JPH0830836B2 - Photometric device - Google Patents

Description

The present invention relates to a photometric device for use in cameras such as electronic still cameras, silver halide cameras and video cameras.

[Conventional technology]

As a recent photometric device for a camera, there is provided a photometric device devised so that an appropriate exposure can be obtained even in the case of backlight.
For example, in the one disclosed in Japanese Patent Laid-Open No. 62-96827, the brightness output from a plurality of photometric regions is compared with a predetermined threshold value, and the brightness output exceeding this threshold value is used as brightness data for calculating the proper exposure. I try not to include it in. This makes it possible to obtain proper exposure even in a backlit scene where there is an extremely high-luminance portion such as the sun in the shooting screen.

[Problems to be Solved by the Invention]

However, in the photometric method described in the above publication, the patterns of a plurality of photometric areas are determined, and there is a problem that, for example, when the sun and the main subject are included in the same photometric area, it cannot be dealt with.

[Object of the Invention]

The present invention has been made in order to solve the above-described problems, and it is possible to determine what kind of object in the shooting screen the subject will be in when the subject is backlit such that an object having extremely high brightness as compared with the subject is in the shooting screen. It is an object of the present invention to provide a photometric device that can calculate a proper exposure even at a position.

[Means for solving the problem]

In order to achieve the above-mentioned object, a photometric device of the present invention divides a shooting screen into a matrix, and a plurality of light-receiving elements that perform photometry for each of the divided areas, and the areas are grouped into a rectangular shape and used as a reference. Determine the metering frame, move the rectangular reduced metering frame smaller than the reference metering frame based on the four corners of the reference metering frame, and reduce the metering position to the position where the average brightness value of the reducing metering frame becomes the minimum. After positioning the frame, the reduced photometric frame is used as a reference photometric frame, and the next reduced photometric frame, which has been further reduced in size, is similarly positioned, and the photometric frame reducing means and the photometric frame reducing means are set. Detecting means for detecting the maximum brightness value for each reduced photometric frame, and the difference between the maximum brightness value sequentially detected by this detecting means and the maximum brightness value when the entire photographic screen is used as the photometric frame is a certain value or more. Became Can, so that and an exposure determining means for determining an exposure based on the brightness data of the reduced photometric frame at that time.

[Action]

According to the above configuration, when the photometric device of the present invention captures a subject in the photographing screen, first, the entire photographing screen is used as a reference photometric frame, and the reduced photometric frame with respect to the reference photometric frame is used as the four corners of the reference photometric frame. To move. After positioning the reduced photometric frame at the position where the average brightness value of the reduced photometric frame is the minimum, the position of the next reduced photometric frame that is further downsized is determined using this reduced photometric frame as the reference photometric frame. By repeating this, a plurality of reduced photometric frames are set. When the difference between the maximum brightness value of each of these reduced metering frames and the maximum brightness value when the entire shooting screen is used as the metering frame exceeds a certain value, exposure is performed based on the brightness data of the reduced metering frame at that time. To decide.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

〔Example〕

In the block diagram of the photometric device of the present invention and FIG. 1 showing the optical system of the electronic still camera 1 incorporating this photometric device, the optical system of the electronic still camera 1 comprises two groups (lenses 10a,
10b) A photographing lens 10 having a configuration, an aperture stop 11 arranged between the lenses 10a and 10b, a beam splitter 12, a movable mirror 13 of a quick return type, a focusing screen 14, a condenser lens 15, and a pentaprism 1
6, consisting of an eyepiece lens 17, and below the beam splitter 12 via a focusing lens 18 a photodiode array for photometry
20 are arranged. Further, behind the movable mirror 13, a CCD 21 for image pickup is arranged via a shutter 22.

A signal processing circuit 23 is connected to the photodiode array 20, and the signal processing circuit 23 has a program ROM 2
The CPU 26, which operates according to the sequence program written in 4, is connected. A frame memory 25 is connected to the CPU 26, and photometric data for each pixel, which is serially output via the photodiode array 20 and the signal processing circuit 23, is stored in the order of addresses. Also, CPU26
A shutter 22, an aperture 11 and a release switch 35, which are opened and closed based on the calculation result calculated from the photometric data and give exposure to the CCD 21, are connected to the.

A signal processing circuit 30 is connected to the CCD 21, and the signal processing circuit 30 writes a video signal to a still video floppy (hereinafter, referred to as video floppy) 33 via an FM modulation circuit 31 and a head amplifier 32. Of magnetic head 34. Below the magnetic head 34,
A motor 36 for rotating the video floppy 33 at a constant speed
Is arranged, and a driver 37 for driving the motor 36 is connected to the motor 36. Also, the driver 37
And the head amplifier 32 has a CPU 2 for driving them.
6 is connected.

A drive circuit 27 and a CCD drive circuit 29 for respectively driving the photodiode arrays 20 and CCD21 are connected, and a synchronization signal generation circuit 28 is connected to the drive circuits 27 and CCD drive circuit 29. ing. The synchronization signal generation circuit 28 is also connected to the CPU 26, and synchronizes various pulses necessary for driving the photodiode array 20 and the CCD 21 with each other, and also generates a master clock pulse for controlling the sequence of the CPU 26. ing.

Next, the operation of the photometric device of the present invention configured as described above will be described. First, when the video floppy 33 is loaded into the electronic still camera 1 and the power is turned on, a master clock pulse is sent from the synchronizing signal generating circuit 28 to the CPU 26, the driving circuit 27, and the CCD driving circuit 29, and the respective driving is started. . A signal is sent from the CPU 26 to the driver 37 and the motor 36
Is driven and the loaded video floppy 33 starts rotating, and reaches a steady rotation speed of 60 rotations per second in about 30 ms.

When the shooting lens 10 is aimed at the subject, the optical image of the subject captured by the shooting lens 10 passes through the beam splitter 12,
Focusing screen 14 reflected by movable mirror 13
Is imaged. The formed subject image is condensed by the condenser lens 15 and is observed by the photographer via the pentaprism 16 and the eyepiece lens 17. On the other hand, a part of the optical image of the subject is guided to the imaging lens 18 by the beam splitter 12 and imaged on the photodiode array 20. The optical image formed on the photodiode array 20 is converted into a luminance signal by the photodiode array 20, amplified and digitized by the signal processing circuit 23, and input to the CPU 26. The CPU 26 temporarily stores the brightness signal in the frame memory 25 according to the program sequence of the program ROM 24.

The photometric area 40 shown in FIG. 2A is a frame memory.
The entire area of the brightness data stored in 25 is displayed,
It corresponds to the exposure frame recorded on the video floppy 33. The CPU 26 processes the photometric data according to the program sequence shown in FIG. First, the maximum brightness value P ₍ max ₎ 1 and the minimum brightness value P ₍ min ₎ 1 are detected from the brightness data from each minute photometric area in the photometric area 40 divided into a matrix.

If P ₍ max ₎ 1-P ₍ min ₎ 1 is less than a fixed value (for example, 2EV), the average brightness obtained by adding the brightness data from all the photometry areas in photometry area 40 and dividing by the number of all the photometry areas The value P ₍ mean ₎ 1 is the final exposure data P. If P ₍ max ₎ 1-P ₍ min ₎ 1 is equal to or more than a certain value, it is determined that the backlight is photographed, and the photometric area 40
The photometric area 41 is newly set by reducing the number of rows by one column from the above. This photometric area 41 is first set in the upper left corner of the photometric area 40 as shown in FIG. 2B, and the average luminance value P ₍ mean ₎ B in this area is calculated. Similarly, set P _(mean) C in the case of setting the upper right corner (Fig. (C) see), P _(mean) D in the case of setting the lower left corner (FIG. (D) refer), the lower right corner In each case (see (E) in the figure), P ₍ mean ₎ E is calculated. By the way, if the brightness value of the back is aEV, the brightness value of the subject photometric area 42 shown by diagonal lines is bEV, the brightness value of the sun 43 is cEV, and the circumference of the sun 43 is dEV, and c>d>a> b, Therefore, P ₍ mean ₎ B> P ₍ mean ₎ C> P ₍ mean ₎ D> P ₍ mean ₎ E
Becomes Therefore, the maximum brightness value P ₍ max ₎ 1 of the photometric area 40
(E) as a photometric area to be compared with
44 is selected.

The maximum luminance value P ₍ max ₎ E of this photometric region 44 is d, and P ₍ m
Since ax ₎ 1 is c, P ₍ max ₎ 1−P ₍ max ₎ E = c−d> constant value (for example, 5 EV). Therefore, the average brightness value P ₍ mean ₎ E of the photometric area 44 having P ₍ max ₎ E is set as the final exposure data P.

When P ₍ max ₎ 1−P ₍ max ₎ E = c−d <constant value, a new photometric region narrowed by one row and one column from the photometric region 44 is newly set, and the photometric region 44 The same procedure may be repeated with the old photometry area as.

Further, in this embodiment, the average brightness value P ₍ mean ₎ E is adopted as the final exposure data P, but P = P ₍ min ₎ E + k (P ₍ max ₎ E-
It may be calculated by P ₍ min ₎ E) (0 ≦ k ≦ 1).

In this state, the final exposure data P is stored by operating the AE lock mechanism (not shown) by half-pressing the release button, and while observing the viewfinder image, determine the composition and press the release button (not shown). Push in. As a result, at the same time when the release switch 35 is turned on, the movable mirror 13 jumps up, and immediately thereafter, the shutter 22 is opened / closed based on the final exposure data P. At the next moment, the movable mirror 13 returns to its original position to restore the viewfinder field, and the optical image controlled by the proper light amount is CCD21.
Is converted into a video signal by the well-known signal processing circuit 30, F
It is input to the head amplifier 32 via the M modulation circuit 31. The head amplifier 32 operates the magnetic head 34 in accordance with a command from the CPU 26, and instantly records the video signal read from the CCD 21 on the video floppy 33.

Although the present embodiment has been described only for “backlit” shooting, even when a “spotlight” shooting is performed in which the main subject has higher brightness than the surroundings, the brightness is extremely similar to the above description. Exclude the brightness data of the low area,
You can decide more appropriate exposure.

〔The invention's effect〕

As described above, according to the photometric device of the present invention,
Each area obtained by dividing the shooting screen into a matrix is grouped into a rectangular shape to determine a photometric frame, and this photometric frame is gradually reduced toward the main subject to create the final photometric frame for exposure determination. I try to figure it out.

Therefore, no matter where the subject is in the shooting screen during backlight photography, it is possible to eliminate the luminance data of the photometric area having a portion having extremely high luminance as compared with the luminance of the subject, and to obtain appropriate exposure data for the subject. Thus, it becomes possible to provide a photometric device capable of calculating.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing the structure of an embodiment of the present invention. FIGS. 2A to 2E are schematic views showing the photometric area of the embodiment of the present invention. FIG. 3 is a flow chart showing the main part of the sequence program of the embodiment of the present invention. 1 ... Electronic still camera 20 ... Photodiode array 21 ... CCD 22 ... Shutter 26 ... CPU 40, 41, 44 ... Photometric area.

Claims (1)

[Claims] 1. A photometric device comprising a plurality of light-receiving elements for dividing a photographic screen into a matrix and measuring light in each of the divided regions, wherein the regions are grouped into a rectangular shape to determine a reference photometric frame. After moving the rectangular reduction metering frame smaller than this reference metering frame based on the four corners of the reference metering frame and positioning the reduced metering frame at the position where the average brightness value of the reducing metering frame is the minimum , A reduction metering frame for repeating the positioning of the next reduced metering frame, which has been further reduced in size, using this reduction metering frame as a reference metering frame, and each reduction metering frame set by this metering frame reducing unit. When the difference between the maximum brightness value detected by the detection means for detecting the maximum brightness value for each and the maximum brightness value sequentially detected by this detection means and the maximum brightness value when the entire photographic screen is used as a photometric frame becomes a certain value or more, And Exposure determining means for determining the exposure based on the luminance data of the reduced photometric frame.