JP4810159B2 - Focus adjustment device, imaging device, and control method of focus adjustment device - Google Patents

Description

  The present invention relates to a focus adjustment technique applied to an imaging apparatus or the like.

  When there are a plurality of areas for detecting the focus of the photographing lens (see, for example, the distance measuring field in FIG. 2 of Patent Document 1), there are so-called arbitrary selection and automatic selection. The arbitrary selection means that the photographer arbitrarily selects a single focus detection area corresponding to a position where the photographer wants to focus on the photographing area. The automatic selection means that the focus state is detected in each of the plurality of focus detection areas, and the camera microcomputer automatically selects the focus detection area from the detection result of the focus state of each focus detection area.

Further, when photographing a moving subject, a technique for selecting a focus detection area to be tracked using a peripheral focus detection area group has been considered. (Patent Document 2)
JP 05-011178 A JP 2001-188164 A

  However, there is a case where the focus is not focused at the position where the focus is originally desired on the photographing area. For example, when the subject that is in focus in the selected focus detection area moves unexpectedly, it does not follow the movement of the subject. Once the focus detection is successful, even if the subject moves unexpectedly, the focus detection region corresponding to the subject position in the shooting region does not move from the currently selected region to another region.

Focusing apparatus according to one aspect of the present invention, the imaging area, the second focal point of which does not correspond to the first focus detection area and the AF frame that can be viewed by the photographer corresponding to the AF frame that is visible to the photographer A focus adjustment device having a detection area, based on detection means for detecting whether or not a subject is moving, and an output signal from at least one focus detection area including the first focus detection area Focus detection means for performing focus detection, and a first focus detection mode in which the first focus detection area can be used without using the second focus detection area as a focus detection area used by the focus detection means for focus detection And a control unit capable of switching between the first focus detection area and the second focus detection mode in which the second focus detection area can be used, and the control means performs the first imaging by the user. When the mode is selected, the first focus detection mode is set, and when the second shooting mode is selected by the user, it is not detected that the subject is moving by the detection unit. The first focus detection mode is set, and when the detection unit detects that the subject is moving, the mode is switched to the second focus detection mode.

Further, another aspect of the present invention, a control method of a focus adjustment device, the imaging area, the first focus detection area and the AF frame that can be viewed by the photographer corresponding to the AF frame that is visible to the photographer A method for controlling a focus adjusting apparatus having a second focus detection area that does not correspond to a detection step for detecting whether or not a subject is moving, and at least one focus including the first focus detection area. A focus detection step for performing focus detection based on an output signal from the detection region, and the first focus detection region without using the second focus detection region as a focus detection region used for focus detection in the focus detection step. A control step capable of switching between a usable first focus detection mode and a second focus detection mode capable of using the first focus detection area and the second focus detection area; In the control step, when the first photographing mode is selected by the user, the first focus detection mode is set, and when the second photographing mode is selected by the user, detection by the detection step is performed. If not, the first focus detection mode is set, and when the detection step detects that the subject is moving, the mode is switched to the second focus detection mode.

  According to the present invention, it is possible to provide a focus adjustment technique for following a subject based on an output signal from a focus detection region suitable for shooting a moving subject.

  Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

<About the configuration of the imaging device, etc.>
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a photographing lens group that guides a subject image to the image sensor surface and the AF sensor unit. The photographing lens group 1 is described as a single lens for simplicity. Reference numeral 2 denotes a stop for adjusting the amount of incident light. The photographing lens group 1 and the diaphragm 2 are provided in a housing of a lens unit 30 that can be attached to and detached from a camera as an imaging device 40 described later. Reference numeral 3 denotes a transflective mirror that splits incident subject light and guides the subject light to the optical viewfinder and the AF sensor unit. The transflective mirror 3 includes a movable mechanism (not shown) and is movable outside the luminous flux of incident subject light. Reference numeral 4 denotes a focusing screen, 5 denotes a pentaprism, and 6 denotes an eyepiece, which is configured as a part of an optical viewfinder. On the focusing screen 4, an optical member 42 having a prism formed so that the photographer can visually recognize the AF frame irradiated by the LED 41 via the eyepiece 6 is provided. As will be described later, the AF frame is provided corresponding to the focus detection area.

  Reference numeral 7 denotes a focal plane shutter that controls the charge accumulation time to adjust the amount of light incident on the image sensor, and 8 denotes an image sensor such as a CCD or CMOS. A sub-mirror 9 guides the subject image to the AF sensor unit system. Similarly to the semi-transmissive mirror 3, the sub mirror 9 is also provided with a movable mechanism and is movable outside the luminous flux of incident subject light. An AF sensor unit 10 includes a field lens 11 and a separator lens 12 for dividing a subject image incident through the field lens 11. The AF sensor unit 10 further includes a light receiving sensor 13 including a line sensor or the like corresponding to a focus detection area described later in order to receive the divided subject image. Then, the light receiving sensor 13 is driven and controlled by the driving circuit 14. Reference numeral 19 denotes a camera-side microcomputer having a built-in memory such as RAM and ROM, and 20 denotes an A / D converter with a built-in microcomputer for taking an AF image signal into the microcomputer 19 from the light receiving sensor 13. The camera-side microcomputer 19 detects the focus state of the subject by the photographic lens group 1 from the phase difference of the image output from the light receiving sensor 13. These are provided in the camera housing 40.

  Through communication with the camera-side microcomputer 19, the lens-side microcomputer 31 controls the focus adjustment motor 15 for adjusting the focus of the taking lens 1 and the drive circuit 18 of the drive amount detector 17 that detects the drive amount of the taking lens 1. To do.

  21 is turned on by a first stroke (half-pressing) operation of a release button (not shown) by a switch SW1. When this switch is turned on, it is a switch for starting preparations for main exposure for recording such as AF (automatic focus adjustment) described later. 22 is turned on by the second stroke (full press) operation of the release button by the switch SW2. This is a switch for starting the main exposure operation to record a photographed image when this is turned ON. Reference numeral 23 denotes a mode switch for instructing the AF mode. In mode 1, the first focus adjustment means is set. In mode 2, the second focus adjusting means is set. In mode 3, the first focus adjustment means or the second focus adjustment means is set according to the result of the moving object detection means. In the initial setting of mode 3, the first focus detection unit is set. The modes 1, 2, and 3 will be described later with reference to FIG.

<Operation flow of imaging device>
Hereinafter, the operation of the microcomputer 19 having the above-described configuration will be described with reference to the flowchart of FIG.

  First, when starting up the camera, various contents in the RAM built in the camera microcomputer 19 are cleared and the input / output circuit is initialized (step S100). When the camera is operating, various contents in the RAM built in the camera microcomputer 19 are cleared. The various contents are a flag indicating that a moving object has been detected in step S106, which will be described later, and information indicating which area has been selected from among a plurality of focus detection areas.

  Then, the camera-side microcomputer 19 confirms the state of the switch SW1 (step S101). If the switch SW1 is OFF, the process proceeds to step S100. On the other hand, if it is ON, the process proceeds to step 102.

  In step S102, the subroutine "AF mode change" is called to set the focus adjustment means and the focus detection area. The processing content of this subroutine “AF mode change” will be described later with reference to FIG. Thereafter, in step S <b> 103, the camera-side microcomputer 19 drives the light receiving sensor 13 via the drive circuit 14. Thus, the subject image incident through the photographing lens group 1, the field lens 11, and the separator lens 12 is photoelectrically converted, and the charge signal accumulation operation is continued until a predetermined condition is satisfied. Here, the predetermined condition is, for example, whether the level of the charge signal accumulated in the light receiving sensor 13 is a certain value or more, or whether the accumulation time is a certain time or more.

  In step S104, the analog image signal group output from the light receiving sensor 13 is taken into the camera side microcomputer 19 through the microcomputer built-in A / D converter 20, and stored as an image signal at a predetermined address in the RAM. In step S105, the microcomputer 19 detects the focus state by the phase difference method using the image signal data. Specifically, when each of the subject images divided by the separator lens 12 is an A image and a B image, the correlation between both image signals is calculated while both image signals are shifted in opposite directions. The correlation between the image signals of the A and B images is calculated for each focus detection area described later. The number of shifts at which the calculated correlation amount becomes an extreme value is calculated as the “defocus amount”.

  In step S106, the subroutine "moving object detection" is called to determine whether the subject is a moving object. The processing content of this subroutine “moving object detection” will be described later with reference to FIG.

  In step S107, the camera-side microcomputer 19 determines whether or not the camera is in focus from signals acquired from a plurality of focus detection areas. Specifically, if the “focus shift amount” is equal to or smaller than a predetermined depth of focus, it is determined that the focus is achieved, and the process proceeds to step S110. On the other hand, if the “defocus amount” is equal to or greater than the predetermined depth of focus, it is determined that the subject is out of focus and the process proceeds to step S108. The focus determination at this time is performed based on the output signal of the focus detection area selected from the plurality of focus detection areas in accordance with the result of changing the AF mode described later.

  If the “focus shift amount” is equal to or greater than the predetermined depth of focus, the camera side microcomputer 19 converts the “focus shift amount” calculated by the focus detection calculation process of step S106 into the drive amount of the photographing lens group 1 in step S108. . This conversion is performed using the defocus sensitivity of the photographing lens group 1 communicated from the lens side microcomputer.

  In step S109, the lens-side microcomputer 31 receives the photographing lens driving amount converted by the camera-side microcomputer 19, drives the focus adjustment motor 15 via the drive circuit 16, and sets the photographing lens group 1. Drive by the amount. Thereafter, the process returns to step S101. That is, if the switch SW1 is ON, the focus detection process is performed again.

  On the other hand, if it is determined in step S107 that the “defocus amount” is equal to or smaller than the depth of focus, that is, in the focused state, the process proceeds from step S107 to step S110 as described above. In step S110, the camera-side microcomputer 19 confirms the state of the switch SW1. If the switch SW1 is OFF, the process proceeds to step S100 to perform initialization processing. If the switch SW1 remains ON, the process proceeds to step S111. In step S111, the state of the switch SW2 is confirmed. If the switch SW2 is OFF, the process proceeds to step S101, and if the switch SW2 is ON, the process proceeds to step S112.

  Subsequently, in step S112, the transflective mirror 3 and the sub mirror 9 are driven out of the reflected light beam from the subject. Then, the shutter 7 is opened and exposure to the image sensor 8 is started. After a predetermined time has elapsed since the shutter 7 was opened, the shutter 7 is closed and the exposure to the image sensor 8 is ended. In addition, the transflective mirror 3 and the sub mirror 9 are driven to return to the original positions. That is, the object light that has passed through the photographing lens group 1 is returned to a state where it reaches the finder system and the AF sensor unit 10 respectively.

<About AF mode change>
Next, the subroutine “AF mode change” executed in step S102 of FIG. 2 will be described according to the flowchart of FIG. The following operation flow is performed in the control of the camera microcomputer 19.

  First, in step S200, the setting of the mode switch 23 is confirmed. When the mode switch 1 is set, the process proceeds to step S201. When the mode 2 is set, the process proceeds to step S202. When the mode 3 is set, the process proceeds to step S203.

  First, a case where mode 1 is set in step S200 will be described. Mode 1 is a one-shot mode. In the one-shot mode, an automatic focus adjustment operation (AF operation) is started in response to depression of SW1, and focusing (focusing) is performed only once. When focus is achieved, an AF frame, which will be described later, is flashed for a moment, and a focus mark (not shown) (for example, ●) is lit in the viewfinder. As a flow, in step S201, the focus adjustment method is set to the first focus adjustment method, and the focus detection region is set for the first focus adjustment method. FIG. 5 is a diagram showing nine AF frame groups corresponding to the focus detection areas for the first focus adjustment method. In the AF frame group, a prism is provided in advance on the optical member 42 as an AF frame group. The photographer can visually recognize through the eyepiece 6 by irradiating the AF frame focused by the LED 41 for a moment from the AF frame group.

  Next, a case where mode 2 is set in step S200 will be described. Mode 2 is an AI servo AF mode. In the AI servo AF mode, an automatic focus adjustment operation (AF operation) is started in response to depression of SW1, and focusing (focusing) is continued on a moving subject that moves toward or away from the imaging apparatus. In the case of mode 2, unlike the case of mode 1, the corresponding AF frame is not lit. As a flow, in step S202, the focus adjustment method is set for the second focus adjustment method. FIG. 6 is a diagram showing 15 AF frame groups corresponding to the focus detection area for the second focus adjustment method. Among them, nine white AF frame groups are the same as the first focus adjustment type AF frame groups as described above. Here, the AF frame group is a pseudo representation. This is because the AF frame in the second focus adjustment method is not illuminated because it is not irradiated by the LED 41 as described above. Further, the six assist AF areas with hatching in the drawing are not provided with prisms corresponding to the optical member 42 in the physical configuration. Therefore, even if the irradiation light from the LED 41 is irradiated to the corresponding area, the assist AF area cannot be visually recognized by the photographer.

  The camera-side microcomputer 19 performs control for selecting a focus detection area corresponding to the position of the subject and focusing the selected focus detection area as described above in accordance with the output signals of the 15 focus detection areas. Do. Specifically, the focus detection area that focuses on the closest subject when viewed from the camera side is selected from among the focus detection successes. Once the focus detection area is selected, focus adjustment is performed in the selected focus detection area until focus detection fails.

  At this time, for example, even when the control is performed in nine focus detection areas as “one-shot AF mode” in mode 1, the number of focus detection areas is increased by switching to mode 2. In other words, the focus detection area is expanded from 9 places to 15 places. This is because it is predicted that the subject is moving in the AI servo AF mode. Therefore, the focus detection area is expanded (or increased) by switching to mode 2 by the mode switch 23 based on the operation of the photographer. Thereby, it is possible to appropriately select the focus detection area corresponding to the movement of the subject. Third, the case where mode 3 is set in step S200 will be described. Mode 3 is an AI focus AF mode. In the AF focus AF mode, the camera-side microcomputer 19 switches the AF mode to “one-shot AF mode” or “AF servo AF mode” according to the state of the subject. The mode 3 is a mode in which focusing (focusing) is performed only once when the mode is switched to the “one-shot AF mode”. In this case, when the subject is in focus, an AF frame that will be described later that is in focus shines momentarily, and a focus mark (not shown) (for example, ●) is lit in the viewfinder. On the other hand, when the “AF servo AF mode” is switched, the AF frame is not turned on. As a flow, in step S203, switching between the “one-shot AF mode” and the “AF servo AF mode” is performed according to the moving object detection result of the subroutine “moving object detection”. Specifically, when the moving object is not detected in step S106 described later (the moving object detected flag is not set in step S303 described later), the process proceeds to step S201, and the first focus adjustment method is set. Is set. On the other hand, when the moving object has been detected in step S106 described later, the process proceeds to step S202, and the second focus adjustment method is set.

  In mode 3, when the moving object has been detected in this way, the focus detection area corresponding to the position of the subject is selected according to the output signals of the 15 focus detection areas as described in FIG. . In addition to the nine AF frames previously provided on the optical member 42, the output signals of 15 focus detection areas including six assist AF areas are added. The camera-side microcomputer 19 performs control to focus on the selected focus detection area as described above. At this time, the number of focus detection areas is not increased by switching to mode 3. When the moving object has been detected, the number of focus detection areas is increased by setting the second focus adjustment method. In other words, the focus detection area is enlarged. This is because the camera-side microcomputer 19 determines whether or not the subject is moving in the AI focus AF mode. That is, if the moving object is already detected, it is predicted that the subject is moving. Therefore, it is possible to appropriately select the focus detection area corresponding to each of the case where the subject is moving or the case where the subject is not moving.

  In this way, the focus detection area is set in accordance with the selected AF mode, and the process returns from the subroutine “AF mode change”.

<About focus detection area and AF frame>
Here, the correspondence between the above-described focus detection area and the AF frame will be described with reference to FIGS.

  FIG. 7 is a diagram showing a region for detecting the focus state in the AF sensor unit 10 corresponding to the photographing region. On the other hand, FIG. 8 is a diagram showing 15 AF frames corresponding to 15 areas from the detection areas A to O shown in FIG. However, as described above, the AF frames B, C, D, F, G, and H are actually invisible to the photographer and are represented in a pseudo manner. As described above, the automatic focus adjustment operation as described above is performed based on the output signals from the 15 detection areas shown in FIG. Note that E and E ′ indicate the same focus adjustment region that is 90 degrees different from each other.

  In this way, the focus detection area is increased, and the output signals from the focus detection areas (B, C, D, F, G, and H shown in FIG. 7) without corresponding AF frames are also effectively used. can do. In addition, by providing a focus detection area that does not have a corresponding AF frame in this way, it is possible to improve the visibility on the optical viewfinder for the photographer while maintaining the accuracy of focusing (focusing) on the moving subject. Can be achieved.

<About motion detection>
Next, the subroutine “moving object detection” executed in step S106 of FIG. 2 will be described according to the flowchart of FIG. The control flow is also performed in the camera-side microcomputer 19.

  First, the setting of the mode switch 23 is confirmed (step S300). When the mode 1 or the mode 2 is set, the process returns from the subroutine “moving object detection” to step S107 in FIG. On the other hand, when the mode 3 is set, the process proceeds to step S301.

  In step S301, the set focus adjustment method is confirmed. If the second focus adjustment method is set, the process returns from the subroutine "moving object detection" to step S107 in FIG. That is, once a moving object is detected, the process proceeds to in-focus determination without performing the moving object determination again until the switch SW1 is turned off to follow the movement of the subject. On the other hand, when the first focus adjustment method is set, the routine proceeds to step 302. In step S302, it is determined whether or not the subject is a moving object from a plurality of past focus detection results at one point automatically selected from the nine focus detection areas. Specifically, the subject is determined to be a moving object when the image plane position has monotonously increased or decreased monotonously in the past. When it is determined by the moving object determination that the subject is stationary, the process returns from the subroutine “moving object detection”. On the other hand, when it is determined that the subject is a moving object, the process proceeds to step S303. In step S303, when a moving object is detected, a flag is set to store that a moving object has already been detected.

  According to the focus adjustment technique described above, it is possible to appropriately follow a moving subject based on an output signal from a peripheral focus detection region and perform AF.

It is a block diagram which shows the structure of an automatic focus adjustment apparatus. It is a flowchart which shows operation | movement of the automatic focus adjustment apparatus which concerns on the Example of this invention. 3 is a flowchart illustrating a subroutine “focus adjustment changing unit” executed in step 102 of FIG. 2. 3 is a flowchart illustrating a subroutine “moving object detection” executed in step 106 of FIG. 2. It is the figure which showed the 1st AF frame group. It is the figure which showed the 2nd AF frame group. It is a figure which shows the ranging area of AF sensor. It is a figure which shows the AF flame | frame corresponding to the ranging area of the AF sensor shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens group 2 Diaphragm 3 Transflective mirror 4 Focus plate 5 Penta prism 6 Eyepiece 7 Focal plane shutter 8 Image sensor 9 Submirror 10 AF sensor unit 11 Field lens 12 Separator lens 13 Light receiving sensor 14 Light receiving sensor 13 drive circuit DESCRIPTION OF SYMBOLS 15 Focus adjustment motor 16 Drive circuit of focus adjustment motor 15 Drive amount detector 18 which detects the drive amount of taking lens 1 18 Drive circuit of drive detector 17 19 Microcomputer 20 A / D converter 21 Switch (SW1)
22 Switch (SW2)
23 Mode switch

Claims (4)

The imaging region, a focusing device provided with a second focus detection area that does not correspond to the AF frame that can be visually recognized by the first focus detection area and photographer corresponding to the AF frame that is visible to the photographer,
Detection means for detecting whether or not the subject is moving;
Focus detection means for performing focus detection based on an output signal from at least one or more focus detection areas including the first focus detection area;
A first focus detection mode in which the first focus detection area can be used without using the second focus detection area as a focus detection area used by the focus detection means for focus detection, and the first focus detection area And control means capable of switching between a second focus detection mode in which the second focus detection area can be used,
The control means includes
When the first shooting mode is selected by the user, the first focus detection mode is set,
When the second photographing mode is selected by the user, if it is not detected that the subject is moving by the detecting means, the first focus detection mode is set, and the subject is moved by the detecting means. A focus adjustment device that switches to the second focus detection mode when it is detected.   In the second shooting mode, when it is detected by the detection means that the subject is moving, at least one focus detection area is selected from the focus detection areas detected by the focus detection means; The focus adjustment apparatus according to claim 1, wherein focus adjustment is performed based on an output signal from the selected focus detection area.   An imaging apparatus comprising: the focus adjustment apparatus according to claim 1; and a light receiving element that receives subject light that has passed through an optical system that has been focused by the focus adjustment apparatus. The imaging region, in the first focus detection area and the control method of the focusing device provided with a second focus detection area that does not correspond to the AF frame that can be viewed by the photographer corresponding to the AF frame that is visible to the photographer There,
A detection step for detecting whether or not the subject is moving;
A focus detection step for performing focus detection based on an output signal from at least one or more focus detection areas including the first focus detection area;
A first focus detection mode in which the first focus detection area can be used without using the second focus detection area as a focus detection area used for focus detection in the focus detection step, and the first focus detection area And a control step capable of switching between a second focus detection mode in which the second focus detection area can be used,
In the control step,
When the first shooting mode is selected by the user, the first focus detection mode is set,
When the second photographing mode is selected by the user, if the detection in the detection step is not performed, the first focus detection mode is set, and the detection step detects that the subject is moving. Then, the control method is switched to the second focus detection mode.

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