JPH01217428A - Photometric device - Google Patents

Abstract

PURPOSE:To attain the calculation of proper exposure by positioning a reduced photometric frame against a reference photometric frame on a maximum or minimum position of an average brightness value, repeating the positioning of the succeeding reduced photometric frame by using said reduced photometric frame as a reference photometric frame and determining exposure based on an average brightness value obtained when changes in respective average brightness values of these reduced photometric frames are converged into a prescribed width value. CONSTITUTION:A photographing screen is divided like a matrix, the divided areas are grouped like a rectangle to determine a reference photometric frame, a rectangular reduced photometric frame smaller than the reference photometric frame is moved based on four corners of the reference photometric frame and the reduced photometric frame is positioned on a position maximizing or minimizing the average brightness value of the contracted photometric frame. The positioning of the succeeding size-reduced reduced photometric frame is similarly repeated by using said reduced photometric frame as a reference photometric frame. An average brightness value in each reduced photometric frame is detected, and when changes in the detected average brightness values are converged into a prescribed width, exposure is determined based on the average brightness value. Consequently, the accurate exposure data of the object can be calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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]

Recent camera photometers are designed to ensure proper exposure even when backlit. For example, the one described in Japanese Patent Publication No. 59-33889 has been published. This involves placing a light-receiving system, which has a large number of tiny light-receiving elements arranged, at a position where it receives the subject light.
Compare the light metering value obtained by spot metering the main subject and the integrated luminance value of the entire screen, and if the difference is above a predetermined level, select the spot light metering value of the main subject, and if the difference is below the predetermined level, select The integrated luminance value of the entire screen is automatically selected.

[Problems to be Solved by the Invention] However, in the photometry method described in the above publication, the photographer must first manually select the spot photometry area corresponding to the main subject. Not only is this operation extremely troublesome, but if the subject moves during manual operation, accurate exposure data may not be obtained. This makes it impractical because it cannot be done.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and automatically detects the subject no matter where the subject is in the shooting screen in backlight or spotlight situations where it is difficult to calculate the exposure value. An object of the present invention is to provide a photometering device that can measure the brightness of the image and calculate the appropriate exposure.

(Means for Solving the Problems) In order to achieve the above object, the photometry device of the present invention divides a photographing screen into a matrix, and includes a plurality of light receiving elements that measure light for each of the divided areas; Group the areas into rectangular shapes to determine a reference metering frame, move a rectangular reduced metering frame smaller than the standard metering frame based on the four corners of the reference metering frame, and calculate the average brightness of the reduced metering frame. After positioning the reduced metering frame at the position where the value is maximum or minimum,
A photometry frame reduction means repeats the positioning of the next reduction photometry frame whose size is further reduced using this reduction photometering frame as a reference photometry frame, and the photometry frame reduction means sets (each reduction photometry frame a detection means for detecting an average brightness value for each time, and a detection means for detecting that a change in the average brightness value sequentially detected by the detection means has converged within a predetermined width,
Exposure determination means for determining exposure based on the average luminance value at that time is provided.

[Effect]

According to the above configuration, when the photometry device of the present invention captures the subject within the ↑most submerged screen, it first sets the entire shooting screen as the reference photometry frame, and sets the reduced photometry frame with respect to this reference photometry frame to the four corners of the reference photometry frame. Move it as a reference. After positioning the reduced photometric frame at a position where the average luminance value of the reduced photometric frame is maximum or minimum, the reduced photometric frame is used as a reference photometric frame to determine the position of the next reduced photometric frame whose size is further reduced. By repeating this process, a plurality of reduced photometry frames are set. It is detected that the change in the average brightness value of each of these reduced photometry frames has converged within a predetermined width, and the exposure is determined based on the average brightness value at that time.

Embodiments of the present invention will be described in detail below with reference to the drawings.

(Example) In FIG. 1 showing a block diagram of a photometric device of the present invention and an optical system of an electronic still camera 1 incorporating this photometric device, the optical system of the electronic still camera 1 has two groups (lens 10
a, 10 b) Photographic lens 10, lens 10 with configuration
an instantaneous diaphragm 11 disposed between the lens 10a and the lens 10b. Beam splitter 12. Quick return movable mirror 13° focusing screen 14. Condenser lens 15. Pentaprism 16. It consists of an eyepiece lens 17, and a photodiode array 20 for photometry is arranged below the beam splitter 12 via an imaging lens 18. Further, behind the movable mirror 13, a CCD 21 for imaging is arranged via a shutter 22.

A signal processing circuit 23 is connected to the photodiode array 20, and a CPU 26 that operates according to a sequence program written in a program ROM 24 is connected to this signal processing circuit 23. This CPU
A frame memory 25 is connected to the photodiode array 20 . Photometric data for each pixel that is serially outputted via the signal processing circuit 23 is stored in address order. The CPU 26 also includes a shutter 22. which is opened and closed based on the calculation result calculated from the photometric data and exposes the CCD 21. The aperture 11 and release switch 35 are connected.

A signal processing circuit 30 is connected to the CCD 21, and this 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. is connected to the magnetic head 34 of. A motor 36 for rotating the video floppy 33 at a constant speed is arranged below the magnetic head 34, and a driver 37 for driving the motor 36 is connected to the motor 36. Further, a CPO 26 is connected to the driver 37 and head amplifier 32 for driving them.

In addition, a photodiode array 20. A drive circuit 27 and a CCD drive circuit 29 are connected to the CCD 21 to drive these, respectively. C.C.
A synchronizing signal generation circuit 28 is connected to the D drive circuit 29. This synchronizing signal generating circuit 28 is also connected to the CPO 26 and the photodiode array 20 . C0D
The various pulses necessary to drive the CPU 21 are synchronized with each other, and a master clock pulse for controlling the sequence of the CPU 26 is generated.

Next, the operation of the photometric device of the present invention configured as above will be explained. First, when the video floppy 33 is loaded into the electronic still camera 1 and the power is turned on, the synchronization signal generation circuit 28 causes the CPU 26° drive circuit 27. A master clock pulse is sent to the CCD drive circuit 29, and each drive is started. A signal is sent from the CPU 26 to the driver 37, the motor 36 is driven, and the loaded video floppy 33 begins to rotate at approximately 30 m5 per second.
A steady rotation speed of 0 rotations is reached.

When the photographic lens 10 is directed toward a subject, an optical image of the subject captured by the photographic lens 10 is transmitted through a beam splitter 12, reflected by a movable mirror 13, and formed on a focusing screen 14. This formed object image is condensed by a condenser lens 15, and a pentaprism 16. It is observed by the photographer through the eyepiece lens 17. On the other hand, a part of the optical image of the object is guided by the beam splitter 12 to the imaging lens 18 and focused 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, subjected to amplification and digitization processing in the signal processing circuit 23, and inputted to the CPU 26. The CPU 26 partially stores this luminance signal in the frame memory 25 according to the program sequence of the program ROM 24.

The photometric area 40 shown in FIG. 2(A) displays the entire area of the luminance data stored in the frame memory 25, and 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, a maximum brightness value Pmax and a minimum brightness value Pm are calculated from brightness data from each minute photometric area in the photometric area 40 divided into a matrix.
1n is detected.

If Pmax-Pmin is less than a certain value (for example, 2EV), the average brightness value P (m
amr+)1 as the final exposure data P.

Furthermore, if Pmax-Pmin is equal to or greater than a certain value, it means that the difference in brightness within the photometry area 40 is large, which indicates either backlight photography or spotlight photography. A photometric area 41 (
The average brightness value within the area (area displayed with halftone dots)
Said P. a, , , l, and P (+esi,
,,1 > P i, Iaan) 2 indicates backlighting, and P (mea,, + 1 < P (mean)
If it is 2, it is spotlight time. Note that during backlighting, a backlight flag is set in a register in the CPU 26, and during spotlighting, the backlight flag is not set.

Next, a new photometric area 42b is set by subtracting one row and one column from the photometric area 40. This photometric area 42b is first set at the upper left corner of the photometric area 40 as shown in (B), and the average luminance value P (mair+1 B
Calculate. Similarly, P is set in the upper right corner (see (C)). an) When set to C + lower left corner ((D)
(Refer to) P(18□n)D+ lower right corner of ((
Calculate P (+5aan)E of (see E) respectively. Incidentally, if the brightness value of the background is aEV, and the brightness value of the subject photometry area 43 indicated by diagonal lines is bEV, then it will be 4 days. Here, if there is the backlight flag, a
>b, so P faufi) B = P (lIa
anlc > P fmainLD = P (main
Since it becomes lE, P + mai, 1) D or P. own
) The photometric area having E is selected, but if there are identical minimum brightness values, the lowest photometric area among them is selected. Also, if the lower two (in this example Pl, □)D and Pman)B)
has the minimum brightness, the right photometric region among them is selected.

Next, from the photometric area 42e selected in this way, a photometric area 44f further narrowed by one row and one column is set at the upper left corner of the photometric area 42e, which is the garden side light area, as shown in (F).
Shown below. After that, new photometric areas are set at the upper right corner, lower left corner, and lower right corner (not shown) of the photometric area 39e in the same manner as above, and the average luminance value of each is calculated. A photometric area with the lowest average brightness value among these average brightness values is set, and a new photometric area is also set. The photometric area 45g set after this procedure is repeated is shown in (G).

With this photometric area 45g as the garden side light area, a photometric area 46h shown in (H), a photometric area 46i shown in (1), a photometric area 46j shown in (J), and a photometric area 46k shown in (K) are set, respectively. . The average brightness value in each photometric area is as follows, so P (meant H= P l+sam
i I > P (+**mn) J = P (mamr
1, and the photometry area 46k is selected as the new photometry area. Furthermore, a new photometric area 471 in which this photometric area 46k is set as the garden side light area is shown in (L). The average luminance value P<m5inlL of this photometric area 471 is as follows, and is converged to b. The final exposure data P is calculated based on this converged average brightness value, and
The flag in the CPU 26 is reset to prepare for the next photometry.

Note that b is the accurate average brightness value of the subject, but it is a very spot-like value when viewed from the entire shooting screen, so even if the subject reproducibility is good, the details of the background may be completely lost. be. Therefore, considering the average photometric value Ptwain)B of the garden side light area 2, for example 42b, this P
By assigning weights to fnssn+B and b and calculating the final exposure data P, it is possible to reproduce the main subject and the background in a well-balanced manner. Also, when there is no backlight flag, the photometry area with the highest average brightness value is selected when setting a new photometry area.
The final exposure data P is determined by the same procedure as when there is a flag.

In this state, the AE lock mechanism (not shown) is activated by pressing the release button halfway, etc., and the final exposure data P is memorized.While observing the viewfinder image, decide on the composition and press the release button (not shown). Push it in. As a result, the release switch 35 is turned on and the movable mirror 13 is simultaneously raised, and immediately after this, the shutter 22 is opened and closed based on the final exposure data P. The next moment,
The movable mirror 13 returns to its original position and the viewfinder field of view is restored, and the optical image, which has been controlled to have an appropriate amount of light, is converted into a video signal by the CCD 21, and then processed by a well-known signal processing circuit 30. The signal is input to the head amplifier 32 via the FM modulation circuit 31.

The head amplifier 32 operates the magnetic head 34 according to instructions from the CPU 26, and instantaneously records the video signal read from the CCD 21 onto the video floppy 33.

〔Effect of the invention〕

As described above, according to the photometry device of the present invention, a photographic screen is divided into a matrix, a plurality of light receiving elements are used to measure light for each divided area, and the areas are grouped into a rectangular shape. Determine the reference metering frame, move a rectangular reduced metering frame smaller than this reference metering frame based on the four corners of the reference metering frame, and find the position where the average brightness value of the reduced metering frame is maximum or minimum. After positioning the reduced photometering frame, the photometry frame reduction means repeats the same process of positioning the next reduced photometry frame, which is further reduced in size, using this reduced photometering frame as a reference photometry frame, and the photometry frame reduction means sets the reduced photometering frame. detecting means for detecting the average luminance value for each reduced photometry frame; detecting that the change in the average luminance value sequentially detected by this detecting means has converged within a predetermined width; and an exposure determining means for determining exposure based on the average brightness value.

Therefore, it is possible to provide a photometry device that can automatically determine whether backlight photography or spotlight photography is being performed, and can automatically calculate accurate exposure data for a subject no matter where the subject is within the photographic screen. become able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing the structure of an embodiment of the present invention. FIGS. 2(A) to 2(L) are schematic diagrams showing the photometric area of the embodiment of the present invention. FIG. 3 is a flowchart showing the main part of the sequence program according to the embodiment of the present invention. 1...Electronic still camera 20...Photodiode array 21...CCD 22...Shutter 26...CPU 40, 41. 42b, 42e, 44f, 45g. 46h, 46i, 46j, 46, 471...
...Photometry area. Figure 2 (C) (D
)(E)
(F) Figure 2

Claims (1)

[Claims] (1) In a photometry device that divides a photographic screen into a matrix and is equipped with a plurality of light-receiving elements that measure light for each divided area, the areas are grouped into rectangular shapes to determine a reference photometry frame, and this After moving the rectangular reduced metering frame, which is smaller in size than the standard metering frame, based on the four corners of the standard metering frame, and positioning the reduced metering frame at the position where the average brightness value of the reduced metering frame is maximum or minimum. , a photometry frame reduction means that similarly repeats the positioning of the next reduction photometry frame whose size is further reduced using this reduction photometering frame as a reference photometry frame, and each reduction photometry frame that is set by this photometry frame reduction means. a detection means for detecting an average brightness value for each time, and a detection means for detecting that a change in the average brightness value sequentially detected by this detection means has converged within a predetermined width, and adjusting the exposure based on the average brightness value at that time. 1. A photometric device comprising: exposure determining means for determining an exposure.