JP4630649B2 - camera - Google Patents

Description

  The present invention relates to a camera to which a photographic lens device can be attached and detached, and in particular, has a focus (focus position) detection function on the camera side and has lens drive control means on the photographic lens device side. The present invention relates to a camera that can be connected to communicate with each other.

As a detection method of the focus adjustment state for the automatic focus adjustment function (AF system), there are a phase difference detection method and a contrast detection method.
The AF system based on the phase difference detection system generally operates as follows.
That is, the light incident from the photographing lens is reflected downward by the sub-mirror attached to the back of the semi-transmissive main mirror disposed at an inclination of 45 degrees with respect to the photographing optical axis, and is reflected by the lens of the secondary optical system. It is separated into two images and enters a pair of AF sensors. The pair of AF sensors are arranged side by side, and the in-focus state, the front pin state, and the rear pin state are determined based on the difference between the two images formed on the pair of AF sensors. Then, focusing is performed by moving the focus adjustment lens (focus lens) so that the image interval becomes the in-focus interval. That is, since the relationship between the shift amount of the two images and the image plane movement amount (defocus amount) is determined by the optical system, the defocus amount is obtained from the shift amount. Then, a lens extension amount is obtained from the defocus amount and lens specific information (sensitivity coefficient, open FNo, etc.), and the focus adjustment lens is moved to obtain in-focus.

On the other hand, there is a perturbation method (a wobbling method) as one type of contrast detection method, and an AF system based on this perturbation method generally operates as follows.
The AF system includes an image pickup system including a two-dimensional image pickup device, a system control unit including a signal generation unit that generates a control signal for the arithmetic unit and the lens, and a lens control unit for moving the lens in the optical axis direction. And a lens part including. First, image light is captured in the imaging system, output as an imaging signal, sent to the system control unit, and a high-frequency component included in the imaging signal is extracted there. Then, the maximum value of the extracted signal is stored, the focus adjustment lens is moved in a certain direction, image light is taken in the same way, and high frequency component extraction is performed. At this time, if the maximum value of the extracted signal is larger than the previously stored value, it is assumed that the moving direction of the focus adjustment lens is approaching the in-focus plane, the current value is stored again, and the focus adjustment lens Are moved in the same direction. Also, if the maximum value of the current extraction signal is smaller than the previous value, it is assumed that the moving direction of the focus adjustment lens is moving away from the in-focus plane, the current value is stored again, and the focus adjustment lens is Is moved in the opposite direction, and the image light is taken in the same way, high frequency components are extracted and the maximum values are compared, and finally the image plane is brought to the focal plane. Here, it has been explained that the lens movement direction is determined by moving the lens only once and comparing the maximum value of the extracted signal before and after the movement. However, in order to increase the reliability of the data, the above operation is actually performed. The lens moving direction is determined repeatedly several times.

  As a single-lens reflex type camera that captures an image on a silver salt film, a single-lens reflex type camera that has an automatic focusing function (AF system) and includes a photographing lens that can be exchanged for the camera is widely used. In a single-lens reflex camera, a phase difference detection method is often used as a detection method of a focus adjustment state of a photographing lens with an emphasis on AF time.

A configuration example of a single-lens reflex type camera using a phase difference detection method will be described below.
The camera has a communication unit for communicating with the lens, a photometric unit for measuring the amount of light incident through the lens, and a distance measuring unit for measuring the distance (defocus amount) to the subject by the phase difference detection method. A shutter control unit for exposing the film for an appropriate time, a film feeding unit for winding and rewinding the film, a release SW for the release operation, and a control unit for controlling and detecting them. The lens includes a communication unit that communicates with the camera, a lens driving unit that drives the focus lens, an aperture driving unit that drives the aperture, and a control unit that controls these.

  Shooting with the autofocus function setting operates according to the following sequence. When the photographer operates the release SW, the camera performs photometry and distance measurement. From the result, the drive amount of the diaphragm and the drive amount of the focus lens are calculated as described above, and each drive command and drive amount are transmitted to the lens. To do. The lens drives the aperture and focus lens by the received drive amount. The camera then controls the shutter to expose the film for an appropriate time.

However, the AF system has problems in improving AF accuracy and shortening AF time. Further, with the digitalization of cameras, further improvement of AF accuracy is necessary for the following reasons.
In the digital camera, the ratio of the imaging surface corresponding to one pixel of the AF sensor increases due to the difference in the size (area) of the silver salt film and the imaging device, that is, the detection pixel becomes rough and the accuracy decreases. Arise. In order to solve this problem, the magnification of the AF optical system may be decreased, or the pixel pitch of the AF sensor may be reduced. However, the system configuration is strictly accurate and costs high.

For this reason, in a digital camera, an AF system based on a contrast detection method is often used.
An operation sequence of a camera having a contrast detection AF and having a lens drive control unit on the lens side and connected to be communicable will be described below with reference to FIG.
[Step 101] This sequence is started by turning on the main switch of the camera.
[Step 102] It is determined whether or not a release switch provided in the camera body is turned on. If ON, go to Step 103, and if OFF, wait.

[Step 103] A counter that counts the number of times a high-frequency component is extracted from the imaging signal at each focus lens position is initialized to zero.
[Step 104] The image pickup signal output from the image pickup device is taken in, a high frequency component is extracted from the taken image pickup signal, and the extracted high frequency component data is temporarily stored in a memory buffer.
[Step 105] The camera communicates with the lens via the communication circuit to drive the focusing lens in a predetermined direction by a predetermined drive amount, and the lens drives the focusing lens by the received drive amount in the received direction.

[Step 106] The image pickup signal output from the image pickup device is taken in, a high frequency component is extracted from the taken image pickup signal, and the extracted high frequency component data is temporarily stored in a memory buffer.
[Step 107] The counter is incremented by one.
[Step 108] If the counter value is 3, go to Step 110, and if it is less than 3, go to 109.
[Step 109] The camera communicates to the lens via the communication circuit that the focusing lens is driven by a predetermined drive amount in the direction opposite to the direction set in Step 105, and the lens is focused by the received drive amount in the received direction. Drive the lens. Thereafter, the process proceeds to step 104.

[Step 110] In-focus determination is performed from the high-frequency component data stored in Step 104 and Step 106. If it is determined to be in focus, the process proceeds to step 111. If it is determined to be out of focus, the lens driving direction is determined, and the process proceeds to step 103 to perform the above operation again.
[Step 111] The camera controls the shutter, exposes the film for an appropriate time, and completes photographing.
FIG. 5 shows the communication between the camera and the lens and the focusing lens position in the sequence steps 103 to 109 described above.
JP 2003-29135 A

  As described above, in the camera system having the focus detection function on the camera side, the lens drive control means on the lens side, and the camera and the lens connected to be communicable, the focus detection function is based on a contrast detection method (wobbling method). If this is the case, the forward rotation and reversal drive of the focus lens must be repeated frequently, so communication to indicate normal rotation and reversal drive must be performed frequently, and during focus detection operations. Increased communication volume. For this reason, unless a high-performance CPU is installed, it becomes difficult for the control unit of the camera and the lens to perform other controls during this period.

  The present invention has been made based on the above circumstances, has a focus detection function based on a contrast detection method (wobbling method) on the camera side, has lens drive control means on the lens side, and can communicate between the camera and the lens. It is an object of the present invention to reduce the amount of communication during the focus detection operation and perform other function control without hindrance in the camera system connected to.

In order to solve the above problems, in the present invention, an imaging lens device having a focus adjustment lens and a means for driving the focus adjustment lens, and an image pickup means that is detachably and communicably connected to the shooting lens. And a camera body having a focus detection means for detecting a focus position according to a high frequency component extracted from an imaging signal obtained by the imaging means, wherein the camera body is a wobbling of the focus adjustment lens. after the information about the driving amounts and the driving frequency of the drive transmitted to the photographic lens unit, and transmits the instruction to start the wobbling drive of the focusing lens based on the information on the photographic lens unit, the imaging lens system, based on the information, the focus from the timing of receiving completed instruction to start the wobbling drive of the focus adjusting lens Starts wobbling drive of the adjusting lens, the camera body, the high-frequency components from the output of the wobbling drive of the focusing lens does not transmit the effect of stopping, the imaging unit further every timing at which the focusing lens is stopped When the extracted high frequency component is smaller than a predetermined value, the driving amount is set to be larger, and when the extracted high frequency component is larger than the predetermined value, the driving amount is set to be smaller .

  The information regarding the wobbling driving of the focus adjustment lens is, for example, a driving cycle and a driving amount.

  It is preferable that the camera body transmits a message to stop wobbling driving of the focus adjustment lens. However, for example, when the number of times of driving is included in the information related to the wobbling driving of the focus adjustment lens, transmission to stop the wobbling driving of the focusing lens for detecting the in-focus position can be omitted.

According to the present invention, after the camera transmits data related to driving (wobbling driving) (for example, the focus lens driving amount and the driving / stopping cycle), the data received by the lens is transmitted by transmitting a driving start command. By adopting a configuration that drives the focus lens based on the above, it is possible to reduce the amount of communication during the focus detection operation and perform other function control without any trouble.

  In a first preferred embodiment of the present invention, a photographic lens apparatus having a photographic optical system including a focus adjustment lens can be attached and detached, and the cameras are connected so as to communicate with each other, and imaging is performed through the photographic optical system. The focus adjustment lens is moved to the in-focus position according to the result of determination of the focus adjustment state by comparing the high-frequency component extracted from the image pickup signal obtained by the image pickup means in each stop state of the focus adjustment lens. A focus adjustment lens based on the information on the drive after transmitting information (drive period, drive amount) about the drive of the focus adjustment lens from the camera to the photographing lens device. By communicating from the camera to the photographic lens device to start / stop driving, the amount of communication during the focus detection operation can be reduced. It makes it possible it is possible to perform the function control without any trouble.

  In the second preferred embodiment of the present invention, time data required to drive the focus adjustment lens by a predetermined driving amount, or driving amount data that can be driven within a predetermined time is previously acquired from the photographing lens device to the camera. The camera determines information (driving period, driving amount) related to the driving of the focusing lens based on the time data or driving amount data, and determines information related to driving the determined focusing lens (driving period, driving). ) Is transmitted from the camera to the photographing lens device, and then communication is performed from the camera to the photographing lens device to start / stop the driving of the focus adjustment lens based on the information related to the driving. It is possible to reduce the amount of communication and control other functions without hindrance, and to make the best use of the capabilities of the taking lens device. Theft is possible.

Hereinafter, the first embodiment will be described based on examples.
FIG. 1 shows a configuration of a camera system including a digital camera and a photographing lens device according to an embodiment of the present invention. In FIG. 1, reference numeral 100 denotes a camera body, and reference numeral 200 denotes an interchangeable photographic lens device (hereinafter referred to as a photographic lens) that can be attached to and detached from the camera body 100.
In the photographing lens 200, a first lens group 201, a zoom lens group 202, a focus lens group 203, and a diaphragm 204 are provided.
A prism 101 with a fixed half mirror is provided in the camera body 100. A light beam from the subject passes through the lens groups 201 to 203 and the diaphragm 204 and enters the prism 101 in the camera body 100 as a photographing light beam.

  In the photographing lens 200, reference numeral 205 denotes an aperture driving circuit that controls the aperture diameter of the aperture 204 in accordance with a signal from the lens CPU 207. Reference numeral 206 denotes an operation switch, which is provided with a zooming, focusing, manual operation switch for aperture, a setting switch for auto / manual switching of focus, and the like. Reference numeral 207 denotes a lens CPU that exchanges information with the camera CPU (control means) 110 via the lens communication circuit 211 and the camera communication circuit 102 and also controls the entire control within the photographing lens 200. Reference numeral 208 denotes a focus drive circuit, which includes a motor and its drive circuit, and drives the focus lens group 203 in the optical axis direction according to a signal from the lens CPU 207. A focal length detection circuit 209 detects the focal length by detecting the position of the zoom lens group 202. In the present embodiment, the position of the zoom lens is detected by a 32 divided gray code pattern. Reference numeral 210 denotes a storage circuit, which has a ROM. The storage circuit 210 includes the ID (product model number, serial number, etc.) of the photographing lens 200, focal length information, focus sensitivity that is a ratio of the image plane displacement amount to the movement amount of the focus lens group 203 for each focal length, and the like. It is stored and read by the lens CPU 207 as needed.

  Next, in the camera main body 100, the photographing light flux that has passed through the fixed half mirror of the prism 101 forms an image on the imaging surface of the imaging element 107 such as a CCD or CMOS. In the fixed half mirror of the prism 101, a part (for example, 1/3) of the photographing light quantity branches upward and enters the pentaprism 103. The light beam that has passed through the pentaprism 103 passes through the finder optical system 105 and is visually recognized by the photographer as an optical finder image. The image sensor 107 photoelectrically converts incident light and outputs an electrical signal. This output signal is amplified and output to the camera CPU 110 as a digital video signal (imaging signal). The camera CPU 110 uses this video signal to form a moving image or a still image. In addition to the output to the camera CPU 110, the digitized video signal is also output to the AF processing circuit 108 serving as focus detection means.

In the AF processing circuit 108, a high frequency component included in the image data for one screen of the digital video signal is extracted through a high pass filter (HPF) or the like, and cumulative addition calculation processing is performed on the high frequency component. Thereby, an AF evaluation value corresponding to the contour component amount on the high frequency side and the like is calculated, and it is possible to detect the focus adjustment state (hereinafter referred to as in- focus position detection) of the photographing lens 200 by a so-called contrast detection method. The AF evaluation value is output to the camera CPU 110. As described above, the camera body 100 detects the in- focus position of the photographic lens 200 using the contrast detection method.

In the camera main body 100, reference numeral 104 denotes a photometric circuit, which transmits photometric information to the camera CPU 110. Reference numeral 106 has a two-stage switch, and when the first-stage switch is turned on, a signal (SW1 signal) for starting photometry, in- focus position detection, and focus adjustment operation is output, and when the second-stage switch is turned on, imaging by the image sensor 107 is performed. (Exposure) This is a release switch circuit that outputs a signal (SW2 signal) for starting to the camera CPU 110.

  In addition to the communication with the lens CPU 207 described above, the camera PU 110 controls the display circuit 111 that displays an image captured by the image sensor 107, a set shooting condition, a shooting mode, and the like, various shooting conditions, and shooting. It is responsible for various controls on the camera body side, such as control of the input from the setting switch circuit 112 for setting the mode, etc., checking of the remaining capacity of the power source 109, and sharing of power. A video signal memory, various buffer memories, and the like are also included in the camera CPU 110.

Next, an operation sequence of the camera CPU 110 in the contrast detection AF used in the camera will be described with reference to FIG.
[Step 201] This sequence is started by turning on a main switch of a camera (not shown).
[Step 202] The camera CPU 110 determines whether or not the switch of the release switch circuit 106 provided in the camera body 100 is half-pressed and the SW1 is turned on. If it is ON, the process goes to step 203 ;
[Step 203] The camera CPU 110 transmits the direction in which the focus lens (focus adjustment lens) is driven, the drive amount, and the drive / stop cycle to the lens via the communication circuit.

[Step 204] A counter that counts the number of times of extracting a high-frequency component from the imaging signal at each focus lens position is initialized to zero.
[Step 205] The camera CPU 110 transmits a wobbling driving start command (to start driving) to the lens CPU 207 via the communication circuits 102 and 211, and the lens receives the focus lens based on the data received in step 203 from the received timing. Start driving.
[Step 206] The camera CPU 110 captures the imaging signal output from the imaging device at each lens stop timing, extracts a high-frequency component from the captured imaging signal, and temporarily stores the extracted high-frequency component data in a memory buffer. The counter is incremented by 1.
[Step 207] If the counter value is 6, go to Step 208, and if it is less than 6, go to 206.

[Step 208] The camera CPU 110 transmits a wobbling driving stop command (to stop driving) to the lens CPU 207 via the communication circuits 102 and 211, and the lens stops driving the focus lens.
[Step 209] Focus determination is performed from the high-frequency component data stored in step 206. If it is determined to be in focus, the process proceeds to step 209. If it is determined to be out of focus, the lens driving direction is determined, and the process proceeds to step 203 to perform the operation again.
[Step 210] The camera controls the shutter, exposes the film for an appropriate time, and completes photographing.

FIG. 3 shows the communication between the camera and the lens and the focusing lens position in the sequence steps 203 to 208 described above. As can be seen from the comparison between the camera and lens communication in the conventional sequence shown in FIG. 5, the amount of communication can be reduced by the present invention.
That is, in the prior art, a drive command and a drive amount are transmitted from the camera side to the lens for each drive and stop cycle. In this embodiment, as shown in FIG. 3, a single focus detection operation is performed. In this case, no matter how many times driving and stopping are performed, transmission of the information relating to the wobbling driving, the wobbling driving start command, and the wobbling driving stop command is sufficient once.

  According to the present embodiment, after the camera transmits data related to wobbling driving (focus lens driving amount and driving / stopping period) to the lens, the wobbling driving start command is transmitted, so that the lens receives the data. In addition, by adopting a configuration in which the wobbling drive of the focus lens is performed, it is possible to reduce the amount of communication during the focus detection operation and perform other function control without any trouble.

[Modification of the embodiment]
In the above embodiment, after the lens starts wobbling driving of the focus lens by the wobbling driving start communication, the number of times that the camera CPU extracts a high frequency component from the imaging signal is counted, and when the desired count value is reached, the wobbling driving is performed. The stop communication is performed and the lens stops the wobbling drive of the focus lens. However, the wobbling number of times (the number of times of driving ) is preliminarily stored together with other wobbling driving communication (direction and amount of driving of the focus lens, and driving / stopping period). ) And the driving is stopped after the number of wobbling times received by the lens is driven, and the wobbling driving stop command communication may be deleted. That is, when the number of times of driving is included in the information related to the driving of the focus lens, it is possible to omit transmission of stopping the driving of the focus lens for detecting the in-focus position.

As for the method for determining the drive amount, for example, when the value of the high frequency component data is small, the drive amount is increased as if it is far from the focus, and when the value of the high frequency component data is large, the drive amount is near the focus. As a matter of course, the driving amount should be reduced.
In addition, the lens focus lens drive capability data (drive amount that can be driven within a predetermined time, time required to drive the predetermined drive amount, etc.) is transmitted from the lens to the camera in advance, and the camera relates to wobbling drive based on the data. By determining (focus lens driving amount and driving / stopping cycle), the lens capability may be utilized to the maximum extent.

It is a block diagram of a camera concerning one example of the present invention. It is a flowchart explaining the contrast detection method AF operation | movement sequence in the camera of FIG. FIG. 3 is an explanatory diagram showing communication between a camera and a lens and a focusing lens position in the contrast detection AF operation sequence of FIG. 2. It is a flowchart explaining the conventional contrast detection system AF operation | movement sequence. It is explanatory drawing which shows the communication of a camera and a lens in a conventional contrast detection system AF operation | movement sequence, and a focusing lens position.

Explanation of symbols

100: Camera 107: Image sensor 108: AF processing circuit 110: Camera CPU
200: Lens 207: Lens CPU

Claims (1)

An imaging lens device having a focus adjustment lens and a means for driving the focus adjustment lens, and connected to the photography lens so as to be detachable and communicable, and extracted from an imaging signal obtained by the imaging means and the imaging means In a camera system including a camera body having a focus detection unit that detects a focus position according to a high-frequency component,
Said camera body, said after the information relating to the driving amounts and the driving frequency of the wobbling drive of the focusing lens transmitted to the photographic lens unit, the imaging lens to the effect that starts wobbling drive of the focus adjusting lens on the basis of the information To the device,
The imaging lens device, based on said information, to start the wobbling drive of the focus adjusting lens from the timing of receiving completed instruction to start the wobbling drive of the focusing lens,
The camera body does not transmit that the wobbling drive of the focus adjustment lens is stopped, and further extracts a high frequency component from the output of the imaging means at each timing when the focus adjustment lens is stopped, and the extracted high frequency The camera system is characterized in that when the component is smaller than a predetermined value, the drive amount is set to be large, and when the component is larger than the predetermined value , the camera system is set to be small .

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