JP2005326506A - Focus detection device and focus detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately perform an auto-focus photographing through glass. <P>SOLUTION: A control circuit 10 detects a focal position of a photographic lens 11 at each object in focusing the photographic lens on each of two or more objects shown in an image photographed through the photographic lens 11, and determines the presence of an effect of the glass on the image pickup performed through the glass, and when judging that this effect exists, the circuit selects one of the focal positions except that of the nearest object from the photographic lens among each focal position of the objects as a result of the focus detection. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for capturing a subject image, and particularly to a so-called autofocus technique in which a lens used for imaging is automatically focused on a subject.

For example, in Patent Document 1, in an autofocus function of a camera that employs a so-called contrast method, a shooting condition related to a shooting distance to a subject (for example, a focus evaluation value when performing a focusing operation (for example, A technique is disclosed in which focus adjustment is appropriately performed on a main subject desired by a photographer among subjects by giving weighting according to a distant view mode or the like.
JP 2003-107331 A

  When the camera's auto-focus function is activated to shoot a subject separated by glass such as a show window through the glass, the focus is not on the subject but on the character or figure drawn on the glass itself or its There may be a problem that the image reflected on the glass is in focus and the original subject appears as a blurred image in the captured image.

  The present invention has been made in view of the above-described problems, and a problem to be solved is to appropriately perform autofocus photographing through glass.

  A focus detection apparatus according to one aspect of the present invention provides a focus position of each photographing lens for each subject when the photographing lens is focused on a plurality of subjects represented in an image captured through the photographing lens. An in-focus position detecting means for detecting, a determining means for determining the presence or absence of the influence of the glass on the imaging performed through the glass, and when it is determined that there is the influence, A focus position selection unit that selects any focus position as a result of focus detection, except for the focus object and the subject closest to the photographic lens. Solve the problem.

In the focus detection apparatus according to the present invention described above, the focus position detection unit may be configured to perform the detection based on the contrast of the image captured through the photographing lens.
In the focus detection apparatus according to the present invention described above, the determination unit may be configured to determine the presence or absence of the influence based on the brightness of an image captured through the photographing lens.

Further, in the focus detection device according to the present invention described above, when it is determined that the focus position selection unit has the influence, the focus position selection unit determines whether the focus lens from the shooting lens among the focus positions of the plurality of subjects. You may comprise so that the thing about the 2nd closest subject may be selected.
At this time, the in-focus position detecting means may be configured to detect the in-focus position for each of the plurality of subjects in order from the subject for the subject close to the photographing lens.

  The focus detection apparatus according to the present invention described above further includes a setting instruction acquisition unit that acquires an instruction for setting an imaging condition when performing imaging. May be configured to perform the selection based on the determination result by the determination unit when the image is taken through the glass.

  At this time, the focus position detection unit performs the detection based on the contrast of the image captured through the photographing lens, and the focus position selection unit determines that the imaging condition according to the setting instruction is over the glass. When imaging other than imaging is indicated, the in-focus position for the subject corresponding to the subject image having the maximum contrast in the image may be selected regardless of the presence or absence of the influence. Good.

  In the focus detection apparatus according to the present invention described above, a plurality of regions obtained by dividing the image are defined in the image captured through the photographing lens, and the in-focus position detection means The in-focus position of the subject corresponding to the subject image represented in the image in the area is detected for the area closest to the subject from the taking lens, and the in-focus position selecting means If it is determined that there is an influence, focus detection is performed on any one of the in-focus positions detected for each area except for the object closest to the photographing lens. You may comprise so that it may select as a result.

At this time, when it is determined that the in-focus position detection unit has the influence, the in-focus position detection unit applies the second closest object to the photographing lens among the in-focus positions detected for each region. You may comprise so that a thing may be selected.
In addition, the focus detection method according to another aspect of the present invention provides a focus position of the photographic lens when the photographic lens is focused on each of a plurality of subjects represented in an image captured through the photographic lens. It is detected for each subject, and the presence or absence of the influence of the glass on the imaging performed through the glass is determined, and when it is determined that there is the influence, the focus position of each subject for the subject The above-described problem is solved by selecting any in-focus position as a result of focus detection except for the object closest to the photographic lens.

  By having the above-described characteristics, the present invention has an effect that the autofocus photographing through the glass can be appropriately performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of a camera that implements the present invention. This camera has an autofocus function using a contrast method.
The control circuit 10 includes a CPU (Central Processing Unit) and a ROM (Read Only Memory) in which a control program executed by the CPU is stored in advance. The operation control of the entire camera is performed by reading the control program from the ROM and executing it.

The photographing lens 11 forms a subject image on the surface of the image sensor 12.
The image sensor 12 is, for example, a CCD (Charge Coupled Device), and converts an optical image representing a subject image into an electrical signal.
The A / D converter 13 converts an electrical signal, which is an analog signal output from the image sensor 12, into a digital signal, and outputs image data representing an image representing a subject image.

The white balance correction circuit 14 corrects a so-called white balance in the image represented by the image data output from the A / D converter 13, that is, a color deviation of the photographed image mainly caused by the influence of illumination in the photographing environment. .
The Y / C separation generation circuit 15 outputs the Y / C (luminance-color difference) component of the image data output from the white balance correction circuit 14 and represented by the luminance values of the three primary colors of RGB light. Perform the conversion process.

The compression / decompression circuit 16 performs data compression processing on the image data output from the Y / C separation generation circuit 15, and also performs data expansion processing on the compressed image data recorded in the memory card 18. Apply.
A memory card I / F (interface) 17 controls writing / reading of various data such as image data compressed by the compression circuit 16 to / from the memory card 18.

The memory card 18 records and stores various data such as image data representing an image taken by the camera.
The display unit 19 is, for example, an LCD (Liquid Crystal Display), and when an imaging mode that is an operation mode for performing an imaging operation is set for the camera, the imaging device 12 The captured image is displayed. In addition, when the playback mode, which is an operation mode for performing the playback operation of the image data stored in the memory card 18, is set for this camera, the image recorded on the memory card 18 is displayed. Display the image represented by the data. In addition to these, various information about the camera is displayed.

A DRAM (Dynamic Random Access Memory) 20 is a memory that is used as a working memory as needed in various processes performed in the above-described units.
The AF signal acquisition circuit 21 outputs from the A / D converter 13 a high-frequency component of the luminance signal in the image data, which is a signal for evaluating the degree of focus of the subject image on the light receiving surface of the image sensor 12. Extracted from the image data, integrated, and supplied to the control circuit 10.

The taking lens driving circuit 22 varies the taking lens 11 in accordance with an instruction from the control circuit 10.
The image sensor drive circuit 23 generates various signals for driving the image sensor 12 under the control of the control circuit 10.

The power supply unit 24 boosts or lowers the voltage of power supplied from a battery built in the camera or an external power supply as necessary. When the power switch 24a is turned on, the power switch 24a is controlled under the control of the control circuit 10. Power is supplied to each component of the camera.
The mode setting circuit 25 includes a switch operated by a user (user) of the camera, and notifies the control circuit 10 of the setting contents of the above-described operation mode associated with the operation on the switch.

  In this camera, the above-described shooting mode and playback mode are defined as operation modes, and a show window mode is defined as one of the shooting modes. The show window mode is a shooting mode selected by the user when shooting a subject through glass, for example, when shooting a subject separated by a show window.

The instruction / operation unit 26 includes various switches operated by the user, and notifies the control circuit 10 of instructions from the user associated with operations on the switches.
The camera shown in FIG. 1 is configured as described above.

Next, FIG. 2 will be described. This figure is a flowchart showing the processing contents of the control processing performed by the control circuit 10 when performing the photographing operation with the camera shown in FIG.
The processing shown in the figure is realized by the CPU of the control circuit 10 executing the above-described control program stored in the ROM, and when the supply of power to the power supply unit 24 is started, the processing of the power switch 24a is performed. Its execution starts regardless of the state.

First, in S101, it is determined whether or not it is detected that the power switch 24a is turned on, and this determination process is repeated until this detection is made.
When it is detected that the power switch 24a is turned on, in S102, a process for determining whether or not the above-described operation mode has been set is performed. If the operation mode has already been set, the process proceeds to S103. On the other hand, when the operation mode is not set, the process of S102 is repeated until the operation mode is set.

The following processing is based on the assumption that the operation mode is set to the shooting mode.
In S103, a process for determining whether or not the first release has been performed by half-pressing the release button of the instruction / operation unit 26, that is, whether or not an instruction for a shooting preparation operation from the user has been acquired, is performed. The process of S103 is repeated until an instruction is acquired.

In S104, AE (Auto Exposure) processing is performed based on the output signal of the image sensor 12 at this time.
In S105, AF (Auto Focus) processing corresponding to the type of shooting mode is performed. Details of this processing will be described later.

  In S106, a process is performed to determine whether or not the user has fully pressed the release button of the instruction / operation unit 26 to release 2nd, that is, whether or not an instruction to execute shooting has been acquired from the user. If it is determined that the process is acquired, the process proceeds to S107. On the other hand, if it is determined that this instruction has not been acquired, the process returns to S103 and the above-described process is repeated.

In S107, processing for temporarily storing the image data of the image captured by the image sensor 12 output from the A / D converter 13 at this time in the DRAM 20 is performed.
In S108, a process for reading the image data stored in the process of the previous step from the DRAM 20 is performed.

In S109, the image data read out in the process of the previous step is sent to the white balance correction circuit 14, and the process of correcting the white balance of the image represented by the image data is performed.
In S110, the image data that has been subjected to the white balance correction process in the process of the previous step is sent to the Y / C separation generation circuit 15, and the color representation is converted from the RGB component representation to the Y / C component representation. Is called.

In S111, the image data after the conversion in the process of the previous step is sent to the compression / decompression circuit 16 to compress the data.
In S112, a process of sending the image data after data compression by the process of the previous step to the memory card I / F 17 and recording it on the memory card 18 is performed, and thereafter the process shown in FIG. .

Next, FIG. 3 will be described. This figure shows the processing contents of the AF processing in a flowchart. This process is the process of S105 in the control process shown in FIG.
First, in S201, a process is performed to determine what the user has specifically set the shooting mode. Here, if the above-described show window mode is set as the shooting mode, AF processing for the show window mode is performed in S202. On the other hand, if another mode which is a shooting mode is set, in S203, a general-purpose, that is, AF processing for a shooting mode other than the show window mode is performed.

After finishing the process of S202 or S203 above, the process shown in FIG. 3 ends, and the process returns to the control process of FIG.
Next, FIG. 4 will be described. This figure is a flowchart showing the contents of the show window mode AF process. This process is the process of S202 in FIG.

First, in step S301, the photographing lens drive circuit 22 is controlled to drive the photographing lens 11 at a high speed, and the focal point on the subject side is moved to a position closest to the photographing lens 11.
In S302, the determination of exceeding the in-focus position for the autofocus function using the contrast method is started. The autofocus operation will be briefly described.

  As described above, the AF signal acquisition circuit 21 outputs a high-frequency component of a luminance signal in an image captured by the image sensor 12 through the photographing lens 11. It can be considered that the amount of the high-frequency component corresponds to the contrast level of the image. In general, it can be considered that a higher-contrast image is more accurately focused. Therefore, the control circuit 10 controls the photographic lens driving circuit 22 to move the photographic lens 11, and the photographic lens 11 when the amount of the high-frequency component obtained from the AF signal acquisition circuit 21 at that time becomes maximum is obtained. The position is set as the in-focus position for the subject represented in the image. The above operation is an autofocus method using a contrast method, which is also called “mountain climbing method”.

  In the determination of exceeding the in-focus position started in S302, the photographic lens drive circuit 22 is controlled to move the photographic lens 11 from the position where the focal point on the subject side is closest to the position where it is farthest. Information on the position of the photographic lens 11 when the signal output from the AF signal acquisition circuit 21 during the period becomes maximum, that is, when the high-frequency component of the luminance signal in the image picked up by the image sensor 12 becomes maximum, one after another. To detect and record. The position of the photographic lens 11 recorded in this way is the focal position of the photographic lens 11 for each of a plurality of subjects included in the image captured by the image sensor 12.

Here, since the photographing lens 11 is moved from the position where the in-focus point on the subject side is the closest to the position where the focal point is the farthest, a plurality of subjects included in the image captured by the image sensor 12 are detected. Among these, detection is performed in order from the in-focus position for the one close to the photographing lens 11.
In S303, a process for determining whether or not the above-mentioned in-focus position determination has been completed is performed. When it is determined that the determination has been completed (when the determination result is Yes), the process proceeds to S304. On the other hand, when it is determined that the process has not been completed yet (when the determination result is No), the process of S303 is repeated until the process is completed.

  In S304, processing is performed to determine whether or not the in-focus position determination has failed, that is, whether or not the maximum of the output signal of the AF signal acquisition circuit 21 has not been detected even when the position of the photographing lens 11 is moved. . Here, when it is determined that the in-focus position determination is unsuccessful (when the determination result is Yes), in S305, an error process, for example, a process of displaying the autofocus failure on the display unit 19 and notifying the user is performed. The control process of FIG. 2 is once ended. On the other hand, when it is determined that the in-focus position excess determination is not a failure (when the determination result is No), that is, when the maximum of the output signal of the AF signal acquisition circuit 21 can be detected, the process proceeds to S306.

  In the above-described processing from S302 to S305, even if the photographing lens 11 is moved by a predetermined movement amount from the position where the focal point on the subject side is closest, the output of the AF signal acquisition circuit 21 during this movement period. If the signal maximum cannot be detected, the determination of exceeding the in-focus position is aborted without further moving the photographing lens 11 to the position where the in-focus point on the subject side is farthest, and it is determined that the in-focus position determination has failed. An error process may be performed after determination. By doing so, the time required for the determination of exceeding the in-focus position is shortened.

In S306, processing is performed to detect the brightness of the image currently captured by the image sensor 12 and determine whether the brightness value is equal to or lower than a predetermined value (that is, whether the brightness of the image is dark). Done.
Here, when it is determined that the luminance value is equal to or less than the predetermined value (when the determination result is Yes), in S307, out of the in-focus positions of the photographing lens 11 detected in the above-described in-focus position determination. For the closest subject, that is, in the in-focus position determination described above, the in-focus position detected by moving the photographic lens 11 from the closest position to the farthest position on the subject side. Of these, the first detected one is selected, and the photographing lens drive circuit 22 is controlled to move the photographing lens 11 to the selected in-focus position.

  On the other hand, when it is determined in S306 that the luminance value is larger than the predetermined value described above (when the determination result is No), in S308, the alignment of the photographing lens 11 detected in the above-described in-focus position determination is determined. For the subject closest to the focus position, that is, in the above-described determination of exceeding the focus position, the photographic lens 11 is moved from the position where the focus on the subject side is the closest to the position where the focus is farthest. A process is performed in which the second detected one of the detected in-focus positions is selected, and the photographic lens 11 is moved to the selected in-focus position by controlling the photographic lens driving circuit 22.

After finishing the process of S307 or S308, the process shown in FIG. 4 is finished, and the process returns to FIG.
The processing from S306 to S308 will be further described with reference to FIGS.

  In FIG. 5, (a) shows an example of a shooting scene in which the brightness of the image captured by the image sensor 12 is sufficiently bright and the determination result in S306 is No. This example is a scene in which a user 31 located outside a dark room at night captures a person 32 located in a bright room across a show window 33 made of glass with a camera 30 through the glass.

  FIG. 5B shows an image viewed by the user 31 through the optical viewfinder (the optical path does not pass through the photographing lens 11) of the camera 30 in this scene. In this image, characters 34 written on the show window 33 are shown together with a person 32 that can be seen through the show window 33. In this case, since the room in which the person 32 is located is extremely brighter than the scenery (background 35) located far behind the user 31 in (a), the background 35 is reflected by the show window 33. Thus, it does not appear in the image of FIG.

  FIG. 5C shows the relationship between the position of the photographic lens 11 of the camera 30 and the contrast of an image captured by the image sensor 12 through the photographic lens 11 in the scene of FIG. In FIG. 5C, the horizontal axis indicates the position of the photographing lens 11 when the focal point on the subject side is closest to the right end, and indicates the position of the photographing lens 11 that is farthest on the left end. Yes. The vertical axis indicates the contrast of the image. The higher the value is, the higher the contrast is, that is, the higher the level of the signal output from the AF signal acquisition circuit 21 is.

  As shown in FIG. 5 (c), in the scene of FIG. 5 (a), when the photographing lens 11 is moved from the position where the in-focus point on the subject side is closest to the position where it is farthest, 2 is obtained. Contrast is maximized at a point. On the other hand, from (b), it can be seen that the character 34 and the person 32 are represented in the image captured by the image sensor 12 through the photographing lens 11.

  Here, when the positional relationship between the character 34 and the person 32 with respect to the camera 30 in (a) is considered, among the maximum points of contrast in (c), the one with the closest focal point on the subject side (that is, the closest one) Is the focus position of the photographic lens 11 with respect to the character 34, and the far side (that is, the second closest one) is the focus position of the photographic lens 11 with respect to the person 32. Therefore, in order to focus on the person 32 through the show window 33, the object closest to the subject (that is, the character 34 of the show window 33) out of the focus position of the photographic lens 11 is ignored. You can select the one for the closest subject.

  In the process of FIG. 4, since the determination result of S306 is No and the process of S308 is executed in the scene of FIG. 5A, the photographing lens 11 is moved to the in-focus position where the person 32 is focused. As a result, an image in which the person 32 is properly focused, not the character 34, is captured.

Next, FIG. 6 will be described.
6A illustrates an example of a shooting scene in which the brightness of an image captured by the image sensor 12 is sufficiently dark and the determination result in S306 is Yes. This example is a scene in which a user 31 located outside a bright room in the daytime takes a picture of a person 32 located in a dark room across a glass window with a camera 30 through a show window 33 made of glass.

  FIG. 6B shows an image viewed by the user 30 through the same optical viewfinder as that described above in this scene. In this image, a background 35 located far behind the user 31 is shown with a person 32 reflected by the show window 33 and seen through the show window 33. At this time, the characters 34 written on the show window 33 are melted into the reflected image of the background 35, resulting in an unclear image.

Since the show window 33 is substantially transparent glass, the brightness of the background 35 incident on the camera 10 due to reflection by the show window 33 is not high.
FIG. 6C shows the relationship between the position of the photographic lens 11 of the camera 30 and the contrast of an image captured by the image sensor 12 through the photographic lens 11 in the scene of FIG. The meanings of the horizontal and vertical axes in FIG. 6C are the same as those in FIG.

  As shown in FIG. 6C, in the scene of FIG. 6A as well, as in the scene of FIG. 5A, the focal point on the subject side is farthest from the closest position. When the photographing lens 11 is moved to the position, the contrast becomes maximum at two points. On the other hand, it can be seen from FIG. 6B that the reflected image of the background 35 and the person 32 are represented in the image captured by the image sensor 12 through the photographing lens 11.

  Here, when the positional relationship between the background 35 and the person 32 with respect to the camera 30 in (a) is taken into consideration, among the maximum contrast points in (c), the one with the closest focal point on the subject side (that is, the closest one). Is the in-focus position of the taking lens 11 with respect to the person 32, and the far side (that is, the second closest one) is the in-focus position of the taking lens 11 with respect to the background 35. Therefore, in order to focus on the person 32 through the show window 33, it is only necessary to select the closest subject among the in-focus positions of the taking lens 11.

  In the process of FIG. 4, in the scene of FIG. 6A, the determination result in S <b> 306 is Yes and the process in S <b> 307 is executed, so the photographing lens 11 is moved to the in-focus position where the person 32 is focused. As a result, not the background 35 shown in the show window 33 but an image in which the person 32 is properly focused is photographed.

  As described above, in the AF processing for the show window mode shown in FIG. 4, whether or not the imaging through the show window 33 is affected by the show window 33 in the processing of S306 is currently imaged by the image sensor 12. The determination is based on the brightness of the image. Here, if it is determined to be affected, in the process of S308, an adjustment other than that for the closest subject among the in-focus positions of the taking lens 11 (that is, for the character 34 of the show window 33). The focal position is selected and the photographing lens 11 is moved. As a result, autofocus photography through glass is appropriate.

Next, FIG. 7 will be described. This figure is a flowchart showing the contents of general AF processing other than the show window mode. This process is the process of S203 in FIG.
First, in S401, a direction determination process is started. The direction determination process is based on the change in the output signal of the AF signal acquisition circuit 21 obtained when the photographing lens drive circuit 22 is controlled to slightly drive the photographing lens 11 with respect to the current position of the photographing lens 11. This is a process for determining in which direction of the close side or the telephoto side the contrast increases (whether the level of the output signal of the AF signal acquisition circuit 21 increases).

In S402, a process for determining whether or not the above-described direction determination is completed is performed. When it is determined that the determination is completed (when the determination result is Yes), the process proceeds to S405.
On the other hand, when it is determined that it has not been completed yet (when the determination result is No), whether or not this direction determination has failed in S403, that is, even if the position of the photographing lens 11 is moved, an AF signal is acquired. A process is performed to determine whether or not a change in the output signal of the circuit 21 could not be detected. Here, when it is determined that the direction determination has failed (when the determination result is Yes), an error process is performed as S404, for example, a process of displaying the autofocus failure on the display unit 19 and notifying the user is performed. Then, the control process of FIG. On the other hand, when it is determined that this direction determination is not a failure (when the determination result is No), for example, when this direction determination is incomplete, the processing is returned to S402 and the above-described processing is repeated.

  In S405, determination of exceeding the in-focus position for the autofocus function using the contrast method is started, and in subsequent S406, processing for determining whether or not the above-described in-focus position excess determination is completed is performed. This in-focus position excess determination is the same as that in S302 to S303 in FIG. 4, but the image is picked up by the image sensor 12 at the in-focus position along with the detection result of the in-focus position of the taking lens 11. The maximum value of the high frequency component of the luminance signal in the image is also recorded.

In the determination process of S406, when it is determined that the in-focus position excess determination is completed (when the determination result is Yes), the process proceeds to S407. On the other hand, when it is determined that the process has not been completed yet (when the determination result is No), the process of S406 is repeated until the process is completed.
In S407, a process is performed to determine whether or not the in-focus position determination has failed, that is, whether or not the output signal maximum of the AF signal acquisition circuit 21 has not been detected even if the position of the photographing lens 11 is moved. .

  If it is determined that the in-focus position excess determination has failed (when the determination result is Yes), an error process is performed in S408, for example, a process of displaying a failure of autofocus on the display unit 19 and notifying the user. The control process of FIG. 2 is once ended. On the other hand, when it is determined that the in-focus position excess determination is not a failure (when the determination result is No), that is, when the maximum of the output signal of the AF signal acquisition circuit 21 can be detected, the process proceeds to S409.

  In S409, the in-focus position of the photographing lens 11 detected in the above-described in-focus position determination has the highest contrast of the image captured by the image sensor 12, that is, the high-frequency component of the luminance signal in the image. Is selected and the photographing lens drive circuit 22 is controlled to move the photographing lens 11 to the selected in-focus position. Thereafter, the processing shown in FIG. 7 ends, and the processing returns to FIG.

When the control circuit 10 in FIG. 1 performs the above processing, the camera shown in FIG. 1 can take an image using the autofocus function according to the present invention.
Next, an embodiment in which the present invention is implemented in the case of using a so-called multi-AF method in which the focus position of the photographing lens 11 is separately detected for a subject included in each of a plurality of regions of a captured image will be described.

  Since the configuration of the camera according to this embodiment is the same as that shown in FIG. 1, the description thereof is omitted. Further, regarding the processing contents of the control processing performed by the control circuit 10 when performing the photographing operation using the multi-AF method with the camera having this configuration, the AF processing for the show window mode in S202 and the show window in S203 in FIG. Except for the general-purpose AF processing for shooting modes other than the mode, the processing is the same as that shown in the flowcharts in FIGS.

Here, FIG. 8 will be described. This figure is a flowchart showing the contents of the show window mode multi-AF process executed as the process of S202 in FIG. 3 during multi-AF.
First, in step S311, the photographing lens driving circuit 22 is controlled to drive the photographing lens 11 at a high speed, and the focal point on the subject side is moved to a position closest to the photographing lens 11.

  In S <b> 312, determination of exceeding the in-focus position for the autofocus function using the same contrast method as described above is started for each region (multi-AF area) defined in advance for the image captured by the image sensor 12. The However, in this in-focus position determination, the photographic lens drive circuit 22 is controlled to move the photographic lens 11 from the position where the focal point on the subject side is closest to the farthest position, and this period of movement. The position of the photographic lens 11 when the signal output from the AF signal acquisition circuit 21 first reaches a maximum, that is, when the high-frequency component of the luminance signal in the image captured by the image sensor 12 first reaches the maximum. Information is sequentially detected and recorded for each multi-AF area. The position of the photographic lens 11 recorded in this way is the focal position of the photographic lens 11 for the closest subject included in each multi-AF area in the image captured by the image sensor 12.

  In S313, a process for determining whether or not the above-described in-focus position determination has been completed in all the multi-AF areas is performed. When it is determined that the determination has been completed (when the determination result is Yes), the process proceeds to S314. To proceed. On the other hand, when it is determined that the process has not been completed yet (when the determination result is No), the process of S313 is repeated until the process is completed.

  In S314, whether or not the in-focus position determination has failed in all the multi-AF areas, that is, the maximum of the output signal of the AF signal acquisition circuit 21 is detected in all the multi-AF areas even if the position of the photographing lens 11 is moved. A process is performed to determine whether or not it could be detected. Here, when it is determined that the in-focus position excess determination has failed in all the multi-AF areas (when the determination result is Yes), error processing such as autofocus failure is displayed on the display unit 19 in S315. A process of notifying the user is performed, and the control process of FIG. On the other hand, when it is determined that the in-focus position excess determination has not failed (when the determination result is No), that is, when the maximum of the output signal of the AF signal acquisition circuit 21 can be detected in any multi-AF area, S316. Proceed with the process.

In S316, a process of detecting the brightness of the image currently captured by the image sensor 12 and determining whether the brightness value is equal to or less than a predetermined value (that is, whether the brightness of the image is dark). Done.
Here, when it is determined that the luminance value is equal to or smaller than the predetermined value (when the determination result is Yes), in S317, the multiple AF areas detected in the above-described in-focus position determination are closest to each other. Of the in-focus position of the photographic lens 11 with respect to the subject, the one closest to the photographic lens 11, that is, in the above-described determination of exceeding the in-focus position, the position on the subject side from the position where the in-focus point is closest. The photographic lens 11 is moved to a far position and the first detected one of the in-focus positions detected for each multi-AF area is selected, and the photographic lens driving circuit 22 is controlled to reach the selected in-focus position. A process for moving the photographic lens 11 is performed, and then the process proceeds to S319.

  On the other hand, when it is determined in S316 that the luminance value is larger than the predetermined value described above (when the determination result is No), in S318, for each multi-AF area detected in the above-described in-focus position determination. Among the in-focus positions of the closest photographing lens 11, the object closest to the second object, that is, the position where the in-focus position on the object side is farthest from the closest position in the above-described in-focus position determination. Of the in-focus position detected for each multi-AF area is selected, and the second detected one is selected, and the photographic lens drive circuit 22 is controlled to the selected in-focus position. The process of moving is performed.

  In S319, a process of superimposing and displaying a frame indicating the multi-AF area in which the in-focus position selected in the process of S317 or S318 has been detected on the captured image of the image sensor 12 being displayed on the display unit 19 is performed. Thereafter, the processing shown in FIG. 8 ends, and the processing returns to FIG.

The processing from S316 to S319 will be further described with reference to FIGS.
First, FIG. 9 will be described. The figure shows an example of definition of a multi-AF area for an image captured by the image sensor 12. In the following description, it is assumed that the multi-AF area is defined as shown in FIG.

Next, FIGS. 10 and 11 will be described.
In FIG. 10A, in the shooting scene in which the brightness of the image captured by the image sensor 12 is sufficiently bright and the determination result in S316 is No, the user 31 passes through the optical viewfinder of the camera 30 (the optical path passes through the shooting lens 11). This is an example of a picture viewed through This shooting scene is assumed to be the same as that shown in FIG.

  In the image shown in FIG. 10A, the characters 34 written on the show window 33 are shown together with the person 32 seen through the show window 33. In this case, since the room in which the person 32 is located is extremely brighter than the scenery (background 35) located far behind the user 31 in FIG. 5A, the background 35 is the show window 33. And is not reflected in the image of FIG.

  Here, FIG. 11 will be described. FIG. 9 shows the relationship between the position of the photographic lens 11 of the camera 30 and the contrast of the image captured by the image sensor 12 through the photographic lens 11 in the photographic scene where the image of FIG. Each multi-AF area shown in FIG.

  11, the horizontal axis indicates the position of the photographing lens 11 when the focal point on the subject side is closest to the right end, and indicates the position of the photographing lens 11 that is farthest on the left end. Yes. The vertical axis indicates the contrast of the captured image in each multi-AF area, and the higher the contrast is, the higher the level of the signal output from the AF signal acquisition circuit 21 is. .

Consider each figure in FIG.
In the shooting scene in which the image of FIG. 10A is obtained, if the shooting lens 11 is moved from the position where the focal point on the subject side is closest to the position where it is farthest, areas (2) and (7) In the multi-AF areas of (8) and (9), the contrast becomes maximum at one point, and the position of the photographing lens 11 at this maximum is the in-focus position with respect to the person 32. Further, in the multi-AF area of area (5), the contrast becomes maximum at two points, and the closest object among the subjects focused at the position of the photographing lens 11 at this maximum is the character 34. On the other hand, the maximum contrast is not detected in each of the multi-AF areas (1), (3), (4), and (6).

In the process of FIG. 8, in the shooting scene where the image of FIG. 10A is obtained, the determination result of S316 is No and the process of S318 is executed. Select the one for the subject closest to the focus position.
In FIG. 11, among the in-focus positions of the closest photographing lens 11 for each multi-AF area, the one for the closest subject is the in-focus position for the character 34 in the area (5). This is the process of S318. Is ignored. Here, the second closest subject is one of the in-focus positions in the multi-AF area of the areas (2), (7), (8), or (9). 32 is the in-focus position. Therefore, since the photographing lens 11 is moved to the in-focus position where the person 32 is focused, an image in which the person 32 is properly focused, not the character 34, is captured.

  FIG. 10B shows an example of a screen displayed on the display unit 19 by the process of S319 as a result of the selection of the in-focus position as described above. The screen example shown in the figure shows a case where the area (8) is selected as the multi-AF area that obtains the in-focus position for the second closest subject.

Next, FIGS. 12 and 13 will be described.
FIG. 12A shows an example of an image viewed by the user 31 through the same optical viewfinder as described above in a shooting scene where the brightness of the image captured by the image sensor 12 is sufficiently dark and the determination result in S316 is Yes. Is shown. This shooting scene is assumed to be the same as that shown in FIG.

  In the image shown in FIG. 12A, a background 35 located far behind the user 31 is reflected along with the person 32 reflected by the show window 33 and seen through the show window 33. . At this time, the characters 34 written on the show window 33 are melted into the reflected image of the background 35, resulting in an unclear image. Here, since the show window 33 is substantially transparent glass, the brightness of the background 35 incident on the camera 30 due to reflection by the show window 33 is never high.

  Here, FIG. 13 will be described. FIG. 9 shows the relationship between the position of the photographic lens 11 of the camera 30 and the contrast of the image captured by the image sensor 12 through the photographic lens 11 in the photographic scene where the image of FIG. Each multi-AF area shown in FIG. The meanings of the horizontal axis and the vertical axis in FIG. 13 are the same as those in FIG.

  In the shooting scene in which the image of FIG. 12A is obtained, if the shooting lens 11 is moved from the position where the focal point on the subject side is closest to the position where it is farthest, areas (1) and (3) In each of the multi-AF areas of (4) and (6), the contrast becomes maximum at one point, and the position of the photographing lens 11 at this maximum is a focus position with respect to the background 35 reflected in the show window 33. In each of the multi-AF areas of areas (2), (5), (7), (8), and (9), the contrast becomes maximum at two points, and the subject is focused at the position of the photographing lens 11 at this maximum. Of these, the closest one is the person 32.

In the process of FIG. 8, in the shooting scene where the image of FIG. 12A is obtained, the determination result of S316 is Yes and the process of S317 is executed. Of the in-focus positions, the one for the closest subject is selected.
In FIG. 13, the area (2), (5), (7), (8), or (9) for the closest subject among the in-focus positions of the closest photographing lens 11 for each multi-AF area. Are in-focus positions in the multi-AF area, and these are all in-focus positions with respect to the person 32. Accordingly, since the photographing lens 11 is moved to a focus position at which the person 32 is focused, an image that is properly focused on the person 32 is captured instead of the background 35 reflected in the show window 33. .

  FIG. 12B shows an example of a screen displayed on the display unit 19 by the process of S319 as a result of the selection of the in-focus position as described above. The screen example shown in the figure shows a case where the area (5) is selected as the multi-AF area that has obtained the in-focus position for the closest subject.

  As described above, in the multi-AF process for the show window mode shown in FIG. 8, whether or not the imaging through the show window 33 is affected by the show window 33 in the process of S316 is currently imaged by the image sensor 12. The determination is based on the brightness of the image. If it is determined that the subject is affected, in the process of S318, the closest subject among the in-focus positions of the nearest photographing lens 11 for each multi-AF area (that is, the characters in the show window 33). The in-focus position other than that for 34 is selected and the taking lens 11 is moved. As a result, autofocus photography through glass is appropriate.

Next, FIG. 14 will be described. This figure is a flowchart showing the contents of a general-purpose multi-AF process other than the show window mode, which is executed as the process of S203 in FIG. 3 during multi-AF.
First, in S411, a direction determination process similar to that in S401 of FIG. 7 is started for each multi-AF area.

  In S412, a process for determining whether or not the above-described direction determination is completed in all the multi-AF areas is performed. When it is determined that the determination is completed (when the determination result is Yes), the process proceeds to S413. On the other hand, when it is determined that the process has not been completed (when the determination result is No), the process of S412 is repeated until the process is completed.

  In S413, whether or not the direction determination described above has failed in all the multi-AF areas, that is, the change in the output signal of the AF signal acquisition circuit 21 can be detected in all the multi-AF areas even if the position of the photographing lens 11 is moved. Processing for determining whether or not there has been is performed. Here, when it is determined that the direction determination has failed (when the determination result is Yes), an error process, for example, a process of displaying the autofocus failure on the display unit 19 and notifying the user is performed as S414. Then, the control process of FIG. On the other hand, when it is determined that this direction determination has not failed (when the determination result is No), that is, when the position of the photographic lens 11 is moved, the change in the output signal of the AF signal acquisition circuit 21 is changed to one of the multi-values. If it can be detected in the AF area, the process proceeds to S415.

  In S415, the determination of exceeding the in-focus position for the autofocus function by the contrast method is started for the multi-AF area for which the above-described direction determination is successful, and in subsequent S416, this alignment is performed for all the target multi-AF areas. Processing for determining whether or not the over-focus position determination has been completed is performed. The determination of exceeding the in-focus position is the same as that from S312 to S313 in FIG. 8, but the image is picked up by the image sensor 12 at the in-focus position together with the detection result of the in-focus position of the photographing lens 11. The maximum value of the high-frequency component of the luminance signal in the image is recorded together for each multi-AF area.

  In the determination process of S416, when it is determined that the in-focus position excess determination has been completed in all of the target multi-AF areas (when the determination result is Yes), the process proceeds to S417. On the other hand, when it is determined that the process has not been completed yet (when the determination result is No), the process of S416 is repeated until the process is completed.

  In S417, whether or not the in-focus position determination has failed in all of the target multi-AF areas, that is, even if the position of the photographic lens 11 is moved, the AF signal acquisition circuit 21 in all of the target multi-AF areas. A process is performed to determine whether or not the maximum of the output signal has been detected. Here, when it is determined that the in-focus position excess determination is unsuccessful (when the determination result is Yes), an error process is performed in S418, for example, a process of displaying the autofocus failure on the display unit 19 and notifying the user. The control process of FIG. 2 is once ended. On the other hand, when it is determined that the in-focus position excess determination has not failed (when the determination result is No), that is, when the maximum of the output signal of the AF signal acquisition circuit 21 can be detected in any multi-AF area, S419. Proceed with the process.

  In S419, among the in-focus positions of the photographing lens 11 for each multi-AF area detected in the above-described in-focus position determination, the subject closest to the in-focus lens 11, that is, the in-focus position determination described above. In this case, the first detected one of the in-focus positions detected for each multi-AF area is selected by moving the photographic lens 11 from the position where the focal point on the subject side is closest to the position where it is farthest. Processing for moving the photographic lens 11 to the selected in-focus position by controlling the photographic lens driving circuit 22 is performed.

In S420, a process of superimposing and displaying a frame indicating the multi-AF area in which the in-focus position selected in the process of S419 has been detected is displayed on the captured image of the image sensor 12 being displayed on the display unit 19, and thereafter. 14 ends, and the process returns to FIG.
When the control circuit 10 in FIG. 1 performs the above processing, the camera shown in FIG. 1 can take an image by multi-AF using the autofocus function according to the present invention.

  In addition, the present invention is not limited to the above-described embodiments, and various improvements and changes can be made without departing from the scope of the present invention.

It is a figure which shows the structure of the camera which implements this invention. It is a flowchart which shows the processing content of the control processing performed by a control circuit. It is a flowchart which shows the processing content of AF process in FIG. It is a flowchart which shows the processing content of AF process for show window modes. FIG. 6 is a diagram (part 1) for explaining an autofocus operation in a show window mode. FIG. 6 is a diagram (part 2) illustrating an autofocus operation in a show window mode. It is a flowchart which shows the processing content of a general purpose AF process. It is a flowchart which shows the processing content of the multi AF process for show window modes. It is a figure which shows the example of a definition of a multi AF area. FIG. 6 is a diagram (part 1) for explaining a multi-AF operation in a show window mode. FIG. 10 is a second diagram illustrating the multi-AF operation in the show window mode. FIG. 10 is a third diagram illustrating the multi-AF operation in the show window mode. FIG. 10 is a diagram (No. 4) for describing the multi-AF operation in the show window mode. It is a flowchart which shows the processing content of a general purpose multi AF process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control circuit 11 Shooting lens 12 Image pick-up element 13 A / D converter 14 White balance correction circuit 15 Y / C separation circuit 16 Compression / decompression circuit 17 Memory card I / F
18 Memory card 19 Display unit 20 DRAM
DESCRIPTION OF SYMBOLS 21 AF signal acquisition circuit 22 Shooting lens drive circuit 23 Image pick-up element drive circuit 24 Power supply part 24a Power switch 25 Mode setting circuit 26 Instruction / operation part

Claims (10)

An in-focus position detecting means for detecting, for each subject, the in-focus position of the photographing lens when the photographing lens is focused on each of a plurality of subjects represented in an image captured through the photographing lens;
Determination means for determining the presence or absence of the influence of the glass on the imaging performed through the glass;
If it is determined that there is an influence, one of the in-focus positions for the subject, excluding that for the subject closest to the photographing lens, is selected as a result of focus detection. Focusing position selection means;
A focus detection apparatus comprising:   The focus detection apparatus according to claim 1, wherein the focus position detection unit performs the detection based on a contrast of an image captured through the photographing lens.   The focus detection apparatus according to claim 1, wherein the determination unit determines the presence or absence of the influence based on brightness of an image captured through the photographing lens.   The in-focus position selecting means selects, when it is determined that there is the influence, the one for the subject closest to the photographing lens among the in-focus positions for the plurality of subjects. The focus detection apparatus according to claim 1, wherein   5. The focus detection according to claim 4, wherein the focus position detection unit detects the focus position of each of the plurality of subjects in order from the subject that is close to the photographing lens. apparatus. It further includes setting instruction acquisition means for acquiring an imaging condition setting instruction when performing imaging,
The in-focus position selection unit performs the selection based on a determination result by the determination unit when an imaging condition according to the setting instruction indicates imaging through glass.
The focus detection apparatus according to claim 1. The in-focus position detecting means performs the detection based on a contrast of an image captured through the photographing lens;
When the imaging condition according to the setting instruction indicates imaging other than imaging through glass, the in-focus position selection unit selects a subject image having the maximum contrast in the image regardless of the presence or absence of the influence. Selecting the in-focus position for the corresponding subject,
The focus detection apparatus according to claim 6. A plurality of areas obtained by dividing the image are defined in the image captured through the photographing lens,
The in-focus position detecting unit is configured to determine, for each region, a subject for the subject closest to the photographing lens among the in-focus positions for the subject corresponding to the subject image represented in the image in each of the regions. To detect
The in-focus position selecting means, when it is determined that the influence is present, any one of the in-focus positions detected for each area except for the subject closest to the photographing lens Select the focus position as the focus detection result,
The focus detection apparatus according to any one of claims 1 to 3, wherein the focus detection apparatus includes:   When it is determined that the influence is present, the focus position detection unit selects a subject that is second closest to the photographing lens from among the focus positions detected for each region. The focus detection apparatus according to claim 8. Detecting the in-focus position of the photographic lens when the photographic lens is focused on a plurality of subjects represented in an image captured through the photographic lens, for each subject;
Determine the presence or absence of the glass effect on the imaging performed through the glass,
When it is determined that there is the influence, one of the in-focus positions for the subject is selected as a focus detection result excluding the one for the subject closest to the photographing lens.
A focus detection method characterized by the above.

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