JP2014150295A - Noise reduction device, display device, noise reduction method, and noise reduction program - Google Patents

Abstract

An object of the present invention is to reduce the capacity of a memory for storing image data when noise superimposed on an image is reduced.
A magnitude relation storage unit that stores information indicating a magnitude relation between a target pixel that is a target for noise reduction and a comparison pixel that is separated by a predetermined interval, and the magnitude relation from the magnitude relation storage unit. And a noise reduction unit 32 that reduces the noise of the target pixel based on the read information, and based on the read information indicating the magnitude relationship.
[Selection] Figure 4

Description

  The present invention relates to a noise reduction device, a display device, a noise reduction method, and a noise reduction program.

  When video is captured in real time from an image input device (for example, a television imaging device), and the captured video is transmitted as a video signal and displayed on the receiver device, noise components are mixed in the transmission path, and the receiver itself But noise components are mixed. For example, in analog television broadcasting, when the signal level of a received video signal is low, a noise component is significantly mixed in the video signal. The same applies to a case where a recorded analog video is digitized and rebroadcast through a transmission line, and noise components are significantly mixed in the video signal.

  In Patent Document 1, the smoothing value of the noise component in the vertical blanking period is subtracted from or added to the input signal using the magnitude relationship between the input video signal and the output of the median filter. Describes a noise reduction circuit for reducing noise components remaining in the circuit.

JP-A-7-250264

  However, in order to reduce noise superimposed between frames, the noise reduction circuit needs to perform noise reduction by using a total of three frames including a target frame to be subjected to noise reduction and two frames before and after. In that case, when reducing noise between frames, the conventional noise reduction circuit needs to include two frame memories for storing data for two fields, which increases the circuit scale of the noise reduction circuit. As a result, there is a problem that the production cost becomes high.

  Therefore, the present invention has been made in view of the above problems, and provides a technique that makes it possible to reduce the capacity of a memory that stores image data when noise superimposed on an image is reduced. Is an issue.

  (1) The noise reduction apparatus according to the present invention has been made in view of the above circumstances, and stores a size relationship in which information indicating a size relationship between a target pixel to be noise-reduced and a comparison pixel separated by a predetermined interval is stored. A storage unit; and a noise reduction unit that reads information indicating the size relationship from the size relationship storage unit and reduces noise of the target pixel based on the read information indicating the size relationship.

  (2) The noise reduction device according to (1), further including a pixel value storage unit that stores information indicating a pixel value of a second comparison pixel that is separated from the target pixel by a predetermined interval, and the noise reduction unit Reads information indicating the pixel value of the second comparison pixel from the pixel value storage unit, and based on the read pixel value of the second comparison pixel, the pixel value of the target pixel, and the magnitude relationship The noise of the target pixel is reduced.

  (3) In the noise reduction device according to (1) or (2), the noise reduction unit calculates a magnitude relationship between a pixel value of the second comparison pixel and a pixel value of the target pixel, and the calculation The information indicating the magnitude relation is stored in the magnitude relation storage unit.

  (4) In the noise reduction device according to any one of (1) to (3), the pixel value of a detection pixel that is a target for detecting the amount of noise included in the image and the image including the detection pixel The pixel value of the previous frame pixel, which is a pixel corresponding to the position of the detection pixel in the previous image by a predetermined number of frames, and a first interval from the detection pixel in the image including the detection pixel A calculation unit that calculates a predetermined pixel value based on a pixel value of the pixel and a pixel value of a pixel that is separated from the detection pixel by a second interval, and based on the frequency of the calculated value, A noise amount estimation unit for estimating the amount of noise on the display.

  (5) In the noise reduction device according to (4), the noise amount estimation unit estimates the mode value of the frequency as the amount of noise included in the image.

  (6) In the noise reduction device according to (4) or (5), the detection pixel is located between a pixel separated by the first interval and a pixel separated by the second interval. And

  (7) In the noise reduction device according to any one of (4) to (6), the first interval and the second interval may be set in advance in a vertical direction in an image including the detection pixel, respectively. It is characterized by a predetermined interval.

  (8) In the noise reduction device according to any one of (1) to (7), an interval between the target pixel and the comparison pixel and an interval between the target pixel and the second comparison pixel are a frame. The noise reduction unit reduces noise between frames of the target pixel.

  (9) In the noise reduction device according to any one of (1) to (8), an interval between the target pixel and the comparison pixel and an interval between the target pixel and the second comparison pixel are It is a horizontal interval in an image including the target pixel, and the noise reduction unit reduces horizontal noise in the image of the target pixel.

  (10) In the noise reduction device according to any one of (1) to (9), an interval between the target pixel and the comparison pixel and an interval between the target pixel and the second comparison pixel are The interval in the vertical direction in the image including the target pixel, and the noise reduction unit reduces noise in the vertical direction in the image of the target pixel.

  (11) A display device according to the present invention includes the noise reduction device according to any one of (1) to (7).

  (12) In the noise reduction method of the present invention, a noise reduction apparatus including a magnitude relation storage unit that stores information indicating magnitude relation between a target pixel that is a target of noise reduction and a comparison pixel that is separated by a predetermined interval. A noise reduction method to be executed, comprising: a noise reduction procedure for reading information indicating the magnitude relationship from the magnitude relationship storage unit and reducing noise of the target pixel based on the read information indicating the magnitude relationship.

  (13) The noise reduction program according to the present invention is a computer including a magnitude relation storage unit that stores information indicating magnitude relation between a target pixel that is a target of noise reduction and a comparison pixel that is separated by a predetermined interval. A noise reduction program for reading information indicating the magnitude relationship from a magnitude relationship storage unit and executing a noise reduction step for reducing noise of the target pixel based on the read information indicating the magnitude relationship.

  According to the present invention, when reducing noise superimposed on an image, it is possible to reduce the capacity of a memory for storing image data.

1 is a schematic block diagram of a display device according to a first embodiment. It is a figure which shows the connection relation of the signal of a liquid-crystal drive part and a liquid crystal panel. It is a schematic block diagram of the noise reduction process part in 1st Embodiment. It is a functional block diagram of the noise reduction part between frames in a 1st embodiment. It is a figure for demonstrating the process of the noise reduction part between flame | frames. It is a functional block diagram of the horizontal noise reduction part in 1st Embodiment. It is a functional block diagram of the vertical noise reduction part in 1st Embodiment. It is a flowchart which shows the flow of a process of the display apparatus in 1st Embodiment. It is the flowchart which showed the detail of the process of the noise reduction process part in step S102 of FIG. It is a schematic block diagram of the display apparatus in 2nd Embodiment. It is a schematic block diagram of the image processing part in 2nd Embodiment. It is a functional block diagram of the vertical noise reduction part in 2nd Embodiment. It is a figure for demonstrating the process of the noise reduction part 52b in 2nd Embodiment. It is the flowchart which showed the detail of the process of the noise reduction process part in FIG.8 S102 in 2nd Embodiment. It is a schematic block diagram of the display apparatus in 3rd Embodiment. It is a schematic block diagram of the noise reduction process part in 3rd Embodiment. It is a functional block diagram of the horizontal noise reduction part in 3rd Embodiment. It is a figure for demonstrating the process of the noise reduction part in 3rd Embodiment. It is the flowchart which showed the detail of the process of the noise reduction process part in FIG.8 S102 in 3rd Embodiment. It is a schematic block diagram of the display apparatus in 4th Embodiment. It is a schematic block diagram of the noise reduction process part in 4th Embodiment. It is a functional block diagram of the noise amount detection part 20d in 4th Embodiment. It is a figure for demonstrating the process of the calculation part in 4th Embodiment. It is an example of the histogram of value Nd for estimating the amount of noise. This is a luminance distribution when Gaussian noise with a standard deviation of 10 is added to an image having a luminance value 128 of all pixels. It is the figure by which the outline | summary of the noise reduction process in the noise reduction part between frames of 4th Embodiment, a horizontal noise reduction part, and a vertical noise reduction part was shown. It is a figure for demonstrating the process performed with respect to the image data which shows the luminance distribution w251 of FIG. A frequency distribution of luminance values after performing noise reduction processing for each noise amount is shown. It is the figure where the relationship between noise amount (alpha) and the dispersion value of a pixel value was shown. It is the figure where an example of the histogram in which the frequency for every value Nd 'for estimating the amount of noise was shown was shown. It is the figure by which an example of the histogram for comparing the frequency for every value Nd 'for estimating noise amount with the frequency for every value Nd for estimating noise amount was shown. It is the flowchart which showed the detail of the process of the noise reduction process part in FIG.8 S102 in 4th Embodiment. It is an example in the schematic block diagram of the conventional inter-frame noise reduction part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 is a schematic block diagram of a display device 1 according to the first embodiment.
In FIG. 1, a display device 1 includes a detection unit 11, a Y / C (luminance signal / color difference signal) separation unit 12, a noise reduction processing unit 13, and RGB (Red: red, Green: green, Blue: blue). A conversion unit 14, a liquid crystal driving unit 15, and a liquid crystal panel 16 are provided. The display device 1 is connected to the antenna 10.

  For example, the detection unit 11 receives a high-frequency signal of image data of a plurality of channels of terrestrial analog television broadcast supplied from an external antenna 10. Then, the detection unit 11 extracts a modulation signal of a desired channel from the high-frequency signal supplied from the antenna, converts the extracted modulation signal into a baseband signal, and outputs it to the Y / C separation unit 12.

The Y / C separation unit 12 demodulates the supplied baseband signal, separates it into a luminance signal, a color difference signal, and a color difference signal, and converts each separated signal into a digital signal at a predetermined sampling frequency. .
Further, the Y / C separation unit 12 outputs the luminance value Y data converted into the digital signal, and the image data including the color difference Cb data and the color difference Cr data to the noise reduction processing unit 13.

  Next, the outline of the processing of the noise reduction processing unit 13 will be described. The noise reduction processing unit 13 calculates the noise level in units of frames or fields. The noise reduction processing unit 13 compares the supplied luminance value Y data, color difference Cb data, and color difference Cr data between frames (pixel space in which the pixels are arranged) or between pixels in the same frame, and processes target pixels. It is determined whether or not noise is superimposed on.

  In addition, the noise reduction processing unit 13 adds or subtracts a noise amount α estimated by a method described later from a target pixel determined to have noise superimposed thereon, thereby reducing noise of the target pixel targeted for noise reduction. Perform the process. The noise reduction processing unit 13 outputs the image signal after the noise reduction processing to the image format conversion unit 14.

  Details of processing for each pixel in the noise reduction processing unit 13 will be described later. Here, when the video signal is interlaced, noise processing is performed for each field. On the other hand, when the video signal is non-interlaced, noise processing is performed for each frame.

If the image signal is an interlace signal, the image format conversion unit 14 converts the image signal supplied from the noise reduction processing unit 13 into a progressive signal. The image format conversion unit 14 adjusts the number of pixels (scaling processing) in accordance with the resolution of the liquid crystal panel 16 for the progressive signal.
Then, the image format conversion unit 14 converts the video signal with the adjusted number of pixels into an RGB signal (Red, Green, Blue color video signal), and outputs the converted RGB signal to the liquid crystal drive unit 15.

  The liquid crystal drive unit 15 generates a clock signal or the like for displaying video data supplied to the liquid crystal panel 16 on a two-dimensional plane of the screen. Then, the liquid crystal drive unit 15 supplies the generated clock signal to the liquid crystal panel 16.

Next, FIG. 2 is a diagram illustrating a signal connection relationship between the liquid crystal driving unit 15 and the liquid crystal panel 16.
As shown in FIG. 2, the liquid crystal driving unit 15 includes a source driver unit 15_1 and a gate driver unit 15_2, and a display element arranged at a point where the source line 19 and the gate line 18 intersect in the liquid crystal panel 16. (Liquid crystal element) PIX, that is, the liquid crystal element PIX arranged on the matrix is controlled to display an image. The liquid crystal element PIX includes a TFT (Thin Film Transistor) and a liquid crystal pixel element into which a voltage corresponding to a gradation described later is written (a voltage is applied).

The source driver unit 15_1 generates a gradation voltage for driving the pixel element from the supplied RGB signal, and uses the gradation voltage (a source signal which is gradation degree information) as a source line of the liquid crystal panel 16. Each 19 (column-direction wiring) is held by a hold circuit provided inside.
The source driver unit 15_1 supplies the source signal to the TFT source line 19 in the liquid crystal element PIX of the liquid crystal panel 16 in synchronization with the clock signal with respect to the vertical arrangement of the screen.
The gate driver unit 15_2 is synchronized with the clock signal for one row of the liquid crystal element PIX on the screen through the gate line 18 (corresponding to the horizontal wiring, main scanning) of the TFT in the liquid crystal element PIX of the liquid crystal panel 16. A predetermined gate signal is supplied.

  The liquid crystal panel 16 includes an array substrate, a counter substrate, and liquid crystal sealed therebetween. At each intersection of the source line 19 and the gate line 18 on the array substrate, a liquid crystal element PIX, that is, a pixel electrode connected to the TFT and the drain electrode of the TFT, and a counter electrode (configured by a strip electrode on the counter substrate) ) Are arranged one by one. Here, in the pixel element, liquid crystal is sealed between the pixel electrode and the counter electrode. The liquid crystal panel 16 has three sub-pixels corresponding to the three primary colors RGB (Red, Green, Blue) for each pixel, that is, for each liquid crystal element PIX. The liquid crystal panel 16 has one TFT for each subpixel.

  The TFT is selected and turned on when the gate signal supplied from the gate driver unit is supplied to the gate electrode and the gate signal is at a high level, for example. The source signal supplied from the source driver is supplied to the source electrode of the TFT, and when the TFT is in an ON state, a gradation voltage is applied to the pixel electrode connected to the drain electrode of the TFT, that is, the pixel element. Is done.

  In accordance with the gradation voltage, the orientation of the liquid crystal of the pixel element changes, thereby changing the light transmittance of the liquid crystal in the region of the pixel element. The gradation voltage is held in a liquid crystal capacitance (which constitutes a hold circuit) of a pixel element formed by a liquid crystal portion between a pixel electrode connected to the drain electrode of the TFT and a counter electrode, and the liquid crystal Orientation is maintained. The alignment of the liquid crystal is maintained until the next signal is supplied to the source electrode and the maintained voltage value is changed by the gradation voltage, so that the light transmittance of the liquid crystal is maintained.

As described above, the liquid crystal panel 16 performs gradation display on the supplied video data.
Although the transmissive liquid crystal panel has been described here, the present invention is not limited to this, and a reflective liquid crystal panel may be used.

  FIG. 3 is a schematic block diagram of the noise reduction processing unit 13 in the first embodiment. The noise reduction processing unit 13 includes a noise amount detection unit 20, an interframe noise reduction unit 30, a horizontal noise reduction unit 40, and a vertical noise reduction unit 50. The noise reduction processing unit 13 performs noise reduction on at least one of the luminance value Y, the color difference Cb, and the color difference Cr among the pixel values. Hereinafter, the noise reduction processing of the noise reduction processing unit 13 will be described using the luminance value Y among the pixel values as an example.

The noise amount detection unit 20 receives image data in which raster-scanned image data is sent sample by sample from the Y / C separation unit 12. The noise amount detection unit 20 detects the noise amount α from the blanking period of the received image data. Specifically, for example, the noise amount detection unit 20 detects the average value of the pixel values in the vertical blanking period as the noise amount α.
Then, the noise amount detection unit 20 outputs information indicating the detected noise amount α to the inter-frame noise reduction unit 30, the horizontal noise reduction unit 40, and the vertical noise reduction unit 50 together with the raster-scanned image data.

  The inter-frame noise reduction unit 30 reduces noise between frames superimposed on an image based on raster-scanned image data supplied from the noise amount detection unit 20 and information indicating the noise amount α. The inter-frame noise reduction unit 30 outputs information indicating the pixel value after noise reduction between frames to the horizontal noise reduction unit 40.

  The horizontal noise reduction unit 40 is based on information indicating the pixel value after noise reduction between frames supplied from the inter-frame noise reduction unit 30 and information indicating the noise amount α supplied from the noise amount detection unit 20. Reduce the horizontal noise superimposed on the image. The horizontal noise reduction unit 40 outputs information indicating the pixel value after noise reduction in the horizontal direction to the vertical noise reduction unit 50.

  The vertical noise reduction unit 50 is based on the information indicating the pixel value after horizontal noise reduction supplied from the horizontal noise reduction unit 40 and the information indicating the noise amount α supplied from the noise amount detection unit 20. Reduce the vertical noise superimposed on the image. The vertical noise reduction unit 50 outputs information indicating the pixel value after noise reduction in the vertical direction to the image format conversion unit 14.

  Next, details of the processing of the interframe noise reduction unit 30 will be described with reference to FIGS. 4, 5, and 33. First, the conventional interframe noise reduction unit 330 will be described with reference to FIG. 33, and then the interframe noise reduction unit 30 of the present embodiment will be described with reference to FIG.

  FIG. 33 is an example of a schematic block diagram of a conventional interframe noise reduction unit 330. The inter-frame noise reduction unit 330 includes a frame memory 331_1, a frame memory 331_2, and a noise reduction unit 332. Of the input image data supplied from the outside, the frame memory 331_2 stores image data of a frame immediately before the target frame, and the frame memory 331_2 stores image data of the target frame.

  The noise reduction unit 332 reads the image data of the target frame from the frame memory 331_1, and reads the image data of the frame immediately before the target frame from the frame memory 331_2. In parallel, the noise reduction unit 332 receives input image data supplied from the outside as image data of a frame immediately after the target frame. Further, the noise reduction unit 332 receives information indicating the amount of noise α supplied from the outside.

  The noise reduction unit 332 reduces inter-frame noise superimposed on pixel values in the target frame based on the three image data and the noise amount α. The noise reduction unit 332 outputs the image data after the interframe noise reduction to the outside as output image data.

  FIG. 4 is a functional block diagram of the inter-frame noise reduction unit 30 in the first embodiment. The interframe noise reduction unit 30 includes a frame memory 31, a noise reduction unit 32, and a magnitude relation storage unit 33.

The processing of the interframe noise reduction unit 30 will be described using a specific example. FIG. 5 is a diagram for explaining processing of the interframe noise reduction unit 30. In the figure, an image of a frame at time t3, an image of a frame at time t2, an image of a frame at time t1, and an image of a frame at time t0 are shown in order along the time axis.
In each frame, the luminance values (Y _t3 , Y _t2 , Y _t1 , Y _t0 , respectively) of pixels (p51, p52, p53, p54) having the same relative position in the image are shown.

  Further, the processing s55 of the noise reduction unit 32 when the pixel p52 in the frame at time t2 is the target pixel that is the target of noise reduction, and the pixel p53 in the frame at time t1 is the target pixel that is the target of noise reduction. The process s56 of the noise reduction part 32 in the case where it did is shown.

Here, the comparison processing between the luminance value _{Y t1} of the luminance values _{Y t2} and pixel p53 of pixel p52 in treatment s55, the comparison processing between the luminance value _{Y t2} and the luminance value _{Y t1} of the pixels p53 pixel p52 in treatment s56 Are shown to be common.
The inter-frame noise reduction unit 30 according to the present embodiment stores the comparison result by the common comparison process in the magnitude relation storage unit 33 as information indicating the magnitude relation. Thereby, the inter-frame noise reduction unit 30 can reduce the frame memory that stores the pixel value data of the frame immediately before the target frame.

  As a result, if the data of each pixel value stored in the reduced frame memory 331_2 is 8 bits and the information indicating the magnitude relationship stored in the magnitude relationship storage unit 33 is 2 bits, the magnitude relationship storage is performed. The capacity of the unit 33 may be a quarter of that of the frame memory 331_2. As a result, the total amount of memory included in the inter-frame noise reduction unit 30 can be reduced from two frame memories to 1.25, and the memory capacity can be reduced (about 35% in this example).

Assuming that the pixel p52 in the frame at time t2 is the target pixel that is subject to noise reduction, the noise reduction unit 32 determines the luminance value Y _t2 of the pixel p52 and the luminance value of the pixel corresponding to the position of the pixel p52 in the preceding and following frames ( Y _t3 , Y _t1 ). The noise reduction unit 32, if the maximum luminance value Y _t2 of the pixel p52 are subtracts the noise amount α from the luminance value Y _t2, if minimum, adds the noise amount α to the luminance value Y _t2.

The noise reduction unit 32 causes the magnitude relationship storage unit 33 to store information indicating the magnitude relationship between the luminance value Y _t2 of the pixel p52 and the luminance value Y _t1 of the pixel p53. When the pixel p53 in the frame at time t1 is the target pixel that is the target of noise reduction, the noise reduction unit 32 displays information indicating the magnitude relationship between the luminance value Y _t2 of the pixel p52 and the luminance value Y _t1 of the pixel p53. Read from the magnitude relationship storage unit 33. Thus, the noise reduction unit 32 does not need to calculate again the magnitude relationship between the luminance value Y _t2 of the pixel p52 and the luminance value Y _t1 of the pixel p53, and the luminance value Y _{t1 of the} pixel p53 that is the target pixel can be calculated. Only the luminance value Y _t0 of the pixel p54 in the next frame may be compared.

As a result, the noise reduction unit 32 does not need to refer to the luminance value Y _t2 of the pixel p52 of the previous frame, so that the frame memory in which the pixel value of the previous frame used in the past is stored is stored. Can be reduced.

Returning to FIG. 4, the frame memory 31 stores raster-scanned image data supplied from the noise amount detection unit 20 for one frame.
The magnitude relation storage unit 33 stores the magnitude relation between the pixel value of the pixel corresponding to the position of the pixel to be noise-reduced included in the target frame and the pixel value of the target pixel in the image one frame before. Information to be stored is stored.

  The noise reduction unit 32 receives the raster-scanned image data supplied from the noise amount detection unit 20 as information indicating the pixel value of the pixel after one frame corresponding to the position of the target pixel. In parallel with this, the noise reduction unit 32 reads information indicating the pixel value of the target pixel of the target frame from the frame memory 31. The noise reduction unit 32 also receives information indicating the magnitude relationship between the pixel value of the pixel at the position corresponding to the position of the target pixel and the pixel value of the target pixel in the image one frame before from the magnitude relationship storage unit 33 (for example, , Large, small, 2-bit data indicating the same).

  The noise reduction unit 32 determines the pixel value of the target pixel based on the pixel value of the target pixel of the target frame, the pixel value of the pixel after one frame corresponding to the position of the target pixel, and the information indicating the magnitude relationship. It is determined whether the pixel value is maximum or minimum among the pixel values of three pixels (target pixel, pixel after one frame corresponding to the position of the target pixel, and pixel before one frame corresponding to the position of the target pixel). At that time, the noise reduction unit 32 has a magnitude relationship between the pixel value of the target pixel of the target frame and the pixel value of the pixel at the position corresponding to the position of the target pixel in the image after one frame (for example, large, small, or the same). To extract.

  In the maximum case, the noise reduction unit 32 subtracts the noise amount α supplied from the noise amount detection unit 20 from the pixel value of the target pixel. On the other hand, in the minimum case, the noise reduction unit 32 adds the noise amount α supplied from the noise amount detection unit 20 from the pixel value of the target pixel.

  The noise reduction unit 32 supplies information indicating the pixel value after the processing to the horizontal noise reduction unit 40. The noise reduction unit 32 obtains information indicating the magnitude relationship between the pixel value of the pixel at the position corresponding to the position of the target pixel and the pixel value of the target pixel stored in the magnitude relation storage unit 33, as the target pixel of the target frame. And information indicating the magnitude relationship between the pixel value of the pixel at the position corresponding to the position of the target pixel in the image after one frame (for example, 2-bit data indicating large, small, or the same) is overwritten.

  In the present embodiment, as an example, the noise reduction unit 32 reads the image data after one frame from the frame memory 31. However, the present invention is not limited to this, and the image signal after the predetermined number of frames is read from the frame memory 31. You may do it. In the frame memory 31, image data after a predetermined number of frames from the target frame is stored by the noise amount detection unit 20.

  FIG. 6 is a functional block diagram of the horizontal noise reduction unit 40 in the first embodiment. The horizontal noise reduction unit 40 includes 2n dot memories 41_i (i is an integer from 0 to 2n) composed of dot memories 41_0,..., 41_n,. Is provided.

  The dot memory 41_0 stores information indicating the pixel value supplied from the inter-frame noise reduction unit 30 for one pixel. The dot memory 41_0 supplies information indicating the stored pixel value for one pixel to the next dot memory 41_1 and the noise reduction unit 42 every time a predetermined time elapses. In parallel with this, the dot memory 41_0 overwrites the information indicating the stored pixel value with the information indicating the next pixel value supplied from the inter-frame noise reduction unit 30.

  The dot memory 41_i (here, i is an integer from 1 to n-1) stores information indicating the pixel value supplied from the dot memory 41_i-1 for one pixel. The dot memory 41_i supplies information indicating the stored pixel value for one pixel to the next dot memory 41_i + 1 every time a predetermined time elapses. In parallel, the dot memory 41_i overwrites the information indicating the stored pixel value with the information indicating the next pixel value supplied from the dot memory 41_i-1.

  The dot memory 41_n stores one pixel of information indicating the pixel value supplied from the dot memory 41_n-1. The dot memory 41_n supplies information indicating the stored pixel value for one pixel to the next dot memory 41_n + 1 and the noise reduction unit 42 every time a predetermined time elapses. In parallel with this, the dot memory 41_n overwrites the information indicating the stored pixel value with the information indicating the next pixel value supplied from the dot memory 41_n-1.

  The dot memory 41 — i (here, i is an integer from n + 1 to 2n−1) stores information indicating the pixel value supplied from the dot memory 41 — i−1 for one pixel. The dot memory 41_i supplies information indicating the stored pixel value for one pixel to the next dot memory 41_i + 1 every time a predetermined time elapses. In parallel, the dot memory 41_i overwrites the information indicating the stored pixel value with the information indicating the next pixel value supplied from the dot memory 41_i-1.

  The dot memory 41_2n stores information indicating the pixel value supplied from the dot memory 41_2n-1 for one pixel. The dot memory 41_2n supplies information indicating the stored pixel value for one pixel to the noise reduction unit 42 every time a predetermined time elapses. In parallel with this, the dot memory 41_2n overwrites the information indicating the stored pixel value with the information indicating the next pixel value supplied from the dot memory 41_2n-1.

  The noise reduction unit 42 receives information indicating the pixel value for one pixel supplied from the dot memory 41_0. In parallel, the noise reduction unit 42 receives information indicating the pixel value for one pixel supplied from the dot memory 41_n and information indicating the pixel value for one pixel supplied from the dot memory 41_2n. In addition, the noise reduction unit 42 receives information indicating the noise amount α from the noise amount detection unit 20.

  Each time the noise reduction unit 42 receives the pixel values for the three pixels, the noise reduction unit 42 compares the received pixel values for the one pixel, and from the dot memory 41_n among the pixel values for the three pixels. If the supplied pixel value for one pixel is the maximum, the noise amount α supplied from the noise amount detection unit 20 is subtracted from the pixel value for one pixel supplied from the dot memory 41_n. Then, the noise reduction unit 42 outputs information indicating the pixel value after subtraction to the vertical noise reduction unit 50.

  On the other hand, if the pixel value for one pixel supplied from the dot memory 41_n is the minimum among the pixel values for the three pixels, the noise reduction unit 42 supplies the pixel for one pixel supplied from the dot memory 41_n. The noise amount α supplied from the noise amount detection unit 20 is added to the value. The noise reduction unit 42 outputs information indicating the pixel value after addition to the vertical noise reduction unit 50.

  Further, the noise reduction unit 42, if the pixel value for one pixel supplied from the dot memory 41_n among the three pixel values for the one pixel is a median value, the noise reduction unit 42 corresponds to one pixel supplied from the dot memory 41_n. Information indicating the pixel value is output to the vertical noise reduction unit 50.

  Here, when the pixel value for one pixel supplied from the dot memory 41_n is the pixel value of the target pixel that is the target of noise reduction, the pixel value for one pixel supplied from the inter-frame noise reduction unit 30 is This corresponds to the pixel value of a pixel n pixels away to the right in the horizontal direction in the image. The pixel value for one pixel supplied from the dot memory 41_2n corresponds to a pixel that is n pixels away to the left in the horizontal direction.

  Thereby, the noise reduction unit 42 is between the target pixel, the pixel that is n pixels away to the left from the target pixel in the image, and the pixel that is n pixels to the right from the target pixel in the image. Pixel values can be compared. And the noise reduction part 42 can reduce the noise superimposed on the horizontal direction within the flame | frame by subtracting or adding the noise amount (alpha) according to a comparison result.

  FIG. 7 is a functional block diagram of the vertical noise reduction unit 50 in the first embodiment. The vertical noise reduction unit 50 includes 2m line memories 51_j (j is an integer from 0 to 2m) including line memories 51_0,..., 51_m,. Is provided.

  The line memory 51_0 sequentially stores information indicating pixel values sequentially supplied from the horizontal noise reduction unit 40. When the line memory 51_0 stores information indicating the pixel value of the number of pixels corresponding to one line of the image, each time the information indicating the pixel value for one pixel supplied from the horizontal noise reduction unit 40 is supplied. In parallel, information indicating the pixel value of one pixel stored at the earliest time among the information indicating the stored pixel value is supplied to the line memory 51_1 and the noise reduction unit 52. Then, the line memory 51_0 overwrites the information indicating the pixel value stored at the earliest time among the information indicating the pixel value stored with the information indicating the pixel value supplied from the horizontal noise reduction unit 40.

  The line memory 51_j (where j is an integer from 1 to m−1) sequentially stores information indicating pixel values sequentially supplied from the line memory 51_j−1. When the line memory 51_j stores information indicating the pixel value of the number of pixels corresponding to one line of the image, each time the information indicating the pixel value for one pixel supplied from the line memory 51_j-1 is supplied. In parallel, information indicating the pixel value for one pixel stored at the earliest time among the information indicating the stored pixel value is supplied to the line memory 51_j + 1. Then, the line memory 51_j overwrites the information indicating the pixel value stored at the earliest time among the information indicating the pixel value stored with the information indicating the pixel value supplied from the line memory 51_j-1.

  The line memory 51_m sequentially stores information indicating pixel values sequentially supplied from the line memory 51_m-1. When the line memory 51_m stores information indicating the pixel value of the number of pixels corresponding to one line of the image, each time the information indicating the pixel value for one pixel supplied from the line memory 51_m-1 is supplied. In parallel, information indicating the pixel value for one pixel stored at the earliest time among the information indicating the stored pixel value is supplied to the line memory 51_m + 1 and the noise reduction unit 52. Then, the line memory 51_m overwrites the information indicating the pixel value stored at the earliest time among the information indicating the stored pixel value with the information indicating the pixel value supplied from the line memory 51_m-1.

  The line memory 51_j (where j is an integer from m + 1 to 2m−1) sequentially receives information indicating the pixel values sequentially supplied from the line memory 51_j−1, and receives the information indicating the received pixel values as 1 of the image. The pixel corresponding to the line is stored. When the line memory 51_j stores pixels corresponding to one line of the image, the line memory 51_j is stored in parallel with the information indicating the pixel value for one pixel supplied from the line memory 51_j-1. The information indicating the pixel value for one pixel stored at the earliest time among the information indicating the existing pixel value is supplied to the line memory 51_j + 1. Then, the line memory 51_j overwrites the information indicating the pixel value stored at the earliest time among the information indicating the pixel value stored with the information indicating the pixel value supplied from the line memory 51_j-1.

  The line memory 51_2m sequentially stores information indicating pixel values sequentially supplied from the line memory 51_2m-1. When the line memory 51_2m stores information indicating the pixel value of the number of pixels corresponding to one line of the image, each time the information indicating the pixel value for one pixel supplied from the line memory 51_2m-1 is supplied. In parallel, information indicating the pixel value for one pixel stored at the earliest time among the information indicating the stored pixel value is supplied to the noise reduction unit 52. The line memory 51_2m overwrites the information indicating the pixel value stored at the earliest time among the information indicating the stored pixel value with the information indicating the pixel value supplied from the line memory 51_2m-1.

  The noise reduction unit 52 receives information indicating the pixel value for one pixel supplied from the line memory 51_0. In parallel, the noise reduction unit 52 receives information indicating the pixel value for one pixel supplied from the line memory 51_m and information indicating the pixel value for one pixel supplied from the line memory 51_2m. Further, the noise reduction unit 52 receives information indicating the noise amount α from the noise amount detection unit 20.

  Each time the noise reduction unit 52 receives the pixel values for the three pixels, the noise reduction unit 52 compares the received pixel values for the one pixel, and from the line memory 51_m among the pixel values for the three pixels. If the supplied pixel value for one pixel is the maximum, the noise amount α supplied from the noise amount detection unit 20 is subtracted from the pixel value for one pixel supplied from the line memory 51_m. Then, the noise reduction unit 52 outputs information indicating the pixel value after the subtraction to the image format conversion unit 14.

  On the other hand, if the pixel value for one pixel supplied from the line memory 51_m is the minimum among the pixel values for the three pixels, the noise reduction unit 52 supplies the pixels for one pixel supplied from the line memory 51_m. The noise amount α supplied from the noise amount detection unit 20 is added to the value. The noise reduction unit 52 then outputs information indicating the pixel value after the addition to the image format conversion unit 14.

  Further, the noise reduction unit 52, if the pixel value for one pixel supplied from the line memory 51_m among the three pixel values for the one pixel is a median value, the noise reduction unit 52 corresponds to one pixel supplied from the line memory 51_m. Information indicating the pixel value is output to the image format converter 14.

  Here, when the pixel value for one pixel supplied from the line memory 51_m is used as the pixel value of the target pixel to be subjected to noise reduction, the pixel value for one pixel supplied from the horizontal noise reduction unit 40 is This corresponds to the pixel value of a pixel that is m pixels below the target pixel. Further, the pixel value for m pixels supplied from the line memory 51_2m corresponds to a pixel value of a pixel that is m pixels away from the target pixel in the image.

  Thereby, the noise reduction unit 52 compares the pixel values between the target pixel, a pixel that is m pixels above the target pixel in the image, and a pixel that is m pixels below the target pixel in the image. can do. And the noise reduction part 52 can reduce the noise superimposed on the perpendicular direction within the flame | frame by subtracting or adding the noise amount (alpha) according to a comparison result.

Next, the overall operation of the display device 1 will be described using the flowchart shown in FIG. FIG. 8 is a flowchart showing the flow of processing of the display device 1 in the first embodiment.
The detection unit 11 is supplied with a broadcast wave signal received from the antenna 10 and outputs the supplied signal to the Y / C separation unit 12. Then, the Y / C separation unit 12 demodulates the signal supplied from the detection unit 11, performs Y / C separation, performs A / D conversion, and performs image data (luminance data Y after the A / D conversion). , Color difference data Cb, color difference data Cr) is output to the image processing unit 20 (step S101).

  Next, the noise reduction processing unit 13 performs noise reduction processing on the image data supplied from the Y / C separation unit 12 (step S102). Next, the image format conversion unit 14 displays video generated for an I (Interlace) / P (Progressive) conversion (interlace video device) in a progressive format from the image signal subjected to the noise reduction processing. To a video suitable for Then, the image format converter 14 converts the I / P converted image signal into an RGB signal (red, green, and blue gradation data) (step S103).

Next, the liquid crystal driving unit 15 generates a clock signal for writing the supplied RGB signals to the liquid crystal elements PIX arranged in a matrix in the liquid crystal panel 16 (step S104).
Next, the liquid crystal driving unit 15 converts the gradation data in the RGB signal into a gradation voltage for performing liquid crystal driving (step S105).
The liquid crystal driver 15 holds the gradation voltage for each source line in the liquid crystal panel 16 by an internal hold circuit.

Next, in synchronization with the generated clock signal, the liquid crystal driver 15 supplies a predetermined voltage to one of the gate lines in the liquid crystal panel 16, and applies the predetermined voltage to the gate electrode of the TFT of the liquid crystal element (step) S106).
Next, in synchronization with the generated clock signal, the liquid crystal driving unit 15 supplies the gradation voltage held for each source line in the liquid crystal panel 16 (step S107).

  By the above-described processing, the gradation voltage is sequentially supplied to the source line within the time when each gate line is selected, and the gradation voltage (gradation degree data) necessary for display is turned on. Data is written to the pixel element connected to the drain of the TFT in the state. As a result, the pixel element changes the transmittance by controlling the orientation of the internal liquid crystal according to the applied gradation voltage. As a result, the video signal received by the detector 11 is displayed on the liquid crystal panel 16 (step S108). Above, the process of this flowchart is complete | finished.

  FIG. 9 is a flowchart showing details of the processing of the noise reduction processing unit 13 in step S102 of FIG. First, the noise amount detection unit 20 detects the noise amount from the image data input from the Y / C separation unit 12 (step S201). Next, the frame memory 31 of the inter-frame noise reduction unit 30 stores information indicating the pixel value of the target frame including the target pixel that is the target of noise reduction (step S202).

Next, the noise reduction unit 32 refers to information indicating the magnitude relationship between the pixel value of the target pixel stored in the magnitude relationship storage unit 33 and the pixel value of the pixel of the previous frame corresponding to the position of the target pixel. (Step S203).
Next, the noise reduction unit 32 compares the pixel value of the target pixel read from the frame memory 31 with the pixel value of the pixel at the position corresponding to the position of the target pixel in the next frame, and the comparison result and reference Noise is reduced based on the information indicating the magnitude relationship that has been made (step S204).

  Next, the noise reduction unit 32 stores information indicating the comparison result in the magnitude relation storage unit 33 (step S205). Next, the horizontal noise reduction unit 40 reduces the horizontal noise superimposed in the horizontal direction of the image on the image data after the inter-frame noise reduction (step S206). Next, the vertical noise reduction unit 50 reduces the vertical noise superimposed in the vertical direction of the image on the image data after the interframe noise reduction (step S207). Above, the process of this flowchart is complete | finished.

  As described above, in the noise reduction processing unit 13 of the present embodiment, the noise reduction unit 32 has the pixel value of the target pixel stored in the magnitude relation storage unit 33 and the pixel of the previous frame corresponding to the position of the target pixel. Information indicating the magnitude relationship of pixel values is referenced, and noise between frames is reduced based on the referenced magnitude information.

  As a result, the noise reduction processing unit 13 of the present embodiment can reduce the frame memory for storing the pixel value of the pixel of the immediately previous frame, which has been conventionally required, and the size relationship storage unit 33 is necessary. Since the memory capacity is smaller than that of the frame memory, the total capacity of the memory included in the noise reduction processing unit 13 can be reduced. As a result, the noise reduction processing unit 13 can reduce the production cost of the noise reduction processing unit 13.

  The noise reduction processing unit 13 compares the pixel values between the target pixel and the pixels of the frame around one frame. However, the present invention is not limited to this, and the noise reduction processing unit 13 does not limit the pixel value between the target pixel and the pixels around the predetermined number of frames. Pixel values may be compared.

<Second Embodiment>
FIG. 10 is a schematic block diagram of the display device 2 according to the second embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the display apparatus 1 in 1st Embodiment of FIG. 1, and the specific description is abbreviate | omitted. In the configuration of the display device 2 in FIG. 10, the noise reduction processing unit 13 is changed to a noise reduction processing unit 13 b with respect to the configuration of the display device 1 in FIG. 1.

Next, the noise reduction processing unit 13b will be described. FIG. 11 is a schematic block diagram of the noise reduction processing unit 13b in the second embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the noise reduction process part 20 in 1st Embodiment of FIG. 3, and the specific description is abbreviate | omitted.
The configuration of the noise reduction processing unit 13b in FIG. 11 is such that the vertical noise reduction unit 50 is changed to a vertical noise reduction unit 50b with respect to the configuration of the noise reduction processing unit 13 in FIG.

  FIG. 12 is a functional block diagram of the vertical noise reduction unit 50b in the second embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the vertical noise reduction part 50 in 1st Embodiment of FIG. 7, and the specific description is abbreviate | omitted. The configuration of the vertical noise reduction unit 50b in FIG. 12 is different from the configuration of the vertical noise reduction unit 50 in FIG. 7 in that m line memories up to the line memories 51_m + 1,..., 51_2m are deleted. 51b_m, the noise reduction unit 52 is changed to the noise reduction unit 52b, and the magnitude relationship storage unit 53 is added.

  That is, the vertical noise reduction unit 50b includes m line memories 51_i (i is an integer from 0 to m) up to line memories 51_0,..., 51_m−1 (m is a positive integer), line memories 51b_m, The noise reduction part 52b and the magnitude relationship memory | storage part 53 are provided.

The line memory 51b_m sequentially receives information indicating pixel values supplied from the line memory 51b_m-1, and stores the received information indicating the pixel values for the number of pixels corresponding to one line of the image. When the line memory 51b_m stores pixel values for pixels corresponding to one line of the image, the information indicating the pixel values for one pixel supplied from the line memory 51b_m-1 is supplied in parallel with the information. The information indicating the pixel value for one pixel stored at the earliest time among the information indicating the pixel value stored is used as the information indicating the pixel value of the target pixel that is the target of noise reduction. Supply.
Then, the line memory 51b_m overwrites the information indicating the pixel value stored at the earliest time among the information indicating the stored pixel value with the information indicating the pixel value supplied from the line memory 51b_m-1.

In the magnitude relation storage unit 53, information indicating the magnitude relation of the pixel value between a certain pixel and a pixel that is m pixels above the certain pixel is stored for m lines above the line including the target pixel. Yes.
The noise reduction unit 52b reads information indicating the magnitude relationship of pixel values between the target pixel and a pixel that is m pixels above the target pixel from the magnitude relation storage unit 53.

  At the same time, the noise reduction unit 52b uses the information indicating the pixel value for one pixel supplied from the line memory 51_0 as the information indicating the pixel value of the pixel that is m pixels below the target pixel, for each pixel. receive. In parallel with this, the noise reduction unit 52b receives information indicating the pixel value of the target pixel supplied from the line memory 51b_m. In addition, the noise reduction unit 52 b receives information indicating the noise amount α from the noise amount detection unit 20.

The noise reduction unit 52b compares the pixel value of the target pixel, the pixel value of the pixel that is m pixels below the target pixel, and the pixel value between the target pixel and the pixel that is m pixels above the target pixel. And noise is reduced based on the noise amount α.
Specifically, for example, every time the noise reduction unit 52b receives information indicating the pixel values for the three pixels, the pixel value of the target pixel and the pixel value of a pixel that is m pixels below the target pixel And the magnitude relationship of the pixel values between the target pixel and the pixel that is m pixels above the target pixel, the target pixel is the target pixel, the pixel that is m pixels below the target pixel, and the target pixel It is determined whether it is the maximum or the minimum among the pixels separated by m pixels. At that time, the noise reduction unit 52b extracts a magnitude relationship (large, small, or the same) of pixel values between the target pixel and a pixel that is m pixels below the target pixel.

If the pixel value of the target pixel is the maximum, the noise reduction unit 52b subtracts the noise amount α supplied from the noise amount detection unit 20 from the pixel value of the target pixel. The noise reduction unit 52 b outputs information indicating the pixel value after subtraction to the image format conversion unit 14.
On the other hand, if the pixel value of the target pixel is the minimum, the noise reduction unit 52b adds the noise amount α supplied from the noise amount detection unit 20 to the pixel value of the target pixel. The noise reduction unit 52b outputs information indicating the pixel value after the addition to the image format conversion unit 14.
Further, if the pixel value of the target pixel is the median value, the noise reduction unit 52b outputs information indicating the pixel value of the target pixel to the image format conversion unit 14.

  The noise reduction unit 52b obtains information indicating the magnitude relationship of pixel values between the target pixel stored in the magnitude relation storage unit 53 and a pixel that is m pixels above the target pixel, from the target pixel and the target pixel. The information is overwritten with information indicating the magnitude relationship of pixel values with pixels separated by m pixels below (for example, 2-bit data indicating large, small, or the same).

Here, details of the above-described processing of the noise reduction unit 52b will be described with reference to FIG. FIG. 13 is a diagram for explaining the processing of the noise reduction unit 52b in the second embodiment. In the figure, an image 130 of one frame is shown. In the image 130, a pixel p132, a pixel p131 that is m pixels above the pixel p132, a pixel p133 that is m pixels below the pixel p132, and a pixel p134 that is m pixels below the pixel p133 are shown. Yes. In addition, the luminance value of the pixel p131 is Y _j−m , the luminance value of the pixel p132 is Y _j , the luminance value of the pixel p133 is Y _{j + m} , and the luminance value of the pixel p134 is Y _{j + 2m} . .

If the pixel p132 is a target pixel for noise reduction, the noise reduction unit 52b performs a process s131 surrounded by a square. That is, the noise reduction unit 52b subtracts the noise amount α from the luminance value Y _j when (Y _j > Y _j−m ) and (Y _j > Y _{j + m} ). The noise reduction unit 52b adds the noise amount α to the luminance value Y _j when (Y _j <Y _j−m ) and (Y _j <Y _{j + m} ).

On the other hand, if the pixel p133 is a target pixel for noise reduction, the noise reduction unit 52b performs a process s133 enclosed by a square. That is, the noise reduction unit 52b subtracts the noise amount α from the luminance value Y _{j + m} when (Y _{j + m} > Y _j ) and (Y _{j + m} > Y _{j + 2m} ). The noise reduction unit 52b adds the noise amount α to the luminance value Y _{j + m} when (Y _{j + m} <Y _j ) and (Y _{j + m} <Y _{j + 2m} ).

Here, the comparison processing between the luminance value _{Y j + m} of the luminance values _{Y j} and the pixel p133 in the pixel p132 in treatment s132, the process of comparison between a luminance value _{Y j + m} of the luminance values _{Y j} and the pixel p133 in the pixel p132 in treatment s134 Indicates that the processing is common.
The noise reduction unit 52b of the present embodiment stores information indicating the magnitude relationship obtained by the common comparison process in the magnitude relationship storage unit 53. Thereby, the noise reduction part 52b can reduce the line memory which stores the information which shows the pixel value on m line rather than the line containing an object pixel.

As a result, the line memory for storing pixel values for m lines from the line memories 51_m + 1 to 51_2m shown in FIG. 7 is reduced, and a memory for storing the magnitude relation for m lines is added to the magnitude relation storage unit 53. The
For example, assuming that the data of each pixel value stored in the line memories 51_m + 1 to 51_2m is 8 bits and the information indicating the magnitude relationship stored in the magnitude relationship storage unit 53 is 2 bits, the magnitude relationship storage unit The capacity of 53 is a quarter of the total capacity of the line memories 51_m + 1 to 51_2m. As a result, the total amount of memory included in the vertical noise reduction unit 50b can be reduced from the line memory 2m to the line memory 1.25m, and the memory capacity (about 35% in this example) can be reduced.

The overall processing flow of the display device 2 in the second embodiment is the same as the overall processing flow of the display device 1 in the first embodiment shown in FIG.
FIG. 14 is a flowchart showing details of the processing of the noise reduction processing unit 13b in step S102 of FIG. 8 in the second embodiment. First, the noise amount detection unit 20 detects the noise amount α from the image data input from the Y / C separation unit 12 (step S301). Next, the interframe noise reduction unit 30 reduces interframe noise (step S302).

  Next, the horizontal noise reduction unit 40 reduces the horizontal noise superimposed in the horizontal direction of the image on the image data after the inter-frame noise reduction (step S303). Next, the vertical noise reduction unit 50b stores, in each of the line memories 51_1 to 51b_m, information indicating pixel values from the target line including the target pixel to the m−1th line down from the target line (step S304). .

  Next, the noise reduction unit 52b refers to the magnitude relationship storage unit 53, and refers to information indicating the magnitude relationship between the target pixel and a pixel that is m pixels above the target pixel (step S305). Next, the noise reduction unit 52b indicates information indicating the pixel value of the target pixel, information indicating the pixel value of a pixel that is m pixels below the target pixel, information indicating the magnitude relationship that has been referenced, and the amount of noise. Based on the information, the vertical noise superimposed in the vertical direction on the target pixel is reduced (step S306).

  The noise reduction unit 52b causes the magnitude relationship storage unit 53 to store information indicating the magnitude relationship between the target pixel and a pixel that is m pixels below the target pixel (step S307). Above, the process of this flowchart is complete | finished.

  As described above, the noise reduction processing unit 13b according to the present embodiment takes the two comparison pixels to be compared with the target pixel at positions symmetrical to the target pixel in the vertical direction, thereby storing the target stored in the magnitude relation storage unit 53. Information indicating the magnitude relationship between a pixel and a pixel that is a predetermined number of pixels above the target pixel is referred to. And the noise reduction process part 13b reduces the noise superimposed on the orthogonal | vertical direction in the object pixel based on the information which shows the magnitude relationship referred.

Thereby, the noise reduction processing unit 13b in the second embodiment has the following effects in addition to the memory capacity reduction effect by the inter-frame noise reduction unit 30 described in the first embodiment.
The noise reduction processing unit 13b can reduce the predetermined number of line memories that have been conventionally required, and the memory capacity required by the magnitude relation storage unit 53 is less than that of the line memory. The total capacity of the memory provided in the unit 13b can be reduced. As a result, the noise reduction processing unit 13b can reduce the production cost of the noise reduction processing unit 13b.

<Third Embodiment>
FIG. 15 is a schematic block diagram of the display device 3 according to the third embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the display apparatus 1 in 1st Embodiment of FIG. 1, and the specific description is abbreviate | omitted. In the configuration of the display device 3 in FIG. 15, the noise reduction processing unit 13 is changed to a noise reduction processing unit 13 c with respect to the configuration of the display device 1 in FIG. 1.

  Next, the noise reduction processing unit 13c will be described. FIG. 16 is a schematic block diagram of the noise reduction processing unit 13c in the third embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the noise reduction process part 20 in 1st Embodiment of FIG. 3, and the specific description is abbreviate | omitted. The configuration of the noise reduction processing unit 13c in FIG. 16 is such that the horizontal noise reduction unit 40 is changed to a horizontal noise reduction unit 40c with respect to the configuration of the noise reduction processing unit 13 in FIG.

  FIG. 17 is a functional block diagram of the horizontal noise reduction unit 40c in the third embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the horizontal noise reduction part 40 in 1st Embodiment of FIG. 6, and the specific description is abbreviate | omitted. The configuration of the horizontal noise reduction unit 40c in FIG. 17 is different from the configuration of the horizontal noise reduction unit 40 in FIG. 6 in that n dot memories up to dot memories 41_n + 1,..., 41_2n are deleted, and the dot memory 41_n is a dot memory. 41c_n, the noise reduction unit 42 is changed to the noise reduction unit 42c, and the magnitude relationship storage unit 43 is added.

The dot memory 41c_n stores information indicating the pixel value supplied from the dot memory 41_n-1 for one pixel. The dot memory 41c_n supplies the stored information indicating the pixel value for one pixel to the noise reduction unit 42c as information indicating the pixel value of the target pixel that is the target of noise reduction every time a predetermined time elapses.
In parallel, the dot memory 41c_n overwrites the information indicating the stored pixel value with the information indicating the next pixel value supplied from the dot memory 41_n-1.

The magnitude relationship storage unit 43 stores information indicating the magnitude relationship of pixel values between a certain pixel and a pixel that is n pixels away to the left from the certain pixel. Are stored for n-1 pixels.
The noise reduction unit 42c reads information indicating the magnitude relationship of pixel values between the target pixel and a pixel that is n pixels away from the target pixel to the right from the magnitude relationship storage unit 43.

  In parallel with this, the noise reduction unit 42c uses the information indicating the pixel value for one pixel supplied from the dot memory 41_0 as information indicating the pixel value of the pixel that is n pixels away from the target pixel to the right. Receive every minute. In parallel with this, the noise reduction unit 42c receives information indicating the pixel value of the target pixel supplied from the dot memory 41c_n. In addition, the noise reduction unit 42 c receives information indicating the noise amount α from the noise amount detection unit 20.

  The noise reduction unit 42c is a pixel between the pixel value of the target pixel, the pixel value of the pixel that is n pixels to the right from the target pixel, and the pixel that is n pixels to the left from the target pixel. Noise is reduced based on the magnitude relationship between the values and the noise amount α.

  Specifically, for example, each time the noise reduction unit 42c receives information indicating the pixel values of the three pixels, the noise reduction unit 42c and the pixel value of the target pixel and the pixel n pixels away from the target pixel to the right are displayed. Based on the pixel value and the magnitude relationship of the pixel value between the target pixel and the pixel that is n pixels left from the target pixel, the target pixel is n pixels left from the target pixel and the target pixel It is determined whether it is the maximum or the minimum among the pixels that are n pixels to the right from the pixel and the target pixel. At that time, the noise reduction unit 42c extracts a magnitude relationship (large, small, or the same) of pixel values between the target pixel and a pixel that is n pixels to the right from the target pixel.

If the pixel value of the target pixel is maximum, the noise reduction unit 42c subtracts the noise amount α supplied from the noise amount α detection unit 20 from the pixel value of the target pixel. The noise reduction unit 42 c outputs information indicating the pixel value after subtraction to the image format conversion unit 14.
On the other hand, if the pixel value of the target pixel is the minimum, the noise reduction unit 42c adds the noise amount α supplied from the noise amount α detection unit 20 to the pixel value of the target pixel. The noise reduction unit 42 c outputs information indicating the pixel value after the addition to the image format conversion unit 14.
In addition, if the pixel value of the target pixel is a median value, the noise reduction unit 42c outputs information indicating the pixel value of the target pixel to the image format conversion unit 14.

  The noise reduction unit 42c obtains information indicating the magnitude relationship of pixel values between the target pixel stored in the magnitude relationship storage unit 53 and a pixel that is n pixels away from the target pixel to the left. Overwriting is performed with information indicating the magnitude relationship of pixel values with pixels that are n pixels away from the pixel to the right (for example, 2-bit data indicating large, small, or the same).

Here, details of the above-described processing of the noise reduction unit 42c will be described with reference to FIG. FIG. 18 is a diagram for explaining the processing of the noise reduction unit 42c in the third embodiment. In the figure, an image 180 of one frame is shown. In the image 180, a pixel p182, a pixel p181 that is n pixels to the left from the pixel p182, a pixel p183 that is n pixels to the right from the pixel p182, and a pixel that is n pixels to the right from the pixel p183 p184 is shown. In addition, the luminance value of the pixel p181 is Y _i−n , the luminance value of the pixel p182 is Y _i , the luminance value of the pixel p183 is Y _{i + n} , and the luminance value of the pixel p184 is Y _{i + 2n} . .

If the pixel p182 is a target pixel for noise reduction, the noise reduction unit 42c performs a process s181 surrounded by a square. That is, the noise reduction unit 42c subtracts the noise amount α from the luminance value Y _i when (Y _i > Y _i−n ) and (Y _i > Y _{i + n} ). The noise reduction unit 42c adds the noise amount α to the luminance value Y _i when (Y _i <Y _i−n ) and (Y _i <Y _{i + n} ).

On the other hand, when the pixel p183 is a target pixel whose noise is to be reduced, the noise reduction unit 42c performs a process s183 surrounded by a square. That is, the noise reduction unit 42c subtracts the noise amount α from the luminance value Y _{i + n} when (Y _{i + n} > Y _i ) and (Y _{i + n} > Y _{i + 2n} ). The noise reduction unit 42c adds the noise amount α to the luminance value Y _{i + n} when (Y _{i + n} <Y _i ) and (Y _{i + n} <Y _{i + 2n} ).

Here, the comparison processing between the luminance value _{Y i + n} of luminance values _{Y i} and the pixel p183 in the pixel p182 in treatment s 182, and comparison process between the luminance value _{Y i + n} of luminance values _{Y i} and the pixel p183 in the pixel p182 in treatment s184 Indicates that the processing is common.
The noise reduction part 42c of this embodiment memorize | stores the comparison result by this common comparison process in the magnitude correlation memory | storage part 43 as information which shows magnitude correlation. Thereby, the noise reduction part 52b can reduce the dot memory which stores the information which shows n pixel values on the left toward a target pixel.

As a result, the dot memory for storing pixel values for n pixels from the dot memory 41_n + 1 to 41_2n shown in FIG. 6 is reduced, and a memory for storing the size relationship for n pixels is added to the size relationship storage unit 43. Will be.
For example, assuming that the data of each pixel value stored in the dot memories 41_n + 1 to 41_2n is 8 bits and the information indicating the magnitude relationship stored in the magnitude relationship storage unit 43 is 2 bits, the magnitude relationship storage unit The capacity of 43 is a quarter of the total capacity of the dot memories 41_n + 1 to 41_2n. As a result, the total amount of memory included in the horizontal noise reduction unit 40c can be reduced from the dot memory 2n to the dot memory 1.25n, and the memory capacity (about 35% in this example) can be reduced.

The overall processing flow of the display device 3 according to the third embodiment is the same as the overall processing flow of the display device 1 according to the first embodiment shown in FIG.
FIG. 19 is a flowchart showing details of the processing of the noise reduction processing unit 13c in step S102 of FIG. 8 in the third embodiment. First, the noise amount detection unit 20 detects the noise amount α from the image data input from the Y / C separation unit 12 (step S401). Next, the interframe noise reduction unit 30 reduces interframe noise (step S302).

  Next, the horizontal noise reduction unit 40c stores information indicating pixel values from the target pixel to a pixel that is n-1 pixels to the right from the target pixel in each of the dot memories 41_n to 41_1 (Step S403). . Next, the magnitude relation storage unit 42 is referred to, and information indicating the magnitude relation between the target pixel and a pixel that is n pixels away from the target pixel to the left is referred to (step S404).

  Next, the horizontal noise reduction unit 40c includes information indicating the pixel value of the target pixel, information indicating the pixel value of the pixel that is n pixels to the right from the target pixel, information indicating the magnitude relationship that has been referred to, and noise Based on the information indicating the amount, the horizontal noise superimposed on the target pixel in the horizontal direction is reduced (step S405).

Next, the horizontal noise reduction unit 40c causes the magnitude relation storage unit 43 to store information indicating the magnitude relation between the target pixel and the pixel that is n pixels away from the target pixel to the right (step S406).
Next, the vertical noise reduction unit 50 reduces the vertical noise superimposed in the vertical direction on the target pixel (step S407). Above, the process of this flowchart is complete | finished.

  As described above, the noise reduction processing unit 13c according to the present exemplary embodiment stores the two comparison pixels to be compared with the target pixel at positions symmetrical with respect to the target pixel in the horizontal direction, thereby storing the target stored in the magnitude relation storage unit 43. The horizontal noise superimposed in the horizontal direction on the target pixel is referred to based on the information indicating the magnitude relationship between the pixel and the pixel that is a predetermined number of pixels left from the target pixel. To reduce.

Accordingly, the noise reduction processing unit 13c in the third embodiment has the following effects in addition to the memory capacity reduction effect by the interframe noise reduction unit 30 described in the first embodiment.
The noise reduction processing unit 13c can reduce a predetermined number of dot memories that are conventionally required, and the memory capacity required by the magnitude relation storage unit 43 is larger than the predetermined number of dot memories. Therefore, the total capacity of the memory included in the noise reduction processing unit 13c can be reduced. As a result, the noise reduction processing unit 13c can reduce the production cost of the noise reduction processing unit 13c.

  The noise reduction processing unit 13b of the second embodiment takes two comparison pixels to be compared with the target pixel at positions symmetrical to the target pixel in the vertical direction, and the noise reduction processing unit 13c of the third embodiment Although the two comparison pixels to be compared with the target pixel are positioned symmetrically with respect to the target pixel in the horizontal direction, the present invention is not limited to this.

The noise reduction processing unit (13b, 13c) only needs to place two comparison pixels to be compared with the target pixel in a point-symmetrical position with respect to the target pixel. For example, the two comparison pixels to be compared with the target pixel are used as the target pixel. On the other hand, the position may be symmetrical to the diagonal direction. Thereby, the noise reduction process part (13b, 13c) can reduce the noise superimposed on the diagonal direction in the object pixel.
Moreover, although described separately as 1st Embodiment, 2nd Embodiment, and 3rd Embodiment, it is not restricted to this, A noise reduction process part (13, 13b, 13c) reduces noise between frames. The noise may be reduced by using at least one of the unit (30), the horizontal noise reduction unit (40c), and the vertical noise reduction unit (50b).

<Fourth Embodiment>
The display devices (1, 2, 3) in the first to third embodiments detect the amount of noise from the vertical blanking period. The display device 4 according to the fourth embodiment estimates the amount of noise using an image of a detection target frame that is a target of noise amount detection and an image of a frame that is a predetermined number before the detection target frame. As a result, the display device 4 does not require a frame memory in which the pixel values of the image of a predetermined number of frames are stored when estimating the amount of noise. Signal), the amount of noise can be estimated while suppressing the capacity of the frame memory.

  FIG. 20 is a schematic block diagram of the display device 4 in the fourth embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the display apparatus 1 in 1st Embodiment of FIG. 1, and the specific description is abbreviate | omitted. The configuration of the display device 4 in FIG. 20 is such that the noise reduction processing unit 13 is changed to a noise reduction processing unit 13d with respect to the configuration of the display device 1 in FIG.

Next, the noise reduction processing unit 13d will be described. FIG. 21 is a schematic block diagram of the noise reduction processing unit 13d according to the fourth embodiment. In addition, the same code | symbol is attached | subjected to the element which is common in the noise reduction process part 20 in 1st Embodiment of FIG. 3, and the specific description is abbreviate | omitted.
The configuration of the noise reduction processing unit 13d in FIG. 21 is such that the noise amount detection unit 20 is changed to a noise amount detection unit 20d with respect to the configuration of the noise reduction processing unit 13 in FIG.

FIG. 22 is a functional block diagram of the noise amount detection unit 20d according to the fourth embodiment. The noise amount detection unit 20 d includes a frame memory 21, a calculation unit 22, and a noise amount estimation unit 23.
The frame memory 21 sequentially stores information indicating pixel values for one pixel subjected to raster scanning sequentially supplied from the Y / C separation unit 12. When the frame memory 21 stores the information indicating the pixel value for one frame, each time the information indicating the pixel value for one pixel is supplied from the Y / C separation unit 12, the pixel value stored at the earliest time is stored. Information to be shown is supplied to the calculation unit 22.

  First, an outline of the processing of the calculation unit 22 will be described. The calculation unit 22 sequentially receives information indicating pixel values for one pixel subjected to raster scanning supplied from the Y / C separation unit 12.

  Specifically, for example, the calculation unit 22 calculates the pixel value of the detection pixel, the pixel value of the pixel corresponding to the position of the detection pixel in the image one frame before the image including the detection pixel, In order to estimate the amount of noise based on the pixel value of a pixel that is one pixel above the detection pixel and the pixel value of a pixel that is one pixel below the detection pixel in an image that includes the detection pixel Is calculated for each pixel in the image including the detected pixel. The calculating unit 22 outputs information indicating the value Nd for estimating the calculated noise amount to the noise amount estimating unit 23.

  In the present embodiment, the calculation unit 22 uses a pixel one pixel above and a pixel one pixel below the detection pixel, but only the first interval from the detection pixel (the first interval is an integer equal to or greater than 1). A pixel separated from the detection pixel by a second interval (the second interval is an integer of 1 or more) may be used. In this case, the first interval and the second interval may be the same or different.

In the present embodiment, the calculation unit 22 uses a pixel one frame before the frame including the detection pixel. However, the calculation unit 22 is not limited thereto, and uses pixels in a frame that is a predetermined number of frames before the frame including the detection pixel. Also good.
In this embodiment, the calculation unit 22 uses a pixel one frame before the frame including the detection pixel. However, the calculation unit 22 is not limited to this, and a predetermined number of frames (one or more frames) after the frame including the detection pixel. You may use the pixel of this frame.

  To summarize the above processing, the calculation unit 22 calculates the pixel value of the detection pixel that is a target for detecting the amount of noise included in the image, and the image in the image that is a predetermined number of frames before the image including the detection pixel. A pixel value of a previous frame pixel that is a pixel corresponding to a position of the detection pixel, a pixel value of a pixel that is separated from the detection pixel by a first interval in an image including the detection pixel, and Based on the pixel values of pixels separated by an interval of 2, a value Nd for estimating the amount of noise is calculated for a predetermined pixel.

  Subsequently, details of the processing will be described in the calculation unit 22. FIG. 23 is a diagram for explaining the processing of the calculation unit 22 in the fourth embodiment. In the drawing, an image 232 of a frame at time t2, an image 231 of a frame at time t1, and an image 230 of a frame at time t0 are shown in order along the time axis.

  If the image 231 of the frame at time t1 is a detection target frame that is a target for detecting noise, the detection pixel p231 that is a target for detecting the amount of noise in the image 231 of the frame at time t1 and the frame of the frame at time t0. In the image 230, a pixel p232 at a position corresponding to the position of the detection pixel p231, a pixel p233 one higher than the detection pixel p231, and a pixel p234 one lower than the detection pixel p231 are shown.

  Since the noise amount detection unit 20d in this embodiment uses only one of the frame memories 21 and does not use the luminance value of the image 232 of the frame at time t2, the image 232 of the frame at time t2 It is shown.

The noise amount detection unit 20d cannot refer to information indicating the pixel value of the pixel at the position corresponding to the position of the detection pixel p231 in the frame at time t2. Instead, the noise amount detection unit 20d uses the pixel values of the pixels around the detection pixel p231 in the frame at time t1, and uses the pixel value Y of the pixel at the position corresponding to the position of the detection pixel p231 in the frame at time t2. Approximate _{t2_v0} .

In the present embodiment, it is assumed that the display frequency of the vertical pixels is closer to the frame frequency than the display frequency of the horizontal pixels. Since the display frequency of the vertical pixel is closer to the frame frequency than the display frequency of the horizontal pixel, noise characteristics are close. Therefore, the calculation unit 22 uses pixels (p233 and p234) that are adjacent to the detection pixel p231 in the vertical direction. Thus, the pixel value Y _{t2_v0} of the pixel at the position corresponding to the position of the detection pixel p231 in the frame at time t2 is approximated.

Specifically, for example, the calculation unit 22 calculates the average value (Y _{t1_v−1} + Y _{t1_v + 1} ) / 2 of the pixel p233 and the pixel p234 adjacent to the detection pixel p231 in the vertical direction in the frame at time t2. The pixel value _{Yt2_v0} of the pixel at a position corresponding to the position of the detection pixel p231 is approximated. That is, the calculation unit 22 calculates a value Nd for estimating the amount of noise for each pixel in the detection target frame according to the following equation (1).

Nd = Abs ( _{Yt1_v0} − (( _{Yt1_v−1} + _{Yt1_v + 1} ) / 2 + _{Yt0_v0} ) / 2) (1)

  Here, Abs is a function that returns the absolute value of the argument. The calculation unit 22 outputs information indicating a value Nd for estimating each noise amount calculated in each pixel to the noise amount estimation unit 23.

  In addition, although the noise amount detection unit 20d in the present embodiment calculates the value Nd for estimating the noise amount using pixels adjacent to the detection pixel p231 in the vertical direction, the present invention is not limited thereto, and the detection pixel p231 and A value Nd for estimating the amount of noise may be calculated using pixels adjacent in the horizontal direction.

  Returning to FIG. 22, the outline of the processing of the noise amount estimation unit 23 will be described. The noise amount estimation unit 23 estimates the noise amount included in the image based on the frequency of the value Nd for estimating the noise amount supplied from the calculation unit 22. More specifically, the noise amount estimation unit 23 estimates the mode value of the frequency of the value Nd for estimating the noise amount calculated by the calculation unit 22 as the noise amount included in the image.

  Specifically, for example, the noise amount estimation unit 23 counts the appearance frequency for each value Nd for estimating the noise amount supplied from the calculation unit 22, and estimates the noise amount when the appearance frequency becomes maximum. The mode value which is the value Nd for the purpose is extracted. The noise amount estimation unit 23 outputs the information indicating the extracted mode value to the inter-frame noise reduction unit 30, the horizontal noise reduction unit 40, and the vertical noise reduction unit 50 as information indicating the noise amount.

  FIG. 24 is an example of a histogram of the value Nd for estimating the noise amount. The vertical axis represents frequency, and the horizontal axis represents a value Nd for estimating the amount of noise. In the figure, the appearance frequency of the value Nd for estimating the amount of noise in a detection target image of one frame is shown for each value Nd for estimating the amount of noise. Here, it is shown that the mode value is 10. The noise amount estimation unit 23 estimates the mode value as the noise amount α.

  Next, the principle of the noise amount detection unit 20d according to the present embodiment will be described with reference to FIGS. FIG. 25 shows a luminance distribution when Gaussian noise with a standard deviation of 10 is added to an image having a luminance value 128 of all pixels. In the figure, the luminance distribution w251 shows a Gaussian distribution with a peak having a luminance value of 128 and a standard deviation of 10. Since typical noise superimposed on video is Gaussian noise, the principle of the noise amount detection unit 20d will be described using a luminance distribution w251 to which Gaussian noise is added.

  FIG. 26 is a diagram illustrating an outline of noise reduction processing in the inter-frame noise reduction unit 30, the horizontal noise reduction unit 40, and the vertical noise reduction unit 50 according to the fourth embodiment. In the figure, a curve w261 indicating the original pixel value and a curve w262 indicating the pixel value on which noise is superimposed are shown. The input video is information indicating pixel values input to each part (30, 40, 50) indicated by round, square, or triangular dots, and the output video is round, square, or triangular dots. This is information indicating the pixel value output from each unit (30, 40, 50) indicated by.

  In the input video, each unit (30, 40, 50) is configured to generate noise from the pixel value at the intermediate time when the pixel value at the intermediate time is the maximum among the three pixel values acquired at predetermined time intervals. Subtract the amount α. On the other hand, each unit (30, 40, 50) adds the noise amount α to the pixel value at the intermediate time when the pixel value at the intermediate time is the minimum among the three pixel values. Further, each unit (30, 40, 50) does not perform addition / subtraction with respect to a pixel value having an intermediate time when the pixel value having an intermediate time among the three pixel values is a median value,

FIG. 27 is a diagram for explaining processing performed on image data indicating the luminance distribution w251 in FIG. In the figure, a luminance value region R271 smaller than the luminance value 128 and a luminance value region R272 larger than the luminance value 128 are shown with the luminance value 128 as a boundary.
Each part (30, 40, 50) tends to add the noise amount α to the pixel value belonging to the region R271 and subtract the noise amount α from the pixel value belonging to the region R272 in the image data indicating the luminance distribution w251 in FIG. It is in.

  FIG. 28 shows a frequency distribution of luminance values after performing noise reduction processing with each noise amount. In FIG. 25, with respect to the luminance distribution w251 of FIG. 25, the luminance distribution w281 when the noise amount α is 5 and noise is reduced, the luminance distribution w282 when the noise amount α is 10 and noise is reduced, and the noise amount A luminance distribution w283 when α is 20 and noise is reduced is shown.

  When the noise amount α is 20 and the noise is reduced, the luminance distribution w283 has a higher frequency at a luminance value that is 11 luminance values or more away from the luminance value 128 than the luminance distribution w251 before noise reduction. The distribution w283 indicates that the noise is higher than the luminance distribution w251 before noise reduction.

  FIG. 29 is a diagram showing the relationship between the noise amount α and the variance value of the pixel value. The vertical axis is the variance value of the pixel value, and the horizontal axis is the noise amount α. In the figure, when the noise amount α is 8, the variance value of the pixel value takes the minimum value, and when the standard deviation of the Gaussian noise is 10, the variance value of the pixel value takes a value close to the minimum value. Has been.

  Here, when the variance of the pixel values is the smallest, the noise variation is most suppressed, and therefore it is considered that the noise is reduced. Therefore, when the noise amount α when each part (30, 40, 50) performs noise reduction processing on an image given Gaussian noise with a standard deviation of 10 is a value smaller than the standard deviation of the noise by a predetermined number. In addition, it can be seen that the noise reduction effect is most obtained.

FIG. 30 is a diagram showing an example of a histogram showing the frequency for each value Nd ′ for estimating the noise amount.
On the upper side of the figure, an image 302 of a frame at time t2, an image 301 of a frame at time t1, and an image 300 of a frame at time t0 are shown in order along the time axis.
Assuming that the pixel p301 in the image 301 of the frame at time t1 is a detection pixel that is a target for detecting the amount of noise, the pixel p302 at the position corresponding to the position of the detection pixel p301 in the image 302 of the frame at time t2, and the time t0 A pixel p301 at a position corresponding to the position of the detection pixel p301 in the image 300 of this frame is shown.

Further, the pixel value of the pixel p302 in _{Y t2,} the pixel value of the pixel p301 in _{Y t1,} the pixel value of the pixel p300 is _{Y t0.} Each image is given Gaussian noise with a standard deviation of 10.
A value Nd ′ for estimating the amount of noise is calculated for all the pixels in the image 301 of the frame at time t1 by the following equation (2).

Nd ′ = Abs (Y _t1 − (Y _t0 + Y _t2 ) / 2) (2)

A histogram showing the frequency for each value Nd ′ for estimating the amount of noise is shown on the lower side of FIG. The mode value in the figure matches the standard deviation 10 of Gaussian noise.
In addition to this example, when the mode value of the value Nd ′ for estimating the amount of noise is calculated for an image given Gaussian noise of various standard deviations, the mode value almost coincides with the standard deviation every time. It is a value obtained by subtracting 1 or 2 from the value or standard deviation.

  Therefore, the noise amount detection unit 20d may perform the following processing. The noise amount detection unit 20d calculates the mode value of the value Nd ′ for estimating the noise amount in order to estimate the standard deviation of the noise distribution in the image. Then, the noise amount detection unit 20d may supply the calculated mode value to each unit (30, 40, 50) as information indicating the noise amount α.

  FIG. 31 is a diagram illustrating an example of a histogram for comparing the frequency for each value Nd ′ for estimating the noise amount and the frequency for each value Nd for estimating the noise amount. In the figure, a frequency H_Nd ′ for each value Nd ′ for estimating the noise amount and a frequency H_Nd for each value Nd for estimating the noise amount are shown. In the figure, the mode value 10 of the frequency H_Nd ′ is the same as the mode value 10 of the frequency H_Nd.

Therefore, the noise amount estimation unit 23 estimates the standard deviation of the Gaussian noise superimposed on the image with the mode value of the frequency Nd for estimating the noise amount, and this mode value is set as the noise amount α. To do.
As a result, the noise amount estimation unit 23 can calculate the noise amount with high accuracy while reducing the frame memory.

  Then, the noise amount estimation unit 23 supplies each mode (30, 40, 50) with the mode value of the frequency of the value Nd for estimating the noise amount as the noise amount α. Thereby, each part (30, 40, 50) of the noise reduction process part 13d can reduce the noise superimposed on the image.

When the noise amount detection unit 20d calculates the noise amount α according to Expression (2), information indicating the pixel value of the detection frame including the detection pixel and information indicating the pixel value of the frame before the detection frame are stored. Therefore, two frame memories are required.
Therefore, the noise amount detection unit 20d of the present embodiment approximates information indicating the pixel value of the frame before the detection frame using the pixel values of the pixels around the detection pixel. Thereby, the frame memory which memorize | stores the information which shows the pixel value of the flame | frame before a detection frame can be reduced.

The overall processing flow of the display device 4 in the fourth embodiment is the same as the overall processing flow of the display device 1 in the first embodiment shown in FIG.
FIG. 32 is a flowchart showing details of the processing of the noise reduction processing unit 13d in step S102 of FIG. 8 in the fourth embodiment. First, the frame memory 21 stores information indicating the pixel value of the detection frame for detecting the noise amount α (step S501). Next, the calculation unit 22 calculates a value Nd for estimating the noise amount for each pixel of the detection frame for detecting the noise amount (step S502). Next, the noise amount estimation unit 23 estimates the mode value of the value Nd for estimating the noise amount as the noise amount α (step S503).

Next, the inter-frame noise reduction unit 30 uses the estimated noise amount α to reduce inter-frame noise superimposed between frames in the target pixel (step S504).
Next, the horizontal noise reduction unit 40 uses the estimated noise amount α to reduce horizontal noise superimposed on the target pixel in the horizontal direction (step S505).

  Next, the vertical noise reduction unit 50 uses the estimated noise amount α to reduce vertical noise superimposed on the target pixel in the vertical direction (step S506). Above, the process of this flowchart is complete | finished.

As described above, the noise amount detection unit 20d of the present embodiment estimates the standard deviation of the Gaussian noise superimposed on the image as the noise amount α by using one frame memory 21. Accordingly, the noise reduction processing unit 13d in the fourth embodiment has the following effects in addition to the memory capacity reduction effect by the interframe noise reduction unit 30 described in the first embodiment.
The noise reduction processing unit 13d can accurately estimate the amount of noise superimposed on an image even for a video without a vertical blanking period. As a result, the noise reduction processing unit 13d can reduce noise superimposed on an image even in a video without a vertical blanking period.

  Note that the display device 4 according to the fourth embodiment estimates the amount of noise using a predetermined number of frames before the detection target frame, but uses a predetermined number of frames after the noise to detect noise. The amount may be estimated. Further, the noise amount detection unit 20d estimates the mode value of the value Nd for estimating the noise amount as the noise amount α. However, the present invention is not limited to this, and a value separated from the mode value by a predetermined number before and after the mode value. The noise amount α may be estimated.

The noise reduction processing unit 13d includes an inter-frame noise reduction unit 30 according to the first embodiment, a vertical noise reduction unit 50b according to the second embodiment, a horizontal noise reduction unit 40c according to the third embodiment, It is only necessary to include at least one of the noise amount detection units 20d of the fourth embodiment.
Thereby, since the noise reduction part process part 13d can make small the size of the memory with which the noise reduction process part 13d is equipped, the circuit scale of the noise reduction part 13d can be made small. As a result, the production cost of the noise reduction processing unit 13d can be reduced.

  Moreover, although it demonstrated that the noise reduction process part (13, 13b, 13c, 13d) was implement | achieved as a part of display apparatus (1, 2, 3, 4) common to all embodiment, it is not restricted to this. Instead, the noise reduction processing units (13, 13b, 13c, 13d) may be realized as one independent noise reduction device.

  Further, a program for executing each process of the noise reduction processing unit (13, 13b, 13c, 13d) of the present embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is recorded on the computer. The above-described various processes related to the noise reduction processing unit (13, 13b, 13c, 13d) may be performed by causing the system to read and execute the system.

  Here, the “computer system” may include an OS and hardware such as peripheral devices. Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used. The “computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.

  Further, the “computer-readable recording medium” refers to a volatile memory (for example, DRAM (Dynamic) in a computer system serving as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Random Access Memory)) that holds a program for a certain period of time is also included. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design etc. of the range which does not deviate from the summary of this invention are included.

1, 2, 3, 4 Display device 10 Antenna 11 Detection unit 12 Y / C separation unit 13, 13b, 13c, 13d Noise reduction processing unit 14 Image format conversion unit 15 Liquid crystal drive unit 16 Liquid crystal panel 20, 20d Noise amount detection unit 21, 31, 331_1, 331_2 Frame memory 22 Calculation unit 23 Noise amount estimation unit 30 Inter-frame noise reduction unit 32, 42, 42c, 52, 52b, 332 Noise reduction unit 33, 43, 53 Size relationship storage unit 40, 40c Horizontal Noise reduction unit 41_1 to 41_2n Dot memory 50, 50b Vertical noise reduction unit 51_1 to 51_2m Line memory

Claims (13)

A magnitude relationship storage unit in which information indicating a magnitude relationship between a target pixel to be noise-reduced and a comparison pixel separated by a predetermined interval is stored;
A noise reduction unit that reads information indicating the magnitude relationship from the magnitude relationship storage unit, and reduces noise of the target pixel based on the read information indicating the magnitude relationship;
A noise reduction device comprising: A pixel value storage unit for storing information indicating a pixel value of a second comparison pixel separated from the target pixel by a predetermined interval;
The noise reduction unit reads information indicating the pixel value of the second comparison pixel from the pixel value storage unit, and the pixel value of the read second comparison pixel, the pixel value of the target pixel, and the magnitude relationship The noise reduction apparatus according to claim 1, wherein the noise of the target pixel is reduced based on the above.   The noise reduction unit calculates a magnitude relationship between a pixel value of the second comparison pixel and a pixel value of the target pixel, and stores information indicating the calculated magnitude relationship in the magnitude relationship storage unit. The noise reduction device according to claim 1 or 2. A pixel value of a detection pixel that is a target for detecting the amount of noise included in the image, and a pixel at a position corresponding to the position of the detection pixel in the image preceding the image including the detection pixel by a predetermined number of frames The pixel value of the previous frame pixel, the pixel value of the pixel that is separated from the detection pixel by the first interval in the image including the detection pixel, and the pixel value of the pixel that is separated from the detection pixel by the second interval A calculation unit for calculating a value based on a predetermined pixel;
Based on the frequency of the calculated value, a noise amount estimation unit that estimates the amount of noise on the image;
The noise reduction device according to any one of claims 1 to 3, further comprising:   The noise reduction device according to claim 4, wherein the noise amount estimation unit estimates a mode value of the frequency as a noise amount included in the image.   6. The noise reduction device according to claim 4, wherein the detection pixel is located between a pixel separated by the first interval and a pixel separated by the second interval. 7.   The said 1st space | interval and the said 2nd space | interval are the space | interval respectively predetermined in the orthogonal | vertical direction within the image in which the said detection pixel is contained, The any one of Claim 4-6 characterized by the above-mentioned. The noise reduction device described in 1. The interval between the target pixel and the comparison pixel and the interval between the target pixel and the second comparison pixel are frame intervals,
The noise reduction device according to any one of claims 1 to 7, wherein the noise reduction unit reduces noise between frames of the target pixel. The interval between the target pixel and the comparison pixel and the interval between the target pixel and the second comparison pixel are horizontal intervals in an image including the target pixel,
The noise reduction device according to any one of claims 1 to 8, wherein the noise reduction unit reduces noise in a horizontal direction in an image of the target pixel. The interval between the target pixel and the comparison pixel and the interval between the target pixel and the second comparison pixel are vertical intervals in an image including the target pixel,
10. The noise reduction device according to claim 1, wherein the noise reduction unit reduces noise in a vertical direction in an image of the target pixel. 11.   A display apparatus provided with the noise reduction apparatus of any one of Claims 1-7. A noise reduction method executed by a noise reduction apparatus including a magnitude relation storage unit that stores information indicating magnitude relation between a target pixel that is subject to noise reduction and a comparison pixel that is separated by a predetermined interval,
A noise reduction method including a noise reduction procedure of reading information indicating the magnitude relationship from the magnitude relationship storage unit and reducing noise of the target pixel based on the read information indicating the magnitude relationship. A computer including a magnitude relationship storage unit in which information indicating the magnitude relationship between a target pixel that is a target for noise reduction and a comparison pixel that is separated by a predetermined interval is stored.
A noise reduction program for reading information indicating the magnitude relationship from the magnitude relationship storage unit and executing a noise reduction step of reducing noise of the target pixel based on the read information indicating the magnitude relationship.

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