JP2007142978A - Image processing method and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To readily obtain proper images, by utilizing an image signal actually photographed underwater, without using information about the depth of water or the like or large stroboscopic devices. <P>SOLUTION: A still image or moving image is photographed by an imaging apparatus (step S12), and CCDRAW data (R, G, B signals) are acquired from a CCD imaging element (step S14). When the acquired R, G, B signals are in underwater photographing, the R, G, B signals are multiplied by an underwater exclusive matrix coefficient, and underwater color-corrected R, G, B signals are obtained (step S18). As the matrix coefficient, a coefficient that would prevent the B signal from overlapping the R signal and the G signal is set, while taking into account the light attenuation factor underwater by respective R, G, B signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing method and an imaging apparatus, and more particularly to a technique for performing signal processing on a color image signal acquired during underwater photography.

  Patent Document 1 discloses a technique for adjusting white balance so as to compensate for attenuation of R light according to a water depth difference between a camera and a subject in order to compensate for red (R) light attenuated by water. Yes.

  In Patent Document 2, a distance measuring light beam is projected toward an underwater subject, the subject distance and the amount of reflected light are measured, and the light attenuation rate in water is estimated based on the measurement result, and the light emission amount of the strobe device A technique for setting is disclosed.

  Patent Document 3 discloses an underwater camera that performs color absorption correction of each color from water depth information, mathematical formulas and light absorption coefficients necessary for color absorption correction of each color.

Patent Document 4 discloses a technique for detecting the depth (water depth) at which the camera is located in water and performing white balance adjustment according to the detected water depth.
Japanese Patent Laid-Open No. 6-351025 JP-A-8-69036 JP 2004-146828 A JP 2004-282460 A

  Many of the current underwater photography failures are due to poor color reproduction due to absorption of R light and insufficient contrast due to insufficient light intensity in water (compact camera strobe light is difficult to provide sufficient strobe light intensity). Due to

  The invention described in Patent Document 1 performs white balance adjustment so as to compensate for attenuation of the R light according to the difference in water depth between the camera and the subject. However, the water depth difference is not related to the absolute water depth, and is appropriate. Control is difficult, and underwater color reproduction cannot be performed satisfactorily only by white balance adjustment.

  Further, the invention described in Patent Document 2 estimates the light attenuation rate in water and sets the flash light emission amount to enable correct exposure. A distance measuring light beam is applied to the subject in order to measure the amount of reflected light. It is highly probable that the user will miss a photo opportunity while projecting, and it is considered difficult to perform appropriate control only with the amount of flash light.

  Furthermore, the inventions described in Patent Documents 3 and 4 perform color absorption correction and white balance adjustment depending on the water depth, but in actual seas, the influence of water quality and weather (sun exposure) is greater than the water depth. Therefore, it is difficult to obtain an image desired by a diver even if the color of an image taken underwater is corrected using depth information.

  The present invention has been made in view of such circumstances, and it is possible to easily obtain a good image using an image signal actually taken underwater without using information such as water depth or a large strobe device. It is an object of the present invention to provide an image processing method and a photographing apparatus that can be used.

  Another object of the present invention is to provide an image processing method and a photographing apparatus capable of displaying a through moving image with high visibility of a subject in water on a monitor.

  In order to achieve the above object, an invention according to claim 1 is an image processing method for processing a color image signal acquired during underwater photography, and acquiring R, G, B signals from an image sensor during underwater photography; A step of performing color correction by multiplying the acquired R, G, B signals by a matrix coefficient, and using the matrix coefficients set so as to prevent the B signal from being covered with the R signal and the G signal. And a step of calculating.

  That is, when performing color correction by multiplying the R, G, and B signals by a matrix coefficient, the light attenuation rate for each of the R, G, and B signals in water is taken into account, and the B signal is converted into the R and G signals. The matrix coefficient is set so as to prevent the covering.

  Specifically, as described in claim 2, the matrix coefficient has a coefficient for the B signal in the diagonal term smaller than a coefficient for the R signal and the G signal and / or R, G in the off-diagonal term. It is characterized in that the coefficient of the B signal with respect to the signal is set to be larger on the minus side.

  According to a third aspect of the present invention, there is provided an image processing method for processing a color image signal acquired at the time of underwater shooting, the step of acquiring R, G, B signals from an image sensor at the time of underwater shooting, and the acquired R, G, B Calculating a histogram evaluation value of at least the R signal of the signals, selecting one of two or more types of signal processing based on the calculated histogram evaluation value, and the acquired R , G, and B signals are subjected to the selected signal processing.

  For example, if it is determined that the amount of R light is large based on the calculated histogram evaluation value, level adjustment is performed so as to make the most of the contrast. If the amount of R light is extremely small, the R signal is ignored and the G signal is ignored. Level adjustment (offset processing, gradation processing, flare correction processing) is performed so as to make the best use of the B signals.

  According to a fourth aspect of the present invention, there is provided an image processing method for processing a color image signal continuously acquired during underwater shooting and outputting the processed color image signal to a camera monitor to display a through moving image on the monitor. Based on the step of acquiring R, G, B signals, calculating the histogram evaluation value of the G signal among the continuously acquired R, G, B signals, and the calculated histogram evaluation value A step of performing signal processing only for the G signal to increase the contrast of the image of the G signal, and the R, B signal of the continuously acquired R, G, B signals and the G signal subjected to the signal processing And displaying a through moving image on a monitor based on the above.

  That is, the G signal is a signal close to the luminance signal, and by performing signal processing so that the contrast of the G signal is increased, the color balance is lost, but the contrast of the through video can be increased, and the through video is clear. become. The through video is used when searching for the main subject underwater and setting the angle of view, so there is no problem even if the color balance is lost.

  According to a fifth aspect of the present invention, in the image processing method for processing an image signal continuously acquired during underwater shooting and outputting the processed image signal to a camera monitor and displaying a through moving image on the monitor, the image signal is continuously acquired from the image sensor during underwater shooting. A step of acquiring an image signal, a step of receiving an instruction to change a gradation characteristic of the continuously acquired image signal, and a gradation of the image signal continuously acquired in response to the instruction of changing the gradation characteristic The method includes a step of performing conversion, and a step of displaying a through moving image on a monitor based on the image signal subjected to gradation conversion.

  In other words, a diver (user) can instruct to change the tone characteristics while watching the through video displayed on the underwater monitor, and can display the through video with the desired tone characteristics. Can be improved.

  According to a sixth aspect of the present invention, in an imaging apparatus capable of underwater photography, a color imaging unit that images a subject, an image acquisition unit that acquires R, G, and B signals indicating the subject via the color imaging unit, and the A histogram evaluation value calculating means for calculating a histogram evaluation value of at least the R signal among the acquired R, G, B signals, and any one of two or more types of signal processing based on the calculated histogram evaluation value Signal processing selecting means for selecting processing and signal processing means for performing the selected signal processing on the acquired R, G, B signals are provided.

  According to a seventh aspect of the present invention, in an imaging apparatus capable of underwater photography, an imaging means for imaging a subject, an image acquisition means for continuously obtaining an image signal indicating the subject via the imaging means, and the continuous A gradation conversion means for converting the gradation of the acquired image signal, a change instruction means for instructing a change in gradation conversion characteristics in the gradation conversion means, and an image that has undergone gradation conversion by the gradation conversion means And a monitor that displays a through video based on the signal.

  As shown in claim 8, in the imaging device according to claim 7, the gradation conversion means includes a plurality of gradation conversion look-up tables from soft to hard, and the conversion instruction means includes the conversion instruction means An arbitrary lookup table is selected from a plurality of lookup tables, and the gradation converting means performs gradation conversion of an input image signal in accordance with the selected lookup table.

  According to the present invention, it is possible to obtain a good image such as color reproducibility and contrast by using an image signal actually taken underwater, and a through video with high visibility of a subject in water can be used as a monitor. Can be displayed.

  Preferred embodiments of an image processing method and an imaging apparatus according to the present invention will be described below with reference to the accompanying drawings.

[Configuration of imaging device]
FIG. 1 is a block diagram showing an embodiment of an imaging apparatus according to the present invention.

  An imaging apparatus 1-1 shown in FIG. 1 is a digital camera having functions for recording and reproducing still images and moving images, and the operation of the entire camera is centrally controlled by a central processing unit (CPU) 10. The CPU 10 functions as a control means for controlling the camera system according to a predetermined program, and performs various calculations such as automatic exposure (AE) calculation, automatic focus adjustment (AF) calculation, and white balance (WB) adjustment calculation. Functions as a means.

  A RAM (Random Access Memory) 16 and a ROM (Read Only Memory) 18 are connected to the CPU 10 via a bus 12 and a memory interface 14. The RAM 16 is used as a program development area and a calculation work area for the CPU 10, and is also used as a temporary storage area for image data. The ROM 18 stores programs executed by the CPU 10, various data necessary for control, various constants / information related to camera operations, and the like.

  The imaging unit 20 includes an optical unit 22 including a photographing lens, a diaphragm, and the like, a color image sensor 24 (hereinafter simply referred to as “CCD”) composed of a CCD or a CMOS, and the like. In the optical unit 22, a focus lens, a diaphragm, and the like are driven via the motor driving unit 32 in accordance with an AF command or AE command from the CPU 10.

  The CCD 24 has a number of photodiodes (light receiving elements) arranged two-dimensionally, and red (R), green (G), and blue (B) primary color filters corresponding to each light receiving element are arranged in a predetermined arrangement. Arranged in a structure (Bayer, G stripe RB complete checkered, etc.). The CCD 24 has an electronic shutter function for controlling the charge accumulation time (shutter speed) of each light receiving element. The CPU 10 controls the charge accumulation time in the CCD 24 via the timing generator 34.

  The CCD signals sequentially read from the CCD 24 are added to the analog signal processing unit 26. The analog signal processing unit 26 includes a CDS circuit, an analog amplifier, and the like. The CDS circuit performs correlated double sampling processing on the input CCD signal, and the analog amplifier outputs from the CDS circuit by a photographing sensitivity setting gain applied from the CPU 10. The CCD signal to be amplified is amplified.

  The CCD signal analog-processed by the analog signal processing unit 26 is added to an A / D converter 28, where it is converted into digital color image data (dot sequential R, G, B signals) for each pixel. .

  The R, G, and B signals are temporarily stored in the RAM 16 via the digital signal processing unit 30. The R, G, and B signals are input to the digital signal processing unit 30, where required signal processing is performed. The details of the image processing in the digital signal processing unit 30 will be described later.

  The operation unit 36 of the imaging apparatus 1-1 has a mode lever 36A for selecting a shooting mode (automatic shooting mode, manual shooting mode, scene position, moving image, etc.) as shown in FIG. A shutter button 36B provided at the center of 36A, a multi-function cross key 36D, a playback button for switching to a playback mode (not shown), a menu button for displaying a menu screen on the display (LCD monitor) 40, and a desired menu screen. To select an item, an OK button for confirming the selected item or executing a process, a desired object such as a selected item is deleted, an instruction content is canceled, or a command for returning to the previous operation state is input. Includes buttons.

  An output signal from the operation unit 36 is input to the CPU 10, and the CPU 10 performs appropriate processing such as shooting and reproduction based on the input signal from the operation unit 36, and reproduces the color of the image underwater as described later. We perform processing to improve.

  This imaging device 1-1 can be photographed underwater by being attached to a waterproof pack (not shown), and has an “underwater mode” suitable for underwater photography. Then, by operating the operation unit 36, a setting instruction for “underwater mode” can be output to the CPU 10.

  That is, the “underwater mode” can be set using a menu screen for selecting a scene position (person, landscape, sport, underwater) as shown in FIG. Further, as shown in FIG. 2B, a dedicated Dive button 36E may be provided, and the “underwater mode” may be set by operating the Dive button 36E.

  The imaging device 1-1 includes a strobe device 42 for irradiating a subject with strobe light. The strobe device 42 is supplied with power from the charging unit 44 in response to a light emission command from the CPU 10 and emits strobe light. .

  The image data (luminance signal Y, color difference signals Cr, Cb) processed by the digital signal processing unit 30 is given to the compression / decompression processing circuit 46, where it is compressed according to a predetermined compression format (for example, JPEG method). . The compressed image data is recorded on the memory card 50 via the external memory interface 48.

  Further, on the LCD monitor 40, a video (through moving image) is displayed during imaging preparation by an image signal applied via the LCD interface 38, and an image recorded on the memory card 50 is displayed in the reproduction mode.

  FIG. 3 is a block diagram showing a detailed circuit configuration of the digital signal processing unit 30 shown in FIG.

  As described above, the R, G, and B signals (CCD RAW data) temporarily stored in the RAM 16 are added to the offset processing circuit 30A of the digital signal processing unit 30 in the order of R, G, and B dots. The R, G, and B signals are subjected to offset processing in the offset processing circuit 30A. The offset processed R, G, B signals output from the offset processing circuit 30A are output to the linear matrix circuit 30B, where color correction processing is performed.

  That is, the linear matrix circuit 30B performs a matrix operation from the input R, G, B signals and the matrix coefficients (A11, A12,..., A33) of 3 rows × 3 columns, and the color corrected R, G , B signals are calculated.

  The details of the 3 × 3 color correction matrix coefficients (A11, A12,..., A33) used for the matrix calculation will be described later.

  The R, G, B signals output from the linear matrix circuit 30B are output to the white balance (WB) adjustment circuit 30C. The WB adjustment circuit 30C performs white balance adjustment by applying a WB gain for white balance adjustment for each of the R, G, and B signals. The R, G, and B signals output from the WB adjustment circuit 30C are output to the gamma correction circuit 30D, where gamma correction for performing gradation correction such as halftone is performed. The gamma corrected R, G, B signals are output to the synchronization processing circuit 30E.

  The synchronization processing circuit 30E performs a process of converting the R, G, B signals into simultaneous equations by interpolating the spatial deviation of the R, G, B signals associated with the CCD color filter array of the single CCD 24. The converted R, G, B signals are output to the RGB / YC conversion circuit 30F.

  The RGB / YC conversion circuit 30F converts the R, G, and B signals into a luminance signal Y and color difference signals Cr and Cb, outputs the luminance signal Y to the contour correction circuit 30G, and outputs the color difference signals Cr and Cb to the color difference matrix circuit 30H. Output to. The contour correction circuit 30G performs processing to emphasize the contour portion (the portion where the luminance change is large) of the luminance signal Y.

  The color difference matrix circuit 30H performs a matrix operation on the color correction matrix coefficients of 2 rows × 2 columns and the input color difference signals Cr and Cb, and performs color correction to realize good color reproducibility.

  The luminance signal Y subjected to the contour correction and the color difference signals Cr and Cb subjected to the color difference matrix conversion are temporarily stored in the RAM 16 and then given to the compression / decompression processing circuit 46, where they are compressed according to the JPEG method. The The compressed image data is recorded on the memory card 50 via the external memory interface 48.

  Returning to FIG. 1, the evaluation value deriving unit 52 derives evaluation values such as an average value, a standard deviation, a median value, a reference minimum value, and a reference maximum value from the histogram for each of the R, G, and B signals. The histogram evaluation value deriving unit 54 derives a histogram evaluation value indicating the frequency distribution of the gradation for each of the R, G, and B images.

  The underwater detection unit 56 detects that the imaging device 1-1 is underwater. For example, the underwater detection unit 56 includes a water pressure detection unit, a unit that acquires information from a diving computer, a unit that detects attachment to a waterproof pack, a GPS, and the like. Composed.

  Next, an image processing method for images taken underwater will be described.

[First Embodiment]
FIG. 4 is a flowchart showing the first embodiment of the image processing method according to the present invention, and particularly shows the image processing method at the time of photographing in the underwater mode.

  When the underwater mode is set by the operation of the operation unit 36 (step S10) and then photographing is performed (step S12), the digital signal processing unit 30 includes the CCD 22, the analog signal processing unit 26, and the A / D converter. The CCD RAW data is taken in via 28 (step S14).

  On the other hand, the CPU 10 automatically determines whether or not the acquired CCD RAW data is for underwater shooting based on a detection signal input from the underwater detection unit 56 (step S16), and in the case of CCD RAW data acquired by underwater shooting. Then, an instruction to use the matrix coefficient for underwater is output to the digital signal processing unit 30 (step S18).

  In this embodiment, the CPU 10 changes the matrix coefficient of 3 rows × 3 columns used in the linear matrix circuit 30B (FIG. 3) of the digital signal processing unit 30 to underwater as shown in the following equation. Instruct.

  As shown in [Formula 1], the matrix coefficient for underwater is such that the coefficient (1.3) for the B signal in the diagonal term is set to be smaller than the coefficient (1.4) for the R signal and the G signal, and non-diagonal The coefficient (−0.3) of the B signal with respect to the R and G signals in the term is set to be larger on the minus side.

  Thereby, the covering of the B signal to the R signal and the G signal is suppressed. During normal shooting other than underwater shooting, the matrix coefficient of the linear matrix circuit 30B corrects the spectral characteristics of the CCD 24 for each of R, G, and B, and corrects them to R, G, and B signals that are close to those of the human eye. The value to do is set.

  Subsequently, the digital signal processing unit 30 performs image processing such as color correction processing, white balance adjustment, and gamma correction by matrix calculation using the matrix coefficients set as described above (step S20). An image signal indicating the final image is output (step S22).

  In this embodiment, the setting of the underwater mode by the operation of the operation unit 36 and the automatic detection of the underwater by the underwater detection unit 56 are used in combination, but only one of them may be used. .

[Second Embodiment]
FIG. 5 is a flowchart showing a second embodiment of the image processing method according to the present invention. The parts common to the flowchart shown in FIG. 4 are denoted by the same step numbers, and detailed description thereof is omitted.

  In FIG. 5, when CCD RAW data is acquired by underwater photography, a histogram for each of R, G, and B is calculated from the acquired CCD RAW data (step S30).

  Since R light is absorbed underwater, the R histogram of the calculated R, G, and B histograms is focused on, and the amount of R component is determined (step S30). That is, it is determined whether or not the width x of the histogram of R is equal to or less than a predetermined value (for example, 20 in 256 gradations). If YES (x ≦ 20), it is determined that the R component is extremely small, and step The process proceeds to S34, and if NO (x> 20), it is determined that the R component is relatively large, and the process proceeds to Step S40.

  In step S34, the R signal is ignored and the presence or absence of black float is determined from the G and B histograms. The presence or absence of black float is determined to be black float when the minimum values of the G and B histograms are above a certain level (when there are no pixels with low gradation). If there is no black float, the process proceeds to step S40, and if there is black float, the process proceeds to step S36.

  In step S36, it is determined whether or not the median x of the G and B histograms is a predetermined value (for example, 128 in 256 gradations) or less. If the median x is less than or equal to the predetermined value, the process proceeds to step S40. If the median value x exceeds the predetermined value, the process proceeds to step S38.

  In step S38, RGB offset processing is performed. Here, the RGB offset processing refers to processing for performing level adjustment (offset processing, gradation processing, flare correction) so as to make the best use of the G and B signals while ignoring the R signal (R signal = 0). .

  FIGS. 6A and 6B are diagrams showing images of underwater images having relatively deep water depth before and after processing, and luminance, R, G, and B histograms of these images.

  As shown in FIG. 6B, the G signal is offset so that the minimum value of the G signal becomes 0 so that there is no black float, and the level of the B signal is adjusted so that the width of the histogram is slightly widened. Has been.

  On the other hand, in step S40, RGB histogram adjustment processing is performed. Here, the RGB histogram adjustment processing refers to processing for performing level adjustment that makes the best use of the contrast of the R, G, and B signals. For example, when the histogram of the G signal is created as shown in FIG. 7, the reference minimum value Gmin and the reference maximum value Gmax of the G signal are obtained. This reference minimum value Gmin counts the number of pixels from the lowest gradation, for example, the gradation when it reaches 1% of the total number of pixels. Similarly, the reference maximum value Gmax determines the number of pixels from the highest gradation. The gray level is counted, for example, when it reaches 1% of the total number of pixels.

Based on the reference minimum value Gmin and the reference maximum value Gmax, an offset value and a gain amount are calculated by the following equations.
[Equation 2]
Offset value = Gmin
Gain amount = 255 / (Gmax-Gmin)
Then, the level adjustment that makes the best use of the contrast can be performed by calculating the following equation using the offset value and the gain amount for the input G signal.
[Equation 3]
G1 = G-Gmin
G2 = G1 × gain amount Note that R and B signals are also processed in the same manner as described above. The offset processing using the offset value can be performed by the offset processing circuit 30A of the digital signal processing unit 30, and the multiplication of the gain amount can be performed by the WB adjustment circuit 30C.

  When the input data is n bits, if there is no data of n-1 bits or less, correction is made up to n-1 bits. By restricting the range in which the level can be adjusted in this way, the color balance is prevented from being greatly lost.

  FIGS. 8A and 8B are diagrams showing images of underwater images with relatively shallow water depth before and after processing, and histograms of luminance, R, G, and B of these images.

  As shown in FIG. 8B, the levels of the R, G, and B signals are adjusted so that they are distributed over all gradations (0 to 255), and the corrected image has a widened contrast and a black float. Become.

  The R, G, and B signals whose levels have been adjusted in steps S38 and S40 are further subjected to normal image processing (step S42), and an image signal indicating the final image subjected to image processing is output (step S22).

[Third Embodiment]
FIG. 9 is a flowchart showing a third embodiment of the image processing method according to the present invention.

  The image processing method of the third embodiment is an image processing method for displaying a through moving image on the LCD monitor 40 during underwater shooting. The parts common to the flowchart shown in FIG. 4 are denoted by the same step numbers, and detailed description thereof is omitted.

  In FIG. 9, a histogram of the G signal among the R, G, and B signals continuously taken in via the CCD 22, the analog signal processing unit 26, and the A / D converter 28 during underwater shooting is calculated (step S50).

  Then, G histogram adjustment processing is performed based on the histogram evaluation value of the G signal (step S52). Here, the G histogram adjustment processing refers to processing for performing automatic level adjustment that makes the best use of the contrast of the G signal. When the G histogram distribution width is 255 or less, the level adjustment is performed so that it becomes 255. .

  Then, during underwater shooting, image processing for through moving image display is performed based on the level-adjusted G signal and the level-unadjusted R and B signals, and the level is not adjusted except for underwater shooting. Based on the B signal, image processing for through moving image display is performed (step S54). The through video display R, G, B signals processed in step S54 are applied to the LCD monitor 40 via the LCD interface 38, and are displayed as a through video here (step S56).

  The through video displayed on the LCD monitor 40 during underwater shooting has the side effect that the color balance is greatly lost because the level of only the G signal is adjusted. However, since the through video contrast can be increased, the through video is clear. Become. The through video is used when searching for the main subject underwater and setting the angle of view, and does not affect the captured image, so there is no problem even if the color balance is lost. In this embodiment, the automatic level adjustment is performed so as to maximize the contrast of the G signal. However, the present invention is not limited to this, and the level adjustment of the G signal may be performed manually.

[Other configuration of imaging apparatus]
FIG. 10 is a block diagram showing another embodiment of the imaging apparatus according to the present invention. Note that portions common to the imaging device 1-1 illustrated in FIG. 1 are denoted by common reference numerals, and detailed description thereof is omitted.

  The imaging apparatus 1-2 illustrated in FIG. 10 is different from the imaging apparatus 1-1 illustrated in FIG. 1 in that a γ change button 60 and a gradation change unit 62 are added.

  When the underwater mode is selected by the operation unit 36, the γ change button 60 functions as a γ change button when the up / down key of the cross key 36D is pressed. When instructed and the down key is pressed, the change of the γ characteristic is instructed so as to make it softer.

  The gradation converting unit 62 has a look-up table (ROM table) having a plurality of γ characteristics as shown in FIG. 11A or 11B, and the γ selected by operating the γ change button 60. Γ conversion (gradation conversion) of the input image signal is performed using a table having characteristics. In FIG. 11, the γ characteristic indicated by a thin line indicates a gradation characteristic that is soft (or standard), and the γ characteristic indicated by a thick line indicates a gradation characteristic that is a hard gradation. The characteristics are not limited to those shown in FIG. 11, and the ROM table may have three or more types of tables having different γ characteristics.

[Fourth Embodiment]
FIG. 12 is a flowchart showing the fourth embodiment of the image processing method according to the present invention.

  The image processing method according to the fourth embodiment is an image processing method for displaying a through moving image on the LCD monitor 40 during underwater shooting.

  In FIG. 12, when the underwater mode is selected (step S10), the diver determines whether or not the through video on the LCD monitor 40 is easy to see (step S60). Then, if it is difficult to see the through moving image, the diver operates the γ change button 60 to the soft adjustment side or the high adjustment side (step S62).

  The gradation conversion unit 62 selects an appropriate γ characteristic table from the ROM table in accordance with the operation of the γ change button 60, and outputs the R, G, B signals to be output to the LCD monitor 40 according to the selected table. γ conversion is performed (step S64).

  The through video display R, G, B signals processed in step S64 are applied to the LCD monitor 40 via the LCD interface 38, and are displayed as a through video here (step S66).

  Then, by repeating the processing from step S60 to step S66, it is possible to display a through video that is most easily seen by divers.

  In the fourth embodiment, the γ characteristic of the through moving image can be changed. However, the present invention is not limited to this, and other gradation characteristics such as a tone curve and level adjustment may be changed.

FIG. 1 is a block diagram showing an embodiment of an imaging apparatus according to the present invention. FIG. 2 is a rear view illustrating an example of the operation unit and the LCD monitor of the imaging apparatus. FIG. 3 is a block diagram showing a detailed circuit configuration of the digital signal processing unit shown in FIG. FIG. 4 is a flowchart showing the first embodiment of the image processing method according to the present invention. FIG. 5 is a flowchart showing a second embodiment of the image processing method according to the present invention. FIGS. 6A and 6B are diagrams showing images of underwater images having relatively deep water depth before and after processing, and luminance, R, G, and B histograms of these images. FIG. 7 is a graph showing an example of a histogram of the G signal. FIGS. 8A and 8B are diagrams showing images of underwater images with relatively shallow water depth before and after processing, and histograms of luminance, R, G, and B of these images. FIG. 9 is a flowchart showing a third embodiment of the image processing method according to the present invention. FIG. 10 is a block diagram showing another embodiment of the imaging apparatus according to the present invention. FIGS. 11A and 11B are graphs showing a plurality of γ characteristics stored in a lookup table (ROM table). FIG. 12 is a flowchart showing the fourth embodiment of the image processing method according to the present invention.

Explanation of symbols

  1-1, 1-2 ... Imaging device (digital camera), 10 ... Central processing unit (CPU), 16 ... RAM, 18 ... ROM, 20 ... Imaging unit, 22 ... Optical unit, 24 ... Color image sensor (CCD) 26 ... analog signal processing unit, 30 ... digital signal processing unit, 30A ... offset processing circuit, 30B ... linear matrix circuit, 30C ... white balance adjustment circuit, 30D ... gamma correction circuit, 30E ... synchronization processing circuit, 30F ... RGB / YC conversion circuit, 30G ... contour correction circuit, 30H ... color difference matrix circuit, 36 ... operation unit, 40 ... display unit (LCD monitor), 50 ... memory card, 52 ... evaluation value deriving unit, 54 ... histogram evaluation value deriving unit 56 ... Underwater detection unit 60 ... γ change button 62 ... Gradation change unit

Claims (8)

In an image processing method for processing a color image signal acquired during underwater shooting,
Acquiring R, G, B signals from the image sensor during underwater photography;
A step of performing color correction by multiplying the acquired R, G, B signal by a matrix coefficient, and using the matrix coefficient set so as to prevent the B signal from being covered with the R signal and the G signal. A matrix calculation step;
An image processing method comprising:   The matrix coefficient is smaller in the coefficient for the B signal in the diagonal term than the coefficient for the R signal and the G signal and / or larger in the negative direction than the coefficient of the B signal for the R and G signals in the non-diagonal terms. The image processing method according to claim 1, wherein the image processing method is set as follows. In an image processing method for processing a color image signal acquired during underwater shooting,
Acquiring R, G, B signals from the image sensor during underwater photography;
Calculating a histogram evaluation value of at least the R signal among the acquired R, G, B signals;
Selecting any one of two or more types of signal processing based on the calculated histogram evaluation value;
Performing the selected signal processing on the acquired R, G, B signals;
An image processing method comprising: In an image processing method of processing a color image signal continuously acquired during underwater shooting and outputting it to a camera monitor, and displaying a through video on the monitor,
Continuously acquiring R, G, B signals from the image sensor during underwater photography;
Calculating a histogram evaluation value of a G signal among the continuously acquired R, G, B signals;
Applying signal processing only to the G signal to increase the contrast of the image of the G signal based on the calculated histogram evaluation value;
Displaying a through moving image on a monitor based on the R, B signals of the continuously acquired R, G, B signals and the G signals subjected to the signal processing;
An image processing method comprising: In an image processing method for processing an image signal continuously acquired during underwater shooting and outputting it to a camera monitor, and displaying a through video on the monitor,
Acquiring image signals continuously from the image sensor during underwater photography;
Receiving an instruction to change the gradation characteristics of the continuously acquired image signals;
Performing gradation conversion of the continuously acquired image signal in response to an instruction to change the gradation characteristics;
Displaying a through video on a monitor based on the image signal subjected to the gradation conversion;
An image processing method comprising: In an imaging device capable of underwater photography,
Color imaging means for imaging a subject;
Image acquisition means for acquiring R, G, B signals indicating the subject via the color imaging means;
A histogram evaluation value calculating means for calculating a histogram evaluation value of at least the R signal among the acquired R, G, B signals;
Signal processing selection means for selecting any one of two or more types of signal processing based on the calculated histogram evaluation value;
Signal processing means for performing the selected signal processing on the acquired R, G, B signals;
An imaging apparatus comprising: In an imaging device capable of underwater photography,
Imaging means for imaging a subject;
Image acquisition means for continuously acquiring image signals indicating the subject via the imaging means;
Gradation converting means for converting the gradation of the continuously acquired image signal;
Change instruction means for instructing change of gradation conversion characteristics in the gradation conversion means;
A monitor that displays a through moving image based on the image signal subjected to gradation conversion by the gradation conversion means;
An imaging apparatus comprising: The gradation converting means includes a plurality of gradation conversion look-up tables from soft to hard, and the conversion instruction means selects an arbitrary look-up table from the plurality of look-up tables, and The imaging apparatus according to claim 7, wherein the tone conversion unit performs gradation conversion of an input image signal according to the selected lookup table.

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