JP2005217504A - Image pickup system with peripheral light amount correcting function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup system with a peripheral light amount correcting function properly correcting the drop of a peripheral light amount regardless of the setting state of a photographing lens, by executing amplification processing to a video signal by an amplification degree for each pixel corresponding to the setting state of the photographing lens, in the image pickup system in which a peripheral light amount ratio fluctuates by the setting state of the photographing lens such as a focal distance. <P>SOLUTION: The lens microcomputer 20 of a lens device 12 reads peripheral light amount ratio data corresponding to a current focal distance, an aperture opening/closing degree, and a focus position from lens characteristic data of a storage element 30; and transmits the peripheral light amount ratio data to the camera microcomputer 36 of a camera body 10. The camera microcomputer 36 sets the amplification degree of the video signal for each pixel point, and executes the amplification processing of the video signal by the amplification degree. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an imaging system with a peripheral light amount correction function, and more particularly to an imaging system with a peripheral light amount correction function applied when the peripheral light amount ratio varies depending on the setting state of a photographing lens such as a focal length.

  The ratio of the amount of light at the peripheral portion to the amount of light at the center of the screen of the image formed by the photographing lens is generally called the peripheral light amount ratio. The image becomes dark. In the case of a long focus zoom lens used in a broadcast television camera or the like, in many cases, the peripheral light amount ratio decreases when the focal length is on the wide-angle side but the peripheral light amount ratio is approximately 1, but when the focal length is on the telephoto side. . When the peripheral light amount ratio varies depending on the focal length, not only the peripheral image becomes dark, but, for example, when zooming in a state where a relatively whitish subject is photographed, the four corners are dark as an afterimage of the eye and a white disk on the screen This also has the adverse effect of generating a shaped image.

Patent Document 1 proposes a video camera in which a video signal acquired from an image sensor is amplified by a gain set for each pixel so as to alleviate a drop in peripheral light amount due to a photographing lens.
JP 2000-69359 A

  However, in the case of a zoom lens having a variable focal length as described above, the peripheral light amount ratio may vary depending on the focal length, and the peripheral light amount ratio may also vary depending on the degree of opening / closing of the aperture and the focus position. In Patent Document 1, since the amplification degree of each pixel is set regardless of the setting state of the photographing lens such as the focal length, it is not possible to deal with the case where the peripheral light amount ratio varies depending on the setting state of the photographing lens.

  The present invention has been made in view of such circumstances, and in the case of using a photographing lens in which the peripheral light amount ratio fluctuates depending on the setting state of the photographing lens, particularly the focal length, the peripheral light amount It is an object of the present invention to provide an imaging system with a peripheral light amount correction function that can reduce depression.

  In order to achieve the above object, the imaging system with a peripheral light amount correction function according to claim 1 is an imaging system in which a photographing lens whose focal length can be changed is used, and an image formed by the photographing lens. In an imaging system that photoelectrically converts an image of an object by an image signal by an imaging unit, a storage unit that stores lens characteristic data related to the characteristics of the shooting lens, a focal length acquisition unit that acquires a current focal length, Amplifying processing means for amplifying the image signal in accordance with the amplification degree set for each pixel on the imaging surface of the imaging means, and a lens for storing the amplification degree for each pixel in the amplification processing means in the storage means Based on the characteristic data and the current setting state of the photographing lens including at least information on the focal length acquired by the focal length acquisition means Set is characterized by comprising a peripheral light amount correction means for correcting the amplification process of the image signal by said amplification means a drop of peripheral light amount of the imaging lens in a current setting state of the imaging lens.

  According to the present invention, since the image signal is amplified by the amplification degree for each pixel in consideration of the setting state of the photographing lens, the drop in the peripheral light amount of the photographing lens is appropriately reduced (corrected) regardless of the setting state of the photographing lens. )can do.

  According to a second aspect of the present invention, there is provided an imaging system with a peripheral light amount correction function according to the first aspect of the invention, wherein the photographing lens can change a focus position and a degree of opening / closing of the aperture, and obtain a current focus position. A focus position acquisition unit that performs the aperture opening / closing degree acquisition unit that acquires a current aperture opening / closing degree, and the peripheral light amount correction unit is considered when setting the amplification degree for each pixel in the amplification processing unit. The current setting state of the photographic lens includes information on the focus position acquired by the focus position acquisition unit and information on the aperture opening / closing degree acquired by the aperture opening / closing degree acquisition unit. That is, it is possible to appropriately correct the drop in the peripheral light amount even when the peripheral light amount ratio varies depending on not only the focal length but also the focus position and the aperture opening / closing degree setting state.

  According to a third aspect of the present invention, in the imaging system with a peripheral light amount correction function according to the first aspect, the lens characteristic data stored in the storage means is a peripheral light amount ratio according to a setting state of the photographing lens. It is characterized by the data showing. According to this, the data of the peripheral light amount ratio in the current setting state of the photographing lens is obtained, and the amplification degree of each pixel for appropriately correcting the drop in the peripheral light amount at that time is calculated from the data of the peripheral light amount ratio. can do.

  According to a fourth aspect of the present invention, there is provided an imaging system with a peripheral light amount correction function according to the first aspect of the present invention. An imaging system is configured by a lens device including the photographing lens. For example, an imaging system such as a broadcast television camera corresponds to this.

  According to a fifth aspect of the present invention, there is provided an imaging system with a peripheral light amount correction function according to the fourth aspect of the invention, wherein the storage device is included in the lens device. In this case, only the lens characteristic data indicating the characteristics of the photographing lens provided in the lens device may be stored in the storage unit.

  The imaging system with a peripheral light amount correction function according to a sixth aspect of the present invention is the imaging system according to the fourth aspect, wherein the storage unit has the camera device and a plurality of lens devices that can be attached to the camera device. The lens characteristic data corresponding to the type is stored, and the peripheral light amount correcting means uses the lens characteristic data corresponding to the type of the lens apparatus mounted on the camera apparatus. The storage means may be provided in a camera device. In this case, the storage means stores lens characteristic data corresponding to various lens devices, and corresponds to the type of lens device actually mounted. The data should be used. However, even if the lens characteristic data corresponding to a plurality of types of lens devices is not necessarily stored in the storage means, the data in the storage means can be rewritten, and the data corresponding to the lens device mounted on the camera body can be transferred from an external device. A method of enabling writing to the storage means is also conceivable.

  According to the imaging system with a peripheral light amount correction function according to the present invention, it is possible to appropriately correct (reduce) the decrease in the peripheral light amount regardless of the setting state of the photographing lens.

  Hereinafter, a preferred embodiment of an imaging system with a peripheral light amount correction function according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of an imaging system to which the present invention is applied. The image pickup system shown in the figure is an image pickup system used for shooting with, for example, a broadcast television camera. In the figure, a camera body 10 with a replaceable lens, for example, a long focus and variable focal length shooting lens (long focus zoom) is shown. A lens device 12 having a lens), a camera control unit (CCU) 14 connected to the camera body 10, and a controller (focus demand 16 and zoom demand 18) connected to the lens device 12 are shown.

  The lens device 12 includes a photographic lens (optical system) and a control system. The photographic lens changes a focus lens group FL movable in the optical axis direction and a zoom magnification (focal length) for focus adjustment. The zoom lens group ZL is movable in the optical axis direction, the aperture I is opened and closed to adjust the amount of light, the master lens group ML that finally forms an image of the subject light on the imaging surface, and the like. In the zoom lens group ZL, a zoom lens unit for zooming and a correction lens unit for correcting a variation in focus due to movement of the zoom lens unit are moved in a predetermined positional relationship. It has become.

  The control system of the lens device 12 includes a lens microcomputer 20 that performs overall control of the lens device 12, driving units 22, 24, and 26 for driving the focus lens group FL, zoom lens group ZL, and diaphragm I, respectively, and necessary data. Is comprised of a storage element (for example, EEPROM) 30 or the like.

  Each of the drive units 22, 24, and 26 includes a motor coupled to the focus lens group FL, the zoom lens group ZL, and the diaphragm I, and these motors are driven according to a drive signal given from the lens microcomputer 20. As a result, the focus lens group FL, the zoom lens group ZL, and the aperture stop I are motor-driven by the drive units 22, 24, and 26.

  Each of the drive units 22, 24, and 26 includes a position sensor that detects the positions of the focus lens group FL, the zoom lens group ZL, and the stop I, and information indicating each position detected by these position sensors. Is appropriately read by the lens microcomputer 20.

  The lens microcomputer 20 is supplied with control signals according to user operations in the demands 16 and 18 from the focus demand 16 and the zoom demand 18 connected to the lens device 12. The drive signals output to the drive units 22 and 24 are used to control the motors of the drive units 22 and 24, and the position or speed of the focus lens group FL or zoom lens group ZL is supplied from the demands 16 and 18. Set to the state indicated by.

  Various signals can be exchanged by serial communication between the lens microcomputer 20 and the camera microcomputer 36 of the camera body 10, and the position of the aperture I (aperture opening / closing degree) is set from the camera microcomputer 36 to the lens microcomputer 20. When the instructing iris control signal is given, the lens microcomputer 20 controls the motor of the driving unit 26 by the driving signal output to the driving unit 26, and sets the aperture I to the aperture opening / closing level designated by the iris control signal.

  The camera body 10 is equipped with a camera microcomputer 36 that performs overall control of the camera body 10, a CCD 32 that photoelectrically converts a subject image formed by a photographing lens and outputs the result as an electrical signal (image signal), and the like. The image signal output from the CCD 32 is converted into a digital signal by the A / D converter 34, read by the camera microcomputer 36, and subjected to predetermined signal processing by the camera microcomputer 36. Although not shown in the figure, the image signal processed by the camera microcomputer 36 is output from the video signal output terminal of the camera body 10 to an external device as a video signal of a predetermined format (for example, NTSC format).

  The camera microcomputer 36 is supplied with control signals relating to various functions in the camera body 10 from a CCU (camera control unit) 14 connected to the camera body 10. For example, in the case of a remote iris, when an iris control signal instructing the opening / closing degree of the iris I (aperture opening / closing degree) is given from the CCU 14 to the camera microcomputer 36 based on a user operation at the CCU 14, the camera microcomputer 36 The given iris control signal is transmitted to the lens microcomputer 20.

  Next, the peripheral light amount correction function in the imaging system will be described. 2 and 3 are views showing the peripheral light amount ratio of an image formed by the photographing lens of the lens device 12 and picked up by the image pickup surface of the CCD 32 of the camera body 10 while changing the setting state of the photographing lens. . 2A to 2C show the case where the aperture stop I is opened, and FIGS. 2A and 2C show the cases where the focal length is the wide-angle end and the telephoto end. (B) shows a case where the focal length is located between the wide-angle end and the telephoto end. On the other hand, FIGS. 3 (A) to 3 (C) show the case where the stop I is stopped to the state of F4.0. FIGS. 3 (A) and 3 (C) show the cases where the focal length is at the wide angle end and at the telephoto end. FIG. 3B shows a case where the focal length is located between the wide-angle end and the telephoto end. In these figures, the horizontal axis is from the center of each pixel point on the imaging surface of the CCD 32 on which an image is formed by the photographing lens (a point on the optical axis of the photographing lens, hereinafter referred to as the screen center). The distance is shown, and the vertical axis shows the ratio of the light quantity of the image at each pixel point (peripheral light quantity ratio) to the light quantity of the image formed at the pixel point at the center of the screen (light quantity incident on the center of the imaging surface). Yes. As can be seen from the graphs in these figures, the peripheral light amount ratio decreases as the distance from the center of the screen increases under any condition, and the degree of decrease in the peripheral light amount ratio increases as the focal length approaches the telephoto end. Tend. The peripheral light amount ratio varies depending on the focal length and the aperture opening / closing degree (F number) even if the pixel points are the same except for some pixel points. Although it cannot be read from these graphs, the peripheral light amount ratio varies depending on the position of the focus lens group FL (focus position).

  In the storage element 30 of the lens device 12, for example, peripheral light amount ratio data indicating peripheral light amount ratios at respective pixel points in a desired setting state of the photographing lens as illustrated in FIGS. 2 and 3 is stored as lens characteristic data. Has been. That is, data indicating the value of the peripheral light amount ratio at each pixel point for each value of the focal length, the aperture opening / closing degree, and the focus position is created in advance and stored in the storage element 30. Therefore, by referring to the peripheral light amount ratio data in the storage element 30, the value of the peripheral light amount ratio at each pixel point when the photographing lens is set to an arbitrary focal length, aperture opening / closing degree, and focus position can be obtained. It is like that. However, the information regarding the peripheral light amount stored as the lens characteristic data in the storage element 30 is not the peripheral light amount ratio data as described above, but indicates the light amount (brightness) of the image at each pixel point in each setting state of the photographing lens. It may be a value (for example, F value), and is not the ratio of the light quantity at each pixel point to the light quantity at the center of the screen, but the light quantity at a predetermined pixel point or a predetermined reference light quantity. As long as it is a value indicating the ratio of the light quantity at each pixel point with respect to, information that can read the ratio of the light quantity between the pixel points in the desired setting state of the photographing lens may be used.

  The lens microcomputer 20 of the lens device 12 acquires the current focus position, zoom position (focal length), aperture position (aperture open / closed degree) by the position sensors of the drive units 22, 24, and 26, and sets them in the set state. Corresponding peripheral light amount ratio data (value of the peripheral light amount ratio at each pixel point) is read from the storage element 30. Then, the peripheral light amount ratio data is transmitted to the camera microcomputer 36 by serial communication as information on the peripheral light amount. It should be noted that the transmission of information relating to the amount of peripheral light from the lens microcomputer 20 to the camera microcomputer 36 is performed when there is a transmission request from the camera microcomputer 36. In addition, the current focus position, focal distance, and aperture opening / closing degree may use the instruction values given from the focus demand 16, the zoom demand 18, and the camera microcomputer 36 instead of using the values acquired from the position sensor. Further, the exchange of signals between the lens microcomputer 20 and the camera microcomputer 36 is not limited to serial communication but may be parallel communication or the like.

  The camera microcomputer 36 obtains the amplification degree of the video signal for each pixel point based on the information regarding the peripheral light amount transmitted from the lens microcomputer 20. The degree of amplification of the video signal for each pixel point represents a value of individual amplification for each pixel point for correcting the drop in peripheral light amount by amplification processing on the video signal. When the peripheral light amount ratio data is acquired as information on the peripheral light amount, the amplification degree of the video signal for each pixel point is obtained as the reciprocal of the peripheral light amount ratio at each pixel point. For example, the degree of amplification of the video signal at each pixel point with respect to the peripheral light amount ratio under the condition of FIG. In the same figure, as in FIG. 2C, a graph (curve A) of the peripheral light amount ratio at each pixel point is shown, and the vertical axis on the right side of the graph shows the degree of amplification of the video signal. The degree of amplification of the video signal is indicated by a curve B. Note that the amplification degree corresponding to the case where the peripheral light amount ratio is 1 (100%) is 1. The amplification degree obtained here indicates the amplification degree for correcting the peripheral light amount ratio, and does not include the amplification degree in the amplification process of the video signal performed for other purposes. For example, although not shown in FIG. 1, an amplification process using a preamplifier connected to the CCD 32 by an A / D converter, an amplification process for amplifying a video signal to a predetermined signal level in the camera microcomputer 36, or the like. Amplification is not included.

  Subsequently, the camera microcomputer 36 amplifies the data of each pixel of the image signal acquired from the CCD 32 via the A / D converter 34 according to the amplification degree at each corresponding pixel point. Thereby, the decrease in the peripheral light amount ratio is corrected by the amplification process of the video signal at each pixel point.

  In the present embodiment, the peripheral light amount ratio data is stored in the storage element 30 as lens characteristic data, and the amplification degree of the video signal at each pixel point in a desired setting state of the photographing lens is determined based on the data. However, the memory element 30 stores not the peripheral light amount ratio data but the data of the amplification degree of the video signal of each pixel point obtained as described above corresponding to each setting state of the photographing lens. You may make it memorize | store as characteristic data. In this case, if the camera microcomputer 36 acquires the amplification degree data corresponding to the setting state of the photographing lens from the lens microcomputer 20, it is not necessary to obtain the amplification degree from the peripheral light amount ratio data.

  Next, processing procedures in the lens microcomputer 20 and the camera microcomputer 36 relating to the peripheral light amount correction function will be described. FIG. 5 is a flowchart showing a processing procedure related to lens control in the lens microcomputer 20. The lens microcomputer 20 performs zoom processing for controlling the zoom lens group ZL via the drive unit 24 based on the control signal given from the zoom demand 18 and via the drive unit 22 based on the control signal given from the focus demand 16. Focus processing for controlling the focus lens group FL is performed (steps S10 and S12).

  In the case of the remote iris, the F-number value of the aperture designated by the remote iris operation at the CCU 14 is given from the camera microcomputer 36 to the lens microcomputer 20 as an iris control signal, and the lens microcomputer 20 Iris processing is performed to control the aperture I via the drive unit 26 so that the aperture opening / closing degree corresponding to the F number is obtained (step S14).

  Subsequently, the lens microcomputer 20 reads the focal length, the focus position, and the aperture opening / closing degree from the position sensors of the driving units 22 to 26, and stores the peripheral light amount ratio data corresponding to these positions in the storage element 30 as lens characteristic data. It is obtained based on the peripheral light amount ratio data that has been made (step S16). Then, after performing other processes not shown in the flowchart (step S18), the process returns to step S10, and the processes from step S10 are repeated. The lens microcomputer 20 transmits the peripheral light amount ratio data obtained in step S <b> 16 to the camera microcomputer 36 when there is a transmission request for information regarding the peripheral light amount from the camera microcomputer 36.

  FIG. 6 is a flowchart showing a processing procedure regarding the peripheral light amount correction in the camera microcomputer 36. First, the camera microcomputer 36 transmits a transmission request for information regarding the peripheral light amount to the lens microcomputer 20 (step S20). Then, it is determined whether or not information on peripheral light quantity (peripheral light quantity ratio data) has been received from the lens microcomputer 20 (step S22). If NO is determined, the determination in step S22 is repeated. If YES is determined in step S22, the degree of amplification of the video signal at each pixel point is obtained based on the peripheral light amount ratio data acquired from the camera microcomputer 36 (step S24). Then, the amplification degree in the individual amplification processing for the image data of each pixel acquired from the CCD 32 is set to the amplification degree of the video signal at each pixel point obtained in step S24 (step S26). When this process ends, after performing other processes such as an amplification process, the processes from step S20 are repeated.

  As described above, in the above embodiment, the lens characteristic data for obtaining the amplification degree is stored in the storage element 30 of the lens device 12 and the data is transmitted from the lens device 12 to the camera body 10. The characteristic data may be stored in a storage unit of the camera body 10. In this case, the storage means of the camera body 10 stores lens characteristic data corresponding to a plurality of types of lens devices 12 that can be mounted on the camera body 10, and the types of lens devices actually mounted on the camera body 10. It is conceivable that the lens characteristic data corresponding to the type can be used by recognizing the image automatically or by predetermined setting means (such as a user operation selection switch). Further, as processing in this case, information on the current setting state (focal length, aperture opening / closing degree, focus position, etc.) of the photographing lens is transmitted from the lens microcomputer 20 to the camera microcomputer 36 to the camera microcomputer 36, thereby 36 can determine the amplification degree of the video signal at each pixel point in the set state based on the lens characteristic data stored in the storage means.

  In the above-described embodiment, the amplification degree of the video signal at each pixel point is obtained by the camera microcomputer 36 that has obtained the peripheral light amount ratio data from the lens microcomputer 20, but the amplification data is obtained by the camera microcomputer 36. Instead, it may be obtained by the lens microcomputer 20 and transmitted from the lens microcomputer 20 to the camera microcomputer 36.

  In the above embodiment, the imaging system in the case where the focus lens group FL, the zoom lens group ZL, and the aperture stop I are driven by a motor has been described. However, the present invention can also be applied to the case where they are driven manually. .

  In the above-described embodiment, the case where the present invention is applied to an imaging system of a broadcast television camera has been described. However, the present invention is not limited to this, and is also applied to a video camera and a digital still camera that captures a still image. be able to. Further, the present invention can be applied to a camera in which a photographic lens (lens device) and a camera body are integrated, even if the camera is not a lens-exchangeable type as in the above embodiment.

FIG. 1 is a block diagram showing the overall configuration of an imaging system to which the present invention is applied. 2A, 2 </ b> B, and 2 </ b> C are diagrams illustrating the peripheral light amount ratio with respect to the distance from the center of the screen under different conditions. FIGS. 3A, 3B, and 3C are diagrams showing the peripheral light amount ratio with respect to the distance from the center of the screen under different conditions. FIG. 4 is a diagram showing the degree of amplification of the video signal at each pixel point under the condition of FIG. FIG. 5 is a flowchart showing a processing procedure related to the peripheral light amount correction in the lens microcomputer. FIG. 6 is a flowchart showing a processing procedure related to the peripheral light amount correction in the camera microcomputer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Camera body, 12 ... Lens apparatus, 14 ... Camera control unit (CCU), 16 ... Focus demand, 18 ... Zoom demand, FL ... Focus lens group, ZL ... Zoom lens group, I ... Aperture, ML ... Master lens group 20 ... lens microcomputer, 22-26 ... drive unit, 30 ... storage element, 32 ... CCD, 34 ... A / D converter, 36 ... camera microcomputer

Claims (6)

In an imaging system in which a photographing lens capable of changing a focal length is used, an image formed by the photographing lens is photoelectrically converted by an imaging unit, and an image of a subject is acquired by an image signal.
Storage means for storing lens characteristic data relating to characteristics of the photographing lens;
A focal length acquisition means for acquiring the current focal length;
Amplification processing means for amplifying the image signal in accordance with the amplification degree set for each pixel of the imaging surface of the imaging means;
The amplification level for each pixel in the amplification processing unit, the lens characteristic data stored in the storage unit, and the current setting state of the photographing lens including at least information on the focal length acquired by the focal length acquisition unit; A peripheral light amount correction unit that corrects a drop in the peripheral light amount of the photographing lens in the current setting state of the photographing lens by amplification processing of an image signal by the amplification processing unit;
An imaging system with a peripheral light amount correction function. The photographing lens is capable of changing a focus position and an aperture opening / closing degree, and includes a focus position acquiring unit for acquiring a current focus position, and an aperture opening / closing degree acquiring unit for acquiring a current aperture opening / closing degree.
The peripheral light amount correction means includes information on the focus position acquired by the focus position acquisition means as the current setting state of the photographing lens to be considered when setting the amplification degree for each pixel in the amplification processing means, The imaging system with a peripheral light amount correction function according to claim 1, further comprising information about an aperture opening / closing degree acquired by the aperture opening / closing degree acquisition unit.   2. The imaging system with a peripheral light amount correction function according to claim 1, wherein the lens characteristic data stored in the storage means is data indicating a peripheral light amount ratio according to a setting state of the photographing lens.   2. A peripheral light amount correcting function according to claim 1, wherein the lens device includes a camera device having an image pickup unit and a lens device that is detachably attached to the camera device and includes the photographing lens. Imaging system.   The imaging system with a peripheral light amount correction function according to claim 4, wherein the storage unit is included in the lens device.   The storage means stores lens characteristic data corresponding to a plurality of types of lens devices that the camera device has and can be attached to the camera device, and the peripheral light amount correction means is a lens attached to the camera device. 5. The imaging system with a peripheral light amount correction function according to claim 4, wherein lens characteristic data corresponding to the type of device is used.

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