JP2537143B2 - camera - Google Patents

Description

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

(Background of the Invention) As a conventional camera photometric system, center-weighted photometry,
There are average metering, partial metering, spot metering, etc., which have been put into 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.

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 of the main subject, the exposure value differs from the aim of the photographer. There was an occasion. Also, in the conventional photometric optical system, if the shooting lens is out of focus, the light from the field is more diffused than when it is in focus. The light from is not well separated and does not enter, and the light that should be guided to a certain photometric area will be guided to the divided photometric area adjacent to it, and each photometry is done when the focus is in focus and when it is out of focus. The information obtained in each area is different, which causes the inconvenience that accurate divided metering cannot be performed.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems and to provide a camera capable of obtaining suitable photometric information in a focused state and a non-focused state.

(Features of the Invention) In order to achieve the above object, the present invention is divided into a first region including at least a focus detection region and an outer region outside the first region, and detects the brightness of each region. Brightness detecting means, a focus adjusting means for moving the lens to the in-focus position based on the focus detection result, a first state in which the lens is moved to the in-focus position by the focus adjusting means, and a out-of-focus position. And a second state in which a different photometric calculation is performed, and a calculation unit that changes the weighting of the luminance of the outer area with respect to the luminance of the first area in the first state and the second state. And having.

(Examples of the Invention) Hereinafter, the present invention will be described in detail based on illustrated examples.

1 and 2 are views showing an embodiment of the present invention. SPD1 ~ S
PD4 is a silicon photodiode that constitutes a photometric sensor that measures the field brightness in a divided pattern corresponding to the shooting screen 1 as shown in FIG. 2, 2 to 5 are logarithmic compression diodes,
Reference numerals 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, 15 is a diode, and the logarithmic compression is performed together with a constant current source 16 for supplying a forward current Iref to the diode 15. A circuit for compensating the reverse saturation current of the diodes 2 to 5 is constructed. Reference numeral 17 denotes an operational amplifier 18, a resistor 19 and resistors having a temperature coefficient for temperature compensation of the logarithmic compression diodes 2 to 5 and the diode 15, 20, 21 resistors which are fixed to the taking lens barrel, and 22 an taking lens. A slider that slides on the resistor 20 in conjunction with the rotation of the distance ring, and a voltage (a voltage obtained by dividing the reference voltage Vref) corresponding to the focus position of the photographing lens is generated on the slider 22. To do. A slider 23 slides on the resistor 21 in association with the rotation of the zoom ring of the photographing lens. The slider 23 has a voltage (reference voltage Vref) corresponding to the zoom position (focal length) at that time. Voltage is generated).

24 is an arithmetic control circuit having an arithmetic function and various control functions,
25 to 27 are analog switches which are turned on and off according to a signal from the arithmetic control circuit 24, and 28 is the analog switch 25.
A / D conversion circuit for converting an analog signal input via 27 to a digital signal, 29 is a decoder for selecting (turning on) the analog switches 10 to 13 according to the signal from the arithmetic control circuit 24, and 30 is a red A distance detection unit including an external light emitting diode and a light receiving element that receives reflected light of the infrared light from a subject, and a motor 31 that moves the photographing lens to a focus position based on a distance signal obtained by the distance detection unit. An AF control circuit having a drive control unit for driving, 32 is a switch that is turned on by the first stroke of the release button, 33 is a release switch that is turned on by the second stroke of the release button, and 34 is a battery that becomes the power source of each circuit. Is. E in FIG. 2 shows a distance measuring area corresponding to a visual field range of a distance measuring sensor (not shown) arranged at 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 AF control circuit 30
The distance detection unit inside is a distance measurement area E in the center of the photographing screen 1.
The operation of obtaining the distance signal to the main subject arranged at is started. On the other hand, a voltage is generated in the slider 22 according to the rotational position of the distance ring of the taking lens, and this signal is input to the A / D conversion circuit 28 via the analog switch 26 and converted into a digital signal. AF is performed via the arithmetic and control circuit 24
Input to the drive control unit in the control circuit 30. When the distance information and the position information of the distance ring are input, the drive control unit in the AF control circuit 30 performs drive control of the motor 31, that is, rotation direction and speed control of the motor 31 based on these information, and the photographing lens When it is determined that 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 indicating that the taking lens (distance ring) is stopped, and simultaneously turns off the analog switch 26 and turns on the analog switch 27 this time. When the analog switch 27 is turned on, a voltage corresponding to the rotational position of the zoom ring generated on the slider 23 is applied to the A / D conversion circuit 2 via the switch.
After being inputted to the digital camera 8 and converted into a digital signal, it is inputted to the arithmetic control circuit 24 and stored together with the position signal of the photographing lens. At this time, 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, and after the focusing is completed, the arithmetic control circuit is based on these information. 24 begins operation to make an exposure decision.

That is, the arithmetic control circuit 24 first turns off the analog switch 27, turns on the analog switch 25, and then the decoder 29.
Only the analog switch 10 is turned on via. As a result, the voltage generated at the output terminal of the operational amplifier 6, that is, the voltage including the field brightness information measured by the silicon photodiode SPD1 is input to the non-inverting input terminal of the operational amplifier 14. This voltage is temperature compensated and the op amp
After being input to the A / D conversion circuit 28 via the 18 and the analog switch 25 and converted into a digital signal, the arithmetic control circuit 24
To enter. The arithmetic control circuit 24 stores the signal as the field brightness information measured by the silicon photodiode SPD1. Next, the arithmetic and control circuit 24 turns on only the analog switch 11 via the decoder 29 to obtain the field luminance information measured by the silicon photodiode SPD2, and inputs through the same process as described above. The field brightness information of is stored. Silicon photodiode SPD3, SPD
The same applies to the case where the field brightness information measured in 4 is obtained.

Here, as an example of determining the exposure, a method of deciding the exposure value by presuming that the main subject is a person and weighting at least an area including the distance measurement area E
This will be described using Figures 3 and 4.

FIG. 3 is a diagram for explaining the relationship between the face 35 of the person who is the main subject, the taking lens 36, and the face 35 'formed on the film surface, where L is the size of the face 35 and 1 is the film. The size of the face 35 'imaged on the surface, D is the distance from the human face 35 to the camera, and f is the focal length of the taking lens 36. L, D,
If the size 1 of the face 35 'is expressed by using f, the following formula is established: 1 = (f / D-f) .L (D> f). That is, in general, the human face 35 is about the same size, and there are few individual differences. Therefore, considering L as a constant, the distance D from the face 35 of the person to the taking lens 36
Then, the size 1 of the face 35 'imaged on the film surface can be known from the focal length f of the taking lens.

Therefore, the three central regions (silicon photodiodes SPD1, SPD2, SP) arranged concentrically as shown in FIG.
Face in the shooting screen 1 that can be obtained by the above formula, where A, B, and C are the diameters of the area measured by D3) from the inside.
The size (ratio) 1 occupied by 35 will be described in four cases.

1) Case of A <1 <B In the case of FIG. 4 (a), if the brightness values measured by the silicon photodiodes SPD1 to SPD4 obtained as described above are BV ₁ to BV ₄ , The weighting ratio of each is BV ₁ : B
_{V 2: BV 3: BV 4} = 1: 0.5: 0.2: the value obtained by weighting the center so that 0.1 to a final brightness in such imaging (photometric information).

2) In the case of B <1 <C In the case as shown in FIG. 4 (b), BV ₁ : BV ₂ : B similarly.
_{V 3: BV 4: 1.0:} 0.8: 0.5: the value weighted by a ratio such that 0.2 to a final brightness in such imaging.

3) When C <1 In the case as shown in Fig. 4 (c), BV ₁ : BV ₂ : B
_{V 3: BV 4: 1.0:} 1.0: 1.0: the value weighted by a ratio such that 0.5 to a final brightness in such imaging.

4) When 1 <A In the case as shown in FIG. 4 (d), the brightness of the face 35 cannot be accurately measured with any region of the silicon photodiodes SPD1 to SPD3. However, in such a case, it is often preferable for the photograph to be properly exposed for the entire field of view than for the person's face 35 to be properly exposed. Therefore, the silicon photodiodes SPD1 to SPD1.
SPD3 and respective luminance values photometry in each region of _{SPD4 (BV 1, BV 2,} BV 3, BV 4) the center-weighted average metering method to, B
_{V 1: BV 2: BV 3} : BV 4: 1.0: 1.0: 0.8: the value weighted by a ratio such that 0.5 to a final brightness in such imaging.

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

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

As described above, in the embodiment, the known AF mechanism is actuated to obtain the brightness information from each of the divided photometry areas after the taking lens is focused, and the distance measurement area E is included based on the brightness information. Since the final brightness information is determined by weighting the areas intensively, it is possible to perform accurate photometry with a focus 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 according to the size is predicted. 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 shooting lens is in focus due to the operation of the AF mechanism (when quick shooting is required). This is an example of a 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 for starting the photometry operation after focusing as described in the above embodiment) to a release priority mode (a photometry is performed immediately by releasing even before focus). A switch that is turned on when switched to a mode for starting operation, 33 is a function of the arithmetic and control circuit 24, and when the switch 37 is on, the analog switch 39 is turned on even when the AF mechanism is operating. At the same time, the arithmetic control circuit having a function of performing ON / OFF control of the analog switches 10 to 13 via the decoder 29 and storing the brightness information input from each region, 40 is an A / D conversion used only when the switch 37 is on. Circuit.

When the release priority mode is selected and the switch 37 is turned on, the arithmetic control circuit 38 uses the AF control circuit 30 for AF
Even if the end signal is not input, that is, even if the AF mechanism is operating, the analog switch 39 is turned on (the analog switch 25 remains off at this time), and then the analog switch 39 is operated via the decoder 29 as described above. The on / off control of 10 to 13 is performed, and the brightness information measured in each area is stored.
Then, 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, the amount of light that passes through the taking lens is the same both in focus and out of focus, and the sum of the brightness information of each photometric area does not change. This is because even if the photometric region outputs incorrect luminance information that is guided to the photometric region, the averaging can cancel it.

When the focus priority mode is selected, that is, when the switch 37 is off, the same operation as in the embodiment of FIG. 1 is performed and the final brightness information is determined.

(Correspondence between Invention and Example) In this example, the silicon photodiodes SPD1 to SPD1 to
SPD4 to the brightness detecting means of the present invention, the AF control circuit 30 and the motor 31 to the focus adjusting means, the arithmetic control circuit 38 to the arithmetic means,
Equivalent to each.

(Modification) In the embodiment shown in FIG. 5, according to the mode selected by the photographer depending on the photographing condition, that is, in the focus priority mode,
The final brightness value is determined by weighting the brightness information of the area including the distance measurement area E intensively, and the final brightness information is determined by the average value of the brightness information from the divided areas in the release priority mode. However, the configuration is not limited to this, but the photometric operation is started from the time when the first stroke of the release button is performed, and each brightness information from the divided area is input until the AF end signal is input from the AF control circuit 30. The average value of is the brightness value,
After the AF end signal is input (after focusing), the value obtained by weighting the brightness information of the area including the distance measurement area E is set as the brightness value, and at what time the second stroke of the release button is performed. The circuit configuration may be such that the final brightness value is determined by making a determination.

(Effect of the Invention) As described above, according to the present invention, the first state in which the lens is moved to the in-focus position and the second state in which the lens is out of the in-focus position.
In this state, the weighting of the luminance of the outer region with respect to the luminance of the first region is changed, and the photometric calculation in consideration of the optical characteristics in each state is performed. Therefore, suitable 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 the photographing screen, and FIG. 3 is a graph showing the object distance, the focal length of the taking lens and the size of the object image. FIG. 4 is a diagram for explaining a method of determining brightness information according to the size of a subject image in one embodiment of the present invention, and FIG. 5 is a block diagram showing another embodiment of the present invention. . 1 ... Shooting 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, 30 ...... AF control circuit, 37 ...... Switch, 38
...... Arithmetic control circuit, 39 ...... Analog switch, SPD1 to SP
D4: Silicon photodiode.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masao Shimizu Inventor Masao Shimizu 770 Shimonoge, Takatsu-ku, Kawasaki City Canon Inc. Tamagawa Plant (56) References JP-A-61-194430 (JP, A)

Claims (1)

(57) [Claims] 1. A first region including at least a focus detection region, a luminance detection unit which 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 adjustment means for moving the lens to the in-focus position, a first state in which the lens is moved to the in-focus position by the focus adjustment means, and different photometric calculation are performed in the second state out of the in-focus position. The camera according to claim 1, further comprising an arithmetic means for changing a weighting of the luminance of the outer area with respect to the luminance of the first area in the first state and the second state.