JP5230538B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to a technique for converting to a higher frame rate.

  A CRT has been used for many years as a moving image display device typified by a television receiver, but in recent years, a panel using a liquid crystal device is becoming mainstream. Features of the liquid crystal device will be described with reference to FIG.

  FIG. 10 is a diagram for explaining display of pixels in the liquid crystal device. In FIG. 10, the horizontal axis indicates time and the vertical axis indicates pixel brightness. The frame rate here is 60z. As shown in FIG. 10, in the case of a liquid crystal device, light emission is sustained for 1/60 second, and therefore, it is called a “hold type” device.

  The hold-type device has a drawback that it tends to cause blurring with respect to movement. This will be described with reference to FIG. FIG. 11 is a diagram for explaining blur caused by movement that occurs in the hold-type device. In FIG. 11, the horizontal axis indicates the position on the screen, and the vertical axis indicates the time. FIG. 11 shows an example in which a rectangular waveform moves from left to right on the screen. When such a movement is followed by the eye, a state in which the pixel stays at the same position for 1/60 second with respect to the movement that the eye follows follows a relative delay with respect to the movement. If the hold time is long, the delay is widened and is perceived as motion blur on the screen. In FIG. 11, reference numeral 1101 indicates the way of viewing when following, and indicates that a blur (shaded portion) having a certain width is detected at the edge portion.

  As an example of measures against motion blur, there is a method of increasing the drive frequency and shortening the hold time. FIG. 12 is a diagram for explaining an example in which a moving image having a frame rate of 60 Hz is displayed at 120 Hz. In FIG. 12, the horizontal axis represents time, and the vertical axis represents pixel brightness. In addition, in order to perform display at a double frame rate, a method is also known in which an image including a high frequency component and an image including only a low frequency component of an input image are divided and displayed in the time direction.

  FIG. 13 is a diagram illustrating image dynamic characteristics in a method of displaying an image including a high frequency component and an image including only a low frequency component of an input image by dividing them in the time direction. In FIG. 13, the horizontal axis indicates the position on the screen, and the vertical axis indicates the time. As can be seen from comparison with FIG. 11, motion blur (shaded area) is greatly reduced. In addition, a field emission type display device has been developed as a device having light emission characteristics similar to those of a CRT.

  FIG. 14 is an explanatory diagram simulating the light emission characteristics of a field emission type display device. In FIG. 14, the horizontal axis represents time, and the vertical axis represents pixel brightness. This type of display device is called “impulse type” because it emits light for an instant of 1/60 second.

  The impulse-type device repeats the presence / absence of light emission at a period of 1/60 seconds, and thus has a drawback that it is easy to perceive this blinking as flicker. Since flicker has a characteristic that it becomes more conspicuous as the area becomes larger, it tends to be a problem particularly in the recent trend toward larger screens of display devices.

  FIG. 15 is a diagram illustrating the dynamic characteristics of the impulse-type device. In FIG. 15, the horizontal axis indicates the position on the screen, and the vertical axis indicates the time. Unlike the characteristics of the hold type device, the impulse type device has the greatest feature that no motion blur that causes an afterimage occurs.

  As an example of flicker countermeasures, it is conceivable to increase the drive frequency. FIG. 16 is a diagram for explaining an example in which a moving image having a frame rate of 60 Hz is displayed at double 120 Hz. In FIG. 16, the horizontal axis represents time, and the vertical axis represents pixel brightness. In the case of an impulse-type device, the same brightness can be obtained by displaying twice the half of the brightness of one time.

  FIG. 17 is a diagram for explaining dynamic characteristics when an image including a high frequency component and an image including only a low frequency component are divided and displayed in the time direction. In FIG. 17, the horizontal axis indicates the position on the screen, and the vertical axis indicates the time. If the same frame is simply displayed twice, a double image is obtained. However, by displaying only the high-frequency component once, visual deterioration is suppressed only by the blur caused by the low-frequency component.

  As described above, as a countermeasure against motion blur in a hold type display device or as a countermeasure against flicker in an impulse type display device, a method of distributing a frame image into two subframes by frequency components is effective.

  As an example of a method for realizing the hold-type double speed drive, there is a technique disclosed in Patent Document 1. A part of the circuit configuration disclosed in Patent Document 1 is shown in FIG. With respect to the input frame image, an LPF (low-pass filter) processing unit 1802 generates a sub-frame image including only a low frequency component.

  The difference detection unit 1803 extracts a difference between the input frame image and the sub-frame image including only the low frequency component generated by the LPF processing unit 1802 as a high frequency component. Then, the adder 1899 in the subsequent stage adds the high-frequency component image obtained by the difference detection unit 1803 and the input frame image, thereby obtaining a subframe image in which the high-frequency component is emphasized.

  The switching circuit 1805 switches the subframe image including only the low frequency component and the subframe image in which the high frequency component is emphasized at a period of 120 Hz and outputs the result to the subsequent stage. By alternately displaying the sub-frame image excluding the high-frequency component and the sub-frame image highlighting the high-frequency component, the original frame image is reproduced when viewed at a time period of 60 Hz. .

  However, when two subframe images are displayed alternately, a frame image that looks as if these two images are combined may not be the same as the original frame image. This will be described with reference to FIG.

  FIG. 19A shows a waveform example of the input frame image. FIG. 19B shows a waveform as a result of processing this input frame image by the LPF processing unit 1802. FIG. 19C shows the difference detection unit when the input frame image having the waveform shown in FIG. 19A and the frame image having the waveform shown in FIG. 19B are input to the difference detection unit 1803. The waveform of the frame image output from 1803 is shown. Since this frame image is a high-frequency component image, its waveform takes positive and negative values. FIG. 19D shows an output from the adder 1899 when the frame image of the waveform shown in FIG. 19C and the frame image of the waveform shown in FIG. The waveform of the frame image is shown.

  Theoretically, the waveform shown in FIG. 19B and the waveform shown in FIG. 19C are alternately displayed at a period of 120 Hz, so that the apparent waveform is shown in FIG. It becomes the same as the waveform shown. However, when the low luminance level portion in the waveform shown in FIG. 19A is zero or a value close thereto, the waveform shown in FIG. 19D has a negative value. Since an image having a negative value cannot be displayed, the negative value is actually displayed as zero as shown in FIG. 19 (e). As a result, the apparent composite waveform is displayed alternately with the frame image of the waveform shown in FIG. 19B and the frame image of the waveform shown in FIG. 19E. The waveform is as shown. For example, when the waveform frame image is an image in which white characters are arranged on a black background, it is perceived as an image in which the outline of the characters is blurred. As described above, depending on the waveform of the input frame image, there is a problem that the image after the distribution process does not look the same as the original image and is perceived as degradation.

  In order to solve the problem that a negative value occurs when the subframe image is divided, in Patent Document 2, as shown in FIG. 8, a minimum value filter unit 1801 is provided in front of the LPF processing unit 1802, and the LPF processing unit 1802 The minimum value filtering process is performed on the processing target area. This minimum value filtering process is a well-known technique in which, for example, a minimum luminance value is searched for in a 9 pixel × 9 pixel block, and the searched luminance value is assigned to the central pixel of this block.

  FIG. 9 shows the waveform of the frame image obtained at each stage by the apparatus having the configuration shown in FIG. FIG. 9A shows the waveform of the input frame image. The minimum value filter unit 1801 performs minimum value filtering on the input frame image, thereby generating a frame image having the waveform shown in FIG. The LPF processing unit 1802 performs a low-pass filter process on the frame image having the waveform shown in FIG. 9B, thereby generating a frame image having the waveform shown in FIG. 9C. In the frame image of this waveform, the gradient region due to the edge is shifted to the high signal value region side by the half-section length by the minimum value filter, so the start point of the gradient is the edge of the waveform frame image shown in FIG. It has the feature of matching.

  The difference detection unit 1803 generates the frame image having the waveform shown in FIG. 9D by subtracting the frame image having the waveform shown in FIG. 9C from the frame image having the waveform shown in FIG. To do. Since the minimum value filter causes the frame image of the waveform shown in FIG. 9C to take a lower value than the frame image of the waveform shown in FIG. 9A in any signal region, FIG. The frame image of the waveform shown always takes a positive value.

  The adder 1899 generates the frame image having the waveform shown in FIG. 9E by adding the frame image having the waveform shown in FIG. 9D to the frame image having the waveform shown in FIG. . In display, the waveform frame image shown in FIG. 9E and the waveform frame image shown in FIG. 9C are alternately displayed as sub-frame images in terms of time. Thereby, the waveform frame image (apparent frame image) shown in FIG. 9F can be matched with the waveform frame image (input frame image) shown in FIG.

  As described above, the minimum value filter has a negative value generation suppression function at the time of subframe division, thereby improving the image quality. By setting the influence range of the minimum value filter to be the same as or wider than the influence range of the low-pass filter, it is possible to prevent the occurrence of a negative value when generating an image of a high frequency component.

JP 2006-184896 A Japanese Patent Application No. 2008-119059

  However, even if the minimum value filter is used, the apparent frame image obtained by synthesizing the two sub-frame images may not appear to be the same as the original frame image, and the distortion may be conspicuous. This point will be described with reference to FIG.

  In FIG. 2A, a small area (dark area) with a low level moves in a flat image area at a speed at which it can be viewed to the right. As shown on the left side of FIG. 2A, the low-frequency component image SL is displaced by the influence of the follow-up vision with respect to the high-frequency component image SH, and the waveform obtained by synthesizing the two sub-frame images is as follows. It will be distorted. As a result, as shown on the left side of FIG. 2A, the apparent signal is perceived as an increase and decrease in level. Depending on the image conditions, a particularly high level is conspicuous, and this is a factor that makes the image appear white. FIG. 2B shows the sub-frame images and the apparent frame images at the normal time.

  FIG. 3 shows examples of specific symptoms. When there is a black area that moves slowly toward the right in a flat area, a blur that is white and blurring to the left is observed. In this symptom, black blurring is observed depending on the level of a flat portion that covers a large area. The waveform at this time is shown on the left side of FIG. 2 (c), and an example of the symptom is shown in FIG. 3 (b). In this case, the blur appears before the traveling direction, and the level decreases. As described above, depending on the waveform of the input image, there is a problem that the image after the distribution process does not look the same as the original image and is perceived as degradation.

  The present embodiment has been made in view of the above problems. When one frame image is divided into a plurality of subframe images and each subframe image is displayed as an image of this frame, the display image quality is deteriorated. It aims at providing the technique for reducing.

In order to achieve the object of the present invention, for example, an image processing apparatus of the present invention comprises the following arrangement. That is, a means for acquiring an image of each successive frame, an acquisition means for acquiring an image feature amount from the image of the target frame, a calculation means for obtaining a motion amount in the image of the target frame, and an image of the target frame A setting unit that sets a tap length of a minimum value filter to be applied according to the image feature amount and the amount of motion, and an image of the frame of interest using a minimum value filter of a tap length set by the setting unit. Filter means for performing minimum value filtering on the image, and means for generating a low-frequency component image composed of low-frequency components by performing low-pass filter processing on the image after the filter processing by the filter means; By subtracting the low frequency component image from the image of the frame of interest, a high frequency component image composed of high frequency components is obtained. Means for forming, characterized in that it comprises a means for outputting said and said high-frequency component image and the low frequency component image alternately.

  According to the configuration of the present invention, when one frame image is divided into a plurality of subframe images and each subframe image is displayed as an image of this frame, it is possible to reduce display image quality degradation.

1 is a block diagram illustrating an example of a functional configuration of an image processing apparatus according to a first embodiment. The figure for demonstrating the display of two sub-frames containing the small area to move. The figure which shows the example of a concrete symptom. The figure for demonstrating the amount of movement. 10 is a flowchart of processing performed by each of an image feature amount calculation unit 104, a motion degree detection unit 106, and a minimum value filter length setting unit 105 for a target rectangular image. The figure which shows the relationship between an image feature-value and tap length. FIG. 5 is a block diagram illustrating an example of a functional configuration of an image processing apparatus according to a second embodiment. The figure which shows the structure which concerns on patent document 2. FIG. The figure which shows the waveform of the frame image obtained at each step by the apparatus which has the structure shown in FIG. 4A and 4B are diagrams for describing display of pixels in a liquid crystal device. The figure for demonstrating the blur resulting from a motion which arises in a hold type | mold device. The figure explaining the example which displays the moving image whose frame rate is 60 Hz at 120 Hz. The figure which shows the dynamic characteristic of an image in the method of dividing | segmenting and displaying the image containing the high frequency component of the input image, and the image containing only a low frequency component in a time direction. Explanatory drawing imitating the light emission characteristics of a field emission type display device. The figure which shows the dynamic characteristic of an impulse type device. The figure for demonstrating the example which displays the moving image whose frame rate is 60 Hz at 120 Hz of double. The figure for demonstrating the dynamic characteristic in the case of dividing | segmenting and displaying the image containing a high frequency component, and the image containing only a low frequency component in a time direction. FIG. 9 is a diagram showing a part of a circuit configuration disclosed in Patent Document 1; The figure for demonstrating the case where the frame image which looks as if these two images are synthesize | combined is not the same as the original frame image by displaying two sub-frame images alternately. The figure which shows the structural example of a Sobel filter. FIG. 2 is a block diagram showing an example of a hardware configuration of a computer applicable to each image processing apparatus described in each embodiment.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The embodiment described below shows an example when the present invention is specifically implemented, and is one of the specific examples of the configurations described in the claims.

[First Embodiment]
FIG. 1 is a block diagram illustrating a functional configuration example of the image processing apparatus according to the present embodiment. In the present embodiment, description will be made assuming that each unit shown in FIG. 1 is configured by hardware.

  In the image processing apparatus according to the present embodiment, images of successive frames (frame images) are sequentially input. The image processing apparatus divides the input frame image into a plurality of subframe images, and outputs each subframe image instead of the frame image. This enables double speed display.

  In the following description, the operation of the image processing device when an image of the frame of interest (frame of interest image) is input to the image processing device will be described. That is, the operation of each unit described below is performed for each frame image.

  The minimum value filter unit 101 generates a processed image by performing minimum value filter processing on the input frame image of interest, and sends the generated processed image to a subsequent LPF (low-pass filter) processing unit 102. To do.

  Here, as is well known, the minimum value filter processing is to perform the following processing for each pixel constituting the image. That is, when the minimum value filtering process is performed on the pixel P, the minimum pixel value is specified by referring to the respective pixel values of a total of nine pixels including the eight pixels surrounding the pixel P and the pixel P. Then, the pixel value of the pixel P is updated to the specified minimum pixel value.

  Therefore, by performing such processing for each pixel constituting the image, it is possible to generate (acquire) a processed image by performing minimum value filtering on the image. In the minimum value filtering process, a low luminance pixel value is selected at a boundary portion where a high luminance pixel value and a low luminance pixel value are adjacent to each other. It will be narrowed inside the area.

  On the other hand, the frame image of interest is also input to the image feature amount calculation unit 104, the motion degree detection unit 106, and the frame memory 107. The image feature amount calculation unit 104 divides the target frame image into a plurality of rectangular images (for example, 16 pixels × 16 pixels), and extracts an image feature amount from each rectangular image. Then, the extracted image feature amount for each rectangular image is sent to the subsequent minimum value filter length setting unit 105.

  The frame memory 107 has an area for storing an image for at least one frame. Therefore, the frame memory 107 stores at least an image of the frame immediately before the frame of interest (previous frame image).

  The motion detection unit 106 reads the previous frame image from the frame memory 107 and generates a difference image between the frame image of interest and the read previous frame image. Then, using this difference image, the amount of motion in the frame image of interest is obtained (calculated). Note that the motion detection unit 106 divides the frame image of interest into a plurality of rectangular images, and obtains the amount of motion for each rectangular image. Then, the degree-of-motion detection unit 106 sends the amount of motion obtained for each rectangular image to the minimum value filter length setting unit 105 in the subsequent stage.

  The minimum value filter length setting unit 105 uses the image feature amount for each rectangular image obtained from the image feature amount calculation unit 104 and the motion amount for each rectangular image obtained from the motion degree detection unit 106 to obtain the minimum value. The tap length of the minimum value filter used in the value filter unit 101 is set for each rectangular image. Therefore, the minimum value filter unit 101 performs minimum value filter processing using a minimum value filter having a different tap length for each rectangular image.

  The LPF processing unit 102 generates a low-frequency component frame image (low-frequency component image) by performing a two-dimensional low-pass filter process on the image subjected to the minimum value filter processing by the minimum value filter unit 101. . The low-pass filter does not particularly define a function, and may be, for example, a Gaussian function or a moving average or weighted moving average filter.

  The distribution ratio processing unit 190 determines a ratio at which each subframe image (two subframe images in the present embodiment) is emitted. In order to make it difficult to perceive flicker, it is desirable that the difference in brightness between the two sub-frame images is small. Therefore, in this embodiment, 50% is distributed. Therefore, the distribution ratio processing unit 190 multiplies the luminance value of the image processed by the LPF processing unit 102 by 0.5 to halve the luminance value of this image.

  The image processed by the distribution ratio processing unit 190 is sent to the difference detection unit 103 and also sent to the switching unit 180. The difference detection unit 103 generates a high-frequency component frame image (high-frequency component image) by subtracting the low-frequency component image sent from the distribution ratio processing unit 190 from the frame image of interest. Then, the difference detection unit 103 sends the generated high frequency component image to the subsequent switching unit 180.

  The switching unit 180 alternately sends the low frequency component image sent from the distribution ratio processing unit 190 and the high frequency component image sent from the difference detection unit 103 to the outside. The destination is not particularly limited, and examples thereof include a CRT and a liquid crystal screen.

  Next, processing performed by the image feature amount calculation unit 104, the motion degree detection unit 106, and the minimum value filter length setting unit 105 will be described in more detail. As described above, the image feature amount calculation unit 104, the motion degree detection unit 106, and the minimum value filter length setting unit 105 perform processing for each rectangular image, and in the following, when processing the target rectangular image in the target frame image Will be described. That is, the image feature amount calculation unit 104, the motion degree detection unit 106, and the minimum value filter length setting unit 105 perform each process described below for each rectangular image.

  FIG. 5 is a flowchart of processing performed by each of the image feature amount calculation unit 104, the motion degree detection unit 106, and the minimum value filter length setting unit 105 for the target rectangular image. First, in step S201, the motion level detection unit 106 obtains a motion amount for the target rectangular image. The amount of motion is a difference between the two frame images F0 and F1, as shown in FIG. Assuming that the low-level small area moves as a state where the problem occurs, the moving direction can be determined by the difference value, and the difference value of the area where the blur occurs due to the trailing is negative.

  Therefore, the motion level detection unit 106 obtains the motion amount in the target rectangular image as follows. First, a difference image between a target rectangular image in the target frame image and an image in an area corresponding to the target rectangular image in the previous frame image is obtained. This difference image is stored in a memory (not shown) of the present apparatus and used in the processing described later. In addition, the value of each pixel constituting the difference image can include not only a positive value but also a negative value. Next, the total sum of the absolute values of the pixels constituting the difference image is obtained as the motion amount DA in the target rectangular image.

  Then, the degree-of-motion detector 106 compares the amount of movement DA with a preset threshold DX. If DA> DX as a result of the size comparison, it is determined that the motion is fast, and the motion detection unit 106 sends the determination result to the minimum value filter length setting unit 105. Then, the process proceeds to step S209.

  In step S <b> 209, the minimum value filter length setting unit 105 sets a specified tap length for the minimum value filter unit 101. As a result, the minimum value filter unit 101 performs minimum value filter processing using a minimum value filter having a specified tap length on the target rectangular image.

  On the other hand, if DA ≦ DX as a result of the size comparison in step S201, it is determined that the movement is slow, and the process proceeds to step S202. In step S202, the image feature amount calculation unit 104 obtains the edge strength in the target rectangular image. The edge strength is obtained by adding the values after the Sobel filter processing in the horizontal direction and the vertical direction. 20A and 20B are diagrams illustrating a configuration example of the Sobel filter. Note that the edge intensity value of each pixel constituting the rectangular image of interest is separately stored as an edge map in a memory (not shown) of the present apparatus and used in the processing described later.

  Then, the image feature amount calculation unit 104 compares the obtained edge strength SA with a predetermined threshold value SX. As a result of the size comparison, if SA <SX, the process proceeds to step S209.

  On the other hand, if SA ≧ SX (greater than or equal to the threshold), the process proceeds to step S203. In step S <b> 203, the image feature amount calculation unit 104 obtains a variance value of pixel values using the pixel values of each pixel constituting the target rectangular image. Then, the obtained variance value BA is compared with a predetermined threshold value BX. As a result of this size comparison, if BA> BX, the process proceeds to step S209.

  On the other hand, if BA ≦ BX, it is determined that the target rectangular image is included in the flat portion of the target frame image, and the process proceeds to step S204. In step S204, the image feature amount calculation unit 104 obtains the contrast in the target rectangular image. In this process, first, the edge map stored in the memory in step S202 is referred to, and among the pixels constituting the target rectangular image, the pixel whose edge intensity value is equal to or smaller than the threshold is specified. Then, the pixel value of the identified pixel is referred to, and the difference CA between the maximum pixel value and the minimum pixel value among the referenced pixel values is obtained as the contrast.

  Next, the image feature amount calculation unit 104 compares the obtained difference CA with a predetermined threshold CX. As a result of this size comparison, if CA <CX, the process proceeds to step S209.

  On the other hand, if CA ≧ CX, the process proceeds to step S205. In step S205, the image feature amount calculation unit 104 refers to the difference image stored in the memory in step S201 and the edge map stored in the memory in step S202. And the pixel which is a pixel with a negative value among the pixels which comprise a difference image, and the edge intensity value in the corresponding pixel position on an edge map becomes below a threshold value is specified. Then, an average value of the pixel values of the specified pixels is obtained. Then, the obtained average value AA is compared with a predetermined threshold value AX. As a result of the size comparison, if AA <AX, the process proceeds to step S207.

  In step S207, the minimum value filter length setting unit 105 resets the tap length of the currently set minimum value filter to a longer tap length. Thus, the minimum value filter unit 101 performs minimum value filter processing using the minimum value filter with the tap length reset by the minimum value filter length setting unit 105 on the target rectangular image. Note that the tap length increment is not particularly limited, but for example, the horizontal and vertical widths of a region composed of pixels having a negative value in the difference image with respect to a predetermined tap length are measured, It is set to 1/2 of the value.

  On the other hand, if the result of the size comparison in step S205 is AA ≧ AX, the process proceeds to step S206. In step S206, the image feature amount calculation unit 104 refers to the difference image stored in the memory in step S201 and the edge map stored in the memory in step S202. Then, a pixel having a positive value among the pixels constituting the difference image and having an edge intensity value at a corresponding pixel position on the edge map equal to or less than a threshold value is specified. Then, an average value of the pixel values of the specified pixels is obtained. Then, the obtained average value AAA is compared with a predetermined threshold value AAX. As a result of the size comparison, if AAA ≦ AAX (below the threshold value), the process proceeds to step S209.

  On the other hand, in the size comparison, if AAA> AAX, the process proceeds to step S208. In step S208, the minimum value filter length setting unit 105 resets the tap length of the currently set minimum value filter to a shorter tap length. Thus, the minimum value filter unit 101 performs minimum value filter processing using the minimum value filter with the tap length reset by the minimum value filter length setting unit 105 on the target rectangular image. The decrement of the tap length is not particularly limited. For example, the horizontal and vertical widths of an area composed of pixels having a positive value in the difference image are measured with respect to a predetermined tap length. , ½ of the value.

  As described above, according to the present embodiment, in the combined display result of each subframe image, the level of white blurring is reduced as shown on the right side of FIG. 2A, and the result of FIG. As shown on the right side, the level of blurring that has sunk in black decreases and becomes inconspicuous. FIG. 6 is a diagram illustrating the relationship between the image feature amount and the tap length.

<Modification 1>
If there is a large difference in the tap length of the minimum value filter used between adjacent rectangular images, discontinuous blurring occurs between adjacent rectangular images. Therefore, it is better to keep the change in tap length within a specified value (within a specified difference PX).

  For example, consider a case in which each rectangular image sequence constituting the frame image is selected in order from the top and each rectangular image constituting one rectangular image sequence is selected in order from the left, and the selected rectangular image is subjected to minimum value filtering. In this case, the change in the tap length of the minimum value filter used for the target rectangular image is used for the left side rectangular image adjacent to the minimum length filter tap length used for the rectangular image immediately above the target rectangular image. The difference from the tap length of the minimum value filter is set to PX.

<Modification 2>
The tap length of the minimum value filter may be a range size by detecting an area composed of a pixel group having an edge intensity value equal to or smaller than a threshold value or an area having a pixel value variance value equal to or smaller than a threshold value.

[Second Embodiment]
FIG. 7 is a block diagram illustrating a functional configuration example of the image processing apparatus according to the present embodiment. In the following description, it is assumed that each unit illustrated in FIG. 7 is configured by hardware. In FIG. 7, the minimum value filter unit 701, the LPF processing unit 702, the distribution ratio processing unit 703, the difference detection unit 708, and the switching unit 709 are respectively the minimum value filter unit 101, the LPF processing unit 102, the distribution ratio processing unit 190, and the difference. The same as the detection unit 103 and the switching unit 180.

  The configuration shown in FIG. 7 removes the image feature amount calculation unit 104, the minimum value filter length setting unit 105, the motion degree detection unit 106, and the frame memory 107 from the configuration shown in FIG. 1, and also includes a minimum value filter unit 701 and an LPF. A switch unit 711 is provided between the processing unit 702 and the processing unit 702. Further, a frame memory 710 is provided immediately before the minimum value filter unit 701, and a saturation detection unit 712 is provided immediately after the difference detection unit 708.

  In such a configuration, each frame image is input to the frame memory 710. Each frame image is sequentially transmitted to the minimum value filter unit 701, the switch unit 711, and the difference detection unit 708. First, the switch unit 711 is connected to the terminal 7a. Therefore, a frame image is input from the frame memory 710 to the LPF processing unit 702 via the switch unit 711, and a low frequency component image is obtained by the LPF processing unit 702 and the distribution ratio processing unit 703. This low frequency component image is sent to the difference detection unit 708 and the switching unit 709. On the other hand, a high frequency component image is input from the difference detection unit 708 to the saturation detection unit 712.

  Here, the saturation detection unit 712 detects a negative signal as shown in FIG. The saturation detection unit 712 does not output anything in the absence of this detection, but in the case of detection, the minimum value filter unit 701 determines the width of the negative value area in units of pixels and uses it as a tap length correction value. Set to. Then, the switch unit 711 is connected to the terminal 7b. Subsequent operations are as described in the first embodiment.

[Third Embodiment]
In the above embodiments, the respective units illustrated in FIGS. 1 and 7 have been described as being configured by hardware. However, each unit excluding the frame memory 107 in FIG. 1 and each unit excluding the frame memory 710 in FIG. 7 may be configured by software. In this case, a computer having a memory for storing the software and a CPU for executing the software stored in the memory functions as an image processing apparatus having the configuration shown in FIGS. FIG. 21 is a block diagram illustrating a hardware configuration example of a computer applicable to each image processing apparatus described in the above embodiments.

  The CPU 2002 controls the entire computer using computer programs and data stored in the ROM 2003 and the RAM 2004, and executes the processes described above as performed by the image processing apparatus according to each of the embodiments to which the computer is applied. To do.

  The ROM 2003 stores setting data and a boot program for the computer. The RAM 2004 has an area for temporarily storing data received from the outside via the network I / F (interface) 2005, computer programs and data loaded from the external storage device 2008, and the like. Furthermore, the RAM 2004 has a work area that is used when the CPU 2002 executes various processes. That is, the RAM 2004 can provide various areas as appropriate. For example, the RAM 2004 functions as the frame memory 107 shown in FIG. 1, the frame memory 710 shown in FIG. 7, and the memory (not shown) described in the first embodiment.

  A network I / F 2005 is used to connect the computer to a network such as a LAN or the Internet, and enables data communication with devices connected on the network.

  The operation unit 2006 is configured by a keyboard, a mouse, and the like, and can input various instructions to the CPU 2002 by being operated by an operator of the computer. The output device 2007 is a display device such as a CRT or a liquid crystal screen, or a printing device such as a printer, and can print or display an image as a result of processing by the computer.

  The external storage device 2008 is a large-capacity information storage device represented by a hard disk drive device. The external storage device 2008 stores an OS (operating system). In addition, the external storage device 2008 stores computer programs and data for causing the CPU 2002 to execute the functions of the respective units except the frame memory 107 in FIG. 1 and the respective units other than the frame memory 710 in FIG. . The external storage device 2008 also stores data described as known data in the above embodiments.

  Computer programs and data stored in the external storage device 2008 are appropriately loaded into the RAM 2004 under the control of the CPU 2002 and are processed by the CPU 2002. A bus 2001 connects the above-described units.

[Other Embodiments]
Further, the object of the present invention is that a computer-readable recording medium (or storage medium) that records a program code (computer program) of software that realizes the functions of the above-described embodiments constitutes the present invention. Needless to say, the case where the functions of the above-described embodiment are realized by the program code read from the recording medium is also included. When the present invention is applied to the recording medium, program code corresponding to the flowchart described above is stored in the recording medium.

Claims (13)

Means for obtaining an image of each successive frame;
Acquisition means for acquiring an image feature amount from the image of the frame of interest;
A calculation means for obtaining a motion amount in the image of the frame of interest;
Setting means for setting a tap length of a minimum value filter to be applied to the image of the frame of interest according to the image feature amount and the motion amount ;
Filter means for performing minimum value filter processing on the image of the frame of interest using the minimum value filter of the tap length set by the setting means;
Means for generating a low-frequency component image composed of low-frequency components by performing low-pass filter processing on the image after filtering by the filter means;
Means for generating a high frequency component image composed of high frequency components by subtracting the low frequency component image from the image of the frame of interest;
An image processing apparatus comprising: means for alternately outputting the low frequency component image and the high frequency component image.   The image processing apparatus according to claim 1, wherein the acquisition unit acquires edge strength, a variance value of pixel values, and a contrast as the image feature amount.   The image processing apparatus according to claim 1, wherein the setting unit sets a predetermined tap length as the tap length when the amount of motion is larger than a predetermined threshold.   The image processing apparatus according to claim 2, wherein the setting unit sets a predetermined tap length as the tap length when the edge strength is smaller than a predetermined threshold value.   The image processing apparatus according to claim 2, wherein the setting unit sets a predetermined tap length as the tap length when the variance value is larger than a predetermined threshold value.   The image processing apparatus according to claim 2, wherein the setting unit sets a predetermined tap length as the tap length when the contrast is smaller than a predetermined threshold value. The setting means is configured such that the amount of motion is equal to or less than a predetermined threshold, the edge strength is equal to or greater than a predetermined threshold, the variance value is equal to or less than a predetermined threshold, and the contrast is equal to or greater than a predetermined threshold. If it is,
Among the pixels constituting the difference image between the image of the frame of interest and the image of the previous frame that is one frame before the frame of interest, the pixel value is negative and the correspondence on the image of the frame of interest edge intensity value at the pixel position that is specified pixel such that less than a predetermined threshold value, the average value of pixel values for each pixel and the identified calculates the average value the calculated predetermined threshold The image processing apparatus according to claim 2, further comprising: a unit that resets the tap length to a longer tap length when the tap length is smaller. The setting means includes
The amount of motion is equal to or less than a predetermined threshold, the edge strength is equal to or greater than a predetermined threshold, the variance is equal to or less than a predetermined threshold, and the contrast is equal to or greater than a predetermined threshold, and the average value Is greater than or equal to a predetermined threshold,
Among the pixels constituting the difference image between the image of the frame of interest and the image of the previous frame that is one frame before the frame of interest, the pixel value is positive and the correspondence on the image of the frame of interest edge intensity value at the pixel position which is to identify the pixels such that below a predetermined threshold, the average value of the pixel values of the respective pixels the specified calculated, mean values the calculated predetermined threshold the case is less than or equal to set the tap length defined as the tap length, when the average value the calculation is greater than a predetermined threshold value, means for resetting the tap length shorter tap length The image processing apparatus according to claim 7 , further comprising:   9. The method according to claim 1, wherein the acquisition unit, the calculation unit, the setting unit, and the filter unit perform processing for each rectangular image constituting the image of the frame of interest. The image processing apparatus described.   The image processing apparatus according to claim 1, wherein the setting unit sets the tap length so that a difference in tap length between adjacent rectangular images is within a predetermined value. . An image processing method performed by an image processing apparatus,
An image acquisition unit of the image processing apparatus acquires an image of each successive frame;
An image feature amount acquisition unit of the image processing apparatus acquires an image feature amount from an image of the frame of interest; and
A calculating step of calculating a motion amount in the image of the frame of interest by the calculation means of the image processing device ;
A setting step in which the setting unit of the image processing apparatus sets a tap length of a minimum value filter to be applied to the image of the frame of interest according to the image feature amount and the motion amount ;
A filter step in which the filter means of the image processing device performs a minimum value filter process on the image of the frame of interest using the minimum value filter of the tap length set in the setting step;
A step of generating a low-frequency component image composed of low-frequency components by performing low-pass filter processing on the image after the filtering processing by the filtering step , wherein the low-frequency component image generating means of the image processing device ; ,
A step of generating a high-frequency component image composed of high-frequency components by subtracting the low-frequency component image from the image of the frame of interest , wherein the high-frequency component image generating means of the image processing device ;
An image processing method, comprising: an output unit of the image processing apparatus that alternately outputs the low-frequency component image and the high-frequency component image. The computer program for functioning a computer as each means of the image processing apparatus of any one of Claims 1 thru | or 10.   A computer-readable storage medium storing the computer program according to claim 12.