JP2007312063A - Photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photographing device that shortens a shutter time lag when taking a picture in a through image display state. <P>SOLUTION: The photographing device computes a first exposure quantity based upon the image signal from a CCD 221 (#15), performs exposure control based upon the first exposure quantity (#19, #21), picks up a subject image by the CCD 221 (#21), drives a movable mirror 201 to a down position (#25), measures subject luminance by a photometric element 211 disposed in a finder optical system to compute a second exposure quantity from the photometric value (#33), and corrects the output of the CCD 221 based upon the difference between the first and second exposure quantities (#35 to #39). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a photographing apparatus having a through image display function, and more specifically, a so-called through image display function (also referred to as a live view display function or an electronic viewfinder function) for displaying an image acquired by an image sensor as a moving image on a display device. The present invention relates to a photographing apparatus.

In conventional compact digital cameras, the subject image was observed using an optical finder, but recently, the optical finder has been eliminated, and the output of an image sensor provided for recording subject image data is used instead. It is also used for display. That is, there are an increasing number of images having a through image display function for displaying an image acquired by an image sensor on a display device such as a liquid crystal monitor for observing a subject image.

Such a live view display function is effective, for example, during macro photography because no parallax occurs. For this reason, various examples mounted on a digital single lens reflex camera have been proposed. For example, the optical viewfinder display mode and the electronic viewfinder display mode can be selected, and when the electronic viewfinder display mode is selected, the movable mirror is retracted from the photographing optical path and the focal plane shutter is fully opened to guide the subject image to the image sensor. A digital single-lens reflex camera has been proposed in which a subject image obtained thereby is displayed on a liquid crystal monitor for observation (Patent Document 1).
JP 2002-369042 A

In a photographing apparatus having such a through image display function, the movable mirror is moved to a position retracted from the photographing optical path for displaying a through image, and therefore, for subject luminance measurement arranged in a finder optical system or the like. The subject luminous flux was not guided to the photometry element, and photometry could not be performed during the through image display. For this reason, when shifting to shooting during live view display, the movable mirror is first lowered and moved to the reflection position, the light flux of the subject is guided to the photometry element, and then the movable mirror is moved to the retracted position. I was shooting from the beginning.

As described above, when the photographing operation is performed, the movable mirror needs to be moved up and down as a preparation stage. Therefore, there is a possibility that the shutter time lag until the photographing becomes large and the shutter chance is missed. There is a method of measuring subject luminance based on the output of the image sensor without using a photometer, but there is a problem that the measurement of the subject luminance by the image sensor cannot obtain accuracy compared to the case of the photometer. is there.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a photographing apparatus that shortens a shutter time lag when photographing from a through image display.

In order to achieve the above object, an imaging apparatus according to a first invention includes an imaging means including an imaging element, a first position for retracting outside the imaging optical path and guiding the subject light flux to the imaging means, and within the imaging optical path. Mirror means movable to the second position for guiding the subject light flux to the finder optical system, and a display device based on the image signal from the imaging means in a state where the mirror means is moved to the first position. And a first exposure amount calculating means for calculating a first exposure amount based on an image signal from the imaging means, and a first exposure amount according to the first exposure amount. A still image acquisition means for controlling the image pickup means to acquire still image data of the subject, a photometry means for measuring the subject brightness when the mirror is located at the second position, and disposed in the finder optical system. , A second exposure amount calculating means for the output of the light measuring means calculates the second exposure comprises a correcting means for correcting the output of the image pickup means in accordance with the difference between the first and second exposure.

According to a second aspect of the present invention, in the first aspect, the correction unit corrects still image data based on the output of the imaging unit.
According to a third aspect of the present invention, in the photographing apparatus according to the first aspect, the correction means corrects an analog signal when an output is read from the imaging means.

In order to achieve the above object, a photographing apparatus according to a fourth invention displays a moving image on a display device based on a photometric sensor for measuring subject luminance, an imaging means including an imaging element, and an image signal from the imaging means. Through image display means, still image acquisition means for acquiring a still image of a subject by the image pickup element with an exposure amount based on an exposure control value determined based on an output from the image pickup element, and stillness by the still acquisition means After the image is acquired, subject luminance is measured by the photometric sensor, and the imaging is performed based on a difference between an exposure amount when the still image acquisition unit acquires the still image and an exposure amount based on the subject luminance by the photometric unit. Compensating means for correcting the output of the means is provided.

According to a fifth aspect of the present invention, in the fourth aspect, the correction means corrects still image data in a digital format based on the output of the image sensor.
According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the correction means corrects the analog image signal read from the image sensor.

According to the present invention, a still image acquisition unit that acquires a still image of a subject with an exposure amount based on an exposure control value determined based on an output from the image sensor, and a still image obtained by the still acquisition unit. After acquisition, the subject brightness is measured by the photometric sensor, and the output of the imaging means is corrected based on the difference between the exposure amount at the time of still image acquisition by the still image acquisition means and the exposure amount based on the subject brightness by the photometry means Since the device is provided, it is possible to provide a photographing apparatus that shortens the time lag when photographing from the through image display.

Hereinafter, a preferred embodiment using a digital single lens reflex camera to which the present invention is applied will be described with reference to the drawings. FIG. 1 is an external perspective view of a digital single-lens reflex camera according to an embodiment of the present invention as seen from the back.
On the upper surface of the camera body 200, a release button 21, a mode dial 22, a control dial 24, and the like are arranged. The release button 21 has a first release switch that is turned on when the photographer is half-pressed and a second release switch that is turned on when the photographer is fully pressed. When the first release switch (hereinafter referred to as 1R) is turned on, the camera performs photographing preparation operations such as focus detection, focusing of the photographing lens, and photometry of the subject brightness, and the second release switch (hereinafter referred to as 2R). When it is turned on, a photographing operation for capturing image data of a subject image is executed based on the output of a CCD (Charge Coupled Devices) 221 (see FIG. 2) as an image sensor.

The mode dial 22 is an operation member that is configured to be rotatable. By matching a picture display or symbol representing a shooting mode provided on the mode dial 22 with an index, a full-auto shooting mode (AUTO) or a program shooting mode is set. (P), aperture priority shooting mode (A), shutter shooting priority mode (S), manual shooting mode (M), portrait shooting mode, landscape shooting mode, macro shooting mode, sports shooting mode, night scene shooting mode, etc. The shooting mode can be selected. The control dial 24 is an operation member configured to be rotatable, and a desired set value, mode, or the like can be selected by rotating the control dial 24 on an information display screen or the like.

On the back of the camera body 200, a liquid crystal monitor 26, a playback button 27, a menu button 28, an up cross button 30U, a down cross button 30D, a right cross button 30R, a left cross button 30L (each of these cross buttons 30U, 30D, 30R, and 30L are collectively referred to as a cross button 30), an OK button 31, a display mode switching button 34, a white balance button 37, and an ISO sensitivity button 38 are arranged. The liquid crystal monitor 26 is a display device for reproducing and displaying a photographed subject image and displaying photographing conditions and menus. Any liquid crystal display can be used as long as it can perform these displays. The playback button 27 is an operation button for instructing the liquid crystal monitor 26 to display a subject image recorded after shooting. The subject image data stored in a later-described SDRAM 237 and recording medium 245 in a compression mode such as JPEG is expanded and displayed.

The cross button 30 is an operation member for instructing the movement of the cursor in the two-dimensional direction of the X direction and the Y direction on the liquid crystal monitor 26, and when displaying the subject image recorded on the recording medium, Also used for instructions. In addition to providing four buttons for up, down, left, and right, it is also possible to replace with a switch that can be operated in a two-dimensional direction, such as a switch that can detect the operation direction in two dimensions, such as a touch switch. is there. The OK button 31 is an operation member for confirming various items selected by the cross button 30, the control dial 24, or the like. The menu button 28 is a button for switching to a menu mode for setting various modes of the digital camera. When the menu mode is selected by operating the menu button 28, a menu screen is displayed on the liquid crystal monitor 26. The menu screen has a plurality of hierarchical structures. Various items are selected with the cross-shaped button 30, and selection is determined by operating the OK button 31.

The display mode switching button 34 is an operation button for switching between a through-image display and an information display, which will be described later. In the through-image display, the subject image is observed on the liquid crystal monitor 26 based on the output of the CCD 221 for recording the subject image. The information display is a mode displayed on the liquid crystal monitor 26 in order to display and set the shooting information of the camera. The white balance button 37 is an operation button for setting the white balance. By operating the white balance button 37, a setting screen is displayed on the liquid crystal monitor 26, and auto, sunlight, cloudy, shade, light bulb, Each mode such as fluorescent lamps 1 to 3 and one-shot is displayed, and can be selected by rotating the control dial 24 and determined by operating the OK button 31.

The ISO sensitivity button 38 is an operation button for setting the ISO sensitivity. When the ISO sensitivity button 38 is operated, a setting screen is displayed on the liquid crystal monitor 26, and each sensitivity of auto and sensitivity 100 to 1600 is set as described above. Can be selected by rotating the control dial 24 and determined by operating the OK button 31. When the camera is left to the camera, auto is selected. When there is an intention to shoot, the photographer can arbitrarily set the sensitivity within a range of 100 to 1600. A recording medium storage lid 40 is attached to the side surface of the camera body 200 so as to be freely opened and closed. When the recording medium storage lid 40 is opened, a loading slot for the recording medium 245 is provided therein, and the recording medium 245 can be detachably loaded into the camera body 200.

Next, the overall configuration of the digital single-lens reflex camera mainly including the electric system will be described with reference to FIG. The digital single-lens reflex camera according to this embodiment includes an interchangeable lens 100 and a camera body 200. In the present embodiment, the interchangeable lens 100 and the camera body 200 are configured separately and are electrically connected by the communication contact 300, but the interchangeable lens 100 and the camera body 200 can also be configured integrally. .

Inside the interchangeable lens 100, lenses 101 and 102 for focus adjustment and focal length adjustment, and a diaphragm 103 for adjusting the aperture amount are arranged. The lens 101 and the lens 102 are driven by a lens driving mechanism 107, and the diaphragm 103 is connected to be driven by a diaphragm driving mechanism 109. The lens driving mechanism 107 and the aperture driving mechanism 109 are each connected to a lens CPU 111, and the lens CPU 111 is connected to the camera body 200 via a communication contact 300. The lens CPU 111 controls the inside of the interchangeable lens 100. The lens CPU 111 controls the lens driving mechanism 107 to perform focusing and zoom driving, and also controls the aperture driving mechanism 109 to perform aperture value control.

Within the camera body 200, there are a position inclined 45 degrees with respect to the lens optical axis in order to reflect the subject image to the observation optical system, and a position raised to guide the subject image to the image sensor (CCD 221 described later). A movable mirror 201 that can be rotated is provided. Above the movable mirror 201, a focusing screen 205 for forming a subject image is disposed, and above this focusing screen 205, a pentaprism 207 for horizontally reversing the subject image is disposed. An eyepiece lens 209 for observing a subject image is disposed on the emission side (right side in FIG. 1) of the pentaprism 207, and a photometric sensor 211 is disposed on the side of the pentaprism 207 so as not to interfere with the observation of the subject image. . The photometric sensor 211 is composed of a multi-division photometric element that divides a subject image for photometry.

Near the center of the movable mirror 201 described above is a half mirror, and on the back surface of the movable mirror 201, a sub mirror 203 for reflecting subject light transmitted through the half mirror portion to the lower part of the camera body 200 is provided. ing. The sub mirror 203 is rotatable with respect to the movable mirror 201. When the movable mirror 201 is flipped up, the sub mirror 203 is rotated to a position that covers the half mirror portion. When the movable mirror 201 is at the subject image observation position, the sub mirror 203 is illustrated. In this way, the position is perpendicular to the movable mirror 201. This movable mirror 201 is driven by a mirror drive mechanism 219. A distance measuring circuit 217 using a TTL phase difference method including a distance measuring sensor is disposed below the sub mirror 203, and this circuit measures the amount of focus shift of the subject image formed by the lenses 101 and 102. It is a circuit for doing.

A focal plane type shutter 213 for controlling the exposure time is disposed behind the movable mirror 201. The shutter 213 is driven and controlled by a shutter drive mechanism 215. A CCD 221 serving as an image sensor is disposed behind the shutter 213 and photoelectrically converts a subject image formed by the lenses 101 and 102 into an electric signal. In the present embodiment, a CCD is used as an image sensor. However, the present invention is not limited to this, and a CMOS (Complementary Metal Oxide) is used.
Needless to say, a two-dimensional imaging device such as Semiconductor) can be used. CCD221 is connected to the CCD driving circuit 223, by the CCD driving circuit 223, amplifies the photoelectric analog signals output from the C CD221 is performed. The CCD drive circuit 223 is connected to the image processing circuit 227 via the CCD interface 225. Analog / digital conversion (AD conversion) is performed by the CCD interface 225, and digital amplification (digital gain adjustment processing) of digital image data, color correction, gamma (γ) correction, contrast correction, and monochrome / color mode processing are performed by the image processing circuit 227. Various image processing such as through image processing is performed.

The image processing circuit 227 is an ASIC (Application Specific Integrated).
Circuit-specific integrated circuit) 271 is connected to the data bus 261. In addition to the image processing circuit 227, the data bus 261 includes a sequence controller (hereinafter referred to as “body CPU”) 229, a compression circuit 231, a flash memory control circuit 233, an SDRAM control circuit 236, an input / output circuit 239, A communication circuit 241, a recording medium control circuit 243, a video signal output circuit 247, and a switch detection circuit 253 are connected.

The body CPU 229 connected to the data bus 261 controls the flow of this digital single lens reflex camera. A compression circuit 231 connected to the data bus 261 is a circuit for compressing the image data stored in the SDRAM 237 with JPEG or TIFF. Note that image compression is not limited to JPEG or TIFF, and other compression methods can be applied. A flash memory control circuit 233 connected to the data bus 261 is connected to a flash memory 235. The flash memory 235 stores a program for controlling the flow of the single-lens reflex camera. The CPU 229 controls the digital single-lens reflex camera according to the program stored in the flash memory 235. Note that the flash memory 235 is an electrically rewritable nonvolatile memory. The SDRAM 237 is connected to the data bus 261 via the SDRAM control circuit 236, and the SDRAM 237 temporarily stores the image data processed by the image processing circuit 227 or the image data compressed by the compression circuit 231. This is a buffer memory.

The input / output circuit 239 connected to the above-described photometric sensor 211, shutter drive mechanism 215, distance measuring circuit 217, and mirror drive mechanism 219 controls input / output of data with each circuit such as the body CPU 229 via the data bus 261. . The communication circuit 241 connected to the lens CPU 111 via the communication contact 300 is connected to the data bus 261, and exchanges data with the body CPU 229 and the like and communicates control commands. A recording medium control circuit 243 connected to the data bus 261 is connected to the recording medium 245 and controls recording of image data and the like on the recording medium 245. The recording medium 245 can be loaded with any rewritable recording medium such as an xD picture card (registered trademark), a compact flash (registered trademark), an SD memory card (registered trademark), or a memory stick (registered trademark). And is detachable from the camera body 200. In addition, the hard disk may be configured to be connectable via a communication contact.

The video signal output circuit 247 connected to the data bus 261 is connected to the liquid crystal monitor 26 via the liquid crystal monitor drive circuit 249. The video signal output circuit 247 is a circuit for converting the image data stored in the SDRAM 237 and the recording medium 245 into a video signal to be displayed on the liquid crystal monitor 26. The liquid crystal monitor 26 is disposed on the back surface of the camera body 200. However, the liquid crystal monitor 26 is not limited to the back surface as long as the photographer can observe the image. A switch for detecting the first and second strokes of the shutter release button, a switch for instructing a playback mode, a switch for instructing an ISO setting mode, a switch for instructing a white balance setting, and instructing the cursor movement on the screen of the liquid crystal monitor 26 Various switches 255 such as a switch for performing shooting, a switch for instructing a photographing mode, an OK switch for determining each selected mode, a switch for instructing switching of a display mode, and the like are connected to the data bus 261 via a switch detection circuit 253. ing.

Next, the outline of the display and operation mode of the camera body 200 will be described with reference to FIG.
The information display M100 is a state when the power switch of the camera body 200 is turned on, and displays basic information when shooting with the camera. The information display M100 displays the shooting mode, shutter speed, aperture, An information display screen such as the AF mode, flash, and the number of pixels is displayed. Shooting modes such as a program mode, a shutter speed priority mode, and a macro shooting mode are set by rotating the mode dial 22. Items such as sensitivity, shutter speed, aperture value, correction value, and number of pixels are selected by operating the cross key 30 on the information display screen, and numerical values are set by operating the control dial 24.

In the state of the information display M100, when the release button 21 is pressed halfway, the 1R switch is turned on, and the shooting preparation operation M130 is entered. When the release button 21 is released and the half-press is released, the information display M100 is displayed. Return. In this photographing operation preparation operation M130, a preparatory operation for photographing such as photometry and distance measurement is performed. Thereafter, when the release button 21 is fully pressed, a shooting operation AM 131 is performed. In this photographing operation A, a photoelectric conversion signal of the subject image is taken from the CCD 221, and image processing is performed on the recording medium 245 after image processing by the image processing circuit 227.

Further, when the display mode switching button 34 is operated in the information display mode M100, the through image display mode M300 is set. In this through image display mode, the subject image is displayed on the liquid crystal monitor 26 for observation using the output of the subject image recording CCD 221 as described above. In the through image display mode M300, no particular operation is performed when the release button 21 is half-pressed. However, when the release button 21 is fully pressed, the photographing operation B M330 is executed. In the shooting operation B, the subject image data acquired by the CCD 221 is recorded on the recording medium 245. When the shooting operation B ends, the display returns to the through image display mode.

Next, details of the above-described through image display mode M300 will be described using the flowchart shown in FIG.
When the through image display mode is entered, the subject brightness is measured based on the output of the photometric sensor 211, and the exposure amount is calculated based on the obtained subject brightness (# 1). Note that the exposure amount EV is obtained by EV = BV + SV where the subject luminance is BV and the ISO sensitivity is SV. Thereafter, preparation for obtaining a subject image is made based on the output of the CCD 221. First, the movable mirror 201 is raised (# 3), and the subject luminous flux from the lenses 101 and 102 is guided from the finder optical system to the CCD 221 side. When the raising operation of the movable mirror 201 is completed, the process proceeds to step # 5 and the shutter 213 is opened. When the shutter 213 is opened, a subject image is formed on the CCD 221.

Thereafter, in order to set the electronic shutter speed and sensitivity conditions for driving the CCD 221, a through image condition setting 1 subroutine is executed using the photometry / exposure amount calculation result obtained in step # 1 (# 7). ). By executing this subroutine, an image with appropriate brightness (brightness) can be displayed on the liquid crystal monitor 26. Details of this subroutine will be described later with reference to FIG. When the through image condition setting 1 is completed, the through image display is ready, and display of the subject image on the liquid crystal monitor 26 is started in step # 9. The through image display operation is controlled by the image processing circuit 227 in response to the start instruction.

Next, in step # 11, it is determined whether the release button 21 has been fully pressed, that is, whether 2R is on. If it is off, the process proceeds to step # 43 to determine whether or not the display mode switching button 34 is on. If the result of determination is that the display mode switching button 34 has been operated and is on, a preparatory operation for returning to the information display mode M100 is performed. First, the power supply to the CCD 221 is stopped, and the live view display on the liquid crystal monitor 26 is stopped (# 45). Subsequently, the shutter 213 is closed (# 47), the movable mirror 201 is lowered, and the subject light flux is switched from the CCD 221 side to the viewfinder optical system side (# 49). When it is detected that the movable mirror 201 is down, the information display mode M100 is entered.

Returning to step # 43, if the result of determination is that the display mode switching button 34 is off, processing proceeds to step # 51, where it is determined whether the power switch (not shown) is off. If it is off, the operation is stopped, but the preparatory operation for that is performed in steps # 53 to # 57, but these steps are the same as the above-mentioned steps # 45 to # 49, so the details are omitted. . Returning to step # 51, if the power switch is on, the process proceeds to step # 61, and a through image condition setting 2 subroutine is executed.

This through image condition setting 2 is a subroutine for the purpose of appropriately maintaining the brightness of the through image display on the liquid crystal monitor 26. Since the through image condition setting 1 in step # 7 was before the through image display, it was performed based on the output of the photometric sensor 211. However, in the through image condition setting 2, the target lightness and the screen lightness based on the previous imaging result are used. Then, the electronic shutter speed and sensitivity at the next imaging are determined from the difference. Here, the brightness is a value corresponding to a weighted average value of each pixel output of the CCD, for example. In the through image condition setting 2, data related to the exposure amount is acquired. When the through image condition setting 2 subroutine is completed, the process returns to step # 11 to repeat the above steps. Therefore, if the through image display mode is entered and none of the release button 21, the display mode switching button 34, and the power switch is operated, steps # 11, # 43, # 51, and # 61 are sequentially and repeatedly executed. The

Returning to step # 11, if 2R is on, the photographing operation from step # 13 is performed. First, the live view display on the liquid crystal monitor 26 is stopped (# 13). Subsequently, the first exposure amount EV1 is calculated based on the data obtained in the through image condition setting 2 in step # 61 (# 15). That is, in the through image condition setting 2, since the shutter speed TV1 and the sensitivity SV1 at the full aperture value AVs are obtained based on the output of the CCD 221, the provisional luminance value BV1 is calculated using them. Next, the first exposure amount EV1 is calculated as EV1 = BV1 + SVs based on the calculated temporary luminance value BV1 and the sensitivity SVs set for photographing, and the exposure control condition is set based on this (# 17). . Although the setting of the exposure control condition varies depending on the photographing mode, for example, when the program mode is set, the shutter speed TV and the aperture value AV are obtained by calculation or table reference based on the first exposure amount EV1. When the exposure control condition setting is completed, an instruction to narrow down the aperture 103 is output to the lens CPU 111 in accordance with the aperture value set in advance or set in step # 17 (# 19).

When the narrowing-down operation is completed, the image is then taken by the CCD 221 (# 21). In other words, the subject luminous flux that has passed through the photographing lenses 101 and 102 has the movable mirror 201 raised and in the retracted position, and the shutter 213 is in an open state, so that a subject image is formed on the CCD 221. In this state, the reset of the electronic shutter of the CCD 221 is released, and charge accumulation of the photoelectric conversion current of the subject image is started. When the exposure time manually set in advance or set in step # 17 has elapsed, the electronic shutter of the CCD 221 stops the charge accumulation of the photoelectric conversion signal. Subsequently, the shutter 213 is closed (# 23), the movable mirror 201 is lowered (reflection position), and an instruction to open the aperture 103 is output to the lens CPU 111 (# 25). In addition, the image signal stored in the CCD 221 is read (# 29), and the image processing circuit 227 or the like performs image processing.

Since the movable mirror 201 is lowered in step # 25, the subject luminous flux is guided onto the photometric sensor 211. Therefore, as in step # 1, the subject brightness BVs is measured based on the output of the photometric sensor 211, and the second exposure amount EV2 is calculated using this and the set ISO sensitivity SVs for shooting (# 33). . That is, the second exposure amount EV2 is obtained by EV2 = BVs + SVs. Subsequently, the difference between the first exposure amount EV1 obtained in step # 15 and the second exposure amount EV2 obtained in step # 33 is calculated (# 35). Based on the difference calculated here, an amplification factor (gain) for adjusting the brightness of the image is obtained as a digital value (# 37), and the obtained digital gain is set in the image processing circuit 227 (# 39). . After performing hardware brightness correction (multiplication according to digital gain) of the image data with a value corresponding to the set digital gain, and performing other image processing and processing such as signal compression in the compression circuit 231, Image data is recorded on the recording medium 245 (# 41). When the recording of the image data ends, the process returns to step # 1 again and the above steps are repeated.

Next, “through image condition setting 1” and “through image condition setting 2” will be described with reference to FIG. As described above, this subroutine is for adjusting the image brightness when displaying the subject image on the liquid crystal monitor 26. First, when the through image condition setting 1 subroutine is entered, in step S201, the electronic shutter speed TV1 and sensitivity SV1 at the time of next imaging are determined based on the output BVs of the photometric sensor 211. Since the aperture value when displaying a through image is an open aperture value, if this aperture value is AVs,
AVs + TV1 = BVs + SV1
There is a relationship
BVs-AVs = TV1-SV1
It becomes. Since the left side of this equation is a known value, TV1 and SV1 may be obtained from the value on the left side according to a program line or a table as appropriate. Thereafter, the determined electronic shutter speed TV1 and sensitivity SV1 are stored and set in the respective registers (S207). The CCD drive circuit 223 performs drive control of the CCD 221 based on the TV1 and SV1 set and stored here, and reads out the photoelectric conversion signal. When the setting of TV1 and SV1 is completed in step S207, the process returns to the original flow.

Next, “through image condition setting 2” will be described. When the setting 2 subroutine is entered, first, a difference ΔEV between the target image brightness (predetermined value) and the image brightness at the time of previous imaging is calculated (S203). Subsequently, the electronic shutter speed TV1 and sensitivity SV1 at the next imaging are determined so that the image brightness is constant (S205). This decision is based on the following factors:
・ Aperture value AVs
-Electronic shutter speed TV0 at the time of previous imaging
・ Sensitivity SV0 at the time of previous imaging
The difference ΔEV between the target image brightness and the previous image brightness
First, as a basic expression of the exposure condition, AVs + TV0 = BV0 + SV0
It is.

Here, BV0 is the previous luminance, but the true value is not known and is a provisional value in the above basic formula. Since the true luminance value BV0 is different from the target, ie, ΔEV,
BV0 = AVs + TV0−SV0 + ΔEV
= AV1 + TV1-SV1
Thus, TV1 and SV1 are obtained from this relational expression. Here, the difference ΔEV may be obtained from, for example, the difference between the weighted average of the output of each pixel of the image sensor and the target value. When step S205 ends, the process proceeds to step S207 described above and returns to the original flow.

As described above, in the present embodiment, when a shooting operation is performed during live view display, first, the first exposure amount is obtained based on the output of the CCD 221 as the image sensor (# 15), and the shutter speed and aperture value are obtained. An exposure control value such as # is set (# 17), and exposure control is performed according to this exposure control value (# 19 and # 21). After the imaging operation is completed, the movable mirror 201 is lowered (# 25), the subject light flux is guided to the photometric sensor 211, and photometry is performed to obtain the second exposure amount (# 33). Thereafter, the amplification factor of the image signal is controlled based on the difference between the first exposure amount and the second exposure amount, and correction is made so as to achieve proper exposure (# 35 to # 39). By performing such control, the shutter time lag can be shortened because the movable mirror 201 does not have to be taken down and metered before imaging to raise it again. In the present embodiment, the digital gain amplification is performed by hardware in the image processing circuit 227, but it goes without saying that it may be processed by software.

Further, after the imaging is completed, the movable mirror 201 is lowered, the subject brightness is measured by the photometric sensor 211, the exposure amount is calculated, and the image signal is corrected based on the difference from the exposure amount based on the CCD 221, so photometry This means that the exposure control is performed with the same accuracy as when the sensor 211 is used. In other words, an image pickup device such as a CCD generally has a small dynamic range because it photoelectrically converts a subject image and accumulates a photoelectric conversion signal, so that exposure control with high accuracy cannot be performed depending on the subject compared to a photometric sensor. In the present embodiment, since the output of the image sensor is corrected based on the output of the photometric sensor 211, it is possible to ensure the same degree of accuracy as when the photometric sensor is used.

Furthermore, since the movable mirror 201 is up and down after imaging, there is less need to worry about the trade-off with the shutter time lag compared to the case before imaging, so the movable mirror 201 is not up and down at high speed. For this reason, the load on the mechanical portion of the movable mirror 201 is reduced, and the durability of the mechanical portion can be the same as that of a normal product.

Note that the exposure amount EV in the exposure amount calculation in steps # 15 and # 33 is not limited to EV = BV + SV, and may be a value appropriately combined using the shutter speed TV, the aperture value AV, the subject luminance BV, and the ISO sensitivity SV. In the image pickup operation in step # 21, the exposure time is controlled using the electronic shutter of the CCD 221. However, the present invention is not limited to this, and a so-called mechanical shutter using the shutter 213 may be used.

Next, a modification of the present embodiment will be described with reference to FIG. In the above-described embodiment, the correction of the difference between the first exposure amount and the second exposure amount is performed by performing digital gain correction on the digital image data. However, in a modified example, the analog image signal output from the CCD 221 is used. The gain is corrected in an analog manner. Since the modified example simply replaces steps # 29 to # 39 with steps # 71 to # 81 shown in FIG. 6 in the flow of the through image display mode of FIG. 4, only the differences will be described.

When the through image display mode is entered and the aperture opening operation in step # 27 is finished, subsequently, in step # 71, photometry / exposure amount calculation is performed in the same manner as in step # 1, and the second exposure amount is obtained. Next, a gain based on the difference between the first exposure amount obtained in step # 15 and the second exposure amount obtained in step # 71 is obtained (# 73), and an analog photoelectric conversion signal variable amplification circuit in the CCD drive circuit 223 is obtained. An amplification factor based on the gain is set (# 75). In accordance with the set gain, the CCD drive circuit 223 amplifies the image signal read from the CCD 221 (# 77), reads the image signal from the CCD 221 (# 79), and performs image processing by the image processing circuit 227 or the like ( # 81), the image data is recorded on the recording medium 245.

As described above, in the modification of the embodiment, when a photographing operation is performed during live view display, first, the first exposure amount is obtained based on the output of the CCD 221 as the image sensor (# 15), and the shutter speed is obtained. And exposure control values such as aperture value are set (# 17), and exposure control is performed according to the exposure control values (# 19 and # 21). After the imaging operation is completed, the movable mirror 201 is lowered (# 25), the subject light flux is guided to the photometric sensor 211, and photometry is performed to obtain the second exposure amount (# 71). Thereafter, the amplification factor of the image signal is controlled based on the difference between the first exposure amount and the second exposure amount, and correction is made so as to achieve proper exposure (# 73 to # 81). By performing such control, the shutter time lag can be shortened because the movable mirror 201 can be taken down before the image pickup and the photometry is not performed again, as in the present embodiment.

As described above, in one embodiment or a modification thereof, provisional exposure control is performed on the basis of the output of the CCD 221 when a photographing operation is performed during live view display based on the output of the CCD 221 for recording image data. A value is determined, exposure control is performed based on this value, and a still image is acquired. For this reason, since the photometric operation by the photometric sensor 211 before photographing is unnecessary, the shutter time lag can be shortened. After photographing, photometry is performed by the photometric sensor 211, and the difference from the exposure amount at the time of still image acquisition is electrically corrected. Therefore, it is almost the same as when exposure control is performed based on the output of the photometric sensor 211. It is possible to obtain a still image with an appropriate exposure with an accuracy of.

In the present embodiment, an example in which a single-lens reflex camera is applied as a photographing apparatus has been described. However, the present invention is not limited to a digital single-lens reflex camera, and can be applied to a digital camera such as a compact camera. In other words, the image sensor for recording image data periodically acquires image information for through image display. Therefore, if the release button is pressed halfway and then fully pressed, it is periodically acquired. Based on the output of the image sensor for recording image data, it is possible to enter an imaging operation with a temporary exposure control value, so that it is not necessary to perform a photometric operation at the half-pressed stage, and the shutter time lag can be shortened. .

In addition, the present invention is not limited to a single-lens reflex type or a compact type digital camera, and can of course be applied to a digital camera provided in a mobile phone. In any case, the present invention can be applied to any digital camera, electronic imaging device, or photographing device that displays the subject image on the monitor for observation using the output of the recording image sensor.

It is the external appearance perspective view which looked at the digital single-lens reflex camera in one Embodiment of this invention from the back. 1 is a block diagram illustrating an overall configuration of a digital single-lens reflex camera according to an embodiment to which the present invention is applied. It is a block diagram which shows the display mode and operation mode in one Embodiment of this invention. It is a flowchart which shows the operation | movement of the through image display mode in one Embodiment of this invention. 6 is a flowchart of through image condition setting 1 and through image condition setting 2 in an embodiment of the present invention. It is a flowchart which shows the modification of the operation | movement of the through image display mode in one Embodiment of this invention.

Explanation of symbols

21 Release button 22 Mode dial 24 Control dial 26 Liquid crystal monitor 27 Playback button 28 Menu button 30 Cross button 31 OK button 34 Display mode switching button 100 Interchangeable lens 103 Aperture 109 Aperture drive mechanism 111 Lens CPU
200 Camera body 201 Movable mirror 203 Sub mirror 211 Photometric sensor 213 Shutter 217 Distance measuring circuit 219 Mirror drive mechanism 221 CCD
223 CCD drive circuit 225 CCD interface circuit 227 Image processing circuit 229 Body CPU
239 I / O circuit 245 Recording medium

Claims (6)

Imaging means including an imaging element;
Mirror means movable to a first position for retracting out of the photographing optical path to guide the subject light flux to the imaging means and a second position for guiding the subject light flux to the finder optical system in the photographing optical path;
Through image display means for displaying a moving image on a display device based on an image signal from the imaging means in a state where the mirror means is moved to the first position;
In a photographing apparatus comprising:
First exposure amount calculating means for calculating a first exposure amount based on an image signal from the imaging means;
Still image acquisition means for controlling the imaging means according to the first exposure amount and acquiring still image data of a subject;
Photometric means disposed in the finder optical system for measuring subject brightness when the mirror is in the second position;
Second exposure amount calculating means for calculating a second exposure amount from the output of the photometric means;
Correction means for correcting the output of the imaging means in accordance with the difference between the first and second exposure amounts;
An imaging apparatus comprising:   The photographing apparatus according to claim 1, wherein the correction unit corrects still image data based on an output of the imaging unit.   The photographing apparatus according to claim 1, wherein the correction unit corrects an analog signal when an output is read from the imaging unit. A photometric sensor for measuring subject brightness;
Imaging means including an imaging element;
Through image display means for displaying a moving image on a display device based on an image signal from the imaging means,
Still image acquisition means for acquiring a still image of a subject with the image sensor with an exposure amount based on an exposure control value determined based on an output from the image sensor;
After acquiring the still image by the still acquisition means, the subject brightness is measured by the photometric sensor, and the difference between the exposure amount at the time of the still image acquisition by the still image acquisition means and the exposure amount based on the subject brightness by the photometry means Correction means for correcting the output of the imaging means based on
An imaging apparatus comprising:   The photographing apparatus according to claim 4, wherein the correction unit corrects digital still image data based on an output of the imaging element. The photographing apparatus according to claim 4, wherein the correction unit corrects the analog image signal read from the image sensor.