JP2008145782A - Camera provided with focusing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera provided with a focusing device that can reduce search time when detecting a face. <P>SOLUTION: The camera provided with the focusing device includes: a focusing means which uses an imaging means to pick up a subject image formed by an imaging optical system having a focusing lens group while moving the focusing lens group along the optical axis between a near focus end and a far focus end, which performs focus search for detecting a focusing position on the basis of image signals acquired in a plurality of positions, and which moves the focusing lens group to the focusing position detected by the focus search; and a face detection means which detects a face image based on the image signals picked up by the imaging means. When the face detection means detects a face image, the focus means performs focus search from the far focus end side if the size of the face image is less than a prescribed threshold value, and from the near focus end side if the size is not less than the prescribed threshold value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a focus adjustment device, and more particularly to a camera including an image contrast type focus adjustment device.

Conventionally, a so-called image contrast type automatic focusing device is moved after the focusing lens group is moved to the focus search start end position at the near end (shortest focus position) or the infinity end (infinity focus position). Digital equipped with a focus adjustment device that performs a focus search operation that captures images while moving to the focus search end position at the infinity end or near end, and detects the focus state (focus position) based on the contrast of the captured images A camera is known that detects the face of a person from the captured image, detects the contrast of the face, and focuses on the face (Patent Document 1). The conventional digital camera starts the in-focus search by pressing the release button halfway. Further, a camera for performing a focus search after determining the focus search start position according to the stop position of the focus adjustment lens group at the start of the focus search process and moving the focus adjustment lens group to the focus search start position A camera that starts a search from a fixed focus search start position regardless of the stop position is known.
JP 2006-208443 A

  However, when searching for a far-distance subject from the near end, or conversely searching a near-distance subject from the infinity end, the search time becomes long and it takes time to focus. there were.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a camera equipped with a focus adjustment device capable of reducing the search time when a face is detected in a camera equipped with a face adjustment function and an image contrast type focus adjustment device.

  The present invention for solving such a problem is formed by an imaging optical system including the focus adjustment lens group while moving the focus adjustment lens group along the optical axis between the short distance focus end and the long distance focus end. The subject image is picked up by the image pickup means, a focus search for detecting a focus position based on image signals acquired at a plurality of positions is executed, and the focus adjustment lens group is placed at the focus position detected by the focus search. A focus adjustment unit that moves, and a face detection unit that detects a face image based on an image signal imaged by the imaging unit, and the focus adjustment unit detects when the face detection unit detects a face image. When the face image size is less than a predetermined threshold value, the focus search is performed from the far-distance focus end side, and when the face image size is equal to or greater than the predetermined threshold value, the focus search is performed from the short-range focus end side. Have.

Actually, when the face detection unit detects a face image, the focus adjustment unit detects a focus position where the face image is in a focused state.
An image area including the face image is set as a focus detection area, and a focus position is detected based on an image signal in the focus detection area. The focus detection area is preferably constant regardless of the size of the image area.
The focus search detects a lens position at which a contrast peak of the image signal in the focus detection area is obtained as a focus position.

In a preferred embodiment, when a contrast peak is obtained during the focus search, the focus search is stopped and the focusing lens group is moved to a position where the peak is obtained.
When the imaging optical system is a zoom lens, the threshold value is set based on the current focal length of the zoom lens.

  In a preferred embodiment, the imaging unit includes a display unit that displays an image captured. When the focus adjustment unit performs a focus search, a face image is included in the captured image signal during the focus search. The image signal of the image area is extracted and enlarged and displayed on the display means. After the focus search process is completed and the focus adjustment lens group is moved to the focus position, the captured image signal is displayed by the display means. Furthermore, when the image area including the face image is focused, it is preferable that the display means display an identification that allows the image area to be visually recognized.

  As described above, according to the present invention, when a face image is detected in a captured image, the face image is larger than a predetermined threshold value, that is, the face is closer than a predetermined distance. When the subject is located at a distance, a focus search is performed from the close-in focus end side. When the face image is less than the predetermined threshold value, that is, when the subject is located at a long distance, the focus is set from the far-in focus end side. Since the search is performed, when the subject is a face, it can be focused in a shorter time.

  The present invention will be described in detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a block diagram showing a main configuration of a so-called compact type digital camera including a contrast AF type focus adjustment apparatus to which the present invention is applied.

  In this digital camera, a subject image is formed on a light receiving surface of an image pickup device (CCD image sensor) 11 as an image pickup means by a zoom lens L as an image pickup optical system including a focus adjustment lens group L1. The image sensor 11 has a large number of pixels (photoelectric conversion elements) arranged vertically and horizontally at predetermined intervals, and each pixel converts the received object image into electric charge, which is accumulated (integrated). When the exposure is completed, the accumulated charge is output to the image signal processing circuit 13 as an image signal in units of pixels. The image signal processing circuit 13 performs predetermined adjustment processing such as white balance adjustment and A / D conversion processing on the input image signal and outputs digital image data to the CPU 15. That is, the image signal processing circuit 13 performs predetermined processing, and the image data digitally converted in units of pixels is output to the CPU 15. The CPU 15 converts the input image data into an image signal that can be displayed on the LCD (monitor) 17 in the through mode (monitor mode), and displays the image on the LCD 17. In the recording mode, the CPU 15 displays a predetermined format set. And is written into the image memory 21 via the image memory control circuit 19. Further, an EEPROM 29 is connected to the CPU 15 as a nonvolatile memory in which variable data and the like are written.

  In normal contrast AF processing, when the photometry switch SWS is turned on, the CPU 15 moves the focus adjustment lens group L1 through the motor driver 27, the AF motor 25, and the lens driving mechanism 23 to a near position (one movement limit position). The image is picked up by the image pickup device 11 while being step-driven from the closest focus position) or the far position (infinite focus position) to the far position or near position, which is the other movement limit position, and the captured image signal is taken in to the internal RAM 15a. And the contrast detection process is executed. Then, the peak of the contrast value is detected, and the focusing lens group L1 is moved to the lens position where the peak is obtained. The captured image signal is displayed on the LCD 17 in the through mode.

  This digital camera includes a zoom motor 28 that power zooms the zoom lens L via the lens driving mechanism 23, and the focal length of the zoom lens L is detected by an encoder built in the lens driving mechanism 23.

  Although details are not shown on the light receiving surface 12 of the image sensor 11, a red (R) filter, a green (G) filter, and a blue (B) filter as primary color filters are provided on the subject side from each pixel (photoelectric conversion element). Each pixel receives red, green, and blue components transmitted through the primary color filters R, G, and B in the subject luminous flux, photoelectrically converts them, and accumulates (integrates) them as electric charges. The charge accumulated for a predetermined time is read out in units of pixels and output as an image signal.

  FIG. 2 shows five focus detection areas 12A, 12B, 12C, 12D, and 12E as an example of the focus detection area on the light receiving surface 12 of the image sensor 11. FIG. 3 is an enlarged view of the central first focus detection area 12A. The first focus detection area 12A is located approximately at the center of the light receiving surface 12, and the second and third focus detection areas 12B and 12C are located on the left and right sides of the first focus detection area 12A, and the fourth and fifth focus. The detection areas 12D and 12E are positioned above and below the first focus detection area 12A. On the light receiving surface 12, a red (R) filter, a green (G) filter, and a blue (B) filter as primary color filters are arranged on the subject side from each pixel (photoelectric conversion element). The red, green, and blue components transmitted through the primary color filters R, G, and B are received in the light beam, photoelectrically converted, and accumulated (integrated) as charges. The charge accumulated for a predetermined time is read out in units of pixels and output as an image signal.

FIG. 3 shows a general primary color filter arrangement pattern (Bayer array). In the contrast AF processing in this embodiment, four pixels in a square of two pieces in the horizontal direction and two pieces in the vertical direction (2 × 2), that is, two filters G and one filter R and B each are included. the combination of 4 pixels as one block, the sum of the magnitudes of the image signals pixels in each block is accumulated as the brightness a _n.
a _n = G + R + B + G

Then, 1 and the brightness a _n blocks, the process of obtaining the difference (a _{n + 2} -a n) between the luminance a _{n + 2} of one block of every other block in the horizontal direction, horizontal in the focus detection area Repeat in the right direction and add the obtained luminance difference (a _{n + 2} −a _n ). When the processing for obtaining the luminance difference (a _{n + 2} −a _n ) reaches the rightmost block in the horizontal direction, the processing for obtaining the luminance difference and the addition processing are performed by shifting one block downward in the vertical direction and then the rightmost block. Repeat until you reach. The above difference addition processing is repeatedly executed for all blocks in the focus detection areas 12A to 12E. This process is executed for each of the five focus detection areas 12A to 12E.

The sum of the luminance differences (a _{n + 2} −a _n ) obtained for the focus detection areas 12A to 12E by the above processing becomes the contrast value of the focus detection areas 12A to 12E at the lens position.

  This digital camera has a face image recognition function for detecting whether an image signal related to a face image is included in the image signal based on an image signal (image data) captured by the image sensor 11 and written in the RAM 15a. The CPU 15 is provided. Facial image recognition and detection is performed by detecting a skin color in the entire captured image signal, detecting feature points such as eyes, nose, or mouth in a human face, or extracting a face outline. The recognition method is used. When a face image is detected, the position of the area including the face image is obtained, the focus detection area 12F centered on the center of the area is set, and the in-focus position is obtained from the image signal in the focus detection area 12F. . In this embodiment, the size of the focus detection area 12F is fixed, and the position is set to be the center of the detected face image.

  Further, this digital camera has an AF mode including an automatic mode including a face detection process and a face detection mode, a multi-mode not including the face detection process, and a spot mode using only the central focus detection area 12A. In the automatic mode or the face detection mode, a face image is detected, and focus processing is performed on the face image (subject image) in the focus detection area including the detected face image. When a face image cannot be detected, or in the multi or spot mode, focusing processing is performed on any of the subject images in the preset focus detection areas 12A to 12E.

  Here, in this embodiment, before executing the focus search process, the face detection process is executed to detect whether or not a face image signal corresponding to the face image exists in the captured image signal. When a face image signal is detected, it is determined whether or not the size of the face image region is larger than a threshold value set in advance according to the focal length. Therefore, the in-focus search process is executed with the near position as the in-focus search start position. When the subject is small, the in-focus search process is executed with the far position as the in-focus search start position. Note that even if the subject constituting the face image is located at the same distance, the face image becomes larger as the focal length becomes longer, so a threshold value corresponding to the current focal length of the zoom lens is set. Note that a plurality of threshold values are stored in the EEPROM 29 for each different focal length, but the threshold value to be stored may be one and corrected by counting according to the focal length. May be corrected by a coefficient.

  If the face image cannot be detected, the in-focus position is detected using all of the focus detection areas 12A to 12E or one set image signal.

  In this embodiment, the position of the focus adjustment lens group L1, the near position (short distance focusing position) and the far position (far distance focusing position) are detected by the origin sensors 23a and 23b, and the number of drive pulses from each position is detected. Count as. The drive pulse is defined as a pulse output from an encoder 26 such as a photo interrupter mounted on the output shaft of the AF motor 25, for example. Normally, several hundred pulses or more are required to drive the focus adjustment lens unit L1 from the near position to the far position. However, in order to simplify the description, in the contrast AF processing in this embodiment, several pulses or several pulses are required. It is assumed that step driving (imaging) is performed in units of ten pulses and driving can be performed with ten or more pulses from a near position to an infinite position, and one step corresponds to one drive pulse and position pulse.

  In this embodiment, the driving and position pulses are PN, the starting position, and in this embodiment, the near position is 0, and is increased by 1 in the far position direction. Whether searching from the near position to the far position or searching from the far position to the near position, the position pulse at the near position is 0, and when step driving from the near position to the far position, the position pulse is added, When step driving in the near position direction, the position pulse is subtracted.

  FIG. 4 shows the person images when the person is located at a short distance and when the person is located at a long distance, that is, face images 101 and 103, a focus detection area (focus detection area) 12F, and a face detection area 12G. The relationship was shown. As can be seen from this figure, for the same person, the face image 101 when positioned at a short distance is larger than the face image 103 when positioned at a long distance.

  FIGS. 5A and 5B show how the focus search start position is varied according to the size of the face image (face detection region 12G). FIG. 5A is a graph showing the relationship between the position of the focusing lens group L1 and the contrast value when the person is located at a short distance, and the movement locus of the focusing lens group L1 in the refocus search process. It was. FIG. 5B is a graph showing the relationship between the position of the focusing lens group L1 and the contrast value when the person is located at a long distance, and the movement locus of the focusing lens group L1 in the refocus search process. It was. In the figure, the position indicated by the symbol x is the position where the focusing lens group L1 has stopped when the AF process is started.

  When the face image 101 (face image detection region 12G) larger than the predetermined threshold is detected by the face detection process, the focus detection area 12F is set at the substantially center position of the face image 101, and the focus adjustment lens group L1 is set. Moving to the near position, the focus search process is executed in the direction of the far position, with the near position as the focus search start position and the far position as the focus search end position (FIG. 5A). Then, when the peak of the image signal in the focus detection area 12F is detected, the focus search is stopped, the focus adjustment lens group L1 is moved to the lens position where the peak is obtained, and the AF process is finished. To do.

  When a face image 103 (face image detection area 12G) smaller than a predetermined threshold value is detected by the face detection process, the focus detection area 12F is set at the substantially center position of the face image 103, and the focus adjustment lens group L1 is set. After moving to the far position, the focus search process is executed in the near position direction with the far position as the focus search start position and the near position as the focus search end position (FIG. 5B). Then, when the peak of the image signal in the focus detection area 12F is detected, the focus search is stopped, the focus adjustment lens group L1 is moved to the lens position where the peak is obtained, and the AF process is finished. To do.

  According to the AF processing of the present embodiment, as is apparent from FIGS. 5A and 5B, the distance of the subject is detected based on the size of the face image, and the face image exceeds a predetermined threshold value. When the face image is less than the predetermined threshold value, the focus search process starts from the far position, so the focus search process starts from the far position. It is possible to reduce the time required to detect, and to reduce the total time required to focus.

  In the illustrated embodiment, when the face image 101 is larger than a predetermined threshold value, for example, when the area ratio with respect to the imaging screen 12 is 1/2 or more, the subject is assumed to be located at a short distance. When the focal length is longer than that in the illustrated embodiment, it is set to 2/3, 3/4 or the like according to the focal length, and when it is short, it is set to 1/3, 1/4 or the like according to the focal length.

  Further, in this digital camera, when a face image is detected in the AF process, the face image is enlarged and displayed on the LCD 17. This is shown in FIG. FIG. 6A is a through image displayed on the LCD 17 before the AF process is started. In this embodiment, it is assumed that the face image 101 is displayed, and when the AF process is started, the face image 101 is detected by the face image detection process. The CPU 15 trims the face image 101 and enlarges it on the LCD 17 (FIG. 6B). In this embodiment, the face portion in the face image 101 is cut out with a one-to-one aspect ratio and enlarged so that the top and bottom are full. This enlarged display is continued during the focus search process. With this enlarged display, the user can visually recognize which subject the user is trying to focus on.

  When the AF processing is completed, the display on the LCD 17 is returned to the normal display (display with all captured image signals), and the emphasis frame 12i surrounding the face image is displayed as a focused display for displaying a focused part. It is displayed (FIG. 6C). With the display of the emphasized frame 12i, the user can visually recognize which part of the image is in focus. Since the highlight frame 12i only needs to allow the user to visually recognize the focused portion, the focus detection frame 12F may be displayed.

  Next, contrast AF processing in this digital camera will be described in more detail with reference to the flowcharts shown in FIGS. FIG. 7 is a flowchart showing the main sequence of this digital camera. This main sequence is entered when a battery (not shown) is loaded.

  When entering the main process, the CPU 15 first executes an initialization process (S101). Next, it is checked whether or not the main switch SWM is turned on (S103). If it is not turned on, the power is turned off and the process is terminated (S103; NO, S105, END). Thereafter, the CPU 15 is periodically activated to repeat the check of the main switch SWM (S103).

  When the main switch SWM is on (S103; YES), it is checked whether the photometry switch SWS is on (S107). When ON (S107; YES), contrast AF processing is executed (S109), and after AF processing, it is checked again whether the photometry switch SWS is on (S111), and the photometry switch SWS is on. When (S111: YES), it is checked whether or not the release switch SWR is ON (S113), and if it is ON, the imaging process is executed and the process returns to S103 (S113; YES, S115, S103). If the release switch SWR is not ON, the process returns to S103 as it is (S113; NO, S103).

  If the photometry switch SWS is not turned on in S107 or S111 (S107: NO or S111: NO), the process returns to S103.

  Next, the details of the contrast AF process executed in S113 will be described with reference to the flowchart shown in FIG.

  When the contrast AF process is started, initialization of each variable and the like is first executed (S201). For example, in this embodiment, clearing of each status, clearing of the contrast value, initialization of the lens position pulse number N (N = 0), setting of the maximum value and minimum value of the contrast (maximum value = 0, minimum value = FFFFFFFF) Then, the midway stop OK flag and the face detection flag are cleared.

Here, variables and the like are defined as follows.
The contrast value is a contrast value actually obtained from the pixels in each focus detection area.
The maximum and minimum values of contrast are the maximum and minimum values of the contrast value actually obtained.
The lens position pulse number N is set to 0 when the focus adjustment lens group L1 is in the near position or the far position, which is the start position, and every time one drive pulse is output from the encoder 26 when the AF motor 25 is driven. This is a variable that is incremented by one. The CPU 15 counts this as a lens position pulse N and grasps the position of the focus adjustment lens group L1.
The halfway stop OK flag (StopOK flag) is a flag that permits a stop in the middle of the AF search process, and “0” is default and “1” is not permitted.
The face detection flag is a flag for identifying that a face image has been detected, and is “0” when default or not detected, and “1” when detected.

  Next, face detection processing for detecting a face image using the read image signal is executed (S203). A known face recognition image process is used for the face detection process. When a face image is detected by this face detection process, “1” is set in the face detection flag.

  Subsequently, a focus initialization process is executed (S205). The focus initialization process is a process of moving the focus adjustment lens unit L1 to a near position or a far position according to conditions. Conditions include whether or not a face is detected and whether or not a multi-AF mode is set. Then, when a face is detected, if the size of the face detection area is greater than or equal to a predetermined threshold value, the position is near, if not, the position is far, and if no face is detected, the position is near in the multi AF mode. In the case of not being in the multi-AF mode, the current position of the focus adjustment lens unit L1 is set to the near position if it is close to the near position, and to the far position if not.

  Next, a focus adjustment area is selected (S207). In the case of face detection, face position information is acquired, and a focus detection area is selected so as to be positioned at the center of the detected face position. When face detection is not performed, five focus detection areas at fixed positions are selected.

  Next, an imaging process is executed to capture an image signal in the selected focus detection area at the focus search start position, and a contrast value calculation process is executed (S209). That is, the contrast value P [0] at the start position is calculated based on the image data input from the image sensor 11, and the maximum value and the minimum value of the contrast value are updated.

  Subsequently, the AF motor 25 is driven one step in the search end direction (S211), and the lens position pulse N is incremented by one according to the driving direction (S213). Then, the contrast value P [N] is calculated based on the image signal captured from the image sensor 11, and the contrast value calculation process for updating the maximum value and the minimum value of the contrast value is executed (S215). Next, a peak check process for checking whether or not the obtained contrast value P [N] is a peak value satisfying the set condition is executed (S217). Although a known algorithm can be used for the peak check processing, in this embodiment, the contrast value at the center position is the peak value among the contrast values of the last nine consecutive lens positions in each selected focus detection area. Judgment by whether or not. Then, when a peak value is obtained in face detection and spot AF, “1” is set to the midway stop OK flag (StopOK flag).

  Next, it is checked whether the midway stop OK flag is “1” (S219). If the midway stop OK flag is not “1” (S219; NO), it is checked whether or not it is a search end point (S221). If it is not the end of the search (S2121; NO), the process returns to S211 and the processes of S211 to S219 and S221 are repeated.

  The AF motor 25 is stopped (S221) when the midway stop OK flag is set to “1” (S219; YES) or when the focusing lens group L1 reaches the search end point (S219; YES). Then, a peak calculation process for approximating the peak value is executed based on the contrast data for nine positions where the peak value is obtained, which is obtained by the loop process from S211 to S221 (S225). That is, since there is a possibility that a true peak value exists before and after the peak value of the contrast value obtained for each step position, the peak value estimated to be more accurate by the approximation calculation and its lens position are approximated.

  Then, in the case of multi-range measurement, based on the lens position obtained for each focus detection area, the focus detection area where the closest distance value is obtained is set as the focus area, and the focus detection area and lens position are selected. The area selection process to be executed is executed (S227). Then, a focus driving process for moving the focusing lens group L1 to a lens position where a peak value is obtained in the selected focus area is executed (S229), and the process returns (RETURN).

  Further, in the contrast AF process described above, when a face is detected by the face detection process (S203), the face detection area image signal is switched to an enlarged display process that is enlarged and displayed on the LCD 17, and the focus drive process (S229) is completed. Then, the image display is returned to the normal display process in which all image signals are displayed on the LCD 17.

"Focus initialization process"
The focus initialization process executed in step S203 will be further described with reference to the flowchart shown in FIG.

  When the focus initialization process is started, first, it is checked whether or not a face is detected (S301). If the face is not detected (S301: NO), it is checked whether or not the multi-AF process is performed (S303). If multi-AF is used (S303: YES), the AF motor is used to move the focusing lens group L1 to a close position. 25 is driven to a near position (S307). In multi-AF, the focus search start end is set to the near position, and the focus search end end is set to the far position. If it is not multi-AF (S303; NO), it is checked whether or not the current position of the focusing lens group L1 is close to the near position (S305). If it is close to the near position (S305: YES), the focusing lens group is checked. The AF motor 25 is driven to the near position to move L1 to the near position (S307). If the AF motor 25 is not close to the near position (S305: NO), the AF motor 25 is moved to the far position to move the focusing lens group L1 to the far position. Drive (S309). Then, it waits for the focus adjustment lens group L1 to reach the near position or the far position and the AF motor 25 stops (S319: NO, S319). When the AF motor 25 stops (S319: YES), the process returns. RETURN).

  On the other hand, when the face is detected in the face detection process (S203) (S301; YES), the threshold value corresponding to the zoom level is set to the threshold value A (S311), and the face detection area size is set to the threshold value. It is checked whether or not it is A or more (S313). When the face detection area size is equal to or larger than the threshold value A (S313: YES), the AF motor 25 is driven to the near position to move the focusing lens group L1 to the near position (S315), and the face detection area size is If it is not equal to or greater than the threshold value A (if it is less than the threshold value A) (S313: NO), the AF motor 25 is driven to the far position to move the focus adjustment lens group L1 to the far position (S317). . Then, it waits for the focus adjustment lens group L1 to reach the near position or the far position and the AF motor 25 stops (S319: NO, S319). When the AF motor 25 stops (S319: YES), the process returns. RETURN).

  When the focus adjustment lens group L1 is moved to the near position, the near position is the search start end, and the far position is the search end end. Conversely, when the focus adjustment lens group L1 is moved to the far position, the far position starts the search. The end or near position is the end of search.

"Area decision processing"
Next, the area position determination process executed in S207 will be described with reference to the flowchart shown in FIG. First, it is checked whether or not a face has been detected (S401). If no face has been detected (S401: NO), five fixed focus detection areas 12A to 12E are selected as focus detection areas (S407), and return is performed. To do. If the face has been detected (S401: YES), the face detection position information is acquired (S403), the focus detection area 12F is selected to be at the center of the face detection position (S405), and the process returns.

It is a figure which shows the main structure of embodiment of the digital camera to which the focus detection method of this invention is applied with a block. 2A and 2B are diagrams illustrating a relationship between a light receiving surface of an image sensor and a focus detection area in the digital camera, where FIG. 3A illustrates a focus frame in which the focus detection area is distributed, and FIG. It is a figure which shows typically the relationship. It is a figure explaining the arrangement pattern of the filter of the image sensor. It is a figure which shows the relationship between the face image and the focus detection area (focus detection area) of the person when the person is located at a short distance and when the person is located at a long distance. In the embodiment of the present invention, it is a diagram for explaining a state in which the focus search start position is changed according to the size of the face image, (A) is a focus when the person is located at a short distance The figure which shows the relationship between the position and contrast value of the adjusting lens group L1, and the movement locus | trajectory in the refocus search process of the focusing lens group L1, (B) is a focusing lens group in case a person is located in a long distance It is a figure which shows the movement locus | trajectory in the refocusing search process of the position and contrast value of L1, and the refocusing search process of the focus adjustment lens group L1. It is a figure which shows the display mode of the display means in AF processing of the digital camera to which this invention is applied, Comprising: (A) is a display at the time of AF processing start, (B) is a display during AF processing when a face is detected, ( C) is a diagram showing a display after face detection and focusing processing. It is a figure which shows the main process in the digital camera of this embodiment with a flowchart. It is a figure which shows the detail of the contrast AF process in the same main process with a flowchart. It is a figure which shows the contrast AF process performed in the main sequence with a flowchart. It is a figure which shows the area position determination process in the same contrast AF process with a flowchart.

Explanation of symbols

11 Imaging device (imaging means)
12 Photosensitive surface 12F Focus detection area 12G Face detection area 13 Image signal processing circuit 15 CPU (face detection means, focus detection means)
15a Internal RAM
17 LCD
19 Memory control circuit 21 Image memory 23 Motor driver 23a Near end origin sensor 23b Far end origin sensor 25 AF motor 26 Encoder 27 Lens drive mechanism 28 Zoom motor 29 EEPROM (nonvolatile memory)
L Zoom lens (imaging optical system)
L1 Focusing lens group

Claims (10)

The subject image formed by the imaging optical system including the focus adjustment lens group is picked up by the imaging means while moving the focus adjustment lens group along the optical axis between the short distance focus end and the long distance focus end. A focus adjustment unit that performs a focus search for detecting a focus position based on image signals acquired at a plurality of positions, and moves the focus adjustment lens group to the focus position detected by the focus search; and
A face detecting means for detecting a face image based on an image signal imaged by the imaging means,
When the face detection unit detects a face image, the focus adjustment unit performs a focus search from the far-distance focusing end side when the size of the face image is less than a predetermined threshold value, and sets a predetermined threshold. A camera equipped with a focus adjustment device, characterized in that when the value is equal to or greater than the value, a focus search is performed from the close focus end. 2. The camera comprising the focus adjustment device according to claim 1, wherein the focus adjustment means detects a focus position at which the face image is in focus when the face detection means detects a face image. Camera with device. 3. The camera having the focus adjustment device according to claim 1, wherein the focus adjustment unit sets an image area including the face image as a focus detection area when the face detection unit detects a face image. A camera including a focus adjustment device that detects a focus position based on an image signal in the focus detection area. 4. The camera with a focus adjustment device according to claim 3, wherein the focus detection area is constant regardless of the size of the image area. 5. The camera comprising the focus adjustment device according to claim 3 or 4, wherein the focus search detects a lens position at which a contrast peak of an image signal within the focus detection area is obtained as a focus position. Camera provided. 6. The camera having the focus adjustment device according to claim 5, wherein when a contrast peak is obtained during the focus search, the focus search is stopped and the focus adjustment lens group is located at a position where the peak is obtained. A camera equipped with a focusing device that moves the camera. 7. The camera having the focus adjustment device according to claim 1, wherein the imaging optical system is a zoom lens, and the threshold value is set based on a current focal length of the zoom lens. Camera provided. A camera comprising the focus adjustment apparatus according to claim 1, further comprising display means for displaying an image picked up by the image pickup means, and the face is adjusted when the focus adjustment means performs a focus search. When the detection unit detects a face image, a focus adjustment device is provided that extracts an image signal of an image region including the face image from the captured image signal and displays the enlarged image on the display unit during the focus search. Camera. 9. The camera having the focus adjustment device according to claim 8, wherein after the focus search processing is completed and the focus adjustment lens group is moved to a focus position, the focus of displaying the captured image signal by the display means. Camera with adjustment device. 10. A camera equipped with the focus adjustment apparatus according to claim 8, wherein when the image area including the face image is focused, an identification display for visually recognizing the image area is displayed on the display means. Camera with focus adjustment device.

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