JP2007121492A - Lens unit and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce defocusing accompanying power variation even when a lens unit is used for one of a plurality of imaging devices whose imaging systems have different specifications. <P>SOLUTION: The lens unit 127 has a variable power lens 102, a correcting lens 105 which corrects image plane displacement accompanying movement of the variable power lens, a data storage means 151 of storing data used to control the position of the correcting lens according to the position of the variable power lens, and a lens control means 116 of controlling the position of the correcting lens based upon the data. The data storage means stores first data 151a and second data 151b corresponding to first and second imaging devices 128' and 128 whose imaging systems have different specifications. The lens control means decides an imaging device on which the lens unit is mounted and selects data to be used between the first data and second data according to the decision result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lens apparatus that can be attached to and detached from an imaging apparatus such as an interchangeable lens video camera.

  An interchangeable lens that is detachably attached to an image pickup apparatus (hereinafter referred to as a camera) is disposed on the image side of the zoom lens and the zoom lens, and corrects the displacement of the image plane as the zoom lens moves. There is an inner focus type having a lens. In such an inner focus type interchangeable lens, cam data relating to the position of the correction lens corresponding to the position of the variable power lens is stored in a memory, and the position of the correction lens is controlled using the cam data, thereby focusing. It is possible to perform zooming in a state where

  However, in an inner focus type interchangeable lens, image blur occurs as a focus position shift due to a mismatch in back focus between the camera and the interchangeable lens. In particular, such image blur is remarkable on the wide side.

Therefore, in Patent Document 1, information on the back focus of the camera itself (deviation information) is communicated from the camera to the interchangeable lens side, and the cam data stored in the memory on the interchangeable lens side is corrected, and the lens interchangeable type. Video camera systems have been proposed.
Japanese Patent Laid-Open No. 9-23366 (paragraphs 0043-0055, FIGS. 3-5, etc.)

  However, the cam data used in the camera system disclosed in Patent Document 1 includes the specifications of an imaging system mounted on a specific camera, for example, the resolution of the imaging element, the size of the imaging element, and the imaging system. It is determined on the assumption of the characteristics of the included color filter. For this reason, when the interchangeable lens is attached to a camera having an imaging system with specifications different from the specifications assumed by the stored cam data, the cam data cannot be corrected and the focus is shifted due to zooming. There is a problem of end.

  For example, when an image sensor having a pixel pitch that is significantly narrower than the pixel pitch of the image sensor assumed by the cam data is used, the cam data correction process disclosed in Patent Document 1 may be performed. There is a possibility that the focus state cannot be maintained. This is because there is a significant difference in the spatial frequency used as a reference when creating cam data.

  Therefore, a dedicated interchangeable lens is required for a camera having different imaging system specifications. In this case, when a user newly uses a camera having an imaging system specification different from that of a conventionally used camera, a special interchangeable lens different from the conventionally used interchangeable lens needs to be prepared.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a lens apparatus and an imaging system capable of reducing a focus shift caused by zooming regardless of which of a plurality of imaging apparatuses have different imaging system specifications. I am trying.

  A lens apparatus (first lens apparatus) according to an aspect of the present invention includes a variable power lens, a correction lens that corrects an image plane displacement accompanying movement of the variable power lens, and correction according to the position of the variable power lens. Data storage means for storing data used for controlling the position of the lens, and lens control means for controlling the position of the correction lens based on the data. The data storage means stores first data and second data corresponding to the first and second imaging devices having different imaging system specifications. Then, the lens control means discriminates the image pickup device on which the lens device is mounted, and selects data to be used from the first data and the second data according to the discrimination result.

  A lens device (second lens device) according to another aspect of the present invention includes a variable power lens, a correction lens that corrects an image plane displacement accompanying movement of the variable power lens, and driving the variable power lens. And a lens control means for controlling the position of the correction lens in accordance with the position of the zoom lens. Then, the lens control means discriminates the imaging device to which the lens device is mounted from among the first and second imaging devices having different imaging system specifications, and the maximum driving speed of the variable power lens according to the discrimination result It is characterized by changing.

  An imaging system including the lens device and the first and second imaging devices also constitutes one aspect of the present invention.

  According to the first lens device, optimum data used for position control of the correction lens is selected according to the determination result (that is, the specification of the imaging system) of the imaging device to which the lens device is attached. Therefore, even when used in any of a plurality of imaging devices having different specifications of the imaging system, it is possible to reliably reduce the focus shift caused by zooming, and to cause the imaging device to shoot a high-quality image.

  Further, according to the second lens device, the maximum zoom lens driving speed is changed according to the determination result (that is, the specification of the imaging system) of the imaging device to which the lens device is attached. Therefore, even when used in any of a plurality of imaging devices with different imaging system specifications (particularly depth of focus), it is possible to reliably reduce the focus shift caused by zooming, and shoot high-quality video on the imaging device. Can be made.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows the configuration of an imaging system that is Embodiment 1 of the present invention. The system includes an interchangeable lens 127 as a lens device, and a video camera 128 as an imaging device to which the interchangeable lens 127 is detachably mounted. A video camera 128 shown in FIG. 1 is an HD camera that outputs a high-definition television signal (HD video). However, as shown in FIG. 4, the interchangeable lens 127 of the present embodiment can also be attached to an SD camera 128 ′ that outputs a standard television signal (SD video). Thereby, the video camera system 180 as shown in FIG. 4 can be constructed.

  The interchangeable lens 127 includes, in order from the subject side, a fixed first lens unit 101, a second lens unit (hereinafter referred to as a variable power lens) 102 that moves in the optical axis direction and performs variable power, a diaphragm 103, and a fixed lens. The third lens unit 104. Furthermore, a fourth lens unit (hereinafter referred to as a correction lens) 105 that moves in the optical axis direction and performs focusing and correction of image plane displacement accompanying zooming is provided on the image side of the third lens unit 104.

  The absolute position of the variable power lens 102 and the correction lens 105 are detected by absolute position detectors 102A and 105A such as encoders, and the detected information is a lens microcomputer 116 as lens control means provided in the interchangeable lens 127. To be supplied.

  The light beam from the subject that has passed through the interchangeable lens 127 reaches the light receiving surface of the image sensor 106 such as a CCD sensor or a CMOS sensor provided in the camera 128. An optical low-pass filter 106 a is provided on the front surface of the image sensor 106. An imaging system is configured by the imaging element 106, the optical low-pass filter 106a, and an amplifier 109 and a camera signal processing circuit 112, which will be described later, that process output signals from the imaging element 106.

  In this embodiment, the case where photoelectric conversion is performed for each color light of RGB by one image sensor is described. However, the present invention is not limited to this, and the case where photoelectric conversion is performed for each color light of RGB by three image sensors. Can also be applied.

  A signal output by the photoelectric conversion function of the image sensor 106 is amplified to an optimum level by the amplifier 109 and input to the camera signal processing circuit 112. The camera signal processing circuit 112 converts the signal input from the amplifier 109 into a high-definition television signal (HD video) and records it on a recording medium (not shown) (magnetic tape, semiconductor memory, optical disk, etc.).

  Although not shown in detail, in the SD camera 128 ′ shown in FIG. 4, the signal from the image sensor is amplified to an optimum level and converted into a standard television signal (SD video) by the camera signal processing circuit. Recording is performed on a recording medium (not shown).

  Further, the television signal output from the camera signal processing circuit 112 is input to the AF signal processing circuit 113.

  The AF signal processing circuit 113 generates an AF evaluation value indicating the contrast state of the video from the television signal. The AF evaluation value signal is read out using the AF data reading program 115 by the camera microcomputer 114 as an imaging control means provided in the camera 128 and transmitted by the lens microcomputer 116. Here, the camera microcomputer 114 and the lens microcomputer 116 can communicate with each other via a communication terminal 190 provided at a mount coupling portion between the camera 128 and the interchangeable lens 127.

  The camera microcomputer 114 reads the state of the zoom switch 130 and the AF switch 131 and transmits operation information indicating the state to the lens microcomputer 116.

  If the lens microcomputer 116 determines that the AF switch 131 is not pressed and the zoom switch 130 is pressed according to the operation information, the lens microcomputer 116 moves the zoom lens 102 in the direction in which the zoom switch 130 is pressed ( Drive in the tele or wide direction). Specifically, the zoom lens 102 is driven by sending a signal to the zoom motor driver 122 and driving the zoom actuator 121.

  At this time, the lens microcomputer 116 drives the correction lens 105 based on the focus cam data stored in advance in the cam data memory 151 in the lens microcomputer 116 in accordance with the zoom drive program stored in the control unit 119. Specifically, the correction lens 105 is driven by sending a signal to the focus motor driver 126 and driving the focus actuator 125. As a result, zooming is performed in a state where there is almost no image plane displacement, that is, focus shift (defocus).

  As in this embodiment, in the inner focus type lens in which the correction lens 105 is arranged on the image side with respect to the zoom lens 102, the position of the correction lens 105 for maintaining the focus at the time of zooming varies depending on the subject distance. To do. Therefore, as shown in FIG. 2A, the focus cam data indicates the driving position of the correction lens 105 for each absolute position of the variable power lens 102 and each subject distance. The control unit (zoom drive program) 119 detects the absolute positions of the variable power lens 102 and the correction lens 105 by the position detectors 102A and 105A. Then, using the focus cam data selected by the absolute position information, the rotation direction and the rotation amount of the focus actuator 125 are determined.

  At this time, the control unit (zoom drive program) 119 refers to the AF evaluation signal transmitted from the camera microcomputer 114, and performs a scaling operation while maintaining the position where the AF evaluation value is maximized. Thereby, erroneous determination of the driving direction of the correction lens 105 using the focus cam data can be prevented.

  When the AF switch 131 is pressed and the zoom switch 130 is not pressed, the AF control unit 117 in the lens microcomputer 116 performs an autofocus operation. Specifically, the AF control unit 117 drives the correction lens 105 via the focus motor driver 126 and the focus motor 125 so that the AF evaluation value signal becomes maximum. Thereby, autofocus is performed.

  The configuration of the HD camera 128 described so far is the same as the configuration of the SD camera 128 ′ except that the method of the output television signal is different. However, specifications such as the resolution of the image sensor 106 constituting the image pickup system, the size of the image sensor 106, and the thickness of the optical low-pass filter 106a are different.

  Here, in the interchangeable lens 127, when the position of the correction lens 105 is controlled based on the focus cam data at the time of zooming as described above, focus cam data for ensuring accurate back focus must be determined. . The focus cam data is determined by correcting basic focus cam data set in advance under a predetermined condition using a predetermined correction value.

  The predetermined correction value here is a correction value (hereinafter referred to as a lens side correction value) possessed by the interchangeable lens 127 itself, a correction value transmitted from the camera 128 (hereinafter referred to as a camera side correction value), This is a total value with defocus correction data to be described later.

  The lens-side correction value is, for example, a fixed correction value for correcting variations in back focus (hereinafter abbreviated as BF) caused by manufacturing errors of the interchangeable lens, and BF fluctuation caused by temperature change. It is a total value with a variable correction value for

  Similarly, the camera-side correction value corrects a fixed correction value (hereinafter referred to as variation measurement data) for correcting BF variation caused by a manufacturing error of the camera 128 and BF variation caused by a temperature change. Variable correction values (hereinafter referred to as temperature compensation data). The temperature compensation data is generated as data corresponding to the temperature detected by the temperature sensor 140 in the temperature compensation control unit 141.

  In the present embodiment, camera A focus cam data (first data) 151a is preliminarily stored in a cam data memory as focus cam data obtained by correcting the basic focus cam data that conforms to the specification of the imaging system of the SD camera with the lens side correction value. 151 is stored. Furthermore, camera B focus cam data (second data) 151b that meets the specifications of the imaging system of the HD camera is stored in the cam data memory 151 in advance. The camera B focus cam data 151b is data obtained by correcting the camera A focus cam data 151a using defocus correction data.

  The defocus correction data is correction data for correcting a focus shift at the time of zooming that occurs because the focus cam data of the interchangeable lens 127 does not correspond to the specifications of the imaging system of the camera. In the case of the present embodiment, the camera A focus cam data 151a is created on the assumption that the camera is mounted on an SD camera having an imaging system of standard (SD) video shooting specifications. For this reason, even if the focus lens data 151a for the camera A is used when the interchangeable lens 127 is mounted on the HD camera and the correction lens 105 is controlled at the time of zooming, a focus shift occurs. Therefore, it is necessary to obtain the camera B focus cam data 151b using the defocus correction data so as not to cause such a focus shift.

  Here, the focus cam data will be described. The basic focus cam data corresponding to the specification of the SD camera is related to the Nyquist frequency of the image sensor used in the SD camera, and is calculated based on the spatial frequency corresponding to the SD camera.

  With respect to this basic focus cam data, the interchangeable lens 127 is mounted on a reference SD camera, and the amount of focus shift (defocus amount) at the time of zooming caused by variations in manufacturing of the interchangeable lens 127 or temperature changes is measured. . From this measurement result, fixed and variable correction values for back focus correction necessary for keeping the defocus within an allowable range are determined as lens side correction values. Then, the basic focus cam data is corrected by the lens side correction value to obtain camera A focus cam data 151a.

  However, an image pickup device mounted on an HD camera usually has a smaller pitch (higher pixel) than pixels on an SD camera. Along with this, the Nyquist frequency of the image sensor increases. Therefore, with the camera A focus cam data 151a based on the SD camera, the best focus position cannot be obtained with the HD camera.

  The cause is the influence of spherical aberration of the interchangeable lens. When the camera on which the interchangeable lens is mounted is changed from an SD camera to an HD camera and the image pickup device has a narrow pitch, the SD camera cannot obtain a high-frequency resolution at the position of the minimum circle of confusion, which is the best defocus, It will be recognized as an image blur. As a result, the best defocus position shifts in the direction of the minimum core position.

  In general, it is known that the resolution is the highest at the minimum core position, but the contrast is low for an image in a low frequency region. However, this drop in MTF or the like can be corrected by the camera signal processing unit 112 that processes the output signal from the image sensor, and a preferable image sufficiently resolved up to a high frequency can be obtained. it can.

  Therefore, in this embodiment, the lens microcomputer 116 identifies the type (model) of the camera to which the interchangeable lens 127 is attached, that is, an SD camera or an HD camera. This identification is performed based on the model information received from the model information memory 160 built in the camera microcomputer 114 when the interchangeable lens 127 is attached to the camera 128.

  If the camera is an SD camera, the lens microcomputer 116 reads the camera A focus cam data 151 a from the cam data memory 151. When the camera is an HD camera, the lens microcomputer 116 reads the camera B focus cam data 151 b from the cam data memory 151.

  FIG. 2B shows an example of camera A focus cam data 151a (solid line) and camera B focus cam data 151b (dotted line). When the BF assumed by the camera B focus cam data 151b is longer than the BF assumed by the camera A focus cam data 151a, this extension (defocus correction data) is used as the camera A focus cam. Subtract from data 151a. Then, camera B focus cam data 151b shifted downward as a whole is obtained. When the BF contracts, the contracted amount is added to the camera A focus cam data 151a to obtain the camera B focus cam data 151b shifted upward as a whole.

  As a result, even when the interchangeable lens 127 is attached to either the HD camera 128 or the SD camera 128 ', the image plane fluctuation at the time of zooming, that is, defocusing can be almost eliminated, and a high-resolution image is taken. be able to.

  The amount of deviation of the best defocus position varies depending on the zoom position, the position of the correction lens (focus position), the difference in the amount of spherical aberration tilt, and the aperture value. For this reason, a process for correcting the focus cam data based on the zoom position information 151 from the position detector 102A, the focus position information 152 from the position detector 105A, and the aperture value information from an aperture position detector (not shown). You may go. Thereby, more accurate focus correction can be performed.

  Next, in this embodiment, a communication operation for transmitting the camera side correction value from the HD camera 128 to the interchangeable lens 127 side will be described. This operation is the same when the camera side correction value is transmitted from the SD camera 128 'to the interchangeable lens 127 side.

  Variations in BF caused by the manufacturing accuracy and attachment error of structural parts in the camera 128 are measured at the manufacturing stage of the camera 128 as variation measurement data. This variation measurement data is written in a rewritable variation data memory 142. A change in the environmental temperature that occurs during the photographing operation is measured by a temperature sensor 140 provided in the camera 128, and BF fluctuation amount data, that is, temperature compensation, is determined by an operation program of the temperature compensation control unit 141 in the camera microcomputer 114. Converted to data. Then, the camera microcomputer 114 transmits the total value of the variation measurement data and the temperature compensation data to the lens microcomputer 116 as a camera side correction value.

  Furthermore, the camera microcomputer 114 transmits model information of the camera 128 (information indicating that it is an HD camera) to the lens microcomputer 116. When the zoom switch 130 is pressed, the camera microcomputer 114 transmits to the lens microcomputer 116 a zoom command indicating whether the zoom switch 130 is pressed (tele direction or wide direction). To do.

  In the lens microcomputer 116, the control unit (zoom drive program) 119 determines whether the camera to which the interchangeable lens 127 is attached is an HD camera or an SD camera based on the transmitted model information. Based on the determination result, data to be used is selected from the camera A focus cam data 151a and the camera B focus cam data 151b. Further, the selected focus cam data is corrected based on the camera side correction value.

  Next, the flow of communication and processing will be described with reference to the flowcharts of FIGS. 3A shows the processing of the lens microcomputer 116, and FIG. 3B shows the processing of the camera microcomputer 114.

  In step 10 of FIG. 3B, the camera microcomputer 114 performs initial communication with the lens microcomputer 116 when the interchangeable lens 127 is attached. This initial communication includes model information and camera-side correction values.

  In step 1 of FIG. 3A, the lens microcomputer 116 performs initial communication with the camera microcomputer 114 and receives the model information and the camera-side correction value. In step 2, it is determined whether the camera 128 is an HD camera or an SD camera based on the model information.

  In the case of the HD camera, the process proceeds to step 3 and the camera B focus cam data 151 b is read from the cam data memory 151. Then, the camera B focus cam data 151b is corrected by the camera side correction value. In the case of an SD camera, the process proceeds to step 4 and the camera A focus cam data 151 a is read from the cam data memory 151. Then, the camera A focus cam data 151a is corrected by the camera side correction value.

  In step 11 of FIG. 3B, the camera microcomputer 114 determines whether or not the zoom switch 130 has been operated. When operated, in step 12, a zoom command indicating the operation direction (tele direction or wide direction) is transmitted to the lens microcomputer 116.

  In step 5 of FIG. 3A, when receiving a zoom command, the lens microcomputer 116 proceeds to step 6 and performs zooming (drive of the variable power lens 102 and the correction lens 105) in the direction indicated by the zoom command.

  Embodiment 2 of the present invention will be described below. In the first exemplary embodiment, the case where the interchangeable lens 127 determines the camera model and selects one of the camera A focus cam data and the camera B focus cam data has been described.

  However, the thickness of the optical low-pass filter 106a varies depending on the number of pixels of the image sensor 106 between the HD camera and the SD camera. In such a case, it is common to provide a dummy glass (not shown) in the camera, but it is difficult to make the optical path lengths completely equivalent.

  Therefore, in this embodiment, as shown in FIG. 5, in addition to the focus cam data described in the first embodiment, the camera A flange back data 151c and the camera B flange back data 151d are combined in the cam data memory 151. To remember.

  Then, the lens microcomputer 116 discriminates the camera to which the interchangeable lens 127 is attached in step 2 of FIG. 3, and switches the focus cam data and the flange back data to the camera A or camera B based on the discrimination result. (Steps 3 and 4).

  When using a high resolution camera such as an HD camera, the depth of focus is shallower than when using an SD camera. Generally, on the telephoto end side of the fourth group rear focus lens, the movement amount of the correction lens 105 according to the focus cam data is larger than the movement amount of the variable power lens 102 which is the second group. In such a case, if the maximum zoom speed (that is, the maximum driving speed of the variable power lens 102) is high, the tracking accuracy of the correction lens 105 with respect to the focus cam data deteriorates, and a focus shift occurs.

  Therefore, in the interchangeable lens 127 according to the third embodiment of the present invention, when the HD camera is used, the maximum in the range from the tele end to the predetermined zoom position near the tele end is greater than when the SD camera is used. The zoom speed is reduced. Since the zoom speed is variable according to the operation amount of the zoom switch 130, the maximum zoom speed here is the zoom speed when the operation amount of the zoom switch 130 is maximized.

  If it is determined in step 2 of FIG. 3A that the camera is an SD camera, the camera A focus cam data is selected in step 4 and the first maximum zoom speed is set. On the other hand, if it is determined that the camera is an HD camera, the camera B focus cam data is selected in step 3 and a second maximum zoom speed lower than the first maximum zoom speed is set.

  However, when using an HD camera, the maximum zoom speed may be lowered over the entire zoom range.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications can be made within the scope of the contents described in the claims.

1 is a block diagram showing a configuration of a video camera system that is Embodiment 1 of the present invention. FIG. 4 is a diagram illustrating focus cam data in the first embodiment. 3 is a flowchart showing a processing operation in the first embodiment. 1 is a schematic diagram illustrating a configuration example of a video camera system according to Embodiment 1. FIG. Schematic which shows the structure of the video camera system which is Example 2 of this invention.

Explanation of symbols

106 Image Sensor 106a Color Filter 114 Camera Microcomputer 116 Lens Microcomputer 151 Cam Data Memory 127 Interchangeable Lens 128, 128 ′ Video Camera 141 Temperature Compensation Control Unit 142 Variation Data Memory 160 Model Information Memory

Claims (7)

A lens device that is detachably attached to an imaging device,
A variable power lens,
A correction lens that corrects an image plane displacement accompanying the movement of the zoom lens;
Data storage means for storing data used to control the position of the correction lens in accordance with the position of the zoom lens;
Lens control means for controlling the position of the correction lens based on the data,
The data storage means stores first data and second data corresponding to the first and second imaging devices having different imaging system specifications,
The lens control unit discriminates an imaging device to which the lens device is attached, and selects data to be used from the first data and the second data according to the discrimination result. .   The lens apparatus according to claim 1, wherein the data is data indicating a position of the correction lens according to a position of the zoom lens.   The lens apparatus according to claim 1, wherein the data is data indicating a flange back of the imaging apparatus. A lens device that is detachably attached to an imaging device,
A variable power lens,
A correction lens that corrects an image plane displacement accompanying the movement of the zoom lens;
Lens control means for controlling the driving of the zoom lens and controlling the position of the correction lens in accordance with the position of the zoom lens;
The lens control means discriminates an imaging device to which the lens device is mounted from among first and second imaging devices having different imaging system specifications, and the maximum driving speed of the zoom lens according to the discrimination result A lens device characterized by changing the lens.   5. The lens control unit according to claim 1, wherein the lens control unit determines an imaging device to which the lens device is attached based on information received from the first and second imaging devices. The lens device described.   The specification of the imaging system includes at least one of a resolution of an imaging device included in the imaging system, a size of the imaging device, and a thickness of an optical filter included in the imaging system. The lens device according to any one of 5 to 5. A lens apparatus according to any one of claims 1 to 6;
An imaging system comprising the first and second imaging devices.