JP2006301004A - Control unit and method therefor, program, and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve focusing capability by improving evaluation value peak detection sensitivity. <P>SOLUTION: A prediction value calculator 152 calculates a prediction value of a current evaluation value on the basis of a past evaluation value acquired by an evaluation value acquiring part 151 by using a least square method. A normalization difference value calculator 153 calculates a normalization difference value normalizing the difference value between a current evaluation value obtained by the evaluation value acquiring part 151 and the prediction value calculated by the prediction value calculator 152 by the current evaluation value. An evaluation peak determining part 154 detects the peak of the evaluation value by comparing the normalization difference value with a threshold holding a threshold holder 155. The unit and the method can be applied to an imaging apparatus such as a digital camera and a video camera. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device and method, a program, and a camera, and more particularly, to a control device and method, a program, and a camera that can improve evaluation value peak detection sensitivity and improve focusing ability.

  2. Description of the Related Art Conventionally, for example, in an imaging apparatus or the like, there is an autofocus (hereinafter referred to as AF (Auto Focus)) process that automatically performs a focus process for focusing a subject on a subject. This AF processing includes, for example, a method (image processing method) of detecting the contrast of a captured image and adjusting the lens position so that the contrast becomes the highest (see, for example, Patent Document 1).

  For example, the imaging apparatus calculates an evaluation value, which is a parameter for evaluating the degree of “blur” of an image, in a predetermined region (evaluation frame) of the captured image from the contrast of the image (for example, a high-frequency component of the luminance value). While the focus position is moved, the maximum value (peak value) of the evaluation value is searched, and the focus is focused on the position where the peak value is obtained. In this way, the captured image is focused on the subject imaged within the range (just pin).

  In the case of such an image processing type AF process, the accuracy generally depends largely on conditions such as a shooting environment and a subject (depending on the content of a captured image to be obtained). Therefore, various methods are considered to perform more accurate AF processing. For example, in order to efficiently search for the focus position, the lens is vibrated (wobbed) in a minute range, and the traveling direction of the focus lens is determined based on the evaluation value of the captured image (for example, see Patent Document 2). There is a method of changing the frame size of an evaluation frame that is a range in which an evaluation value is calculated according to conditions (see, for example, Patent Document 3) so that satisfactory AF processing can be performed under a wide range of shooting conditions.

  There are also methods of performing AF processing using a plurality of types of evaluation values and preparing a plurality of methods for detecting the maximum value (peak value) of evaluation values. For example, for a normal subject, the imaging device calculates a difference value of evaluation values between field images, detects a field (peak) having a maximum value based on the inclination, and detects a peak by this method. For subjects that cannot be performed, for example, subjects that are dark or have low contrast, the maximum and minimum ratios of the evaluation values are checked between multiple fields, and if the ratio is greater than or equal to a predetermined value, the maximum value is set. There is a method of detecting a field to be taken (or a field in the vicinity thereof) as a peak.

  In this peak detection method for a dark subject or a low-contrast subject, in order to identify the peak of the noise component and detect the peak of the accurate evaluation value, the magnitude of the evaluation value peak is Emax, When the upper limit of the evaluation value in the state (obviously not in focus), that is, the upper limit of the noise component level (noise level) is n_max and the lower limit is n_min, the following equations (1) and (2) It is necessary to satisfy both of the two conditional expressions.

Emax / n_min> β (1)
n_max / n_min ≦ β (2)
Where β is a constant

  Expression (1) is a conditional expression for detecting the peak of the evaluation value, and Expression (2) is a conditional expression for preventing an erroneous peak from being detected due to fluctuation due to noise.

  For example, when the evaluation value changes as shown by curve 1 in the graph shown in FIG. 1, Emax in equation (1) is point 4 and nmin is point 5. In addition, n_max in the equation (2) is a point 2 and n_min is a point 3.

  In recent years, as the technology has improved, the quality of images has been improved, and technologies related to HD (High Definition) images have begun to spread, and there are video cameras that support HD images. In the case of such an HD image, the number of pixels in one field image increases as compared with an SD (Standard Definition) image, so that the noise level increases and the S / N ratio decreases significantly.

  FIG. 2 is a diagram comparing the relationship between the evaluation value peak and the noise level between the SD image and the HD image.

  In the case of the SD image shown in FIG. 2A, the value (evaluation value A) at the noise level (before time T1 and after time T3) is sufficiently larger than the value (evaluation value B) at the evaluation value peak (time T2). small. On the other hand, as shown in FIG. 2B, in the case of an HD image, the value (evaluation value A ′) at the noise level (before time T1 and after time T3) is evaluated as compared with the case of an SD image. There is a possibility that the value (evaluation value B) at the value peak (time T2) becomes so large that it cannot be ignored.

International Publication WO 97/25812 JP-A-10-215403 Japanese Patent Laid-Open No. 10-161016

  However, as described above, in order to accurately detect the evaluation value peak, it is necessary to satisfy the conditions of the expressions (1) and (2). For example, the evaluation value of the point 2 is 1295, and the point 3 Assuming that the evaluation value of 1225, the evaluation value of point 4 is 1370, and the evaluation value of point 5 is 1280, the left side of equation (1) and the left side of equation (2) are as follows.

Emax / n_min = 1370/1280 = 1.07 (3)
n_max / n_min = 1295/1225 = 1.06 (4)

  That is, as shown in Expression (3) and Expression (4), there is almost no difference between the left side of Expression (1) and the left side of Expression (2), and the margin of β is very small. That is, it is difficult to satisfy the conditions of the expressions (1) and (2), and the focusing ability may be reduced.

  For example, as in the case of the HD image shown in FIG. 2B, when the noise level increases, the value of n_min with respect to Emax further increases, and the value β needs to be set smaller to satisfy Equation (1). It may become more difficult to satisfy the expression (2) (a margin for satisfying the expression (2) may be reduced).

  That is, in the case of an HD image, it is more difficult to detect an accurate evaluation value peak than in the case of an SD image, and the focusing ability may be further reduced.

The present invention has been made in view of such a situation, and is intended to improve the evaluation value peak detection sensitivity and improve the focusing ability.

  The control device of the present invention is a parameter for adjusting the focus position, and predicts the current evaluation value corresponding to the current field image of the evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. Based on the difference between the predicted value calculated by the predicted value calculating means and the predicted value calculated by the predicted value calculating means and the current evaluated value corresponding to the predicted value. Evaluation value peak determination means for determining whether or not there is provided.

  The predicted value calculation means can perform a least square method calculation using a plurality of past evaluation values corresponding to past field images, and calculate a predicted value from the obtained approximate straight line.

  The difference value is calculated, and the obtained difference value is normalized with a current evaluation value, thereby further comprising a normalized difference value calculation means for calculating a normalized difference value, and the evaluation value peak determination means includes a normalization Based on the normalized difference value calculated by the difference value calculation means, it can be determined whether or not the current evaluation value is the peak of the evaluation value.

  Threshold value holding means for holding a predetermined threshold value determined in advance is further provided, and the evaluation value peak determination means includes the normalized difference value calculated by the normalized difference value calculation means as a threshold value held in the threshold value holding means. It is possible to compare and determine whether or not the current evaluation value is the peak of the evaluation value based on the comparison result.

  The evaluation value peak determination means can determine that the current evaluation value is the peak of the evaluation value when the normalized difference value is larger than the threshold value.

  The image processing apparatus may further include evaluation value calculation means for calculating an evaluation value for each field image of the captured image from an image signal corresponding to the captured image of the subject.

  Evaluation value holding means for temporarily holding the evaluation value calculated by the evaluation value calculation means is further provided, and the predicted value calculation means uses the plurality of evaluation values held by the evaluation value holding means to calculate the predicted value. It can be calculated.

  When the evaluation value peak determination unit determines that the current evaluation value is the peak of the evaluation value, the evaluation value peak determination unit may further include a focusing operation instruction unit that instructs a focusing operation to focus the focus on the peak. it can.

  The control method of the present invention is a parameter for adjusting the focus position, and predicts the current evaluation value corresponding to the current field image of the evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. , Based on the predicted value calculation step for calculating the predicted value, and the difference value between the predicted value calculated by the processing of the predicted value calculation step and the current evaluated value corresponding to the predicted value, If the current evaluation value is determined to be the peak of the evaluation value by the evaluation value peak determination step for determining whether or not it is a peak and the processing of the evaluation value peak determination step, the focus is adjusted to the peak. A focusing step.

  The program of the present invention is a parameter for adjusting the focus position, and predicts the current evaluation value corresponding to the current field image of the evaluation value for evaluating the degree of blur of the captured image of the subject for each field image, Based on a prediction value calculation step for calculating a prediction value, and a difference value between the prediction value calculated by the processing of the prediction value calculation step and the current evaluation value corresponding to the prediction value, the current evaluation value is a peak of the evaluation value. When the current evaluation value is determined to be the peak of the evaluation value by the processing of the evaluation value peak determination step and the evaluation value peak determination step for determining whether or not the focus is the peak of the evaluation value, the focus is focused on the peak And a step.

  The camera of the present invention is a parameter for adjusting the focus position, and predicts the current evaluation value corresponding to the current field image of the evaluation value for evaluating the degree of blur of the captured image of the subject for each field image, The current evaluation value is the peak of the evaluation value based on the prediction value calculation means for calculating the prediction value and the difference value between the prediction value calculated by the prediction value calculation means and the current evaluation value corresponding to the prediction value. When the evaluation value peak determination unit and the evaluation value peak determination unit determine that the current evaluation value is the peak of the evaluation value, the driving unit adjusts the focus to the peak. Focusing operation instruction means for instructing a focusing operation is provided.

  In the control device and method, the program, and the camera of the present invention, the parameter for adjusting the focus position corresponds to the current field image of the evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. The current evaluation value is predicted, the prediction value is calculated, and the current evaluation value is the peak of the evaluation value based on the difference value between the calculated prediction value and the current evaluation value corresponding to the prediction value It is determined whether or not.

  According to the present invention, the imaging apparatus can perform more appropriate focus processing so that a stable captured image can be obtained.

  Embodiments of the present invention will be described below. The correspondence relationship between the invention described in this specification and the embodiments of the invention is exemplified as follows. This description is intended to assure that embodiments supporting the claimed invention are described in this specification. Therefore, although there is an embodiment which is described in the embodiment of the invention but is not described here as corresponding to the invention, it means that the embodiment is not It does not mean that it does not correspond to the invention. Conversely, even if an embodiment is described herein as corresponding to an invention, that means that the embodiment does not correspond to an invention other than the invention. Absent.

  Further, this description does not mean all the inventions described in this specification. In other words, this description is an invention described in the present specification and is not claimed in this application, that is, an invention that will be filed in the future or added by amendment. Is not to deny.

  In the present invention, a drive unit (e.g., adjusting the focus position when imaging an object by driving an optical element (e.g., the focus lens or wobbling lens in Fig. 3) of an imaging device (e.g., the imaging device in Fig. 3)). , A control device (for example, the AF control unit in FIG. 3) that performs processing related to the control of the AF drive unit in FIG. 3 is provided. In this control device, a parameter for adjusting the focus position, an evaluation value for evaluating the degree of blur of the captured image of the subject for each field image is predicted, and a current evaluation value corresponding to the current field image is predicted. Based on a difference value between a predicted value calculating unit (for example, a predicted value calculating unit in FIG. 4) that calculates a value and a current evaluation value corresponding to the predicted value calculated by the predicted value calculating unit and the predicted value. Evaluation value peak determination means for determining whether or not the evaluation value is a peak of the evaluation value (for example, an evaluation value peak determination unit in FIG. 4).

  Normalized difference value calculating means for calculating a normalized difference value by calculating the difference value and normalizing the obtained difference value with a current evaluation value (for example, a normalized difference value calculating unit in FIG. 4) The evaluation value peak determining means may determine whether or not the current evaluation value is a peak of the evaluation value based on the normalized difference value calculated by the normalized difference value calculating means. it can.

  A threshold value holding unit (for example, a threshold value holding unit in FIG. 4) that holds a predetermined threshold value that is set in advance is further provided, and the evaluation value peak determination unit calculates the normalized difference value calculated by the normalized difference value calculation unit, It can be compared with the threshold value held in the threshold value holding means, and based on the comparison result, it can be determined whether or not the current evaluation value is the peak of the evaluation value.

  An evaluation value calculation unit (for example, an evaluation value calculation unit in FIG. 3) that calculates an evaluation value for each field image of the captured image from an image signal corresponding to the captured image of the subject can be further provided.

  Evaluation value holding means (for example, the evaluation value holding unit in FIG. 3) that temporarily holds the evaluation value calculated by the evaluation value calculation means is further provided, and the predicted value calculation means is held by the evaluation value holding means. The predicted value can be calculated using a plurality of evaluation values.

  When the evaluation value peak determination means determines that the current evaluation value is the peak of the evaluation value, a focus operation instruction means for instructing a focus operation to focus the focus on the peak (for example, the focus in FIG. 3). An operation instructing unit).

  In the present invention, a drive unit (e.g., adjusting the focus position when imaging an object by driving an optical element (e.g., the focus lens or wobbling lens in Fig. 3) of an imaging device (e.g., the imaging device in Fig. 3)). , A control method of a control device (for example, the AF control unit in FIG. 3) that executes processing related to control of the AF drive unit in FIG. 3 is provided. In this control method, it is a parameter for adjusting the focus position, the evaluation value for evaluating the degree of blur of the captured image of the subject for each field image, the current evaluation value corresponding to the current field image is predicted, Based on the difference value between the prediction value calculation step (for example, step S22 in FIG. 9) for calculating the prediction value and the current evaluation value corresponding to the prediction value calculated by the processing of the prediction value calculation step, The evaluation value peak determination step (for example, step S24 in FIG. 9) for determining whether or not the current evaluation value is the peak of the evaluation value, and the processing of the evaluation value peak determination step, the current evaluation value becomes the evaluation value. If it is determined to be a peak, a focusing step (for example, step S6 in FIG. 8) for focusing the focus on the peak is included.

  Also in the program of the present invention, the embodiment (however, an example) corresponding to each step is the same as the control method of the present invention.

  In the present invention, when an imaging unit (for example, the CCD in FIG. 3) that images a subject and an optical element (for example, the focus lens or wobbling lens in FIG. 3) are driven, the imaging unit captures the subject. A camera (for example, the imaging apparatus of FIG. 3) having a drive unit (for example, the AF drive unit of FIG. 3) for adjusting the focus position is provided. In this camera, it is a parameter for adjusting the focus position, and an evaluation value for evaluating the degree of blur of the captured image of the subject for each field image is predicted for the current evaluation value corresponding to the current field image. Based on a difference value between a predicted value calculating unit (for example, a predicted value calculating unit in FIG. 4) that calculates a value and a current evaluation value corresponding to the predicted value calculated by the predicted value calculating unit and the predicted value. An evaluation value peak determination unit (for example, the evaluation value peak determination unit in FIG. 4) for determining whether or not the evaluation value is an evaluation value peak, and the evaluation value peak determination unit sets the current evaluation value to the peak of the evaluation value When it is determined that the focus is in focus, the drive unit is provided with a focus operation instructing unit (for example, a focus operation instruction unit in FIG. 3) for instructing a focus operation to focus on the peak.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a diagram illustrating a configuration example according to an embodiment of an imaging apparatus to which the present invention is applied.

  In FIG. 3, an imaging device 50 has an AF (Auto Focus) driving unit 51, an image processing unit 52, and an AF control unit 53, and is a device that captures an image of a subject and obtains image data of a moving image or a still image. is there. The imaging device 50 records the obtained image data on a recording medium or outputs it to the outside. In FIG. 3, only the portion related to the present invention is shown in the configuration of the imaging device 50.

  The AF drive unit 51 includes a focus lens 61, a wobbling lens 62, a lens drive unit 63, a drive control unit 64, a sensor 65, and a switch (SW) 66, and based on the control of the AF control unit 53, optical The system is driven to perform a focus position adjustment process for light taken into the image processing unit 52.

  The focus lens 61 is driven in the optical axis direction of the light incident on the image processing unit 52, and controls the focus position of the light (the focus position of the obtained captured image). The wobbling lens 62 slightly vibrates (wobbles) in the optical axis direction of the light incident on the image processing unit 52, and slightly shifts the focus position of the captured image. The wobbling lens 62 is used to determine the moving direction of the focus lens 61 during the focus adjustment process (focus process). The focus lens 61 and the wobbling lens 62 may be realized by a set of lenses (the wobbling operation is performed using the focus lens 61 as the wobbling lens 62).

  The lens driving unit 63 controls the focus position by controlling the position and operation of the focus lens 61 and the wobbling lens 62 based on the control information supplied from the drive control unit 64 (operation for controlling the focus position). To do). As will be described later, the drive control unit 64 is connected to the AF control processing unit 82 of the AF control unit 53 through a serial bus. Control information such as a focus control command and a wobbling control command supplied from the AF control processing unit 82 is included in the drive control unit 64. Based on this, control information relating to driving of the focus lens 61 and the wobbling lens 62 is supplied to the lens driving unit 63. For example, the drive control unit 64 supplies control information to the lens driving unit 63 to instruct the lens driving unit 63 to move the position of the focus lens 61 or to start a wobbling operation of the wobbling lens 62.

  Further, the drive control unit 64 supplies information relating to the iris value and focus position supplied from the sensor 65 to the AF control processing unit 82 via the serial bus. Further, the operation of the drive control unit 64 is controlled according to the state of the switch (SW) 66. For example, the drive control unit 64 performs the above-described control processing and communication processing only when the switch 66 is in an on state, and when the switch 66 is in an off state, the drive control unit 64 enters a sleep state and does not execute each processing.

  The sensor 65 is a sensor that measures a focus position, a zoom position (focal length), an iris value, and the like, and supplies the measured information to the AF control processing unit 82 via the drive control unit 64. The switch (SW) 66 is a switch for the user to control whether or not to perform AF processing, and notifies the drive control unit 64 of the state.

  The image processing unit 52 is a processing unit that generates an image signal of an electrical signal from light incident on the imaging device 50, and includes a CCD (Charge Coupled Devices) 71, an amplification unit 72, and a signal processing unit 73. .

  The CCD 71 is an image pickup device using a CCD having a photoelectric conversion element such as a photodiode. When the incident light incident through the focus lens 61 and the wobbling lens 62 is photoelectrically converted, a charge corresponding to the incident light amount is accumulated. The image signal of the electric signal is obtained by discharging it. The CCD 71 supplies the image signal to the amplification unit 72. Note that an image sensor using CMOS (Complementary Metal Oxide Semiconductor) or the like may be used instead of the CCD 71.

  The amplifying unit 72 includes a CDS circuit (Correlated Double Sampling circuit), an AGC circuit (Automatic Gain Control circuit), an A / D (Analog / Digital) conversion circuit, and the like, and removes reset noise of the image signal supplied from the CCD 71. Or amplifying the image signal or converting the analog image signal into a digital signal, and then supplying the digital image signal to the signal processing unit 73.

  The signal processing unit 73 performs AE (Auto Exposure) processing, AWB (Auto White Balance) processing, image processing such as γ correction, and the like on the supplied image signal, and then outputs the image signal to the subsequent stage. At the same time, it is supplied to the evaluation value calculation unit 81 of the AF control unit 53. In addition, the signal processing unit 73 supplies a control synchronization signal such as a horizontal synchronization signal and a vertical synchronization signal of the image signal and a system clock signal to the evaluation value calculation unit 81.

  The AF control unit 53 controls the AF driving unit 51 based on the image signal supplied from the image processing unit 52 and performs processing related to control of AF processing. The AF control unit 53 includes an evaluation value calculation unit 81 and an AF control processing unit 82.

  The evaluation value calculation unit 81 is based on the image signal and synchronization signal supplied from the signal processing unit 73 of the image processing unit 52, the setting data supplied via the AF control processing unit 82, and the like. ) Is evaluated for each field image (a frame image in the case of the progressive method). The evaluation value calculation unit 81 supplies the calculated evaluation value to the AF control processing unit 82. In the following, only the case where the captured image (captured image) is the interlace method will be described. However, this description can be applied to the progressive method only by replacing the field unit with the frame unit.

  The AF control processing unit 82 predicts the next evaluation value from the past evaluation values supplied from the evaluation value calculation unit 81, and the evaluation value actually supplied from the evaluation value calculation unit 81. The peak of the evaluation value is detected by monitoring the difference. Although details will be described later, the AF control processing unit 82 detects that the difference exceeds the threshold value (becomes unpredictable) as a peak because the gradient of the change in the evaluation value is reversed from positive to negative at the peak time. . Then, the AF control processing unit 82 controls the drive control unit 64 via the serial bus based on the peak detection. Further, the AF control processing unit 82 acquires sensor information such as a focus position and an iris value from the drive control unit 64 via the serial bus, and generates setting data for evaluation value calculation based on the sensor information. The setting data is supplied to the evaluation value calculation unit 81.

  The AF control processing unit 82 includes an evaluation value holding unit 91, an evaluation value peak searching unit 92, a focusing operation instruction unit 93, and a search operation instruction unit 94.

  The evaluation value holding unit 91 temporarily holds the evaluation value for each field supplied from the evaluation value calculation unit 81. The evaluation value holding unit 91 has a storage area that can hold evaluation values for a predetermined number of fields (for example, M fields, M is a natural number), and the maximum evaluation values for M fields from the latest field ( The latest M evaluation values) are held. Then, the evaluation value holding unit 91 supplies the latest N (N is a natural number, N ≦ M) to the evaluation value peak searching unit 92 from the held evaluation values as necessary. Note that the value of N (that is, the number of evaluation values supplied from the evaluation value holding unit 91 to the evaluation value peak searching unit 92 at a time) may be the same each time or may be different each time. .

  The evaluation value peak search unit 92 uses the evaluation value supplied from the evaluation value holding unit 91 to search for the peak of the evaluation value (the field that takes the maximum value, its focus position, or its evaluation value). When the evaluation value peak search unit 92 acquires N evaluation values from the evaluation value holding unit 91, the evaluation value peak search unit 92 performs a least-squares calculation using the past evaluation values, and predicts the next evaluation value. Then, the evaluation value peak search unit 92 obtains a difference value between the predicted value and the latest evaluation value, and detects the point as a peak if the difference value is equal to or greater than a threshold value. Details will be described later.

  When the search for the peak of the evaluation value is performed as described above, the evaluation value peak search unit 92 supplies the search result to the focusing operation instruction unit 93. When a peak is detected, the focusing operation instruction unit 93 supplies an instruction to the operation control unit 64 so as to focus the peak. When the peak is not detected, the focusing operation instruction unit 93 supplies the fact to the search operation instruction unit 94.

  When the peak of the evaluation value is not detected, the search operation instruction unit 94 controls the drive control unit 64 to supply an instruction to shift the focus position, etc., and performs an operation necessary for searching for the peak in the focus lens 61 or wobbling. Let the lens 62 perform this.

  The AF control unit 53 further includes a bus 100, a ROM (Read Only Memory) 101, an input unit 102, an output unit 103, a storage unit 104, a communication unit 105, and a drive 106. A bus 100 is connected to the AF control processing unit 82, and the ROM 101 to the drive 106 are connected via the bus 100.

  The ROM 101 has a read-only storage medium, and programs and data to be executed in the AF control processing unit 82 are stored in advance. Programs and data stored in the ROM 101 are read by the AF control processing unit 82 via the bus 100 as necessary. The input unit 102 includes an input device such as a switch or a button. For example, the input unit 102 receives instruction information input by a user and supplies the information to the AF control processing unit 82 via the bus 100. The output unit 103 includes a display unit including an LED (Light Emitting Diode) display, an LCD (Liquid Crystal Display), or an organic EL (Electro Luminescence) display, an audio output unit including a speaker, and the like. Information supplied from the processing unit 82 via the bus 100 is displayed or output.

  The storage unit 104 includes a hard disk, a semiconductor memory, and the like, and stores programs and data executed by the AF control processing unit 82 and stores data supplied from the AF control processing unit 82. The communication unit 105 is, for example, a modem, a LAN (Local Area Network) adapter, a USB (Universal Serial Bus) interface, an IEEE (Institute of Electrical and Electronic Engineers) 1394 interface, a SCSI (Small Computer System Interface), or an IEEE 802.11x adapter. Etc., perform interface processing based on a predetermined communication standard, communicate with other devices via a network, for example, receive information from other devices and supply it to the AF control processing unit 82 Or the information from the AF control processing unit 82 is transmitted to another device.

  The drive 106 is a read / write processing unit to which a removable medium 107 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is appropriately attached. For example, the drive 106 reads a program and data from the mounted removable medium 107 and installs it in the storage unit 104 or supplies it to the AF control processing unit 82 as necessary. Further, the drive 106 records, for example, the program and data acquired from the AF control processing unit 82 via the bus 100 on the attached removable medium 107.

  When the processing executed by the AF control processing unit 82 is executed by software, a program constituting the software is installed from a network or a recording medium.

  This recording medium is, for example, a magnetic disk (including a flexible disk) on which a program is recorded, an optical disk (CD-ROM (Compact Disk-Read), which is distributed to distribute the program to the user separately from the apparatus main body. The apparatus is not only constituted by a removable medium 107 made up of only memory), DVD (including digital versatile disk), magneto-optical disk (including MD (Mini-Disk) (registered trademark)), or semiconductor memory. It is composed of a ROM 101 on which a program is recorded and a hard disk and a semiconductor memory included in the storage unit 104, which are distributed to the user in a state of being incorporated in the main body in advance.

  Next, the operation will be described.

  When shooting is started, the CCD 71 of the image processing unit 52 photoelectrically converts light incident through the focus lens 61 and the wobbling lens 62 of the AF driving unit 51 along the optical axis as indicated by the dotted arrow 111, Obtain image information (image signal) of the electrical signal. Then, the CCD 71 supplies the image signal to the amplifying unit 72 as indicated by an arrow 112. When the amplification unit 72 amplifies the image signal by a predetermined method, the amplification unit 72 supplies the amplified image signal to the signal processing unit 73 as indicated by an arrow 113. The signal processing unit 73 performs image processing on the supplied image signal, and then outputs the processed image signal to a subsequent stage (not shown) as indicated by an arrow 114A and also performs AF control as indicated by an arrow 114B. This is supplied to the evaluation value calculation unit 81 of the unit 53. Further, the signal processing unit 73 supplies the synchronization signal to the evaluation value calculation unit 81 as indicated by the arrow 115.

  The evaluation value calculation unit 81 “blurs” of the captured image corresponding to the image signal supplied from the signal processing unit 73 based on the setting data supplied from the AF control processing unit 82 as indicated by the arrow 117. An evaluation value for evaluating the condition is calculated by a predetermined calculation method. For example, the evaluation value is a value indicating the magnitude of contrast in a part of the image area (in the evaluation frame) of the frame image, and is calculated based on the total value of the high frequency components of the luminance values in the evaluation frame. The When the evaluation value calculation unit 81 calculates such an evaluation value for each field, the evaluation value calculation unit 81 supplies the evaluation value to the evaluation value holding unit 91 of the AF control processing unit 82 as indicated by an arrow 118.

  The evaluation value holding unit 91 temporarily holds the evaluation value supplied for each field from the evaluation value calculation unit 81 as indicated by an arrow 118. Then, the held evaluation value is supplied to the evaluation value peak searching unit 92 as necessary as indicated by an arrow 119.

  The evaluation value peak search unit 92 predicts the latest (current) evaluation value based on the past evaluation value supplied as indicated by the arrow 119 by using the least square method calculation. Then, the evaluation value peak search unit 92 performs peak detection using a difference value between the predicted value and the actual evaluation value, and the peak search result is input to the focusing operation instruction unit 93 as indicated by an arrow 120. Supply. When the peak is detected, the focusing operation instruction unit 93 supplies control information for focusing the focus position to the peak to the drive control unit 64 via the serial bus as indicated by an arrow 121. When no peak is detected, the focusing operation instruction unit 93 supplies the fact to the search operation instruction unit 94 as indicated by an arrow 122.

  The search operation instruction unit 94 controls the drive control unit 64 via the serial bus as shown by the arrow 123 to drive the optical system such as the focus lens 61 and the wobbling lens 62 to detect a peak. For example, the focus position is moved.

  As described above, when controlled by the focusing operation instruction unit 93 or the search operation instruction unit 94 of the AF control processing unit 82 (arrow 121 or arrow 123), the drive control unit 64 is indicated by an arrow 127 based on the control. The lens driving unit 63 is controlled so that the focus lens 61 and the wobbling lens 62 are driven. However, the drive control unit 64 performs such processing only when it is notified that the switch 66 is in the ON state as indicated by the arrow 126. For example, when the switch 66 is in the OFF state, the drive control unit 64 enters a pause state and does not accept control of the AF control processing unit 82 (the focusing operation instruction unit 93 and the search operation instruction unit 94).

  Further, when the drive control unit 64 acquires sensor information such as a focus position, a zoom position (focal length), and an iris value from the sensor 65 as indicated by an arrow 125, it is obtained as indicated by an arrow 116. It is supplied to the AF control processing unit 82 via the serial bus. The AF control processing unit 82 generates setting data for evaluation value calculation from the sensor information, and supplies it to the evaluation value calculation unit 81 as indicated by an arrow 117.

  In the imaging apparatus 50, the AF process is controlled in this way.

  FIG. 4 is a block diagram illustrating a detailed configuration example of the evaluation value peak search unit 92 of FIG.

  In FIG. 4, the evaluation value peak search unit 92 includes an evaluation value acquisition unit 151, a predicted value calculation unit 152, a normalized difference value calculation unit 153, an evaluation value peak determination unit 154, a threshold value holding unit 155, and a flag update unit 156. have.

  The evaluation value acquisition unit 151 acquires, for example, N evaluation values held in the evaluation value holding unit 91 in order from the newest one in the field period, and obtains them as a predicted value calculation unit 152 and a normalized difference value calculation unit 153. To supply. The predicted value calculation unit 152 performs a least square method calculation using the past evaluation values supplied from the evaluation value calculation unit 152, and predicts the current (latest) evaluation value.

  For example, as in the graph shown in FIG. 5, assuming that ten evaluation values 161 to 170 are supplied as evaluation values in the past from the evaluation value acquisition unit 151, the predicted value calculation unit 152 uses these evaluation values. The following method of least squares is used to obtain an approximate line 171.

y = C1 × x + C0 (5)
C1 = {(average of xy) − (average of x) × (average of y)} / {(average of x ² ) − (average of x) × (average of x)} (6)
C0 = (average of y) −C1 × (average of x) (7)

  And the predicted value calculation part 152 calculates the predicted value y (point on the straight line 171) of the newest evaluation value based on Formula (5). The predicted value calculation unit 152 supplies the predicted value y to the normalized difference value calculation unit 153.

  The normalized difference value calculation unit 153 is a difference value between the current (latest) evaluation value supplied from the evaluation value acquisition unit 151 and the prediction value y of the current evaluation value supplied from the prediction value calculation unit 152. (Predicted value−current evaluation value) is calculated, and the difference value is normalized with the current evaluation value, that is, the normalized difference value S as represented by the following equation (8). Is calculated.

  S = (predicted value−current evaluation value) / current evaluation value (8)

  As shown in Expression (8), by normalizing the difference value with the current evaluation value, the evaluation value peak determination unit 154 sets the difference value in each field to the same threshold value regardless of the luminance of the subject. Can be compared under the same conditions (as a ratio to the current evaluation value). Then, the normalized difference value calculation unit 153 supplies the normalized difference value S to the evaluation value peak determination unit 154. When the evaluation value peak determination unit 154 obtains a predetermined threshold value Th previously stored in the threshold value holding unit 155 from the threshold value holding unit 155, the evaluation value peak determination unit 154 determines the magnitude of the threshold value Th and the normal difference value S. A comparison is made to determine whether or not an evaluation value peak has been detected.

  For example, the evaluation value and the predicted value vary as in the graph shown in FIG. In the graph of FIG. 6, a curve 181 indicates the transition of the actual evaluation value, and the dotted line curve 191 indicates the transition of the predicted value. The curve 181 in the graph of FIG. 6 corresponds to the curve 1 of FIG. As shown in the graph of FIG. 6, at the peak position of the evaluation value (portion 201), the actual evaluation value shifts from increase to decrease (slope shifts from positive to negative), and the value also fluctuates greatly. . Since the predicted value calculation unit 152 predicts the current evaluation value from the past evaluation values (calculates the predicted value), it cannot predict such fluctuation. Therefore, the normalized difference value S corresponding to the difference value between the predicted value and the current evaluation value calculated by the normalized difference value calculation unit 153 varies as a curve 211 shown in the graph of FIG. That is, the curve 211 in FIG. 7 indicates the difference value between the curve 191 and the curve 181 in FIG. 6, and the portion 212 of the curve 211 corresponds to the portion 201 in FIG. 6. Thus, since it is difficult to predict the peak portion, the value of the normalized difference value becomes large (fluctuates greatly).

  The evaluation value peak determination unit 154 detects such a fluctuation portion (a portion 212 in the case of FIG. 7) having a large normalized difference value using a predetermined threshold, and detects that portion as a peak. When the peak is detected (when the normalized difference value exceeds the threshold value), the evaluation value peak determination unit 154 supplies the determination result to the flag update unit 156. The flag update unit 156 sets an evaluation value peak detection flag indicating that an evaluation value peak has been detected, and supplies the flag information to the focusing operation instruction unit 93. When no peak is detected, the evaluation value peak determination unit 154 supplies the determination result to the focusing operation instruction unit 93 without causing the flag update unit 156 to update the evaluation value peak detection flag.

  The focusing operation instructing unit 93 determines whether or not an evaluation value peak is detected based on whether or not the evaluation value peak detection flag is set. If an evaluation value peak is detected, the peak position is determined. The drive control unit 64 is instructed to focus on.

  As described above, the evaluation value peak search unit 92 calculates the predicted value of the current evaluation value from the past evaluation value using the least square method, calculates the normalized difference value using the predicted value, A peak is detected by comparing the normalized difference value with a threshold value. By detecting the peak in this way, the evaluation value peak searching unit 92 greatly increases the focusing ability for a subject having a poor condition for calculating an evaluation value, such as a dark subject or a low-contrast subject. Can be improved. That is, the evaluation value peak searching unit 92 can perform a higher sensitivity evaluation value peak search by using the above-described evaluation value peak searching method. That is, the imaging device 50 can improve the evaluation value peak detection sensitivity and improve the focusing ability.

  Next, the flow of each process described above will be described. First, an example of the flow of focus processing executed by the AF control unit 53 will be described with reference to the flowchart of FIG.

  In step S1, the search operation instruction unit 94 of the AF control processing unit 82 controls the drive control unit 64 via the serial bus and causes each unit to execute a search operation. When an image signal (field image or frame image) is supplied from the signal processing unit 73 by the search operation, the evaluation value calculation unit 81 of the AF control unit 53 calculates an evaluation value from the image signal in step S2. In step 3, the evaluation value holding unit 91 holds the calculated evaluation value. In step S4, the evaluation value peak searching unit 92 performs an evaluation value peak searching process using the least square method. Details of the evaluation value peak search process will be described later with reference to the flowchart of FIG.

  In step S5, the focusing operation instruction unit 93 refers to the search result in step S4 to determine whether or not the evaluation value peak detection flag is set. The evaluation value peak detection flag is set and the peak of the evaluation value is detected. When it determines with having carried out, a process is advanced to step S6, control information is supplied with respect to the drive control part 64, and a focus is focused on a peak position. When the process of step S6 is completed, the focusing operation instruction unit 93 ends the focus process.

  If it is determined in step S5 that the evaluation value peak detection flag is not set and the evaluation value peak is not detected, the focusing operation instruction unit 93 advances the processing to step S7 and ends the focus processing. If it is determined whether or not to end, the end process is performed in step S8, and then the focus process is ended. If it is determined in step S7 that the focus process is not to be ended, the focusing operation instruction unit 93 returns the process to step S1, and causes the search operation instruction unit 94 to execute a search operation, and so on, and thereafter repeats the subsequent processes. .

  Next, the detailed flow of the evaluation value peak search process executed in step S4 of FIG. 8 will be described with reference to the flowchart of FIG.

  In step S21, the evaluation value acquisition unit 151 acquires N evaluation values from the evaluation value holding unit 91 from the newer one. In step S <b> 22, the predicted value calculation unit 152 performs a least square method calculation using past evaluation values among the evaluation values, and calculates a predicted value of the current evaluation value. In step S23, the normalized difference value calculation unit 153 calculates a normalized difference value from the current evaluation value and its predicted value. In step S24, the evaluation value peak determination unit 154 acquires a threshold value from the threshold value holding unit 155, compares it with a normalized difference value, and determines whether or not an evaluation value peak is detected from the comparison result. When it determines with having detected, the flag update part 156 sets an evaluation value peak detection flag in step S25, complete | finishes an evaluation value peak search process, returns a process to step S4 of FIG. 8, and performs the process after step S5 Let

  If it is determined in step S24 that the evaluation value peak has not been detected, the evaluation value peak determination unit 154 omits the process in step S25, ends the evaluation value peak search process, and performs the process in step S4 in FIG. Returning to step S5, the processing after step S5 is executed.

  As each unit performs each process in this manner, the AF control unit 53 greatly improves the focusing ability for a subject having a bad condition for calculating an evaluation value, such as a dark subject or a low-contrast subject. Can be improved. That is, the AF control unit 53 can perform the evaluation value peak search with higher sensitivity by using the evaluation value peak search method described above. That is, the imaging device 50 can improve the evaluation value peak detection sensitivity and improve the focusing ability.

  In the above description, the evaluation value acquisition unit 151 of the evaluation value peak search unit 92 has been described as acquiring N evaluation values in order from the newest, but the evaluation value acquisition unit 151 acquires at least the current evaluation value. The past evaluation values to be acquired other than that may not be in order from the new one.

  In the above description, the prediction value calculation unit 152 in FIG. 4 has been described as calculating the prediction value of the current evaluation value using the least squares method calculation. However, the current evaluation value can be predicted with a predetermined accuracy or higher. If so, the prediction value may be calculated by performing prediction using any method.

  The series of processes described above can be executed by hardware or can be executed by software. When the above-described series of processing is executed by software, a program constituting the software is installed from a network or a recording medium.

  For example, as described above, this recording medium is configured not only by the removable medium 107 distributed to distribute the program to the user, but also by being installed in the apparatus main body in advance. Are composed of a ROM 101 in which a program is recorded and a hard disk included in the storage unit 104.

  In the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in chronological order according to the described order, but is not necessarily performed in chronological order. It also includes processes that are executed individually.

  Further, in this specification, the configuration described as one device may be divided and configured as a plurality of devices. Conversely, the configurations described above as a plurality of devices may be combined into a single device. Of course, configurations other than those described above may be added. Further, if the configuration and operation of the entire apparatus are substantially the same, a part of the configuration of a certain part may be included in the configuration of the other part.

It is a figure explaining the fluctuation | variation of the evaluation value in a peak search. It is a figure explaining the difference in the noise level of the evaluation value by an image. It is a figure which shows the structural example which concerns on one Embodiment of the imaging device to which this invention is applied. It is a block diagram which shows the detailed structural example of the evaluation value peak search part of FIG. It is a figure explaining the least squares method calculation. It is a figure explaining the fluctuation | variation of the evaluation value in the peak search, and its prediction value. It is a figure explaining the fluctuation | variation of the normalization difference value corresponding to the graph of FIG. It is a flowchart explaining the example of the flow of a focus process. It is a flowchart explaining the example of the detailed flow of an evaluation value peak search process.

Explanation of symbols

  50 imaging device, 51 AF drive unit, 52 image processing unit, 53 AF control unit, 61 focus lens, 62 wobbling lens, 63 lens drive unit, 64 drive control unit, 73 signal processing unit, 81 evaluation value calculation unit, 82 AF Control processing unit, 91 evaluation value holding unit, 92 evaluation value peak searching unit, 93 focusing operation instruction unit, 94 search operation instruction unit, 151 evaluation value acquisition unit, 152 predicted value calculation unit, 153 normalized difference value calculation unit, 154 evaluation value peak determination unit, 155 threshold holding unit, 156 flag update unit

Claims (11)

In a control device that executes processing related to control of a drive unit that adjusts a focus position when driving an optical element of an imaging device to image a subject,
It is a parameter for adjusting the focus position, and a prediction value is calculated by predicting a current evaluation value corresponding to the current field image of an evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. Predicted value calculation means for
Whether or not the current evaluation value is a peak of the evaluation value is determined based on a difference value between the prediction value calculated by the prediction value calculation means and the current evaluation value corresponding to the prediction value. An evaluation value peak determination means for performing control. The predicted value calculation means performs a least square method calculation using a plurality of past evaluation values corresponding to past field images, and calculates the predicted value from the obtained approximate straight line. The control device described in 1. Further comprising a normalized difference value calculating means for calculating a difference value, and normalizing the obtained difference value with the current evaluation value to calculate a normalized difference value,
The evaluation value peak determination means determines whether or not the current evaluation value is a peak of the evaluation value based on the normalized difference value calculated by the normalized difference value calculation means. The control device according to claim 2. Further comprising a threshold value holding means for holding a predetermined threshold value,
The evaluation value peak determination means compares the normalized difference value calculated by the normalized difference value calculation means with the threshold value held in the threshold value holding means, and based on the comparison result, the current value It is determined whether an evaluation value is the peak of the said evaluation value. The control apparatus of Claim 3 characterized by the above-mentioned. The control device according to claim 4, wherein the evaluation value peak determination unit determines that the current evaluation value is a peak of the evaluation value when the normalized difference value is larger than the threshold value. The control apparatus according to claim 1, further comprising: an evaluation value calculation unit that calculates the evaluation value for each field image of the captured image from an image signal corresponding to the captured image of the subject. An evaluation value holding means for temporarily holding the evaluation value calculated by the evaluation value calculating means;
The control device according to claim 6, wherein the predicted value calculating unit calculates the predicted value using a plurality of the evaluation values held by the evaluation value holding unit. When the evaluation value peak determination unit determines that the current evaluation value is the peak of the evaluation value, the evaluation value peak determination unit further includes a focusing operation instruction unit that instructs a focusing operation to focus a focus on the peak. The control device according to claim 1, wherein A control method for a control device that executes processing related to control of a drive unit that adjusts a focus position when driving an optical element of an imaging device to image a subject,
It is a parameter for adjusting the focus position, and a prediction value is calculated by predicting a current evaluation value corresponding to the current field image of an evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. A predicted value calculating step,
Whether or not the current evaluation value is a peak of the evaluation value based on a difference value between the prediction value calculated by the processing of the prediction value calculation step and the current evaluation value corresponding to the prediction value An evaluation value peak determination step for determining
A control method comprising: a focusing step of focusing a focus on the peak when the current evaluation value is determined to be a peak of the evaluation value by the processing of the evaluation value peak determination step. . A program that causes a computer to perform processing related to control of a drive unit that adjusts a focus position when an optical element of an imaging device is driven to image a subject,
It is a parameter for adjusting the focus position, and a prediction value is calculated by predicting a current evaluation value corresponding to the current field image of an evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. A predicted value calculating step,
Whether or not the current evaluation value is a peak of the evaluation value based on a difference value between the prediction value calculated by the processing of the prediction value calculation step and the current evaluation value corresponding to the prediction value An evaluation value peak determination step for determining
And a focusing step of focusing a focus on the peak when the current evaluation value is determined to be a peak of the evaluation value by the processing of the evaluation value peak determination step. In a camera having an imaging unit that images a subject, and a drive unit that drives an optical element and adjusts a focus position when imaging the subject by the imaging unit.
It is a parameter for adjusting the focus position, and a prediction value is calculated by predicting a current evaluation value corresponding to the current field image of an evaluation value for evaluating the degree of blur of the captured image of the subject for each field image. Predicted value calculation means for
Whether or not the current evaluation value is a peak of the evaluation value is determined based on a difference value between the prediction value calculated by the prediction value calculation means and the current evaluation value corresponding to the prediction value. Evaluation value peak determination means to perform,
When the evaluation value peak determination means determines that the current evaluation value is the peak of the evaluation value, a focusing operation that instructs the driving unit to perform a focusing operation to focus the peak. And a camera.

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