JP2013061545A - Photographing device and exposure control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photographing device capable of performing proper exposure control when performing autofocusing and to provide an exposure control method.SOLUTION: A photographing device (100) includes a photometric part (16) measuring a first luminance of an object, an auxiliary light emitting part (30) emitting auxiliary light to the object, when the first luminance is not enough to perform autofocusing, and a control part (10) performing exposure control for performing autofocusing. The photometric part (16) measures a second luminance of the object after being irradiated with the auxiliary light and the control part (10) sets a value obtained by adding a correction amount corresponding to the kind of the auxiliary light to the second luminance as a third luminance and performs exposure control for autofocusing on the basis of the third luminance.

Description

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

  Some photographing apparatuses such as cameras emit AF (autofocus) auxiliary light when focusing on a dark subject (see, for example, Patent Document 1).

JP 2001-051185 A

  However, the AF auxiliary light is light having a wavelength different from ambient light such as sunlight. When AF auxiliary light having such a wavelength is irradiated, the balance between the actual subject and RGB (red, green, blue) is different. In that case, if exposure control is performed based on a subject irradiated with AF auxiliary light, the exposure control may not match the actual subject.

  An object of the present invention is to provide a photographing apparatus and an exposure control method capable of appropriate exposure control during autofocus.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

According to the first aspect of the present invention, a metering unit (16) that measures the first luminance of the subject, and auxiliary light to the subject when the first luminance is insufficient for autofocusing. An auxiliary light emitting unit (30) for emitting light, and a control unit (10) for performing exposure control for performing the autofocus, wherein the photometric unit (16) is configured to emit the auxiliary light after being irradiated with the auxiliary light. The second luminance of the subject is measured, and the control unit (10) sets the third luminance to a value obtained by adding a correction amount according to the type of the auxiliary light to the second luminance, and based on the third luminance. The camera (100) is characterized by performing exposure control for autofocus.
A second aspect of the present invention is the photographing apparatus (100) according to the first aspect, wherein the type of the auxiliary light varies depending on the color temperature.
According to a third aspect of the present invention, the first luminance of the subject is measured, and when the first luminance is insufficient to perform autofocus, auxiliary light is emitted to the subject, and the auxiliary light is emitted. The second luminance of the subject after irradiation is measured, a value obtained by adding a correction amount according to the wavelength of the auxiliary light to the second luminance is set as the third luminance, and based on the third luminance An exposure control method for autofocus, characterized in that exposure control for autofocus is performed.
Note that the configuration described with reference numerals may be modified as appropriate, and at least a part of the configuration may be replaced with another component.

  According to the present invention, it is possible to provide a photographing apparatus and an exposure control method capable of appropriate exposure control during autofocus.

It is a figure which shows the structure of the camera of embodiment. It is a functional block diagram of the camera of the embodiment. It is a flowchart of exposure control at the time of AF.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram illustrating a configuration of a camera 100 according to the present embodiment.
The camera 100 includes a camera body 1 and a lens unit 2. Here, the lens unit 2 is attached to the camera body 1 in a replaceable manner. The lens unit 2 includes a photographing lens 3, a motor 4 that drives the photographing lens 3, and an in-lens memory 18 that records information on the lens unit.

  The camera body 1 includes a main mirror 5, a sub mirror 6, a focal plane shutter 8, a first image sensor 9 that photoelectrically converts a subject image, a finder optical system 20, and a second image sensor 16 that photoelectrically converts the subject image. A focus detection unit 7, a control unit 10, a camera shake sensor 17 (for example, an angular velocity sensor), a display unit 19, and an AF auxiliary light generation unit 30.

  The main mirror 5, the sub mirror 6, the focal plane shutter 8, and the first image sensor 9 are arranged along the optical axis of the photographing lens 3, the finder optical system 20 is in the upper region of the main mirror 5, and the focus detection unit 7 is the sub mirror. 6 is arranged in the lower region.

Here, when the photographer observes the object scene through the finder optical system 20, that is, other than still image shooting and live view, the main mirror 5 has a shooting optical path from the shooting lens 3 to the first image sensor 9. The light beams that intersect and pass through the photographing lens 3 are reflected upward and guided to the finder optical system 20 (solid line position).
On the other hand, at the time of live view and still image shooting, the main mirror 5 is flipped upward, and the light beam that has passed through the shooting lens 3 is guided to the focal plane shutter 8 and the first image sensor 9, and the image of the first image sensor 9 is displayed. Based on the signal, photographic image data of the subject can be generated (position of dotted line).

  Further, the central portion of the main mirror 5 is a half mirror that transmits light, and a part of the light beam that has transmitted through the main mirror 5 during non-shooting is reflected downward by the sub mirror 6 and guided to the focus detection unit 7. It is like that.

  The finder optical system 20 includes a diffusing screen 11, a condenser lens 12, a pentaprism 13, an eyepiece lens 14, and a re-imaging lens 15.

  The diffusing screen 11 is disposed above the main mirror 5 and once forms an image of the light beam reflected by the main mirror 5 at the position of the solid line. The light beam formed on the diffusion screen 11 passes through the condenser lens 12, the pentaprism 13, and the eyepiece lens 14 and reaches the eyes of the photographer. A part of the light beam diffused by the diffusing screen 11 passes through the condenser lens 12, the pentaprism 13, and the re-imaging lens 15 and reaches the second imaging sensor 16.

  The AF auxiliary light generation unit 30 is for irradiating a light subject with auxiliary light when the subject luminance is low, and capturing the reflected light with an imaging unit to improve AF (autofocus) accuracy. In the present embodiment, the AF auxiliary light generation unit 30 generates, for example, red light (for example, infrared rays).

  FIG. 2 is a functional block diagram of the camera 100 of the embodiment. As shown in FIG. 2, the camera 100 includes a timing generator 20, a signal processing unit 21, an A / D conversion unit 22, a buffer memory 23, a bus 24, a card interface 25, and a compression / decompression unit 26 in addition to the configuration of FIG. Each part of the image display unit 27 is provided. The timing generator 20 supplies output pulses to the first image sensor 9. Further, the image data generated by the first imaging sensor 9 is temporarily stored in the buffer memory 23 via the signal processing unit 21 (including a gain adjustment unit corresponding to the imaging sensitivity) and the A / D conversion unit 22. . The buffer memory 23 is connected to the bus 24. The bus 24 is connected to the card interface 25, the control unit 10, the compression / decompression unit 26, and the image display unit 27 described in FIG. The card interface 25 is connected to a removable memory card 28 and records image data on the memory card 28.

  The control unit 10 is connected to a switch group 29 (including a release button (not shown)) of the camera 100, a timing generator 20, and the second imaging sensor 16. Further, the image display unit 27 displays an image or the like on the display unit 19 provided on the back surface of the camera 100.

Next, the operation of the camera 100 of this embodiment will be described. FIG. 3 is a flowchart showing the operation of the control unit 10 in the AF exposure control.
First, when the switch of the camera 100 is turned on, the main mirror 5 and the sub mirror 6 are reflected by the main mirror 5 at the position of the solid line in FIG. Then, the light is guided to the second imaging sensor 16 through the recombination lens 15.
The subject light is reflected by the main mirror 5, passes through the diffusing screen 11, the condenser lens 12, and the pentaprism 13, and then the light guided to the eyepiece 14 can be observed in the viewfinder.

Next, FIG. 3 is a flowchart of exposure control during AF. When a release button (not shown) is pressed halfway (step S01), the control unit 10 determines based on a signal from the second image sensor 16 whether the subject has sufficient luminance for performing AF (step S01). Step S02).
If the subject is sufficiently exposed (step S02, YES), the process proceeds to step S07.

When the control unit 10 determines that the brightness of the subject is insufficient for performing AF, for example, when a human subject is backlit and dark (step S02, NO), the control light generation unit 30 outputs the AF auxiliary light. Is caused to emit light (step S03).
The subject is irradiated with AF auxiliary light. At this time, depending on the light source wavelength of the AF auxiliary light, the color of the subject is different from the actual color under ambient light. For example, when the AF auxiliary light is red light, the light incident on the lens unit 2 from the subject is reddish light.
The incident light is reflected by the main mirror 5 and measured by the second image sensor 16 (step S16).

  In the control unit 10, the luminance Y 1 of the subject is calculated from the photometric information measured by the second image sensor 16. However, when AF auxiliary light is emitted, the actual object and color balance differ depending on the light source wave of the AF auxiliary light as described above. Therefore, when exposure control is performed based on Y1, there may be cases where the brightness is not appropriate for AF. Therefore, it is necessary to correct the luminance Y1 according to the type of AF auxiliary light.

Here, the luminance Y is expressed by the following equation, for example.
Y = 0.3 * R + 0.6 * G + 0.1 * B (Formula 1)
R, G, and B are intensities of red, green, and blue, respectively.
In the calculation based on this formula, the coefficient of R (red) is smaller than that of G (green). Therefore, when R is dominant, the luminance Y is lower. When exposure control is performed based on this luminance, there is a possibility that the exposure will be brighter than the proper exposure.
For this reason, Y1 is corrected according to the color of the AF auxiliary light, and the corrected luminance Y2 is obtained. This correction amount varies depending on the color balance and intensity of the auxiliary light, but is measured and obtained in advance and stored in the memory.

Next, based on the corrected luminance Y2, the control unit 10 performs exposure control for AF (step S06).
Next, an image with an appropriate exposure value for AF is incident from the lens unit 2, is reflected by the sub-mirror 6 through the main mirror 5, and a focus state is detected by the focus detection unit 7. The control unit 10 drives the lens 3 (focusing lens) according to the in-focus state (step S08), detects that the release button is fully pressed (step S09), and performs photographing (step S10).

  As described above, according to the present embodiment, since the exposure control for AF is performed with the luminance Y2 corrected according to the color of the AF auxiliary light, appropriate exposure control can be performed regardless of the type of the AF auxiliary light. A system with good AF can be performed.

(Deformation)
The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
In the present embodiment, the lens detachable camera has been described. However, the present invention is not limited to this, and a so-called compact camera in which the lens cannot be detached may be used. Further, in the embodiment, the state in which the lens of the lens detachable camera is mirrored has been described, but it may be a case where the through image is observed with the mirror up.
In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  9: first image sensor, 16: second image sensor, 30: auxiliary light generator, 100: camera

Claims (3)

A photometric unit for measuring the first luminance of the subject;
An auxiliary light emitter that emits auxiliary light to the subject when the first luminance is insufficient to perform autofocus;
A control unit for performing exposure control for performing the autofocus,
The photometry unit measures a second luminance of the subject after the auxiliary light is irradiated;
The control unit sets a value obtained by adding a correction amount according to the type of the auxiliary light to the second luminance as the third luminance, and performs exposure control for autofocus based on the third luminance. An imaging device as a feature. The imaging device according to claim 1,
A photographing apparatus, wherein the type of the auxiliary light varies depending on a color temperature. Measure the first brightness of the subject,
If the first luminance is insufficient to perform autofocus, an auxiliary light is emitted to the subject,
Measuring a second luminance of the subject after the auxiliary light is irradiated;
A value obtained by adding a correction amount corresponding to the color type of the auxiliary light to the second luminance is set as the third luminance, and exposure control for autofocus is performed based on the third luminance. , Exposure control method for autofocus.

Images