JP2009258308A - Lens interchangeable type digital camera system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high-speed AF in a lens interchangeable type digital camera system. <P>SOLUTION: A controlling/processing part 11 of a camera body 10 collects information of a lens unit 20 mounted in the camera body 10 by means of a lens information collection part 25, and obtains an AF evaluated value threshold for deciding a decrease amount of the AF evaluated value for determining whether it exceeds a peak of the AF evaluated value necessary for AF, obtained by an AF evaluated value output part 13 from output of an imaging device 12 from the information of the lens unit 20 acquired through a communication part 26 on a lens side and a communication part 16 on a camera side, thereby lessening a moving amount of a focus lens necessary to detect that the decrease amount of the AF evaluated value exceeds the threshold, and achieving high-speed AF. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an interchangeable lens digital camera system having an autofocus function.

  Conventionally, a TTL (Through The Lens) phase difference AF is used as an autofocus (AF) mechanism of a still camera of a single-lens reflex type (hereinafter, simply referred to as a single lens reflex) of a lens interchangeable type. . This phase difference AF mechanism is provided with a dedicated mechanism for detecting a focal position deviation in the camera body, and a focus adjustment lens (focus lens) in the interchangeable lens unit is detected based on the focal deviation amount detected by the mechanism. ) Is determined.

  On the other hand, compact digital cameras, video cameras, and the like often use so-called imager AF that uses contrast information of an image sensor as disclosed in Patent Document 1, for example. The imager AF is also called a hill-climbing detection method. While moving the focus lens of the lens unit in the optical axis direction, the AF evaluation value, for example, a high frequency component of contrast is repeatedly detected, and the peak position at which the AF evaluation value becomes maximum is adjusted. Determine as the focal position.

  The TTL phase difference AF and the imager AF have features such as, for example, the TTL phase difference AF is focused at a higher speed, and the imager AF is focused at a higher accuracy. .

Even with interchangeable-lens digital single-lens reflex cameras, the mirror that guides light to the optical viewfinder and phase difference AF sensor is retracted, images are continuously captured by the image sensor, and images are displayed in real time on the LCD monitor on the back of the camera. Imager AF can be performed while looking at a liquid crystal monitor like a digital camera.
JP-A-8-265631

  However, unlike a compact digital camera, an interchangeable lens camera is equipped with lenses having various characteristics, so that the difference in lens characteristics greatly varies the shape of the AF evaluation value.

  For example, the shape of the AF evaluation value is related to the depth of the lens, and as shown in FIG. 8, the shape of the AF evaluation value becomes steeper as the lens depth is shallower. As parameters affecting the lens depth, as shown in FIG. 9, there are an F value, a focal length, a subject distance, an image magnification, and the like.

  In the imager AF, when the relationship between the previous AF evaluation value and the current AF evaluation value exceeds a predetermined determination value (threshold), for example, when the change rate exceeds a predetermined change rate, When the difference between the two exceeds a predetermined difference, a quadratic approximate curve is drawn from, for example, three points of data including the maximum value of the AF evaluation value detected up to that point, and the peak position of the quadratic approximate curve Is used to determine the in-focus position with the AF evaluation value being maximized.

  Therefore, for example, in the case of detecting the change ratio, when the lens depth is shallow and the shape of the AF evaluation value is steep, the change ratio Y1 / Y2 is a threshold value as shown in FIG. When the focus lens movement necessary to detect that the distance exceeds the limit is ΔX1, but the depth of the lens is deep and the shape of the AF evaluation value is gentle, as shown in FIG. In addition, the focus lens movement necessary to detect that the change ratio Y3 / Y4 exceeds the threshold value is ΔX2. As described above, when the depth of the lens is deep and the shape of the AF evaluation value is gentle, the amount of movement of the focus lens increases, and it takes time from the start of lens driving to the calculation of the peak position. I couldn't focus.

  The present invention has been made in view of the above points, and an object thereof is to provide an interchangeable lens digital camera system capable of performing autofocus at high speed.

One aspect of the interchangeable lens digital camera system of the present invention is a interchangeable lens digital camera system including a camera body and a lens unit that can be attached to and detached from the camera body.
The lens unit is
A focus lens for adjusting the focal position of the lens unit;
Focus lens driving means for driving the focus lens;
Focus lens position output means for outputting the focus lens position;
Lens information recording means for recording information of the lens unit;
Lens side communication means for communicating with the camera body;
Have
The camera body
An image sensor for repeatedly photographing a subject imaged by the lens unit;
Control means for generating a command for controlling the driving of the focus lens of the lens unit;
Camera-side communication means for communicating with the lens unit;
AF evaluation value output means for outputting an AF evaluation value necessary for AF from the output of the imaging device, and
The control means includes
The AF evaluation value output from the AF evaluation value output means is related to the focus lens position output from the focus lens position output means acquired via the lens side communication means and the camera side communication means. A position corresponding to the peak of the image is obtained, and the focus lens driving means is controlled via the camera side communication means and the lens side communication means to adjust the focus position to move the focus lens to the peak position, and
A determination value for determining a reduction amount or a reduction ratio of the AF evaluation value for determining that the peak of the AF evaluation value has been exceeded is transmitted from the lens information recording unit via the lens side communication unit and the camera side communication unit. From the information obtained
It is characterized by that.

  According to the present invention, information on the lens unit is acquired from the mounted lens unit, and the determination value depends on the shape (lens depth) of the AF evaluation value corresponding to the predicted focus lens position. Therefore, it is possible to provide an interchangeable lens digital camera system capable of performing autofocus at high speed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a lens interchangeable digital camera system according to an embodiment of the present invention.

  The interchangeable lens digital camera system according to the present embodiment includes a camera body 10 and a lens unit 20 that is detachable from the camera body 10 and can communicate with the camera body 10 side.

  The lens unit 20 includes an optical system 21 including a focus lens 21A and a zoom lens 21B, a focus lens drive unit 22, a focus lens position detection unit 23A, a zoom position detection unit 23B, a lens information recording unit 24, and lens information collection. Part 25 and communication part 26.

  The focus lens 21A is a lens for adjusting the focal position of the lens unit 20. The focus lens 21A is driven by the focus lens driving unit 22, and the focus lens position is detected by the focus lens position detecting unit 23A. The zoom lens 21B is a lens for adjusting the image magnification of the lens unit 20. The zoom lens 21B is manually operated by a user with respect to a zoom ring (not shown) of the lens unit 20 or a user with respect to a zoom button (not shown) provided on the camera body 10. It is driven by a zoom lens drive unit (not shown) according to the operation, and the zoom position is detected by the zoom position detection unit 23B.

  The lens information recording unit 24 is a memory that records information such as the F value and image magnification of the lens unit 20. The lens information collecting unit 25 includes information on the lens unit 20 recorded by the lens information recording unit 24, focus lens position information and zoom position detected by the focus lens position detection unit 23A and the zoom position detection unit 23B. Collect information (focal length information). Thus, the lens information recording unit 24 and the lens information collecting unit 25 function as lens information recording means. The communication unit 26 is a lens side communication unit that performs communication with the camera body 10.

  On the other hand, the camera body 10 includes a control / processing unit 11, an image sensor 12, an AF evaluation value output unit 13, an information collation unit 14, a captured signal generation unit 15, and a communication unit 16.

  The control / processing unit 11 controls each unit in the camera body 10 in accordance with user operations of various buttons and switches (not shown) including a power switch and a release button, and is configured by a CPU, for example. For example, the control / processing unit 11 performs an AF operation in response to a first-stage operation of a release button that is a two-stage push button, a so-called 1ST release operation, and a second-stage operation, a so-called 2ND release operation. Depending on the actual shooting operation.

  That is, in the AF operation, a subject image that has entered through the optical system 21 is converted into an analog video signal by the imaging device 12 such as a CCD or CMOS sensor at a predetermined frame rate, and the analog video is processed by a signal processing circuit (not shown). Predetermined signal processing including conversion of the signal into a digital image signal is performed, and the obtained image signal is displayed on an image display unit (not shown) such as a liquid crystal monitor disposed on the back surface of the camera body 10.

  The image signal is also sent to the AF evaluation value output unit 13 where an AF evaluation value necessary for AF is obtained. As the AF evaluation value, an integrated value in the AF area of the contrast of the image or the high frequency component is used, and the larger the value is, the more the focus is achieved. The information collation unit 14 is a camera-side communication unit and the output of the AF evaluation value output unit 13 at a predetermined timing for acquiring the output of the AF evaluation value output unit 13 generated by the captured signal generation unit 15. The focus lens position obtained by the communication unit 16 is related. Then, the control / processing unit 11 obtains a position corresponding to the peak of the AF evaluation value based on the AF evaluation value and the focus lens position associated with each other by the information collating unit 14, and passes through the communication units 16 and 26. Then, the focus lens drive unit 22 is controlled to adjust the focus position to move the focus lens 21A to the peak position. The control / processing unit 11 generates various commands (commands) and transmits them to the lens unit 20 via the communication units 16 and 26. Further, the control / processing unit 11 collects the information from the lens unit 20 from the lens information recording unit 24 collected by the lens information collecting unit 25 and acquired through the communication units 26 and 16. A determination value for determining an AF evaluation value decrease amount for determining that the evaluation value peak has been exceeded is calculated. Thus, the information collating unit 14, the captured signal generating unit 15, and the control / processing unit 11 function as control means.

  The operation of the interchangeable lens digital camera system configured as described above will be described in detail below.

  In the present embodiment, an AF operation using a hill-climbing detection method as shown in FIG. 2 is performed. That is, the AF evaluation value output unit 13 extracts and accumulates a predetermined high-frequency component from an image signal repeatedly taken by the image pickup device 12 and given from a signal processing circuit (not shown) by a high-pass filter or the like, thereby integrating the AF evaluation value. create. Here, an AF evaluation value obtained at a position where the focus lens position is x is Y (x). The AF evaluation value, which is the level of the high-frequency component of the image signal, rapidly increases as the sharpness of the image formed on the image sensor 12 increases, that is, as the focus lens 21A approaches the in-focus state. The peak is reached when the image is in focus. Accordingly, the AF evaluation value Y (x) is associated with the focus lens position x by the information matching unit 14 while moving the focus lens 21A, and the control / processing unit 11 focuses when the AF evaluation value is increased. When it is determined that the lens 21A is moving in the direction approaching in-focus, and conversely, when the level of the selected frequency component is decreasing, the focus lens 21A is moving in a direction away from the in-focus. Can be determined.

  Therefore, the control / processing unit 11 first instructs the focus lens driving unit 22 via the communication units 16 and 26 to move the focus lens 21A in a direction approaching the in-focus state.

  After that, the maximum value (peak) of the AF evaluation value is detected. That is, the top of the mountain is determined based on the amount of change in the AF evaluation value. In other words, the more focused the image is, the more detailed details appear in the image. This indicates that the higher the image is focused, the more high frequency components of the image. The hill-climbing detection method uses this to evaluate AF by evaluating a value obtained by extracting and integrating high-frequency components of an image.

  Here, the lens position (i−1) where Y (i) <Y (i−1) is set as the maximum value of the AF evaluation value. Then, it is determined whether or not the threshold value has been exceeded after detection of the maximum value, that is, whether or not Y (j−1) / Y (j)> threshold value (where j ≧ i). This is because it is not preferable to determine that the peak position has been exceeded because it may be reduced by the influence of noise if it is simply determined that an AF evaluation value smaller than the maximum value is detected. Then, if it is determined that the threshold value is exceeded, the peak position with the lens position at that time (in the example of FIG. 2, Y (j) / Y (j + 1)> threshold value is the lens position (j + 1) when (j + 1)). It is judged that it exceeded. However, if the maximum value condition is not satisfied during the determination of exceeding the threshold value, the maximum value detection is started again. Then, for example, a quadratic approximate curve is drawn from, for example, three points of data including the detected maximum values, and a focus calculation is performed to determine the peak position of the quadratic approximate curve as a focus position where the AF evaluation value is maximized. Is. The control / processing unit 11 instructs the focus lens driving unit 22 to move the focus lens 21A to the in-focus position detected as the peak position.

  In the present embodiment, the AF evaluation value threshold obtained by, for example, the following formula (1) from the information of the lens unit 20 acquired from the lens information recording unit 24 is used as the AF evaluation value threshold in the determination of exceeding the threshold. Use.

AF evaluation value threshold = standard threshold × (standard F value / F value obtained from lens information) × (focal length obtained from lens information / standard focal length) × image magnification obtained from lens information (1)
FIG. 3 is a view showing an operation flowchart of the AF operation of the camera body 10 and the lens unit 20 of the interchangeable lens digital camera system according to the present embodiment, and FIGS. 4A and 4B are timing charts of the AF operation. FIG. Here, the same reference numerals are given to clarify where each process in FIG. 3 corresponds to in the timing charts of FIGS. 4A and 4B.

  That is, first, the control / processing unit 11 of the camera body 10 transmits a lens information collection command to the lens information collection unit 25 by communication with the lens unit 20 by the communication unit 16 (hereinafter referred to as lens communication) (step S1). S101).

  When the lens information collection unit 25 of the lens unit 20 receives the lens information collection command by communication with the camera body 10 by the communication unit 26 (hereinafter referred to as camera body communication) (step S201), the lens information collection unit 25 The lens information collected from the lens information recording unit 24 is transmitted to the camera body 10 by camera body communication (step S202). At this time, the focus lens 21A is in a stopped state.

  The control / processing unit 11 of the camera body 10 acquires the lens information through lens communication (step S102), and calculates an AF evaluation value threshold based on the acquired lens information (step S103). Then, the information collation unit 14 starts to fetch the AF evaluation value from the AF evaluation value output unit 13 and starts the operation of the fetch signal generation unit 15 (step S104). A lens drive start command is transmitted to 22 (step S105). After that, it waits for the AF evaluation value capturing timing (AF evaluation value output timing of the information matching unit 14) based on the capturing signal from the capturing signal generator 15 (step S106).

  When the focus lens drive unit 22 receives the lens drive start command through camera body communication (step S203), the focus lens drive unit 22 drives the focus lens 21A (step S204). Thereby, the focus lens 21A in the stopped state starts to move, and the focus lens position detection unit 23A detects the lens position.

  When the AF evaluation value capture timing comes (step S106), the information collation unit 14 transmits a lens position acquisition command to the lens information collection unit 25 by lens communication (step S107).

  When the lens information collection command is received by camera body communication (step S205), the lens information collection unit 25 collects the focus lens position detected by the focus lens position detection unit 23A at that time, and performs camera body communication. Is transmitted to the camera body 10 (step S206).

  When the information collation unit 14 acquires the focus lens position by lens communication (step S108), the information collation unit 14 records and stores the acquired focus lens position and the AF evaluation value output by the AF evaluation value output unit 13 (step S109). Then, an information matching process for associating the recorded and stored focus lens position with the AF evaluation value is performed (step S110). The control / processing unit 11 determines whether or not the AF evaluation value associated with the focus lens position by the information matching unit 14 exceeds the peak, that is, whether or not the AF evaluation value is smaller than the maximum value of the AF evaluation value. Determination is made (step S111). If it is determined that the peak of the AF evaluation value has not yet been exceeded, the process returns to step S106.

  Actually, as described above, when the AF evaluation value is increasing, the control / processing unit 11 determines that the focus lens 21A is moving in the direction approaching the in-focus state, and vice versa. In addition, when the level of the selected frequency component is decreasing, it is determined that the focus lens 21A is moving away from the focus, and the focus lens 21A is moved in a direction approaching the focus. The instruction is given to the focus lens driving unit 22 via the communication units 16 and 26, but since this is a known operation, it is omitted here for simplification of the drawings and description.

  On the other hand, if it is determined in step S111 that the peak of the AF evaluation value has been exceeded, it is further determined whether or not the AF evaluation value has exceeded the AF evaluation value threshold calculated in step S103 (step S112). If it is determined that the AF evaluation value threshold has not yet been exceeded, for example, the focus lens 21A has been driven to the end of the movable range, or the 1ST release operation of a release button (not shown) has been released. It is determined whether or not the AF operation end condition is satisfied (step S113). If such an end condition is not satisfied, the process returns to step S106. If the end condition is satisfied, the AF operation is ended with an out-of-focus result.

  Thus, if it is determined in step S112 that the AF evaluation value has exceeded the AF evaluation value threshold, the control / processing unit 11 stops the operation of the capture signal generation unit 15 and associates it with the information collation unit 14. An in-focus focus position is obtained by performing a known peak position calculation process based on the focus lens position and the AF evaluation value (step S114). Then, a lens drive stop command is transmitted to the focus lens drive unit 22 by lens communication (step S115).

  When receiving the lens drive stop command through the camera body communication (step S207), the focus lens drive unit 22 stops driving the focus lens 21A (step S208).

  Then, the control / processing unit 11 transmits a lens driving command to the calculated peak position by the lens communication to the focus lens driving unit 22 (step S116), and ends the AF operation.

  When the focus lens drive unit 22 receives a lens drive command to the peak position through camera body communication (step S209), the focus lens drive unit 22 drives the focus lens 21A to the peak position, that is, the in-focus focus position (step S210). End the operation.

  As described above, according to the present embodiment, information on the lens unit 20 is acquired from the mounted lens unit 20 and depends on the shape (lens depth) of the AF evaluation value with respect to the predicted focus lens position. An AF evaluation value threshold is set. Therefore, for example, when the lens unit 20 is mounted so that the depth of the lens is deep and the shape of the AF evaluation value becomes gentle, the AF evaluation value threshold is set to a value where the lens depth is shallow and the shape of the AF evaluation value is low. By setting an optimum AF evaluation value threshold according to the lens unit 20 to be mounted, such as setting smaller than a steep case, it is detected that the AF evaluation value reduction amount exceeds the threshold. It is possible to reduce the amount of movement of the focus lens necessary for autofocusing and to perform autofocus at high speed.

  In the above-described embodiment, the AF evaluation value threshold is obtained with respect to the ratio of the AF evaluation values. However, it is obvious that the same effect can be obtained by providing the AF evaluation value threshold for the difference value.

  In addition, as information of the lens unit 20 acquired from the lens information recording unit 24 in order to set an AF evaluation value threshold, the F value, zoom position (focal length), image magnification, and the like of the lens unit 20 are given as examples. However, other information may be used.

  For example, as shown in FIG. 5, the MTF characteristic of the lens differs depending on the F value, and the lens MTF characteristic differs between the center and the periphery of the AF area, so it is desirable to change the AF evaluation value threshold. . As shown in FIG. 6, the AF area value A in FIG. 5 is the center area 18A of the shootable area 17, and the AF area value B in FIG. It is.

  Therefore, for example, if the MTF information of the lens as shown in FIG. 7 is recorded in the lens information recording unit 24 as one of the information of the lens unit 20, the AF evaluation value threshold value is used by using the MTF information of the lens. Can be changed.

  Similarly, lens aberration information may also be recorded in the lens information recording unit 24 as one piece of information of the lens unit 20 and used to change the AF evaluation value threshold.

  Further, instead of individually recording the F value, image magnification, MTF information, aberration information, etc. of the lens unit 20 as described above in the lens information recording unit 24, ID information that can identify the lens unit 20 is recorded. In addition, the above information for each ID information may be stored on the camera body 10 side. Even in this way, on the camera body 10 side, based on the ID information acquired from the lens unit 20, the information corresponding to the ID information can be selected and the AF evaluation value threshold value can be calculated.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

FIG. 1 is a diagram showing a configuration of a lens interchangeable digital camera system according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the hill climbing control of the AF operation. FIG. 3 is a diagram showing an operation flowchart of the AF operation of the camera body and the lens unit. FIG. 4A is a diagram illustrating a first part of a series of timing charts of the AF operation. FIG. 4B is a diagram illustrating a second part of a series of timing charts of the AF operation. FIG. 5 is a diagram showing the MTF characteristics of the lens. FIG. 6 is a diagram showing a shootable area and an AF area. FIG. 7 is a diagram illustrating an example of lens MTF information recorded in the lens information recording unit as one piece of information of the lens unit. FIG. 8 is a diagram illustrating the relationship between the depth of the lens and the shape of the AF evaluation value. FIG. 9 is a diagram illustrating parameters that affect the depth of the lens. FIG. 10A shows a focus lens movement amount necessary to detect that the amount of decrease in the AF evaluation value exceeds the threshold when the depth of the lens is shallow and the shape of the AF evaluation value is steep. FIG. 10B shows the amount of movement of the focus lens necessary for detecting that the amount of decrease in the AF evaluation value exceeds the threshold when the depth of the lens is deep and the shape of the AF evaluation value is gentle. FIG.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 10 ... Camera body, 11 ... Control / processing part, 12 ... Image pick-up element, 13 ... AF evaluation value output part, 14 ... Information collation part, 15 ... Capture signal generation part, 16, 26 ... Communication part, 17 ... Shootable area 18A ... Central region, 18B ... Peripheral region, 20 ... Lens unit, 21 ... Optical system, 21A ... Focus lens, 21B ... Zoom lens, 22 ... Focus lens drive unit, 23A ... Focus lens position detection unit, 23B ... Zoom position detection unit, 24 ... lens information recording unit, 25 ... lens information collection unit.

Claims (2)

An interchangeable lens digital camera system comprising a camera body and a lens unit that can be attached to and detached from the camera body,
The lens unit is
A focus lens for adjusting the focal position of the lens unit;
Focus lens driving means for driving the focus lens;
Focus lens position output means for outputting the focus lens position;
Lens information recording means for recording information of the lens unit;
Lens side communication means for communicating with the camera body;
Have
The camera body
An image sensor for repeatedly photographing a subject imaged by the lens unit;
Control means for generating a command for controlling the driving of the focus lens of the lens unit;
Camera-side communication means for communicating with the lens unit;
AF evaluation value output means for outputting an AF evaluation value necessary for AF from the output of the imaging device, and
The control means includes
The AF evaluation value output from the AF evaluation value output means is related to the focus lens position output from the focus lens position output means acquired via the lens side communication means and the camera side communication means. A position corresponding to the peak of the image is obtained, and the focus lens driving means is controlled via the camera side communication means and the lens side communication means to adjust the focus position to move the focus lens to the peak position, and
A determination value for determining a reduction amount or a reduction ratio of the AF evaluation value for determining that the peak of the AF evaluation value has been exceeded is transmitted from the lens information recording unit via the lens side communication unit and the camera side communication unit. From the information obtained
This is an interchangeable lens digital camera system.   The information of the lens information recording unit used by the control unit to obtain the determination value includes any one of F value, zoom position, image magnification, MTF, or aberration of the lens unit. The interchangeable lens digital camera system according to claim 1.

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