JP5581838B2 - Automatic focusing control device, electronic camera and automatic focusing control method - Google Patents

Description

  The present invention relates to an automatic focusing control device, an electronic camera, and an automatic focusing control method for performing contrast detection type autofocus control (AF control).

  In recent years, electronic cameras such as digital cameras and video cameras have been provided with an autofocus device (autofocus device). In an autofocus device, a contrast detection method is widely used as one of main methods. The contrast detection method is a method of obtaining a contrast value of a captured image at each position while moving the focus lens in the optical axis direction, and detecting a lens position having the highest contrast value as a focus position (for example, Patent Document 1).

  In particular, the focus detection apparatus disclosed in Patent Document 1 detects a plurality of edge portions of subject light over a predetermined range, detects edge detection means for detecting the number of pixels in each edge portion, and the detected number of pixels in the plurality of edge portions. The discriminating means for discriminating the in-focus state of the subject based on the gravity center value calculated from the frequency is provided.

JP-A-4-274405

  By the way, in recent digital still cameras, there is a problem in that since the contrast value is obtained while displaying an image on a monitor, the image is disturbed due to wobbling and the AF lens group search time is required.

  For example, the contrast detection method using luminance information as in Patent Document 1 has a problem in that an AF lens is driven in a wide range, resulting in a blurred image due to wobbling during live view display or moving image shooting. .

  The present invention has been made in view of the above problems, and an object thereof is an automatic focusing control capable of reducing image blurring due to wobbling during a focusing operation in an autofocus apparatus employing a contrast detection method. An apparatus, an electronic camera, and an automatic focusing control method are provided.

  In order to solve the above-described problems, the present invention provides a first driving unit that moves the photographic lens in the optical axis direction, and the photographic lens is arranged at a focus position based on a contrast value of an image acquired by the imaging unit. A first focusing control means for controlling the first driving means, and an optical path between the photographing lens and the imaging means, provided so as to be insertable / removable, and a deviation from the focusing position of the photographing lens At least one filter having a refractive index capable of compensating the amount, second drive means for inserting / removing the filter with respect to the optical path, detection means for detecting a shift amount with respect to a focus position of the photographing lens, and the detection And a second focus control means for controlling the second drive means so as to insert and remove a filter having a refractive index corresponding to the deviation detected by the means with respect to the optical path. Toss .

  The automatic focusing control device according to the present invention includes a plurality of the filters, and the second focusing control unit arranges the plurality of filters on the optical path so that the refractive index varies depending on the combination of the plurality of filters. It is preferable to produce.

  In the automatic focusing control device according to the present invention, the second focusing control means performs focusing by inserting and removing the filter on the optical path and movement of the filter inserted on the optical path in the optical axis direction. Preferably it is done.

  In the automatic focusing control device of the present invention, the zoom lens, the third driving means for adjusting the zoom amount by moving the zoom lens in the optical axis direction and changing the focal length, and the second focusing control. The means preferably selects a filter to be inserted on the optical path in accordance with the zoom amount and the shift amount.

  In the automatic focusing control device according to the present invention, the detection means includes at least one of three sensitivity ratios indicated by a ratio of combinations of two colors among the RGB three-color signal values of the image acquired by the imaging means. It is preferable that a sensitivity ratio calculation unit is provided for calculating a deviation amount from the in-focus position based on the at least one sensitivity ratio.

  In the automatic focusing control device of the present invention, there is provided an inclination calculation means for obtaining an inclination when the RGB signal value acquired by the imaging means crosses an edge portion in the image, and the first signal is obtained when the inclination is not less than a threshold value. When the second focus control by the second focus control means is performed and the inclination becomes less than the threshold value, the second focus control is switched to the first focus control by the first focus control means. It is preferable.

The gist of the present invention is an electronic camera comprising an imaging means for photographing a subject and the automatic focusing control device according to the invention.
The present invention provides a first focus control step for performing focus control so as to place the photographing lens at a focus position based on the contrast value of the image acquired by the imaging means while moving the photographing lens in the optical axis direction. A detecting step for detecting a shift amount of the photographing lens that has been focused by the first focusing control step with respect to a focus position, and a filter having a refractive index that can compensate for the shift amount. And a second focusing control step of focusing by inserting and removing a filter with respect to the optical path so as to be disposed on the optical path.

  According to the present invention, in an autofocus device that employs a contrast detection method, an excellent effect is obtained that image blur due to wobbling during a focusing operation can be reduced.

The perspective view of an electronic camera. The rear view of an electronic camera. The block diagram which shows the electric constitution of an electronic camera. The graph explaining AF control by a contrast detection system. (A) The model side view which shows the structure of a filter apparatus, (b) The model front view. The schematic side view explaining the principle of a filter insertion / extraction system. FIG. 3 is a schematic side view showing axial chromatic aberration in an imaging optical system. FIG. 6 is a schematic diagram of a main subject image for explaining edge detection. The graph which shows normalized output R (x), G (x), and B (x). The graph which shows the fluctuation | variation of the inclination of the edge by AF lens position. The graph which shows the fluctuation | variation of the sensitivity ratio by AF lens position. The schematic side view which shows the imaging optical system at the time of filter non-insertion. The schematic side view which shows the imaging optical system at the time of filter insertion. The flowchart which shows AF control processing. The schematic side view which shows the structure of the filter apparatus in a modification.

Hereinafter, an embodiment in which the present invention is embodied in a digital camera which is a kind of electronic camera will be described with reference to FIGS.
FIG. 1 is a perspective view of a digital camera, and FIG. 2 is a rear view thereof. As shown in FIG. 1, the digital camera of the present embodiment (hereinafter simply referred to as “camera 11”) has a camera body 12 having a substantially rectangular parallelepiped shape. The camera body 12 is provided with a telescopic lens barrel 13a with an imaging lens 13 in the front (front) substantially central portion thereof, and a strobe 14 (flash) and in-focus at two positions above the lens barrel 13a. A light emitting body that irradiates infrared rays or the like toward a subject during operation and an irradiation window portion 15 that irradiates light such as a self LED that blinks when performing self-photographing are provided.

  Further, on the upper surface of the camera body 12, a power switch 17 and a release switch 18 are provided at two positions on the left side, and a speaker 19 is provided at a position near the center. The power switch 17 is pressed down by the photographer when the camera 11 is turned on. The release switch 18 is an operation button that is pushed down (ie, turned on) by the photographer when the camera 11 starts an imaging operation.

  On the other hand, as shown in FIG. 2, a rectangular monitor 20 is provided on the back side of the camera body 12. As an example, the monitor 20 includes a liquid crystal display (LCD). A mode selection switch 21 that can be switched between the still image mode and the moving image mode is provided at a position on the upper right side of the monitor 20. A zoom button 22 that is mainly operated when zooming up or down the imaging lens 13 is provided at the upper right position of the monitor 20 on the back of the camera body 12. A menu button 23 that is operated mainly when displaying a menu screen on the monitor 20 is provided below the zoom button 22.

  In addition, a shooting button 24 and a playback button 25 are provided below the menu button 23. When the shooting button 24 is operated during the playback mode, the mode is switched to the shooting mode, and when the playback button 25 is operated during the shooting mode, the mode is switched to the playback mode. When performing moving image shooting, the moving image mode is set to the shooting mode and the release switch 18 is operated to start moving image shooting. When the release switch 18 is operated during the moving image shooting, the moving image shooting is ended.

  Further, a select button 26 (select button) capable of selecting in a plurality of directions including four directions of up, down, left and right is provided at a lower position of each button 24, 25, and an enter button 27 (OK button) is provided at the center. ) Is provided. The select button 26 is mainly used for an operation of selecting an item on the menu screen and changing a setting content. The determination button 27 is used for an operation of confirming (determining) an item or setting content selected on the menu screen.

  Next, the circuit configuration of the camera 11 of the present embodiment will be described based on the block diagram shown in FIG. As shown in FIG. 3, the camera 11 includes an engine 30 including an MPU (Micro Processing Unit) that comprehensively controls various operations. The engine 30 includes a computer 31 and controls the camera 11 by the computer 31 executing various programs. In addition, the camera 11 has an imaging element 32 in the camera body 12 for forming an image of subject light that has passed through the lens group of the imaging lens 13 on the image space side of the imaging lens 13. The imaging element 32 is composed of, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and accumulates signal charges corresponding to the subject image formed on the imaging surface. The signal charge is output as an analog signal called a pixel signal. It should be noted that the imaging element 32 can output a pixel signal of a through image that changes with time in the subject even in the standby mode before the release switch 18 is pressed after the power switch 17 is pressed down. It is configured.

  The imaging lens 13 shown in FIG. 3 includes a zoom lens 33a for changing the shooting angle of view and a focus lens 33b for focusing in the lens barrel 13a. A diaphragm 34 and a shutter 35 are provided in the lens barrel 13a. Further, a filter device 36 is provided between the focus lens 33 b and the image pickup device 32 so that the filter 37 can be inserted into and removed from the optical path of the image pickup lens 13. In this example, a plurality of filters 37 are provided.

  The engine 30 includes a filter driving circuit 38, a focus driving circuit 39, a shutter driving circuit 40, an aperture driving circuit 41, and the like in order to drive and control the imaging lens 13, the diaphragm 34, the shutter 35, the filter device 36, and the like according to the shooting conditions. A zoom drive circuit 42 is connected.

  The zoom lens 33 a is configured to be movable along the optical axis direction by driving the zoom motor 43. The engine 30 drives and controls the zoom motor 43 via the zoom drive circuit 42, and changes the shooting angle of view by moving the zoom lens 33a in the optical axis direction.

  The focus lens 33b is configured to be movable along the optical axis direction by driving a focus motor (hereinafter referred to as “AF motor 44”). The engine 30 drives and controls the AF motor 44 via the focus drive circuit 39 to focus by moving the focus lens 33b in the optical axis direction, for example, subject light transmitted through the imaging lens 13 is image plane of the imaging device 32. To form an image. At this time, the engine 30 acquires the position of the focus lens 33b in the optical axis direction based on the detection signal of the AF sensor 45.

  The diaphragm 34 is driven by an actuator (not shown) driven by the diaphragm drive circuit 41. The engine 30 adjusts the amount of light passing through the imaging lens 13 by adjusting the diaphragm 34 by driving and controlling the actuator via the diaphragm drive circuit 41.

  The shutter 35 can be opened and closed by an actuator (not shown) driven by a shutter drive circuit 40. The engine 30 controls the exposure time by operating the shutter 35 by controlling the driving of the actuator via the shutter driving circuit 40.

  In addition, an imaging control circuit 47 and a video circuit 48 connected to the imaging device 32 are connected to the engine 30. The imaging control circuit 47 drives the imaging device 32 to control exposure time control, conversion of the formed image into an electrical signal, output of the converted electrical signal, and the like.

  The video circuit 48 amplifies the electrical signal output from the image sensor 32, converts it into a digital signal, and outputs it to the engine 30. Specifically, the video circuit 48 connected in series to the output side of the image sensor 32 has an AFE (Analog Front End) unit and an A / D converter. The AFE unit samples a pixel signal composed of an analog signal that has been photoelectrically converted by the image pickup device 32 and outputs it at a predetermined timing (correlated double sampling), and amplifies the signal to a predetermined signal level based on, for example, ISO sensitivity. Let The A / D converter converts the amplified pixel signal (analog signal) output from the AFE unit into a digital signal, and outputs the digital pixel signal to the engine 30.

  The engine 30 generates predetermined image data by performing image processing such as color interpolation processing, gradation correction, white balance processing, and contour compensation on the digital pixel signal input from the video circuit 48.

  Furthermore, a nonvolatile memory 49 and a buffer memory 50 are connected to the engine 30 via a bus. Further, a monitor control circuit 51 (LCD drive circuit), a memory control circuit 52, an operation detection circuit 53, and the like are connected to the engine 30.

  The nonvolatile memory 49 stores a program that is executed by the computer 31 in the engine 30 in order to operate the engine 30. In the present embodiment, a program for automatic focusing control (AF control) shown in the flowchart of FIG. Further, the nonvolatile memory 49 stores map data M1, M2,... Mm used in automatic focusing control using the filter device 36. The map data M1 to Mm will be described later.

  The buffer memory 50 temporarily stores captured image data, and is used for temporary storage of data in the image processing process, data after image processing, data after image compression, and data in other processing processes of the engine 30. . The buffer memory 50 is composed of, for example, a DRAM.

  Image data generated by the image processing by the engine 30 is temporarily stored in the buffer memory 50. The engine 30 sends the image data temporarily stored in the buffer memory 50 to the monitor control circuit 51, and the monitor control circuit 51 causes the monitor 20 to display an image based on the image data. On the monitor 20, for example, a through image, a moving image being photographed, a confirmation image (still image) immediately after photographing, and a reproduced image (reproduced moving image / reproduced still image) are displayed.

  Thereafter, the engine 30 reads the image data from the buffer memory 50, performs data compression processing by, for example, the JPEG method, generates an image file including the image data after the compression processing, and sends the generated image file to the memory control circuit 52. The data is stored in a memory card 54 that can be attached to and detached from the camera 11 through a connected card slot (not shown). The engine 30 also reads the image file from the memory card 54 and decompresses the image data, temporarily stores the image data in the buffer memory 50, and reproduces the reproduced image (reproduced moving image / reproduced image) on the monitor 20 via the monitor control circuit 51. (Still image) is displayed.

  The monitor control circuit 51 outputs the display data output from the engine 30 to the monitor 20 and controls the monitor 20 to turn on / off and display, thereby causing the monitor 20 to display a through image, a reproduced image, and the like.

  The memory control circuit 52 has a slot having a structure in which the memory card 54 can be inserted and removed, and transfers and stores a photographed image file in the memory card 54 inserted in the slot, or an image file stored in the memory card 54 Etc., and has a function of outputting the information to the engine 30.

  Various operation switches such as a power switch 17, a release switch 18, a mode selection switch 21, a zoom button 22, a menu button 23, a shooting button 24, a playback button 25, a select button 26, and an enter button 27 are connected to the operation detection circuit 53. (However, only some switches (buttons) are shown in FIG. 3). The operation detection circuit 53 detects a switch operation by the user and outputs the operation information to the engine 30.

  The computer 31 in the engine 30 executes a program stored in the non-volatile memory 49 to control the operation of the camera 11 and processes and reproduces the captured image. The engine 30 turns on (ON) / cuts off (OFF) the power of the camera 11 in response to the operation of the power switch 17. In addition, the engine 30 performs a zooming operation in which the zoom lens 33a is moved by driving the zoom motor 43 via the zoom drive circuit 42 in response to the operation of the zoom button 22 under the power ON state. The AF motor 44 is driven via the drive circuit 39 to perform a focusing operation for moving the focus lens 33b. Further, the engine 30 controls the exposure by driving the aperture driving circuit 41 and the shutter driving circuit 40 to adjust the aperture 34 and the opening time of the shutter 35.

  The engine 30 opens the shutter 35 and forms an image of the light transmitted through the imaging lens 13 on the imaging element 32 in the shooting preparation stage. The subject image formed on the image sensor 32 is periodically subjected to image processing by the engine 30, and the subject is projected on the monitor 20 as a moving image, whereby a through image is displayed on the monitor 20.

  Further, the engine 30 detects the contrast of the image, moves the focus lens 33b, searches for the focus lens position with the highest contrast, and moves the focus lens 33b to that position, thereby performing autofocus control (AF control). Do.

The engine 30 detects the brightness level of the image, and controls the shutter speed of the diaphragm 34 and the shutter 35 based on the detected brightness level to perform automatic exposure control (AE control).
FIG. 4 shows a functional configuration constructed in the engine 30 when a CPU (computer) in the engine 30 executes a program. As shown in FIG. 4, the computer 31 in the engine 30 includes a main control unit 61, an image processing unit 62, a zoom control unit 63, a switching control unit 64, a first focusing control unit 65, and a second focusing control unit. 66, a display control unit 67, and the like. In addition, each function part in the computer 31 shows only a part related to AF control and zoom control, and other function parts related to various controls are omitted.

The main control unit 61 performs overall control of each unit, and performs aperture control, shutter control, and the like in addition to AF control and zoom control.
The image processing unit 62 performs image processing for generating image data by performing various types of image processing (white balance processing or the like) based on pixel signals input from the image sensor 32 via the video circuit 48 (see FIG. 3). Has the function to perform. The image processing unit 62 includes a face detection unit 62A. The face detection unit 62A performs face detection for detecting a human face in the image. Features of facial parts such as binoculars, nose and mouth are extracted, each part of the face is extracted based on the feature amount, and a face is detected using each positional relationship between both eyes, nose and mouth. The face detection unit 62A performs various detection processes relating to the detected face, such as pupil detection, face orientation detection, face contour detection, and facial expression detection (smile detection). In AF control, focus lens position control is performed so as to focus on the detected face. For this reason, focus lens position control is performed so that the detected contrast evaluation value of the face is maximized.

  The zoom control unit 63 drives the zoom motor 43 in the rotation direction corresponding to the operation direction of the wide-angle side and the telephoto side based on the operation of the zoom button 22, thereby moving the zoom lens 33a between the wide-angle side and the telephoto side. The zoom (magnification) is adjusted by moving in the direction corresponding to the operation direction.

  The switching control unit 64, the first focusing control unit 65, and the second focusing control unit 66 constitute a control unit of the AF control device, and AF control is performed by each of these control units 64-66. Then, the switching control unit 64 selects one of the first focusing control unit 65 and the second focusing control unit 66 and switches the subject of the AF control between them.

  Here, the first focus control unit 65 performs AF detection using a contrast detection method. The first focus control unit 65 includes a contrast detection unit 71, a lens control unit 72, and a search unit 73. The contrast detection unit 71 detects the contrast of the face area detected by the face detection unit 62 </ b> A from the image data captured by the image sensor 32 and input to the engine 30. The lens control unit 72 performs lens position control for driving the AF motor 44 to move the focus lens 33b in the optical axis direction.

  The search unit 73 sequentially acquires the contrast evaluation values detected and calculated by the contrast detection unit 71 for each lens position while the lens control unit 72 drives the AF motor 44 to move the focus lens 33b in the optical axis direction. The so-called “mountain climbing control” is performed while comparing the current evaluation value with the previous evaluation value, and the lens position (the number of AF motor pulses) that provides the maximum contrast evaluation value is searched.

  FIG. 4 is a graph for explaining AF control by the contrast detection method. In this graph, the horizontal axis is the lens position (number of AF motor pulses), and the vertical axis is the contrast evaluation value. For example, if the AF control start position is P1, the contrast evaluation value C is calculated while moving the focus lens 33b one pulse at a time in the optical axis direction, and the contrast evaluation values C1, C2 are calculated for each lens position P1, P2,. ,... Are sequentially calculated to obtain a lens position Pmax (number of AF motor pulses) at which the maximum contrast evaluation value Cmax is obtained. As shown in FIG. 5, for example, when the position P1 → P2 →... → Pn → Pn + 1, when the evaluation value Cn at the position Pn is compared with the evaluation value Cn + 1 at the position Pn + 1, When the evaluation value that has been increased decreases or takes the same value, the search unit 73 sets the lens position Pn (number of AF motor pulses) that takes the maximum evaluation value Cn (= Cmax) as the in-focus position. get.

  The lens control unit 72 obtains the moving direction and moving amount to the in-focus position defined by the lens position Pn (AF motor pulse number Pn) obtained by the search by the search unit 73, and drives the AF motor 44 to focus. The lens 33b is moved in the moving direction by the moving amount. When the focus lens 33b reaches the in-focus position, the lens control unit 72 stops driving the AF motor 44. The first focus control unit 65 performs AF control by the contrast detection method in such a procedure.

  Here, in the AF control based on the contrast detection method, the search unit 73 searches over a relatively wide range, so that the display is displayed on the monitor 20 by the display control of the display control unit 67 due to the movement of the focus lens 33b during the search. Wobbling that causes the image to wiggle is likely to occur. Since the through image is data that is not stored in the memory card 54, there is no problem even if some wobbling occurs. However, if wobbling caused by search occurs during movie shooting, a low-quality movie with blurred images is saved. become. For this reason, in the present embodiment, as the AF control, in addition to the contrast detection method performed by the first focus control unit 65, a filter by the second focus control unit 66 that can perform AF control without moving the focus lens 33b. AF control by the insertion / extraction method is also adopted.

  The filter insertion / extraction method by the second focus control unit 66 is AF control by inserting / extracting the filter 37 with respect to the optical path of the imaging lens 13. Specifically, the second focus control unit 66 filters the amount of defocusing when the subject is defocused, for example, when the subject moves after being focused by the contrast detection method by the first focus control unit 65. The object light transmitted through the imaging lens 13 is compensated by insertion / removal 37 and is imaged on the image plane of the imaging element 32.

  In order to control the filter device 36 and realize the AF control of the filter insertion / extraction method, the second focus control unit 66 shown in FIG. 3 includes an edge detection unit 81, an edge inclination calculation unit 82, a determination unit 83, and a sensitivity ratio calculation. Unit 84, filter selection unit 85, and filter control unit 86.

  Here, the principle of AF control by the filter insertion / extraction method will be briefly described. As shown in FIG. 6, when the focal position of the imaging lens 13 through which the subject light is transmitted is located on the photographer side (right side in FIG. 6) with respect to the imaging element 32, “front blur”, and the focal position is the imaging element 32. When the lens is located closer to the imaging lens (the left side in FIG. 6), it becomes “rear blur”. Since the light transmitted through the imaging lens 13 is refracted by the filter 37, the focal position is shifted in the front-rear direction (optical axis direction) by inserting and removing the filter 37. Therefore, before the filter is inserted, as shown by a broken line in FIG. 6, even if the focal position is close to the front blur, if the filter 37 is inserted, the subject light is transmitted to the image sensor 32 as shown by a solid line in FIG. It is possible to form an image on the image plane 32a. However, the refractive index of the filter 37 is different for each color of light (that is, for each wavelength). In FIG. 6, the front blur and the rear blur are expressed by changing the position of the image sensor 32 in the optical axis direction.

  FIG. 7 shows the state of axial chromatic aberration for each color of light transmitted through the imaging lens 13. As shown in FIG. 7, the light transmitted through the imaging lens 13 is subject to axial chromatic aberration due to the difference in wavelength, and the focal position is shifted. The tendency of axial chromatic aberration varies depending on the design value of the optical system. The imaging lens 13 shown as an example in FIG. 7 has a refractive index of both red (R) and green (G) rays larger than that of blue (B) rays, and red (R) and green (G). The focal positions of the two light beams are located closer to the imaging lens than the focal position of the blue (B) light beam. For this reason, in the camera 11 having the imaging lens 13 shown in FIG. 7, a filter 37 is selected in which the refractive index of blue (B) light is larger than that of red (R) and green (G) light. ing. As described above, the optical wavelength characteristic of the optical system including the imaging lens 13 differs depending on the design value of the optical system. Therefore, the refractive index filter 37 that can match the focal positions of the RGB colors is selected in consideration of this.

  FIG. 5 is a schematic diagram showing the structure of the filter device 36. FIG. 5A is a schematic side view, and FIG. 5B is a schematic front view. As shown in FIG. 5A, the plurality of (N) filters 37 included in the filter device 36 have different refractive indexes. Further, as described above, the refractive index of each filter 37 is set to a value that can compensate for the defocus of each RGB color in consideration of the light wavelength characteristics that differ depending on the design value of the optical system including the imaging lens 13. In this example, the N (five as an example) filters 37a, 37b, 37c, 37d, and 37e included in the filter device 36 shown in FIG. 5 have different defocus amounts that can be compensated according to their refractive indexes. .

  Each filter 37 is supported at the distal end portion of the arm 91, and the base end portion of each arm 91 is fixed to the rotation shaft 92. Each rotating shaft 92 is configured to be able to rotate forward and backward by driving N filter motors 46 to rotate forward and backward.

  As shown in FIG. 5B, when the filter motor 46 is driven forward or backward, the filter 37 rotates in the forward direction or the reverse direction about the rotation shaft 92. It moves between the retracted position indicated by the dotted line and the insertion position indicated by the solid line in the figure. For this reason, the filter 37 can be inserted into and removed from the optical path between the imaging lens 13 and the imaging element 32. The N filters 37a to 37e are arranged at different positions in the optical axis direction, and one filter motor 46 is provided for each filter. Therefore, in this example, N filters Arbitrary J of 37a to 37e can be overlapped and inserted at the same time. Then, the engine 30 drives and controls the N filter motors 46 so as to select and insert the J filters 37 to be inserted into the optical path. For example, an ultrasonic motor that can have a thin structure is used as the filter motor 46.

  Here, the amount of deviation of the focus of the focus lens 33b from the in-focus position can be expressed by the number of AF motor pulses P corresponding to the position of the focus lens 33b in the optical axis direction. In the AF control, the position of the focus lens 33b is controlled by the number of motor pulses of the AF motor 44, and the AF control by the contrast detection method is performed with the accuracy that the minimum movement unit of the focus lens 33b is one pulse. This is because the focus accuracy at the time of still image shooting is determined by AF control using the contrast detection method.

  On the other hand, the AF control by the filter insertion / extraction method is a control for the purpose of reducing wobbling of an image displayed on the monitor 20 during live view display or moving image shooting, and is mainly used in the moving image shooting mode. In still image shooting mode, it is used only during live view display. For this reason, the AF control by the filter insertion / extraction method is performed with an accuracy that uses “two pulses” in terms of the number of AF motor pulses as a minimum movement unit of the focus lens 33b.

  In the case of this example, the N filters 37a to 37e provided in the filter device 36 shown in FIG. 5 can represent a defocus amount that can be compensated, which is determined according to the refractive index, by the number of AF motor pulses. The N filters 37a, 37b, 37c, 37d, and 37e have a refractive index that increases stepwise in this order, and the amount of defocus that can be compensated is calculated in terms of the number of AF motor pulses in ascending order of refractive index. “2 pulses”, “4 pulses”, “8 pulses”, “16 pulses”, and “32 pulses” are set.

  The second focus control unit 66 shown in FIG. 3 controls the filter device 36 by using an edge detection unit 81, an edge inclination calculation unit 82, a determination unit 83, a sensitivity ratio calculation unit 84, a filter selection unit 85, and a filter control. A portion 86 is provided.

  The edge detection unit 81 detects an edge in the area of the main subject. Here, the main subject refers to a subject to be focused. For example, when a person is a subject, the face detected by the face detection unit 62A is the main subject. A main subject area (for example, a face area) shown in FIG. 8 is an AF determination area FA, and an edge having a large contrast difference is detected in the AF determination area FA. The edge detection is performed by the edge detection unit 81 searching in the AF determination area FA for each RGB or by luminance / hue / saturation.

  In FIG. 8, the x coordinate axis is given in the horizontal direction and the y coordinate axis is given in the vertical direction. In this example, an edge is detected at the position of x = q in the AF determination area FA. The edge detection unit 81 acquires RGB color signal values in the direction across the edge (the x direction in FIG. 8). At this time, if a signal value of only one pixel row in the AF determination area FA is acquired, there is a possibility that the one pixel row includes noise and an incorrect value is acquired. Therefore, in this example, n pixel values in one pixel row are integrated over the width of n pixels in the y direction, and an average value obtained by dividing the integrated value by n is determined for each RGB crossing the edge located at x = q. Is obtained as the color signal value of and calculated by the following equations (1) to (3).

ここで、ｒ（ｘ，ｋ）、ｇ（ｘ，ｋ）、ｂ（ｘ，ｋ）は、ｙ方向のｎピクセル幅におけるｎ本（ｋ＝１，２，…，ｎ）の１ピクセル行のＲ信号値、Ｇ信号値、Ｂ信号値をそれぞれ示す。但し、ｘは、図８の例ではｘ＝ｑを含む所定範囲Ｑ（例えばＡＦ判定領域ＦＡの一部の範囲（一例としてｑ−Ｑ／２≦ｘ≦ｑ＋Ｑ／２））を変域とする１行幅分の値をとる。ｙ方向のｎピクセル幅内の各１ピクセル行を指すｙ座標をｙ＝ｙ１，ｙ２，…，ｙｎ（但し、ｙ１＜ｙ２＜…＜ｙｎ）とすると、ｒ（ｘ，ｋ）、ｇ（ｘ，ｋ）、ｂ（ｘ，ｋ）は、ｙ座標がｙ＝ｙ１＋１−ｋの１ピクセル行のＲ信号値、Ｇ信号値、Ｂ信号値をそれぞれ示す。

Here, r (x, k), g (x, k), and b (x, k) are n (k = 1, 2,..., N) one pixel row in the n pixel width in the y direction. R signal value, G signal value, and B signal value are shown, respectively. However, in the example of FIG. 8, x is a predetermined range Q including x = q (for example, a partial range of the AF determination area FA (for example, q−Q / 2 ≦ x ≦ q + Q / 2)). Takes the value for one line width. .., yn (where y1 <y2 <... <yn), where r (x, k), g (x , K) and b (x, k) respectively indicate an R signal value, a G signal value, and a B signal value of one pixel row whose y coordinate is y = y1 + 1−k.

  Further, the edge detection unit 81 normalizes r_ave (x), g_ave (x), and b_ave (x) to the maximum value and the minimum value of the edge. The edge detection unit 81 calculates normalized outputs R (x), G (x), and B (x) at the RGB edge (x = q) by the following equations (4) to (6).

ここで、ｘminは、エッジ検出対象範囲ＥＡ内で信号値が最小（例えば図８の黒領域）となるｘ座標値を示し、ｘmaxは、エッジ検出対象範囲ＥＡ内で信号値が最大（例えば図８の白領域）となるｘ座標値を示す。

Here, xmin indicates an x-coordinate value at which the signal value is minimum (for example, the black region in FIG. 8) within the edge detection target range EA, and xmax is the maximum (for example, FIG. 8) within the edge detection target range EA. (8 white area)).

  FIG. 9 is a graph showing normalized outputs R (x), G (x), and B (x). In this graph, the horizontal axis indicates the x coordinate axis (the coordinate axis in the direction crossing the edge), and the vertical axis indicates the normalized output. In the example shown in FIG. 9, the lines of the normalized outputs R (x), G (x), and B (x) are almost overlapped. FIG. 9 shows normalized outputs R (x), G (x), and B (x) at the time of focusing by, for example, contrast detection AF control. After the in-focus state, the current position of the focus lens 33b may deviate from the in-focus position due to, for example, movement of the subject. The closer the current position of the focus lens 33b is to the in-focus position, the steeper the slope of each line of the normalized outputs R (x), G (x), B (x), and the slope takes a value close to “1”. . As the current position of the focus lens 33b gradually shifts from the in-focus position, the gradients at the edges (x = q) of the normalized outputs R (x), G (x), and B (x) gradually decrease. For this reason, if the inclination is a value equal to or greater than a certain threshold value, it can be seen that the amount of defocus is within a predetermined range (second AF control range W2).

  The edge inclination calculation unit 82 detects the edge inclination detected by the edge detection unit 81. Here, the slope of the edge refers to the rate of change of the pixel value (RGB signal value) in the direction crossing the edge (x direction in the example of FIG. 8). The slopes KR, KG, KB of the RGB signal values at the edge are calculated by substituting x = q into the differential expression of the normalized outputs R (x), G (x), B (x). In this example, the edge inclination calculation unit 82 has KR = | R (x + Δp) −R (x) |, KG = | G (x + Δp) −G (x) |, KB = | B (x + Δp) −B (x ) | Is used to calculate by substituting x = q indicating the position of the edge. However, Δp is a predetermined minute value.

  FIG. 10 shows a graph in which the slope K of the edge is plotted against the number of AF motor pulses. The horizontal axis indicates the number of AF motor pulses (lens position), and the vertical axis indicates the inclination K. In the example of FIG. 10, each line of the gradients KR, KG, and KB of the RGB signal values at the edge substantially overlaps.

  In the example of FIG. 10, the inclination K becomes maximum at the in-focus position (number of AF motor pulses = about 170), and the inclination K gradually decreases as the position of the focus lens 33b deviates from the in-focus position. In this embodiment, after focusing by the first AF control of the contrast detection method, the position of the focus lens 33b (AF lens position) at the time of focusing moves in the optical axis direction due to the movement of the subject or the like. While the amount of deviation from the position is in the second AF control range W2 within the predetermined range, the second AF control of the filter insertion / extraction method is continued. When the AF lens position deviates from the second AF control range W2 and enters the first AF control range, the control shifts to the first AF control of the contrast detection method.

  The determination unit 83 determines whether the AF lens position is within the second AF control range or the first AF control range after focusing by the first contrast detection method. Specifically, the determination unit 83 determines that the AF lens position is in the second AF control range W2 if the inclination K calculated by the edge inclination calculation unit 82 every predetermined period is larger than the threshold value Ko, while the inclination K is the threshold value Ko. When it is below, it is determined that the AF lens position is in the first AF control range W1. In this example, the threshold value Ko for two colors (R, G) of RGB is set in advance by the differential characteristics in the example of FIG. 9, and the determination unit 83 determines whether the slopes KR, KG of these two colors are larger than the threshold value Ko. It is determined whether or not. In the example of FIG. 10, the threshold value Ko is set to about 0.85 as an example.

  The sensitivity ratio calculation unit 84 calculates sensitivity ratios R / G, B / G, and R / B. Here, the sensitivity ratios R / G, B / G, and R / B are the normalized outputs R (x), G (x), and B (x) of each RGB signal value at the edge. Is the ratio. Therefore, the sensitivity ratio calculation unit 84 uses the formulas R / G = R (q) / G (q), B / G = B (q) / G (q), R / B = R (q) / B ( Each sensitivity ratio R / G, B / G, R / B is calculated by q).

  FIG. 11 is a plot of sensitivity ratios R / G, B / G, and R / B obtained in the process of moving the focus lens 33b in the optical axis direction. The horizontal axis represents the number of AF motor pulses (AF lens position), and the vertical axis represents the sensitivity ratio. The sensitivity ratios R / G, B / G, and R / B depend on the design value of the optical system including the imaging lens 13, and the tendency varies depending on the zoom amount (the position of the zoom lens 33a in the optical axis direction). In the example of the zoom amount shown in FIG. 11, when the AF control is appropriately performed, the focus lens 33b is in the in-focus position, and the sensitivity ratios R / G, B / G, and R / B are “almost 1”. . When the subject comes from here toward the photographing side (camera side), the sensitivity ratios R / G, B / G, and R / B change to the values at the position A. On the other hand, when the subject moves away from the photographing side (camera side) from the state where the focus lens 33b is at the in-focus position, the sensitivity ratios R / G, B / G, and R / B change to the values at the position B.

  As shown in FIG. 11, the sensitivity ratio B / G increases uniformly as the number of AF motor pulses increases in the range between A and B, while the sensitivity ratio R / B increases in the range between A and B. As the number of AF motor pulses increases, it decreases uniformly. On the other hand, the sensitivity ratio R / G has a small variation and increases or decreases in the range between A and B. By using B / G and R / B in which the change in the sensitivity ratio is substantially uniform in the range between A and B, the shift amount from the in-focus position can be determined from the sensitivity ratios B / G and R / B.

  The sensitivity ratio calculation unit 84 calculates the sensitivity ratios Ro / Go, Bo / Go, Ro / Bo at the time of focusing when the focus lens 33b is disposed at the in-focus position by AF control (first AF control) using a contrast detection method. . After this in-focus, the sensitivity ratio calculation unit 84 calculates the sensitivity ratios R / G, B / G, R / B at a predetermined time (for example, a predetermined value within a range of 10 microseconds to 100 milliseconds). Then, the sensitivity ratio calculation unit 84 calculates the sensitivity ratio Ro / Go, Bo / Go, Ro / Bo at the time of focusing and the current sensitivity ratios R / G, B / G, R / B for each predetermined time period. Differences ΔR / G, ΔB / G, and ΔR / B are calculated.

  If the differences ΔR / G, ΔB / G, and ΔR / B are known, the focus point by the first AF control is determined from the relationship between the sensitivity ratios R / G, B / G, and R / B in the range between A and B in FIG. The distance from the in-focus position to the AF lens position to be focused at present can be calculated in terms of the number of AF motor pulses. Then, data indicating the relationship between the number of AF motor pulses and the sensitivity ratios R / G, B / G, R / B as shown in FIG. 11 is measured for each zoom amount, and the differences ΔR / G, ΔB / G are measured. , ΔR / B and map data showing the relationship between the in-focus position deviation amount ΔP. In this way, the entire zoom range is divided into a plurality of divisions (m divisions), and m pieces of map data M1 to Mm for each of the m divisional zoom amounts are stored in the nonvolatile memory 49.

  In the range between A and B, AF control by a filter insertion / extraction method is possible, and the threshold value Ko is set in accordance with the range between A and B. Therefore, if the slope K is larger than the threshold value Ko, the sensitivity ratios R / G, B / G, and R / B at that time are within the range between A and B.

  Based on the differences ΔR / G, ΔB / G, ΔR / B calculated by the sensitivity ratio calculation unit 84, the filter selection unit 85 refers to the map data M read from the nonvolatile memory 49 according to the zoom amount at that time. Then, a defocus amount ΔP corresponding to the differences ΔR / G, ΔB / G, ΔR / B is obtained. Then, the filter selection unit 85 selects the filter 37 to be inserted from the obtained defocus amount ΔP. The first AF control of the contrast detection method is performed by inserting a filter 37e that can compensate for “32 pulses”. For this reason, the filter selection unit 85 adds the number of pulses (= “− ΔP”) necessary for compensation of the defocus amount ΔP to “32 pulses” for the initial insertion (default) and adds the number of compensation pulses ΔPt (= 32−ΔP), and the filter 37 corresponding to the number of compensation pulses ΔPt is selected. In this embodiment, the N (5) filters 37a to 37e have 2, 4, 8, 16, and 32 compensation pulses, respectively. Therefore, N (5) filters 37a to 37e are combined. By superimposing and inserting as necessary, it is possible to perform AF control with an accuracy of every two pulses within a range of 0 to 62 pulses.

  The filter control unit 86 controls driving of the filter motor 46 corresponding to the filter 37 selected by the filter selection unit 85 via the filter driving circuit 38, and the selected filter 37 is interposed between the imaging lens 13 and the imaging element 32. Insert it into the optical path. At this time, the drive for removing the filter 37 inserted so far and the drive for newly inserting the filter 37 are simultaneously performed. However, if the filter 37 that has been inserted is removed before the new filter 37 is inserted, the focus is shifted for a moment. Therefore, when there are a plurality of replacements, a step-by-step process is performed even during the replacement process. It is desirable to adopt control that replaces For example, the filter 37 having the smallest number of compensation pulses is first inserted and the filter 37 having the smallest number of compensation pulses among the filters that have been inserted is simultaneously performed. Next, the insertion of the filter 37 with the second smallest number of compensation pulses and the extraction of the filter with the second smallest number of compensation pulses among the filters that have been inserted are performed simultaneously. Thereafter, this procedure may be performed in the same manner to replace the filter 37 stepwise. At this time, if the number of compensation pulses of each filter 37 is greatly different between insertion and extraction, the filter 37 to be replaced is selected at each stage so as to avoid a large change in the number of compensation pulses in the replacement process. Good.

  The display control unit 67 displays on the monitor 20 via the monitor control circuit 51 a through image, a moving image being shot, a still image immediately after shooting, a still image at the time of reproduction, a moving image being reproduced, a menu screen, and the like. Take control.

  Next, AF control in the camera 11 will be described. When the power switch 17 is operated and the camera 11 is turned on, the computer 31 in the engine 30 executes an AF control processing program shown in the flowchart of FIG.

  Hereinafter, the AF control in the camera 11 will be described according to the flowchart shown in FIG. 14 and using FIGS. 12 and 13 as appropriate. Here, when the camera 11 is turned on, the camera 11 is in the shooting mode, and a through image is displayed on the monitor 20. When the release switch 18 is operated in the moving image shooting mode, moving image shooting is started. When the zoom button 22 is operated by the user during the live view display or the moving image shooting, the computer 31 in the engine 30 drives the zoom motor 43 via the zoom drive circuit 42 to move the zoom lens 33a. It is moved along the optical axis direction and adjusted to a zoom amount corresponding to the operation of the zoom button 22. During the through image display and the moving image shooting, the computer 31 executes the AF control shown in FIG.

First, in step S <b> 10, the computer 31 reads a map corresponding to the current zoom amount (initial zoom amount) from the nonvolatile memory 49.
In the next step S20, the computer 31 performs AF control by the contrast detection method (first AF control). Specifically, the first AF control is performed by the first focus control unit 65 of the computer 31. When starting the first AF control, the filter 37e for “32 pulses” is inserted first, and the first AF control is performed in this filter insertion state. While the lens control unit 72 drives the AF motor 44 to move the focus lens 33b along the optical axis direction, the contrast detection unit 71 sequentially detects the contrast of the main subject and calculates its contrast evaluation value C. The focus lens 33b is moved in the direction in which the evaluation value C increases. Then, the search unit 73 performs “mountain climbing control” shown in FIG. 4 to search for the lens position Pmax (number of AF motor pulses) at which the maximum contrast evaluation value Cmax is reached, and the lens control unit 72 searches the focus lens 33b for the lens position Pmax. The lens is moved to the lens position Pmax (focus position). In this way, the focus lens 33b is disposed at the in-focus position so that the main subject light is focused on the image plane 32a of the image sensor 32.

  In the next step S30, the computer 31 performs RGB detection of the edge of the main subject. Specifically, the RGB detection is performed by the edge detection unit 81 of the computer 31. After focusing by AF control using the contrast detection method (S20), the edge detection unit 81 detects the edge (see FIG. 8) in the AF determination area FA of the main subject at the time of focusing, and further detects the regularity at the detected edge. The calculated outputs R (x), G (x), and B (x) are calculated (see FIG. 9).

  In the next step S40, the computer 31 determines whether or not the zoom amount has changed by a predetermined amount or more. That is, it is determined whether or not the zoom amount has changed so that the map data M needs to be changed. If the zoom amount has changed enough to change the map data M, the process proceeds to step S50. If the zoom amount has not changed so much that the map data M needs to be changed, the process proceeds to step S60.

  In step S50, the computer 31 reads map data M corresponding to the zoom amount, and changes the map data M to be used. In this example, it is assumed that map data M based on, for example, sensitivity ratio characteristic data shown in FIG. 11 has been read.

In step S60, the computer 31 calculates the sensitivity ratios Ro / Go, Bo / Go, Ro / Bo at the edge of the main subject at the time of focusing by contrast detection AF control.
In the next step S70, the computer 31 determines whether or not the power is off. That is, it is determined whether or not the end condition of this AF control routine is satisfied. If the power is off, the routine ends. If the power is not off (that is, if the power is on), the process proceeds to step S80. However, normally, the user does not turn off the power until shooting is completed.

  In step S80, the computer 31 calculates the inclinations KR and KG of the edge of the main subject. The slopes KR and KG are calculated in detail by the edge slope calculation unit 82 of the computer 31. The edge inclination calculation unit 82 uses the expressions KR = | R (x + Δp) −R (x) | and KG = | G (x + Δp) −G (x) to calculate the inclinations KR and KG of the R signal value at the edge (x = q). ) | Is substituted by x = q indicating the position of the edge.

  In the next step S90, the computer 31 determines whether or not the slopes KR and KG are larger than the threshold value Ko. This determination is performed in detail by the determination unit 83 of the computer 31. If it is determined that the slopes KR and KG are greater than the threshold value Ko, the determination unit 83 proceeds to step S100, and determines that the slopes KR and KG are not greater than the threshold value Ko (that is, the slopes KR and KG are less than or equal to the threshold value Ko). If so, the process proceeds to step S120.

  In step S100, the computer 31 calculates the sensitivity ratios R / G, B / G, and R / B at the edge of the main subject, and the current sensitivity ratios R / G, B / G, and R / B are in focus. ΔR / G, ΔB / G, ΔR / B from the sensitivity ratios Ro / Go, Bo / Go, and Ro / Bo are calculated (ΔR / G = R / G−Ro / Go, ΔB / G = B / G-Bo / Go, [Delta] R / B = R / B-Ro / Bo). The sensitivity ratio and the difference between the sensitivity ratios are calculated in detail by the sensitivity ratio calculator 84 of the computer 31.

  In the next step S110, the computer 31 inserts a filter 37 suitable for the differences ΔR / G, ΔB / G, ΔR / B. This process is specifically performed by the filter selection unit 85 and the filter control unit 86 of the computer 31. For example, when the sensitivity ratio fluctuates as shown in FIG. 11 in the optical system characteristics of the imaging lens 13 and the current zoom amount, R / G ranges from one value to two AF motor pulses within the range between A and B. Therefore, it is inappropriate to use the difference ΔR / G for filter selection. Therefore, in the example of FIG. 11, first, the filter selection unit 85 selects the filter 37 to be inserted based on the differences ΔB / G and ΔR / B in which one AF motor pulse number is always determined from one sensitivity ratio. .

  For example, in FIG. 11, if the sensitivity ratios Bo / Go and Ro / Bo at the in-focus position are “about 1” and the current position of the focus lens 33b is at the A position in FIG. 11, the current sensitivity ratio B / Since G and R / B are “0.88” and “1.13”, respectively, the difference ΔB / G = −0.12 and the difference ΔR / B = 0.13 are calculated. The filter selection unit 85 obtains the defocus amount ΔP = “− 20 pulses” by referring to the map data M based on the difference ΔB / G = −0.12, and ΔR / B = 0.13. By referring to the map data M based on the above, the defocus amount ΔP = “− 20 pulses” is acquired. The filter selection unit 85 selects the filter 37 that can compensate for the defocus amount ΔP = −20 pulses.

  In this example, AF control (first AF control) by the contrast detection method is performed with the filter 37e for “32 pulses” inserted first. For this reason, the filter selection unit 85 adds the number of pulses (= “− ΔP”) necessary for compensation of the defocus amount ΔP to “32 pulses” for initial insertion (default) to obtain the number of compensation pulses ΔPt ( = 32−ΔP), and the filter 37 corresponding to the number of compensation pulses ΔPt is selected. In this example, since the number of compensation pulses ΔPt = 52 pulses, it is only necessary to insert filters 37 for “52 pulses”. Therefore, the filter selection unit 85 adds a filter 37d capable of compensating for "16 pulses" and a filter 37b capable of compensating for "4 pulses" to the filter 32e of "32 pulses" at the time of focusing, for a total of three sheets. Filters 37b, 37d, and 37e are selected.

  Then, the filter control unit 86 includes two filter motors 46 corresponding to the two filters 37b and 37d other than the filter 37e that is already inserted among the three selected filters 37b, 37d, and 37e. The two filters 37b and 37d are further inserted by driving. As a result, the three filters 37b, 37d, and 37e are inserted, and the main subject is focused on the image plane 32a of the image sensor 32.

  If the current position of the focus lens 33b is at position B in FIG. 11, the current sensitivity ratios B / G and R / B are “1.10” and “0.93”, respectively. Calculated as ΔB / G = 0.10 and the difference ΔR / B = −0.07. The defocus amount ΔP when these differences ΔB / G, ΔR / B are both calculated as “+18 pulses”. Since the filter selection unit 85 calculates the number of compensation pulses ΔPt = 32−ΔP = 32−18 = 14 pulses, it is only necessary to insert “14 pulses” of filters 37. Therefore, the filter selection unit 85 selects the three filters 37a, 37b, and 37c that can compensate for “2 pulses”, “4 pulses”, and “8 pulses”. Then, the filter control unit 86 drives the four filter motors 46, and inserts the selected three filters 37a, 37b, and 37c in place of the filter 37e that has already been inserted. As a result, the main subject is imaged on the image plane 32 a of the image sensor 32.

  In the above description, an extreme example of the boundary position of the second AF control range, that is, the A position and the B position has been described. However, in practice, the filter 37 is inserted / removed each time the focus is slightly shifted from the in-focus position. For this reason, in the second AF control range, the in-focus state is always maintained substantially by the second AF control by the filter insertion / removal method executed sequentially. As a result, it is possible to avoid image wobbling caused by a search during contrast detection AF control during moving image shooting. Therefore, it is possible to shoot and store a high-quality moving image with a low frequency of wobbling.

  On the other hand, when it is determined in step S90 that the slopes KR and KG are equal to or smaller than the threshold value Ko, in step S120, the computer 31 determines whether or not the filter 37 is in an initial state. Specifically, the switching control unit 64 of the computer 31 determines whether or not the filter 37e to be initially inserted is inserted and the other filters 37a to 37d are not inserted. If the filter 37 is not in the initial state, the process proceeds to step S130, and if the filter 37 is in the initial state, the process proceeds to step S140.

  In step S130, the computer 31 sets the filter 37 to an initial state. Specifically, the filter control unit 86 of the computer 31 drives the filter motor 46 so that only the filter 37e to be initially inserted is inserted and the other filters 37a to 37d are removed.

  In step S140, the computer 31 executes AF control (first AF control) using a contrast detection method. Specifically, the first AF control is executed by the first focusing control unit 65 of the computer 31. When the first AF control is finished and focused, the process returns to step S40 to shift to the second AF control of the filter insertion / removal method, and after performing the processes of S40 to S60, the processes of S70 to S110 are repeated to obtain a predetermined time period. The second AF control of the filter insertion / extraction method is performed every time. If the slopes KR and KG become equal to or smaller than the threshold value Ko during the second AF control (No in S90), the switching control unit 64 sets the filter 37 to an initial state as necessary (S130), and then the contrast detection method. Switch to the first AF control (S140).

As described above in detail, according to the first embodiment, the following effects can be obtained.
(1) Since AF control using the filter insertion / extraction method is performed after focusing by AF control using the contrast detection method, the occurrence frequency of wobbling caused by the search operation during AF control using the contrast detection method is reduced, and an image caused by wobbling is reduced. The blur can be reduced.

  (2) A plurality of (N) filters 37 are provided, and the second focusing control unit 66 creates a different refractive index depending on the combination of the plurality of filters by overlapping the plurality of filters 37 and arranging them on the optical path. Therefore, the AF control can be finely performed with a small number of filters 37.

  (3) In particular, the number of pulses that can be compensated for the N filters 37 is 2, 4, 8, 16, and 32 pulses. That is, when the number of pulses in the minimum movement unit is D, the N filters 37 have respective refractive indexes that can compensate for D, 2D, 4D, 8D,..., 2 ^ (N−1) · D pulses. Different filters. For this reason, the number of filters 37 can be reduced for the accuracy of the second AF control. Therefore, the filter device 36 can be downsized (thinned) for the accuracy of the second AF control, and the camera 11 can be configured compactly.

(4) Since map data is prepared for each zoom amount, appropriate second AF control according to the zoom amount can be realized.
(5) Since the slope K of the color signal value at the edge is obtained and the first AF control and the second AF control are switched by comparing the slope K with the threshold value Ko, appropriate switching between the first AF control and the second AF control is performed. It can be performed.

  (6) Using the sensitivity ratios R / G, B / G, and R / B, differences ΔR / G and ΔB / from the sensitivity ratios Ro / Go, Bo / Go, and Ro / Bo at the time of focusing by the first AF control. Since the filter 37 to be inserted is selected based on G and ΔR / B, the second AF control can be performed appropriately.

The said embodiment is not limited above, It can also change into the following aspects.
As shown in FIG. 15, a slider 94 and a linear motor 95 for moving the filter 37 in the optical axis direction are further provided. The filter 37 can be inserted into and removed from the optical path by driving the filter motor 46 and driven by the linear motor 95. A configuration capable of moving in the optical axis direction can also be employed. In this case, the second AF control is performed by inserting the filter 37 and moving the inserted filter 37 in the optical axis direction. According to this configuration, since the AF control can be performed also by the movement of the filter 37 in the optical axis direction, the number of the filters 37 can be reduced, and instead of the intermittent second AF control as in the above embodiment, Continuous second AF control becomes possible. In the example of FIG. 15, a plurality of (two) filters 37 having different refractive indexes are provided, but the number of the filters 37 may be one, or may be three or more.

  It is determined whether or not the defocus amount ΔPa or ΔPa corresponding to the A position and the B position in the graph of FIG. 11 is reached, and the first AF control is performed based on the comparison result between the defocus amount ΔP and ΔPa or ΔPa. It is good also as a structure which switches between 2nd AF control.

In the above-described embodiment, a configuration in which only one selected from the plurality of filters 37 is inserted instead of the configuration in which the filters are overlaid and inserted.
In the above embodiment, the filter may be transparent or colored such as smoke.

-In the said embodiment, you may also employ | adopt the structure used as the filter apparatus provided with only one filter.
The electronic camera is not limited to a digital camera, but may be a video camera, a PDA (Personal Digital Assistant) having a camera function, a mobile phone, a portable game machine, or the like.

DESCRIPTION OF SYMBOLS 11 ... Camera as an electronic camera, 13 ... Imaging lens, 17 ... Power switch, 18 ... Release switch, 20 ... Monitor, 21 ... Mode selection switch, 22 ... Zoom button, 24 ... Shooting button, 30 ... Engine, 31 ... Computer 32 ... an image sensor constituting an imaging means, 33a ... a zoom lens, 33b ... a focus lens as a photographic lens, 34 ... aperture, 35 ... shutter, 36 ... filter device, 37, 37a to 37e ... filter, 38 ... second. Filter driving circuit constituting driving means 39. Focus driving circuit constituting first driving means 40. Shutter driving circuit 41. Diaphragm driving circuit 42. Zoom driving circuit constituting third driving means 43. Zoom motor constituting three drive means, 44... Focus motor constituting first drive means (AF 45 ... AF sensor, 46 ... filter motor constituting second drive means, 47 ... imaging control circuit, 48 ... video circuit, 49 ... nonvolatile memory, 51 ... monitor control circuit, 52 ... memory control circuit 53 ... Operation detection circuit 54 ... Memory card 61 ... Main control unit 62 ... Image processing unit 62A ... Face detection unit 63 ... Zoom control unit 64 ... Switch control unit 65 ... First focus control First focusing control unit as means 66 66 Second focusing control unit 67 Display control unit 71 Contrast detection unit 69 Lens control unit 73 Search unit 81 Edges constituting detection unit Detecting unit, 82... Edge tilt calculating unit as tilt calculating unit, 83... Determining unit, 84... Detecting unit and sensitivity ratio calculating unit as sensitivity ratio calculating unit, 85. Filter selection 86: Filter control unit constituting second focusing control means, R / G, B / G, R / B: Sensitivity ratio, ΔR / G, ΔB / G, ΔR / B: Difference, ΔP: Deviation amount Defocus amount, ΔPt: number of compensation pulses.

Claims (8)

First driving means for moving the photographic lens in the optical axis direction;
First focusing control means for controlling the first driving means so as to arrange the photographing lens at a focusing position based on a contrast value of an image acquired by the imaging means;
At least one filter having a refractive index provided so as to be able to be inserted into and removed from an optical path between the photographing lens and the imaging unit and capable of compensating for a deviation amount from the in-focus position of the photographing lens;
A second driving means for inserting and removing the filter with respect to the optical path; and a detecting means for detecting a shift amount with respect to a focusing position of the photographing lens;
Second focus control means for controlling the second drive means to focus so that a filter having a refractive index corresponding to the amount of deviation detected by the detection means is inserted into and removed from the optical path;
An automatic focusing control device characterized by comprising: A plurality of the filters;
2. The automatic focusing control according to claim 1, wherein the second focusing control unit creates a different refractive index depending on a combination of the plurality of filters by superimposing a plurality of filters on the optical path. apparatus.   The second focusing control means performs focusing by inserting / removing the filter on the optical path and moving the filter inserted on the optical path in the optical axis direction. 2. The automatic focusing control device according to 2. A zoom lens,
Third driving means for adjusting the zoom amount by moving the zoom lens in the optical axis direction and changing the focal length;
The automatic focusing control apparatus according to claim 2, wherein the second focusing control unit selects a filter to be inserted on the optical path in accordance with the zoom amount and the shift amount.   The detection means includes sensitivity ratio calculation means for calculating at least one of three sensitivity ratios indicated by a ratio of combinations of two colors among the RGB three color signal values of the image acquired by the imaging means. 5. The automatic focusing control device according to claim 1, wherein the shift amount from the in-focus position is obtained based on the at least one sensitivity ratio. Inclination calculation means for obtaining an inclination when the RGB signal value acquired by the imaging means crosses an edge portion in the image,
When the tilt is equal to or greater than a threshold value, second focus control is performed by the second focus control unit. When the tilt is less than the threshold value, the second focus control is changed to the first focus control. The automatic focusing control device according to claim 1, wherein the first focusing control is switched to first focusing control by means. Imaging means for photographing a subject;
An automatic focusing control device according to any one of claims 1 to 6,
An electronic camera characterized by comprising: A first focusing control step for performing focusing control so that the photographing lens is arranged at a focusing position based on a contrast value of an image acquired by the imaging unit while moving the photographing lens in the optical axis direction;
A detecting step for detecting a shift amount of the photographing lens that has been focused by the first focusing control step with respect to a focusing position;
A second focusing control step of focusing by inserting and removing the filter with respect to the optical path so that a filter having a refractive index capable of compensating the shift amount is disposed on the optical path of the photographing lens;
An automatic focusing control method comprising:

Images