JP2004179868A - Electronic camera with automatic focus adjustment function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic camera for properly performing automatic focus adjustment of a multipoint AF even when a lens with a different image size is mounted on the camera. <P>SOLUTION: The electronic camera is provided with: an object recognition means for dividing the areas of a picked up image and comparing a distance difference in the two areas with a threshold value to discriminate a principal object; a focus adjustment means for focusing the principal object; an adapting means for adapting the picked up image of a camera main body to the image size of an interchangeable lens through electronic zooming in accordance with the image size of the interchangeable lens; and a threshold value change means for changing the threshold value on the basis of a magnification of electronic zooming or the image size information when the adapting means performs electronic zooming. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an interchangeable lens electronic camera having an automatic focusing function.
[0002]
[Prior art]
Conventionally, some interchangeable lens electronic cameras have different mount diameters for different camera bodies and interchangeable lenses having different image sizes, but such interchangeable lenses are less versatile. . However, if all mounts are shared, there is no problem with a camera body for a small image size if the interchangeable lens has a large image size. And the like.
[0003]
On the other hand, as shown in, for example, JP-A-2-33267 and JP-A-2-33268, an interchangeable lens having a small image size cannot be mechanically attached to a camera body having a large image size. In addition, it is possible to prevent problems such as vignetting. Further, as disclosed in JP-A-2-39777, the interchangeable lens and the camera main body are electrically connected, and the camera main body is connected to the camera main body based on the information related to the image size of the interchangeable lens stored in the lens side. If it is determined that the image size of the interchangeable lens does not match the image size of (i.e., the image size on the interchangeable lens side is small), a configuration may be considered in which a warning is issued.
[0004]
On the other hand, when the image size of the interchangeable lens is not compatible with the camera body, the electronic camera is designed to prevent the occurrence of problems such as vignetting by avoiding the mounting of the interchangeable lens. The versatility of the lens has not been sufficiently secured.
[0005]
Therefore, in order to provide an electronic camera capable of obtaining a good captured image without vignetting even when an interchangeable lens having an image size that is not compatible with the camera body is mounted, a camera body having a camera-side mount is provided. And an interchangeable lens having a lens-side mount coupled to the camera-side mount, wherein: input means for inputting information representing the image size of the interchangeable lens to the camera body; and Determining means for determining whether or not the image size of the interchangeable lens is compatible with the camera body based on the information; and an image sensor formed by the interchangeable lens when the determining means determines that the image is incompatible. By performing signal processing on the image signal representing the above image with electronic circuits, There has also been proposed an electronic zoom in which the camera body is adapted to an image size of the interchangeable lens by an electronic zoom for enlarging an image on the imaging element to an image corresponding to a predetermined range.
[0006]
On the other hand, conventionally, in a camera having a plurality of focus detection areas in a shooting screen, the shooting screen is finely divided into blocks, these divided blocks are each measured for distance, and distance distribution information (distance map) is created. Area division (grouping) is performed to separate each object constituting the object scene on the screen, and if the difference between the distances of two adjacent blocks is within a predetermined threshold, “the objects constituting the two blocks are By determining that the same object is formed, and if the difference between the distances of two adjacent blocks is greater than a predetermined threshold, it is determined that "the objects constituting the two blocks are different objects". After estimating the existence area of the main subject in the camera (the camera automatically determines the subject intended by the photographer) and determining one focus adjustment distance based on the distance information, the lens is driven to drive the subject. Automatically focusing the camera is disclosed having an automatic focusing device.
[0007]
[Problems to be solved by the invention]
By the way, when a lens having a small image size is attached to a camera equipped with the automatic focusing device, shooting with the camera adapted to the image size means shooting with a camera having a small shooting screen. However, in general, the permissible circle of confusion that defines the in-focus state on the photographing screen changes according to the screen size (diagonal length), and the smaller the photographing screen, the smaller the permissible circle of confusion.
[0008]
At this time, in the camera equipped with the automatic focusing device, the threshold value for estimating the existence area of the main subject in the scene needs to be changed according to the permissible circle of confusion.
[0009]
However, conventionally, even when a lens having a small image size is attached, the threshold value is not changed, so that the recognition result differs depending on the screen size even for the same object, and the subject originally intended by the photographer is accurately determined as the subject. There was a problem that said it would not.
[0010]
The present invention has been made in view of the above-described problems, and has as its object to cut out a captured image by electronic zoom when a lens having a small image size with respect to the screen size of the camera body side is cut out, and the image area is reduced. It is another object of the present invention to provide a camera that performs focus adjustment control by changing a threshold value for estimating a region where a main subject is present in a scene according to the size of the cut-out image.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a camera body having a camera-side mount, and an interchangeable lens having a lens-side mount coupled to the camera-side mount, based on a result of focus detection means and the focus detection means. Focusing control means for controlling the focus adjustment operation of the lens, and based on information on the distance or defocus distribution in the target space, compares the threshold or the difference or ratio of the information or distance on the distance or defocus between the two distribution points. Subject recognition means for determining whether or not areas corresponding to the two distribution points are the same object in accordance with the comparison result, and input means for inputting information representing the image size of the interchangeable lens to the camera body Whether the image size of the interchangeable lens is compatible with the camera body based on the information input by the input unit. A determination unit, and when the determination unit determines that the image is incompatible, the electronic circuit performs signal processing on an image signal representing an image formed on the image sensor formed by the interchangeable lens. Electronic zoom for enlarging an image corresponding to a predetermined range of the image, adapting means for adapting the camera body to the image size of the interchangeable lens, and replacing the lens with at least a lens having a different image size. When performed, the object is achieved by changing the threshold based on the information indicating the image size or the enlargement ratio of the electronic zoom.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a configuration diagram of a main part of a digital single-lens reflex camera system according to the present invention.
[0014]
As shown in FIG. 1, the digital camera system according to the present embodiment includes a camera body 1 constituting a digital camera body, and a shooting lens 2 having a plurality of shooting lenses. It is arranged to be detachable.
[0015]
In this embodiment, the taking lens 2 is shown as two lenses of 3 and 4 for the sake of convenience. However, it is well known that the taking lens 2 is actually composed of a larger number of lenses.
[0016]
Reference numeral 5 denotes a main mirror composed of a half mirror, which is rotatably supported by a hinge shaft (not shown), is obliquely provided in a photographing optical path in an observation state, and transmits a light beam transmitted through the photographing lens 2 to a finder and a sub mirror. Guided and departed during shooting. Reference numeral 6 denotes a sub-mirror, which is rotatably supported on the main mirror 5 by a hinge axis (not shown), and reflects a light beam transmitted through the main mirror 5 downward in the camera body in an observation state, In the photographing state, it retracts in conjunction with the main mirror 5.
[0017]
Reference numeral 7 denotes a shutter, and an optical filter 8 having an optical low-pass filter and an infrared cut filter integrated therewith is arranged behind the shutter 7, and further behind the image pickup device 9 such as a CCD for recording a captured image. Is arranged. Reference numeral 11 denotes a well-known phase-difference focus detection system including a field lens 11a, reflection mirrors 11b and 11c, a secondary imaging lens 11e, an aperture 11d, and an area sensor 11f including a CCD and the like arranged near the imaging plane. The apparatus is configured to be able to focus-detect a plurality of regions of the object scene. The area sensor 11f includes two imaging screens. Light beams are guided from different pupil positions of the imaging lens 2 to each other on the respective imaging screens, and an image determined by the field lens 11a and the secondary imaging lens 11e. It is re-imaged at magnification. The area sensor 11f is disposed at a position optically equivalent to the imaging element 9 with respect to the imaging lens 2, and the two imaging screens of the area sensor 11f have the same visual field as the imaging screen of the imaging element 9. ing. Reference numeral 12 denotes a focusing plate arranged on a predetermined imaging plane of the photographing lens 2. Reference numeral 13 denotes a field mask formed of a transmissive liquid crystal for forming a field of view corresponding to a shooting screen size to be described later and informing the photographer of the shooting area. Reference numeral 15 denotes a penta roof prism for changing a finder optical path. An eyepiece 16 is arranged behind the pentaprism 15, and the luminous flux of the subject image formed on the focus plate 12 reaches the eyeball 17 of the photographer and is observed. Reference numerals 18 and 19 denote an imaging lens and a photometric sensor for measuring the luminance of the subject in the observation screen. The imaging lens 18 conjugates the focusing plate 12 and the photometric sensor 19 via a reflection optical path in the penta roof prism 15. Positioned in a relationship. Reference numeral 21 denotes an LCD in the finder for displaying photographing information outside the finder visual field. Light transmitted through the finder LCD 21 by being illuminated by the illumination LED 20 is guided into the finder by the triangular prism 22, and the photographing information is displayed. Displayed outside. This allows the photographer to know the photographing information. Reference numeral 23 denotes an aperture provided in the taking lens 2, reference numeral 24 denotes an aperture driving device including an aperture control circuit 110 described later, reference numeral 25 denotes a lens driving motor, reference numeral 26 denotes a lens driving member including a driving gear and the like, reference numeral 27 denotes a photocoupler, The rotation of the pulse plate 28 linked to the driving member 26 is detected and transmitted to the lens focus adjustment circuit 109. The focus adjustment circuit 109 drives the lens drive motor 25 by a predetermined amount based on this information and the information on the lens drive amount from the camera side, and moves the photographing lens 3 to a focus position. Reference numeral 29 denotes a mount contact serving as an interface between the camera body 1 and the photographing lens 2, and various kinds of information communication between the camera and the lens are performed through the mount contact. Reference numeral 31 denotes a monitor LCD composed of a TFT liquid crystal for displaying image data obtained by the image sensor 9.
[0018]
FIG. 2 is a block diagram showing an electrical configuration incorporated in the digital camera system having the above-described configuration, and the same components as those in FIG. 1 are denoted by the same reference numerals.
[0019]
A central processing unit (hereinafter referred to as a CPU) 100 of a microcomputer built in the camera body is, for example, a one-chip microcomputer having a ROM, a PAM, and an A / D conversion function therein, and includes a digital circuit 101, a photometry circuit 102, an automatic focus detection. The circuit 103, the signal input circuit 104, the LCD drive circuit 105, the LED drive circuit 106, the shutter control circuit 107, and the motor control circuit 108 are connected. Further, it controls a focus adjustment circuit 109 and an aperture control circuit 110 disposed in the photographing lens 2 so that various kinds of information specific to the photographing lens, such as an open F number, a focal length, various focus correction amounts, and image circle information described later, are provided. Signals are transmitted to the in-lens control circuit 111 having storage means such as a ROM stored in advance via the mount contact 29 shown in FIG.
[0020]
The digital circuit 101 drives the image sensor 9, reads an image signal from the image sensor 9, an image sensor drive circuit 101 a, a RAM 101 b for storing the read image signal, and an image signal stored in the RAM 101 b into a predetermined image. It comprises a signal processing circuit 101c for converting data into data and a flash memory 101d for storing image data.
[0021]
The photometry circuit 102 amplifies the luminance signal output corresponding to the brightness of the object scene from the photometry sensor 19, performs logarithmic compression and A / D conversion, and sends the result to the CPU 100 as object scene luminance information of each sensor. The photometric sensor 19 is composed of a plurality of photodiodes corresponding to each area of the viewfinder field (not shown) which is divided into many parts.
[0022]
The area sensor 11f is a known CCD line sensor, and the automatic focus detection circuit 103 performs A / D conversion of the voltage obtained from the line sensor 11f and sends it to the CPU 100.
[0023]
For example, the signal input circuit 104 is turned on by a first stroke of a release button (not shown), a switch SW1 for starting photometry, distance measurement, and the like of the camera, and turned on by a second stroke of the release button. SW2 which is a switch for starting the operation, SW-M provided in a mode dial (not shown) for selecting a photographing mode of the camera, etc., and setting values which can be further selected from the selected modes. SW-DIAL which is a dial switch provided in the electronic dial (not shown) for selection and SW-SI which is a switch for selecting whether or not to automatically perform a focus detection area are connected. The signal of each switch is input to the signal input circuit 104 and transmitted to the CPU 100 via the data bus. The SW-DIAL signal is input to an up / down counter in the signal input circuit 104, and is transmitted to the CPU 100 after counting the amount of rotation click of the electronic dial.
[0024]
The LCD driving circuit 105 is a known LCD driving circuit for driving the LCD 21 in the finder and the LCD 31 for monitoring, and controls the display content of each LCD according to a signal from the CPU 100.
[0025]
The LED drive circuit 106 controls lighting of the illumination LED 20 (F-LED).
[0026]
When energized, the shutter control circuit 107 controls the magnet MG-1 for running the front curtain and the magnet MG-2 for running the rear curtain, and causes the image sensor 9 to store a predetermined amount of light.
[0027]
The motor control circuit 108 controls the motor M for charging the main mirror 5 and the shutter 7. The shutter control circuit 107 and the motor control circuit 108 operate a series of camera release sequences.
[0028]
The aperture control circuit 110 and the focus adjustment circuit 109 are arranged in the photographing lens 2 shown in FIG. 1, and signals are transmitted to the CPU 100 via the mount contacts 29, and the aperture 23, the lens driving motor 25, the photocoupler 27 etc. are controlled.
[0029]
Next, an image circle which is one of the unique information of the photographing lens will be described.
[0030]
By connecting a predetermined mounting portion (not shown) of the camera body 1 and a predetermined mounted portion (not shown) of the photographing lens 2 by predetermined means, an electrical connection therebetween can be established by a mounting contact 29. It will be in the secured state.
[0031]
In this state, when the main power supply of the camera body 1 is turned on, the digital camera system enters a shooting preparation state in which a shooting / recording operation can be started. That is, when the main power is turned on, the CPU 100 is activated, and the CPU initializes the entire circuit in the digital camera system. When the predetermined initialization processing is completed, the CPU subsequently reads the image size information from the storage means in the in-lens control circuit 111 via the mount contact 29. The image size information read at this time is information specific to the photographing optical system constituting the photographing lens 2 mounted as described above.
[0032]
The image size information read into the camera body 1 by the CPU 100 in this manner is temporarily stored in, for example, an internal storage area of the CPU 100.
[0033]
Note that the image size information temporarily stored in the memory as described above is treated as invalid information when the main power of the camera body 1 is turned off, and is initialized by the initialization process at the next system startup. Will be erased. Then, predetermined image size information is read from storage means in the in-lens control circuit 111 of the taking lens 2.
Control is performed again.
[0034]
The image size information temporarily stored in the memory is also invalidated when the taking lens 2 is detached from the camera body 1 and the electrical connection between them is cut off. In this case, after the other photographing lens 2 is attached to the camera body 1 and the electrical connection between them is newly established, the CPU 100 automatically transmits predetermined image size information from the storage means. Execute read control. As a result, the new image size information is overwritten on the memory with the invalidated information.
[0035]
The reading of the image size information is performed as described above.
[0036]
As shown in FIG. 3, the read image size information is identified as three types of 50 “large”, 51 “medium”, and 52 “small”, and the CPU 100 responds to the read image size information. The image of the image sensor 9 is cut out for three types 9a, 9b, and 9c. As a result, even when an interchangeable lens having an image size that is not compatible with the camera body is mounted, a good captured image without vignetting can be obtained.
[0037]
4A and 4B are views showing the display contents of the field mask 13 and the LCD 21 in the viewfinder. FIG. 4A shows the display contents when a lens having a large image size is mounted, and FIG. (C) shows the display contents when a lens having a small image size is attached.
[0038]
The field mask 13 is linked to the image size of the image sensor 9 determined by the image size information of the photographic lens 2 described above, forms a field of view corresponding to the determined image size, and informs the photographer of the shooting area. At the same time, a display corresponding to the image size information is also performed on the LCD 21 in the finder to inform the photographer of the image size information of the lens attached to the photographer. That is, "L" is displayed on the LCD 21 when a lens having a large image size is mounted, "M" is displayed when a lens having a medium image size is mounted, and "S" is displayed when a lens having a small image size is mounted. .
[0039]
In the present embodiment, the image size of the lens mounted for convenience of explanation is limited to three types of "large", "medium", and "small", but is not limited to this.
[0040]
Next, the overall operation of the digital camera system will be described with reference to the flowchart shown in FIG.
[0041]
When the mode dial SW-M is rotated to a predetermined position, the power of the camera is turned on (S100), and the camera initializes the entire circuit (S101). Then, it waits until SW1 is turned on (S102).
[0042]
When the signal input circuit 104 detects that the SW1 has been turned on, the CPU 100 starts communication with the photographing lens 2 (S103), and determines image size information that is information unique to the photographing lens 2 (S104). Here, when the image size information is determined to be “large”, the CPU 100 sets the imaging range of the image sensor 9 to “large” (FIG. 4: 9a) (S105). When the image size information is determined to be “medium”, the CPU 100 sets the imaging range of the image sensor 9 to “medium” (FIG. 4: 9b) (S106). When the image size information is determined to be "small", the CPU 100 sets the imaging range of the image sensor 9 to "small" (FIG. 4: 9c) (S107). Subsequently, based on the determined image size information, the display of the visual field mask 13 (S108) and the display of the LCD 21 in the finder (S109) are switched to the above-described FIGS. 4A, 4B, and 4C.
[0043]
Thereafter, the camera waits until SW1 is turned on (S110).
[0044]
Next, the CPU 100 checks the setting of the SW-SI for selecting whether to automatically select the focus detection area (S111).
[0045]
If the SW-SI is ON, the process enters a focus detection area manual selection mode (S112). In the focus detection area manual selection mode, the photographer can operate the electronic dial switch SW-DIAL to select an arbitrary position from among a plurality of areas of the object scene.
[0046]
If the SW-SI is OFF, a focus detection area automatic selection mode is entered (S113), and a specific focus detection area is selected by a focus detection area automatic selection subroutine.
[0047]
Here, the focus detection area automatic subroutine will be described with reference to FIGS.
[0048]
FIG. 6 is a diagram showing an example in which a defocus (or distance) distribution information is created to recognize an object arrangement state, a main subject is detected, a lens is focused on the main subject, and the light quantity of the main subject is measured. 9 is a flowchart illustrating an operation of a camera having a function of adjusting exposure to a subject, particularly an operation of selecting a focus detection area for recognizing an environment and determining a main subject.
[0049]
When the photographer presses the release button, the switch SW1 is turned on, and when the focus detection area automatic selection mode is selected, the CPU starts the control shown in the flowchart of FIG. 6 according to the program recorded in the ROM ( S200).
[0050]
Next, the image of the area sensor 11f is captured (S201). The capture of the image of the area sensor 11f is performed as follows. First, the area sensor 11f is reset. Specifically, the reset operation is performed inside the automatic focus detection circuit by reading the output of the area sensor 11f and simultaneously setting the reset signals φV, φH, and φR to “H” for a certain period of time in the CPU 100.
[0051]
Next, an accumulation start command is sent from the CPU 100 to start accumulation, and the end of accumulation is detected later.
[0052]
Then, φV and φH are driven to sequentially read the sensor output IMAGE, A / D converted by the CPU 100 and stored in predetermined areas IMG1 and IMG2 on the RAM, and the capture of the output signal of the sensor is completed.
[0053]
Next, defocus distribution information (defocus map) composed of m × n blocks (m and n are positive numbers of 1 or more) is created (S202).
[0054]
Here, a flowchart of the defocus map creation will be described with reference to FIG.
[0055]
First, variables x and y indicating the coordinates of a block are initialized (S301).
[0056]
Next, a signal necessary for the defocus calculation of the block (x, y) is extracted from the image data IMG1 on the RAM, copied to a predetermined address A on the RAM (S302), and the block (x, y). The other signal necessary for the defocus calculation of (1) is extracted from the IMG2 and copied to a predetermined address B on the RAM (S303).
[0057]
Next, a known correlation operation COR (A, B) is performed on the luminance distribution signals recorded at the address A and the address B, and a deviation δ between the two image signals is calculated (S304).
[0058]
Next, the defocus is calculated by a known function h (δ), and the defocus value is stored at a predetermined address D (x, y) reserved for recording the distance distribution on the RAM (S305). .
[0059]
Next, the value of x is increased by one, and the processing target is moved to an adjacent block (S306).
[0060]
Next, x is compared with the resolution m of the defocus map in the x direction (S307). When x <m is determined to be true (YES), the process returns to step S302, and the next block in the x direction is read. On the other hand, the defocus value is calculated and stored in the same manner as described above. If x <m is determined to be false (NO), x is initialized and y is increased by 1 (S308).
[0061]
Next, when the value of y is evaluated and it is determined that y <n is true, the process returns to step S302 again, and the operation on the next block sequence is started. When it is determined that y <n is false, the defocus calculation for all the blocks is completed, and the creation of the distance map ends (S310).
[0062]
Returning to the description of FIG.
[0063]
After the map is created, area division is performed (S203).
[0064]
For example, as shown in FIG. 8, when performing division processing while performing raster scanning from the upper left block of the screen as indicated by the arrow in the figure, the block G (x, y-1) above the block of interest G (x, y) ) And the left block G (x−1, y), it is possible to determine whether or not the adjacent block is the same block as a result. At this time, the blocks on the upper side (y = 0) and the left side (x = 0) of the screen do not have the upper block and the left block, respectively, so that no processing is performed on them.
[0065]
The result of the determination is recorded in the memories G (0,0) to G (m-1, n-1) on the RAM. First, a block of (x, y) = (0, 0) is registered as a group number g = 1, and when a group having a different area is detected, the number of g is increased by one and set as the group number of the block. .
[0066]
By this processing, for example, a shooting scene as shown in FIG. 9A is given a number for each group as shown in FIG. 9B.
[0067]
Since the numbering process itself is a known technique called "labeling method", a flowchart of the entire area division is omitted. Next, an "algorithm for determining whether or not adjacent blocks are in the same group" performed in the area division processing will be described below.
[0068]
FIG. 10 shows whether two blocks are the same object or different objects between a block of interest G (x, y) being scanned and a block G (x−1, y) on the left. It is a flowchart in the case of doing.
[0069]
The defocus value D (x, y) of the target block (G (x, y)) is set to the work variable d1 (S401), and the defocus value D (x-1, y) of the comparison block G (x-1, y). y) is copied to the work variable d2 (S402).
[0070]
Next, the function f is calculated using the defocus d1 of the target block G (x, y) as an argument, and the result is set as a threshold value T8 (S403).
[0071]
Here, the content of the function f (d) for determining the optimum threshold value for the defocus d of the target block will be described.
[0072]
As a high-accuracy method to suppress the imbalance of region division that occurs for objects at short distances and long distances, it is necessary to determine whether the angle between the object plane composed of two blocks and the optical axis is greater than a certain angle. There is a method of making a judgment.
[0073]
This will be described with reference to FIG. In the figure, point 0 is considered to be the origin of the coordinate system and at the same time to be the ideal optical center of the imaging system. The horizontal axis is the optical axis, and the left side of the origin is the object space. The plane parallel to the vertical axis on the right side in the drawing is the image plane of the optical system. Here, a case where distance information measured at two adjacent distance measuring points p0 and p1 on the imaging plane (considered here by distance information) is compared.
[0074]
When p0 and p1 are connected to the origin, respectively, assuming that the angles formed by the optical axis are φ0 and φ1, respectively, the existence areas of the objects observable by p0 and p1 are represented by straight lines p = −Ltanφ0 and p = −Ltanφ1 respectively. is there.
[0075]
If the observation results at the observation points p0 and p1 are the distances L0 and L1, respectively, the objects exist at A (L0, -L0 tan φ0) and B (L1, -L1 tan φ1) in the figure. Therefore, the plane formed by these two points can be considered as the object plane, and the angle θ between this plane and the optical axis is
θ = tan ^-1 [(L1tanφ1-L0tanφ0) / (L0-L1)]
Required by If the absolute value of this angle is larger than a predetermined threshold angle, the object can be considered to be the same object because it constitutes a surface nearly perpendicular to the optical axis, and if smaller than the threshold angle, it is determined to be another object. it can.
[0076]
Here, assuming that the distance between the intersection C of the object plane and the optical axis is LC, the distance differences L0 to L1 are
L0−L1 = [(tan θ / (tan θ−tan φ1)) − (tan θ / (tan θ−tan φ1))] × Lc
It can be seen that the distance difference increases in proportion to LC even when the angle is constant. Therefore, in order to detect a certain angle based on the difference in distance, the relationship between the threshold and the distance L must be determined.
TS = C1 L
What is necessary is just to make a proportional relationship like this. Here, C1 is a constant determined from the threshold angle θT, the distance a from the optical center to the imaging plane, the position of the distance measurement point, and the like.
C1 == [(1 / (tan θ− (p0 / a)) − (tan θ / (1 / (tan θ− (p1 / a))) × tan θ)
Can be represented by
[0077]
Since C1 includes p0 and p1, it must be calculated for every adjacent relationship. However, when the intervals between distribution points are equal and the difference between p0 and p1 is sufficiently small with respect to a, the screen is displayed. No matter where the adjacency relationship is, the value of C1 does not change much. Therefore, only one representative C1 value may be calculated, and this value may be used for calculation of another adjacent relationship.
[0078]
Thus, a means for calculating a threshold value for detecting a uniform angle from the distance has been found. Next, consider a means for setting a threshold for detecting a uniform angle from defocus.
d = (1 / fL-1 / L) -1-C2
There is a relationship. Here, fL is the focal length of the optical system, C2 is a value determined by the focal length fL and the assumed focal position LF,
C2 = (1 / fL−1 / LF) −1
Can be represented by
[0079]
Now, from the above relationship, the function f for determining the threshold from the defocus is
f (d) = C1 (1 / fL−1 / (d + C2) −1)
Can be represented by
[0080]
If this function is used as a threshold value, it is possible to obtain the same effect as determining whether or not an object at any distance is the same object based on a certain angle. Can be finely divided, and a distant object can be roughly divided.
[0081]
Further, in the "assumed focal position" LF, the initial position may be set in a camera such as a lens shutter camera in which the initial focal position is fixed, and the focal position may fluctuate, such as in a single-lens reflex camera. In this case, it is preferable to set the shooting distance (for example, about 2 m) which is considered to be used most frequently. In addition, in a camera having interchangeable lenses, values such as C1 and C2 are appropriately set according to the focal length of the lens, so that appropriate recognition can be performed regardless of what lens is attached.
[0082]
Also, in the case of a zoom lens or the like, appropriate recognition can be performed at any focal length by detecting the current focal length and appropriately setting C1 and C2.
[0083]
The above is a method of accurately eliminating the influence of distance.However, it is not necessary to completely eliminate the influence, and in cases such as when it is preferable to reduce the amount of calculation, the threshold value is reduced with an increase in defocus. It is conceivable to define a monotonically decreasing function as f as For example, f (d) = C3 / d (C3 is an appropriate constant). By introducing such a function, it is possible to improve the recognition result compared to the related art despite the relatively small amount of calculation. It is.
[0084]
Returning to the description of FIG.
[0085]
It is checked whether the absolute value of the difference between the defocus amounts is larger than a threshold value (S404).
If the difference is equal to or smaller than the threshold value, the flag variable Flag indicating whether the two blocks are the same is set to 1 (S405). If the difference is larger than the threshold value, the flag is set to 0 and the process ends (S406). ). Flag = 1 indicates that the two objects are the same, and Flag = 0 indicates that the two objects are distinct.
[0086]
The above determination is made for all the adjacencies of all the blocks, and the area division is completed.
[0087]
TS is set by the above expression f (d) = C1 (1 / fL−1 / (d + C2)) − 1 or f (d) = C3 / d.
[0088]
In the above expression, d may be d2 or an average value of d1 and d2.
[0089]
Returning to the description of FIG.
[0090]
After the area division, the characteristics of each area (each group) constituting the photographing space are evaluated, and a group representing the main subject is determined from all the groups (S204).
[0091]
As a method of determining the group representing the main subject, for each of the groups, characteristics such as average defocus, an area width, a height, and a position on a screen are respectively calculated and comprehensively evaluated. To determine a region considered to be the main subject.
[0092]
For example, the following main subject degree evaluation function can be considered.
(Main subject degree) = W1 × (width) × (height) + W2 / (distance from screen center) −W3 × (average defocus)
In the above equation, W1, W2, and W3 are weighting constants, the distance from the screen center is the distance between the screen center and the center of gravity of the area, and the average defocus is the average of the defocus of all blocks in the area. Represents. The main subject degree is calculated for all areas, and the subject having the highest main subject degree is determined as the main subject.
[0093]
As described above, one defocus is determined based on the defocus information in the area representing the main subject. As a method of determining the defocus, an average of all the blocks included in the area, a defocus of the closest block in the area, and the like can be considered.
[0094]
In the present embodiment, the image size information of the photographing lens 2 is determined. However, for example, when a lens having a small image size is attached, photographing by adapting the camera to the image size means that the photographing screen In this case, the diameter of the permissible circle of confusion, which generally defines the focusing state on the photographing screen, changes according to the screen size (diagonal length). The diameter also becomes smaller.
[0095]
At this time, even if the same object is used, the recognition result differs depending on the screen size, and in order to prevent the problem that the subject originally intended by the photographer is not correctly determined as the subject, the above-described main control in controlling the focus adjustment operation is performed. It becomes necessary to change the threshold value in the subject area estimation method according to the permissible circle of confusion.
[0096]
Hereinafter, the setting of the threshold based on the image size will be described.
[0097]
As described above, there are three types of image sizes (large, medium, and small) used in this embodiment, as described above.
[0098]
Reference numeral 50 denotes an image size “large”, and reference numeral 9a denotes an area of the imaging element 9 at that time. The diagonal length of this image sensor 9 is denoted by A. Reference numeral 51 denotes an image size "medium" which is 2/3 of the 50 image size. Reference numeral 9b denotes an area of the image sensor 9 having the image size 51, and the diagonal length is B. Reference numeral 52 denotes an image size "small", which is 1/3 of the image size. Reference numeral 9c denotes an area of the image sensor 9 having the image size 52, and the diagonal length is C.
[0099]
At this time, the following relationship is established between the three types of image sizes.
A: B: C = A: A × 2/3: A × 1/3
Therefore, by applying the above threshold value to the above-described relationship according to the image size, an appropriate threshold value is obtained.
[0100]
Returning to the main text, the CPU 100 controls the focus detection circuit 109 and the lens driving motor 25 so that the main subject determined in the subroutine is focused, and performs focus detection by the line sensor 11f based on the defocus information (S114). .
Next, it is determined whether or not the distance measurement of the determined main subject is possible (S115). If the distance measurement is not possible, the CPU 100 sends a signal to the LCD drive circuit 105 to display a warning on the LCD 21 in the finder (not shown). FIG.), The photographer is warned that the distance measurement is NG (S116), and this operation is continued until SW1 is turned off (S117).
[0101]
If the distance can be measured in the determined focus detection area and the position of the taking lens 3 is not in the focused position (S118), the CPU 100 sends a signal to the lens focus adjusting circuit 109 to drive the taking lens 3 by a predetermined amount (S118). S119). After driving the lens, the auto focus circuit 103 measures the distance again (S115), and determines whether or not the photographing lens 3 is at the in-focus position (S118).
[0102]
If the position of the photographing lens 3 is at the in-focus position in the predetermined focus detection area, the CPU 100 sends a signal to the LCD drive circuit 105 to perform in-focus display on the LCD 21 in the finder (not shown). It is notified that there is (S120).
[0103]
The photographer recognizes that the selected or selected focus detection area is incorrect (want to change) and turns off SW1 (S121), and then the camera waits until SW1 is turned on (S102). If the photographer continues to turn on SW1 (S121), the CPU 100 transmits a signal to the photometric circuit 102 to perform photometry (S122).
[0104]
At this time, in the case of the present embodiment, a known photometric calculation is performed by weighting a photometric region (not shown) including the focused focus detection region, and the exposure value is calculated. Further, it is determined whether or not SW2 is ON (S123). If SW2 is OFF, the state of SW1 is confirmed again (S121). As a result, if the switch SW2 is turned on, the CPU 100 controls the shutter control circuit 107, the motor control circuit 108, and the aperture control circuit 110, respectively, and starts capturing an image into the image sensor 9 (S124). After a predetermined exposure time has elapsed, the image signals stored in the image sensor 9 are temporarily stored in the memory 101b via the signal processing circuit 101c.
[0105]
Next, from the image data, the CPU 100 cuts out the image data within the imaging range set based on the image size information (S125), stores the data in the CPU 100, and ends a series of shutter release sequence operations. (S126).
[0106]
Thereafter, the camera waits until SW1 is turned on again (S102).
[0107]
In the present embodiment, the threshold for estimating the area where the main subject is present is changed based on the image size information. However, there is no problem if the threshold is changed based on the information based on the enlargement ratio of the electronic zoom.
[0108]
【The invention's effect】
According to an embodiment of the present invention, in an electronic camera capable of mounting interchangeable lenses having different image sizes, an electronic zoom that enlarges an image corresponding to a predetermined range of an image captured by an image pickup device has an image size of the interchangeable lens. In a camera that adapts the camera body, to obtain the image size information from the photographing lens to inform the photographer of the effective image size range and to estimate the existence area of the main subject in the scene according to each image size By properly setting the threshold of, it is possible to solve the problem that the recognition result differs depending on each image size (screen size) even for the same object, and to accurately determine a subject originally intended by the photographer. A camera that can be provided can be provided.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram of a digital single-lens reflex camera system according to the present invention.
FIG. 2 is a block diagram showing an electrical configuration of FIG.
FIG. 3 is an explanatory diagram of an image size.
FIG. 4 is a view for explaining the inside of a finder visual field of FIG. 1;
FIG. 5 is a flowchart for explaining the operation of the entire camera of FIG. 1;
FIG. 6 is a flowchart illustrating an operation of automatic focus detection area selection for recognizing an environment and determining a main subject.
FIG. 7 is a flowchart showing details of the map creation step of FIG. 6;
FIG. 8 is an explanatory diagram of a region dividing method.
FIG. 9 is a diagram showing an example of a labeling result.
FIG. 10 is a flowchart illustrating an operation of boundary determination.
FIG. 11 is a diagram for explaining an ideal threshold value.
[Explanation of symbols]
1: Camera body
2: Shooting lens
9: Image sensor
11: Focus detection device
11f: Area sensor
13: Field mask
50, 51, 52: Image size
100: CPU
101: Digital circuit
103: focus detection circuit
111: In-lens control circuit

Claims (1)

A camera body having a camera-side mount, and an interchangeable lens having a lens-side mount coupled to the camera-side mount;
Focus control means for controlling a focus adjustment operation of the lens based on a result of the focus detection means and the focus detection means,
Based on the information on the distance or defocus distribution of the target space, the difference or ratio of the information or the distance or defocus of the two distribution points is compared with a threshold, and the area corresponding to the two distribution points is determined according to the comparison result. Subject recognition means for determining whether are the same object,
Input means for inputting information representing the image size of the interchangeable lens to the camera body; and determining whether or not the image size of the interchangeable lens fits the camera body based on the information input by the input means. And an electronic circuit performing signal processing on an image signal representing an image on the image sensor formed by the interchangeable lens when the image is determined to be incompatible by the determiner. Adapting means for adapting the camera body to the image size of the interchangeable lens by electronic zoom for enlarging an image corresponding to a predetermined range of
An electronic camera having a threshold changing unit that changes the threshold based on information representing the image size or an enlargement ratio of the electronic zoom when at least the lens is replaced with a lens having a different image size and the electronic zoom is performed by the adapting unit. .

Images