JP2007121580A - Automatic focusing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the time necessary for automatic focusing processing. <P>SOLUTION: When a focusing position of a lens is specified for example, evaluated value data is calculated based on an image signal input to a sensor circuit through a lens while the lens is moved in steps and the focusing position is specified based on the value of the evaluated value data. At this point, the movement of the lens is controlled based on an origin position detected only once after the automatic focusing device is powered on according to its relative relation. Further, when the focusing position is specified while the lens 1 is moved in steps, the lens is moved to a specified position on a very close side (S401) and then continuously moved from the specified position on the very near side toward an infinite-distance side (S402, S403). Consequently, the time necessary for detecting the origin position and focusing times for images on very near sides which increase during practical use can be shortened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an autofocus device, and more particularly to a technique effective when applied to an autofocus device mounted on a camera-equipped mobile phone system or the like.

  Usually, in an autofocus device in a digital camera or the like, focus adjustment is performed on an image signal obtained by photographing a subject using a method called hill climbing control. The hill-climbing control is a method of acquiring an image signal from an image sensor such as a CCD while moving the position of the imaging lens, and searching for the position of the imaging lens where the contrast value in the focus area of the image signal shows a peak. . A stepping motor, a linear motor, or the like is used for moving the imaging lens.

  By the way, as a result of the inventor's examination of the technology of the autofocus device as described above, the following has been clarified.

  For example, the hill climbing control as described above is performed as follows. FIG. 8 is an explanatory diagram showing an example of processing contents using hill-climbing control in the autofocus device studied as a premise of the present invention. For example, when a subject is captured by a digital camera or the like and autofocus (hereinafter sometimes abbreviated as AF) processing is executed, the imaging lens (hereinafter abbreviated as “lens”) is first moved from the lens position at the start of operation as shown in FIG. It moves to the origin position and the origin position is detected (S801).

  This origin position is normally set at a position farther from infinity, which is the imaging range in the camera specifications. On the lens moving mechanism, this position corresponds to, for example, the position of a stopper or a photo sensor installed at a position where the movement is limited. When the lens moves and reaches the origin position, a signal is output from a stopper, a photo sensor, or the like to the lens position control circuit. The lens position control circuit recognizes the position that received this signal as the origin position, and then controls the position of the lens relative to the origin position.

  Subsequently, the lens is moved from the origin position to a position at infinity (S802). From this infinite position, a search operation is performed while obtaining evaluation value data (S803). That is, while moving the lens position to the closest side, an image signal is acquired by an image sensor such as a CCD each time, and evaluation value data is obtained from this image signal. Subsequently, the lens position is moved to the closest side until the evaluation value data exceeds the apex (focus position) (S804). When it is recognized that the evaluation data exceeds the vertex, the lens is returned to the position of the previous vertex (focus position) (S805), and the AF process is completed.

  However, as a result of studies by the present inventors, it has been found that the AF processing as shown in FIG. 8 has the following problems, for example. First, every time AF processing is performed, since the origin position is detected by moving the lens position to the infinity side as in S801 of FIG. 8, the AF processing time becomes long. Second, since the search operation is performed from the infinity side to the close side as in S803 and S804 in FIG. 8, the AF processing time is wasted particularly in a digital camera mounted on a mobile phone system or the like. Yes.

  Therefore, an object of the present invention is to shorten the processing time in an autofocus device. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  An autofocus device according to the present invention includes an imaging lens, a sensor circuit that converts an image input via the imaging lens into an electrical signal, and a motor that moves the position of the imaging lens toward the near side and / or the infinity side. And a control circuit that performs control of the motor and processing of electric signals acquired from the sensor circuit. Specifically, the control circuit moves the imaging lens by controlling the motor, sequentially acquires electrical signals from the sensor circuit along with the movement, and compares the magnitudes of the acquired electrical signals to obtain the imaging lens. A process for specifying the in-focus position is performed.

  Here, one feature of the present invention is that the control circuit moves the imaging lens by controlling the motor after turning on the power of the autofocus device, detects the origin position in the process of moving the imaging lens, and thereafter supplies power. While the process continues, each process is performed based on the detected origin position, and the origin position is not detected again. Therefore, when performing the autofocus process of specifying the in-focus position of the imaging lens, the in-focus position is specified in a relative relationship with the origin position detected only once after the power is turned on as the reference position. The origin position is a position that is fixed in advance at a specific location on the moving mechanism of the imaging lens.

  As described above, in the prior art, the origin position is detected every time the autofocus process is performed, but by detecting the origin position only once after turning on the power as in the present invention, The time required for autofocus processing can be shortened.

  Another feature of the present invention resides in that the movement of the imaging lens performed in the process of specifying the in-focus position described above is performed in the direction from the closest side to the infinity side. As a result, the time required for autofocus processing can be shortened particularly in a camera-equipped cellular phone system that often captures images on the near side.

  If the effect obtained by a representative one of the inventions disclosed in the present application is briefly described, the time required for the autofocus process can be shortened.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is a block diagram showing a configuration example of a mobile phone system equipped with an autofocus device according to an embodiment of the present invention. 1 includes, for example, an audio input unit 100, an audio output unit 101, an antenna 102, an LCD (Liquid Crystal Display) 103, a lens unit 104, and the like as external interfaces, and additionally controls these external interfaces. Various LSIs are provided. The audio interface LSI 105 includes an A / D, D / A converter, and the like, and controls the audio input unit 100 and the audio output unit 101. The high frequency interface LSI 106 includes a modulation / demodulation function and the like, and transmits and receives radio waves via the antenna 102. The liquid crystal controller LSI 107 includes a drive driver and the like, and controls the LCD 103.

  The baseband LSI 108 inputs and outputs various baseband signals between the audio interface LSI 105 and the high frequency interface LSI 106. The camera signal processing LSI 110 performs various processes related to imaging including control of the lens unit 104. The application processor LSI 109 transmits and receives signals to and from the baseband LSI 108, the liquid crystal controller LSI 107, the camera signal processing LSI 110, the nonvolatile memory LSI 111, and the volatile memory LSI 112 via the bus 113, and controls these LSIs.

  In such a configuration, the camera signal processing LSI 110 and the lens unit 104 constitute a camera unit 114 having an imaging function, and this camera unit 114 is included in the autofocus device (or its main part) of the present embodiment. Applicable. FIG. 2 is a block diagram showing a detailed configuration example of the camera unit (autofocus device) in the mobile phone system of FIG.

  The camera unit 114 illustrated in FIG. 2 includes, for example, an imaging lens (lens) 104a, a sensor circuit 104b including an imaging element such as a CCD, a lens driving motor 104c such as a stepping motor, a camera signal processing LSI 110, and the like. It is. The camera signal processing LSI 110 includes a camera circuit 110a, an image scale adjustment circuit 110b, a digital interface circuit 110c, a volatile memory circuit 110d, a CPU (Central Processing Unit) circuit 110e, and the like. 110f is connected.

  An image obtained through the lens 104a is converted into an image signal (electric signal) by the sensor circuit 104b. The camera circuit 110a extracts high-frequency components from the image signal by a high-pass filter or the like, and calculates evaluation value data for evaluating the in-focus state by integrating and averaging them. The image scale adjustment circuit 110b performs zoom up / down scale adjustment on the image data from the camera circuit 110a as necessary. The scale-adjusted image data is output as a video output via the digital interface 110c, and this output data is sent to, for example, the application processor LSI 109 [liquid crystal controller LSI 107] in FIG.

  For example, the CPU circuit 110e acquires evaluation value data for evaluating the in-focus state from the camera circuit 110a, and performs auto focus processing (AF processing) using this data. Then, the CPU circuit 110e drives the lens driving motor 104c based on the calculation result to move the position of the lens 104a to a position where the lens 104a is brought into focus.

  FIG. 3 is an explanatory diagram showing an example of processing contents in the camera unit (autofocus device) of FIG. FIG. 4 is an explanatory diagram showing another example of the processing contents in the camera unit (autofocus device) of FIG.

  The autofocus device of the present embodiment performs the origin position detection operation consisting of S301 and S302 in FIG. 3 only once when its own power is turned on. Specifically, after the camera unit 114 is turned on, an origin position detection execution command is issued using the IIC I / F, for example, from the application processor LSI 109 in FIG. 1 to the CPU circuit 110e in FIG. When this command is received, the CPU circuit 110e in FIG. 2 drives the lens driving motor 104c to move the lens 104a. As a result, for example, the lens 104a moves from the position at the previous power-off to the origin position beyond infinity, and when the origin position is reached, the origin position detection signal is output by the lens moving mechanism (S301). ).

  Upon receiving the origin position detection signal, the CPU circuit 110e recognizes the origin position, and moves the lens 104a toward a specific position on the closest side determined in advance by a relative value from the origin position (the number of steps in the case of a stepping motor). (S302). Note that after the origin position detection operation such as S301 and S302 is performed once when the power is turned on, the origin detection operation is not performed again due to the AF process until the power is turned off. That is, when the AF process is performed, the process of returning the lens position to the specific position on the closest side is first performed as shown in S401 in FIG. 4 without performing the origin detection operation.

  After returning the position of the lens 104a to the specific position on the near side from the previous focus position for each AF process as in S401 of FIG. 4, the search operation using the hill climbing control described above is started. Here, unlike FIG. 8 described above, the lens 104a is moved by a fixed number of lens driving steps from the closest side to the infinity side. At that time, evaluation value data calculated by the camera circuit 110a of FIG. 2 is acquired by the CPU circuit 110e, and the lens position having the largest evaluation value data is searched while comparing the size of the evaluation value data (S402, S403). By this search, the lens position with the largest evaluation value data is determined as the focus position, and the lens position is returned to this focus position (S404).

  As described above, in the conventional AF processing, the origin position detection operation is first executed as shown in FIG. 8, but in the AF processing of the present embodiment, the origin position detection operation is performed only once when the camera is turned on. In the subsequent normal AF processing, the origin position detection operation is not performed. As a result, the time required for the AF process can be reduced by the time required for the origin position detection operation.

  Also, in the AF processing of the present embodiment, unlike the AF processing of the prior art, a focus position search operation is performed from the closest side to the infinity side. As a result, it is possible to reduce the focusing time for the subject on the close side while maintaining the focusing accuracy as in the prior art. Therefore, when used in combination with the omission of the origin position detection operation described above, the AF processing time can be significantly shortened particularly when focusing on the closest side. For example, a digital camera mounted on a mobile phone system or the like often captures an image of a subject on the near side, and in such a system, the effects described above are particularly remarkable.

  Furthermore, when the subject is photographed in a backlight condition, when two vertices of the evaluation value data are generated within the search range, the AF processing of the prior art searches from infinity, so the background (infinite Although focusing on the far side), the effect of focusing on the subject (near side) can be obtained by searching from the near side.

  Incidentally, the processes shown in FIGS. 3 and 4 described above are realized by, for example, a program process of the CPU circuit 110e in FIG. FIG. 5 is a flowchart showing an example of the main routine in the program processing performed by the CPU circuit of FIG. FIG. 6 is a flowchart showing an example of processing of the subroutine in the main routine of FIG. FIG. 7 is a flowchart showing an example of further subroutine processing in the subroutine of FIG. These programs are stored, for example, in a ROM or the like built in the CPU circuit 110e.

  In FIG. 5, AF control processing is executed (S501), then other camera control processing is executed (S502), and these processing are repeated. The AF control process in S501 has the process contents as shown in FIG. 6, for example. In FIG. 6, first, the presence or absence of the V synchronization flag is detected (S601). The V synchronization flag is set in an interrupt process activated by a V (vertical) synchronization signal. Thus, the AF control process in S501 is a process synchronized with the V synchronization signal. If there is a V synchronization flag in S601, the V synchronization flag is cleared (S602). If not, the process returns to the main routine of FIG. 5 at S608 and continues to the process of S502.

  After clearing the V synchronization flag in S602, it is determined whether or not an AF control command is received (S603). If there is a command, various parameters for AF control are set (S604), and then an evaluation value detection range is set (S605). Specifically, for example, the AF operation flag is set to ON in S604, and in S605, a focus area is set from an image frame obtained from the sensor circuit 104b in FIG. 2 via the camera circuit 110a. Thereafter, evaluation value data for this focus area is acquired from the camera circuit 110a (S606), and the process proceeds to AF focusing calculation processing (S607). On the other hand, if the AF control command is not received in S603, it is determined whether the AF operation flag is on or off (S609). If it is on, the process proceeds to S606. If it is off, the process proceeds to S608. To return to the main routine of FIG.

  In the AF focusing calculation process in S607, as shown in FIG. 7, first, it is determined whether or not an origin position detection execution command, which is one of AF control commands, has been received (S701). This origin position detection execution command is issued from, for example, the application processor LSI 109 of FIG. 1 after the camera unit is turned on as described in FIG. If an origin position detection execution command is received, it is determined in S702 whether the origin position detected flag is on or off. If not received, in S708, it is determined whether the origin position detected flag is on / off.

  If the origin position detected flag is ON in S702, the process returns to the subroutine of FIG. 6 in S717, and then returns to the main routine of FIG. 5 in the subroutine of FIG. On the other hand, if the origin position detected flag is off, it is determined in S703 whether the AF operation mode is set to the initial position movement. Immediately after the camera unit is turned on, the origin position detected flag in S702 is off, and the AF operation mode in S703 is not set to the initial position movement. Therefore, in this case, in S704 and S705, a process of moving the lens to the origin position is performed as in S301 of FIG. 3 described above.

  In S704, the number of motor drive steps for detecting the origin position is set. Specifically, for example, a somewhat large number of steps for moving the lens in the direction toward infinity is set for the lens driving motor 104c in FIG. 2, as in S301 in FIG. In S705, the AF operation mode is set to the initial position movement. Thereafter, in S716, the motor drive request flag is turned on, so that the lens drive motor 104c in FIG. 2 starts driving according to the set number of steps. This motor drive request flag is used in timer interrupt processing performed in synchronization with the V synchronization signal. In the timer interrupt process, if the motor drive request flag is on, the CPU 110e outputs a motor drive pulse.

  Note that when moving the lens to the origin position, it is not always completed in one cycle of the V synchronization signal, and a plurality of cycles may be required. Even in such a case, the lens moves toward the origin position over a plurality of periods until the origin position is detected in the timer interrupt process of S716. When the origin position is detected, the motor drive request flag is turned off and the interrupt process is exited.

  In this way, when the lens reaches the origin position and the CPU 110e in FIG. 2 detects the origin position based on the signal generated by the stopper, photosensor, etc. at the origin position, the process returns from S717 to the routines in FIGS. Through these processes, the AF focusing calculation process of S607 in FIG. 7 is performed again. This time, when S703 is reached through S701 and S702, since the AF operation mode is set to the initial position movement in S705 described above, the process proceeds to S706 and S707.

  The processing in S706 and S707 corresponds to the processing in S302 in FIG. In S706, the number of motor drive steps for moving to the closest side is set. In S707, the origin position detected flag is set to ON. Thereafter, in S716, the motor drive request flag is turned on, so that the lens drive motor 104c in FIG. 2 starts driving according to the set number of steps. That is, in S706, since the relative number of steps up to the specific position on the near side is set based on the detected origin position, the lens moves by this number of steps by the interrupt processing in S716, and the near side is moved. Stop at a specific position. When the lens is stopped, the motor drive request flag is turned off, the interrupt process of S716 is exited, and the process returns from S717 to the routines of FIGS.

  As described above, in response to the origin position detection execution command after the power is turned on, the origin position is detected, and after moving the lens to the specific position (initial position) on the closest side, the application processor LSI 109 in FIG. While the operation continues, the origin position detection execution command is not generated, and a normal AF control command that is an autofocus execution command for the image is generated. Even if the origin position detection execution command is generated again, since the origin position detected flag is set to ON in S707, the process directly moves from S702 to S717, and the actual origin position is not detected.

  When the application processor LSI 109 generates a normal AF control command along with imaging, various settings are made in S603 to S605 in FIG. 6, and AF focusing calculation processing in S607 is performed. In the AF focus calculation process in this case, the process proceeds from S701 to S708 in FIG. 7, and the presence or absence of the origin position detected flag is determined in S708. If the origin position detected flag is off, the process returns to the routines of FIGS. 6 and 5 via S717. On the other hand, after the process of S707 described above, since the origin position detected flag is on, the process proceeds to S709.

  In S709, it is determined whether or not the AF operation mode is search movement. If it is a search movement, the process proceeds to S712. If it is not a search movement, the process proceeds to S710 and S711. The processing of S710 and S711 corresponds to the processing of S401 in FIG. 4 described above, and is processing for returning the lens position from the previous focusing position to a specific position on the closest side. In S710, the number of motor drive steps for returning the lens to the specific position on the near side is set. In S711, the AF operation mode is set to search movement. Thereafter, when the motor drive request flag is turned on in S716, the lens moves toward the specific position on the near side in the interrupt process, and when reaching this position, the motor drive request flag is turned off and the interrupt process is exited.

  Thereafter, the process returns to the routines of FIGS. 6 and 5 via S717, and this time through the processes of S603 → S609 → S606 of FIG. 6, the AF focusing calculation process of S607 is performed. In the AF focusing calculation process in this case, since the AF operation mode is set to search movement in S711, the process proceeds to S712 through the processes of S701 → S708 → S709 in FIG. In S712, whether or not the evaluation value data acquired by the CPU 110e from the camera circuit 110a in the process of S606 described above is continuously reduced as compared with the evaluation value data acquired in the process of the previous S606. Is determined. If continuously decreasing, the process proceeds to S714, S715, and if not, the process proceeds to S713.

  The process of S713 corresponds to the processes of S402 and S403 in FIG. In S713, the number of motor drive steps for search is set, and then in S716, the motor drive request flag is turned on. Here, for example, it is set to move one step at a time from the specific position on the near side toward the infinity side. Then, the motor drive request flag is turned off each time one step is moved in the interrupt process of S716, the interrupt process is exited, and the process returns to the routines of FIGS. 6 and 5 via S717. Thereafter, evaluation value data is acquired again via the sensor circuit 104b and the camera circuit 110a with the lens 104a of FIG. 2 moved by one step by the processing of S603 → S609 → S606 of FIG.

  Then, in the AF focusing calculation process of S607, the evaluation value data is compared and determined again in S712 through the processes of S701 → S708 → S709 in FIG. According to such processing, the lens is sequentially moved until the evaluation value data continuously decreases as in S403 of FIG. In S712, when it is recognized that the evaluation value data continuously decreases, the processes of S714 and S715 are performed. The processing of S714 and S715 corresponds to the processing of S404 in FIG.

  In S714, the number of motor drive steps necessary to return to the position where the evaluation value data is the largest (that is, the focus position) is set. In S715, the AF operation flag is set to OFF. After that, when the motor drive request flag is turned on in S716, the lens moves to the in-focus position within the interrupt process, and the motor drive request flag is turned off to exit the interrupt process. This completes the autofocus process. Thereafter, since the AF operation flag is turned off in S715, the process proceeds from S609 to S608 in FIG. 6, and the lens is not moved until the next imaging is performed.

  As described above, by causing the CPU 110e in FIG. 2 to execute the processing program described in FIGS. 5 to 8, the origin position is detected once after the power is turned on as shown in FIG. 3, and the subsequent imaging process is performed. As shown in FIG. 4, it is possible to realize a process of performing hill climbing control from the closest side to the infinity side using the detected origin position. Thereby, the time required for the AF process can be shortened.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the above description, the stepping motor is used as the lens driving motor. However, the present invention is not limited to this, and any motor that can uniquely determine the lens position with respect to the moving step can be applied. It is.

  The autofocus device of the present invention is a technique that is particularly useful when applied to a camera-equipped mobile phone system, and is not limited to this, and can be widely applied to a single digital camera or the like.

It is a block diagram which shows the structural example of the mobile telephone system carrying the autofocus apparatus by one embodiment of this invention. FIG. 2 is a block diagram illustrating a detailed configuration example of the camera unit (autofocus device) in the mobile phone system of FIG. 1. FIG. 3 is an explanatory diagram showing an example of processing contents in the camera unit (autofocus device) of FIG. 2. FIG. 4 is an explanatory diagram showing another example of the processing contents in the camera unit (autofocus device) of FIG. 2. FIG. 3 is a flowchart showing an example of a main routine in program processing performed by the CPU circuit of FIG. 2. FIG. 6 is a flowchart showing an example of processing of the subroutine in the main routine of FIG. 5. FIG. 7 is a flowchart showing an example of further subroutine processing in the subroutine of FIG. 6. It is explanatory drawing which shows an example of the processing content using hill-climbing control in the autofocus apparatus examined as a premise of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Audio | voice input part 101 Audio | voice output part 102 Antenna 103 LCD
104 Lens portion 104a Lens 104b Sensor circuit 104c Lens drive motor 105 Audio interface LSI
106 High-frequency interface LSI
107 LCD controller LSI
108 Baseband LSI
109 Application processor LSI
110 Camera signal processing LSI
110a Camera circuit 110b Image scale adjustment circuit 110c Digital interface circuit 110d Volatile memory circuit 110e CPU circuit 110f Bus 111 Nonvolatile memory LSI
112 Volatile memory LSI
113 Bus 114 Camera

Claims (5)

An imaging lens;
A sensor circuit that converts an image input through the imaging lens into an electrical signal;
A motor that moves the position of the imaging lens toward the near side and / or the infinity side;
The imaging lens is moved under the control of the motor, the electrical signal is sequentially acquired from the sensor circuit as the movement is performed, and the in-focus position of the imaging lens is compared by comparing the plurality of the acquired electrical signals. An autofocus device including a control circuit for specifying,
The control circuit is a reference position for controlling the position of the imaging lens in the moving process of the imaging lens by moving the imaging lens by controlling the motor after turning on the power of the autofocus device, and is fixed in advance. When the imaging is performed while the power supply of the autofocus device continues after the detection of the origin position, the origin position is not detected again, and the power source is detected. An autofocus device characterized in that the in-focus position is specified based on an origin position detected after being turned on. The autofocus device according to claim 1, further comprising:
The autofocus device, wherein the movement of the imaging lens performed in the process of specifying the in-focus position is performed in a direction from the closest side toward the infinity side. The autofocus device according to claim 2, wherein
The autofocus device, wherein the motor is a stepping motor. The autofocus device according to claim 2, wherein
The origin position is set on the infinity side,
When the imaging is performed while the power supply of the autofocus device is continued after the detection of the origin position, the control circuit first takes the imaging at a specific position on the near side relatively determined from the origin position. An autofocus device characterized by moving a lens, and then specifying the in-focus position while gradually moving the imaging lens from the specified position on the near side toward the infinity side. An imaging lens;
A sensor circuit that converts an image input through the imaging lens into an electrical signal;
A motor that moves the position of the imaging lens toward the near side and / or the infinity side;
The imaging lens is moved under the control of the motor, the electrical signal is sequentially acquired from the sensor circuit as the movement is performed, and the in-focus position of the imaging lens is compared by comparing the plurality of the acquired electrical signals. An autofocus device including a control circuit for specifying,
The autofocus device, wherein the movement of the imaging lens performed in the process of specifying the in-focus position is performed in a direction from the closest side toward the infinity side.

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