JP4800827B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to a photographing apparatus that includes an image sensor and generates an image signal by forming a subject image on the image sensor.

  Conventionally, a technique called a zoom flash has been proposed in which the flash irradiation field is changed in accordance with the movement of the zoom lens barrel (see Patent Document 1). In the technique of Patent Document 1, the zoom lens barrel and the flash unit are connected to the connecting member, and the movement of the zoom lens barrel is transmitted to the flash unit by the connecting member, so that the flash light is automatically emitted at the irradiation angle corresponding to the zoom magnification. Is irradiated. However, when manufacturing a zoom flash, if you try to connect the zoom lens barrel and the flash unit with a connecting member, the size of the imaging device will inevitably increase, so recently the imaging optical system and zoom flash are configured using liquid lenses and liquid crystal lenses. In addition, techniques for electrically adjusting the focal length and adjusting the irradiation angle of the photographing auxiliary light have been proposed (see Patent Documents 2 and 3).

  By the way, a xenon tube has been conventionally used as a light emission source of such a flash, but recently there has been a movement to use an LED instead of the xenon tube. When this LED is used as a flash light source, the LED can also be used as a light source for auxiliary light for focus detection (hereinafter referred to as AF auxiliary light).

  When the AF auxiliary light is emitted from the LED toward the subject, it is assumed that the subject exists at a predetermined position within the angle of view, and the AF auxiliary light is emitted in a spot toward the center. When spot irradiation is performed in this way, the AF auxiliary light can reach a relatively long distance.

However, when the AF auxiliary light is spot-irradiated as described above, when a plurality of people are standing side by side at a relatively close distance, the AF auxiliary light passes between the plurality of people. It may pass through and not hit the subject. Thus, if the AF assist light does not hit the subject, the subject distance cannot be measured accurately.
JP-A-8-240843 JP 2005-303843 A JP 2005-345520 A

  In view of the above circumstances, an object of the present invention is to provide a photographing apparatus including an auxiliary light emitting unit capable of increasing a hit rate of AF auxiliary light to a main subject.

An imaging device of the present invention that achieves the above object includes an imaging device, and forms an object image on the imaging device to generate an image signal.
A focus detection unit that detects the in-focus position by detecting the contrast of the image signal while moving the focus;
The focus detection unit includes an auxiliary light emitting unit that emits auxiliary light toward the subject while detecting the contrast of the image signal while moving the focus.
The auxiliary light emitting unit includes an irradiation angle changing unit that changes the irradiation angle of the auxiliary light in synchronization with the movement of the focus while the focus detection unit detects the contrast of the image signal while moving the focus. It is characterized by.

  According to the photographing apparatus of the present invention, while the focus detection unit detects the contrast of the image signal while moving the focus, the irradiation angle of the AF auxiliary light is changed in synchronization with the movement of the focus by the irradiation angle changing unit. Is done. That is, while the focus is detected, the irradiation angle of the AF auxiliary light can be relatively widened or conversely narrowed.

  Then, for example, the auxiliary light can be irradiated over a wide region by widening the irradiation angle of the AF auxiliary light by the irradiation angle changing means when the same focus position is reached.

  If a plurality of people are standing side by side at a predetermined focus position, the AF auxiliary light may pass through the person. However, the irradiation angle changing means can change the irradiation angle of the AF auxiliary light. If it can be spread, the hit rate of the auxiliary light can be increased by irradiating the AF auxiliary light over the entire region where the plurality of persons are present. Further, by narrowing the irradiation angle of the AF auxiliary light by the irradiation angle changing means, the AF auxiliary light can reach a far distance as before. Note that the liquid lens and the liquid crystal lens described above are applied to the irradiation angle changing means.

  That is, an imaging apparatus including an auxiliary light emitting unit that can increase the hit rate of AF auxiliary light to the main subject is realized.

  Here, while the focus detection unit detects the contrast of the image signal while the focus detection unit moves the focus, the irradiation angle changing unit irradiates the auxiliary light with an irradiation angle that is narrower as the focus position is farther away. It is preferable.

  In the preferred embodiment, when the focus detection unit detects the contrast while moving the focus from a close distance to a distant distance, the irradiation angle is increased as the focus is close by the irradiation angle changing unit. Auxiliary light is emitted at, and the auxiliary light is emitted at an irradiation angle narrower as the focus is farther away.

  Then, since the auxiliary light is emitted with a wider irradiation angle as the focus is closer, the auxiliary light is emitted so that the AF auxiliary light does not pass between a plurality of people. Further, since the auxiliary light is irradiated at a narrower irradiation angle as the focus is further away, the auxiliary light is irradiated so that the subject farther reaches the subject far away as before.

Further, this photographing apparatus has a plurality of photographing modes having different distance ranges with a high probability that a subject exists,
The focus detection unit first performs focus position detection for a distance range in which there is a high probability that the subject exists in accordance with the shooting mode. In-focus position detection for
The auxiliary light emitting unit changes to an auxiliary light irradiation angle corresponding to a distance range during focus position detection while the focus detection unit detects the contrast of the image signal while moving the focus. Is preferred.

  By doing so, it is possible to reduce the time required to detect the focus by detecting the in-focus position first in the distance range where there is a high probability that the subject exists in accordance with the shooting mode.

   As described above, the photographing apparatus including the auxiliary light emitting unit that can increase the hit rate of the AF auxiliary light to the main subject is realized.

  Embodiments of the present invention will be described below.

  FIG. 1 is a view showing an appearance of a digital camera 1 according to an embodiment of the present invention.

  A lens barrel 100 is provided at the front center of the digital camera 1 shown in FIG. A photographing lens 1021 is built in the lens barrel 100. A finder 101 is provided above the lens barrel 100, and a light emission window 102 is provided beside the finder 101. From this light emitting window 102, when it is determined by the system control circuit described later that irradiation of shooting assistance light is necessary, shooting assistance light is emitted toward the subject.

  A release button 104, a mode dial 105, and a single / continuous shooting switch 106 are provided on the upper surface of the camera body.

  FIG. 2 is a block diagram showing the internal configuration of the digital camera 1 shown in FIG.

  The internal configuration of the digital camera 1 will be described with reference to FIG.

  In the digital camera 1 of the present embodiment, all processing is controlled by the system control circuit 110. 1 is connected to the operation buttons such as the release button 104, the mode dial 105, the single shooting / continuous shooting switch 106, etc. shown in FIG. When an operation signal is supplied to the system control circuit 110 by an operation, processing corresponding to any one of these operators is started.

  Although not shown in FIG. 1, the digital camera 1 according to the present embodiment has a detachable storage medium 200 such as a memory card mounted in the medium loading chamber 100A and the memory card 200 loaded in the medium loading chamber 100A. Since image data representing a photographed image is recorded, a storage medium attachment / detachment detecting means 108 for detecting whether a memory card as a storage medium is mounted in the medium loading chamber 100A is provided. Yes. Further, although not shown in FIG. 1, an image for detecting opening / closing of a protective door for covering and protecting the image display ON / OFF switch 107 and the display screen provided on the rear side on the rear side. A display means opening / closing detection means 109 is also provided. Signals from the storage medium attachment / detachment detection means 108, the image display ON / OFF switch 107, and the image display section opening / closing detection means 109 are also supplied to the system control circuit 110, and the system control circuit 110 receives these signals. In response to this, processing is executed as appropriate. The system control circuit 110 instructs the zoom control means 1020 to move the zoom lens in the photographing lens 1021 even in response to an operation of a zoom switch (not shown).

  In the system control circuit 110, the TTL photometry is performed together with the TTL distance measurement by the system control circuit 110 based on the image signal generated by the CCD solid-state imaging device 120. In the TTL distance measurement, the system control circuit 110 instructs the distance measurement control means 1030 to move the focus lens in the photographing lens 1021 along the optical axis, thereby moving the focus while the CCD solid-state imaging device 120 is moved. The focus is detected by generating an image signal at predetermined timings and detecting the contrast of the generated image signal. In the following description, the focus detection is referred to as AF search while the focus lens is moved along the optical axis to move the focus from near to far. In TTL photometry, TTL photometry is performed by the system control circuit 110 detecting the luminance of the image signal generated by the CCD solid-state imaging device 120.

  Depending on the photometric result of the TTL photometry, the system control circuit 110 instructs the exposure control means 1040 to adjust the aperture of the aperture 1041 to the exposure control means 1040, and further, based on the photometric result at the time of shooting. By instructing the light emission amount control means 112A in the auxiliary light emission section 11 and driving the LED 114 to the LED drive circuit 113 under the control of the light emission amount control means 112A, the photographing auxiliary light is emitted from the LED 114 with a predetermined light emission amount. It is irradiating towards.

  In this embodiment, the liquid lens 116 is inserted in front of the LED 114 and the curvature of the liquid lens 116 (the curvature of the concave lens, the curvature of the convex lens, and the switching between the concave lens and the convex lens) is adjusted by the lens control unit 115. By doing so, the irradiation angle of the photographing auxiliary light can be widened or narrowed according to the operation position of the zoom switch. In the present embodiment, the focus detection capability is improved by irradiating the AF auxiliary light from the LED 114 during the AF search so that the contrast of the image signal can be detected more clearly.

  Further, when the AF auxiliary light is irradiated during the AF search, the liquid lens 116 narrows the irradiation angle as the AF search proceeds to the far side in synchronism with the AF search, thereby passing through the AF auxiliary light at a short distance. The hit rate is increased by ensuring the same reach as before.

  The light emitting section 11 corresponds to the auxiliary light emitting section according to the present invention, and the liquid lens 116 and the lens control means 115 correspond to the irradiation angle changing means according to the present invention. Details will be described later.

  Further, a white balance adjustment unit, a γ correction unit, a YC conversion unit, and the like are also provided in the system control circuit 110, and the white balance adjustment unit performs white balance adjustment based on the color temperature detected by the color temperature detection circuit 141. R, G, and B colors after the γ correction is performed by the γ correction unit in order to obtain a signal suitable for the display specifications of the display screen included in the image display unit 150, or after the γ correction is performed. The YC conversion unit converts the signal into a YC signal so that the signal is displayed on any display unit.

  Here, an outline of the operation of the digital camera will be described first with reference to FIG.

  First, when a power switch (not shown) of the digital camera 1 is turned on, the entire operation of the digital camera 100 is comprehensively controlled by the system control circuit 110 in accordance with the procedure of the entire processing program in the nonvolatile memory 1101. Is started. In this example, the power switch of the digital camera 100 is turned on to suppress the power consumption of the battery Bt, and the power switch is turned on by the system control circuit 110 (the power from the battery Bt is always supplied to the system control circuit 110). Only when it is detected that power has been detected, power is supplied to each block from the battery Bt via the power control means 111b.

  First, the configuration and operation of the digital camera 1 that is in an operating state by supplying power to each block will be briefly described with reference to FIG.

  As shown in FIG. 2, the lens barrel 100 shown in FIG. 1 is provided with a photographing lens 1021 such as a focus lens and a zoom lens, and a diaphragm 1041 for adjusting the amount of light. In this example, a lens barrier 1011 for protecting the lens is provided. When the power switch is turned on, the lens barrier 1011 is released, and the photographing lens 1021 is placed on the surface as shown in FIG. It is configured to be exposed to.

  When the mode dial 105 is switched to the photographing side when the power switch is turned on, the subject image first formed on the CCD solid-state photographing element 120 through the photographing lens 1021 exposed on the surface is the timing. Based on the timing signal from the generation circuit 121, the data is thinned out at predetermined intervals (for example, 33 ms) and output to the A / D conversion circuit 130. The output image signal is converted from an analog image signal to a digital image signal by the A / D conversion circuit 130, and the digital image signal is further guided to the image processing circuit 140 under the control of the memory control unit 111a. The processing circuit 140 separates the RGB image signals into R color signals, G color signals, and B color signals, respectively. Further, the color signals separated into the R color signal, the G color signal, and the B color signal are led to the system control circuit 110 and the color temperature detection circuit 141 through the bus under the control of the memory control unit 111a. Information on the color temperature detected by the color temperature detection circuit 141 is supplied to the system control circuit 110, and the white balance is adjusted by the white balance adjustment unit in the system control circuit 110.

  Further, after the white balance is adjusted by the white balance adjustment unit, γ correction is performed by the γ correction unit in the system control circuit 110 so that it can be displayed on the display screen of the digital camera 1, and further YC conversion is performed. The YC signal is stored in the image display memory 151 after the conversion to the YC signal is performed by the unit. Thus, the YC signal for one frame stored in the image display memory 151 is read out under the control of the memory control unit 111a, guided to the D / A conversion circuit 160, and converted into an analog image signal. It is supplied to the display means 150.

  In this example, an image display memory 151 is provided so that new image signals can be supplied to the image display means 150 at predetermined intervals, and image signals for at least two frames are stored in the image display memory 151. By storing, it is possible to display a through image that is switched so that images are connected at predetermined intervals so that the supply timing of the image signal to the image display unit can be adjusted well.

  Here, the operation of each unit shown in FIG. 2 will be described in detail along with the flow of the image signal.

  First, the operation of each unit will be briefly described along the flow of the image signal of the through image.

  In response to a timing signal from the timing generation circuit 121 (for example, every 33 ms), an image signal representing a subject image formed on the light receiving surface on the CCD solid-state image sensor 120 by the photographing lens 1021 is supplied to the CCD solid-state image sensor 120. It is generated and output to the A / D conversion circuit 130 at the subsequent stage. The A / D conversion circuit 130 performs conversion from an analog image signal to a digital image signal, and the digital image signal is guided to the image processing circuit 140 under the control of the memory control unit 111a. In this image processing circuit 140, separation into R, G, and B signals is performed, and each color signal is supplied to the color temperature detection circuit 141 via the bus under the control of the memory control unit 111a. Or supplied to the system control circuit 110. In this example, a gain corresponding to each color temperature is set in each color amplifier in the white balance adjustment unit included in the system control circuit 110 according to the color temperature of the external light detected by the color temperature detection circuit 141, and the white color of the image signal is set. The balance is adjusted.

  In this way, the white balance of the image signal is suitably adjusted, and the R, G, B color signals after the γ correction by the γ correction unit are converted into YC signals for display by the color conversion matrix, and the converted YC signals are converted. The image data is supplied to and stored in the subsequent image display memory 151 under the control of the memory control unit 111a. The image display memory 151 stores at least two frames of image signals. Of the two frames of image signals, one frame of image signals stored at an old time is D / A converted. It is led to the circuit 160, converted into an analog signal, supplied to the image display unit 150, and a through image is displayed on the display screen.

  Further, as described above, the system control circuit 110 instructs the distance measurement control means 1030 based on the distance measurement result by the AF search to always place the focus lens in the photographing lens 1021 at the focal point, or a zoom (not shown). When the switch is operated, the zoom control means 1020 is instructed, and the zoom lens in the photographing lens 1021 is arranged at a position corresponding to the zoom magnification by the operation of the zoom switch. A live view image with a zoom magnification according to the zoom switch operating position is displayed.

  When this through image is visually recognized by the photographer and the release button 104 is half-pressed at a photo opportunity, the system control circuit 110 starts the photographing process.

  When the release button 104 is half-pressed, the system control circuit 110 first determines whether the aperture diameter of the diaphragm is adjusted according to the photometry result of the photometry unit in the system control circuit 110 or whether it is necessary to emit photographing auxiliary light. It is judged. Here, when the aperture of the diaphragm is adjusted by the system control circuit 110 and it is further determined that it is necessary to emit the photographing auxiliary light, the photographing auxiliary light is emitted from the LED 114 in synchronization with the full depression of the release button 104. Ready for light emission. Further, as described above, in this embodiment, the LED 114 is also used for emitting AF auxiliary light, and the AF search is performed by the system control circuit 110 while causing the LED 114 to emit AF auxiliary light before the shooting auxiliary light is emitted. The focus is detected. Thus, when focus detection is performed while emitting AF auxiliary light during AF search, the focus lens is placed at the in-focus position corresponding to the focus position.

  After that, when the release button 104 is fully pressed, the system control circuit 110 instructs the timing generation circuit 121 to supply the timing generation circuit 121 with an exposure start signal toward the CCD solid-state image sensor 120, and to the CCD solid-state image sensor 120. Start exposure. Further, when photographing auxiliary light is necessary, the light emission amount control means 112A is instructed to cause the LED driving circuit 113 to drive the LED 114, thereby causing the LED 114 to emit photographing auxiliary light. When a predetermined shutter time elapses, the system control circuit 110 instructs the timing generation circuit 121 to supply an exposure end signal to the CCD solid-state image sensor 120.

  Then, an image signal for which exposure has been completed is output from the CCD solid-state imaging device 120 to the A / D conversion circuit 130 in synchronization with the exposure end signal. The analog image signal output from the CCD solid-state imaging device 120 is converted into a digital image signal by the A / D conversion circuit 130, and the digital image signal is further controlled by the memory control unit 111a to be stored in the memory via the bus. 180. When all the image signals composed of all the pixels included in the CCD solid-state imaging device 120 are stored in the memory 180, this image signal is read out under the control of the system control circuit 110, and the white in the system control circuit 110 is read. The white balance adjustment of the image signal is performed with the gain set in the color amplifier by the balance adjustment unit. Further, the image signal that has been subjected to gamma correction and conversion to the YC signal is supplied to the compression / decompression circuit 190 via the bus, and the image signal composed of the YC signal is compressed and stored in the storage medium 200, here the memory card. .

  In this way, the photographing operation of the digital camera is controlled by the system control circuit 110, and an image signal obtained by photographing is recorded on a recording medium, here a memory card.

  In addition, a communication unit 1104 that can perform wireless communication with the outside when an antenna is connected to a connector 1105 provided on the camera body via a cable, a display unit 1102 that transmits operation contents to a user, and the like are also provided. ing.

  Here, how the irradiation angle of the AF auxiliary light is adjusted by the liquid lens 116 and the lens control unit 115 which are the irradiation angle changing means according to the present invention will be described.

  FIG. 3 is a diagram for explaining the lens effect of the liquid lens. FIG. 4 is a diagram for explaining how to change the irradiation angle when performing an AF search.

  FIG. 3A shows an example in which the liquid lens 114 acts as a convex lens without applying a voltage signal between the electrodes of the liquid lens 114, and FIG. FIG. 3C shows an example in which a voltage signal that generates a potential difference between the electrodes of the lens is applied to prevent the liquid lens from exhibiting the lens effect, and FIG. An example in which the voltage signal causing the above potential difference is applied to cause the liquid lens to act as a concave lens is shown. It is known that the shape of a liquid lens changes from a convex lens to a concave lens when the curvature changes due to the potential difference between the electrodes as shown in FIGS. 3 (a) to 3 (c).

  In the present embodiment, when an AF search is performed by the TTL distance measuring unit in the system control circuit 110, assuming that the subject is at the closest distance, the focus lens is first positioned farthest from the CCD solid-state imaging device 120 (subject side). The CCD solid-state image sensor 120 generates image signals at predetermined intervals and sequentially detects the contrast of these image signals while gradually moving the focus lens closer to the CCD solid-state image sensor 120. Thus, it is detected whether the focus position is between the near distance and the far distance.

  In order to achieve the above object, in this embodiment, first, the system control circuit 110 instructs the lens control means 115 to make the liquid lens 116 a concave lens as shown in FIG. At a distance, the light emitting unit 11 is irradiated with AF auxiliary light at a wide irradiation angle. In this example, when the system control circuit 110 widens the illumination angle at the AF search start position, the lens control means 115 is provided with a curvature so that the AF auxiliary light is uniformly irradiated around the center of the shooting field angle. Instructed to adjust the curvature of the liquid lens 116.

  Thus, when the system control circuit 110 causes the lens control means 115 to adjust the curvature of the liquid lens 116, the system control circuit 110 starts an AF search. When the system control circuit 110 starts an AF search, the liquid lens is gradually instructed by instructing the lens control unit 115 in synchronization with moving the focus lens by instructing the distance measurement control unit 1030 to move the focus lens. The curvature of 116 is adjusted to approach the shape having no lens effect shown in FIG. 3B from the shape of the concave lens shown in FIG. Further, as the system control circuit 110 moves the focus lens, this time, the lens control means 115 is instructed to adjust the liquid lens 116 to have the curvature of the convex lens shown in FIG. If it is determined that the convex lens has started to reach, the curvature of the convex lens is adjusted to a convex shape that further increases the light collection rate.

  Then, at the start of the AF search, the AF assist light is emitted from the light emitting unit 11 at a wide irradiation angle assuming that the focus position is at a short distance, so that the reaching distance is shortened, but a plurality of persons are arranged at a short distance, for example. Even if they are standing apart, the AF auxiliary light is irradiated over the entire plurality of persons. In addition, since the irradiation angle is narrower when the focus position is farther away, the energy density of the light emitted from the light emitting unit is concentrated within the narrower irradiation angle, and the energy density is increased as before. The AF auxiliary light reaches far away.

  In other words, by adjusting the irradiation angle of the AF auxiliary light during the AF search according to the focus position by using the liquid lens, the irradiation angle is widened at a close distance, and the reflected light amount is ensured while securing the reflected light amount. The hit rate to the main subject of AF auxiliary light is increased while securing the amount of reflected light by increasing the hit rate to the subject and narrowing the irradiation angle at a long distance.

  Here, a procedure of imaging processing including AF search performed by the system control circuit 110 will be described with reference to FIG.

  FIG. 5 is a flowchart showing a procedure of photographing processing performed by the system control circuit 110.

  When the power is turned on, the processing of the flow shown in FIG. 5 is started.

  In step S501, it is determined based on a photometric value based on a live view signal representing a live view whether or not AF auxiliary light needs to be emitted. If it is determined in step S501 that the contrast of the through image signal representing the subject is unclear and it is difficult to detect the focus, the process proceeds to Yes, and the lens controller 115 is instructed in step S502 to narrow the illumination angle of the LED 114. The curvature of the liquid lens 116 is adjusted. If it is determined in step S501 that the contrast of the through image signal is clear and it is not necessary to emit AF auxiliary light, the process proceeds to No and the AF auxiliary light is emitted toward the shooting angle of view in step S505. To adjust the curvature of the liquid lens.

  The processing from step S501 to step S502 or the processing from step S501 to step S506 is repeated until half-pressing is detected in step S503 or step S506.

  In step S501, it is determined that AF auxiliary light needs to be emitted, and the process proceeds to step S502. If half-pressing is detected in step S503, the process proceeds to step S504 to cause the LED 114 to emit AF auxiliary light. In the next step S507, the distance search control means 1030 and the timing adjustment circuit 121 are instructed to start the AF search.

  In step S508, an AF search is performed. In step S509, the focus is detected and the AF search is completed. In step S510, the lens control unit 115 is instructed to adjust the curvature of the liquid lens 116 to the shooting angle of view. Let them adjust. When full press is detected in the next step S511, the flash light is emitted to the LED 114 in step S512, and the processing up to the compression / recording process of the image signal obtained by photographing is performed in step S513, and the processing of this flow is completed.

  Here, details of Step S508 will be described.

  FIG. 6 is a flowchart showing details of step S508.

  As described with reference to FIG. 4, when an AF search is started, focus detection is sequentially performed from a distance side closer to the subject distance to a distance side farther away. Therefore, first in step S5081, a predetermined area α in the near focus position is detected. Then, the lens driving means is instructed to adjust the curvature of the liquid lens 114 so that the AF auxiliary light from the LED is irradiated at a wider irradiation angle.

  When the curvature of the liquid lens (initially a concave lens) is adjusted in step S5081, the focus detection area α that is at the first focus position is set according to the irradiation angle. In step S5083, the contrast of the image signal in the focus detection area α is detected. In the next step S5084, it is determined whether or not the contrast of the image signal is a peak value (focus position). If it is determined that the contrast is not a peak value, the process proceeds to NO side and proceeds to step S5085 to shift the focus position to the far side. In order to achieve this, the focus lens is slightly moved toward the CCD solid-state imaging device. Returning to step S5081, the lens instruction means 115 is instructed in accordance with the focus position set in step S5085, and the curvature of the liquid lens 115 is adjusted in a direction to narrow the irradiation angle of the AF auxiliary light. Thereafter, the processing from step S5081 to step S5085 is repeatedly performed, and when it is determined in step S5084 that a contrast peak has been detected, the process proceeds to step S509 to end the AF search.

  When processing is performed according to the flow procedure of FIG. 6, when the focus is moved by AF search, the irradiation angle is adaptively adjusted for each focus position, and AF auxiliary light is emitted. For example, even if a plurality of people stand side by side at a relatively close focus position, the AF auxiliary light is emitted over the entire area of the subject even when the irradiation angle is relatively widened toward a subject at a close distance. , AF assist light hit rate is higher than ever. In other words, the AF assist light is irradiated at a wider focus angle at a close focus position to prevent the above-mentioned AF assist light from passing through, and the AF assist light is irradiated at a narrower focus angle when the subject is at a far focus position. As a result, the reach distance of the AF auxiliary light is secured as before.

  As described above, a photographing apparatus including an auxiliary light emitting unit capable of increasing the hit rate of AF auxiliary light to a main subject is realized.

  7-9 is a figure explaining 2nd Embodiment.

  Note that the imaging device of the second embodiment has the same configuration as that shown in FIGS. 1 and 2, and the description of the configuration in the description of the second embodiment is omitted.

  In the first embodiment, when performing an AF search, an example is shown in which irradiation is performed with a narrower irradiation angle as the focus position is farther in synchronization with the AF search. As described above, when the AF search is performed while the auxiliary light is irradiated at a predetermined irradiation angle and the in-focus state is not obtained, the irradiation angle may be widened and the next AF search may be performed.

  In the second embodiment, the process of step S508 in the process shown in FIG. 7 (same as the process of FIG. 5) is changed to the process of step S508B. FIG. 8 shows details of the changed processing in step S508B.

  Differences from the processing of FIG. 5 will be described with reference to FIG.

  In step S5081B, the lens control unit 115 is instructed to adjust the curvature of the liquid lens 116 so that the convex lens has a high condensing rate, and the irradiation angle of the auxiliary light is made the narrowest so that the small irradiation area α in the center (this α is combined). AF assist light is irradiated toward the focus detection area. At the time of the processing in step S5081B, the focus lens is disposed at a position farthest from the CCD solid-state imaging device 120 (see FIG. 2) (corresponding to the subject being at a short distance), and in the next step S5082B, the focus lens The contrast of the image signal (with respect to the focus detection area α to which the auxiliary light is applied) is detected at the position, and it is confirmed whether or not the position of the focus lens is the focus position. If it is determined in the next step S5083B that it is the in-focus position, the process proceeds to the YES side and proceeds to step S509 in FIG.

  If it is determined in this step S5083B that the in-focus state cannot be obtained, the process proceeds to the NO side, and in the next step S5084B, it is determined whether or not the AF search has been performed up to the farthest distance. If it is determined in step S5084B that the AF search has not yet reached the farthest distance and has not been completed, the process proceeds to the NO side, and in step S5085B, the focus lens is moved a little toward the CCD solid-state imaging device to move the focus position far away. Shift to the side. Returning to step S5082B, the processes from step S5082B to step S5084B are repeated, and the focus is detected up to the farthest distance in step S5084B. It is determined whether or not the light irradiation angle is a photographing field angle, that is, MAX. If it is determined in step S5086B that it is not yet MAX, the process proceeds to the NO side, and in step S5087B, the lens control means 115 is instructed to adjust the curvature of the liquid lens 116 (to reduce the condensing rate). Widen the irradiation angle. In the next step S5088B, preparation for performing the second AF search is made with the range excluding the range where the focus position is detected in the first AF search as the focus detection area α. Returning to step S5082B, the processing from step S5082B to step S5086B is repeated.

  FIG. 9 shows an irradiation area when the AF auxiliary light is irradiated according to the flow of FIGS. 7 and 8. As shown on the left side of FIG. 9, when the AF search is performed for the first time, the irradiation angle is narrowed, and when the irradiation angle is increased as the second time (center of the figure) and the third time (right side of the figure) are overlapped, either The AF auxiliary light hits the main subject in the AF search of this time. That is, in the examples shown in FIGS. 7 to 9, the AF time becomes shorter as the subject is at the center and far away, and the in-focus position is detected in a few AF searches.

  In the above example, the irradiation angle is narrowed to the narrowest at the start of the AF search, and the energy of the light emitted from the light emitting unit is concentrated and irradiated with the AF auxiliary light within the narrowed irradiation angle. Even if the subject at the focus position is, for example, a black system in which the amount of reflected light is reduced, the amount of light hitting the subject increases due to an increase in the energy density within the irradiation angle, and the amount of reflected light is secured.

  In the lower part of FIG. 9, when the system control circuit 110 detects the contrast peak of the image signal by the AF search and detects the in-focus position for all the areas in the imaging surface, the processing is redundant and useless. In this AF search, an area other than the area in which the contrast is detected in the previous AF search is set as the focus detection area α, and the contrast of the image signal in the area α is increased. It is shown that the detection time is reduced to shorten the processing time.

  10 and 11 are diagrams showing a modification of the second embodiment.

  FIG. 10 is the same as the flowchart shown in FIG. 8 except that the processing contents of steps S5081C, S5087C, and step S5088C are changed. FIG. 11 shows a diagram corresponding to FIG.

  As shown in FIG. 9, when the AF search is performed with the auxiliary light being irradiated at a predetermined irradiation angle and the in-focus state is not achieved, the irradiation angle may be widened and the next AF search may be performed. As shown in FIG. 11, the AF assist light irradiation angle may be set to MAX (widest) at the AF search start position, and the irradiation angle may be gradually narrowed.

  In this way, in contrast to the examples shown in FIGS. 7 to 9, when the subject is at a short distance, the in-focus position is detected in a small number of AF searches.

  As shown in FIG. 11, when the AF auxiliary light is irradiated, in the process of the flow of FIG. 10, when the irradiation angle is maximized in step S5081C of FIG. 10 and the current AF search is completed, the irradiation angle is determined in step S5087C. The next AF search may be performed by narrowing the range.

  According to this modified example, the focus detection is performed over the entire angle of view in the first AF search, and a more remarkable effect is exhibited when the frequency of photographing a subject at a close distance is high.

  FIG. 12 is a diagram for explaining the third embodiment.

  Note that the imaging apparatus of the third embodiment has the same configuration as that shown in FIGS. 1 and 2 as in the second embodiment, and the configuration presented in the description of the third embodiment is as follows. Omitted.

  1 is assumed to have photographing modes such as a macro mode, a portrait mode, a landscape mode, a sports mode, and a night view mode.

  These shooting modes are a plurality of shooting modes with different distance ranges with a high probability of existence of a subject, and it is better to first detect the focus position in a distance range with a high probability of existence of a subject according to the shooting mode. Processing time is reduced.

  Therefore, the system control circuit 110 (see FIG. 2) determines the range in which the focus lens is moved (the range in which the focus position is present) as shown in FIG. 12A, the macro area (0 to 1 m) and the area A ( 1 m to 2 m), area B (2 m to 4 m), and area C (4 m to ∞) are divided into four areas according to the shooting mode, and one of these areas has a high probability range where the subject exists. First, the in-focus position is detected. Further, in this embodiment, when the focus position detection fails in the area where the focus position has been previously performed, the focus position detection is performed by sequentially moving to a distance range where there is a low probability that the subject exists. .

  For example, in the macro mode, the system control circuit 110 first detects the in-focus position in the macro area (0 to 1 m) by moving the focus lens from a position closest to the subject side to a predetermined position. If the focus position detection fails after performing an (AF search), the focus position is detected in the area A (AF search) by moving the focus lens away from the subject from a predetermined position. Just do it.

  In the person mode, if the focus position is detected (AF search) first in the region B, then in the region A, and finally in the region C, the focus position is efficiently detected. be able to. Further, at this time, for example, assuming that a person is most frequently located at 2 m, it is more efficient to change the search direction of the AF search from 2 m to 4 m around 2 m and then from 2 m to 1 m. .

  Also, in the landscape mode, if the focus position is detected in the manner of the area C first, then the area B, and finally the area A in the same manner as described above, the focus position can be detected efficiently. Can do. At this time, for example, it is more efficient to change the AF search direction from 4 m to ∞, then from 4 m to 2 m, and from 2 m to 1 m, assuming that the frequency of shooting a landscape near 4 m is the highest. Become.

  As shown in FIG. 12, if the same is applied to the sports mode and the night view mode, the photographing process including the AF search of the system control circuit 110 becomes more efficient.

  Further, when the AF control is performed for each area in this way, the system control circuit 100 detects the contrast of the image signal while moving the focus, and the auxiliary light irradiation corresponding to the distance range during the in-focus position detection. When AF auxiliary light is emitted to the auxiliary light emitting unit 11 at a corner, the accuracy of detecting the in-focus position is further increased.

  As described above, a photographing apparatus including an auxiliary light emitting unit capable of increasing the hit rate of AF auxiliary light to a main subject is realized.

It is a figure which shows the external appearance of the digital camera 1 which is one Embodiment of this invention. FIG. 2 is a configuration block diagram showing an internal configuration of the digital camera 1 in FIG. 1. It is a figure explaining the lens effect of a liquid lens. It is a figure explaining how an irradiation angle is changed when performing an AF search. 3 is a flowchart illustrating a procedure of photographing processing performed by a system control circuit 110. It is a flowchart which shows the detail of step S508 shown in FIG. It is a figure which shows 2nd Embodiment. It is a figure which shows 2nd Embodiment. It is a figure which shows 2nd Embodiment. It is a figure which shows the modification of 2nd Embodiment. It is a figure which shows the modification of 2nd Embodiment. It is a figure which shows 3rd Embodiment.

Explanation of symbols

1 Digital Camera 110 System Control Circuit 11 Auxiliary Light Emitting Unit 114 LED
115 Lens control means (irradiation angle changing means)
116 Liquid lens (irradiation angle changing means)

Claims (3)

In an imaging device that includes an image sensor and generates an image signal by forming a subject image on the image sensor,
A focus detection unit that detects the in-focus position by detecting the contrast of the image signal while moving the focus;
An auxiliary light emitting unit that emits auxiliary light toward the subject while the focus detection unit detects the contrast of the image signal while moving the focus;
Said auxiliary light emitting portion, while the focus detection unit detects the contrast of the image signal while moving the focus, in synchronism with the movement of the focus, the irradiation angle of auxiliary light when the focus position is at the far An imaging apparatus comprising irradiation angle changing means for changing the irradiation angle so as to become narrower . This photographing apparatus has a plurality of photographing modes with different distance ranges with a high probability that a subject exists,
The focus detection unit first performs focus position detection for a distance range in which there is a high probability that a subject exists, depending on the shooting mode. The focus position is detected for the range.
While the focus detection unit detects the contrast of the image signal while moving the focus, the auxiliary light emitting unit is narrowed as the distance range is farther according to the distance range during focus position detection. The photographing apparatus according to claim 1, wherein the photographing apparatus is changed to an auxiliary light irradiation angle . In a shooting method for generating an image signal by forming a subject image on an image sensor,
  While moving the focus and synchronizing with the movement of the focus, the assist light is irradiated toward the subject while changing the illumination angle of the auxiliary light so that it becomes narrower as the focus position is farther away. However, the imaging method is characterized in that the in-focus position is detected by detecting the contrast of the image signal.

Images