance information and the position information of the distance ring are input, the AF is performed based on the information.
The drive control unit in the control circuit 30 controls the drive of the motor 31,
That is, when the rotation direction and the speed of the motor 31 are controlled and it is determined that the photographing lens has reached the in-focus position, the motor 31 is stopped, and at the same time, an AF end signal is output to the arithmetic and control circuit 24.

When the AF end signal is input, the arithmetic control circuit 24 stores the position signal of the stop of the photographing lens (distance ring), and at the same time, turns off the analog switch 26 and then turns on the analog switch 27. . After the analog switch 27 is turned on, a voltage corresponding to the rotational position of the zoom ring generated in the slider 23 is input to the A / D conversion circuit 28 via the switch and is converted into a digital signal. , Is input to the arithmetic and control circuit 24 and is stored together with the position signal of the photographing lens. At this point, the arithmetic control circuit 24 has stored the distance information from the main subject to the camera and the focal length information of the photographing lens.
After the focusing is completed in this way, the arithmetic and control circuit 24 starts the operation to determine the exposure based on the information.

That is, the arithmetic control circuit 24 first turns off the analog switch 27, turns on the analog switch 25, and then outputs the analog switch 10 through the decoder 29.
Only turn on. As a result, the voltage generated at the output terminal of the operational amplifier 6, that is, the silicon photodiode S
The voltage including the field luminance information measured by the PD 1 is input to the non-inverting input terminal of the operational amplifier 14. This voltage is temperature-compensated, input to the A / D conversion circuit 28 via the operational amplifier 18 and the analog switch 25, is converted into a digital signal, and then is input to the operation control circuit 24. The arithmetic control circuit 24 stores the signal as the field luminance information measured by the silicon photodiode SPD1. Next, the arithmetic and control circuit 2 is used to obtain field luminance information measured by the silicon photodiode SPD2.
4 turns on only the analog switch 11 via the decoder 29, and stores the field brightness information at this time which is input through the same process as described above. Silicon photodiode S
The same applies to the case where the field luminance information measured by the PD3 and the SPD4 is obtained.

As an example of the exposure determination, FIGS. 3 and 4 show a method of determining an exposure value by weighting at least an area including a distance measurement area E assuming a main subject as a person. I will use it.

FIG. 3 is a view for explaining the relationship between the face 35 of the person as the main subject, the photographing lens 36, and the face 35 'formed on the film surface, where L is the size of the face 35, l
Is the size of the face 35 ′ formed on the film surface, D is the distance from the human face 35 to the camera, and f is the focal length of the taking lens 36. When the size l of the face 35 'is represented using the L, D, and f, the following expression holds: l = (f / D-f) .L (D> f). That is, generally, the face 35 of a person is almost the same size, and there is little individual difference. Therefore, if L is considered as a constant, the size l of the face 35 'to be imaged on the film surface can be determined from the distance D from the person's face 35 to the taking lens 36 and the focal length f of the taking lens.

Therefore, the three central regions (silicon photodiode S shown in FIG. 2) arranged concentrically are formed.
Assuming that the diameters of the areas measured by PD1, SPD2, and SPD3) are A, B, and C from the inside, the size (ratio) 1 of the face 35 in the photographing screen 1 that can be obtained by the above formula is 4 The two cases will be explained separately. In 1) A <l <case such as FIG. 4 the case of B (a), when the luminance values photometry by silicon photodiode SPD1~SPD4 obtained as described above and BV ₁ to BV _4, The ratio of each weight is expressed as BV ₁ : BV ₂ : BV ₃ : BV ₄ = 1: 0.5:
A value weighted at the center, such as 0.2: 0.1, is defined as the final luminance (photometric information) at the time of such photographing. 2) Case of B <l <C In the case as shown in FIG. 4B, similarly, BV ₁ : BV ₂ :
A value weighted by a ratio such as BV ₃ : BV ₄ = 1.0: 0.8: 0.5: 0.2 is defined as such a final luminance at the time of shooting. 3) When C <l In the case as shown in FIG. 4 (c), similarly, BV ₁ : BV ₂ :
A value weighted by a ratio such as BV ₃ : BV ₄ = 1.0: 1.0: 1.0: 0.5 is defined as such a final luminance at the time of shooting. 4) Case of l <A In the case as shown in FIG. 4 (d), the face 35 has any region of the silicon photodiodes SPD1 to SPD3.
Cannot accurately measure the brightness of the image. However, in such a case, it is often preferable for a photograph to make the exposure of the entire object scene proper rather than the person face 35 to be properly exposed, so that the silicon photodiodes SPD1 to SPD3 and The respective brightness values (BV ₁ , BV ₂ , BV ₃ ,
BV ₄ : BV ₁ : BV
₂ : BV ₃ : BV ₄ = 1.0: 1.0: 0.8: 0.5
A value weighted by such a ratio is set as the final brightness at the time of such photographing.

As described above, the arithmetic control circuit 24 predicts the size l of the face 35 'using the distance information D from the main subject to the camera and the focal length information f of the photographing lens, and l and the diameter A,
Based on the relationship between B and C, the final luminance value at that time is determined as in the above 1) to 4). Then, the exposure value is determined using the brightness value and the shooting information such as the ISO of the film.

If the release switch 33 is turned on by the second stroke of the release button, the aperture and the shutter are controlled based on the exposure value determined as described above, and a series of photographing operations is completed. I do.

As described above, in this embodiment, after the known AF mechanism is operated and the photographic lens is focused, luminance information from each of the divided photometric areas is obtained, and distance measurement is performed based on each of the luminance information. Since the final luminance information is determined by weighting the area including the area E with priority, it is possible to accurately perform the photometry with the target focused on the main subject. Also,
Using the information on the distance from the main subject to the camera and the focal length of the shooting lens, the size (ratio) of the main subject image to the shooting screen is predicted, and the final photometric information is determined according to that size. Therefore, the main subject can be more appropriately exposed.

By the way, depending on the shooting conditions, there are cases where it is desired to shoot even before the photographic lens is in focus due to the operation of the AF mechanism (a case where quick-shooting is required). Shows the form of the circuit configuration in consideration of such a case, and the same portions as those in FIG. 1 are represented by the same reference numerals. In FIG. 5, reference numeral 37 denotes a focus priority mode (a mode in which a photometric operation is started after focusing as described in the above embodiment) to a release priority mode (even before focusing, the shutter is immediately released. Switch to be turned on when switched to the mode for starting photometric operation), 3
Reference numeral 8 denotes the operation of the arithmetic and control circuit 24. When the switch 37 is on, the analog switch 39 is turned on even when the AF mechanism is operating, and the on / off control of the analog switches 10 to 13 is performed via the decoder 29. And an arithmetic control circuit 39 having a function of storing luminance information input from each area, and an A / D conversion circuit 39 used only when the switch 37 is turned on.

When the release priority mode is selected and the switch 37 is turned on, the arithmetic and control circuit 38 operates in the AF mode.
Even if the AF end signal is not input from the control circuit 30, that is, even if the AF mechanism is operating, the analog switch 39 is turned on (at this time, the analog switch 25 remains off).
Then, similar to the above, the on / off control of the analog switches 10 to 13 is performed through the decoder 29, and the brightness information measured in each area is stored. The average value of the stored brightness values BV ₁ , BV ₂ , BV ₃ , and BV ₄ , that is, (BV ₁ + BV ₂ + BV ₃ + BV ₄ ) / 4 is set as the final brightness at the time of shooting in such a mode. In other words, this means that the amount of light passing through the taking lens is the same both when in focus and when out of focus,
Since the sum of the luminance information of each photometric region does not change, even when light to be incident on a certain divided region during out-of-focus is guided to a photometric region adjacent thereto, and the photometric region outputs incorrect luminance information, This is because averaging can offset it.

When the focus priority mode is selected, that is, when the switch 37 is off, the same operation as in the embodiment shown in FIG. (Correspondence between the invention and the embodiment) In this embodiment, the silicon photodiodes SPD1 to SPD4 serve as the luminance detecting means of the present invention, the AF control circuit 30 and the motor 31 serve as the focus adjusting means, and the arithmetic control circuits 24 and 38 detect the magnification. The operation control circuits 24 and 38 correspond to the means, respectively. (Modification) In the embodiment shown in FIG. 5, the luminance information of the area including the distance measurement area E is intensively weighted according to the mode selected by the photographer according to the shooting situation, that is, in the focus priority mode. In the release priority mode, the average value of the brightness information from the divided areas is used to determine the final brightness information, but this is not the only option. The photometry operation is started from the time when one stroke is performed, and the AF control circuit 30 starts the AF operation.
Until the end signal is input, the average value of each brightness information from the divided areas is used as the brightness value, and after the AF end signal is input (after focusing), the brightness information of the area including the distance measurement area E is weighted with emphasis. A circuit configuration may be adopted in which the final brightness value is determined by setting the calculated value as the brightness value and determining at which point in time the second stroke of the release button is performed.

[0019]

As described above, according to the present invention,
When the lens moves to the in-focus position, the photometric calculation for exposure is performed using the luminance of each area detected by the luminance detecting means, so that the shooting target that has performed focus detection is aimed at It is possible to output narrowed photometric information. Further, since the weighting of the luminance of the outer region with respect to the luminance of the first region is changed based on the information corresponding to the photographing magnification obtained by the magnification detecting means, the calculation of the photometric information in consideration of the size of the photographing target is performed. And more accurate photometric information can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a photometric area corresponding to a shooting screen.

FIG. 3 is a diagram illustrating a subject distance, a focal length of a photographing lens, and a size of a subject image.

FIG. 4 is a diagram illustrating a method for determining luminance information according to the size of a subject image according to an embodiment of the present invention.

FIG. 5 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Photographing screen 6-9 Operational amplifier 10-13 Analog switch 20,21 Resistor 22,23 Slider 24 Arithmetic control circuit 25-27 Analog switch 29 Decoder 31 Motor 30 AF control circuit 37 Switch 38 Arithmetic control circuit 39 Analog switch SPD1 ~ SPD4 Silicon photodiode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masao Shimizu Inventor Masao Shimizu 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant

Claims (1)

[Claims] 1. A first region including at least a focus detection region, a luminance detection unit that is divided into an outer region outside the first region, and detects the luminance of each region, and based on a focus detection result. Focus adjusting means for moving the lens to the in-focus position, magnification detecting means for obtaining information corresponding to the photographing magnification of the photographing target by the distance to the photographing target and the focal length,
A photometric calculation for exposure is performed using the brightness of each of the areas detected by the brightness detection means when the lens is moved to the in-focus position by the focus adjustment means. And a calculating unit that changes the weighting of the luminance of the outer region with respect to the luminance of the first region based on the information corresponding to the photographing magnification obtained by the detecting unit.