JP2000004380A - Image display method and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display method for improving contrast with a small circuit scale and operation quantity and displaying the image of high dynamic range, without being affected by a non-image boundary around an image and without deteriorating the relative contrast at the center of the image. SOLUTION: A common low frequency attenuation circuit 8 is used for an optical illusion waveform generation circuit 2 and a gradation conversion circuit 1 corresponding to luminance frequency near an edge, by using an IIR filter for a low-pass filter in the vertical direction. Thus, contrast can be improved, while a circuit scale is suppressed. Then, the contrast corresponding to a display device can be improved by adding γ-correction function.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display method and apparatus capable of obtaining a higher quality image on a display for displaying, for example, a television signal.

[0002]

2. Description of the Related Art In recent years, the size of television screens has increased, and
For a screen having a screen size of inches or more, a projection type system using a liquid crystal panel is promising. In addition, broadcasting of high-definition television has started, and the need for a high-resolution, large-area display device has been increasing. Further, imaging with a high dynamic range can be performed by a three-panel camera or the like.
However, a display device with a high resolution and a large area does not have sufficient contrast performance, and an image with a high dynamic range cannot be sufficiently expressed by a conventional display device. As a method for improving this, Japanese Patent Application Laid-Open No. 7-17042
No. 8 (Japanese Patent Application No. 6-3457) has been proposed. Hereinafter, the conventional contrast improving method will be described.

FIG. 13 is a block diagram of the entire processing.
01 is a gradation conversion circuit for converting the gradation of the input luminance, 102
Is an illusion waveform generation circuit that generates a waveform that causes an illusion from the input luminance, and obtains an image with improved contrast by superimposing an illusion waveform on the luminance whose gradation has been converted by the gradation conversion circuit 101. Below, the gradation conversion circuit 101
The details of the illusion waveform generation circuit 102 will be described.

FIG. 14 is a block diagram of the gradation conversion circuit 101. The frame memory 123 stores the luminance input for one frame. The edge extraction circuit 124 detects an edge from the luminance input. The gradation conversion table calculation circuit 125 calculates a gradation conversion table at nine points q1 to q9 in the nine regions shown in FIG. The gradation conversion table interpolation circuit 129 reads coordinate values for performing gradation conversion from the read control circuit 127, and interpolates the gradation conversion tables for q1 to q9 according to the coordinate values (for example, the gradation conversion table at four neighboring points). Is linearly interpolated by weighting and adding according to the distance between the four points and the pixel of interest) and written into the table memory 128. The read control circuit 127
The luminance data is read out from the frame memory 123 in the order of scanning, the read coordinate values are output to the gradation conversion table interpolation circuit, the conversion value corresponding to the luminance is read from the table memory 128, and the converted luminance is output.

Next, the illusion waveform generation circuit 102 will be described. 16 and 17 show the step input and the step response of the illusion waveform generation circuit 102. 16 and 17
For simplicity, the luminance distribution is represented one-dimensionally. The step response of the illusion waveform generation circuit 102 is obtained by attenuating a low-frequency component of a step input and converting an output characteristic (gain characteristic) into a luminance amplitude range that does not cause a sense of discomfort during observation.

FIG. 18 shows a luminance distribution perceived when the step response of the illusion waveform circuit 102 is superimposed on the step input and observed. In FIG. 18, the solid line is the illusion waveform circuit 102.
Is a luminance level obtained by superimposing the step response on the step input, and the dashed line is a luminance distribution perceived during observation. FIG.
8 indicates that the psychological contrast is improved by superimposing the output of the illusion waveform generation circuit 102.
Further, with respect to the luminance distribution as shown by the solid line in FIG. 19, the luminance difference of i1-i0 is perceived at the position x1, and the luminance difference of i2-i1 is perceived at the position x2, as indicated by the broken line. Since the brightness difference between i1 and i2 is not perceived between x2, the brightness differences I1-I0 and I3-I2 in the brightness range I3-I0 are larger than the brightness range I3-I0.
Can be displayed, and the contrast can be improved.

As described above, conventionally, both the local gradation conversion based on the luminance distribution near the edge and the superposition of the illusion waveform are applied to effectively utilize the gradation reproduction capability of the display device. Further, the contrast perceived during image observation is improved.

[0008]

However, in the above-described conventional configuration, 1) a boundary of a non-image portion (corresponding to a horizontal or vertical blank period) at an end of an image is extracted as an edge, and a boundary near the boundary is extracted. The luminance frequency distribution (that is, the luminance frequency distribution at the peripheral portion of the image) greatly affects the processing result, and the contrast at the central portion of the image is relatively reduced as compared with the peripheral portion. 2) When the entire image is divided into nine local regions, a region that originally had uniform luminance over the entire screen is converted to be bright at the periphery of the image and dark at the center, or conversely, dark at the periphery and dark at the center. The image is converted to a bright image, which may cause discomfort during observation. 3) The circuit scale is large as compared with other conventional methods (luminance frequency equalization). There was a problem that.

In view of the above, the present invention is not affected by the boundary of the non-image portion around the image, does not cause a relative decrease in contrast at the center of the image, and has a small circuit scale and a small amount of calculation.
It is an object of the present invention to provide an image display method for displaying a high dynamic range image with improved contrast.

[0010]

SUMMARY OF THE INVENTION The present invention improves the contrast perceived during observation by generating an image that causes an illusion from an input image and superimposing the image on a gradation-converted image of the input image. An image display method,
(A) gamma correction of the luminance after the illusion image is superimposed in accordance with the characteristics of the display device; (b) gamma correction of the gradation-converted signal; or (c) floor used for gradation conversion. The value of the tone conversion table is corrected according to the characteristics of the display device, or (d) the luminance value of the pixel of the input image is previously set to γ
An image display method characterized by performing contrast correction to improve contrast according to characteristics of a display device.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a display device which superimposes a waveform which causes an illusion of a luminance level on an image whose luminance level is converted in accordance with a local luminance frequency near an edge and a coordinate value of a pixel. An image display method characterized by effectively utilizing the tone reproduction ability of an image and improving an apparent (psychological) contrast of an image displayed on a display device, and an input image, A gradation conversion circuit for converting a luminance level in accordance with a local luminance frequency near an edge and a coordinate value of a pixel; and an illusion waveform generation circuit for generating a waveform that causes an illusion of the luminance level. An image display device that effectively utilizes a reproducibility and improves an apparent or psychological contrast of an image displayed on a display device.

According to the present invention, a waveform which causes an illusion of a luminance level is superimposed on an input image by transforming a luminance level according to a local luminance frequency near an edge and a coordinate value of a pixel with the above-mentioned configuration. To effectively use the gradation reproduction capability of a display device and improve the apparent (psychological) contrast of an image displayed on the display device.

(Embodiment 1) FIG. 1 shows a configuration diagram of an image display device according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a gradation conversion circuit that converts a luminance level according to a local luminance frequency near an edge and a coordinate value of a pixel, 2 denotes an illusion waveform generation circuit that generates a waveform that causes an illusion of a luminance level, Reference numeral 3 denotes a delay circuit that outputs input luminance after a delay time corresponding to the delay time of the illusion waveform generation circuit 2, 4 denotes an edge extraction circuit that extracts an edge of the input luminance, and 5 denotes a local luminance frequency near the edge. 6 is a table memory for storing a gradation conversion table for each representative area set in the image, and 7 is the luminance of the pixel of interest according to the coordinate value of the pixel of interest. A conversion value interpolation circuit that interpolates and calculates the conversion result of each gradation conversion table, 8 is a low frequency attenuating circuit that attenuates the low spatial frequency component of the input luminance, and 9 is an amplitude characteristic of the output of the low frequency attenuating circuit 8. It is a characteristic conversion circuit for outputting the illusion waveform by conversion.

The operation of the above configuration will be described below.
The delay circuit 3 holds the input luminance for a certain period of time, and outputs the input luminance after a delay time corresponding to the delay time of the illusion waveform generation circuit 2. The edge extraction circuit 4 extracts and outputs a high-frequency component of the input luminance.

The gradation conversion table calculation circuit 5 counts the luminance frequencies of the four representative areas shown in FIG. 2 for pixels whose absolute value of the output of the edge extraction circuit 4 is equal to or larger than the threshold value. FIG. 2 is a diagram showing the four images set in the field image.
FIG. 5 is a diagram showing two representative regions, in which p1, p2, p3,
p4 indicates the barycentric coordinates of each representative area. In FIG. 2, by setting the representative area away from a single part of the image, the boundary with the non-image part is extracted as an edge, and the luminance frequency at the image edge strongly affects the gradation conversion result at the center of the image. In this way, it is possible to prevent the contrast from being relatively lowered at the center of the image.

Next, a gradation conversion table calculation circuit 5 calculates a normalized cumulative luminance frequency according to (Equation 1) from the luminance frequencies counted for each representative area, and generates a table memory as a gradation conversion table. Write to 6.

[0017]

(Equation 1)

Here, hi (j) is the frequency of the quantized luminance j in the i-th representative area, and Hi (I)
Is the normalized cumulative frequency (gradation conversion table) of the i-th representative area of the quantized luminance I, and maxI is the maximum value of the quantized luminance (255 for 8-bit quantization and 10 for 10-bit quantization). If so, it is 1023). If the luminance frequency counted in each representative area has a large deviation,
Since the conversion result is uncomfortable or noise is conspicuous, the gradient of the gradation conversion table is controlled by setting a restriction in advance (Equation 2) and correcting the distribution of the luminance frequency.

[0019]

(Equation 2)

Here, α is a positive coefficient greater than 1, mean
hi is the average frequency in the i-th representative area, and min () is the selection of the minimum value. By setting α, the gain of the luminance expansion at the time of conversion is controlled. further,
By correcting the luminance frequency distribution according to (Equation 3), the gain of the gradation conversion table can be reliably reduced to the set value α or less.

[0021]

(Equation 3)

Here, hi2 (j) is the frequency after correction according to (Equation 2), and hi1 (j) is the frequency before correction. (Equation 3)
Indicates that the frequency of clipping according to (Equation 2) is evenly distributed to all gradations. With this correction, even when the frequency distribution near the edge is extremely biased toward a certain gradation, the gain of the gradation conversion table can be reliably limited to a set value or less.

Writing to the table memory 6 is performed by providing a restriction on time change shown in (Equation 4).
When the change of the image in the time direction is abrupt, it is possible to prevent the gradation conversion table from abruptly changing over time and causing a sense of incongruity in the conversion result.

[0024]

(Equation 4)

Here, Hiold () is the gradation conversion table for the i-th representative area previously written in the table memory 6, and Hinow () is the i-th representative calculated by the gradation conversion table calculation circuit 5 for the current field. The tone conversion table in the area, Hinew (), is updated by the current field and is newly written in the table memory 6, and β is a non-negative decimal number of 1 or less. By setting β, a change in the time direction of the gradation conversion table can be restricted, and it is possible to prevent the gradation conversion table from suddenly changing over time and giving a strange feeling to the conversion result. The value of β is from 1/16 to 1/64
By changing the gradation conversion table for each field, the gradation conversion table can be smoothly changed over a period of one or two seconds even when the gradation frequency suddenly changes at the time of a scene change or the like. , So that the conversion result does not cause discomfort.

The conversion value interpolation circuit 7 refers to the four gradation conversion tables stored in the table memory 6 and converts the gradation conversion values H 1 (I) and H 2 of the input luminance I from the delay circuit 3.
(I), H3 (I) and H4 (I) are obtained. Then, the conversion value interpolation circuit 7 performs an interpolation (or extrapolation) calculation using the gradation conversion value and the barycentric coordinates p1 to p4 of the representative area in accordance with the coordinate value of the input luminance I in the image, and Determine and output the converted value for I.

FIG. 3 is a diagram showing an example of a method of interpolating conversion values by the conversion value interpolation circuit 7. In the figure, the dashed line is the representative area set in the field image, p1 to p4 are the centers of gravity of the representative areas, and the hatched area A is the gradation based on the gradation conversion table calculated for the nearest representative area. 3 shows an area where tone conversion is performed. The shaded area B performs tone conversion by interpolating the conversion values calculated by the tone conversion table calculated in the two representative areas in the vicinity according to the coordinate values of the pixels and the coordinates of the center of gravity of the representative area. Indicates the area to be performed. The area C at the center is an area in which gradation conversion is performed by interpolating the conversion values based on the gradation conversion table calculated for the four representative areas according to the coordinate values of the pixels and the coordinate values of the center of gravity of the representative area. Show. The areas A, B, C
May pass through the center of gravity of the representative area as shown in FIG. 3A, or may be as shown in FIG. 3B. In FIG. 3A, the areas A, B, and C are wider in this order, and in FIG. 3B, the areas A, B, and C are reversed.
It becomes narrow in the order of C.

The low-frequency attenuating circuit 8 attenuates low-frequency components of spatial frequency in the horizontal and vertical directions of the input luminance. The characteristic conversion circuit 9 converts the amplitude characteristic of the output of the low frequency component attenuation circuit 8 and outputs an illusion waveform. FIG. 4 shows an example of the input / output characteristics of the characteristic conversion circuit 9. The output of the illusion waveform generation circuit is superimposed on the output of the gradation conversion circuit 1 and output as output luminance.

As described above, according to the present embodiment, the luminance is converted so that the luminance level of the image largely changes near the edge, and a waveform that causes the illusion of the luminance level is superimposed on the luminance, thereby displaying the image. The contrast of the image displayed on the device can be improved.

Further, the counting of the gradation frequency of the pixel near the edge is not performed at the end of the image, so that
The gradation conversion table is strongly influenced by the frequency of the pixels near the edges in the peripheral portion of the image, so that it is possible to prevent a feeling of strangeness at the central portion of the image and a decrease in contrast at the central portion of the image during observation.

Further, by limiting the change in the time direction of the gradation conversion table, it is possible to reduce discomfort during observation due to the change in the brightness of the object in the image in the time direction.

In the calculation of the gradation conversion table, the gradation conversion tables in several representative regions in the image are calculated based on the frequency distribution of the pixels near the edges. The amount of calculation can be reduced by interpolating and extrapolating the gradation conversion value in the region.

In the present embodiment, the same effect can be obtained and the circuit scale can be reduced even if the edge extraction circuit 4 and the low frequency attenuation circuit 8 are shared and the configuration shown in FIG. 5 is used. Are included in the present invention.

(Embodiment 2) FIG. 9 shows the configuration of an image display device according to a second embodiment of the present invention. In FIG. 9, the same operations as those of the image display device according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The following describes the gradation conversion table calculation circuit 16, the table memory 17, The operation of the value interpolation circuit 18 will be described.

The gradation conversion table calculation circuit 16 counts the luminance frequencies of the four representative regions shown in FIG. 2 for pixels whose absolute value of the output of the low frequency attenuation circuit 8 is equal to or larger than the threshold value. FIG. 2 is a diagram showing the four images set in the field image.
FIG. 7 is a diagram showing two representative regions, in which p1, p2, p
3 and p4 indicate the coordinates of the center of gravity of each representative area.

FIG. 10 shows a gradation conversion table calculation circuit 16.
FIG. 3 is a block diagram showing an example of the configuration of FIG. In FIG. 10, 19 is a write control circuit, 20a to 20d are counters for counting the tone frequency in each representative area, 21 is a tone conversion table calculated from the tone frequency in each representative area, and the tone conversion table is stored in a table. M to output to memory
PU. The operation of each configuration will be described below.

The write control circuit 19 determines whether the absolute value of the edge component of the input luminance output from the low-frequency attenuation circuit 8 is equal to or larger than the threshold value and the coordinates of the input luminance are within the representative area shown in FIG. The frequency value corresponding to the input luminance of the frequency counter corresponding to the representative area including the coordinates of the input luminance is incremented.

The frequency counters 20a to 20d count the gradation frequency in each representative area. The gradation frequency count is performed for all gradations (256 gradations for 8 bits, 10 gradations for 10 bits).
The circuit scale can be reduced by dividing (about 23 gradations) into about 16 (that is, counting the frequency of the upper 4 bits of luminance).

The MPU 21 calculates the gradation conversion table by performing the operations shown in (Equation 1) to (Equation 4) with respect to the frequency obtained by dividing and counting all the gradations, and calculates the gradation conversion table during the vertical blanking period. Writing to the table memory 17, the frequency value of the frequency counter 20 is cleared to zero.

The conversion value interpolation circuit 18 interpolates the value of the gradation conversion table written in the table memory 17 for each representative area, and performs gradation conversion of the input luminance. FIG. 11 is a diagram showing a method of interpolating the data of the gradation conversion table and performing gradation conversion of the input luminance. In FIG. 11, a black point is gradation conversion table data calculated based on the frequency of dividing and counting all gradations into about 16 sections in one representative area. The conversion value interpolation circuit 18 linearly interpolates the gradation conversion table data discretely calculated for each representative area to convert the input luminance. Then, the conversion result in each representative area is interpolated according to the coordinates of the input luminance and output as output luminance.

FIG. 3 is a diagram showing an example of a method of interpolating conversion values by the conversion value interpolation circuit 18. In the figure, the dashed line is the representative area set in the field image, p1 to p4 are the centers of gravity of the representative areas, and the hatched area A is the gradation based on the gradation conversion table calculated for the nearest representative area. 3 shows an area where tone conversion is performed. In the shaded area B, tone conversion is performed on the converted values of the tone conversion table calculated in the two representative areas in the vicinity according to the coordinate values of the pixels and the coordinate values of the center of gravity of the representative area. Indicates the area. The area of C in the center is 4
An area where tone conversion is performed by interpolating conversion values based on the tone conversion table calculated in one representative area according to the coordinate values of pixels and the coordinate values of the center of gravity of the representative area. The areas A, B,
The boundary of C may pass through the center of gravity of the representative area as shown in FIG. 3A, or may be as shown in FIG. 3B.

As described above, according to the present embodiment, the gradation conversion table is calculated based on the frequency obtained by dividing and counting the gradation for each section, so that the circuit scale of the frequency counter and the table memory Capacity can be reduced,
(That is, if the 8-bit gradation frequency is measured in, for example, 16 sections, the number of counters required for the measurement is reduced from 256 to 16 compared to measuring all the gradation frequencies. Also, the number of data of the gradation conversion table value can be similarly reduced.) Further, by performing gradation conversion on the luminance input by interpolating the gradation conversion table, gradation conversion can be performed with a small circuit scale and a small amount of calculation. It can be carried out.

In all the embodiments of the present invention, the luminance frequency count is weighted according to the coordinate value of the pixel (the weight coefficient is increased in the central portion of the image, and reduced in the peripheral portion of the image). This can eliminate the relative decrease in contrast at the center of the image, and is included in the present invention.

Note that edge extraction may be performed by a one-dimensional filter in the horizontal direction, and the circuit can be simplified, which is included in the present invention.

The calculation of the gradation conversion table in the representative region described in the first and second embodiments is sequentially performed for one representative region in one field period, and at the same time, the time change of the gradation conversion table is calculated. The coefficient β to be controlled (Equation 4) is increased according to the number of representative regions (first
(In the case of the second embodiment, for example, four times), the same effect can be obtained by reducing the calculation amount, and is included in the present invention.

In all the embodiments of the present invention, as shown in FIG. 6, the low frequency attenuating circuit 8 is an LPF including a horizontal FIR LPF and a vertical IIR circuit.
Is used, the circuit has a symmetric phase characteristic in the horizontal direction and an asymmetric phase characteristic in the vertical direction, but can be configured with a small circuit scale, and is included in the present invention. FIG. 6 shows an example of the configuration of the low-frequency attenuating circuit 8. In FIG. 6, reference numeral 10 denotes a delay circuit for delaying an input signal according to a delay time by a horizontal and vertical LPF, and 11 denotes an FIR type horizontal LP.
F and 12 are vertical LPFs including an IIR type circuit. The output of the vertical LPF, which is a low frequency component in the horizontal and vertical directions, is subtracted from the delayed input signal, and a low frequency attenuation component of the input signal is output. The arrangement of the FIR type LPF 11 and the vertical LPF 12 may be reversed from that shown in FIG.

In all the embodiments of the present invention, the low-frequency attenuating circuit 8 uses the output of the vertical LPF including the IIR type circuit as the input of the FIR type horizontal LPF as shown in FIG. Most of the circuit 10 can be shared with the vertical LPF, and the circuit size can be reduced, which is included in the present invention. In FIG. 7, reference numeral 13 denotes a delay circuit that delays and outputs data for one line, 14 denotes a multiplier that multiplies the data by a constant, and 15 denotes data delayed by a delay (about several pixels) by the FIR horizontal LPF and output. It is a delay circuit. The constant M4 is a decimal number less than 1 (condition for preventing the output from diverging), and M0 to M3 are set so that the sum becomes 1-M4 (condition for the gain after time elapses to become 1).

In the first and second embodiments of the present invention, the case where four representative areas are set has been described. However, as shown in FIG. 8, a representative area is also set at the center of an image. It is also possible to reduce the occurrence of discomfort and a decrease in contrast at the center of the screen, which are included in the present invention.

The output luminance (luminance after the illusion waveform is superimposed) of all the embodiments of the present invention is γ-corrected in accordance with the characteristics of the display device, the output of the gradation conversion circuit is γ-corrected, The tone conversion table is corrected in accordance with the characteristics of the display device, the frequency is weighted in accordance with the gradation, or the frequency is counted. By changing the length or correcting the input luminance in advance, the contrast can be improved in accordance with the characteristics of the display device, and this is included in the present invention.

The counting of the frequency weighted according to the gradation is performed by calculating the gradation conversion table by multiplying the frequency in each section by the weight coefficient shown in FIG. 12 when calculating the gradation conversion table by the MPU 21 in FIG. Accordingly, it can be performed easily and without increasing the circuit scale. Multiplying by the weight coefficient shown in FIG. 12 indicates that the gradation conversion shown in (Equation 5) is performed in advance. That is, the γ correction before the gradation correction is 2
This means that the conversion is approximated by the following equation.

[0051]

(Equation 5)

In (Equation 5), a · I + b indicates a weighting factor for gradation I.

It should be noted that the distribution of the weighting coefficients is not limited to the linearly changing distribution shown in FIG. 12, but may be a distribution that changes in a curved line.

The MPU 21 similarly corrects the gradation conversion table according to the characteristics of the display device by simply multiplying the value of the gradation conversion table by the γ correction value without increasing the circuit scale. be able to. Multiplying the value in the gradation conversion table by the γ correction value is equivalent to performing γ correction on the value after gradation conversion.

[0055]

As described above, according to the present invention, the luminance is converted so that the luminance level of the image largely changes near the edge, and a waveform that causes an illusion of the luminance level is superimposed on this. The contrast of the image displayed on the display device can be improved.

Further, the counting of the gradation frequency of the pixel in the vicinity of the edge is not performed at the end of the image.
The gradation conversion table is strongly affected by the frequency of the pixels near the edge in the peripheral portion of the image, so that it is possible to prevent a discomfort in the central portion of the image during observation and prevent the contrast from decreasing in the central portion of the image.

Further, by limiting the change in the time direction of the gradation conversion table, it is possible to reduce discomfort at the time of observation due to the change in the brightness of the same object in the image in the time direction.

The tone conversion table is calculated based on the frequency distribution of the pixels near the edge in the representative area, and for each pixel, the tone conversion value in the representative area is calculated. By interpolating and extrapolating
The amount of calculation can be reduced.

The calculation of the gradation conversion table is performed based on the frequency obtained by dividing and counting the gradation for each section, and interpolating the gradation conversion table to perform gradation conversion of the luminance input. In addition, the circuit size of the frequency counter and the capacity of the table memory can be reduced.

Further, a low frequency attenuation circuit and an edge extraction circuit,
The circuit scale can be reduced by sharing the delay circuit and part of the IIR vertical LPF.

The luminance after the illusion waveform is superimposed is γ-corrected according to the characteristics of the display device, the output of the gradation conversion circuit is γ-corrected, and the gradation conversion table is corrected according to the characteristics of the display device. Or counting the frequency weighted according to the gradation, changing the section length according to the gradation when dividing all the gradations into sections, and counting the frequency, and correcting the input luminance in advance by γ. Thereby, the contrast can be improved according to the characteristics of the display device, and the effect is large.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image display device according to a first embodiment of the present invention.

FIG. 2 Local luminance frequency (local histogram)
Diagram showing the area for calculating

FIGS. 3A and 3B are diagrams showing interpolation and extrapolation of a gradation conversion result.

FIG. 4 is a diagram illustrating an example of input / output characteristics of a characteristic conversion circuit;

FIG. 5 is a configuration diagram of an image display device that shares an edge extraction circuit and a low-frequency attenuation circuit.

FIG. 6 is a diagram illustrating an example of a configuration of a low-frequency attenuation circuit.

FIG. 7 is a diagram showing an example of a configuration of a low-frequency attenuation circuit with a reduced circuit scale.

FIG. 8: Local luminance frequency (local histogram)
Diagram showing the area for calculating

FIG. 9 is a configuration diagram of an image display device according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating an example of a configuration of a gradation conversion table calculation circuit.

FIG. 11 is a diagram showing gradation conversion by a gradation conversion table approximated by a polygonal line;

FIG. 12 is a diagram showing a distribution of weighting coefficients for correcting a gradation conversion value.

FIG. 13 is a configuration diagram of a conventional image display device.

FIG. 14 is a configuration diagram of a gradation conversion circuit in a conventional image display device.

FIG. 15 is a diagram showing an area for calculating a local luminance frequency (local histogram).

FIG. 16 shows a step input.

FIG. 17 is a diagram showing a step response of a low-frequency attenuation circuit.

FIG. 18 is a view showing a result of contrast improvement.

FIG. 19 is a diagram showing a result of contrast improvement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gradation conversion circuit 2 Illusion waveform generation circuit 3 Delay circuit 4 Edge extraction circuit 5 Gradation conversion table calculation circuit 6 Table memory 7 Conversion value interpolation circuit 8 Low frequency attenuation circuit 9 Characteristic conversion circuit

Claims (4)

[Claims] 1. An image generating an illusion from an input image,
This is an image display method in which the contrast perceived during observation is improved by superimposing the image on a gradation-converted image of the input image. (A) The luminance after the illusion image is superimposed on the basis of the characteristics of the display device gamma correction, or
(B) performing gamma correction on the signal whose gradation has been converted, or
(C) correcting the value of the gradation conversion table used for gradation conversion according to the characteristics of the display device, or (d) correcting the luminance value of the pixel of the input image in advance by gamma correction, An image display method characterized by performing contrast improvement in accordance with the following. 2. An image generating an illusion from an input image is generated.
This is an image display method for improving the contrast perceived during observation by superimposing the input image on a gradation-converted image, and using an IIR filter in the vertical direction when generating an image that causes an illusion. Characteristic image display method. 3. A representative region is set in an image, a gradation conversion table is obtained based on a gradation frequency distribution of luminance of pixels in the vicinity of the edge of the image in the representative region, and the gradation conversion table is used. An output image from the gradation conversion circuit and the illusion waveform by using a gradation conversion circuit that performs different gradation conversion for each pixel, and an illusion waveform generation circuit that generates an image that causes an illusion from an input image. An image display method for improving a contrast perceived during observation by superimposing an output image from a circuit, comprising: a low-frequency attenuation circuit used for edge detection in the gradation conversion circuit; and an illusion waveform in the illusion waveform generation circuit. An image display method characterized by sharing a low-frequency attenuating circuit used for generating an image. 4. An image display device driven by the image display method according to claim 1.