Patent Description:
A technique called visual effects (hereinafter "VFX"). VFX is known. It is used for combining computer graphics (hereinafter "CG") with actually shot images.

In a case in which an actually shot image and CG are to be combined in VFX, the actually shot image may need to be subjected to a correction to address distortion of the lens of the camera used to shoot the image, prior to being combined with the CG, because a difference in size between the actually shot image and the CG could occur if such combining is performed without taking the distortion into consideration. In such cases, the distortion may need to be corrected in accordance with image height because the distortion can vary depending on image height.

While the distortion can be corrected in accordance with image height if distortion-related information is provided as metadata associated with the lens attached to the camera, some lenses are not provided with distortion-related information.

If the lens is not provided with distortion-related information, information relating to the distortion of the lens needs to be acquired by shooting a calibration chart (hereinafter "chart") for correcting such lens distortion. However, the shooting of the chart involves positioning the camera lens and the chart so as to directly face one another, aligning the optical center of the camera and the center of the chart, and adjusting the angle of view to the chart.

<CIT> and <CIT> disclose methods for presenting the direction in which a user should rotate or move a camera in order to position the camera so as to directly face a target object.

In <CIT> and <CIT>, because the rotation and movement amounts for positioning the camera and the target object so as to directly face one another, aligning the optical center of the camera and the center of the target object, and adjusting the angle of view to the target object are not presented, it may take time and effort to adjust the positional relationship between the camera and the target object. A further prior art document is <CIT> showing a measurement apparatus, image capturing apparatus, control method, and recording medium.

Various embodiments of the present invention realize techniques allowing more detailed information to be presented regarding operations that need to be carried out by a user during a calibration process.

According to one embodiment, the present invention provides an image capture apparatus as specified in claims <NUM> to <NUM>.

According to another embodiment, the present invention provides a control method as specified in claims <NUM> to <NUM>.

According to yet another embodiment, the present invention provides a program as specified in claim <NUM> and a computer-readable storage medium as specified in claim <NUM>.

According to various embodiments of the present invention, the time and effort it takes to carry out adjustment during calibration can be reduced because more detailed information regarding the operations that need to be carried out by a user during calibration can be presented.

Further features of the present invention will become apparent from the following description of example embodiments (with reference to the attached drawings).

Note, the following embodiments are not intended to limit the scope of the claimed invention as defined by the claims.

An embodiment in which the image capture apparatus according to the present invention is applied to a digital video camera will be described in detail below with reference to the attached drawings. Note that the image capture apparatus is not limited to being applied to a digital video camera, and is applicable to lens-replaceable digital single-lens reflex cameras and electronic devices which have a camera function and to which lenses can be attached.

First, with reference to <FIG>, the configuration and functions of the image capture apparatus according to the present embodiment will be described.

An image capture apparatus (hereinafter "camera") <NUM> according to the present embodiment includes a lens control device <NUM> and a camera control device <NUM>. The lens control device <NUM> can be attached to and detached from the camera control device <NUM>. At the same time as the lens control device <NUM> is mechanically connected to the camera control device <NUM> via an unillustrated lens mount of the camera control device <NUM>, the lens control device <NUM> is electrically connected to the camera control device <NUM> via later-described electric contacts <NUM>.

The lens control device <NUM> is a lens unit that includes a fixed lens group <NUM>, a zoom lens <NUM>, an aperture <NUM>, an image-stabilization lens <NUM>, and a focus lens <NUM> that form an image capture optical system. While the lenses <NUM>, <NUM>, <NUM>, and <NUM> are each usually constituted from a plurality of lenses, only one lens is illustrated here for simplicity.

The lens control device <NUM> includes a lens control unit <NUM> that communicates with a camera control unit <NUM> of the camera control device <NUM> via the electric contacts <NUM>. The lens control unit <NUM> is communicably connected to a zoom driving unit <NUM>, an aperture driving unit <NUM>, an image-stabilization driving unit <NUM>, and a focus driving unit <NUM> via a bus <NUM>.

A lens operation unit <NUM> includes operation members such as ring members for operating the zoom lens <NUM>, the aperture <NUM>, and the focus lens <NUM>, and a switch for enabling or disabling an image-stabilization function. When an operation member is operated as a result of a user operation being performed, the lens operation unit <NUM> outputs operation information corresponding to the operation type to the lens control unit <NUM>. The lens control unit <NUM> performs control in accordance with the operation information received from the lens operation unit <NUM>.

The lens control unit <NUM> performs arithmetic processing for controlling the lens control device <NUM>. The lens control unit <NUM> includes a processor, such as a CPU, for controlling the constituent elements of the lens control device <NUM>.

The lens control unit <NUM> communicates with the camera control unit <NUM> of the camera control device <NUM> via electric contacts to receive control information from the camera control unit <NUM> and transmit lens information (optical information, etc.) held by the lens control device <NUM> to the camera control device <NUM> in response to transmission requests from the camera control unit <NUM> (the communication between the lens control unit <NUM> and the camera control unit <NUM> is hereinafter referred to as "lens communication").

Furthermore, the lens control unit <NUM> controls the zoom driving unit <NUM>, the aperture driving unit <NUM>, and the focus driving unit <NUM> in accordance with the operation information from the lens operation unit <NUM>. In addition, the lens control unit <NUM> controls the zoom driving unit <NUM>, the aperture driving unit <NUM>, the image-stabilization driving unit <NUM>, and the focus driving unit <NUM> in accordance with the control information from the camera control unit <NUM> of the camera control device <NUM>.

The zoom driving unit <NUM> changes the focal distance by driving the zoom lens <NUM>. The aperture driving unit <NUM> adjusts the light amount during shooting by driving the aperture <NUM> and adjusting the opening size of the aperture <NUM>. The image-stabilization driving unit <NUM> reduces camera shake by driving the image-stabilization lens <NUM> in accordance with the shake of the lens control device <NUM>. The focus driving unit <NUM> controls the focus state by driving the focus lens <NUM>.

The camera control device <NUM> is a camera body that generates image data by capturing a subject image transmitted through the lens control device <NUM>.

The camera control unit <NUM> performs arithmetic processing for controlling the camera control device <NUM>. The camera control unit <NUM> includes a processor, such as a CPU, for controlling the constituent elements of the camera control device <NUM>.

The camera control unit <NUM> communicates with the lens control unit <NUM> of the lens control device <NUM> via the electric contacts <NUM>. The camera control unit <NUM> transmits control signals to the lens control unit <NUM> to drive the lenses and the aperture in the lens control device <NUM>, and receives, from the lens control unit <NUM>, the lens information (optical information, etc.) held by the lens control device <NUM>. The electric contacts <NUM> include a pair of communication terminals (camera-side terminal and lens-side terminal) corresponding to a pair of communication lines via which the lens control device <NUM> and the camera control device <NUM> can bidirectionally communicate.

A light flux transmitted through the lens control device <NUM> is made into an image by the image capture optical system and received by an image sensor <NUM> as an optical image (subject image) of a subject. The subject image received by the image sensor <NUM> is converted into an electric signal by a photoconversion element such as a CMOS sensor of the image sensor <NUM>. The electric signal generated by the image sensor <NUM> is processed as an image signal (image data) by an image capture signal processing unit <NUM>.

In the image sensor <NUM>, a plurality of pixels are arrayed two-dimensionally. The plurality of pixels each include a pair of photoelectric conversion units (photodiodes), and one microlens that is provided so as to correspond to the photoelectric conversion units. Light incident on each pixel is subjected to pupil division by the microlens, and a pair of subject images are formed on the pair of photoelectric conversion units. The photoelectric conversion units constituting the pair each accumulate electric charge by performing photoelectric conversion.

A divided-image generation unit <NUM> reads, as focus detection signals (an A image signal and a B image signal), output signals having voltages in accordance with the electric charge accumulated in the pair of photoelectric conversion units in each pixel. Furthermore, the divided-image generation unit <NUM> combines the A image signal and the B image signal read from each pixel of the image sensor <NUM>. The A image signal and the B image signal are used for focus detection according to the phase difference detection method. The signal obtained by combining the A image signal and the B image signal is used to generate the image signal.

A focus detection unit <NUM> calculates the phase difference between the A image signal and the B image signal by performing a correlation operation on the A image signal and the B image signal. Furthermore, the focus detection unit <NUM> calculates a defocus amount indicating a focusing state of the image capture optical system from the phase difference between the A image signal and the B image signal.

Based on defocus amounts calculated by the focus detection unit <NUM>, the camera control unit <NUM> performs autofocus (AF) processing in which the focus lens <NUM> is driven by controlling the lens control unit <NUM> and the focus driving unit <NUM> of the lens control device <NUM>. Thus, a focusing state of the image capture optical system can be achieved.

The image data output from the image capture signal processing unit <NUM> is output to a sensor control unit <NUM>, and is temporarily stored in a volatile memory <NUM>. Furthermore, the image data is stored to a recording medium <NUM>, which is a memory card or the like, after correction processing and compression processing are executed thereon by an image processing unit <NUM>.

Furthermore, concurrently with the AF processing, processing for decreasing or increasing the size of the image data stored in the volatile memory <NUM> to a size that is most suitable for a display unit <NUM> that is built into the camera control device <NUM> or attached to the camera control device <NUM> is performed by a display control unit <NUM> in accordance with control by the camera control unit <NUM>. The image data processed into the most-suitable size is temporarily stored in the volatile memory <NUM> once again, this time in an area that is different from that prior to the processing. Furthermore, the display control unit <NUM> outputs the image data to the display unit <NUM> in a state in which various types of image information such as shooting settings are overlaid on the image data as characters, icons, and the like, and the display unit <NUM> displays the image data having various types of information overlaid thereon on a display device that is constituted from an organic EL or liquid-crystal panel, or the like. Thus, the user can monitor an image (live view image) captured by the image sensor <NUM> in real time.

In accordance with control by the camera control unit <NUM>, an image-stabilization control unit <NUM> controls an image-stabilization driving unit <NUM> and moves the image sensor <NUM> in a direction in which camera shake is reduced. Furthermore, by cooperating with the image-stabilization driving unit <NUM> of the lens control device <NUM>, the image-stabilization driving unit <NUM> can also drive the image sensor <NUM> and the image-stabilization lens <NUM> in an interlocked state. In this case, image stabilization stronger than that when the image sensor <NUM> and the image-stabilization lens <NUM> are individually driven can be achieved.

An operation unit <NUM> is constituted from operation members such as switches, buttons, rings, and levers for receiving user operations, and outputs, to the camera control unit <NUM>, operation signals corresponding to the operation members operated by the user. The camera control unit <NUM> outputs control signals to the constituent elements of the camera control device <NUM> based on the operation signals and controls the constituent elements. For example, the operation members also include a touch panel that is formed integrally with the display unit <NUM>, etc..

The volatile memory <NUM> is a RAM, for example. Not only is the volatile memory <NUM> used to temporarily store image data, but the volatile memory <NUM> is also used as a work area for temporarily storing data used in processing for controlling the constituent elements of the camera control device <NUM>, the lens information acquired from the lens control device <NUM>, etc..

A non-volatile memory <NUM> has stored therein a control program that is necessary for the camera <NUM> to operate. When the power is turned on by a user operation and the camera <NUM> is activated, the control program stored in the non-volatile memory <NUM> is loaded to a section of the volatile memory <NUM>. The camera control unit <NUM> controls the operation of the camera <NUM> in accordance with the control program loaded to the volatile memory <NUM>.

In a calibration chart (hereinafter "chart") that the camera <NUM> shoots in order to correct lens distortion, position detection markers <NUM>, 304a, and 304b are provided at the center position and end portions on both sides of the center in a direction that is horizontal to the ground, as in the image (captured image) <NUM> illustrated in <FIG> obtained by shooting the chart. It is sufficient that the positions of the markers <NUM>, 304a, and 304b can be detected, and a method of forming specific patterns in the center and end portions of the chart and detecting the specific patterns may also be adopted, for example. A chart characterized as such is arranged horizontally with respect to the ground and is shot for calibration.

Next, calibration-related processing by the camera <NUM> according to the present embodiment will be described.

<FIG> is a plan view schematically illustrating positional relationships between the chart and the camera according to the present embodiment.

In <FIG>, A is the optical center (optical axis) of the camera <NUM>, Θ is the angle of view of the camera <NUM>, and O is the center of a chart <NUM>. The present embodiment allows the user to easily correct the positional relationship between the camera <NUM> and the chart <NUM> from a state <NUM> in which the camera <NUM> and the chart <NUM> are not directly facing one another to a state <NUM> in which the camera <NUM> and the chart <NUM> are directly facing one another. Thus, in the present embodiment, the angle Φ formed by a line AO connecting the chart center O and the optical center A of the camera <NUM> and a normal line Z extending from the chart center O, and the distance H between the normal line Z and the optical center A of the camera <NUM> are calculated. Furthermore, in the present embodiment, the user can easily perform correction to the directly facing positional relationship between the camera <NUM> and the chart <NUM> as a result of information indicating the amount and direction in which the camera <NUM> is to be rotated and moved being presented to the user based on the deviation angle Φ and the deviation movement amount H. In the present embodiment, the directly facing positional relationship between the camera <NUM> and the chart <NUM> is a state in which the angle Φ formed by the line AO connecting the chart center O and the optical center A of the camera <NUM> and the normal line Z extending from the chart center O, and the distance H between the normal line Z and the optical center A of the camera <NUM> have each fallen below a corresponding predetermined determination threshold.

<FIG> is a flowchart illustrating a processing procedure during the calibration according to the present embodiment.

Note that the processing in <FIG> is realized by the camera control unit <NUM> of the camera control device <NUM> controlling the constituent elements of the camera control device <NUM> by executing the program stored in the non-volatile memory <NUM>. Furthermore, the processing in <FIG> is started in step S401 when the user operates the operation unit <NUM> and inputs a calibration start instruction to the camera <NUM>.

Processing for correction to the directly facing state of the camera <NUM> relative to the chart <NUM> is performed in step S402, and processing advances to step S403. The processing in step S402 will be described later with reference to <FIG>.

Processing for correcting the distance between the center of the chart <NUM> and the optical center of the camera <NUM> in the directly facing state to an appropriate distance is performed in step S403, and processing advances to step S404. The processing in step S403 will be described later with reference to <FIG> and <FIG>.

The calibration can be performed accurately because shooting can be performed in a state in which the camera <NUM> has been placed in the directly facing state relative to the chart <NUM>, and the chart <NUM> is included within a shootable range (within the angle of view) of the camera <NUM> through the processing in steps S402 and S403, as described above.

Next, the processing for correction to the directly facing state in step S402 in <FIG> will be described with reference to <FIG>.

<FIG> is a flowchart illustrating the processing for correction to the directly facing state in step S402 in <FIG>.

Processing is started in step S501 and advances to step S502.

In step S502, the camera control unit <NUM> executes AF processing using an image (captured image) of the chart <NUM> captured using the image sensor <NUM>.

In step S503, the camera control unit <NUM> performs chart-center detection processing by detecting, in the captured image acquired from the image processing unit <NUM>, the center detection marker (<NUM> in <FIG>) indicating the chart center.

In step S504, the camera control unit <NUM> determines whether or not the distance between the chart center acquired in step S503 and the center of the captured image (screen center) is less than a predetermined determination threshold. In order to facilitate the operation of positioning the camera <NUM> and the chart <NUM> relative to one another, assistance may be provided such that a mark is displayed at the screen center using the display control unit <NUM>. The camera control unit <NUM> advances processing to step S505 upon determining that the distance between the chart center and the screen center is more than or equal to the predetermined determination threshold. The camera control unit <NUM> advances processing to step S506 upon determining that the distance between the chart center and the screen center is less than the predetermined determination threshold.

In step S505, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, first information indicating to the user that the camera <NUM> is to be moved so that the screen center approaches the chart center. Subsequently, the camera control unit <NUM> returns processing to step S502, and repeats the processing from step S502 to step S505 until the distance between the chart center and the screen center falls below the predetermined determination threshold in step S504.

In step S506, the camera control unit <NUM> performs chart-end-portion detection processing by detecting, in the captured image acquired from the image processing unit <NUM>, the end-portion detection markers (304a and 304b in <FIG>) indicating the chart end portions, and stores the detected number of chart end portions in the volatile memory <NUM>.

In step S507, the camera control unit <NUM> acquires the defocus amount of each pixel from the focus detection unit <NUM>, and, based on the defocus amount, calculates a focus driving amount for driving the focus lens <NUM> so that the image capture optical system is in the focusing state. Furthermore, the camera control unit <NUM> calculates a subject distance based on the focus driving amount, the current focus-lens position information, and focal distance information. Thus, a defocus map indicating the subject distance at each position of the captured image can be acquired.

In step S508, the camera control unit <NUM> performs processing for calculating an angle variable Ψ that will be described later with reference to <FIG>.

In step S509, the camera control unit <NUM> calculates the deviation angle Φ based on the angle variable Ψ calculated in step S508.

<FIG> are plan views schematically illustrating positional relationships between the chart and the camera in the processing for correction to the directly facing state in <FIG>. <FIG> is a diagram illustrating a positional relationship between the chart <NUM> and the camera <NUM> in a case in which the screen ends (both ends of the angle of view) of the camera <NUM> are located within the chart <NUM>. <FIG> is a diagram illustrating a positional relationship between the chart <NUM> and the camera <NUM> in a case in which one end of the angle of view of the camera <NUM> is located within the chart <NUM>. <FIG> is a diagram illustrating a positional relationship between the chart <NUM> and the camera <NUM> in a case in which one end of the angle of view of the camera <NUM> is located within the chart <NUM> and the other end is not. <FIG> is a diagram illustrating a positional relationship between the chart <NUM> and the camera <NUM> in a case in which the chart <NUM> is located within the angle of view of the camera <NUM>. In the examples in <FIG>, A is the optical center (the optical axis of the image capture optical system) of the camera <NUM>, O is the chart center, B is a limit position at which subject distance can be detected as a result of the camera <NUM> performing ranging, and the angle OAB is the angle variable Ψ.

Angle-of-view information Θ of the camera <NUM> can be calculated using Equation <NUM> below, where D is the distance from the optical center A of the camera <NUM> to the chart center O, l [mm] is the focal distance of the camera <NUM>, and s [mm] is the image-sensor size of the camera <NUM>.

Furthermore, using the angle variable Ψ, the following relational expressions hold true regarding the angle Θc formed by AO and the chart <NUM> based on the law of cosines, focusing on the triangle OAB.

In this case, the deviation angle Φ can be calculated by substituting distance information DL and D for AB and AO in Equation <NUM> above. The distance information D is information corresponding to the distance from the optical center A of the camera <NUM> to the chart center O. The distance information DL is information corresponding to the distance from the optical center A of the camera <NUM> to the angle-of-view end B. If the end-portion detection markers are successfully detected, a value calculated from the defocus amount at a chart end portion is substituted for AB, and, if the end-portion detection markers are not successfully detected, a value calculated from the defocus amount at an end portion (screen end) of the captured image is substituted for AB. Furthermore, the subject distance at the chart center O is substituted for AO because the center-position detection marker is successfully detected.

Returning to <FIG>, in step S510, the camera control unit <NUM> calculates the deviation distance H to the chart <NUM>. The deviation distance H can be calculated from Equation <NUM> below.

The deviation distance H can be calculated by substituting the deviation angle Φ into Equation <NUM> above and substituting the distance D for AO in Equation <NUM>.

In step S511, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, information based on the deviation angle Φ and the deviation distance H calculated in steps S509 and S510.

<FIG> illustrates an example of display of the information based on the deviation angle Φ and the deviation distance H displayed on the display unit <NUM> in step S511. On the screen of the display unit <NUM>, a captured image <NUM> of the chart <NUM> is displayed, and information <NUM> indicating the amount and direction in which the camera <NUM> is to be rotated and moved is displayed based on the deviation angle Φ and the deviation distance H necessary for correcting the position of the camera <NUM> to place the camera <NUM> and the chart <NUM> in the directly facing positional relationship. The user can place the camera <NUM> and the chart <NUM> in the directly facing positional relationship by performing fine adjustment of the position of the camera <NUM> while viewing the rotation direction and moving direction indicated in the information <NUM>.

In step S512, the camera control unit <NUM> determines whether or not the number of chart end portions detected in step S506 is two. Upon determining that the number of chart end portions is one or less, the camera control unit <NUM> determines that the chart <NUM> is not located within the angle of view of the camera <NUM> (the captured image), and advances processing to step S513. Upon determining that the number of chart end portions is two, the camera control unit <NUM> determines that the chart <NUM> is located within the angle of view of the camera <NUM> (the captured image), and advances processing to step S514.

In step S513, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, second information indicating to the user that the camera <NUM> is to be moved so that the two chart end portions are located within the angle of view of the camera <NUM> (the captured image). Subsequently, the camera control unit <NUM> returns processing to step S502, and repeats the processing from step S502 to step S513 until the two chart end portions are located within the angle of view of the camera <NUM> (the captured image) in step S512.

In step S514, the camera control unit <NUM> determines whether or not the deviation angle Φ and the deviation distance H are each less than the corresponding predetermined determination threshold. The camera control unit <NUM> terminates processing in step S516 upon determining that the deviation angle Φ and the deviation distance H are each less than the corresponding determination threshold, and advances processing to step S515 upon determining that the deviation angle Φ and the deviation distance H are each more than or equal to the determination threshold.

In step S515, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, third information indicating the amount and direction in which the camera <NUM> is to be rotated and moved based on the deviation angle Φ and the deviation distance H calculated in steps S509 and S510. Subsequently, the camera control unit <NUM> returns processing to step S502, and repeats the processing from step S502 to step S515 until the deviation angle Φ and the deviation distance H each fall below the corresponding determination threshold in step S514.

Note that a configuration may be adopted such that the determination thresholds in step S504 and S514 can be changed by the user using the operation unit <NUM>, and the smaller the values, the more accurately the camera <NUM> and the chart can be placed in the directly facing positional relationship.

<FIG> is a flowchart illustrating the processing for correction to the appropriate distance in step S403 in <FIG>. <FIG> is a plan view schematically illustrating positional relationships between the chart and the camera in the processing for correction to the appropriate distance in step S403 in <FIG>.

As illustrated in <FIG>, A is the optical center of the camera <NUM> prior to the correction in <FIG>, B is the left end of the chart <NUM>, O is chart center, and Θ is the angle of view of the camera <NUM>. The processing illustrated in <FIG> is processing for correcting the distance between the camera <NUM> and the chart <NUM> to the appropriate distance by moving the camera <NUM> in a direction that is perpendicular to the chart center (front-rear direction; normal line direction).

Processing is started in step S801 in <FIG> and advances to step S802.

In step S802, the camera control unit <NUM> executes AF processing using an image (captured image) of the chart <NUM> captured using the image sensor <NUM>.

In step S803, the camera control unit <NUM> performs chart-center detection processing by detecting, in the captured image acquired from the image processing unit <NUM>, the center detection marker (<NUM> in <FIG>) indicating the chart center.

In step S804, the camera control unit <NUM> determines whether or not the distance between the chart center acquired in step S803 and the center of the captured image (screen center) is less than a predetermined determination threshold. In order to facilitate the operation of positioning the camera <NUM> and the chart <NUM> relative to one another, assistance may be provided such that a mark is displayed at the screen center using the display control unit <NUM>. The camera control unit <NUM> advances processing to step S805 upon determining that the distance between the chart center and the screen center is more than or equal to the predetermined determination threshold. The camera control unit <NUM> advances processing to step S806 upon determining that the distance between the chart center and the screen center is less than the predetermined determination threshold.

In step S805, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, fourth information indicating to the user that the camera <NUM> is to be moved so that the screen center approaches the chart center. Subsequently, the camera control unit <NUM> returns processing to step S802, and repeats the processing from step S802 to step S805 until the distance between the chart center and the screen center falls below the predetermined determination threshold in step S804.

In step S806, the camera control unit <NUM> performs chart-end-portion detection processing by detecting, in the captured image acquired from the image processing unit <NUM>, the end-portion detection markers (304a and 304b in <FIG>) indicating the chart end portions, and stores the detected number of chart end portions in the volatile memory <NUM>.

In step S807, the camera control unit <NUM> acquires the defocus amount of each pixel from the focus detection unit <NUM>, and, based on the defocus amount, calculates a focus driving amount for driving the focus lens <NUM> so that the image capture optical system is in the focusing state. Furthermore, the camera control unit <NUM> calculates a subject distance based on the focus driving amount, the current focus-lens position information, and focal distance information. Thus, a defocus map indicating the subject distance at each position of the captured image can be acquired.

In step S808, as illustrated in <FIG>, the camera control unit <NUM> calculates distance information D from the optical center of the camera <NUM> to the chart center O, and distance information DL from the optical center of the camera <NUM> to the chart end portion B from the chart center position, the chart end portion position, and the defocus amounts acquired in steps S803, S806, and S807. Note that, while the left-side chart end portion B is chosen in the example in <FIG>, the right-side chart end portion may be chosen.

In step S809, the camera control unit <NUM> calculates the chart size L using the distance information DL and D calculated in step S808. In <FIG>, the chart size L can be calculated using Equation <NUM> below by applying the Pythagorean theorem to the triangle AOB.

In step S810, the camera control unit <NUM> calculates the appropriate distance D1 of the subject distance D at the chart center O. The appropriate distance D1 can be calculated using Equation <NUM> below.

In this case, a movement distance ΔD of the subject distance D to the appropriate distance D1 at the chart center O can be calculated using Equation <NUM> below.

In step S811, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, information regarding the movement amount ΔD of the camera <NUM> to the appropriate distance D1 calculated in step S811. Thus, the user can perform fine adjustment of the position of the camera <NUM> while viewing the information regarding the movement amount ΔD.

In step S812, the camera control unit <NUM> determines whether or not the camera <NUM> and the chart <NUM> have approached one another to the appropriate distance D1, or in other words, whether or not the movement distance ΔD is less than a predetermined determination threshold. Upon determining that the camera <NUM> and the chart <NUM> have approached one another to the appropriate distance D1, or in other words, that the movement distance ΔD is less than the predetermined determination threshold, the camera control unit <NUM> advances processing to step S813. Upon determining that the camera <NUM> and the chart <NUM> have not approached one another to the appropriate distance D1, or in other words, that the movement distance ΔD is more than or equal to the predetermined determination threshold, the camera control unit <NUM> returns processing to step S802, and repeats the processing in steps S802 to S812 until the camera <NUM> and the chart <NUM> approach one another to the appropriate distance D1, or in other words, the movement distance ΔD falls below the predetermined determination threshold.

In step S813, the camera control unit <NUM> controls the display control unit <NUM> and displays, on the display unit <NUM>, fifth information indicating that the camera <NUM> and the chart <NUM> have approached one another to the appropriate distance D1, and terminates processing in step S814.

Note that a configuration may be adopted such that the determination thresholds in step S804 and S812 can be changed by the user using the operation unit <NUM>, and the smaller the values, the more accurately the distance between the camera <NUM> and the chart can be brought closer to the appropriate distance D1.

Here, with reference to <FIG>, the processing in step S508 in <FIG> for calculating the angle variable Ψ (angle OAB) to be used to calculate the deviation angle Φ will be described.

<FIG> is a flowchart illustrating the angle-variable calculation processing in step S508 in <FIG>.

Processing is started in step S601 in <FIG> and advances to step S602.

In step S602, the camera control unit <NUM> refers to the number of chart end portions that have been detected and stored in the volatile memory <NUM> in step S506 in <FIG>, and determines whether or not the number of chart end portions is two. The camera control unit <NUM> advances processing to step S604 upon determining that the number of chart end portions is two, and advances processing to step S603 upon determining that the number of chart end portions is one or less.

In step S603, the camera control unit <NUM> substitutes a value obtained by halving the angle of view Θ (Θ/<NUM>; first angle-of-view information) for the angle variable Ψ. For example, this corresponds to the cases in <FIG> (cases in which the angle-of-view end B is located within the chart).

In step S604, the camera control unit <NUM> calculates an approximate angle λ (second angle-of-view information), and substitutes the approximate angle λ for the angle variable Ψ. For example, this corresponds to the case in <FIG> (case in which the two ends of the angle of view are both located outside the chart end portions). In the example in <FIG>, the value (Θ/<NUM>) obtained by halving the angle of view Θ cannot be adopted as the angle variable Ψ because neither one of the two ends of the angle of view is located within the chart. Thus, the camera control unit <NUM> calculates the approximate angle λ based on Equation <NUM> below using the ratio between the distance OC from the angle-of-view center (chart center O) to the angle-of-view end C and the distance OB from the angle-of-view center (chart center O) to the chart end B in the captured image.

In step S605, the camera control unit <NUM> substitutes the approximate angle λ calculated in step S604 for the angle variable Ψ, and advances processing to step S509 in <FIG>.

As described above, according to the present embodiment, information regarding the direction and amount in which the camera <NUM> is to be rotated and moved relative to the chart center O in order to correct the position of the camera <NUM> to the state in which the camera <NUM> is directly facing the chart <NUM> is presented to the user. Furthermore, according to the present embodiment, information regarding the movement amount ΔD of the camera <NUM> to the appropriate distance D1 is presented to the user in the state in which the camera <NUM> and the chart <NUM> are directly facing one another so that the distance between the camera <NUM> and the chart <NUM> can be corrected to the appropriate distance D1. As a result of more detailed information regarding operations that need to be performed by the user during calibration being presented in such a manner, the time and effort it takes to carry out operations necessary for positioning the camera <NUM> and the chart <NUM> relative to one another during calibration can be reduced.

Various embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a 'non-transitory computer-readable storage medium') to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s).

Claim 1:
An image capture apparatus that is configured to capture, by an image sensor, an image of a chart for correcting distortion of a lens, comprising:
first obtaining means (<NUM>) configured to obtain a deviation angle (Φ) indicating an angle of deviation of the image capture apparatus from a directly facing positional relationship relative to the chart based on first distance information (D) from an optical center of the image capture apparatus to a center of the chart, and second distance information (DL) from the optical center of the image capture apparatus to a first end portion of the chart;
second obtaining means (<NUM>) configured to obtain a deviation distance (H) indicating a distance of deviation from the directly facing positional relationship based on the deviation angle and the first distance information;
third obtaining means (<NUM>) configured to obtain an appropriate distance (D1) between the chart and the image capture apparatus in the directly facing positional relationship based on angle-of-view information and a size (L) of the chart; and
presenting means (<NUM>) configured to present information indicating an amount and direction in which the image capture apparatus is to be rotated and moved so as to place the camera and the chart in the directly facing positional relationship, based on the deviation angle and the deviation distance, and present information (ΔD) regarding the appropriate distance in a case in which the deviation distance and the deviation angle have each fallen below a predetermined determination threshold, wherein
the first obtaining means (<NUM>) is configured to obtain the deviation angle (Φ)additionally based on an angle-of-view (Θ) of the image capture apparatus,
the angle-of-view (Θ) is a shootable range of the image capture apparatus.