JP2011133729A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which picks up good images regardless of distance to an object. <P>SOLUTION: A digital camera 100 includes: a CCD image sensor 201 which picks up the object and generates an image signal; a flash light 113 which radiates a flash to the object; a white-light LED 114 which illuminates the object; a controller 110 which determines a distance to the object; and a controller 110 which determines whether to irradiate the object with the flash from the flash light 113 or to illuminate it by the white-light LED 114. With this configuration, the digital camera 100 can pick up the good image regardless of the distance to the object. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging device equipped with a light emitting device that emits light during imaging. In particular, the present invention relates to an imaging device equipped with a light emitting device capable of changing light emitting means.

  2. Description of the Related Art An imaging device that turns on illumination so that a photographer can check a subject even when the surroundings are dark is known. For example, Patent Document 1 discloses an imaging device that switches the amount of light that illuminates a subject between a period until a release switch is operated and a still image shooting after the release switch is operated.

Japanese Patent Laid-Open No. 2003-174587

  However, although the camera of Patent Document 1 emits LEDs during still image shooting, when the subject distance is long, the light emission does not reach the subject, resulting in the subject being underexposed. Further, in a conventional camera, when a subject is illuminated with a strong flash by a flash during still image shooting, the subject may be overexposed because it is close to the subject.

  The present invention has been made in view of the above problems, and an object thereof is to provide an imaging apparatus that captures a good image regardless of the distance to the subject.

  In order to solve the above-described problems, an imaging apparatus according to the present invention includes an imaging unit that captures a subject image and generates an image signal, a flash unit that emits flash on the subject, an illumination unit that illuminates the subject, and the subject. And a light emission determination unit that determines whether to flash by the flash unit or to illuminate by the illumination unit during imaging according to the determination result.

  According to the present invention, it is possible to provide an imaging apparatus that captures a good image regardless of the distance to the subject.

Front view of digital camera 100 Rear view of digital camera 100 Electrical configuration diagram of the digital camera 100 Light emission necessity determination flowchart of the digital camera 100 Light emission means determination flowchart of the digital camera 100 Diagram for explaining the reflection level during pre-emission The figure for demonstrating the light emission menu screen displayed on the liquid crystal display 204 The figure for demonstrating the icon displayed on the liquid crystal display 204

[1. Embodiment 1]
The digital camera 100 according to Embodiment 1 uses either a white light emitting diode (hereinafter referred to as a white LED) or an electronic flash (hereinafter referred to as a flash) during imaging depending on the reflection level from the subject during pre-emission before imaging. Determine whether to emit light. Hereinafter, the configuration and operation of the digital camera 100 will be described.

[1-1. Constitution〕
Hereinafter, the configuration of the digital camera 100 will be described with reference to the drawings.

[1-1-1. Configuration of Digital Camera 100]
FIG. 1 is a front view of the digital camera 100. The digital camera 100 includes a lens barrel that houses the optical system 200, a flash 113, and a white LED 114 on the front surface. The digital camera 100 also includes operation unit buttons such as a release button 110, a zoom lever 111, and a power source 112 on the upper surface.

  FIG. 2 is a rear view of the digital camera 100. The digital camera 100 includes a liquid crystal display 204 and operation buttons such as a menu button 120 and a cross button 121 on the back.

  FIG. 3 is an electrical configuration diagram of the digital camera 100. The digital camera 100 captures a subject image formed via the optical system 200 with a CCD image sensor 201. The CCD image sensor 201 generates image data based on the captured subject image. The image data generated by the imaging is subjected to various processes in an AFE (analog front end) 202 and an image processing unit 203. The generated image data is stored in the flash memory 222 or the memory card 221. The image data stored in the flash memory 222 or the memory card 221 is reproduced and displayed on the liquid crystal display 204 in response to an operation of the operation unit 223 by the user.

  Details of the components shown in FIGS. 1 to 3 will be described below.

  The optical system 200 includes a focus lens, a zoom lens, a diaphragm, a shutter, and the like. The optical system 200 may include an optical camera shake correction lens OIS (Optical Image Stabilizer). The various lenses constituting the optical system 200 may be composed of any number of lenses or groups.

  The focus lens is used to adjust the focus state of the subject. The zoom lens is used to adjust the enlargement / reduction magnification. The diaphragm is used to adjust the amount of light incident on the CCD image sensor 201. The shutter adjusts the exposure time of light incident on the CCD image sensor 201. The focus lens, zoom lens, diaphragm, and shutter are driven in accordance with control signals notified from the controller 210 by corresponding driving means such as a DC motor and a stepping motor.

  The CCD image sensor 201 captures a subject image formed through the optical system 200 and generates image data. The CCD image sensor 201 generates image data of a new frame at regular intervals. The CCD image sensor 201 adjusts the amount of exposure light by an electronic shutter operation. In the present invention, instead of the CCD image sensor 201, another image sensor such as a CMOS image sensor or an NMOS image sensor may be used.

  The AFE 202 performs processing such as correlated double sampling and gain adjustment on the image data generated by the CCD image sensor 201. Also, conversion from analog image data to digital image data is performed. Thereafter, the AFE 202 outputs the image data to the image processing unit 203.

  The image processing unit 203 performs various processes on the image data output from the AFE 203. Examples of various processing include, but are not limited to, gamma correction, white balance correction, YC conversion processing, electronic zoom processing, compression processing, expansion processing, and the like. Further, the image processing unit 203 generates luminance information in a specific subject area from image data continuously output from the AFE 203. Note that the image processing unit 203 may be configured with a hard-wired electronic circuit or a microcomputer using a program. Further, it may be constituted by one semiconductor chip together with the controller 210 and the like.

  The controller 210 controls the overall operation of the digital camera 100. The controller 210 includes a ROM that stores information such as a program, and a CPU that processes information such as a program. The ROM stores a program for overall control of the entire operation of the digital camera 100 in addition to a program relating to autofocus control (AF control), automatic exposure control (AE control), and flash control of the flash 113 and white LED 114 described later. ing.

  The controller 210 performs AF control. First, the controller 210 acquires a contrast value in a specific subject area of image data from the image processing unit 203. The controller 210 determines the focus state of a specific subject area from the continuously acquired contrast values, and drives the focus lens to focus on the subject area. The timing at which the controller 210 executes the AF control may be when a half-press operation of the release button 110 by the user is accepted, or the AF control may be always performed during the photographing mode of the subject.

  The controller 210 performs AE control. First, the controller 210 acquires luminance information in a specific subject area of the image data from the image processing unit 203. The controller 210 calculates an exposure value in order to obtain an appropriate exposure of the subject from the continuously acquired luminance information. The controller 210 determines an aperture value and a shutter speed according to the calculated exposure value and a predetermined program diagram. The controller 210 monitors luminance information acquired from the image data, and always executes AE control. The exposure value at the time of shooting may be fixed by accepting a half-press operation of the release button 110 by the user or may be fixed by accepting a full-press operation.

  The controller 210 may be configured with a hard-wired electronic circuit or a microcomputer. Further, it may be constituted by one semiconductor chip together with the image processing unit 203 and the like. The ROM does not have to be an internal configuration of the controller 210, and may be provided outside the controller 210.

  The buffer memory 205 is a storage unit that functions as a work memory for the image processing unit 203 and the controller 210. The buffer memory 205 can be realized by a DRAM (Dynamic Random Access Memory) or the like.

  The flash memory 222 functions as an internal memory for storing image data and the like.

  The card slot 220 is a connection means to / from which the memory card 221 can be attached / detached. The card slot 220 can connect the memory card 221 electrically and mechanically. The card slot 220 may have a function of controlling the memory card 221.

  The memory card 221 is an external memory provided with a storage unit such as a flash memory. The memory card 221 can store data such as image data processed by the image processing unit 203. In this embodiment, the memory card 221 is shown as an example of the external memory, but the present invention is not limited to this. For example, a storage medium such as an optical disk may be used as the external memory.

  The controller 210 records the image data processed by the image processing unit 203 in the flash memory 222 or the memory card 221.

  A liquid crystal display 204 is provided on the back of the digital camera 100. The liquid crystal display 204 displays an image based on the image data processed by the image processing unit 203. The image displayed on the liquid crystal display 204 includes a through image and a stored image. The through image is an image in which images of new frames generated by the CCD image sensor 201 at regular intervals are continuously displayed. The user can take a picture while confirming the composition of the subject by referring to the through image displayed on the liquid crystal display 204. The stored image is an image stored in the memory card 221 or the flash memory 222. The liquid crystal display 204 displays an image based on the already stored image data in accordance with a user operation. In addition to the image, the liquid crystal display 204 can display the setting conditions of the digital camera 100 and the like.

  The operation unit 223 is a general term for operation buttons and operation dials provided on the exterior of the digital camera 100, and accepts an operation by a user. For example, the release button 110, the zoom lever 111, the power button 112, the menu button 120, the cross button 121, and the like shown in FIGS. When receiving an operation by the user, the operation unit 223 notifies the controller 210 of various operation instruction signals.

  The release button 110 is a two-stage press button that is half pressed and fully pressed. When the release button 110 is half-pressed by the user, AF (Auto Focus) control or AE (Auto Exposure) control is executed to determine the photographing condition. Subsequently, when the release button 110 is fully pressed by the user, the image data captured at the timing of the full press is recorded in the memory card 221.

  The zoom lever 111 is a center-position self-returning lever having a wide-angle end and a telephoto end. When operated by the user, the zoom lever 111 notifies the controller 210 of an operation instruction signal for driving the zoom lens. That is, when the zoom lever 111 is operated to the wide angle end, the controller 210 drives the zoom lens so that the subject can be captured at a wide angle. Similarly, when the zoom lever 111 is operated to the telephoto end, the controller 210 drives the zoom lens so that the subject can be captured at the telephoto end.

  The power button 112 is a push-down button for turning on / off the power supply to each part constituting the digital camera 100. When the power button 112 is pressed by the user when the power is turned off, the controller 210 supplies power to each unit constituting the digital camera 100 and activates it. When the power button 112 is pressed by the user when the power is turned on, the controller 210 stops the power supply to each unit.

  The menu button 120 is a push button. When the menu button 120 is pressed by the user while the liquid crystal display 204 is displaying a recorded image or a through image, the controller 210 displays a menu screen on the liquid crystal display 204. The menu screen is a screen for setting various conditions for shooting / playback. When pressed when a setting item for various conditions is selected, the menu button 120 also functions as an enter button.

  The cross button 121 is a push button that is provided in the vertical and horizontal directions. The user can select various condition items displayed on the liquid crystal display 204 by pressing any direction of the cross button 121.

  The flash 113 includes a xenon tube, a capacitor, a booster circuit, a light emission trigger circuit, and the like. The booster circuit applies a high voltage to the capacitor in accordance with a control signal from the controller 210. The light emission trigger circuit discharges the high voltage of the applied and charged capacitor in accordance with a control signal from the controller 210 to instantaneously emit xenon gas in the xenon tube. The light emission trigger circuit discharges the high voltage of the capacitor in synchronization with still image shooting. Accordingly, the digital camera 100 can take a still image of the lighted subject. The flash 113 can supplement the brightness of the subject by instantaneously emitting light to the subject at the time of imaging. Further, the guide number, which is a unit representing the light amount of the flash 113, is represented by a shooting distance, an aperture value, and ISO sensitivity. Here, the shooting distance represents the distance that the flash 113 can reach. The shooting distance is proportional to the guide number, inversely proportional to the aperture value, and proportional to the square root of the ISO sensitivity. Therefore, the digital camera 100 has a distance range in which flash light emission can be reached according to the guide number of the flash 113 that can be set, the aperture value of the aperture, and the ISO sensitivity. Note that light emission of the flash 113 includes pre-light emission and main light emission. Details of the pre-light emission and the main light emission will be described later.

  The white LED 114 includes a light emitting diode and a voltage circuit. The white LED 114 can be realized by, for example, a pseudo white LED by covering a blue light emitting diode with a YAG-based phosphor, or a three-color LED chip of red, green, and blue. The white LED 114 emits light by applying a voltage in the forward direction by a voltage circuit in accordance with a control signal from the controller 210. The white LED 114 can continue to emit light as long as a voltage is applied in the forward direction.

[1-1-2. Correspondence with the present invention]
The CCD image sensor 201 is an example of an imaging unit of the present invention. The flash 113 is an example of a flash unit of the present invention. The white LED 114 is an example of an illumination unit of the present invention. The controller 210 is an example of a distance determination unit of the present invention. The controller 210 is an example of a light emission determination unit of the present invention. The digital camera 100 is an example of an imaging apparatus of the present invention.

[1-2. Operation)
The operation of the digital camera 100 will be described below with reference to the drawings.

[1-2-1. (Judgment of necessity of light emission)
First, the necessity determination of light emission of the digital camera 100 will be described. FIG. 4 is a flowchart for determining whether or not the digital camera 100 needs to emit light. The digital camera 100 determines whether light emission is necessary when an image is captured.

  When the digital camera 100 is in the shooting mode, the controller 110 monitors whether or not the user has pressed the release button 110 halfway (S400). When the controller 110 detects a half-pressing operation of the release button 110 by the user, the controller 110 executes autofocus control so as to focus on the subject included in the focus frame in the captured image (S401). The focus frame is a frame displayed on the liquid crystal display 123 in order to specify a subject to be focused. The user can focus on the subject by placing the focus frame on the subject to be focused and pressing the release button 110 halfway.

  In addition, the controller 110 always performs automatic exposure control, and calculates an exposure value when shooting based on image data captured by the CCD image sensor 201. The controller 110 fixes the exposure value calculated according to the timing at which the user half-pressed the release button 110 is received as the exposure value for capturing an image to be recorded on the memory card 221 (S401). At this time, the controller 110 determines whether or not light emission is necessary for photographing by comparing the fixed exposure value and the threshold value of whether or not light emission is necessary (S403). The threshold value of necessity of light emission is a reference value of an exposure value for determining whether or not the flash 113 or the white LED 114 emits light. In general, the threshold value for necessity of light emission is set to a relatively low exposure value. In other words, the threshold value for necessity of light emission is set to emit light when the shooting environment is dark. When the fixed exposure value of the controller 110 is higher than the threshold value of whether or not light emission is necessary, the controller 110 determines that no light is emitted. On the other hand, when the exposure value fixed by the controller 110 is lower than the threshold value for necessity of light emission, the controller 110 determines to emit light.

  If the controller 110 determines that light emission is not necessary, the digital camera 100 performs normal shooting that does not emit light (S405). If the controller 110 determines that light emission is necessary, the digital camera 100 performs light emission photography described later (S404).

[1-2-2. (Judgment of light emission means)
Next, determination of light emission means of the digital camera 100 will be described. FIG. 5 is a flowchart of determining the light emitting means of the digital camera 100. The digital camera 100 determines which of the light emitted from the flash 113 and the light emitted from the white LED 114 is used when light is emitted during shooting. Hereinafter, as described above with reference to FIG. 4, description will be made on the assumption that the release button 110 is half-pressed by the user and the controller 110 determines that light emission is necessary.

  The controller 110 monitors whether or not the user has fully pressed the release button 110 after the user has pressed the release button 110 halfway (S500). When a full pressing operation of the release button 110 by the user is accepted, the controller 110 causes the flash 113 to pre-emit the subject (S501). In the pre-flash, the distance to the subject is determined based on the degree of the amount of light reflected from the subject by flash emission (hereinafter referred to as the reflection level), and the light emission amount of the flash 113 at the time of shooting is determined according to the determination result. This is light emission before shooting.

  FIG. 6 shows a change in the reflection level during pre-emission depending on the distance from the digital camera 100 to the subject. The vertical axis in FIG. 6 represents the reflection level during pre-emission. The horizontal axis indicates the distance from the digital camera 100 to the subject. The reflection level at the time of pre-emission becomes a large value when the distance to the subject is short, and monotonically decreases as the distance to the subject becomes longer. When the flash 113 pre-emits, the CCD image sensor 201 measures light incident through the optical system 200. The light measured by the CCD image sensor 201 is calculated as luminance information by the image processing unit 203. Then, the controller 110 determines the reflection level from the subject associated with the pre-flash based on the calculated luminance information (S502). Subsequently, the controller 110 compares the determined reflection level with a predetermined threshold R (S503). The predetermined threshold R corresponds to a predetermined distance D to the subject. The predetermined distance D is a distance at which the possibility of overexposure due to flash emission is high and the light emission of the white LED can reach. This predetermined distance D is a distance in the range of about 10 cm to 30 cm. The predetermined threshold R is set in accordance with the predetermined distance D according to a reflection level curve as shown in FIG.

  When the determined reflection level is smaller than the predetermined threshold R, that is, when the distance to the subject is longer than the predetermined distance D, the controller 110 determines to shoot with the flash 113 emitted. At this time, an appropriate amount of light emitted from the flash 113 is set according to the reflection level determined at the time of pre-light emission. Then, the controller 110 captures an image of the subject by causing the flash 113 to emit light according to the set light emission amount (S507).

  On the other hand, when the determined reflection level is larger than the predetermined threshold R, that is, when the distance to the subject is closer than the predetermined distance D, the controller 110 determines that the white LED 114 emits light and emits light to shoot. Then, the controller 110 starts illuminating the subject with the white LED 114 (S504).

  The controller 110 unlocks the exposure value calculated in step S401 in FIG. Then, the controller 110 calculates the exposure value of the subject when the white LED 114 is illuminated, and fixes it again to the calculated exposure value (S505). The controller 110 determines the aperture value and the shutter speed according to the exposure value calculated when the subject is illuminated by the white LED 114 and a predetermined program diagram. Then, the controller 110 captures an image of the subject with the determined aperture value and shutter speed while the white LED 114 is illuminated (S506).

[1-3. (Summary)
As described above, the digital camera 100 according to Embodiment 1 includes the CCD image sensor 201 that captures a subject image and generates an image signal, the flash 113 that emits a flash to the subject, and the white that illuminates the subject. The LED 114, a controller 210 that determines the distance to the subject, and a controller 210 that determines whether to flash with the flash 113 or illuminate with the white LED 114 during imaging according to the determination result. As a result, the digital camera 100 can select whether to flash with the flash 113 or to illuminate with the white LED 114 at the time of imaging according to the distance to the subject. In short, the digital camera 100 can select an appropriate light source according to the distance to the subject.

  Further, in the digital camera 100, the controller 210 controls that the distance to the subject is illuminated by the white LED 114 up to a predetermined distance D close to the own device, and in a distance range farther from the own device than the predetermined distance D. It is determined that the flash 113 is flashing. Accordingly, the digital camera 100 illuminates with the white LED 114 until the distance to the subject reaches a predetermined distance D close to the subject apparatus, and flashes with the flash 113 when the distance to the subject is longer than the predetermined distance D. . Accordingly, the digital camera 100 illuminates the subject with the white LED 114 in order to prevent overexposure when the distance to the subject is short, and a flash to prevent underexposure when the distance to the subject is far. 113 can be flashed.

  The digital camera 100 further includes a controller 210 that sets an exposure value of a subject after illumination when it is determined to illuminate with the white LED 114, and the CCD image sensor 201 has a subject image with the set exposure value. Image. Thus, the digital camera 100 can reset the exposure conditions such as the aperture value and the shutter speed in accordance with the exposure value of the subject illuminated by the white LED 114, and can capture the subject image.

[2. Other Embodiments]
The present invention is not limited to the above embodiment, and various embodiments are conceivable. Other embodiments are collectively described below.

  Although the case of a compact camera has been described above, the present invention is not limited to this. That is, the present invention can be applied to an interchangeable lens removable camera.

  In the above description, either the flash 113 or the white LED 114 is alternatively selected according to the distance from the digital camera 100 to the subject, but the present invention is not limited to this. That is, the white LED 114 emits light when the distance from the digital camera 100 to the subject is short, the white LED 114 and the flash 113 both emit light when the distance is medium, and the flash 113 emits light when the distance is far. Good. Accordingly, the digital camera 100 can reduce overexposure at a short distance, can reduce underexposure at a long distance, and can realize appropriate exposure even at an intermediate distance. For example, the controller 110 calculates the amount of light to be emitted from the flash 113 based on the exposure value calculated in the state in which the white LED 114 is caused to emit light at the time of middle distance shooting. While the white LED 114 is made to emit light, it is also possible to perform shooting with flash emission according to the calculated light emission amount. Thereby, the low exposure value can be compensated by white LED light emission while avoiding flash light emission due to an excessive light emission amount.

  In the above, the controller 110 determines the distance to the subject by determining the reflection level due to the pre-flash of the flash 113, but the present invention is not limited to this. For example, a distance measuring sensor for autofocus control may be provided, and the controller 110 may determine the distance to the subject based on the output of the distance measuring sensor. That is, the present invention may be any method as long as the distance to the subject can be determined.

  FIG. 7 shows a light emission menu screen 600 displayed on the liquid crystal display 204. The light emission menu screen 600 is displayed, for example, when the user presses the menu button 120 when the digital camera 100 is in the shooting mode. In the digital camera 100 according to the first embodiment, on the flash menu screen 600, the user can select the flash setting of the digital camera 100 from auto flash setting, flash prohibition setting, forced flash setting, macro LED setting, and the like. You may be able to do it. The auto flash setting is a light emission setting in which the controller 110 automatically determines whether to turn on or off the flash 113 according to the exposure value. In the auto flash setting, the flash 113 emits light regardless of the distance to the subject. The flash prohibition setting is a light emission setting that prohibits the flash 113 from always flashing regardless of the exposure value. The forced flash setting is a light emission setting that always causes the flash 113 to emit light regardless of the exposure value. As described in the first embodiment, the macro LED setting is a light emission setting in which the white LED 113 emits light when close to the subject and the flash 114 emits light when far away. As described above, when the user sets the light emission to the macro LED setting, the controller 110 may execute the operation described in the first embodiment.

  FIG. 8 shows a macro LED icon displayed on the liquid crystal display 204. The macro LED icon is displayed on the liquid crystal display 204 when, for example, the above-described auto flash setting, flash prohibition setting, or forced flash setting is performed. The macro LED icon is displayed on the liquid crystal display 204 when the subject has an exposure value that requires light emission and the distance from the digital camera 100 to the subject is short. At this time, the light emission setting is set so that light emission by the white LED 114 is not performed. However, for example, when the menu button 120 is pressed while the macro LED icon is displayed, the light emission setting may be switched to light emission by the white LED 114. In this state, the user may operate to return to the light emission setting originally set by pressing the menu button 120 again. Accordingly, when performing macro photography close to the subject, the user can easily shoot with the light emitted by the white LED 114 or the light emitted by the flash 113 while viewing the through image of the subject displayed on the liquid crystal display 204. You can switch to In particular, since the white LED 114 can continuously emit light, the user can easily select a desired light emission setting while confirming a subject illuminated by the white LED 114 with a through image.

  As described above, the digital camera 100 can capture a good image regardless of the distance to the subject.

  The present invention is not limited to the implementation on the digital camera 100. That is, the present invention can be applied to an imaging apparatus that emits light during imaging, such as a movie camera or a mobile phone with a camera.

100 Digital Camera 110 Release Button 111 Zoom Lever 112 Power Supply 113 Flash (Electronic Flash)
114 White LED (white light-emitting diode)
120 Menu Button 121 Cross Button 200 Optical System 201 CCD Image Sensor 202 AFE (Analog Front End)
DESCRIPTION OF SYMBOLS 203 Image processing part 204 Liquid crystal display 205 Buffer memory 210 Controller 220 Card slot 221 Memory card 222 Flash memory 223 Operation part 600 Light emission menu screen 601 Menu selection frame 602 Icon

Claims (5)

An imaging unit that captures a subject image and generates an image signal;
A flash part that emits a flash on the subject;
An illumination unit that illuminates the subject;
A distance determination unit that determines the distance to the subject;
In accordance with the determination result, a light emission determination unit that determines whether to flash with the flash unit or to illuminate with the illumination unit during the imaging,
Imaging device. The light emission determining unit controls the distance to the subject to be illuminated by the illumination unit in a first distance range close to the subject device, and a second distance range farther from the subject device than the first distance range. In, it is determined to flash by the flash unit,
The imaging device according to claim 1. When it is determined to illuminate by the illuminating unit, further comprising an exposure setting unit for setting the exposure value of the subject after illumination,
The imaging unit captures a subject image at the set exposure value;
The imaging device according to claim 1 or 2. The distance determination unit determines a distance to the subject based on a reflected light level of flash to the subject by the flash unit immediately before the imaging.
The imaging device according to claim 1. The illumination unit is a white LED.
The imaging device according to claim 1.

Images