JP2021007218A - Imaging apparatus, control method thereof, and program - Google Patents

Abstract

To obtain a desired image in consideration of any input transfer characteristics.SOLUTION: An imaging apparatus includes: an output means configured to image a subject and output a first color signal; a first signal processing means configured to process the first color signal to generate a second color signal; an input means configured to input conversion characteristics for converting the second color signal into a third color signal; a second signal processing means configured to convert the second color signal into the third color signal to be output on the basis of the conversion characteristics; a specifying means configured to specify a required signal range of the first color signal required to generate the third color signal using the conversion characteristics input by the input means; and a signal increasing means configured to increase the first color signal within a range in which a signal of the required signal range does not exceed an upper limit value of a predetermined signal range when the required signal range specified by the specifying means is smaller than the predetermined signal range of the first color signal.SELECTED DRAWING: Figure 8

Description

The present invention relates to a technique for converting an image by inputting arbitrary conversion characteristics.

In video production, there is a process called color grading. This is a process of correcting the gradation and color of the image taken by the video camera to those intended by the creator, and is mainly performed by color grading software operating on the PC. At this time, in order to secure the degree of freedom of color grading as much as possible, it is often recorded in a format such as Log for shooting with underexposure. Then, the gradation and color tone are adjusted, and unnecessary parts are overexposed to create an image suitable for viewing.

The video conversion process by color grading can be written out in a format such as 3DLUT (3D lookup table). This makes it possible to perform the same color grading process on another image, or to perform the same process with software different from that at the time of color grading. In addition, by using hardware such as a conversion box that can read 3DLUT, it is possible to apply conversion processing to the output video from the video camera in real time and check it on a monitor or the like. Further, in recent years, it has become possible to read the 3DLUT by the video camera itself, and it is also possible to directly record the video to which the conversion process is applied. Therefore, it is possible to realize a so-called user LUT function that enables the video camera to read a 3D LUT prepared by the user for performing an arbitrary conversion process.

As described above, the 3D LUT is often created so as to input an image shot underexposed such as Log. Therefore, instead of retaining all the input gradations, it may have a characteristic of converting a part so as to cause overexposure. Therefore, Patent Document 1 describes a method of suppressing overexposure by gradation correction to improve image quality.

Japanese Patent No. 5591026

However, since the conversion characteristics such as 3DLUT are created in order to obtain the image desired by the user, it cannot be said that the processing that changes the final signal level is preferable. On the other hand, considering that arbitrary conversion characteristics are input, it may be preferable to change the shooting conditions.

The imaging apparatus according to the present invention includes an output means that captures a subject and outputs a first color signal, and a first signal processing means that processes the first color signal to generate a second color signal. An input means for inputting a conversion characteristic for converting the second color signal into a third color signal, and a second signal processing for converting the second color signal into a third color signal and outputting the second color signal based on the conversion characteristic. The means, the specific means for specifying the required signal range of the first color signal required to generate the third color signal using the conversion characteristics input by the input means, and the specific means for specifying. When the required signal range is smaller than the predetermined signal range of the first color signal, the first color signal is increased within a range in which the signal in the required signal range does not exceed the upper limit value of the predetermined signal range. The first signal processing means and the second signal processing so as to compensate for the change in the signal level of the third color signal due to the increase of the first color signal by the signal increasing means and the signal increasing means. It is characterized by having a compensating means for controlling at least one of the means to compensate for the signal level.

According to the present invention, it is possible to obtain a desired image in consideration of any input conversion characteristics.

Block diagram showing the internal configuration of the video camera 100 A block diagram showing the internal configuration and related parts of the image processing unit 115 in the first embodiment. The figure which shows the 3DLUT data A flowchart illustrating the processing of the first embodiment Diagram showing 3DLUT data sorted by maximum input value Flowchart explaining detailed processing of 3DLUT data analysis The figure which shows the upper part of 3DLUT data sorted by the maximum input value. The figure which shows the gradation characteristic for maintaining a signal level Block diagram showing the inside of the imaging unit 105 in the second embodiment Block diagram showing the internal configuration of the image processing unit 115 in the third embodiment

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
Hereinafter, an example of application to a video camera will be described as an example of an imaging device, but the present invention can be applied to various devices having an imaging function.

FIG. 1 is a block diagram showing an internal configuration of the video camera 100. In FIG. 1, the photographing lens 102 is a lens group including a zoom lens and a focus lens, and forms a subject image. The diaphragm 103 is a diaphragm used for adjusting the amount of light. The ND 104 is an ND filter used for dimming. The image pickup unit 105 is an image pickup device composed of a CCD, a CMOS element, or the like that converts an optical image into an electric signal. Further, the imaging unit 105 also has functions such as storage control by an electronic shutter, analog gain, and change of reading speed. The A / D converter 106 converts an analog signal into a digital signal. The A / D converter 106 is used to convert an analog signal output from the imaging unit 105 into a digital signal. The barrier 101 covers the imaging system of the video camera 100 including the photographing lens 102 to prevent the imaging system including the photographing lens 102, the aperture 103, the ND 104, and the imaging unit 105 from being soiled or damaged.

The image processing unit 115 performs color conversion processing, gamma correction, addition of digital gain, and the like on the data from the A / D converter 106 or the data from the memory control unit 116. In addition, a predetermined calculation process is performed using the captured image data, and the calculation result is transmitted to the system control unit 114. Based on the transmitted calculation result, the system control unit 114 performs exposure control, distance measurement control, white balance control, and the like. As a result, TTL (through the lens) type AF (auto focus) processing, AE (auto exposure) processing, AWB (auto white balance) processing, and the like are performed. Details of the image processing unit 115 will be described later.

The output data from the A / D converter 106 is written directly to the memory 119 via the image processing unit 115 and the memory control unit 116, or via the memory control unit 116. The memory 119 stores image data captured by the imaging unit 105 and converted into digital data by the A / D converter 106, and image data to be displayed on the display unit 118. The memory 119 has a storage capacity sufficient to store moving images and sounds for a predetermined time.

Further, the memory 119 also serves as a memory (video memory) for displaying an image. The D / A converter 117 converts the image display data stored in the memory 119 into an analog signal and supplies it to the display unit 118. In this way, the image data for display written in the memory 119 is displayed by the display unit 118 via the D / A converter 117. The display unit 118 displays on a display such as an LCD according to the analog signal from the D / A converter 117. The digital signal once A / D converted by the A / D converter 106 and stored in the memory 119 is analog-converted by the D / A converter 117 and sequentially transferred to the display unit 118 for display as an electronic viewfinder. It functions and can display through images.

The non-volatile memory 113 is a memory that can be electrically erased and recorded, and for example, EEPROM is used. The non-volatile memory 113 stores constants, programs, and the like for the operation of the system control unit 114. The program referred to here is a program for executing various flowcharts described later in the embodiment of the present invention.

The system control unit 114 controls the entire video camera 100. By executing the program recorded in the non-volatile memory 113 described above, each process of the first embodiment of the present invention described later is realized. RAM is used as the system memory 121, and constants and variables for operation of the system control unit 114, a program read from the non-volatile memory 113, and the like are developed. The system control unit 114 also controls the display by controlling the memory 119, the D / A converter 117, the display unit 118, and the like.

The system timer 120 is a time measuring unit that measures the time used for various controls and the time of the built-in clock. The mode changeover switch 109, the recording switch 108, and the operation unit 107 are operation means for inputting various operation instructions to the system control unit 114.

The mode changeover switch 109 switches the operation mode of the system control unit 114 to any one of a moving image recording mode, a still image recording mode, a playback mode, and the like. Modes included in the moving image recording mode and the still image recording mode include an auto shooting mode, an auto scene discrimination mode, a manual mode, various scene modes for shooting settings for each shooting scene, a program AE mode, a custom mode, and the like. The mode changeover switch 109 directly switches to any of these modes included in the moving image shooting mode. Alternatively, after switching to the moving image shooting mode once with the mode changeover switch 109, the mode may be switched to any of these modes included in the moving image shooting mode by using another operating member. The recording switch 108 switches between a shooting standby state and a shooting state. The system control unit 114 starts a series of operations from reading a signal from the imaging unit 105 to writing moving image data to the recording medium 123 by the recording switch 108.

The power switch 110 is a switch for turning on / off the power of the video camera 100.

Each operation member of the operation unit 107 is assigned a function as appropriate for each scene by selecting and operating various function icons displayed on the display unit 118, and acts as various function buttons. Examples of the function buttons include an end button, a back button, an image feed button, a jump button, a narrowing down button, an attribute change button, and the like. For example, when the menu button is pressed, various configurable menu screens are displayed on the display unit 118. The user can intuitively make various settings by using the menu screen displayed on the display unit 118 and the cross keys and SET buttons in four directions of up, down, left, and right.

The power supply control unit 111 includes a battery detection circuit, a DC-DC converter, a switch circuit for switching a block to be energized, and the like, and detects whether or not a battery is installed, the type of battery, and the remaining battery level. Further, the power supply control unit 111 controls the DC-DC converter based on the detection result and the instruction of the system control unit 114, and supplies a necessary voltage to each unit including the recording medium 123 for a necessary period. The power supply unit 112 includes a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as a NiCd battery, a NiMH battery, or a Li ion battery, an AC adapter, or the like. The I / F 122 is an interface with a recording medium 123 such as a memory card or a hard disk, or an external output device. The figure shows the state at the time of connection with the recording medium 123. The recording medium 123 is a recording medium such as a memory card for recording a captured image, and is composed of a semiconductor memory, a magnetic disk, or the like.

The image conversion unit 124 performs gradation conversion, color conversion, and the like on the signal input from the image processing unit 115.

Next, the internal configuration of the image processing unit 115 according to the embodiment of the present invention will be described. FIG. 2 is a block diagram showing the internal configuration of the image processing unit 115 and related parts. The image processing unit 115 can acquire all the data inside the image pickup apparatus through the system control unit 114, and realizes the functions of each unit under the control of the system control unit 114. The function of the image processing unit 115 may be performed by using one hardware, or may be performed by a plurality of hardware in cooperation with each other. Further, the system control unit 114 may function as the image processing unit 115 by executing the image processing program. Further, a part or all of the functions of the image processing unit 115 may be realized by a circuit.

The gain correction unit 20 amplifies the RGB signal output from the A / D converter 106 by multiplying it by the same magnification. The WB correction unit 21 corrects the white balance by multiplying the R signal and the B signal of the signals output from the gain correction unit 20 by a gain. The matrix calculation unit 22 corrects the color tone by multiplying the signal output from the WB correction unit 21 by a matrix. The gradation conversion unit 23 performs gradation conversion on the signal output from the matrix calculation unit 22. The output from the gradation conversion unit 23 is output to the image conversion unit 124 and the recording medium 123.

The 3DLUT processing unit 24 performs color conversion with reference to the 3DLUT data as shown in FIG. In FIG. 3, the RGB values of the input values and the RGB values of the corresponding output values are shown side by side, but since the RGB values of the input values are often separated at equal intervals, the actual data is the output values. It is common that only are listed. If the same RGB value as the input RGB value is in the conversion source table, it is converted to the conversion destination RGB value as it is. If the input RGB value does not exist in the conversion source table, interpolation is performed from the points around the input RGB value. Generally, a tetrahedron containing RGB values is extracted and interpolation is performed using a method called tetrahedron interpolation, but other interpolation methods may also be used. Further, in the present embodiment, it is assumed that the data corresponding to the through (the values of R, G, and B do not change after the LUT is applied) is set so that the RGB values do not change in the initial state.

Subsequently, the process when the user inputs an arbitrary 3D LUT to the video camera 100 will be described using the flowchart of FIG. In the present embodiment, for the sake of explanation, the range of the signal is normalized to 0 to 1 in all of the A / D converter 106 to the 3DLUT processing unit 24. Further, the input of the WB correction unit 21 is (R ₀ , G ₀ , B ₀ ), the input of the matrix calculation unit 22 is (R ₁ , G ₁ , B ₁ ), and the input of the gradation conversion unit 23 is (R ₂ ,, G _{2, B 2),} placing the inputs of the 3DLUT processor 24 and _{(R 3, G 3, B} 3). At this time, in the present embodiment, it is assumed that the WB correction unit 21, the matrix calculation unit 22, and the gradation conversion unit 23 each perform calculations according to Equations 1 to 3.

First, in step S41, the system control unit 114 reads the 3DLUT data specified by the user and expands it into the system memory 121. As for the 3DLUT data prepared by the user, for example, the user records the 3DLUT data as a file on the recording medium 123 using a PC or the like in advance, and attaches the recording medium 123 to the digital camera 100. Then, the system control unit 114 reads the 3DLUT data recorded on the recording medium 123 in response to the user's menu operation or the like.

In step S42, the system control unit 114 analyzes the 3DLUT data read in step S41 to obtain the signal range of the input signal of the WB correction unit 21 required to generate the output signal from the 3DLUT processing unit 24. Hereinafter, this method will be described with reference to the flowchart shown in FIG.

In step S51, the system control unit 114 converts the input value of the 3DLUT data shown in FIG. 3 into the input value of the WB correction unit 21. The conversion method will be described below.

From Equations 1 to ₃ , the relationship between the input values (R ₀ , G ₀ , B ₀ ) of the WB correction unit 21 and the input values (R ₃ , G ₃ , B ₃ ) of the 3D LUT processing unit 24 is expressed by Equation 4. Can be done.

That is, in order to convert the input value (R ₃ , G ₃ , B ₃ ) of the 3DLUT processing unit 24 into the input value (R ₀ , G ₀ , B ₀ ) of the WB correction unit 21, the calculation shown in Equation 5 can be performed. Good.

FIG. 6 shows the input value converted into the input value of the WB correction unit 21 by this calculation. That is, FIG. 6 shows the relationship between the input values (R ₀ , G ₀ , B ₀ ) of the WB correction unit 21 and the input values (R ₃ , G ₃ , B ₃ ) of the 3D LUT processing unit 24.

In step S52, the system control unit 114 sorts the 3DLUT data generated in step S51 based on the maximum value of the input value. The maximum value of the input value is a calculation of max (R, G, B), which is the maximum value among the input values (R, G, B) of each row, for each row. FIG. 7 shows 3DLUT data sorted in ascending order of max (R, G, B). Hereinafter, in the description of FIG. 7, the “input value” refers to max (R, G, B).

In step S53, the system control unit 114 extracts a reference output value corresponding to the maximum input value. The maximum input value is the largest input value of all rows. In the example of FIG. 7, only the last line 701 has the largest input value "1". Therefore, in this step, the system control unit 114 extracts the output value (R, G, B) = (1,1,1) corresponding to this input value as the reference output value. In this embodiment, only one line has the maximum input value, but there may be a plurality of lines having the maximum input value depending on the processing contents of the WB correction unit 21 to the gradation conversion unit 23. In that case, all the output values corresponding to those input values are extracted, and those with the same value are combined into one. For example, there are three rows with maximum input values, and the corresponding output values are (R, G, B) = (1,1,1), (1,1,1), (0.9,1). , 1), (R, G, B) = (1,1,1), (0.9,1,1) are extracted as reference output values.

In step S54, the system control unit 114 determines whether or not the number of reference output values extracted in step S53 is one. If there is one, the process proceeds to step S55, and if there are a plurality, the process ends.

In step S55, the system control unit 114 searches for the maximum input value among the rows having an output value different from the reference output value. In the example of FIG. 7, line 702 has an output value "0.969567" different from the reference output value "1", and is the largest input value among the lines having an output value different from the reference output value "1". It has "0.670114". Upon obtaining this input value, the system control unit 114 ends FIG. 5, that is, the 3DLUT data analysis process in step S42.

The explanation is returned to FIG. In step S43, the system control unit 114 determines whether or not the signal range of the input signal of the WB correction unit 21 can be reduced. In step S42, the maximum input value having an output value different from the output value corresponding to the maximum input value of the WB correction unit 21 is known. In the present embodiment, the input value "0.670114" is the corresponding input value. It can be seen that the output value of the 3DLUT processing unit 24 is always (1,1,1) if it has an input value of "0.672886" or more, which is the next largest input value after this input value. Therefore, it can be determined that the input signal of the WB correction unit 21 can be expressed (reduced in the signal range) in a smaller signal range. Hereinafter, on the other hand, when the maximum input value of the result of step S42 is 1, or when the input value next to the maximum input value of the result of step S42 is 1, the system control unit 114 may reduce the signal range. Judge that it cannot be done. Further, even when it is determined in step S53 that there are a plurality of reference output values and the analysis process of FIG. 5 is completed, the system control unit 114 determines that the signal range cannot be reduced. When the system control unit 114 determines that the signal range can be reduced, the process proceeds to step S44, and when it is determined that the signal range cannot be reduced, the system control unit 114 ends the process.

In step S44, the system control unit 114 calculates the amount of reduction in the signal range. As described in step S43, if the input value of the WB correction unit 21 is 0.672886 or more, it is output from the 3DLUT processing unit 24 as (R, G, B) = (1,1,1). In other words, when the input value of the WB correction unit 21 is in the range of 0.672886 to 1, it is not necessary to distinguish between them, and the required signal range for expressing the input value is smaller than 0 to 1. Therefore, in the example of this embodiment, the signal range of the input signal of the WB correction unit 21 can be reduced to 0.670114 times.

In step S45, the system control unit 114 increases the exposure amount so as to increase the input value of the WB correction unit 21 based on the reduction amount of the signal range determined in step S44. First, since a value larger than 0.6701114 of the input value signal of the WB correction unit 21 is not required, the system control unit 114 changes the exposure amount of the imaging unit 105. In the present embodiment, it is assumed that the relationship between the output of the imaging unit 105 and the exposure amount is linear, and the exposure amount is set to 1 / 0.670114 = about 1.49 times. The exposure amount is changed by using any one or more of the aperture 103, the ND 104, or the electronic shutter of the imaging unit 105.

Due to the drive resolution of the electronic shutters of the aperture 103, ND 104, and image pickup unit 105, it is possible that the exposure amount cannot be changed accurately. In that case, the system control unit 114 changes the exposure amount so as not to exceed the desired exposure amount. For example, when the exposure amount can be changed only by 1.45 times or 1.55 times, the system control unit 114 sets the exposure amount to 1.45 times and reduces the signal range determined in step S44 by 1 /. Correct it to 1.45 times.

By performing the above processing, the exposure amount is increased and the S / N ratio of the captured image is improved. On the other hand, the output value from the 3DLUT processing unit 24 changes due to the change in the exposure amount in step S45.

In consideration of the above, in step S46, the system control unit 114 changes the processing of the image processing unit 115 so as to compensate for the change in the output value due to the change in the exposure amount. As in the above example, it is assumed that the exposure amount of the imaging unit 105 is increased by n times and the input value of the WB correction unit 21 is also increased by n (= 1.49) times. At this time, there are mainly the following three methods for compensating for the change in the output value of the 3D LUT processing unit 24.

1) The system control unit 114 that changes the characteristics of the gain correction unit 20 compensates the gain correction unit 20 so that the input value and subsequent values of the WB correction unit 21 are the same as the original by multiplying the amplification factor by 1 / n. can do. However, if the original amplification factor set in the gain correction unit 20 is small, the amplification factor becomes less than 1, and the gradation may be sacrificed.

2) Changing the characteristics of the gradation conversion unit 23 The system control unit 114 corrects the gradation conversion characteristics of the gradation conversion unit 23 so that the output value and subsequent values of the gradation conversion unit 23 are the same as the original. Can be compensated. Assuming that the new output values of the gradation conversion unit 23 are f'(R), f'(G), and f'(B), the original output values f (R), f (G), and f (B) are set. It can be expressed as in Equation 6.

What is the relationship between the original output values f (R), f (G), f (B) for the inputs R, G, B and the new output values f'(R), f'(G), f'(B)? It becomes as shown in FIG. The gradation conversion characteristic 81 represents the original conversion characteristic, and the gradation conversion characteristic 82 represents the conversion characteristic that compensates for the change in the signal level due to the change in the exposure amount.

3) Changing the characteristics of the 3DLUT processing unit 24 The system control unit 114 changes the 3DLUT data itself read in step S41 so that the output value of the 3DLUT processing unit 24 almost matches the original output value. Can be compensated. If the output value for the original 3DLUT data input value (R, G, B) is set to L (R, G, B) and the changed output value of the 3DLUT data is set to L'(R, G, B), then L '(R, G, B) can be expressed as in Equation 7 using L and g.

Here, since L (R, G, B) has only output values for discrete input values, it is necessary to perform interpolation calculation such as tetrahedral interpolation in order to perform the calculation of Equation 7. Since the output value of the gradation conversion unit 23 is larger than that of the methods 1) and 2) in the method 3), the gradation is obtained when the bit width of the output value of the gradation conversion unit 23 is limited. It is advantageous.

When the methods 1) and 2) are adopted, the system control unit 114 sets the 3DLUT data read in step S41 as it is in the 3DLUT processing unit 24. When the method of 3) is adopted, the system control unit 114 sets the 3DLUT data calculated by the equation 7 in the 3DLUT processing unit 24. The three methods considered to be typical have been shown above, but any other method may be used as long as the signal level of the output value from the 3D LUT processing unit 24 can be maintained. Further, when the method 2) is used, the system control unit 114 may read the conversion characteristics and the 3DLUT data calculated in advance according to the reduction amount of the signal range from the non-volatile memory 113 or the like and set them. Further, it is not always necessary to completely maintain the signal level of the output value, and for example, the above-mentioned signal level compensation processing may be performed until the signal level approaches a predetermined threshold value. That is, the system control unit 114 improves the S / N ratio by increasing the exposure amount, while the signal level change due to the increase in the exposure amount is the signal before the exposure amount is increased by the signal level compensation processing. Various processes can be performed to approach the level.

In the present embodiment, a method of analyzing arbitrary 3DLUT data input by the user and maintaining the signal level of the finally output signal while increasing the exposure amount to the imaging unit 105 as much as possible has been described. According to this embodiment, it has an effect of improving the S / N ratio of the final output signal according to arbitrary 3DLUT data input by the user.

<Second embodiment>
In the first embodiment, an example in which the image processing unit 115 is composed of the gain correction unit 20, the WB correction unit 21, the matrix calculation unit 22, the gradation conversion unit 23, and the 3DLUT processing unit 24 has been described. On the other hand, in the present embodiment, as shown in FIG. 9, the configuration including the 3DLUT processing unit 25 before the 3DLUT processing unit 24 will be described. The initial state of the 3DLUT processing unit 24 is set to be equivalent to through as in the first embodiment, but the 3DLUT processing unit 25 has some kind of 3DLUT (converts R, G, B values) in advance as a part of image processing. It is assumed that the data has been set. For example, it is conceivable that the 3DLUT processing unit 25 is used as an auxiliary because the desired color reproduction cannot be achieved only by the matrix calculation unit 22. It is assumed that the same setting values as in the first embodiment are applied to the WB correction unit 21, the matrix calculation unit 22, and the gradation conversion unit 23.

The present embodiment will be described with reference to the flowchart shown in FIG. 3 as in the first embodiment.

In step S41, the system control unit 114 reads the 3DLUT data as in the first embodiment.

In step S42, the system control unit 114 analyzes the 3DLUT data read in step S41 and obtains a signal range required as an input value of the WB correction unit 21 as in the first embodiment. However, depending on the 3DLUT data, the inverse conversion may not be obtained correctly. For example, in the case of 3DLUT data in which different input values are converted into the same output value, it is impossible to correctly obtain the input value corresponding to the output value. Therefore, as in the first embodiment, the input value of the 3DLUT processing unit 24 cannot be converted into the input value of the WB correction unit 21. Therefore, the system control unit 114 synthesizes the 3DLUT data set in the 3DLUT processing unit 25 and the 3DLUT data read by the user, and generates the synthesized 3DLUT data. This corresponds to converting the input values (R, G, B) of the 3DLUT processing unit 25 through the 3DLUT processing unit 25, and then obtaining the converted value through the 3DLUT processing unit 24. If the combined 3DLUT data is read and it is considered that there is no 3DLUT processing unit 25, it is possible to obtain a signal range required as an input value of the WB correction unit 21 as in step S42 of the first embodiment. However, the RGB value converted by the synthetic 3DLUT data and the RGB value actually converted through the 3DLUT processing unit 25 and the 3DLUT processing unit 24 are strictly different. When obtaining accuracy, it is possible to approach the actual conversion result by preparing RGB values used as input values of the 3DLUT processing unit 25 at the time of synthesis in finer increments.

Step S43 and step S44 are the same as those in the first embodiment.

In step S45, the signal range reduction process is executed. First, when the methods 1) and 2) of steps S45 shown in the first embodiment are used, they are the same as in the case of the first embodiment. Further, when the method of 3) is used, the signal level can be compensated at the time of the input value of the 3DLUT processing unit 24 by applying the method of 3) to the 3DLUT data of the 3DLUT processing unit 25. At this time, 3DLUT data corresponding to the amount of reduction of the signal range may be prepared in advance in the non-volatile memory 113 and set in the 3DLUT processing unit 25.

As described above, in the present embodiment, there are two 3DLUT processing units, a front stage and a rear stage, and a process for causing the 3DLUT processing unit in the rear stage to read 3DLUT data has been described. According to the present embodiment, even if the circuit configuration is as described above, the signal range of the signal output from the A / D converter 106 according to any 3DLUT data input by the user is the same as in the first embodiment. Has the effect of reducing the S / N ratio of the final output signal.

<Third embodiment>
In the first and second embodiments, the output signal from the imaging unit 105 is increased by changing the exposure amount using any one or more of the aperture 103, the ND 104, or the electronic shutter of the imaging unit 105, and finally. The S / N ratio of a typical output signal has been improved. In this embodiment, a case where the S / N ratio of the final output signal is improved by a method different from that of Examples 1 and 2 will be described.

In the present embodiment, as shown in FIG. 10, the imaging unit 105 is composed of a light receiving unit 1051 and a gain correction unit 1052. The light receiving unit 1051 converts the incident light into an electric signal, and the gain correction unit 1052 amplifies and outputs the electric signal output from the light receiving unit 1051.

The present embodiment will be described with reference to the flowchart shown in FIG. 3 as in the first embodiment.

Since steps S41 to S44 are the same as those in the first embodiment, the description thereof will be omitted.

In step S45, the exposure amount to the imaging unit 105 was increased in the first embodiment, but in the present embodiment, the gain correction unit 1052 included in the imaging unit 105 is used instead, and the exposure amount is not changed. Increase the output signal from 105. Then, in step S46, the signal level compensation process is performed in the same manner as in the first and second embodiments. As a result, the amount of signal amplification after the imaging unit 105 is the same as before the steps S45 and S46. However, in the present embodiment, since a part of the signal amplification processing is performed by the gain correction unit 1052, the amount of noise amplified thereafter can be reduced. For example, the amount of amplification for noise generated in the light receiving unit 1051 does not change before and after performing steps S45 and S46, but for noise added to the signal in the A / D converter 106, after performing steps S45 and S46. The amplification amount is smaller in. That is, the total amount of noise is reduced, and the S / N ratio can be improved. Further, since the electronic shutter of the aperture 103 and the imaging unit 105 is not changed, there is an advantage that the depth of field, the smoothness of the moving image, the afterimage feeling, and the like can be maintained. However, the effect of improving the S / N ratio is smaller than that of the first embodiment.

According to the present embodiment, since the signal is amplified by using the gain correction unit 1052 of the imaging unit 105, it is possible to avoid the amplification of noise generated by the A / D converter 106 or the like, and the final output signal S. It has the effect of improving the / N ratio.

<Other Embodiments>
In the first to third embodiments, a method of analyzing the 3DLUT data input by the user and increasing the exposure amount of the imaging unit 105 has been described for the purpose of improving the S / N ratio of the signal output from the image processing unit 115. .. However, it is considered that there are cases where the content of the 3DLUT data itself is data that causes overexposure contrary to the user's expectation, or there are cases where the improvement of the S / N ratio is not automatically performed. For example, when a sense of noise is important for video expression. Therefore, whether to notify the user through the display unit 118 of the reciprocal of the reduction amount of the signal range determined in step S44 as the "exposure amount expansion possible amount", and execute the process of reducing the signal range and expanding the exposure amount in step S45. You may let the user choose whether or not. This notification enables the user to recognize an unintended error when creating 3DLUT data, and also prevents the signal range from being reduced when the user does not want to change the noise feeling of the image.

Further, in the first and third embodiments, it was assumed that the initial value of the 3DLUT data set in the 3DLUT processing unit 24 is equivalent to through. However, there are cases where the 3DLUT processing unit 24 is already used in the original image processing. For example, there is a case where it is desired to use the 3DLUT as an auxiliary as in the second embodiment, but there is only one 3DLUT processing unit 24 for the purpose of suppressing the circuit scale and power consumption. In such a case, new 3DLUT data obtained by synthesizing the preset 3DLUT data and the 3DLUT data read by the user is set in the 3DLUT processing unit 24. After that, the process can be performed in the same manner as in the second embodiment.

Further, in the first, second, and third embodiments, the calculation is performed in consideration of the set value of the WB correction unit 21 in order to obtain the signal range required as the input value of the WB correction unit 21. However, since the WB correction unit 21 normally amplifies only the R and B signals, it is often necessary to have the widest signal range of the G signal. It can be seen from FIG. 7 that a large signal range of the G signal is often required. Therefore, the calculation of the WB correction unit 21 may not be taken into consideration, and the signal range required as the input value of the WB correction unit 21 may be calculated using only the G signal.

In the first, second, and third embodiments, it was necessary to recalculate the reduction amount of the signal range each time the white balance changed, but the reduction amount of the signal range is calculated using only the G signal that is not affected by the white balance. There is no need to recalculate because it can be done. Further, since the signal range of the G signal is often required to be the largest, it can be said that this calculation is sufficient in many cases.

In the first and third embodiments, a method of increasing the exposure amount and a method of using the gain correction unit 1052 of the imaging unit 105 have been described as processes for improving the S / N ratio, but the user can decide which method is better. It is considered that it differs depending on the application of. Further, it is considered that there are cases where it is inconvenient to change automatically, or there are cases where it is desired to fix the amplification factor of the gain correction unit 1052 regardless of the input 3DLUT data depending on the subject. Therefore, it is possible to take the form of making these selectable by the user and determining how to operate according to the selection result. Further, when the S / N ratio improvement process is automatically operated, a form of notifying the user to that effect is also conceivable.

In addition, even when it is possible to read characteristics such as 1DLUT (one-dimensional lookup table) data and CDL (Color Decision List) instead of 3DLUT data, the processing in the first to third embodiments is executed based on the same idea. Good.

Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various embodiments within the scope of the gist of the present invention are also included in the present invention. included. Some of the above-described embodiments may be combined as appropriate.

The present invention is also realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiment is supplied to the system or device via a network or various storage media, and the computer (or CPU, MPU, etc.) of the system or device reads the program. This is the process to be executed.

Claims (12)

An output means that captures the subject and outputs the first color signal,
A first signal processing means that processes the first color signal to generate a second color signal, and
An input means for inputting a conversion characteristic for converting the second color signal into a third color signal, and
A second signal processing means that converts and outputs a second color signal into a third color signal based on the conversion characteristics, and
A specific means for specifying a required signal range of the first color signal required to generate the third color signal using the conversion characteristics input by the input means, and a specific means.
When the required signal range specified by the specific means is smaller than the predetermined signal range of the first color signal, the first signal in the required signal range does not exceed the upper limit value of the predetermined signal range. Signal increasing means to increase the color signal,
At least one of the first signal processing means and the second signal processing means so as to compensate for the change in the signal level of the third color signal due to the increase of the first color signal by the signal increasing means. An image pickup apparatus comprising: a compensating means for controlling one to compensate for a signal level. An exposure amount control means for increasing the exposure amount in the imaging within a range in which the signal in the required signal range does not exceed the upper limit value of the predetermined signal range is provided.
The imaging device according to claim 1, wherein the signal increasing means increases the first color signal by the exposure amount controlling means. The output means includes a signal amplification means for amplifying the first color signal.
The imaging device according to claim 1, wherein the signal increasing means increases the first color signal by the signal amplifying means. In the compensation of the signal level by the compensating means, the signal level of the third color signal after increasing the first color signal is the signal of the third color signal before increasing the first color signal. The imaging apparatus according to claim 1 to 3, wherein at least one of the first signal processing means and the second signal processing means is controlled so as to approach the level. Compensation of the signal level by the compensating means is performed by controlling at least the first signal processing means.
The imaging device according to claim 4, wherein the first signal processing means performs signal processing using at least one or more of gain, gradation conversion, look-up table, and matrix calculation. The imaging device according to claim 4, wherein the compensation means compensates for the signal level by controlling the conversion characteristics input to the second signal processing means to be changed. Claim 1 further includes a notification means for notifying that the exposure amount can be increased when the required signal range specified by the specific means is smaller than a predetermined signal range of the first color signal. 6. The imaging apparatus according to any one of 6. The notification means further notifies the user to select whether to increase the exposure amount.
The imaging apparatus according to claim 7, wherein when the selection to increase the exposure amount is accepted, the exposure amount is increased by the exposure control means and the signal level is compensated by the compensation means. The imaging apparatus according to any one of claims 1 to 8, further comprising a notification means for notifying that the signal level compensation has been performed by the compensation means. The imaging device according to any one of claims 1 to 9, wherein the conversion characteristic is a lookup table arbitrarily generated based on a user operation. It is a control method of the image pickup device.
An output process that captures the subject and outputs the first color signal,
A first signal processing step of processing the first color signal to generate a second color signal, and
An input step of inputting a conversion characteristic for converting the second color signal into a third color signal, and
A second signal processing step of converting a second color signal into a third color signal and outputting it based on the conversion characteristics, and
A specific step of specifying a required signal range of the first color signal required to generate the third color signal using the conversion characteristics input in the input step, and a specific step of specifying the required signal range of the first color signal.
When the required signal range specified in the specific step is smaller than the predetermined signal range of the first color signal, the first is within a range in which the signal in the required signal range does not exceed the upper limit value of the predetermined signal range. Has a signal increasing step, which increases the color signal of
Of the first signal processing step and the second signal processing step, the change in the signal level of the third color signal due to the increase of the first color signal in the signal increasing step is compensated for. A method for controlling an imaging device, which comprises compensating for a signal level with at least one. A program that can be executed by a computer, which causes the computer to function as the imaging device according to any one of claims 1 to 10.

Images