JP2017146328A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which excludes a focus detection point possibly existing on the ground surface from selection objects and thereby selects an appropriate focus detection pint on a main subject when automatically selecting a focus detection pint.SOLUTION: An imaging device of the present invention comprises: focus detection means for detecting a focus state at a plurality of focus detection points set in a photographing screen; selection means for selecting one focus detection point from among the plurality of focus detection points on the basis of the result of the focus detection means; focus adjustment means for adjusting a focus on the basis of the focus state at the focus detection point selected by the selection means; and a spirit level for detecting an angle formed by the optical axis of the imaging device against the horizontal plane as a tilt angle. The selection means includes selection disabled area setting means for setting a selection disabled area in the lower part of the photographing screen, and means for excluding focus detection points included in the selection disabled area from selection objects, irrespective of the focus state, the selection disabled area setting means determining the range of a selection disabled area on the basis of the tilt angle.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus typified by a digital camera, and more particularly to a focus detection point selection unit used for automatic focus adjustment.

  2. Description of the Related Art Conventionally, in an imaging apparatus that performs autofocus based on the focus state of a focus detection point, a function of automatically selecting one focus detection point used for focus adjustment from a plurality of focus detection points is known. An imaging apparatus having such an automatic selection function has an advantage that an operation procedure at the time of photographing can be simplified because the photographer does not need to manually select a focus detection point.

  However, as a result of automatic selection, a focus detection point for a subject different from the main subject intended by the photographer may be selected depending on the shooting environment. In particular, when another subject is closer to the imaging device than the main subject intended by the photographer, it is easy to select a focus detection point for the other subject. As a result, for example, when a person standing on the ground is desired to be photographed, the camera is focused on the ground in front of the person as viewed from the imaging device.

  To solve such a problem, there is a solution method in which a focus detection point at the bottom of the screen is excluded from automatic selection targets. Japanese Patent Application Laid-Open No. 2004-133620 discloses a method of determining a lower area of a shooting screen by detecting the attitude of an imaging apparatus and excluding focus detection points located in the lower area from focus adjustment targets.

JP 2003-255216 A

  However, in the conventional technique disclosed in the above-mentioned Patent Document 1, the position of the lower area of the shooting screen is automatically determined, but no reference is made to a method for setting the size of the area. Therefore, depending on the shooting situation, there are cases where the ground as described above cannot fit in the set lower region. For example, it is possible to assume a composition in which the ground is also reflected in the vicinity of the center of the shooting screen when the imaging device is directed obliquely downward. In such a case, there is a problem that the ground cannot be excluded from the focus adjustment target.

  Therefore, an object of the present invention is to provide an imaging apparatus that can dynamically set a focus detection point to be excluded from automatic selection based on the tilt angle of the imaging apparatus obtained from a level. is there.

In order to achieve the above object, an imaging apparatus according to the present invention includes:
An image pickup apparatus that takes an image of a subject formed by a taking lens with an image pickup device,
Focus detection means for detecting a focus state at a plurality of focus detection points set in the photographing screen;
Selection means for selecting one focus detection point from the plurality of focus detection points based on the result of the focus detection means;
Focus adjusting means for performing focus adjustment based on the focus state of the focus detection point selected by the selection means;
A level that detects an angle formed by an optical axis of the imaging device with respect to a horizontal plane as a tilt angle;
The selection means is a selection invalid area setting means for setting a selection invalid area at the bottom of the photographing screen;
Means for excluding focus detection points included in the selection invalid region from selection targets regardless of the focus state;
The selection invalid area setting means determines a range of the selection invalid area based on the tilt angle.

  According to the present invention, imaging that selects an appropriate focus detection point on the main subject when automatically selecting a focus detection point by excluding focus detection points that may be present on the ground from the selection target. An apparatus can be provided.

It is a figure which shows the focus detection point selection procedure of the imaging device concerning 1st Embodiment. 1 is a diagram illustrating an overall configuration of an imaging apparatus according to a first embodiment. It is a figure which shows the operation | movement procedure regarding the imaging of the imaging device in connection with 1st Embodiment. It is a figure which shows arrangement | positioning of the focus detection point in the imaging | photography screen of the imaging device concerning 1st Embodiment. It is a figure shown about the angle of the imaging device which the electronic level of the imaging device concerning 1st Embodiment detects. It is a figure shown about the selection invalid area | region set when the angle of an imaging device is near horizontal in the imaging device concerning 1st Embodiment. It is a figure shown about the selection invalid area | region set when the imaging device is facing down at a comparatively small angle in the imaging device concerning 1st Embodiment. It is a figure shown about the selection invalid area | region set when the imaging device is facing up with a comparatively small angle in the imaging device concerning 1st Embodiment. It is a figure shown about the selection invalid area | region set when the imaging device is facing down at a comparatively big angle in the imaging device concerning 1st Embodiment. It is a figure shown about the selection invalid area | region set when the imaging device is facing upwards with a comparatively big angle in the imaging device concerning 1st Embodiment.

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

  FIG. 2 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention, FIG. 2A is a schematic diagram of the imaging apparatus, and FIG. 2B is a connection relationship of each apparatus included in the imaging apparatus.

  Reference numeral 201 denotes a digital single-lens reflex camera body, and a photographing lens 220 is attached to the front surface thereof. The photographing lens 220 can be exchanged, and the camera body 201 and the photographing lens 220 are also electrically connected via the mount contact group 223. The photographing lens 220 includes a focusing lens 221 and an aperture shutter 222, and the amount of light taken into the camera and the focal position can be adjusted by control via the mount contact group 223. Further, the focusing lens 221 can be manually adjusted by the photographer.

  A control device 202 controls each part of the camera body 201 and the photographing lens 220, and includes a calculation CPU, a memory, and a logic circuit.

  Reference numerals 203 and 204 denote quick return mirrors. Reference numeral 203 denotes a main mirror, which is a half mirror. The main mirror 203 is obliquely arranged on the photographing optical path in the finder observation state, and reflects the light beam incident from the photographing lens 220 to the finder optical system. On the other hand, the light transmitted through the main mirror 203 is reflected by the sub-mirror 204 and enters the distance measuring sensor 205.

  Reference numeral 205 denotes a distance measuring sensor, which generates a distance image signal corresponding to a plurality of focus detection points by forming a secondary imaging surface of the photographing lens 220 on a line sensor for focus detection. The generated distance image signal is transmitted to the control device 202, and the control device 202 detects the focus state of the photographing lens 220 using the distance image signal. Further, the control device 202 performs focus adjustment by controlling the focusing lens 221 based on the focus detection result. FIG. 4 is a diagram showing the arrangement of the focus detection points 402 on the shooting screen 401.

  Reference numeral 206 denotes a focusing plate disposed on the planned imaging plane of the photographing lens 220 constituting the finder optical system.

  Reference numeral 207 denotes a pentaprism for changing the finder optical path.

  Reference numeral 208 denotes a photometric sensor, which generates a photometric image signal from the irradiated optical signal. The generated photometric image signal is transmitted to the control device 202, and the control device 202 performs photometric calculation using the photometric image signal.

  Reference numeral 209 denotes an eyepiece. The photographer can confirm the photographing screen and the focus detection point display by observing the focus plate 206 from here.

  Reference numeral 210 denotes a shutter, and 211 denotes an image sensor. A display unit 212 displays shooting information and a shot image transmitted from the control device 202.

  The imaging operation is performed by exposing the imaging sensor 211 by causing the control device 202 to retract the mirrors 203 and 204 from the imaging optical path and drive the shutter 210. The exposed image sensor 211 generates image data and transmits it to the control device 202. The control device 202 stores the received image data in the image storage device 241 and displays a captured image on the display 212. When the imaging is completed, the control device 202 installs the mirrors 203 and 204 again on the imaging optical path.

  Reference numeral 213 denotes an electronic level which detects an angle formed by the optical axis of the camera body 201 with respect to a horizontal plane as a tilt angle. Further, the rotation angle with respect to the horizontal plane with the optical axis of the camera body 201 as the rotation axis is detected as the roll angle.

  The operation unit 240 detects an operation performed by a user via a release button, a switch, a dial, a connected device, etc. (not shown) attached to the camera body 201 and transmits a signal corresponding to the operation content to the control device 202.

  Next, the operation procedure of the image pickup apparatus in the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart illustrating a procedure until the imaging apparatus performs imaging.

  In step S <b> 301, the photometric sensor 208 performs photometric calculation accumulation and image signal readout, and transmits the generated photometric image signal to the control device 202. The control device 202 performs photometric calculation by a known method using the received photometric image signal, and determines the aperture value (AV value), shutter speed (TV value), and ISO sensitivity (ISO value). The AV value, TV value, and ISO value are determined using a program diagram stored in advance in the control device 202.

  In step S <b> 302, the distance measurement sensor 205 performs focus detection accumulation and image signal readout, and transmits the generated distance measurement image signal to the control device 202. The control device 202 detects the focus state of each focus detection point from the received ranging image signal.

  In S303, the control device 202 selects at least one focus detection point used for focus adjustment based on the focus state detected in S302. Here, a focus detection point having a focal point at a position closest to the imaging device is selected. However, when a focus detection point having a focus closest to the image pickup location is simply selected, there is a possibility that a focus detection point for the ground on which the main subject stands is selected.

  Therefore, depending on the vertical tilt of the camera body 201, some focus detection points located at the lower part of the shooting screen may be excluded from selection regardless of the focus state. Details of these selection methods will be described later.

  In S304, the control device 202 adjusts the focus position of the focusing lens 221 based on the focus state of the focus detection point selected in S303. However, when the photographing lens 220 is set to perform manual focus adjustment, the focus adjustment of the focusing lens 221 in this step is not performed.

  In S305, if the control apparatus 202 has received the release instruction signal from the operation unit 240, the process proceeds to S306, and shifts to the imaging operation. If the release instruction signal has not been received, the frame is advanced by 1 and the process returns to S301. The frame here is for counting the number of executions of the photometric calculation S301 and the focus detection S302.

  In step S <b> 306, the imaging device 202 performs an imaging operation, stores the image data acquired from the imaging sensor 211 in the image storage device 241, and displays the image data on the display unit 212.

  The operation procedure until the imaging apparatus according to the present embodiment performs imaging is as described above.

  Subsequently, a detailed processing procedure of the focus detection point selection S303 in the imaging apparatus of the present embodiment will be described with reference to FIGS. FIG. 1 is a flowchart showing an operation procedure of focus detection point selection S303.

  In S101, the electronic level 213 detects the angle between the optical axis of the camera body 201 and the horizontal plane as the tilt angle θ. A schematic representation of the tilt angle θ is shown in FIG. In FIG. 5A, the tilt angle θ is an angle generated between the camera optical axis and the horizontal plane when the camera 501 is tilted downward. In this embodiment, the tilt angle generated when tilted upward is a positive angle, and the tilt angle generated when tilted downward is a negative angle. Therefore, in the state of FIG. 5A, θ is a negative value. Then, the electronic level 213 transmits the detected tilt angle to the control device 202.

  In S <b> 102, the electronic level 213 detects the rotation angle in the optical axis direction with respect to the horizontal plane of the camera body 201 as a roll angle, and transmits it to the control device 202. The control device 202 determines that the camera body 201 is held horizontally if the received roll angle is within a predetermined numerical range, and is held vertically if it is outside the predetermined numerical range. Subsequently, when it is determined that the camera body 201 is held sideways, the control device 202 sets the vertical width 403 of the focus detection area in FIG. 4 as the focus detection area width d. On the other hand, when it is determined that the camera body 201 is held vertically, the horizontal width 404 of the focus detection area in FIG. 4 is set as the focus detection area width d.

Then, the control device 202 calculates the focus area angle of view α of the focus detection area based on the focus detection area width d and the focal length f of the photographing lens 220. The focal area angle of view α can be calculated by the following equation.
α = 2 arctan (d / (2f))
In S103, four types of angle threshold values N2, N1, P1, and P2 are calculated based on the focal region angle of view α calculated in S102. These four types of angle threshold values are used for comparison with the tilt angle θ in the next step S104. Here, as shown in FIG. 5B, the magnitudes of the four types of angle thresholds are set to satisfy N2 <N1 <P1 <P2. N2 and N1 are negative values because they are threshold values used for a negative tilt angle, and P1 and P2 are positive values because they are threshold values used for a positive tilt angle. As a calculation method of the four types of angle thresholds, first, N2 and P2 are calculated by the following equations.
N2 = −α / 2
P2 = α / 2
By calculating N2 and P2 in this way, when the camera body 201 is facing downward with respect to the horizontal plane to be larger than the angle N2, the upper end of the focus detection area is below the horizontal plane, so that focus detection is performed. There is a high possibility that the ground is reflected in a wide area within the area. On the other hand, when the camera body 201 is directed upward with respect to the horizontal plane by a larger angle than the angle P2, the lower end of the focus detection area is above the horizontal plane, so that the ground in the focus detection area may be hardly reflected. Increases nature. Subsequently, N1 and P1 are set to be intermediate values between the tilt angle 0 ° and N2 and P2, for example, N1 = N2 / 2 and P1 = P2 / 2.

  In S104, the control device 202 compares the tilt angle θ received in S101 with the four types of angle thresholds N2, N1, P1, and P2 calculated in S103, and determines which range the tilt angle θ is in. Based on the comparison result, the control device 202 branches to the following five steps.

  First, if the tilt angle θ is greater than or equal to N1 and less than or equal to P1, the control device 202 determines that the orientation of the camera body 201 is relatively horizontal, and proceeds to S105.

  If the tilt angle θ is greater than or equal to N2 and less than N1, the control device 202 determines that the camera body 201 is facing downward at a relatively small angle, and proceeds to S106.

  If the tilt angle θ is greater than P1 and less than or equal to P2, the control device 202 determines that the camera body 201 is facing upward at a relatively small angle, and proceeds to S107.

  If the tilt angle θ is less than N2, the control device 202 determines that the camera body 201 is facing downward at a relatively large angle, and proceeds to S108.

  If the tilt angle θ is larger than P2, the control device 202 determines that the camera body 201 is facing upward at a relatively large angle, and proceeds to S109.

  S105 to S109 described below are areas in which the possibility that the main subject is present in the focus detection area is relatively low so that the focus detection point for the ground is not selected when one focus detection point is selected in S110 described later. Is set to the selection invalid area.

  In S105, as shown in FIG. 6A, the orientation of the camera body 201 is almost horizontal. Therefore, there is a possibility that the ground is reflected below the focus detection area. Therefore, as shown in FIG. 6B, the control device 202 sets an area including the lower two lines of the focus detection point array as a selection invalid area.

  In S106, as shown in FIG. 7A, the camera body 201 faces downward at a relatively small angle. Therefore, it is more likely that the ground is reflected even closer to the center of the focus detection area than in the state where the camera body 201 is horizontally oriented. Therefore, as shown in FIG. 7B, the control device 202 sets an area that is wider than the selection invalid area set in S105 and includes the lower three rows of the focus detection point array as the selection invalid area.

  In S107, as shown in FIG. 8A, the camera body 201 faces upward at a relatively small angle. Therefore, it is highly possible that the ground is reflected more narrowly below the focus detection area as compared with the state where the camera body 201 is oriented horizontally. Therefore, as shown in FIG. 8B, the control device 202 sets an area that is narrower than the selection invalid area set in S105 and includes only the lower one line of the focus detection point array as the selection invalid area.

  In S108, as shown in FIG. 9A, the camera body 201 faces downward at a relatively large angle. For this reason, the ground may be reflected in a wide range of the focus detection area, for example, when shooting a landscape spreading downward from a high place. In such a case, the main subject may be present everywhere in the focus detection area. Therefore, the control device 202 does not set the selection invalid area as shown in FIG.

  In S109, as shown in FIG. 10A, the camera body 201 faces upward at a relatively large angle. Therefore, for example, when shooting fireworks from the ground, there is a high possibility that the ground is hardly reflected. Therefore, the control device 202 does not set the selection invalid area as shown in FIG.

  In S110, the control device 202 selects one focus detection point having a focus at the position closest to the imaging device from the focus detection points not included in the selection invalid area set in any of S105 to S109, A focus detection point for focus adjustment.

  However, all focus detection points not included in the selection invalid area are in a state where focus detection is not possible or the focus is at infinity, and focus detection is possible among the focus detection points included in the selection invalid area and the focus is not infinite. An exception is when there is a focus detection point. In this case, one focus detection point having a focus at a position closest to the imaging device is selected from the focus detection points included in the selection invalid region, and is used as a focus detection point for focus adjustment.

  In the focus detection S302, if the focus position has changed by a predetermined value or more at the same focus detection point in the previous frame and the current frame, the corresponding focus detection point is included in the selection invalid area. Are also subject to selection. This is a moving object determination, and it is highly likely that a subject whose focal position changes by a predetermined value or more is not the ground and can be a candidate for the main subject.

  The above is the detailed processing procedure of the focus detection point selection S303 in the imaging apparatus of the present embodiment. By selecting a focus detection point used for focus adjustment in such a procedure, the possibility of focusing on a subject that the photographer does not intend, such as the ground, is reduced in accordance with the vertical tilt of the camera body 201. be able to.

201 Camera body 202 Control device 203 Main mirror 204 Sub mirror
205 Distance sensor

Claims (4)

An image pickup apparatus that takes an image of a subject formed by a taking lens with an image pickup device,
Focus detection means (S302) for detecting focus states at a plurality of focus detection points set in the photographing screen;
Selection means (S303) for selecting one focus detection point from the plurality of focus detection points based on the result of the focus detection means;
Focus adjusting means (S304) for performing focus adjustment based on the focus state of the focus detection point selected by the selection means;
A level (213) for detecting, as a tilt angle, an angle formed by an optical axis of the imaging device with respect to a horizontal plane,
The selection means is a selection invalid area setting means (S105, S106, S107, S108, S109) for setting a selection invalid area at the bottom of the shooting screen;
Means (S110) for excluding focus detection points included in the selection invalid region from selection targets regardless of the focus state;
The selection invalid area setting unit determines a range of the selection invalid area based on the tilt angle (S104). The selection means determines a range of the selection invalid region based on a size of an arrangement region of the plurality of focus detection points and a focal length of the photographing lens in addition to the tilt angle. The imaging device described in 1. The selection means is in a state where all focus detection points not included in the selection invalid region are in a state where focus detection is impossible or the focus is at infinity, and focus detection is possible in the focus detection points included in the selection invalid region; The imaging apparatus according to claim 1, wherein when there is a focus detection point whose focus is not infinity, the one focus detection point is selected from focus detection points included in the selection invalid region. The selection means performs the focus detection at different timings in the focus detection means, and as a result, if the focus position at each timing has changed by a predetermined value or more at the same focus detection point, the corresponding focus detection is performed. The imaging apparatus according to claim 1, wherein even if a point is included in the selection invalid region, the imaging device is selected.