JP2005070077A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera that eliminates the need for switching operation between normal photography and close-up photography and is capable of stereo photography. <P>SOLUTION: The digital camera 2 is equipped with a 1st photograph lens 3, a 2nd photograph lens 4, and a 1st imaging element 5 and a 2nd imaging element 6. The 1st photograph lens 3 and 2nd photograph lens 4 are provided with focus lenses 25 and 27. The focusing lenses 26 and 27 move within a range from infinite-distance photography to macrophotography and the movement range is divided into a long-distance area and a short-distance area. One focusing lens is moved within the long-distance area, and the other focusing lens is moved in the short-distance area. The focusing lenses stop at positions where subject images in the respective areas become sharpest. Image signals outputted from the two imaging elements are compared with each other, to decide which image is sharper, and to the stop position of the focusing lens through which the sharper image is obtained, the other focusing lens is moved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera capable of recording a stereo image for stereoscopic viewing and performing autofocus control based on an image signal output from an image sensor.
[0002]
[Prior art]
There is known a stereo camera that simultaneously captures two images having parallax with two sets of photographing lenses arranged in parallel in the horizontal direction at an interval approximately equal to the distance between human eyes. Two images taken with a stereo camera can be viewed by placing the viewpoints of both eyes on two adjacent images and overlaying them in the field of view, or by using a stereo viewer. Can be observed as a stereoscopic image with a sense of presence.
[0003]
Patent Document 1 below describes a digital camera that can perform stereoscopic shooting for shooting a stereo image and normal shooting for obtaining one still image using one of the shooting lenses. This digital camera is provided with two sets of photographing lenses and imaging elements, and can be arbitrarily switched between a stereoscopic photographing mode and a normal photographing mode by a switch operation. Further, when focusing, the other photographic lens is driven to the same in-focus position after one photographic lens has finished focusing.
[0004]
Many photographic lenses used in digital cameras enable macro photography with a short photographic distance because of ease of design. For this reason, if the entire range from infinity to a short distance during macro shooting is set as a focus target, it takes time for focus control and inconvenient points such as missing a photo opportunity. Therefore, conventionally, the photographer is made to input whether to perform macro photography or normal photography by dialing or the like, and the range for focusing is narrowed down in advance to devise a technique for minimizing the time required for focus control. .
[0005]
[Patent Document 1]
JP-A-8-317425 [0006]
[Problems to be solved by the invention]
However, in the digital camera capable of stereo shooting described in Patent Document 1, since an appropriate focus position is searched with only one shooting lens, and the other shooting lens waits until the focus position is specified, There is waste in reducing the time required for focus control. In addition, an input operation is required to select macro shooting and normal shooting, and there is a problem that inconvenience for the photographer remains.
[0007]
The present invention has been made in view of the above problems, and provides a digital camera that reduces the time required for focusing and eliminates the need for a selection operation for switching operation modes when performing macro photography or normal photography. For the purpose.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides two imaging optical systems that are provided apart from each other according to the binocular distance, and an imaging element that converts a subject image formed by each imaging optical system into an image signal. Accordingly, in the digital camera that records two subject images having parallax, the focus lens provided in each photographing optical system is driven in the optical axis direction, and the subject image is sharpened based on the image signal output from the image sensor. Assigned to a first focus control means for stopping driving of the focus lens at a position where a peak of sharpness is obtained, and a first area suitable for short-distance photography and a second area suitable for long-distance photography Each focus lens is driven within a given movement range, one focus lens is moved within the short distance area, and the other focus lens is moved over the long distance. Compare the sharpness of the subject image formed by each photographing optical system after the driving of each focus lens is stopped at the position where the peak of sharpness is obtained, with the second focus control means that moves in the area Computation means and third focus control means for moving the other focus lens to a position corresponding to the stop position of one focus lens where a subject image with high sharpness is obtained are provided. The search range of the focus position by driving the focus lens is shared by the two photographing optical systems.
[0009]
The digital camera according to claim 2 is provided with control means for switching between a first operation mode for recording a subject image formed by each photographing optical system and a second operation mode for recording one of the subject images. When the second operation mode is executed, the third focus control means is prohibited from operating, and the subject image with the higher sharpness is recorded.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, the digital camera 2 includes a first photographing lens 3 and a second photographing lens 4 having the same lens configuration. The first photographic lens 3 and the second photographic lens 4 are adjusted in focus within a photographic distance range of infinity to 10 cm, and are capable of photographing landscapes and macro photography at a short distance. Behind the first photographic lens 3 and the second photographic lens 4, a first imaging element 5 and a second imaging element 6 are provided. The first image sensor 5 captures an optical image of a subject formed through the first photographing lens 3. Similarly, the second imaging element 6 images subject light incident on the second photographing lens 4. The image signals output from the first image sensor 5 and the second image sensor 6 are sent to the image signal input circuit 9, where noise reduction processing, auto gain control processing, and digital conversion processing are performed.
[0011]
The image signal input circuit 9 outputs digital image signals to the focus evaluation circuit 10 and the image processing circuit 11, respectively. The focus evaluation circuit 10 decomposes the input image signal into spatial frequency components, and determines the sharpness of imaging from the contrast of the high frequency components of the subject image. The image processing circuit 11 performs image quality correction processing such as white balance adjustment processing and gamma correction processing on the input digital image signal, and encoding and compression processing and restoration processing of still images and moving images. Further, the image processing circuit 11 performs image and sound multiplexing processing when shooting a moving image with sound recording.
[0012]
The recording media controller 12 writes a moving image or still image signal output from the image processing circuit 11 to the memory card 13 as still image data or moving image data. The memory card 13 is an interchangeable IC memory that can be attached to and detached from the digital camera 2. The recording media controller 12 reads still image data and moving image data recorded on the memory card 13 and inputs them to the image processing circuit 11. At this time, the image processing circuit 11 performs a restoration process for reproducing the input still image data or moving image data.
[0013]
The liquid crystal driver 14 converts the digital image signal input from the image processing circuit 11 into an analog signal and performs control for displaying a captured image on the screen of the liquid crystal display device 15. The liquid crystal display device 15 displays a finder image and a reproduced image at the time of shooting and at the time of reproduction, respectively.
[0014]
The audio circuit 16 performs audio recording by operating the microphone 17 when recording a moving image. In the audio circuit 16, the audio signal output from the microphone 17 is digitally converted and output to the image processing circuit 11. In addition, when the moving image data with sound is reproduced, the sound circuit 16 outputs a sound signal obtained by analog conversion of the input sound data to the speaker 18 via an amplifier (not shown). Sound is output from the speaker 18 at the same time as an image is reproduced and displayed on the liquid crystal display device 15.
[0015]
The system controller 19 manages the flow of electrical operation of the digital camera 2 and operates each circuit according to a predetermined sequence programmed in advance. Further, the system controller 19 appropriately switches the control sequence in accordance with the operation mode specified by the input operation.
[0016]
The CCD drivers 20 and 21 output timing pulses for performing signal charge accumulation, signal charge read-out, and signal charge transfer at regular intervals, and drive the first image sensor 5 and the second image sensor 6, respectively. The motor drivers 22 and 23 output drive pulses to the focus motors 24 and 25, respectively, and control the drive of the focus motors 24 and 25 with high accuracy. The focus motors 24 and 25 move the focus lenses 26 and 27 provided in the first photographing lens 3 and the second photographing lens 4 in the optical axis direction, respectively, and adjust the focus of each lens.
[0017]
The operation mode changeover switch 28 includes a first mode switch 28a, a second mode switch 28b, and a third mode switch 28c. The first mode switch 28a is operated when switching between a shooting mode for shooting and a playback mode for playing back a shot image. The second mode switch 28b includes a stereo mode in which two images are simultaneously photographed using the first photographing lens 3 and the second photographing lens, and the first imaging element 5 and the second imaging element 6, and one photographing lens and the imaging element. It is operated when switching to the normal mode in which shooting using is performed. The third mode switch 28c is operated when switching between a moving image mode for recording moving images and audio and a still image mode for recording still images. The shooting button 30 is used as an input button for determining the start and stop of moving image recording under the shooting mode, and is used as a shutter button when recording a still image.
[0018]
In FIG. 2, the focus lenses 26 and 27 move within a predetermined range along the optical axis 3 a of the first photographing lens 3 and the optical axis 4 a of the second photographing lens 4. The movement range of each focus lens is divided into a short-distance area that is in focus on the short distance side where the shooting distance is small, and a long-distance area that is in focus on the infinity side, and still images can be taken in stereo mode. When moving, one focus lens moves in the short distance area and the other focus lens moves in the long distance area. A focus lens that moves in the long-distance area moves from the infinity point toward the short distance side, and a focus lens that moves in the short-distance area moves from the short-distance shooting limit point toward the infinity side. . When either one of the focus lenses reaches a position where the sharpest subject image is formed, the other focus lens is moved to the same position as the position where one of the focus lenses has reached.
[0019]
Next, the operation of the digital camera 2 will be described with reference to FIG. When the digital camera 2 is activated, the system controller 19 monitors the signal from the operation mode changeover switch 28 and confirms the operation mode. First, the state of the first mode switch 28a is detected, and the shooting mode and the playback mode are confirmed. In the reproduction mode, still image data or moving image data is read from the memory card 13 by the recording media controller 12 and input to the image processing circuit 11. The image processing circuit 11 decodes the compressed still image data or moving image data and outputs a reproduced image signal to the liquid crystal driver 14. The liquid crystal driver 14 drives the liquid crystal display device 15 based on the input reproduced image signal, and displays a photographed image on the liquid crystal screen. In the moving image data, an audio signal separated from the image signal is sent to the audio circuit 16, and audio is output from the speaker 18 in synchronism with the reproduction and display of the image.
[0020]
In the shooting mode, a control signal is sent from the system controller 19 to the CCD drivers 20 and 21 to drive the first image sensor 5 and the second image sensor 6. In the shooting mode, after confirming the stereo mode and the normal mode, the still image mode and the moving image mode are further confirmed, and the process branches to the following four steps according to the type of the set operation mode.
[0021]
When the stereo mode and the still image mode are set, the first sequence shown in FIG. 4 is executed. In the first sequence, the system controller 19 sends control signals to the motor drivers 22 and 23 to drive the focus motors 24 and 25 so that the focus lens 26 of the first photographing lens 3 is in the long distance area and the second photographing lens. The focus lens 27 is moved to the short distance area. The focus lens 26 moves from the infinity point to the near distance area side, and the focus lens 27 moves from the proximity limit point to the far distance area side. During this time, the first image sensor 5 and the second image sensor 6 capture the subject light that has passed through the first photographing lens 3 and the second photographing lens 4, respectively, and the image signal input circuit 9 receives image signals from the respective image sensors. Entered.
[0022]
The image signal input circuit 9 outputs the image signal input from the first image sensor 5 to the image processing circuit 11, and outputs the image signal input from each image sensor to the focus evaluation circuit 10. The image processing circuit 11 performs an image quality correction process on the input image signal and outputs it to the liquid crystal driver 14. On the liquid crystal display device 15, the subject image formed on the imaging surface of the first imaging element 5 is continuously displayed as a finder image. The focus evaluation circuit 10 analyzes the contrast of each subject image based on the image signals output from the first image sensor 5 and the second image sensor 6 and calculates a focus evaluation value representing the sharpness of the image. The calculated focus evaluation value is output to the system controller 19. The system controller 19 refers to each focus evaluation value and sends a command to the motor drivers 22 and 23. The motor drivers 22 and 23 drive the focus lenses 26 and 27 so that a subject image with the highest sharpness can be obtained. .
[0023]
As shown in FIG. 5, the system controller 19 obtains the peak value of the focus evaluation value at which the sharpness of the subject image formed on the first image sensor 5 and the second image sensor 6 is the highest, P1, P2 in the figure. And the focus lenses 26 and 27 are stopped at the respective positions. A curve a in the figure represents a measurement example of the focus evaluation value for the first photographing lens 3, a curve b represents a measurement example of the focus evaluation value for the second photographing lens 4, and a one-dot chain line in the figure represents one focus lens. An example of measurement when the entire range of the long-distance and short-distance areas is searched is shown. After stopping each focus lens, the system controller 19 compares the focus evaluation values at the positions P1 and P2, and determines the higher focus evaluation value as a focus point.
[0024]
At this time, when the stop position of the focus lens 26 searched in the long-distance area is determined as the focus point, the system controller 19 sends a control signal to the motor driver 23 to move the focus lens 27 to the determined focus point. . When the stop position of the focus lens 27 searched in the short distance area is determined as the focus point, the focus lens 26 is driven to the same position as the stop position of the focus lens 27.
[0025]
When a shooting operation is performed, the subject images formed on the respective imaging surfaces of the first imaging element 5 and the second imaging element 6 at that time are input to the image signal input circuit 9 as image signals. The input image signal is sent from the image signal input circuit 9 to the image processing circuit 11 and subjected to image quality correction processing and image compression processing. On the liquid crystal display device 15, a dialog for selecting whether or not to save the photographed image is displayed together with the photographed image obtained by the first image sensor 5. When saving is selected, two stereo image data are sent to the recording media controller 12 and written to the memory card 13. On the other hand, when selecting to cancel the storage, each image data is deleted from the image processing circuit 11.
[0026]
In FIG. 6, when the stereo mode and the moving image mode are set, the second sequence is executed. In the second sequence, the image signal output from the first image sensor 5 is input to the focus evaluation circuit 10 every 0.5 seconds, for example, and a focus evaluation value is calculated. The system controller 19 sends a control signal to the motor drivers 22 and 23 so as to drive the focus lens 26 and the focus lens 27 by the same amount in the same direction every time a focus evaluation value is calculated. Focus control is performed. The focus lens 26 and the focus lens 27 always move in the same manner, and can take a stereo moving image.
[0027]
In FIG. 7, when the normal mode and the still image mode are set, the third sequence is executed. In the third sequence, as in the first sequence, the focus lens 26 moves in the long-distance area and the focus lens 27 moves in the short-distance area, and the position where the subject image with the highest sharpness is obtained is determined, and each focus is determined. The lens is stopped. After stopping each focus lens, the system controller 19 compares the focus evaluation values at the positions P1 and P2, and determines the higher focus evaluation value as a focus point.
[0028]
At this time, when the stop position of the focus lens 26 searched in the long-distance area is determined as a focus point, the image signal output from the first image sensor 5 is sent from the image signal input circuit 9 to the image processing circuit 11. The recorded image is recorded in the memory card 13. On the other hand, when the stop position of the focus lens 27 searched in the short-distance area is determined as the focus point, an image obtained by the second image sensor 6 is recorded.
[0029]
In FIG. 8, when the normal mode and the moving image mode are set, the fourth sequence is executed. In the fourth sequence, only the image signal output from the first image sensor 5 is sent from the image signal input circuit 9 to the image processing circuit 11, and the display of the finder image and the image storage processing to the memory card 13 are performed.
[0030]
In the above-described embodiment, an imaging device is provided for each photographing lens so that a stereo moving image and a stereo still image can be captured. However, in a camera limited to still image capturing, two imaging devices are not necessarily provided. There is no need to provide a single image sensor. If an object element is captured in a time-division manner by incorporating an optical element (for example, a mirror) for instantaneously switching the subject image guided to the imaging surface, only one image sensor is required. You can also. Alternatively, two image display devices may be provided, or a stereo image may be divided and displayed on the left and right on a single display screen so that the image can be stereoscopically viewed on the spot. In addition, if the photographer can arbitrarily set the movement range of the focus lens and the shooting purpose is fixed, the focus lens range can be narrowed down further for long-distance shooting or short-distance shooting. The speed can be further improved.
[0031]
【The invention's effect】
As described above, according to the digital camera of the present invention, when the still image is recorded by the two photographing lenses, the focus movement can be shared by the two focus lenses, so that the focus point can be quickly found. Therefore, when performing short-distance shooting, switching between normal shooting and macro shooting is not necessary, and it is possible to perform shooting comfortably without troublesome operations.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a digital camera.
FIG. 2 is an explanatory diagram showing a range in which each focus lens moves.
FIG. 3 is a flowchart showing an operation flow of the digital camera.
FIG. 4 is a flowchart showing a flow of a first sequence.
FIG. 5 is a graph showing an example of measurement of sharpness when the first sequence is executed.
FIG. 6 is a flowchart showing a flow of a second sequence.
FIG. 7 is a flowchart showing a flow of a third sequence.
FIG. 8 is a flowchart showing a flow of a fourth sequence.
[Explanation of symbols]
2 Digital Camera 3 First Shooting Lens 4 Second Shooting Lens 5 First Image Sensor 6 Second Image Sensor 10 Focus Evaluation Circuit 19 System Controller 22, 23 Motor Driver 24, 25 Focus Motor 26, 27 Focus Lens 28 Operation Mode Changeover Switch 30 Shooting button

Claims (2)

Two subject images having parallax are recorded by two photographing optical systems provided at a predetermined interval and an image sensor that converts subject images formed by the photographing optical systems into image signals. In digital cameras,
The focus lens provided in each photographic optical system is moved in the optical axis direction to obtain the sharpness of the subject image based on the image signal output from the image sensor, and the focus is obtained at the position where the peak of sharpness is obtained. First focus control means for stopping the driving of the lens;
Driving each focus lens within a movement range assigned to a first area suitable for short-distance shooting and a second area suitable for long-distance shooting, and moving one focus lens within the short-distance area; Second focus control means for moving the other focus lens within the long distance area;
An arithmetic means for comparing the sharpness of the subject image formed by each photographing optical system after the driving of each focus lens is stopped at the position where the peak of sharpness is obtained,
A digital camera comprising a third focus control means for moving the other focus lens at a position corresponding to a stop position of the one focus lens where a subject image with high sharpness is obtained. Control means for switching between a first operation mode for recording a subject image formed by each photographing optical system and a second operation mode for recording any one of the subject images is provided,
2. The digital camera according to claim 1, wherein when the second operation mode is executed, the third focus control unit is prohibited from operating and a subject image having a higher sharpness is recorded.

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