JP2008102275A - Camera system - Google Patents

Abstract

An optimum control method can be switched according to the drive characteristics of a focus lens of an interchangeable lens, and high-speed and accurate autofocus control can be performed.
Communication between a camera body and an interchangeable lens enables communication of the control width of the interchangeable lens at a constant speed to the camera body. When the camera body 1 obtains a control width at the time of constant speed control of the interchangeable lens 2, it becomes possible to recognize the drive characteristics of the focus lens 21 of the interchangeable lens 2. As a result, the camera body 1 performs autofocus control by an optimal control method at the time of autofocus, and a camera system with a short time until accurate focusing is obtained.
[Selection] Figure 1

Description

  The present invention relates to a camera system used in an interchangeable lens or a camera.

  In general, a TTL phase difference method is often employed as an autofocus mechanism mounted on a single-lens reflex camera. In this method, a defocus detection mechanism for autofocus is provided in the camera body, and focusing is performed by driving and controlling the focus lens of the interchangeable lens according to the detected defocus amount. In this case, since the drive amount from the current focus lens position to the in-focus position can be obtained by calculation, driving to the target position of the focus lens must be quick and accurate so that autofocus can be performed quickly. Is required.

  As another method, for example, a so-called TVAF method is used in a digital camera or a video camera as disclosed in Patent Document 1. In this TVAF system, in an electronic image pickup apparatus having a two-dimensional image pickup device, the sharpness of the screen is detected from the video signal of the subject, and the focus lens is controlled to focus so that the sharpness is maximized. This sharpness detection method uses the intensity of the high-frequency component of the video signal extracted by the bandpass filter, or the detection intensity of the blur width at the edge of the subject obtained by differentiating the video signal by a differentiation circuit or the like. It is done.

  When a normal subject is photographed, the sharpness is small when the subject is out of focus, increases as the subject is in focus, and reaches a maximum value when the subject is completely in focus. The so-called hill-climbing AF is generally used to move the focus lens in the direction in which the sharpness increases when the sharpness is small, and gradually decrease this speed as the sharpness increases and stop the focus lens accurately at the top of the sharpness mountain. It is used.

  Further, full scan AF is used as another control means. In this method, the focus lens position is gradually moved from the near end to the infinite end before the main shooting, the subject is shot each time, and the sharpness obtained by passing the multiple images through the sharpness detection means is the most. A focus lens position where an image with a high sharpness is obtained is defined as a focus point.

  Control of the focus lens in these hill-climbing and scan-type autofocuses requires that a certain amount of drive be accurately driven within a certain time rather than the speed. Further, it is not always necessary to stop the focus lens during the detection of the sharpness, and accurate focus detection can be performed by driving it stably at a constant speed.

  Thus, the required driving characteristics of the focus lens differ in the TTL phase difference method, the hill-climbing method, and the scan method autofocus. In order to satisfy these different characteristics, an automatic focusing apparatus provided with two actuators having different characteristics is known, for example, as in Patent Document 2.

JP 2004-198715 A JP 2004-219581 A

  However, in the conventional example, there is an increase in cost such as providing two actuators, and there is a problem of increasing the size in order to secure a mounting space, which is difficult to implement.

  An object of the present invention is to provide a camera system capable of high-speed and accurate autofocus control by enabling switching of an optimal control method in accordance with the drive characteristics of a focus lens of an interchangeable lens.

  In order to achieve the above object, the technical feature of the camera system according to the present invention is that, in the camera system configured to be able to communicate between the interchangeable lens and the camera body, the interchangeable lens includes a focus lens, a drive unit for the focus lens, A control means for controlling the speed of the focus lens based on focus lens speed information transmitted from the camera body by communication, and a communication means for communicating information on the control width of the controllable speed to the camera body. The camera body is communicated with the interchangeable lens by communication means for enabling communication of drive amount information for driving the focus lens, autofocus control means for performing autofocus, and transmitted from the interchangeable lens by communication. In addition, based on the information on the control width of the speed, the replacement level during the autofocus is In that a control switching means for switching the control of FIG.

  According to the camera system of the present invention, it is possible to recognize the drive characteristics of the focus lens of the interchangeable lens by obtaining the control width of the interchangeable lens at the time of constant speed control. In addition, the camera body performs autofocus control by an optimal control method during autofocus, and the time required for accurate focusing is shortened.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a block circuit configuration diagram of the first embodiment. An interchangeable lens 2 is detachably attached to the camera body 1, and a camera electrical circuit unit 11 and a power source 12 are provided in the camera body 1. An in-camera CPU 13 is provided in the camera electrical circuit unit 11, and a photometry unit 14, a distance measurement unit 15, a shutter 16, an image sensor 17, a display unit 18, and a communication unit 19 are connected to the in-camera CPU 13.

  The power supply 12 operates the camera system, and the photometry unit 14 measures the amount of light that has passed through the interchangeable lens 2. The distance measuring unit 15 is composed of a CMOS sensor or the like, measures the defocus amount to the subject based on the image output of the image sensor 17 by the subject imaged by the interchangeable lens 2, and the shutter 16 is suitable for the image sensor 17. Time exposure. The in-camera CPU 13 controls the system in the camera body 1 and the display means 18 displays various information of the camera. The communication means 19 performs serial communication with the interchangeable lens 2.

  In the interchangeable lens 2, an optical system including a focus lens 21, a zoom lens 22, and a diaphragm 23 is provided. The lens electrical circuit unit 24 in the interchangeable lens 2 is provided with an in-lens CPU 25, and a lens drive control unit 26, an aperture control unit 27, and a communication means 28 are connected thereto. Further, a zoom brush 29, a zone brush 30, and an A / M switch 31 are connected to the lens CPU 25.

  The lens drive control unit 26 moves the focus lens 21 via the lens drive motor 32, and the output of the pulse generation means 33 that outputs a pulse signal along with this movement is connected to the in-lens CPU 25. The diaphragm control unit 27 performs drive control of the diaphragm 23 via the diaphragm drive motor 34. The communication unit 28 performs serial communication with the communication unit 19 of the camera body 1. The zoom brush 29 detects the position of the zoom lens 22, and the zone brush 30 detects the position of the focus lens 21. The A / M switch 31 switches between auto focus and manual focus.

  FIG. 2 is a flowchart of the autofocus operation according to the first embodiment.

  Step S101: The processing on the camera body 1 side is started.

  Step S102: Distance measurement is performed by the distance measuring unit 15 in the camera body 1.

  Step S103: If it is determined that the in-focus state is obtained as a result of the distance measurement in step S102, the process proceeds to step S116, and the autofocus process in this embodiment is terminated. If not in focus, the process proceeds to step S104.

  Step S104: If a subject is detected by the distance measurement in step S102, the process proceeds to step S105. If not detected, the process proceeds to step S112.

  Step S105: The in-camera CPU 13 calculates the defocus amount from the distance measurement result in step S102 to the subject by calculation, and further calculates the drive amount of the focus lens 21 from the calculated defocus amount.

  Step S106: Information on the speed control width when the focus lens 21 is driven and controlled at a constant speed from the communication means 28 of the interchangeable lens 2 via the communication means 19 is acquired by communication.

  Here, the speed control width is a value indicating how much the control can be performed with respect to the specified speed. In step S106, for example, the control with a percentage of the specified speed is performed. Data indicating whether or not to perform is acquired by communication. As shown in FIG. 3, the control means in the lens performs control so as to drive the lens at a specified speed, but the actual speed has a certain width, which is the control width. This is because there are errors and widths in speed detection depending on the resolution of the encoder and timer used to detect the speed, and the value that is recognized as the specified speed to prevent control oscillation. This is because the width is given to some extent. The range of control varies depending on the ability of the microcomputer to perform control.

  Step S107: The accuracy of the speed control when the focus lens 21 is driven at a constant speed based on the speed control width information acquired in step S106 is more than a predetermined reliability even when the distance measurement is performed during driving. Judge whether the degree can be obtained. If it is determined that the accuracy is high, the process proceeds to step S109. If it is determined that the precision is low, the process proceeds to step S108.

  Step S108: Since it is determined in step S107 that the accuracy of control during constant speed driving is low, the focus lens 21 is stopped a predetermined amount before the target position calculated in step S105.

  Specifically, a command to drive the interchangeable lens 2 by a drive amount that is a predetermined amount smaller than the drive amount of the focus lens 21 calculated in step S105 is transmitted. Here, the predetermined amount is an amount within a permissible circle of confusion that cannot be recognized even if it is deviated from the in-focus position. The reason for stopping the vehicle by a predetermined amount before the target position is that when the driving amount is the same as the target position, there is a possibility that the target position may be passed due to an error during distance measurement.

  If the target position is passed, the next focus lens 21 is driven in the reverse direction with respect to the previous drive direction, so that the stop position accuracy may be deteriorated due to the influence of mechanical backlash and the like. In order to avoid this problem, the vehicle is stopped at a position close to the target position. In this way, even when the focus lens 21 is driven at the next distance measurement, the direction is the same as the previous driving direction, so that there is no error due to mechanical backlash and the like, and an accurate stop position accuracy can be obtained.

  Step S109: Since it is determined in step S107 that the accuracy during constant speed driving is high, the focus lens 21 is driven by the driving amount calculated in step S105. Specifically, a drive command to drive the interchangeable lens 2 by the drive amount of the focus lens 21 calculated in step S105 is transmitted. The interchangeable lens 2 that has received the drive command is driven by a designated drive amount from the current position of the focus lens 21.

  The interchangeable lens 2 performs acceleration control until the focus lens 21 starts driving until reaching a constant speed, and when the constant lens speed is reached, the focus lens 21 is driven within the control width of the speed transmitted to the camera body 1 side by communication in step S106. Control the speed. Thereafter, when approaching the target position, deceleration control is performed and the vehicle stops at the target position.

  Step S110: It is determined whether or not the focus lens 21 started to be driven in Step S109 or Step S115 described later is being driven at a constant speed. Specifically, the determination is performed by communicating with the interchangeable lens 2 and receiving data indicating whether or not driving at a constant speed. If driving at a constant speed, the process returns to step S102, and if accelerating or decelerating, the process proceeds to step S111.

  If it is determined that the constant speed driving is being performed, the process returns to step S102, which is a so-called overlap control. Although this is a known technique, a detailed description is omitted, but this is a control method for improving the distance measurement accuracy by performing distance measurement again at a position closer to the target while the focus lens 21 is being driven. However, since the distance is measured while the focus lens 21 is being driven, a large error occurs in the distance measurement result if the drive speed of the focus lens 21 is not constant. Therefore, in Example 1, the control accuracy at a constant speed of the interchangeable lens 2 is determined in Step S107 or Step S113, and the overlap control is prohibited if the accuracy is not greater than a predetermined value.

  Step S111: It is determined whether or not the driving of the focus lens 21 is finished. Specifically, the determination is made by communicating with the interchangeable lens 2 and communicating information indicating whether or not the focus lens 21 is being driven. If the driving of the focus lens 21 has been completed, the process returns to step S102.

  Step S112: The processing from step S112 to S115 is processing when the subject is not detected in step S104. In step S112, as in the process of step S106, information on the speed control width when the interchangeable lens 2 is driven and controlled at a constant speed is obtained through communication via the communication means 19 with the interchangeable lens 2.

  Step S113: Similar to the processing in step S107, the accuracy of speed control when the interchangeable lens 2 is driven at a constant speed can be obtained with a certain degree of reliability even when distance measurement is performed during lens driving. Determine whether or not. If it is determined that the accuracy is high, the process proceeds to step S115. If it is determined that the precision is low, the process proceeds to step S114, and the control of the interchangeable lens 2 is switched.

  Step S114: Since it is determined in step S113 that the accuracy of speed control during constant speed driving is low, the focus lens 21 is driven by a predetermined amount. Specifically, the focus lens 21 is driven by an amount corresponding to the maximum defocus amount that can be measured by the distance measuring unit 15 in the camera body 1.

  Step S115: Since it is determined in step S113 that the accuracy of speed control is high, the focus lens 21 is driven at a constant speed. Specifically, after transmitting information specifying the driving speed to the interchangeable lens 2 by communication, a command for driving the focus lens 21 at a constant speed in a certain direction is transmitted.

  By this communication, the interchangeable lens 2 starts driving the focus lens 21 at a specified driving speed in a specified direction. The interchangeable lens 2 performs acceleration control until the focus lens 21 starts driving until reaching a constant speed. When the constant lens reaches the constant speed, the communication of the focus lens 21 is performed within the control width of the speed transmitted to the camera body 1 side by communication in step S112. Control drive speed. After that, when approaching the end of the control width, deceleration control is performed and the end stops.

  Step S116: Since it is determined in step S103 that the focus is achieved, the autofocus process in the embodiment is terminated.

  Thus, in this embodiment, when performing autofocus by the TTL phase difference method, the accuracy of speed control when the interchangeable lens 2 is driven at a constant speed is transmitted to the camera body 1 by communication. On the camera body 1 side, it is determined from this information whether so-called overlap control is performed.

  Thereby, when the control accuracy at the time of constant speed driving is high, the ranging accuracy in the overlap control is improved, and the focus lens 21 can be driven to the in-focus position by one driving. Further, when the control accuracy is poor, the overlap control is prohibited, the focus lens 21 is controlled to stop before the target position, and the control is performed while avoiding the reverse driving of the focus lens 21 as much as possible. I have to. Thereby, the influence of errors such as machine backlash can be eliminated, and accurate stopping accuracy can be ensured.

  When autofocus control is performed using so-called TVAF, it is possible to operate with an optimum driving method according to the driving characteristics of the interchangeable lens 2. For this reason, in the interchangeable lens 2 with high accuracy of speed control during constant speed driving while maintaining the focusing accuracy in all the interchangeable lenses 2, it is possible to further shorten the time until focusing.

  In the first embodiment, the autofocus control is performed by the TTL phase difference method, but in the second embodiment, the autofocus control is performed by so-called TVAF. FIG. 4 is a flowchart of the autofocus operation according to the second embodiment.

  Step S201: The processing on the camera body 1 side is started.

  Step S202: The focus lens 21 is driven to the initial position.

  Step S203: A sharpness signal at the initial position of the focus lens 21 is detected and stored. Also, the initial position of the focus lens 21 is stored.

  Step S204: Information on the speed control width when the focus lens 21 is driven and controlled at a constant speed is obtained through communication via the communication means 19 with the interchangeable lens 2.

  Step S205: The speed control accuracy when the focus lens 21 is driven at a constant speed based on the speed control width information obtained in step S204 is also present when the sharpness signal is detected during lens driving. It is determined whether or not a certain degree of reliability is obtained. If it is determined that the accuracy is high, the process proceeds to step S206. If it is determined that the precision is low, the process proceeds to step S213, and the control of the interchangeable lens 2 is switched.

  Step S206: Since it is determined in step S205 that the accuracy of speed control is high, the focus lens 21 is driven at a constant speed. Specifically, after transmitting information specifying the driving speed to the interchangeable lens 2 by communication, a command for driving the focus lens 21 at a constant speed in a certain direction is transmitted.

  By this communication, the interchangeable lens 2 starts driving the focus lens 21 at a specified drive speed in a specified direction. After the focus lens 21 starts to be driven, the interchangeable lens 2 performs acceleration control until the speed reaches a constant speed. When the speed reaches the constant speed, the focus lens 21 is driven within the control width of the speed transmitted to the camera body 1 through the communication in step S204. Control the speed. After that, when approaching the end of the control width, deceleration control is performed and the end stops.

  Step S207: It is determined whether the focus lens 21 started to be driven in step S206 is accelerating or decelerating. Specifically, the determination is made by communicating with the interchangeable lens 2 and receiving data indicating whether the vehicle is accelerating or decelerating. If it is determined that the vehicle is accelerating or decelerating, it waits until the acceleration and deceleration are completed. If it is determined that acceleration and deceleration are complete, the process proceeds to step S208.

  Step S208: When the vehicle is decelerating, it is determined whether the focus lens 21 has stopped at the closest end or the infinite end after the end of deceleration. If it is determined that the focus lens 21 has stopped at the lens end, the process proceeds to step S219, otherwise the process proceeds to step S209.

  Step S209: Since it is determined that the state of the focus lens 21 is not stopped at the lens end in step S208, the focus lens 21 is being driven at a constant speed. Furthermore, since it is determined in step S205 that the accuracy of control at a constant speed is sufficiently high, the sharpness signal is detected while the focus lens 21 is being driven.

  Step S210: The sharpness signal detected in step S209 is compared with the sharpness signal stored previously. If the sharpness signal detected in step S209 is larger than the sharpness signal stored previously, the process proceeds to step S211. If the sharpness signal is less than the previously stored sharpness signal, the process proceeds to step S212.

  Step S211: The sharpness signal detected in the current step S209 is stored, and the position of the focus lens 21 at the time when the sharpness signal is detected is also stored.

  Step S212: It is determined whether or not a predetermined time has elapsed since the sharpness signal was detected in step S209. If the predetermined time has elapsed, the process returns to step S207, and if not, the process waits until it elapses. Here, the predetermined time is a time during which the focus changes by a predetermined amount within the permissible circle of confusion when the focus lens 21 is driven at a constant speed.

  As described above, by performing the processing from step S207 to S212, the largest sharpness signal can be stored between the initial position of the focus lens 21 and the lens end position, and the lens position at that time can also be stored. it can. In addition, since the overlap control can be performed while the focus lens 21 is driven to detect the sharpness signal, the operation is smoother and the time can be shortened than when the sharpness signal is acquired by repeating small driving.

  Step S213: Since it is determined in Step S205 that the control at a constant speed cannot maintain the accuracy exceeding the predetermined level, the focus lens 21 is driven by a predetermined amount. Here, the predetermined amount is a driving amount in which the focus changes by a predetermined amount within the allowable confusion circle diameter.

  Step S214: It is determined whether or not the lens driven in step S213 has been driven. Specifically, the determination is made by communicating with the interchangeable lens 2 and communicating information indicating whether or not the focus lens 21 is being driven. If the driving of the focus lens 21 has been completed, the process proceeds to step S215.

  Step S215: The driving of the focus lens 21 is finished, and it is determined whether or not the stopped position is the closest end or the infinite end. If it is the close end or the infinite end, the process proceeds to step S219, and if it is not the lens end, the process proceeds to step S216.

  Step S216: A sharpness signal is detected.

  Step S217: The sharpness signal detected in step S216 is compared with the sharpness signal previously stored. If the sharpness signal detected in step S216 is larger than the sharpness signal stored previously, the process proceeds to step S218, and if it is less, the process returns to step S213.

  Step S218: The sharpness signal detected in the current step S216 is stored, and the current position of the focus lens 21 is stored.

  From these steps S213 to S218, the minute driving of the focus lens 21 and the detection of the sharpness signal are repeatedly performed to store the lens position where the maximum sharpness signal is detected from the initial lens position to the lens end position. can do.

  Step S219: The focus lens 21 is driven to the lens position stored in the processing in steps S207 to S212 or the processing in steps S213 to S218. As a result, the focus lens 21 is driven to the position where the sharpness signal is the largest, and the focus can be adjusted.

  Step S220: The focusing operation using TVAF is terminated.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

1 is a block circuit configuration diagram of Embodiment 1. FIG. FIG. 5 is a flowchart of the autofocus operation according to the first embodiment. It is explanatory drawing of the control width | variety of speed. FIG. 10 is a flowchart of the autofocus operation according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera main body 2 Interchangeable lens 11 Camera electric circuit part 12 Power supply 13 CPU in camera
DESCRIPTION OF SYMBOLS 14 Photometry part 15 Distance measurement part 16 Shutter 18 Display means 19, 28 Communication means 21 Focus lens 22 Zoom lens 23 Aperture 24 Lens electric circuit part 25 In-lens CPU
26 Lens Drive Control Unit 27 Aperture Control Unit 32 Lens Drive Motor 33 Pulse Generation Means

Claims (5)

  In the camera system configured to be communicable between the interchangeable lens and the camera body, the interchangeable lens includes a focus lens, a driving unit for the focus lens, and the focus lens speed information transmitted from the camera body by communication. A control unit configured to control the speed of the focus lens; and a communication unit configured to communicate information about a control range of a controllable speed to the camera body, wherein the camera body drives the interchangeable lens to drive the focus lens Communication means for enabling communication of information, autofocus control means for performing autofocus, and the exchange at the time of autofocus based on the control width information transmitted by communication from the interchangeable lens And a control switching means for switching the control of the lens. Temu.   The communication unit of the interchangeable lens communicates information on the control range of the speed that can be controlled when the speed control is performed so that the focus lens has a constant speed to the camera body. Camera system.   The communication means of the camera body includes a command for driving the focus lens at a constant speed, a command for driving the focus lens by a certain amount, speed information for designating a speed of the focus lens, and a drive amount of the focus lens. The camera system according to claim 1, wherein specified drive amount information is communicated to the interchangeable lens.   An interchangeable lens comprising the camera system according to claim 1.   A camera comprising the camera system according to claim 1.

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