JP2009021929A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus and imaging method in which focusing is performed utilizing contrast of an image and accurate focusing can be performed even when a subject or the imaging apparatus moves. <P>SOLUTION: An imaging apparatus according to the present invention comprises a motion detection unit 41 which includes a horizontal contrast component detecting section 421 and a vertical contrast component detecting section 422 for detecting contrast components in horizontal and vertical directions and which detects a motion that is generated in a subject or in the imaging apparatus, from a video signal; a weight coefficient control section 424 for setting a weight coefficient to be integrated to the contrast components in the horizontal direction and the vertical direction on the basis of a detection result of the motion detection unit 41; and a focusing evaluation value calculating section 423 for obtaining a region evaluation value by summing up the contrast components to which the weight coefficient is integrated, and for obtaining a focusing evaluation value by summing up or averaging the region evaluation value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device whose imaging is controlled based on a video signal, and an imaging method thereof.

  In an imaging device typified by a digital still camera capable of creating still image data and a digital video camera capable of creating moving image data and still image data including audio data, an image sensor is used. There is a case where a TTL (Through The Lends) focusing control method is used in which focusing is performed by detecting the contrast of an image formed and adjusting the focal length of the lens.

  In this focus control method, a partial region of the image frame is set as a focus evaluation region, a high frequency component in the focus evaluation region is extracted, and an integrated value of the extracted high frequency component is focused evaluation. Calculate as a value. Further, since the focus evaluation value is approximately proportional to the contrast in the focus evaluation area, the optimum focus is obtained when the contrast becomes maximum and the image becomes the most clear, that is, when the focus evaluation value becomes maximum. The distance is assumed to be selected.

  However, the subject or the imaging device is not always stationary and may be moving. When the subject or the imaging apparatus moves, the captured image extends along the moving direction, and the focus evaluation value may be inaccurate. For example, when the subject or the imaging device is moving in the horizontal direction, the obtained image is blurred in the horizontal direction, so that the contrast in the horizontal direction of the focus evaluation area becomes poor, and the subject or the imaging device is Compared with the case where it is stationary, accurate focusing cannot be performed.

In particular, since the conventional imaging device uses only the contrast in the horizontal direction to obtain the focus evaluation value, it is difficult to focus accurately when the subject or the imaging device moves in the horizontal direction. It was. In view of this problem, an image pickup apparatus that provides a sensor for measuring the amount of movement of the subject in the horizontal direction and the vertical direction and predicts the movement of the subject based on a signal obtained from the sensor and focuses the subject is proposed. (See Patent Document 1).
Japanese Patent Laid-Open No. 11-295587

  However, in the method in the above-mentioned Patent Document 1, it is necessary to install two sensors for detecting the amount of movement, and there is a problem that the imaging apparatus becomes large. In addition, since focusing cannot be performed using a focus evaluation value based on the contrast of an image actually formed on the image sensor, focusing based on uncertain prediction is performed.

  In view of such a problem, the present invention performs focusing using the contrast of an image, and enables accurate focusing even when the subject or the imaging apparatus moves. The purpose is to provide.

  In order to achieve the above object, an imaging apparatus according to the present invention detects an image of a subject or an imaging apparatus from an imaging unit that performs imaging and outputs a video signal, and a video signal output from the imaging unit. A motion detection unit that outputs a motion signal, a high-frequency component detection unit that detects a horizontal high-frequency component and a vertical high-frequency component of the video signal, and outputs the horizontal high-frequency component and the vertical high-frequency component from the motion detection unit A focus evaluation value calculation unit that calculates a focus evaluation value by adding and summing horizontal weighting factors and vertical weighting factors based on the motion signal, and the imaging device based on the focus evaluation value And a focusing control unit that performs focusing control.

  In the imaging apparatus having the above-described configuration, the magnitude relationship between the horizontal component and the vertical component of the motion signal and the magnitude relationship between the horizontal weighting factor and the vertical weighting factor may be reversed. Furthermore, the ratio of the vertical component to the horizontal component of the motion signal may be equal to the ratio of the horizontal weighting factor to the vertical weighting factor.

  In the imaging apparatus having the above-described configuration, the high-frequency component detection unit detects the horizontal high-frequency component and the vertical high-frequency component for each of a plurality of predetermined regions of the video signal, and the focusing evaluation value calculation unit The horizontal weighting factor and the vertical weighting factor are added to the horizontal high-frequency component and the vertical high-frequency component obtained from each of the regions and added to obtain a region evaluation value corresponding to each of the regions, and the region evaluation The focus evaluation value may be obtained by adding or averaging the values.

  In the imaging apparatus having the above-described configuration, the focus evaluation value calculation unit sets the horizontal weighting factor and the vertical weighting factor for each region, and each of the horizontal high-frequency component and the vertical high-frequency component of the region is set. The region evaluation value may be obtained by summing and summing to the same, and the horizontal weighting factor and the vertical weighting factor that are equal for all the regions are set, and the horizontal high-frequency component and the vertical of the region are set. The region evaluation value may be obtained by adding up and summing up each of the high frequency components.

  In the imaging apparatus having the above-described configuration, the lens included in the imaging apparatus may be moved to a position where the focus evaluation value is maximized.

  In the imaging device having the above-described configuration, the motion detection unit may output the motion signal when the motion detection unit detects that the motion of the subject or the imaging device is in the same direction for a predetermined period. .

  In the imaging apparatus having the above configuration, when the motion signal is not output from the motion detection unit, the focus evaluation value calculation unit may obtain the focus evaluation value based only on the horizontal high-frequency component. Alternatively, the in-focus evaluation value may be obtained by adding the horizontal weighting coefficient to the horizontal high-frequency component.

  The imaging method according to the present invention includes a first step of imaging and outputting a video signal, and a motion signal is generated by detecting a motion generated in the subject or the imaging device from the video signal output in the first step. A second step, a third step of detecting a horizontal high-frequency component and a vertical high-frequency component of the video signal, and each of the horizontal high-frequency component and the vertical high-frequency component obtained in the third step, A fourth step of calculating a focus evaluation value by adding and summing a horizontal weighting factor and a vertical weighting factor based on the motion signal created by the second step, and based on the focus evaluation value, And a fifth step of performing focusing control of the image pickup apparatus.

  According to the present invention, when performing focus control, the horizontal weighting factor and the vertical weighting factor are added to the horizontal high-frequency component and the vertical high-frequency component, respectively. Even when the apparatus moves and the high-frequency component in the horizontal direction becomes defective, the focus control value can be determined by determining the focus evaluation value based on the high-frequency component in the vertical direction. Therefore, the focus control can be performed with high precision regardless of the direction of the subject or the image pickup apparatus.

<Configuration of imaging device>
First, an example of an outline of a configuration of an imaging apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of the imaging apparatus. Here, a digital video camera capable of creating moving image data and still image data will be described as an imaging apparatus. However, only a still image data such as a digital still camera may be created. I do not care.

  An imaging apparatus 1 shown in FIG. 1 includes an imaging unit 2 that performs imaging and outputs an analog video signal, an AFE (Analog Front End) unit 3 that amplifies and digitizes an analog video signal obtained by the imaging unit 2, and The video signal processing unit 4 that performs various processes such as blurring and gradation processing on the digital video signal output from the AFE unit 3 and outputs it as a video signal including luminance information and color difference information; An audio input unit 5 that outputs an analog audio signal, an audio signal processing unit 6 that digitizes an analog audio signal output from the audio input unit 5, and a video signal and an audio signal output from the video signal processing unit 4 A compression processing unit 7 that compresses the audio signal output from the processing unit 6, a decompression processing unit 8 that decompresses the compressed video signal and audio signal, and a decompressed video signal. In order to output to a display device (not shown) such as a liquid crystal display, for example, a video signal output unit 9 that performs processing such as analogization, and to output a decompressed audio signal to a speaker (not shown), for example. And an audio signal output unit 10 that performs processing such as analogization.

  Furthermore, the imaging apparatus 1 operates the entire imaging apparatus 1 according to a user instruction input to the operation unit 11 and an operation unit 11 to which a user instruction such as start and stop of moving image recording and still image shooting is input. The CPU 12 that controls the overall operation of the imaging apparatus 1, the SDRAM and 13 that temporarily holds the video signal and the audio signal, the memory card 14 that stores the compressed video signal and the audio signal, and each part of the imaging apparatus 1 (For example, a timing control signal that outputs a timing control signal for controlling the timing of each operation in the imaging unit 2, the video signal processing unit 4, the audio signal processing unit 6, the compression processing unit 7, the expansion processing unit 8, and the CPU 12) An output unit 15 (hereinafter referred to as a TG unit) is provided. Also provided are buses 16 and 17 through which signals for controlling each part of the imaging apparatus 1 and video and audio signals pass.

  The video signal processing unit 4 also includes a motion detection unit 41 that detects the movement of the subject or the imaging apparatus 1 from the input video signal, and a focus evaluation unit 42 that calculates a focus evaluation value for performing focus control. And comprising.

  The memory card 14 may be anything as long as it can store video signals and audio signals. For example, a semiconductor memory, an optical disk, a magnetic disk, or the like can be used as the memory card 14.

  Further, the configuration of the imaging unit 2 shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the imaging unit. As shown in FIG. 2, the imaging unit 2 includes an optical system 22 including a zoom lens 22a, a focus lens 22b, and a correction lens 22c, an imaging element 24, a diaphragm 23 that adjusts the amount of light incident on the imaging element 24, and a zoom. And a driver 21 that drives the lens 22a, the focus lens 22b, and the correction lens and adjusts the opening of the diaphragm 23. In the drawing, the optical axis of the optical system 22 is indicated by a one-dot chain line.

  The image sensor 24 is composed of, for example, a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like, and converts a signal of light incident on the image sensor 24 during an exposure time into an electric signal and holds it. And sequentially output to the subsequent AFE unit 3 in synchronization with the timing control signal input from the TG unit 15.

<Operation of imaging device>
Next, the operation of the imaging apparatus, in particular, the moving image recording operation will be described with reference to FIGS. The recording operation is started when a recording start instruction is input from the user to the operation unit 11 in FIG. 1, and the CPU 12 controls the imaging apparatus 1 to record video and audio.

  At this time, the imaging unit 2 shown in FIG. 2 operates, and an image formed on the imaging element 24 that is incident on the optical system 22 and passes through the various lenses 22a to 22c and the diaphragm 23 is held as an electrical signal. The driver 21 moves the zoom lens 22 a and the focus lens 22 b on the optical axis, focuses an image with a desired magnification, and forms an image on the image sensor 24.

  Furthermore, the driver 21 forms a good image on the image sensor 24 by driving the correction lens 22c in a direction that cancels the shake generated in the image pickup apparatus 1. Further, the diaphragm 23 is controlled so that the amount of light of the image formed on the image sensor 24 is appropriate. Note that the direction, size, and amount of blur may be detected when the video signal is processed by the motion detection unit 42 of the video signal processing unit 4 shown in FIG. It is also possible to detect blur using

  In addition, in synchronization with the timing control signal input from the TG unit 15, the electrical signal held in the image sensor 24 at a predetermined frame period (for example, 1/60 second) is sequentially supplied to the AFE unit 3 as an analog video signal. Is output. Then, the AFE unit 3 converts the input electric signal to create a digital video signal. Then, as shown in FIG. 1, the video signal output from the AFE unit 3 is input to the video signal processing unit 4 and subjected to various processes. At this time, from the input video signal, the motion detection unit 41 detects the movement of the imaging device 1 or the subject, or the focus evaluation unit 42 calculates a focus evaluation value for focusing. Further, the SDRAM 13 operates as a frame memory and temporarily holds a video signal when the video signal processing unit 4 performs processing. Details of the configuration and operation of the focus evaluation unit 42 of the video signal processing unit 4 will be described later.

  Similarly to the video signal described above, the audio signal converted into an electrical signal in the audio input unit 5 is input to the audio signal processing unit 6 and digitized. The video signal output from the video signal processing unit 4 and the audio signal output from the audio signal processing unit 6 are both input to the compression processing unit 7 and compressed by the compression processing unit 7 using a predetermined compression method. The At this time, the video signal and the audio signal are temporally associated with each other, and are configured so that the video and the sound are not shifted during reproduction. The compressed video signal and audio signal are output to the memory card 14 and recorded.

  The compressed video and audio signals recorded on the memory card 14 are read by the expansion processing unit 8 when the user inputs a predetermined instruction to the operation unit 11. The decompression processing unit 8 decompresses the compressed video signal and audio signal, and outputs the video signal to the video signal output unit 9 and the audio signal to the audio signal output unit 10, respectively, so that it can be reproduced on the display device or the speaker. It is converted and output.

  The display device and the speaker may be integrated with the imaging device 1 or may be separate and connected to the imaging device 1 using a cord or the like.

  Simultaneously with the compression processing in the compression processing unit 7, a video signal is output from the video signal processing unit 4 and output to the video signal output unit 9 via the bus 16. In this way, by outputting a video signal to the video signal output unit 9, a so-called preview may be performed in which the user can confirm what the recorded video is. The same applies to the audio signal, and the audio signal may be input from the audio signal processing unit 6 to the audio signal output unit 10 via the bus 16.

  In the above-described operation example, the recording operation for creating moving image data has been described. However, the same operation is performed even when creating still image data. At this time, in order to perform motion detection and focus control of the subject or the imaging apparatus 1, it is possible to capture several frames before an instruction to create still image data is issued automatically or by a user instruction.

<Configuration of focus evaluation unit>
Next, the configuration of the focus evaluation unit 42 included in the video signal processing unit 4 illustrated in FIG. 1 will be described with reference to FIG. FIG. 3 is a block diagram illustrating the configuration of the focus evaluation unit. As shown in FIG. 3, the focus evaluation unit 42 includes a horizontal contrast component detection unit 421 that calculates a horizontal contrast component C _H [i, j] that is a high-frequency component in the horizontal direction of the input video signal, and a vertical direction. Vertical contrast component detector 422 that detects a vertical contrast component C _V [i, j], which is a high-frequency component, and a horizontal weight for the horizontal contrast component C _H [i, j] and the vertical contrast component C _V [i, j]. A focus evaluation value calculation unit 423 that calculates and calculates a focus evaluation value by adding and summing the coefficient K _H [i, j] and the vertical weight coefficient K _V [i, j], and a horizontal weight coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] based on the detection result of the motion detection unit 41, and a weighting coefficient control unit 424.

  Furthermore, the configuration of the horizontal contrast component detection unit 421 and the vertical contrast component detection unit 422 shown in FIG. 3 will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of each of the two contrast component detection units in the horizontal direction and the vertical direction shown in FIG.

As shown in FIG. 4, the horizontal contrast component detection unit 421 includes an extraction unit 421a that extracts luminance information from the video signal in the measurement region, and a high-frequency component that is equal to or higher than a predetermined frequency with respect to the luminance information output from the extraction unit 421a. HPF (High Pass Filter) 421b that passes through the HPF, and an integration unit 421c that calculates the horizontal contrast component C _H [i, j] by integrating or averaging high-frequency components that have passed through the HPF. Similarly, the vertical contrast component detection unit 422 includes an extraction unit 422a, an HPF 422b, and an integration unit 422c.

<Operation of focus evaluation unit>
In addition to FIG. 3 and FIG. 4 described above, the operation of the focus evaluation unit 42 will be described with reference to FIG. FIG. 5 is a schematic diagram showing a video signal for one frame.

  First, as shown in FIG. 3, the input video signal is input to the motion detection unit 41 and the focus evaluation unit 42 and processed. At this time, the video signal for one frame input to the motion detection unit 41 and the focus evaluation unit 42 is divided for each region for convenience of processing, and various processes are performed for each region.

  The video signal for one frame input to the focus evaluation unit 42 will be described with reference to FIG. As shown in FIG. 5A, the video signal 100 for one frame is divided into areas AR [1, 1] to AR [M, N], and the focus evaluation value is calculated in units of the areas. Done. In particular, in the horizontal contrast component detection unit 421 and the vertical contrast component detection unit 422, the middle region 101 (for example, 8 × 8 as shown in FIG. 5B) located at the center of the screen as shown in FIG. 5B. For example, the horizontal contrast component and the vertical contrast component are extracted. Note that pixel scanning itself may be performed on all pixels regardless of the region, and scanning along the horizontal direction and scanning along the vertical direction may be performed simultaneously.

First, in each of the horizontal contrast component detection unit 421 and the vertical contrast component detection unit 422, the luminance information of each region in the middle region 101 shown in FIG. 5B is extracted by the extraction units 421a and 421b in FIG. For example, when obtaining the horizontal contrast component C _H [s, t] in the AR [s, t] region in FIG. 5B, first, the horizontal luminance change in the AR [s, t] region is extracted. After being obtained from 421a, high-frequency components are extracted by passing through HPF 421b. Then, the horizontal frequency component C _H [s, t] in the AR [s, t] region is obtained by integrating or averaging the extracted high-frequency components in the integration unit 421c.

The vertical direction is also calculated in the same way, and the vertical contrast component C _V [s, t] is also obtained in the same way. 3, the horizontal weighting coefficient K _H [s, t] is added to the horizontal contrast component C _H [s, t] as shown in the following equation (I), The area evaluation value α [s, t] in the area AR [s, t] is obtained by adding the vertical weighting coefficient K _V [s, t] to the vertical contrast component C _V [s, t] and adding up. . Note that the values of the horizontal weighting coefficient K _H [s, t] and the vertical weighting coefficient K _V [s, t] vary depending on the output result of the motion detection unit 41, but the horizontal weighting coefficient K _H [s, t]. The calculation method of the vertical weighting coefficient K _V [s, t] will be described later.

α [s, t] = K _H [s, t] × C _H [s, t] + K _V [s, t] × C _V [s, t] (I)

  When the area evaluation values of the respective areas in the middle area 101 are obtained, the in-focus evaluation value calculation unit 423 adds all these area evaluation values α [s, t] to α [s + 7, t + 7] or Averaging is performed to obtain a focus evaluation value. Then, using the focus evaluation value, focus control as described later is performed.

<Operation of motion detector>
The motion detection unit 41 detects whether or not a motion has occurred in the subject or the imaging device from the input video signal. When the motion is detected, the horizontal weight coefficient K _H [i, j] and the vertical weight described above are detected. The coefficient K _V [i, j] is changed. A method for detecting this movement will be described with reference to FIG. 6 while taking as an example the case where the image pickup apparatus moves and the image is stretched.

  FIG. 6 is a schematic diagram illustrating a motion vector obtained from a difference between a video signal input to the motion detection unit and successive frames of the video signal. In FIG. 6, 16 regions of 4 × 4 are schematically illustrated. However, this is an example, and any position and number of regions may be selected, but the focus evaluation value was calculated. The same area as the area may be used. FIG. 6 shows a case where the imaging device moves in the horizontal direction, and shows a case where the image extends in the horizontal direction.

  FIG. 6A shows the video signal of the first frame, (b) shows the video signal of the second frame, (c) shows the video signal of the third frame, and (d) shows the video signal of the fourth frame. (E) shows the motion vector obtained from the difference between the first and second frames, (f) shows the difference between the second and third frames, and (g) shows the third and fourth frames. The motion vectors obtained from the difference from the frame are shown. Note that the differences in (e) to (g) are obtained for each region, and various matching methods such as a block matching method and a representative point matching method can be used.

  Also, in FIGS. 6E to 6G, the case indicated by the white arrow indicates that the reliability does not exceed a predetermined value, and the black arrow indicates that the reliability is a predetermined value. The thing beyond is shown. Judgment as to whether or not the reliability exceeds a predetermined value is made in the above matching process, and if it is difficult to detect a motion vector, such as when feature points for comparison are scarce or hardly move, reliability is determined. Becomes lower.

  Further, in order to distinguish from small movements such as camera shake, a comprehensive determination over a plurality of frames (for example, 4 frames) is performed. For example, it may be determined that the imaging apparatus has moved when motion vectors in substantially the same direction are detected in all of the plurality of frames. Furthermore, when motion vectors with reliability greater than a predetermined value are averaged, a condition that the average motion vector does not determine that the motion has not been determined to be greater than a predetermined value, or a predetermined motion vector is determined. The motion may vary depending on various conditions, such as the condition that the area where the motion vector in the size of the range is detected is a predetermined ratio or more, and the condition that the motion vector of each area is almost equal to half or more. It may be determined whether or not there has been. If the motion is detected under the above conditions, it is possible to more accurately detect the motion when the imaging apparatus moves and the entire image extends in a certain direction.

  Even in the case where the subject moves or the imaging device follows the movement of the subject, even when the entire image does not stretch uniformly but partially stretches, the above-mentioned area is determined within the region where the presence or absence of movement is determined. If such a motion vector is detected, it can be recognized that there is motion.

  Further, in all cases between a plurality of frames, when it is detected that there is a group with high reliability and motion vectors of a plurality of adjacent regions that are substantially equal, it is estimated that a part of the image is moving and there is motion. It is also possible to detect this. Also, the number of frames at this time may be small.

  Further, the respective motion detection methods described above may be switched according to an imaging mode such as a stationary object imaging mode or a moving object imaging mode. Alternatively, these motion detection methods may be performed simultaneously, and when motion is detected by any one of the detection methods, it may be detected that there has been motion.

Also, FIG. 7 is used to explain the calculation method of the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] and the focus evaluation value obtained by this when motion is detected. I will explain. FIG. 7A is a graph showing an example of a motion vector, and FIGS. 7B to 7D are positions of the focus lens and focus evaluation when the subject or the imaging apparatus moves as shown in FIG. It is the graph shown about the relationship with a value. 7B is a graph obtained by adding or averaging only the horizontal contrast components, FIG. 7C is a graph obtained by adding or averaging only the vertical contrast components, and FIG. is a graph obtained by summing and integrating the horizontal weighting factor K _H [i, j] and the vertical weighting factor K _V [i, j] in the vertical contrast component.

As shown in FIG. 7A, the motion vector can be represented by two components (horizontal component b _H and vertical component b _V ). In particular, in the example shown in FIGS. 6E to 6G, since the horizontal component b _H is mainly large, the image extends in the horizontal direction to form an image like a so-called horizontal stripe. Therefore, the contrast in the horizontal direction is deteriorated because the image is stretched, and only the horizontal contrast components are summed or averaged (the vertical weighting coefficient K _V [s, t] = 0 in the equation (I) is set as the region evaluation value). And the region evaluation values α [s, t] to α [s + 7, t + 7] are summed or averaged), and as shown in FIG. It becomes a graph.

On the other hand, in the vertical direction, even if the image extends in the horizontal direction, the influence on the contrast is much less than in the horizontal direction. Therefore, only the vertical contrast components are summed or averaged (the region evaluation value is calculated with the horizontal weighting coefficient K _H [s, t] = 0 in equation (I), and the region evaluation values α [s, t] to α [ s + 7, t + 7] are added or averaged), and in this case, a graph as shown in FIG. 7C can be clearly confirmed.

From the above, although the direction is substantially parallel to the detected motion vector (horizontal direction in FIG. 7), the image is elongated, resulting in poor contrast, but in the direction substantially perpendicular to the motion vector (vertical direction in FIG. 7) The contrast is good because it is not greatly affected. Therefore, when the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] are set so as to be an inverse ratio of the horizontal component b _H and the vertical component b _V of the detected motion vector, As shown in FIG. 7D, the focus control can be performed by applying a weight to the horizontal contrast component C _H [i, j] or the vertical contrast component C _V [i, j] in a direction with good contrast. . If the relationship between the motion vector components b _H and b _V and the weighting coefficients K _H [i, j] and K _V [i, j] are expressed as equations, for example, as shown in the following equation (II): Become.

b _H : b _V = K _V [i, j]: K _H [i, j] (II)

By calculating the focus evaluation value as described above, even when the subject or the imaging device moves in either the horizontal direction or the vertical direction, the contrast in the direction in which the contrast is more clearly confirmed based on the movement. Since the focus evaluation value can be obtained by applying a weight to the components C _H [i, j] and C _V [i, j], accurate focusing can be performed. Furthermore, since it is not necessary to newly install a device such as a sensor in the imaging apparatus, the imaging apparatus can be reduced in size, simplified, and reduced in weight.

It is not always necessary to use the relational expression as shown in the above formula (II), the magnitude relationship between the motion vectors b _H and b _V in the horizontal direction and the vertical direction, and the weighting coefficients K _H [i, j], K _V Any relational expression may be used as long as the magnitude relation in [i, j] is reversed.

When one of the motion vector components b _H and b _V is smaller than a predetermined value, or when one of the motion vector components b _H and b _V is very small, the smaller one of the motion vectors The focus evaluation value may be calculated by ignoring the contrast components C _H [i, j] and C _V [i, j] in a direction substantially perpendicular to the other component and using only the other component. .

If the motion detection unit 41 does not detect the motion of the subject or the imaging device, focusing may be performed using only the horizontal contrast component C _H [i, j]. That is, unless the motion detection unit 41 detects a motion and notifies the weighting factor control unit 424, the vertical weighting factor K _V [i, j] in all regions is set to 0 and the horizontal weighting factor K _H in all regions is set. The calculation may be performed with [i, j] set to a predetermined value, or the calculation of the focus evaluation value in the vertical direction may not be performed.

In the above-described method, the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] are values for each region. However, the same value may be used for all regions. . That is, in the case shown in the above formula (I), K _H [s, t] = K _H [s + 1, t] =... = K _H [s + 7, t + 7], K _V [s, t] = K _V [ s + 1, t] =... = K _V [s + 7, t + 7]. Further, at this time, the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] may be determined based on the average value of the motion vectors in the highly reliable region. By using this method, focusing can be performed with high accuracy, particularly when the image pickup apparatus moves and the entire image extends uniformly.

Further, the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] of the detected motion vector are used for the high reliability area, and the motion is applied to the low reliability area. The horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] may be used in the case where the signal is not detected. When this method is used, when a partial area of the image is stretched, the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j] based on the stretching of the stretched area are used. Will be calculated. For other regions, the growth of a part of the image is not reflected. Therefore, focusing can be performed with high precision, particularly when a part of the image is stretched, such as when the subject moves or when the imaging apparatus is moved following the movement of the subject.

Further, the setting method of these weighting factors K _H [i, j] and K _V [i, j] may be switched depending on the imaging mode. Further, the state of the motion vector when detecting the motion is, for example, a weight coefficient K _H [i, j], K _V [i, j] depending on whether a uniform motion vector is detected in the entire region. The setting method may be determined.

<Example of focus control method>
Next, an example of the focus control method will be described with reference to FIGS. FIG. 8 is a flowchart showing an example of the focus control method, and FIG. 9 is a graph showing the relationship between the focus lens position and the focus evaluation value similar to FIG. 7, and FIG. It is the same as the graph shown.

As shown in FIG. 8, when the focus control operation is started, first, as described above, the horizontal contrast component C _H [i, j] and the vertical contrast component C _V [i, j] in each region are obtained. (STEP 1). Next, it is confirmed whether or not the motion detection unit 41 shown in FIG. 3 has detected the motion of the subject or the imaging device (STEP 2). The operation of the motion detection unit 41 in STEP 2 is as described above, and the motion vectors of the respective regions are confirmed over a plurality of frames, and these are combined to determine whether motion has occurred.

In STEP2, when the motion detection unit 41 detects the motion of the subject or the imaging device (STEP2, YES), the horizontal contrast component C _H [i, j] and the vertical contrast component C _V are expressed as in the above equation (I). The area evaluation value α [i, j] is calculated by adding and adding the horizontal weighting coefficient K _H [i, j] and the vertical K _V [i, j] to [i, j]. Then, the area evaluation values α [i, j] of the respective areas are added or averaged to obtain a focus evaluation value (STEP 4). Here, as a method for determining the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V [i, j], the method shown in the above equation (II) can be used.

On the other hand, when the motion detection unit 41 does not detect the motion of the subject or the imaging device in STEP 2 (STEP 2, NO), a large contrast does not occur in the subject or the imaging device, and thus sufficient contrast for performing focus control. And the focus evaluation value is calculated based only on the horizontal contrast component C _H [i, j] (STEP 5).

  When the focus evaluation value is obtained in STEP 4 or STEP 5, next, focus control is performed using the obtained focus evaluation value. First, it is determined whether or not the focus operation is the first time, that is, whether or not the focus lens has been moved even once during the focus control operation (STEP 6). Here, the focus operation is performed. If is the first time, the focus lens is moved in a predetermined direction (STEP 8). This predetermined direction is a preset direction. In the first time, the focus lens is assumed to move in that direction regardless of the result.

  Then, after moving the focus lens in STEP 7, the next frame is captured in order to obtain a focus evaluation value in the state after the movement (STEP 9). Then, returning to STEP 1, the contrast component is extracted, the motion is detected, and the focus evaluation value is calculated again (STEP 1 to 5).

  In STEP 6, it is determined whether or not the focusing operation has already been performed once, but since the focusing operation has been performed once this time, the process proceeds to NO in STEP 6. Then, it is determined whether or not the focus evaluation value obtained for the second time has decreased compared to the first time (STEP 7).

  At this time, if the focus evaluation value has decreased compared to the first time (STEP 7, YES), it is determined whether or not the focus operation is the second time (STEP 10). If the focus operation is the second time (STEP 10, YES), it indicates that the direction of the focus lens moved in STEP 7 in the first focus operation is a direction to lower the focus evaluation value. The focus lens is moved to the start position (STEP 11).

  The operation of moving to the start position in STEP 11 will be specifically described with reference to FIG. Here, in order to perform the operation of STEP11, it is premised that the focus lens is moved from L1 which is the start position in the first focusing operation to L2 where the focus evaluation value decreases. Then, in STEP7 and STEP10, it is confirmed that the first movement from L1 to L2 lowers the focus evaluation value, so in STEP11 the position of the focus lens is shifted from L2 to L1, which is the start position. Moved.

  On the other hand, if the focus evaluation value has increased in the second focusing operation (STEP 7, NO), there is still room for the focus evaluation value to increase due to movement, so the same direction as the direction moved last time (first time) Control to move the focus lens. In FIG. 9, this corresponds to the case where the focus lens is moved from L1 to L3 in the first STEP8.

  However, after confirming the increase in focus evaluation value in STEP 7, if it is confirmed that the movable range of the focus lens is limited and cannot be moved (STEP 12, NO), the position of the focus lens is changed. Focus control is terminated as the focus position. On the other hand, if it is movable (STEP 12, YES), the focus lens is moved in the same direction as the previous time (first time) (STEP 13), and the next frame is captured (STEP 9). In FIG. 9, this corresponds to the case of moving from L3 to L4 for the second time.

  Then, after fetching the next frame in STEP9, the process returns to STEP1, and again extraction of contrast components, detection of motion, and calculation of focus evaluation values are performed (STEPs 1 to 5). The operation after the third time is the same as the second time. If it is confirmed in STEP 7 that the focus evaluation value has increased, STEPs 12 and 13 are performed as in the second time. In FIG. 9, this corresponds to the case of moving from L4 to L5 for the third time.

  Note that the focus evaluation value decreases because the process proceeds from L1 to L2 in FIG. 9 in the first time and returns to the position of L1 from L2 in the second STEP11, the third movement is from L1. Move to L3.

  After the focus lens is moved (STEP 13) and the next frame is captured (STEP 9), the process returns to STEP 1 as before, and contrast components are extracted, motion is detected, and a focus evaluation value is calculated again. (STEP 1-5). As long as the focus evaluation value increases (STEP 7, NO) and the focus lens does not exceed the movable range (STEP 12, YES), the above-described operation (STEPs 12 and 13) is performed three times, four times, five times,. And repeat.

  On the other hand, the case where the focusing evaluation value decreases (STEP 7, YES) and the focusing operation is the third time or later (STEP 10, NO) will be described below.

  In this case, it is assumed that the focus evaluation value has been moved in the direction of decreasing in the previous focusing operation. For example, this corresponds to the case where the previous movement was a movement from L5 to L6 in FIG. At this time, the focus evaluation value increases when moved from L4 to L5 two times before, and the focus evaluation value decreases when moved from L5 to L6 last time. It can be estimated that the evaluation value is a maximum value.

  Therefore, when the focus evaluation value decreases (STEP 7, NO) and the third and subsequent times (STEP 10, NO), the focus lens is moved to the position before the previous movement (the position of L5 in FIG. 9) which is the maximum value. Is moved (STEP 14), and the focus control is terminated with the position of the focus lens as the focus position. In FIG. 9, the case of moving from L6 to L5 corresponds to this.

By performing the focusing control as described above, focusing can be easily performed based on the focusing evaluation value. Further, as described above, the horizontal weighting coefficient K _H [i, j] and the vertical weighting coefficient K _V based on the motion vector in the horizontal contrast component C _H [i, j] and the vertical contrast component C _V [i, j]. Since a focus evaluation value obtained by adding and averaging [i, j] can be used, even if one of the contrast components becomes defective due to the movement of the subject or the imaging device, the other good contrast component Focus can be performed with emphasis on. Therefore, it is possible to focus accurately even when the subject or the imaging apparatus moves.

  The present invention relates to an imaging device controlled based on a captured video signal and an imaging method thereof. In particular, the present invention relates to an imaging apparatus that automatically performs focusing control and an imaging method that includes the focusing control method.

These are block diagrams which show the structure of the imaging device in this invention. These are block diagrams which show the structure of the imaging part of the imaging device in this invention. These are block diagrams which show the structure of the focus evaluation part of the imaging device in this invention. These are block diagrams which show the structure of the horizontal contrast component detection part and the vertical contrast component detection part of the imaging device in this invention. FIG. 4 is a schematic diagram showing a video signal for one frame. These are the schematics of the motion vector calculated | required from the video signal input into a motion detection part, and a video signal. These are graphs showing an example of a motion vector and the relationship between the position of the focus lens and the focus evaluation value. These are the flowcharts shown about an example of the focusing control method in this invention. These are graphs showing the relationship between the position of the focus lens and the focus evaluation value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Imaging part 3 AFE part 4 Video signal processing part 5 Audio input part 6 Audio signal processing part 7 Compression processing part 8 Decompression processing part 9 Video signal output part 10 Audio signal output part 11 Operation part 12 CPU
13 SDRAM
DESCRIPTION OF SYMBOLS 14 Memory card 15 Timing control signal output part 16 Bus 17 Bus 41 Motion detection part 42 Focus evaluation part 421 Horizontal contrast component detection part 422 Vertical contrast component detection part 423 Focus evaluation value calculation part 424 Weight coefficient control part

Claims (5)

An imaging unit that performs imaging and outputs a video signal;
A motion detection unit that detects a motion generated in the subject or the imaging device from the video signal output from the imaging unit and outputs a motion signal;
A high-frequency component detector that detects a horizontal high-frequency component and a vertical high-frequency component of the video signal;
Focus evaluation for calculating a focus evaluation value by adding a horizontal weighting factor and a vertical weighting factor based on the motion signal output from the motion detection unit to the horizontal high-frequency component and the vertical high-frequency component and adding them together. A value calculator,
A focus control unit that performs focus control of the imaging device based on the focus evaluation value;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein a magnitude relationship between a horizontal component and a vertical component of the motion signal is opposite to a magnitude relationship between the horizontal weighting factor and a vertical weighting factor. The high-frequency component detection unit detects the horizontal high-frequency component and the vertical high-frequency component for each of a plurality of predetermined regions of the video signal;
The focus evaluation value calculation unit adds the horizontal weighting factor and the vertical weighting factor to the horizontal high-frequency component and the vertical high-frequency component obtained from each of the regions, and adds the horizontal weighting factor and the vertical weighting factor to correspond to each region. The imaging apparatus according to claim 1, wherein an area evaluation value is obtained, and the area evaluation values are added or averaged to obtain the focus evaluation value.   The motion signal is output when the motion detection unit detects that the motion of the subject or the imaging device is in the same direction for a predetermined period. An imaging apparatus according to claim 1. A first step of imaging and outputting a video signal;
A second step of detecting a motion generated in the subject or the imaging device from the video signal output in the first step and creating a motion signal;
A third step of detecting a horizontal high-frequency component and a vertical high-frequency component of the video signal;
A horizontal weighting factor and a vertical weighting factor based on the motion signal created by the second step are integrated and added to each of the horizontal high frequency component and the vertical high frequency component obtained in the third step, A fourth step of calculating a focus evaluation value;
A fifth step of performing focusing control of the imaging device based on the focusing evaluation value;
An imaging method comprising:

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