JP2010119042A - Imaging apparatus, and zoom control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus and zoom control method in which a photographic image can be prevented from becoming non-sharp because of camera shake or subject shake or from becoming much noisy because of sensitivity elevation when a photographer performs photographing with a zooming operation. <P>SOLUTION: When a photographer performs a zooming operation, not only an optical zoom but also an electronic zoom are used together. Thus, a change in open F factor at a telephotographic side can be suppressed and it is not necessary to decelerate a shutter speed, thereby suppressing occurrence of shake not-intended by the photographer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus in which an open aperture value changes according to a focal length, and a zoom control method thereof.

  If shooting is performed with the camera held unstable, the camera body may move during exposure due to camera shake, image blurring may occur, and the shot image may become blurred due to image blurring. Further, when the subject moves quickly, subject blurring may occur due to the subject's own movement, and part of the captured image may become unclear.

  These image blur (hereinafter referred to as camera shake) and subject blur phenomena due to camera shake tend to occur when the subject is usually dark and the shutter speed is slow to maintain proper exposure. However, in a camera equipped with a zoom lens in which the wide aperture side open aperture value (open F value) is larger than the wide angle side open F value, the amount of incident light even when zoomed to the telephoto side using optical zoom Decrease. In this case, in order to maintain proper exposure, the shutter speed becomes slow, and camera shake and subject blur are likely to occur.

Therefore, Patent Document 1 proposes a technique for suppressing camera shake when a photographer performs optical zoom. In this proposal, if the set shutter speed is slower than the camera shake limit shutter speed at that time, there is a possibility that camera shake may occur. Therefore, the zoom lens is moved to the wide angle side to a focal length where no camera shake occurs. Also, when the set shutter speed is faster than the camera shake limit speed at that time, when the switch is operated by the photographer and the zoom lens is about to move to the telephoto side, the zoom control unit moves the zoom lens to the telephoto side. Move to. However, when the focal length reaches the focal length on the camera shake limit line, the movement of the zoom lens is forcibly stopped.
JP 2001-215549 A

In zoom lenses used in recent digital cameras, there is a case where the brightness of the telephoto side is significantly lower than the wide-angle side. Zoom lenses used in recent digital cameras are required to be miniaturized in response to ultra-miniaturization of the camera body. As a result, the F-number indicating brightness is 2 or more, and further changes greatly depending on the focal length. Because it is.
Therefore, when shooting a low-luminance subject, camera shake and subject blurring may occur when zooming up, resulting in an unclear image, and even if the sensitivity is increased, image noise will increase and the expected image quality There was a problem that could not be obtained.

  In order to solve such a problem, camera shake is also prevented by causing the flash to automatically emit light in a camera having a built-in flash. However, there is a problem that an image intended by the photographer cannot be obtained due to artificial light, or an image with an underexposure that exceeds the reach of the flash. Also, you cannot use the flash when shooting in places where flash is prohibited.

  Further, in the technique of Patent Document 1, the optical zoom operation is prohibited and the optical zoom is automatically limited to the wide angle side, and the angle of view is different from the angle of view intended by the photographer. There was a problem that the photographer felt uncomfortable.

  It is an object of the present invention to prevent a photographed image from being blurred due to camera shake or subject blur or a noisy image due to an increase in sensitivity when the photographer performs zoom operation. An imaging device and a zoom control method that can be used are provided.

  An image pickup apparatus according to a first aspect of the present invention is an image pickup apparatus that picks up an image obtained through a lens barrel whose open aperture value changes according to the focal length, and is obtained through the lens barrel. An image pickup means for picking up an image, an exposure control means for setting and controlling an exposure condition when image pickup is performed by the image pickup means, an optical zoom for changing the focal length of the lens barrel and changing the magnification, and Control means for controlling an electronic zoom for changing a photographing range of an image obtained through a lens barrel by image processing, and the control means includes an open aperture value that changes according to a focal length and the exposure control means. The optical zoom and the electronic zoom are switched based on the exposure condition set by.

  A zoom control method according to a second aspect of the present invention includes an imaging unit that captures an image obtained through a lens barrel whose open aperture value changes in accordance with a focal length, and when the imaging unit performs imaging. The exposure control means for setting and controlling the exposure conditions, the optical zoom for changing the magnification by changing the focal length of the lens barrel, and the imaging range of the image obtained through the lens barrel are changed by image processing. A zoom control method for an imaging apparatus including a control unit that controls electronic zoom, wherein the control unit is based on an open aperture value that changes according to a focal length and an exposure condition set by the exposure control unit. It is characterized by switching between optical zoom and electronic zoom.

  According to the present invention, even when a photographer performs a zoom operation, it is possible to prevent a blurred image due to camera shake or subject blur, or a noisy image due to excessively high sensitivity. Can do.

The best mode for carrying out the present invention will be described below with reference to the drawings.
In the following description, specific numerical values, configurations, operations, and the like are shown and described, but these can be changed as appropriate.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a first embodiment of an imaging apparatus according to the present invention.
The imaging device 100 is a digital camera, a digital video camera, or the like, and images a subject image obtained by the imaging lens 10 included in the lens barrel by forming it on the imaging surface of the imaging element 14.
The taking lens 10 is composed of a plurality of optical lenses (not shown), and has a zoom mechanism for changing the focal length and a focus mechanism for moving the focal position. By driving the zoom mechanism of the photographing lens 10, optical zoom that optically changes the magnification of the image can be performed.
A shutter 12 having a diaphragm function is provided between the photographing lens 10 and the image sensor 14. The taking lens 10, the shutter 12, and the protection unit 102 described later are provided in the lens barrel of this embodiment.
In the photographing lens 10 according to the present embodiment, when the focal length is changed by performing optical zoom, an open aperture value (hereinafter, open F value) is changed. Specifically, when zooming to the telephoto side, the open F value increases.

The image sensor 14 is a photoelectric conversion unit that converts an optical image into an electric signal. The image sensor 14 of the present embodiment uses a CCD (Charge Coupled Device) image sensor. The image sensor may be another type of image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor.
The A / D converter 16 converts the analog signal output of the image sensor 14 into a digital signal.
The timing generation circuit 18 supplies a clock signal and a control signal to the image sensor 14, the A / D converter 16, and the D / A converter 26. The timing generation circuit 18 is controlled by the memory control circuit 22 and the system control circuit 50.

  The image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on the data from the A / D converter 16 or the data from the memory control circuit 22. In addition, the image processing circuit 20 cuts out a necessary shooting range from the shot image and performs an enlargement process to realize an electronic zoom that changes the magnification. Further, the image processing circuit 20 performs predetermined arithmetic processing using the captured image data. Based on the calculation result obtained by this calculation process, the system control circuit 50 controls the exposure control unit 40 and the focus control unit 42. For example, the system control circuit 50 performs TTL (through-the-lens) AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash pre-flash) processing. Furthermore, the image processing circuit 20 performs predetermined arithmetic processing using the captured image data, and also performs TTL AWB (auto white balance) processing based on the obtained arithmetic result.

The memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32.
The digital data output from the A / D converter 16 is sent to the image display memory 24 or the memory via the image processing circuit 20, the memory control circuit 22, or directly from the A / D converter 16 via the memory control circuit 22. 30 is written.

The image display unit 28 is a TFT-LCD (Thin Film Transistor-Liquid).
Crystal Display). The image display unit 28 displays the display image data written in the image display memory 24 via the memory control circuit 22 and the D / A converter 26. The display image data has the same number of pixels as the number of pixels of the image display unit 28.
If image data captured using the image display unit 28 is sequentially displayed, an electronic viewfinder (EVF: Electronic)
(View Finder) function can be realized.
The image display unit 28 can arbitrarily turn on / off the display according to an instruction from the system control circuit 50. When the display is turned off, the power consumption of the imaging apparatus 100 can be significantly reduced. Can do.

The memory 30 is a storage unit that stores captured still images and moving images, and has a storage capacity sufficient to store a predetermined number of still images and a moving image for a predetermined time. This makes it possible to write a large amount of images to the memory 30 at high speed even in continuous shooting or panoramic shooting in which a plurality of still images are continuously shot. The memory 30 can also be used as a work area for the system control circuit 50.
The compression / decompression circuit 32 is provided with an adaptive discrete cosine transform (ADCT: Adaptive Discrete).
Image data is compressed and decompressed by Cosine Transform). The compression / decompression circuit 32 reads an image stored in the memory 30, performs a compression process or an expansion process, and writes the processed data to the memory 30.

  The exposure control unit 40 controls the shutter 12 based on the exposure condition, performs a predetermined calculation on the captured image data by the image processing circuit 20, and performs an AE (automatic exposure) process based on the obtained calculation result. ing. The exposure control unit 40 detects the luminance of the subject image by the image sensor 14 and controls the exposure by setting the aperture value and the shutter speed as exposure conditions based on the luminance detection result. Further, when the aperture value, shutter speed, sensitivity, and the like are set by the photographer through the operation unit 70 or the like, the exposure control unit 40 controls the exposure according to the set exposure conditions. The exposure control unit 40 also has a flash light control function that performs light control of the flash 48 in cooperation with the flash 48.

The focus control unit 42 controls the focusing operation of the photographic lens 10.
The exposure control unit 40 and the focus control unit 42 are controlled using the TTL method. That is, the system control circuit 50 controls the exposure control unit 40 and the focus control unit 42 based on the calculation result obtained by calculating the image data captured through the photographing optical system by the image processing circuit 20.

The zoom control unit 44 controls zooming of the taking lens 10.
The barrier control unit 46 controls the operation of the protection unit 102 that is a so-called lens barrier.
The flash 48 is a flash light emitting unit that emits light to compensate for the amount of light in a dark place or the like, and also has an AF auxiliary light projecting function and a flash light control function.
The system control circuit 50 is a control unit that controls the entire imaging apparatus 100 and is configured by a microcomputer.
The memory 52 stores constants, variables, programs, and the like for operating the system control circuit 50.

The display unit 54 displays an operation state, a message, and the like using characters, images, sounds, and the like according to the execution of the program in the system control circuit 50. One or a plurality of the display units 54 are installed at positions in the vicinity of the operation unit of the imaging apparatus 100 that are easily visible. For example, an LCD (Liquid Crystal Display) or an LED (Light Emitting) is provided.
Diode), a combination of sound generation elements and the like. The display unit 54 has a part of its function installed in the optical viewfinder 104.
Among the display contents of the display unit 54, what is displayed on the LCD or the like includes single shot / continuous shooting display, self-timer display, compression rate display, number of recorded pixels, number of recorded pixels, number of remaining images that can be captured, shutter There are speed display, aperture value display, exposure compensation display, and so on. In addition, flash display, red-eye reduction display, macro shooting display, buzzer setting display, watch battery remaining amount display, battery remaining amount display, error display, information display with multiple digits, display / removal state display of recording media 200 and 210, Communication I / F operation display, date / time display, etc. are also displayed on the LCD.
On the other hand, among the display contents of the display unit 54, what is displayed in the optical viewfinder 104 includes in-focus display, camera shake warning display, flash charge display, shutter speed display, aperture value display, exposure correction display, and the like.

The non-volatile memory 56 is an electrically erasable and recordable non-volatile storage means, for example, an EEPROM (Electrically Erasable Programmable ROM) or the like.
The mode dial switch 60, shutter switches 62 and 64, image display ON / OFF switch 66, single / continuous shooting switch 68, and operation unit 70 are operation means for inputting various operation instructions of the system control circuit 50. is there. These are composed of one or a plurality of combinations such as a switch, dial, touch panel, pointing by line-of-sight detection, and a voice recognition device.

Here, a specific description of these operating means will be given.
The mode dial switch 60 is operated to switch and set each function mode such as power-off, automatic shooting mode, shooting mode, panoramic shooting mode, playback mode, multi-screen playback / erase mode, and PC connection mode.
The shutter switch 62 is a switch (SW1) that is turned on in a so-called half-pressed state during the operation of a shutter button (not shown). When the shutter switch 62 (SW1) is turned on, the system control circuit 50 starts operation such as AF (autofocus) processing, AE (automatic exposure) processing, AWB (auto white balance) processing, and EF (flash pre-flash) processing. Directs.

The shutter switch 64 is a switch (SW2) that is turned on when the shutter button (not shown) is fully pressed. When the shutter switch 64 (SW2) is turned on, the system control circuit 50 instructs the start of a series of processing operations such as exposure processing, development processing, and recording processing.
In this exposure processing, the image data is written into the memory 30 via the A / D converter 16 and the memory control circuit 22 from the signal read from the image sensor 14.
In the development process, the image processing circuit 20 and the memory control circuit 22 perform calculations.
Further, in the recording process, the image data is read from the memory 30, compressed by the compression / decompression circuit 32, and written to the recording media 200 and 210.

  The image display ON / OFF switch 66 can set ON / OFF of the image display unit 28. With this function, when shooting using the optical viewfinder 104, it is possible to save power by cutting off the current supply to the image display unit 28 such as an LCD.

  The single-shot / continuous-shot switch 68 is continuously in a single-shot mode in which one frame is shot when the shutter switch 64 (SW2) is turned on and is in a standby state, and while the shutter switch 64 (SW2) is turned on. You can set the continuous shooting mode to continue shooting.

  The operation unit 70 includes various buttons, a touch panel, and the like, and has functions such as a menu button, a set button, a macro button, a multi-screen playback page break button, a flash setting button, and a single shooting / continuous shooting / self-timer switching button. The operation unit 70 also includes a menu movement + (plus) button, menu movement-(minus) button, reproduction image movement + (plus) button, reproduction image-(minus) button, shooting image quality selection button, exposure correction button, date. / Has functions such as time setting buttons. Further, the operation unit 70 has functions such as a print output button, a recording button, a zoom lever (telephoto / wide angle), a cross button (up, down, left, right), a cursor display button, and the like.

The power control means 80 is configured by a battery detection circuit, a DC-DC converter, a switch circuit that switches a block to be energized, and the like. The power supply control means 80 detects the presence / absence of a battery, the type of battery, the remaining battery level, controls the DC-DC converter based on the detection result and an instruction from the system control circuit 50, and supplies the necessary voltage for a necessary period, It supplies to each part including the recording media 200 and 210.
The connectors 82 and 84 connect the inside of the imaging apparatus 100 and a power source 86 such as a battery or an AC adapter accommodated in the battery accommodating portion.
The power source 86 is a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a Li battery, an AC adapter, or the like.

The interfaces 90 and 94 mediate connection with recording media 200 and 210 such as a memory card and a hard disk.
The connectors 92 and 96 connect to recording media 200 and 210 such as a memory card and a hard disk.
The recording medium attachment / detachment detecting means 98 detects whether or not the recording medium 200 or 210 is attached to at least one of the connectors 92 and 96.

  In the present embodiment, it is assumed that there are two interfaces and connectors for attaching the recording medium. Not only this but the interface and connector which attach a recording medium are good also as a structure provided with any number of system | strains of single or multiple. Moreover, it is good also as a structure provided with combining the interface and connector of a different standard. As the interface and the connector, those compliant with a standard such as a PCMCIA card or a compact flash (registered trademark) card can be used.

  Further, when the interfaces 90 and 94 and the connectors 92 and 96 are configured using a PCMCIA card, a compact flash (registered trademark) card, or the like, it can be used for data communication. That is, by connecting various communication cards to this portion, it is possible to transfer image data and management information attached to the image data to and from peripheral devices such as other computers and printers. As the communication card, for example, a LAN card, a modem card, a USB card, an IEEE 1394 card, a P1284 card, a SCSI card, a PHS, or the like can be used.

The protection unit 102 is a barrier that prevents the imaging unit from being stained or damaged by covering the imaging unit including the photographing lens 10 of the imaging device 100.
The optical viewfinder 104 can confirm the composition using only the optical image without using the electronic viewfinder function of the image display unit 28. Further, in the optical viewfinder 104, a small display unit that performs some functions of the display unit 54, such as a focus display, a camera shake warning display, a flash charge display, a shutter speed display, an aperture value display, an exposure correction display, and the like. Is installed.

The communication unit 110 has various communication functions such as RS232C, USB, IEEE1394, P1284, SCSI, modem, LAN, and wireless communication.
The connector 112 connects the imaging device 100 to other devices via the communication unit 110. Note that an antenna may be used instead of the connector 112 in the case of wireless communication.

The recording medium 200 is a memory card or a hard disk. The recording medium 200 includes a recording unit 202 composed of a semiconductor memory, a magnetic disk, or the like, an interface 204 with the imaging device 100, and a connector 206 that connects to the imaging device 100.
The recording medium 210 is a memory card, a hard disk, or the like. The recording medium 210 includes a recording unit 212 composed of a semiconductor memory, a magnetic disk, or the like, an interface 214 with the imaging device 100, and a connector 216 that connects to the imaging device 100.

Next, optical zoom and electronic zoom will be described.
The optical zoom is to change the magnification of the image formed on the image sensor by driving the photographing lens 10 including a plurality of optical lenses, that is, to change the focal length between the optical lens and the image sensor.
On the other hand, the electronic zoom is to enlarge an image by performing digital processing on a part of the image captured by the image sensor.

FIG. 2 is a graph showing the brightness when the focal length of the photographic lens 10 is changed, that is, the change in the open F value. The vertical axis in FIG. 2 indicates the open F value of the photographing lens 10, and the horizontal axis indicates the focal length of the photographing lens 10. The vertical axis shows one scale for one stop.
As shown in FIG. 2, the photographic lens 10 has F = 2.8 at the wide-angle end, but F = 5.6 at the telephoto end, and the brightness is about four times, that is, changes corresponding to two stops of the aperture. Yes. Thus, the taking lens 10 has a characteristic that the telephoto side is very dark with respect to the wide angle side. Here, the F value is represented by the following formula (1), and is a numerical value indicating the transmitted light amount of the lens, that is, the brightness of the lens.

F = f / D Formula (1)
f: focal length, D: effective aperture of lens

FIG. 3 shows an image displayed on the image display unit 28 when zooming from the wide-angle side to the telephoto side using only the optical zoom in the imaging apparatus 100 having the zoom lens having the characteristics as shown in FIG. It is a figure which shows the example of a shutter speed and F value.
In FIG. 3, a display image 300 shows a display image at the wide-angle end before zooming, and a display image 301 shows a display image when the optical zoom is performed 6 times.

FIG. 4 is a graph showing the zoom magnification and F value of the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side corresponding to FIG.
The solid line in FIG. 4 indicates the F value at the time of shooting, and the broken line indicates the open F value. FIG. 4 shows that the open F value increases as the zoom magnification increases.

  Assume that the shutter speed and the F value for the proper exposure value when the AE (automatic exposure) is performed at the wide-angle end before the zoom operation are 1/125 seconds (hereinafter, seconds are omitted) and F4.0, respectively. . When zooming from the wide-angle side to the telephoto side with an optical zoom magnification of 6x, if the proper exposure value obtained on the wide-angle side does not change even on the telephoto side, the image is taken with the open F value when the magnification is 2x or more. F value of the hour goes up. In this case, in order to maintain an appropriate exposure value, the shutter speed is slowed instead of increasing the F value at the time of shooting, and the shutter speed and F value are 1/60 and F5.6, respectively. When the optical zoom is performed, as the open F value changes from F2.8 to F5.6, the F value at the time of photographing becomes darker by one stop from F4.0 to F5.6. However, in order to brighten the aperture by one step, the shutter speed becomes slow and becomes 1/60. Lowering the shutter speed causes camera shake and subject blur.

On the other hand, in this embodiment, electronic zoom is used together.
FIG. 5 shows an image displayed on the image display unit 28 and the shutter speed and F at that time when the zoom operation is performed using the optical zoom and the electronic zoom in the imaging apparatus 100 having the zoom lens having the characteristics as shown in FIG. It is an example of a value.

  In FIG. 5, a display image 500 shows a display image at the wide-angle end before zooming, a display image 501 shows a display image when the optical zoom is doubled, and a display image 502 shows a double optical zoom. After the operation, a display image when the electronic zoom is further tripled is shown. A frame 503 indicates a boundary frame for switching from the optical zoom to the electronic zoom.

FIG. 6 is a graph showing the zoom magnification and F value of the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side corresponding to FIG.
The solid line in FIG. 6 indicates the F value at the time of shooting, and the broken line indicates the open F value.
Assume that the shutter speed and the F value with respect to the appropriate exposure value when the AE is performed at the wide angle end before the zoom operation are 1/125 and F4.0, respectively. When the zoom operation is performed from the wide angle side to the telephoto side when the optical zoom magnification is 6 times, if the appropriate exposure value does not change, the F value at the time of shooting increases with the open F value when the magnification is 2 times or more. . Therefore, in the present embodiment, switching to the electronic zoom is performed when the zoom magnification is 2 times or more. Even if the zoom operation is performed by the electronic zoom, the F value does not change, so that it is not necessary to slow down the shutter speed. Therefore, the shutter speed and F value before the zoom operation are not changed even on the telephoto side where the zoom magnification is 6 times, and the shutter speed and F value are 1/125 and F4.0, respectively. Thus, since it is not necessary to change the shutter speed even on the telephoto side, it is possible to prevent the occurrence of camera shake and subject blur as compared with the case where only the optical zoom is used.

FIG. 7 is a flowchart illustrating processing in the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side according to the first embodiment.
First, in step (hereinafter referred to as S) 700, a photographing mode is selected.
In step S701, the exposure control unit 40 performs AE control, and obtains an appropriate exposure value from the luminance information of the subject being imaged.
In step S702, the exposure control unit 40 sets an F value and a shutter speed at which proper exposure is achieved.
In S703, the system control circuit 50 sets a switching boundary between optical zoom and electronic zoom from the F value set in S702. Thus, the maximum magnification for performing optical zoom (the magnification of optical zoom when switching from optical zoom to electronic zoom) is set. The switching boundary between the optical zoom and the electronic zoom set here is changed every time a proper exposure value is changed by performing AE at regular intervals and changing the luminance of the subject.

In step S <b> 704, the switching boundary frame 503 is displayed on the image display unit 28 of the imaging apparatus 100. The frame 503 displayed here is subjected to AE at regular intervals, and changes in size each time the luminance of the subject changes and the appropriate exposure value changes.
In S705, it is determined whether the photographer has operated the zoom lever of the operation unit 70 to the telephoto side. If the zoom lever is operated to the telephoto side, the process proceeds to S706, and if the zoom lever is not operated to the telephoto side, the process returns to S701.
In S706, the optical zoom is performed up to the switching boundary between the optical zoom and the electronic zoom.
In step S707, the electronic zoom is performed by switching from the switching boundary between the optical zoom and the electronic zoom to the electronic zoom.
Note that when the zoom lens reaches the telephoto end or zooms to the magnification desired by the photographer and the photographer stops operating the zoom lever, the zoom operation stops.

FIG. 8 shows an image displayed on the image display unit 28 when the image pickup apparatus 100 having the zoom lens having the characteristic as shown in FIG. 2 is zoomed from the telephoto side to the wide angle side using the optical zoom and the electronic zoom. It is a figure which shows the example of the shutter speed and F value at that time.
In FIG. 8, a display image 800 shows a display image at the telephoto end, a display image 801 shows a display image when the optical zoom is 3/4 times, and a display image 802 is an optical zoom 3/4 times. A display image when the electronic zoom is performed 1/3 times after performing the above is shown. A display image 803 shows a display image when the optical zoom is 2/3 times after the optical zoom 3/4 times and the electronic zoom 1/3 times.
FIG. 9 is a graph showing the zoom magnification and F value of the imaging apparatus 100 when zooming from the telephoto side to the wide-angle side corresponding to FIG.
8 and 9 show a case where the luminance of the subject is lowered.

In the example shown in FIGS. 8 and 9, the zoom position is on the telephoto side, and the shutter speed and F value for the appropriate exposure value when AE is performed are 1/80 and F4.0, respectively. If it is determined that the subject is darker than when AE is performed at the telephoto end before the zoom operation and the amount of exposure necessary for proper exposure is increased, the optical zoom is given priority to the wide-angle side until the switching boundary A. To work.
When the optical zoom is operated to the wide angle side, the open F value is decreased, and accordingly, the F value at the time of photographing is decreased. The shutter speed and F value for the appropriate exposure value at the switching boundary A are 1/125 and F3.5, respectively, and the shutter speed can be increased by the amount the F value has decreased.

  Then, when it is on the wide angle side from the switching boundary A, the optical zoom is stopped and the electronic zoom is operated up to the switching boundary B. If the appropriate exposure value does not change, the shutter speed and the F value for the appropriate exposure value at the switching boundary B are not different from the switching boundary A, and are 1/125 and F3.5, respectively. Thereafter, the electronic zoom magnification becomes equal at the switching boundary B, and the optical zoom operates again up to the wide angle end. The shutter speed and F value for the proper exposure value at the wide angle end are 1/125 and F3.5, respectively. By performing such control when the subject becomes dark, it is possible to shoot an image in which resolution degradation due to electronic zoom is suppressed while suppressing camera shake and subject blur.

FIG. 10 shows an image displayed on the image display unit 28 when the image pickup apparatus 100 having the zoom lens having the characteristic as shown in FIG. 2 performs a zoom operation from the telephoto side to the wide angle side using the optical zoom and the electronic zoom. It is a figure which shows the example of the shutter speed and F value at that time.
In FIG. 10, a display image 900 shows a display image at the telephoto end before the zoom operation, and a display image 901 shows a display image when the electronic zoom is performed 1/3 times. A display image 902 shows a display image when the optical zoom is ½ times after the electronic zoom is １ ／ times.
FIG. 11 is a graph showing the zoom magnification and F value of the imaging apparatus when zooming from the telephoto side to the wide-angle side corresponding to FIG.
10 and 11 show a case where the luminance of the subject is increased or the luminance does not change.

  In the example shown in FIGS. 10 and 11, the zoom position is on the telephoto side, and the shutter speed and F value for the appropriate exposure value when AE is performed are 1/125 and F5.4, respectively. If it is determined that the subject becomes brighter and the appropriate exposure value is smaller than when AE is performed at the telephoto end before the zoom operation, the electronic zoom operates preferentially toward the wide-angle side until the switching boundary C. Deterioration of resolution can be suppressed by operating the electronic zoom to the wide angle side. If the appropriate exposure value does not change, the shutter speed and the F value for the appropriate exposure value at the switching boundary C are not different from the telephoto end, and become 1/125 and F5.4, respectively. When the switching boundary C is exceeded, the electronic zoom stops and the optical zoom operates to the wide angle end. When the optical zoom is operated, the open F value is decreased.

FIG. 12 is a flowchart illustrating processing in the imaging apparatus 100 when zooming from the telephoto side to the optical side.
First, in S1200, a shooting mode is selected. At this time, it is assumed that the zoom position is on the telephoto side.
In step S1201, the exposure control unit 40 performs AE control, and obtains an appropriate exposure value from the luminance information of the subject being imaged.
In S1202, the exposure control unit 40 sets an F value and a shutter speed at which proper exposure is achieved.
In S1203, the system control circuit 50 sets a switching boundary between the optical zoom and the electronic zoom from the F value set in S1202.

In S1204, it is determined whether or not the photographer has operated the zoom lever of the operation unit 70 to the wide angle side. If the zoom lever is operated to the wide-angle side, the process proceeds to S1205. If the zoom lever is not operated to the wide-angle side, the process returns to S1201, and until the photographer moves the zoom lever to the wide-angle side, the process proceeds from S1201 to S1203. Repeat until.
In S1205, AE is performed again, and the current time is compared with the time when AE is performed at the telephoto end in S1201. If the subject becomes dark, the process proceeds to S1206. On the other hand, if the subject is not dark, that is, if the subject is bright or the luminance of the subject does not change, the process proceeds to S1209.

In S1206, the optical zoom operates preferentially up to the switching boundary A. Then, when it reaches the switching boundary A, the process proceeds to S1207.
In S1207, the optical zoom is stopped, and the electronic zoom is operated up to the switching boundary B. When it reaches the switching boundary B, the process proceeds to S1208.
In S1208, the electronic zoom is stopped and the optical zoom is operated up to the wide-angle end.

In S1209, the electronic zoom operates preferentially up to the switching boundary C. When the switching boundary C is reached, the process proceeds to S1210.
In S1210, the electronic zoom is stopped and the optical zoom is operated up to the wide-angle end.

Next, in the first embodiment, an operation when the luminance of the subject changes when the zoom position is on the telephoto side and there is no zoom operation will be described.
When the zoom position is on the telephoto side, proper exposure is achieved by changing the shutter speed. Here, the optical zoom, electronic zoom, F value, sensitivity, etc. are not changed. When the brightness of the subject decreases and the exposure amount necessary to achieve proper exposure increases from the result of AE, control is performed so as to achieve proper exposure by reducing the shutter speed. On the other hand, when the brightness of the subject becomes high and the exposure amount necessary to obtain the proper exposure from the result of AE decreases, the shutter speed is increased to control the exposure appropriately.

Here, the maximum zoom magnification that can be zoomed with respect to the maximum zoom magnification capability of the optical zoom and the electronic zoom of the imaging apparatus according to the first embodiment will be described.
In the present embodiment, the maximum magnification obtained by combining the electronic zoom and the optical zoom is changed by changing the magnification at which the optical zoom is switched to the electronic zoom depending on the luminance of the subject. Therefore, in this embodiment, the maximum zoom magnification is limited by the same magnification as the maximum zoom magnification of the electronic zoom.

FIG. 13 is a diagram illustrating a relationship between the F value, the zoom magnification, and the focal length regarding the limitation of the maximum magnification according to the first embodiment.
In FIG. 13, the vertical axis indicates the F value, and the horizontal axis indicates the calculated focal length converted from the angle of view corresponding to the image obtained together with the zoom magnification. When the maximum zoom magnification is not limited to the maximum zoom magnification of the electronic zoom, when the subject is bright and the F value is set to F5.6 or more, the zoom can be zoomed up to 12 times, which is the maximum magnification of the optical zoom and the electronic zoom. However, when the subject is dark and the open F value is F2.8 at the wide-angle end, the F value cannot be set to F2.8 if the zoom magnification is 4 times or more. You can only zoom in. Therefore, the maximum zoom magnification is limited to 4 times the maximum zoom magnification of the electronic zoom. By limiting the maximum zoom magnification, the zoomable magnification is constant regardless of the brightness of the subject, and the photographer does not feel uncomfortable.

  As described above, according to the first embodiment, zooming is performed by appropriately switching between the optical zoom and the electronic zoom according to the luminance of the subject, so that it is difficult to cause camera shake and subject blur due to a decrease in shutter speed. Can be obtained. In addition, since it is not necessary to increase the sensitivity too much, an image with less noise can be obtained.

  Note that the present invention described in the first embodiment described above is an image pickup apparatus having a photographing lens composed of a zoom lens in which the brightness of the telephoto side is significantly lower than that on the wide-angle side, and an image pickup having a high pixel image pickup element. This is particularly effective for the device. The same applies to the present invention described in the second to fourth embodiments described below.

(Second Embodiment)
Next, a second embodiment of the imaging device according to the present invention will be described.
In addition, the same code | symbol is attached | subjected to the part which fulfill | performs the same function as 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted suitably.
The maximum zoom magnification capable of zooming with respect to the maximum zoom magnification capability of each of the optical zoom and electronic zoom of the imaging apparatus according to the second embodiment will be described. As described in the first embodiment, when the magnification at which the optical zoom is switched to the electronic zoom is changed according to the luminance of the subject, the maximum magnification obtained by combining the electronic zoom and the optical zoom is changed. Therefore, in the second embodiment, by increasing the sensitivity, the zoom operation can be performed without limiting to a magnification obtained by combining the maximum zoom magnification of the optical zoom and the maximum zoom magnification of the electronic zoom.

FIG. 14 is a diagram illustrating an example of an image displayed on the image display unit 28 when the zoom operation is performed using the optical zoom and the electronic zoom from the wide-angle side to the telephoto side, and the shutter speed and the F value at that time.
In FIG. 14, a display image 1400 shows a display image at the wide-angle end before zooming, a display image 1401 shows a display image when the optical zoom is 1.5 times, and a display image 1402 shows the optical zoom 1 A display image when electronic zoom is performed 4 times after 5 times is performed is shown. A display image 1403 shows a display image when the optical zoom is doubled after the optical zoom of 1.5 times and the electronic zoom of 4 times.

FIG. 15 is a graph showing the zoom magnification and F value of the imaging apparatus when the zoom operation is performed using the optical zoom and the electronic zoom from the wide-angle side to the telephoto side corresponding to FIG.
The solid line in FIG. 15 indicates the F value at the time of shooting, and the broken line indicates the open F value. Here, the maximum zoom magnification of the optical zoom is 3 times, the maximum zoom magnification of the electronic zoom is 4 times, and the maximum zoom magnification combining the optical zoom and the electronic zoom is 12 times.

Assume that the shutter speed and the F value with respect to the appropriate exposure value when the AE is performed at the wide angle end before the zoom operation are 1/125 and F4.0, respectively. If the appropriate exposure value does not change, if only the optical zoom is performed, the F value at the time of shooting increases with the open F value when the magnification is 1.5 times or more. Therefore, when the zoom magnification is 1.5 times or more. Switches to electronic zoom.
Even if the zoom operation is performed by the electronic zoom, the F value does not change, so that it is not necessary to slow down the shutter speed. Therefore, on the telephoto side where the zoom magnification is up to 6 times, the shutter speed and F value before the zoom operation are not changed, and the shutter speed and F value are 1/125 and F4.0, respectively.

When the zoom magnification is 6 times, the electronic zoom is at the telephoto end. Here, if the photographer does not release the zoom lever, the optical zoom operation is again switched to the optical zoom operation until the telephoto end of the optical zoom is increased. Works. Here, when the optical zoom is performed, the value of the open F value becomes large, and the shutter speed becomes slow in order to maintain an appropriate exposure value. Therefore, in the present embodiment, the optical zoom operation can be performed without increasing the sensitivity and changing the shutter speed. The shutter speed and F value when the zoom magnification at the telephoto end is 12 times are 1/125 and F5.6, respectively.
Thus, in this embodiment, since it is not necessary to change the shutter speed even on the telephoto side, it is possible to prevent the occurrence of camera shake and subject blur as compared with the case where only the optical zoom is used.

FIG. 16 is a flowchart illustrating processing in the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side according to the second embodiment.
Since S1500 to S1507 in the flow of FIG. 16 are the same operations as S700 to S707 of FIG. 7 of the first embodiment, description thereof will be omitted.
In step S1507, the electronic zoom is performed up to the telephoto end of the electronic zoom.
In S1508, it is determined whether or not the optical zoom is at the telephoto end. If it is the telephoto end of the optical zoom, the process proceeds to S1510 to end the zoom operation. On the other hand, if it is not the telephoto end of the optical zoom, the process proceeds to S1509.
In step S1509, shooting sensitivity is increased and optical zoom is performed. Here, when the optical zoom is performed, the open F value is increased and the shutter speed for the appropriate exposure value is decreased. However, by increasing the sensitivity, the shutter speed before the optical zoom can be maintained even if the F value is increased. . As a result, camera shake and subject blur can be prevented even when optical zoom is performed. When the processing of S1509 is completed, the process returns to S1508, and the operation of S1509 is repeated until the telephoto end of the optical zoom is reached.
If the photographer releases the zoom lever in step S1507, the zoom operation is stopped, and the same operation as in the first embodiment is performed.

  According to the second embodiment, by increasing the sensitivity, in addition to the effect obtained by the first embodiment, it is not limited to a magnification that combines the maximum zoom magnification of the optical zoom and the maximum zoom magnification of the electronic zoom, Zoom operation can be performed.

(Third embodiment)
Next, a third embodiment of the imaging device according to the present invention will be described.
In addition, the same code | symbol is attached | subjected to the part which fulfill | performs the same function as 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted suitably.
The third embodiment differs from the first embodiment in the operation when the subject brightness changes when the zoom position is on the telephoto side and there is no zoom operation. The operation at this time will be described below.
In the third embodiment, when the brightness of the subject changes when the zoom position is not at the wide-angle end, the sensitivity is changed to achieve proper exposure. At this time, the optical zoom, electronic zoom, F value, and shutter speed are not changed. When the brightness of the subject is reduced and the exposure amount necessary to achieve proper exposure increases as a result of AE, control is performed to increase the sensitivity to achieve proper exposure. When the brightness of the subject becomes high and the exposure amount necessary for achieving proper exposure is reduced as a result of AE, control is performed so as to achieve proper exposure by lowering the sensitivity.

In the third embodiment, an arbitrary shutter speed may be set.
For example, the shutter speed at which no camera shake is set in advance is arbitrarily set, or the camera shake limit shutter speed is set in advance so as not to become slower than the set shutter speed. Here, the camera shake limit shutter speed is generally represented by 1 / f. However, the camera shake limit shutter speed is not limited to this, and may be arbitrarily set by the photographer, or may be appropriately set by the imaging apparatus 100 according to the shooting situation by calculation. By arbitrarily setting a shutter speed at which camera shake does not occur in advance or by setting a camera shake limit shutter speed in advance, control that emphasizes suppression of camera shake and subject blur becomes possible.

  According to the third embodiment, since the sensitivity is also changed, it is difficult to cause camera shake and subject blur while maintaining the magnification intended by the photographer, and a good image can be obtained.

(Fourth embodiment)
Next, a fourth embodiment of the imaging device according to the present invention will be described.
In addition, the same code | symbol is attached | subjected to the part which fulfill | performs the same function as 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted suitably.
The fourth embodiment differs from the first embodiment in the operation when the subject brightness changes when the zoom position is on the telephoto side and there is no zoom operation. The operation at this time will be described below.
In the fourth embodiment, when the zoom position is on the telephoto side, the brightness of the subject decreases, and when the exposure amount necessary for proper exposure increases as a result of AE, the zoom lens is automatically moved to the wide-angle side. The F value is decreased by moving the lens so as to achieve proper exposure.

FIG. 17 illustrates the zoom magnification and F value of the imaging apparatus 100 when the zoom lens is automatically moved to the wide-angle side when the luminance of the subject is lowered in the imaging apparatus having the same characteristics as those in FIG. It is a graph.
A solid line in FIG. 17 represents changes in zoom magnification and F value when the zoom lens is automatically moved from a certain zoom position to the wide angle side. In this example, the maximum zoom magnification of the optical zoom is 3 times, the maximum zoom magnification of the electronic zoom is 4 times, and the maximum zoom magnification combining the optical zoom and the electronic zoom is 12 times.
Further, there is no limitation on the maximum zoom magnification that combines the optical zoom and the electronic zoom. In FIG. 17, by automatically moving the zoom lens to the wide angle side from any arbitrary zoom position when the brightness of the subject decreases, the open F value can be reduced and the F value at the time of shooting can also be reduced. it can. As a result, it is possible to perform photographing with appropriate exposure without changing the shutter speed.

  According to the present embodiment, zooming is automatically performed on the wide-angle side when the luminance of the subject becomes low, so that it is difficult to cause camera shake and subject blur due to a decrease in shutter speed, and a good image can be obtained. In addition, since it is not necessary to increase the sensitivity too much, an image with less noise can be obtained.

(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the scope of the present invention.
For example, in each of the embodiments, the description has been given by taking an example in which the photographing lens 10 cannot be replaced with the imaging device 100. However, the present invention is not limited to this, and an imaging device that is used by attaching a removable interchangeable lens. Also good.

  In addition, although 1st Embodiment-4th Embodiment and modification can also be used in combination suitably, detailed description is abbreviate | omitted. Further, the present invention is not limited by the embodiments described above.

It is a figure which shows the structure of 1st Embodiment of the imaging device by this invention. It is a graph which shows the brightness at the time of changing the focal distance of the photographic lens 10, ie, change of open F value. In the image pickup apparatus 100 having the zoom lens having the characteristics as shown in FIG. 2, the image displayed on the image display unit 28 and the shutter speed and F at that time when zooming from the wide-angle side to the telephoto side using only the optical zoom are performed. It is a figure which shows the example of a value. 4 is a graph showing a zoom magnification and an F value of the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side corresponding to FIG. 3. FIG. 2 shows an example of an image displayed on the image display unit 28 and a shutter speed and F value at that time when the zoom operation is performed using the optical zoom and the electronic zoom in the imaging apparatus 100 having the zoom lens having the characteristics as shown in FIG. is there. 6 is a graph showing the zoom magnification and F value of the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side corresponding to FIG. 5. 6 is a flowchart illustrating processing in the imaging apparatus 100 when zooming from the wide-angle side to the telephoto side according to the first embodiment. In the image pickup apparatus 100 having the zoom lens having the characteristics as shown in FIG. 2, an image displayed on the image display unit 28 when the zoom operation is performed from the telephoto side to the wide angle side using the optical zoom and the electronic zoom, and at that time It is a figure which shows the example of a shutter speed and F value. It is a graph showing the zoom magnification and F value of the imaging device 100 when zooming from the telephoto side corresponding to FIG. 8 to the wide angle side. In the image pickup apparatus 100 having the zoom lens having the characteristics as shown in FIG. 2, an image displayed on the image display unit 28 when the zoom operation is performed from the telephoto side to the wide angle side using the optical zoom and the electronic zoom, and at that time It is a figure which shows the example of a shutter speed and F value. 11 is a graph showing zoom magnification and F value of the imaging apparatus when zooming from the telephoto side to the wide angle side corresponding to FIG. 10. 6 is a flowchart illustrating processing in the imaging apparatus 100 when zooming from the telephoto side to the optical side. It is a figure which shows the relationship between F value regarding the restriction | limiting of the maximum magnification in 1st Embodiment, zoom magnification, and a focal distance. It is a figure which shows the example displayed on the image display part 28 at the time of zooming using an optical zoom and an electronic zoom from a wide angle side to a telephoto side, and the shutter speed and F value at that time. 15 is a graph showing a zoom magnification and an F value of the imaging apparatus when a zoom operation is performed from the wide-angle side to the telephoto side corresponding to FIG. 14 using optical zoom and electronic zoom. It is a flowchart showing the process in the imaging device 100 when zooming from the wide angle side to a telephoto side of 2nd Embodiment. 14 is a graph showing the zoom magnification and F value of the imaging apparatus 100 when the zoom lens is automatically moved to the wide-angle side when the brightness of the subject is lowered in the imaging apparatus having the zoom lens having the same characteristics as in FIG. 13.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Shooting lens 12 Shutter 14 Image pick-up element 16 A / D converter 18 Timing generation circuit 20 Image processing circuit 22 Memory control circuit 24 Image display memory 26 D / A converter 28 Image display part 30 Memory 32 Compression / decompression circuit 40 Exposure control Unit 42 Focus control unit 44 Zoom control unit 46 Barrier control unit 48 Flash 50 System control circuit 52 Memory 54 Display unit 56 Non-volatile memory 60 Mode dial switch 62 Shutter switch (SW1)
64 Shutter switch (SW2)
66 Image display ON / OFF switch 68 Single shooting / Continuous shooting switch 70 Operation unit 100 Imaging device 102 Display unit 104 Optical finder 110 Communication unit 112 Connector 200 Recording medium 210 Recording medium 300 Display image at wide angle end before zooming 301 Optical zoom Display image when zooming 6 times 500 Display image at wide-angle end before zooming 501 Display image when zooming 2 times optical zoom 502 When zooming 2 times after zooming optical zoom 2 times Display image 503 Boundary frame for switching from optical zoom to electronic zoom 800 Display image at telephoto end before zoom operation 801 Display image when optical zoom 3/4 is performed 802 After optical zoom 3/4 is performed In addition, a display image when the electronic zoom is performed 1/3 times is performed. Display image when performing optical zoom 2/3 magnification after zooming 1/3 times 900 Display image at telephoto end before zoom operation 901 Display image when electronic zoom 1/3 magnification is performed 902 Display image when the optical zoom is 1/2 times after performing the electronic zoom 1/3 times 1400 Display image at the wide angle end before zooming 1401 Display image when the optical zoom is 1.5 times 1402 Display image when electronic zoom is performed 4 times after performing optical zoom 1.5 times 1403 Optical zoom 1.5 times is performed, electronic zoom 4 times is performed, and optical zoom 2 times is performed Display image when

Claims (12)

An imaging device that captures an image obtained through a lens barrel whose open aperture value changes according to a focal length,
Imaging means for capturing an image obtained through the lens barrel;
Exposure control means for setting and controlling an exposure condition when imaging is performed by the imaging means;
Control means for controlling an optical zoom for changing a magnification by changing a focal length of the lens barrel and an electronic zoom for changing a photographing range of an image obtained through the lens barrel by image processing;
With
The control means switches between an optical zoom and an electronic zoom based on an open aperture value that changes according to a focal length and an exposure condition set by the exposure control means,
An imaging apparatus characterized by the above. Having luminance detection means for detecting the luminance of the subject;
The control means switches between an optical zoom and an electronic zoom based on a luminance detection result by the luminance detection means;
The imaging apparatus according to claim 1. The exposure control means sets at least one of a shutter speed, an aperture value, and a sensitivity as an exposure condition based on the luminance of the subject or in accordance with a photographer's instruction;
The imaging device according to claim 1 or 2, wherein The control means, when zooming from the wide angle side to the telephoto side, switching from optical zoom to electronic zoom so that the aperture value is not larger than the aperture value set by the exposure control means;
The imaging apparatus according to any one of claims 1 to 3, wherein The control means, when zooming from the telephoto side to the wide angle side, switching from the electronic zoom to the optical zoom so that the aperture value is not larger than the aperture value set by the exposure control means;
The imaging device according to any one of claims 1 to 4, wherein the imaging device is characterized in that: The control means switches between the optical zoom and the electronic zoom based on the result of comparing the aperture value set by the exposure control means and the open aperture value when performing the electronic zoom.
The imaging device according to any one of claims 1 to 5, wherein The control means operates the optical zoom to the wide angle side based on the result of comparing the aperture value set by the exposure control means and the open aperture value when the brightness of the subject is lowered.
The imaging device according to any one of claims 1 to 6, wherein A display unit for displaying an image;
The control means causes the display unit to display a boundary for switching between optical zoom and electronic zoom;
The imaging device according to any one of claims 1 to 7, wherein The exposure control means sets the shutter speed designated by the photographer as an exposure condition,
The control means switches between optical zoom and electronic zoom so that the shutter speed instructed by the photographer can be maintained.
The imaging device according to any one of claims 1 to 8, wherein: The control means switches between optical zoom and electronic zoom so that the shutter speed is not slower than the camera shake limit shutter speed set so as to prevent image blur due to camera shake,
The imaging device according to any one of claims 1 to 9, wherein: When the electronic zoom is at the maximum zoom magnification and the photographer performs a zoom operation toward the telephoto side, the control means performs appropriate exposure without changing the shutter speed set by the exposure control means while operating the optical zoom. Increase the sensitivity so that
The imaging device according to any one of claims 1 to 10, wherein An image pickup means for picking up an image obtained through a lens barrel whose open aperture value changes according to the focal length;
Exposure control means for setting and controlling an exposure condition when imaging is performed by the imaging means;
Control means for controlling an optical zoom for changing a magnification by changing a focal length of the lens barrel and an electronic zoom for changing a photographing range of an image obtained through the lens barrel by image processing;
A zoom control method for an imaging apparatus comprising:
The control means switches between an optical zoom and an electronic zoom based on an open aperture value that changes according to a focal length and an exposure condition set by the exposure control means,
Zoom control method characterized by the above.

Images