JP2006165725A - Imaging apparatus and its exposure determination method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take a still image photograph while utilizing the wide dynamic range of an image sensor. <P>SOLUTION: When a release button is half-pushed, exposure value is set at 8 EV and the luminance of an object in the range of 4-9.5 EV is measured on the basis of the exposure results from a CCD image sensor. Subsequently, the exposure value is set at 12 EV, 16 EV and the luminance of the object is measured in each range of 9.5-13.5 EV, 13.5-18 EV. The photography screen is divided into a plurality of small regions and the luminance of the object is measured for each small region. Luminance of the object in the measurement range is extracted for each measurement of the luminance of the object and an appropriate exposure value is calculated according to the luminance them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photographing apparatus and an exposure determination method thereof.

  Digital cameras that take a subject image with an image sensor such as a CCD image sensor are widely used. In such a digital camera, when the release button is not pressed, an image sensor is used to shoot a moving image, and a subject image being shot is displayed as a through image on a display device such as an LCD so that the photographer can perform framing. There is something.

  When photographing, for example, a through image is observed to determine framing, and then the release button is pressed. When the release button is pressed halfway, the AE process for determining the aperture and shutter speed for taking a still image, and the AF process for adjusting the focus of the taking lens are performed, and then the moving image is taken again to display a through image. Is done. When the release button is further pushed down and fully depressed, exposure for still image shooting is performed by the image sensor with the content determined by the AE process when half-pressed.

On the other hand, when receiving an instruction to shoot a still image while shooting a movie with the image sensor, exposure control for the still image is performed using the output from the image sensor or photometric information at that time. Such an imaging apparatus is known from Patent Documents 1 and 2.
Japanese Patent Publication No. 2-30633 Japanese Patent Publication No. 2-30634

  In addition, a large number of main light-receiving elements with a large light-receiving area and high sensitivity and sub-light-receiving elements with a small light-receiving area and low sensitivity are formed. There is also known a digital camera equipped with a CCD image sensor capable of greatly improving the reproducible light / dark range, that is, the dynamic range. Some of these digital cameras have a dynamic range that is, for example, about four times that of the conventional digital camera.

  By the way, in order to take a still image by taking advantage of the characteristics of the wide dynamic range as described above, it is necessary to measure the subject luminance within a measurement range corresponding to the dynamic range. The normal shooting scene is in the range of 4 EV to 18 EV, but the luminance difference that can be measured based on the shooting signal obtained while shooting the moving image with the CCD image sensor is about 4 EV, and the accuracy is reduced to some extent. Even if it is allowed, it is about 6 EV. The measurable luminance difference is the same even when a shooting signal is used during moving image shooting with the CCD image sensor having a wide dynamic range as described above. For this reason, as in Patent Documents 1 and 2, the subject luminance information obtained based on the shooting signal during moving image shooting cannot perform still image shooting utilizing a wide dynamic range.

  Furthermore, in a CCD image sensor, smear occurs when strong external light is incident on the charge transfer path. When exposure control is performed using a shooting signal in which this smear has occurred, subject brightness is recognized brightly by the amount of smear. As a result, there was a problem of underexposure. Also, with digital cameras, there is a tendency for the release time lag from when the release button is fully pressed to when a still image is actually taken to be shortened.

  The present invention has been made in consideration of the above-mentioned problems, and can measure the subject luminance corresponding to a wide dynamic range, can eliminate the influence of smear, and can further reduce the release time lag. It is an object of the present invention to provide a photographing apparatus that can perform the exposure and a method for determining exposure thereof.

  In order to achieve the above object, according to the exposure determining method of the photographing apparatus according to claim 1, the luminance of the subject for each of the small areas obtained by dividing the photographing screen based on the photographing signal from the image sensor for photographing the subject image. The photometric operation is measured multiple times by shifting the measurement range by changing the exposure value, and the brightness measured within the measurement range is obtained for each small area, and still images are taken using each obtained brightness The exposure value is obtained.

  In the exposure determining method of the photographing apparatus according to claim 2, when the release button is not operated and the half-pressed state is maintained, the moving image is captured by the image sensor and the image is being shot. The subject image is displayed on a display device, and in response to a full press of the release button, a still image is taken with the image sensor. In response.

  In the exposure determination method of the photographing apparatus according to claim 3, in the pressed release state, luminance measurement is performed for each small area based on a photographing signal during moving image photographing, and the first light measurement is performed by half-pressing the release button. This is an acquisition operation for acquiring the luminance of each small region measured immediately before, and a predetermined luminance range corresponding to the exposure value at the time of moving image shooting corresponding to the luminance acquired by this acquisition operation is set as the measurement range of the first photometry. Is. The exposure determination method for an image taking apparatus according to claim 4, wherein the second and subsequent measurement operations are performed with the higher luminance side of the measurement range of the first photometry as the measurement range. In the determination method, when the luminance of each small area measured by the m-th (m is 1, 2,...) Metering is within the m-th measurement range, the metering after “m + 1” is not performed. It is a thing.

  7. The exposure determining method for an image taking apparatus according to claim 6, wherein only a smear component generated in the image sensor is output as a smear signal together with the photometry for a plurality of times, and a smear component is calculated for each of the small regions based on the smear. The smear measurement operation to measure is performed, and the measurement result of photometry is corrected using the obtained smear component. According to a seventh aspect of the present invention, there is provided a method for determining exposure of a photographing apparatus, wherein a smear measurement operation is performed when a shutter speed of an image sensor during photometry is higher than a predetermined shutter speed.

  9. The photographing apparatus according to claim 8, wherein the exposure control means for adjusting the exposure amount of the image sensor by changing the exposure value, and each of the small areas obtained by dividing the photographing screen into a plurality based on the photographing signal from the image sensor. A photometric means for measuring the luminance of the subject and a photometric means for performing a plurality of luminance measurements with different measurement ranges by changing the exposure value of the exposure control means in response to a half-press of the release button. Photometry control means and exposure for acquiring the brightness measured within the measurement range among the subject brightness measured in each brightness measurement for each small area, and determining an exposure value at the time of still image shooting based on each acquired brightness And a determination means.

  According to a ninth aspect of the present invention, when the release button is not pressed and the release button is not operated, the image sensor performs moving image shooting, and the through image mode operation is performed to display the subject image being shot on the display device. The photometry means is the first luminance measurement in which the acquisition operation for acquiring the luminance of each small area measured immediately before the release button is half-pressed in response to the half-press of the release button, and the exposure determination means The measurement range is a predetermined luminance range corresponding to the exposure value at the time of moving image shooting corresponding to the luminance acquired by the acquisition operation.

  According to a tenth aspect of the present invention, the photometric control means is characterized in that the second and subsequent measurement operations are performed with the higher luminance side than the measurement range of the first luminance measurement as the measurement range. Further, in the photographing apparatus according to claim 11, the photometry control unit is configured such that the luminance of each small region measured by the m-th luminance measurement (m is 1, 2,...) By the photometry unit is the m-th measurement range. In this case, the luminance measurement after “m + 1” is not performed.

  In the photographing apparatus according to claim 12, smear measurement means for performing a smear measurement operation for outputting only the smear component generated in the image sensor as a smear signal and measuring the smear component for each of the small regions based on the smear, And a correcting means for correcting the measurement result of the photometric means using a smear component obtained from the smear measuring means.

  According to the present invention, based on the photographing signal from the image sensor, the measurement range is shifted and the subject brightness is measured by measuring a plurality of times, thereby measuring the wide brightness range. Since the exposure value is obtained for photographing, it is possible to determine the exposure value so that the image sensor can perform photographing utilizing the effect of a wide dynamic range. In addition, the first subject brightness measurement should be performed after half-pressing the release button by obtaining the subject brightness measured based on the shooting signal obtained during moving image shooting before the release button is half-pressed. Processing can be reduced, and a still image can be taken in a short time from the half-press point. Furthermore, since the smear signal is output from the image sensor to detect the smear component and the brightness measured by the smear component is corrected, the exposure value can be accurately determined without the influence of the smear component.

  The front of the digital camera embodying the present invention is shown in FIG. 1, and the back is shown in FIG. On the front surface of the camera body 2 of the digital camera, a photographing lens 3, a release button 4, and a strobe light emitting unit 5 are provided. On the back side, an operation unit 7 including various operation buttons 7a and cursor keys 7b and an LCD 9 are provided. The LCD 9 constitutes a so-called electronic viewfinder that displays in real time a subject image photographed through the photographing lens 3, and is used for image reproduction and the like. By operating the operation unit 7, it is possible to select a still image shooting mode for shooting a still image, a moving image shooting mode for shooting a moving image, a shot still image, and a playback mode for playing back a moving image.

  The release button 4 can be pressed both half-pressed and fully pressed from the half-press. Under the still image shooting mode, the through image mode is set when the release button 4 is not pressed. In the through image mode, a moving image of a subject is photographed by the CCD image sensor 10 (see FIG. 3) disposed on the ridge of the photographing lens 3, and the photographed subject image is displayed on the LCD 9 as a so-called through image.

  When the release button 4 is pressed halfway, the AE process for determining the electronic shutter speed, the aperture value, and the shooting sensitivity for still image shooting, the AF process for matching the focus of the shooting lens 3 to the subject, and the drive mode of the CCD image sensor 10 are set. A first preparation process including a process to be changed is performed. After the first preparation process, the live view mode is set again while the release button 4 is being pressed halfway.

  When the release button 4 is fully pressed in the still image shooting mode, the still mode is set, and the electronic shutter speed, shooting sensitivity, and aperture value determined in response to the previous half-press are set. After performing a second preparation process including a setting process for performing the process and a process of changing the operation of the CCD image sensor 10 to a drive mode for taking a still image, still image exposure by the CCD image sensor 10 is performed. The still image obtained by this still image exposure is converted into image data and recorded on the removable memory card 11 (see FIG. 3).

  In the through image mode, the aperture value, the charge accumulation time of the CCD image sensor 10, that is, the electronic shutter speed, and the photographing sensitivity are changed according to the subject luminance as in the case of the conventional digital camera. Note that when the release button 4 is fully pressed, shooting is performed using a fixed aperture value for still image shooting in the through image mode while the release button 4 is half-pressed. The aperture switching operation may be eliminated so that still image exposure can be performed with a small delay.

  FIG. 3 shows the configuration of the digital camera. The operation unit 7 sends an operation signal corresponding to the operation of the operation button 7a and the cursor key 7b constituting the operation unit 7 to the CPU 15. The switch unit 16 includes release switches S1 and S2 that are turned on and off in conjunction with the pressing of the release button 4. The release switch S1 is turned on when the release button 4 is half-pressed, and the release switch S2 is turned on when the release button 4 is fully pressed. On / off of the release switches S1, S2 is sent to the CPU 15.

  The CPU 15 controls each unit based on various signals from the operation unit 7 and the switch unit 16. The CPU 15 is connected to a ROM 15a and a RAM 15b. In the ROM 15a, programs for executing various sequences, programs corresponding to various program diagrams for determining combinations of shutter speeds, aperture values, and photographing sensitivities, and the like are written. To control. The RAM 15b is used as a work memory that temporarily stores data necessary for executing a shooting sequence or the like.

  The taking lens 3 includes a zoom mechanism 21, a focus mechanism 22, a diaphragm device 23, and a mechanical shutter device 24. The zoom mechanism 21 performs zooming by moving the lens constituting the photographing lens 3 in response to the zoom operation of the operation unit 7. The focus mechanism 22 moves the focus lens 22a to perform focusing. Focusing by the focus mechanism 22 is always performed so as to follow the change in the subject distance when the release button 4 is released in the shooting mode. This is a so-called focus lock state in which the subject at the time of pressing is fixed at a position where the subject is in focus. The diaphragm device 23 adjusts the light intensity of the subject light incident on the CCD image sensor 10 by adjusting the diaphragm (diaphragm aperture diameter).

  The zoom mechanism 21, the focus mechanism 22, and the diaphragm device 23 are controlled by the CPU 15 through corresponding drivers 25 to 27.

  The mechanical shutter device 24 is normally in an open state in which the shutter blades are opened, and is in a closed state in which the shutter blades are closed when the exposure of the still image of the CCD image sensor 10 is completed. This prevents external light from entering the CCD image sensor 10 after completion of exposure of the subject during still image shooting, thereby preventing smear. The mechanical shutter device 24 is connected to a timing generator 30 via a driver 28 and is operated by a mechanical shutter drive signal from the timing generator 30.

  A CCD image sensor 10 is arranged behind the photographic lens 3, and subject light transmitted through the photographic lens 3 is incident on the light receiving surface of the CCD image sensor 10. The CCD image sensor 10 is provided with a large number of light receiving portions on its light receiving surface, and is driven by various drive signals from a timing generator 30 as a drive means, and subject images exposed by the light receiving portions are converted into analog shooting signals. Convert and output. The CCD image sensor 10 has an electronic shutter function that adjusts a charge accumulation time by sweeping out and erasing charges accumulated so far by inputting an electronic shutter pulse from the timing generator 30. The electronic shutter speed can be adjusted by adjusting the input period. An image sensor other than the CCD image sensor 10 can be used as long as it converts a subject image into a photographing signal and outputs it.

  In the CCD image sensor 10, as will be described later, one light receiving portion (pixel) is composed of a high-sensitivity main light-receiving element and a low-sensitivity sub-light-receiving element. In the still mode, a subject image is captured by the main light-receiving element. The photographed image signal and the image signal obtained by photographing the subject image with the sub light receiving element are output. In the following description, when the imaging signals are distinguished, the main light receiving element is referred to as a main imaging signal, and the sub light receiving element is referred to as a sub imaging signal. For example, the CCD image sensor 10 outputs a main photographing signal for one frame and then outputs a sub photographing signal for one frame. In the through image mode, only the main shooting signal is output.

  In the timing generator 30, various parameters for performing various operations at predetermined timings are set (loaded) by the CPU 15, and a vertical synchronization signal VI serving as a reference for the operation of each unit and a drive signal for driving the CCD image sensor 10. Various signals such as are generated. When various parameters are set, the timing generator 30 validates the set parameters at the falling edge of the vertical synchronization signal VI after the setting is completed, that is, at the start of the next frame period. Note that one frame period is from the fall of the vertical synchronization signal VI to the next fall.

  Parameters set in the timing generator 30 include, for example, a shooting frame rate parameter of the CCD image sensor 10, a parameter of an electronic shutter speed, a parameter that specifies whether to perform moving image shooting or still image shooting, and a mechanical shutter device 24. There are parameters related to the operation of the above, parameters of the charge transfer form inside the CCD image sensor 10, and the like.

  A photographing signal from the CCD image sensor 10 is sent to the analog signal processing unit 31. The analog signal processing unit 31 includes a CDS circuit 31a, an AMP circuit 31b, and an A / D converter 31c. When the synchronization pulse from the timing generator 30 is input, the charge reading operation of the CCD image sensor 10 is performed. Operates synchronously.

  The CDS circuit 31a removes noise from the photographic signal by performing correlated double sampling. The AMP circuit 31b amplifies the photographing signal with a gain corresponding to the photographing sensitivity set by the CPU 15. The A / D converter 31c digitally converts the photographic signal from the AMP circuit 31b and outputs it as image data.

  Image data from the A / D converter 31 c is sent to the image input controller 32. The image input controller 32 controls input of image data to the bus 33. Connected to the bus 33 are a CPU 15, an image processing unit 34, a compression processing unit 35, an AF detection unit 36, an AE / AWB detection unit 37, a media controller 38, an internal memory 39, an LCD driver 40, and a timer 41. Each unit is controlled by the CPU 15 via the bus 33 and can exchange data with each other.

  In the through image mode, the image processing unit 34 performs image processing such as γ correction and white balance correction on the main image data obtained from the main photographing signal. In the still mode, the image processing unit 34 performs gradation synthesis processing to generate a composite image having a wide dynamic range, and then performs image processing such as γ correction and white balance correction on the image data of the composite image. Do. In the gradation composition process, the main image data and the sub-image data obtained from the sub-photographing signal are used, for example, the main image data in the high luminance region is corrected with the corresponding sub-image data, and then the predetermined gradation width is obtained. In this way, gradation compression is performed.

  The compression processing unit 35 performs data compression, for example, in JPEG format on the image data from the image processing unit 34 under the still mode. In addition, the compression processing unit 35 decompresses the compressed image data read from the memory card 11 in the reproduction mode.

  The AF detection unit 36 detects the contrast of the image being photographed using the image data output from the image input controller 32 for focusing the photographing lens 3, and sends the contrast information to the CPU 15. The CPU 15 refers to the contrast information and drives the focus mechanism 22 via the driver 26 so that the contrast of the image being shot is maximized.

  Based on the image data from the image input controller 32, the AE / AWB detection unit 37 detects the subject brightness and the type of light source, and sends them to the CPU 15. The CPU 15 sets the white balance parameter of the image processing unit 34 based on the type of light source.

  As will be described later, the AE / AWB detection unit 37 divides the shooting screen into a plurality of small areas, detects subject brightness for each of the small areas, and sends the subject brightness to the CPU 15. The CPU 15 uses the subject brightness from the AE / AWB detection unit 37 to calculate the exposure value in the through image mode and the still mode. The exposure value in the still mode is the first to third photometry in which the subject luminance measurement range is shifted as will be described later in the AE process of the first preparation process performed in response to the half-press of the release button 4. It is determined from the subject brightness obtained in the sequence. In this example, three photometric sequences are executed, but two or four or more photometric sequences may be used.

  The CPU 15 converts the exposure value in the through image mode into a combination of the aperture value, the shutter speed, and the photographing sensitivity according to the through image program, and the exposure value in the still mode according to the still program. Convert to a combination of The determined electronic shutter speed, shooting aperture, and shooting sensitivity are set in the corresponding units in the second preparation process performed in response to the full press of the release button 4.

  The media controller 38 controls writing and reading of data in the memory card 11. The image data to be recorded is processed by the image processing unit 34 and the compression processing unit 35, sent to the media controller 38, and written to the memory card 11. At the time of reproduction, the image data recorded on the memory card 11 is read out by the media controller 38, sent to the compression processing unit 35 and decompressed, and then sent to the internal memory 39.

  The internal memory 39 is, for example, an SDRAM capable of high-speed reading and writing. In the internal memory 39, image data to be displayed on the LCD 9 and image data to be recorded on the memory card 11 in still image shooting are written. Under each moving image mode, image data is sequentially input and written in the internal memory 39 in synchronization with the vertical synchronization signal VI.

  The LCD driver 40 reads the image data from the internal memory 39 in synchronization with the vertical synchronizing signal VD for reproduction under the through image mode and the reproduction mode, and drives the LCD 9 based on the image data. As a result, the LCD 9 displays the subject being photographed by the CCD image sensor 10 and the image read from the memory card 11.

  The timer 41 measures the elapsed time with reference to the vertical synchronization signal VI. The CPU 15 determines the timing for setting various parameters in the timing generator 30 based on the elapsed time counted by the timer 41.

  FIG. 4 schematically shows the CCD image sensor 10. Each light receiving unit 50 of the CCD image sensor 10 includes a pair of main light receiving elements 51 and sub light receiving elements 52. In this example, by increasing the light receiving area of the main light receiving element 51 and making the light receiving area of the sub light receiving element 52 smaller than the light receiving element 51, the light receiving element 51 has a relatively high sensitivity and the light receiving element 52 has a low sensitivity. It is as.

  A vertical transfer path 53 is provided for each column of the light receiving units 50, and a horizontal transfer path 54 is provided at the end of each vertical transfer path 53. Each transfer path 53, 54 is provided with a transfer electrode (not shown). By applying a voltage to each transfer electrode at a predetermined timing, the charges accumulated in the respective light receiving elements 51 and 52 are serially read out to the output amplifier 55 via the vertical transfer path 53 and the horizontal transfer path 54. . Each charge is converted into a voltage corresponding to the amount of charge by the output amplifier 55 and output as a photographing signal. This charge reading is first performed from the main light receiving element 51, and after the charge reading of all the main light receiving elements 51 is completed, the charge of the sub light receiving elements 52 is read. As a result, the main shooting signal and the sub shooting signal are output frame by frame.

  FIG. 5 shows an example of the state of the shooting screen 57 when the subject brightness is detected and the weights given to the small areas 58. The AE / AWB detection unit 37 divides the shooting screen 57 into n (in this example, 64) small areas 58 and detects subject luminance in each of the small areas 58. The numbers given in each small area 58 represent “weight” when calculating the appropriate exposure value. The CPU 15 performs an exposure calculation process with a weight corresponding to the subject luminance for each small region 57a, and calculates an appropriate exposure value. The appropriate exposure value is E, the subject brightness for each small area 58 is Di (i = 1, 2,... N), and the weight for each small area 58 is Wi (i = 1, 2,... N). Sometimes, it is calculated by the following equation (1).

  In the AE process, first to third luminance detection sequences, an exposure calculation process, and a set value conversion process are performed. Each luminance detection sequence includes photometry including detection processing for detecting subject luminance by the AE / AWB detection unit 37 as described above based on exposure by the CCD image sensor 10 and its image data (photographing signal), and within the photometry range. It consists of an extraction process of the CPU 15 for extracting subject luminance. Note that the subject luminance is detected based on the main photographing signal.

  FIG. 6 shows the photometric range of each luminance detection sequence. Note that the dotted line in FIG. 6 represents a portion where the subject luminance can be measured but is outside the measurement range. The measurement ranges of the first to third luminance detection sequences are set in advance so as not to overlap. In the first luminance detection sequence, the exposure value is set to 8 EV under the control of the CPU 15, exposure by the CCD image sensor 10 is performed, and photometry is performed for the first photometric range of 4 EV or more and less than 9.5 EV. Similarly, in the second luminance detection sequence, the exposure value is set to 12 EV, exposure by the CCD image sensor 10 is performed, and photometry is performed in the second photometry range of 9.5 EV to less than 13.5 EV. In the third luminance detection sequence, the exposure value is set to 16 EV, and photometry is performed in the third photometry range of 13.5 EV to 18 EV.

  For example, in the first luminance detection sequence, the aperture value is F2.8 (= AV3), the electronic shutter speed is 1/30 second (= TV5), and the second luminance is combined in each luminance detection sequence. In the detection sequence, the aperture value is F4 (= AV4) and the electronic shutter speed is 1/250 second (= TV8). In the third luminance detection sequence, the aperture value is F8 (= AV6) and the electronic shutter speed is 1/1000 second. (= TV10), and the photographing sensitivity is ISO100 in any photometry sequence.

  In the luminance detection sequence extraction process, the subject luminance within the photometric range of the corresponding luminance detection sequence is extracted. The exposure calculation process and the set value conversion process are performed by the CPU 15 after the third photometry sequence. In the exposure calculation processing, n subject luminances extracted in three luminance detection sequences are applied to the above equation (1) to calculate an appropriate exposure value. In the set value conversion process, the appropriate exposure value calculated in the exposure calculation process is converted into an aperture value, an electronic shutter speed, and a photographing sensitivity using a still program.

  Note that the subject brightness and exposure values are based on the photographing sensitivity ISO100. Further, the subject brightness of each small area 58 detected by the AE / AWB detection unit 37 is not the absolute subject brightness but the relative subject brightness based on the exposure value when the photometry is performed. For this reason, when performing the exposure calculation process, the CPU 15 performs a process of converting the measured subject brightness into an absolute subject brightness using the aperture value at the time of photometry, the photographing sensitivity, and the electronic shutter speed. Furthermore, the proper exposure calculation may be sequentially performed every time subject brightness is extracted.

  Next, the operation of the above configuration will be described with reference to FIGS. When shooting a still image, the digital camera is turned on to select a shooting mode, and further select a still image shooting mode. When the still image shooting mode is set, the through image mode is set and moving image shooting is started.

  When the CCD image sensor 10 starts operating, the subject image exposed by each main pixel 51 is output as a main photographing signal, and converted into main image data via the CDS circuit 31a, the AMP circuit 31b, and the A / D converter 31c. After that, the image data is sent to the image processing unit 34, the AF detection unit 36, the AE / AWB detection unit 37, and the internal memory 39 via the image input controller 32 and the bus 33, respectively.

  Then, contrast information based on the main image data from the AF detection unit 36 is sent to the CPU 15, and the focus mechanism 22 is controlled by the CPU 15 to adjust the focus to the subject currently being photographed. Since this focus adjustment is performed as needed, even if the shooting distance to the subject changes, the focus is adjusted following the change.

  Further, the AE / AWB detection unit 37 sends the subject luminance for one screen detected for each small area 58 and the type of light source to the CPU 15. In this through image mode, the CPU 15 calculates an appropriate exposure value using a predetermined algorithm based on the subject luminance for one screen obtained in this way, and the calculation result is applied to the through image program so that the electronic The shutter speed, shooting sensitivity, and aperture value are obtained. Then, the electronic shutter speed thus obtained is set in the timing generator 30, the photographing sensitivity is set in the AMP circuit 31b, and the aperture device 23 is controlled via the driver 27 so that the aperture value is obtained. If the subject brightness changes, the electronic shutter speed, aperture, and shooting sensitivity are obtained again accordingly, and are set and controlled, so that the subject being shot is always adjusted to an appropriate exposure.

  On the other hand, the type of the light source is specified by the CPU 15 based on the type of the light source, the white balance parameter corresponding to the light source is set in the image processing unit 34, and the image processing unit 34 performs processing on the image data input thereto. Image processing such as white balance correction and γ correction is performed. As with the subject brightness, if the type of light source changes, the white balance parameter is reset accordingly, so that an appropriate white balance is always maintained.

  When the electronic shutter speed, aperture, and shooting sensitivity are adjusted according to the subject brightness as described above, exposure by the CCD image sensor 10 is performed under the electronic shutter speed and aperture value, and the main shooting signal to be output is The signal is amplified by the AMP 31b with a gain corresponding to the photographing sensitivity. The obtained image data is subjected to image processing by the image processing unit 34, written once in the internal memory 39, and then read out by the LCD driver 40. Thereby, the subject image photographed by the CCD image sensor 10 is displayed on the LCD 9 as a moving image.

  When the release button 4 is pressed halfway, the release switch S1 is turned on. A first preparation process is performed in response to the release switch S1 being turned on. In the first preparation process, first, the AE process shown in FIG. 8 is performed, the first to third luminance detection sequences are sequentially performed, and an appropriate exposure value used for still image shooting is calculated.

  As shown in an example in FIG. 9, when the frame period in which the release switch S1 is turned on is set to 0th, the first luminance detection sequence is started in the first frame period. First, parameter setting processing P1 is performed during the first frame period, and various parameters including parameters for setting the electronic shutter speed to 1/30 seconds are set in the timing generator 30.

  In the second frame period, at the start of the period, the diaphragm device 23 is driven by the control of the CPU 15 to set the diaphragm value to F2.8, and then the exposure E1 by the CCD image sensor 10 is started. Since the exposure E1 is based on the parameters of the parameter setting process P1, the exposure time, that is, the electronic shutter speed is 1/30 second.

  When the third frame period comes after completion of the exposure E1, the CPU 15 sets a gain corresponding to the ISO 100 photographing sensitivity to the AMP 31b, and then the main pixel 51 among the charges accumulated in the CCD image sensor 10 by the exposure E1. Is started, and a main imaging signal is output (R1). The main photographing signal is converted into main image data through the CDS circuit 31a, the AMP circuit 31b, and the A / D converter 31c, and sent to the AE / AWB detection unit 37 through the image input controller 32. As a result, the AE / AWB detection unit 37 receives main image data that has been exposed with an aperture value of F2.8, an electronic shutter speed of 1/30 seconds, and an imaging sensitivity of ISO100. The AE / AWB detection unit 37 detects the subject brightness for each small region 58 from the main image data and sends it to the CPU 15.

  The subject luminance for one screen input to the CPU 15 is once written and held, for example, in the RAM 15b during the third frame period. When the fourth frame period is reached, the CPU 15 performs the extraction process S1 and accesses only the subject brightness within the first photometric range (4 EV or more and less than 9.5 EV) among the recorded subject brightness by accessing the RAM 15b. Extract. When the extraction is completed, the first luminance detection sequence is completed.

  On the other hand, the second luminance detection sequence is started in the second frame period during which the exposure E1 of the first luminance detection sequence is performed. The parameter setting process P2 is performed during the second frame period, and various parameters including a parameter for setting the electronic shutter speed to 1/250 seconds are set in the timing generator 30. When the third frame period is reached, the diaphragm device 23 After the aperture value is set to F4, exposure E2 by the CCD image sensor 10 is performed. The exposure E2 has an aperture value of F4 and an electronic shutter speed of 1/250 seconds.

  When the fourth frame period is reached, the main shooting signal by the exposure E2 is output (R2), and is sent to the AE / AWB detection unit 37 via the CDS circuit 31a, the AMP circuit 31b, the A / D converter 31c, and the image input controller 32. Sent. At this time, a gain corresponding to the ISO 100 imaging sensitivity is set in the AMP circuit 31b during the first luminance detection sequence. Therefore, main image data that has been exposed with an aperture value of F4, an electronic shutter speed of 1/250 seconds, and a photographing sensitivity of ISO 100 is input to the AE / AWB detection unit 37. The subject brightness detected for each region 58 is sent to the CPU 15.

  Similarly to the case of the first luminance detection sequence, the subject luminance of the second luminance detection sequence is also stored in the RAM 15b and is within the second photometric range (9.5 EV or more and less than 13.5 EV) in the fifth frame period. Only subject brightness is extracted.

  Further, in the third frame period during which the exposure E2 is performed, the third luminance detection sequence is started and performed in the same manner as the first and second luminance detection sequences. At this time, in the third luminance detection sequence, the electronic shutter speed is 1/1000 second, and the aperture value is F8. In the third luminance detection sequence, only subject luminance within the third photometric range (13.5 EV or more and 18 EV or less) is extracted in the sixth frame period.

  As described above, one subject brightness is obtained for each of the n small regions 58 by performing the photometry sequence three times and extracting the subject brightness in the corresponding photometry range. Then, after completion of the third photometry sequence, the CPU 15 performs an exposure calculation process C0, and the n extracted subject luminances are applied to the equation (1). As a result, an appropriate exposure value based on each subject brightness measured with 4 EV to 18 EV as a measurement range is calculated.

  FIG. 10 schematically shows an example of a subject luminance measurement state. Note that the numbers shown in the small area 58 in FIG. 10 are the subject brightness extracted by the corresponding brightness detection sequence, and the circle indicates that the measured subject brightness is higher than the measurement range. The mark indicates that it is lower than the measurement range.

  In the first luminance detection sequence, as shown in FIG. 10A, subject luminance with a first photometric range of 4 EV or more and less than 9.5 EV is extracted, but other subject luminance is invalidated. Further, in the second luminance detection sequence, since the second photometric range is not less than 9.5 EV and less than 15 EV, only the subject luminance within that range is extracted and the other subject luminance is invalid as shown in FIG. It becomes. Of course, the subject luminance of the small area extracted in the first luminance detection sequence is invalid in the second luminance detection sequence. Further, in the third luminance detection sequence, since the third photometry range is 15 EV or more and 18 EV or less, the subject luminance of 15 EV or more and 18 EV or less is extracted, and other subject brightness is invalid as shown in FIG. It becomes. As a result, the distribution of the subject luminance in the photographing screen 57 is measured with the range of 4 EV or more and 18 EV or less as a photometry range as a result of the three times of photometry as described above. An appropriate exposure value based on the above is calculated.

  After the appropriate exposure value is calculated, a setting conversion process for applying the appropriate exposure value to the still image program is performed, and the electronic shutter speed, the shooting aperture, and the shooting sensitivity used for still image shooting are determined. The determined content is held in the CPU 15 and the AE process is completed.

  Subsequently, AF processing is performed, the focus lens 22a is driven based on the contrast information, and the focus of the photographing lens 3 is readjusted. The position of the readjusted focus lens 22a is fixed until the release button 4 is released, and the focus is locked.

  When the first preparation process is completed as described above, the through image mode is set again, and moving image shooting is performed by the CCD image sensor 10 as described above, and the through image is displayed on the LCD 9.

  When the release button 4 is fully pressed and the release switch S2 is turned on, the second preparation process is performed. In the second preparation process, parameters for driving in the still mode, electronic shutter speed for still image shooting determined in response to half-pressing of the release button 4, and parameters for driving timing of the mechanical shutter device 24 are used. Are set in the timing generator 30. An aperture value for still image shooting is set in the aperture device 23, and a gain corresponding to shooting sensitivity is set in the AMP 31b.

  When the second preparation process is completed as described above, still image exposure by the CCD image sensor 10 is performed. In this still image exposure, charge accumulation is performed at the set electronic shutter speed, and the mechanical shutter device 24 is closed at the end of the exposure.

  After the still image exposure is performed, a main photographing signal is output from the CCD image sensor 10, converted into main image data via the analog signal processing unit 31, and then sent to the image processing unit 34, and the image processing unit 20. Written to the buffer memory. Subsequently, a sub photographing signal is output from the CCD image sensor 10, and the sub photographing signal is converted into sub image data via the analog signal processing unit 31 and sent to the image processing unit 34 in the same manner as the main photographing signal. Then, the sub image data is written into the buffer memory of the image processing unit 20.

  After the main image data and the sub image data are written in the buffer memory, gradation synthesis processing is performed using each of the image data, and a synthesized image having a wide dynamic range is generated. Then, image processing such as γ correction and white balance correction is performed on the composite image data of the composite image. After these processes, the composite image data is sent to the compression processing unit 35 and compressed, and then recorded on the memory card 11 by the media controller 38.

  As described above, a still image is shot with an appropriate exposure value determined based on the photometric result obtained by widening the measured luminance of the subject by performing photometry three times while shifting the photometric range. It is possible to obtain a still image having gradation using the 10 wide dynamic range.

  FIG. 11 shows a second embodiment in which the subject brightness measured during the through image mode is used. In addition, except being demonstrated below, it is the same as that of the said embodiment, The same code | symbol is attached | subjected to the same structural member, and the description is abbreviate | omitted.

  When the release button 4 is pressed halfway, the subject brightness measured during the through image mode is acquired as a measurement value (subject brightness) of the first brightness detection sequence in response to this, and the acquired subject brightness is described as follows. When the subject brightness higher than the upper limit of measurement is included in the determined first measurement range, the second and third photometry sequences are executed.

  In the live view mode, the subject brightness is measured to determine the exposure value during movie shooting, and the subject brightness is input from the AE / AWB detection unit 37 to the CPU 15 for each frame period. Is temporarily stored in the RAM 15b, for example, so that the subject brightness measured immediately before the release button 4 is half-pressed can be acquired.

  In this example, the subject brightness immediately before half-pressing of the release button 4 is the latest subject brightness acquired in the RAM 15 at the time of half-pressing. For example, the exposure result by the CCD image sensor 15 during the frame period at the time of half-pressing. Alternatively, it may be subject brightness obtained based on the output photographing signal. Further, these may be switched according to the half-press timing of the release button 4 with respect to the vertical synchronization signal VI. In order to shorten the release time lag, it is preferable to use the latest acquired subject brightness.

  As the first measurement range, on the low luminance side and the high luminance side based on the exposure value (hereinafter referred to as a through image exposure setting value) at the time of exposure obtained with the subject luminance acquired as the subject luminance of the first luminance detection sequence. It is set to have an appropriate width. In this example, the first measurement range is set to “through image exposure setting value−2.5 EV” or more and less than “through image exposure setting value + 1.5 EV”).

  When the subject brightness acquired as the measurement value of the first brightness detection sequence includes a value equal to or higher than the upper limit of the first photometry range, the second and third brightness detection sequences after the release button 4 is pressed halfway as shown in FIG. Is executed. The second luminance detection sequence is performed by shifting the second measurement range to the higher luminance side than the first measurement range. Since the first measurement range is “through image exposure setting value−2.5 EV” or more and less than “through image exposure setting value + 1.5 EV”, the second luminance detection sequence sets the exposure value to “through image exposure setting value”. The exposure is performed as “+4 EV”, and the second measurement range is set to be less than “(through image exposure setting value + 4 EV) −2.5 EV” “(through image exposure setting value + 4 EV) +1.5 EV”. Similarly, in the third luminance detection sequence, exposure is performed with an exposure value “through image exposure setting value + 8 EV”, and the third photometry range is “(through image exposure setting value + 8 EV) −2.5 EV” or more “(through image exposure). Set value +8 EV) +1.5 EV ”or less.

  In FIG. 13 showing an example when the second and third luminance detection sequences are performed, when the through image setting exposure value (exposure value of exposure E1 in FIG. 12) is 9.5 EV, the first measurement range is 7EV or more and less than 11EV. In the second luminance detection sequence, the exposure value is set to 13.5 EV and exposure E2 is performed, and the second measurement range is 11 EV or more and less than 15 EV. Further, in the third luminance detection sequence, the exposure value is set to 17.5 EV and exposure E3 is performed, so that the third measurement range is 15 EV or more and less than 19 EV.

  On the other hand, when all the subject luminances acquired as the measurement values of the first luminance detection sequence are within the first measurement range, the second and third luminance detection sequences are performed after the release button 4 is pressed halfway as shown in FIG. Without performing the above, the appropriate exposure value is calculated only from the subject brightness acquired as the measurement value of the first brightness detection sequence. For example, as shown in FIG. 15, when the through image exposure setting value is 9.5 EV, and the subject brightness acquired as the measurement value of the first brightness detection sequence is in the range of 7.5 EV to 10.8 EV. Does not execute the second and third luminance detection sequences.

    According to this example, since the luminance detection sequence is not performed after the release button 4 is pressed halfway, it is possible to shorten the time until the calculation of the appropriate exposure value is completed. There is an advantage that the time until it becomes possible, that is, the release time lag can be shortened.

  In the above embodiment, the second and third luminance detections for measuring the higher luminance range when the subject luminance acquired as the measurement value of the first luminance detection sequence is greater than or equal to the upper limit of the first photometric range. The sequence is executed, but when a value lower than the first photometric range is included, a luminance detection sequence for measuring a lower luminance area than the first photometric range may be executed. Furthermore, the third luminance detection sequence may be executed only when the measurement result of the second luminance detection sequence includes subject luminance that is equal to or higher than the upper limit of the second photometry range.

  16 and 17 show a third embodiment in which an appropriate exposure value is calculated by removing the influence of the smear component. In the following, except for the description, the same components as those in the first embodiment are used, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  In this example, the smear detection sequence is performed together with the first to third luminance detection sequences. In the smear detection sequence, for example, as in the third luminance detection sequence, exposure E4 by the CCD image 10 and output R4 of the photographing signal are performed to generate image data. The parameter is set in the timing generator 30 so as to transfer the charges in the vertical and horizontal transfer paths 53 and 54 without moving to the transfer path 53 (P4). In this way, by performing charge transfer without moving the charge of each light receiving unit 50 to the vertical transfer path 53, a photographing signal (hereinafter referred to as a smear signal) having only a smear component not including a component of the subject image is output. .

  When image data obtained by digitally converting the smear signal is input, the AE / AWB detection unit 37 generates smear luminance using the image data. This smear luminance represents the smear component of each small region 57 in the same manner as the subject luminance. The CPU 15 performs a smear correction operation CS for each small region 58 by subtracting the corresponding smear luminance from the subject luminance extracted in the third luminance detection sequence of the same small region 58. In this way, the subject luminance or smear component of each small region 58 obtained in the third luminance detection sequence is removed. It should be noted that when exposure is performed using a high electronic shutter speed, the influence of smear components becomes large. In this example, the subject luminance in the third luminance detection sequence is corrected.

  After correcting the subject brightness extracted in the third brightness detection sequence as described above, the CPU 15 performs exposure calculation processing using the corrected subject brightness and the subject brightness extracted in the first and second brightness detection sequences. C0 is performed to calculate an appropriate exposure value. Thereby, it is possible to calculate an appropriate exposure value that eliminates the influence of the smear component.

  FIG. 18 shows a fourth embodiment in which the proper exposure value is calculated by removing the smear component in the configuration using the subject luminance measured during the through image mode as in the second embodiment. In addition, except being demonstrated below, it is the same as that of the said embodiment, The same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted. In addition, the subject brightness in the through image mode immediately before the release button 4 is half-pressed is acquired as the subject brightness of the first sequence, and it is determined whether or not the second and third brightness detection sequences are executed according to the subject brightness. The point is the same as in the second embodiment, and the smear component detection and correction operations are the same as in the third embodiment.

  When the release button 4 is pressed halfway, the subject brightness measured during the through image mode is acquired as a measurement value of the first brightness detection sequence in response to this, and it is determined whether to execute the second and third photometry sequences. Is performed by the CPU 15.

  For example, if the acquired subject luminance is greater than or equal to the upper limit of the first measurement range determined according to the through image exposure setting value, the second and third luminance detection sequences are executed as shown in FIG. A smear detection sequence is performed after the sequence. The result of the third luminance detection sequence is corrected using the result from the smear detection sequence, and an appropriate exposure value is calculated in the exposure calculation process.

  On the other hand, when the acquired subject luminance is within the first measurement range, the effect of smear increases when the electronic shutter speed is high, and the effect can be ignored if the electronic shutter speed is low, so smear detection is performed according to the electronic shutter speed. It is determined whether or not the sequence is performed. In this example, when the through image setting exposure value is 15 EV or more, exposure conversion processing is performed so as to achieve an electronic shutter speed at which the influence of smear becomes large. Therefore, whether or not the through image exposure setting value is 15 EV or more is determined. Investigate.

  When the through image setting exposure value is less than 15 EV, exposure calculation processing is performed using only the subject luminance acquired as the measurement value of the first luminance detection sequence. Therefore, in this case, the operation shown in FIG. 15 of the second embodiment is performed.

  When the through image setting exposure value is 15 EV or more, as shown in FIG. 20, the smear detection sequence is performed after the release button 4 is pressed halfway. Then, using the result obtained in the smear detection sequence, the measurement value of the first luminance detection sequence, that is, the subject luminance measured during the through image mode acquired in response to the half-press of the release button 4 is corrected, and the correction is performed. The appropriate exposure value is calculated using the subject brightness.

  Even when the second and third luminance detection sequences are executed, whether or not the smear detection sequence is executed may be determined depending on the electronic shutter speed.

It is explanatory drawing which shows the front side of the digital camera which implemented this invention. It is explanatory drawing which shows the back side of a digital camera. It is a block diagram which shows the structure of a digital camera. It is explanatory drawing which shows the light-receiving part of a CCD image sensor. It is explanatory drawing which shows the photometry state of an imaging | photography screen, and the weight of a small area | region. It is a graph which shows the measurement range of each brightness | luminance detection sequence. It is a flowchart which shows the outline of imaging | photography operation | movement. It is a flowchart which shows the process sequence of AE process. It is a timing chart which shows the operation timing of the principal part. It is explanatory drawing which shows the state of multiple times photometry. 10 is a flowchart of a second embodiment using subject brightness acquired during the through image mode as subject brightness of the first brightness detection sequence. It is a timing chart which shows the operation timing of the principal part in a 2nd embodiment. It is a graph which shows an example of the measurement range of each brightness | luminance detection sequence in 2nd Embodiment. It is a timing chart which shows the operation timing when not performing the 2nd and 3rd brightness detection sequences after half-pressing a release button in a 2nd embodiment. It is a graph which shows an example of the relationship between the measurement range and object brightness | luminance when not performing the 2nd, 3rd brightness | luminance detection sequence after half-pressing the release button in 2nd Embodiment. It is a flowchart which shows the AE process of 3rd Embodiment which detects and correct | amends a smear component. It is a timing chart which shows the operation timing in a 3rd embodiment. It is a flowchart which shows the AE process in 4th Embodiment which uses the object brightness | luminance acquired during the through image mode as a subject brightness | luminance of a 1st brightness | luminance detection sequence, and selectively detects a smear component. It is a timing chart which shows the operation timing in the case of performing up to the 3rd luminance detection sequence in a 4th embodiment. It is a timing chart which shows the operation timing in the case of performing a smear detection sequence, without performing the 2nd, 3 brightness | luminance detection sequence in 4th Embodiment.

Explanation of symbols

4 Release button 9 LCD
10 CCD image sensor 15 CPU
23 Aperture device 30 Timing generator 34 Image processing unit 37 AE / AWB detection unit

Claims (12)

  Based on the image signal from the image sensor that captures the subject image, the photometric operation that measures the brightness of the subject for each of the small areas in which the shooting screen is divided into multiple areas is performed multiple times by shifting the measurement range by changing the exposure value. An exposure determination method for an imaging apparatus, characterized in that brightness measured within a measurement range for each small area is acquired, and an exposure value for still image shooting is obtained using each acquired brightness.   When the release button is not operated and the half-pressed state is maintained half-pressed, the image sensor is used to shoot a moving image, and the subject image being shot is displayed on the display device. 2. The camera according to claim 1, wherein the image sensor is configured to take a still image in response to a full press of the camera, and the photometry is performed a plurality of times in response to a half-press of a release button. Method for determining the exposure of the photographing apparatus.   In the pressed release state, luminance measurement is performed for each small area based on a shooting signal during moving image shooting, and the first photometry is acquired to obtain the luminance of each small area measured immediately before half-pressing the release button. The imaging apparatus according to claim 2, wherein a predetermined luminance range corresponding to an exposure value at the time of moving image shooting corresponding to the luminance acquired by the acquisition operation is set as a measurement range of the first photometry. Exposure determination method.   4. The exposure determination method for an imaging apparatus according to claim 3, wherein the second and subsequent measurement operations are performed with a higher luminance side than the measurement range of the first photometry as a measurement range.   The metering after “m + 1” is not performed when the luminance of each small area measured by m-th (m is 1, 2,...) metering is within the m-th measurement range. Item 5. A method for determining exposure of an imaging apparatus according to Item 4.   Along with the photometry multiple times, only the smear component generated in the image sensor is output as a smear signal, and a smear measurement operation is performed for measuring the smear component for each of the small regions based on the smear, and the resulting smear component is used. 6. The method according to claim 1, wherein the measurement result of photometry is corrected.   7. The exposure determination method for an imaging apparatus according to claim 6, wherein the smear measurement operation is performed when a shutter speed of the image sensor at the time of photometry is higher than a predetermined shutter speed. A release button that can be operated half-pressed and fully pressed, and an image sensor that captures and outputs the subject image, and determines the exposure value for still image shooting in response to the half-press of the release button. An exposure control unit that adjusts an exposure amount of the image sensor by changing an exposure value in an imaging device that captures a still image with the image sensor in response to a full press of a release button; Measured by changing the exposure value of the exposure control means in response to half-pressing of the release button and a photometric means for measuring the brightness of the subject for each of the small areas obtained by dividing the shooting screen based on the shooting signal A photometry control means for causing the photometry means to perform a plurality of brightness measurements with different ranges, and a subject brightness measured in each brightness measurement within the measurement range. An exposure apparatus comprising: an exposure determination unit that acquires a predetermined brightness for each small region and determines an exposure value at the time of still image shooting based on the acquired brightness.   When the release button is not operated and the release state is in a pressed state, the image sensor performs moving image shooting, and a through image mode operation in which a subject image being shot is displayed on a display device is operated. In response to the half-pressing of the release button, the acquisition operation for acquiring the luminance of each small area measured immediately before the half-pressing of the release button is the first luminance measurement, and the exposure determining means 9. The photographing apparatus according to claim 8, wherein a predetermined luminance range corresponding to an exposure value at the time of moving image photographing corresponding to the acquired luminance is set as a measurement range.   10. The photographing apparatus according to claim 8, wherein the photometry control unit causes the second and subsequent measurement operations to be performed with a higher luminance side than the measurement range of the first luminance measurement as a measurement range.   The photometry control means is “m + 1” or later when the luminance of each small area measured by the mth (m is 1, 2,...) Luminance measurement by the photometry means is within the mth measurement range. The imaging apparatus according to claim 10, wherein luminance measurement is not performed. A smear measurement means for performing a smear measurement operation for outputting only a smear component generated in the image sensor as a smear signal and measuring the smear component for each of the small regions based on the smear, and a smear obtained from the smear measurement means 12. The photographing apparatus according to claim 9, further comprising a correction unit that corrects a measurement result of the photometry unit using a component.

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