JP2006189641A - Camera system and camera module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably reduce automatic focusing time and improve focusing accuracy. <P>SOLUTION: An AF controller 14a moves a lens, for example, every two steps (first step interval) from the infinity position toward the closest focusing distance side, thereby starting primary search for roughly detecting a focused position. Subsequently, in the secondary search, the AF controller 14a moves the lens one step toward the infinity from the focused proximity position in the primary search, moves the lens up to two steps every one step from that position toward the closest focusing distance side, and, at the same time, captures detection data for each step. In the secondary search, the AF controller 14a terminates the automatic focusing operation by moving the lens to the position that has the largest value of the detection data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a camera autofocus control technique, and more particularly to a technique effective for autofocus software control in a camera mounted on a mobile phone or the like.

  An autofocus in-focus search technique is widely used in digital cameras and the like provided in mobile phones and the like. As this autofocus in-focus search technique, so-called hill climbing control is known.

  The hill-climbing control is a technology that performs a search from the infinity side to the close side of the focus once and stops the lens at a position where the detection data is the largest (in focus).

As an in-focus search technique for autofocus by hill-climbing control, an approximate focus position is obtained by a rough search (primary search) that starts a search from infinity, and then a detailed search (2 After obtaining the in-focus position by performing a rough search (primary search) and by moving the lens at a high speed from an infinite position (referring to Patent Document 1 and Patent Document 2). The vicinity of the in-focus approximate value is searched while reducing the amount of movement of the lens, and three adjacent points including the position where the detection data is the highest are compared to find the in-focus (secondary search) (see Patent Document 3) )and so on.
JP 2002-318341 A JP 2002-277727 A Japanese Patent Application Laid-Open No. 07-135596

  However, the present inventors have found that the above-described camera autofocus in-focus search technology has the following problems.

  In the case of a technique for obtaining a focal point by reversing the lens movement direction after obtaining the approximate focal point position by rough search and performing a detailed search, the lens movement direction is reversed to infinity in the secondary search, and fine steps There is a problem that the in-focus time becomes long because the search is performed by the width.

  Further, in the technique for obtaining the focal point by comparing the three adjacent points including the position where the detection data is the highest after obtaining the focal point approximation value by the rough search, the focal point approximation obtained by the primary search in the secondary search. To narrow down the focal point by moving the lens at low speed while searching for the three points adjacent to the infinity side, near side, and the position with the highest detection data while moving the lens at low speed. The lens movement direction frequently changes, complicating the lens movement control, and the lens movement direction frequently changes, resulting in a large fluctuation of an image displayed on a monitor or the like. There is a problem.

  An object of the present invention is to provide an autofocus control technique capable of significantly reducing the focusing time by autofocus and improving the focusing accuracy.

  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.

  The present invention is a camera system that performs an autofocus operation when a shutter button is pressed, an autofocus activation unit that activates autofocus when the shutter button is pressed, and an input from the autofocus activation unit And a camera module that shoots the captured image by performing autofocus processing based on the received command, and the camera module performs autofocus control when receiving a command from the autofocus activation unit. The auto-focus control unit detects the in-focus approximate position by acquiring detection data by moving the lens for each first step width from the infinity position to the closest position. Then, move the lens so that it is located near the in-focus approximate position detected in the first search. Then, the detection data including the in-focus approximate position detected by the first search is moved for each second step width by moving the lens for each second step width having a smaller moving amount than the first step width. A second search is performed to acquire each and detect the in-focus position.

  In addition, according to the present invention, when the autofocus control unit moves the lens to the vicinity of the in-focus approximate position detected by the first search, the auto-focus control unit moves the lens so that it is located on the infinity side from the detected in-focus position. For each second step width, the lens is moved to an arbitrary position on the closest side to obtain detection data, and the focal position is detected.

  Moreover, the outline | summary of the other invention of this application is shown briefly.

  The present invention is a camera module that receives an autofocus execution instruction signal input from the outside and starts an autofocus operation. When receiving an autofocus execution instruction signal, the lens is moved from an infinite position to a close position. Is moved for each first step width, detection data is acquired and a first search is performed to detect the in-focus position, and the lens is moved so as to be positioned near the in-focus approximate position detected in the first search. Then, the detection data including the in-focus approximate position detected by the first search is moved for each second step width by moving the lens for each second step width having a smaller moving amount than the first step width. Each is provided with an autofocus control unit that performs a second search for obtaining and detecting the in-focus position.

  In addition, according to the present invention, when the autofocus control unit moves the lens to the vicinity of the in-focus approximate position detected by the first search, the auto-focus control unit moves the lens so that it is located on the infinity side from the detected in-focus position. For each second step width, the lens is moved to an arbitrary position on the closest side to obtain detection data, and the focal position is detected.

  Further, according to the present invention, when the autofocus control unit detects the in-focus position by the second search, it outputs an end signal indicating that the autofocus has ended.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  (1) Focusing accuracy can be improved while significantly reducing the focusing time of autofocus.

  (2) Further, in the second search, only the vicinity of the in-focus approximate position is detected in detail, so that it is possible to prevent the in-focus accuracy from being lowered even if the subject is displaced due to camera shake or the like.

  (3) According to the above (1) and (2), it is possible to improve the reliability while greatly improving the autofocus performance in the camera module or the camera system equipped with the camera module.

  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.

  1 is a block diagram of a mobile phone according to an embodiment of the present invention, FIG. 2 is a block diagram of a camera module provided in the mobile phone of FIG. 1, and FIG. 3 is an operation process in the camera module of FIG. FIG. 4 is a flowchart showing an example of an autofocus process in the camera module shown in FIG. 3, FIG. 5 is a flowchart showing an example of the autofocus calculation process in FIG. 4, and FIG. FIG. 7 is a flowchart illustrating an example of a motor drive control operation when the motor drive request flag is turned on in the focus calculation process, and FIG. 7 is an explanatory diagram illustrating an example of an autofocus operation of the camera module by the autofocus calculation process of FIG.

  In the present embodiment, the mobile phone system 1 which is one of mobile communication systems has, for example, a function as a telephone and a camera function for taking an image.

  As shown in FIG. 1, the mobile phone system 1 includes a camera module 2, a high frequency interface 3, a baseband processing unit 4, a flash memory 5, a RAM 6, a display unit 7, a liquid crystal controller 8, a power supply unit 9, and an application processor (auto Focus starting unit) 10 and the like.

The camera module 2 is a module having a camera function for taking an image. For example, the camera module 2 is connected to the application processor 10 via an I ² C bus that is one of control buses, and its operation is controlled by command communication. The

  The high frequency interface 3 demodulates the reception signal or modulates the transmission signal. The baseband processing unit 4 converts transmission data into an I signal and a Q signal and controls a high frequency interface.

  The flash memory 5 stores a control program and a control program for the entire mobile phone system 1 including display control and the like.

  The RAM 6 records a work area of each program in the application processor 10 and the like, user information such as a telephone number, and the like. The display unit 7 includes, for example, a liquid crystal display and displays an image captured by the camera module 2 and information input by a key.

  The liquid crystal controller 8 manages display control of the display unit. The power supply unit 9 generates an arbitrary power supply voltage from a power supply supplied from a built-in battery or the like, and supplies it to each module of the mobile phone system 1. The application processor 10 executes processing such as image input and image encoding / decoding.

  FIG. 2 is a block diagram illustrating a configuration example of the camera module 2.

  As illustrated, the camera module 2 includes a lens unit 11, a sensor 12, an image processing unit 13, a CPU (autofocus control unit) 14, a motor driver 15, a motor 16, and the like.

  The lens unit 11 is composed of a plurality of lenses, and forms a captured image. A sensor 12, for example, a CMOS (Complementary Metal Oxide Semiconductor) sensor, a CCD (Charge Coupled Device), or the like, converts an image formed by the lens unit 11 into a voltage signal.

  The image processing unit 13 includes an AF (autofocus) detection processing unit 13a, a signal processor 13b, and the like.

  The AF detection processing unit 13a detects two detection data of a middle / low range integration value and a high / middle range integration value obtained by passing the voltage signal converted by the sensor 12 through a high-pass filter. The detection data has a large value when the focus is in focus, and the data value decreases as the focus shifts. The signal processor 13b generates a video signal.

  The CPU 14 controls the entire camera module 2, and the CPU 14 includes an AF (autofocus) controller 14a. The AF controller (autofocus control unit) 14a performs autofocus in-focus calculation processing based on the mid-low range integration value and high-mid range integration value detected by the AF detection processing unit 13a, and based on the processing result. To control the motor driver 15.

  The motor driver 15 drives the motor 16 based on the control of the CPU 14. The motor 16 drives and moves the lens of the lens unit 11 to the infinity side and the close side.

  Next, the operation of autofocus control of the camera module 2 in the present embodiment will be described.

  First, as shown in the flowchart of FIG. 3, the camera module 2 has auto focus (AF) processing (step S101) and processing other than auto focus (step S102). Is always started.

  FIG. 4 is a flowchart of autofocus processing in the camera module 2.

  The autofocus processing of the camera module 2 is performed at a timing synchronized with V (vertical), including autofocus operation determination. Therefore, the autofocus process shown in FIG. 4 is started a plurality of times by vertical synchronization.

  First, when receiving the vertical synchronization signal output from the image processing unit 13, the AF controller 14a turns on the vertical synchronization flag (step S201) and then turns off the vertical synchronization flag (step S202).

  When the application processor 10 issues an autofocus activation request by pressing the shutter button, the AF controller 14a determines whether or not the autofocus activation flag is ON (step S203).

  When the autofocus activation flag is received from the application processor 10 by command communication between the application processor 10 and the camera module 2, the AF controller 14a turns on the autofocus activation flag.

  If the autofocus activation flag is ON, the AF controller 14a turns off the autofocus activation flag (step S204), and then initializes parameters related to the autofocus operation (step S205). At this time, since the autofocus operation in the camera module 2 is started, the power consumption of the camera module 2 can be reduced.

  Subsequently, the AF controller 14a sets an instruction parameter for setting the movement of the initial autofocus position of the lens (step S206), and sets an autofocus detection range (step S207).

  After obtaining the detection data set in the process of step S207 (step S208), an autofocus calculation process is executed (step S209). If the autofocus activation flag is OFF in the process of step S203, the AF controller 14a determines whether or not the camera module 2 is in autofocus operation (step S210), and when the autofocus is in operation. Performs the processing of steps S208 and S209.

  FIG. 5 is a flowchart showing details of the process in step S209 of FIG.

  In the autofocus calculation process, the AF controller 14a detects whether or not the lens of the lens unit 11 has moved to the initial position (infinite position) (step S301).

  If the lens has moved to the initial position, the AF controller 14a sets a motor drive step for moving the lens (step S302), turns on the motor drive request flag (step S303), and performs a primary search (step S303). The process proceeds to the first search.

  Subsequently, when the lens is other than the initial position movement in the process of step S301, the AF controller 14a determines whether or not the autofocus operation is a primary search (step S304).

  In the case of the primary search, the AF controller 14a determines whether or not the data value of the detection data output from the AF detection processing unit 13a is decreasing (step S305).

  When the detection data is decreased, the AF controller 14a stops the movement of the lens, and the lens is moved infinitely by an arbitrary number of steps (n steps) from the in-focus approximation value (the most focused position in the primary search). Setting to move to the far side is performed (step S306), and the process proceeds to the secondary search (second search).

  Further, in the process of step S305, if the detection data has not decreased, the in-focus approximate position has not been detected, so the number of motor drive steps is set so as to continue the primary search (step S307).

  Next, when the primary search is completed in the process of step S304, the AF controller 14a determines whether or not the secondary search from the in-focus approximate position to an arbitrary step (n steps) on the closest side is incomplete. Is determined (step S308).

  If the secondary search has not been completed, the AF controller 14a performs setting to move the lens one step to the closest side (step S309) and continues the secondary search. Further, when the secondary search is completed, settings (motor driving direction, number of steps, etc.) are performed so as to move the lens to the position of the largest detection data value in the secondary search (step S310).

  With the above processing, the autofocus operation is completed.

  FIG. 6 is a flowchart showing the motor drive control operation in the AF controller 14a when the motor drive request flag (FIG. 5, step S303) is turned on in the autofocus calculation process of FIG. This motor drive control is activated, for example, at the time of vertical synchronization interruption, and outputs a motor drive pulse when there is a motor drive request.

  First, when the motor drive request flag is turned ON in step S303 in FIG. 5 (step S401), the AF controller 14a sets a drive excitation pattern for driving the motor 16 (step S402).

  Thereafter, the AF controller 14a outputs a drive pulse generated based on the drive excitation pattern to the motor driver 15 (step S403). The motor driver 15 receives the drive pulse output from the AF controller 14a and drives the motor 16.

  Subsequently, the AF controller 14a turns off the motor drive flag (step S404), and the motor drive control operation ends.

  FIG. 7 is an explanatory diagram showing an example of an autofocus operation of the camera module 2 by the autofocus calculation process of FIG. In FIG. 7, the horizontal axis indicates the lens step position, the vertical axis indicates the detection data value, and one step is a unit of the lens movement width of one time in the secondary search.

  First, from the infinite position to the closest side, for example, the lens is moved every two steps (first step width), and a primary search for detecting a rough focal position is started (line L1). In the primary search, when the in-focus position is passed and the detection data value decreases, the primary search ends.

  Subsequently, in the secondary search, the lens is moved to the infinity side (line L2) from the focus approximate position (FIG. 7, position La) in the primary search to n steps (for example, 1 step), and the position of the position is determined. After acquiring the detection data, the detection data for each step is acquired while moving to the nearest side by an arbitrary number of steps (up to two steps in FIG. 7) by one step (second step width) (line L3). , L4).

  When the secondary search is completed, the lens is moved to a position (line L5) with the largest detection data value and stopped, and the autofocus operation is completed.

  In FIG. 7, the start position of the secondary search is a position moved by one step toward the infinity side from the in-focus approximate position in the primary search (position La in FIG. 7). May be arbitrary, and may be a position moved from the in-focus approximate position in the primary search to the infinity side by two steps or more.

  Further, the movement width of the lens is not limited to the movement width shown in the primary search and the secondary search in FIG. 7, and the lens movement width of the secondary search should be smaller than the lens movement width of the primary search. That's fine.

  Thereby, according to the present embodiment, the in-focus approximate position is detected at high speed in the primary search, and then the in-focus approximate position is searched in detail by the secondary search to detect the in-focus position. As a result, the in-focus time of autofocus can be significantly shortened and the in-focus accuracy can be improved.

  Further, in the secondary search, only the vicinity of the in-focus approximate position is detected in detail, so that a decrease in in-focus accuracy can be prevented even if the subject is displaced due to camera shake or the like.

  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.

  The present invention is suitable for a technique of autofocus operation control in a camera module and a camera system.

1 is a block diagram of a mobile phone according to an embodiment of the present invention. It is a block diagram of the camera module provided in the mobile phone of FIG. 3 is a flowchart illustrating an example of operation processing in the camera module of FIG. 2. It is a flowchart which shows an example of the autofocus process in the camera module shown in FIG. It is a flowchart which shows an example of the autofocus calculation process in FIG. 6 is a flowchart illustrating an example of a motor drive control operation when a motor drive request flag is turned on in the autofocus calculation process of FIG. 5. FIG. 6 is an explanatory diagram illustrating an example of an autofocus operation of the camera module by the autofocus calculation process of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mobile phone system 2 Camera module 3 High frequency interface 4 Baseband processing part 5 Flash memory 6 RAM
7 Display unit 8 Liquid crystal controller 9 Power supply unit 10 Application processor (autofocus activation unit)
11 Lens unit 12 Sensor 13 Image processing unit 13a AF detection processing unit (autofocus control unit)
13b Signal processor 14 CPU
14a AF controller (autofocus controller)
15 Motor driver 16 Motor

Claims (5)

A camera system that performs an autofocus operation when a shutter button is pressed,
An autofocus activation unit that activates autofocus when the shutter button is pressed;
A camera module for performing an autofocus process on a captured image based on a command input from the autofocus activation unit;
The camera module is
An autofocus control unit that performs autofocus control when receiving a command from the autofocus activation unit;
The autofocus control unit
After performing a first search that moves the lens from the infinity position to the closest position for each first step width to acquire detection data and detect the in-focus approximate position,
After the lens is moved so as to be positioned near the in-focus approximate position detected by the first search, the lens is moved for each second step width that is smaller than the first step width. And a second search for detecting the in-focus position by obtaining detection data including the in-focus approximate position detected in the first search. The camera system according to claim 1,
The autofocus control unit
When the lens is moved to the vicinity of the in-focus approximate position detected by the first search, the lens is moved so as to be located on the infinity side from the detected in-focus position, and the lens is moved for each second step width. A camera system, wherein the lens is moved to the nearest position to an arbitrary position, detection data is acquired, and the in-focus position is detected. A camera module that starts an autofocus operation in response to an autofocus execution instruction signal input from the outside,
When an autofocus execution instruction signal is received, a first search is performed to detect the in-focus position by acquiring detection data by moving the lens for each first step width from the infinity position to the closest position,
After the lens is moved so as to be positioned near the in-focus approximate position detected by the first search, the lens is moved for each second step width that is smaller than the first step width. A camera module, comprising: an autofocus control unit that obtains detection data including an approximate focal point position detected by the first search and performs a second search for detecting the focal point position. The camera module according to claim 3,
The autofocus control unit
When the lens is moved to the vicinity of the in-focus approximate position detected by the first search, the lens is moved so as to be located on the infinity side from the detected in-focus position, and the lens is moved for each second step width. A camera module characterized in that a lens is moved to a close position to an arbitrary position to obtain detection data and detect a focal point position. The camera module according to claim 3 or 4,
The autofocus control unit
A camera module that externally outputs an end signal indicating that autofocusing has ended when the in-focus position is detected by the second search.

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