JP3604750B2 - Automatic focusing device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an automatic focusing device used for an electronic still camera, a video camera, and the like.
[0002]
[Prior art]
2. Description of the Related Art Generally, in an autofocus device (hereinafter, referred to as an AF device) of an electronic still camera or a video camera, a method of driving a focus lens using a stepping motor is used. As is well known, a stepping motor can perform so-called open-loop control that does not require feedback control, and can obtain highly accurate focus lens position information by counting the number of pulses. It can be said that there is. In the case of obtaining the position information of the focus lens by counting the number of pulses as described above, conventionally, first, the focus lens is first moved to a predetermined position (hereinafter, referred to as a reset position), and the number of pulses from that position and the motor 1 The lens position information is obtained from the lens movement amount per step. Note that a photo interrupter or the like is used to detect the reset position.
[0003]
As a conventional AF method for a video camera that stores moving images, a so-called hill-climbing AF method that extracts a luminance signal from a video signal read from an image sensor and uses the high-frequency component as a focus detection signal has been used. In this method, the focusing operation is performed by moving the focus lens to a position where the focus detection signal is maximized. Further, in this method, since the AF operation is performed using the signal read from the image pickup device, a special AF sensor is not required, and it can be realized at low cost.
[0004]
Conventionally, electronic still cameras and video cameras have been provided with various shooting modes, and some of them have a limited subject distance to some extent. For example, a so-called macro mode for shooting a very close subject, or a mode for shooting a subject of a specific size in close proximity, for example, loading a film of silver halide photography into an adapter or the like and attaching the adapter to the end of the lens There are a shooting mode (hereinafter referred to as a film adapter mode) and a mode for shooting credit cards, licenses, business cards, and the like (hereinafter referred to as a card mode). Since the subject position is different between the close-up shooting mode and the normal shooting mode, the scan range for detecting the in-focus point in the AF operation is different from the normal shooting mode in the close-up shooting mode. Further, even when performing flash photography, it can be said that the subject range is substantially limited because the illumination range is limited by the light emitting ability.
[0005]
[Problems to be solved by the invention]
In the above-mentioned hill-climbing AF method, the time required for the AF operation depends on the time interval for reading out the electric charges accumulated in the image sensor, so that a fast operation cannot be performed. That is, the focus detection signal can be obtained only a predetermined number of times (60 times per second in NTSC) within a unit time. In an electronic still camera that shoots a still image, it is required to perform an AF operation at a high speed. However, in the case of a camera having a shooting mode different from the normal shooting mode as described above, the subject distance is limited to a certain extent. In other words, despite the limited movement range of the focus lens, after moving the focus lens to the reset position, the same control as in normal shooting is performed without performing any special control. For this reason, in the macro mode and the film adapter mode described above, since the subject is on the closest side, even if the focus is within a predetermined range from the closest end, if the AF operation is started from the reset position, the lens will be in focus. It takes time to move to the vicinity, and it is useless to scan an area other than the in-focus range. If the reset position is located far from the closest end, the AF operation itself takes more time, and it is very inconvenient to use the hill-climbing AF method which is disadvantageous for the high-speed AF operation.
[0006]
Conversely, in the normal shooting mode, it is useless to scan near the closest end even though the subject distance is longer than in the macro mode or the film adapter mode, and more time is required.
[0007]
In addition, since the amount of movement of the lens per step of the stepping motor is very small, about 10 μm, it is very difficult to set the reset position to a desired position by adjusting the mounting position of the photo interrupter during manufacturing. Was.
[0008]
Furthermore, even if the subject is scanned out of the illuminable range at the time of flash photography, even if the subject is in focus, only a photograph with an insufficient amount of exposure is actually taken, and such a photograph becomes meaningless.
[0009]
An object of the present invention is to solve the problems of the conventional AF control as described above, and an object of the present invention is to achieve a reduction in the AF operation time according to a shooting mode when a hill-climbing AF method is used in an electronic still camera. It is in. Another object of the present invention is to perform an AF operation over an effective distance range during flash photography.
[0010]
[Means for Solving the Problems]
An automatic focusing apparatus according to the present invention includes a focus lens that adjusts the focus of a subject image, and a focus lens that is closer to or within a first range than the first range. And narrow In the second range Respectively Focus Scan to get focus detection signal for Focus lens driving means for driving, lens initial position detecting means for detecting an initial position of the focus lens, mode setting means for setting an operation mode, and the lens initial position detecting means detecting the initial position, and After the focus lens is stopped at a reset position within the first range, when the mode setting means sets a predetermined operation mode for driving the focus lens in the second range, the focus lens is temporarily moved to the second position. Scan while moving to the closest end side of the range and moving to the infinite end side A luminance signal is extracted from the video signal obtained by this, and a high-frequency component of the extracted luminance signal is used as the focus detection signal. Controlling the focus lens driving means so that the mode setting means sets a predetermined operation mode for driving the focus lens in the first range. Scanning while moving to the nearest end side A luminance signal is extracted from the video signal obtained by this, and a high-frequency component of the extracted luminance signal is used as the focus detection signal. Control means for controlling the focus lens driving means as described above.
[0013]
[Action]
Since the present invention includes the above technical means, the time required for AF because the movement of the focus lens is restricted from the initial position to the predetermined position can be shortened, and the driving range of each focus lens according to the operation mode can be reduced. It is possible to reliably scan from the nearest end side to the infinite end side.
[0016]
【Example】
(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an electronic camera to which the present invention is applied. In FIG. 1, 101 is a fixed lens, 102 is a light amount control member such as an aperture and a shutter, 103 is an aperture, a motor for driving a shutter 102, 104 is a mechanical drive circuit for driving an aperture, a shutter, and the like, and 105 is an imaging device to be described later. A focus lens for focusing on the element 109, a photo interrupter 106 as a lens initial position detecting means for detecting a reset position of the focus lens 105, a motor 107 for moving the focus lens 105, and a motor 108 for driving the motor 107 This is a focus lens driving circuit that moves the focus lens 105, and forms a focus lens driving unit together with the motor 107.
[0017]
Reference numeral 109 denotes an image sensor as a light amount conversion unit that converts reflected light from a subject into an electric signal; 110, a timing signal generating circuit that generates a timing signal required to operate the image sensor 109; 111, an output of the image sensor 109; A pre-processing circuit including a CDS circuit for removing noise and a non-linear amplifier circuit for performing A / D conversion, 112 is an A / D converter, 113 is a buffer memory, 114 is reading / writing of the buffer memory 113 and refreshing of the DRAM. A memory controller 115 for controlling the operation, 115 is a microcontroller including a CPU for controlling the system such as a photographing sequence, and a control unit also serving as control means extracting means, 116 is a display for assisting operation and the state of the camera An operation display unit 117 represents an operation unit for operating the camera from outside, and 118 represents an operation unit. An electrically rewritable nonvolatile memory.
[0018]
Reference numeral 119 denotes an interface with an extension unit 120 described later, reference numeral 120 denotes a detachable extension unit that is connected to the electronic camera body to perform various processes and operations, reference numeral 121 denotes an interface for connection with a recording medium 122 described later, and reference numeral 122 denotes Is a recording medium such as a memory card or a hard disk; 123 is a main switch for turning on the power to the system; 124 is a switch (hereinafter referred to as SW1) for performing a shooting standby operation such as AF or AE (auto exposure); Is a photographing switch (hereinafter referred to as SW2) for photographing after the photographing standby switch 124 is operated, 126 is a mode switch as mode setting means for setting a photographing mode, 127 is a strobe, and 128 is a photograph of a silver halide film image. This is a film adapter for loading and using a film.
[0019]
Next, the operation of the AF device according to the present invention will be described with reference to the flowchart of FIG. First, in step S201 (hereinafter, steps are omitted), the state of the main switch 123 is detected, and if the power is ON, the process proceeds to S202. In S202, the remaining capacity of the recording medium 122 is checked. If the remaining capacity is 0, the process proceeds to S203; otherwise, the process proceeds to S204. In S203, a warning is issued that the remaining capacity of the recording medium 122 is 0, and the process returns to S201. The warning is displayed on the operation display unit 116, a warning sound is output from an audio output unit (not shown), or both are performed. In step S204, the focus lens 105 is reset according to the flowchart of FIG.
[0020]
Next, in step S205, the state of the mode switch 126 is detected. If the macro mode or the film adapter mode has been set, the process proceeds to step S206; otherwise, the process proceeds to step S208. In step S206, the position of the focus lens 105 is detected based on the number of steps of the motor 107 from the reset position. If the lens is at the closest end, the process proceeds to step S210. In step S207, the focus lens 105 is driven to move to the closest end. In this case, the closest end is the closest end in the macro mode or the film adapter mode, and is a position where an object closer to the close end than in the normal shooting mode can be focused. In step S208, the position of the focus lens 105 is detected based on the number of steps from the reset position. If the lens is at the infinite end, the process proceeds to step S210; otherwise, the process proceeds to step S209. In step S209, the focus lens 105 is driven to move to the infinity end.
[0021]
In S210, the state of SW1 is checked. If it is ON, the process proceeds to S212; otherwise, the process proceeds to S211. In S211, the state of the main switch 123 is checked. If the switch is ON, the process returns to S205; otherwise, the process returns to S201. In S212, a shooting standby operation including an AF operation is performed according to a flowchart of FIG. 5 described later. In step S213, the state of SW2 is checked. If it is ON, the process proceeds to step S215; otherwise, the process proceeds to step S214. In S214, the state of SW1 is checked. If it is ON, the process proceeds to S213; otherwise, the process proceeds to S205. In S215, the photographing operation is performed according to the flowchart of FIG.
[0022]
In S216, the remaining capacity of the recording medium 122 is checked. If the remaining capacity is 0, the process proceeds to S218; otherwise, the process proceeds to S217. In S217, the state of SW2 is checked. If it is not ON, the process proceeds to S214. In S218, as in S203, a warning is issued that the remaining capacity of the recording medium 122 is 0, and the process proceeds to S219. The warning is displayed on the operation display unit 116, a warning sound is output from a sound output unit (not shown), or both. In S219, the state of the main switch 123 is checked. If it is ON, the process returns to S216; otherwise, the process returns to S201.
[0023]
FIG. 3 is a subroutine showing the content of the focus lens reset in S204 in FIG. Here, as shown in FIG. 4, when the focus lens 105 is at the infinite end side with respect to the photo interrupter output switching position in FIG. 4, the output of the photo interrupter 106 is “Lo”, and when the focus lens 105 is at the closest end side, it is “Lo”. Hi ". First, in step S301, the state of the output of the photointerrupter 106 is checked. If “Lo”, the process proceeds to step S302; otherwise, the process proceeds to step S303. In step S302, the focus lens 105 is determined to be at the infinite end side with respect to the photo interrupter output switching position based on the output of the photo interrupter 106 in step S301. Therefore, the focus lens 105 is moved by one step to the closest end side. In step S303, the state of the output of the photointerrupter 106 is checked. If "Hi", the process proceeds to step S304; otherwise, the process returns to the main routine. In S304, since the focus lens 105 is determined to be on the closest end side with respect to the photo interrupter output switching position by the output of the photo interrupter 106 in S303, the focus lens 105 is moved one step toward the infinite end side.
[0024]
Next, an operation when the focus lens 105 is reset as described above will be described. First, when the position of the focus lens 105 when the main switch 123 is turned on is on the infinite end side with respect to the photo interrupter output switching position, the output of the photo interrupter 106 is “Lo”. In S302, the focus lens 105 is moved one step at a time toward the near end until the output of the photo interrupter 106 becomes “Hi”. Since the output of the photointerrupter 106 is switched to “Hi” when the output of the photointerrupter 106 in FIG. 4 is exceeded, the infinity end is maintained until the output of the photointerrupter 106 becomes “Lo” according to S303 and S304 in FIG. Is moved one step at a time.
[0025]
Thus, the focus lens 105 finally stops at the reset position in FIG. When the position of the focus lens 105 when the main switch 123 is turned on is on the closest end side with respect to the photo interrupter output switching position, the focus lens 105 is moved only to the infinite end side, and the position of the photo interrupter 106 is changed. Stop when the output becomes "Lo". In the same manner as when the position of the focus lens 105 when the main switch 123 is turned on is on the infinite end side with respect to the photo interrupter output switching position, the focus lens 105 is finally moved to the reset position in FIG. Stop at.
[0026]
FIG. 5 is a subroutine showing the contents of the shooting standby operation of S212 in FIG. First, in step S501, the state of the mode switch 126 is detected. If the mode is the macro mode, the process proceeds to step S502; otherwise, the process proceeds to step S506. In step S502, the subject brightness is measured. In S503, it is checked whether or not the subject luminance measured in S502 is equal to or more than a predetermined value, and if it is equal to or more than the predetermined value, the process proceeds to S504; otherwise, the process proceeds to S505. In step S504, the scan range of the AF operation, that is, the range in which the focus motor 105 is moved is set to a predetermined value (1). At the time of macro shooting, the subject is very close, so it is sufficient to scan only near. Therefore, the predetermined value (1) in this case is set in a range close to the fixed lens 101, for example, in a range of 5 to 50 cm.
[0027]
In S505, similarly to S504, the scan range of the AF operation is set to a predetermined value (2). In this case, since the subject brightness is determined to be equal to or less than the predetermined value in S503, shooting using the strobe 127 is performed. For this reason, if the distance is too close, the strobe light is emitted, so the range is set so that the light is not emitted, for example, a range of 15 to 50 cm. In step S506, the state of the mode switch 126 is detected. If the mode is the film adapter mode, the process proceeds to step S507; otherwise, the process proceeds to step S508. In step S507, the scan range of the AF operation is set to a predetermined value (3). At this time, assuming that the distance from the fixed lens 101 to the silver halide film loaded in the film adapter 128 is 10.5 cm as a design value, the scan range is set to 10 to 11 cm as the predetermined value (3).
[0028]
In S508, the subject brightness is measured. In S509, it is checked whether or not the subject luminance measured in S508 is equal to or more than a predetermined value. If it is equal to or more than the predetermined value, the process proceeds to S511; otherwise, the process proceeds to S510. In S510, the scan range is set to a predetermined value (4). In this case, since neither the macro mode nor the film adapter mode is used, there is no need to scan a close range. Further, since the subject brightness is determined to be equal to or less than the predetermined value in S509, shooting using the strobe 127 is performed. Since the illuminable range of the strobe 127 is limited, if the illuminable range is up to 5 m as an example, the predetermined value (4) is set to 50 cm to 5 m as the scan range.
[0029]
Since neither the macro mode nor the film adapter mode is selected in step S511, it is not necessary to scan a close range. Further, since the subject luminance is determined to be equal to or higher than the predetermined value in step S509, no strobe light is used. Therefore, in this case, for example, the scan range is set to 50 cm or more. These scan ranges to be set are not limited to the values stored in the camera in advance, and may be set by the user.
[0030]
Next, in S512, the AF operation is performed by moving the focus lens 105 within the scan range set in S504, S505, S507, S510, and S511. At this time, the above-mentioned hill-climbing AF method is used. If the maximum value of the focus detection signal is equal to or less than the predetermined value, the above-described hill-climbing AF is repeated. If the result is the same even after performing the predetermined number of times, it is stored that the maximum value of the focus detection signal is equal to or less than the predetermined value. Proceed to. In S513, it is checked whether or not the maximum value of the focus detection signal obtained by the above-mentioned hill-climbing AF is equal to or less than a predetermined value. As is well known, in the hill-climbing AF, the focusing operation is performed by moving the focus lens to the position where the focus detection signal is maximized. Therefore, the focusing operation cannot be performed unless the maximum value can be detected.
[0031]
Therefore, when the maximum value of the focus detection signal is equal to or less than a predetermined value, the focus lens 105 is moved to a predetermined position. If the maximum value of the focus detection signal is equal to or less than the predetermined value, the process proceeds to S514; otherwise, the process skips this subroutine and returns to the main routine. In step S514, the state of the mode switch 126 is detected. If the mode is the macro mode, the process proceeds to step S515; otherwise, the process proceeds to step S516. In S515, the focus lens 105 is moved to a predetermined position (1). The predetermined position (1) at this time is set to a position corresponding to a general subject distance in macro photography. Alternatively, the angle of view may be set at a position corresponding to the size of the business card.
[0032]
In step S516, the state of the mode switch 126 is detected. If the mode is the film adapter mode, the process proceeds to step S517; otherwise, the process proceeds to step S518. In S517, the focus lens 105 is moved to the predetermined position (2). At this time, the predetermined position (2) is, for example, a position corresponding to a subject distance of 10.5 cm, assuming that the distance from the fixed lens 101 to the silver halide film loaded in the film adapter 128 is 10.5 cm in design value. The focus lens 105 is moved. In S518, the focus lens 105 is moved to a predetermined position (3). In this case, since neither the macro mode nor the film adapter mode is set, the focus lens 105 is moved to the infinite end.
[0033]
FIG. 6 is a subroutine showing the contents of the photographing operation in S215 in FIG. First, in step S601, the subject brightness is measured. In step S602, exposure to the image sensor 109 is performed according to the subject luminance measured in step S601. Next, in step S603, output noise removal of the image sensor 109, nonlinear processing performed before A / D conversion, and the like are performed. In S604, the analog signal from the pre-processing circuit 111 is converted into a digital signal. In S605, the output data from the A / D converter 112 is temporarily stored in the buffer memory 113 via the memory controller 114. In S606, the data in the buffer memory 113 is transferred to the recording medium 122 such as a memory card mounted on the camera body via the memory controller 114 and the recording medium interface 121.
[0034]
FIG. 7 shows a scan range of the focus lens 105 in the photographing mode. (A) shows the entire scan range of the focus lens 105. The focus lens 105 scans a specific portion of this range according to the shooting mode, as described below. It is assumed that the reset position is at the position shown in the figure. If the shooting mode is the macro mode and no strobe is used, the range shown in FIG. 7B is scanned. That is, scanning is performed between the normal closest end and the macro closest end that can focus on a subject that is even closer.
[0035]
When the flash mode is used in the macro mode, the area (c) is scanned. This scan range is shorter on the macro-close side than the scan range in the macro mode without using a strobe. This is because stroboscopic light is emitted at a very short distance. In the case of the film adapter mode, the range (d) is scanned. This scan range is a very short range between the normal closest end and the macro closest end. In the case of the film adapter mode, since the subject distance can be almost specified, the scan range may be very short. In the normal photographing mode, the range (e) is scanned. This scan range is between the normal closest end and infinity end. In the flash photography mode, the range (f) is scanned. This scan range is shorter on the infinite end side than the scan range in the normal shooting mode. This is to avoid scanning the area where the strobe light does not reach.
[0036]
In the configuration shown in FIG. 1, if the camera is set to the macro mode or the film adapter mode, the focus lens 105 is reset and then moved to the closest end. In the normal photographing mode, the focus lens 105 is reset and then moved to the infinity end. This makes it possible to reduce the time required for the focus lens 105 to move in a range that does not need to be scanned when the SW1 is turned on next and the AF operation is started. Further, since the scan range is changed and set according to the shooting mode and the shooting conditions, it is not necessary to scan a useless range, and the time required for the AF operation can be reduced.
[0037]
Further, when the strobe 127 is used, the scan range is set according to the effective illumination range, so that it is possible to eliminate the waste of scanning the range where the strobe light does not reach. Further, when the maximum value of the focus detection signal is less than or equal to a predetermined value as a result of performing the AF operation, the focus cannot be adjusted, and the focus lens 105 is moved to a preset position corresponding to the shooting mode. Shooting large blurs can be avoided.
[0038]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. This is obtained by replacing S207 and S209 in FIG. 2 in the first embodiment with S807 and S809. The other processes in S201 to S208 and S210 to S219 are the same as those in FIG. In FIG. 8, in step S807, the focus lens 105 is moved out of the close-range distance measurement range, that is, out of the range where the distance can be actually measured by several steps from the close end. By doing so, it is possible to reliably scan the near end of the distance measurement range during the actual AF operation. Similarly, in step S809, the focus lens 105 is moved out of the infinity-side distance measurement range, that is, out of the range in which the distance can be actually measured by several steps from the infinity end. By doing so, the infinite end of the distance measurement range can be reliably scanned during the actual AF operation.
[0039]
As described above, according to each embodiment, when the shooting mode is set to the macro mode or the film adapter mode, the focus lens 105 is moved to the closest end after the focus lens 105 is reset. When the shooting mode is set to the normal shooting mode, the focus lens 105 is moved to the infinite end after the focus lens 105 is reset. Further, the scan range of the AF is changed and set according to the shooting mode and the shooting conditions. Further, when it is difficult to detect the focus, the focus lens is moved to a preset position.
[0040]
In the above description, the scan range corresponding to each mode and shooting conditions, and the predetermined position for moving the focus lens 105 when the maximum value of the focus detection signal is equal to or less than a predetermined value are indicated by specific numerical values. However, this is only an example, and the present invention is not limited to this. Alternatively, a warning may be issued when the maximum value of the focus detection signal is equal to or less than a predetermined value, and the photographing may not be performed. In the film adapter mode, the focus lens 105 is moved to the closest end after reset, but may be moved to a predetermined position in the scan range instead of the close end. Further, similar control may be performed not only in the film adapter mode but also in a mode for photographing a credit card, a license, a business card, or the like.
[0041]
【The invention's effect】
According to the present invention, the time required for AF can be shortened, and the scanning can be reliably performed from the closest end to the infinite end in the drive range of each focus lens according to the operation mode.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic camera showing first and second embodiments of the present invention.
FIG. 2 is a flowchart illustrating a basic operation of the electronic camera according to the first embodiment.
FIG. 3 is a flowchart showing a reset operation of the focus lens in FIG. 2;
FIG. 4 is an explanatory diagram of an operation.
FIG. 5 is a flowchart showing a shooting standby operation of FIG. 2;
FIG. 6 is a flowchart showing the photographing operation of FIG. 2;
FIG. 7 is an explanatory diagram showing a relationship between an operation mode and a lens position.
FIG. 8 is a flowchart showing a second embodiment of the present invention.
[Explanation of symbols]
105 Focus lens
106 Photo interrupter
107 motor
108 Focus lens drive circuit
109 Image sensor
115 control unit
117 Operation unit
126 Mode switch

Claims (4)

A focus lens for adjusting the focus of the subject image,
A focus lens driving unit that scans driven to obtain focus detection signal for each focus a narrow second range a close than the first range or the first range of the focusing lens,
Lens initial position detecting means for detecting an initial position of the focus lens,
Mode setting means for setting an operation mode;
After the lens initial position detecting means detects the initial position, and stops the focus lens at a reset position within the first range,
When the mode setting means sets a predetermined operation mode in which the focus lens is driven in the second range, the focus lens is temporarily moved to the closest end side from the second range and then to the infinite end side. A luminance signal is extracted from a video signal obtained by scanning while moving, and the focus lens driving unit is controlled so that a high-frequency component of the extracted luminance signal is used as the focus detection signal .
When the mode setting means sets a predetermined operation mode for driving the focus lens in the first range, the focus lens is once moved to the infinity end side from the first range and then to the closest end side. Control means for extracting a luminance signal from a video signal obtained by scanning while moving, and controlling the focus lens driving means so that a high-frequency component of the extracted luminance signal is used as the focus detection signal. An automatic focusing device. 2. The automatic focusing apparatus according to claim 1, wherein the predetermined operation mode for driving the focus lens in the second range is a close-up shooting mode. 2. The automatic focusing apparatus according to claim 1, wherein the predetermined operation mode for driving the focus lens in the second range is a mode for photographing a subject at a predetermined distance and a predetermined size. The automatic focusing device according to claim 2, wherein the predetermined operation mode for driving the focus lens in the first range is a normal shooting mode.

Images