JPH0534657B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure control device used in cameras, cine cameras, television cameras, and the like.

The metering method for subject brightness is 1 or 2.
The most commonly used methods are average photometry in which the brightness of the entire image plane is measured using two photometric elements, and center-weighted photometry in which the central part of the image plane is intensively measured.

Recently, many photometric elements are used to measure each part of the image plane, and the outputs of the individual photometric elements are compared to detect the maximum and minimum brightness, and these intermediate values or the distribution of subject brightness are A method has also been proposed in which the exposure is controlled by selecting either the maximum brightness or the minimum brightness accordingly.

However, this method has the drawback of being underexposed due to a high maximum brightness in backlighting, or overexposed due to a low minimum brightness in a dark background scene.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure control device that can obtain an appropriate exposure depending on the subject even if the subject has an uneven brightness distribution.

The exposure control device of the present invention has at least three or more photometric elements, and a photometric section that measures the brightness of each part of a subject using each of these photometric elements; A central zone that measures the brightness of Based on a grouping pattern determined to group by grouping, the average brightness Bmi of each zone i (i = 1,..., n; n is an integer of 2 or more) is calculated from the brightness of each part. The detection unit calculates the object brightness B from the average brightness Bmi (i=1,...,n) using the formula 2B=K ₁ + _o 〓 ⁱ⁼¹ K _(i+1)・B _ni (however, K ₁ , K _(i+1) (i=1,...,n) is a coefficient,
And at least two of K _(i+1) (i=1,...,n) are not zero but have mutually different values. ); and an exposure control section that controls the exposure of the camera according to the subject brightness B.

Further, it has at least four or more photometric elements,
a photometering unit that measures the brightness of each part of the object using each of these photometering elements; a center zone that measures the brightness at approximately the center of the object; and a center zone in which the photometers are formed to surround the entire circumference of the center zone. a first peripheral zone in which
Grouping according to the subject scene into one or more second peripheral zones (at least one zone consists of a plurality of photometric elements) formed so as to surround all or part of the outer periphery of the peripheral zone. Based on the grouping pattern determined as follows, each zone i (i=
1, 2, ..., n; n is an integer of 3 or more); and a zone brightness detection unit that calculates the average brightness Bmi for each area (n is an integer of 3 or more), and calculates the subject brightness B from the average brightness Bmi (i = 1, 2, ..., n) using the formula 2B=K ₁ + _o 〓 ⁱ⁼¹ K _(i+1)・B _ni (However, K ₁ , K _(i+1) (i=1, 2,..., n) are coefficients, and K _{(i +1)} (At least two of (i = 1, 2, ..., n) are not zero and have mutually different values.) The present invention is characterized by comprising an exposure control section that controls exposure.

The average brightness Bmi is calculated by adding logarithmically converted values of photometric brightness and dividing the result by the number of elements in the zone. The feature of this invention is that, as mentioned above, the average luminance Bmi of each concentrically divided zone such as the central zone, first peripheral zone, and second peripheral zone is obtained as the average of the logarithm value, so it is different from the conventional method. The large effect on the average brightness of high-brightness areas, as seen in center-weighted photometry, can be suppressed. Furthermore, the central zone,
From the distribution of the average brightness of each peripheral zone, it is possible to know in detail the brightness distribution of the subject and the size of the main subject, which is often present in the center, and determine the subject scene in relation to the main subject. Accuracy can be increased.

Note that the central zone may be one that measures the average brightness at approximately the center of the object, and may, for example, measure the average brightness in a certain range centered slightly below the center of the object.

Further, the second peripheral zone is not limited to one zone that surrounds the first peripheral zone in a single layer, but may be a plurality of zones that surround the first peripheral zone in a double or more manner. ,
The first peripheral zone may be surrounded by a plurality of consecutive second peripheral zones, or a combination thereof may be used.

The second feature of this invention is that in a concentric zone pattern, it is possible to use an arbitrary weighting coefficient determined according to the subject scene for the average brightness Bmi of each zone i, resulting in more appropriate exposure than before. It is possible to make decisions.

For example, in the case of spot illumination, the center gives a larger weighting factor, and in the case of backlighting, the periphery gives a smaller weighting factor.

As a correction term, the average brightness Bo of the entire photometric area may be determined, weighted, and added to equation (1).

Further, in the present invention, the zone pattern may be changed depending on the subject scene. For example, in the case of spot lighting, the subject is at the center, so the subject is divided into zones concentric with the center, and in the case of backlighting, the subject is below the center, so the subject is divided into zones concentric with the center. Furthermore, the weighting coefficient of the average brightness of each zone is changed depending on the subject scene.

Further, since the zone pattern is not symmetrical horizontally and vertically, if the position of the zone relative to the subject changes depending on the attitude of the camera, the subject brightness will change depending on the attitude of the camera even for the same subject. Therefore, the pose of the camera may be detected and the concentric zone pattern may be the same regardless of the pose of the camera.

Further, according to the above configuration, the correspondence relationship between each photometric element and each zone is determined, and the average brightness Bmi is determined based on that relationship.

That is, the photometric value of the peripheral zone does not include the photometric value of the central zone, and even if the central zone is changed depending on the subject scene, photometry can be performed from the peripheral zone that does not include the central zone. Although photometry of the peripheral zone including the central zone may cause erroneous detection of background brightness, the above configuration can prevent such a risk and make it possible to determine an accurate exposure amount.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows a large number of photometric elements 2 that make up the photometric section.
FIG. 2 is a plan view showing the substrate 1 on which elements a, 2b, . . . , 2n are formed. As these photometric elements 2a to 2n, photodiodes, photovoltaic elements, phototransistors, CdS, photocharge accumulation type CCDs, etc. are used.
CCDs have a narrow dynamic range, so it is best to use them while adjusting the sensitivity by changing the storage time depending on the brightness of the subject.

FIGS. 2 to 5 show the arrangement of the photometric section. FIG. 2 shows an embodiment in which external photometry is performed. The light passing through the objective lens 3 passes through an aperture 4 and enters a photometry section 5, where each part of the object is measured. On the other hand, the photographing light passes through the photographic lens 6 and the aperture 7 and reaches the photographic film 8.

FIG. 3 shows an embodiment in which the photometric section 5 is provided in the viewfinder. The light passing through the objective lens 9 is
The light passes through the half mirror 10 and enters the eyepiece lens 11. On the other hand, the light reflected by the half mirror 10 is
An image is formed on the photometry section 5 through the lens 12.

FIG. 4 shows an embodiment in which a photometric section 5 is provided in a single-lens reflex camera. A part of the mirror 14 is a half mirror, and a concave mirror 15 is provided behind it. Therefore, the photographing lens 16 and the aperture 17
The light that has passed through passes through the mirror 14 and enters the concave mirror 15. The light reflected downward by the concave mirror 15 passes through the lens 90 and is imaged on the photometry section 5.

FIG. 5 shows an embodiment in which the photometric section 5 is arranged around the pentaprism 18. mirror 1
The light reflected upward by the focusing glass 19,
Pentaprism 18 via condenser lens 20
to go into. The photometry section 5 is installed at the upper part A, the front part B, or the rear part C of the pentaprism 18. An imaging lens 21 is arranged in front of the photometry section 5.

FIG. 6 shows an example of division of the photometric area. That is, the photometry area is concentrically divided into four zones _Z1 to _Z4 . When divided in this way, the subject brightness will be the same regardless of the camera orientation.

When this division method is used, the coefficient K in equation (1) takes, for example, the following value.

K ₁ = 1.43 K ₂ = 0.53 (Coefficient of zone Z ₁ ) K ₃ = 0.12 (Coefficient of zone Z ₂ ) K ₄ = -0.08 (Coefficient of zone Z ₃ ) K ₅ = 0.34 (Coefficient of zone Z ₄ ) FIG. 7 shows an exposure control device used when zone division as shown in FIG. 6 is performed.
By dividing the large number of light receiving elements 2a to 2n (see FIG. 1) of the photometry section 5 into a plurality of sections (four sections in this case), the photometry section 5 can detect light within the photometry area (each zone) corresponding to each section. It is divided into zone photometry sections 5a to 5d that measure the amount of light. The outputs of the photometric elements 2a to 2n included in these zone photometric units 5a to 5d are input to the logarithmic conversion circuit 30. The logarithmic conversion circuit 30 is composed of an operational amplifier and a log diode inserted into its feedback circuit, and the photometric element 2a
A plurality of them are provided corresponding to the number of ~2n.

The logarithmically converted signal is sent to the zone brightness detection unit 31
Addition circuits 31a to 31 provided for each zone within
d and is added. This addition circuit 31a~
As 31d, an adder using an operational amplifier is used.

The outputs of the adder circuits 31a to 31d are sent to the divider circuit 3.
2a to 32d and divided by a coefficient according to the area of the zone. As a result, the average brightness Bmi (i=1, 2, . . . ) for each zone is calculated.

These average luminances Bmi are input to the luminance detection section 33, weighted by the coefficient K _i+1 , and then
Addition and subtraction. Therefore, the brightness detection section 33 is expressed by formula (1)
is calculated to calculate the subject brightness B.

film sensitivity from the exposure information setting circuit 34a;
The aperture value or shutter speed value is determined by the exposure calculation circuit 34.
b, and together with the subject brightness B, a photographic calculation is performed to calculate an aperture value or a shutter speed value. This aperture value or shutter speed value is sent to the exposure control circuit 34c to control the aperture or shutter. Here, the exposure information setting circuit 34a, the exposure calculation circuit 34b, and the exposure control circuit 34c constitute an exposure control section 34 that controls the exposure of the camera according to the subject brightness B.

FIG. 8 shows an embodiment in which the photometric area is divided into three zones. In this zone division, since the top and bottom are not symmetrical, the position of the zone changes depending on the attitude of the camera. In this figure, the 25 photometric elements are numbered to help you understand the zone division.

In Fig. 8, A shows the camera in the horizontal position, B shows the camera in the upper left position (the left side of the figure is the top), and C shows the camera in the upper right position (the right side of the figure is the top). ), and the zones are changed according to each posture.

FIG. 9 is a block diagram of an exposure control device used for zone division shown in FIG. 8. Light receiving element 2a
The outputs from 2n to 2n are logarithmically converted by a logarithmic conversion circuit 30 and then input to a matrix circuit 40 of a zone brightness detection section 31'. This matrix circuit 4
0, three groups are created by dividing the light receiving elements 2a to 2n into three groups according to the camera posture.

That is, in the case of the horizontal position shown in A of FIG.
0, 21, 25, and photometric elements 12 to 14, 17,
It is divided into three groups: 19, 22-24, and photometric element 18, and the output of each group is input to three adder circuits 41a, 41b, and 41c.

In addition, in the case of the upper left position (vertical position) shown in B, photometric elements 1 to 5, 6, 7, 11, 12, 1
6, 17, 21 to 25, and photometric elements 8 to 10, 1
Addition circuits 42a, 42b, 42 are divided into three groups: 3, 15, 18 to 20, and photometric element 14.
Enter c.

In the case of the upper right position (vertical position) shown in C, photometric elements 1 to 5, 9, 10, 14, 15, 19, 2
0,21-25 and photometric elements 6-8,11,1
The photometric elements 3, 16 to 18, and the photometric element 12 are divided into three groups and input to adder circuits 43a, 43b, and 43c, respectively.

These adder circuits 41a, 41b, 41c, 4
2a, 42b, 42c, 43a, 43b, 43c
The addition results of the division circuits 44a, 44b, 44
c, 45a, 45b, 45c, 46a, 46b,
46c, respectively. This division circuit is
The addition result is divided according to the number of photometric elements included in the zone. In this way, the average brightness for each zone (if one photometric element is included in the zone, the brightness measured by that element) is calculated.

These average brightnesses are determined by the analog switch circuit 4.
Selected at 7. That is, when the camera is in the horizontal position, the analog switches 47a, 47b, and 4
7c turns ON, and the division circuits 44a, 44b, 44
The output of c is sent to the brightness calculation circuit 33. In addition, in the case of the upper left position, analog switches 47d and 47
When e and 47f are turned on and in the upper right position, analog switches 47g, 47h and 47i are turned on.

FIG. 10 shows an embodiment of the attitude detection section. Mercury 51 is sealed in a Y-shaped glass tube 50. This mercury 51 moves according to the posture of the camera, and switches 52 to 54 are selectively moved.
Turn it on.

When divided into three as above, the coefficient K of equation (1)
K ₁ = 1.64 K ₂ = 0.22 (inner zone coefficient) K ₃ = 0.42 (center zone coefficient) K ₄ = 0.27 (outer zone coefficient) are used.

FIG. 11 is a block diagram showing a digital exposure control device. The outputs of the photometric elements 2a to 2n are input to logarithmic conversion circuits 60a to 60n, respectively.

The outputs of these logarithmic conversion circuits 60a to 60n are input to comparators 61a to 61n, respectively. These comparators 61a to 61n
performs the comparison based on the comparison signal from the D/A conversion circuit 62.

Multiplexer 63 selects one of a number of comparators in response to multiplexer address signal 65 from microcomputer 64. After selecting a comparator, for example 61a, by the multiplexer 63, a set value signal 66 to be counted up is sent to the D/A converter 62 to obtain an analog comparison signal. This gradually increasing comparison signal and the signal from the logarithmic conversion circuit 60a are compared by a comparator. A match signal 67 output from the comparator 61a when the two match is input to the microcomputer 64.

The address of the photometric element is divided by the multiplexer address signal 65, and the setting signal 66
Since the digital value is determined by , when the coincidence signal 67 is output, the setting value is written to the address of the RAM 68 corresponding to the address of the photometric element.

Next, after incrementing the multiplexer address signal 65, the output signal of the logarithmic conversion circuit 60b is A/D converted in the same manner as described above, and the RAM 6
Write in 8.

The ROM 69 stores a data acquisition procedure, a procedure for creating groups according to camera posture and calculating their average brightness, a procedure for calculating exposure, and a procedure for controlling the camera mechanism.

From the camera side, signals 70 indicating film sensitivity, aperture or shutter speed, and camera attitude are input to the microcomputer 64.

The shutter control circuit 71 is a buffer that also serves as a timer, and receives a code signal from the microcomputer 64 and outputs a shutter control signal 72.
Output. 73 is an aperture control signal.

Figure 12 shows data that is A/D converted and stored in RAM 68.
This is a flowchart showing the input method for importing the signals into the computer, and each signal is as follows.

DM: Logarithmically converted photometric element output DA: D/A converter setting value NM: Photometric element address N: Number of photometric elements DMAX: Maximum value that can be set with the D/A converter DN: DA Contents of FIG.
is used to convert it into a digital signal 76 and store it in RAM 6.
8 shows an example in which the information is incorporated into the 8.

FIGS. 14 and 15 show examples of zone division. FIG. 14 shows an embodiment in which the photometric area is divided into four zones.

FIG. 15 shows an embodiment in which the photometric area is divided into two zones. Since this zone division is not vertically symmetrical, the position of the zone changes depending on the camera orientation. In this Figure 15, A
shows the case where the camera orientation is horizontal, B indicates the upper left, C indicates the upper right, and the zones are changed according to each orientation.

The present invention having the above configuration divides the photometry area into a plurality of zones and calculates the subject brightness by adding and subtracting the weighted average brightness of these zones. Even if the subject is photographed, it is possible to obtain an appropriate exposure according to the subject.

Further, in the case of a division pattern unrelated to the orientation of the camera as shown in FIG. 6, or when the zones are divided according to the orientation of the camera, no problem occurs even if the orientation of the camera changes.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a substrate on which a large number of photometric elements constituting a photometric section are formed, and FIGS.
6 shows an example of zone division, FIG. 7 is a block diagram of an exposure control device, FIG. 8 shows an example of zone division, and FIG. 9 shows an example of zone division. A block diagram showing an exposure control device that can change zone division depending on the camera attitude; FIG. 10 is a diagram showing an embodiment of the camera attitude detection unit;
FIG. 11 is a block diagram of a digital exposure control device, FIG. 12 is a flowchart showing a data input method, FIG. 13 is a block diagram of another exposure control device, and FIGS. 14 and 15 are zoning. It is a figure which shows the further different Example of. 2a to 2n...photometric element, 5...photometric section, 30
... Logarithmic conversion circuit, 31, 31' ... Zone luminance detection section, 31a to 31d... Addition circuit, 32a to
32d...Division circuit, 33...Brightness calculation unit, 34
...Exposure control section, 34a...Exposure information setting circuit,
34b...Exposure calculation circuit, 34c...Exposure control circuit, 40...Matrix circuit, 41a, 41
b, 41c, 42a, 42b, 42c, 43a,
43b, 43c...addition circuit, 44a, 44b,
44c, 45a, 45b, 45c, 46a, 46
b, 46c...Division circuit, 47...Analog switch, 48...Attitude detection unit, 51...Mercury, 60
a to 60n...logarithmic conversion circuit, 61a to 61n...
... Comparator, 63 ... Multiplexer, 62
...D/A converter, 64...Microcomputer, 68...RAM, 69...ROM, 71...
Shutter control circuit, 75...A/D converter.

Claims (1)

[Scope of Claims] 1. A photometric unit having at least three photometric elements and measuring the brightness of each part of a subject using each of these photometric elements; A central zone for measuring brightness, and one or more peripheral zones formed to surround the entire circumference of the central zone (at least one zone consists of a plurality of photometric elements), depending on the subject scene. Zone brightness detection that calculates the average brightness Bmi for each zone i (i=1,...,n; n is an integer of 2 or more) from the brightness of each part based on a grouping pattern determined for grouping. and the subject brightness B from the average brightness Bmi (i=1,...,n) using the formula 2B=K ₁ + _o 〓 ⁱ⁼¹ K _(i+1)・B _ni (however, K ₁ , K _{( i+1)} (i=1,...,n) is a coefficient,
Moreover, at least two of K _(i+1) (i=1, . . . , n) are not zero but have mutually different values. ); and an exposure control unit that controls exposure of the camera according to the subject brightness B. 2. A photometric section that has at least four photometric elements and measures the brightness of each part of the object using each of these photometric elements, and a central zone that measures the brightness of approximately the center of the object by each of the photometric elements. , a first peripheral zone formed to surround the entire circumference of the central zone;
Grouping according to the subject scene into one or more second peripheral zones (at least one zone consists of a plurality of photometric elements) formed so as to surround all or part of the outer periphery of the peripheral zone. Based on the grouping pattern determined as follows, each zone i (i=
1, 2, ..., n; n is an integer of 3 or more); and a zone brightness detection unit that calculates the average brightness Bmi for each area (n is an integer of 3 or more), and calculates the subject brightness B from the average brightness Bmi (i = 1, 2, ..., n) using the formula 2B=K ₁ + _o 〓 ⁱ⁼¹ K _(i+1)・B _ni (However, K ₁ , K _(i+1) (i=1, 2,..., n) are coefficients, and K _{(i +1)} (At least two of (i = 1, 2, ..., n) are not zero and have mutually different values.) 1. An exposure control device for a camera, comprising: an exposure control section that controls exposure.