Digital photographing apparatus and method of controlling the same

A digital photographing apparatus and a method of controlling the digital photographing apparatus are provided. The digital photographing apparatus stores an image signal in a memory at the same time with the calculation of a horizontal AF evaluation value with respect to the image signal, and calculates a vertical AF evaluation value by using the stored image signal. Accordingly, exact AF detection may be performed with respect to images of all patterns.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2009-0111542, filed on Nov. 18, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

The invention relates to a digital photographing apparatus and a method of controlling the same.

In digital photographing apparatuses such as digital cameras and digital camcorders, focus adjustment is performed to obtain clear images. For focus adjustment, a contrast auto focusing (AF) method is usually used. The contrast AF method comprises calculating an AF evaluation value with respect to an image signal generated by an imaging device and detecting a focus position from the AF evaluation value to drive a focus lens.

In detail, in the contrast AF method, from among image signals generated by an imaging device including a plurality of photoelectric converting units that are arranged in an n×m matrix, image signals in a row direction, that is, image signals in a horizontal direction, from a first row to an n-th row, are sequentially read, and AF detection is performed with respect to the read horizontal image signals, thereby calculating AF evaluation values. Then a time when a peak of the AF evaluation values exists is detected from the variation of the generated AF evaluation values. Then a lens position at the detected time is calculated and a lens is driven to the calculated lens position, thereby performing AF.

SUMMARY

Various embodiments of the invention provide a digital photographing apparatus capable of performing exact auto focusing (AF) for an image of any pattern.

According to an embodiment of the invention, there is provided a digital photographing apparatus comprising: an imaging device comprising a plurality of photoelectric converting units for converting image light from a subject into an electric signal to generate an image signal; an imaging device control unit for generating a timing signal and controlling such that horizontal image signals are sequentially read among the image signals in synchronization with the timing signal; a memory for storing the read horizontal image signals; an AF evaluation value calculation unit for calculating horizontal AF evaluation values by using the sequentially read horizontal image signals and calculating vertical AF evaluation values by sequentially reading vertical image signals from the image signals stored in the memory; and a main control unit for performing an AF operation by using the horizontal AF evaluation values or the vertical AF evaluation values.

When the calculation of the horizontal AF evaluation values is completed, the vertical AF evaluation values may be calculated.

The horizontal AF evaluation values and the vertical AF evaluation values may be calculated for every predetermined number of timing signals.

The predetermined number may vary according to a period of the timing signal.

A ratio of the horizontal AF evaluation values and the vertical AF evaluation values may vary according to time needed for calculation of the vertical AF evaluation values.

The main control unit may perform an AF operation by using the vertical AF evaluation values when the horizontal AF evaluation values are less than a reference value or by using the horizontal AF evaluation values when the vertical AF evaluation values are less than a reference value.

When a focus position is not to be detected by using either the horizontal AF evaluation values or the vertical AF evaluation values, the focus position may be detected by using other AF evaluation values.

The main control unit may perform an AF operation by using the horizontal AF evaluation values while driving a lens from one side to the other side, and an AF operation is performed by using the vertical AF evaluation values while driving the lens in a reverse direction.

The horizontal image signals may be stored in the memory at the same time with the calculation of the horizontal AF evaluation values.

The AF evaluation value calculation unit may start calculation of the vertical AF evaluation values when all of the image signals included in the AF area are stored in the memory by reading the horizontal image signals.

According to another embodiment of the invention, there is provided a method of controlling a digital photographing apparatus, the method comprising: generating an image signal by converting image light from a subject into an electric signal; sequentially reading horizontal image signals among the image signal in synchronization with a timing signal; storing the read horizontal image signals; calculating a horizontal AF evaluation value by using the sequentially read horizontal image signals; sequentially reading vertical image signals from the image signal stored in a memory; calculating a vertical AF evaluation value by using the read vertical image signals; and performing an AF operation by using the horizontal AF evaluation values or the vertical AF evaluation values.

DETAILED DESCRIPTION

The invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

Structure and Operation of Digital Photographing Apparatus

FIG. 1is a schematic view illustrating a digital photographing apparatus1according to an embodiment of the invention.

Referring toFIG. 1, the digital photographing apparatus1includes an interchangeable lens100and a main body portion200. The interchangeable lens100includes a focal point detection function, and the main body portion200has the function of allowing the interchangeable lens100to drive a focus lens104.

The interchangeable lens100, hereinafter, referred to as the lens100, includes an imaging optical system101, a zoom lens position detecting sensor103, a lens driving actuator105, a focus lens position detecting sensor106, an aperture driving actuator108, a lens control unit110, and a lens mount109.

The imaging optical system101includes a zoom lens102for zoom adjustment, the focus lens104for changing a focal position, and an aperture107. The zoom lens102and the focus lens104may be formed of a lens group including a plurality of lenses.

The zoom lens position detecting sensor103and the focus lens position detecting sensor106sense a position of the zoom lens102and the focus lens104, respectively. Timing of detecting the position of the focus lens104may be set by the lens control unit110or a camera control unit209which is described later. For example, timing for detecting a position of the focus lens104may be a timing of performing AF detection from an image signal.

The lens driving actuator105and the aperture driving actuator108are controlled by the lens control unit110to drive the focus lens104and the aperture107, respectively. In particular, the lens driving actuator105drives the focus lens104in an optical axis direction.

The lens control unit110includes a first timer111for time measurement. Also, the lens control unit110transmits detected position data of the focus lens104to the main body portion200. If the position of the focus lens104is changed or if a request for position data of the focus lens104is sent from the camera control unit209, the lens control unit110may transmit the detected position data of the focus lens104to the main body portion200. Also, the first timer111may be reset by a reset signal transmitted from the main body portion200, and the timings of the lens100and the main body portion200may be synchronized by the resetting operation.

The lens mount109includes a communication pin of the lens100, which is coupled to a communication pin of a camera to be described later, thereby being used as a transmission path for data, control signals, etc.

Next, a structure of the main body portion200will be described.

The main body portion200may include an electronic view finder (EVF)201, a shutter203, an imaging device204, an imaging device control unit205, a display unit206, a manipulation unit207, a camera control unit209, and a camera mount208.

The EVF201may include a liquid crystal display (LCD)202, and an image being captured may be viewed in real-time through the EVF201.

The shutter203determines the time during when light is incident to the imaging device204, that is, an exposure time.

The imaging device204captures image light that has transmitted through the imaging optical system101of the lens100to generate an image signal. The imaging device204may include a plurality of photoelectric converting units that are arranged in a matrix and a vertical and/or horizontal transmission path for reading an image signal from the photoelectric converting units by moving charges. The imaging device204may be a charge-coupled device (CCD) sensor, a complementary metal-oxide semiconductor (CMOS) sensor or the like.

The imaging device control unit205generates a timing signal, and controls the imaging device204to be synchronized with the timing signal to capture an image. Also, the imaging device control unit205allows that horizontal image signals are sequentially read when charge accumulation is completed in each scanning line. The read horizontal image signals are used in AF detection in the camera control unit209.

The manipulation unit207is a unit through which various commands of the user are input for manipulating the digital photographing apparatus1. The manipulation unit207may include various buttons such as a shutter release button, a main switch, a mode dial, a menu button or the like.

The camera control unit209performs AF detection with respect to an image signal generated by the imaging device204to calculate an AF evaluation value. Also, the camera control unit209stores AF evaluation values at each of the AF detection times according to timing signals generated by the imaging device control unit205, and calculates a focus position by using lens position information transmitted from the lens100and the stored AF evaluation values. Results of the calculation of the focus position are transmitted to the lens100. The camera control unit209may include a second timer228for time measurement, wherein the second timer228may be reset at the same time with the first timer111so that the lens100and the main body portion200may measure identical times.

The camera mount208includes a communication pin of the main body portion200.

Hereinafter, an operation of the lens100and the main body portion200will be described.

When photographing a subject, a main switch included in the manipulation unit207is manipulated to initiate an operation of the digital photographing apparatus1. The digital photographing apparatus1provides a live view display in the following manner.

Image light of a subject that has transmitted through the imaging optical system101is incident to the imaging device204. Here, the shutter203is open. The incident image light is converted into an electric signal in the imaging device204, thereby generating an image signal. The imaging device204is operated by a timing signal generated by the imaging device control unit205. The generated image signal of the subject is converted to data displayable by the camera control unit209and is output to the EVF201and the display unit206. This operation is referred to as a live view display, and a live view image displayed by live view display is a moving image being continuously displayed.

After a live view display is performed, when a shutter release button, which is one of the inclusions of the manipulation unit207, is half-pressed, the digital photographing apparatus1initiates an AF operation. An AF operation is performed by using an image signal generated by the imaging device204. In a contrast AF method, a focus position is calculated based on AF evaluation values related to contrast values, and the lens100is driven based on results of the calculation. The AF evaluation values are calculated by the camera control unit209. The camera control unit209calculates information for controlling the focus lens104based on the AF evaluation values, and transmits the information to the lens control unit110via the communication pins included in the lens mount109and the camera mount208, respectively.

The lens control unit110controls the lens driving actuator105based on the received information to drive the focus lens104in an optical axis direction to perform an AF operation. A position of the focus lens104is monitored by the focus lens position detecting sensor106, thereby providing controlling feedback.

When the zoom lens102zooms by manipulation of the user, a position of the zoom lens102is detected by the zoom lens position detecting sensor103, and the lens control unit110varies AF control parameters of the focus lens104to perform AF again.

When a focal point of a subject image is adjusted in the above-described manner, the shutter release button is completely pressed (S2), and the digital photographing apparatus1performs exposure. The camera control unit209here completely closes the shutter, and transmits photometry information obtained until this point to the lens control unit110as aperture control information. The lens control unit110controls the aperture driving actuator108based on the aperture control information, and the aperture107gets smaller with appropriate aperture values. The camera control unit209controls the shutter203based on the photometry information, and opens the shutter204for an appropriate period of exposure time, thereby capturing a subject image that has been captured.

Image signal processing and compression are performed on the captured image, and the captured image is stored in a memory card212. Also, the captured image is output to the EVF201and the display unit206for displaying a subject at the same time. This image is called a quick view image.

A series of photographing operations are completed as in the above-described manner.

FIG. 2is a schematic view illustrating a digital photographing apparatus2according to another embodiment of the invention.

The digital photographing apparatus2has a similar structure and similar functions as the digital photographing apparatus1and thus the following description will focus on differences between them. In the digital photographing apparatus2, a lens100and a main body portion200are integrally formed, and thus the lens100is not changeable. Also, since the lens100and the main body portion200are integrally formed, the lens mount109and the camera mount208ofFIG. 1are not included. Accordingly, the camera control unit209directly controls the lens driving actuator105, the aperture driving actuator108, etc. to drive the zoom lens102, the focus lens104, and the aperture107. Also, the camera control unit209directly receives position information from the zoom lens position detecting sensor103and the focus lens position detecting sensor106. That is, the camera control unit209according to the current embodiment performs the function of the lens control unit110ofFIG. 1.

Also, according to the current embodiment, AF evaluation values and lens positions are synchronized by using the second timer228.

Structure and Operation of the Camera Control Unit

FIG. 3is a block diagram illustrating the camera control unit209according to an embodiment of the invention.

Referring toFIG. 3, the camera control unit209may include a pre processing unit220, a signal processing unit221, a compression/decompression unit222, a display controller223, a central processing unit (CPU)224, a memory controller225, an audio controller226, a card controller227, a second timer228, and a main bus230.

The camera control unit209transmits commands and data to each element via the main bus230.

The pre processing unit220receives an image signal generated by the imaging device204and performs calculations of auto white balance (AWB), auto exposure (AE), and AF. That is, AF evaluation values for focus adjusting, AE evaluation values for exposure adjustment, and AWB evaluation values for white balance adjustment are calculated. The AF evaluation values may include horizontal AF evaluation values denoting horizontal contrast and vertical AF evaluation values denoting vertical contrast. The horizontal AF evaluation values are calculated by directly receiving horizontal image signals read from the imaging device204. On the other hand, the vertical AF evaluation values may be calculated by storing the horizontal image signals in the memory210, which is described later, and then reading the stored horizontal image signals as a vertical image signal component. That is, the pre processing unit220may be an example of an AF evaluation value calculation unit.

The signal processing unit221performs a series of image signal processing operations such as gamma correction to create a live view image or a captured image that are displayable on the display unit206.

The compression/decompression unit222performs compression or decompression to an image signal to which image signal processing is performed. Regarding compression, for example, the image signal is compressed in a JPEG compression format or an H.264 compression format. An image file including image data generated by the compression is transmitted to the memory card212to be stored thereto.

The display controller223controls image output to a display screen such as the LCD202of the EVF201or the display unit206.

The CPU224controls operations of the units of the main body portion200ofFIG. 1overall. Also, the CPU224of the digital photographing apparatus1ofFIG. 1performs communication with the lens100.

The memory controller225controls the memory210that temporarily stores data such as a captured image or calculation information, and the audio controller226controls a microphone or speaker211. Also, the card controller227controls the memory card212that stores a captured image.

Meanwhile, when the horizontal image signals are read from the imaging device204, the memory controller225sequentially stores the read horizontal image signals to the memory210. The storage location of the horizontal image signals may be determined by the memory controller225. According to the current embodiment, a vertical image signal component needs to be sequentially read with respect to an image signal corresponding to an AF detection area subsequently. Accordingly, the memory controller225controls such that the horizontal image signals are stored in the memory210so that reading of the vertical image signal is easily performed.

The second timer228is reset with the first timer111at the same time, thereby measuring time.

Hereinafter, an operation of the camera control unit209will be described.

When manipulation of the manipulation unit207is sensed by the CPU224, the CPU224operates the imaging device control unit205via the pre processing unit220. The imaging device control unit205outputs a timing signal to operate the imaging device204. When an image signal is input to the pre processing unit220from the imaging device204, AWB and AE calculations are performed. Results of the AWB and AE calculations are sent to the imaging device control unit205so that image signals of appropriate color and appropriate exposure are obtained from the imaging device204.

When the operation of the digital photographing apparatus1or2is started, a live view display is conducted. The camera control unit209inputs an image signal of an image that is captured with appropriate exposure, to the pre processing unit221to calculate an AE evaluation value, etc. An image signal for a live view display is directly applied to the signal processing unit221without passing through the main bus230, and the signal processing unit221performs on the image signal image signal processing such as interpolation processing of pixels. An image signal to which image signal processing is performed passes through the main bus230and the display controller223and an image of the image signal is displayed on the LCD202or the display unit206. Basically, the live view display is renewed at 60 frames per second (fps) but is not limited thereto, and may also be renewed at, for example, 120 fps, 180 fps, or 240 fps. A renewal rate is set by the CPU224according to results of photometry or AF conditions, and setting of the renewal rate may be performed by the imaging device control unit205by changing a timing signal.

When a shutter release button is half-pressed, the CPU224senses inputting of a half-pressing signal S1, and commands the lens control unit110to initiate driving of the focus lens104for an AF operation via communication pins included in the camera mount208and the lens mount109. Alternatively, upon sensing inputting of a half-pressing signal S1, the CPU224directly controls driving of the focus lens104for an AF operation. That is, the CPU224may be an example of a main control unit.

The CPU224obtains an image signal from the imaging device204, and the pre processing unit220calculates an AF evaluation value. The AF evaluation value is calculated based on movement of the focus lens104. A position of the focus lens104at which contrast of a subject image is highest, that is, where an AF evaluation value is greatest, is calculated based on a change of AF evaluation values, and the focus lens104is moved to the calculated position. The above-described operations are referred to as an AF operation, and a live view image is continuously displayed during the AF operation. The image signal used for the live view image and the image signal used in calculating an AF evaluation value are the same image signal.

Meanwhile, in the digital photographing apparatus1using the lens100, as illustrated inFIG. 1, communication pins installed to the camera mount208and the lens mount109are used for communication between the lens100and the main body portion200, and normally, the communication pins operate in serial communication to transmit lens information of control information. In the serial communication, time delay is generated. However, if position information of the focus lens104with respect to an AF evaluation value is not recorded without a time delay, exact AF adjustment is not possible. In order that the main body unit200provides a timing for obtaining an AF evaluation value to the lens100or reduce time for transmitting a position of the focus lens104from the lens100to the main body portion200, the time delay of serial communication needs to be extremely reduced with respect to a moving speed of the focus lens104. However, it is difficult to extremely reduce the time delay of serial communication. Thus, a communication pin for adjusting synchronization may be installed. However, if communication pins that are used only for adjusting synchronization are included, the number of communication pins increases, thereby increasing the size of the camera mount208and the lens mount109and also the manufacturing costs of the digital photographing apparatus1. Accordingly, according to the current embodiment of the invention, a timer function for adjusting synchronization between the lens100and the main body portion200is included. Also, a predetermined communication pin is set to operate in real-time communication at first, and then after the timer function of the lens100is reset by the real-time communication, the communication pin is set to operate in serial communication, which is non-real-time communication.

A position of the focus lens104at which contrast is greatest, that is, a peak position of an AF evaluation value, may be calculated based on the knowledge of a track of positions of the focus lens104at which the imaging device204obtains an image signal and a transition in AF evaluation values.

Next, an AF area, which is an object of calculation of AF evaluation values when performing an AF operation, will be described.

FIG. 4illustrates an auto focusing (AF) area, andFIG. 5illustrates a scanning line in an area e8.FIG. 6is a conceptual diagram illustrating an image signal included in the area e8, divided into a plurality of vertical image signals.

As illustrated inFIG. 4, an AF area, which is divided into fifteen areas in a 3×5 formation symmetrically, is set. Hereinafter, the area e8will be described as an AF detection area according to various embodiments of the invention.

In the imaging device204, first through n-th scanning lines are sequentially arranged from top, and a plurality of scanning lines of AFareaL8[1] through AFareaL8[a] are included in the area e8as illustrated inFIG. 5. According to the controlling of the imaging device control unit205, the imaging device204sequentially outputs a horizontal image signal of the first scanning line to a horizontal image signal of the n-th scanning line.

Meanwhile, when dividing an image signal of the area e8in a vertical direction, the image signal is formed of b vertical image signals from AFareaL8[1] through AFareaL8[b]. A vertical image signal is not of a form that can be directly read from the imaging device204, and thus the read horizontal image signal is first stored in the memory210. The memory controller225reads a vertical image signal from the stored horizontal image signals later upon necessity.

Hereinafter, various examples of an AF operation by using AF evaluation values will be described in detail, wherein a digital photographing apparatus according to the embodiments of the invention is assumed to be the digital photographing apparatus1that uses the lens100ofFIG. 1.

First Embodiment

Hereinafter, an AF operation according to an embodiment of the invention will be described with reference toFIGS. 7,8,9A, and9B.

Operation of Digital Photographing Apparatus

FIG. 7is a timing diagram illustrating an AF operation of the digital photographing apparatus1, according to an embodiment of the invention.

Referring toFIG. 7, sequentially from top, timing diagrams of an accumulation initiation signal, a charge accumulation signal of a first scanning line, charge accumulation signals AFareaL8[1] through AFareaL8[a] used in AF detection, a charge accumulation signal of an n-th scanning line, and a reading initiation signal are illustrated. Also, a calculation timing for a horizontal AF evaluation value, a calculation timing for a vertical AF evaluation value, an AF detection central position, and lens position information at the timing corresponding to the central position for the AF detection are illustrated inFIG. 7.

When accumulation initiation signals p1, p2, . . . are applied, charges generated by image light that is incident to the first through n-th scanning lines are accumulated. When the accumulation of charges of the first scanning line is completed, reading initiation signals i0, i1, . . . of an image signal are generated. According to the reading initiation signal, horizontal image signals are read sequentially from the first scanning line. The read horizontal image signals are applied to the camera control unit209. After the accumulation of charges of AFareaL8[1] through AFareaL8[a] that are included in the area e8, which is an AF detection area, is completed, horizontal AF evaluation values L(s1), L(s2), . . . are calculated by using horizontal image signals read by the pre processing unit220. While the horizontal AF evaluation values are calculated, the focus lens104continuously moves at a predetermined speed.

According to the current embodiment, not only the horizontal AF evaluation values but also vertical AF evaluation values are calculated. In a conventional contrast AF method, an AF operation is performed only by using AF evaluation values obtained from scanning lines, that is, only based on horizontal AF evaluation values, and thus when a contrast of a subject is distributed in a vertical direction, for example, regarding horizontal striped patterns, it is difficult to adjust a focal point. Thus, according to the current embodiment of the invention, vertical AF evaluation values are calculated.

However, a vertical AF evaluation value cannot be directly calculated based on a horizontal image signal read from the imaging device204. Accordingly, referring to the timing diagram ofFIG. 7, when reading horizontal image signals of AFareaL8[1] through AFareaL8[a], the horizontal image signals of AFareaL8[1] through AFareaL8[a] are transmitted to the pre processing unit220and also to the memory210at the same time to be stored there.

When all of the horizontal image signals included in the AF detection area are stored in the memory210and a horizontal AF evaluation value L is detected by a read horizontal image signal, a vertical image signal is read. By sequentially reading vertical image signals and detecting contrast that exists in a vertical direction with respect to each of the vertical image signals, a vertical AF evaluation value V is calculated. An image signal stored in the memory210may be read by using a direct memory access (DMA) method. Also, an operation of reading a vertical image signal from the memory210may take a shorter time than reading a horizontal image signal from the imaging device204.

According to the current embodiment of the invention, a vertical AF evaluation value V is calculated before a horizontal image signal of an AF detection area of a subsequent period is read, and then AF detection in a horizontal direction of the subsequent period starts again.

A horizontal AF evaluation value L and a vertical AF evaluation value V are calculated for every frame by using the above-described operations.

Meanwhile, in order to detect a peak value of AF evaluation values, horizontal AF evaluation values L(s1), L(s2), . . . that are calculated for every frame and timings at which image signals used for calculating the horizontal evaluation values are obtained need to be known. The timings that the image signals are obtained are assumed to be a central time point of a period of charge accumulation times from AFareaL8[1] through AFareaL8[a], that is, a central time point between a charge accumulation initiation time of AFareaL8[1] and a charge accumulation end time of AFareaL8[a]. A detection central position illustrated inFIG. 7corresponds to a timing when an image signal is obtained.

A lens position disposed under the detection central position corresponds to a position of the focus lens104corresponding to the detection central position. A position of the focus lens104may be obtained by communication between the lens100and the main body portion200.

Hereinafter, a method of calculating a peak value of AF evaluation values from the calculated horizontal AF evaluation values L and the calculated vertical AF evaluation values V will be described.

FIG. 8is a graph illustrating detection of a peak value of AF evaluation values in a contrast AF method. InFIG. 8, a horizontal axis denotes a detection central position, and a vertical axis denotes an AF evaluation value.

The horizontal AF evaluation values are discrete and thus an actual peak value may be calculated by performing an interpolation calculation with respect to horizontal AF evaluation values. The actual peak is a point PK when a detection central position is LVpk, whereas a horizontal AF evaluation peak is Lpk. Interpolation calculation for calculating a peak value may be performed by using LV3, LV4, and LV5and three types of data of L(s3), L(s4), and L(s5) which respectively correspond thereto.

When the peak value of the horizontal AF evaluation values is calculated, a detection central position at the timing of the peak value is determined, and a lens position is detected at a timing that is synchronized with the determined detection central position, thereby driving the focus lens104to a target position with an adjusted focal point.

A peak value with respect to vertical AF evaluation values may also be calculated by using the same method used regarding the horizontal AF evaluation values.

Method of Controlling Digital Photographing Apparatus

FIGS. 9A and 9Bare a flowchart illustrating a method ofFIG. 7of controlling the digital photographing apparatus1, according to an embodiment of the invention.

Power is supplied to the digital photographing apparatus1, and when a shutter release button is half-pressed by the user, an AF operation A is started. When the AF operation A is started, an image is captured periodically by the imaging device204to generate an image signal in operation S101. In operation S102, since an AF operation is performed using a contrast AF method, the focus lens104is driven from one side to the other side. In operation S103, a photographing timing signal is input to the CPU224. The photographing timing signal denotes a timing that initiates AF detection. The photographing timing signal is generated in correspondence with a set AF detection area. The CPU224counts a frequency of a driving signal is generated by the imaging device control unit205, and determines a timing at which a predetermined frequency is counted as a timing for initiating AF detection.

When the photographing timing signal is input, an image signal of an AF area is input from the imaging device204to an AF detection circuit of the pre processing unit220in the camera control unit209, thereby performing AF detection. At the same time, an image signal of an AF area is stored in the memory210in operation S104. In operation S105, a horizontal AF evaluation value L is calculated by the AF detection. After calculating a horizontal AF evaluation value, a vertical image signal of the stored image signal of the AF area is sequentially read from the memory210in operation S106. Reading of image signals from the memory210may be performed using a DMA method. In operation107, the read vertical image signals are input to the AF detection circuit to calculate vertical AF evaluation values V. In operation S108, position information of the focus lens104is obtained at an AF detection timing, and is recorded together with AF evaluation values in a set.

In operation S109, while calculating horizontal and vertical AF evaluation values L and V, whether the horizontal and vertical AF evaluation values L and V have passed peak values or the focus lens104is driven to an end of one side is determined. Whether the horizontal and vertical AF evaluation values have passed peak values is determined by assuming an initial value of an AF evaluation value as a virtual peak value, and then the new AF evaluation value is changed to a virtual peak value if the calculated AF evaluation value according to the driving of the focus lens104is greater than the virtual peak value. If the new AF evaluation value is smaller than the virtual peak value, it is determined that a peak value of the AF evaluation values had existed during AF detection. If the focus lens104is not driven to an end of one side yet and a peak value is not detected, the method goes back to operation S103to further calculate AF evaluation values.

Otherwise, if a peak value of AF evaluation values had existed or the focus lens104is driven to an end of one side, actual peak values of horizontal and vertical AF evaluation values L and V are calculated in operation S110. Since the AF evaluation values not always have peak values at the calculated timings, the actual peak values may be obtained by an interpolation calculation as described with reference toFIG. 8. Otherwise, when the focus lens104is driven up to an end of one side and operation S110starts, the horizontal AF evaluation values may be obtained by deduction.

In operation S111, whether a peak value Lpk of the horizontal AF evaluation value L is greater than a reference value is determined. If the peak value Lpk is greater than the reference value, AF adjustment is determined as possible and a target position of the focus lens104is set as a lens position at a timing that is determined as a timing where the peak value Lpk of the horizontal AF evaluation values is calculated, in operation S112.

Otherwise, if the peak value Lpk is determined to be smaller than the reference value, it is determined that AF detection is not able to be performed using horizontal contrast. Accordingly, whether a peak value Vpk of the vertical AF evaluation value V is greater than the reference value is determined, in operation S113. If it is determined that the peak value Vpk of the vertical AF evaluation value V is greater than the reference value, also, AF adjustment is determined as possible, and a target position of the focus lens104is set as a lens position at a timing that is determined as a timing where the peak value Vpk of the vertical AF evaluation value is calculated, in operation S114.

After setting the target position of the focus lens104in operation S112or operation S114, the focus lens104is driven in a reverse direction to a direction the focus lens104is first driven to drive the focus lens104to the target position, in operation S115. In operation S116, it is displayed that the AF operation is successful.

Otherwise, if the peak value Lpk of the horizontal AF evaluation value L and the peak value Vpk of the vertical AF evaluation value V are determined as smaller than the reference value, it is determined that contrast is not clear to the subject in a horizontal direction and in a vertical direction. Accordingly, in operation S117, driving of the focus lens104is stopped, and NG denoting that AF adjustment is not successful is displayed in operation S118.

The AF operation A according to the current embodiment of the invention is completed according to the above-described operations.

Second Embodiment

Hereinafter, an AF operation using AF evaluation values, according to another embodiment of the invention, will be described with reference toFIG. 10andFIGS. 11A and 11B.

Operation of Digital Photographing Apparatus

The structure and basic operation of the digital photographing apparatus1is the same as the first embodiment. Thus the description of the second embodiment will focus on the differences from the first embodiment. Here, a photographing period will be assumed as 120 fps, which is a higher speed than the first embodiment.

FIG. 10is a timing diagram illustrating an AF operation of the digital photographing apparatus1, according to another embodiment of the invention.

Referring toFIG. 10, an accumulation period of the imaging device204is half of the accumulation period of the first embodiment. Also, a scanning time of an AF detection area is also reduced according to the accumulation period, thereby outputting an image signal at a high speed. When reading of an image signal of an AF detection area by scanning of AFareaL8[1] through AFareaL8[a] is completed, a horizontal AF evaluation value L(s1) is calculated. Also, at the same time, an image signal of the area e8, which is an AF detection area, is stored in the memory210. Then, an image signal is read in a vertical direction with respect to the image of the area e8to calculate a vertical AF evaluation value V(s1) via an AF detection circuit of the pre processing unit220.

However, according to the current embodiment, at a time point when the calculation of the vertical AF evaluation value V(s1) is completed, a scanning operation starts already in a second frame, and thus detection of a horizontal AF evaluation value is not able to be performed. However, in a third frame, since the timing is before a scanning operation starts in the third frame, a horizontal AF evaluation value and a vertical AF evaluation value may be calculated from an image signal of the third frame. Accordingly, by skipping the second frame, a horizontal AF evaluation value and a vertical AF evaluation value are calculated again in the third frame.

Even when the accumulation period of the imaging device204changes from 60 fps to 120 fps, a period of AF detection is still60fps. The change in the accumulation period may correspond to a case when an accumulation time is reduced because a subject is bright.

Once the horizontal AF evaluation value and the vertical AF evaluation value are calculated as described above, peak values of the horizontal and vertical AF evaluation values are calculated as in the first embodiment, thereby driving the focus lens104to a focus position.

According to the current embodiment of the invention, the horizontal AF evaluation value and the vertical AF evaluation value are calculated in odd-numbered frames but AF detection is skipped in even-numbered frames. Accordingly, a timing of a detection central position of AF detection may be LV1, LV2, . . . but detection central positions that are needed to calculate the peak values of the horizontal and vertical AF evaluation values are only odd-numbered values. Accordingly, the position of a lens may be also sensed at a timing that is synchronized with odd-numbered detection central positions.

Method of Controlling Digital Photographing Apparatus

FIGS. 11A and 11Bare flowcharts illustrating a method ofFIG. 10of controlling the digital photographing apparatus1, according to another embodiment of the invention.

Power is supplied to the digital photographing apparatus1, and when a shutter release button is half-pressed by the user, an AF operation B is started. When the AF operation B starts, an image is captured periodically by the imaging device204to generate an image signal in operation S201. In operation S202, whether a photographing period related to an accumulation period in the imaging device204is 60 fps or less is determined. If the photographing period is determined to be 60 fps or less, AF detection is performed by the AF operation A as in the first embodiment. Otherwise, if the photographing period is determined to be greater than 60 fps, the focus lens104is driven from one side to the other side in operation S203. In operation S204, the CPU224awaits application of an interrupt signal by a photographing timing signal. The photographing timing signal is a signal denoting a timing for initiating AF detection. According to the current embodiment, the AF operation is performed by interrupt controlling to the CPU224but the invention is not limited thereto. For example, an AF detection timing may be waited for while a driving signal generated by the imaging device control unit205is directly counted by the CPU224.

When an interrupt signal of the photographing timing signal is input to the CPU224, whether inputting of the interrupt signal has been performed an odd number of times is determined in operation S211. If inputting of the interrupt signal has been performed an even number of times, it is determined that it is a timing where calculation of AF evaluation values is not able to be performed as described with reference toFIG. 10, and thus inputting of an interrupt signal by a next photographing timing signal is waited for.

Otherwise, if inputting of an interrupt signal has been performed an odd number of times, an AF detection operation is performed in operations S212through S227. Operations S212through227are the same as operations S104through S118ofFIG. 9B, respectively, and thus the description thereof will not be repeated here.

If it is determined that the horizontal and vertical AF evaluation values L and V have not passed peak values or the focus lens104is not driven to an end of one side, an interrupt signal is waited for again in operation S219.

The AF operation B according to the current embodiment of the invention is completed as in the above-described operations.

Third Embodiment

Hereinafter, an AF operation using AF evaluation values according to another embodiment of the invention will be described with reference toFIG. 12andFIGS. 13A and 13B.

Operation of Digital Photographing Apparatus

The structure and basic operation of the digital photographing apparatus1is the same as the first embodiment. Thus the description of the third embodiment will focus on the differences from the first embodiment. Here, a photographing period will be assumed as 240 fps. However, the current embodiment may also be applied to a case in which a photographing period is shorter than 240 fps and the time for AF detection and calculation of vertical AF evaluation values by using a vertical image signal that is longer than the second embodiment.

FIG. 12is a timing diagram illustrating an AF operation of the digital photographing apparatus1, according to another embodiment of the invention.

Referring toFIG. 12, an accumulation period of the imaging device204is half of that of the second embodiment. Also, the scanning time of an AF detection area is reduced according to the accumulation period, and thus an image signal is read at a high speed. When reading of the image signal of an AF detection area by scanning of AFareaL8[1] through AFareaL8[a] is completed, a horizontal AF evaluation value L(s1) is calculated. At the same time, an image signal of an area e8, which is an AF detection area, is stored in the memory210. Then, an image signal is read in a vertical direction with respect to the image of the area e8to calculate a vertical AF evaluation value V(s1) via an AF detection circuit of the pre processing unit220.

However, according to the current embodiment, a scanning operation starts in second and third frames already at a time point where calculation of the vertical AF evaluation value V(s1) is completed, and thus detection of the horizontal AF evaluation value is not able to be performed. However, there is still time before a start of a scanning operation of a fourth frame, and an AF evaluation is calculated additionally during the time. However, if a horizontal AF evaluation value is calculated again after the vertical AF evaluation value V(s1), then consequently, AF evaluation values are calculated for every third frame. According to the current embodiment, it is impossible to calculate a horizontal AF evaluation value from an image signal of a third frame; however an image signal of the third frame is stored in the memory210and then a vertical AF evaluation value V(s3) is calculated again by using the stored image signal. After calculation of the vertical AF evaluation value V(s3) is completed, a horizontal AF evaluation signal is calculated again from a fifth frame. The horizontal AF evaluation value may be calculated at a period of 60 fps using the above-described method, and a vertical AF evaluation value may be calculated at a period of 120 fps.

According to the current embodiment, the calculation of the horizontal AF evaluation value and/or the vertical AF evaluation value is performed in odd-numbered frames, but an AF detection operation is skipped in even-numbered frames. Accordingly, there are timings LV1, LV2, . . . of a detection central position of AF detection but detection central positions needed for calculation of peak values of the horizontal and vertical AF evaluation values are only odd-numbered. Thus, a lens position only needs to be sensed at timings that are synchronized with the odd-numbered detection central positions.

Method of Controlling Digital Photographing Apparatus

FIGS. 13A and 13Bare a flowchart illustrating a method ofFIG. 12of controlling the digital photographing apparatus1, according to another embodiment of the invention.

Power is supplied to the digital photographing apparatus1, and when a shutter release button is half-pressed by the user, an AF operation C is started. When the AF operation C starts, an image is captured periodically by the imaging device204to generate an image signal in operation S301. In operation S302, whether a photographing period related to the accumulation period in the imaging device204is 60 fps or less is determined. If the photographing period is determined to be 60 fps or less, AF detection is performed by the AF operation A as in the first embodiment. Otherwise, if the photographing period is determined to be greater than 60 fps, whether a photographing period is 120 fps or less is determined in operation S303. If it is determined that the photographing period is 120 fps or less, AF detection is performed using an AF operation B as in the second embodiment. Otherwise, if it is determined that a photographing period is greater than 120 fps, the focus lens104is driven from one side to the other side in operation S304. Then, in operation S305, the CPU224waits for application of an interrupt signal by a photographing timing signal.

When an interrupt signal of the photographing timing signal is input to the CPU224, whether the inputting of the interrupt signal has been performed an odd number of times is determined in S311. If inputting of an interrupt signal has been performed an even number of times, it is determined that the calculation of AF evaluation values is not able to be performed, as described with reference toFIG. 12, and thus inputting of an interrupt signal by a next photographing timing signal is waited for.

Otherwise, in operation S312, if inputting of an interrupt signal has been performed an odd number of times, whether the inputting has been performed 4X+1 times (X=0, 1, 2 . . . ) is determined. When inputting the interrupt signal satisfies the above condition, an image signal of an AF area is input from the imaging device204to an AF detection circuit of the pre processing unit220in the camera control unit209to perform AF detection. At the same time, the image signal of the AF area is stored in the memory210in operation S313. In operation S314, a horizontal AF evaluation value L is calculated by the AF detection.

Otherwise if the inputting of an interrupt signal does not satisfy the condition, as has been described above with reference toFIG. 12, it is determined that it is a timing where the calculation of a horizontal AF evaluation value among the AF evaluation values is not able to be performed and the image signal of the AF area is temporarily stored in the memory210in operation S315, and then the method proceeds to operation S316.

AF detection is performed by operations S316through S329. Operations S316through S329are the same as operations S106through S118ofFIG. 9AandFIG. 9Bor operations S214through S227ofFIG. 11AandFIG. 11B, and thus the description thereof will not be repeated.

The AF operation C according to the current embodiment of the invention is completed by the above-described operations.

Fourth Embodiment

Hereinafter, an AF operation using AF evaluation values, according to another embodiment of the invention, will be described with reference toFIGS. 14,15,16A, and16B.

Operation of Digital Photographing Apparatus

The structure and basic operation of the digital photographing apparatus1is the same as the first embodiment. Thus the description of the fourth embodiment will focus on the differences from the first embodiment. Here, a photographing period will be assumed as 240 fps. However, the current embodiment may also be applied to a case in which a photographing period is shorter than 240 fps and the time for AF detection and calculation of vertical AF evaluation values by using a vertical image signal is longer than the second embodiment.

FIGS. 14 and 15are timing diagrams illustrating AF operations of the digital photographing apparatus1ofFIG. 1, according to other embodiments of the invention.

Referring toFIG. 14, an accumulation period of the imaging device204is half of that of the second embodiment. Also, the scanning time of an AF detection area is reduced according to the accumulation period, and thus an image signal is read at high speed. When reading of the image signal of the AF detection area by scanning of AFareaL8[1] through AFareaL8[a] is completed, a horizontal AF evaluation value L(s1) is calculated. Unlike other embodiments, subsequent horizontal AF evaluation values L(s2), L(s3), . . . are sequentially calculated by using an image signal of a next frame. Calculation of vertical AF evaluation values is not performed, and thus there is no need to store the read horizontal image signals in the memory210.

A target position of the focus lens104may be calculated by using the calculated horizontal AF evaluation values.

Referring toFIG. 15, a horizontal AF evaluation value is not calculated with respect to the read horizontal image signals in the imaging device204but the read horizontal image signals are first stored in the memory210, and when all of the image signals corresponding to AF detection areas are stored in the memory210, vertical image signals are sequentially read to calculate a vertical AF evaluation value V(s1). Similar toFIG. 14, vertical AF evaluation values are continuously calculated. Here, while an image signal of a next frame is read while calculating a vertical AF evaluation value in a first frame, the calculation of vertical AF evaluation values may be possible for every frame by storing the read horizontal image signal in the memory210.

By using the calculated vertical AF evaluation values, a target position of the focus lens104may be calculated.

During the AF operation, the focus lens104is first driven from one side to the other side, and after the focus lens104is completely driven up to the other side, the focus lens104is driven in a reverse direction. Thus, AF detection is performed by using the horizontal AF evaluation values at a first time of driving as illustrated inFIG. 14, and then at a second time of driving, AF detection may be performed by using the vertical AF evaluation values as illustrated inFIG. 15.

According to the above-described embodiments, there are frames for which AF detection is skipped. This results in inexact detection of peak values of AF evaluation values and thus an exact AF operation is not able to be performed. However, according to the current embodiment, since AF detection is performed with respect to all frames, a more exact AF operation may be performed.

Method of Controlling Digital Photographing Apparatus

FIGS. 16A and 16Bare a flowchart illustrating methods ofFIGS. 14 and 15controlling the digital photographing apparatus1, according to another embodiment of the invention.

Power is supplied to the digital photographing apparatus1, and when a shutter release button is half-pressed by the user, an AF operation D is started. When the AF operation D is started, an image is captured periodically by the imaging device204to generate an image signal in operation S401. In operation S402, since an AF operation is performed using a contrast AF method, the focus lens104is driven from one side to the other side. In operation S403, a photographing timing signal is input to the CPU224. The photographing timing signal is a signal denoting a timing for initiating AF detection. The signal is generated in correspondence with a set AF detection area. The CPU224counts a frequency of a driving signal is generated by the imaging device control unit205, and determines a timing at which a predetermined frequency is counted as a timing for initiating AF detection.

In operation S404, when the photographing timing signal is input, AF detection is performed by inputting an image signal of the AF area from the imaging device204to an AF detection circuit of the pre processing unit220in the camera control unit209. In operation S405, a horizontal AF evaluation value L is calculated by AF detection. In operation S406, position information of the focus lens104at the timing of AF detection is obtained and recorded together with AF evaluation values in a set.

In operation S407, while calculating the horizontal AF evaluation value L, whether the horizontal AF evaluation L has passed a peak value or the focus lens104is driven to an end of one side is determined. Since the method of determining whether the horizontal AF evaluation value L passes the peak value has been described with reference to the first embodiment, description thereof will not be repeated. If the focus lens104is not driven up to an end of one side yet and a peak value is not detected, the method goes back to operation S403to calculate horizontal AF evaluation values.

In operation S408, otherwise, if a peak value of the horizontal AF evaluation value exists or the focus lens104is driven to an end of one side, an actual peak value of the horizontal AF evaluation value L is calculated. Since the horizontal AF evaluation value does not always have a peak value at the calculated timing, the peak value may be obtained by an interpolation calculation as has been described with reference toFIG. 8. Otherwise, if the focus lens104is driven to an end of one side and the method starts operation S408, the horizontal AF evaluation value may be obtained by deduction.

In operation S409, whether a peak value Lpk of the horizontal AF evaluation value L is greater than a reference value is determined. In operation S410, if the peak value Lpk is determined to be greater than the reference value, it is determined that AF adjustment is possible and thus a target position of the focus lens104is set as a lens position at a timing that is determined to be a timing where the peak value Lpk of the horizontal AF evaluation value is calculated. In operation S411, when the target position of the focus lens104is set, the focus lens104is driven in a reverse direction to a direction the focus lens104is initially driven, and the focus lens104is driven to the target position. In operation S412, it is displayed that the AF operation is successful.

In operation S413, otherwise, if it is determined that the peak value Lpk is not greater than the reference value, the focus lens104is driven in the reverse direction, and in operation S414, a photographing timing signal is applied again. In operation S415, image signals of images that are captured while the focus lens104is driven in the reverse direction are sequentially read and stored in the memory210. The stored image signal may be all of the image signals or image signals included in the AF area.

In operation S416, when all of the image signals included in the AF area are stored, vertical image signals of the image signals of the AF area are sequentially read from the memory210. Reading of the image signal from the memory210may be performed using a DMA method. In operation S417, a vertical AF evaluation value V is calculated by inputting the read vertical image signals to the AF detection circuit. In operation S418, position information of the focus lens104at the AF detection timing is obtained and recorded together with the vertical AF evaluation values in a set.

In operation S419, while calculating the vertical AF evaluation values V, whether the vertical AF evaluation values V have passed a peak value or the focus lens104is driven to an end of one side is determined. Since the method of determining whether an AF evaluation value has passed the peak value has been described with reference to the first embodiment, description thereof will not be repeated. If the focus lens104is not driven up to an end of one side yet and a peak value is not detected, the method goes back to operation S414to calculate vertical AF evaluation values.

In operation S420, otherwise, if a peak value of the vertical AF evaluation values exists or the focus lens104is driven to an end of one side, an actual peak value of the vertical AF evaluation value V is calculated. Since the vertical AF evaluation values do not always have a peak value at the calculated timing, the peak value may be obtained by an interpolation calculation as described above with reference toFIG. 8. Otherwise, when the focus lens104is driven to an end of one side and the method starts operation S420, AF evaluation values may be obtained by deduction.

In operation S421, whether a peak value Vpk of the vertical AF evaluation values V is greater than a reference value is determined. In operation S410, if the peak value Vpk is determined to be greater than the reference value, it is determined that AF adjustment is possible and thus a target position of the focus lens104is set as a lens position at a timing that is determined to be a timing where the peak value Vpk of the vertical AF evaluation values is calculated. In operation S422, when the target position of the focus lens104is set, the focus lens104is driven in a reverse direction to a direction the focus lens104is initially driven, and the focus lens104is driven to the target position in operation S423. In operation S424, it is displayed that the AF operation is successful.

The AF operation D according to the current embodiment of the invention is completed using the above-described operations.

As described above, the digital photographing apparatus according to the embodiments of the invention performs an AF operation by using not only horizontal AF evaluation values that are calculated using horizontal image signals but also vertical AF evaluation values that are calculated by using vertical image signals, thereby capturing an image with a focal point adjusted also with respect to a subject that has no contrast in a horizontal direction.

Programs for executing the method of performing AF detection according to the embodiments of the invention in the digital photographing apparatus may be stored in a recording medium. The recording medium may be the memory210as illustrated inFIG. 3or other recording media. Examples of the recording medium include magnetic storage media (e.g., hard disks, etc.), optical recording media (e.g., digital versatile discs (DVDs)).

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated as incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) should be construed to cover both the singular and the plural. Furthermore, recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Finally, the steps of all methods described herein are performable in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. Numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention.