JP4921651B2 - Digital camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera having an autofocus function.
[0002]
[Prior art]
In recent years, as an alternative to a silver salt film, a digital camera that takes a picture by receiving light from an object on a CCD (Charge-Coupled Device) has become widespread. In the case of a digital camera, contrast AF (Auto Many systems perform focusing by the Focus method. At that time, the contrast is detected by using a CCD as an image pickup surface without using a separate distance measuring device. This simplifies the configuration and reduces costs.
[0003]
Here, when the subject distance is short and within the range to be macro-photographed, the depth of field becomes shallow and the position change of the image plane becomes large. For this reason, in focusing control, it is necessary to perform search driving for finding a focus position while moving the photographing lens over a longer distance than when the subject is in a range where normal photographing is possible. The photographing lens is generally driven by a stepping motor, and the amount of movement of the photographing lens by one step unit driving of the stepping motor is constant. Therefore, when the subject is located at a short distance to be macro-photographed, proper focusing cannot be obtained unless the photographing lens is moved by a larger number of steps. Moving the lens with a larger number of steps means that it takes time to focus.
[0004]
Therefore, a conventional digital camera includes a macro switch that allows the user to switch between a normal shooting mode (normal mode) and a macro shooting mode (macro mode). In addition, the lens movement area is divided into a normal area with a relatively large depth of field and a small number of lens movement steps (a narrow search drive range) and a macro area with a large number of steps as described above (a wide search drive range). is doing. When the normal mode is selected, the search drive range is set only within the normal region without moving the lens to the macro region, and focusing is performed in a short time. Further, when the macro mode is selected, the range for search driving is enlarged, that is, the lens is set to move in the macro area having the number of steps larger than the number of steps in the normal area.
[0005]
However, providing a macro switch leaves the user with a decision as to whether or not to perform macro shooting, and reduces the convenience of the autofocus function. For example, when the subject to be photographed is in a position where it is difficult to determine whether the subject is within the macro photographing range, there is a problem that the user cannot perform desired photographing by mistakenly selecting a mode. In addition, when the user wants to take a macro shot, he forgot to turn on the macro switch, so that the proper focusing is not performed and the desired shooting cannot be performed.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a digital camera that enables autofocus in a shooting mode corresponding to a subject distance more accurately while maintaining an inexpensive and simple configuration. .
[0007]
[Means for Solving the Problems]
For this reason, the digital camera according to claim 1 has a normal autofocus function for driving the photographing lens so as to automatically focus on a subject from a predetermined position to infinity, and from the predetermined position to the shortest distance that can be photographed. A macro autofocus function for driving the taking lens to automatically focus on the subject of the camera, and angle detecting means for detecting the current depression angle of the digital camera, and when the depression angle satisfies a predetermined condition Control means for controlling the focus by operating the macro autofocus function, and the control means determines whether the depression angle satisfies a predetermined condition only when the focus is not focused by the normal autofocus function. this If is does not satisfy the predetermined condition, which does not operate the macro auto focus function, an error message is displayed, to end the focusing process The features.
[0008]
According to the digital camera of claim 1, even when the user cannot determine whether or not to perform macro shooting, the focusing in the macro mode can be automatically performed according to the depression angle of the camera, and the subject distance can be more accurately determined. Can be used for autofocus and shooting.
[0011]
The digital camera according to claim 2 is characterized in that the predetermined condition is that the depression angle is a predetermined angle or more.
[0012]
According to the digital camera of the third aspect, it is preferable to search for the position of the photographing lens where the subject image is focused by the contrast autofocus method. More specifically, the photographing lens is step-driven by a stepping motor. Then, the photographing lens is usually first number of steps in the auto-focus function, the macro in the autofocus function is driven within a second number of steps greater than the first number of steps (claim 4).
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing the configuration of a digital camera 100 according to an embodiment of the present invention. The digital camera 100 includes an angle detection sensor 1, a CPU 2, a motor driver 3, a motor 4, a focus adjustment lens 5 as a photographing lens, a CCD 6, an image signal processing circuit 7, an LCD monitor 8, a main switch 9, a photometric switch 10a, and a release switch. 10b, a memory card control circuit 11, and a memory card 12. The digital camera 100 has two types of shooting modes, specifically, a macro mode for shooting a subject at a short distance without blurring and a normal mode for general shooting.
[0014]
The angle detection sensor 1 is not unique to the present invention, and a known sensor mounted on the conventional digital camera 100 is used to detect the tilt of the digital camera 100 when shooting. The angle detection sensor 1 is in a state in which the camera 100 is normally used as indicated by a solid line in FIG. 2 (here, it is assumed that the optical axis of the focus adjustment lens 5 is in a horizontal state in a horizontal plane). As shown by a broken line in FIG. 2, an angle θ (referred to as a depression angle in this specification) θ formed by the optical axis of the focus adjustment lens 5 when it is tilted toward the ground is obtained. The depression angle θ is 0 degree at the minimum (at this time, the camera 100 is in a horizontal state) and 90 degrees at the maximum (at this time, the optical axis of the focus adjustment lens 5 is orthogonal to the ground).
[0015]
The CPU 2 performs focusing by driving the stepping motor 4 via the motor driver 3 and moving the focus adjustment lens 5 in the optical axis direction in units of predetermined steps. The focus adjustment lens 5 moves on the basis of the macro switching position M when moving in the normal mode, and moves in the area closer to the CCD 6 than the macro switching position M (normal area), and when focusing in the macro mode, the macro switching position. It moves in an area (macro area) closer to the subject than M. In the macro area, the number of steps is set larger than when the focus adjustment lens 5 moves in the normal area. The closer the subject is to the camera, the shallower the depth of field, and the greater the change in the position of the subject image formed by the taking lens. On the other hand, since the lens movement amount by one step driving of the stepping motor is constant, the focus adjustment lens 5 can be driven for search over a longer distance than the normal region by setting a large number of driving steps by the stepping motor. Become. Therefore, it is possible to focus with high accuracy even in the macro mode. The CCD 6 outputs charges corresponding to the optical image formed on the light receiving surface to the image signal processing circuit 7 by the light incident through the focus adjustment lens 5. The image signal processing circuit 7 performs a predetermined process based on the input charge, and then transmits an image signal to the CPU 2. The CPU 2 stores the image signal as image data in the memory card 12 that can be attached to and detached from the camera 100 main body via the memory card control circuit 11.
[0016]
The metering switch 10a and the release switch 10b are switches that are turned on according to the operation amount of one release button (not shown) in appearance of the camera 100. When the release button is pressed halfway, the metering switch 10a is turned on. The release switch 10b is turned on when fully pressed.
[0017]
Hereinafter, with reference to FIG. 3, a series of photographing processing for releasing through the autofocus of the digital camera 100 will be described in detail. FIG. 3 is a flowchart showing processing of the CPU 2 of the digital camera 100. The camera 100 according to the present embodiment first improves the convenience of the user and the effectiveness of the autofocus function by automatically shifting to the macro mode only when focusing is not performed after focusing in the normal mode and then focusing again. Is.
[0018]
The CPU 2 of the digital camera 100 is in a power saving mode that uses only the minimum power necessary for maintaining the function, such as saving various setting data such as date (S1), but the main switch 9 is turned on. (S3: YES) switches to an operation mode in which shooting, image editing, and the like are possible (S5).
[0019]
When the CPU 2 switches to the operation mode, the CPU 2 initializes the position of the focus adjustment lens 5 via the motor driver 3 and the motor 4 (S7). In the present embodiment, the focus adjustment lens 5 is moved to the infinitely focused position.
[0020]
When the initialization of the position of the focus adjustment lens 5 is completed, the CPU 2 enters a standby state until the photometric switch 10a is turned on (S9: NO, S25: YES). When the metering switch 10a is turned on (S9: YES), the shooting mode is set to the normal mode (S11), and focusing in the normal mode is performed (S13). That is, while moving the focus adjustment lens 5, the contrast of the subject image is obtained based on the image signal obtained by the CCD 6, and the focus adjustment lens 5 is driven by hill-climbing control. In the normal mode, the distance that the focus adjustment lens 5 can move from the initialization position (infinite focus position), that is, the maximum lens movement distance in the normal area is defined by a predetermined first driving step number. The maximum lens movement distance in the normal area in this embodiment corresponds to the total number of drive steps from the initialization position to the macro switching position M that is the boundary position with the macro area, and is, for example, 50 steps. When the main switch is turned off when the CPU 2 is in the standby state (S25: NO), the so-called power is turned off, and the CPU 2 is switched to the power saving mode (S1).
[0021]
The digital camera 100 employs a contrast AF method. That is, the CPU 2 drives the motor 4 via the motor driver 3 to detect the position where the contrast (spatial frequency) of the image photographed by the CCD 6 is highest while moving the focus adjustment lens 5 to perform focusing. Do. In S13, since the focusing is in the normal mode, the lens 5 is moved only in the normal region (see FIG. 1).
[0022]
When the lens is moved to a position where the subject image has the highest contrast by the focusing, in other words, when the lens is focused (S15: YES), the CPU 2 fixes the lens at the current position (S17), and releases the lens. It will be in a standby state until the switch 10b is turned on (S19: NO, S27: YES). At this time, if the user releases the half-pressed state of the release button (S27: NO), the CPU 2 performs the above-described autofocus process (S9 to S19) again.
[0023]
When the CPU 2 determines that the release switch is turned on in S19 (S19: YES), the charge corresponding to the light beam incident on the CCD 6 is transmitted to the image signal processing circuit 7, and after various processes are performed, the CPU 2 Then, it is recorded on the memory card 12 (S21, S23). The above photographing process is performed when the subject is at a distance that can be photographed in the normal mode. In other words, when shooting in normal mode, no focusing is performed in macro mode.
[0024]
In the present embodiment, focusing is performed in the macro mode only when focus is not achieved in S15 (S15: NO). In general, when the user performs macro shooting, the digital camera 100 according to the present embodiment determines whether or not to shift to the macro mode from the tilt of the camera 100 in view of the fact that the camera 100 is tilted toward the ground. If the CPU 2 determines that the subject is not in focus in S15, the CPU 2 compares the current depression angle θ of the camera 100 transmitted from the angle detection sensor 1 with a predetermined reference angle α (S29). Here, the reference angle α means a depression angle of the camera 100 that is at least necessary for macro photography, and is set to 20 degrees in the present embodiment.
[0025]
When determining that the depression angle θ is equal to or larger than the reference angle α, the CPU 2 drives the motor 4 to move the focus adjustment lens 5 to the macro switching position M (S31). Subsequently, the CPU 2 sets the photographing mode to the macro mode (S33), and displays on the LCD monitor 8 that the macro mode is set (S35).
[0026]
Then, the CPU 2 performs hill-climbing control driving of the focusing lens 5 within a range of a macro region (see FIG. 1) defined by a predetermined second driving step number that is larger than the first driving step number in the normal mode, and focusing. (S37). In the macro mode, the distance that the focus adjustment lens 5 can be moved by search driving is set to a second driving step number that is larger than the first driving step number, for example, 200 steps.
[0027]
As a result of focusing, when the in-focus state is obtained (S39: YES), the processing after S17 described above is performed. That is, macro shooting is performed.
[0028]
As a result of focusing, when the focus is not achieved (S39: NO), that is, at the time of search driving, the focus adjustment lens 5 is moved within a macro region where the movable distance of the focus adjustment lens 5 is longer than the normal region. However, if the position at which the maximum contrast is achieved cannot be detected, the CPU 2 displays an error display indicating that the in-focus state has not been achieved on the monitor 8 (S41), and enters a standby state (S43: YES). When the user releases the half-pressed state of the release button and the photometric switch 10a is turned off (S43: NO), the CPU 2 turns off the error display (S45) and performs the processing from S3 again. Even when it is determined in S29 that the depression angle θ is smaller than the reference angle α, the CPU 2 performs similar error processing.
[0029]
The above is the embodiment of the present invention. The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.
[0030]
In the above-described embodiment, the configuration in which the focusing in the normal mode is first performed and the focusing in the macro mode is performed in accordance with the depression angle value when the in-focus state is not achieved. However, the present invention is not limited to this configuration. . For example, when the photometry switch is turned on in S9, the current depression angle θ is immediately detected and compared with the reference angle α. Depending on the comparison result, it is possible to adopt a configuration for performing focusing in either the normal mode or the macro mode.
[0031]
In the above embodiment, the reference angle α is set to 20 degrees. However, the reference angle α can be arbitrarily set. The reference angle α is preferably set between approximately 10 degrees and approximately 90 degrees. Furthermore, in S29 of the above embodiment, whether or not to shift to the macro mode is determined based on the magnitude of the depression angle θ and the reference angle α, but instead of the reference angle α, a reference angle range is set and the depression angle θ May be configured to shift to the macro mode when the angle is within the reference angle range. The reference angle α and the reference angle range may be set at the time of product shipment, or may be arbitrarily changed by the user as one item of function setting.
[0032]
【Effect of the invention】
As described above, according to the present invention, when a subject is in the normal shooting range, focusing can be performed in a very short time by performing focusing without moving the lens to the macro area. In addition, by automatically switching to the macro mode and performing focusing according to the depression angle of the camera when shooting, even if it is difficult for the user to determine whether to shoot macro, shooting with less failure is possible Become.
[0033]
Furthermore, the digital camera of the present invention can be configured to be simple and excellent in cost performance by detecting the depression angle of the camera using the angle detection means already mounted on the conventional digital camera. it can.
[Brief description of the drawings]
FIG. 1 is a block diagram of a digital camera of the present invention.
FIG. 2 shows a state in which the digital camera of the present invention is tilted toward the ground.
FIG. 3 is a flowchart showing autofocus and photographing processing of the digital camera of the present invention.
[Explanation of symbols]
100 Digital camera 1 Angle detection sensor 2 CPU
5 Focus adjustment lens 6 CCD

Claims (5)

A normal autofocus function that drives the photographic lens to automatically focus on a subject from a predetermined position to infinity, and a photographic lens to automatically focus on a subject from the predetermined position to the shortest possible distance In a digital camera having a macro autofocus function for driving
Angle detection means for detecting a current depression angle of the digital camera;
Control means for controlling the focus by operating the macro autofocus function when the depression angle satisfies a predetermined condition;
The control means determines whether or not the depression angle satisfies a predetermined condition only when the normal autofocus function does not focus, and if the depression angle does not satisfy the predetermined condition, the macro autofocus function is A digital camera that displays an error without operating and ends the focusing process .   The digital camera according to claim 1, wherein the predetermined condition is that the depression angle is equal to or greater than a predetermined angle. Wherein, while moving the photographing lens, the contrast autofocus system, to control to find the position of the taking lens object image is focused, according to claim 1 or claim 2, wherein Digital camera. The photographing lens is step-driven by a stepping motor,
The driving range of the photographing lens, the normal in autofocus feature, the first step number, the macro in the autofocus function, and characterized by being set to the second number of steps is greater than the first number of steps The digital camera according to any one of claims 1 to 3. The normal autofocus function that drives the taking lens to automatically focus on the subject from the predetermined position to infinity, and the shooting lens to automatically focus on the subject from the predetermined position to the shortest distance In digital cameras with a macro autofocus function,
Focusing is performed by operating the normal autofocus function, and only when the focus is not focused by the normal autofocus function, the following processes A to C are performed in order.
A. Detecting the current depression angle of the digital camera,
B. Determining whether the depression angle satisfies a predetermined condition;
C. When a predetermined condition is satisfied, the macro auto focus function is operated have rows focusing and does not satisfy a predetermined condition, without operating the macro auto focus function, an error message is displayed, the process ends automatic focusing method in <br/> digital camera.

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