JP2009157656A - Image processor, image processing method, program and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor, capable of converting an input image signal to an image signal having a gradation number larger than that of the input signal by determining a gradation area based on an input image signal and selectively smoothing the image signal, an image processing method, a program, and a display device. <P>SOLUTION: The image processor comprises a smoothing area detection part which generates, based on an input image signal of N bits (N is a positive integer), a control signal for regulating a gradation area for each pixel; a tap length adjustment part which specifies a smoothing area to be smoothed based on the control signal, and generates, for each pixel, an adjustment signal for adjusting the tap length of a smoothing filter based on respective positions of an area end of the smoothing area and a pixel contained in the smoothing area; and a gradation number extension part having the smoothing filter varied in tap length based on the adjustment signal, which selectively smoothes the N-bit input image signal based on the control signal by the smoothing filter, and outputs, for each pixel, an output image signal of N+k bit with the gradation number being extended by a predetermined number. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing device, an image processing method, a program, and a display device.

  In recent years, organic EL displays (also referred to as organic light emitting diode displays) or FEDs (Field Emission Displays) as display devices that replace CRT displays (Cathode Ray Tube displays). Various display devices such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), and projectors have been developed.

  Further, for example, an image signal transmitted from a broadcasting station or the like can generally represent 256 gradations with 8 bits. A display panel having a display has appeared.

  Under such circumstances, a technique for correcting the number of gradations of an input image signal has been developed in order to bring out the gradation performance of the display panel. If the difference between adjacent pixels is less than or equal to a predetermined value, it is determined to be a gradation area and smoothed. If it exceeds a predetermined value, it is determined to be an edge area and smoothed. As a technique for extending the number of gradations, for example, Patent Document 1 can be cited.

JP 2007-213460 A

  In the conventional technology that smoothes and expands the number of gradations according to the difference value between adjacent pixels, the difference value between adjacent pixels is used to determine the region indicating gradation and the region indicating edge, Smoothing is performed on an area determined to be an area showing gradation. Here, in a region showing gradation in which brightness and color gradually change, a phenomenon called false contour (Contouring) may occur, and smoothing of the image signal is an effective means for preventing the occurrence of the false contour. One.

  However, the region indicating the gradation determined by the conventional technique in which smoothing is performed according to the difference value between adjacent pixels and the number of gradations is expanded (region where the difference value between adjacent pixels is a predetermined value or less) Further, it can be further divided into a region with a small number of irregularities (hereinafter referred to as “gradation region”) and a region with a large number of irregularities (hereinafter referred to as “texture region”). Here, in the conventional technique in which smoothing is performed according to a difference value between adjacent pixels and the number of gradations is expanded, an area is determined depending on whether or not the difference value between adjacent pixels is equal to or less than a predetermined value. Therefore, it is impossible to distinguish the gradation area from the texture area. Further, in the conventional technique in which smoothing is performed in accordance with the difference value between adjacent pixels and the number of gradations is expanded, not only the gradation area but also the texture area is smoothed.

Therefore, in an image processing apparatus using a conventional technique that performs smoothing according to a difference value between adjacent pixels and expands the number of gradations, fine irregularities are lost by correcting the image signal. For example, a wall or a distant mountain The quality of the image will be degraded.

  Further, the conventional technique that performs smoothing according to a difference value between adjacent pixels and expands the number of gradations performs smoothing using a low-pass filter. However, in an image processing apparatus using a conventional technique that performs smoothing according to a difference value between adjacent pixels and expands the number of gradations, no consideration is given to the tap length of a filter that performs smoothing. . Therefore, in an image processing apparatus using a conventional technique, for example, the following problems [i] and [ii] are likely to occur.

[I] Problem of smoothing even an area showing an edge In an image processing apparatus using a conventional technique, not only an area determined to be a gradation area but also an area showing an edge that is another area. However, there is a risk of smoothing. Here, when the region indicating the edge is smoothed, for example, image quality deterioration such as a reduction in sharpness occurs.

[Ii] The problem that smoothing is not performed on the entire area showing gradation In addition, in order to avoid the occurrence of the above problem [i], for example, for an area smaller than the area determined as the area showing gradation When smoothing is performed, smoothing is not performed on the entire area determined as an area showing gradation. In the above case, an unsmoothed area is generated in the area determined to be a gradation area, so that the image quality is deteriorated.

  Therefore, an image processing apparatus using a conventional technique that performs smoothing according to a difference value between adjacent pixels and expands the number of gradations cannot achieve high image quality.

  The present invention has been made in view of the above problems, and an object of the present invention is to determine a gradation region based on an input image signal, and to change the tap length of the smoothing filter according to the determination result. New and improved image processing apparatus, image processing method, program, and display capable of selectively smoothing an image signal and converting it to an image signal having a larger number of gradations than an input image signal To provide an apparatus.

  In order to achieve the above object, according to the first aspect of the present invention, a control signal for defining a gradation region is generated for each pixel based on an input N-bit (N is a positive integer) input image signal. The smooth area detection unit to be generated, the smooth area to be smoothed based on the control signal is specified, and the tap length is determined based on the end of the specified smooth area and the position of each pixel included in the smooth area. A tap length adjusting unit that generates an adjustment signal for adjusting the tap length of a smoothing filter that smoothes the signal for each pixel, and a smoothing filter that varies the tap length based on the adjustment signal. The N-bit input image signal is selectively smoothed by the smoothing filter on the basis of the control signal generated in step S5, and an N + k-bit output image signal having a predetermined number of gradations is output for each pixel. The image processing apparatus and a gradation number extension that is provided.

  With such a configuration, the gradation region is determined based on the input image signal, and the gradation length is higher than the input image signal by selectively smoothing the image signal by varying the tap length of the smoothing filter according to the determination result. It can be converted into a large number of image signals.

  In addition, the smoothing area detecting unit detects each pixel based on a frequency component detecting unit that detects a signal of a predetermined frequency band from the input image signal that is input for each pixel, and a detection signal detected by the frequency component detecting unit. A detection value smoothing unit that smoothes the detection signal corresponding to each of the detection values, and a control signal generation unit that generates the control signal for each pixel based on the detection signal smoothed by the detection value smoothing unit. .

  With this configuration, the gradation area can be determined based on the input image signal.

  The frequency component detection unit may include a single bandpass filter that detects a signal in a predetermined frequency band for each pixel.

  With this configuration, a detection signal can be obtained for each pixel.

  In addition, the frequency component detection unit detects a plurality of bandpass filters that detect signals of different predetermined frequency bands for each pixel, and a signal output from each of the plurality of bandpass filters. A coefficient multiplier that multiplies a coefficient corresponding to the bandpass filter that is output, and a maximum value selector that selects and outputs the maximum signal for each pixel based on the signal output from the coefficient multiplier; May be provided.

  With this configuration, a detection signal can be obtained for each pixel.

  In addition, the frequency component detection unit detects a plurality of bandpass filters that detect signals of different predetermined frequency bands for each pixel, and a signal output from each of the plurality of bandpass filters. A coefficient multiplier that multiplies a coefficient corresponding to the bandpass filter to which the signal is output, and an adder that adds and outputs the signal output from the coefficient multiplier for each pixel.

  With this configuration, a detection signal can be obtained for each pixel.

  Further, the smoothing area detecting unit is configured to detect an inter-pixel difference value detecting unit that detects an inter-pixel difference value based on the input image signal that is input, and to detect the difference value detected by the inter-pixel difference value detecting unit. A smooth region for smoothing may be determined based on the smoothing region determination unit that generates the control signal corresponding to the determination result for each pixel.

  With this configuration, the gradation area can be determined based on the input image signal.

  In addition, the image processing apparatus further includes a first pseudo gradation processing unit that converts the number of gradations of the output image signal output from the gradation number extending unit to an N-bit image signal using a pseudo intermediate gradation. Also good.

  With such a configuration, the gradation performance of the gradation area can be improved.

  A first non-linear tone conversion unit that non-linearly corrects an output image signal output from the tone number expansion unit according to a signal level; and a corrected output image output from the non-linear tone conversion unit A second pseudo gradation processing unit that converts the number of gradations of the signal into an N-bit image signal using a pseudo intermediate gradation may be further provided.

  With this configuration, the gradation area can be smoothed and the gradation performance can be improved.

  In addition, the image processing apparatus further includes a second nonlinear gradation conversion unit that nonlinearly corrects the N-bit input image signal according to a signal level, and the gradation number expansion unit includes the second nonlinear gradation conversion unit. The corrected input image signal output from the terminal may be input.

  With this configuration, the gradation area can be smoothed without erroneous detection.

  In order to achieve the above object, according to a second aspect of the present invention, there is provided an image signal processing apparatus to which a plurality of N-bit (N is a positive integer) input image signals are input, A frequency component detection unit that detects a signal of a predetermined frequency band from each signal for each pixel, and a detection signal in each pixel corresponding to each of the plurality of input image signals based on the detection signal detected by the frequency component detection unit. A maximum value selection unit that selects a maximum detection signal, a detection value smoothing unit that smoothes each detection signal corresponding to each pixel based on the detection signal selected by the maximum value selection unit, and the detection value smoothing unit Based on the smoothed detection signal, a control signal generation unit that generates a control signal for defining a gradation region for each pixel, and a smooth region to be smoothed based on the control signal are specified and specified. Tap length adjustment that generates an adjustment signal for each pixel that adjusts the tap length of a smoothing filter that smoothes the signal according to the tap length based on the edge of the smoothing region and the position of each pixel included in the smoothing region And a smoothing filter whose tap length is variable based on the adjustment signal, and each of the N-bit input image signals is selectively smoothed by the smoothing filter based on the control signal generated for each pixel. An image processing apparatus is provided that includes an N + k-bit output image signal in which the number of gradations is expanded by a predetermined number, and outputs a gradation number expansion unit for each pixel.

  With this configuration, it is possible to determine gradation regions based on a plurality of input image signals, selectively smooth each of the image signals, and convert the image signals into image signals having a larger number of gradations than the input image signals. .

  In order to achieve the above object, according to a third aspect of the present invention, there is provided an image signal processing apparatus to which a plurality of N-bit (N is a positive integer) input image signals are input, Based on the input image signal, the inter-pixel difference value detection unit that detects the difference value between the pixels for each input image signal, and the smoothing region is input based on the difference value detected by the inter-pixel difference value detection unit. A smooth region determination unit that determines for each image signal and generates a determination signal indicating a determination result for each of the input image signals for each pixel, and the determination signal for each pixel corresponding to each of the input image signals is input, If the logical product of the judgment signals indicates a gradation area, specify a control signal output unit that outputs a control signal indicating the gradation area for each pixel, and a smoothing area that performs smoothing based on the control signal. Generates an adjustment signal for each pixel that adjusts the tap length of a smoothing filter that smoothes the signal according to the tap length, based on the region edge of the specified smoothing region and the position of each pixel included in the smoothing region. And a smoothing filter whose tap length is variable based on the adjustment signal, and each of the N-bit input image signals is converted by the smoothing filter based on the control signal generated for each pixel. An image processing apparatus is provided that includes an N + k-bit output image signal that is selectively smoothed and the number of gradations is expanded by a predetermined number, and outputs a gradation number expansion unit for each pixel.

  With this configuration, it is possible to determine gradation regions based on a plurality of input image signals, selectively smooth each of the image signals, and convert the image signals into image signals having a larger number of gradations than the input image signals. .

  In order to achieve the above object, according to a fourth aspect of the present invention, an image processing method that can be used in an image processing apparatus including a smoothing filter for smoothing a signal according to a tap length for each pixel. A first generation step for generating a control signal for defining a gradation area for each pixel based on an input N-bit (N is a positive integer) input image signal, and generation in the first generation step. The smoothing area to be smoothed is identified based on the control signal and the tap length of the smoothing filter is adjusted based on the edge of the identified smoothing area and the position of each pixel included in the smoothing area. Adjusting the tap length of the smoothing filter based on the adjustment signal generated in the second generation step, and a second generation step for generating an adjustment signal for each pixel. An N + k-bit output image signal in which the N-bit input image signal is selectively smoothed by the smoothing filter based on the control signal generated for each pixel in the first generation step and the number of gradations is expanded by a predetermined number. For each pixel, an image processing method is provided.

  By using such a method, the gradation region is determined based on the input image signal, and the tap length of the smoothing filter is varied according to the determination result, and the image signal is selectively smoothed. Can also be converted into an image signal having a large number of gradations.

  In order to achieve the above object, according to a fifth aspect of the present invention, there is provided a program that can be used in an image processing apparatus that includes a smoothing filter for smoothing a signal according to a tap length for each pixel. Then, based on the input N-bit (N is a positive integer) input image signal, a first generation step for generating a control signal for defining a gradation area for each pixel, and the above-mentioned generation generated in the first generation step An adjustment signal that specifies a smoothing area to be smoothed based on a control signal and adjusts the tap length of the smoothing filter based on the end of the specified smoothing area and the position of each pixel included in the smoothing area A second generation step for generating each pixel, a tap length of the smoothing filter is adjusted based on the adjustment signal generated in the second generation step, and the first Based on the control signal generated for each pixel in the generation step, the N-bit input image signal is selectively smoothed by the smoothing filter, and an N + k-bit output image signal whose number of gradations is expanded by a predetermined number of pixels A program for causing a computer to execute the step of outputting each time is provided.

  With such a program, the gradation region is determined based on the input image signal, the tap length of the smoothing filter is varied according to the determination result, the image signal is selectively smoothed, and the gradation is higher than the input image signal. It can be converted into a large number of image signals.

  In order to achieve the above object, according to a sixth aspect of the present invention, N + k based on an image signal correction unit that corrects an input image signal and an image signal corrected by the image signal correction unit. An image display unit capable of displaying an image indicated by an image signal of bits (N and k are positive integers), and the image signal correction unit is configured to display a gradation region based on the input N-bit input image signal. A smoothing area detection unit that generates a control signal to be defined for each pixel, a smoothing area that performs smoothing based on the control signal, and an area end of the specified smoothing area and each pixel included in the smoothing area A tap length adjusting unit that generates, for each pixel, an adjustment signal that adjusts the tap length of a smoothing filter that smoothes the signal according to the tap length based on the position, and a smoothing that varies the tap length based on the adjustment signal. An N + k-bit output image having a filter and selectively smoothing the N-bit input image signal with the smoothing filter based on the control signal generated for each pixel and extending the number of gradations by a predetermined number There is provided a display device including a gradation number extending unit that outputs a signal for each pixel.

  With such a configuration, the gradation region is determined based on the input image signal, and the gradation length is higher than the input image signal by selectively smoothing the image signal by varying the tap length of the smoothing filter according to the determination result. An image can be displayed after being converted into a large number of image signals. Further, with such a configuration, it is possible to make use of the gradation performance of the display unit that has higher gradation performance than the input image signal.

  In order to achieve the above object, according to a seventh aspect of the present invention, an image signal correction unit that corrects an input image signal, and an image signal that is corrected by the image signal correction unit, N An image display unit capable of displaying an image indicated by a bit (N is a positive integer) image signal, and the image signal correction unit defines a gradation region based on the input N-bit input image signal A smoothing region detecting unit that generates a control signal for each pixel; a smoothing region that performs smoothing based on the control signal; a region end of the specified smoothing region; and a position of each pixel included in the smoothing region; A tap length adjusting unit that generates an adjustment signal for each pixel that adjusts the tap length of a smoothing filter that smoothes the signal according to the tap length, and a smoothing filter that varies the tap length based on the adjustment signal And an N + k-bit output image signal whose number of gradations is expanded by a predetermined number by selectively smoothing the N-bit input image signal by the smoothing filter based on the control signal generated for each pixel. A gradation number expanding unit that outputs each pixel, and a pseudo gradation that converts the number of gradations of the output image signal output from the gradation number expanding unit into an N-bit image signal using a pseudo intermediate gradation. A display device including a tone processing unit is provided.

  With this configuration, an image with improved gradation performance in the gradation area can be displayed.

  According to the present invention, the gradation region is determined based on the input image signal, and the tap length of the smoothing filter is varied according to the determination result, and the image signal is selectively smoothed. It can be converted into an image signal having a large number of gradations.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(Outline of processing of display device according to embodiment of present invention)
Before describing the display device according to the embodiment of the present invention, first, an outline of processing of the display device according to the embodiment of the present invention will be described. In the following description, it is assumed that an image signal is input to the display device according to the embodiment of the present invention. However, the image signal input to the display device may indicate a still image, or It may be a moving image (so-called video).

  In the following description, it is assumed that the image signal input to the display device according to the embodiment of the present invention is a digital signal. However, the present invention is not limited to the above. For example, an analog signal used in analog broadcasting or the like It can also be converted into a digital signal by (Analog to Digital converter). In addition, the image signal input to the display device according to the embodiment of the present invention can be transmitted from a broadcast station and received by the display device, for example, but is not limited thereto. For example, the image signal input to the display device according to the embodiment of the present invention may be transmitted from an external device via a network such as a LAN (Local Area Network) and received by the display device, or The display device may read a video file or an image file held in a storage unit included in the display device.

  The processing in the display device according to the embodiment of the present invention is divided into [1] an image processing phase for correcting the input image signal and [2] a display phase for displaying the corrected image signal.

[1] Image Processing Phase In the image processing phase, the display device according to the embodiment of the present invention performs, for example, the following processes [1-1] to [1-3] and inputs N bits (N is a positive value). Image signal (hereinafter referred to as “input image signal”) is converted into an image signal (hereinafter referred to as “output image signal”) of N + k (k is a positive integer). Here, the value of k can be a value corresponding to the gradation performance of the display unit on which the display device according to the embodiment of the present invention displays an image. In addition, when the display device according to the embodiment of the present invention has N-bit gradation performance of the display unit that displays an image, the display device according to the embodiment of the present invention outputs N + k bits. The image signal can be further corrected to N bits.

[1-1] Judgment of gradation area The display device according to the embodiment of the present invention uses an “edge area” indicating an edge and an “gradation” indicating an area having a small number of irregularities other than the edge area. The “region” and the “texture region” indicating a region having a large number of irregularities other than the edge region are roughly classified, and the gradation region is determined based on the input image signal. Here, the display device according to the embodiment of the present invention determines the gradation region for each pixel corresponding to the input image signal, for example.

[1-2] Adjustment of Tap Length of Smoothing Filter Performing Smoothing The display device according to the embodiment of the present invention specifies a smooth region to be smoothed based on the determination result in [1-1]. More specifically, the display device according to the embodiment of the present invention sets a region determined as a gradation region as a smooth region. And the display apparatus which concerns on embodiment of this invention adjusts the tap length of a smoothing filter for every pixel based on the area | region edge of the identified smooth area | region, and the position of the pixel contained in the said smooth area | region. Here, the adjustment of the tap length is performed so that the entire specified smooth region is smoothed.

[1-3] Correction of Image Signal The display device according to the embodiment of the present invention performs image signal as shown in (A) and (B) below for each pixel based on the determination result in [1-1]. Perform the correction.

(A) When it is determined that the region is not a gradation region The display device according to the embodiment of the present invention does not perform smoothing when it is determined that the region is not a gradation region (that is, an edge region or a texture region). The N + k-bit output image signal is output by adding a k-bit fixed value to the lower order of the N-bit input image signal.

(B) When judged to be a gradation region When the display device according to the embodiment of the present invention is judged to be a gradation region, the display device is smoothed by performing smoothing of the input image signal with an accuracy of N + k bits. N + k-bit output image signals are output. Here, the smoothing is performed using a smoothing filter whose tap length is adjusted in [1-2].

  The display device according to the embodiment of the present invention performs the above processing (A) or (B) for each pixel on the input image signal corresponding to each pixel, thereby converting the N-bit input image signal to N + k bits. The output image signal can be corrected.

  In addition, the display device according to the embodiment of the present invention determines a gradation area based on the input image signal, and smoothes the input image signal for the gradation area based on the determination result, thereby obtaining an edge area or a texture area. In contrast, the input image signal is not smoothed. Therefore, in the display device according to the embodiment of the present invention, fine irregularities are not lost by the correction of the input image signal, and for example, the texture of walls and distant mountains is not impaired, so that high image quality can be achieved. it can.

  Furthermore, the display device according to the embodiment of the present invention can smooth the entire area determined as the gradation area by adjusting the tap length of the smoothing filter. Therefore, in the display device according to the embodiment of the present invention, the image quality is not deteriorated due to the occurrence of an unsmoothed region in the region determined as the gradation region.

[2] Display Phase The display device according to the embodiment of the present invention displays an image based on the image signal (output image signal) corrected in the image processing phase of [1].

  The display device according to the embodiment of the present invention determines the gradation area based on the input image signal by the above-described processing, smoothes the input image signal, and converts it to an output image signal having a larger number of gradations than the input image signal. And an image can be displayed.

  Therefore, the display device according to the embodiment of the present invention can bring out the display performance of the display unit even when the gradation performance of the display unit is higher than that of the input image signal, and can correct the input image signal. As a result, fine irregularities are not lost, so that high image quality can be achieved.

  The configuration of the display device according to the embodiment of the present invention will be specifically described below. In addition, in the following, as the display device according to the embodiment of the present invention, a configuration including the [1] “image processing unit” responsible for the image processing phase and the [2] “display unit” responsible for the display phase is shown. . The embodiment of the present invention is not limited to the above configuration, and for example, the following image processing unit can be realized as an independent device (image processing device).

(First embodiment)
FIG. 1 is a block diagram showing a display device 1000 according to the first embodiment of the present invention. FIG. 1 shows a configuration in which the image processing unit 100 performs a monochrome image process or a process for one channel among a plurality of channels of a color image as the display device 1000.

[Configuration of Display Device 1000]
Referring to FIG. 1, the display device 1000 includes an image processing unit 100 and a display unit 190.

  The display device 1000 includes, for example, a control unit (not shown) configured by an MPU (Micro Processing Unit) or the like that can control the entire display device 1000, a program used by the control unit, an operation parameter, and the like. ROM (Read Only Memory) (not shown) in which control data is recorded, RAM (Random Access Memory (not shown)) that primarily stores programs executed by the control unit, image signals transmitted from broadcast stations, etc. A receiving unit (not shown) for receiving video, a storage unit (not shown) capable of storing video files and image files, an operation unit (not shown) operable by the user, and an external device (not shown) You may provide the communication part (not shown) etc. for performing communication. The display device 1000 connects the above-described constituent elements by, for example, a bus as a data transmission path.

  Here, as the storage unit (not shown), for example, a magnetic recording medium such as a hard disk, an EEPROM (Electronically Erasable and Programmable Read Only Memory), a flash memory, a MRAM (Magnetoresistive Random Access) Non-volatile memory such as Memory (RAM), FeRAM (Ferroelectric Random Access Memory), PRAM (Phase change Random Access Memory), and the like, but is not limited thereto. Further, examples of the operation unit (not shown) include operation input devices such as a keyboard and a mouse, buttons, direction keys, and combinations thereof, but are not limited thereto.

  The display device 1000 and an external device (not shown) include, for example, a USB (Universal Serial Bus) terminal, an IEEE 1394 standard terminal, a DVI (Digital Visual Interface) terminal, or an HDMI (High-Definition Multimedia Interface) terminal. It may be physically connected via a wireless LAN, or may be connected wirelessly using WUSB (Wireless Universal Serial Bus), IEEE 802.11, or the like. Furthermore, the display device 1000 and an external device (not shown) can be connected via a network, for example. As the network, for example, a wired network such as LAN or WAN (Wide Area Network), a wireless network such as WLAN (Wireless Local Area Network) using MIMO (Multiple-Input Multiple-Output), or TCP / IP (Transmission Control) Examples include the Internet using a communication protocol such as Protocol / Internet Protocol, but are not limited to the above. Therefore, the communication unit (not shown) has an interface corresponding to the connection form with the external device (not shown).

  The image processing unit 100 converts the input N-bit (N is a positive integer) input image signal Di into an N + k (k is a positive integer) -bit output image signal Do. More specifically, the image processing unit 100 is based on a smooth region detecting unit 102 that determines a gradation region for each pixel of the image indicated by the input image signal Di, and a control signal Dc output from the smooth region detecting unit 102. A tap length adjusting unit 104 that outputs an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel, and an input image signal Di selectively based on the control signal Dc output from the smoothing region detecting unit 102. A gradation number expansion unit 106 that performs smoothing and expands the number of gradations. Here, the gradation number expanding unit 106 performs smoothing by including a smoothing filter, and the tap length of the smoothing filter is adjusted based on the adjustment signal Dtp output from the tap length adjusting unit 104. Details of the image processing unit 100 will be described later.

  The display unit 190 has N + k bit gradation performance and displays an image indicated by the N + k bit output image signal Do output from the image processing unit 100.

[Configuration Example of Display Unit 190]
The display unit 190 includes, for example, an image display unit (not shown), a row driving unit (not shown), a column driving unit (not shown), a power supply unit (not shown), and a display control unit. (Not shown).

  The image display unit includes, for example, a plurality of pixels arranged in a matrix (matrix). For example, an image display unit that displays an SD (Standard Definition) resolution image has at least 640 × 480 = 307200 pixels (data lines × scanning lines), and the pixels are red for color display. In the case of being composed of green and blue sub-pixels, it has sub-pixels of 640 × 480 × 3 = 921600 (data lines × scanning lines × number of sub-pixels). Similarly, for example, a display unit that displays an HD (High Definition) resolution image has 1920 × 1080 pixels, and has 1920 × 1080 × 3 sub-pixels for color display.

  Further, the image display unit may include, for example, a pixel circuit for controlling the amount of voltage / current applied to each pixel. The pixel circuit includes, for example, a switch element and a drive element for controlling the amount of current by an applied scanning signal and a voltage signal, and a capacitor for holding a voltage signal. The switch element and the drive element are composed of, for example, a thin film transistor.

  For example, the row driving unit and the column driving unit apply voltage signals to a plurality of pixels included in the image display unit to cause each pixel to emit light. Here, one of the row driving unit and the column driving unit applies a voltage signal (scanning signal) that determines ON / OFF of the pixel, and the other applies a voltage signal (image signal) corresponding to an image to be displayed. Can be fulfilled. In addition, as a driving method of the row driving unit and the column driving unit, for example, a dot sequential driving scanning method in which light is emitted for each pixel arranged in the matrix, and a line in which the pixels arranged in the matrix are emitted for each column. Examples include a sequential driving scanning method, and a surface sequential driving scanning method in which all the pixels arranged in the matrix form emit light.

  The power supply unit supplies power to the row driving unit and the column driving unit, and a voltage is applied to the row driving unit and the column driving unit. The magnitude of the voltage applied by the power supply unit to the row driving unit and the column driving unit varies according to the output image signal Do output from the image processing unit 100.

  The display control unit is configured by, for example, an MPU, and in accordance with an output image signal Do output from the image processing unit 100, a voltage for determining ON / OFF of the pixel is applied to one of the row driving unit and the column driving unit A control signal to be applied to is input, and an image signal is input to the other. The display control unit can also control the supply of power to the row driving unit and the column driving unit by the power supply unit according to the output image signal Do output from the image processing unit 100.

  The display unit 190 displays an image according to the output image signal Do with the above configuration. Here, examples of the display unit 190 include an organic EL display, a self-luminous display device such as an FED and a PDP, and a backlight display device such as an LCD, but are not limited thereto.

  The display apparatus 1000 according to the first embodiment of the present invention has a configuration as shown in FIG. 1 and determines a gradation area for each corresponding pixel based on an input image signal, and the input image signal according to the determination result. Di is selectively smoothed to expand the number of gradations. The display apparatus 1000 can display an image based on an image signal with an expanded number of gradations, that is, an output image signal Do. Next, the image processing unit 100 according to the first embodiment of the present invention will be described in more detail. In the following, for simplification of description, description will be made by taking an example of processing in the horizontal direction.

[Image Processing Unit 100 According to First Embodiment]
FIG. 2 is a block diagram showing the image processing unit 100 according to the first embodiment of the present invention. Referring to FIG. 2, the image processing unit 100 includes a smooth region detection unit 102, a tap length adjustment unit 104, and a gradation number expansion unit 106. Further, the smooth region detection unit 102 includes a frequency component detection unit 108, a detection value smoothing unit 110, and a control signal generation unit 112.

[Smooth area detection unit 102]
The frequency component detection unit 108 detects a predetermined frequency component from the input image signal Di for each pixel, and outputs the detection result as a frequency component detection value Df.

  FIG. 3 is a block diagram illustrating a configuration example of the frequency component detection unit 108 according to the first embodiment of the present invention. Referring to FIG. 3, the frequency component detection unit 108 includes a band-pass filter 114 (Band-Pass Filter; hereinafter sometimes referred to as “BPF”) and an absolute value conversion unit 116.

  The bandpass filter 114 passes only the image signal of a specific frequency band and attenuates the image signal of the other band, thereby outputting the BPF output Dbpf for each pixel. FIG. 4 is an explanatory diagram showing an example of the frequency characteristics of the bandpass filter 114 according to the first embodiment of the present invention. Referring to FIG. 4, the band pass filter 114 has a pass band having a peak at the frequency f. Here, the frequency f can be determined so that, for example, many components near the frequency f are included in the texture region according to the frequency characteristics of the texture region. The frequency f can be set according to the screen size and the number of pixels of the display unit 190 and the assumed viewing distance.

  The absolute value converter 116 calculates the absolute value of the BPF output Dbpf and outputs it as the frequency component detection value Df.

  The components of the image processing unit 100 will be described with reference to FIG. 2 again. The detection value smoothing unit 110 smoothes the frequency component detection value Df for each pixel based on the frequency component detection value Df corresponding to each pixel output from the frequency component detection unit 108, and smoothed average detection. Outputs the value Dave. Here, the average detection value Dave is used for gradation region determination in the control signal generation unit 112 described later.

  The detection value smoothing unit 110 sets a predetermined smoothing region including a target pixel corresponding to the pixel to be smoothed for each pixel, and calculates an average value of the frequency component detection values Df corresponding to the pixels included in the smoothing region. By calculating, the average detection value Dave is output for each pixel. FIG. 5 is an explanatory diagram for explaining an example of the smoothing process in the detection value smoothing unit 110 according to the first embodiment of the present invention, and an area having a size of 8 pixels in the horizontal direction as a smooth area. A set example is shown. Here, the smoothing region set by the detection value smoothing unit 110 is not limited to the region of the size of 8 pixels in the horizontal direction shown in FIG. 5, but is a region of any size in the horizontal direction and / or the vertical direction. be able to. In addition, the smooth region is not limited to being set to the same size for all the target pixels, and for example, the size may be changed according to the position on the screen.

  Further, the average value calculated by the detection value smoothing unit 110 can be obtained by, for example, an arithmetic average, but is not limited to such a calculation method, and may be, for example, a geometric average or a weighted average with a predetermined weight. You can also

  The components of the image processing unit 100 will be described with reference to FIG. 2 again. Based on the average detection value Dave output from the detection value smoothing unit 110, the control signal generation unit 112 performs gradation region determination for each pixel by threshold processing.

[Significance of performing determination based on average detection value Dave]
Here, the significance of the image processing unit 100 determining the gradation area based on the average detection value Dave will be described.

  The frequency component detection value Df increases in the edge region, while the frequency component detection value Df decreases in both the gradation region and the texture region. Therefore, when attention is paid only to the magnitude of the frequency component detection value Df, the gradation area and the texture area cannot be distinguished.

  Here, focusing on the frequency of detection of the frequency component detection value Df in the smooth area, the frequency of detection of the frequency component detection value Df is low in the gradation area, but the detection frequency is relatively high in the texture area. Further, the frequency component detection value Df included in the smooth region has the same size in both the gradation region and the texture region. That is, focusing on the average frequency component detection value Df in the smooth region, that is, the average detection value Dave, the average detection value Dave in the texture region is larger than the average detection value Dave in the gradation region.

  Therefore, if threshold processing based on the average detection value Dave and an appropriate threshold TH for distinguishing the gradation area and the texture area is performed, if the average detection value Dave is smaller than the threshold TH, the gradation area or the average detection When the value Dave is larger than the threshold value TH, it can be distinguished as a texture region or an edge region. Here, the value of the threshold value TH can be determined using, for example, an image signal indicating an image having an area clearly showing gradation and an image signal showing an image having an area clearly showing texture.

  FIG. 6 is an explanatory diagram for explaining threshold processing in the control signal generation unit 112 according to the first embodiment of the present invention. As shown in FIG. 6, when the average detection value Dave is smaller than the threshold value TH, the control signal generator 112 outputs “1” indicating the gradation area as the control signal Dc, and when the average detection value Dave is equal to or larger than the threshold value TH, the texture is output. “0” indicating an area or edge area, that is, other than the gradation area, is output as the control signal Dc.

  Here, the information about the threshold TH used by the control signal generation unit 112 to determine the gradation area is stored in, for example, a storage unit included in the image processing unit 100 and is input from the storage unit. Here, examples of the storage means included in the image processing unit 100 include a nonvolatile memory such as an EEPROM or a flash memory, but are not limited thereto. Note that the threshold TH information can be held by the control signal generation unit 112 with a storage unit, for example, and stored in a storage unit (not shown) of the display device 1000. Needless to say, the data may be appropriately read from the storage unit (not shown).

  The smooth region detection unit 102 includes the frequency component detection unit 108, the detection value smoothing unit 110, and the control signal generation unit 112 as described above, thereby determining a gradation region for each pixel based on the input image signal Di. Can do.

[Tap length adjustment unit 104]
With reference to FIG. 2 again, components of the image processing unit 100 will be described. The tap length adjustment unit 104 is configured by, for example, an MPU, and specifies a gradation region, that is, a smooth region to be smoothed, based on the control signal Dc output from the smooth region detection unit 102. Here, the tap length adjustment unit 104 can specify a smooth region based on a change in the value of the control signal Dc. For example, the tap length adjustment unit 104 determines the position when the control signal Dc changes from “0” indicating a region other than the gradation region to “1” indicating the gradation region as the smoothing start position (smoothing region end). Further, the position when the control signal Dc changes from “1” to “0” is determined as the smoothing end position (smoothing region end).

  Then, the tap length adjustment unit 104 determines the tap length for each pixel so that the entire smoothed region is smoothed based on the region end of the specified smoothed region and the position of the pixel in the smoothed region. The adjustment signal Dtp corresponding to the determined tap length is output for each pixel. Here, for example, the tap length adjusting unit 104 may generate and output the adjustment signal Dtp that defines the tap length, or may generate and output the adjustment signal Dtp that defines the adjustment amount of the tap length. Yes, but not limited to the above.

  Here, the significance of the image processing unit 100 including the tap length adjusting unit 104 will be described. FIG. 7 is a first explanatory diagram for explaining the significance of the image processing unit 100 according to the first embodiment of the present invention including the tap length adjusting unit 104. FIG. 7A shows an example of the input image signal Di, and FIG. 7B shows a control signal Dc generated based on the input image signal Di shown in FIG. Yes.

  As shown in FIG. 7A, when an input image signal Di indicating an image having a gradation region between two edge regions is input to the image processing unit 100, the control signal generation unit 112 displays ), The control signal Dc indicating “1” is output for the gradation area, and the control signal Dc indicating “0” is output for the edge area. Therefore, in the example of FIG. 7, the areas p to q where the control signal Dc indicating “1” is output are the smooth areas to be smoothed. Occurrence can be effectively prevented. Here, for example, if p is a smoothing start position (smoothing region end) at which smoothing is started, q can be a smoothing end position (smoothing region end) at which smoothing ends.

  However, when the image processing unit 100 does not include the tap length adjusting unit 104 and performs smoothing using a smoothing filter with a fixed tap length, for example, the following [a-1] and [a-2] are shown. Problems arise. Hereinafter, with reference to FIG. 8, a problem when smoothing is performed with a smoothing filter having a fixed tap length will be described.

  FIG. 8 is an explanatory diagram for explaining a problem when the image processing unit 100 according to the first embodiment of the present invention does not include the tap length adjustment unit 104. FIG. 8A shows the pixels A to I existing in the gradation area shown in FIG. 7A, and the pixels 1 and 2 in the edge area. FIG. 8B is an explanatory diagram for explaining the first problem when the image processing unit 100 does not include the tap length adjusting unit 104, and FIG. 8C illustrates the second problem. It is explanatory drawing for doing. Here, p shown in FIGS. 8A to 8C indicates the smoothing start position p shown in FIG. 7, and q shows the smoothing end position q shown in FIG. Yes.

[A-1] First problem (FIG. 8B)
For example, TAP11 to TAP13 are given as smoothing filters for smoothing pixels included in the smoothing start position p to the smoothing end position q (that is, in the smoothing region). TAP11 is a smoothing filter corresponding to the pixel A at the position of the smoothing start position p among the pixels in the smoothing region. Here, for example, the TAP 11 performs smoothing by converting an average value of pixel data (input image signal Di) corresponding to each pixel in the tap centered on the pixel A into pixel data corresponding to the pixel A. However, it is not limited to the above. Further, TAP13 is a smoothing filter corresponding to the pixel I at the smoothing end position q at the pixel in the smoothing region, and TAP12 is a smoothing filter corresponding to the pixel E located near the center in the smoothing region. .

  When the tap lengths of TAP11 to TAP13 are fixed, as shown in FIG. 8B, TAP11 and TAP13, for example, calculate the average value calculated using pixel data corresponding to the pixels in the edge region, This results in pixel data of pixel I.

  In the above case, since the influence of the signal corresponding to the edge area is large when smoothing the gradation area, for example, the generation of false contours cannot be effectively prevented, or the smoothing of the gradation area is broken. This may cause problems such as degradation of image quality. Therefore, smoothing in the state shown in FIG.

[A-2] Second problem (FIG. 8C)
As a solution for preventing the occurrence of the first problem, for example, not using TAP that uses pixel data corresponding to pixels in the edge region, such as TAP11 and TAP13. In the above case, for example, as shown in FIG. 8C, TAP14 to TAP15 that do not use pixel data corresponding to the pixels in the edge region are used for smoothing. However, in the above case, smoothing is performed only to the positions of the pixels C to G corresponding to TAP14 to TAP15, that is, p ′ to q ′ in the smoothing region. Therefore, in the above case, the entire smooth area, that is, the entire gradation area to be smoothed cannot be smoothed.

  Therefore, an area that is not smoothed is generated in the gradation area, so that the image quality is lowered, and smoothing in the state shown in FIG. 8C is also undesirable.

[B] Solution Means According to the Embodiment of the Present Invention Accordingly, the image processing unit 100 according to the first embodiment of the present invention adjusts the tap length of the smoothing filter, thereby adjusting the first problem and the second problem. Prevent problems. Hereinafter, a method for preventing the occurrence of the first problem and the second problem in the image processing unit 100 will be described with reference to FIG.

  FIG. 9 is a second explanatory diagram for explaining the significance of the image processing unit 100 according to the first embodiment of the present invention including the tap length adjusting unit 104. Here, p shown in FIGS. 9A to 9D indicates the smoothing start position p shown in FIG. 7, and q shows the smoothing end position q shown in FIG. Yes.

[B-1] First state before adjustment of tap length of smoothing filter (FIG. 9A)
As an example, TAP1 to TAP3 are given as smoothing filters for smoothing pixels included in the smooth region. Here, TAP1 is a smoothing filter corresponding to the pixel A located in the smoothing start position p among the pixels in the smoothing region, and TAP3 is a pixel in the smoothing region located in the smoothing end position q. Corresponding smoothing filter. TAP2 is a smoothing filter corresponding to the pixel E near the center in the smooth region.

  FIG. 9A shows a state before adjustment of the tap length of the smoothing filter, which is the same state as FIG. 8A. Therefore, when smoothing is performed in the state of FIG. 9A, the first problem occurs.

[B-2] First state after adjustment of tap length of smoothing filter (FIG. 9B)
FIG. 9B shows the first state after adjusting the tap length of the smoothing filter. As illustrated in FIG. 9B, the image processing unit 100 adjusts the tap length so that the tap does not include pixels in the edge region for TAP1 corresponding to the pixel A located at the smoothing start position p. (TAP1 ′ in FIG. 9B). In addition, the image processing unit 100 adjusts the tap length of the TAP3 corresponding to the pixel I located at the smoothing end position q so that the edge region pixels are not included in the tap (TAP3 in FIG. 9B). '). In the above case, the tap lengths of TAP1 ′ and TAP3 ′ are 1, and the pixels A and I are not actually smoothed.

[B-3] Second state before adjusting tap length of smoothing filter (FIG. 9C)
As an example, TAP4 and TAP5 are given as smoothing filters for smoothing pixels included in the smooth region. Here, TAP4 is a smoothing filter corresponding to the pixel B located near the smoothing start position p among pixels in the smoothing region, and TAP5 is a pixel located near the smoothing end position q in the pixels within the smoothing region. A smoothing filter corresponding to H.

  FIG. 9C shows a state before adjustment of the tap length of the smoothing filter, and is a state in which pixels in the edge region are included in the tap, as in FIG. 8A. Therefore, when smoothing is performed in the state of FIG. 9C, the first problem occurs.

[B-4] Second state after adjustment of tap length of smoothing filter (FIG. 9D)
FIG. 9D shows a second state after adjusting the tap length of the smoothing filter. As illustrated in FIG. 9D, the image processing unit 100 adjusts the tap length so that the pixel in the edge region is not included in the tap for TAP4 corresponding to the pixel B located near the smoothing start position p. (TAP4 ′ in FIG. 9D). Further, the image processing unit 100 adjusts the tap length of the TAP 5 corresponding to the pixel H located near the smoothing end position q so that the edge region pixels are not included in the tap (see FIG. 9D). TAP 5 ').

  By adjusting the tap length of the smoothing filter in the smooth region so that the pixels in the smooth region do not include the pixels in the edge region for each pixel in the smoothing start position p to the smoothing end position q as described above. The processing unit 100 can smooth the entire smooth area, that is, the determined gradation area. Furthermore, since pixel data corresponding to pixels in the edge region is not used for smoothing, the image processing unit 100 can perform smoothing without being affected by the edge region. Therefore, in the display device 1000 according to the first embodiment, since the first problem and the second problem do not occur, the generation of false contours can be effectively prevented, and the image quality is also deteriorated due to smoothing. Absent.

  Therefore, the significance that the image processing unit 100 includes the tap length adjusting unit 104 is that, for example, the first problem and the second problem are not caused by adjusting the tap length of the smoothing filter.

[Other examples of tap length adjustment]
In FIG. 9B and FIG. 9D, the tap length adjusting unit 104 has the center of the smoothing filter (for example, the pixel to be smoothed) as indicated by TAP1 ′, TAP3 ′, TAP4 ′, and TAP5 ′. Although the example in which the tap length is adjusted so as to be symmetric from the (position) has been shown, it is not limited to the above.

  FIG. 10 is an explanatory diagram illustrating another example of tap length adjustment in the tap length adjustment unit 104 of the image processing unit 100 according to the first embodiment of the present invention. Here, FIG. 10A shows the state before the tap length adjustment of the smoothing filters (TAP1 to TAP3) as in FIG. 9A, and FIG. 10B shows the tap of the smoothing filter. The state after length adjustment is shown.

  As illustrated in FIG. 10B, the tap length adjustment unit 104 uses a smoothing filter for TAP1 corresponding to the pixel A located at the smoothing start position p so that no edge region pixels are included in the tap. The tap length is adjusted asymmetrically from the center (TAP1 ″ in FIG. 10B). Similarly, the tap length adjustment unit 104 sets the tap length asymmetrically from the center of the smoothing filter so that the tap region does not include pixels in the edge region for TAP3 corresponding to the pixel I located at the smoothing start position q. Adjust (TAP3 ″ in FIG. 10B).

  As described above, the tap length adjusting unit 104 adjusts the tap length asymmetrically from the center of the smoothing filter, whereby the number of pixel data used for smoothing can be increased. Here, the tap length adjustment unit 104 performs smoothing by, for example, calculating an average value of the pixel data in the smoothing filter. Therefore, the tap length adjusting unit 104 can improve the smoothing accuracy in the smooth region, that is, in the determined gradation region.

  Further, the tap length adjusting unit 104 is not limited to adjusting the tap length symmetrically / asymmetrically, and can also change the filter coefficient of each smoothing filter in accordance with the amount of tap length adjustment. By changing the filter coefficient, the tap length adjusting unit 104 can further finely perform smoothing according to the adjusted tap length.

  Here, the tap length adjustment unit 104 calculates the filter coefficient based on, for example, a tap length adjustment amount, and a look-up table in which the tap length adjustment amount and the filter coefficient are associated with each other. Can be determined uniquely. In addition, the lookup table in which the tap length adjustment amount and the filter coefficient are associated with each other can be held in, for example, a storage unit included in the tap length adjustment unit 104. Examples of the storage means included in the tap length adjustment unit 104 include non-volatile memories such as an EEPROM and a flash memory, but are not limited thereto. Needless to say, the lookup table is stored in, for example, a storage unit (not shown) of the display device 1000, and the tap length adjustment unit 104 may appropriately read from the storage unit (not shown). .

[Gradation number expansion unit 106]
With reference to FIG. 2 again, components of the image processing unit 100 will be described. The gradation number expansion unit 106 includes a smoothing filter whose tap length varies according to the adjustment signal, and performs the following processes [a] and [b] based on the control signal Dc output from the control signal generation unit 112. As a result, an output image signal Do of N + k bits is output.

[A] When the control signal Dc is “1” indicating a gradation region The gradation number expanding unit 106 performs a smoothing operation on the input image signal Di with an accuracy of N + k bits, and a smoothed output image signal of N + k bits. Do is output. Here, the smoothing is performed using a smoothing filter whose tap length is adjusted according to the adjustment signal.

[B] When the control signal Dc is “0” indicating an area other than the gradation area The gradation number expansion unit 106 does not perform smoothing, and adds N bits to k bits to the lower order of the input image signal Di. The output image signal Do is output.

  As shown in [a] and [b] above, the gradation number expanding unit 106 performs smoothing when the control signal Dc is “1” indicating the gradation region, and the control signal Dc is other than the gradation region. In the case of “0” indicating the region (that is, the edge region or the texture region), the input image signal Do can be selectively smoothed by not performing smoothing.

  Further, the gradation number expanding unit 106 can use, for example, a low-pass filter (not shown) that attenuates an image signal having a frequency higher than the cutoff frequency as a smoothing filter, but is not limited thereto. For example, the gradation number expanding unit 106 can also use an ε filter (ε-Filter), a bilateral filter (Bilateral Filter), or the like as a smoothing filter. It is known that the filter has a characteristic that only a minute image change is smoothed and a large image change is not smoothed. By using these, even if the determination result of the region is wrong, the deterioration of the edge region can be suppressed to the minimum.

  The gradation number expanding unit 106 adjusts the tap length of the smoothing filter in accordance with the adjustment signal Dtp output from the tap length adjusting unit 104 and controls the control signal Dc output from the smooth region detecting unit 102 with the above configuration. The N + k-bit output image signal Do can be output by selectively performing smoothing on the N-bit input image signal Di based on the above.

[Each signal in the image processing unit 100]
With the above-described configuration, the image processing unit 100 according to the first embodiment determines a gradation area based on the input image signal Di, performs smoothing selectively based on the determination result, and outputs an N + k-bit output image signal. Do can be output. Here, each signal described above in the image processing unit 100 is shown for each of the gradation region, the texture region, and the edge region.

  FIG. 11 is an explanatory diagram illustrating an example of each signal in the image processing unit 100 according to the first embodiment of the present invention. Here, FIG. 11A shows the input image signal Di, and FIG. 11B shows the BPF output Dbpf. Similarly, FIGS. 11C to 11F show the frequency component detection value Df, the average detection value Dave, the control signal Dc, and the output image signal Do, respectively.

[A] gradation area (FIG. 11 (1))
(A-1) FIG. 11 (a)
As an example of the input image signal Di, a gradation region that changes stepwise by one gradation is given as an example.

(A-2) FIG. 11B
The amplitude of the BPF output Dbpf output from the bandpass filter 114 is small and the frequency of detection is low.

(A-3) FIG. 11 (c)
The BPF output Dbpf is converted into an absolute value by the absolute value converter 116, and a frequency component detection value Df is output. The frequency component detection value Df is small and the frequency of detection is low.

(A-4) FIG. 11 (d)
In the detection value smoothing unit 110, the average value of the frequency component detection values Df in the smooth region is calculated for each corresponding pixel, and the average detection value Dave is output. The average detection value Dave is a value smaller than the threshold value TH.

(A-5) FIG. 11 (e)
By performing threshold processing in the control signal generation unit 112, the control signal Dc is output. Since the average detection value Dave shown in FIG. 11D is smaller than the threshold value TH, the control signal Dc indicates “1” representing the gradation area.

(A-6) FIG. 11 (f)
Since the control signal Dc shown in FIG. 11E is “1” indicating the gradation region, the gradation number expanding unit 106 outputs the smoothed output image signal Do of N + k bits. Here, since the output image signal Do has an accuracy of N + k bits, the image changes more smoothly than the N-bit input image signal Di.

  As shown in FIG. 11, since the smoothed N + k-bit output image signal Do is output in the gradation area, the gradation area changes more smoothly.

[B] Texture area (FIG. 11 (2))
(B-1) FIG.
As an example of the input image signal Di, a texture region in which irregularities are formed while changing one gradation at a time.

(B-2) FIG. 11B
Compared with the gradation region in FIG. 11A, the BPF output Dbpf output from the bandpass filter 114 has the same amplitude, but is detected more frequently.

(B-3) FIG. 11C
The BPF output Dbpf is converted into an absolute value by the absolute value converter 116, and a frequency component detection value Df is output. Compared with the gradation region in FIG. 11A, the frequency component detection value Df is comparable, but the frequency of detection is high.

(B-4) FIG. 11 (d)
In the detection value smoothing unit 110, the average value of the frequency component detection values Df in the smooth region is calculated for each corresponding pixel, and the average detection value Dave is output. In addition, the average detection value Dave is a relatively larger value than the threshold value TH.

(B-5) FIG. 11 (e)
By performing threshold processing in the control signal generation unit 112, the control signal Dc is output. Since the average detection value Dave shown in FIG. 11D is larger than the threshold value TH, the control signal Dc indicates “0” representing an area other than the gradation area.

(B-6) FIG. 11 (f)
Since the control signal Dc shown in FIG. 11E is “0” indicating a region other than the gradation region, the gradation number expanding unit 106 adds a k-bit fixed value to the lower order of the input image signal Di and adds N + k The output image signal Do converted into bits is output.

  As shown in FIG. 11, in the texture region, the output image signal Do converted to N + k bits by adding a k-bit fixed value to the lower order of the input image signal Di is output, so that the unevenness change is not impaired. . Therefore, blurring of the image can be prevented.

[C] Edge region ((3) in FIG. 11)
(C-1) FIG.
As an example of the input image signal Di, an edge region that changes sharply is given.

(C-2) FIG. 11 (b)
The BPF output Dbpf output from the bandpass filter 114 has a range in amplitude.

(C-3) FIG. 11 (c)
The BPF output Dbpf is converted into an absolute value by the absolute value converter 116, and a frequency component detection value Df is output. Compared with the gradation area of FIG. 11 (1) and the texture area of FIG. 11 (2), the frequency component detection value Df is very large.

(C-4) FIG. 11 (d)
In the detection value smoothing unit 110, the average value of the frequency component detection values Df in the smooth region is calculated for each corresponding pixel, and the average detection value Dave is output. The average detection value Dave is sufficiently larger than the threshold value TH in the vicinity of the edge.

(C-5) FIG. 11 (e)
By performing threshold processing in the control signal generation unit 112, the control signal Dc is output. Since the average detection value Dave shown in FIG. 11D is larger than the threshold value TH in the area near the edge, the control signal Dc indicates “0” representing an area other than the gradation area. In the region far from the vicinity of the edge, the average detection value Dave shown in FIG. 11D is smaller than the threshold value TH, so the control signal Dc indicates “1” representing the gradation region.

(C-6) FIG. 11 (f)
In the region near the edge, since the control signal Dc shown in FIG. 11E is “0” indicating a region other than the gradation region, the gradation number expanding unit 106 fixes k bits below the input image signal Di. An output image signal Do converted to N + k bits by adding a value is output. In the region far from the vicinity of the edge, the control signal Dc shown in FIG. 11E is “1” indicating the gradation region, so that the gradation number expanding unit 106 performs the smoothed N + k-bit output image signal Do. Is output. Since the output image signal Do has an accuracy of N + k bits, the image changes more smoothly than the N-bit input image signal Di, but the sharpness of the edge is dull.

  As shown in FIG. 11, in the edge region, the image is not smoothed in the vicinity of the edge, and the image is smoothed and smoothed in a region with a small change other than in the vicinity of the edge.

  Based on the input input image signal Di, the image processing unit 100 generates an output image signal Do suitable for preventing degradation in image quality for each of the gradation area, texture area, and edge area, as shown in FIG. Can be output.

[Signal when the image processing unit does not include a detection value smoothing unit]
Next, as a comparative example of FIG. 11, when the image processing unit does not include the detection value smoothing unit, that is, when the threshold value processing is performed on the frequency component detection value Df, [I] the threshold value TH is large. , [II] Each case where the threshold value is small is shown.

[I] When Threshold TH is Large FIG. 12 is an explanatory diagram illustrating a first example of a signal when the image processing unit does not include a detection value smoothing unit. Here, FIG. 12A shows the frequency component detection value Df, and FIG. 12B shows the control signal Dc.

  Referring to FIG. 12A, as described above, the frequency component detection value Df is a small value of the same degree in both the gradation area and the texture area. Here, as shown in FIG. 12A, when the threshold value TH is set slightly larger so that the frequency component detection value Df in the gradation region is lower than the threshold value TH, the frequency component detection value Df is lower than the threshold value TH in the texture region. Probability is high. At this time, as shown in FIG. 12B, the control signal Dc indicates “1” indicating the gradation region in both the gradation region and the texture region.

  Accordingly, the gradation number expanding unit 106 outputs the N + k-bit output image signal Do that has been smoothed for both the gradation region and the texture region. In the above case, since the smoothed output image signal Do is output also to the texture region, a change in the unevenness of the texture region is impaired, that is, the image is blurred.

  In the edge region, the frequency component detection value Df is sufficiently larger than the threshold value TH near the edge. Therefore, since the control signal Dc is “0” indicating an area other than the gradation area only in the vicinity of the edge, it is not smoothed in the vicinity of the edge, and the gradation area other than the edge is smoothly converted. That is, no particular problem occurs in the edge region.

[II] When Threshold TH is Small FIG. 13 is an explanatory diagram illustrating a second example of a signal when the image processing unit does not include a detection value smoothing unit. Here, FIG. 13A shows the frequency component detection value Df, and FIG. 13B shows the control signal Dc.

  As shown in FIG. 13A, when the threshold value TH is set slightly smaller so that the frequency component detection value Df in the gradation area exceeds the threshold value TH, there are places where the frequency component detection value Df exceeds the threshold value TH in the gradation area. Come. Here, the place where the frequency component detection value Df exceeds the threshold value TH means a place where the input image signal Di changes, but as shown in FIG. 13B, the control signal Dc is other than the gradation area. It becomes “0” indicating an area. Accordingly, there is a problem in that the portion where the input image signal Di changes is not smoothed, and the step-like change in the gradation area as shown in FIG. 11 (1) cannot be smoothed.

  Further, in the edge area, the control signal Dc is “0” indicating the area other than the gradation area even in the gradation area other than the vicinity of the edge.

  As shown in FIGS. 12 and 13, when the image processing unit does not include the detection value smoothing unit, a problem occurs in each of the gradation region, the texture region, and the edge region.

  On the other hand, the image processing unit 100 according to the first embodiment of the present invention includes the detection value smoothing unit 110 and performs the detection value smoothing process, whereby a gradation region and a region other than the gradation region (texture region) And edge regions). In particular, since the image processing unit 100 can accurately discriminate between the texture area and the gradation area, it is possible to prevent image quality deterioration such as a reduction in sharpness due to erroneous smoothing of the texture area.

  As described above, the display apparatus 1000 according to the first embodiment of the present invention includes the image processing unit 100 that corrects the N-bit input image signal Di to the N + k-bit output image signal Do, and the N + k-bit gradation performance. And a display unit 190 having. The image processing unit 100 includes a smooth region detection unit 102, a tap length adjustment unit 104, and a gradation number expansion unit 106. The smooth region detection unit 102 determines the gradation region for each pixel based on the input image signal Di and outputs a control signal Dc. The tap length adjustment unit 104 determines the tap length of the smoothing filter based on the control signal Dc. An adjustment signal Dtp to be adjusted is output for each pixel. Then, the gradation number expanding unit 106 adjusts the tap length of the smoothing filter according to the adjustment signal Dtp, selectively smoothes the input image signal Di based on the control signal Dc, and outputs an N + k-bit output image signal. Do is output. Therefore, the display apparatus 1000 determines a gradation region based on the input image signal, and selectively smoothes the image signal by changing the tap length of the smoothing filter in accordance with the determination result. Can be converted into an image signal having a large number of gradations and displayed.

  In addition, since the display apparatus 1000 determines the gradation area and selectively corrects the gradation area more smoothly, the gradation performance of the gradation area can be improved. In addition, since the display apparatus 1000 does not smooth the input image signal Di in the edge region or the texture region, the image indicated by the output image signal Do does not lose sharpness.

  In general, when the gradation performance is insufficient, the image quality deterioration such as a false contour is generated visually in the gradation area, and the image quality deterioration is observed in the edge area and the texture area. Inconspicuous. Since the display device 1000 selectively improves the gradation performance of the gradation area, it is possible to visually obtain the same effect as the gradation performance is improved on the entire image.

  The display apparatus 1000 detects a signal (BPF output Dbpf) in a predetermined frequency band, and performs threshold processing based on the result of smoothing the detection value in a predetermined smooth region. Accordingly, the display device 1000 can accurately discriminate between the texture area and the gradation area, and can prevent image quality deterioration such as a reduction in sharpness due to erroneous smoothing of the texture area.

  Furthermore, the display apparatus 1000 adjusts the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation area in accordance with the smoothing area that corresponds to the smoothing area (corresponding to the gradation area). Can be adjusted. Therefore, since the first problem and the second problem described above do not occur in the display device 1000, the display device 1000 can effectively prevent the occurrence of false contours, and does not cause deterioration in image quality due to smoothing. .

[Modification of Display Device 1000]
[First Modification]
In the above, as the display apparatus 1000 according to the first embodiment, the configuration in which the frequency component detection unit 108 includes one bandpass filter 114 and outputs the frequency component detection value Df as illustrated in FIG. . However, the frequency component detection unit according to the first embodiment of the present invention is not limited to the configuration of FIG. 3, and may be configured to include a plurality of bandpass filters.

  FIG. 14 is a block diagram illustrating a frequency component detection unit according to a first modification of the first embodiment of the present invention. FIG. 14 shows an example of a configuration including two bandpass filters. However, a modification of the frequency component detection unit according to the first embodiment of the present invention includes two bandpass filters. Needless to say, the configuration is not limited.

  Referring to FIG. 14, the frequency component detector according to the first modification includes a first bandpass filter 114a, a first coefficient multiplier 118a, a first absolute value converter 116a, A band-pass filter 114b, a second coefficient multiplier 118b, a second absolute value converter 116b, and a maximum value selector 120 are provided.

  The input image signal Di is input to the first bandpass filter 114a, and the BPF output Dbpf1 is output based on the frequency characteristics having the peak at the frequency f1.

  The first coefficient multiplier 118a multiplies the BPF output Dbpf1 by a predetermined coefficient K1 and outputs a weighted BPF output Dk1. Here, the information on the coefficient K1 used for multiplication by the first coefficient multiplication unit 118a is stored in, for example, a storage unit included in the image processing unit 100, and is input from the storage unit, but is not limited thereto. For example, the information on the coefficient K1 can be held by the first coefficient multiplication unit 118a with a storage unit, and is stored in a storage unit (not shown) of the display device, and the first coefficient multiplication unit 118a. Can be appropriately read from the storage unit (not shown).

  The first absolute value converter 116a calculates the absolute value of the weighted BPF output Dk1 and outputs the first frequency component detected value Df1.

  The second band pass filter 114b receives the input image signal Di and outputs a BPF output Dbpf2 based on the frequency characteristic having the peak at the frequency f2. The second coefficient multiplication unit 118b multiplies the BPF output Dbpf2 by a predetermined coefficient K2 and outputs a weighted BPF output Dk2, and the second absolute value conversion unit 116b outputs the weighted BPF output Dk2. The absolute value is calculated and the second frequency component detection value Df2 is output. Here, the information on the coefficient K2 used for multiplication by the second coefficient multiplier 118b is stored in, for example, a storage unit included in the image processing unit 100, similarly to the coefficient K1 used for multiplication by the first coefficient multiplier 118a. However, it is not limited to the above.

  The maximum value selection unit 120 selects the larger one of the frequency component detection values Df1 and Df2 for each corresponding pixel, and outputs the selected value as the frequency component detection value Df.

  Here, the significance of the frequency component detection unit according to the first modification taking the configuration of FIG. 14 will be described. FIG. 15 is an explanatory diagram for explaining a frequency component detection unit according to a first modification of the first embodiment of the present invention. FIG. 15 shows an example in which the coefficient K1 = 1 and the coefficient K2 = 0.5 are shown, but the values of the coefficients K1 and K2 are not limited to the above.

  FB shown in FIG. 15 is a band of main frequency components included in a large amount in the texture region, and the first bandpass filter 114a is set so that the main frequency component in the texture region becomes the frequency f1. Here, the first band-pass filter 114a has a characteristic that peaks at the frequency f1, but the first band-pass filter 114a alone cannot cover the entire range of the frequency band FB. For example, when the texture region includes many components near the frequency f2, the BPF output Dbpf1 takes a value almost close to 0 (zero), and the frequency component detection value Df is almost 0 (zero). There is a risk of erroneous detection as a gradation area.

  Dk1 shown in FIG. 15 indicates a characteristic obtained by multiplying the BPF output Dbpf1 by a coefficient K1 = 1, and Dk2 indicates a characteristic obtained by multiplying the BPF output Dbpf2 by a coefficient K2 = 0.5. By selecting the maximum value of the first frequency component detection value Df1 and the second frequency component detection value Df2 obtained by converting Dk1 and Dk2 into absolute values, the first frequency component detection value Df1 is selected in the vicinity of the frequency f1, and the frequency f2 In the vicinity, the second frequency component detection value Df2 is selected.

  Therefore, the entire band FB can be covered by using a plurality of bandpass filters having different frequency characteristics as shown in FIG.

  The display device according to the first modification of the first embodiment of the present invention is different in frequency component detection unit from the frequency component detection unit 108 shown in FIG. 3, but the frequency component is based on the input image signal Di. The detection value Df can be output. Further, the other configuration of the display device according to the first modification is the same as that of the display device 1000 according to the first embodiment. Therefore, the display device according to the first modification can achieve the same effect as the display device 1000 according to the first embodiment described above.

[Second Modification]
Moreover, the frequency component detection part which concerns on the 1st Embodiment of this invention is not restricted to the structure shown in FIG. 3, FIG. FIG. 16 is a block diagram illustrating a frequency component detection unit according to a second modification of the first embodiment of the present invention.

  Referring to FIG. 16, the frequency component detection unit according to the second modification basically has the same configuration as the frequency component detection unit according to the first modification shown in FIG. The selection unit 120 is replaced with an addition unit 122.

  The adder 122 adds the first frequency component detection value Df1 and the second frequency component detection value Df2 for each corresponding pixel, and outputs a frequency component detection value Df (= Df1 + Df2). At this time, the ratio of the first frequency component detection value Df1 to the frequency component detection value Df is high near the frequency f1, and the ratio of the second frequency component detection value Df2 to the frequency component detection value Df is high near the frequency f2. Therefore, even in the above case, the frequency component detection value Df can be output satisfactorily over the entire band FB shown in FIG.

  The display device according to the second modification of the first embodiment of the present invention differs from the frequency component detection unit 108 shown in FIG. 3 in the configuration of the frequency component detection unit, but the first modification shown in FIG. Similarly to the frequency component detection unit according to the above, the frequency component detection value Df can be output based on the input image signal Di. In addition, the other configuration of the display device according to the second modification is the same as that of the display device 1000 according to the first embodiment. Therefore, the display device according to the second modification can achieve the same effect as the display device 1000 according to the first embodiment described above.

[Third Modification]
In the above description, the processing in the horizontal direction has been described as an example of the display device according to the first embodiment and the first and second modifications, but the image of the display device according to the first embodiment of the present invention is described. The processing performed by the processing unit is not limited to horizontal processing. Therefore, a configuration in which the image processing unit sequentially performs processing in the horizontal direction and the vertical direction will be described as a display device according to a third modification of the first embodiment of the present invention.

  FIG. 17 is a block diagram showing a display device 1500 according to a third modification of the first embodiment of the present invention. Referring to FIG. 17, the display device 1500 includes an image processing unit 150 and a display unit 190. Here, the display unit 190 has the same configuration as the display unit 190 illustrated in FIG. 1 and has N + k-bit gradation performance.

  The image processing unit 150 includes a horizontal smoothing region detection unit 102h, a tap length adjustment unit 104h, a horizontal gradation number expansion unit 106h, a vertical smoothing region detection unit 102v, a tap length adjustment unit 104v, and a vertical gradation number expansion. Unit 106v.

  The horizontal smooth region detection unit 102h outputs a horizontal control signal Dhc indicating whether or not the pixel is a horizontal gradation region for each pixel based on the input image signal Di input. Here, the horizontal smoothing area detection unit 102h can output the horizontal control signal Dhc, for example, by adopting the same configuration as the smoothing area detection unit 102 shown in FIG.

  The tap length adjustment unit 104h outputs the adjustment signal Dtp for each pixel based on the horizontal control signal Dhc output from the horizontal smooth region detection unit 102h. Here, the tap length adjusting unit 104h can output the adjustment signal Dtp by adopting the same configuration as the tap length adjusting unit 104 shown in FIG.

  The horizontal tone number expansion unit 106h adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and selectively smoothes the image in the horizontal direction for each corresponding pixel based on the horizontal control signal Dhc to obtain N + k bits. The image signal Dho is output. Here, the gradation performance of the image signal Dho is improved in the horizontal direction, but the gradation performance is not improved in the vertical direction, and is equivalent to the input image signal Di. Further, the horizontal gradation number expanding unit 106h can output the image signal Dho by adopting the same configuration as the gradation number expanding unit 106 shown in FIG.

  Based on the input image signal Dho, the vertical smooth region detection unit 102v outputs a vertical control signal Dvc indicating whether or not the pixel is a vertical gradation region for each pixel. Here, the vertical smooth region detection unit 102v can output the vertical control signal Dvc, for example, by adopting the same configuration as the smooth region detection unit 102 shown in FIG.

  The tap length adjustment unit 104v outputs the adjustment signal Dtp for each pixel based on the horizontal control signal Dvc output from the horizontal smooth region detection unit 102v. Here, the tap length adjusting unit 104v can output the adjustment signal Dtp by adopting the same configuration as the tap length adjusting unit 104 shown in FIG.

  The vertical tone number expansion unit 106v adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and selectively smoothes the image in the vertical direction for each corresponding pixel based on the vertical control signal Dvc, thereby N + k bits. The output image signal Do is output. Here, the output image signal Do has improved gradation performance in the vertical direction in addition to the horizontal direction. Further, the vertical gradation number expanding unit 106v can output the output image signal Do by adopting the same configuration as the gradation number expanding unit 106 shown in FIG.

  As illustrated in FIG. 17, by sequentially executing the horizontal processing and the vertical processing, the display device 1500 according to the third modified example allows the texture region and the edge region in both the horizontal direction and the vertical direction. The gradation performance of the gradation area can be improved without impairing the sharpness of the image.

  Further, since the display device 1500 according to the third modification can perform the horizontal processing and the vertical processing in the same manner as the display device 1000 according to the first embodiment, the first implementation described above. The same effect as the display device 1000 according to the embodiment can be obtained.

  In the above description, the display device 1500 according to the third modification example is configured such that the image processing unit 150 sequentially executes horizontal processing and vertical processing, but the first embodiment of the present invention. The display device according to is not limited to the above. For example, the display device according to the first embodiment can also execute the horizontal direction and the vertical direction in a batch by two-dimensional processing. Even with such a configuration, as in the display device according to the third modification, the gradation performance of the gradation area is improved without deteriorating the sharpness of the texture area and the edge area in both the horizontal direction and the vertical direction. Can be made.

  Further, in the display device according to the third modification of the first embodiment, the tap length adjusting unit 104h and the tap length adjusting unit 104v illustrated in FIG. 17 can be configured as an integral part.

(Image processing apparatus according to the first embodiment)
In the above, the display device according to the first embodiment has been described. However, the image processing unit included in the display device according to the first embodiment described above (including modifications) is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the first embodiment)
[Programs related to display devices]
The program for causing the display device according to the first embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and receives the input image signal Can be converted into an image signal having a larger number of gradations.

[Program for image processing apparatus]
An image that is selectively smoothed by determining a gradation area based on an input image signal and selectively smoothing the image signal by a program for causing the image processing apparatus according to the first embodiment of the present invention to function as a computer It can be converted into an image signal having a larger number of gradations than the signal.

(Image processing method according to the first embodiment)
Next, an image processing method according to the first embodiment of the present invention will be described. FIG. 18 is a flowchart showing an example of an image processing method according to the first embodiment of the present invention. In the following description, the image processing method shown in FIG. 18 is described as being performed by the display device 1000, but it goes without saying that the image processing method can be applied to the image processing device according to the first embodiment of the present invention.

  The display apparatus 1000 detects a predetermined frequency component for each pixel from the N-bit input image signal Di (S100). The detection in step S100 can be performed using, for example, one or a plurality of bandpass filters.

  The display apparatus 1000 smoothes the detection value (frequency component detection value Df) detected in step S100 (S102), and generates the control signal Dc based on the smoothed detection value (average detection value Dave) (S104). ).

  The display apparatus 1000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S104 (S106). The display device 1000 can generate, for example, a signal that defines the tap length and a signal that defines the adjustment amount of the tap length as the adjustment signal Dtp, but is not limited thereto.

  The display apparatus 1000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S106, and selectively selects the input image signal Di for each pixel based on the control signal Dc generated in step S104. Smoothing and outputting an N + k-bit image signal (output image signal Do) (S108).

  By using the image processing method shown in FIG. 18, the display apparatus 1000 determines a gradation area based on an input image signal, and selectively changes the tap length of the smoothing filter according to the determination result to selectively output the image signal. Can be converted into an image signal having a larger number of gradations than the input image signal.

(Second Embodiment)
In the above description, as the display device according to the first embodiment, the smooth region detection unit 102 of the image processing unit 100 includes the frequency component detection unit 108, the detection value smoothing unit 110, and the control signal generation unit 112. A configuration for outputting Dc is shown. However, the configuration of the image processing unit of the display device according to the embodiment of the present invention is not limited to the above. Therefore, as a display device according to the second embodiment, a configuration in which the generation unit of the control signal Dc includes an image processing unit different from the image processing unit 100 according to the first embodiment will be described.

  FIG. 19 is a block diagram showing a display device 2000 according to the second embodiment of the present invention. Referring to FIG. 19, the display device 2000 includes an image processing unit 200 and a display unit 190.

  The image processing unit 200 includes a smooth region detection unit 202, a tap length adjustment unit 104, and a gradation number expansion unit 106, and converts the input N-bit input image signal Di into an N + k-bit output image signal Do. And output.

  The display unit 190 has N + k bit gradation performance like the display unit 190 according to the first embodiment shown in FIG. 1, and displays an image based on the N + k bit output image signal Do. Hereinafter, the configuration of the image processing unit 200 will be specifically described.

[Configuration Example of Image Processing Unit 200]
FIG. 20 is a block diagram showing an image processing unit 200 according to the second embodiment of the present invention. Referring to FIG. 20, the image processing unit 200 includes a smooth region detection unit 202, a tap length adjustment unit 104, and a gradation number expansion unit 106.

[Smooth area detection unit 202]
The smooth region detection unit 202 includes an inter-pixel difference value detection unit 204 and a smooth region determination unit 206.

  The inter-pixel difference value detection unit 204 detects the inter-pixel difference value Dd based on the input image signal Di. FIG. 21 is an explanatory diagram illustrating a detection method of the difference value Dd in the inter-pixel difference value detection unit 204 according to the second embodiment of the present invention.

  As illustrated in FIG. 21, for example, the inter-pixel difference value detection unit 204 subtracts an input image signal Di corresponding to another pixel from an input image signal Di corresponding to one pixel for two adjacent pixels. Thus, the difference value Dd can be detected. Note that the detection method of the difference value Dd in the inter-pixel difference value detection unit according to the second embodiment of the present invention is not limited to the above.

  The inter-pixel difference value detection unit 204 can detect the difference value Dd from the input image signal Di corresponding to the pixels arranged in the horizontal direction, for example, but is not limited thereto. For example, the inter-pixel difference value detection unit 204 can detect the difference value Dd using the input image signal Di corresponding to pixels arranged in various directions such as a vertical direction or an oblique direction.

  The smooth region determination unit 206 determines a smooth region to be smoothed, that is, a gradation region, based on the difference value Dd detected by the inter-pixel difference value detection unit 204, and outputs a control signal Dc according to the determination result. . FIG. 22 is an explanatory diagram illustrating a method of outputting the control signal Dc in the smooth region determination unit 206 according to the second embodiment of the present invention.

  For example, the smooth region determination unit 206 determines a monotonically increasing region or a monotonically decreasing region using the sign of the difference value Dd, and determines a region where the monotonically increasing region or the monotonically decreasing region is a predetermined size or more as a gradation region. Is determined. Then, the smooth region determination unit 206 outputs a control signal Dc according to the determination result.

  As shown in FIG. 22A, the smooth region determination unit 206, for example, “1” indicating a gradation region when the number of consecutive identical symbols in the difference value Dd detected by the inter-pixel difference value detection unit 204 is larger than the threshold value TH2. ”Is output as the control signal Dc, and when the number of consecutive identical signs in the difference value Dd is equal to or less than the threshold value TH2,“ 0 ”indicating a texture region or an edge region, that is, other than the gradation region is output as the control signal Dc. Here, for example, when the difference value Dd is “0”, the smooth region determination unit 206 can handle “0” as a gradation region. More specifically, for example, the smooth region determining unit 206 determines that “0” is monotonically increasing (when the positive sign of the difference value Dd is continuous) and is monotonically decreasing ( “0” in the case where the negative sign of the difference value Dd continues) is determined as a monotonic decrease. In addition, the smooth region determination unit 206, for example, when “0” continues after it is determined as an edge region or a texture region (other than a gradation region), or when “0” continues immediately after the determination is started, It is determined as monotonic increase or monotonic decrease (whether it is monotonic increase or monotonous decrease is determined by, for example, the sign of the difference value Dd when the difference value Dd changes from “0”). Needless to say, the case where the value of the difference value Dd in the smooth region determination unit 206 is “0” is not limited to the above.

  By determining as described above, the smooth region determining unit 206 determines a gradation region and a texture region having a large number of irregularities as shown in FIG. 11B, for example, and a control signal Dc corresponding to the determination result. Can be output.

  In addition, the smooth region determination unit 206 can perform the above determination by allowing a certain number of code changes of the difference value Dd in order to prevent erroneous determination that may be caused by a code change of the difference value Dd due to noise or the like. . For example, as shown in FIG. 22B, the smooth region determination unit 206 allows the code change when the number of code changes in the difference value Dd detected by the inter-pixel difference value detection unit 204 is smaller than the threshold value TH3. Is output, and when the number of code changes in the difference value Dd is equal to or greater than the threshold value TH3, an allowable determination value indicating “0” that does not allow code change is output. The smooth region determination unit 206 ignores the change of the sign when the allowable determination value indicates “1”, even if the sign of the difference value Dd changes, and the same sign continues. And handle. Therefore, the smooth region determination unit 206 can prevent erroneous determination that may occur due to noise or the like.

  Furthermore, in order to exclude that the edge area as shown in FIG. 11C, for example, is determined as a gradation area, the smooth area determination unit 206 has a difference value Dd whose absolute value of the difference value Dd is smaller than a predetermined value. Can be determined as a gradation region determination target. For example, as shown in FIG. 22 (c), the smooth region determination unit 206 validates the determination based on the sign of the difference value Dd when the absolute value of the difference value Dd detected by the inter-pixel difference value detection unit 204 is smaller than the threshold value TH4. A determination exclusion value indicating “0” is output. When the absolute value of the difference value Dd is equal to or greater than the threshold value TH4, a determination exclusion value indicating “1” that invalidates the determination based on the sign of the difference value Dd is output. Then, even if the smooth region determination unit 206 determines that the determination by the sign of the difference value Dd is monotonic increase or monotonic decrease, if the determination exclusion value indicates “1”, the smooth region determination unit 206 It is not judged as a decrease. Therefore, the smooth area determination unit 206 can prevent the edge area from being determined as a gradation area.

  Here, the information on the thresholds TH2 to TH4 used by the smooth region determination unit 206 is stored in, for example, a storage unit included in the image processing unit 200, and is input from the storage unit to the smooth region determination unit 206. Examples of the storage means included in the image processing unit 200 include non-volatile memories such as an EEPROM and a flash memory, but are not limited thereto. Note that the information on the thresholds TH2 to TH4 can be held, for example, by the smooth region determination unit 206 having a storage unit, and is stored in a storage unit (not shown) of the display device 2000, and the smooth region determination unit It goes without saying that 206 may appropriately read from the storage unit (not shown).

  The smooth region determination unit 206 determines the gradation region and regions other than the gradation region (texture region and edge region) by using the sign and absolute value of the difference value Dd as described above, and according to the determination result. A control signal Dc can be output. In addition, the smooth area determination unit 206 appropriately combines the determination illustrated in FIG. 22A and the determination illustrated in FIGS. 22B and 22C to allow an exception and allow a gradation area and a gradation area. Regions other than (texture region and edge region) can be discriminated.

  The smooth region detection unit 202 includes the inter-pixel difference value detection unit 204 and the smooth region determination unit 206, so that the gradation region can be determined for each pixel based on the input image signal Di.

  The tap length adjustment unit 104 has the same configuration as that of the tap length adjustment unit 104 according to the first embodiment shown in FIG. 1, and based on the control signal Dc output from the smooth region detection unit 202, the adjustment signal Dtp. Is output for each pixel.

  The gradation number expansion unit 106 has the same configuration as the gradation number expansion unit 106 according to the first embodiment shown in FIG. 1, adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and controls the control signal. Based on Dc, the input image signal Di is selectively smoothed for each corresponding pixel to output an N + k-bit output image signal Do.

  The image processing unit 200 includes the smooth region detection unit 202, the tap length adjustment unit 104, and the gradation number expansion unit 106, thereby determining the gradation region for each pixel based on the input image signal Di, and the determination result. Accordingly, smoothing can be performed selectively and an output image signal Do of N + k bits can be output.

  As described above, the display device 2000 according to the second embodiment of the present invention includes the image processing unit 200 that corrects the N-bit input image signal Di to the N + k-bit output image signal Do, and the N + k-bit gradation performance. And a display unit 190 having. The image processing unit 200 includes a smooth region detection unit 202, a tap length adjustment unit 104 and a gradation number expansion unit 106 having the same configuration as the tap length adjustment unit 104 and the gradation number expansion unit 106 according to the first embodiment. With. The smooth region detection unit 202 determines the gradation region for each pixel based on the input image signal Di and outputs a control signal Dc. The tap length adjustment unit 104 adjusts the tap length of the smoothing filter based on the control signal Dc. The adjustment signal Dtp is output for each pixel. Then, the gradation number expanding unit 106 adjusts the tap length of the smoothing filter according to the adjustment signal Dtp, selectively smoothes the input image signal Di based on the control signal Dc, and outputs an N + k-bit output image signal. Do is output. Therefore, the display device 2000 determines the gradation region based on the input image signal, and varies the tap length of the smoothing filter in accordance with the determination result, and selectively smoothes the image signal from the input image signal. Can be converted into an image signal having a large number of gradations and displayed.

  In addition, since the display device 2000 determines the gradation area and selectively corrects the gradation area more smoothly, the gradation performance of the gradation area can be improved. In addition, since the display device 2000 does not smooth the input image signal in the edge region or the texture region, the image indicated by the output image signal Do does not lose sharpness.

  In addition, since the display device 2000 selectively improves the gradation performance of the gradation area, the gradation performance is visually improved over the entire image as in the display device 1000 according to the first embodiment. Similar effects can be obtained.

  Further, the display device 2000 smoothes the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation area, similarly to the display device 1000 according to the first embodiment. It can be adjusted according to the smoothing area (corresponding to the gradation area). Therefore, since the first problem and the second problem described above do not occur in the display device 2000, the display device 2000 can effectively prevent the occurrence of false contours, and does not cause deterioration in image quality due to smoothing. .

(Image processing apparatus according to the second embodiment)
In the above, the display device according to the second embodiment has been described. However, the image processing unit included in the display device according to the second embodiment described above (including modifications) is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the second embodiment)
[Programs related to display devices]
The program for causing the display device according to the second embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and receives the input image signal Can be converted into an image signal having a larger number of gradations.

[Program for image processing apparatus]
A program for causing an image processing apparatus according to the second embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and inputs an image It can be converted into an image signal having a larger number of gradations than the signal.

(Image processing method according to the second embodiment)
Next, an image processing method according to the second embodiment of the present invention will be described. FIG. 23 is a flowchart showing an example of an image processing method according to the second embodiment of the present invention. In the following, the image processing method shown in FIG. 23 is described as being performed by the display device 2000, but it goes without saying that the image processing method can be applied to the image processing device according to the second embodiment of the present invention.

  The display device 2000 detects the difference value Dd between the pixels based on the N-bit input image signal Di (S200). Then, the display device 2000 determines a gradation area based on the difference value Dd detected in step S200, and generates a control signal Dc corresponding to the determination result (S202). The display device 2000 can determine the gradation area using, for example, the sign of the difference value Dd and the absolute value.

  The display device 2000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S202, similarly to step S106 shown in FIG. 18 (S204).

  The display device 2000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S204, and performs input based on the control signal Dc generated in step S202, similarly to step S108 shown in FIG. The image signal Di is selectively smoothed for each pixel and an N + k-bit image signal (output image signal Do) is output (S206).

  By using the image processing method shown in FIG. 23, the display apparatus 2000 determines a gradation area based on an input image signal, and selectively changes the tap length of the smoothing filter according to the determination result to selectively output the image signal. Can be converted into an image signal having a larger number of gradations than the input image signal.

(Third embodiment)
In the above description, the display device according to the first and second embodiments has been configured to perform monochrome image processing or processing for one channel among a plurality of channels of a color image. However, the display device according to the embodiment of the present invention is not limited to the above configuration. Accordingly, a configuration for processing a plurality of channels of a color image will be described next as a display device according to the third embodiment. In the following, red (hereinafter referred to as “R”), green (hereinafter referred to as “G”), and blue (hereinafter referred to as “B”) image signals are input as a plurality of channels of a color image. An example is shown.

  FIG. 24 is a block diagram showing a display device 3000 according to the second embodiment of the present invention. Referring to FIG. 24, the display device 3000 includes an image processing unit 300 and a display unit 190. The image processing unit 300 includes a smooth region detection unit 302, a tap length adjustment unit 104, a tone number expansion unit 304, and the like. Is provided.

  The image processing unit 300 receives N-bit R / G / B input image signals Ri, Gi, Bi, respectively, and converts them into N + k-bit output image signals Ro, Go, Bo for output. The display unit 190 has N + k-bit gradation performance like the display unit 190 according to the first embodiment shown in FIG. 1, and displays an image based on the N + k-bit output image signals Ro, Go, and Bo. indicate. Hereinafter, the configuration of the image processing unit 300 will be specifically described.

[Configuration Example of Image Processing Unit 300]
FIG. 25 is a block diagram showing an image processing unit 300 according to the third embodiment of the present invention. Referring to FIG. 25, the image processing unit 300 includes a smooth region detection unit 302, a tap length adjustment unit 104, and a gradation number expansion unit 304.

[Smooth area detection unit 302]
The smooth region detector 302 includes a first frequency component detector 108a, a second frequency component detector 108b, a third frequency component detector 108c, a maximum value selector 306, and a detected value smoother 110. And a control signal generation unit 112. In addition, the gradation number expansion unit 304 includes a first gradation number expansion unit 304a, a second gradation number expansion unit 304b, and a third gradation number expansion unit 304c.

  The input image signal Ri is input to the first frequency component detector 108a, the input image signal Gi is input to the second frequency component detector 108b, and the input image signal Bi is input to the third frequency component detector 108c. Is done. Here, each of the first frequency component detection unit 108a to the third frequency component detection unit 108c can have the same configuration as the frequency component detection unit 108 according to the first embodiment shown in FIG. Therefore, the first frequency component detection unit 108a detects a predetermined frequency component from the input image signal Ri and outputs the frequency component detection value Rf. Similarly, the second frequency component detection unit 108b detects the frequency component detection value. Gf, the third frequency component detection unit 108c can output the frequency component detection value Bf.

  The maximum value selection unit 306 selects the maximum value for each corresponding pixel from the frequency component detection values Rf, Gf, and Bf, and outputs the maximum detection value Dmax.

  Similar to the detection value smoothing unit 110 according to the first embodiment shown in FIG. 2, the detection value smoothing unit 110 calculates the average value of the maximum detection values Dmax in the smooth region and outputs the average detection value Dave.

  Similar to the control signal generation unit 112 according to the first embodiment illustrated in FIG. 2, the control signal generation unit 112 determines the gradation region by threshold processing using the average detection value Dave and the threshold TH, and controls the determination result. Output as signal Dc.

[Tap length adjustment unit 104]
The tap length adjustment unit 104 has the same configuration as the tap length adjustment unit 104 according to the first embodiment shown in FIG. 1, and the adjustment signal Dtp based on the control signal Dc output from the control signal generation unit 112. Is output for each pixel.

[Gradation number expansion unit 304]
Each of the first gradation number expansion unit 304a, the second gradation number expansion unit 304b, and the third gradation number expansion unit 304c is a gradation number expansion unit 106 according to the first embodiment shown in FIG. It has the same configuration as. Therefore, the first gradation number expanding unit 304a adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and selectively smoothes the input image signal Ri for each corresponding pixel based on the control signal Dc. Thus, an output image signal Do of N + k bits can be output. Similarly, the second gradation number expanding section 304b and the third gradation number expanding section 304c can output the output image signals Go and Bo, respectively.

  As described above, the image processing unit 300 can output the output image signals Ro, Go, and Bo with the configuration of FIG.

  Next, the significance of using the maximum value of the R / G / B frequency component detection result by the image processing unit 300 will be described. FIG. 26 is an explanatory diagram illustrating an example of each signal in the image processing unit 300 according to the third embodiment of the present invention. Here, FIG. 26 shows an example of each signal in the texture region. In a texture area in a color image, the R / G / B image signals of the three colors do not always change at the same frequency, but rather, the frequency of change is generally different between R / G / B. is there.

  FIGS. 26A to 26C show the input image signals Ri, Gi, and Bi, respectively. FIGS. 26D to 26F show frequency component detection values Rf, Gf, and Bf, respectively. Here, since the input image signal Ri in FIG. 26A is relatively uneven, the frequency component detection value Rf in FIG. 26D is detected at a relatively high frequency. Also, since the input image signals Gi and Bi in FIGS. 26B and 26C have little change, the detection of the frequency component detection value Gf in FIG. 26E and the frequency component detection value Bf in FIG. The frequency is low.

  FIG. 26G shows the maximum detection value Dmax. Here, since the image processing unit 300 selects the maximum value of the frequency component detection values Rf, Gf, and Bf for each pixel, the maximum detection value Dmax is higher than that of the frequency component detection values Rf, Gf, and Bf alone. The frequency of detection increases.

  FIG. 26 (h) shows the average detection value Dave, and FIG. 26 (i) shows the control signal Dc. Here, since the detection frequency of the maximum detection value Dmax is high, the average detection value Dave takes a value larger than the threshold value TH, and the control signal Dc is “0” indicating an area other than the gradation area.

  Here, if the region is determined for each color without selecting the maximum value for the frequency component detection values Rf, Gf, and Bf, G and B with little change in the input image signal are used as gradation regions. It may be detected and the image may be smoothed. Even in the case of an image signal with little change such as the input image signals Gi and Bi shown in FIG. 26, since the width of the change in the image signal is small in the texture region, the contribution to the sharpness cannot be ignored. That is, in the texture region, the sharpness is lost by smoothing the input image signal with little change. The image processing unit 300 can prevent the occurrence of the above problem by using the maximum value of the R / G / B frequency component detection result.

  The image processing unit 300 performs smoothing of the detection value and threshold processing on the maximum value (maximum detection value Dmax) of the frequency component detection values Rf, Gf, and Bf, thereby detecting the gradation region without making a mistake with the texture region. can do. Therefore, it is possible to suppress image quality deterioration such as a reduction in sharpness caused by smoothing the texture region.

  As described above, the display device 3000 according to the third embodiment of the present invention receives a plurality of channels of input image signals Ri, Gi, Bi (N-bit input image signals) indicating a color image, respectively, by N + k bits. An image processing unit 300 that corrects the output image signals Ro, Go, and Bo, and a display unit 190 having a gradation performance of N + k bits are provided. The image processing unit 300 includes a smooth region detection unit 302, a tap length adjustment unit 104 having the same configuration as the tap length adjustment unit 104 according to the first embodiment, and a gradation number expansion unit 304. The smooth region detection unit 302 determines the gradation region for each pixel based on the input image signals Ri, Gi, Bi and outputs the control signal Dc. The tap length adjustment unit 104 determines the smoothing filter based on the control signal Dc. An adjustment signal Dtp for adjusting the tap length is output for each pixel. Then, the gradation number expanding unit 304 adjusts the tap length of the smoothing filter according to the adjustment signal Dtp, and selectively smoothes each of the input image signals Ri, Gi, Bi based on the control signal Dc to obtain N + k. Bit output image signals Ro, Go, Bo are output. Accordingly, the display device 3000 determines the gradation area based on the input image signal and selects the smoothing filter by changing the tap length of the smoothing filter according to the determination result, similarly to the display device 1000 according to the first embodiment. In addition, the image signal can be smoothed, converted into an image signal having a larger number of gradations than the input image signal, and displayed.

  Further, as with the display device 1000 according to the first embodiment, the display device 3000 can determine the gradation region and selectively correct the gradation region more smoothly, so that the gradation performance of the gradation region can be improved. Can be improved. In addition, since the display device 3000 does not correct the input image in the edge region or the texture region, the image indicated by the output image signals Ro, Go, and Bo does not lose sharpness.

  In addition, the display device 3000 selectively improves the gradation performance of the gradation area, similarly to the display device 1000 according to the first embodiment, so that the gradation performance is visually improved in the entire image. Similar effects can be obtained.

  Further, the display device 3000 smoothes the detection value and performs threshold processing on the maximum value (maximum detection value Dmax) of the frequency component detection values Rf, Gf, and Bf, so that the gradation region is not mistaken for the texture region. Can be detected. Therefore, the display device 3000 can suppress image quality deterioration such as a reduction in sharpness caused by smoothing the texture region.

  Further, the display device 3000 smoothes the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation area, similarly to the display device 1000 according to the first embodiment. It can be adjusted according to the smoothing area (corresponding to the gradation area). Accordingly, since the display device 3000 does not cause the first problem and the second problem described above, the display device 3000 can effectively prevent the occurrence of false contours, and does not cause a decrease in image quality due to smoothing. .

[Modification of Display Device 3000]
The display device according to the third embodiment can take a modification similar to the modification of the display device according to the first embodiment described above.

(Image processing apparatus according to the third embodiment)
In the above, the display device according to the third embodiment has been described. However, the image processing unit included in the display device (including the modification example) according to the third embodiment described above is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the third embodiment)
[Programs related to display devices]
The program for causing the display device according to the third embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and receives the input image signal Can be converted into an image signal having a larger number of gradations.

[Program for image processing apparatus]
A program for causing an image processing apparatus according to the third embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and inputs an image It can be converted into an image signal having a larger number of gradations than the signal.

(Image processing method according to the third embodiment)
Next, an image processing method according to the third embodiment of the present invention will be described. FIG. 27 is a flowchart showing an example of an image processing method according to the third embodiment of the present invention. In the following, the image processing method shown in FIG. 27 is described as being performed by the display device 3000, but the image processing method can also be applied to the image processing device according to the third embodiment of the present invention.

  The display device 3000 detects a predetermined frequency component for each pixel from each of the N-bit input image signals Ri, Gi, Bi (S300).

  The display device 3000 selects the maximum value for each pixel based on the detection values (frequency component detection values Rf, Gf, Bf) detected in step S300 (S302).

  The display device 3000 smoothes the maximum value (maximum value Dmax) selected in step S302 (S304), and generates a control signal Dc based on the smoothed detection value (average detection value Dave) (S306).

  The display device 3000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S306, similarly to step S106 in FIG. 18 (S308).

  The display device 3000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S308, and based on the control signal Dc generated in step S306, the input image signals Ri, Gi, Bi is selectively smoothed for each pixel and an N + k-bit image signal (output image signals Ro, Go, Bo) is output (S310).

  By using the image processing method shown in FIG. 27, the display device 3000 determines the gradation area based on the input image signal, and selectively changes the tap length of the smoothing filter according to the determination result to selectively output the image signal. Can be converted into an image signal having a larger number of gradations than the input image signal.

(Fourth embodiment)
In the above, as a display device that processes a plurality of channels of a color image, a gradation region is determined (a control signal Dc is generated) by a method similar to that of the display device 1000 according to the first embodiment (third embodiment). )showed that. However, the display device according to the embodiment of the present invention is not limited to the above. Then, next, the structure which determines a gradation area | region by the method similar to the display apparatus 2000 which concerns on 2nd Embodiment as a display apparatus which concerns on 4th Embodiment, and processes several channels of a color image is demonstrated.

  FIG. 28 is a block diagram showing a display device 4000 according to the fourth embodiment of the present invention. Referring to FIG. 28, the display device 4000 includes an image processing unit 400 and a display unit 190. The image processing unit 400 includes a smooth region detecting unit 402, a tap length adjusting unit 104, a gradation number expanding unit 304, and the like. Is provided.

  The image processing unit 400 receives N-bit R / G / B input image signals Ri, Gi, Bi, respectively, and converts them into N + k-bit output image signals Ro, Go, Bo for output. The display unit 190 has N + k-bit gradation performance like the display unit 190 according to the first embodiment shown in FIG. 1, and displays an image based on the N + k-bit output image signals Ro, Go, and Bo. indicate. Hereinafter, the configuration of the image processing unit 400 will be specifically described.

[Configuration Example of Image Processing Unit 400]
FIG. 29 is a block diagram showing an image processing unit 400 according to the fourth embodiment of the present invention. Referring to FIG. 29, the image processing unit 400 includes a smooth region detection unit 402, a tap length adjustment unit 104, and a gradation number expansion unit 304.

[Smooth area detection unit 402]
The smooth region detection unit 402 includes a first inter-pixel difference value detection unit 204a, a second inter-pixel difference value detection unit 204b, a third inter-pixel difference value detection unit 204c, and a first smooth region determination unit. 206 a, a second smooth region determination unit 206 b, a third smooth region determination unit 206 c, and a logical product operation unit 404.

  An input image signal Ri is input to the first inter-pixel difference value detection unit 204a, an input image signal Gi is input to the second inter-pixel difference value detection unit 204b, and an input to the third inter-pixel difference value detection unit 204c. Each of the image signals Bi is input. Here, each of the first inter-pixel difference value detector 204a to the third inter-pixel difference value detector 204c has the same configuration as the inter-pixel difference value detector 204 according to the second embodiment shown in FIG. Can take. Accordingly, the first inter-pixel difference value detection unit 204a outputs the difference value Dd1 based on the input image signal Ri, and similarly, the second inter-pixel difference value detection unit 204b includes the difference value Dd2 and the third pixel. The inter-difference value detection unit 204c can output the difference value Dd3.

  The difference value Dd1 is input to the first smooth region determination unit 206a, the difference value Dd2 is input to the second smooth region determination unit 206b, and the difference value Dd3 is input to the third smooth region determination unit 206c. Here, the first smooth region determination unit 206a to the third smooth region determination unit 206c can have the same configuration as the smooth region determination unit 206 according to the second embodiment shown in FIG. Therefore, the first smooth region determination unit 206a outputs the control signal Dc1 (determination signal) based on the difference value Dd1, and similarly, the second smooth region determination unit 206b outputs the control signal Dc2 (determination signal), 3 smooth region determination unit 206c can output control signal Dc3 (determination signal).

  The logical product operation unit 404 receives the control signals Dc1 to Dc3 output from the first smooth region determination unit 206a to the third smooth region determination unit 206c, and performs a logical product operation for each pixel. Then, the logical product operation unit 404 outputs the operation result as the control signal Dc. Therefore, the AND operation unit 404 outputs the control signal Dc indicating “1” when all of the control signals Dc1 to Dc3 are “1” indicating the gradation region. That is, the logical product operation unit 404 serves as a control signal output unit in the image processing unit 400.

  Here, the AND operation unit 404 can be configured by, for example, an AND circuit, but is not limited to the above, and can also be configured by an MPU. In addition, the image processing unit 400 includes the logical product calculation unit 404, so that the same effect as that of the image processing unit 300 according to the third embodiment includes the maximum value selection unit 306 can be obtained.

[Tap length adjustment unit 104]
The tap length adjustment unit 104 has the same configuration as the tap length adjustment unit 104 according to the first embodiment shown in FIG. 1, and the adjustment signal Dtp is based on the control signal Dc output from the AND operation unit 404. Is output for each pixel.

[Gradation number expansion unit 304]
The gradation number expansion unit 304 has the same configuration as the gradation number expansion unit 304 according to the third embodiment shown in FIG. Therefore, the first gradation number expanding unit 304a adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and selectively smoothes the input image signal Ri for each corresponding pixel based on the control signal Dc. Thus, an output image signal Do of N + k bits can be output. Similarly, the second gradation number expanding section 304b and the third gradation number expanding section 304c can output the output image signals Go and Bo, respectively.

  As described above, the image processing unit 400 can output the output image signals Ro, Go, and Bo with the configuration of FIG.

  As described above, the display device 4000 according to the fourth embodiment of the present invention receives a plurality of channels of input image signals Ri, Gi, and Bi (each N-bit input image signal) indicating a color image by N + k bits. An image processing unit 400 that corrects the output image signals Ro, Go, and Bo and a display unit 190 having N + k-bit gradation performance are provided. The image processing unit 400 includes a smooth region detecting unit 402, a tap length adjusting unit 104 having the same configuration as the tap length adjusting unit 104 according to the first embodiment, and a gradation number extending unit according to the second embodiment. And a gradation number expansion unit 304 having the same configuration as that of 304. The smooth region detection unit 402 uses the difference value as in the smooth region detection unit 202 according to the second embodiment to determine and control the gradation region for each pixel based on the input image signals Ri, Gi, Bi. The signal Dc is output. The tap length adjustment unit 104 outputs an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc. Then, the gradation number expanding unit 304 adjusts the tap length of the smoothing filter according to the adjustment signal Dtp, and selectively smoothes each of the input image signals Ri, Gi, Bi based on the control signal Dc to obtain N + k. Bit output image signals Ro, Go, Bo are output. Therefore, the display device 4000 determines the gradation area based on the input image signal and selects the smoothing filter by changing the tap length of the smoothing filter according to the determination result, similarly to the display device 2000 according to the second embodiment. In addition, the image signal can be smoothed, converted into an image signal having a larger number of gradations than the input image signal, and displayed.

  Further, as with the display device 2000 according to the second embodiment, the display device 4000 can determine the gradation region and selectively correct the gradation region more smoothly, so that the gradation performance of the gradation region can be improved. Can be improved. Further, the display device 4000 does not correct the input image in the edge region or the texture region, so that the image indicated by the output image signals Ro, Go, Bo does not lose sharpness.

  In addition, since the display device 4000 selectively improves the gradation performance of the gradation area, similarly to the display device 2000 according to the second embodiment, the gradation performance is visually improved over the entire image. Similar effects can be obtained.

  In addition, the display device 4000 sets the logical product of the determination signals (control signals Dc1 to Dc3 in FIG. 29) based on the input image signal of each channel as the control signal Dc. Accordingly, the display device 4000 can detect the gradation area without mistakenly with the texture area, similarly to the display device 3000 according to the third embodiment. Therefore, the display device 4000 can suppress image quality deterioration such as a decrease in sharpness caused by smoothing the texture region.

  Furthermore, the display device 4000 smoothes the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation area, as in the display device 1000 according to the first embodiment. It can be adjusted according to the smoothing area (corresponding to the gradation area). Therefore, since the display apparatus 4000 does not cause the first problem and the second problem described above, the display apparatus 4000 can effectively prevent the generation of false contours, and does not cause a decrease in image quality due to smoothing. .

[Modification of display device 4000]
The display device according to the fourth embodiment can take a modification similar to the modification of the display device according to the first embodiment described above.

(Image processing apparatus according to the fourth embodiment)
Although the display device according to the fourth embodiment has been described above, the image processing unit included in the display device (including the modification example) according to the above-described fourth embodiment is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the fourth embodiment)
[Programs related to display devices]
The program for causing the display device according to the fourth embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and receives the input image signal Can be converted into an image signal having a larger number of gradations.

[Program for image processing apparatus]
A program for causing an image processing apparatus according to the fourth embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and inputs an image It can be converted into an image signal having a larger number of gradations than the signal.

(Image processing method according to the fourth embodiment)
Next, an image processing method according to the fourth embodiment of the present invention will be described. FIG. 30 is a flowchart showing an example of an image processing method according to the fourth embodiment of the present invention. In the following description, the image processing method shown in FIG. 30 is described as being performed by the display device 4000, but the image processing method can also be applied to the image processing device according to the fourth embodiment of the present invention.

  The display device 4000 detects a difference value Dd between pixels for each input image signal based on the N-bit input image signals Ri, Gi, Bi (S400). The display device 4000 determines a gradation region based on the difference value Dd for each input image signal detected in step S400, and determines a determination signal (control signals Dc1 to Dc1 in FIG. 29) according to the determination result for each input image signal. Dc3) is generated for each pixel (S402).

  The display device 4000 calculates the logical product of the determination signals generated in step S402 for each pixel, and outputs the calculation result as the control signal Dc (S404).

  Display device 4000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel, based on control signal Dc generated in step S404, as in step S106 shown in FIG. 18 (S406).

  The display device 4000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S406, and based on the control signal Dc generated in step S404, the input image signals Ri, Gi, Each Bi is selectively smoothed for each pixel and an N + k-bit image signal (output image signals Ro, Go, Bo) is output (S408).

  By using the image processing method shown in FIG. 30, the display device 4000 determines the gradation area based on the input image signal, and selectively changes the tap length of the smoothing filter according to the determination result to selectively output the image signal. Can be converted into an image signal having a larger number of gradations than the input image signal.

(Fifth embodiment)
In the above description, the configuration in which the display unit has the gradation performance of N + k bits has been described as the display device according to the first to fourth embodiments. However, the display unit included in the display device according to the embodiment of the present invention is not limited to the N + k-bit gradation performance, and may have N-bit gradation performance. Thus, next, a configuration in which the display unit has N-bit gradation performance as a display device according to the fifth embodiment of the present invention will be described.

  FIG. 31 is a block diagram showing a display device 5000 according to the fifth embodiment of the present invention. Referring to FIG. 31, the display device 5000 includes an image processing unit 500 and a display unit 590.

  The image processing unit 500 includes a smooth region detection unit 102, a tap length adjustment unit 104, a gradation number expansion unit 106, and a pseudo gradation processing unit 502. The smooth region detecting unit 102, the tap length adjusting unit 104, and the gradation number expanding unit 106 are the smooth region detecting unit 102, the tap length adjusting unit 104, and the image processing unit 100 according to the first embodiment shown in FIG. And it has the same configuration as that of the gradation number expansion unit 106. That is, the smooth region detection unit 102 generates the control signal Dc based on the input image signal Di, and the tap length adjustment unit 104 outputs the adjustment signal Dtp for each pixel based on the control signal Dc. The gradation number expanding unit 106 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and selectively smoothes the input image signal Di for each corresponding pixel based on the control signal Dc to generate an N + k bit image. The signal De is output.

  The pseudo gradation processing unit 502 converts the N + k-bit image signal De into an N-bit output image signal Do using a pseudo intermediate gradation.

  Here, the pseudo gradation processing in the pseudo gradation processing unit 502 will be described. FIG. 32 is an explanatory diagram for explaining an example of the pseudo gradation processing in the pseudo gradation processing unit 502 according to the fifth embodiment of the present invention, and an example in which dither processing is used as the pseudo gradation processing. Show. FIG. 32A shows a 2 × 2 pixel area where dither processing is performed, and FIG. 32B shows an example of a dither pattern.

  In the dither processing, after adding a value corresponding to each pixel position of the dither pattern in FIG. 32B to the pixels a to d in the N + k bit image signal De in FIG. This is a process of outputting the upper N bits as an output image signal by rounding. Here, the dither processing is a kind of pseudo gradation processing, and it is known that gradation with a larger number of bits can be displayed in a pseudo manner with a smaller number of bits.

  The pseudo gradation processing unit 502 converts the N + k-bit image signal De by using dither processing as the pseudo gradation processing, and outputs an N-bit output image signal Do that improves the gradation performance of the gradation region. be able to.

[Another example of pseudo gradation processing]
Note that the pseudo gradation processing in the pseudo gradation processing unit 502 is not limited to the dither processing. For example, the pseudo gradation processing unit 502 can use error diffusion processing as the pseudo gradation processing. Here, the error diffusion processing is performed by adding or subtracting a value of lower k bits (referred to as “error data”) obtained by rounding an N + k-bit image signal to N bits to the surrounding pixel signal, and converting the error data. This is a method of obtaining pseudo halftones by diffusing. Even if the pseudo gradation processing unit 502 performs the pseudo gradation processing using the error diffusion processing, the same effect as in the case of using the dither processing can be obtained.

  With reference to FIG. 31 again, the components of the display device 5000 will be described. The display unit 590 has N-bit gradation performance and displays an image indicated by the N-bit output image signal Do output from the image processing unit 500.

  As described above, in the display device 5000, after the image processing unit 500 temporarily converts the N-bit input image signal Di into the N + k-bit image signal De by expanding the number of gradations, pseudo gradation such as dithering is performed. By converting the output image signal Do into N bits using processing, the gradation performance of the gradation area can be improved. Accordingly, the display device 5000 can display an image in which the gradation performance of the gradation area is improved even if the gradation performance of the display unit 590 is N bits.

  In FIG. 31, the input image signal is described as an example of an input image signal of a monochrome image (or an image signal corresponding to one channel among a plurality of channels of a color image) Di. Like the display device 3000 according to the embodiment, for example, the same effect can be obtained for an image signal of a color image composed of R / G / B.

  As described above, the display device 5000 according to the fifth embodiment of the present invention converts the N-bit input image signal Di into the N + k-bit image signal De and then converts the N-bit input image signal Di into the N-bit Do using the pseudo gradation processing. An image processing unit 500 for conversion and a display unit 590 having N-bit gradation performance are provided. The image processing unit 500 includes a smooth region detecting unit 102 having the same configuration as the smooth region detecting unit 102, the tap length adjusting unit 104, and the gradation number expanding unit 106 according to the first embodiment, and a tap length adjusting unit 104. And a gradation number expansion unit 106, selectively smoothing the input image signal Di and outputting an N + k-bit image signal De. Therefore, the display device 5000 determines the gradation area based on the input image signal and selects the smoothing filter by changing the tap length of the smoothing filter according to the determination result, as in the display device 1000 according to the first embodiment. Thus, the image signal can be smoothed and converted into an image signal having a larger number of gradations than the input image signal.

  In addition, the display device 5000 smoothes the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation area, similarly to the display device 1000 according to the first embodiment. It can be adjusted according to the smoothing area (corresponding to the gradation area). Therefore, since the first problem and the second problem described above do not occur in the display device 5000, the display device 5000 can effectively prevent the occurrence of false contours, and does not cause deterioration in image quality due to smoothing. .

  Further, in the display device 5000, the image processing unit 500 includes a pseudo gradation processing unit 502, and converts an N + k-bit image signal De into an N-bit output image signal Do using pseudo gradation processing such as dither processing. Thus, the gradation performance of the gradation area is improved. Accordingly, the display device 5000 can display an image in which the gradation performance of the gradation area is improved even if the gradation performance of the display unit 590 is N bits.

[Modification of Display Device 5000]
[First Modification]
In the above description, as the display device according to the fifth embodiment, the image processing unit includes the smooth region detection unit 102 according to the first embodiment, and the gradation region is obtained by the same method as the display device 1000 according to the first embodiment. The configuration in which the control signal Dc is determined (the control signal Dc is generated) is shown. However, the display device according to the embodiment of the present invention is not limited to the above. For example, in the display device according to the first modification of the fifth embodiment of the present invention (hereinafter referred to as “display device 5500”), the image processing unit includes the smooth region detection unit 202 according to the second embodiment. It can also be set as the structure provided. Even with the above configuration, the gradation region can be determined based on the input image signal Di, and therefore, the same effect as that of the display device 5000 described above can be obtained.

[Second Modification]
Further, the display device according to the fifth embodiment can take a modification similar to the modification of the display device according to the first embodiment described above.

(Image processing apparatus according to the fifth embodiment)
In the above, the display device according to the fifth embodiment has been described. However, the image processing unit included in the display device according to the fifth embodiment (including the modification example) is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the fifth embodiment)
[Programs related to display devices]
The program for causing the display device according to the fifth embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and receives the input image signal The gradation performance can be improved by performing the pseudo gradation process after converting the image signal to a larger number of gradations.

[Program for image processing apparatus]
A program for causing an image processing apparatus according to the fifth embodiment of the present invention to function as a computer determines gradation regions based on an input image signal, selectively smoothes the image signal, and inputs the image signal The gradation performance can be improved by performing the pseudo gradation process after converting the image signal to an image signal having a larger number of gradations than the image signal.

(Image processing method according to the fifth embodiment)
Next, an image processing method according to the fifth embodiment of the present invention will be described.

[1] First Image Processing Method FIG. 33 is a flowchart showing an example of a first image processing method according to the fifth embodiment of the present invention. In the following description, the first image processing method according to the fifth embodiment is described as being performed by the display device 5000. However, the first image processing method may be applied to the image processing device according to the fifth embodiment of the present invention.

  The display device 5000 detects a predetermined frequency component for each pixel from the N-bit input image signal Di as in step S100 shown in FIG. 18 (S500).

  The display device 5000 smoothes the detection value (frequency component detection value Df) detected in step S500 (S502), similarly to steps S102 and S104 shown in FIG. 18, and smoothes the detection value (average detection value Dave). ) To generate a control signal Dc (S504).

  The display device 5000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S504, similarly to step S106 shown in FIG. 18 (S506).

  The display device 5000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S506, and performs input based on the control signal Dc generated in step S504, similarly to step S108 shown in FIG. The image signal Di is selectively smoothed for each pixel and an N + k-bit image signal (image signal De) is output (S508).

  The display device 5000 performs pseudo gradation processing on the image signal (image signal De) output in step S508 and converts the image signal into an N-bit image signal (output image signal Do) (S510). Here, the display device 5000 can perform the pseudo gradation processing in step S510 by using, for example, dither processing or error diffusion processing.

  By using the image processing method shown in FIG. 33, the display device 5000 determines a gradation area based on the input image signal, selectively smoothes the image signal, and has a gradation number higher than that of the input image signal. The gradation performance can be improved by performing pseudo gradation processing after converting the image signal into a large amount of image signal.

[2] Second Image Processing Method FIG. 34 is a flowchart showing an example of a second image processing method according to the fifth embodiment of the present invention. In the following description, the second image processing method of the fifth embodiment is described as being performed by the display device 5500 according to the first modification. However, the first modification of the fifth embodiment of the present invention will be described. It can also be applied to such an image processing apparatus.

  The display device 5500 detects the difference value Dd between the pixels based on the N-bit input image signal Di as in step S200 shown in FIG. 23 (S600). Then, similarly to step S202 shown in FIG. 23, display device 5500 determines the gradation area based on difference value Dd detected in step S600, and generates control signal Dc corresponding to the determination result (S602). .

  The display device 5500 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S602, similarly to step S106 shown in FIG. 18 (S604).

  Display device 5500 adjusts the tap length of the smoothing filter based on adjustment signal Dtp generated in step S604, as in step S108 shown in FIG. 18, and inputs based on control signal Dc generated in step S602. The image signal Di is selectively smoothed for each pixel, and an N + k-bit image signal (image signal De) is output (S606).

  Similar to step S510 shown in FIG. 33, display device 5500 performs pseudo gradation processing on the image signal (image signal De) output in step S606, and generates an N-bit image signal (output image signal Do). Conversion is performed (S608).

  By using the image processing method shown in FIG. 34, the display device 5500 determines a gradation area based on the input image signal, selectively smoothes the image signal, and has a gradation number higher than that of the input image signal. The gradation performance can be improved by performing pseudo gradation processing after converting the image signal into a large amount of image signal.

(Sixth embodiment)
Next, a display device according to a sixth embodiment, which is another embodiment of the display device according to the embodiment of the present invention, will be described. FIG. 35 is a block diagram showing a display device 6000 according to the sixth embodiment of the present invention.

  Referring to FIG. 35, the display device 6000 includes an image processing unit 600 and a display unit 590. The image processing unit 600 basically has the same configuration as the image processing unit 500 according to the fifth embodiment shown in FIG. 31, but further includes a nonlinear gradation conversion unit 602. In addition, the display unit 590 has N-bit gradation performance similarly to the display unit 590 according to the fifth embodiment shown in FIG.

  The smooth region detection unit 102 generates a control signal Dc based on the input image signal Di, and the tap length adjustment unit 104 outputs the adjustment signal Dtp for each pixel based on the control signal Dc. The gradation number expanding unit 106 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp, and selectively smoothes the input image signal Di for each corresponding pixel based on the control signal Dc to generate an N + k bit image. The signal De is output.

  The non-linear tone conversion unit 602 receives the image signal De output from the tone number expansion unit 106, and performs non-linear tone conversion such as contrast enhancement processing and gamma processing to output the image signal Dg. Here, a case where contrast enhancement processing is performed as nonlinear gradation conversion processing in the nonlinear gradation conversion unit 602 will be described.

  FIG. 36 is an explanatory diagram for explaining nonlinear gradation conversion processing in the nonlinear gradation conversion unit 602 according to the sixth embodiment of the present invention, and shows an example of input / output conversion characteristics for performing contrast enhancement. ing.

  Referring to FIG. 36, the gradation difference is compressed in the dark portion L1 and the bright portion L3, and the gradation difference is widened in the intermediate gradation L2. For example, the nonlinear tone conversion unit 602 can output the image signal Dg in which the contrast of the image is enhanced by correcting the image signal De as shown in FIG.

  The pseudo gradation processing unit 502 converts the N + k-bit image signal Dg by using a dither process or an error diffusion process as the pseudo gradation process, thereby improving the gradation performance of the gradation area. Do can be output.

  Here, an example of each signal in the image processing unit 600 is shown. FIG. 37 is an explanatory diagram showing an example of each signal in the image processing unit 600 according to the sixth embodiment of the present invention, and shows a gradation region in the same manner as FIG. 8 (1). FIG. 37 (a) shows the input image signal Di, and FIG. 37 (b) shows the frequency component detection value Df. Similarly, FIG. 37 (c) to FIG. 37 (f) show the average detection value Dave, the control signal Dc, the image signal De whose number of gradations is expanded, and the image signal Dg after nonlinear gradation conversion processing, respectively. Yes.

  As an example of the input image signal Di, a gradation region that changes in a step-by-step manner is exemplified as in FIG. 11A (FIG. 37A). Similarly to FIG. 11C, the frequency component detection value Df is small and the frequency of detection is low (FIG. 37B). Similarly to FIG. 11D, the average detection value Dave is The value is smaller than the threshold value TH (FIG. 37 (c)). Further, since the average detection value Dave shown in FIG. 37C is smaller than the threshold value TH, the control signal Dc indicates “1” representing the gradation area (FIG. 37D). Since the control signal Dc shown in FIG. 37 (d) is “1” indicating the gradation area, the gradation number expanding unit 106 outputs the smoothed N + k-bit image signal De (FIG. 37 (e)). .

  Since the image signal De shown in FIG. 37 (e) output from the gradation number expansion unit 106 is input to the nonlinear gradation conversion unit 602, the gradation area can be smoothed without erroneous detection ( FIG. 37 (f)).

[Modification of Image Processing Unit According to Sixth Embodiment]
In the image processing unit 600 according to the sixth embodiment shown in FIG. 35, the configuration in which the nonlinear gradation conversion process is performed after the number of gradations is expanded is shown. However, after the nonlinear gradation conversion process is performed, the number of gradations is changed. It is also possible to expand. FIG. 38 is a block diagram showing an image processing unit 650 according to a modification of the sixth embodiment of the present invention.

  Referring to FIG. 38, the image processing unit 650 basically has the same configuration as the image processing unit 600 shown in FIG. 35. However, the input image signal Di is input to the nonlinear gradation conversion unit 602, and nonlinear gradation conversion is performed. The image processing unit 600 is different from the image processing unit 600 in that the number of gradations is expanded based on the image signal Dg after nonlinear gradation conversion output from the unit 602.

  Here, an example of each signal in the image processing unit 650 is shown. FIG. 39 is an explanatory diagram showing an example of each signal in the image processing unit 650 according to the modification of the sixth embodiment of the present invention, and shows a gradation area as in FIG. FIG. 39A shows the input image signal Di, and FIG. 39B shows the image signal Dg after nonlinear gradation conversion processing. Similarly, FIGS. 39C to 39F show the frequency component detection value Df, the average detection value Dave, the control signal Dc, and the image signal De in which the number of gradations is expanded.

  As an example of the input image signal Di, as in FIG. 37A, a gradation region that changes stepwise by one gradation is given as an example (FIG. 39A). The input image signal Di shown in FIG. 39A is input to the nonlinear gradation conversion unit 602, and nonlinear gradation conversion processing is performed on the input image signal Di. The part where the difference in tone spreads appears (FIG. 39B).

  Since the smoothed area detecting unit 102 determines the gradation area based on the image signal Dg after the nonlinear gradation conversion processing shown in FIG. 39B, the gradation area is partially detected at a portion where the gradation difference partially spreads. It may be determined as a region other than (Fig. 39 (c) to Fig. 39 (e)).

  The gradation number expanding unit 106 performs smoothing selectively according to the control signal Dc shown in FIG. 39 (e) and outputs an N + k-bit image signal De. Therefore, since the gradation number expanding unit 106 does not perform smoothing at a portion where the difference in gradation is widened, the gradation area may not be converted smoothly (FIG. 39 (f)).

  As shown with reference to FIGS. 38 and 39, the image processing unit according to the sixth embodiment can take a modified example in which the number of gradations is expanded after performing the nonlinear gradation conversion processing. However, the processing order may affect the processing result.

  As described above, the display device 6000 according to the sixth embodiment of the present invention converts the N-bit input image signal Di into the N + k-bit image signal De, performs the non-linear gradation conversion process, and further performs pseudo gradation. An image processing unit 600 that converts the data into N-bit Do using processing and a display unit 590 having N-bit gradation performance are provided. The image processing unit 600 includes a smooth region detecting unit 102 having the same configuration as the smooth region detecting unit 102, the tap length adjusting unit 104, and the gradation number expanding unit 106 according to the first embodiment, and a tap length adjusting unit 104. And a gradation number expansion unit 106, selectively smoothing the input image signal Di and outputting an N + k-bit image signal De. Therefore, the display device 6000 determines the gradation area based on the input image signal, and selects the smoothing filter by changing the tap length of the smoothing filter according to the determination result, similarly to the display device 1000 according to the first embodiment. Thus, the image signal can be smoothed and converted into an image signal having a larger number of gradations than the input image signal.

  Further, similarly to the display device 1000 according to the first embodiment, the display device 6000 smoothes the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation region. It can be adjusted according to the smoothing area (corresponding to the gradation area). Therefore, since the display device 6000 does not cause the first problem and the second problem described above, the display device 6000 can effectively prevent the generation of false contours, and does not cause deterioration in image quality due to smoothing. .

  Further, the display device 6000 includes a non-linear gradation conversion unit 602 that performs non-linear gradation conversion such as contrast enhancement processing and gamma processing on the N + k-bit image signal De output from the gradation number expansion unit 106. The gradation area can be smoothed while performing non-linear gradation conversion without erroneous detection.

  Further, in the display device 6000, similarly to the display device 5000 according to the fifth embodiment, the image processing unit 600 includes a pseudo gradation processing unit 502, and a non-linear gradation using pseudo gradation processing such as dither processing. By converting the N + k-bit image signal Dg output from the conversion unit 602 into an N-bit output image signal Do, the gradation performance of the gradation area is improved. Therefore, as with the display device 5000 according to the fifth embodiment, the display device 6000 displays an image with improved gradation performance in the gradation area even if the gradation performance of the display unit 590 is N bits. can do.

[Modification of Display Device 6000]
[First Modification]
In the above description, as the display device according to the sixth embodiment, the image processing unit includes the smooth region detection unit 102 according to the first embodiment, and the gradation region is obtained by the same method as the display device 1000 according to the first embodiment. The configuration in which the control signal Dc is determined (the control signal Dc is generated) is shown. However, the display device according to the embodiment of the present invention is not limited to the above. For example, in the display device according to the first modification of the sixth embodiment of the present invention (hereinafter referred to as “display device 6500”), the image processing unit includes the smooth region detection unit 202 according to the second embodiment. It can also be set as the structure provided. Even with the above configuration, the gradation region can be determined based on the input image signal Di, and therefore, the same effect as that of the display device 6000 described above can be obtained.

[Second Modification]
35 shows a configuration in which the display unit 590 has N-bit gradation performance and the image processing unit 600 includes the pseudo gradation processing unit 502, but the display device according to the sixth embodiment The configuration is not limited to that of FIG. For example, the display device according to the sixth embodiment may include a display unit having a gradation performance of N + k bits, and the image processing unit may not include a pseudo gradation processing unit. Even with such a configuration, the display device according to the second modification of the sixth embodiment can smooth the gradation area without erroneous detection.

[Third Modification]
Furthermore, the display device according to the sixth embodiment can take a modification similar to the modification of the display device according to the first embodiment described above.

(Image processing apparatus according to the sixth embodiment)
In the above, the display device according to the sixth embodiment has been described. However, the image processing unit included in the display device according to the sixth embodiment (including the modification example) is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the sixth embodiment)
[Programs related to display devices]
The program for causing the display device according to the sixth embodiment of the present invention to function as a computer determines a gradation region based on the input image signal, selectively smoothes the image signal, and the input image signal The gradation area can be smoothed and the gradation performance can be improved by performing the nonlinear gradation conversion process and the pseudo gradation process after the conversion to an image signal having a larger number of gradations.

[Program for image processing apparatus]
A program for causing an image processing apparatus according to the sixth embodiment of the present invention to function as a computer determines a gradation region based on an input image signal, selectively smoothes the image signal, and inputs the image signal By converting the image signal into an image signal having a larger number of gradations than the image signal, and further performing nonlinear gradation conversion processing and pseudo gradation processing, the gradation region can be smoothed and the gradation performance can be improved.

(Image Processing Method According to Sixth Embodiment)
Next, an image processing method according to the sixth embodiment of the present invention will be described.

[1] First Image Processing Method FIG. 40 is a flowchart showing an example of a first image processing method according to the sixth embodiment of the present invention. In the following description, the first image processing method according to the sixth embodiment is described as being performed by the display device 6000. However, the first image processing method may be applied to the image processing device according to the sixth embodiment of the present invention.

  The display device 6000 detects a predetermined frequency component for each pixel from the N-bit input image signal Di as in step S100 shown in FIG. 18 (S700).

  The display device 6000 smoothes the detection value (frequency component detection value Df) detected in step S700 (S702), similarly to steps S102 and S104 shown in FIG. 18, and smoothes the detection value (average detection value Dave). ) To generate a control signal Dc (S704).

  The display device 6000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S704, similarly to step S106 shown in FIG. 18 (S706).

  The display device 6000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S706, and performs input based on the control signal Dc generated in step S704, similarly to step S108 shown in FIG. The image signal Di is selectively smoothed for each pixel and an N + k-bit image signal (image signal De) is output (S708).

  The display device 6000 performs nonlinear gradation conversion processing on the N + k-bit image signal (image signal De) output in step S708 (S710). Here, examples of the non-linear gradation conversion processing in step S710 include contrast enhancement processing and gamma processing, but are not limited thereto.

  The display device 6000 performs pseudo gradation processing on the image signal (image signal Dg) on which the nonlinear gradation conversion processing has been performed in step S710 in the same manner as in step S510 shown in FIG. The output image signal Do) is converted (S712).

  By using the image processing method shown in FIG. 40, the display device 6000 determines a gradation area based on the input image signal, selectively smoothes the image signal, and has a gradation number higher than that of the input image signal. By converting the image signal into a large amount of image signal and further performing nonlinear gradation conversion processing and pseudo gradation processing, the gradation area can be smoothed and the gradation performance can be improved.

[2] Second Image Processing Method FIG. 41 is a flowchart showing an example of the second image processing method according to the sixth embodiment of the present invention. In the following description, the second image processing method of the sixth embodiment is described as being performed by the display device 6500 according to the first modification. However, the first modification of the sixth embodiment of the present invention will be described. It can also be applied to such an image processing apparatus.

  The display device 6500 detects the difference value Dd between the pixels based on the N-bit input image signal Di as in step S200 shown in FIG. 23 (S800). Then, similarly to step S202 shown in FIG. 23, display device 6500 determines the gradation area based on difference value Dd detected in step S800, and generates control signal Dc corresponding to the determination result (S802). .

  The display device 6500 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S802 as in step S106 shown in FIG. 18 (S804).

  The display device 6500 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S804, as in step S108 shown in FIG. 18, and inputs based on the control signal Dc generated in step S802. The image signal Di is selectively smoothed for each pixel and an N + k-bit image signal (image signal De) is output (S806).

The display device 6500 performs nonlinear gradation conversion processing on the N + k-bit image signal (image signal De) output in step S806, similarly to step S710 shown in FIG. 40 (S808).
The display device 6500 performs pseudo gradation processing on the image signal (image signal Dg) on which the nonlinear gradation conversion processing has been performed in step S808 in the same manner as in step S510 shown in FIG. The output image signal Do) is converted (S810).

  By using the image processing method shown in FIG. 41, the display device 6500 determines a gradation area based on the input image signal, selectively smoothes the image signal, and has a gradation number higher than that of the input image signal. By converting the image signal into a large amount of image signal and further performing nonlinear gradation conversion processing and pseudo gradation processing, the gradation area can be smoothed and the gradation performance can be improved.

[Modification of Image Processing Method According to Sixth Embodiment]
40 and 41 show the image processing method for converting the N + k-bit image signal into the N-bit image signal by the pseudo gradation processing in steps S712 and S810, the image processing method according to the sixth embodiment. Is not limited to the method shown in FIGS. For example, the display device according to the sixth embodiment can display the N + k-bit image signal on the N + k-bit display unit without performing the processing of Step S712 shown in FIG. 40 and Step S810 shown in FIG. Even when the image processing method according to the above modification is used, the display device according to the sixth embodiment can obtain the same effects as when the image processing method shown in FIGS. 40 and 41 is used.

(Seventh embodiment)
In the above, as a modification of the image processing unit according to the sixth embodiment, a configuration in which nonlinear gradation conversion processing is performed on the input image signal Di as shown in FIG. 38 is shown, and the order of processing is as shown in FIG. It was shown that the processing result might be affected. However, the display device according to the embodiment of the present invention can smoothly correct the gradation area even when the nonlinear gradation conversion process is performed on the input image signal Di. Therefore, next, a display device according to a seventh embodiment of the present invention will be described.

  FIG. 42 is an explanatory diagram showing a display device 7000 according to the seventh embodiment of the present invention. Referring to FIG. 42, the display device 7000 includes an image processing unit 700 and a display unit 590. The image processing unit 700 basically has the same configuration as that of the image processing unit 650 according to the modification of the sixth embodiment shown in FIG. 38, but the input image signal Di is input to the smooth region detection unit 102, and the input The point which determines a gradation area | region based on the image signal Di differs from the image process part 650 which concerns on the modification of 6th Embodiment. In addition, the display unit 590 has N-bit gradation performance similarly to the display unit 590 according to the fifth embodiment shown in FIG.

  Here, an example of each signal in the image processing unit 700 is shown. FIG. 43 is an explanatory diagram showing an example of each signal in the image processing unit 700 according to the modification of the seventh embodiment of the present invention, and shows a gradation region as in FIG. FIG. 43A shows the input image signal Di, and FIG. 43B shows the image signal Dg after nonlinear gradation conversion processing. Similarly, FIGS. 43C to 43F show the frequency component detection value Df, the average detection value Dave, the control signal Dc, and the image signal De in which the number of gradations is expanded.

  As an example of the input image signal Di, a gradation region that changes in a step-by-step manner is given as in FIG. 37A (FIG. 43A). The input image signal Di shown in FIG. 43A is input to the non-linear gradation conversion unit 602, and non-linear gradation conversion processing is performed on the input image signal Di. The part where the difference in tone spreads appears (FIG. 43 (b)).

  The smoothed area detection unit 102 receives the input image signal Di and determines a gradation area based on the input image signal Di. Accordingly, the frequency component detection value Df is small and the frequency of detection is low (FIG. 43 (c)) as in FIG. 37 (b), and the average detection value Dave is the same as in FIG. 37 (c). Becomes a value smaller than the threshold value TH (FIG. 43 (d)). Further, since the average detection value Dave shown in FIG. 43 (d) is smaller than the threshold value TH, the control signal Dc indicates “1” representing the gradation area (FIG. 43 (e)).

  Since the control signal Dc shown in FIG. 43 (e) is “1” indicating the gradation region, the gradation number expanding unit 106 outputs the smoothed N + k-bit image signal De (FIG. 43 (f)). .

  Therefore, the image processing unit 700 can smooth the gradation area without erroneous detection, as shown in FIG.

  As described above, the display device 7000 according to the seventh embodiment of the present invention includes the image processing unit 700 and the display unit 590 having N-bit gradation performance. The image processing unit 700 performs nonlinear gradation conversion processing on the N-bit input image signal Di, and after the nonlinear gradation conversion processing, according to the control signal Dc generated based on the N-bit input image signal Di. The image signal Dg is converted into an N + k-bit image signal De. Further, the image processing unit 700 converts the N + k-bit image signal De into N-bit Do by using pseudo gradation processing. Here, the image processing unit 700 includes a nonlinear gradation conversion unit 602 according to the sixth embodiment, a smooth region detection unit 102, a tap length adjustment unit 104, and a gradation number expansion unit 106 according to the first embodiment. Smoothing region detecting section 102, tap length adjusting section 104, and gradation number expanding section 106 having the same configuration as the above, and selectively smoothing the image signal Dg after the nonlinear gradation conversion processing to obtain N + k bits The image signal De is output. Therefore, the display device 7000 determines the gradation area based on the input image signal, and smoothly converts the gradation area without erroneous detection and converts the gradation area into an image signal having a larger number of gradations than the input image signal. can do.

  In addition, the display device 7000 smoothes the tap length of the smoothing filter that performs smoothing based on the control signal Dc corresponding to the determination result of the gradation area, similarly to the display device 1000 according to the first embodiment. It can be adjusted according to the smoothing area (corresponding to the gradation area). Accordingly, since the display device 7000 does not cause the first problem and the second problem described above, the display device 7000 can effectively prevent the occurrence of false contours, and does not cause a decrease in image quality due to smoothing. .

  Further, in the display device 7000, as in the display device 5000 according to the fifth embodiment, the image processing unit 700 includes the pseudo gradation processing unit 502, and the number of gradations is determined using pseudo gradation processing such as dither processing. By converting the N + k-bit image signal De output from the extension unit 106 into an N-bit output image signal Do, the gradation performance of the gradation area is improved. Therefore, as with the display device 5000 according to the fifth embodiment, the display device 7000 displays an image with improved gradation performance in the gradation area even if the gradation performance of the display unit 590 is N bits. can do.

[Modification of Display Device 7000]
[First Modification]
In the above description, as the display device according to the seventh embodiment, the image processing unit includes the smooth region detection unit 102 according to the first embodiment, and the gradation region is obtained by the same method as the display device 1000 according to the first embodiment. The configuration in which the control signal Dc is determined (the control signal Dc is generated) is shown. However, the display device according to the embodiment of the present invention is not limited to the above. For example, in the display device according to the first modification of the seventh embodiment of the present invention (hereinafter referred to as “display device 7500”), the image processing unit includes the smooth region detection unit 202 according to the second embodiment. It can also be set as the structure provided. Even with the above configuration, the gradation region can be determined based on the input image signal Di, and therefore, the same effect as that of the display device 7000 described above can be obtained.

[Second Modification]
The display device according to the seventh embodiment includes a display unit having N + k-bit gradation performance, and the image processing unit is a pseudo-level, as in the modification of the display device according to the sixth embodiment described above. It can also be set as the structure which is not provided with a tone processing part. Even with this configuration, the display device according to the second modification of the seventh embodiment can achieve the same effects as the display device 7000 described above.

[Third Modification]
Furthermore, the display device according to the seventh embodiment can take a modification similar to that of the display device according to the first embodiment described above.

(Image processing apparatus according to the seventh embodiment)
In the above, the display device according to the seventh embodiment has been described. However, the image processing unit included in the display device according to the seventh embodiment (including the modification example) is independent of the display unit. It can also be realized as an apparatus, that is, an image processing apparatus.

(Program according to the seventh embodiment)
[Programs related to display devices]
A program for causing a display device according to a seventh embodiment of the present invention to function as a computer determines a gradation area based on an input image signal, and inputs the gradation area smoothly corrected without erroneous detection. The gradation performance can be improved by converting the image signal into an image signal having a larger number of gradations than the image signal to be processed and further performing pseudo gradation processing.

[Program for image processing apparatus]
A program for causing an image processing apparatus according to the seventh embodiment of the present invention to function as a computer determines a gradation area based on an input image signal and smoothly corrects the gradation area without erroneous detection. By converting the image signal into an image signal having a larger number of gradations than the input image signal and performing pseudo gradation processing, the gradation performance can be improved.

(Image Processing Method According to Seventh Embodiment)
Next, an image processing method according to the seventh embodiment of the present invention will be described.

[1] First Image Processing Method FIG. 44 is a flowchart showing an example of a first image processing method according to the seventh embodiment of the present invention. In the following description, the first image processing method according to the seventh embodiment is described as being performed by the display device 7000. However, the first image processing method may be applied to the image processing device according to the seventh embodiment of the present invention.

  The display device 7000 detects a predetermined frequency component for each pixel from the N-bit input image signal Di as in step S100 shown in FIG. 18 (S900).

  The display device 7000 smoothes the detection value (frequency component detection value Df) detected in step S900 (S902), similarly to steps S102 and S104 shown in FIG. 18, and smoothes the detection value (average detection value Dave). ) To generate a control signal Dc (S904).

  The display device 7000 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S904, similarly to step S106 shown in FIG. 18 (S906).

  The display device 7000 performs nonlinear gradation conversion processing on the N-bit input image signal Di in the same manner as in step S710 shown in FIG. 40 (S908). FIG. 44 shows an example in which the process of step S908 is performed after the process of steps S900 to S906, but the process of steps S900 to S906 and the process of step S908 can be performed independently. Therefore, for example, the display device 7000 can perform the processing of steps S900 to S906 after the processing of step S908, and can also perform the processing of steps S900 to S906 and the processing of step S908 in synchronization.

  The display device 7000 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S906, and performs the step based on the control signal Dc generated in step S904, similarly to step S108 shown in FIG. The image signal (image signal Dg) after the nonlinear gradation conversion process that has been subjected to the nonlinear gradation conversion process in 908 is selectively smoothed for each pixel, and an N + k-bit image signal (image signal De) is output (S910). ).

  The display device 7000 performs pseudo gradation processing on the image signal (image signal De) output in step S910 in the same manner as in step S510 illustrated in FIG. 33, and generates an N-bit image signal (output image signal Do). Conversion is performed (S912).

  By using the image processing method shown in FIG. 44, the display device 7000 determines the gradation area based on the input image signal, and smoothly corrects the gradation area while performing nonlinear gradation conversion without erroneous detection. The gradation performance can be improved by converting the input image signal into an image signal having a larger number of gradations than that of the input image signal and performing pseudo gradation processing.

[2] Second Image Processing Method FIG. 45 is a flowchart showing an example of the second image processing method according to the seventh embodiment of the present invention. In the following description, the second image processing method of the seventh embodiment is described as being performed by the display device 7500 according to the first modification. However, the first modification of the seventh embodiment of the present invention is described below. It can also be applied to such an image processing apparatus.

  The display device 7500 detects the difference value Dd between the pixels based on the N-bit input image signal Di as in step S200 shown in FIG. 23 (S1000). Then, similarly to step S202 shown in FIG. 23, display device 7500 determines the gradation area based on difference value Dd detected in step S1000, and generates control signal Dc corresponding to the determination result (S1002). .

  The display device 7500 generates an adjustment signal Dtp for adjusting the tap length of the smoothing filter for each pixel based on the control signal Dc generated in step S1002, similarly to step S106 shown in FIG. 18 (S1004).

  The display device 7500 performs non-linear gradation conversion processing on the N-bit input image signal Di as in step S710 shown in FIG. 40 (S1006). FIG. 45 shows an example in which the process of step S1006 is performed after the process of steps S1000 to S1004, but the process of steps S1000 to S1004 and the process of step S1006 can be performed independently. Therefore, for example, the display device 7500 can perform the processing of steps S1000 to S1004 after the processing of step S1006, and can also perform the processing of steps S1000 to S1004 and the processing of step S1006 in synchronization.

  The display device 7500 adjusts the tap length of the smoothing filter based on the adjustment signal Dtp generated in step S1004, as in step S108 shown in FIG. 18, and performs the step based on the control signal Dc generated in step S1002. The image signal (image signal Dg) after the nonlinear gradation conversion process that has been subjected to the nonlinear gradation conversion process in 1006 is selectively smoothed for each pixel and an N + k-bit image signal (image signal De) is output (S1008). ).

  The display device 7500 performs pseudo gradation processing on the image signal (image signal De) output in step S1008 in the same manner as in step S510 illustrated in FIG. 33, and generates an N-bit image signal (output image signal Do). Conversion is performed (S1010).

  By using the image processing method shown in FIG. 45, the display device 7500 determines the gradation area based on the input image signal, and smoothly corrects the gradation area while performing nonlinear gradation conversion without erroneous detection. The gradation performance can be improved by converting the input image signal into an image signal having a larger number of gradations than that of the input image signal and performing pseudo gradation processing.

[Modification of Image Processing Method According to Seventh Embodiment]
44 and 45 show the image processing method for converting the N + k-bit image signal into the N-bit image signal by the pseudo gradation processing in steps S912 and S1010, the image processing method according to the seventh embodiment. Is not limited to the method shown in FIGS. For example, the display device according to the seventh embodiment can display an N + k-bit image signal on an N + k-bit display unit without performing the processing of step S912 shown in FIG. 44 and step S1010 shown in FIG. Even when the image processing method according to the above modification is used, the display device according to the seventh embodiment can obtain the same effects as when the image processing method shown in FIGS. 44 and 45 is used.

  As described above, the display device has been described as the first to seventh embodiments. However, the embodiment of the present invention is not limited to such a form. For example, an organic EL display, a self-luminous display such as an FED, a PDP, or the like. The present invention can be applied to a device, a backlight-type display device such as an LCD, and a receiving device that receives a television broadcast. The embodiments of the present invention can be applied to computers such as PCs (Personal Computers) and servers (Servers), portable communication devices such as mobile phones, and the like.

  The image processing apparatuses according to the first to seventh embodiments can be applied to display devices such as organic EL displays and LCDs, computers such as PCs, and portable communication devices such as mobile phones.

  Moreover, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the display devices according to the fifth to seventh embodiments, a configuration has been described in which a monochrome image is processed as an input image signal, or one channel of a plurality of channels of a color image is processed. The embodiment of the invention is not limited to such a configuration. For example, the display device according to the embodiment of the present invention processes a plurality of channels of a color image by combining the third embodiment (or the fourth embodiment) with each of the fifth to seventh embodiments. You can also

  The configuration described above shows an example of the embodiment of the present invention, and naturally belongs to the technical scope of the present invention.

1 is a block diagram illustrating a display device according to a first embodiment of the present invention. It is a block diagram which shows the image process part which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the frequency component detection part which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows an example of the frequency characteristic of the band pass filter which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating an example of the smoothing in the detection value smoothing part which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating the threshold value process in the control-signal production | generation part which concerns on the 1st Embodiment of this invention. It is the 1st explanatory view for explaining the meaning with which the image processing part concerning a 1st embodiment of the present invention is provided with a tap length adjustment part. It is explanatory drawing for demonstrating the problem in case the image processing part which concerns on the 1st Embodiment of this invention is not provided with a tap length adjustment part. It is the 2nd explanatory view for explaining the meaning with which the image processing part concerning a 1st embodiment of the present invention is provided with a tap length adjustment part. It is explanatory drawing which shows another example of tap length adjustment in the tap length adjustment part of the image processing part which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows an example of each signal in the image processing part which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the 1st example of a signal in case an image process part is not provided with a detection value smoothing part. It is explanatory drawing which shows the 2nd example of a signal in case an image process part is not provided with a detection value smoothing part. It is a block diagram which shows the frequency component detection part which concerns on the 1st modification of the 1st Embodiment of this invention. It is explanatory drawing for demonstrating the frequency component detection part which concerns on the 1st modification of the 1st Embodiment of this invention. It is a block diagram which shows the frequency component detection part which concerns on the 2nd modification of the 1st Embodiment of this invention. It is a block diagram which shows the display apparatus which concerns on the 3rd modification of the 1st Embodiment of this invention. 3 is a flowchart illustrating an example of an image processing method according to the first embodiment of the present invention. It is a block diagram which shows the display apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the image process part which concerns on the 2nd Embodiment of this invention. It is explanatory drawing explaining the detection method of the difference value in the inter-pixel difference value detection part which concerns on the 2nd Embodiment of this invention. It is explanatory drawing explaining the output method of the control signal in the smooth area | region determination part which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows an example of the image processing method which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the display apparatus which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the image process part which concerns on the 3rd Embodiment of this invention. It is explanatory drawing which shows an example of each signal in the image process part which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows an example of the image processing method which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the display apparatus which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the image process part which concerns on the 4th Embodiment of this invention. It is a flowchart which shows an example of the image processing method which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the display apparatus which concerns on the 5th Embodiment of this invention. It is explanatory drawing for demonstrating an example of the pseudo gradation process in the pseudo gradation process part which concerns on the 5th Embodiment of this invention. It is a flowchart which shows an example of the 1st image processing method which concerns on the 5th Embodiment of this invention. It is a flowchart which shows an example of the 2nd image processing method which concerns on the 5th Embodiment of this invention. It is a block diagram which shows the display apparatus which concerns on the 6th Embodiment of this invention. It is explanatory drawing for demonstrating the nonlinear gradation conversion process in the nonlinear gradation conversion part which concerns on the 6th Embodiment of this invention. It is explanatory drawing which shows an example of each signal in the image processing part which concerns on the 6th Embodiment of this invention. It is a block diagram which shows the image process part which concerns on the modification of the 6th Embodiment of this invention. It is explanatory drawing which shows an example of each signal in the image process part which concerns on the modification of the 6th Embodiment of this invention. It is a flowchart which shows an example of the 1st image processing method which concerns on the 6th Embodiment of this invention. It is a flowchart which shows an example of the 2nd image processing method which concerns on the 6th Embodiment of this invention. It is a block diagram which shows the image process part which concerns on the modification of the 7th Embodiment of this invention. It is explanatory drawing which shows an example of each signal in the image process part which concerns on the modification of the 7th Embodiment of this invention. It is a flowchart which shows an example of the 1st image processing method which concerns on the 7th Embodiment of this invention. It is a flowchart which shows an example of the 2nd image processing method which concerns on the 7th Embodiment of this invention.

Explanation of symbols

100, 150, 200, 300, 400, 500, 600, 650, 700 Image processing unit 102, 202, 302, 402 Smooth region detection unit 104 Tap length adjustment unit 106, 304 Tone number expansion unit 108 Frequency component detection unit 110 Detection value smoothing section 112 Control signal generation section 120, 306 Maximum value selection section 122 Addition section 190, 590 Display section 204 Inter-pixel difference value detection section 206 Smooth area determination section 404 AND operation section 502 Pseudo gradation processing section 602 Non-linear floor Key conversion unit 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000 Display device

Claims (15)

A smoothing area detection unit that generates a control signal for defining a gradation area for each pixel based on an input image signal of N bits (N is a positive integer);
A smoothing area to be smoothed is specified based on the control signal, and the signal is smoothed according to the tap length based on the end of the specified smoothing area and the position of each pixel included in the smoothing area. A tap length adjusting unit that generates an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
A smoothing filter whose tap length is variable based on the adjustment signal, and selectively smoothing the input image signal of N bits by the smoothing filter based on the control signal generated for each pixel; A gradation number expansion unit for outputting an N + k-bit output image signal whose number is expanded by a predetermined number for each pixel;
An image processing apparatus comprising: The smooth region detection unit
A frequency component detection unit that detects a signal of a predetermined frequency band from the input image signal that has been input for each pixel;
A detection value smoothing unit that smoothes the detection signal corresponding to each pixel based on the detection signal detected by the frequency component detection unit;
A control signal generating unit that generates the control signal for each pixel based on the detection signal smoothed by the detection value smoothing unit;
The image processing apparatus according to claim 1, further comprising:   The image processing apparatus according to claim 2, wherein the frequency component detection unit includes one band-pass filter that detects a signal in a predetermined frequency band for each pixel. The frequency component detector
A plurality of bandpass filters that detect signals of different predetermined frequency bands for each pixel;
A coefficient multiplier that multiplies a signal output from each of the plurality of bandpass filters by a coefficient corresponding to the bandpass filter from which the signal is output;
A maximum value selection unit that selects and outputs the maximum signal for each pixel based on the signal output from the coefficient multiplication unit;
The image processing apparatus according to claim 2, further comprising: The frequency component detector
A plurality of bandpass filters that detect signals of different predetermined frequency bands for each pixel;
A coefficient multiplier that multiplies a signal output from each of the plurality of bandpass filters by a coefficient corresponding to the bandpass filter from which the signal is output;
An adder that adds and outputs the signal output from the coefficient multiplier for each pixel;
The image processing apparatus according to claim 2, further comprising: The smooth region detection unit
An inter-pixel difference value detection unit that detects a difference value between pixels based on the input image signal input;
A smooth region determination unit that determines a smooth region to be smoothed based on the difference value detected by the inter-pixel difference value detection unit, and generates the control signal according to the determination result for each pixel;
The image processing apparatus according to claim 1, further comprising:   The image processing apparatus further includes a first pseudo gradation processing unit that converts the number of gradations of the output image signal output from the gradation number expanding unit into an N-bit image signal using a pseudo intermediate gradation. The image processing apparatus according to claim 1. A first non-linear gradation converting unit that non-linearly corrects an output image signal output from the gradation number expanding unit according to a signal level;
A second pseudo gradation processing section that converts the number of gradations of the corrected output image signal output from the nonlinear gradation conversion section into an N-bit image signal using a pseudo intermediate gradation;
The image processing apparatus according to claim 1, further comprising: A second non-linear gradation conversion unit that non-linearly corrects the N-bit input image signal according to a signal level;
The image processing apparatus according to claim 1, wherein a corrected input image signal output from the second nonlinear gradation conversion unit is input to the gradation number expansion unit. An image signal processing apparatus to which a plurality of N-bit (N is a positive integer) input image signals are input,
A frequency component detector that detects a signal of a predetermined frequency band for each pixel from each of the input image signals;
Based on the detection signal detected by the frequency component detection unit, a maximum value selection unit that selects a detection signal with the maximum detection signal in each pixel corresponding to each of the plurality of input image signals;
A detection value smoothing unit that smoothes each detection signal corresponding to each pixel based on the detection signal selected by the maximum value selection unit;
Based on the detection signal smoothed by the detection value smoothing unit, a control signal generating unit that generates a control signal for defining a gradation region for each pixel;
A smoothing area to be smoothed is specified based on the control signal, and the signal is smoothed according to the tap length based on the end of the specified smoothing area and the position of each pixel included in the smoothing area. A tap length adjusting unit that generates an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
A smoothing filter whose tap length is variable based on the adjustment signal, and each of the N-bit input image signals is selectively smoothed by the smoothing filter based on the control signal generated for each pixel; A gradation number expansion unit that outputs an N + k-bit output image signal in which the key number is expanded by a predetermined number for each pixel;
An image processing apparatus comprising: An image signal processing apparatus to which a plurality of N-bit (N is a positive integer) input image signals are input,
An inter-pixel difference value detection unit that detects a difference value between pixels for each of the input image signals based on a plurality of the input image signals;
A smooth region determination unit that determines a smooth region for each of the input image signals based on the difference value detected by the inter-pixel difference value detection unit, and generates a determination signal that indicates a determination result for each of the input image signals for each pixel. When,
A control signal output unit that inputs the determination signal for each pixel corresponding to each of the input image signals, and outputs a control signal indicating the gradation region for each pixel when the logical product of the determination signals indicates a gradation region;
A smoothing area to be smoothed is specified based on the control signal, and the signal is smoothed according to the tap length based on the end of the specified smoothing area and the position of each pixel included in the smoothing area. A tap length adjusting unit that generates an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
A smoothing filter whose tap length is variable based on the adjustment signal, and each of the N-bit input image signals is selectively smoothed by the smoothing filter based on the control signal generated for each pixel; A gradation number expansion unit that outputs an N + k-bit output image signal in which the key number is expanded by a predetermined number for each pixel;
An image processing apparatus comprising: An image processing method that can be used in an image processing apparatus provided with a smoothing filter for smoothing a signal according to a tap length for each pixel,
A first generation step of generating, for each pixel, a control signal for defining a gradation area based on an input N-bit (N is a positive integer) input image signal;
A smoothing area to be smoothed is identified based on the control signal generated in the first generation step, and based on the end of the specified smoothing area and the position of each pixel included in the smoothing area, A second generation step of generating an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
The tap length of the smoothing filter is adjusted based on the adjustment signal generated in the second generation step, and the N-bit input image signal based on the control signal generated for each pixel in the first generation step Outputting an N + k-bit output image signal for each pixel, which is selectively smoothed by the smoothing filter and the number of gradations is expanded by a predetermined number;
An image processing method characterized by comprising: A program that can be used for an image processing apparatus that includes a smoothing filter for smoothing a signal according to a tap length for each pixel,
A first generation step of generating, for each pixel, a control signal for defining a gradation area based on an input N-bit (N is a positive integer) input image signal;
A smoothing area to be smoothed is identified based on the control signal generated in the first generation step, and based on the end of the specified smoothing area and the position of each pixel included in the smoothing area, A second generation step of generating an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
The tap length of the smoothing filter is adjusted based on the adjustment signal generated in the second generation step, and the N-bit input image signal based on the control signal generated for each pixel in the first generation step Outputting an N + k-bit output image signal for each pixel, which is selectively smoothed by the smoothing filter and the number of gradations is expanded by a predetermined number,
A program that causes a computer to execute. An image signal correction unit for correcting the input image signal;
An image display unit capable of displaying an image represented by an image signal of N + k bits (N and k are positive integers) based on the image signal corrected by the image signal correction unit;
With
The image signal correction unit
A smoothing region detecting unit that generates a control signal for defining a gradation region for each pixel based on the input N-bit input image signal;
A smoothing area to be smoothed is specified based on the control signal, and the signal is smoothed according to the tap length based on the end of the specified smoothing area and the position of each pixel included in the smoothing area. A tap length adjusting unit that generates an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
A smoothing filter whose tap length is variable based on the adjustment signal, and selectively smoothing the input image signal of N bits by the smoothing filter based on the control signal generated for each pixel; A gradation number expansion unit for outputting an N + k-bit output image signal whose number is expanded by a predetermined number for each pixel;
A display device comprising: An image signal correction unit for correcting the input image signal;
An image display unit capable of displaying an image indicated by an image signal of N bits (N is a positive integer) based on the image signal corrected by the image signal correction unit;
With
The image signal correction unit
A smoothing region detecting unit that generates a control signal for defining a gradation region for each pixel based on the input N-bit input image signal;
A smoothing area to be smoothed is specified based on the control signal, and the signal is smoothed according to the tap length based on the end of the specified smoothing area and the position of each pixel included in the smoothing area. A tap length adjusting unit that generates an adjustment signal for adjusting the tap length of the smoothing filter for each pixel;
A smoothing filter whose tap length is variable based on the adjustment signal, and selectively smoothing the input image signal of N bits by the smoothing filter based on the control signal generated for each pixel; A gradation number expansion unit for outputting an N + k-bit output image signal whose number is expanded by a predetermined number for each pixel;
A pseudo gradation processing unit for converting the number of gradations of the output image signal output from the gradation number expansion unit into an N-bit image signal using a pseudo intermediate gradation;
A display device comprising:

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