JP5457845B2 - Color characteristic correction apparatus and camera - Google Patents

Description

  The present invention relates to a color characteristic correction apparatus for television cameras and movie cameras, and more particularly to a color characteristic correction apparatus and a camera for matching color characteristics among a plurality of cameras.

Conventionally, various techniques for adjusting the color of an image photographed by a single photographing apparatus have been proposed. For example, Patent Document 1 discloses a photographing apparatus including a color correction unit that acquires color correction parameters and performs color correction of a captured image using the color correction parameters.
Further, for example, Patent Document 2 discloses a photographing apparatus including an image correcting unit that corrects the color of a photographed image.

  Here, in a broadcasting system (multi-camera system) using a plurality of cameras such as a studio program and a sports broadcast, a mechanism for transmitting a video at a desired angle by switching a camera that captures an object in accordance with the effect is common. It is.

  Cameras and films used in such multi-camera systems usually have different characteristics. For example, FIG. 10 shows response curves d to i showing the relationship of normalized pixel values to exposure amounts of conventional cameras and films as an example, but the conventional cameras and films are different from these response curves d to i. It turns out that it has a characteristic.

  For this reason, in a multi-camera system using a plurality of cameras, in order to prevent the viewer from feeling uncomfortable that the same subject is being photographed when the viewer views the video transmitted by switching the cameras, Basic color adjustment is performed for each of a plurality of cameras before broadcasting (color adjustment before broadcasting). Generally, for pre-broadcast color adjustment, after making optical settings such as lenses and filters for each camera, take a grayscale chart and use the achromatic part between white and black as the subject of photography. And adjust the color.

  Also, during broadcasting, especially when outdoors, it is necessary to adjust the iris of the multiple cameras according to the shooting conditions to maintain an appropriate exposure amount and to adjust the colors of the multiple cameras. For this reason, conventionally, an operator such as a video engineer manually adjusts all of a plurality of cameras while checking the video monitor and the waveform monitor to adjust the color tone (broadcast color adjustment).

JP 2007-194794 A JP 2005-260657 A

  However, the conventional pre-broadcast color adjustment is performed using a simple adjustment method in which an achromatic color is obtained for a small number of discrete luminance samples under a fixed exposure amount. Calibration results could not be obtained.

  The conventional camera color adjustment is centered on matrix calculation for a specific color space, and is adjusted by a small number of parameters such as a color conversion coefficient. For this reason, it is accurate between multiple cameras, including differences in the characteristics of the optical system and individual differences in response to the creation of red (R), green (G), and blue (B) signals for the input light of a single camera. It was difficult to match the colors.

  Furthermore, conventional color adjustment during broadcasting absorbs fundamental color differences among multiple cameras in addition to adjustments such as changing exposure (iris and shutter speed) and filters depending on the object and effects. Therefore, the operator switches the output video of each camera on the display monitor and adjusts the color of each camera (gain, gamma, setup, flare of two or more of the three primary colors of R signal, G signal, and B signal) Etc.) manually. However, in this manual adjustment method, in addition to being troublesome, it is possible to match some colors on the screen, such as the main object and the overall main color. It was difficult to match the colors.

  The present invention has been made to solve the above-described problems of the prior art, and provides a technique capable of aligning the colors of images transmitted from a plurality of cameras with high accuracy in a multi-camera system. Let it be an issue.

  In order to solve the above-described problem, the color characteristic correction apparatus according to claim 1 is a camera that converts a video imaged through an optical system into a digital video signal and then performs color adjustment of the video signal by a color adjustment unit. In a multi-camera system that uses a plurality of images, and switches and sends out images captured by the plurality of cameras, a color characteristic correction device provided in the camera for matching the color characteristics between the plurality of cameras, 1 lookup table storage means, lookup table output means, lookup table input means, second lookup table storage means, first camera characteristic conversion means, second camera characteristic conversion means, , Parameter input means, color adjustment means, and parameter output means.

  According to such a configuration, the color characteristic correction apparatus uses the first look-up table storage unit to set a reference value predetermined for each exposure amount input to the image sensor via the optical system and pixels output by the image sensor. The correspondence with the normalized pixel value obtained by normalizing the value is stored as a lookup table indicating the characteristics of the camera. This lookup table may be provided in advance or may be generated when the camera is used.

In addition, the color characteristic correction apparatus outputs the lookup table stored in the first lookup table storage unit to another camera by the lookup table output unit.
The color characteristic correction apparatus inputs the look-up table output from the look-up table output means of another camera by the look-up table input means.
The color characteristic correction apparatus, by the second look-up table storage device stores a look-up table entered in Le click up table input means.
The color characteristic correction apparatus refers to the lookup table stored in the first lookup table storage means by the first camera characteristic conversion means, and uses the normalized pixel value corresponding to the current exposure state as the reference value. Convert to Thereby, the normalized pixel value of the lookup table can be converted into a reference value that is a value that can be matched with the lookup table of another camera.

Furthermore, the color characteristic correction apparatus corresponds to the reference value converted by the first camera characteristic conversion unit from the lookup table stored in the second lookup table storage unit by the second camera characteristic conversion unit. The normalized pixel value to be read is read and converted into a pixel value corresponding to the normalized pixel value.
Furthermore, the color characteristic correction apparatus inputs parameters for color adjustment by parameter input means. Here, the parameter is at least one of pedestal, gain, gamma, white clip, knee, and detail.
Then, the color characteristic correction apparatus performs color adjustment of the pixel value converted by the second camera characteristic conversion unit based on the parameter input to the parameter input unit by the color adjustment unit.
Then, the color characteristic correction apparatus outputs parameters to other cameras by the parameter output means.

Here, when the camera provided with the color characteristic correction device functions as a master camera, the lookup table output unit outputs the lookup table stored in the first lookup table storage unit to the slave camera. The parameter input means inputs a parameter from the outside, and the parameter output means outputs the parameter to the slave camera.
On the other hand, when a camera equipped with the color characteristic correction device is to function as a slave camera, the lookup table input means inputs the lookup table output from the master camera, and the parameter input means outputs from the master camera. Enter the parameters.

Thus, before broadcasting, the characteristics of the slave camera can be matched with the characteristics of the master camera serving as a reference.
Also, during broadcasting, when the color of the pixel value is adjusted in the master camera, the slave camera can acquire the color adjustment parameters, so the color of the pixel value in the slave camera is the same as that of the master camera. Can be adjusted. For this reason, the slave camera can reproduce the same color as that of the reference master camera with high accuracy. Further, the color adjustment performed for the effect on the reference master camera can be reproduced with high accuracy by the remaining slave cameras.

  A color characteristic correction apparatus according to a second aspect of the present invention is the color characteristic correction apparatus according to the first aspect, further comprising a lookup table creating unit.

According to such a configuration, the color characteristic correction apparatus normalizes pixel values obtained by photographing a chart having a plurality of portions with known reflectivities for each exposure amount by the look-up table creating unit to obtain normalized pixel values. A lookup table is created by using the normalized pixel value and a reference value predetermined for each exposure amount.
When the camera equipped with the color characteristic correction device is to function as a master camera, the lookup table created by the lookup table creation means is stored in the first lookup table storage means and the second lookup table storage means. When the camera having the color characteristic correction device is stored and functioning as a slave camera, the lookup table created by the lookup table creation unit is stored in the first lookup table storage unit.
According to this, a detailed look-up table can be created over the entire response range of the image sensor of the camera, so that the characteristics of the camera can be expressed more accurately.

  According to a third aspect of the present invention, there is provided a plurality of cameras that use a plurality of cameras that perform color adjustment of the video signal by color adjusting means after converting a video shot through an optical system into a digital video signal. A camera for use in a multi-camera system that switches and sends out images shot in step 1, wherein the first look-up table storage means, the look-up table output means, the look-up table input means, and the second look-up table The storage unit, the first camera characteristic conversion unit, the second camera characteristic conversion unit, the parameter input unit, the color adjustment unit, and the parameter output unit are provided.

  According to this configuration, the camera uses the first lookup table storage unit to normalize the reference value predetermined for each exposure amount input to the image sensor via the optical system and the pixel value output by the image sensor. The correspondence relationship with the normalized pixel values is stored as a look-up table indicating the characteristics of the camera. This lookup table may be provided in advance or may be generated when the camera is used.

Further, the camera outputs the lookup table stored in the first lookup table storage means to the other camera by the lookup table output means.
The camera inputs the look-up table output from the look-up table output means of another camera by the look-up table input means.
In addition, the camera stores the lookup table input by the lookup table input means by the second lookup table storage means.
The camera refers to the lookup table stored in the first lookup table storage means by the first camera characteristic conversion means, and converts the normalized pixel value corresponding to the current exposure state into a reference value. Thereby, the normalized pixel value of the lookup table can be converted into a reference value that is a value that can be matched with the lookup table of another camera.

Further, the camera performs normalization corresponding to the reference value converted by the first camera characteristic conversion unit from the lookup table stored in the second lookup table storage unit by the second camera characteristic conversion unit. The pixel value is read and converted into a pixel value corresponding to the normalized pixel value.
Furthermore, the camera inputs parameters for color adjustment by parameter input means. Here, the parameter is at least one of pedestal, gain, gamma, white clip, knee, and detail.
Then, the camera performs color adjustment of the pixel value converted by the second camera characteristic conversion unit based on the parameter input to the parameter input unit by the color adjustment unit.
And a camera outputs a parameter to another camera by a parameter output means.

When this camera functions as a master camera, the look-up table output means outputs the look-up table stored in the first look-up table storage means to the slave camera, and the parameter input means outputs parameters from the outside. In addition to the input, the parameter output means outputs the parameter to the slave camera.
On the other hand, when this camera functions as a slave camera, the lookup table input means inputs the lookup table output from the master camera, and the parameter input means inputs the parameters output from the master camera.

As a result, the characteristics of the master camera can be transmitted to the slave camera before broadcasting, so that the slave camera can share the characteristics of the master camera.
Further, during broadcasting, the slave camera can reproduce the same color as that of the master camera serving as a reference with high accuracy. Further, the color adjustment performed for the effect on the reference master camera can be reproduced with high accuracy by the remaining slave cameras.

According to the present invention, the following excellent effects can be obtained.
According to the first aspect of the present invention, the other camera can reproduce the color of the reference camera with high accuracy. As a result, in the multi-camera system, the colors of the images transmitted from the respective cameras can be aligned with high accuracy, so that the uncomfortable feeling caused by the difference in the color tone of the images when the cameras are switched can be reduced.
According to the second aspect of the present invention, since a detailed look-up table can be generated over the entire response range of the image sensor of the camera, the characteristics of each camera can be expressed more accurately.
According to the third aspect of the invention, since the parameter for color adjustment of the reference camera can be transmitted to the other camera, the other camera is the same as the reference camera based on this parameter. It is possible to adjust the color. That is, the slave camera can reproduce the same color as that of the reference master camera with high accuracy.

It is a conceptual diagram for demonstrating the multi camera system with which the color characteristic correction apparatus which concerns on this embodiment is used. It is a block block diagram for demonstrating the structure of the camera provided with the color characteristic correction apparatus which concerns on this embodiment. It is a block configuration diagram for explaining a detailed configuration of a color characteristic correction apparatus according to the present embodiment. It is a conceptual diagram for demonstrating a mode that each camera image | photographs a gray scale chart before broadcast. (A) is a figure which shows the relationship between the brightness | luminance of an imaging | photography scene, and an image pick-up element input (exposure amount), and (b) is a figure which shows the change of the pixel value with respect to an image pick-up element input (exposure amount). It is the figure which showed the characteristic curve which shows the correspondence of the normalized pixel value with respect to the reference curve and the image pick-up element input (exposure amount) of two cameras. (A) is the figure which showed the look-up table created by the look-up table preparation means of the color characteristic correction apparatus of a master camera, (b) is the look-up table preparation means of the color characteristic correction apparatus of a slave camera. It is the figure which showed the look-up table created by. It is the flowchart which showed the flow of the process performed with a master camera. It is the flowchart which showed the flow of the process performed with a slave camera. It is the figure which showed an example of the response curve of the conventional camera or film.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overview of multi-camera system]
First, an outline of a multi-camera system including a master camera and a slave camera of the present invention will be described with reference to FIG.

The multi-camera system 1A uses the plurality of cameras 10 to photograph the same object from different viewpoints, and appropriately switches the images transmitted from the plurality of cameras 10, thereby allowing viewers to view images from various viewpoints. It is to provide.
As shown in FIG. 1, the multi-camera system 1A includes a single master camera 10A and two slave cameras 10B and 10C.

The master camera 10A is a camera that serves as a reference for color adjustment of each camera in the multi-camera system 1A, and is appropriately determined by an operator.
The slave cameras 10B and 10C are cameras that perform color adjustment in accordance with the color adjustment of the master camera 10A, and each is connected to the master camera 10A.

The master camera 10A inputs process control parameters from the outside, adjusts the color of the video signal based on the parameters, and outputs the adjusted video signal.
The master camera 10A outputs characteristic data indicating the characteristics of the master camera 10A to the slave cameras 10B and 10C in advance before broadcasting. On the other hand, the slave cameras 10B and 10C acquire the characteristic data from the master camera 10A before broadcasting, so that the characteristics of the slave cameras 10B and 10C are matched with the characteristics of the master camera 10A.
The master camera 10A outputs color adjustment parameters to the slave cameras 10B and 10C when adjusting the color of the pixel value during broadcasting. On the other hand, the slave cameras 10B and 10C acquire the parameter for color adjustment from the master camera 10A, and adjust the color of the pixel value according to the adjustment of the color of the pixel value performed by the master camera 10A based on this parameter. The adjusted video signal is output.
In this way, the colors of the images transmitted from all the cameras 10 used in the multi-camera system 1A can be matched.

Next, the configuration of the camera 10 will be described with reference to FIG.
As shown in FIG. 2, the camera 10 mainly includes a lens 31, an image sensor 32, a low-pass filter 33, a front correction circuit 34, an A / D converter 35, and the color characteristic correction device 1. It is prepared for.

The lens 31 forms an image of an object, and is connected to an iris adjustment unit (not shown). By automatically or manually adjusting the iris adjustment unit, the iris changes from an open state to a close state. It is supposed to be made. Each time the iris of the lens 31 is changed, the current exposure state is output to the color characteristic correction apparatus 1. Further, the lens 31 is configured such that the iris is adjusted by an iris control signal input from the color characteristic correction apparatus 1 to an iris adjustment unit (not shown).
The image formed by the lens 31 is input to the image sensor 32.

  The image pickup device 32 decomposes the image transmitted through the lens 31 into three primary color image signals (G signal, B signal, and R signal). Video signals (G signal, B signal, and R signal) decomposed by the image sensor 32 are input to the low-pass filter 33.

  The low-pass filter 33 removes high-frequency components from the video signal input from the image sensor 32. The video signal from which the high frequency component has been removed by the low pass filter 33 is input to the precorrection circuit 34.

  The pre-correction circuit 34 corrects the video signal input from the low-pass filter 33 before input to the color characteristic correction apparatus 1, and has a function of performing, for example, three processes of a preamplifier, a pre-gamma, and a penny. Have. The preamplifier amplifies the output of the video signal, the pregamma corrects the clarity of the image of the video signal, and the pliny compresses the gradation of the high-brightness portion of the video signal. Is reproduced. The video signal corrected by the precorrection circuit 34 is input to the A / D converter 35.

The A / D converter 35 converts the analog video signal corrected by the precorrection circuit 34 into a digital video signal. The digital video signal converted by the A / D converter 35 is input to the color characteristic correction apparatus 1. In addition, when the chart C (see FIG. 4) is photographed in the color adjustment before broadcasting, the A / D converter 35 outputs the pixel value at the measurement point of the chart C (see FIG. 4) to the color characteristic correction apparatus 1. To do.
As the lens 31, the image sensor 32, the low-pass filter 33, the precorrection circuit 34, and the A / D converter 35 described above, known ones can be used as appropriate.

The color characteristic correction apparatus 1 corrects the color characteristic of a video signal. Next, the detailed configuration of the color characteristic correction apparatus 1 will be described with reference to FIG.
As shown in FIG. 3, the color characteristic correction apparatus 1 includes an LUT creation unit (lookup table creation unit) 11, an LUT storage unit (first lookup table storage unit) 12, and a master LUT output unit (lookup). Table output means) 13, master LUT input means (lookup table input means) 14, master LUT storage means (second lookup table storage means) 15, and camera characteristic conversion means (first camera characteristic conversion means). ) 16, master camera characteristic conversion means (second camera characteristic conversion means) 17, parameter input means 18, color adjustment means 19, and parameter output means 20.

  As shown in FIG. 3, the LUT creation means (lookup table creation means) 11 is provided for each exposure amount input to the image sensor 32 (see FIG. 2) via an optical system such as a lens 31 (see FIG. 2). A look-up table (characteristic data) indicating the characteristics of the camera 10 with the correspondence between the predetermined reference value and the normalized pixel value obtained by normalizing the pixel value output from the A / D converter 35 (see FIG. 2). Is to create as. Here, the predetermined reference value may be a value having a linear relationship with the exposure amount, or may be a logarithm of the exposure amount. In addition, the normalized pixel value is represented by replacing a pixel value described in, for example, 8 bits (256 gradations) with a value of 0 to 1.

Here, a procedure for creating a lookup table by the LUT creation means 11 will be described with reference to FIG.
First, the master camera 10A and the slave cameras 10B and 10C are arranged close to each other in the broadcasting studio. In this state, optical elements such as lenses and filters are set for each camera 10 by the operator. A display screen 40 on which a chart C with a known reflectance is displayed is placed on the front side of each camera 10, and the position of each camera 10 is set at a position where this chart C can be captured at the center of the screen of each camera 10. Fix it. Here, a gray scale chart is used as the chart C. Then, while automatically or manually changing the iris of the lens 31 (see FIG. 2) of each camera 10 from an open state to a close state, for example, the exposure amount in the current exposure state and the measurement of the chart C in the current exposure state Measure and accumulate the pixel value of a point.

  Here, when a video is shot with a television camera including the camera 10, the iris, shutter speed, and zoom zoom of the zoom lens are obtained before the luminance of the measurement point of the shooting scene is obtained as a pixel value at one corresponding point through the image sensor. The amount of light reaching the image sensor changes due to a change in the F value related to the amount. Here, the setting for controlling the amount of light is used as the exposure amount. However, in the case of a television camera, this exposure amount can be calculated by acquiring F-number, shutter speed, etc. from the lens as data. In this case, the relative change in the exposure amount can be calculated from the relative change in the exposure. For example, if the exposure doubles, the amount of light that reaches, that is, the exposure amount doubles.

  FIG. 5A shows the correspondence between the real-world scene luminance to be imaged and the image sensor input (exposure amount) when the lens iris is changed. It can be seen that the exposure amount with respect to the brightness of the shooting scene changes between when the iris is on the open side and when the iris is on the close side. FIG. 5B shows the relationship of the pixel value to the exposure amount of the channel of the video signal, for example, the G signal. FIG. 5B illustrates a case where the vertical axis is described by a pixel value of 8 bits (256 gradations). The horizontal axis may be a logarithmic axis depending on the characteristics of the image sensor 32 and the like. Normally, the pixel value has a non-linear relationship with the exposure amount, and it can be assumed that the pixel value has a monotonous relationship except for the saturated region.

Further, FIG. 5B shows the response characteristic of the camera separated from the exposure amount. If the response characteristic of the camera becomes known, the luminance of the photographic scene on the image is determined when a certain exposure amount is determined. A correspondence of how many pixel values are obtained is obtained. On the other hand, if the exposure amount is known, the relative luminance of the photographic scene can be obtained from the current pixel value. In FIG. 5B, only the G signal channel is illustrated, but the same can be said for the remaining two channels in the case where the image pickup device has three plates of R signal, G signal, and B signal.
In the color characteristic correction apparatus 1 of the present invention, on the premise of such a correspondence relationship between the exposure amount and the pixel value of the measurement point of the shooting scene, the exposure amount in the current exposure state and the current exposure state by the LUT creation unit 11 The look-up table indicating the characteristics of each camera 10 is created by analyzing the pixel values at the measurement points on the chart C in FIG.

The LUT creating unit 11 receives an input of the exposure amount in the current exposure state from an iris adjustment unit (not shown) connected to the lens 31 and also receives a chart corresponding to the exposure amount in the current exposure state from the A / D converter 35. Accepts the input of the pixel value of the measurement point.
Further, the LUT creation unit 11 stores the exposure amount in the current exposure state and the pixel value of the measurement point on the chart corresponding to the exposure amount in association with each other.

  The LUT creation unit 11 analyzes this accumulated data and creates a lookup table indicating the characteristic data of the camera 10. For example, Non-Patent Document 1 (DEBEVEC, PE, AND MALIK, J. 1997. Recovering high dynamic range radiance maps from photographs. In SIGGRAPH 97 Conference Proceedings, Addison Wesley T. Whitted, Ed., Annual Conference Series. , ACM SIGGRAPH, 369/78). Accordingly, it is possible to calculate a pixel value that is assumed to be observed by a camera having an ideal response characteristic from a pixel value of an image photographed in a certain exposure state.

  Here, FIG. 6 shows the relationship between the characteristic curves a and b indicating the characteristics of the master camera 10A and the slave camera 10B in a certain exposure state, and the reference line s in which the pixel value is linear with respect to the exposure amount. Indicated. When the camera 10 including the color characteristic correction apparatus 1 is caused to function as the master camera 10A, the LUT creation unit 11 uses a lookup table indicating the correspondence between the reference straight line s and the characteristic curve a of the master camera 10A illustrated in FIG. A lookup table shown in FIG. On the other hand, when the camera 10 provided with the color characteristic correction apparatus 1 is caused to function as the slave camera 10B, the LUT creation unit 11 looks up the correspondence relationship between the reference straight line s and the characteristic curve b of the slave camera 10B shown in FIG. As shown in FIG. 7, a lookup table shown in FIG.

The lookup table created by the LUT creation unit 11 in this way is stored in the LUT storage unit 12.
When the camera 10 including the color characteristic correction apparatus 1 is caused to function as the master camera 10 </ b> A, the lookup table created by the LUT creation unit 11 is further stored in the master LUT storage unit 15.

The LUT storage means (first lookup table storage means) 12 stores the lookup table created by the LUT creation means 11. When the camera 10 including the color characteristic correction apparatus 1 is caused to function as the master camera 10A, the LUT storage unit 12 stores a lookup table shown in FIG. Further, when the camera 10 including the color characteristic correction apparatus 1 is caused to function as the slave camera 10B, the LUT storage unit 12 stores a lookup table illustrated in FIG.
The look-up table stored in the LUT storage unit 12 is appropriately referred to by the camera characteristic conversion unit 16 described later.

  The master LUT output means (lookup table output means) 13 uses the lookup table created by the LUT creation means 11 of the color characteristic correction apparatus 1 of the master camera 10A as the master lookup table as slave cameras 10B, 10C (others). Output to the camera). The master LUT output means 13 outputs the lookup table shown in FIG. 7A to the slave cameras 10B and 10C as the master lookup table.

  The master LUT input means (lookup table input means) 14 inputs the master lookup table output from the master LUT output means 13 of the color characteristic correction apparatus 1 of the master camera 10A. Here, the master look-up table shown in FIG. 7A is input from the master camera 10A by the master LUT input means 14 of the color characteristic correction apparatus 1 of the slave cameras 10B and 10C, and is input to the master LUT storage means 15 respectively. Remember.

  As described above, the color characteristic correction apparatus 1 of the master camera 10A and the color characteristic correction apparatuses 1 of the slave cameras 10B and 10C each store the lookup table shown in FIG. 7A by the master LUT storage unit 15. .

The master LUT storage unit (second lookup table storage unit) 15 stores a master lookup table indicating the characteristics of the master camera 10A.
The master lookup table stored in the master LUT storage unit 15 is appropriately referred to by the master camera characteristic conversion unit 17.

The camera characteristic conversion means (first camera characteristic conversion means) 16 converts the camera characteristics of the master camera 10A or the slave cameras 10B and 10C into data independent of the device.
When the camera characteristic conversion unit 16 receives an input of a current exposure state from an iris adjustment unit (not shown) connected to the lens 31, and receives an input of a pixel value (video signal) of an object from the A / D converter 35. The normalized pixel value corresponding to the current exposure state is converted into a reference value for each exposure amount by referring to the lookup table stored in the LUT storage unit 12. The video signal converted into the reference value is output to the master camera characteristic conversion means 17.

The master camera characteristic conversion means (second camera characteristic conversion means) 17 converts the camera characteristics of the master camera 10A or the slave cameras 10B and 10C into the camera characteristics of the master camera 10A.
When the master camera characteristic conversion unit 17 receives the input of the video signal converted to the reference value from the camera characteristic conversion unit 16, the master camera characteristic conversion unit 17 refers to the master lookup table stored in the master LUT storage unit 15 and performs the corresponding normalization. Read the pixel value. Further, the master camera characteristic conversion unit 17 converts the normalized pixel value into a bit amount as a video signal required for processing by the color adjustment unit 19, and sets it as an input pixel value of the color adjustment unit 19.

Thereby, the camera characteristics of the master camera 10A or the slave cameras 10B and 10C can be converted into the camera characteristics of the master camera 10A.
That is, the pixel value in the input stage of the color adjustment unit 19 of the color characteristic correction apparatus 1 of the master camera 10A is matched with the pixel value in the input stage of the color adjustment unit 19 of the color characteristic correction apparatus 1 of the slave cameras 10B and 10C. be able to.
The pixel value calculated by the master camera characteristic conversion unit 17 is output to the color adjustment unit 19.

The parameter input unit 18 inputs parameters for adjusting the pixel value by the color adjusting unit 19. For example, when gain adjustment is performed by the color adjusting unit 19, a volume value or a numerical value is directly input as a parameter. When the color characteristic correction apparatus 1 is provided in the master camera 10A, for example, parameters input by an operator via an input unit such as an external remote controller or a volume knob (not shown) are input to the parameter input unit 18. On the other hand, when the color characteristic correction apparatus 1 is provided in the slave cameras 10 </ b> B and 10 </ b> C, parameters output from the parameter output unit 20 described later are input to the parameter input unit 18.
The parameters input to the parameter input unit 18 are output to the color adjustment unit 19.

The color adjusting unit 19 adjusts the color of the pixel value input from the master camera characteristic converting unit 17.
In the color characteristic correction apparatus 1 of the master camera 10A, the color adjustment unit 19 adjusts the color of the pixel value based on the parameter input to the parameter input unit 18 from the operator. The color adjusting unit 19 has a function of performing a plurality of processes (pedestal, gain, etc.) for adjusting the color of the pixel value, and based on the parameters input from the parameter input unit 18, the plurality of processes. To adjust the color of the pixel value.

  On the other hand, in the color characteristic correction apparatus 1 of the slave cameras 10B and 10C, the color adjustment unit 19 performs a plurality of processes as described above based on the color adjustment parameters acquired from the master camera 10A by the parameter input unit 18. Adjust the color of the pixel value by doing.

  The parameter output unit 20 outputs the color adjustment parameters input to the parameter input unit 18 of the color characteristic correction apparatus 1 of the master camera 10A to the slave cameras 10B and 10C.

[Operation of Color Correction Device]
Next, with reference to FIGS. 4 to 9, the operation of the color characteristic correction apparatus and the color adjustment method between the cameras 10A, 10B, and 10C in the multi-camera system 1A will be described. Similarly to the above, the camera 10A is a master camera, and the cameras 10B and 10C are slave cameras. Since the operation of the slave camera is the same, the following description will be given using the camera 10B as a representative as appropriate.

(Color adjustment before broadcasting)
First, the operation of the color characteristic correction apparatus 1 before broadcasting will be described.
In the color characteristic correction apparatus 1, the current exposure state is input from the lens 31 and the pixel value is input from the A / D converter 35 by the LUT creation unit 11. Then, a correspondence relationship between a reference value predetermined for each exposure amount input to the image sensor 32 and a normalized pixel value is created as a lookup table indicating the characteristics of the master camera 10A or the slave camera 10B. Specifically, the color characteristic correction apparatus 1 of the master camera 10A creates a master lookup table shown in FIG. 7A, and the color characteristic correction apparatus 1 of the slave camera 10B uses the look shown in FIG. 7B. Create an uptable.
Each LUT creation unit 11 stores the created lookup table in each LUT storage unit 12.

Next, the color characteristic correction apparatus 1 of the master camera 10A outputs the lookup table created by the LUT creation unit 11 to the slave camera 10B as a master lookup table by the master LUT output unit 13.
Then, the color characteristic correction apparatus 1 of the slave camera 10 </ b> B receives the master lookup table output from the master camera 10 </ b> A by the master LUT input unit 14 and stores it in the master LUT storage unit 15.
Thereby, the characteristic of the slave camera 10B is matched with the characteristic of the master camera 10A.

(Color adjustment during broadcasting)
Next, the operation of the color characteristic correction apparatus 1 during broadcasting will be described with particular reference to FIG. 7, FIG. 8, and FIG.

First, the operation of the color characteristic correction apparatus 1 of the master camera 10A will be described.
When an object is photographed by the master camera 10A during broadcasting, the current exposure state is output from the lens 31 (see FIG. 2), and a video signal corresponding to the exposure amount from the image sensor 32 (see FIG. 2). Is output, and the current exposure state and video signal are input to the camera characteristic conversion means 16 of the color characteristic correction apparatus 1 (step S1).

Here, for example, when the camera 10A is photographing an object in a certain exposure state, it is assumed that the exposure amount corresponding to the luminance at a certain point of the object is 0.6. In this case, as a characteristic of the camera A, an output having a normalized pixel value of 0.325 with respect to an exposure amount of 0.6 is obtained.
Next, the color characteristic correcting apparatus 1 stores the reference value corresponding to the normalized pixel value 0.325 by the camera characteristic converting unit 16 in FIG. 7A stored in the LUT storage unit 12 of the camera 10A. The master lookup table shown is referred to (step S2).
The color characteristic correction apparatus 1 converts the normalized pixel value 0.325 to the reference value 0.6 by the camera characteristic conversion unit 16 (step S3). The color characteristic correction apparatus 1 outputs the video signal converted into the reference value by the camera characteristic conversion unit 16 to the master camera characteristic conversion unit 17 as a normalized pixel value.

When the master camera characteristic conversion unit 17 receives the input of the normalized pixel value 0.6 from the camera characteristic conversion unit 16, the color characteristic correction apparatus 1 is shown in FIG. 7A stored in the master LUT storage unit 15. The master lookup table is referred to (step S4). Then, the color characteristic correcting apparatus 1 converts the normalized pixel value 0.6 into the normalized pixel value 0.325 indicating the characteristic of the master camera 10A by the master camera characteristic converting unit 17 (step S5). Further, the color characteristic correcting apparatus 1 converts the normalized pixel value 0.325 into a bit amount as a video signal required for processing by the color adjusting means 19 by the master camera characteristic converting means 17, (Step S6).
Then, the color characteristic correction apparatus 1 outputs the pixel value to the color adjustment unit 19 by the master camera characteristic conversion unit 17.

When the color input correction unit 1 of the master camera 10A receives an input of a parameter for color adjustment from the outside by the parameter input unit 18, the color characteristic correction device 1 outputs the parameter to the color adjustment unit 19 (step S7).
Next, the color characteristic correction apparatus 1 adjusts the color of the video signal (pixel value) input from the master camera characteristic conversion unit 17 by the color adjustment unit 19 based on the parameters (step S8).
Further, the color characteristic correcting apparatus 1 outputs the color adjustment parameter to the parameter output unit 20 by the color adjustment unit 19, and outputs the parameter for color adjustment to the slave camera 10B by the parameter output unit 20 (step S9).

The color characteristic correction apparatus 1 of the master camera 10A operates as described above.
Note that in the color characteristic correction apparatus 1 of the master camera 10A, the camera characteristic conversion unit 16 and the master camera characteristic conversion unit 17 refer to the lookup table in FIG. The pixel value obtained by converting the pixel value input from FIG. 2) by the camera characteristic conversion unit 16 and the master camera characteristic conversion unit 17 is the same as the pixel value input from the image sensor 32 (see FIG. 2). Become. For this reason, in the color characteristic correction apparatus 1 of the master camera 10A, the camera characteristic conversion unit 16 and the master camera characteristic conversion unit 17 may be bypassed.

Next, the operation of the color characteristic correction apparatus 1 of the slave camera 10B (10C) will be described.
When an object is photographed by the slave camera 10B during broadcasting, an exposure amount is output from the lens 31 (see FIG. 2), and a video signal corresponding to the current exposure state is output from the image sensor 32 (see FIG. 2). Is output, and the current exposure state and video signal are input to the camera characteristic conversion means 16 of the color characteristic correction apparatus 1 (step S21).

Here, for example, when the master camera 10A and the slave camera 10B are shooting in an exposure state in which the master camera 10A and the slave camera 10B are directed in substantially the same direction from the substantially same position, the exposure amount corresponding to the luminance at a certain point of the object is 0.6. Suppose. In this case, as a characteristic of the slave camera B, an output of a normalized pixel value of 0.5161 is obtained with respect to an exposure amount of 0.6. The color characteristic correction apparatus 1 uses the look shown in FIG. 7B stored in the LUT storage unit 12 of the slave camera 10B in order to find the reference value corresponding to the normalized pixel value 0.5161 by the camera characteristic conversion unit 16. The up table is referred to (step S22).
Then, the color characteristic correction apparatus 1 converts the normalized pixel value 0.5161 into the reference value 0.6 by the camera characteristic conversion unit 16 (step S23). The color characteristic correction apparatus 1 outputs the reference value as a normalized pixel value to the master camera characteristic conversion unit 17 by the camera characteristic conversion unit 16.

When the master camera characteristic conversion unit 17 receives the input of the video signal and the normalized pixel value 0.6 from the camera characteristic conversion unit 16, the color characteristic correction apparatus 1 stores the image characteristics stored in the master LUT storage unit 15 as shown in FIG. ) Is referred to (step S24). Then, the color characteristic correcting apparatus 1 converts the normalized pixel value 0.6 into the normalized pixel value 0.325 indicating the characteristic of the master camera 10A by the master camera characteristic converting unit 17 (step S25). Further, the color characteristic correcting apparatus 1 converts the normalized pixel value 0.325 into a bit amount as a video signal required for processing by the color adjusting means 19 by the master camera characteristic converting means 17, (Step S26).
Then, the color characteristic correction apparatus 1 outputs the pixel value to the color adjustment unit 19 by the master camera characteristic conversion unit 17.

  The color characteristic correction apparatus 1 acquires the parameter for color adjustment output from the parameter output means 20 of the color characteristic correction apparatus 1 of the master camera 10A by the parameter input means 18, and inputs it to the color adjustment means 19 (step S27). ).

In the color characteristic correction apparatus 1, the color adjusting unit 19 adjusts the color of the video signal (pixel value) input from the master camera characteristic conversion unit 17 based on the parameter input from the parameter input unit 18 ( Step S28).
The color characteristic correction apparatus 1 of the slave camera 10B (10C) operates as described above.

  According to the color characteristic correcting apparatus 1 according to the present embodiment, the characteristics of the slave cameras 10B and 10C can be matched with the characteristics of the master camera 10A before broadcasting, that is, the image sensors of all the cameras 10 before broadcasting. Therefore, the slave cameras 10B and 10C can reproduce the same color as the reference master camera 10A with high accuracy. Thereby, the color reproducibility between the plurality of cameras 10 can be maintained at a higher level than when the color adjustment is performed individually by each camera 10.

  The present invention is not limited to the above-described embodiment, and can be modified without departing from the spirit of the present invention. For example, in the above-described embodiment, the color characteristic correction apparatus 1 is a constituent element of the camera 10, but is not limited thereto, and may be externally attached to an existing camera. According to this, since the operation of the color characteristic correction apparatus 1 can be obtained while using the existing camera as it is, the existing camera can be used effectively and the introduction cost is reduced.

  In the above-described embodiment, the configuration of the color characteristic correction apparatus 1 of the master camera 10A and the color characteristic correction apparatus 1 of the slave cameras 10B and 10C are the same, but the configuration is not limited thereto. For example, when the color characteristic correction apparatus 1 dedicated to the master camera 10A is configured, the master LUT storage unit 15, the camera characteristic conversion unit 16, and the master camera characteristic conversion unit 17 may not be provided.

  In the above-described embodiment, the imaging element 32 is configured by three plates of the R signal, the G signal, and the B signal. However, the present invention is not limited to this and may be a single plate. In this case as well, the same effect can be obtained in the color characteristic correcting apparatus 1.

  Furthermore, in the above-described embodiment, the lookup table is created by the LUT creation unit 11 before broadcasting, but the present invention is not limited to this. For example, a lookup table created in advance may be stored in the LUT storage unit 12 or the master LUT storage unit 15 of the master camera 10A or the slave cameras 10B, 10C. For example, if the optical elements of the master camera 10A or the slave cameras 10B and 10C are the same as the conditions at the time of creating an existing lookup table, the existing lookup table may be used. Thereby, the color adjustment before broadcasting is further simplified.

  Furthermore, in the above-described embodiment, the case where the color characteristic correction apparatus 1 corrects the color characteristics of the plurality of cameras 10 used in the multi-camera system 1A for television broadcasting has been described as an example, but the present invention is not limited thereto. Instead, it may be used for correcting the color characteristics of a plurality of cameras 10 existing at remote points such as fixed point cameras and surveillance cameras. Further, by correcting the color characteristics of the plurality of cameras 10 by the color characteristic correction apparatus 1, it becomes possible to improve the performance when acquiring three-dimensional model information and textures using the plurality of cameras 10.

DESCRIPTION OF SYMBOLS 1A Multi camera system 1 Color characteristic correction apparatus 10 Camera 10A Master camera 10B, 10C Slave camera 11 LUT creation means (lookup table creation means)
12 LUT storage means (lookup table storage means)
13 Master LUT output means (master lookup table output means)
14 Master LUT input means (master lookup table input means)
15 Master LUT storage means (master lookup table storage means)
16 Camera characteristic conversion means 17 Master camera characteristic conversion means 18 Parameter input means 19 Color adjustment means 20 Parameter output means

Claims (3)

A multi-camera that uses a plurality of cameras that perform color adjustment of the video signal by color adjustment means after the video shot through the optical system is converted into a digital video signal, and switches and sends the video shot by the plurality of cameras. In the system, in order to match the color characteristics among the plurality of cameras, a color characteristic correction device provided in the camera,
A correspondence relationship between a reference value predetermined for each exposure amount input to the image sensor via the optical system and a normalized pixel value obtained by normalizing a pixel value output from the image sensor indicates the characteristics of the camera. First lookup table storage means for storing as a lookup table;
Lookup table output means for outputting the look-up table stored in the first look-up table storage means to another camera;
Lookup table input means for inputting the lookup table output from the lookup table output means of the other camera;
Second lookup table storage means for storing the lookup table input by the lookup table input means;
First camera characteristic conversion means for referring to the look-up table stored in the first look-up table storage means and converting a normalized pixel value corresponding to a current exposure state to the reference value;
A normalized pixel value corresponding to the reference value converted by the first camera characteristic conversion unit is read from the lookup table stored in the second lookup table storage unit, and the normalized pixel value Second camera characteristic conversion means for converting into a pixel value corresponding to
Parameter input means for inputting at least one of pedestal, gain, gamma, white clip, knee, and detail as parameters for color adjustment;
The color adjustment unit that performs color adjustment of the pixel value converted by the second camera characteristic conversion unit based on the parameter input to the parameter input unit;
Parameter output means for outputting the parameter to the other camera;
With
When a camera equipped with the color characteristic correcting apparatus is to function as a master camera, the lookup table output means outputs the lookup table stored in the first lookup table storage means to a slave camera. The parameter input means inputs the parameter from the outside, and the parameter output means outputs the parameter to the slave camera.
When the camera having the color characteristic correction device is to function as a slave camera, the lookup table input means inputs the lookup table output from the master camera, and the parameter input means causes the master camera to A color characteristic correction apparatus characterized in that the parameter output from (2) is input. The pixel value obtained by photographing a chart having a plurality of portions with known reflectivities for each exposure amount is normalized to obtain the normalized pixel value, and the normalized pixel value and the exposure amount are determined in advance. Lookup table creation means for creating the lookup table according to the reference value,
When the camera having the color characteristic correcting apparatus is caused to function as a master camera, the lookup table created by the lookup table creation means is stored in the first lookup table storage means and the second lookup table storage. Memorize the means,
When the camera having the color characteristic correction device is caused to function as a slave camera, the lookup table created by the lookup table creation unit is stored in the first lookup table storage unit. Item 2. The color characteristic correction apparatus according to Item 1. A multi-camera that uses a plurality of cameras that perform color adjustment of the video signal by color adjustment means after the video shot through the optical system is converted into a digital video signal, and switches and sends the video shot by the plurality of cameras. A camera used in the system,
A correspondence relationship between a reference value predetermined for each exposure amount input to the image sensor via the optical system and a normalized pixel value obtained by normalizing a pixel value output from the image sensor indicates the characteristics of the camera. First lookup table storage means for storing as a lookup table;
Lookup table output means for outputting the look-up table stored in the first look-up table storage means to another camera;
Lookup table input means for inputting the lookup table output from the lookup table output means of the other camera;
Second lookup table storage means for storing the lookup table input by the lookup table input means;
First camera characteristic conversion means for referring to the look-up table stored in the first look-up table storage means and converting a normalized pixel value corresponding to a current exposure state to the reference value;
A normalized pixel value corresponding to the reference value converted by the first camera characteristic conversion unit is read from the lookup table stored in the second lookup table storage unit, and the normalized pixel value Second camera characteristic conversion means for converting into a pixel value corresponding to
Parameter input means for inputting at least one of pedestal, gain, gamma, white clip, knee, and detail as parameters for color adjustment;
The color adjustment unit that performs color adjustment of the pixel value converted by the second camera characteristic conversion unit based on the parameter input to the parameter input unit;
Parameter output means for outputting the parameter to the other camera;
With
If the functioning of the person 該Ka camera as the master camera, the by a look-up table output means, and outputs the look-up table stored in the first look-up table storage unit to the slave camera, said parameter input means By inputting the parameter from outside, the parameter output means outputs the parameter to the slave camera,
If the functioning of the person 該Ka camera as a slave camera, by the look-up table input means inputs the look-up table output from the master camera, by the parameter input means, output from the master camera the A camera characterized by inputting parameters.

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