JP2005055570A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera capable of obtaining a picture on which a main object is clearly photographed without bringing about an increase in cost and upsizing of the camera. <P>SOLUTION: The camera comprises a range finding part 10 which takes image of the object in a range finding area (step #6) after calculation of exposure control value (step #4), a main and sub object detection part 38 which calculates an object range at every small area and detects a main object and a sub object by using the object range (step #7, #8), a guide number calculation part 39 which calculates a guide number from the object range d1 of the main object detected by the main and sub object detection part 38 and an aperture value Fno calculated by an exposure control value calculation part (step #9) and, further, a guide number correction part 40 which reads out a flush light distribution characteristic and an image surface illumination characteristic from a storage part 43 (step #10, #11) and performs correction in accordance with the characteristics and the positions of the main objects in a photographing area by using the guide number calculated in the step #9 (step #12). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a camera including a flash light emitting unit such as a flash for irradiating a subject with a flash, and more particularly to a camera for controlling an exposure amount of a main subject when shooting is performed by irradiating a flash with the flash light emitting unit.

  For example, in a camera that performs a focusing operation using an image in the center of the shooting area, and the subject is placed on the periphery side of the shooting area, the photographer is focused on the main subject. Lock and change the camera orientation to place the subject at the desired position on the periphery of the shooting area, and then issue a shooting instruction with the shutter button to focus on the main subject placed on the periphery Can be obtained.

  By the way, when the flash is used to shoot a subject with a flash, the amount of the flash that is normally irradiated on the subject in the shooting area is set to the subject located at the center of the shooting area. And is smoothly reduced from the center of the imaging region toward the periphery. In addition, when the photographic lens is incident on the outer periphery of the photographic lens at an angle, the amount of light incident per unit area of the photographic lens is incident on the center of the photographic lens. As a result, it becomes darker as it goes to the peripheral side of the imaging region.

  Therefore, conventionally, when shooting is performed by irradiating the subject with flash with the main subject arranged on the peripheral side of the imaging region as described above, the optical image of the main subject is appropriate for the imaging surface of the image sensor. As a result, the main subject is a dark image.

In the following Patent Document 1, for the purpose of appropriately exposing a main subject, a xenon tube that emits illumination light, a reflector that reflects the light in the direction of the subject, and an optical panel that spreads a light beam And any one of the xenon tube, the reflector and the optical panel is configured to move relative to other members by driving an actuator.
Japanese Patent Laid-Open No. 2001-21962

  However, in Patent Document 1, a member or mechanism for driving any one of a xenon tube, a reflector, and an optical panel is required, resulting in an increase in the cost and size of the camera.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a camera capable of obtaining an image in which a main subject is clearly captured without increasing the cost and size of the camera. To do.

  The invention according to claim 1 is an imaging unit that photoelectrically converts a light image of a subject formed by an optical system, a flash output unit that irradiates a subject with flash, a main subject detection unit that detects a main subject, An exposure amount deriving unit for deriving an exposure amount to the imaging unit, a storage unit for storing light distribution characteristics of the flash output unit and an image plane illuminance characteristic of the optical system, and flashing the subject by the flash output unit Then, when the light image of the subject is photoelectrically converted by the imaging unit, the exposure for correcting the derived exposure amount according to the light distribution characteristic and the image plane illuminance characteristic and the position of the main subject in the photographing region. And a quantity correction unit.

  According to a second aspect of the present invention, in the camera according to the first aspect of the present invention, the camera includes a subject luminance detection unit that detects a luminance of a subject including the main subject, and the exposure amount correction unit includes the subject luminance of the main subject. The corrected exposure amount is corrected again according to the relationship with the subject brightness of other subjects.

  According to a third aspect of the present invention, in the camera according to the first or second aspect, the main subject detection unit has a function of detecting a sub-subject having the second highest importance after the main subject, and the exposure amount correction unit. Is characterized in that the corrected exposure amount is corrected again in accordance with the relationship between the subject distance of the main subject and the subject distance of the sub-subject.

  According to a fourth aspect of the present invention, in the camera according to any one of the first to third aspects, the main subject detection unit has a function of detecting a sub-subject having the second highest importance after the main subject, and the exposure. The amount correction unit corrects the corrected exposure amount again according to the relationship between the distance from the center of the imaging region to the main subject and the distance from the center to the sub-subject. .

  According to a fifth aspect of the present invention, in the camera according to any one of the first to fourth aspects, the aperture control for controlling the aperture diameter of the aperture based on the aperture and the exposure amount corrected by the exposure amount correction unit. And a section.

  According to a sixth aspect of the present invention, in the camera according to any one of the first to fifth aspects, the amount of flash light emitted from the flash output unit is controlled based on the exposure amount corrected by the exposure amount correction unit. And a flash control unit.

  According to the first aspect of the present invention, when the flash output unit irradiates the subject with flash light and photoelectrically converts the light image of the subject to the imaging unit, the light distribution characteristic, the image plane illuminance characteristic, and the main subject Since the derived exposure amount is corrected according to the position in the imaging region, the light image of the main subject is exposed to the imaging unit with an appropriate exposure amount.

  According to the second aspect of the present invention, since the corrected exposure amount is corrected again according to the relationship between the subject brightness of the main subject and the subject brightness of another subject, an optical image of the main subject is obtained. By correcting the exposure amount so that the imaging unit is exposed with an appropriate exposure amount, it is possible to prevent or suppress the image of another subject from becoming a white image.

  According to the third aspect of the invention, since the corrected exposure amount is corrected again according to the relationship between the subject distance of the main subject and the subject distance of the sub-subject, the optical image of the main subject is By correcting the exposure amount so that the imaging unit is exposed with an appropriate exposure amount, it is possible to prevent or suppress the image of another subject from becoming a white image.

  According to the fourth aspect of the present invention, the corrected exposure amount is corrected again according to the relationship between the distance from the center of the imaging region to the main subject and the distance from the center to the sub-subject. By correcting the exposure amount so that the light image of the main subject is exposed to the imaging unit with an appropriate exposure amount, it is possible to prevent or suppress the image of the other subject from becoming a white image.

  According to the fifth aspect of the present invention, since the aperture diameter of the diaphragm is controlled based on the corrected exposure amount, the main subject or the entire subject including the main subject is too dark or too bright. A beautiful image can be obtained.

  According to the sixth aspect of the present invention, since the amount of flash light emitted from the flash output unit is controlled based on the corrected exposure amount, the main subject or the entire subject including the main subject is too dark. A beautiful image can be obtained without being too bright.

  Embodiments of a camera according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a front view showing the configuration of the camera, and FIG. 2 is a rear view of the camera.

  As shown in FIGS. 1 and 2, the camera 1 includes an imaging optical system 2 disposed at an appropriate position on the front surface, a mode setting dial 3 disposed at an appropriate position on the upper surface, and a shutter button disposed at an upper corner. 4. LCD (Liquid Crystal Display) 5 disposed below the viewfinder, cross selection button 6 disposed on the side of the LCD 5, setting button 7 disposed below the LCD 5, and a suitable position on the back. An electronic view finder EVF 8, a photometric unit 9 disposed above the imaging optical system 2, a distance measuring unit 10 disposed adjacent to the photometric unit 9, and an electronic view And a flash 11 disposed above the viewfinder.

  Referring to FIG. 5, the imaging optical system 2 is provided with a photographing lens and a diaphragm 18 including a zoom lens 16 for changing the photographing magnification and a focus lens 17 for adjusting the focal point, protruding from the camera body 1a. The optical image of the subject is formed on the image sensor 20 (see FIG. 5). The zoom lens moves in the direction of the optical axis by operating the cross selection button 6.

  The mode setting dial 3 is a substantially disk-shaped member that can be rotated in a plane substantially parallel to the upper surface of the camera 1, and is a shooting mode for shooting a still image or a moving image, a playback mode for playing back a shot image, or a power source. This is for selectively selecting a mode and a function mounted on the camera 1 such as ON / OFF switching. Although not shown, on the upper surface of the mode setting dial 3, characters indicating the respective functions are written at predetermined intervals along the outer peripheral edge, and are set at positions facing an index provided on the camera body 1a side. The function corresponding to the selected character is executed.

  The shutter button 4 is a button that is pressed in two stages of half-press (S1: ON) and full-press (S2: ON). In the shooting mode, when the shutter button 4 is not operated, the optical image of the subject is captured every 1/30 (second), the live view image is displayed on the LCD 5, and the shutter button 4 is half-pressed. Then, in addition to the display of the live view image, the camera 1 is set in an imaging standby state in which the shutter speed is set and further pressed, and when it is fully pressed, the subject image to be recorded in the image storage unit 32 described later is captured. Is done.

  The LCD 5 includes a color liquid crystal panel, displays a captured image on a monitor (corresponding to a live view image display) and a recorded image reproduction display, and displays a setting screen for functions and modes installed in the camera 1. Is.

  The cross selection button 6 includes buttons Z1 to Z4 arranged in a cross shape, and is used for changing the shooting magnification by moving the zoom lens in the wide direction or the tele direction, or performing exposure correction. .

  The setting button 7 is a button for performing operations for various functions mounted on the camera 1.

  The camera 1 of this embodiment includes a mode in which a photographer designates a distance measuring point and performs focus adjustment using a distance value (subject distance) at the distance measuring point. Is added to this mode, and the cross-select button 6 has a function for designating a distance measuring point. These functions will be described later.

  The EVF 8 is provided with a color liquid crystal panel and an eyepiece, and displays an image of the subject in the shooting area. The subject image can be viewed by looking into the eyepiece window 8a.

  Although not shown, the photometric unit 9 includes a photometric optical system and a photometric sensor that captures a light image formed by the optical system, and performs photometry using these members. The subject brightness is calculated from the output of the photometry unit 9, and the detected subject brightness is used to determine the exposure control value (the exposure time of the image sensor 20 corresponding to the aperture value and the shutter speed).

  FIG. 3A is a cross-sectional view showing the internal configuration of the distance measuring unit 10 in the present embodiment, and FIG. 3B is a diagram showing the configuration of the distance measuring unit 10.

  As shown in FIG. 3A, the distance measuring unit 10 has a pair of distance measuring optical systems 11 and 12 which have an optical axis different from the optical axis of the imaging optical system 2 and are arranged in parallel. A distance measuring sensor unit 13 disposed substantially on the imaging plane of the distance optical systems 11 and 12 is used, and a subject is imaged by a passive method using these optical systems 11 and 12 and the distance measuring sensor unit 13. The distance measurement unit 10 changes the distance measurement range relative to the change in imaging magnification, and the distance measurement sensor unit 13 captures an image in a range specified by an unillustrated index provided on the LCD 5 and the EVF 8. .

  As shown in FIG. 3B, the distance measuring sensor unit 13 includes a plurality of line sensors L1 to L10 made of a solid-state imaging device such as a CCD, and a drive signal for data transfer to each of the line sensors L1 to L10. And a control circuit (not shown) for generating

  When the longitudinal direction of the line sensors L1 to L10 is the X-axis direction and the direction perpendicular to the X-axis direction is the Y-axis direction, the line sensors L1 to L5 are composed of line sensors L1 to L5 arranged substantially parallel to the Y-axis direction at predetermined intervals. A line sensor group 14 and a line sensor group 15 including line sensors L6 to L10 disposed substantially parallel to the Y axis direction at the predetermined interval are arranged in parallel at a predetermined interval in the X axis direction. .

  A subject optical image is formed on the imaging surface of the line sensor group 14 by the ranging optical system 11, while a subject optical image is formed on the imaging surface of the line sensor group 15 by the ranging optical system 12. Then, based on the pixel signals output from each of the line sensor groups 14 and 15, the distance to the subject (subject distance) is detected based on the principle of triangulation, which is a well-known technique.

  As shown in FIG. 3 and FIG. 4A, a range (hereinafter referred to as a distance measurement area) AR2 measured by the line sensor group 14 or the line sensor group 15 is, for example, 70% of the shooting area (shooting range) AR1. Is set in a range indicated by hatching having an area of.

  As described above, the camera 1 according to the present embodiment includes a function in which a photographer designates a distance measuring point and performs focus adjustment using a distance value (subject distance) calculated for the distance measuring point. ing.

  As shown in FIG. 4A, when the mode is set so that the photographer can designate a distance measuring point, a cursor X for designating the distance measuring point is displayed in the photographing screen of the LCD 5 or EVF 8. . Then, when one person is arranged as a main subject in the left peripheral area of the shooting area AR1, and two people lined up on the left and right are arranged as sub-subjects at a substantially central portion of the shooting area AR1, the image is taken. As shown in 4 (b), when the operation of determining the subject to be focused is input with the cross selection button 6 by aligning the position of the cursor X with the position of the person, the subject calculated by the distance measuring unit 10 is input. The focusing operation is performed based on the subject distance. Note that an arrow A in FIG. 4A shows a state in which the cursor X moves by performing an operation for adjusting the position of the cursor X to the position of the main subject.

  The flash 11 is an arc tube composed of a xenon tube or the like that outputs electric energy by discharging electric energy, a reflector that reflects flash light (flash light) emitted from the arc tube toward the front of the camera 1, and a flash light within a predetermined range. And a flash control circuit (see FIG. 5) for outputting electric energy to the discharge tube.

  FIG. 5 is a block diagram showing the configuration of the camera 1.

  The camera 1 includes a photographing optical system 2, an image sensor 20, a signal processing unit 21, an A / D conversion unit 22, a timing control circuit 23, an image processing unit 24, an image memory 28, VRAMs 29 and 30, a drive unit 31, and an image storage unit. 32, an input operation unit 33 and a control unit 34.

  The photographing optical system 2 corresponds to the photographing optical system shown in FIG. The zoom lens 16 is driven in the optical axis direction by the motor M1, the focus lens 17 is driven in the optical axis direction by the motor M2, and the diaphragm 18 is driven by the motor M3.

  The photographic optical system 2 includes an encoding plate in which a plurality of code patterns are formed at a predetermined pitch in the optical axis direction within a moving range of the photographic lens, and a photographic lens while being in sliding contact with the encoding plate. A lens position detector 19 including an encoder brush that moves integrally is disposed. The lens position detection unit 19 detects the position of the photographing lens by reading the code pattern on the encoding plate with an encoder brush. The detected position of the photographing lens is used for calculating the focal length.

  The imaging element 20 has a plurality of photoelectric conversion elements, such as photodiodes, arranged in a two-dimensional matrix, and R (red), G (green), and B (blue) colors on the light receiving surface of each photoelectric conversion element. This is a CCD (Charge Coupled Device) color area sensor in which filters are arranged at a ratio of 1: 2: 1. The image sensor 20 converts the light image of the subject formed by the photographing lens into analog electrical signals (image signals) of R (red), G (green), and B (blue) color components, and R, G, Output as B color image signals. Note that the imaging device 20 may be configured by a solid-state imaging device such as a CMOS (Complementary Metal-Oxide Semiconductor).

  The image pickup device 20 performs an image pickup operation such as start and end of an exposure operation of the image pickup device 20 and reading of an output signal of each pixel (horizontal synchronization, vertical synchronization, transfer) by the timing control circuit 23 described later. Be controlled.

  The signal processing unit 21 performs predetermined analog signal processing on the analog image signal output from the image sensor 20. The signal processing unit 21 includes a CDS (correlated double sampling) circuit and an AGC (auto gain control) circuit. The CDS circuit reduces noise of the image signal, and the AGC circuit adjusts the level of the image signal.

  The A / D conversion unit 22 converts the analog R, G, B image signals output from the signal processing unit 21 into digital image signals (hereinafter referred to as digital signals) composed of a plurality of bits. is there.

  The timing control circuit 23 generates clocks CLK1 and CLK2 based on the reference clock CLK0 output from the control unit 34, and outputs the clock CLK1 to the image sensor 20 and the clock CLK2 to the A / D conversion unit 22. Thus, the operations of the image sensor 20 and the A / D converter 22 are controlled.

  The image processing unit 24 applies a black level correction circuit 25 that corrects the black level to a reference black level for each of the R, G, and B digital signals that have been A / D converted by the A / D conversion unit 22. A white balance circuit 26 that performs level conversion of digital signals of R (red), G (green), and B (blue) color components and R (red), G (green), B ( A γ correction circuit 27 that corrects the γ characteristics of the digital signals of each color (blue) is provided.

  The image memory 28 is a memory that temporarily stores the image data output from the image processing unit 24 and is used as a work area for performing processing described later on the image data by the control unit 34.

  The VRAM 29 has a pixel signal recording capacity corresponding to the number of pixels of the LCD 5, and is a buffer memory between the control unit 34 and the LCD 5. The VRAM 30 has a pixel signal recording capacity corresponding to the number of pixels of the EVF 8. This is a buffer memory for the control unit 34 and the EVF 8.

  The drive unit 31 includes a motor M1 that drives the zoom lens in the optical axis direction, a motor M2 that drives the focus lens in the optical axis direction, a motor M3 that drives the diaphragm, and the like.

  The image storage unit 32 includes a memory card, a hard disk, and the like, and stores an image generated by the control unit 34.

  The input operation unit 33 includes the mode setting dial 3, the shutter button 4, the cross selection button 6, the setting button 7, and the like described above.

  The control unit 34 includes a microcomputer having a storage unit (a storage unit 43 described later) including, for example, a ROM that stores a control program and a RAM that temporarily stores data, and each of the members included in the camera 1. The drive is associated with each other and controlled. The control unit 34 includes a subject luminance detection unit 35, an exposure control value calculation unit 36, and a focal length calculation unit 37.

  The subject brightness detection unit 35 detects the subject brightness based on the output of the photometry unit 9.

  The exposure control value calculation unit 36 calculates an exposure control value (shutter speed and aperture value) based on the subject brightness detected by the subject brightness detection unit 35. The exposure control value calculation unit 36 calculates the exposure control value based on the subject brightness at the center, assuming that the main subject is located at the center of the shooting area.

  The focal length calculation unit 37 calculates the focal length based on the output of the lens position detection unit 19.

  By the way, when the subject is irradiated with the above-described flash 11, the amount of flash light applied to the subject in the shooting region is normally set so that the subject located at the center of the shooting region is irradiated with an appropriate amount of flash light. The distribution is set and decreases smoothly from the center of the imaging region toward the periphery.

  FIG. 6 shows an example of an EV (Exposure Value) when the subject in the imaging area indicated by the arrow B is irradiated with flash light, and an example of the difference in the amount of irradiation light between the central area a and the peripheral areas b to d of the imaging area. It is a value.

  In FIG. 6, the peripheral region b outside the central region a is deficient by 0.2 EV, for example, compared to the central region a, and the peripheral region c outside the peripheral region b is, for example, 0.4 EV, the central region a. This indicates that the peripheral region d outside the peripheral region c is insufficient compared with the central region a by, for example, 1.0 EV. Hereinafter, the light quantity characteristic of the irradiation light of the flash 11 having such a light quantity distribution is referred to as a flash light distribution characteristic.

  Further, in the photographic lens, the light incident on the outer peripheral side of the photographic lens is incident on the photographic lens obliquely, so that the amount of light incident per unit area of the photographic lens enters the central region of the photographic lens. As a result of being less than light, it has the characteristic of becoming darker as it goes to the peripheral side of the imaging region.

  FIG. 7 shows an example of the difference in the amount of transmitted light between the center region e and the peripheral regions f and g in the photographing region when the light image of the subject in the photographing region indicated by the arrow C is transmitted through the photographing lens. This is expressed in terms of Exposure Value.

  In FIG. 7, the peripheral region f outside the central region e is deficient by, for example, 0.2 EV compared to the central region e, and the peripheral region g outside the peripheral region f is, for example, 0.4 EV, the central region a. It is shown that there is a shortage compared to. Hereinafter, the light quantity characteristic of the transmitted light of the photographing lens having such a light quantity distribution is referred to as an image plane illuminance characteristic.

  Due to these characteristics, when flash shooting is performed in a state where the main subject is arranged in the peripheral region of the shooting region, the exposure amount of the light image of the main subject on the imaging surface of the image sensor 20 becomes insufficient, and the main subject The image becomes darker.

  Therefore, in the present embodiment, the flash irradiation amount is adjusted so that the light image of the main subject is exposed on the imaging surface of the image sensor 20 with an appropriate exposure amount.

  In addition, when there is a subject (hereinafter referred to as a sub-subject) that is considered to be the next most important after the main subject in the shooting area, the exposure amount of the sub-subject becomes excessive due to the adjustment of the irradiation amount described above, In order to prevent or suppress the occurrence of so-called whitening, in which the image of the sub-subject becomes a white flying image, the adjusted irradiation amount is adjusted again.

  In order to realize such a function, the control unit 34 further includes a main / sub-subject detection unit 38, a guide number calculation unit 39, a guide number correction unit 40, a guide number re-correction unit 41, and a light emission control unit 42. And a storage unit 43.

  The main / sub-subject detection unit 38 detects the main subject and the sub-subject using the pixel signal output from the distance measuring unit 10. Hereinafter, this detection method will be described.

  As will be described later, in the present embodiment, the imaging region of the imaging device 20 is divided into a plurality of blocks, subject distances are calculated for the images of the respective blocks, and a main subject and a sub-subject are detected from these subject distances. On the other hand, since the subject distance is calculated from the output of the distance measuring unit 10, in order to derive the subject distance of each block from the output of the distance measuring unit 10, each pixel and block of the distance measuring unit 10 Need to be associated.

  FIG. 8 is a diagram showing a method of associating each pixel of the distance measuring unit 10 with a block. FIG. 8A shows an image of a subject in the area indicated by the arrow D by the distance measuring unit 10, and FIG. ) Shows a case where a subject in substantially the same area is imaged by the image sensor 20.

  First, as shown in FIG. 8A, the main / sub-subject detection unit 38 divides the imaging area of each line sensor of the distance measurement unit 10 into a predetermined number (i) of small areas in the longitudinal direction. The subject distance is calculated for each small area from the pixel data in each small area.

On the other hand, as shown in FIG. 8B, the main / sub-subject detection unit 38 divides the imaging area of the imaging device 20 into small blocks of m vertical and n horizontal. At that time, the imaging region of the imaging device 20 is divided in the vertical direction by the number of line sensors of the distance measuring unit 10, and is divided in the horizontal direction by the number of divisions of one line sensor (i). That is, if the number of line sensors is j, m = j and n = i.
Then, each small block of the imaging area and the small area of the line sensor are made to correspond one-to-one, and the subject distance corresponding to each small area of the line sensor is set as the subject distance of the corresponding small block. That is, the line sensor is located at the bth from the top (1 ≦ b ≦ 5 (the number of line sensors in the line sensor group in the present embodiment)), and is the ath sensor from the left (1 ≦ a ≦ i). If the area corresponds to a small block (x, y) (1 ≦ x ≦ n, 1 ≦ y ≦ m) of the imaging area, the subject distance of the subject in the small area (a, b) is reduced. The subject distance in block (X, Y) is used.

  Then, for example, the technique of Japanese Patent Laid-Open No. 14-298138 proposed by the present applicant is adopted to detect the main subject (person). That is, a three-dimensional coordinate system is set in which the horizontal direction of the shooting area is the X axis, the vertical direction is the Y axis, and the subject distance is an axis perpendicular to the XY plane (Z axis), corresponding to each distance measuring point. A three-dimensional distance image obtained by plotting the subject distance in this coordinate system is generated. Then, a person is detected from the distance image based on the ratio of the actual human face width and body width.

  When there is one person in the shooting area, the main / sub-subject detection unit 38 sets the person as a main subject and, in addition to the main subject, at a position relatively close to the camera 1 (a position where the subject distance is relatively small) If a subject other than a person (for example, a car or a building) exists, that subject is set as a sub-subject. When there are two or more persons separated from each other in the shooting area, the subject (or a plurality of subjects) arranged at a position specified by a method described later is set as the main subject, and the remaining subjects are set as sub-subjects. To do.

  When the main subject and the sub-subject are both persons, the main / sub-subject detection unit 38 distinguishes between the main subject and the sub-subject as follows, for example.

  Normally, when photographing two or more persons who are separated from each other, it is considered that the main subject is arranged closer to the center of the photographing region than the sub-subject. Then, the person located closer to the center in the shooting area is set as the main subject. Also, since the main subject is often closer to the camera 1 than the sub-subject, a subject with a shorter subject distance (subject located closer to the camera 1) is set as the main subject.

  Further, as described above, the camera 1 of the present embodiment has a mode for designating a distance measuring point, and when a distance measuring point is designated in this mode, the position designated as the distance measuring point. Is set as the main subject, and other persons are set as sub-subjects. In this case, the main subject and the sub-subject can be distinguished even when the main subject is arranged on the peripheral side of the shooting area from the sub-subject or when the main subject is located farther from the camera 1 than the sub-subject. .

  When the main / sub-subject detection unit 38 detects the main subject / sub-subject as described above, the main / sub-subject detection unit 38 sets the subject luminance of the block to which the main subject / sub-subject belongs as the main subject / sub-subject luminance.

  The guide number calculation unit 39 calculates a guide number GN based on the following equation 1 from the subject distance d1 of the main subject detected by the main sub-subject detection unit 38 and the aperture value Fno calculated by the exposure control value calculation unit 36. Is to be calculated. The guide number calculation unit 39 constitutes an exposure amount deriving unit in the claims.

GN = d1 × Fno (1)
The guide number correction unit 40 is operated by the guide number calculation unit 39 according to the position of the main subject detected by the main / sub-subject detection unit 38 and the flash light distribution characteristic and the image plane illuminance characteristic stored in the storage unit 43. The calculated guide number GN is corrected. The guide number correction unit 40 constitutes an exposure amount correction unit in the claims.

  For example, the flash light distribution characteristics and the image plane illuminance characteristics are as shown in FIGS. 6 and 7, and the flash light distribution distribution is in the −0.4 EV region and the image plane illuminance distribution is in the region of −0.2 EV. When the main subject is arranged, the guide number correction unit 40 corrects the guide number GN as follows.

  First, in the flash light distribution characteristic, if a relative light amount value (hereinafter referred to as a relative light amount value) with respect to the center region a is represented by D1, the main subject is arranged in a region of −0.4 EV of the flash light distribution. In this case, D1 = −0.4EV. Further, in the image plane illuminance characteristic, if the relative light quantity value with respect to the center area e is expressed as D2, when the main subject is arranged in a region of −0.2 EV of the image plane illuminance distribution, D2 = −0.2 EV. Become. Therefore, due to the flash light distribution characteristic and the image plane illuminance characteristic, the relative light quantity value with respect to the central area a of the main subject arranged at this position is D1 + D2 = −0.6 EV, which is 0.6 EV compared to the central area a. Only the amount of light will be insufficient.

  FIG. 9 shows the light quantity distribution of the relative light quantity values obtained for all the areas in the photographing area based on the flash light distribution characteristics shown in FIG. 6 and the image plane illuminance characteristics shown in FIG. . This light quantity distribution is obtained by adding the relative light quantity values D1 and D2 of the corresponding regions in the light distribution of the flash and the image plane illuminance distribution of the photographing lens.

  That is, as shown in FIG. 9, the sizes of the regions a to d in FIG. 6 and the regions e to g in FIG. 7 are region a = region e, region c <region f, and region d = region g. In this case, the relative light quantity value of the center area a (or area e) is 0 EV. The relative light amount value in the peripheral region b is −0.4 EV (= −0.2 EV + (− 0.2 EV)), and the relative light amount value in the peripheral region c is −0.6 EV (= −0.4 EV + (− 0. 2EV)), the relative light amount value of the peripheral region f is -1.2 EV (= -0.2 EV + (-1.0 EV)), and the relative light amount value of the peripheral region d (g) is -1.4 EV (= -1. 0EV + (− 0.4EV)).

  As described above, when the guide number correction unit 40 obtains the relative light quantity value based on the flash light distribution characteristic and the image plane illuminance characteristic, the light image of the main subject is exposed on the imaging surface of the image sensor 20 with an appropriate exposure amount. In other words, in the above example, as shown in FIG. 10, the guide number GN is corrected so that the relative light quantity value of the main subject is 0 EV.

  The guide number for setting the relative light amount value of the main subject to 0 EV is based on the following equations (2) and (3) using the relative light amount value based on the flash light distribution characteristic and the image plane illuminance characteristic calculated as described above. Can be calculated.

ΔEV = D1 + D2 (2)
GN ′ = GN / (√2) Δ ^EV (3)
For example, when the subject distance d1 is 3 (m), the aperture value Fno is 4.0, and the guide number GN is calculated as 3 × 4.0 = 12, the main subject is in the shooting area. If the above example arranged in the peripheral region is applied, ΔEV = D1 + D2 = −0.6 (EV), and thus the corrected guide number GN ′ is GN ′ = GN / (√2) Δ ^EV = 12 / (√2) ^−0.6 = 14.8.

  The guide number re-correction unit 41, when performing flash photography based on the guide number GN ′ calculated by the guide number correction unit 40, the exposure amount of the sub subject becomes excessive, and the image of the sub subject flies white. When it is determined that a so-called white-out occurs as an image, the calculated guide number GN ′ is changed.

  That is, when the guide number is corrected so that the exposure amount of the main subject is appropriate, the exposure amount to the image sensor 20 becomes larger as the subject on the center side of the photographing region becomes, as shown in FIG. When the sub-subject is located closer to the center of the shooting area than the main subject, the sub-subject exposure amount is larger than the main subject exposure amount, and when the difference between the exposure amounts is large, the sub-subject image flies white . In this case, the difference between the exposure amount of the sub-subject and the exposure amount of the main subject is determined by the relative relationship between the distances from the center of the shooting area to the main subject and the sub-subject.

  Further, since the exposure amount increases as the subject distance becomes smaller (the subject closer to the camera 1), as shown in FIG. 11B, when the sub subject is located on the camera 1 side with respect to the main subject, When the exposure amount is larger than the exposure amount of the main subject and the difference between the exposure amounts is large, the sub-subject image flies white. In this case, the difference between the exposure amount of the sub subject and the exposure amount of the main subject is determined by the relative relationship between the subject distances of the main subject and the sub subject.

  Furthermore, if the subject is bright, for example, a sub-subject wearing red clothes or a yellow car, the image of the sub-subject may fly white when flash photography is performed.

  From the above, the guide number re-correction unit 41 is the ratio r1 / r2 between the distance r1 from the center of the shooting area to the main subject and the distance r2 to the sub-subject, the subject distance d1 of the main subject and the subject distance of the sub-subject. The guide number GN ′ corrected by the guide number correction unit 40 according to the ratio d2 / d1 to d2 and the luminance of the sub-subject obtained from the output of the photometry unit 9 is again calculated based on the following equation (4). to correct.

GN ″ = GN ′ × k (where k is a positive decimal number) (4)
In other words, the expression (4) indicates that the guide number GN ′ in which the light emission amount of the flash 11 is corrected by the guide number correction unit 40 in order to prevent or suppress the white image of the sub-subject from flying white due to the flash light emitted from the flash 11 It means to make it smaller than the light emission amount corresponding to.

  However, when the sub-subject is not a person, the ratio d2 / d1 between the subject distance d1 of the main subject and the subject distance d2 of the sub-subject, the distance r1 from the center of the shooting area to the main subject, and the sub-subject From the ratio r1 / r2 to the distance r2 and the luminance of the sub-subject, only when the light image of the sub-subject exceeds a preset allowable value from the exposure value that is appropriately exposed on the imaging surface of the image sensor 20. Re-correct the guide number GN '.

  In the case of something other than a person, even if it is slightly white, it is often within the allowable range. Therefore, when it is within the allowable range, the re-correction process is not performed, so that the shutter button 4 When fully depressed, the imaging operation can be executed promptly. The above-described allowable value corresponds to the upper limit value of the allowable range.

  Based on the guide number GN ′ calculated by the guide number correction unit 40 or the guide number GN ″ after correction when the guide number is corrected again by the guide number re-correction unit 41, the light emission control unit 42 11, in this embodiment, the light emission time of the flash 11 is controlled.

  The storage unit 43 stores the above-described flash light distribution characteristics and image plane illuminance characteristics. Since the flash light distribution characteristic varies depending on the focal length, the storage unit 43 stores the flash light distribution characteristic corresponding to the focal distance.

  FIG. 12 is a flowchart showing a series of imaging operations including exposure amount correction processing according to the present invention. In the following imaging operation, it is assumed that the flash 11 is irradiated with flash light.

  As shown in FIG. 12, when the shutter button 4 is half-pressed (S1: ON) (YES in step # 1), the photometry unit 9 captures a light image of the subject (step # 2), and the subject luminance detection unit 35 Detects the subject luminance from the output of the photometry unit 9 (step # 3), and the exposure control value calculation unit 36 calculates the exposure control value (shutter speed and aperture value) based on the calculated subject luminance (step # 3). # 4). Further, the focal length calculation unit 37 calculates the focal length from the position of the photographing lens detected by the lens position detection unit 19 (step # 5).

  Further, the distance measuring unit 10 captures an image of the subject in the distance measuring area (step # 6), and the main / sub-subject detection unit 38 calculates the subject distance for each small area, and uses the subject distance and the main subject and the sub-subject. A subject is detected (steps # 7 and # 8). At this time, the main sub-subject detection unit 38 also determines whether or not the sub-subject is a person, and also detects the subject distance of the main subject and the sub-subject, the subject brightness, and the distance from the center of the shooting area. To do.

  Then, the guide number calculation unit 39 calculates the guide number GN from the subject distance d1 of the main subject detected by the main / sub-subject detection unit 38 and the aperture value Fno calculated by the exposure control value calculation unit (step) # 9).

  Next, the guide number correction unit 40 reads the flash light distribution characteristic and the image plane illuminance characteristic from the storage unit 43 (steps # 10 and # 11), and according to these characteristics and the position of the main subject in the photographing region, The guide number GN calculated in step # 9 is corrected using the above-described equations (2) and (3) (step # 12). This is because the light image of the main subject is exposed to the image pickup surface of the image pickup device 20 with an appropriate exposure amount.

  Further, when there is a sub-subject (YES in step # 13) and the sub-subject is a person (YES in step # 14), the guide number re-correction unit 41 determines the subject distance d1 of the subject and the sub-subject. The ratio d2 / d1 to the subject distance d2, the ratio r1 / r2 between the distance r1 from the center of the shooting area to the main subject and the distance r2 to the sub-subject, and the sub-subject subject obtained from the output of the photometry unit 9 Depending on the brightness, the guide number GN calculated in step # 9 is re-corrected using the equation (4) (step # 15). The reason for this processing is to prevent or suppress the image of a person as a sub-subject from flying white.

  On the other hand, if the sub-subject is something other than a person (NO in step # 14), it is determined whether or not the sub-subject is within a predetermined value from the appropriate exposure value (step # 16), and the sub-subject is appropriate. When the exposure value exceeds a predetermined value (NO in step # 16), the guide number re-correction unit 41 sets the ratio d2 / d1 between the subject distance d1 of the subject and the subject distance d2 of the sub-subject from the center of the shooting area. According to the ratio r1 / r2 between the distance r1 to the subject and the distance r2 to the sub-subject, and the luminance of the sub-subject obtained from the output of the photometry unit 9, the guide number GN ′ corrected in step # 12 is obtained. Recorrection is performed using equation (4) (step # 17). In the case of processing other than a person in this way, even if it is slightly white, it is often within the allowable range, so that if it is within the allowable range, the re-correction processing is not performed. Thus, when the shutter button 4 is fully pressed, the imaging operation can be performed promptly.

  On the other hand, when the sub-subject is within the predetermined value from the appropriate exposure value (YES in step # 16), the guide number re-correction unit 41 does not perform the re-correction processing of the guide number GN ', but in step # 18. Proceed to processing. Also, in step # 13, if there is no sub-subject (NO in step # 13), the guide number GN 'is not re-corrected and the process proceeds to step # 18.

  When the shutter button 4 is fully pressed (S2: ON, YES in step # 18), the flash 11 is set to the guide number GN 'corrected in step # 12 or the guide number GN in steps # 15 and # 17. If 'is re-corrected, light is emitted with the flash emission amount of the guide number GN "after the change, and the image sensor 20 is exposed (step # 19).

  Thereafter, the pixel signal of the image sensor 20 is subjected to processing such as gamma correction and white balance (step # 20), and an image to be recorded in the image storage unit 32 is displayed on the LCD 5 or EVF 8 (step # 21). Recording is performed in the image storage unit 32 (step # 22).

  As described above, since the calculated guide number GN is corrected in accordance with the flash light distribution characteristic and the image plane illuminance characteristic and the position of the main subject in the shooting area, the main subject is dark when performing flash shooting. An image can be prevented or suppressed.

  If there is a sub-subject, the ratio of the subject distance of the subject to the sub-subject distance, the ratio of the distance from the center of the shooting area to the main subject and the sub-subject, and the photometry unit 9 Since the corrected guide number GN ′ is recorrected in accordance with the luminance of the sub-subject obtained from the output of, the optical image of the main subject is exposed to the imaging surface of the image sensor 20 with an appropriate exposure amount. Thus, by correcting the guide number GN, the sub-subject can be prevented or suppressed from being blown out.

  The present invention is not limited to the above embodiment, and modifications described in the following (1) to (4) can also be adopted.

  (1) In the above embodiment, the calculated guide number GN is corrected according to the position of the main subject in the shooting area, and the flash 11 is irradiated with the flash 11 with the corrected guide number GN. The exposure for correcting the exposure control value calculated by correcting the aperture value calculated by the exposure control value calculation unit 36 instead of the form of correcting the guide number calculated by the guide number calculation unit 39 is not limited thereto. When the shutter button 4 is fully pressed, the control value correction unit is provided, and the flash 11 emits flash light with the guide number GN calculated by the exposure control value calculation unit 36, and the image pickup device 20 displays an image for recording. The aperture value at the time of performing the main exposure operation for obtaining may be set to the above-described corrected aperture value so that the image sensor 20 performs the exposure operation.In this case, the above-described exposure control value correction unit constitutes an exposure amount correction unit in the claims.

  In addition to this, the main subject can be appropriately corrected by correcting the level (pixel value) of the pixel signal output from the image sensor 20 by the signal processing unit 21 without correcting the guide number and the aperture value. An image captured with brightness can be obtained.

  Further, the correction process may be performed by appropriately selecting two elements or selecting all of them among the guide number, aperture value, and pixel level, and combining them.

  (2) The flash light distribution characteristic and the image plane illuminance characteristic described in the above embodiment are expressed by the relative light amount value of the peripheral area when the central area of the photographing area is set as a reference (0EV). However, the ratio may be expressed as a ratio (%) to the light amount of the central region. For example, in the flash light distribution characteristic shown in FIG. 6, the relative light quantity value of each area is set to the light quantity ratio D1 ′ (%) with respect to the light quantity of the central area, and in the image plane illuminance characteristic shown in FIG. May be converted into a ratio D2 ′ (%) with respect to the amount of light in the central region.

  In this case, the guide number correction unit 40 uses the light quantity ratios D1 ′ and D2 ′ based on the flash light distribution characteristic and the image plane illuminance characteristic as a guide number GN ′ for setting the relative light quantity value of the main subject to 0 EV, and the following formula: It can be calculated based on (5) and (6).

ΔD = D1 ′ × D2 ′ (5)
GN ′ = GN / √ΔD (6)
For example, when the subject distance d1 is set to 3 (m), the aperture value Fno is set to 4.0, and the guide number calculation unit 39 calculates the guide number GN as 3 × 4.0 = 12, the center in the above embodiment is used. When the light quantity ratio D1 ′ in the flash light distribution characteristic is 87% and the light quantity ratio D2 ′ in the image plane illuminance characteristic is 76% for the main subject whose relative light quantity value with respect to the region is −0.6 EV, ΔD = D1 Since “× D2” = − 0.66, the corrected guide number GN ′ is GN ′ = GN / (√0.66) = 14.8.

  (3) In the above embodiment, the subject at the position designated as the distance measuring point is set as the main subject, and the other person is set as the sub subject, so that the main subject is arranged closer to the periphery of the shooting area than the sub subject. As described above, the main subject and the sub-subject can be distinguished from each other even in the case where the subject is captured. However, in addition to this form, for example, the distance measurement unit 10 captures the optical image of the subject at predetermined time intervals and performs distance measurement. A mode for detecting a moving subject by detecting a change in subject distance and a contour of the subject based on pixel signals sequentially output from the unit 10 and tracking the subject (hereinafter referred to as a tracking mode) is provided. Even when the camera 1 is equipped with a function for designating a target to be tracked in advance, the main subject and the sub-subject can be distinguished from each other.

  That is, as shown in FIG. 13 (a), when the tracking mode is selected, when a tracking target such as a child walking around is designated by the frame F displayed on the display screen of the LCD 5, the tracking target is selected as the main subject. And Note that the frame F may be moved by the operation of the cross selection button 6 or the size of the surrounding area may be changed. FIG. 13B shows a state in which the tracking target specified by the frame F has moved from the state of FIG.

  When the shutter button 4 is half-pressed and there is a person other than the main subject in the shooting area, that person is set as a sub-subject. Thus, even when the main subject is located on the peripheral side of the shooting area with respect to the sub-subject, or when the main subject is located farther from the camera 1 than the sub-subject, the main subject and the sub-subject can be distinguished. it can.

  In short, when the camera 1 is equipped with a function for designating a subject to be most emphasized or focused on, if the subject is designated using the function, the subject is regarded as a main subject, and the shutter button 4 is When a person other than the main subject exists in the shooting area when half-pressed, the main subject and the sub-subject can be distinguished by regarding the person as a sub-subject.

  (4) In the above embodiment, the distance measuring sensor unit of the distance measuring unit 10 is configured by arranging the line sensors substantially in parallel at a predetermined interval in the Y-axis direction. Area sensors arranged in a shape may be used.

  (5) In the above embodiment, the flash output unit is configured by the flash 11 using a xenon tube as a light source. However, the present invention is not limited to this, and even if a light source such as a high-intensity LED (light emitting diode) is used, the arrangement is not limited to this. The light characteristics are the same as the above-described flash light distribution characteristics, and the present invention can be applied.

  The embodiments of the present invention described above include the inventions described in the following supplementary notes in addition to the inventions described in the claims.

  [Supplementary Note 1] An imaging unit that photoelectrically converts a light image of a subject imaged by an optical system, a flash output unit that irradiates a subject with flash light, a main subject detection unit that detects a main subject, and an input to the imaging unit An exposure amount calculation unit that calculates an exposure amount, a storage unit that stores a light distribution characteristic of the flash output unit and an image plane illuminance characteristic of the optical system, a light distribution characteristic and an image plane illuminance characteristic, and photographing of the main subject A camera comprising: a pixel level adjustment unit that adjusts a pixel value of a pixel signal output from the imaging unit according to a position in a region.

  According to the present invention, the pixel value of the pixel signal output from the imaging unit is adjusted according to the light distribution characteristic and the image plane illuminance characteristic and the position of the main subject in the photographing region. It is possible to obtain an image captured with a high brightness.

  [Supplementary Note 2] A subject brightness detection unit that detects brightness of a subject including the main subject, wherein the pixel level adjustment unit is configured to determine the subject brightness of the main subject and the subject brightness of another subject according to a relationship between the subject brightness of the main subject and the subject brightness of other subjects. The camera according to appendix 1, wherein the pixel value of the pixel signal is readjusted.

  According to this invention, since the pixel value of the pixel signal is readjusted according to the relationship between the subject brightness of the main subject and the subject brightness of the other subject, the pixels of the pixel signal output from the imaging unit By adjusting the value, it is possible to prevent or suppress the image of another subject from becoming a white image.

  [Supplementary Note 3] The main subject detection unit includes a function of detecting a sub-subject having the second highest importance after the main subject, and the pixel level adjustment unit includes a subject distance of the main subject and a subject distance of the sub-subject. The camera according to appendix 1 or 2, wherein the pixel value of the pixel signal is readjusted according to the relationship.

  According to this invention, since the pixel value of the pixel signal is readjusted according to the relationship between the subject distance of the main subject and the subject distance of the sub-subject, the pixels of the pixel signal output from the imaging unit By adjusting the value, it is possible to prevent or suppress the sub-subject image from becoming a white image.

  [Supplementary Note 4] The main subject detection unit has a function of detecting a sub-subject having the next highest importance after the main subject, and the pixel level adjustment unit is configured such that the distance from the center of the imaging region to the main subject and the center The camera according to any one of appendices 1 to 3, wherein the pixel value of the pixel signal is readjusted according to a relationship with a distance from the unit to the sub-subject.

  According to this invention, the pixel value of the pixel signal is readjusted according to the relationship between the distance from the center of the imaging region to the main subject and the distance from the center to the sub-subject. By adjusting the pixel value of the pixel signal output from the unit, it is possible to prevent or suppress the image of another subject from becoming a white image.

It is a front view which shows the structure of the camera which concerns on this invention. It is the rear view of a camera similarly. (A) is sectional drawing which shows the internal structure of the ranging part in this embodiment, (b) is a figure which shows the structure of a ranging part. It is a figure for demonstrating the mode which a photographer can designate a ranging point. It is a block diagram which shows the structure of a camera. FIG. 6 is a diagram illustrating an example of a difference in light amount of irradiation light between a central region and a peripheral region of an imaging region when an object in the imaging region is irradiated with flash light by an EV value. FIG. 5 is a diagram illustrating an example of an EV value representing a light amount difference between transmitted light between a central region and a peripheral region of a photographing region when a light image of a subject in the photographing region is transmitted through a photographing lens. It is a figure for demonstrating the method of matching each pixel and block of a ranging part. It is the figure which calculated | required the light quantity distribution of the relative light quantity value about all the area | regions in an imaging | photography area | region based on the flash light distribution characteristic shown in FIG. 6, and the image surface illumination characteristic shown in FIG. It is a figure for demonstrating the light quantity correction | amendment according to the position in the imaging | photography area | region of a main photographic subject and flash light distribution characteristic and an image surface illumination characteristic. It is a figure for demonstrating the condition where the image of a sub-subject blows out. It is a flowchart which shows a series of imaging operation | movement including an exposure amount correction process. It is a figure for demonstrating tracking mode. It is a figure which shows the deformation | transformation form of a ranging sensor part.

Explanation of symbols

2 Imaging Optical System 10 Distance Measuring Unit 11 Flash 18 Aperture 20 Imaging Element 21 Signal Processing Unit 35 Subject Luminance Detection Unit 36 Exposure Control Value Calculation Unit 37 Focal Length Calculation Unit 38 Main Sub-Subject Detection Unit 39 Guide Number Calculation Unit 40 Guide Number Correction Unit 41 guide number re-correction unit 42 light emission control unit

Claims (6)

An imaging unit that photoelectrically converts a light image of a subject formed by an optical system;
A flash output unit for irradiating the subject with flash,
A main subject detection unit for detecting the main subject;
An exposure amount deriving unit for deriving an exposure amount to the imaging unit;
A storage unit for storing light distribution characteristics of the flash output unit and image plane illuminance characteristics of the optical system;
When the flash output unit irradiates the subject with flash light and photoelectrically converts the light image of the subject to the imaging unit, according to the light distribution characteristic and the image plane illuminance characteristic and the position of the main subject in the shooting region, A camera comprising: an exposure amount correction unit that corrects the derived exposure amount. A subject brightness detection unit that detects brightness of a subject including the main subject, wherein the exposure amount correction unit corrects the exposure amount according to the relationship between the subject brightness of the main subject and the subject brightness of another subject. The camera according to claim 1, wherein the camera is corrected again. The main subject detection unit has a function of detecting a sub subject having the next highest importance after the main subject, and the exposure amount correction unit is configured according to a relationship between the subject distance of the main subject and the subject distance of the sub subject. The camera according to claim 1, wherein the corrected exposure amount is corrected again. The main subject detection unit has a function of detecting a sub subject having the next highest importance after the main subject, and the exposure amount correction unit is configured to detect a distance from the center of the imaging region to the main subject and the sub subject from the center. 4. The camera according to claim 1, wherein the corrected exposure amount is corrected again according to the relationship with the distance to the camera. 5. 5. The camera according to claim 1, further comprising: an aperture and an aperture control unit that controls an aperture diameter of the aperture based on the exposure amount corrected by the exposure amount correction unit. 6. The camera according to claim 1, further comprising a flash control unit that controls the amount of flash light emitted from the flash output unit based on the exposure amount corrected by the exposure amount correction unit. .

Images