JP5879809B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

  A single-lens reflex camera is provided with a charge accumulation type photometric sensor so that the brightness distribution of the object scene can be monitored even in a mirror-down state. The output of the photometric sensor is used for scene analysis in addition to photometric calculation, and the result of the scene analysis is used for focus control as necessary. For example, this is a case where the focus mode of the camera is set to a subject tracking type such as an auto area AF mode or a 3D-tracking mode.

  Usually, since the charge accumulation time of the photometric sensor suitable for photometric calculation is different from the charge accumulation time of the photometric sensor suitable for scene analysis, the charge accumulation of the photometric sensor is performed twice in one photometry cycle, One charge accumulation time is set as a charge accumulation time for photometric calculation, and the other charge accumulation time is set as a charge accumulation time for scene analysis.

JP 2011-2688 A

  In recent years, with the improvement in the number of pixels of a photometric sensor, the amount of photometric calculation and scene analysis tends to increase, which may affect the responsiveness of focus control using scene analysis.

  SUMMARY An advantage of some aspects of the invention is that it provides an imaging apparatus having a configuration suitable for effectively using a high-performance photometric sensor having a large number of pixels for focus control.

An image pickup apparatus according to the present invention includes a photometric means for measuring a field of an imaging optical system, a focus detection means for detecting an in-focus state of the imaging optical system for a plurality of positions of the object scene, and an output of the photometric means A scene analysis unit that repeats a scene analysis for recognizing a subject in the scene based on a focus calculation that generates a defocus signal of the imaging optical system based on an output of the scene analysis unit and an output of the focus detection unit The scene calculation repetition speed when the focus calculation means performs the focusing operation by following the movement of the subject and when the focusing operation is performed without following the movement of the subject. Switching means for switching between.

  According to the present invention, an imaging device having a configuration suitable for effectively using a high-performance photometric sensor with a large number of pixels for focus control is realized.

1 is an overall configuration diagram of a camera system. It is a block diagram of the body drive control device 24 and its periphery. 4 is a timing chart of the body drive control device 24. FIG. 10 is a schematic diagram for explaining a change of a defocus signal in a period in which a focus mode is set to an auto area AF mode and a release button is pressed halfway.

[Embodiment]
Hereinafter, a single-lens reflex digital still camera system will be described as an embodiment of the present invention.

  FIG. 1 is an overall configuration diagram of the camera system. As shown in FIG. 1, the camera system includes a camera body 1 and a lens barrel 2 attached to the camera body 1, and the lens barrel 2 attached to the camera body 1 is replaced with another lens barrel. It is also possible to do.

  The lens barrel 2 includes a photographing lens 31 (including a zooming lens and a focusing lens), a diaphragm 32, a lens drive control device 33, and the like. The photographing lens 31 forms an image of a light beam (field light beam) emitted from the object scene (the object space of the photographing lens 31).

  The lens drive control device 33 includes a microcomputer (not shown), a ROM, a RAM, a lens drive actuator, an aperture drive actuator, and the like, and performs focus adjustment of the photographing lens 31, aperture adjustment of the aperture 32, and the like.

  The camera body 1 includes a main mirror 11, a sub mirror 12, a shutter 13, an image sensor 14, a focus detection device 15, a diffusion screen 16, a condenser lens 17, a penta roof prism 18, an eyepiece lens 19, a photometric optical element 20, a photometric lens 22, A photometric sensor 23, a body drive control device 24, and the like are provided.

  The photometric sensor 23 is a charge storage type imaging device composed of a CCD, a CMOS, or the like, and it has an R pixel for detecting the intensity of red light, a G pixel for detecting the intensity of green light, and an intensity of blue light. The B pixels to be detected are arranged in a mosaic pattern. The total number of pixels of the photometric sensor 23 is 86000, for example. In the present embodiment, it is assumed that an A / D conversion circuit is mounted inside the photometric sensor 23 and the photometric signal output from the photometric sensor 23 is a digital signal.

  The image sensor 14 is a charge storage type image sensor composed of a CCD, a CMOS, or the like, and has an R pixel that detects the intensity of red light, a G pixel that detects the intensity of green light, and an intensity of blue light. The B pixels to be detected are arranged in a mosaic (for example, in a Bayer arrangement pattern). The total number of pixels of the image sensor 14 is larger than that of the photometric sensor 23.

  The focus detection device 15 is a pupil division phase difference detection type focus detection device, and generates a signal indicating the focus adjustment state of the photographing lens 31 for each of a plurality of areas in the object scene.

  The body drive control device 24 includes a sequence microcomputer and an image processing IC, which will be described later, and controls each element mounted on the camera body 1. The body drive control device 24 is electrically connected to the lens drive control device 33 of the lens barrel 2 through an electrical contact (not shown) provided on the mount portion of the lens barrel 2.

  At the time of non-photographing, as shown by a broken line in FIG. 1, the main mirror 11 and the sub mirror 12 are inserted into the optical path of the field light flux (become in the mirror down state), and a part of the field light flux that has passed through the photographing lens 31. Is reflected by the main mirror 11 and forms an object scene image on the diffusing screen 16. The luminous flux emitted from the object scene image is guided to the photographer's eyes through the condenser lens 17, the penta roof prism 18, and the eyepiece lens 19. Further, the light beam emitted from the object scene image on the diffusing screen 16 forms an object scene image on the photometric sensor 23 via the condenser lens 17, the penta roof prism 18, the photometric optical element 20, and the photometric lens 22, and photometry is performed. It is converted into a photometric signal by the sensor 23 and taken into the body drive control device 24.

  On the other hand, the remaining part of the field light beam that has passed through the photographing lens 31 is transmitted through the central transmission part of the main mirror 11, reflected by the sub mirror 12, and incident on the focus detection device 15. And is taken into the body drive control device 24.

  At the time of shooting, as indicated by the solid line in FIG. 1, the main mirror 11 and the sub mirror 12 are separated from the optical path of the object beam (in a mirror-up state), and the object beam that has passed through the shooting lens 31 is An object scene image is formed thereon, and is taken into the body drive control device 24, which is converted into an image signal by the image sensor 14.

  A release button is provided on the upper surface of the camera body 1, and a monitor, a multi selector, a live view display switch, and the like are provided on the rear surface of the camera body 1. Of these, the release button is a switch for inputting shooting timing, the multi selector is a switch for switching the mode of the camera body 1 (photometry mode, focus mode, etc.), and the live view display switch is a subject. This is a switch for projecting the scene on the monitor. Therefore, when the live view display switch is turned on during non-photographing, the main mirror 11 and the sub mirror 12 are in the mirror-up state, and the field light flux is guided to the image sensor 14.

  FIG. 2 is a block diagram of the body drive control device 24 and its surroundings. The body drive control device 24 includes a sequence microcomputer 50 constituted by an MCU and an image processing IC 40 (ASIC) that executes image processing under the control of the sequence microcomputer 50. Data transmission / reception between the sequence microcomputer 50 and the image processing IC 40 is performed by communication.

  The sequence microcomputer 50 includes a sensor control unit 50a and a focus calculation unit 50b, and the image processing IC 40 includes an accumulation calculation unit 40a, a photometry calculation unit 40b, and a scene analysis unit 40c.

  That is, in this embodiment, the mounting destination of the photometric calculation unit 40b and the scene analysis unit 40c is not the sequence microcomputer 50 side but the image processing IC 40 side (conventionally, the photometry calculation unit 40b and the scene analysis unit 40c). And the focus calculation unit 50b are mounted on the sequence microcomputer 50 side).

  Therefore, in this embodiment, the focus calculation by the focus calculation unit 50b and the scene analysis by the scene analysis unit 40c (and the photometry calculation by the photometry calculation unit 40b) are distributed to the sequence microcomputer 50 and the image processing IC 40.

  Based on the photometric signal generated by the photometric sensor 23, the accumulation calculation unit 40a calculates the amplifier gain of the photometric sensor 23 suitable for the current scene and the charge accumulation time of the photometric sensor 23 suitable for the current scene. Calculate the combination.

  Here, there are two combinations of the amplifier gain and the charge accumulation time calculated by the accumulation calculation unit 40b. One is a combination for photometry calculation, and the other is a combination for scene analysis. Among these combinations, the combination for photometric calculation is a combination in which the photometric signal of the photometric sensor 23 relating to the brightest part of the object scene is a target value, and the combination for scene analysis is the metering sensor relating to each part of the object scene. The combination is such that the average value of the 23 photometric signals becomes the target value. These two combinations calculated by the accumulation calculation unit 40b are referred to by the sensor control unit 50a mounted on the sequence microcomputer 50 side.

  The sensor control unit 50a controls the amplifier gain and the charge accumulation time of the photometric sensor 23 according to the two combinations calculated by the accumulation calculation unit 40a. Under this control, the photometric sensor 23 alternately repeats charge accumulation and charge readout by the charge accumulation time and amplifier gain for photometric calculation, and charge accumulation and charge readout by the scene analysis charge accumulation time and amplifier gain. By this control, the photometric signal generated by the photometric sensor 23 during the charge accumulation period for photometric calculation is controlled so that the photometric signal related to the brightest part of the object field substantially matches the target value (peak AGC), and scene analysis The photometric signal generated by the photometric sensor 23 during the electric charge accumulation period is controlled so that the photometric signal relating to each part of the object scene substantially matches the target value (subject-oriented AGC).

  The photometry calculation unit 40b performs photometry calculation based on the photometry signal generated by the photometry sensor 23 during the charge accumulation period for photometry calculation and the photometry mode being set in the camera body 1, and calculates the subject brightness. The shutter speed to be set for the shutter 13 during shooting and the aperture value to be set for the aperture 32 during shooting are controlled (exposure control) based on the subject luminance.

  When the scene analysis unit 40c performs scene analysis processing on the photometric signal (color information and luminance information) generated by the photometric sensor 23 during the charge accumulation period for scene analysis and recognizes a main subject area in the object scene, A signal indicating the position and movement of the main subject area is generated. This signal is referred to by a focus calculation unit 50b mounted on the sequence microcomputer 50 side as necessary.

  Here, when the focus mode of the camera body 1 is the auto area AF mode, the scene analysis unit 40c separates the background area of the object scene from the subject area, and further performs the template matching so that the human face area is the main area. The subject area.

  When the focus mode of the camera body 1 is the 3D-tracking mode, the scene analysis unit 40c detects a specific subject area designated in advance by the user by template matching, and sets the specific subject area as the main subject area. .

  The focus calculation unit 50b is based on the signal generated by the scene analysis unit 40c (the signal indicating the position and movement of the main subject area), the signal generated by the focus detection device 15 for each area, and the focus mode of the camera body 1. A focus calculation is performed to generate a defocus signal for the photographic lens 31. This defocus signal is sent to the lens drive control device 33 and used for focus control (feedback control) of the photographing lens 31. By this control, the focusing destination of the photographic lens 31 coincides with an area designated in advance by the user or a main subject area recognized by the scene analysis unit 40c.

  Here, when the focus mode of the camera body 1 is a fixed area type (single point AF mode or the like, the focus destination of the photographic lens 31 is not made to follow the main subject area), the focus calculation unit 50b includes the scene analysis unit 40c. The defocus signal for making the focus destination of the photographic lens 31 coincide with the area designated in advance by the user is generated as the defocus signal of the photographic lens 31 without referring to the signal generated by.

  On the other hand, when the focus mode of the camera body 1 is a subject tracking type (automatic AF mode, 3D-tracking mode, or the like type in which the photographing lens 31 is focused on the main subject area), the focus calculation unit 50b With reference to the signal generated by the scene analysis unit 40c, a defocus signal for causing the focus destination of the photographing lens 31 to follow the main subject area is generated as a defocus signal of the photographing lens 31.

  However, even if the focus mode of the camera body 1 is the subject tracking type, if the scene analysis unit 40c fails to recognize the main subject area, the focus calculation unit 50b sets the focus destination of the photographic lens 31 as the priority area ( For example, a defocus signal for setting a close-up area) is generated as a defocus signal for the photographing lens 31.

  FIG. 3 is a timing chart of the body drive control device 24. FIG. 3A is a conventional timing chart, and FIGS. 3B and 3C are timing charts of the present embodiment. In FIG. 3, blocks with diagonal lines indicate photometric calculation periods, blocks with double diagonal lines indicate scene analysis periods, and blocks with grid lines are The focus calculation period is shown. Incidentally, the length of the conventional photometry cycle is about 100 ms.

  Conventionally, as shown in FIG. 3 (a), both the calculation related to the photometry cycle (photometry calculation and scene analysis) and the calculation related to the AF cycle (focus calculation) are executed by the sequence microcomputer (MCU). Calculations related to the cycle (photometry calculation and scene analysis) and calculations related to the AF cycle (focus calculation) cannot be processed in parallel, and the photometry calculation and scene analysis are not performed within one photometry cycle. , Assigned focus calculation (subdivided). For this reason, if the number of pixels of the photometric sensor 23 is improved and the amount of calculation of photometry calculation and scene analysis is increased, there is a possibility that the period assigned to the focus calculation is insufficient (or the photometry cycle is extended). Conventionally, since the AF cycle cannot be set independently of the photometry cycle, both the photometry cycle and the AF cycle tend to be long.

  On the other hand, in the present embodiment, as shown in FIG. 3B, calculations relating to the photometry cycle (photometry calculation and scene analysis) are executed by the image processing IC (ASIC), and calculations relating to the AF cycle (focus calculation) are performed by the sequence microcomputer ( Since the processing is executed by the MCU), computation relating to the photometry cycle (photometry computation and scene analysis) and computation relating to the AF cycle (focus computation) can be processed in parallel. Therefore, even if the number of pixels of the photometric sensor 23 is improved and the amount of calculation of photometry calculation and scene analysis is increased, the calculation load of the sequence microcomputer (MCU) does not become excessive. In the present embodiment, since the AF cycle can be set independently of the photometry cycle, it is possible to individually speed up the photometry cycle and the AF cycle.

  That is, in this embodiment, since the AF cycle can be set regardless of the photometry cycle, it is possible to increase the speed of the AF cycle, for example, as shown in FIG. Of course, in this embodiment, since the functions are allocated to the sequence microcomputer and the image processing IC, the photometry cycle can be speeded up as shown in FIG.

  However, if the photometric cycle is always set to the highest speed, the frequency of driving the photometric sensor 23 increases and the power consumption may become excessive.

  On the other hand, when the focus mode of the camera body 1 is the subject tracking type, if the photometry cycle is slower than the AF cycle, there is not enough opportunity to reflect the result of the scene analysis for the frequently performed focus calculation. Therefore, the responsiveness of the focus control is deteriorated. This does not take advantage of the present embodiment that the AF cycle can be speeded up.

  Therefore, the body drive control device 24 of the present embodiment switches the photometry cycle as follows according to the focus mode of the camera body 1 and the presence / absence of the release operation of the camera body 1. Here, it is assumed that the AF cycle is always set to a high speed.

  (I) Period in which the focus mode is set to the area fixed type: the photometry cycle is set to a low speed. This photometric cycle may be slower than the AF cycle (for example, FIG. 3B).

  (Ii) The period when the focus mode is set to the subject tracking type and the release button is not operated (the period when the half-press timer is ON): the photometric cycle is the same as the photometric cycle in the period (i) The speed is set (for example, FIG. 3B).

  (Iii) Period in which the focus mode is set to the subject tracking type and the release button is operated (half-pressed or fully-pressed period): The photometric cycle is longer than the photometric cycle in the periods (i) and (ii) Is also set fast. In addition, the photometric cycle in this period (iii) is set to a high speed equal to or higher than the AF cycle in the same period (iii) (for example, FIG. 3C).

  However, if the light source that illuminates the object scene has flicker, the photometry signal may be affected by flicker if the photometry cycle is increased. Therefore, the body drive control device 24 according to the present embodiment determines whether it is necessary to deal with the flicker based on the photometric signal generated by the photometric sensor 23, and if necessary, the flicker of the flicker for the photometric signal is determined. It is desirable to set a photometric cycle to a cycle that does not show the influence of flicker, that is, a cycle that shows an influence does not appear as a candidate for the photometric cycle.

  As a method for avoiding the influence of flicker, for example, methods described in JP-A-8-146487, JP-A-2011-2688, and the like can be employed. Incidentally, in the method described in JP-A-8-146487, a plurality of cycles are stored in advance, and the best cycle is selected and used.

  FIG. 4 is a schematic diagram for explaining the shift of the defocus signal during the period when the focus mode of the camera body 1 is set to the auto area AF mode and the release button is half-pressed. In FIG. 4, t indicates the elapsed time from the start of half-pressing, and T indicates the length of the photometric cycle. Note that FIG. 4 is a schematic diagram to the last, and the actual number of repetitions of the photometry cycle is not always as shown in FIG.

  In the example shown in FIG. 4, since the image of the face area formed on the photometric sensor is blurred at an early time (t = T) from the start of half-pressing, the main subject area is recognized by the scene analysis unit 40c (FIG. 4). In the example, face recognition) is not successful. In this case, the defocus signal generated by the focus calculation unit 50b is not a face area defocus signal but a priority area (closest area) defocus signal. Therefore, in this case, the focus control works so that the focusing destination of the photographic lens 31 is brought close to the priority area, not the face area.

  Thereafter, the scene analysis unit 40c makes the face recognition successful when the amount of blur in the face area becomes somewhat small (t = 3T). Therefore, the defocus signal generated by the focus calculation unit 50b after that time (t = 3T) is not the priority area defocus signal but the face area defocus signal. Therefore, in this case, the focus control works so that the focusing destination of the photographic lens 31 is brought closer to the face area instead of the priority area.

  Here, as described above, in the present embodiment, the photometry cycle in the half-press period of the release button is set to a high speed equal to or higher than the AF cycle. Therefore, the frequency of face recognition during the half-press period of the release button is higher than the frequency of focus calculation.

  Therefore, in the present embodiment, the time required from when the release button is half-pressed until focus control for the face area is started is shortened (3T in the example of FIG. 4). As a result, the time required until the focusing destination of the photographing lens 31 matches the face area is also shortened (5T in the example of FIG. 4).

  Further, such an effect of improving the focus performance can be obtained similarly when the focus mode is set to another subject tracking type (3D-tracking mode or the like).

  As described above, the camera system according to the present embodiment includes the photometric means (photometric sensor 23) for measuring the object field of the imaging optical system (imaging lens 31) and the imaging optical system (imaging lens 31) for a plurality of positions of the object field. Focus detection means (focus detection device 15) for detecting the in-focus state, and scene analysis means (scene analysis unit 40c) for repeating scene analysis for recognizing a subject in the object scene based on the output of the photometry means (photometry sensor 23) And a focus calculation unit that repeats a focus calculation for generating a defocus signal of the photographic optical system (shooting lens 31) based on the output of the scene analysis unit (scene analysis unit 40c) and the output of the focus detection unit (focus detection device 15). (Focus calculation unit 50b) and repetition rate of scene analysis (photometry cycle) according to the operation contents of the focus calculation means (focus calculation unit 50b) And a switching means for switching the speed) (body drive control device 24).

  Therefore, the camera system of the present embodiment can effectively use high-performance photometric means (photometric sensor 23) having a large number of pixels for focus control.

  The focus calculation means (focus calculation section 50b) of the present embodiment reflects the output of the scene analysis means (scene analysis section 40c) in the defocus signal as necessary. The apparatus 24) determines the repetition rate of the scene analysis (the speed of the photometric cycle) during the period in which the output of the scene analysis means (scene analysis unit 40c) is reflected in the defocus signal (the period in which the focus mode is the subject tracking type). The speed is higher than the repetition speed (speed of photometry cycle) in a period in which reflection is not performed (period in which the focus mode is an area fixed type).

  In this way, if the scene analysis repetition rate (photometric cycle rate) is appropriately switched in accordance with the focus mode, the consumption of the photometric means (photometric sensor 23) is reduced without reducing the responsiveness of various focus controls. Electric power can be minimized.

  In addition, the switching means (body drive control device 24) of the present embodiment is configured so that the scene during the period in which the output of the scene analysis means (scene analysis unit 40c) is reflected in the defocus signal (the period in which the focus mode is the subject tracking type). The analysis repetition speed (photometry cycle speed) is set to a speed equal to or higher than the focus calculation repetition speed (AF cycle speed) during that period, so a relatively new scene analysis result is used for each focus calculation. be able to. Therefore, the responsiveness of subject tracking focus control can be improved.

  Further, the switching means (body drive control device 24) of the present embodiment is a period in which the output of the scene analysis means (scene analysis unit 40c) is reflected in the defocus signal (a period in which the focus mode is the subject tracking type). However, since speeding up is refrained during the non-operation period of the release button of the image pickup apparatus (camera body 1), the power consumption of the photometric means (photometric sensor 23) can be more efficiently suppressed.

  Further, the switching means (body drive control device 24) of the present embodiment makes the scene analysis repetitive speed (photometric cycle) difficult to be affected by the flicker of illumination of the object scene when the speed is increased. Therefore, the accuracy of the scene analysis process, and hence the responsiveness of the focus control can be maintained regardless of the presence or absence of flicker.

[Supplement of embodiment]
In the camera system of the above-described embodiment, a face detection module for processing an image acquired by the image sensor 14 may be mounted on the image processing IC. In that case, the face detection module may also be used for face detection by the scene analysis unit 40c described above.

  In the above-described embodiment, the body drive control device 24 sets the AF cycle to be constant (highest speed) regardless of the mode of the camera body 1, but the AF cycle when the release button is not operated is used when the release button is operated. It may be set slower than the AF cycle.

  In this way, the period during which the focus control responsiveness is improved can be limited to only a necessary period, so that the power consumption of the photometric sensor 23 can be further suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Camera body, 2 ... Lens barrel, 31 ... Shooting lens, 32 ... Aperture, 33 ... Lens drive controller, 11 ... Lens drive controller, 11 ... Main mirror, 12 ... Sub mirror, 13 ... Shutter, 14 ... Imaging Elements: 15 ... Focus detection device, 16 ... Diffusion screen, 17 ... Condenser lens, 18 ... Pentadaha prism, 19 ... Eyepiece lens, 20 ... Photometric optical element, 22 ... Photometric lens, 23 ... Photometric sensor, 24 ... Body drive control device

Claims (6)

A photometric means for measuring the field of the photographing optical system;
A focus detection means for detecting a focusing state of the photographing optical system with respect to a plurality of positions of the object scene;
Scene analysis means for repeating scene analysis for recognizing a subject in the object scene based on the output of the photometry means;
A focus calculation unit that repeats a focus calculation to generate a defocus signal of the photographing optical system based on the output of the scene analysis unit and the output of the focus detection unit;
Switching means for switching the repetition rate of the scene analysis between when the focus calculating means performs a focusing operation following the movement of the subject and when performing a focusing operation without following the movement of the subject ;
An imaging apparatus comprising: The imaging device according to claim 1,
The focus calculation means includes
The output of the scene analysis means is reflected on the defocus signal as necessary,
The switching means is
An imaging apparatus, wherein a repetition speed of the scene analysis in a period in which an output of the scene analysis unit is reflected in the defocus signal is made faster than the repetition speed in a period in which the output is not reflected. The imaging device according to claim 2,
The switching means is
An imaging apparatus, wherein a repetition rate of the scene analysis in a period in which an output of the scene analysis unit is reflected in the defocus signal is set to a high speed equal to or higher than a repetition speed of the focus calculation in the period. In the imaging device according to claim 2 or 3,
The switching means is
The imaging apparatus characterized in that, even during a period in which the output of the scene analysis means is reflected in the defocus signal, the speeding up is refrained during a non-operation period of the release button of the imaging apparatus. In the imaging device according to any one of claims 2 to 4,
The switching means is
In the speeding-up, the scene analysis repetition speed is set to a speed that is not easily affected by illumination flicker of the object scene. In the imaging device according to any one of claims 1 to 5,
The switching means is
The imaging apparatus characterized in that the repetition speed of the focus calculation during the operation period of the release button of the imaging apparatus is made faster than the repetition speed of the focus calculation during the non-operation period.