JP4326997B2 - Imaging apparatus, focusing method, control program, and recording medium - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly, to an imaging apparatus having an autofocus (hereinafter abbreviated as “AF”) function.

  Continuous autofocus that performs continuous (intermittent) focusing to capture images that are always in focus during movie shooting, or to reduce shutter time lag by always focusing. There is a digital still camera capable of setting a method (hereinafter abbreviated as “CAF”).

  As a method for performing autofocus, specifically, a so-called “automatic focus adjustment of a TV camera by a hill-climbing servo system” which is a focus position detection method in one focus operation (see Non-Patent Document 1). The method shown in is widely adopted. In this method, the focus lens is moved from the closest position to the infinity position or from the infinity position to the close position, and the focus lens position where the high frequency component or edge component in the image data is maximized is set as the focus position. .

  In the CAF, methods for continuously performing the focusing operation include a method for performing a focusing operation at a constant time interval, a method disclosed in Patent Document 1, and the like. Specifically, in the method disclosed in Patent Document 1, the current image data is compared with the AF evaluation value, AE evaluation value, and AWB evaluation value of the image data during the previous focusing operation or immediately after the focusing. Then, it is determined whether or not the focusing state in the previous focusing operation is maintained. If the focusing state in the previous focusing operation is not maintained, the focusing operation is performed.

Further, the method disclosed in Patent Document 2 discloses that “color information” is used for controlling the autofocus operation, and “saturation peak value” is used as a specific example of “color information”.
JP 2003-232984 A (publication date; August 22, 2003) Japanese Patent Laid-Open No. 5-236330 (Release Date; September 10, 1993) "NHK Technology Research" Vol. 17, No. 1, p. 21 Issued in 1965, Ishida et al.

  However, autofocus automatically adjusts the focus. However, the conventional technique has a problem in that a focusing operation may be performed even when the focus is achieved.

  Specifically, when performing the focusing operation at a constant interval, the focusing operation is performed regardless of whether or not the focusing state in the previous focusing operation is maintained. For this reason, the current consumption increases because the focus lens is moved by the motor during the focusing operation. Also, if the in-focus operation is performed even though the in-focus state in the previous in-focus operation is maintained, the image is blurred because the focus is not in focus during the in-focus operation. Will be displayed.

  In the method disclosed in Patent Document 1, it is determined whether or not the focusing operation needs to be performed again by using an AF evaluation value, an AE evaluation value, or the like as a determination method when performing the focusing operation again. ing. Since the AF evaluation value and the AE evaluation value vary depending on the brightness, the AF evaluation value and the AE evaluation value vary even when the distance to the subject does not change. In other words, focusing is performed for focusing when imaging a subject. However, in the method disclosed in Patent Document 1, focusing operation is performed again using AF evaluation values, AE evaluation values, and the like. For example, when shooting outdoors, the sun may be hidden behind the clouds, or the sun hidden behind the clouds may be sunny. When the brightness changes, the focusing operation is performed regardless of the focus.

  The method disclosed in Patent Document 2 discloses that “color information” is used to control the autofocus operation, and “saturation peak value” is used as a specific example of “color information”. The “saturation peak value” in Patent Document 2 is, for example, “maximum values CRMAX and CBMAX of the amplitudes of the color difference signals RY and BY” as described in paragraph [0024]. The CRMAX and CBMAX are strongly influenced by the brightness (brightness) component, and even when autofocus is performed by the method disclosed in Patent Document 2, if the brightness of the subject or the surroundings of the subject changes, the focus is increased. The focusing operation is performed regardless of whether or not. Further, Patent Document 2 does not have a technical idea of continuously performing autofocus.

  As described above, the conventional method has a problem that the focusing operation may be performed even when it is not necessary to perform the focusing operation.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus and a focusing method that do not perform useless focusing operation.

  In order to solve the above-described problem, an imaging apparatus according to the present invention outputs an optical image formed on an imaging plane as image data, image data output from the imaging unit, and the image data Whether or not the in-focus state is maintained based on the amount of change in saturation and / or hue in the three attributes of color with the image data output from the imaging unit before output from the imaging unit And a focusing operation control unit that adjusts the focus of the imaging unit when the in-focus state is not maintained based on the determination result of the determination unit. Yes.

  The determination means determines whether or not the in-focus state is maintained based on whether or not the amount of change in saturation and / or hue is within a predetermined range. Further, “whether or not the in-focus state is maintained” means that the focus lens determined based on the image data output from the imaging unit before outputting the image data to be newly acquired from the imaging unit. This is the same as whether or not the in-focus position has changed.

  The above three attributes of color indicate lightness, saturation, and hue. According to the above configuration, the determining unit determines whether or not to perform the focusing operation again (whether or not the focused state is maintained) based on the saturation and / or hue of the image data. . In other words, since the above determination is performed using the hue expressed by the saturation and / or the wavelength of the spectral monochromatic light, which is less influenced by the brightness and indicates the degree of vividness of the color, for example, the focus is achieved. Nevertheless, it is possible to reduce the focusing operation due to the change in the brightness of the subject or the surroundings of the subject. Accordingly, it is possible to provide a photographing apparatus that does not perform the focusing operation by operating the focus lens even though the focusing operation is useless, that is, the focal length is correct.

  Also, with the above configuration, the current consumption is reduced to prevent the focusing operation from being restarted when the distance to the subject does not change and the brightness of the subject or the subject changes. An imaging device with a long battery life can be provided. In addition, since it is possible to reduce performing a useless focusing operation, it is possible to further reduce shooting and display of a blurred image during the useless focusing operation.

  In the imaging apparatus according to the present invention, the determination unit may further include image data output from the imaging unit and image data output from the imaging unit before the image data is output from the imaging unit. More preferably, it is configured to determine whether or not the focused state is maintained based on the required luminance information.

  The luminance information includes, for example, an AF (Auto Focus) value and / or an AE (Auto Exposure) value. The AF value indicates a high frequency component in a predetermined region in the image data or a luminance difference integral value of adjacent pixels. The AE value indicates an integral value of luminance values in a predetermined area in the image data. That is, the luminance information indicates an AF value and / or an AE value.

  According to the above configuration, in addition to the saturation and / or hue, it is further determined whether or not the in-focus state is maintained using the luminance information, and therefore, further unnecessary focusing operation is performed. What is done can be reduced.

An imaging apparatus according to the present invention includes a conversion unit that converts the image data into an L * a * b * color space.
The determination means is based on a * and b * respectively obtained from the image data output from the imaging unit and the image data output from the imaging unit before the output of the image data from the imaging unit. Therefore, it is more preferable to determine whether or not the in-focus state is maintained.

  According to the above configuration, it is determined whether or not the in-focus state is maintained using a * and b * in the L * a * b * color space. In the L * a * b * color space, L * indicates brightness, and the other a * and b * are parameters that are less affected by brightness. Therefore, the determination using a * and b * makes it possible to perform the focusing operation even when the distance to the subject does not change due to changes in the brightness of the subject and its surroundings. It can be further reduced.

  The imaging apparatus according to the present invention includes a conversion unit that converts the image data into an L * u * v * color space, and the determination unit includes the image data output from the imaging unit and the imaging unit of the image data. It is more preferable that the in-focus state is determined based on u * and v * respectively obtained from the image data output from the imaging unit before output from .

  According to the above configuration, it is determined whether or not the in-focus state is maintained using u * and v * in the L * u * v * color space. In the L * u * v * color space, L * indicates lightness, and the other u * and v * are parameters that are less affected by brightness. Therefore, by determining using u * and v *, it is possible to perform the focusing operation even when the distance to the subject does not change due to changes in the brightness of the subject and its surroundings. It can be further reduced.

  In order to solve the above-described problem, the focusing method according to the present invention includes an imaging step of outputting an optical image formed on the imaging plane by the imaging unit as image data, and image data output from the imaging unit. And the image data output from the image pickup unit before the image data is output from the image pickup unit, the focus state is maintained based on the saturation and / or hue change amount in the three attributes of color. A determination step for determining whether or not the focus has been maintained, and a focusing operation control step for adjusting the focus of the imaging unit when the in-focus state is not maintained based on the determination result of the determination step. It is characterized by.

  According to said structure, it is determined whether the focused state is maintained based on the saturation and / or hue in the three attributes of color. Thereby, for example, it is possible to reduce the fact that the focusing operation is performed due to a change in the brightness of the subject or the surroundings of the subject even though the focus is achieved.

  The control program for the imaging apparatus of the present invention is a computer program that causes a computer to function as each of the means described above.

  With the configuration described above, the imaging device can be realized by realizing each unit of the imaging device with a computer.

  A computer-readable recording medium recording the control program for the imaging apparatus of the present invention is a computer-readable recording medium that records the control program for the imaging apparatus that causes the computer to realize the above-described units and operate the imaging apparatus. It is a recording medium.

  With the above configuration, the imaging device can be realized on a computer by the control program of the imaging device read from the recording medium.

  An imaging apparatus according to the present invention includes an imaging unit that outputs an optical image formed on an imaging plane as image data, image data output from the imaging unit, and before output of the image data from the imaging unit. Determining means for determining whether or not the in-focus state is maintained based on the amount of change in saturation and / or hue in the three attributes of color with the image data output from the imaging unit; Based on the determination result of the determination unit, the focus operation control unit adjusts the focus of the imaging unit when the in-focus state is not maintained.

  Therefore, for example, it is possible to reduce the fact that the focusing operation is performed due to a change in the brightness of the subject or the surroundings of the subject even though the focus is achieved. Accordingly, it is possible to provide a photographing apparatus that does not perform the focusing operation by operating the focus lens even though the focusing operation is useless, that is, the focal length is correct.

  An embodiment of the present invention will be described as follows. In other words, the imaging apparatus according to the present embodiment is an imaging apparatus that intermittently performs focusing operation, and uses the saturation and / or hue in the three attributes of color that are less affected by brightness, In this configuration, it is determined whether or not it is necessary to newly perform a focusing operation from the focusing state in the focusing operation, and the focusing operation is performed as necessary based on the determination result.

  In the following description, a digital still camera will be described as an example. However, the imaging apparatus is not limited to the above, and includes, for example, a video camera.

  FIG. 2 is a block diagram showing a schematic configuration of a digital still camera (imaging apparatus, hereinafter referred to as a camera) 50 according to the present embodiment.

  The camera 50 includes a focus lens 1, a CCD (imaging unit) 2, a CDS / AGC / ADC circuit 3, a motor 4, a timing signal generator 5, a signal processing unit 10, a recording medium 6, an LCD controller 7 and an LCD 8. Yes. The focus lens 1, the CCD 2, and the motor 4 constitute a camera unit 30.

  The signal processing unit 10 includes an interpolation circuit 11, a white balance / gamma correction circuit 12, a luminance / color difference signal generation circuit 13, an image compression processing circuit 14, a video encoder circuit 15, an AF / AE evaluation value calculation circuit 16, a color A space conversion / color evaluation value calculation circuit (conversion means) 17 and a system controller 18 are provided.

  The motor 4, the system controller 18, and the AF / AE evaluation value calculation circuit 16 constitute a focusing means.

  Light from the subject is incident on an imaging device 2 (CCD sensor, CMOS sensor, etc., which uses a CCD sensor, hereinafter referred to as “CCD”) through the focus lens 1. More specifically, the light condensed by the focus lens 1 is imaged on the light receiving surface provided with the light receiving element of the CCD 2. The light receiving surface of the CCD 2 is composed of a large number of light receiving elements, and charges corresponding to the amount of incident light are accumulated in each light receiving element, and analog image data is read out by reading the accumulated charges within a predetermined exposure time from each light receiving element. Is obtained.

  FIG. 2 shows only the focus lens necessary for the description of the present invention in the actual lens system. The focus lens 1 adjusts the focus of the subject image by moving back and forth in the optical axis direction. The focus lens 1 is driven by a motor 4. The motor 4 is controlled by a system controller 18 described later of the signal processing unit 10.

  The CCD 2 has an imaging surface in which a plurality of pixels that perform photoelectric conversion are two-dimensionally arranged. The CCD 2 converts an optical image formed on the imaging surface upon incidence of subject light into an electrical signal, and converts it into an analog signal. Output as image data.

  The image data output from the CCD 2 is subjected to noise component removal, gain addition, and conversion from an analog signal to a digital signal by the CDS / AGC / ADC circuit 3.

  The CCD 2 and the CDS / AGC / ADC circuit 3 are timing-controlled by a timing signal generator 5 (hereinafter abbreviated as “TG”). The TG 5 is controlled by the system controller 18.

  The image signal digitized by the CDS / AGC / ADC circuit 3 is input to the signal processing unit 10, but at this time, each pixel has only one component signal of RGB, so that the interpolation circuit 11 performs other signal processing. Component signals (RGB signals) are generated.

  Next, the white balance / gamma correction circuit 12 performs gain adjustment and gamma correction for matching the white balance.

  Subsequently, the luminance / color difference signal generation circuit 13 converts the RGB signals into luminance / color difference signals. In addition, processing such as edge enhancement is added to the luminance signal.

  The luminance / color difference signal is converted into a format that can be displayed on a liquid crystal screen (hereinafter abbreviated as “LCD”) by the video encoder circuit 15 and displayed on the LCD 8 via the LCD controller 7 (hereinafter abbreviated as “LCDC”). The

  When a still image is shot, the luminance / color difference signal is subjected to JPEG compression processing by the image compression processing circuit 14, and JPEG compressed data is stored in the recording medium 6.

  The AF / AE evaluation value calculation circuit 16 calculates an AF evaluation value from a high frequency component or an edge component in a predetermined area in the luminance signal, and calculates an AE evaluation value from the luminance value in the predetermined area in the luminance signal.

  The color space conversion / color evaluation value calculation circuit 17 receives the RGB signal after white balance adjustment, performs color space conversion, and calculates a color evaluation value. This is because the RGB signals vary depending on the brightness and are correlated with each other, so that a color evaluation value with little influence of brightness is obtained by color space conversion.

  The system controller 18 is for controlling the entire camera 50. Although not shown, the system controller 18 is a CPU that performs various arithmetic processes according to a program, a ROM that stores a program, a RAM that stores data of each process, and the like. Consists of.

  Then, the system controller 18 determines whether or not the previous in-focus state is maintained based on signals from the color space conversion / color evaluation value calculation circuit 17 and the AF / AE evaluation value calculation circuit 16. If it is determined that the in-focus state is not maintained, the in-focus operation is performed again. This will be described below.

  FIG. 1 is a block diagram showing a schematic configuration of the system controller. For convenience of explanation, only the members directly related to autofocus are shown in the drawing.

  As shown in FIG. 1, the system controller 18 includes a storage unit 21, a comparison unit (determination unit) 22, and an AF control unit (focusing operation control unit) 23. The storage unit 21 stores various data input to the system controller 18. Specifically, the storage unit 21 outputs the AF evaluation value and the AE evaluation value output from the AF / AE evaluation value calculation circuit 16 and the color output from the color space conversion / color evaluation value calculation circuit 17. The evaluation value is stored.

  For the AF evaluation value, the AE evaluation value, and the color evaluation value stored in the storage unit 21, the comparison unit 22 uses the latest AF evaluation value, the AE evaluation value, and the color evaluation value (current evaluation value) and before the latest. The AF evaluation value, the AE evaluation value, and the color evaluation value (previous evaluation value) are compared. A specific determination method and the like will be described later.

  The AF control unit 23 operates the camera unit 30 to perform a focusing operation.

  Here, the color space conversion / color evaluation value calculation circuit 17 will be described in detail. The color space conversion / color evaluation value calculation circuit 17 performs color space conversion processing of a predetermined area on the RGB signal after the white balance is adjusted by the white balance / gamma correction circuit 12, and the saturation of the three attributes of the color And / or hue. In this embodiment, the saturation and / or hue in the uniform color space is calculated. More specifically, in the present embodiment, the RGB signal after white balance adjustment is converted into L * a * b * or CIE 1976 (L * u * v *) in the CIE 1976 (L * a * b *) color space. ) Convert to L * u * v * in color space.

  Here, the RGB signal is converted into L * a * b * or L * u * v * using, for example, the following conversion formula.

X = 0.6068R + 0.1735G + 0.2004B
Y = 0.2989R + 0.5866G + 0.1145B
Z = 0.0000R + 0.0661G + 1.1163B
L * = 116 (Y / Yn) ¹ /3-16
a * = 500 ((X / Xn) ¹ /3-(Y / Yn) ^1/3 )
b * = 200 ((Y / Yn) ¹ /3-(Z / Zn) ^1/3 )
Xn, Yn, and Zn are the tristimulus values of the perfect diffuse reflection surface, and are normalized as Yn = 100.

U = 4X / (X + 15Y + 3Z)
V = 9Y / (X + 15Y + 3Z)
L * = 116 (Y / Yn) ¹ /3-16
u * = 13L * (U-Un)
v * = 13L * (V-Vn)
Yn, Un, and Vn are the tristimulus value Y and chromaticity coordinates of the perfect diffuse reflection surface, and are normalized as Yn = 100.

When the color space conversion / color evaluation value calculation circuit 17 converts the color space into the CIE 1976 (L * a * b *) color space, the color space conversion / color evaluation value calculation circuit 17 calculates tan ⁻¹ (b * / a *) from the conversion result. Obtain the histogram of the hue angle. On the other hand, when the color space conversion / color evaluation value calculation circuit 17 converts to the CIE 1976 (L * u * v *) color space, the color space conversion / color evaluation value calculation circuit 17 calculates tan ⁻¹ (v * / u *) from the conversion result. Obtain the histogram of the hue angle. Then, the calculation result is transmitted to the system controller 18. Note that when calculating tan ⁻¹ (v * / u *) or tan ⁻¹ (b * / a *) by converting to L * u * v * or L * a * b *, L * Since (brightness) is not used, only u *, v * or a *, b * (chromaticness index) may be obtained from the RGB signal after the white balance is adjusted.

  The signal processing unit 10 includes each block (interpolation circuit 11, white balance / gamma correction circuit 12, luminance / color difference signal generation circuit 13, image compression processing circuit 14, video encoder circuit 15, AF / AE evaluation value calculation circuit. 16, the color space conversion / color evaluation value calculation circuit 17 and the system controller 18) may be realized by hardware logic, and at least some of these functions may be implemented by a CPU as follows. And may be realized by software.

  That is, the signal processing unit 10 of the camera 50 includes a CPU (central processing unit) that executes instructions of a control method of the camera 50 that realizes the function of each block, a ROM (read only memory) that stores the program, and the program. A RAM (random access memory) to be developed, a storage device (recording medium) such as a memory for storing the program and various data, and the like are provided. Then, the signal processing unit 10 records a recording medium on which a program code (execution format program, intermediate code program, source program) of a control program for the camera 50, which is software for realizing the above-described functions, is recorded so as to be readable by a computer. This can also be realized by supplying the processing unit 10 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU). In this case, the program code itself read from the recording medium realizes the above-described function, and the recording medium recording the program code constitutes the present invention.

  Thus, in this specification, the means (unit) does not necessarily mean a physical means, but includes cases where the function of each means is realized by software. Further, the function of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means.

  Next, the focus operation restart determination of the present invention will be described based on the flowchart of FIG. In FIG. 3, the step is denoted as “S”.

  After the digital still camera is turned on, when the operator sets the still image or moving image shooting mode and the CAF is set as the AF method, the AF control unit 23 of the system controller 18 performs a normal focusing operation. (Step 1).

That is, first, the system controller 18 controls the motor 4 to move the focus lens 1 to the infinity position or the close position. Then, the system controller 18 operates the motor 4 to sequentially move the focus lens 1 to each AF evaluation value acquisition position. The CCD 2 continuously obtains image data when the focus lens 1 is moved. The obtained image data is digitized through the CDS / AGC / ADC circuit 3, interpolated with other pixels by the interpolation circuit 11, and white balance adjustment by the white balance / gamma correction circuit 12. Are converted into RGB signals. The RGB signals are converted into luminance / color difference signals by the luminance / color difference signal generation circuit 13 and input to the AF / AE evaluation value calculation circuit 16. The AF / AE evaluation value calculation circuit 16 calculates an AF evaluation value based on the input luminance / color difference signal. Then, the system controller 18 acquires the AF evaluation value from the AF / AE evaluation value calculation circuit 16 and stores the AF evaluation value in the storage unit 21 of the system controller 18. In this way, the system controller 18 operates the motor 4 to move the focus lens 1 to the next AF evaluation value acquisition position, and acquires the AF evaluation value from the AF / AE evaluation value calculation circuit 16. This operation is repeated until the maximum value of the AF evaluation value is detected, or until the focus lens 1 reaches a close position (when starting from an infinite position) or an infinite position (when starting from a close position) ( Step 2). Then, the comparison unit 22 of the system controller 18 determines the position of the focus lens 1 corresponding to the maximum value or the maximum value of the acquired AF evaluation value as the focus position. Then, the system controller 18 moves the focus lens 1 to a position where the maximum value or maximum value of the AF evaluation value is detected, and ends the focusing operation. Then, the system controller 18 acquires the AF evaluation value and the AE evaluation value at the in-focus position from the AF / AE evaluation value calculation circuit 16, and the color evaluation value (tan ⁻¹ (v * / u *) or tan ⁻¹ (b * / a *)) is acquired and stored in the storage unit 21 of the system controller 18 (step 3).

  Next, the system controller 18 determines whether or not the CCD 2 has acquired new image data (step 4).

  When it is determined in step 4 that new image data has been acquired, the system controller 18 receives the AF evaluation value and the AF evaluation value from the AF / AE evaluation value calculation circuit 16 when the signal processing unit 10 acquires image data from the CCD 2. The AE evaluation value is acquired from the color space conversion / color evaluation value calculation circuit 17 (step 5). Then, the system controller 18 stores the acquired AF evaluation value, AE evaluation value, and color evaluation value in the storage unit 21 of the system controller 18. For convenience of explanation, the newly acquired AF evaluation value, AE evaluation value, and color evaluation value are used as the current evaluation value, and the AF evaluation value, AE evaluation value, and color evaluation value acquired immediately before the new acquisition are used as the previous evaluation value. explain. That is, the current evaluation value indicates an evaluation value acquired one time after the previous evaluation value among the evaluation values acquired intermittently.

  Then, the comparison unit 22 of the system controller 18 determines whether or not a new focusing operation needs to be performed by comparing the current evaluation value stored in the storage unit 21 with the previous evaluation value. More specifically, the comparison unit 22 compares the previous color evaluation value and the current color evaluation value, and the difference (α) between the current color evaluation value and the previous color evaluation value is within a predetermined range. (Step 6). In other words, the comparison unit 22 compares the color evaluation value acquired in step 5, that is, the current color evaluation value, with the color evaluation value acquired in step 3, that is, the previous color evaluation value, and the variation amount (difference between both) is the same. It is determined whether or not the value is equal to or greater than a predetermined value α2. If the comparison unit 22 determines that the difference between the current color evaluation value and the previous color evaluation value is equal to or greater than the predetermined value α2, that is, the difference between the previous color evaluation value and the current evaluation value is large, the comparison unit 22 It is determined that the in-focus state in the focusing operation is not maintained, and the AF control unit 23 is operated to perform the focusing operation (return to step 1).

  If it is determined in step 6 that the difference (α) between the current color evaluation value and the previous color evaluation value is smaller than the predetermined value α2, the comparison unit 22 compares the previous AF evaluation value with the current AF evaluation value. Then, it is determined whether or not the difference (β) between the current AF evaluation value and the previous AF evaluation value is within a predetermined range (step 7). In other words, the comparison unit 22 compares the AF evaluation value acquired in step 5, that is, the current AF evaluation value, with the AF evaluation value acquired in step 3, that is, the previous AF evaluation value, and the variation amount (difference between both) is calculated. It is determined whether or not it is equal to or greater than a predetermined value β2. If it is determined that the difference between the current AF evaluation value and the previous AF evaluation value is greater than or equal to the predetermined value β2, the comparison unit 22 determines that the in-focus state in the previous focusing operation is not maintained, and AF The controller 23 is operated to perform the focusing operation (return to step 1).

  If it is determined in step 7 that the difference (β) between the current AF evaluation value and the previous AF evaluation value is smaller than the predetermined value β2, the comparison unit 22 compares the previous AE evaluation value with the current AE evaluation value. Then, it is determined whether or not the difference (β) between the current AE evaluation value and the previous AE evaluation value is within a predetermined range (step 8). In other words, the comparison unit 22 compares the AE evaluation value acquired in step 5, that is, the current AE evaluation value with the AE evaluation value acquired in step 3, that is, the previous AE evaluation value, and the variation amount (difference between the two) is calculated. It is determined whether or not a predetermined value γ2 or more. If it is determined that the difference between the current AE evaluation value and the previous AE evaluation value is equal to or greater than the predetermined value γ2, the comparison unit 22 determines that the in-focus state in the previous focusing operation is not maintained, and AF The controller 23 is operated to perform the focusing operation (return to step 1).

  If it is determined in step 8 above that the difference (γ) between the current AE evaluation value and the previous AE evaluation value is smaller than the predetermined value γ2, the comparison unit 22 determines the difference between the current color evaluation value and the previous color evaluation value ( α), the difference (β) between the current AF evaluation value and the previous AF evaluation value, and the difference (γ) between the current AE evaluation value and the previous AE evaluation value are equal to or greater than predetermined values α1, β1, and γ1, respectively. It is determined whether or not there is (step 9). The predetermined values α1 and α2, the predetermined values β1 and β2, and the predetermined values γ1 and γ2 are as follows: predetermined value α2> predetermined value α1, predetermined value β2> predetermined value β1, and predetermined value γ2> predetermined value γ1. Satisfies the relationship.

  If it is determined that α is α1 or more, β is β1 or more, and γ is γ1 or more, the comparison unit 22 does not maintain the focusing state in the previous focusing operation. And the AF control unit 23 is operated to perform a focusing operation (return to step 1). If it is determined that α is smaller than α1, β is smaller than β1, or γ is smaller than γ1, the comparing unit 22 determines an AF evaluation value, an AE evaluation value, and a color evaluation based on new image data. Wait for the value to be retrieved. Specifically, the process returns to step 4.

  As described above, the camera 50 according to the present invention includes the camera unit 30 that outputs an optical image formed on the imaging surface as image data, the current image data output from the camera unit 30, and the current image data. And / or saturation in three attributes of color and / or image data that has been output from the camera unit 30 before the output of the image data from the camera unit 30 immediately after focusing in the previous focusing operation. A comparison unit 22 that determines whether or not the in-focus state in the previous focusing operation is maintained based on the hue change amount, and an in-focus operation in the previous focusing operation based on the determination result of the comparison unit 22. The AF control unit 23 adjusts the focus of the camera 50 based on the current image data when the focus state is not maintained. According to the above configuration, the comparison unit 22 determines whether to perform the focusing operation again based on the saturation and / or hue of the image data (whether the focusing state in the previous focusing operation is maintained). )). In other words, since the above determination is performed using the hue expressed by the saturation and / or the wavelength of the spectral monochromatic light, which is less influenced by the brightness and indicates the degree of vividness of the color, for example, the focus is achieved. Nevertheless, it is possible to reduce the focusing operation due to the change in the brightness of the subject or the surroundings of the subject. Accordingly, it is possible to provide the camera 50 that does not perform the focusing operation by operating the focus lens even though the focusing operation is useless, that is, the focal length is correct.

  In addition, about the determination procedure of whether to perform the said focusing operation | movement again, said description is only an example and is not limited to the said procedure. As for the focusing operation, in order to improve the system for the first time, the entire operating range of the focus lens 1 is searched with a predetermined step width, and the time required for restarting (when performing the focusing operation again) is shortened. In addition, the vicinity (periphery) of the focus position in the previous focus operation may be searched. This will be specifically described. In the case of the CAF that performs the focusing operation intermittently after the focusing operation is completed once, the focusing operation is performed in a state where not much time has passed since the previous focusing operation. In this case, the subject is rarely moved, and the focusing operation is performed only in the vicinity of the previous focusing position without performing the focusing operation by moving the focus lens 1 from the infinity position to the closest position. By doing so, it is often possible to create a focused state. Further, during the focusing operation, the camera is out of focus, and if shooting is performed in this state, a blurred image can be obtained. Therefore, it is more preferable to create a focused state with a minimum focusing operation.

  Therefore, in the camera 50 according to the present invention, when the focusing operation is intermittently performed (CAF mode) and it is determined that the focusing state in the previous focusing operation is not maintained, the system controller The (focusing operation control means) 18 may operate the focusing means only in the vicinity of the area including the focusing position detected by the previous focusing operation. Note that the area in the vicinity including the in-focus position is a distance from which the focus lens 1 is operated in a normal in-focus operation, that is, a distance from an infinite position that is a movable distance of the focus lens 1 to a close position. Is also a short distance. Then, the system controller 18 causes the focusing operation to be performed on a region in the vicinity including the focusing position, and if the focusing position is not detected, causes the focusing means to perform a normal focusing operation. May be.

In the above description, the RGB signal after white balance adjustment is converted into the CIE 1976 (L * a * b *) color space or the CIE 1976 (L * u * v *) color space, and tan ⁻¹ ( Based on the value of b * / a *) or tan ⁻¹ (v * / u *), it is determined whether or not the previous in-focus state is maintained. However, the method for determining whether or not the previous in-focus state is maintained is not limited to the above. For example, the determination is performed using C * ab (chroma) or hab (hue angle). May be. In other words, in the present invention, a parameter that is less influenced by brightness is used as a determination as to whether or not the previous in-focus state is maintained.

  In the above description, the digital still camera is described. However, the imaging apparatus according to the present invention is not limited to the above, and can be suitably used for, for example, a video camera. When the present invention is used in a video camera, for example, when the sun is hidden behind a cloud outdoors, or when the sun hidden behind a cloud is clear, that is, even if the brightness of the subject or the surroundings of the subject changes. In this case, it is possible to prevent the in-focus operation from being restarted and the out-of-focus state.

  Further, the focusing method according to the present invention includes an imaging step for converting an optical image formed on the imaging surface into image data, and a focus lens for moving the focus to adjust the focus of the optical image. And a focusing process that continuously performs a focusing operation to stop the focus lens at the detected focusing position, the current image data obtained by the imaging process, and The AF evaluation value, the AE evaluation value, the color of the image data obtained by the imaging process prior to the imaging process for obtaining the current image data, and the image data immediately after focusing in the previous focusing operation. The evaluation values (color evaluation values) relating to the saturation and / or hue in the three attributes are compared to determine whether or not the in-focus state in the previous focusing operation is maintained. The focus is maintained Focusing operation controlling step performs the focusing operation when had emitting layer may include a.

  The camera 50 according to the present invention includes a CCD (imaging unit) 2 that converts an optical image formed on the imaging surface into image data, and a focus lens that moves the focus of the optical image. A motor 4, an AF / AE evaluation value calculation circuit 16, and a system controller 18 (focusing means) that continuously perform a focusing operation for detecting a focusing position and stopping the focus lens at the detected focusing position are provided. In the imaging device, current image data output from the CCD 2 and image data output from the CCD 2 before the output of the current image data from the CCD 2 are image data immediately after focusing in the previous focusing operation. And the AF evaluation value, the AE evaluation value, the saturation in the three attributes of color and / or the evaluation value (color evaluation value) relating to the hue, and the in-focus state in the previous focusing operation Determines whether it is maintained, it may be configured to include a system controller 18 (focusing operation control means) for performing focusing operation when a focus state in the previous focusing operation is not maintained.

  The saturation and / or hue in the three attributes of the color may be saturation and / or hue in a uniform color space.

The camera 50 according to the present invention converts the image data into the L * u * v * color space and calculates tan ⁻¹ (v * / u *), a color space conversion / color evaluation value calculation circuit 17. The system controller 18 is configured to determine whether or not the focused state in the previous focusing operation is maintained based on the obtained tan ⁻¹ (v * / u *). Good. In other words, the saturation and / or hue in ^{Ironosanzokusei, tan -1 (v * / u} *) using, tan obtained from each of the above current image data and previous image data ^{-1 (v} * / U *), it may be determined whether or not the focused state in the previous focusing operation is maintained.

Further, the camera 50 according to the present invention converts the image data into the L * a * b * color space and calculates tan ⁻¹ (b * / a *), a color space conversion / color evaluation value calculation circuit 17. The system controller 18 is configured to determine whether or not the focused state in the previous focusing operation is maintained based on the obtained tan ⁻¹ (b * / a *). Good. In other words, the saturation and / or hue in ^{Ironosanzokusei, tan -1 (b * / a} *) by using, tan obtained from each of the above current image data and previous image data ^{-1 (b} * It may be determined whether or not the in-focus state in the previous focusing operation is maintained based on the change amount of / a *).

  In addition, the camera 50 according to the present invention includes a focus lens 1 and a CCD 2 that output an optical image formed on the imaging surface as image data, current image data output from the CCD 2, and current image data. By comparing the saturation and / or hue in the three attributes of color with image data output from the CCD 2 before output from the CCD 2 and image data immediately after focusing in the previous focusing operation, The comparison unit 22 determines whether or not the in-focus state in the previous focusing operation is maintained based on whether or not the saturation and / or hue change amount in the image data between the previous and the previous image data is within a predetermined range. And when the in-focus state in the previous focusing operation is not maintained based on the determination result of the comparison unit 22, Carcass may be configured to and a AF control unit 23 for adjusting.

  The imaging apparatus according to the present invention can be suitably applied to a digital camera, a video camera, or the like having a focusing function (autofocus function) that performs a focusing operation based on image data acquired by an imaging element such as a CCD.

It is a block diagram which shows the structure of the principal part of the digital camera concerning this Embodiment. It is a block diagram which shows schematic structure of the said digital camera. It is a flowchart which shows an example of the focusing operation | movement determination procedure in the said digital camera.

Explanation of symbols

1 Focus lens (imaging part)
2 CCD (imaging part)
3 CDS / AGC / ADC circuit 5 Timing signal generator 6 Recording medium 7 LCD controller 8 LCD
DESCRIPTION OF SYMBOLS 10 Signal processing part 11 Interpolation circuit 12 White balance / gamma correction circuit 13 Luminance / color difference signal generation circuit 14 Image compression processing circuit 15 Video encoder circuit 16 AF / AE evaluation value calculation circuit 17 Color space conversion / color evaluation value calculation circuit (conversion means)
18 System controller 21 Storage unit 22 Comparison unit (determination means)
23 AF control unit (focusing operation control means)
30 Camera unit (imaging unit)
50 cameras

Claims (7)

An imaging unit that outputs an optical image formed on the imaging surface as image data;
And image data output by the imaging unit, the image data immediately before between the imaging unit or RaIzuru force once was image data, based on the amount of change in saturation and / or hue in Ironosanzokusei, Determining means for determining whether or not the in-focus state is maintained;
Based on the determination result of the determination unit, a focusing operation control unit that adjusts the focus of the imaging unit when the in-focus state is not maintained ;
Conversion means for converting the image data into an L * a * b * color space;
Said determining means, based on the image data output from the imaging unit, the a * and b * obtained from each of the image data that has been output from the imaging unit immediately before the image data, tan ^-1 ( An imaging apparatus characterized by obtaining a histogram of hue angles calculated by (b * / a *) and determining whether or not the in-focus state is maintained according to the histogram . An imaging unit that outputs an optical image formed on the imaging surface as image data;
Focusing is performed based on the amount of change in saturation and / or hue in the three color attributes of the image data output by the imaging unit and the image data output from the imaging unit immediately before the image data. Determining means for determining whether or not the state is maintained;
Based on the determination result of the determination unit, a focusing operation control unit that adjusts the focus of the imaging unit when the in-focus state is not maintained;
Conversion means for converting the image data into an L * u * v * color space;
Said determining means, based on the image data output from the imaging section, the image data u * and obtained respectively from the image data that has been output from the imaging section immediately before the v *, tan ^-1 ( An image pickup apparatus characterized by obtaining a histogram of hue angles calculated by (v * / u *) and determining whether or not an in-focus state is maintained according to the histogram . Said determination means further based on the luminance information obtained from each of the image data output from the imaging unit, an image data that has been the imaging unit or RaIzuru force immediately before the image data, focus state the imaging apparatus according to claim 1 or 2, characterized in that but is intended to determine whether it is maintained. An imaging step of outputting an optical image formed on the imaging surface by the imaging unit as image data;
In the imaging process, the image data outputted by the imaging section, the image data that has been the imaging unit or RaIzuru force immediately before the image data, the change in saturation and / or hue in Ironosanzokusei A determination step of determining whether the in-focus state is maintained based on the amount; and
Based on the determination result of the determination step, when the in-focus state is not maintained, a focusing operation control step of adjusting the focus of the imaging unit ,
Converting the image data into an L * a * b * color space,
Based on a * and b * obtained from the image data output from the imaging unit and the image data output from the imaging unit immediately before the image data in the determination step, tan ⁻¹ ( b * / a *), a histogram of hue angles calculated, and determining whether or not the in-focus state is maintained according to the histogram . An imaging step of outputting an optical image formed on the imaging surface by the imaging unit as image data;
In the imaging step, the amount of change in saturation and / or hue in the three attributes of color between the image data output by the imaging unit and the image data output from the imaging unit immediately before the image data. A determination step for determining whether or not the in-focus state is maintained, and
Based on the determination result of the determination step, when the in-focus state is not maintained, a focusing operation control step of adjusting the focus of the imaging unit,
Converting the image data into an L * u * v * color space,
Based on u * and v * respectively obtained from the image data output from the imaging unit and the image data output from the imaging unit immediately before the image data in the determination step, tan ^-1 A focusing method characterized by obtaining a histogram of hue angles calculated by (v * / u *) and determining whether or not the in-focus state is maintained according to the histogram. An imaging apparatus control program for operating the imaging apparatus according to claim 1 , wherein the computer functions as each of the above-described means.   A computer-readable recording medium on which the control program for the imaging apparatus according to claim 6 is recorded.

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