JP2009169238A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decide a lens position of an AF lens when photographing. <P>SOLUTION: A CPU 109 controls a lens driving circuit 101a to move the position of the AF lens to a plurality of positions, and controls to illuminate a subject at respective lens positions, and then it calculates AF evaluated values at the respective lens positions. The CPU 109 decides the position of the AF lens when photographing based on the calculated AF evaluated value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a camera.

  The following imaging devices are known. This imaging apparatus predicts the in-focus position based on the brightness of the subject and the light source color when photographing in a dark place (for example, Patent Document 1).

JP 2005-77924 A

  However, in the conventional imaging device, when shooting under the same shooting conditions, the same in-focus position is always predicted. Therefore, when the lens position of the focus adjustment lens (focus lens) is determined based on the prediction result Has a problem that its determination accuracy is low.

The camera according to the present invention includes an illuminating device control unit that controls an illuminating device that illuminates a subject, an imaging element that captures an image of a subject that is incident through the imaging optical system, and outputs an image signal, and a focus that the imaging optical system has. Focus adjustment means for adjusting the focus by the photographing optical system by moving the position of the adjustment lens, and moving the focus adjustment lens to a plurality of positions by the focus adjustment means, and the illumination device control means at each lens position by the illumination device control means For adjusting the focus based on the focus adjustment evaluation value calculated by the evaluation value calculating means and the evaluation value calculating means for calculating the focus adjustment evaluation value at each lens position. Lens position determining means for determining a lens position at the time of photographing of the lens.
The present invention further includes an automatic focus adjustment unit that automatically adjusts the focus of the photographing optical system and automatically determines the lens position at the time of shooting, and the lens position determination unit is a case where the focus adjustment by the automatic focus adjustment unit is successful. The lens position determined by the automatic focus adjustment unit is determined as the lens position at the time of shooting, and when the focus adjustment by the automatic focus adjustment unit fails, the focus adjustment evaluation value calculated by the evaluation value calculation unit is set. Based on this, the lens position at the time of photographing may be determined.
The lens position determining means determines a lens position at which the focus adjustment evaluation value is equal to or greater than a threshold as a lens position at the time of shooting. When there are a plurality of lens positions at which the focus adjustment evaluation value is equal to or greater than the threshold, The lens position at the time of shooting may be determined based on the lens position.
The lens position determination means determines a lens position at which the focus adjustment evaluation value is equal to or greater than a threshold value as a lens position at the time of shooting, and is set in advance when there are a plurality of lens positions at which the focus adjustment evaluation value is equal to or greater than the threshold value. The predetermined lens position may be the lens position at the time of shooting.
The focus adjustment evaluation value at the first lens position (focus adjustment evaluation value at the time of non-illumination) is recorded in a state where the subject is not illuminated by the illumination device, and the lens position determination means calculates the evaluation value at the first lens position. The difference (evaluation value difference) between the focus adjustment evaluation value calculated by the means and the focus adjustment evaluation value during non-illumination at the first lens position is calculated. When the lens position is at infinity and the evaluation value difference is larger than the threshold value, the lens position at the time of photographing may be set to a predetermined lens position set in advance.
The camera further includes shooting mode setting means for accepting setting by the user and setting the shooting mode, and the lens position determining means is set in the shooting mode for shooting a person in the night view by the shooting mode setting means. In other words, even when the evaluation value difference is within the threshold, the lens position at the time of shooting may be set to a predetermined lens position set in advance without setting the lens position to infinity.
The evaluation value calculation means may calculate a focus adjustment evaluation value based on an output signal from the image sensor.
The evaluation value calculation means may calculate a focus adjustment evaluation value based on an output signal from a focus detection sensor different from the image sensor.
The illumination timing control means determines the elapsed time since the last determination of the lens position at the time of shooting, and moves the focus adjustment lens to the first plurality of positions if the elapsed time is a predetermined time or more. If the elapsed time is less than the predetermined time, the focus adjustment lens is moved to a plurality of second positions smaller than the first plurality of positions to illuminate the subject. Also good.

  According to the present invention, the lens position of the focus adjustment lens can be determined with high accuracy even in a dark place.

  FIG. 1 is a block diagram illustrating a configuration of an embodiment of a camera according to the present embodiment. The camera 100 includes a lens 101, a lens driving circuit 101a, a diaphragm 102, a diaphragm driving circuit 102a, a shutter 103, a shutter driving circuit 103a, an image sensor 104, an AFE (Analog Front End) circuit 105, and an image. A processing circuit 106, a memory card slot 107, a flash 108, a flash drive circuit 108a, a CPU 109, an operation member 110, a RAM 111, a flash memory 112, and a monitor 113 are provided.

  The CPU 109 controls the entire camera 100 by reading the control program recorded in the flash memory 112 into the RAM 111 and executing it. The RAM 111 is a volatile memory, and is used as a work memory for the CPU 109 to develop a program when the program is executed, or as a buffer memory for temporarily recording data. The flash memory 112 is a non-volatile memory in which data of a program executed by the CPU 109, various parameters read during program execution, and the like are recorded.

  The lens 101 includes a plurality of optical lenses, and forms a subject image on the image sensor 104 via the diaphragm 102 and the shutter 103. The lens 101 in the present embodiment includes a focus adjusting lens, that is, an AF (Auto Focus) lens. The AF lens is moved by the lens driving circuit 101a, whereby the lens position is determined. The diaphragm drive circuit 102 a adjusts the aperture diameter of the diaphragm 102. The shutter drive circuit 103a opens and closes the shutter 103. The lens driving circuit 101a, the aperture driving circuit 102a, and the shutter driving circuit 103a operate in response to an instruction from the CPU 109.

  The image sensor 104 is an image sensor such as a CCD or a CMOS, for example. The image sensor 104 photoelectrically converts a subject image to generate an analog image signal, and outputs the generated analog image signal to the AFE circuit 105. In the present embodiment, the image sensor 104 is used as an AF sensor (AF sensor), and the CPU 109 determines an AF evaluation value (focus adjustment based on the contrast of the image based on the charge accumulated in the image sensor 104. (Evaluation value) is calculated. Then, the CPU 109 determines the AF lens position where the calculated AF evaluation value is the highest as the in-focus position, that is, the lens position of the AF lens at the time of shooting.

  The AFE circuit 105 performs gain adjustment on the analog image signal, for example, signal amplification according to the set ISO sensitivity. The AFE circuit 105 further converts the analog image signal into digital image data by a built-in A / D conversion circuit, and outputs the image data to the image processing circuit 106.

  The image processing circuit 106 performs various types of image processing on the digital image data, for example, color interpolation processing, gradation conversion processing, contour enhancement processing, white balance adjustment processing, etc. , Referred to as “image data”) is output to the RAM 111 as a buffer memory. The CPU 109 records the image data recorded in the RAM 111 on a flash memory 112 as a built-in memory or a memory card 107a inserted in a memory card slot 107 as an external memory.

  The flash 108 is a flash device for illuminating a subject. The flash drive circuit 108 discharges the capacitor in accordance with an instruction from the CPU 109 and supplies the discharge power to the light emitting unit included in the flash 108. The light emitting portion of the flash 108 is composed of, for example, a xenon tube or the like and emits light by discharge power from the capacitor.

  The operation member 109 includes various operation members operated by the user, such as a power button, a release button, a zoom button, a cross key, an enter button, a play button, and a delete button. The monitor 113 is a liquid crystal monitor (rear monitor) mounted on the back of the camera 100, and the CPU 109 sets an image of image data stored in the memory card 107a on the monitor 113, a setting menu for setting the camera 100, and the like. Is displayed by outputting.

  When shooting in the dark using the camera 100, generally, the subject is illuminated by irradiating auxiliary light for autofocus (AF auxiliary light), and focusing is performed. However, in this case, it is necessary to mount an apparatus for irradiating the camera 100 with AF auxiliary light, which is disadvantageous in terms of cost. Furthermore, since it is necessary to secure a space for mounting a device for irradiating the AF auxiliary light to the camera 100, it has been a factor that hinders downsizing of the camera 100. In addition, since the AF auxiliary light illuminates only the substantially central portion of the object scene, the conventional camera cannot adjust the focus when the main subject does not exist in the center of the object scene. In addition, even when a low-contrast subject exists at the center of the field, the conventional camera cannot perform focus adjustment.

  In order to avoid the above problem, there is an invention (see, for example, Japanese Patent Application Laid-Open No. 2005-77924) that determines a focus prediction point by determining shooting conditions from the brightness of a subject and a light source color. However, in this case, when shooting under the same shooting conditions, the focus is always on the same point, and there is a problem that the focus accuracy is low.

  In this embodiment, in order to avoid such a problem, the CPU 109 performs processing as follows. That is, the CPU 109 controls the lens driving circuit 101a to sequentially move the lens positions of the AF lenses included in the lens 101 to a plurality of preset lens positions. Then, at each lens position of the AF lens, the CPU 109 controls the flash control circuit 108a to illuminate the subject by causing the flash 108 to emit light. At this time, the analog image signal output from the AF sensor, that is, the image sensor 104, is output. get.

  The CPU 109 calculates the AF evaluation value at each lens position based on the analog image signal acquired at each lens position as described above, and determines the lens position with the highest calculated AF evaluation value as the lens position at the time of shooting. . This makes it possible to focus with high accuracy even when shooting in a dark place.

  It is assumed that the lens position for calculating the AF evaluation value is set in advance, and the lens position information is recorded in the flash memory 112. That is, the CPU 109 reads lens position information recorded in the flash memory 112. Then, the CPU 109 controls the lens driving circuit 101a based on the read lens position information, and sequentially moves the lens position of the AF lens to a plurality of preset lens positions. For example, as shown in FIG. 2, a case will be described in which four points F1 to F4 are set by lens position information as lens positions for calculating AF evaluation values.

  In this case, first, the CPU 109 moves the lens position of the AF lens to F1, for example, an AF point corresponding to the subject distance = 3 m, and illuminates the subject by causing the flash 108 to emit light at the time point 2a. Then, the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F1 based on the charge accumulated in the image sensor 104 at this time, and records the calculation result in the RAM 111.

  Next, the CPU 109 moves the lens position of the AF lens to F2, for example, an AF point corresponding to the subject distance = 2.5 m, and illuminates the subject by causing the flash 108 to emit light at time 2b. Then, the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F2 based on the charge accumulated in the image sensor 104 at this time, and records the calculation result in the RAM 111.

  Thereafter, the CPU 109 moves the lens position of the AF lens to F3, for example, an AF point corresponding to the subject distance = 2 m, and illuminates the subject by causing the flash 108 to emit light at time 2c. Then, the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F3 based on the charge accumulated in the image sensor 104 at this time, and records the calculation result in the RAM 111.

  Further, the CPU 109 moves the lens position of the AF lens to F4, for example, an AF point corresponding to the subject distance = 1.5 m, and illuminates the subject by causing the flash 108 to emit light at time 2d. The CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F4 based on the charge accumulated in the image sensor 104 at this time, and records the calculation result in the RAM 111.

  The CPU 109 specifies the largest AF evaluation value recorded at each lens position in the RAM 111. Then, the CPU 109 determines the lens position corresponding to the largest evaluation value as the lens position Fx at the time of shooting. Thereafter, at time 2e, when the release switch included in the operation member 110 is fully pressed by the user, the CPU 109 moves the AF lens to the lens position Fx at the time of shooting and causes the flash 108 to emit light (main emission). To shoot.

  At this time, if there are two lens positions having the largest AF evaluation value, the CPU 109 determines the lens position Fx at the time of shooting based on the two lens positions. For example, when the AF evaluation value at the lens position F2 and the AF evaluation value at the lens position F3 are the same value and the maximum value, the CPU 109 captures an intermediate position between the lens position F2 and the lens position F3. It is determined as the lens position Fx at the time.

  Note that the CPU 109 cannot determine the lens position at the time of shooting based on the AF evaluation value when the AF evaluation value at each lens position does not change as a result of performing the above-described processing. For example, when the user is shooting a distant view or when the subject distance is longer than the distance corresponding to the AF points F1 to F4, the AF evaluation value at each lens position is almost the same even when the above processing is performed. Since there is no difference, the focus point cannot be specified.

  Therefore, in this embodiment, in such a case, the CPU 109 determines the lens position at the time of shooting as follows. That is, as described above, after moving the lens position of the AF lens to F1, the CPU 108 accumulates in the image sensor 104 without causing the flash 108 to emit light at the time 2e before the time 2a when the flash 108 emits light. Based on the obtained electric charge, an AF evaluation value at the time of non-illumination at the lens position F1 is calculated. Then, the CPU 109 records the AF evaluation value during non-illumination at the lens position F1 in the RAM 111.

  Thereafter, if there is no difference in AF evaluation values during illumination at the respective lens positions F1 to F4 calculated by the above-described processing, the CPU 109 cannot identify the maximum value of the AF evaluation values. The AF evaluation value during non-illumination at the position F1 is compared with the AF evaluation value during illumination at the lens position F1. As a result of this comparison, if the difference in AF evaluation values is larger than the threshold value, it can be said that the difference in contrast between the images is large when illuminated and when not illuminated. Therefore, the CPU 109 determines that there is a high possibility that some subject exists, and sets the lens position at the time of shooting to a predetermined lens position set in advance, for example, F1 (lens position corresponding to subject distance = 3 m). To do.

  On the other hand, when the difference between the AF evaluation value at the lens position F1 during non-illumination and the AF evaluation value at the lens position F1 during illumination is equal to or less than a threshold value, the image contrast between the illumination and non-illumination It can be said that the difference is small. For this reason, the CPU 109 determines that there is no possibility that the subject is present and the user is likely to photograph a distant view, and sets the lens position at the time of photographing to a position where the AF point is at infinity.

  When the camera 100 can set a scene mode at the time of shooting and the mode is set to a shooting mode for shooting a person in a night view (night view portrait mode), the user Is going to be taken as a subject. Therefore, the CPU 109 sets the lens position at the time of shooting to infinity even when the difference between the AF evaluation value at the lens position F1 when not illuminated and the AF evaluation value at the lens position F1 during illumination is equal to or less than a threshold value. Is set to a predetermined lens position set in advance, for example, F1 (lens position corresponding to subject distance = 3 m).

  In the present embodiment, the CPU 109 determines that the four lenses F1 to F4 described above are used when the elapsed time since the last determination of the lens position is less than a predetermined time, for example, less than 1 minute. Among the positions, the AF evaluation value is calculated with respect to two lens positions, one of the lens position at the time of the previous photographing and the lens position before and after the lens position. For example, when the lens position at the time of the previous photographing is F2, the CPU 109 calculates the AF evaluation value at two lens positions, that is, the previous lens position F2 and the F3 closer to the AF point.

  Then, the CPU 109 determines the lens position corresponding to the larger one of the two calculated evaluation values as the lens position at the time of shooting. As a result, when the elapsed time from the previous shooting is short, the processing speed is increased by reducing the number of times the AF evaluation value is calculated, taking into account that there is a high possibility that the distance to the subject has not changed much. Can be

  Hereinafter, the processing by the CPU 109 will be described in detail with reference to the flowchart shown in FIG. The processing shown in FIG. 3 is executed by the CPU 109 as a program that is activated when the user presses the release button included in the operation member 110 halfway. Note that the data of this program is recorded in the flash memory 112.

  In step S <b> 10, the CPU 109 performs a known AF (Auto Focus / automatic focus adjustment) process and an AE (Automatic Exposure / automatic exposure adjustment) process based on the electric charge accumulated in the image sensor 104. That is, when the user sets the mode of the camera 100 to the above-described shooting mode, the CPU 109 controls the shutter driving circuit 103a to open the shutter 103, and performs the AF process and the AE process at regular time intervals. Execute. Then, it progresses to step S20.

  In step S20, the CPU 109 determines whether or not the release button included in the operation member 110 has been fully pressed by the user. If a negative determination is made, the process returns to step S10 and the process is repeated. On the other hand, if a positive determination is made, the process proceeds to step S30.

  In step S30, the CPU 109 determines whether or not the AF has succeeded in the AF process in step S10, that is, whether or not the lens position at the time of photographing has been determined by determining the AF point by the AF process. . If a positive determination is made, the process proceeds to step S40. In step S40, the CPU 109 sets the AF point determined by the AF process in step S10, and proceeds to step S50. In step S50, the CPU 109 controls the lens driving circuit 101a to move the position of the AF lens included in the lens 101 to the lens position corresponding to the determined AF point, that is, the lens position at the time of shooting, and then step S50. Proceed to S60.

  In step S60, the CPU 109 controls the shutter drive circuit 103a to close the shutter 103. Thereafter, the process proceeds to step S70, where the CPU 109 sweeps out all the charges accumulated in the image sensor 104, and proceeds to step S80. In step S80, the CPU 109 controls the AFE circuit 105 to set the ISO sensitivity based on the set value, and proceeds to step S90. In step S90, the CPU 109 controls the shutter drive circuit 103a to open the shutter 103, and proceeds to step S100.

  In step S100, the CPU 109 controls the flash drive circuit 108a to cause the flash 109 to perform main light emission for shooting, and simultaneously controls the image sensor 104 to perform imaging. Thereafter, the process proceeds to step S110, where the CPU 109 controls the AFE circuit 105 and the image processing circuit 106 to generate the above-described image data, and generates an image file of a predetermined format including the generated image data, for example, a JPEG format. . Thereafter, the CPU 109 records the generated image file on the flash memory 112 as the internal memory or the memory card 107a inserted in the memory card slot 107 as the external memory, and ends the processing.

  On the other hand, if a negative determination is made in step S30, the process proceeds to step S120. In step S120, the CPU 109 controls the AFE circuit 105 to set the ISO sensitivity to the maximum sensitivity. This is because the present invention aims at focusing in the dark. Thereafter, the process proceeds to step S121, and the CPU 109 determines whether or not an elapsed time since the last determination of the lens position at the time of shooting is less than one minute. If a negative determination is made, the process proceeds to step S130.

  In step S130, the CPU 109 sets the AF point F1 corresponding to the subject distance of 3 m at the time point 2e shown in FIG. 2, controls the lens driving circuit 101a, and shows the lens position of the AF lens in FIG. Move to lens position F1. Thereafter, the process proceeds to step S140, and the CPU 109 calculates an AF evaluation value during non-illumination at the lens position F1 based on the charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Thereafter, the process proceeds to step S150.

  In step S150, the CPU 109 controls the flash drive circuit 108a to cause the flash 108 to emit light while the lens position of the AF lens is F1 at the time point 2a shown in FIG. Thereafter, the process proceeds to step S160, and the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F1 based on the electric charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Thereafter, the process proceeds to step S170.

  In step S170, the CPU 109 sets the AF point F2 corresponding to the subject distance of 2.5 m, controls the lens driving circuit 101a, and moves the lens position of the AF lens to the lens position F2 shown in FIG. Thereafter, the process proceeds to step S180, and the CPU 109 controls the flash drive circuit 108a to cause the flash 108 to emit light at the time 2b shown in FIG. Thereafter, the process proceeds to step S190, and the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F2 based on the electric charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Then, it progresses to step S200.

  In step S200, the CPU 109 sets the AF point F3 corresponding to the subject distance of 2 m, controls the lens driving circuit 101a, and moves the lens position of the AF lens to the lens position F3 shown in FIG. Thereafter, the process proceeds to step S210, and the CPU 109 controls the flash drive circuit 108a to cause the flash 108 to emit light at the time 2c shown in FIG. Thereafter, the process proceeds to step S220, and the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F3 based on the charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Thereafter, the process proceeds to step S230.

  In step S230, the CPU 109 sets the AF point F4 corresponding to the subject distance of 1.5 m, controls the lens driving circuit 101a, and moves the lens position of the AF lens to the lens position F4 shown in FIG. Thereafter, the process proceeds to step S240, and the CPU 109 controls the flash drive circuit 108a to cause the flash 108 to emit light at the time 2d shown in FIG. Thereafter, the process proceeds to step S250, and the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position F4 based on the electric charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Thereafter, the process proceeds to step S260.

  In step S260, the CPU 109 reads the AF evaluation value calculated at each lens position described above from the RAM 111, and determines the AF point corresponding to the AF evaluation value having the highest value from all the AF evaluation values. Thereafter, the process proceeds to step S270, and the CPU 109 determines whether or not the AF evaluation value determined as the maximum value in step S260 is one. If the determination is affirmative, the process proceeds to step S280, and the CPU 109 sets the AF point with the highest AF evaluation value as the AF point at the time of shooting. Then, it progresses to step S50 mentioned above.

  On the other hand, if a negative determination is made in step S270, the process proceeds to step S290, and the CPU 109 determines whether there are two AF evaluation values determined as the maximum value in step S260. If the determination is affirmative, the process proceeds to step S340, and the CPU 109 sets an intermediate point between the two AF points having the highest AF evaluation value as an AF point at the time of shooting. Then, it progresses to step S50 mentioned above. In this step S290, the difference between the highest AF evaluation value and the second largest AF evaluation value is not more than a predetermined threshold value, and the difference between the highest AF evaluation value and the third largest AF evaluation value. If is greater than or equal to a predetermined threshold, an affirmative determination is made.

  On the other hand, if a negative determination is made in step S290, the process proceeds to step S300. In step S300, the CPU 109 determines whether or not the scene mode of the camera 100 is set to the night view portrait trade mode described above. If the determination is affirmative, the process proceeds to step S330, and the CPU 109 sets the AF point at the time of shooting to a predetermined position set in advance. Then, it progresses to step S50 mentioned above.

  On the other hand, if a negative determination is made in step S300, the process proceeds to step S310. In step S310, as described above, the CPU 109 compares the AF evaluation value during non-illumination at the lens position F1 with the AF evaluation value during illumination at the lens position F1, and determines whether or not the difference is within a threshold value. Judging. If the determination is affirmative, the process proceeds to step S330, and the CPU 109 sets the AF point at the time of shooting to a predetermined position set in advance, and then proceeds to step S50 described above. On the other hand, if a negative determination is made in step S310, the process proceeds to step S320, and the CPU 109 sets the AF point to infinity, and then proceeds to step S50 described above.

  If an affirmative determination is made in step S121, the process proceeds to step S122. In step S122, the CPU 109 selects AF points corresponding to two lens positions, that is, the lens position at the previous photographing and one of the lens positions before and after the lens position as a processing target. Thereafter, the process proceeds to step S123.

  In step S123, the CPU 109 sets one of the two AF points selected in step S122 as the first point, controls the lens driving circuit 101a, and sets the lens position of the AF lens to the first AF point. Move to the corresponding lens position. Thereafter, the process proceeds to step S124, and the CPU 109 calculates an AF evaluation value during non-illumination at the first lens position based on the electric charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Thereafter, the process proceeds to step S125.

  In step S125, the CPU 109 controls the flash drive circuit 108a to cause the flash 108 to emit light in a state where the lens position of the AF lens is in the first lens position described above. Thereafter, the process proceeds to step S126, and the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position of the first point based on the electric charge accumulated in the image sensor 104 at this time, and records it in the RAM 111. Thereafter, the process proceeds to step S127.

  In step S127, the CPU 109 sets the AF point to the second point that is not the first point among the two AF points selected in step S122, and controls the lens driving circuit 101a to control the lens of the AF lens. The position is moved to the lens position corresponding to the second AF point. Thereafter, the process proceeds to step S128.

  In step S128, the CPU 109 controls the flash drive circuit 108a to cause the flash 108 to emit light in a state where the lens position of the AF lens is at the second lens position described above. Thereafter, the process proceeds to step S129, and the CPU 109 calculates an AF evaluation value at the time of illumination at the lens position of the second point based on the electric charge accumulated in the imaging element 104 at this time, and records it in the RAM 111. Then, it progresses to step S260 mentioned above.

According to the present embodiment described above, the following operational effects can be obtained.
(1) The CPU 109 controls the lens driving circuit 101a to move the position of the AF lens to a plurality of positions, illuminates the subject at each lens position, and calculates an AF evaluation value at each lens position. Then, the CPU 109 determines the position of the AF lens at the time of shooting based on the calculated AF evaluation value. Thereby, the lens position of the focus adjustment lens can be determined with high accuracy even in a dark place.

(2) The CPU 109 determines the lens position at the time of shooting based on the AF point determined by the AF process when the AF is successful in the AF process in step S10. Thereby, the time required for the AF process can be shortened. On the other hand, when AF fails, the lens position at the time of shooting is determined based on the AF evaluation value acquired at each lens position. As a result, when it is impossible to focus by the known AF processing, it is possible to perform focusing with high accuracy using the method described above in the present embodiment.

(3) When there are a plurality of AF evaluation values determined as the maximum value, the CPU 109 sets an intermediate point between two AF points having the highest AF evaluation value as an AF point at the time of shooting. Accordingly, an AF point that is an intermediate point between the AF points for which the evaluation values are calculated can be set.

(4) When there are a plurality of AF evaluation values determined as the maximum value, the CPU 109 sets a predetermined lens position set in advance as the lens position at the time of shooting. As a result, even when there are a plurality of AF evaluation values, it is possible to photograph by specifying an AF point.

(5) The CPU 109 calculates an AF evaluation value during non-illumination at the lens position F1 and records it in the RAM 111. Then, the CPU 109 calculates the AF evaluation value at the time of illumination at the lens positions F1 to F4. As a result, when there is no difference between the AF evaluation values, the maximum value of the AF evaluation values cannot be specified. Compared the AF evaluation value at the lens position F1 when not illuminated with the AF evaluation value at the lens position F1 when illuminated. Then, as a result of comparing the two evaluation values, when the difference between the AF evaluation values is larger than the threshold value, the CPU 109 sets the lens position at the time of shooting to a predetermined lens position set in advance. Further, as a result of comparing the two evaluation values, when the difference between the AF evaluation values is equal to or smaller than the threshold value, the CPU 109 sets the lens position at the time of shooting to a position where the AF point is at infinity. As a result, when the difference in image contrast between illumination and non-illumination is large, there is a high possibility that a certain subject exists, so that the lens position at the time of photographing can be set to a predetermined lens position. On the other hand, if the difference in image contrast between illuminated and non-illuminated is small, there is no subject and there is a high possibility that the user is shooting a distant view. Can be set to

(6) When the scene mode of the camera 100 is set to the night view portrait mode, the CPU 109 calculates the non-illuminated AF evaluation value at the lens position F1 and the AF evaluation value at the lens position F1 during illumination. Even when the difference is less than or equal to the threshold value, the lens position at the time of shooting is not set to infinity, but is set to a predetermined lens position set in advance. As a result, when the scene mode is set to the night view portrait mode, it is clear that the user intends to photograph a person as a subject, and thus it is possible to photograph with a lens position that matches the user's intention.

(7) If the elapsed time since the last determination of the lens position at the time of shooting is less than a predetermined time, for example, less than 1 minute, the CPU 109 selects the previous one of the four lens positions F1 to F4 described above. The AF evaluation value is calculated for two lens positions, one of the lens position at the time of shooting and the lens position before and after the lens position. Thereby, when the elapsed time from the previous shooting is short, it is highly possible that the distance to the subject has not changed so much, and by reducing the number of AF evaluation value calculations, Processing can be speeded up.

(8) Since the CPU 109 emits the flash 108 and illuminates the subject to calculate the AF evaluation value, unlike the case where the AF auxiliary light is used, the CPU 109 calculates the AF evaluation value by illuminating the entire subject. Can do. For this reason, there is a problem that occurs when the subject is illuminated with AF auxiliary light as in a conventional camera, that is, when the main subject does not exist in the center of the object scene or there is a subject with low contrast in the center of the object field. In some cases, it is possible to solve the problem that the focus cannot be adjusted.

-Modification-
The camera according to the above-described embodiment can be modified as follows.
(1) In the above-described embodiment, the example in which the image sensor 104 is used as an AF sensor has been described. However, the present invention can be applied even when an AF sensor different from the image sensor 104 is used. In this case, an AF sensor may be incorporated in the image sensor 104.

(2) In the above-described embodiment, the example in which the camera 100 includes the lens 101 and the flash 108 has been described. However, the lens 101 may be an interchangeable lens that can be attached to and detached from the camera 100. The flash 108 may be a flash device that can be attached to and detached from the camera 100, or may be a remote flash device that emits light by performing remote communication with the camera 100.

(3) In the above-described embodiment, the CPU 109 explained an example in which the processing from step S130 to step S320 is executed after the ISO sensitivity is set to the highest sensitivity in step S120 in FIG. However, the CPU 109 may set the ISO sensitivity to a sensitivity lower than the maximum sensitivity.

(4) In the above-described embodiment, the CPU 109 moves the AF lens to each lens position from F1 to F4, calculates an AF evaluation value at the time of illumination at each lens position, and records it in the RAM 111. did. Then, after completing the calculation of the AF evaluation values at all lens positions, the CPU 109 specifies the maximum AF evaluation value from the AF evaluation values recorded in the RAM 111. However, the CPU 109 may move the AF lens to each lens position from F1 to F4, cause the flash 108 to emit light at each lens position, acquire image data, and record it in the RAM 111. Then, the CPU 109 may calculate an AF evaluation value at each lens position based on the image data at each lens position recorded in the RAM 111, and specify the maximum AF evaluation value from among the AF evaluation values.

(5) In the above-described embodiment, the CPU 109 specifies the highest value from the AF evaluation values calculated at each lens position, and determines the lens position corresponding to the highest AF evaluation value as the lens position at the time of shooting. The example to do was demonstrated. However, the CPU 109 specifies an AF evaluation value larger than a preset threshold value from the middle of the AF evaluation values calculated at the respective lens positions, and sets the lens position corresponding to the AF evaluation value larger than the threshold value to the lens position at the time of shooting. You may make it determine as. As a result, when all the AF evaluation values are small and are not in focus, even if the AF evaluation value that takes the maximum value is selected and the lens position at the time of shooting is determined, the in-focus image will be Such a problem can be avoided because it cannot be obtained.

  Further, when there are a plurality of AF evaluation values larger than the threshold value, the CPU 109 may determine the lens position at the time of shooting using the midpoint between the AF points corresponding to the AF evaluation values as the AF point at the time of shooting.

  Note that the present invention is not limited to the configurations in the above-described embodiments as long as the characteristic functions of the present invention are not impaired. Moreover, it is good also as a structure which combined the above-mentioned embodiment and a some modification.

It is a block diagram which shows the structure of one Embodiment of a camera. It is the figure which showed concrete each timing of the movement of AF lens, light emission of flash, and calculation of AF evaluation value. FIG. 6 is a flowchart showing processing of the camera 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Camera, 101 Lens, 101a Lens drive circuit, 102 Aperture, 102a Aperture drive circuit, 103 Shutter, 103a Shutter drive circuit, 104 Image sensor, 105 AFE circuit, 106 Image processing circuit, 107 Memory card slot, 107a Memory card, 108 Flash, 108a Flash drive circuit, 109 CPU, 110 operation member, 111 RAM, 112 Flash memory, 113 Monitor

Claims (9)

Lighting device control means for controlling a lighting device that illuminates a subject;
An image sensor that picks up an image of a subject incident via a photographing optical system and outputs an image signal;
Focus adjusting means for moving the position of a focus adjustment lens included in the photographing optical system and performing focus adjustment by the photographing optical system;
Illumination timing control means for illuminating a subject by moving the focus adjustment lens to a plurality of positions by the focus adjustment means and controlling the illumination apparatus by the illumination device control means at each lens position;
Evaluation value calculation means for calculating a focus adjustment evaluation value at each lens position;
A camera comprising: lens position determining means for determining a lens position at the time of photographing of the focus adjustment lens based on the focus adjustment evaluation value calculated by the evaluation value calculating means. The camera of claim 1,
It further comprises automatic focus adjustment means for performing focus adjustment of the photographing optical system and automatically determining a lens position at the time of photographing,
The lens position determining means determines the lens position determined by the automatic focus adjusting means as the lens position at the time of photographing when the focus adjustment by the automatic focus adjusting means is successful, and by the automatic focus adjusting means. A camera characterized in that, when focus adjustment fails, a lens position at the time of photographing is determined based on the focus adjustment evaluation value calculated by the evaluation value calculation means. The camera of claim 1,
The lens position determining means determines a lens position at which the focus adjustment evaluation value is equal to or greater than a threshold as a lens position at the time of photographing, and when there are a plurality of lens positions at which the focus adjustment evaluation value is equal to or greater than the threshold. A camera that determines a lens position at the time of photographing based on the plurality of lens positions. The camera of claim 1,
The lens position determining means determines a lens position at which the focus adjustment evaluation value is equal to or greater than a threshold as a lens position at the time of photographing, and when there are a plurality of lens positions at which the focus adjustment evaluation value is equal to or greater than the threshold. A camera having a predetermined lens position set in advance as the lens position at the time of photographing. The camera according to claim 4, wherein
Recording the focus adjustment evaluation value at the first lens position (focus adjustment evaluation value during non-illumination) in a state where the subject is not illuminated by the illumination device,
The lens position determining means is a difference between the focus adjustment evaluation value calculated by the evaluation value calculation means at the first lens position and the focus adjustment evaluation value at the first lens position during the non-illumination ( When the evaluation value difference is within a threshold, the lens position at the time of shooting is set to infinity, and when the evaluation value difference is larger than the threshold, the lens position at the time of shooting is calculated. A camera having a predetermined lens position set in advance. The camera according to claim 5, wherein
The camera further includes shooting mode setting means for receiving a setting by a user and setting a shooting mode,
The lens position determining means is set to the shooting mode setting means when the shooting mode setting means is set to a shooting mode for shooting a person in a night view even when the evaluation value difference is within a threshold value. A camera characterized in that a predetermined lens position is set in advance without setting the lens position to infinity. The camera of claim 1,
The evaluation value calculation means calculates the focus adjustment evaluation value based on an output signal from the image sensor. The camera of claim 1,
The evaluation value calculation means calculates the focus adjustment evaluation value based on an output signal from a focus detection sensor different from the image sensor. The camera of claim 1,
The illumination timing control means determines an elapsed time since the lens position at the time of photographing was previously determined, and when the elapsed time is equal to or longer than a predetermined time, the focus adjustment lens is moved to the first plurality of lenses. The subject is moved to a position to illuminate the subject, and when the elapsed time is less than a predetermined time, the focus adjustment lens is moved to a plurality of second positions smaller than the first plurality of positions. A camera characterized by illuminating.

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