JPH01105222A - Exposure controller - Google Patents

Abstract

PURPOSE:To obtain appropriate exposure even if the brightness distribution of an object is uneven by dividing a photometric area into plural zones, operating addition and subtraction of the weighted mean brightness of these zones and calculating the object brightness. CONSTITUTION:Three or above photometric elements measure the brightness of each part of the object. They are divided into a central zone, a first peripheral zone surrounding the full periphery of the central zone, and one or plural second peripheral zones surrounding the full or the partial periphery of the first zone. The mean brightness Bmi of each zone i (i=1-1n; n is an integral number of 3 or above.) is obtained a zone brightness detecting part 31. In the next step, the object brightness B is calculated from the mean brightness Bmi (i=1-n) according to a formula in a brightness arithmetic part 33. In the formula, K1 and K(i+1) (i=1-n) are coefficients and at least two of the K(i+1) are not zero, but are values different from each other. According to object brightness B, camera exposure is controlled. Thus, the appropriate exposure can be obtained even if the brightness distribution of the object is uneven.

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 most common methods for measuring subject brightness are average metering, which uses one or two photometric elements to measure the brightness of the entire image plane, and center-weighted metering, which focuses on the center of the image plane. is being carried out.

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 disadvantage that a high maximum brightness in backlighting may lead to underexposure, or a low minimum brightness in a dark background scene may lead to overexposure.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure control device that can obtain proper exposure even for objects with uneven brightness distribution.

The exposure control device of the present invention has at least three photometric elements arranged on the image plane of the camera or a plane conjugate to the image plane, and each of these photometric elements measures the brightness of each part of the subject. a central zone that measures the luminance of the approximate center of the subject, and a photometric section formed to surround the entire circumference of the central zone, which measures the luminance of the three or more photometric elements based on the luminance of each part; Each zone i (i=1.2.- ,n;
a zone brightness detection unit that calculates the average brightness BIIli for each zone (n is an integer of 3 or more), and the average brightness Bmi (i-1, 2
, ..., n), the subject brightness B is calculated from the formula %) and K(1+11 At least two of (i-1, 2, -, n) are not zero and have different values.)
The present invention is characterized by comprising: a brightness calculation unit that calculates the brightness using the subject brightness B; and an exposure control unit that controls the exposure of the camera according to the subject brightness B.

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 brightness Bmi of each concentrically divided zone such as the central zone, first peripheral zone, and second peripheral zone is determined as the average of the logarithm value. The large effect on the average brightness of high-brightness areas, as seen in center-weighted photometry, can be suppressed. Furthermore, from the distribution of the average brightness of the central zone and each peripheral zone, it is possible to know in detail the brightness distribution of the subject and the size of the subject, which is often present in the central area, and to find information related to the subject. This can improve the accuracy of determining the subject scene.

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

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;
Furthermore, a combination of these may be used.

The second feature of the present invention is that in a concentric zone pattern, it is possible to use an arbitrary weighting coefficient for the average brightness Bn+i of each zone l, making it possible to determine exposure more appropriately than before. .

This weighting coefficient may be changed depending on the subject scene.

For example, in the case of spot light 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 light illumination, the subject is in the center, so it is divided into zones concentric with the center, and in the case of backlighting, the main station is below the center, so it is divided into zones concentric with the center. Furthermore, the weighting coefficient of the average brightness of each zone may be changed depending on the subject scene.

Also, 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 if the subject is the same. Therefore, the pose of the camera may be detected so that the concentric zone pattern is the same regardless of the pose of the camera.

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

FIG. 1 shows a large number of photometric elements 2a constituting a photometric section.

2b, . . . , 2n are formed on the substrate 1. FIG. As these photometric elements 2a to 2n, photodiodes, photovoltaic elements, phototransistors, CdS, photocharge accumulation type COD, etc. are used. Since a CCD has a narrow dynamic range, it is desirable to use it while adjusting the sensitivity by changing the storage time depending on the brightness of the subject.

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 photographic light passes through a photographic lens 6 and an aperture 7 and reaches a photographic film 8.

FIG. 3 shows an embodiment in which the photometric section 5 is provided in the finder. The light passing through the objective lens 9 is transmitted to the half mirror 1
0 and enters the eyepiece lens 11.

On the other hand, the light reflected by the half mirror 10 is transmitted to the lens 12.
It passes through and is imaged on the photometry section 5.

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 made into a half mirror,
A concave mirror 15 is provided behind it. therefore,
The light that has passed through the photographic lens 16 and the aperture 17 passes through the mirror I.
4 and enters the concave mirror 15.

The light reflected downward by the concave mirror 15 passes through the lens 90,
An image is formed on the photometry section 5.

FIG. 5 shows an embodiment in which the photometric section 5 is arranged around the pentaprism 18. The light reflected upward by the mirror 14 is passed through a focusing glass 19 and a condenser lens 20.
After that, it enters Pentaprism 18. 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 located in front of the photometry section 5.
will be arranged.

FIG. 6 shows an example of division of the photometric area. That is, the photometry area is concentrically divided into four zones 21 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 coefficients of equation (1) take, for example, the following values.

K1-1.43 to 2-0.53 (coefficient of zone Zl) K3-0
．． 12 (C:/z2(7) coefficient) K, −−0,
08 (Coefficient of zone z3) K, Shizu 0.34 (Zone Z
6) 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 includes photometric elements 2a to 2.
A plurality of them are provided corresponding to the number of n.

The logarithmically converted signals are input to adding circuits 31a to 31d provided for each zone in the zone brightness detection section 31 and added. Adders using operational amplifiers are used as the adder circuits 31a to 31d.

The outputs of the adder circuits 31a-31d are sent to the divider circuits 32a-3.
．． 2d and is divided by a coefficient depending on the area of the zone. As a result, the average brightness Bml (1
=1,2. ) is calculated.

These average luminances Bmi are input to the luminance detection section 33 and are calculated by a coefficient K14. are weighted by , and then added and subtracted. Therefore, the brightness detection unit 33 calculates the subject brightness B by calculating equation (1).

The film sensitivity, aperture value or shutter speed value from the exposure information setting circuit 34a is input to the exposure calculation circuit 34b,
A photographic calculation is performed along with the subject brightness B,
The aperture value or shutter speed value is calculated. 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 34b1, 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, numbers are attached to the 25 photometric elements so that the zone division can be seen.

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 upper part), and (C) shows the camera in the upper right position ( The right side of the figure is the upper part), 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. The outputs of the light receiving elements 2a 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 40 divides the light receiving elements 2a to 2n into three groups and creates three sets according to the camera posture.

That is, in the case of the horizontal position shown in FIG. 8(A), photometric elements 1 to 10.11.15.1B, 20.21.2
5, photometric elements 12 to 14, 17, 19, 22 to 24, and photometric element 18, and the output of each group is added to three adder circuits 41a and 41b.
, enter in 41c.

In addition, in the case of the upper left position (vertical position) shown in (B), photometric elements 1 to 5.6.7.11.12.1B, 17°2
1 to 25, photometric element 8 to, 13.15.18 to
20 and the photometric element 14, and input them to adder circuits 42a, 42b, and 42c.

In the case of the upper right position (vertical position) shown in (C), photometric elements 1 to 5. 9.10.14.15.19.20.21～
25, photometric elements 6-8.11.18.16-18,
The adding circuit 43a divides the photometric elements 12 into three groups.
.

43b and 43c, respectively.

These adder circuits 41a, 41b, 41c,
42a, 42b, 42c, 43a,
The addition results of 43b and 43c are sent to the division circuits 44a and 43c.
44b, 44c, 45a, 45b,
45c, 46a.

4Bb and 4Bc are respectively input. This division circuit divides the addition result 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 luminances are selected by analog switch circuit 47. That is, when the camera is in the horizontal position, the analog switches 47a, 47b, and 47c are turned ON by a signal from the orientation detection unit 4B that detects the orientation of the camera, and the dividing circuit 4 is turned on.
The outputs of 4a, 44b, and 44c are sent to the brightness calculation circuit 3.
Sent to 3. Furthermore, in the case of the upper left position, the analog switches 47d, 47e, and 471' are ONL, and in the case of the upper right position, the analog switches 47g, 47h, and 47i are OFF.
Do N.

FIG. 10 shows an embodiment of the attitude detection section.

Mercury 51 is sealed in a 7-shaped glass tube 50. This mercury 51 moves according to the attitude of the camera and selectively turns on the switches 52 to 54.

In the case of dividing into three as above, the coefficient of equation (1) is -1,64 2-0.22 (inner zone coefficient) K3-0.4
2 (coefficient for the central zone) K4-0.27 (coefficient for the outer zone) is used.

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

The outputs of these logarithmic conversion circuits 60a-Son are input to comparators 61a-81n, respectively. These comparators 81a to Bln perform comparisons based on the comparison signal from the D/A conversion circuit 62.

The multiplexer 63 selects one of the many comparators in response to a multiplexer address signal 65 from the microcomputer 64. multiplexer 63
After selecting a comparator, for example, 81a, the count-up set value signal B6 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 known from the multiplexer address signal 65, and the digital value is known from the setting signal 66, so when the match signal 67 is output, the setting value corresponds to the address of the photometric element. RAM8
Write to address 8.

Next, the multiplexer address signal 65 is incremented, and the output signal of the logarithmic conversion circuit 60b is A/D converted and written into the RAM 68 in the same manner as described above.

The ROM 89 stores a data acquisition procedure, a procedure for creating groups according to the 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 B4.

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

FIG. 12 is a flowchart showing an input method for A/D converting data and loading it into the RAM 88, and each signal is as follows.

DM = Logarithmically transformed 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 by the D/A converter DN : Contents of DA Figure 13 shows the logarithm after multiplexer B3. Conversion circuit 60
is provided, and this logarithmically converted signal is sent to the control signal 7.
4 shows an embodiment in which the digital signal 7B is converted into a digital signal 7B and taken into the RAM 68 using an A/D converter 75 controlled by a digital signal 7B.

FIG. 14 shows an example of zone division.

FIG. 14 shows an embodiment in which the photometric area is divided into four zones.

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.
Appropriate exposure can be obtained even for objects with uneven brightness distribution.

For example, in the case of a division pattern that is 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 will occur even if the orientation of the camera changes.

[Brief explanation of the drawing]

Figure 1 is a plan view showing a substrate on which a large number of photometric elements constituting the photometry section are formed, Figures 2 to 5 are diagrams showing the arrangement of the photometry unit, and Figure 6 shows seven examples of zone division. 7 is a block diagram of an exposure control device, FIG. 8 is a diagram illustrating an embodiment of zone division, and FIG. 9 is a block diagram of an exposure control device that can change zone division depending on the camera posture. FIG. 10 is a diagram showing an embodiment of the camera attitude detection section, FIG. 11 is a block diagram of a digital exposure control device, FIG. 12 is a flowchart showing a data input method, and FIG.
This figure is a block diagram showing another exposure control device, and FIG. 14 is a diagram showing still another embodiment of zone division. 2a-2n...1111J optical element 5...
Photometry section 30...logarithmic conversion circuit ai, at'...zone luminance detection sections 31a to 31d
...Addition circuits 32a to 32d...Divide circuit 33...Brightness calculation section 34...Exposure control section 34a...Exposure information setting circuit 34b...Exposure calculation circuit 34c...Exposure control circuit 40... Matrix circuits 41a, 41b, 41c, 42a, 42b, 42c, 4
3a, 43b, 43c...addition circuits 44a, 44b, 44c, 45a, 45b, 45c, 4
6a, 46b, 48c...Division circuit 47...Analog switch 48...Attitude detection section 51...Mercury 80a
~Son...Logarithmic conversion circuit 81a-61n...Comparator 68...Multiplexer 62...D/A converter 64...Microcomputer B8...RAM 89...ROM7
1...Shutter control circuit 75...A/D converter Fig. 1 n 2FA Fig. 3 Fig. 10 Fig. 11 Fig. 12 BJ Fig. 13 Fig. 14

Claims (1)

[Claims] (1) A photometric unit having at least three photometric elements arranged on the image plane of the camera or a plane conjugate to the image plane, and measuring the brightness of each part of the subject with each of these photometric elements; a central zone in which the three or more photometric elements measure the brightness of a substantially central portion of the subject based on the brightness of each portion; a first peripheral zone formed to surround the entire circumference of the central zone; Each zone i (i=1, 2, . . . , n;
a zone brightness detection unit that calculates the average brightness B_m_i for each zone (n is an integer of 3 or more);
2, ..., n), calculate the subject brightness B using the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, K_1, K_(_i_+_1_) (i = 1, 2
, ..., n) is a coefficient and K_(_i_+_1_)
At least two of (i=1, 2, . . . , n) are not zero and have different values. ); and an exposure control unit that controls exposure of the camera according to the subject brightness B.