JP2010130211A - Imaging apparatus and method for calibrating shutter characteristics of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus for attaining matching of the exposure characteristics of an image picked up by using an electronic shutter for a leading curtain and a mechanical shutter for a trailing curtain and an image picked up by using the mechanical shutters for both leading and trailing curtains. <P>SOLUTION: When the imaging apparatus is set to the shutter calibration mode, the apparatus generates first image data with a hybrid shutter (electronic shutter for the leading and the mechanical shutter 3 for the trailing curtain) and also generates second image data with an M shutter (mechanical shutter 3 for both leading and trailing curtains). Moreover, a CPU 21 calibrates characteristics of the electronic shutter for the leading of the hybrid shutter to attain matching between the first image data and the second image data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus capable of performing imaging by determining an exposure time by using an electronic shutter and a mechanical shutter in combination, and a shutter characteristic calibration method for the imaging apparatus.

  2. Description of the Related Art Conventionally, an image pickup apparatus that uses an electronic shutter and a mechanical shutter together (using an electronic shutter for one of the front curtain and the rear curtain and a mechanical shutter for the other) to determine an exposure time and perform imaging has conventionally been used. Proposed. In the case of such a combined shutter, it is necessary that the running characteristics of the mechanical shutter match the running characteristics (operation timing) of the electronic shutter. This is because if they do not match, the exposure time differs between the upper end side and the lower end side in the traveling direction of the mechanical shutter (for example, the upper end side and the lower end side of the image), resulting in uneven brightness. is there.

  Thus, for example, Japanese Patent Application Laid-Open No. 2006-101492 describes a technique for matching the running characteristics of an electronic shutter with the running characteristics of a mechanical shutter in an imaging apparatus that uses both an electronic shutter and a mechanical shutter. In the technique described in the publication, the first image data is acquired using both the electronic shutter and the mechanical shutter, and the second image data is acquired using only the electronic shutter. At this time, the second image data is accurate because it is obtained only by the electronic shutter, whereas the first image data is inaccurate when there is a deviation between the electronic shutter and the mechanical shutter. It is thought that it is exposure. Therefore, based on the first image data and the second image data, the running characteristics of the electronic shutter at the combined shutter are adjusted so as to match the running characteristics of the mechanical shutter at the combined shutter. Such adjustment is performed in a manufacturing process of an imaging device such as an electronic camera.

  However, since the mechanical shutter operates mechanically, the travel characteristics of the shutter curtain change when the number of operations increases (for example, the number of operations increases due to a longer usage time, etc.). This is especially true for digital cameras where the number of shots has increased dramatically. Therefore, it is desirable that not only the adjustment in the manufacturing process but also after the product is shipped, the adjustment can be performed by the user operation so that the running characteristics of the mechanical shutter and the running characteristics of the electronic shutter can be matched.

  Incidentally, for example, in a single-lens reflex type electronic camera, a focal plane shutter is often used as a mechanical shutter, and the curtain speed of the focal plane shutter is, for example, about 1/200 sec to 1/250 sec. On the other hand, the number of image sensors installed in electronic cameras that have been commercialized in recent years is relatively large with 6 million pixels or more, and image data is sequentially read out line by line from such multi-pixel image sensors. The time required for this is slower than the curtain speed of the focal plane shutter described above, and is about 1/60 second even for the fastest product.

On the other hand, when using the electronic shutter and the mechanical shutter described above in combination,
(1) Front curtain: electronic shutter, rear curtain: mechanical shutter (2) Front curtain: mechanical shutter, rear curtain: electronic shutter are considered, but when taking a still image (when reading all pixels) In the case of (2), since it is difficult to match the readout speed of the electronic shutter with the curtain speed of the mechanical shutter, it is difficult to put it to practical use at present. On the other hand, in the case of (1), it is not necessary to read out the pixel charge in the front curtain by the electronic shutter, and it is sufficient to simply reset each pixel sequentially for each line (so-called rolling reset is performed). Therefore, processing in accordance with the curtain speed of the mechanical shutter is also possible.

  Therefore, at present, it is considered necessary for practical use to use a shutter having a combination of (1) (hereinafter referred to as a “hybrid shutter” as appropriate). It is also advantageous in combination with live view, which has been increasingly installed in reflex type electronic cameras in recent years. In other words, it is necessary to open the mechanical shutter during live view, but when taking a still image using only the mechanical shutter during live view, the exposure is started after the mechanical shutter is closed once. It is necessary to open the mechanical shutter, then close the mechanical shutter to finish the exposure, and then open the mechanical shutter to continue the live view. On the other hand, in the case of a hybrid shutter, since it is sufficient to perform a rolling reset of the image sensor without having to close the mechanical shutter that is open during live view, the time required for opening and closing the mechanical shutter (that is, required for charging the mechanical shutter). (Including time etc.) is unnecessary, and there is an advantage that the release time lag can be shortened and the moving image stop time during live view can be shortened.

Therefore, in an imaging apparatus that includes a mechanical shutter and can be used in combination with an electronic shutter and a mechanical shutter, for example, when taking a picture while observing only the optical viewfinder, a mechanical shutter (this is used for both the front curtain and the rear curtain). Hereinafter, it will be referred to as “M shutter” as appropriate), and it is effective to use a hybrid shutter when shooting while observing a live view.
JP 2006-101492 A

  By the way, the technique described in Japanese Patent Application Laid-Open No. 2006-101492 uses a shutter for a hybrid shutter because an electronic shutter is used for both the front curtain and the rear curtain when acquiring image data with an accurate curtain speed. The characteristics are set according to the electronic shutter. However, as described above, since the operation of the shutter in the imaging apparatus is considered to be practical, the case of the M shutter and the case of the hybrid shutter, it is adjusted by the technique described in the publication. In the imaging apparatus, an image captured using the M shutter (for example, an image captured while observing the optical viewfinder) and an image captured using the hybrid shutter (for example, an image captured while observing the live view) However, there is a possibility that the image will be in a different exposure state. It is not preferable for the imaging apparatus that the exposure characteristics differ depending on the way of shooting.

  The present invention has been made in view of the above circumstances, and an image captured using an electronic shutter as a front curtain and a mechanical shutter as a rear curtain, and an image captured using a mechanical shutter as both a front curtain and a rear curtain, An imaging device capable of adjusting the running characteristics of the electronic shutter of the front curtain when a mechanical shutter is used as the rear curtain so that the exposure characteristics of the imaging apparatus are matched, and a shutter characteristic calibration method of the imaging apparatus are provided. Yes.

  In order to achieve the above object, an imaging apparatus according to an aspect of the present invention electronically controls exposure start and mechanically controls exposure end in the first shooting mode, and performs exposure in the second shooting mode. An imaging apparatus that mechanically controls the start and end of exposure, and that can calibrate shutter characteristics in a shutter calibration mode, in which an imaging lens and a plurality of pixels are arranged in a two-dimensional manner, An image sensor that photoelectrically converts an optical image formed by a lens, an electronic shutter that electronically controls an exposure time of the image sensor, a mechanical shutter that mechanically controls an exposure time of the image sensor, and the shutter In the calibration mode, when the exposure start is controlled by the electronic shutter and the exposure end is controlled by the mechanical shutter, the first image data is generated. In addition, an exposure control unit that generates second image data by controlling the start and end of exposure using the mechanical shutter, and the first photographing mode so that the first image data matches the second image data. And an electronic shutter characteristic calibration unit that calibrates the characteristics of the electronic shutter.

  According to another aspect of the present invention, there is provided a method for calibrating shutter characteristics of an imaging device, wherein the exposure start is electronically controlled and the exposure end is mechanically controlled in the first shooting mode, and the exposure start is started in the second shooting mode. And a shutter characteristic calibration method for an image pickup apparatus capable of calibrating the shutter characteristics in the shutter calibration mode, wherein the exposure start time of the image sensor is set in the shutter calibration mode. The first image data is generated by controlling the electronic shutter controlled electronically and controlling the exposure end by a mechanical shutter mechanically controlling the exposure time of the image sensor, and the exposure start and exposure end are controlled by the mechanical shutter. Generating the second image data under the control of the shutter, and the first image data is the second image data. Comprises a step of calibrating the characteristics of the electronic shutter in the first imaging mode to match the data, the.

  According to the imaging device and the shutter characteristic calibration method of the imaging device of the present invention, an image captured using the electronic shutter for the front curtain and the mechanical shutter for the rear curtain, and the mechanical shutter for both the front curtain and the rear curtain are captured. It is possible to adjust the running characteristics of the electronic shutter of the front curtain when using the mechanical shutter for the rear curtain so that the exposure characteristics of the image and the captured image are matched.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
1 to 9 show Embodiment 1 of the present invention, and FIG. 1 is a block diagram showing a configuration of an imaging apparatus.

  As shown in FIG. 1, the imaging apparatus includes a lens 1, a diaphragm 2, a mechanical shutter 3 (abbreviated as “shutter 3” in FIG. 1), an imaging element 4, a lens controller 5, a diaphragm. Control unit 6, shutter control unit 7, signal processing unit 8, TG circuit 9, bus 10, built-in memory 11, AE processing unit 12, AF processing unit 13, image processing unit 14, and display A drive unit 15, a display unit 16, a nonvolatile memory 17, a recording medium 18, an input unit 19, a power supply unit 20, and a CPU 21 are provided. Further, this imaging apparatus is provided with an optical viewfinder (not shown).

  The lens 1 is a photographing lens for forming an optical image of a subject on the image sensor 4. The lens 1 may be provided fixed to the imaging apparatus, but may be configured to be detachable via a bayonet mount or the like.

  The diaphragm 2 is for controlling the amount of light passing through by defining the passage range of the light flux reaching the image sensor 4 from the lens 1.

  The mechanical shutter 3 defines the passage time of the light beam reaching the imaging device 4 from the lens 1 and is configured as, for example, a focal plane shutter.

  The image pickup device 4 photoelectrically converts the formed optical image to generate an image signal, and is configured as a CMOS type image pickup device, for example. The image sensor 4 is arranged so that the main scanning direction coincides with the curtain running direction of the mechanical shutter 3, and pixels can be reset in line units along the main scanning direction. That is, the imaging device 4 can control the timing of starting exposure in the electronic shutter (that is, the leading shutter travel characteristic of the electronic shutter) by controlling the timing of sequentially resetting the signal charges in the pixel row. It is configured.

  The lens control unit 5 is a focus position control unit that performs focus adjustment control of the lens 1.

  The aperture control unit 6 performs control for adjusting the aperture value of the aperture 2.

  The shutter controller 7 controls curtain running, shutter charge, etc. of the mechanical shutter 3.

  The signal processing unit 8 performs processing such as correlated double sampling CDS (Correlated Double Sampling) and signal amplification on the image signal output from the image sensor 4, and further performs A / D conversion to output as digital image data. To do.

  The TG circuit 9 generates a timing signal and outputs it to the image sensor 4 and the signal processing unit 8.

  The bus 10 includes a signal processing unit 8, a built-in memory 11, an AE processing unit 12, an AF processing unit 13, an image processing unit 14, a display driving unit 15, a nonvolatile memory 17, a recording medium 18, A CPU 21 is connected to transmit data, control signals, and the like.

  The built-in memory 11 stores the image data output from the signal processing unit 8, and also stores the image data processed by the image processing unit 14, the image data read from the recording medium 18, and the like. ing. Further, this built-in memory is also used as a working memory by the CPU 21.

  The AE processing unit 12 is a photometric unit that calculates an AE evaluation value related to a predetermined area in the image data stored in the built-in memory 11 and outputs the calculation result to the CPU 21. The CPU 21 determines an aperture value, shutter speed, ISO sensitivity, and the like based on the acquired AE evaluation value (that is, the CPU 21 also functions as an exposure time calculation unit), the aperture control unit 6, the shutter control unit 7, The TG circuit 9 is controlled.

  The AF processing unit 13 is a distance measuring unit that calculates an AF evaluation value based on image data stored in the built-in memory 11 and outputs the calculation result to the CPU 21. The CPU 21 controls the lens control unit 5 based on the acquired AF evaluation value.

  The image processing unit 14 performs white balance adjustment, edge processing, and the like on the image data stored in the built-in memory 11, and compresses the processed image data, and is read from the recording medium 18. It also performs processing to decompress the compressed image data. Further, the image processing unit 14 performs processing such as converting image data into display image data, and superimposing character data on the display image data.

  The display drive unit 15 drives the display unit 16 to display based on display image data (for example, a through image, a still image for display after shooting, an image on a menu screen, etc.).

  The display unit 16 is driven by the display driving unit 15 to perform live view display, to display a still image after shooting, or to display a menu screen.

  The nonvolatile memory 17 stores various programs and parameters executed by the CPU 21 in a nonvolatile manner, and further stores setting data and the like by the user in a nonvolatile manner.

  The recording medium 18 is for recording image data obtained by imaging, and is composed of, for example, a removable memory card. Therefore, the recording medium 18 may not have a configuration unique to the imaging apparatus.

  The input unit 19 is displayed on a power switch for turning on / off the power of the imaging device, a mode setting switch for setting an operation mode, a release button for starting still image capturing, and the display unit 16. It includes a cross button, a confirmation button, and the like for selecting and confirming menu items. In this imaging apparatus, it is possible to select a photographing mode for photographing an image and a shutter calibration mode for calibrating shutter characteristics as an operation mode. In the shooting mode, a live view shooting mode (first shooting mode) in which shooting is performed while observing a live view, and an optical viewfinder shooting mode (second shooting mode) in which shooting is performed while observing the optical viewfinder are provided. , Can also be selected.

  The power supply unit 20 includes a rechargeable secondary battery (rechargeable battery) or a primary battery (dry battery or the like), a power supply circuit, and the like. Then, power is supplied from the power supply unit 20 to each circuit in the imaging apparatus.

  The CPU 21 controls the operation of the entire imaging apparatus based on a control program stored in the nonvolatile memory 17. The CPU 21 serves as an exposure control unit, an electronic shutter characteristic calibration unit, an exposure time calculation unit, and a focus position control unit. For example, in the optical viewfinder shooting mode (second shooting mode), the CPU 21 controls the shutter control unit 7 so that the mechanical shutter 3 is used for both the front curtain and the rear curtain (the shutter controlled in this way). As described above, it will be referred to as “M shutter” as appropriate), and in the live view shooting mode (first shooting mode), the TG circuit 9 is controlled to use the electronic shutter for the front curtain and the rear curtain. The shutter control unit 7 is controlled so as to use the mechanical shutter 3 (the shutter controlled in this way is appropriately referred to as “hybrid shutter” as described above).

  Next, FIG. 2 is a flowchart showing processing for calibrating the front curtain electronic shutter of the hybrid shutter. The processing shown in FIG. 2 is started when the user operates the input unit 19 to set the shutter calibration mode on the menu screen of the imaging apparatus.

  When this processing is started, the CPU 21 first determines whether or not the lens 1 is a lens within a specified range suitable for executing calibration of the electronic shutter (step S1). Specifically, it is confirmed whether or not the focal length of the lens 1 is not less than a predetermined lower limit value and not more than a predetermined upper limit value.

  When the focal length of the lens 1 is less than the predetermined lower limit value, the lens 1 is a wide-angle lens. However, the wide-angle lens tends to cause distortion in the peripheral image or decrease in the light amount of the peripheral image. is there. Therefore, the predetermined lower limit value is set in advance as a value to such an extent that such a tendency does not affect the calibration.

  When the focal length of the lens 1 is larger than the predetermined upper limit value, the lens 1 is a telephoto lens, but the telephoto lens tends to have a large camera shake. As will be described later, this calibration compares the image captured by the M shutter with the image captured by the hybrid shutter, and adjusts the traveling characteristics (rolling reset operation timing) of the front shutter electronic shutter of the hybrid shutter. By doing so, the image captured by the hybrid shutter is matched with the image captured by the M shutter. For this reason, the subject imaged by the M shutter and the subject imaged by the hybrid shutter need to be the same, and it is desirable that the influence of camera shake can be ignored. Therefore, the predetermined upper limit value is set in advance as a value to such an extent that such a shake does not affect the calibration.

  Here, the focal length of the lens 1 is checked, but in addition to this, the open aperture value of the lens 1 and other information related to the lens 1 may be checked.

  In this way, when it is determined that the lens 1 of the imaging device is within the predetermined range, the CPU 21 then displays a message for the user on the display unit 16 (step S2). Here, for example, the CPU 21 controls to display a message such as “Please direct the camera to a bright sky during the day while keeping the sun out”. This is due to the following reason.

  In order to detect luminance unevenness in the screen based on the difference in traveling speed between the front curtain and the rear curtain, it is desirable to irradiate the imaging surface of the imaging device 4 with uniform light using a collimator or the like. In the shutter calibration mode executed by operation, it is almost impossible to use such a device. Therefore, a flat and bright subject is desirable so that as uniform light as possible is irradiated on the imaging surface of the image sensor 4 (the reason why it is desirable to be brighter in addition to being flat will be described later). Furthermore, the light irradiated onto the imaging surface is made more uniform and high-frequency edges are eliminated (if there is a high-frequency edge in the calibration image, there is a difference between the two images that are taken consecutively. It is desirable to drive the lens 1 so that the subject is out of focus. It is desirable that as much blur as possible be obtained on the entire screen when out-of-focus is achieved. For this purpose, it is not preferable to have several subjects in a wide distance range from the closest side to the infinity side in the screen, and only a subject at infinity exists in the screen (the lens 1 is close to the screen). If the lens 1 is driven to the side, a large blur can be obtained), or there is only a subject that is only in the immediate vicinity of the lens 1 in the screen (a large blur can be obtained by driving the lens 1 to the infinity side). Is desirable. A very general representative example of subjects that satisfy these conditions, as a typical example, a message is displayed to the user to select the daytime sky without the sun as the subject here. It is.

  Next, the reason why it is desirable that the subject is bright is that the shutter speed is increased (exposure time is shortened) to prevent camera shake and the measurement accuracy is further improved. That is, for example, it is assumed that 0.005 seconds are required for the front curtain to travel and 0.0055 seconds are required for the rear curtain to travel. Then, assuming that the trailing curtain starts to be driven 1/2000 seconds (0.0005 seconds) after the start of the leading curtain, the exposure time of the image sensor 4 on the shutter traveling start side is approximately 0.0005 seconds. On the other hand, the exposure time of the image sensor 4 on the shutter travel end side is approximately 0.001 seconds, which is twice the exposure amount on the shutter travel start side. On the other hand, if the second curtain starts to travel 1 second after the start of the front curtain, the exposure time of the image sensor 4 on the shutter travel start side is approximately 1 second, while the shutter travel end side The exposure time of the image sensor 4 is approximately 1.0005 seconds, and the difference in exposure amount is almost negligible. That is, it can be seen that it is desirable to acquire image data for calibration at the fastest possible shutter speed in order to detect exposure unevenness due to the difference in shutter travel speed between the front curtain and the rear curtain with high accuracy. For this reason, a message is displayed so as to select as bright a subject as possible.

  Then, the CPU 21 causes the AF processing unit 13 to perform distance measurement (step S3), and determines whether or not the subject distance obtained by the distance measurement is infinity (when the subject is empty) (step S4). ).

  If it is determined that the subject distance is infinite, the CPU 21 drives the lens 1 to the closest position via the lens control unit 5 (step S5). As a result, an infinite subject is imaged on the image sensor 4 in a largely blurred state. In addition, when the subject is not “daytime sky without the sun” as in the example described above, a process of shifting the focal length of the lens 1 by a predetermined amount from the focus position of the subject is performed. It is possible to do it.

  Subsequently, the CPU 21 causes the AE processing unit 12 to perform photometry. Based on the photometric value obtained by photometry, the CPU 21 refers to a program diagram created in advance for the shutter calibration mode and stored in the nonvolatile memory 17. Thus, the shutter speed, aperture value, ISO sensitivity, etc. are determined (step S6). Here, the program diagram for the shutter calibration mode shows that the shutter speed is as fast as possible (the reason is as described above), the aperture value is reduced by about two steps from the fully open position (to prevent a reduction in exposure around the screen), and as much as possible. The program diagram is designed to have a lower ISO sensitivity (to prevent noise increase due to sensitization).

  Then, it is determined whether or not each of the determined parameters is within a specified range suitable for executing electronic shutter calibration (step S7).

  When it is determined that at least one of the parameters determined in step S7 is not within the specified range (for example, when the calculated exposure time is longer than a predetermined time), the parameter is used in step S1 described above. If it is determined that the lens 1 is not within the specified range, if it is determined in step S4 that the distance measurement result is not infinity (when the subject is empty), the processing in the shutter calibration mode proceeds. Therefore, the first error process is performed such as displaying an error message to that effect on the display unit 16 functioning as a warning unit (step S8). In the first error processing, it is preferable to display on the display unit 16 a preferable shooting condition for eliminating the error according to the cause of the error. For example, when the lens 1 is a zoom lens and the current focal length is on the telephoto side, a message such as “Return the lens to the standard focal length” may be displayed.

  On the other hand, if it is determined in step S7 that all the parameters are within the specified range, shooting is performed using the M shutter, that is, the mechanical shutter for both the front curtain and the rear curtain (step S9).

  Next, the shading amount Sm of the image data obtained by the M shutter is calculated as described later and stored in the built-in memory 11 (step S10).

  Subsequently, after the shortest possible time after taking the M shutter in step S9 (to prevent camera shake), shooting is performed using a hybrid shutter, that is, an electronic shutter for the front curtain and a mechanical shutter for the rear curtain. It performs (step S11).

  Then, the shading amount Se of the image data obtained by the hybrid shutter is calculated as described later and stored in the built-in memory 11 (step S12).

  Further, the correction amount of the electronic shutter is calculated so that the difference between the shading amount Sm calculated in step S10 and the shading amount Se calculated in step S12 is zero (step S13).

  Then, it is determined whether or not the correction amount obtained by the calculation is within a specified range (step S14).

  Here, when it is determined that the correction amount is not within the specified range, the travel speed of the shutter curtain is greatly deviated from the allowable range, indicating that the state is not suitable for shooting. Second error processing such as displaying an error message to that effect on the display unit 16 is performed (step S15).

  On the other hand, if it is determined in step S14 that the correction amount is within the specified range, the electronic shutter correction amount is stored in the nonvolatile memory 17 (step S16), and the shutter calibration mode processing is terminated. .

  In the processing shown in FIG. 2, the M shutter is used for the first shooting and the hybrid shutter is used for the shooting. However, this order may be reversed. In particular, when performing live view, the time delay due to the M shutter described above occurs, so the reverse order has the advantage that the elapsed time is shorter.

  Next, the calculation of the shading amount in the vertical direction performed in step S10 and step S12 described above will be described with reference to FIGS. Here, FIG. 3 is a diagram showing the distribution of partial areas used to calculate the shading amount in the image data acquired for calibration, and FIG. 4 shows a difference in traveling speed between the front curtain and the rear curtain in the hybrid shutter. It is a timing chart which shows the shift | offset | difference of the exposure amount at the time.

  In the timing chart of FIG. 4, the vertical axis indicates each line position on the image sensor 4, and the lower side corresponds to the front curtain: closed, the rear curtain: open, the upper side corresponds to the front curtain: open, and the rear curtain: closed. It shall be. The hybrid shutter uses the electronic shutter ES1 as the front curtain and the mechanical shutter MS2 as the rear curtain. Reference numeral K1 indicates the front curtain travel line, and reference numerals K2 and K3 indicate the rear curtain travel line. . At this time, if the traveling speed of the front curtain (inclination of the traveling line K1) matches the traveling speed of the rear curtain (inclination of the traveling line K2), the exposure time TA on one end side in the curtain traveling direction and the other The exposure time TB on the end side matches. The adjustment for matching the inclination of the travel line K1 and the inclination of the travel line K2 is performed in the assembly process of the imaging device.

  However, when the user repeats imaging with the imaging device many times, etc., and the curtain speed of the rear curtain mechanical shutter decreases due to aging and wear, the running line is as shown by the symbol K3, for example. Thus, the exposure time on one end side becomes (TA + TC), which does not coincide with the exposure time on the other end side, and uneven exposure occurs. In such a case, since the traveling speed of the mechanical shutter cannot be adjusted at the user level, calibration that eliminates uneven exposure is performed by adjusting the traveling speed of the electronic shutter according to the traveling speed of the mechanical shutter. Do.

  As shown in FIG. 3, when calculating the shading amount in the vertical direction from the image data IMG acquired in step S9 or step S11, the image data IMG is arranged in a line from the upper end side to the lower end side. For example, 16 block areas B1 to B16 are set, and the average luminance value in each block area is calculated. The luminance value to be calculated is not limited to the luminance signal Y. When the image sensor 4 is an image sensor with a primary color Bayer array, for example, the G signal is used as a substitute for the luminance value, and the average of only the G pixels is calculated. The level may be calculated.

  Then, the average luminance values of the block areas B1 to B16 arranged in order are set as the shading amount in the vertical direction. That is, the vertical shading amount Sm obtained in step S10 from the image data acquired in step S9 is more specifically determined by the 16 average luminance values Sm (1) to Sm (16) corresponding to the block regions B1 to B16. Composed. Similarly, the vertical shading amount Se calculated in step S12 from the image data acquired in step S11 is more specifically, the 16 average luminance values Se (1) to Se (16) corresponding to the block regions B1 to B16, respectively. Consists of.

  When x is a block area number, the vertical shading amount Se (x) matches the vertical shading amount Sm (x) (that is, the exposure amount at the time of the hybrid shutter becomes the exposure amount at the time of the M shutter). The shutter speed of the electronic shutter (the electronic shutter is not a mechanically moving shutter curtain, but for convenience, the speed at which the pixels are reset for each line is referred to as the curtain speed) Adjust.

Specifically, the time from when the first curtain passes through an arbitrary line in the block area Bx until the rear curtain passes (that is, the exposure time of this line) is expressed as Tm (step S9). x) Te (x) is set for the hybrid shutter (step S10). If an image with proper exposure is obtained by AE and the luminance change of the subject in the screen is relatively flat, it may be assumed that the exposure time and the pixel value are proportional to any pixel in the screen. (That is, it can be assumed that the exposure time and the pixel value are proportional to each other as long as a portion where the exposure characteristic of the image sensor is approximately linear is used). In this case, the following formula is established.
Tm (x) / Te (x) = Sm (x) / Se (x)
Transforming this formula,
Tm (x) = {Sm (x) / Se (x)} × Te (x)
Therefore, it can be seen that the same exposure characteristic as that of the M shutter can be obtained by multiplying the exposure time Te (x) of the hybrid shutter by the correction coefficient Sm (x) / Se (x).

The difference Δt in exposure time between the M shutter and the hybrid shutter is
Δt = Tm (x) −Te (x)
= [{Sm (x) −Se (x)} / Se (x)] × Te (x)
However, when the shift in the running characteristics of the rear curtain mechanical shutter in the hybrid shutter is not so large, Te (x) can be approximated to the shutter speed (exposure time) t calculated by AE in step S6. Therefore, the difference Δt in exposure time between the M shutter and the hybrid shutter is
Δt≈ [{Sm (x) −Se (x)} / Se (x)] × t
It becomes. Therefore, for each line that is the same as the line constituting the block region Bx, the exposure characteristics substantially similar to those of the M shutter can be obtained by shifting (correcting) the pixel reset timing in the electronic shutter by this exposure time difference Δt. .

  Next, in the live view shooting mode, there will be described an advantage that using the hybrid shutter can shorten the release time lag compared to using the M shutter, with reference to FIGS.

  FIG. 5 is a flowchart showing processing when a still image is shot using the M shutter in the live view shooting mode, FIG. 6 is a timing chart showing a curtain running when the live view is started, and FIG. 7 is a live view. 6 is a timing chart showing a curtain running when shooting a still image using an M shutter during execution.

  When the process shown in FIG. 5 is started, first, it waits for an operation to turn on the live view through the input unit 19 (step S21). At this time, as shown in FIG. 6, the front curtain mechanical shutter MS1 is closed and the rear curtain mechanical shutter MS2 is opened.

  When the live view is turned on, the front shutter mechanical shutter MS1 in the closed state is opened, and the mechanical shutter 3 is opened as shown in FIG. Step S22). Then, a live view operation is executed (step S23).

  During execution of the live view operation, the CPU 21 monitors whether or not an operation for turning off the live view at an appropriate time interval is performed via the input unit 19 (step S24).

  If the operation for turning off the live view has not been performed, the CPU 21 further checks whether or not the release button of the input unit 19 has been pressed (step S25). If it is determined that the release button has not been pressed, the process returns to step S23 to continue the live view operation.

  If it is determined in step S25 that the release button has been pressed, the front curtain mechanical shutter MS1 is temporarily closed as shown in FIG. 7 (step S26).

  Thereafter, the front curtain mechanical shutter MS1 is opened again to start exposure (step S27).

  Then, when the predetermined exposure time has elapsed, the rear curtain mechanical shutter MS2 is closed to complete the exposure (step S28). After completion of the exposure and after reading from the image sensor 4, although not shown, the mechanical shutter is opened by charging the rear curtain mechanical shutter MS2 to the open position, and the process returns to S23. Continue the live view operation.

  If it is determined in step S24 that the operation for turning off the live view has been performed, the moving image capturing by the image pickup device 4 is finished, and the front curtain mechanical shutter MS1 is charged to the closed position, and the live view is turned off. (Step S29), and this process is terminated.

  Next, FIG. 8 is a flowchart showing processing when a still image is shot using a hybrid shutter in the live view shooting mode, and FIG. 9 is a curtain running when shooting a still image using the hybrid shutter during live view execution. It is a timing chart which shows a mode.

  First, the processes in steps S21 to S25 after the process is started are the same as those in FIGS.

  Next, when it is determined in step S25 that the release button has been pressed, the front curtain electronic shutter ES1 travels without performing the closing and opening operations of the front curtain mechanical shutter MS1, as shown in FIG. (In other words, pixel reset for each line is sequentially performed in the same direction as the traveling direction of the front curtain mechanical shutter MS1 (so-called rolling reset)) (step S31).

  Then, when the predetermined exposure time has elapsed, similarly to step S28 described above, the rear curtain mechanical shutter MS2 is closed to complete the exposure. The processing after this exposure is the same as the processing shown in FIG.

  As described above, when a still image is shot in the live view shooting mode, when the hybrid shutter is used, the closing operation and opening operation of the front curtain mechanical shutter MS1 before the still image exposure, which is necessary when the M shutter is used, is performed. Therefore, there is an advantage that the release time lag from when the release button is pressed to when the still image exposure is started can be greatly shortened. In addition, the video stop time during live view can be shortened.

  Note that the number of operations of the mechanical shutter 3 is held in the nonvolatile memory 17 of the imaging device, and the number of operations held exceeds the specified number that may change the curtain running characteristics of the mechanical shutter 3. In such a case, a display that prompts the user to calibrate the electronic shutter (for example, a display such as “I recommend performing the shutter calibration mode”) may be performed on the display unit 16 or the like.

  According to the first embodiment, by adjusting the curtain speed of the front shutter electronic shutter in the hybrid shutter, that is, the pixel rolling reset speed, it is possible to adjust the user level without changing to the manufacturer. It is possible to correct a change in running characteristics of the mechanical shutter.

  Since this calibration can be performed so that the exposure characteristics of the image captured using the hybrid shutter and the image captured using the M shutter match, the image is captured in the live view shooting mode. It is possible to keep the exposure characteristics of the image and the image photographed in the optical viewfinder photographing mode the same.

  In the above description, the image pickup apparatus has been mainly described. However, there are a shutter characteristic calibration method for the image pickup apparatus, a shutter characteristic calibration program for the image pickup apparatus, a recording medium for recording the shutter characteristic calibration program for the image pickup apparatus, and the like. It doesn't matter.

  Further, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, you may delete some components from all the components shown by embodiment. Furthermore, the constituent elements over different embodiments may be appropriately combined. Thus, it goes without saying that various modifications and applications are possible without departing from the spirit of the invention.

1 is a block diagram illustrating a configuration of an imaging apparatus according to Embodiment 1 of the present invention. 7 is a flowchart showing processing for calibrating the front curtain electronic shutter of the hybrid shutter in the first embodiment. FIG. 5 is a diagram showing a distribution of partial areas used for calculation of shading amounts in image data acquired for calibration in the first embodiment. 3 is a timing chart showing a difference in exposure amount when a difference in traveling speed occurs between the front curtain and the rear curtain in the hybrid shutter in the first embodiment. 9 is a flowchart illustrating processing when a still image is shot using an M shutter in the live view shooting mode in the first embodiment. In the said Embodiment 1, the timing chart which shows the mode of curtain driving | running | working when a live view is started. In the said Embodiment 1, the timing chart which shows the mode of curtain driving | running | working when a still image is image | photographed using M shutter at the time of live view execution. 9 is a flowchart illustrating processing when a still image is shot using a hybrid shutter in the live view shooting mode in the first embodiment. In the said Embodiment 1, the timing chart which shows the mode of curtain driving | running | working when a still image is image | photographed using a hybrid shutter at the time of live view execution.

Explanation of symbols

1 ... Lens (photographing lens)
2 ... Aperture 3 ... Mechanical shutter 4 ... Image sensor (electronic shutter)
5. Lens control unit (focus position control unit)
6 ... Aperture control unit 7 ... Shutter control unit 8 ... Signal processing unit 9 ... TG circuit 10 ... Bus 11 ... Built-in memory 12 ... AE processing unit (photometry unit)
13. AF processing unit (ranging unit)
DESCRIPTION OF SYMBOLS 14 ... Image processing part 15 ... Display drive part 16 ... Display part (warning part)
DESCRIPTION OF SYMBOLS 17 ... Nonvolatile memory 18 ... Recording medium 19 ... Input part 20 ... Power supply part 21 ... CPU (exposure control part, electronic shutter characteristic calibration part, exposure time calculating part, focus position control part)

Claims (5)

In the first photographing mode, the exposure start is electronically controlled and the exposure end is mechanically controlled. In the second photographing mode, the exposure start and exposure end are mechanically controlled. In the shutter calibration mode, the shutter is controlled. An imaging apparatus capable of calibrating characteristics,
A taking lens,
An image sensor in which a plurality of pixels are two-dimensionally arranged and photoelectrically convert an optical image formed by the photographing lens;
An electronic shutter for electronically controlling the exposure time of the image sensor;
A mechanical shutter for mechanically controlling the exposure time of the imaging device;
In the shutter calibration mode, the exposure start is controlled by the electronic shutter and the exposure end is controlled by the mechanical shutter to generate the first image data, and the exposure start and exposure end are controlled by the mechanical shutter. An exposure control unit for generating image data;
An electronic shutter characteristic calibrating unit that calibrates the characteristics of the electronic shutter in the first photographing mode so that the first image data matches the second image data;
An imaging apparatus comprising: The mechanical shutter is a focal plane shutter,
The electronic shutter is configured to start exposure by sequentially resetting signal charges of the pixel columns of the image sensor along the traveling direction of the focal plane shutter.
The electronic shutter characteristic calibrating unit corrects the timing of resetting the signal charge of the pixel column based on the difference data between the first image data and the second image data, so that the first shutter mode correction unit The imaging apparatus according to claim 1, wherein the characteristic of the electronic shutter is calibrated. A metering unit that measures the brightness of the subject;
An exposure time calculation unit for calculating an exposure time based on a photometric result by the photometry unit;
A warning unit that gives a predetermined warning when the exposure time calculated by the exposure time calculation unit is longer than a predetermined time in the shutter calibration mode;
The imaging apparatus according to claim 1, further comprising: A distance measuring unit that calculates the distance to the subject;
In the shutter calibration mode, the focus position control for controlling the focus position of the photographing lens so that the subject position where the photographing lens is focused is shifted by a predetermined amount with respect to the subject position measured by the distance measuring unit. And
The imaging apparatus according to claim 1, further comprising: In the first photographing mode, the exposure start is electronically controlled and the exposure end is mechanically controlled. In the second photographing mode, the exposure start and exposure end are mechanically controlled. In the shutter calibration mode, the shutter is controlled. A method for calibrating shutter characteristics of an imaging apparatus capable of calibrating characteristics,
In the shutter calibration mode,
The start of exposure is controlled by an electronic shutter that electronically controls the exposure time of the image sensor, and the end of exposure is controlled by a mechanical shutter that mechanically controls the exposure time of the image sensor and generates first image data. A step of controlling the start and end of exposure by the mechanical shutter to generate second image data;
Calibrating characteristics of the electronic shutter in the first photographing mode so that the first image data matches the second image data;
A shutter characteristic calibration method for an imaging apparatus, comprising:

Images