JP2010081547A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform imaging while taking into account balance between image quality and a field depth. <P>SOLUTION: An imaging apparatus includes: an imaging device 20 for capturing a subject image through a photographing lens 100; a range finding means 11 for measuring a distance to a subject; a focal distance detecting means 14 for detecting a focal distance of the photographing lens; a luminance detecting device 15 for detecting subject luminance; and at least two or more program diagrams for determining a shutter speed, a stop value and exposure sensitivity for obtaining proper exposure using the subject luminance wherein the program diagrams are switched in accordance with subject distance and lens focal distance information. Furthermore, in the case that the shutter speed is higher than a predetermined value, the program diagram that changes the exposure sensitivity to a lower sensitivity side is adopted and in the second program diagram, a stop is set to an open side rather than the first program diagram. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic still camera that captures a subject image with an imaging device.

  In an imaging apparatus provided with program AE means, the shutter speed, aperture, and exposure sensitivity are determined according to the size of the subject brightness. In the APEX display, when the subject brightness is Bv, the exposure sensitivity is Sv, the shutter speed is Tv, and the aperture is Av, the following equation is established.

Sv + Bv = Ev = Tv + Av
FIG. 1 is an example of a program diagram with a focal length of 30 mm and F4.0. First, the shutter speed Tvh at which camera shake is expected during shooting is determined using the focal length f as follows.

Tvh = 1 / f
The program diagram is such that the shutter speed Tv and the aperture Av are increased at a ratio of 1: 1 based on the obtained Tvh and the minimum aperture Avmin. In the program diagram of FIG. 1, the exposure sensitivity is further changed according to the magnitude of the shutter speed Tv. The exposure sensitivity is ISO 100 when Tv ≧ Tvs, ISO 200 when 1 / f ≦ Tv <Tvs, and ISO 800 when Tv <1 / f.
JP 2004-191853 A JP 2007-133313 A

  In general, the image quality of a captured image when the exposure sensitivity is high is worse than when the exposure sensitivity is low. In the program diagram of FIG. 1, when the subject brightness is relatively high (Bv12 or higher), shooting is performed with low exposure sensitivity that can be expected to provide high image quality. However, when the subject brightness is smaller than that, shooting is performed with high exposure sensitivity, so that the image quality is deteriorated as compared with shooting with low exposure sensitivity.

  SUMMARY OF THE INVENTION In view of the above-described problems, an object of the present invention is to provide an imaging apparatus that can increase the number of photographing opportunities with exposure sensitivity that can be expected to provide high image quality.

  According to a first aspect of the present invention, there is provided an image pickup device for picking up a subject image through a photographing lens, a distance measuring means for measuring a distance of the subject, and a focal point of the photographing lens. A focal length detecting means for detecting a distance; a luminance detecting device for detecting subject luminance; a shutter speed of the imaging device for obtaining appropriate exposure using the subject luminance; an aperture value of the imaging device; and Having at least two program diagrams for determining exposure sensitivity, and switching the program diagram based on the subject distance measured by the distance measuring unit and the lens focal length information detected by the focal length detecting unit. The imaging device is characterized.

  A specific configuration for realizing the object of the invention according to the present application is, as described in claim 2, in the imaging apparatus according to claim 1, wherein the program diagram shows that the shutter speed is larger than a predetermined value. Is a program diagram for changing the exposure sensitivity to the low sensitivity side, and the second program diagram has a program diagram characterized in that the aperture is set closer to the open side than the first program diagram. In the device.

  According to the configuration of the first aspect, although the depth of field changes depending on the focal length of the photographing lens and the subject distance, an optimal program diagram can be selected depending on the size of the depth of field.

  According to the configuration of claim 2, when the shutter speed is higher than a predetermined value, the second program diagram is the first program when the exposure sensitivity is changed to the low sensitivity side. By setting the aperture to the open side from the diagram, it is possible to provide a program diagram that takes into account the balance between image quality and depth of field.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Hereinafter, the electronic still camera according to the first embodiment of the present invention will be described in detail with reference to FIG.

  FIG. 5 is a block diagram of the electronic still camera according to the first embodiment.

  Reference numeral 100 denotes a lens unit on which an interchangeable photographic lens is mounted. Reference numeral 200 denotes the entire imaging apparatus. The lens 5 is usually composed of a plurality of lenses, but here, only a single lens is shown for simplicity. Reference numeral 6 denotes a communication terminal for the lens to communicate with the camera side, and reference numeral 10 denotes a communication terminal for the camera to communicate with the lens side. The lens unit 100 communicates with the microcomputer 39 via the communication terminals 6, 10, controls the aperture 1 via the aperture drive circuit 2 by the internal lens system control circuit 4, and passes through the AF drive circuit 3. The focus is adjusted by displacing the position of the lens 5. Further, the lens system control circuit 4 can notify the microcomputer 39 of lens information such as a focal length, a focus position, and an aperture setting possible range via the communication terminals 6 and 10.

  Reference numeral 15 denotes an AE sensor that measures the luminance of the subject that has passed through the lens unit 100.

  Reference numeral 11 denotes an AF sensor that outputs defocus amount information to the microcomputer 39 and controls the lens unit 100 based on the defocus amount information.

  A quick return mirror 12 is instructed by the microcomputer 39 at the time of exposure, and is raised and lowered by an actuator (not shown).

  Reference numeral 13 denotes a focusing screen. The photographer can check the focus and composition of the optical image of the subject obtained through the lens unit 100 by observing the focusing screen through the pentaprism 14 and the finder 16.

  Reference numeral 17 denotes a focal plane shutter, which can freely control the exposure time of the image sensor 20 under the control of the microcomputer 39.

  An optical filter 18 is generally composed of a low-pass filter or the like, and cuts a high-frequency component of light entering from the focal plane shutter 17 and guides the subject image to the image sensor 20.

  As the image pickup device 20, an image pickup device such as a CCD or a CMOS is generally used, and a subject image formed on the image pickup device 20 through the lens unit 100 is photoelectrically converted and captured as an electric signal.

  Reference numeral 21 denotes an A / D conversion circuit that converts an analog signal converted into an electric signal by the image sensor 20 into a digital signal.

  An image processing circuit 22 performs filter processing, color conversion processing, and gamma / knee processing on the image data converted into a digital signal by the A / D conversion circuit 21 and outputs the result to the memory controller 26. The image processing circuit also includes a D / A conversion circuit, which converts the image data converted into a digital signal by the A / D conversion circuit 21 and the image data input by the memory controller 26 into an analog signal. It is also possible to output to the liquid crystal display unit 24 via the liquid crystal driving circuit 23. Image processing and display processing by these image processing circuits 22 are switched by the microcomputer 39. The microcomputer 39 performs white balance adjustment based on the color balance information of the captured image.

  The liquid crystal display unit 24 displays information such as the set shutter speed, aperture, and ISO sensitivity according to instructions from the microcomputer 39 before photographing.

  The memory controller 26 stores unprocessed image data input from the image processing circuit 22 in the buffer memory 25, stores image processed image data in the memory 27, or conversely, the buffer memory 25 and the memory 27. The image data is taken in and output to the image processing circuit 22. In addition, the memory controller 26 is connected to an external memory 28 such as USB (Universal Serial Bus), IEEE (Institut of Electrical and Electronics Engineers), or HDMI (High-Definition Multimedia Interface) 27 via an external memory image. It is also possible to store the image data or to output the image data stored in the memory 27 to the outside via the external interface 28. The memory 27 may be detachable. In FIG. 1, the memory 27 is illustrated as a detachable memory. Specifically, a small flash memory card can be used.

  Reference numeral 31 denotes a shutter control circuit, through which the microcomputer 39 controls the focal plane shutter 17.

  Reference numeral 34 denotes a power supply control circuit. Power is supplied from the AC power supply unit 29 or the secondary battery unit 30 and is turned on and off in response to an instruction from the microcomputer. The microcomputer 39 is also notified of the current power supply type information detected by the power supply type detection circuit 32 and the current power supply type information.

  Reference numeral 35 denotes an attitude detection circuit of the imaging apparatus, which notifies the microcomputer 39 of current attitude state information of the imaging apparatus.

  Reference numeral 36 denotes a circuit for detecting the position and size of dust attached to the optical filter 18, and the position / size information of the dust output by this circuit is input to the microcomputer 39.

  An optical filter vibration control circuit 37 is a circuit that vibrates the piezoelectric element 19 connected to the optical filter 18. It vibrates according to the instruction of the microcomputer 39 so that the piezoelectric element is vibrated at predetermined values for the vibration amplitude, vibration time, and vibration axial direction.

  The operation member 38 transmits the state of the operation member to the microcomputer 39, and the microcomputer 39 controls each part according to the change in the state of the operation member. The operation members 38 are connected to switches (not shown) such as a shutter speed setting button, an aperture setting button, an exposure sensitivity setting button, a release start button, and a shooting mode setting button, and the switch state is detected.

  Next, the photographing operation of the camera will be described using the flowchart of FIG. First, processing is started in the first step S200. Next, in step S201, AF control for focusing on the subject position is performed. In the AF control, focusing is performed by displacing the position of the lens 5 via the AF driving circuit 3 of the lens unit 100 based on information from the AF sensor 11. The subject distance can be obtained by detecting the position of the lens 5 after focusing. As a focusing method, a known phase difference AF method or contrast AF method is used. In step S202, AE control is performed to determine the shutter speed, aperture, and exposure sensitivity. In the APEX display, when the subject brightness is Bv, the exposure sensitivity is Sv, the shutter speed is Tv, and the aperture is Av, the following equation is established.

Sv + Bv = Ev = Tv + Av
Details of the method for determining the shutter speed, aperture, and exposure sensitivity will be described later. Next, in step S203, it is determined whether or not the release start button has been pressed. If the release start button has been pressed, the process proceeds to step S204 to perform shooting using the shutter speed, aperture, and exposure sensitivity determined in step S202. If not, the process returns to step S201. In step S204, the diaphragm 1 is driven to a predetermined diaphragm via the diaphragm driving circuit 2, the quick return mirror 12 is brought into an up state, and the exposure sensitivity of the image sensor 20 is set to a predetermined exposure sensitivity. In step S205, the focal plane shutter 17 is driven at a predetermined shutter speed via the shutter control circuit 31, and the image sensor 20 is exposed. After the exposure is completed, image data is transferred from the image sensor 20 to the buffer memory 25 via the A / D conversion circuit 21, the image processing circuit 22, and the memory controller 26 in step S206. The memory controller 26 further performs control to store the image data in the buffer memory 25 in the memory 27 and control to transfer the image data to the outside via the interface 28. Thereby, the photographing operation is finished (S207).

  Next, AE control, which is a feature of the present invention, will be described with reference to FIG. FIG. 1 illustrates a method for determining shutter speed, aperture, and exposure sensitivity, and is an operation included in step S202 of FIG.

  First, the setting value set in the imaging device in step S101 is acquired. As setting values, a photometry mode such as evaluation photometry, spot photometry, and average photometry, a shooting mode such as a high image quality mode, and a subject depth priority mode are acquired. In step S102, the AE sensor 15 is driven to obtain a photometric value. In the AE sensor, photometric elements are arranged in a lattice pattern, and the luminance that enters each area of each photometric element can be acquired as a photometric value. In step S103, AF information such as a distance measuring point position, subject distance, lens focal length, and aperture setting range is acquired. The subject distance is acquired from the AF control result performed in step S201 in FIG. In step S104, the representative photometric value is calculated using information such as the photometric mode and the distance measuring point position, and this is set as the subject luminance Bv.

  In step S105, it is determined whether the shooting mode is the high image quality mode or the subject depth priority mode. If the high image quality mode is selected, the process proceeds to step S108; otherwise, the process proceeds to step S106.

  In step S106, depth determination is performed. Since the depth of field increases as the subject distance increases and the lens focal length decreases, for example, the subject distance R [mm] and the lens focal length f [mm] detected in step S201 in FIG. The determination is made as follows.

(R ^ 2) / (f ^ 2)> 6400 ... [Formula 1]
If Equation 1 is true, the process proceeds to step S108, and if it is false, the process proceeds to step S107. In the present embodiment, the first program diagram and the second program diagram are selected by Formula 1, but another determination formula considering depth of field may be used.

  In step S107, a first program diagram as shown in FIG. 3 is prepared and is selected. The shutter speed Tvh at which camera shake is expected during shooting is determined using the focal length f as follows.

Tvh = 1 / f
The first program diagram is a program diagram in which the shutter speed Tv and the aperture Av are increased at a ratio of 1: 1 based on the obtained Tvh and the minimum aperture Avmin. In the first program diagram, the exposure sensitivity is further changed according to the shutter speed Tv. The exposure sensitivity is ISO 100 when Tv ≧ Tvs, ISO 200 when 1 / f ≦ Tv <Tvs, and ISO 800 when Tv <1 / f. Here, Tvs is a shutter speed at which subject blurring is relatively reduced when a subject moving at a certain speed is photographed, and Tvs = 1/500 in FIG.

  By using the program diagram as described above, when the subject brightness is sufficiently bright and shooting at a high shutter speed is possible, it is possible to use ISO 100, which is the exposure sensitivity with which high-quality shooting can be expected. When the subject brightness is low, the exposure sensitivity is set to ISO 800, so that the shutter speed can be increased and camera shake can be reduced. When the subject brightness is medium, the exposure sensitivity is set to ISO 200 in consideration of the balance between subject blur and image quality.

  In step S108, a second program diagram as shown in FIG. 4 is prepared and is selected. The shutter speed Tvh at which camera shake is expected during shooting is determined using the focal length f as follows.

Tvh = 1 / f
The second program diagram is based on the obtained Tvh and the minimum aperture Avmin, and increases the shutter speed Tv and aperture Av at a ratio of 2: 1 in the interval Tv <Tvs, and the interval Tv ≧ Tvs is 1: 1. The program diagram will increase as a percentage. In the second program diagram, the exposure sensitivity is further changed according to the magnitude of the shutter speed Tv. The exposure sensitivity is ISO 100 when Tv ≧ Tvs, ISO 200 when 1 / f ≦ Tv <Tvs, and ISO 800 when Tv <1 / f. Here, Tvs is a shutter speed at which subject blur is relatively reduced when a subject moving at a certain speed is photographed, and Tvs = 1/500 in FIG.

  By using the program diagram as described above, when the subject brightness is sufficiently bright and shooting at a high shutter speed is possible, it is possible to use ISO 100, which is the exposure sensitivity with which high-quality shooting can be expected. When the subject brightness is low, the exposure sensitivity is set to ISO 800, so that the shutter speed can be increased and camera shake can be reduced. When the subject brightness is medium, the exposure sensitivity is set to ISO 200 in consideration of the balance between subject blur and image quality.

  Further, in the interval of Tv <Tvs, the shutter speed Tv and the aperture Av are increased by a ratio of 2: 1, so that even with a subject brightness lower than that of the first program diagram, shooting is performed with ISO 100, and image quality is suppressed while suppressing subject blurring. You can expect to shoot in

  In step S109, the shutter speed, aperture, and exposure sensitivity are calculated using the selected program diagram, AE control is terminated (S110), and the process proceeds to step S203 in FIG.

It is a flowchart which shows operation | movement of this invention. It is a flowchart which shows operation | movement of an imaging device. It is a 1st program diagram concerning one embodiment of the present invention. It is a 2nd program diagram concerning one embodiment of the present invention. It is a block diagram which shows the structure of the camera which concerns on one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diaphragm 2 Aperture drive circuit 3 AF drive circuit 5 Lens 11 AF sensor 15 AE sensor 17 Focal plane shutter 20 Imaging element 31 Shutter control circuit 39 Microcomputer 100 Lens unit 200 Imaging device

Claims (2)

An image pickup device (20) for picking up a subject image through the taking lens (5);
Ranging means (11) for measuring the distance of the subject;
A focal length detecting means (4) for detecting a focal length of the photographing lens;
A luminance detection device (15) for detecting subject luminance;
Having at least two or more program diagrams for determining the shutter speed of the imaging device for obtaining appropriate exposure using the subject brightness, the aperture value of the imaging device, and the exposure sensitivity of the imaging device;
An image pickup apparatus, wherein a program diagram is switched based on subject distance measured by the distance measuring means and lens focal length information detected by the focal distance detecting means. The imaging apparatus according to claim 1, wherein the program diagram is a program diagram for changing the exposure sensitivity to a low sensitivity side when the shutter speed is larger than a predetermined value.
2. The imaging apparatus according to claim 1, wherein the second program diagram has a program diagram for setting an aperture closer to the open side than the first program diagram.

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