JP2018128542A - Focal position detector and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focal position detector capable of achieving excellent response performance and focusing position detection accuracy by using the hybrid AF method which controls to prevent occurrence of lens wobbling phenomenon by combining image plane phase difference AF and contrast AF while reducing the focusing time, and an imaging apparatus.SOLUTION: Disclosed focal position detector 32 monitors the predetermined image plane phase difference AF evaluation value and the contrast AF evaluation value calculated during the movement of an imaging lens 2 for detecting the in-focus position in parallel using an image pickup device 1 in which the pixel group of one set of two phase difference detection pixels 112 for detecting the phase difference between pixels is arranged in a pixel portion 11 constituting the pixel group of an image pickup pixel 111 to thereby control the automatic focusing by setting the drive speed of imaging lens 2 to be changeable.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a focus position detector and an imaging apparatus related to focus position detection.

  In auto focus (AF) technology that automatically detects and adjusts the in-focus position by an image pickup device, in order to detect a phase difference between pixels separately from the image pickup pixels for forming an image in the image pickup device. An image plane phase difference detection AF method (hereinafter referred to as an AF method) that adjusts the in-focus position by detecting the defocus amount (image shift amount) by the phase difference output between the phase difference detection pixels. , Referred to as “image plane phase difference AF”) and an AF method that adjusts the in-focus position based on image contrast detection (hereinafter referred to as “contrast AF”). Yes.

  For example, as this hybrid AF method, a technique is known in which the in-focus position of the imaging lens is coarsely adjusted based on image plane phase difference detection, and the in-focus position is finely adjusted by finely driving the imaging lens based on image contrast detection. (For example, refer to Patent Document 1). The technique of Patent Document 1 improves the responsiveness when finely adjusting with contrast AF and the accuracy of detecting the in-focus position after driving the imaging lens to the in-focus position obtained by the image plane phase difference AF. It is aimed.

  In the image plane phase difference AF method, there are various methods for calculating the AF evaluation value (hereinafter referred to as “image plane phase difference AF evaluation value”). A technique is known in which the absolute value of the difference is added to obtain an image plane phase difference AF evaluation value (correlation calculation value COR) (see, for example, Patent Document 2).

  In contrast AF methods, there are various methods for calculating the AF evaluation value (hereinafter referred to as “contrast AF evaluation value”). In general, the focus is focused on the position where the contrast of the image is the highest. As an AF evaluation value for guiding the position, since it can be implemented only by image analysis, it is introduced in many digital cameras.

  These techniques of Patent Documents 1 and 2 are disclosed as a digital camera that mainly drives an imaging lens for photographing as an imaging device, but in a television camera, for the focus adjustment of a cameraman, A technique for superimposing a high-contrast portion (focused area) of an image on a viewfinder (VF) image is disclosed (for example, see Patent Document 3).

  In general, a television camera is provided with a low-resolution viewfinder, and in order to improve the visibility of this viewfinder image, strong contour compensation called peaking is performed, and processing to make the contour of the focused area stand out is performed. It has been broken. In ordinary television cameras, the bandwidth of the captured camera image and the viewfinder image input to the viewfinder are approximately equal, so even if the viewfinder resolution is low, the peaking signal is generated based on the viewfinder image. Can be generated.

  However, even if peaking processing is applied to the viewfinder image, the high-frequency spatial frequency component useful for focus adjustment is lost, and the cameraman cannot fully check the best focus state. The selection operation is required.

  Therefore, in the technique of Patent Document 3, a low-resolution video corresponding to the resolution of the viewfinder video is generated from the ultra-high-definition video captured by the television camera, and the focus area of the television camera is generated from the ultra-high-definition video. A focus adjustment auxiliary signal is generated, and the generated low-resolution video and the focus adjustment auxiliary signal are combined to generate a viewfinder image, thereby maintaining the visibility of the focus state in the viewfinder image. However, the selection operation of the focus adjustment area is unnecessary.

JP 2010-256824 A JP 2010-91991 A JP 2011-176788 A

  In the technique of Patent Document 1, parallax is calculated using the phase difference output of the phase difference detection pixel by determining the start position of contrast AF by the operation of the image plane phase difference AF, and imaging to a lens focus value that is uniquely determined. The lens position is coarsely adjusted, and fine adjustment of AF is performed according to the contrast of the image while repeating minute driving of the imaging lens.

  However, in the technique of Patent Document 1, the image plane phase difference AF evaluation value and the contrast AF evaluation value are not monitored while the imaging lens is moved by the image plane phase difference AF up to the contrast AF start position. When the focus position estimation by the surface phase difference AF has failed, the focus speed may be slower than when only the contrast AF is performed. In addition, since it is impossible to determine whether the position after moving the imaging lens to the contrast AF start position by the image plane phase difference AF is the front side or the back side of the in-focus position, it is finely driven to either of them and the position is adjusted. A forward / backward search operation for confirming the focal position, that is, a lens wobbling phenomenon occurs, which hinders speeding up to focusing.

  Furthermore, unlike digital camera imaging lenses, television camera imaging lenses are designed so that they can be used from various manufacturers. The value control is not incorporated in the television camera or the focus value specified by the cameraman is converted into the physical relative position of the imaging lens with respect to the television camera body (hereinafter referred to as “lens relative position”). There are various things, such as those configured to control.

  Therefore, even if the technique of Patent Document 1 is applied to such a television camera, the focus position estimation accuracy based on the image plane phase difference AF is lacking from the viewpoint of enabling use of various imaging lenses. Therefore, there is a problem that AF does not operate accurately.

  In addition, the image pickup lens of a television camera is larger than the image pickup lens for a digital camera based on AF, and is premised on manual focus adjustment by a cameraman, which places a relatively large load (stickiness) on the operability of the image pickup lens. Therefore, even if the image pickup lens is driven to the in-focus position obtained by the image plane phase difference AF as in the technique of Patent Document 1, an attempt is made to finely adjust the contrast with the contrast AF. Often not suitable for improvement.

  Therefore, not only digital cameras but especially imaging devices such as television cameras are controlled so that lens wobbling does not occur while shortening the time to focus, and excellent responsiveness and focus position detection accuracy A hybrid AF method that combines image plane phase difference AF and contrast AF is desired.

  In view of the above-described problems, the object of the present invention is to combine the image plane phase difference AF and the contrast AF, and to improve the hybrid AF method that controls the lens wobbling phenomenon while reducing the time until focusing. Another object of the present invention is to provide an in-focus position detector and an imaging apparatus that can realize the responsiveness and the in-focus position detection accuracy.

  An in-focus position detector according to the present invention includes an image sensor in which a pixel group of two sets of phase difference detection pixels for detecting a phase difference between pixels is arranged in a pixel portion that constitutes a pixel group of image pickup pixels. An in-focus position detector for detecting the in-focus position of the imaging lens capable of adjusting the focal position, based on the phase difference output obtained from the pixel group of the phase difference detection pixels of the two pixels, First evaluation value calculation means for calculating a predetermined evaluation value for detecting a defocus amount as an image plane phase difference AF evaluation value, and an image in a predetermined region of interest obtained from the pixel group of the imaging pixels Second evaluation value calculation means for calculating a predetermined evaluation value for detecting the maximum contrast at the in-focus position as a contrast AF evaluation value, and the image plane position calculated at the start of detection of the in-focus position Based on the phase difference AF evaluation value, the imaging lens An initial setting means for initially setting a moving direction and a changeable driving speed; and a lens drive control means for starting and controlling the driving of the imaging lens in order to detect a focus position of the imaging lens from the initial setting. Evaluation value monitoring means for monitoring the image plane phase difference AF evaluation value and the contrast AF evaluation value calculated during the movement of the imaging lens for detection of the in-focus position, and the evaluation value Feedback control means for performing feedback control so as to detect the in-focus position based on the result of the monitoring means.

  In the in-focus position detector according to the present invention, the evaluation value monitoring unit is configured to monitor the position and the moving direction of the imaging lens with respect to the in-focus position based on the contrast AF evaluation value. By comparing the contrast AF evaluation values obtained in predetermined time units, a focus flag indicating whether or not the imaging lens has passed the focusing position, and whether or not the driving direction of the imaging lens is the reverse direction. The reverse rotation flag shown is sequentially updated and set in units of the first predetermined time, and the second predetermined time from the initial setting time when the driving speed of the imaging lens can be changed by the image plane phase difference AF evaluation value is monitored. By comparing the contrast AF evaluation values obtained in units, it is determined whether or not the position of the imaging lens is close to the in-focus position, and the position of the imaging lens is in the in-focus position. Characterized in that it comprises means for sequentially updating set the speed flag to Ihodo low speed by the second predetermined time unit.

  In the in-focus position detector of the present invention, the feedback control means may be set to a position at the time when the imaging lens passes the in-focus position when the in-focus flag indicates that the in-focus lens has passed the in-focus position. The in-focus flag indicates that the imaging lens has passed the in-focus position while instructing the lens drive control means to position the in-lens lens and controlling the drive to complete the detection operation of the in-focus position. The driving direction of the imaging lens is instructed to be changeable based on the reverse rotation flag, and the lens driving control means is instructed to drive and control the driving speed of the imaging lens based on the speed flag. Feedback control is performed so as to instruct the lens drive control means to perform drive control.

  Further, in the in-focus position detector of the present invention, the lens drive control means performs a stepwise speed control that makes the speed lower as the position of the imaging lens is closer to the in-focus position according to the speed flag. It is characterized by having.

  In the in-focus position detector according to the present invention, the initial setting unit may calculate the image plane phase difference AF calculated in one frame of a moving image obtained from a pixel group of the imaging pixels at the start of detection of the in-focus position. Based on the evaluation value, the driving direction of the imaging lens and the changeable driving speed are initially set, or obtained from a plurality of frames of a moving image obtained from the pixel group of the imaging pixels at the start of detection of the in-focus position. And a means for initially setting the driving direction of the imaging lens and the changeable driving speed based on the image plane phase difference AF evaluation value calculated by the addition average.

  In the in-focus position detector according to the present invention, the evaluation value monitoring means may use the first predetermined time unit as a frame time unit of a moving image obtained from the pixel group of the imaging pixels, and the contrast AF in the frame time unit. It has a means for calculating and monitoring an evaluation value.

  Further, in the in-focus position detector of the present invention, the evaluation value monitoring means uses the second predetermined time unit as a frame time unit of a moving image obtained from the pixel group of the imaging pixels, and the contrast AF evaluation in the frame time unit. The contrast AF evaluation value is calculated by calculating a value, or by using the second predetermined time unit as a plurality of frame time units of a moving image obtained from the pixel group of the imaging pixels, and by averaging the values obtained in the plurality of frame time units. And a means for monitoring.

  In the in-focus position detector of the present invention, when the reverse rotation flag indicates that the drive direction of the imaging lens is the reverse direction, the feedback control means continuously indicates that the reverse direction is the reverse direction. And a means for forcibly terminating the operation of detecting the in-focus position when the indicated count value is equal to or greater than a predetermined count threshold value.

  Furthermore, the imaging apparatus of the present invention includes a focusing position detector of the present invention and a pair of phase difference detection pixels for detecting a phase difference between the pixels in a pixel portion constituting a pixel group of the imaging pixels. An image pickup device in which a pixel group is arranged and an image pickup lens capable of adjusting a focal position are provided.

  According to the present invention, since the contrast AF evaluation value is constantly monitored while the imaging lens is being driven, AF correction can be performed immediately even if the AF based on the image plane phase difference AF evaluation value is erroneous. In addition, according to the present invention, it is not necessary to perform a back-and-forth operation for in-focus position search, so that the lens wobbling phenomenon can be prevented while shortening the time until in-focus, and excellent responsiveness and alignment are achieved. The focal position detection accuracy can be realized.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention. It is a figure which illustrates roughly a part of pixel arrangement | sequence of the pixel part in the image pick-up element which concerns on the imaging device of one Embodiment by this invention. It is a figure which illustrates the region of interest for performing contrast AF specified by cutting out a part from the entire region of the pixel portion by the focus adjustment auxiliary signal in the imaging apparatus according to the embodiment of the present invention. The image plane phase difference AF based on the image plane phase difference AF evaluation value and the contrast AF based on the contrast AF evaluation value when the AF is performed by the focus position detector of Example 1 in the image pickup apparatus according to the embodiment of the present invention. It is a figure which shows the relationship with the focus position of a lens. It is a flowchart which shows the main process of the focus position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a flowchart which shows the sub process with respect to the main process of the focus position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a flowchart which shows the sub process with respect to the main process of the focus position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a flowchart which shows the sub process with respect to the main process of the focus position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a flowchart which shows the sub process with respect to the main process of the focus position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a figure which shows an example of operation | movement of the focusing position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a figure which shows another example of operation | movement of the focusing position detector of Example 1 in the imaging device of one Embodiment by this invention. It is a figure which shows the further another example of operation | movement of the focusing position detector of Example 1 in the imaging device of one Embodiment by this invention.

  Hereinafter, with reference to the drawings, in-focus position detectors 32 of Examples 1 to 3 will be described in order with respect to an imaging apparatus 50 according to an embodiment of the present invention. In the imaging device 50, the focus position detector 32 is configured as a functional unit that detects the focus position (calculates the defocus amount) using the pixel output of the phase difference detection pixel obtained from the image sensor 1.

[Imaging device]
FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus 50 according to an embodiment of the present invention. The imaging apparatus 50 detects a phase difference between pixels separately from imaging pixels for configuring an image. The image sensor 1 in which the phase difference detection pixels are arranged and the in-focus position detector 32 according to the present invention will be described as an example in which the image sensor 1 is configured as a television camera equipped with an autofocus (AF) system. To do.

  The imaging device 50 is configured to form an image of a subject on the imaging element 1 by the imaging lens 2, perform image processing on the output of the imaging element 1, and output the image data to the display unit 6 and the recording unit 7. The optical system 51, the signal processing system 52, and the input / output system 53 can be divided. The imaging optical system 51 forms an image of a subject on the imaging device 1 by the imaging lens 2, and the imaging device 1 outputs a digital amount of pixel signals (unit signals corresponding to pixel values).

  The signal processing system 52 receives an operation instruction from the operation unit 8 of the input / output system 53 by the interface (IF) control unit 4, and the IF control unit 4 receives a control signal related to the received operation from the imaging lens 2 and the digital signal processing. Output to the control unit 3. The IF control unit 4 has a function of not only sending a control signal to the digital signal processing control unit 3 but also obtaining various parameters (for example, a gamma value) relating to image processing and outputting them to the operation unit 8. In particular, the IF control unit 4 acquires lens parameters such as an aperture, a focal length, and a focus value from the imaging lens 2 and outputs them to the digital signal processing control unit 3 and the operation unit 8, and the operation of the input / output system 53. When the operation instruction from the unit 8 is automatic focus adjustment, the imaging lens control signal related to the change of the lens parameter is output to the imaging lens 2.

  The digital signal processing control unit 3 controls various operations according to operation instructions from the IF control unit 4. In particular, the digital signal processing control unit 3 includes a digital signal processing unit 31, a focus position detector 32, and a drive control unit 33.

  The digital signal processing unit 31 stores the pixel signals of the RGB imaging pixels obtained from the imaging device 1 in the memory 5, further reads out the pixel signals from the memory 5, performs predetermined image processing, and displays display pixel signals (TV) A display output pixel signal in accordance with the video format of the John camera) and output to the display unit 6 or the recording unit 7 of the input / output system 53, and a phase difference detection pixel among the pixel signals obtained from the image sensor 1. A function of outputting a signal (pixel value of a phase difference detection pixel) to the focus position detector 32 and a focus adjustment auxiliary signal (pixel value of a pixel group indicating a focus target area) are output to the focus position detector 32. And having a function.

  However, the display unit 6 is composed of a viewfinder that can be viewed by a cameraman, and the digital signal processing unit 31 is a low-resolution image corresponding to the resolution of the viewfinder image in the display unit 6 from the captured image captured through the imaging optical system 51. And generating a focus adjustment auxiliary signal indicating the in-focus area of the imaging lens 2 from the captured image or the low-resolution image, and combining the low-resolution image and the focus adjustment auxiliary signal to generate a viewfinder image And output to the display unit 6.

  In addition, the drive control unit 33 has a function of supplying the image sensor 1 with an image sensor drive signal for controlling the imaging operation of the image sensor 1.

  Although the focus position detector 32 of each embodiment according to the present invention will be described in detail later, a phase difference detection pixel signal (pixel value of the phase difference detection pixel) and a focus adjustment auxiliary signal (focusing point) from the digital signal processing unit 31. Obtain the pixel value of the pixel group indicating the target area (region of interest), calculate the image plane phase difference AF evaluation value based on the phase difference detection pixel signal, and calculate the contrast AF evaluation value based on the focus adjustment auxiliary signal To do. Then, the focus position detector 32 of each embodiment calculates a defocus amount that is a defocus amount based on the image plane phase difference AF evaluation value and the contrast AF evaluation value, and determines a focus position. And has a function of outputting information of a control amount for performing automatic focus adjustment to the IF control unit 4. Thereby, since the IF control unit 4 outputs and drives the imaging lens control signal to the imaging lens 2, AF by the in-focus position detector 32 is possible, and the lens parameter relating to the automatic focus adjustment can be changed.

  Therefore, since the imaging device 50 can perform transmission and reception of electrical signal communication between the imaging lens 2 and the IF control unit 4, the imaging optical system 51 and the signal processing system 52 have a diaphragm, focal length, Lens parameters such as a focus value, exposure information of the image sensor 1 can be shared. Then, based on the control of the focus position detector 32, various lens parameters of the imaging lens 2 can be changed by a command (imaging lens control signal) from the IF control unit 4.

  In the example of the imaging device 50 shown in FIG. 1, an example in which the input / output system 53 includes the display unit 6, the recording unit 7, and the operation unit 8 is illustrated, but the imaging device 50 according to the present invention includes a relay. For example, the display unit 6, the recording unit 7, or the operation unit 8 such as a television camera may be configured as a separate device, and a transmission device that communicates with these devices may be provided in the input / output system 53.

  In particular, the in-focus position detector 32 of each embodiment, which will be described in detail later, describes an image plane for estimating the object position from the parallax, which is the amount of imaging deviation between the phase difference detection pixels in the image sensor 1. The hybrid AF method using two evaluation values of the phase difference AF evaluation value and the contrast AF evaluation value using the focus adjustment auxiliary signal used by the photographer to adjust the focus on the viewfinder enables accurate and high-speed AF. Configured to perform control.

  Further, the imaging device 50 of the present embodiment is designed so that various manufacturers can be used as the imaging lens 2 when configured as a television camera, and the absolute value of the focus value when driving the imaging lens 2 is designed. Whether or not it is a configuration incorporating value control, and a focus value designated by a cameraman is converted into a physical relative position (lens relative position) of the imaging lens 2 with respect to the television camera body and controlled. The in-focus position detector 32 according to the present invention can be applied regardless of whether or not this is the case.

[Image sensor]
FIG. 2 schematically illustrates a part of the pixel array of the pixel unit 11 in the imaging device 1 according to the imaging device 50 of the embodiment of the present invention. The image sensor 1 typically includes a red (R) color filter (CFR), a green (G) color filter (CFG), and a blue (B) color filter (CFB) arranged in a Bayer array (GGBR). ) To form a pixel portion 11 in a set of four pixels.

  However, the image pickup device 1 according to the present invention is an RGBW array in which one of the G color filters is replaced with a white (W) color filter in a set of four pixels, and other color filter arrays are used. It can also be configured. In the present specification, a pixel in which such a color filter is arranged is referred to as an “imaging pixel” 111.

  By the way, as shown in FIG. 2, the pixel unit 11 in the image pickup device 1 has a set of two pixels for detecting a phase difference between the pixels (not shown) separately from the pixel group of the image pickup pixels 111 by these color filters. A pixel group of phase difference detection pixels 112 (A pixel, B pixel) is provided, and this phase difference detection pixel 112 functions as a phase difference detection element for image plane phase difference AF for detecting a focus. The pair of A pixel and B pixel phase difference detection pixels 112 are a left-eye phase difference detection pixel and a right-eye phase difference detection pixel, respectively.

  The phase difference detection pixel 112 may be provided with an ND filter that limits the amount of light only by a predetermined amount without affecting color development, but an example in which a color filter is not provided to improve the SN ratio is shown. ing. In the pixel unit 11, one set of two pixels of phase difference detection pixels 112 are discretely arranged at a plurality of locations. A mask 113 is formed so that the pupil division directions of the A pixel and the B pixel in the phase difference detection pixel 112 are mirror images of each other. The phase difference detection pixel 112 of a pair of A pixel and B pixel has an aperture ratio of 50% in the X direction as shown in FIG. Masks 113 are formed so that the pupil division directions of the two are mirror images of each other. Various shapes are assumed for the shape of the mask 113, and it is not necessary to limit to the illustrated example.

  The pair of phase difference detection pixels 112 of the two pixels is used for image plane phase difference AF that calculates a defocus amount that is a focus shift amount, determines a focus position, and performs automatic focus adjustment.

  In the present specification, the pupil division direction (left and right direction in FIG. 2) of the A pixel and B pixel is the X direction, and the direction perpendicular to the X direction (vertical direction in FIG. 2) on the pixel unit 11 is the Y direction. The direction perpendicular to the plane (the front side with respect to the illustrated surface in FIG. 2) is the Z direction.

(Image plane phase difference AF evaluation value)
First, the image plane phase difference AF evaluation value will be described. The in-focus position detector 32 obtains the phase difference detection pixel signal (pixel value of the phase difference detection pixel) from the digital signal processing unit 31 and outputs the phase difference output obtained from the pixel group of the phase difference detection pixel of one set of two pixels. Based on this, a predetermined evaluation value for detecting the defocus amount is calculated as an image plane phase difference AF evaluation value. Various methods are assumed as the defocus amount calculation method using the phase difference detection pixel 112. As an example of the conventional technique, the absolute value of the difference between a pair of images as shown in Expression (1) is used. Some have been added (see, for example, Patent Document 2).

In equation (1), A _ij and B _ij are two sets of phase difference detection pixels 112 (for the right eye and the left eye) that are discretely arranged in the pixel unit 11 in which a plurality of imaging pixels 111 are arranged in a grid. J represents the i-th pixel value of the j-th column of the phase difference detection pixels A and B), ni is the number of pixels used for the correlation calculation, nj is the number in the column direction of the pair of images on which the correlation calculation is performed, and ni , nj are appropriately set according to the distance measuring field length (field length to be measured).

  The calculation of the defocus amount based on the equation (1) is to obtain the parallax k that minimizes the correlation calculation value COR (k) as the in-focus position. That is, the correlation calculation value COR (k) can be used as the image plane phase difference AF evaluation value α. The in-focus position detector 32 obtains a phase difference detection pixel signal for each frame from the digital signal processing unit 31, and calculates an image plane phase difference AF evaluation value α (that is, COR (k)) for each frame. .

  When calculating the defocus amount, it is common to provide a threshold value for determining whether or not to perform automatic focus adjustment according to the signal level of the phase difference detection pixel 112 in consideration of the SN ratio of the pixel value. In addition, the number of pixels (ni, nj) used for the correlation calculation is determined by a reference value determined in advance by the detection position of the pixel unit 11, the image height, the imaging lens performance (lens parameter) of the imaging lens 2, and the signal level thereof. Among them, the phase difference detection pixel 112 is determined as a target of correlation calculation.

  By the way, with the conventional technique of Patent Document 1, the in-focus position is uniquely calculated from the value of k in Equation (1), the imaging lens 2 is moved to that position, and fine adjustment is performed by contrast AF. Become. The detection accuracy of the image plane phase difference AF evaluation value is improved as the phase difference detection pixels 112 are embedded more densely in the image sensor 1, but the phase difference detection pixels 112 cannot be used as the image pickup pixels 111. The image quality deteriorates as the phase difference detection pixel 112 is embedded. In other words, in the conventional technique of Patent Document 1, a certain amount sufficient for this control to move the imaging lens 2 to a substantially in-focus position in accordance with the image plane phase difference AF within a range that can be finely adjusted by contrast AF. Note that it is necessary to embed the other phase difference detection pixels 112.

(Contrast AF evaluation value)
Next, the contrast AF evaluation value will be described. The focus position detector 32 obtains a focus adjustment auxiliary signal (pixel value of a pixel group indicating the focus target area) from the digital signal processing unit 31 and calculates a predetermined evaluation value for performing contrast AF. Contrast AF is a technique for guiding the focus position to a position where the contrast of the image is the highest. That is, the focus position detector 32 performs a predetermined evaluation for detecting the maximum contrast at the focus position based on the image in the region of interest (focus target area) obtained from the pixel group of the imaging pixels 111. The value is calculated as a contrast AF evaluation value.

  FIG. 3 illustrates a region of interest 114 for performing contrast AF that is specified by cutting out a part from the entire region of the pixel unit 11 using a focus adjustment auxiliary signal. In the region of interest 114 illustrated in FIG. 3, the total value of the focus adjustment auxiliary signals represented by Expression (2) is the contrast AF evaluation value.

C _{ij in} Expression (2) represents the signal value of the j-th column i-th pixel of the focus adjustment auxiliary signal, mi is the number in the row direction used for the calculation, and mj is the number in the column direction used for the calculation. mi and mj are set as regions equivalent to the region of interest 114 of the image plane phase difference AF. CAF indicates a contrast AF evaluation value, which means that the region of interest 114 is in focus when the CAF is maximized. The focus position detector 32 obtains a focus adjustment auxiliary signal for each frame from the digital signal processing unit 31, and calculates a contrast AF evaluation value CAF for each frame.

  However, in this example, the imaging device 50 having the function of generating the focus adjustment auxiliary signal is described. However, in the case of the imaging device 50 having no function of generating the focus adjustment auxiliary signal, the digital signal processing unit 31 performs contrast. What is necessary is just to comprise so that a high contrast part may be extracted for AF, a signal equivalent to a focus adjustment auxiliary signal may be generated, and output to the in-focus position detector 32. Alternatively, the digital signal processing unit 31 may be configured to generate a peaking signal indicating the region of interest from the captured image or viewfinder image and to output the peaking signal indicating the region of interest to the in-focus position detector 32. In this case, the peaking signal can be used in place of the focus adjustment auxiliary signal.

[Focus position detector]
Example 1
The focus position detector 32 according to the first embodiment is configured to drive and control the imaging lens 2 by performing hybrid AF using the image plane phase difference AF evaluation value and the contrast AF evaluation value described above.

  The focus position detector 32 according to the first embodiment calculates an image plane phase difference AF evaluation value and a contrast AF evaluation value for each frame of a moving image to be captured, and performs high-precision and high-speed AF. Since the imaging device 50 configured with a television camera has a higher calculation capability than a digital camera, calculation of an AF evaluation value for each frame of a moving image to be captured can be easily realized.

  In particular, the in-focus position detector 32 according to the first embodiment determines the driving direction of the imaging lens 2 at the start of AF and determines the driving speed of the imaging lens 2 based on the image plane phase difference AF based on the image plane phase difference AF evaluation value. The contrast AF based on the contrast AF evaluation value is controlled, and the focus position is always monitored.

  FIG. 4 shows the relationship between the image plane phase difference AF based on the image plane phase difference AF evaluation value and the contrast AF based on the contrast AF evaluation value by the focus position detector 32 according to the first embodiment, and the focus position of the imaging lens 2. Is shown. Specific processing of the in-focus position detector 32 of the first embodiment will be described later. In order to improve the understanding of the present invention, the main operation will be described with reference to FIG.

  Referring to FIG. 4, when AF is started at the focus position (lens focus position) A of the imaging lens 2 in the figure, an image plane phase difference AF evaluation value α is calculated. The driving direction (tele side, wide side) of the imaging lens 2 is determined by the ± sign of α. Thereafter, the image plane phase difference AF evaluation value is continuously calculated while moving the lens focus position in the in-focus direction (in-focus direction) at the speed Va.

  When the image plane phase difference AF evaluation value becomes 2α / 3 or less at the lens focus position B in the drawing, the drive speed of the imaging lens 2 is reduced to the speed Vb (Vb <Va). Further, when the image plane phase difference AF evaluation value becomes 1α / 3 or less at the lens focus position C in the drawing, the driving speed of the imaging lens 2 is further reduced to a speed Vc (Vc <Vb). That is, the in-focus position detector 32 according to the first exemplary embodiment has the speed Va from the lens focus position A to B, the speed Vb from the lens focus position B to C, and the speed Vc from the lens focus position C to the in-focus point. The imaging lens 2 is driven and controlled.

  In the example of the focus position detector 32 of the first embodiment, the speed can be adjusted in three stages of speeds Va, Vb, and Vc. However, if the number of speed divisions (number of stages) is two or more. Well, the division ratio need not be divided equally and is arbitrary. With respect to the image plane phase difference AF evaluation value α calculated at the start of detection of the in-focus position, a lower limit is provided in order to cope with the case where the AF start position is near the in-focus position, and the image plane phase difference AF evaluation value α is If it is lower than the lower limit value, the driving speed of the imaging lens 2 is set to the lowest (speed Vc in this example) from the beginning.

  Further, as error processing, the absolute value of the image plane phase difference AF evaluation value α increases while the imaging lens 2 is driven, the ± sign of α is inverted, and the driving direction of the imaging lens 2 is reversed by monitoring with the contrast AF evaluation value. In this case, since it can be determined that the reliability of the image plane phase difference AF evaluation value is low, the focus movement speed is fixed to the minimum speed until the end of the AF sequence.

  Since the contrast AF evaluation value has a large amount of change in the vicinity of the in-focus position, the higher the number of sampling times for calculating the contrast AF evaluation value in the vicinity of the in-focus, the higher the precision control becomes possible. For this reason, the focus position detector 32 according to the first embodiment calculates the contrast AF evaluation value for each frame and determines the focus position. However, it is not necessarily limited to each frame, and the in-focus position may be determined by calculating in units of a predetermined time such as every intermittent frame. Moreover, since the focus position detector 32 of Example 1 decelerates the drive speed of the imaging lens 2 as it approaches the focus position, the focus accuracy can be increased. In addition, the in-focus position detector 32 according to the first embodiment reduces the driving speed of the imaging lens 2 stepwise, and does not need to be stopped suddenly, so that the load on the imaging lens 2 can be reduced.

  Further, in the in-focus position detector 32 according to the first embodiment, the pixel unit 11 is not required to have such high accuracy that the focus position of the imaging lens 2 must be uniquely determined using the image plane phase difference AF evaluation value. The pixel number density of the phase difference detection pixels 112 to be embedded in the image may be sparse so that the number of the phase difference detection pixels 112 is smaller than that of the technique of Patent Document 1. Can be reduced.

  Hereinafter, specific processing of the in-focus position detector 32 according to the first embodiment will be described in detail with reference to FIGS. FIG. 5 is a flowchart showing main processing of the focus position detector 32 of Example 1 in the imaging apparatus according to the embodiment of the present invention. FIGS. 6 to 9 are flowcharts showing sub-processes for the main process of the in-focus position detector 32 according to the first embodiment.

  Here, an example of operating as so-called one-shot AF will be described. In one-shot AF, a start trigger is generated by, for example, operating a physical button for starting AF, and the sequence is terminated when in-focus. An example in which the control is divided into three speeds shown in FIG. 4 will be described.

  Referring to FIG. 5, the focus position detector 32 first initializes the values of various flags (focus flag, reverse rotation flag, speed flag, etc.) to be described later after generating an AF start start trigger. (Step S1).

  Here, for the AF by the focus position detector 32, a focus flag, a reverse rotation flag, a speed flag, and a reverse rotation flag are used.

  The in-focus flag has two values, “0” indicating that the in-focus position is not present and “1” indicating that the in-focus position is present.

  The reverse rotation flag needs to reverse “0” indicating that there is no need to reverse the moving direction of the imaging lens 2 for focusing, and reverse the moving direction of the imaging lens 2 for focusing. It has a binary value of “1” indicating the state.

  In this example, the speed flag is set to 3 of “0” indicating the speed Va, “1” indicating the speed Vb, and “2” indicating the speed Vc as driving speeds of the imaging lens 2 in three stages. Has a value.

  “Lens relative position hold” to be described later refers to information on the physical relative position (lens relative position) of the imaging lens 2 with respect to the main body of the imaging device 50 as a position target for driving the imaging lens 2 (that is, the imaging lens). 2 position information) is temporarily stored. The positional information of the imaging lens 2 is specified based on a return signal (lens parameter) from the imaging lens 2 obtained via the IF control unit 4.

  The “number of reverse rotations” to be described later is a value obtained by counting the number of inversions every time driving for reversing the moving direction of the imaging lens 2 for focusing is performed. The initial value at the start of AF is 0.

  Subsequently, the focus position detector 32 performs initial setting of the driving direction and driving speed of the imaging lens 2 shown in FIG. 6 (step S2). Note that the driving direction and speed of the imaging lens 2 are initially set by the image plane phase difference AF evaluation value.

Referring to FIG. 6, the focus position detector 32 first calculates an image plane phase difference AF evaluation value α ₀ and a contrast AF evaluation value CAF ₀ (step S20).

Subsequently, the focus position detector 32 determines whether or not the value of the image plane phase difference AF evaluation value α ₀ is greater than 0 (step S21). If the value of α ₀ is greater than 0 (step S21: yes), the setting of the lens rotational direction flag of the imaging lens 2 to 1 (tele side) (step S22), and if the value of alpha ₀ is 0 or less (step S21: No), the imaging lens rotating direction flag 0 ( wide side) (step S23).

Next, the in-focus position detector 32 determines whether or not the value of the image plane phase difference AF evaluation value α ₀ is larger than a threshold α _threshold that is arbitrarily set (step S24), and the value of α ₀ is the threshold α. If it is equal to or less than _threshold (step S24: No), it is determined that AF is already close to the in-focus state, and the speed flag is set to 2 (speed Vc) (step S26). The value of the threshold α _threshold is determined according to the number of image plane phase difference detection pixels 112 embedded in the pixel unit 11 and the calculation method of the image plane phase difference AF evaluation value (in this example, the evaluation value COR based on Expression (1)). Set as desired. When the speed flag is 2 (speed Vc), the set speed is not changed in the subsequent sequences regardless of the value of the image plane phase difference AF evaluation value. On the other hand, when the value of α ₀ is larger than the threshold α _threshold (step S24: Yes), the speed flag is set to 0 (speed Va).

  Referring to FIG. 5, when initial setting of the driving direction and driving speed of the imaging lens 2 shown in FIG. 6 is performed, the focus position detector 32 relates to the lens rotation direction and driving speed of the initial setting of the imaging lens 2. Based on the lens rotation direction flag and the speed flag, the imaging lens control signal is transmitted via the IF control unit 4 to start driving the imaging lens 2 (step S3).

  After the driving of the imaging lens 2 is started, an AF (automatic focus control) feedback loop based on subsequent steps S4, S5, and S6 is started. The start of the feedback loop is synchronized with the start of one frame of the video, and is completed within one frame unless the reverse rotation operation of the imaging lens 2 is performed. In this feedback loop, the focus position monitoring process based on the contrast AF evaluation value (step S4) and the imaging lens 2 drive speed monitoring process based on the image plane phase difference AF evaluation value (step S5) are performed in parallel (simultaneously). Then, drive control of the imaging lens 2 is performed based on the focus flag, the reverse rotation flag, and the speed flag (step S6), and AF is performed by the loop processing of steps S4, S5, and S6.

  First, the focus position monitoring process using the contrast AF evaluation value (step S4) will be described with reference to FIG.

In the focus position monitoring process using the contrast AF evaluation value shown in FIG. 7, the focus position detector 32 first calculates a predetermined contrast AF evaluation value (CAF based on the equation (2) in this example) (step). S40). Hereinafter, the maximum CAF value is CAF _max , and the CAF value one frame before is CAF- ₁ .

  Subsequently, the in-focus position detector 32 determines that the position of the imaging lens 2 is the moving end (the end of the lens moving range) based on the return signal (lens parameter) from the imaging lens 2 obtained via the IF control unit 4. ) (Step S41), and when it is determined that the position of the imaging lens 2 is the moving end (step S41: No), the reverse rotation flag = 1 is set and the lens relative position at this time is set. Hold (temporary hold) (step S46), maintain the focus flag = 0, and continue the AF feedback loop (step S47). When the position of the imaging lens 2 is at the moving end, no further movement is possible unless the reversing control is performed. On the other hand, when the position of the imaging lens 2 is not the moving end, it means that the imaging lens 2 is moving.

If it is determined that the position of the imaging lens 2 is not the moving end (step S41: Yes), the focus position detector 32 determines whether or not the CAF is smaller than CAF ₋₁ (step S42). If it has a value equal to or greater than CAF ₋₁ (step S42: No), the CAF value is set to CAF _max , the lens relative position at this time is held (temporarily held) (step S48), and the in-focus flag = 0 is maintained. Then, the AF feedback loop is continued (step S49). In the AF feedback loop based on the steps S4, S5, and S6, since the process of step S48 is repeatedly passed, the lens relative position obtained by sequentially updating the CAF _max is held until the in-focus flag = 1. While (temporarily held), the peak position (that is, the focal point) of the contrast AF evaluation value CAF shown in FIG. 4 is searched.

When CAF has a value smaller than CAF ₋₁ (step S42: Yes), there is a possibility that the position of the imaging lens 2 has passed the peak position (ie, in-focus point) of the contrast AF evaluation value CAF shown in FIG. In order to determine whether the in-focus position detector 32 has passed the peak position of the CAF or is a decrease in CAF due to an error, the value of “CAF _max− CAF” is determined from a set value threshold arbitrarily determined. It is determined whether it is larger (step S43).

When the value of “CAF _max −CAF” is equal to or less than the set value threshold (step S43: No), the focus position detector 32 determines that the CAF is decreased due to an error, and maintains the focus flag = 0 and performs AF. The feedback loop is continued (step S49).

On the other hand, when the value of “CAF _max −CAF” is larger than the set value threshold (step S42: Yes), the possibility that the CAF peak position has been passed and the initial image plane phase difference AF evaluation value indicate that the imaging lens 2 Since the driving direction may be wrong and the moving direction of the imaging lens 2 (the rotating direction in which the imaging lens 2 rotates) may be opposite to the focal point, the in-focus position detector 32 is used to determine this. _It is determined whether _max is greater than CAF ₀ (step S44).

When CAF _max has a value equal to or less than CAF ₀ (step S44: No), the in-focus position detector 32 indicates that the original moving direction of the image pickup lens 2 (the rotational direction in which it rotates) is opposite to the focal point. The reverse rotation flag = 1 is set and the lens relative position at this time is held (temporarily held) (step S46), and the focusing flag = 0 is set (step S47).

On the other hand, when CAF _max has a value greater than CAF ₀ (step S44: Yes), the focus position detector 32 determines that the peak position of the CAF has been passed, and sets the focus flag to 1 (step S45). ). When the in-focus flag is set to 1, the imaging lens 2 is driven to the lens relative position set and held at CAF _max in step S48 by subsequent processing (step S61 described later).

  Next, the monitoring process (step S5) of the driving speed of the imaging lens 2 based on the image plane phase difference AF evaluation value will be described with reference to FIG.

  In the monitoring process of the driving speed of the imaging lens 2 based on the image plane phase difference AF evaluation value shown in FIG. 8, the focus position detector 32 first calculates the image plane phase difference AF evaluation value α (step S50).

Subsequently, the in-focus position detector 32 determines that “the speed flag is not 2 (speed Vc)”, “the number of reverse rotations is 0”, and “± sign of α is the same as α ₋₁ ”. And “the absolute value of α is equal to or smaller than the absolute value of α ₋₁ (| α | ≦ | α ₋₁ |)”, and “the absolute value of α is larger than the absolute value of (1/3) α ₀ ( It is determined whether or not the five conditions of | α |> (1/3) | α ₀ |) ”are satisfied (step S51).

  When not in a state satisfying all the above five conditions (step S51: No), the focus position detector 32 always sets the speed flag to 2 (speed Vc) (step S55). In the AF feedback loop based on the steps S4, S5, and S6, once the speed flag becomes 2 (speed Vc), the above five conditions are not satisfied (the condition that the speed flag is not 2). Therefore, the drive speed of the imaging lens 2 is constant at the speed Vc. The state of the speed Vc means that it has reached the vicinity of the focal point as shown in FIG. 4 or that the reliability of the image plane phase difference AF evaluation value α is low.

When in a state that satisfies all of the above five conditions (step S51: No), the focus position detector 32, the absolute value of α is (2/3) determines whether α greater than the absolute value of ₀ ( step S52), the absolute value of alpha is the (2/3) alpha ₀ speed flag is greater than the absolute value of the change to 0 (velocity Va) (step S52: Yes, step S53), the absolute value of alpha is (2/3) If the absolute value of α ₀ or less, the speed flag is changed to 1 (speed Vb) (step S52: No, step S54). Since there is a condition that “the absolute value of α is equal to or less than the absolute value of α− ₁ ”, the driving speed of the imaging lens 2 does not accelerate from the speed Vb to the speed Va.

  Next, drive control (step S6) of the imaging lens 2 based on the focus flag, the reverse rotation flag, and the speed flag will be described with reference to FIG.

  In the drive control of the imaging lens 2 shown in FIG. 9, the focus position detector 32 monitors the focus position based on the contrast AF evaluation value (step S4) and drives the imaging lens 2 based on the image plane phase difference AF evaluation value. Based on the focus flag, the reverse rotation flag, and the speed flag obtained by performing the speed monitoring process (step S5) in parallel (simultaneously), drive control (feedback loop control) of the imaging lens 2 related to AF is started.

First, the focus position detector 32 determines whether or not the focus flag is 1 (step S60). When the in-focus flag is 1 (step S60: Yes), the in-focus position detector 32 exits the AF feedback loop based on the steps S4, S5, and S6, and controls the imaging lens through the IF control unit 4. A signal is transmitted, and the drive of the imaging lens 2 is controlled so that the imaging lens 2 is positioned at the holding lens relative position (step S61). The lens relative position held at this time is the lens relative position set to CAF _max in step S48 with respect to the frame when the in-focus flag is 1. That is, the imaging lens 2 is driven and controlled at the speed Vc so as to be positioned at the focal point shown in FIG.

  On the other hand, when the focus flag is 0 (step S60: No), the focus position detector 32 first determines whether or not the reverse rotation flag is 1 (step S62).

  If the reverse rotation flag is 1 (step S62: Yes), the in-focus position detector 32 increments the count value of the reverse rotation count by +1 (1 addition) (step S63), It is confirmed whether it is less than the count threshold value X (step S64). When the number of reverse rotations added by 1 is equal to or greater than the count threshold value X (step S64: No), the reverse rotation of the moving direction of the imaging lens 2 has already been repeated X-1 times, and the AF operates normally. It is determined that it has not been performed, and it is forcibly terminated. The value of the count threshold value X can be an arbitrary number equal to or greater than 2. However, since the in-focus position detector 32 according to the present invention functions normally even when only one reverse rotation is allowed, X = 2. Can be set to

  When the number of reverse rotations obtained by adding 1 is less than the count threshold value X (step S64: Yes), the focus position detector 32 focuses to ensure the movement of the imaging lens 2 for a predetermined time of several frames. The processing of the position detector 3 is in a standby state, and the position of the imaging lens 2 is intentionally advanced (step S65).

  After waiting for the predetermined number of frames, the in-focus position detector 32 transmits an imaging lens control signal via the IF control unit 4 so that the imaging lens 2 is positioned at the holding lens relative position. The drive of the imaging lens 2 is controlled (step S66). The lens relative position held at this time is a position where the imaging lens 2 does not reach the focal point because the focus flag is 0 and the reverse rotation flag is 1.

  Subsequently, the in-focus position detector 32 monitors a return signal (lens parameter) from the imaging lens 2 obtained via the IF control unit 4, and temporarily holds the imaging lens 2 at the held lens relative position. After stopping, the lens rotation direction flag set in step S22 (or S23) is reversed, the speed flag is set to 2 (Vc), and the reverse rotation flag is returned to 0. In this state, driving of the imaging lens 2 is resumed by an operation corresponding to the lens rotation direction flag and the speed flag, and the process returns to the start sequence of the AF feedback loop of “FB” shown in FIG. 5, and steps S4 and S5 in the next frame The process proceeds to (Step S67).

  The processes of steps S65 to S67 are performed in the AF feedback loop due to the overshoot phenomenon of the rotation of the imaging lens 2 that occurs because the imaging lens 2 is not instantaneously switched even after the reverse rotation (reverse movement) instruction is given. This is to prevent the reverse rotation flag from continuing to be 1 after this frame and immediately forcibly terminating. Only when entering this operation, the AF feedback loop may not be completed within one frame.

  When the focus flag is 0 and the reverse rotation flag is 0 (step S62: No), the focus position detector 32 determines whether or not the speed flag has changed from the previous value (one frame before) (step S62). S68).

  When the speed flag has not changed from the previous value (step S68: No), the focus position detector 32 returns to the start sequence of the AF feedback loop of “FB” shown in FIG. The process proceeds to steps S4 and S5.

  When the speed flag has changed from the previous value (step S68: Yes), the in-focus position detector 32 receives the imaging lens control signal via the IF control unit 4 so that the speed corresponds to the changed speed flag. And the drive of the imaging lens 2 is controlled (step S69).

  As described above, when AF is performed by the focus position detector 32 through the AF feedback loop of steps S4, S5, and S6 shown in FIG. 5, if the focus flag is 1, the process leaves the AF feedback loop. The imaging lens 2 can be moved to the held lens relative position corresponding to the peak contrast AF evaluation value CAF. If the in-focus flag is 0, the AF feedback loop is started in synchronization with the next video frame.

  Examples of AF operations performed by the focus position detector 32 of the first embodiment are shown in FIGS. 10 to 16 in association with FIG.

In FIG. 10, starting from the lens focus position A, the lens focus positions A to B at the speed Va, the lens focus positions B to C at the speed Vb, and the lens focus positions C to D at the speed Vc toward the telephoto side. Shows the state of driving. In this case, when the in-focus flag becomes 1 at the lens focus position D, the in-focus position detector 32 according to the first embodiment controls to return the imaging lens 2 to the in-focus point that is CAF _max .

FIG. 11 shows an example in which the driving direction of the imaging lens 2 is erroneous due to the first image plane phase difference AF evaluation value, and the moving direction of the imaging lens 2 (the rotational direction in which the imaging lens 2 rotates) is opposite to the focal point. is there. When the lens focus position E is set as the AF start point, the focus position detector 32 of the first embodiment determines that the reverse rotation flag becomes 1 at the time of the lens focus position F, and overshoots to the lens focus position G. Then, control is performed so that the position of the imaging lens 2 is returned to the lens focus position F. Thereafter, the focus position detector 32 according to the first embodiment moves the imaging lens 2 at the speed Vc from the lens focus position F to D, and the focus flag is set to 1 at the lens focus position D, and the focus is CAF _max. Control is performed to move the imaging lens 2 to the position.

FIG. 12 shows an example when the driving direction of the imaging lens 2 is erroneous due to the first image plane phase difference AF evaluation value and the imaging lens 2 has moved to the moving end. When the lens focus position B is set as the AF start point, the focus position detector 32 according to the first embodiment detects that the imaging lens 2 moves to the lens focus position H at the moving end at the speed Vb. Thus, the reverse rotation flag is set to 1, and the imaging lens 2 is controlled to move from the lens focus position H to D at the speed Vc. After that, as in FIG. 10, when the focus flag is set to 1 at the lens focus position D, the focus position detector 32 according to the first embodiment controls to return the imaging lens 2 to the focus at CAF _max .

  As described above, since the focus position detector 32 according to the first embodiment constantly monitors the contrast AF evaluation value while the imaging lens 2 is being driven, the AF based on the image plane phase difference AF evaluation value is erroneous. Even in such a case, AF correction can be performed immediately, and accurate AF can be performed relatively quickly even when the reliability of the image plane phase difference AF evaluation value is low. Further, since the in-focus position detector 32 according to the first embodiment does not require a front-and-back operation for in-focus position search, it is possible to prevent the lens wobbling phenomenon from occurring while reducing the time until in-focus, Excellent responsiveness and focus position detection accuracy can be realized.

(Example 2)
As described above with reference to FIGS. 10 to 12, the in-focus position detector 32 of the first embodiment described above is based on whether the driving direction of the imaging lens 2 is determined by the initial image plane phase difference AF evaluation value. The time to focus changes. As can be seen from FIG. 5, the setting sequence (step S2) of the driving direction / speed of the imaging lens 2 based on the image plane phase difference AF evaluation value is not in the AF feedback loop of steps S4, S5, and S6. It may take.

Therefore, the television camera configured as the imaging device 50 uses the fact that the pixel value is always acquired at a high speed of 60 fps, and the first imaging for starting AF as the in-focus position detector 32 of the second embodiment. Only the image plane phase difference AF evaluation value α ₀ for determining the driving direction of the lens 2 can be configured to average the values of the phase difference detection pixels 112 for several frames in order to improve the calculation accuracy. . For example, even if 10 frames are added and averaged, the calculation is completed within 1/6 second in time, and the S / N of the pixel value of each phase difference detection pixel 112 at this time is improved by √10 times. In general, the accuracy of the image plane phase difference AF by the phase difference detection pixel 112 is significantly reduced in a low luminance state. However, with this configuration, the accuracy in determining the first direction can be increased, and the focal point can be further increased. Responsiveness can be improved.

(Example 3)
In the in-focus position detector 32 of the first embodiment described above, in the monitoring process of the driving speed of the imaging lens 2 based on the image plane phase difference AF evaluation value (step S5), the image plane phase difference AF evaluation value α is set for each frame. The example in which the phase difference detection pixel 112 is referred to has been described. Here, since the image plane phase difference AF evaluation value α is only used for controlling the driving speed of the imaging lens 2, the exact accuracy of the value of the image plane phase difference AF evaluation value α is not important. There is no need to perform processing for each frame because the speed determination is not questioned about the speed.

  Therefore, in order to calculate the value of the image plane phase difference AF evaluation value α as the in-focus position detector 32 of the third embodiment, the value of the phase difference detection pixel 112 is set for several frames according to the driving speed of the imaging lens 2. , And calculating by averaging. In this case, of course, since the imaging lens 2 is moving even during the frame to be added, the accuracy of the image plane phase difference AF evaluation value is lost, but the pixel value of the phase difference detection pixel 112 is small (the luminance value is low). In this case, it is possible to reduce the frequency at which the evaluation value due to the specific pattern of the subject or the subject causes a significant error.

  Further, the in-focus position detector 32 according to the third embodiment may be configured to adjust the frame addition average number of the phase difference detection pixels 112 according to the driving speed of the imaging lens 2 to be different. For example, in FIG. 4, when the imaging lens 2 is driven at the speed Va, the addition average value of the phase difference detection pixels 112 of two frames with the immediately preceding frame is used, and when the imaging lens 2 is driven at the speed Vb, the immediately preceding frame, A mode in which the addition average value of the phase difference detection pixels 112 of three frames from the previous frame is used is assumed. The number of frames to be added may be arbitrarily set in view of the driving speed of the imaging lens 2 to be set.

  Moreover, it can also be set as the structure which combined the focus position detector 32 of Example 2 and Example 3. FIG.

  As described above, the focus position detector 32 of each embodiment according to the present invention takes advantage of the processing speed of the imaging device 50 (particularly, a television camera) and performs real-time image plane phase difference AF even while the imaging lens 2 is moving. As control in which the evaluation value and the contrast AF evaluation value are calculated in parallel (simultaneously), and the contrast AF evaluation value is constantly monitored while the imaging lens 2 is being driven, so that there is no need for a back-and-forth operation for in-focus position search. Therefore, it is possible to prevent the lens wobbling phenomenon from occurring while shortening the time to focus, and it is possible to realize excellent responsiveness and focus position detection accuracy.

  Further, since the focus position detector 32 of each embodiment according to the present invention is controlled so that the strictness of the image plane phase difference AF evaluation value is not required, the phase difference detection embedded in the pixel unit 11 of the image sensor 1 is performed. The number of the pixels 112 can be reduced as compared with the conventional technique, and thereby deterioration of image quality can be suppressed as compared with the conventional technique.

  Further, the in-focus position detector 32 of each embodiment according to the present invention detects the in-focus position of each embodiment according to the present invention even for the image pickup apparatus 50 that cannot control the focus value of the image pickup lens 2 with an absolute value. The above-described operation can be realized only by incorporating the device 32.

  Furthermore, since the focus position detector 32 of each embodiment according to the present invention is configured to stop the driving speed of the imaging lens 2 stepwise, the load on each mechanism in the imaging device 50 is reduced. be able to.

  The present invention has been described above with reference to specific embodiments. However, the present invention is not limited to the above-described examples, and various modifications can be made without departing from the technical concept thereof. Limited only by.

  According to the present invention, it is possible to realize excellent responsiveness and focus position detection accuracy with respect to AF, which is useful for an application of an imaging apparatus that requires an AF function.

DESCRIPTION OF SYMBOLS 1 Image sensor 2 Imaging lens 3 Digital signal processing control part 4 IF control part 5 Memory 6 Display part 7 Recording part 8 Operation part 11 Pixel part 31 Digital signal processing part 32 Focus position detector 33 Drive control part 50 Imaging device 51 Imaging Optical system 52 Signal processing system 53 Input / output system 111 Imaging pixel 112 Phase difference detection pixel (A pixel, B pixel)
113 Mask 114 Region of Interest for Contrast AF

Claims (9)

Imaging capable of adjusting the focal position using an imaging device in which a pixel group of two sets of phase difference detection pixels for detecting a phase difference between pixels is arranged in a pixel portion constituting a pixel group of imaging pixels. A focus position detector for detecting a focus position of a lens;
A first evaluation value for calculating a predetermined evaluation value for detecting a defocus amount as an image plane phase difference AF evaluation value based on a phase difference output obtained from a pixel group of a pair of phase difference detection pixels of the two pixels A calculation means;
A second evaluation value for calculating a predetermined evaluation value for detecting the maximum contrast at the in-focus position as a contrast AF evaluation value based on an image in a predetermined region of interest obtained from the pixel group of the imaging pixels A calculation means;
Based on the image plane phase difference AF evaluation value calculated at the start of detection of the in-focus position, initial setting means for initially setting the driving direction of the imaging lens and a changeable driving speed;
Lens driving control means for starting and controlling driving of the imaging lens in order to detect the in-focus position of the imaging lens from the initial setting;
Evaluation value monitoring means for monitoring the image plane phase difference AF evaluation value calculated during movement of the imaging lens for detecting the in-focus position and the contrast AF evaluation value in parallel;
Feedback control means for performing feedback control so as to detect the in-focus position based on the result of the evaluation value monitoring means;
An in-focus position detector.   The evaluation value monitoring means compares the contrast AF evaluation values obtained in units of a first predetermined time from the initial setting when monitoring the position and moving direction of the imaging lens with respect to the in-focus position based on the contrast AF evaluation values. Thus, a focusing flag indicating whether or not the imaging lens has passed the focusing position, and a reverse rotation flag indicating whether or not the driving direction of the imaging lens is the reverse direction, in the first predetermined time unit. By sequentially updating and setting, by comparing the contrast AF evaluation value obtained in the second predetermined time unit from the initial setting time when monitoring the drive speed of the imaging lens to be changeable by the image plane phase difference AF evaluation value, It is determined whether or not the position of the imaging lens is close to the in-focus position, and a speed flag that sets a lower speed as the position of the imaging lens is closer to the in-focus position is the second flag. Characterized in that it comprises means for sequentially updating set at a constant time unit, the focus position detector according to claim 1.   The feedback control unit is configured to control the lens driving control unit so that the imaging lens is positioned at a position when the imaging lens has passed the focusing position when the focusing flag indicates that the imaging lens has passed the focusing position. To complete the detection operation of the in-focus position, and while the in-focus flag does not indicate that the imaging lens has passed through the in-focus position, based on the reverse rotation flag The lens drive control means is instructed to drive the imaging lens so that the drive direction can be changed, and the lens drive control means is instructed to drive and control the drive speed of the imaging lens based on the speed flag. The in-focus position detector according to claim 2, wherein feedback control is performed.   The lens driving control means includes means for performing stepwise speed control to lower the speed as the position of the imaging lens is closer to the in-focus position in accordance with the speed flag. 4. A focus position detector according to 3.   The initial setting means includes a driving direction of the imaging lens based on the image plane phase difference AF evaluation value calculated in one frame of a moving image obtained from the pixel group of the imaging pixels at the start of detection of the in-focus position. The image plane phase difference AF calculated by averaging the variable drive speed obtained from the plurality of frames of the moving image obtained from the pixel group of the imaging pixel at the initial setting of the changeable driving speed or the detection of the in-focus position 5. The in-focus position detector according to claim 1, further comprising means for initially setting a driving direction of the imaging lens and a changeable driving speed based on an evaluation value. 6.   The evaluation value monitoring means includes means for setting the first predetermined time unit as a frame time unit of a moving image obtained from the pixel group of the imaging pixels, and calculating and monitoring the contrast AF evaluation value in the frame time unit. The in-focus position detector according to any one of claims 1 to 5, wherein   The evaluation value monitoring means calculates the contrast AF evaluation value in the frame time unit using the second predetermined time unit as a frame time unit of a moving image obtained from the pixel group of the imaging pixels, or the second predetermined time. A unit for calculating and monitoring the contrast AF evaluation value by an average of values obtained in units of a plurality of frame times, wherein a unit is a unit of a plurality of frame times of a moving image obtained from the pixel group of the imaging pixels. The in-focus position detector according to any one of claims 1 to 6.   The feedback control means manages a count value continuously indicating the reverse direction when the reverse rotation flag indicates that the drive direction of the imaging lens is the reverse direction, and the count value is predetermined. The in-focus position detector according to any one of claims 2 to 7, further comprising means for forcibly terminating the operation of detecting the in-focus position when the count threshold is exceeded. A focusing position detector according to any one of claims 1 to 8,
An image sensor in which a pixel group of two sets of phase difference detection pixels for detecting a phase difference between pixels is arranged in a pixel portion constituting the pixel group of the imaging pixels;
An imaging lens with adjustable focal position;
An imaging apparatus comprising: