RU2251160C2 - Image quality correction circuit - Google Patents

Abstract

FIELD: image correction technologies.

SUBSTANCE: image quality correction circuit has a counter of frequency of appearance of brightness levels for counting frequency of appearance of multiple brightness levels, selection of which is performed from video signals, sent to video signal input, linear interpolator for forming correcting characteristics by means of interpolation on basis of points of calculated value, taken from output of appearance frequency counter, and image quality corrector for correction of received video signals in accordance to correcting characteristic points.

EFFECT: better image quality.

5 cl, 21 dwg

Description

Technical field

The present invention relates to an image quality correction scheme for correcting image quality (for example, color tone correction) depending on the image content when display panels are used, in particular a plasma display panel (PDD), a liquid crystal display panel (LCD), etc. .

State of the art

The traditional image quality correction scheme shown in FIG. 1 is configured to extract an average image level (IMS) for each frame (or field) using an average level calculator 10, read from the ROM 14 corresponding correction data according to the IMS, which serves as an address for correction of the input video signal produced using the corrector 16 image quality in accordance with the characteristic conversion of the input signal to the output corresponding to the correction data, and the subsequent the output of the corrected signal to the output of the corrector 18. IMSs are obtained, for example, by dividing the sum of the products of the total number of point image elements of each frame (or each field) and the distribution of the appearance frequency (number of occurrences) of each brightness level by the total number of point image elements.

According to the traditional solution illustrated in FIG. 1, since the image quality correcting data is based on the IMS, the image display quality can be improved in image areas with a uniform brightness distribution. However, the image quality cannot be improved in the case of a real image, if you do not take into account the histogram of the brightness level (frequency distribution of the appearance of the brightness level).

Consider, for example, case 1 of the distribution of the frequency of occurrence of the brightness level when the brightness levels prevail on the bright side - according to Figure 2 (a); and case 2 of the distribution of the frequency of occurrence of the brightness level, when the brightness levels prevail on the dark side - according to Figure 2 (b). If we assume that the MIS are equal regardless of the different brightness levels, then the problem arises that in the case according to Figure 2 (a), the resolution on the bright side is degraded, while in the case according to Figure 2 (b) The resolution on the dark side deteriorates. For the case according to FIG. 3, the distribution of the frequency of occurrence of the brightness level prevails in a narrow region on the dark side with a low brightness level, the correction characteristic has a large steepness section, which leads to negative consequences, which are reflected in the fact that the image brightness is amplified beyond the need and therefore the resolution Images on the light side are reduced. The same happens when the frequency distribution of the appearance of the brightness level prevails on the bright side of the image.

To solve the above problems, the applicant has already proposed a video signal correction circuit according to FIG. 5 in accordance with Japanese Patent Application Laid-Open No. 8-23460. According to the proposed scheme, the input video signals SO containing analog K, Z, C signals, or signals of red, green, and blue tones are converted into digital K, Z, and C signals using analog-to-digital converter 20 and input as an address of a lower rank in ROM 22 for converting an input signal to an output, that is, for correcting a color tone, using the look-up table method. On the other hand, the Y signal (luminance signal) is formed from the analog signals K, 3, and C by the matrix circuit 24, and the Y signal is converted to a digital signal using an analog-to-digital converter 26 for input into the histogram circuit 28. The histogram circuit 28 counts the frequency (distribution) of the appearance of the brightness level for each range of the brightness level, divided into several ranges (for example, 4 ranges). The decoder 30 decodes the counting result using a histogram circuit 28 for introducing, as an address of a higher rank, into the ROM 22 to select the color tone correction characteristics previously stored in the ROM 22, thereby correcting the color tones of the input digital K, Z, C signals, output as digital K, Z, C signals 31.

Using the video correction circuit shown in FIG. 5, it is possible to correct the gradation of brightness according to the distribution of the frequency of occurrence of the brightness level of the input video signal, however, this circuit also does not allow to obtain a correction characteristic corresponding to the frequency of occurrence of each brightness level.

The present invention is based on the task of eliminating the aforementioned disadvantages inherent in technical solutions from the prior art and creating an image quality correction scheme for correcting all types of images based on the optimal correction characteristics corresponding to the frequency of occurrence of each brightness level.

Disclosure of invention

The first embodiment of the present invention encompasses an image quality correction circuit comprising an average value calculator 10 for calculating an average value of brightness levels of each of the multiple image elements of a video signal supplied to video signal input 12, a counter 13 for counting the frequency of occurrence of each level selected from a plurality of levels brightness calculated by the average value calculator 10, a linear interpolator 15 for generating a correction characteristic, and a corrector 16 image properties for correcting the input video signal in accordance with the correction characteristic.

According to the invention, the video signal input 12 is processed in the average value calculator 10 to determine the average value (brightness levels) of multiple picture elements by calculating the frequency of occurrence of each brightness level. Linear interpolator 15 graphically provides a characteristic — a linear interpolation line consisting of several continuous segments; moreover, the brightness level values are plotted along the y axis, and the appearance frequency values are plotted along the x axis.

The image quality corrector 16 processes the video signal input 12 to correct the image quality according to the correction characteristic provided by the linear interpolator to obtain the corrected video signal at the output 18.

A second embodiment of the present invention is an image quality correction circuit comprising a counter 13 for counting the frequency of occurrence of a plurality of brightness levels extracted from the video signal input 12 for each of the predetermined levels, a correction curve generator 25 to generate a new correction curve based on data obtained at the output of the counter 13 of the frequency of occurrence of the brightness level, and data of predefined points entered along with the points of delivery, and the corrector 16 image quality for the correction of the input video signal according to the correction characteristics provided by the correction curve generator 25.

According to the invention, the data of every second frequency of occurrence (brightness level) of the video signal input 12 is used, and, on the other hand, set values corresponding to predefined brightness levels drawn on a straight line connecting the starting and ending points of the graph are entered, resulting in these values can be rearranged in accordance with a given brightness level, with the aim of their mutual interpolation to form a Bezier curve. The video signal supplied to input 12 is processed to correct the image quality according to the Bezier curve and removed from output 18.

The circuit according to the third embodiment of the invention contains a counter for the frequency of occurrence of the brightness level of each image element of the input video signal in N frames (N = any integer from 1 and above) for each of the set of level ranges, a change controller for monitoring the change in the calculated value of the frequency counter at the output the appearance of a linear interpolator prior to some change during a period equal to several periods of the N-frame, to provide a correction characteristic by interpolating based on the count value obtained from the output of the controller and changes the image quality corrector for correcting the input video signal by the linear interpolator according to the correcting characteristic line provided by the interpolator.

In accordance with this technical solution, when the video signal is subsequently fed into the counter of the appearance frequency of the brightness level, the appearance frequency of the brightness level of each image element in the N-number of frames is counted by the appearance frequency counter for each of a plurality of ranges of a given level. Since the change in the calculated value of the appearance frequency counter is controlled to a certain change during the multiple ranking period of the N-frame period by the change controller, the change in the correction characteristic generated by the linear interpolator is simultaneously controlled. The image quality corrector corrects the input video signal according to the correction-controlled correction characteristic.

The fourth embodiment of the invention implies the presence of a counter for counting the frequency of occurrence of the brightness level of each image element in N-frames for each multiple range of a given level, a change controller for monitoring the output, changing the calculated value of the counter of the frequency of occurrence to a certain change during a multiple ranking period of period N -frame, correction curve generator for generating a new correction curve based on the calculated value, output of the change controller, and a predetermined predetermined value, and an image quality corrector for correcting the input video signal according to the correction curve generated by the correction curve generator.

In accordance with this technical solution, when a video signal is supplied to the counter of the appearance frequency of the brightness level, the appearance frequency of the brightness level of each image element is calculated for each multiple range of a given level. Since the change in the calculated value of the counter of the frequency of occurrence is controlled to a certain change during the multiple ranking period of the N-frame period and this change is introduced into the correction curve generator, the change in the correction curve generated by the correction curve generator is also controlled. For quality correction processing, the image quality corrector corrects the input video signal according to a change-controlled correction curve.

To simplify the execution of the appearance frequency counter, an average value calculating means is used to calculate the average value of brightness levels for each of the m image elements, as a result of which the appearance frequency counter calculates the frequency of appearance of the brightness level for each predetermined multiple range of a given level.

The appearance frequency counter is simplified by eliminating the adder. Moreover, the counter contains a plurality of discriminators in order to determine whether the brightness level of each image element corresponds to each of the multiple ranges of a given level, a plurality of first counters for counting the discrimination frequency performed by each of the discriminators, a plurality of comparators for comparing the calculated value of the first counter with a predetermined reference value and for setting the reading of the first counter according to the output signal of the comparator and A set of second counters for counting the frequency of the output signal of the comparator and determining the frequency of occurrence (brightness level).

To simplify the implementation of the counter frequency of occurrence due to the exclusion of the adder, the counter frequency of occurrence is performed containing a number of discriminators in order to determine whether the brightness level calculated by means of calculating the average value, each of the multiple ranges of a given level; a plurality of first counters for counting the frequency of discrimination performed by each of the discriminators; a plurality of comparators for comparing the calculated value of the first counter with a predetermined reference value and for setting a reading of the first counter taking into account the output signal of the first comparator; and a plurality of second counters for counting the frequency of the output signal of the comparator in order to determine the frequency of occurrence.

To simplify the implementation of the change controller, the latter contains a difference detector, a constant multiplier, an adder, and an N-frame decelerator, while the difference detector distinguishes the difference between the value generated by the appearance frequency counter and the value of the output signal of the N-frame decelerator, a constant multiplier allows you to obtain the product of the output signal of the difference detector by 1 × X (X = an integer equal to 2 or greater), the adder sums the signal from the output of the multiplier by a constant with the signal from the output from As a means of slowing down the N-frame, the means for slowing down the N-frame delays the signal from the output of the adder to N-frames for supplying to the difference detector and to the adder the signal from its output not only as such, but also as the output signal, the change of which is regulated.

A fifth embodiment of the present invention is an image quality correction circuit comprising an occurrence frequency counter 13 for counting an occurrence frequency of multiple brightness levels selected from a video signal input to video signal input 12 for each of a predetermined brightness levels, a correction characteristic point control circuit 29 for selectively deriving the upper limit value when the calculated value of the correction characteristic point taken from the counter 13 of the occurrence frequency, exceeds a predetermined upper limit value, or to derive a lower limit value when this value is less than a (predetermined) lower limit value, or to derive a calculated value when the calculated value is within the range from the upper limit value to the lower the limit value, the shaper 48 of the correction curve for generating a correction curve in accordance with the output signal from the circuit 13 of the correction point control unitary enterprise adjustments and corrector 16 of the image quality for correcting the input video signal in accordance with the correction characteristic generated by the corrector 48, and the image quality correction circuit is also configured to set the upper limit value and lower limit value of the calculated value of the correction characteristic point at + w and - w for the purpose of the corresponding ramp.

The sixth embodiment of the invention is based on the image quality correction scheme in accordance with the fifth embodiment, wherein the upper limit value and the lower limit value are set to the upper limit value YHn and the lower limit value YLn, varying near the middle of the quadratic curve passing through the starting point of the graph, and the end point of the graph in the rectangular coordinates of the correction characteristic, on the x axis of which the values of the input brightness level are plotted, and on the y axis, the values of the output The level of brightness, in rectangular coordinates.

Brief Description of the Drawings

Figure 1 depicts a block diagram of a conventional image quality correction scheme.

Figure 2 depicts a distribution diagram of the frequency of occurrence of the brightness level of the video signal, in which (a) represents the case when the brightness levels are concentrated mainly around the average value, and (b) represents the case when the brightness levels are concentrated mainly within the low values.

Figure 3 depicts a frequency distribution pattern of appearance, depicting the brightness levels of video signals concentrated in a narrow range on the low level side.

Figure 4 depicts a correction characteristic in accordance with the variant according to Figure 3.

5 is another example of a conventional image quality correction scheme.

6 depicts a block diagram of image quality correction according to a first embodiment of the present invention.

Fig.7 depicts a block diagram of a counter 13 of the appearance frequency depicted in Fig.6, 9, 12 and 15.

Fig. 8 depicts a correction characteristic according to a first embodiment of the invention.

Fig. 9 depicts an image quality correction circuit according to a second embodiment of the invention.

10 depicts a correction characteristic according to a second embodiment of the invention.

11 depicts yet another correction characteristic according to a second embodiment of the invention.

12 depicts a block diagram of image quality correction according to a third embodiment of the invention.

Fig.13 depicts a block diagram of the controller 31 changes shown in Fig.12.

Fig. 14 is a timing chart illustrating the function of the change controller 31 ₀ shown in Fig. 13.

15 depicts a block diagram of image quality correction in accordance with a fourth embodiment of the invention.

Fig. 16 depicts a block diagram of image quality correction in accordance with a fifth embodiment of the invention.

17 is a diagram corresponding to a correction characteristic in accordance with a fifth embodiment of the invention.

Fig depicts a block diagram of the correction of image quality according to the sixth embodiment of the invention.

Fig. 19 is a correction characteristic diagram in accordance with a sixth embodiment of the invention.

Embodiments of the invention

An image quality correction circuit according to a first embodiment of the invention is hereinafter described with reference to FIGS. 6, 7 and 8.

6, numeral 12 denotes a video signal input, numeral 10 denotes means for calculating an average value for calculating an average value of brightness levels at m points (m = an integer equal to 2 or greater); 13 - appearance frequency counter for sequentially calculating the appearance frequency of predefined various brightness levels, starting from zero, 11 - input output of the reference comparison value, 15 - linear interpolator to obtain a correction characteristic point based on the appearance frequency data, 16 - image quality corrector for image quality correction based on linear interpolation, 18 is a video signal output for outputting a corrected video signal.

Figure 7 presents a more detailed circuit diagram of the counter frequency of occurrences.

Means 10 calculating the average value is configured to calculate average values, for example, 16 levels of brightness, which reduces the number of bits for the subsequent counter 13 occurrence frequency.

The appearance frequency counter 13 contains, for example, 16 discriminators 17 ₀ , 17 ₁ , ... 17 ₁₅ ; first counters 19 ₀ , 19 ₁ , ... 19 ₁₅ connected in series to discriminators, comparators 21 ₀ , 21 ₁ , ... 21 ₁₅ , second counters 23 ₀ , 23 ₁ , ... 23 ₁₅ , input 11 of the reference value comparisons connected to other inputs of comparators; moreover, the output signals of the comparators 21 ₀ , 21 ₁ , ... 21 _{15 are} repeatedly fed as an unencrypted signal to the first counters 19 ₀ , 19 ₁ , ... 19 _{15 of the} previous stage, while the output signals of the second counters 23 ₀ , 23 ₁ , ... 23 ₁₅ served on the linear interpolator 15.

Hereinafter, the purpose of the first embodiment based on the above scheme will be described in detail.

The video signal supplied to the video signal input 12 is processed by the average value calculator 10 to obtain at its output an average value of the brightness levels of 16 image elements.

The average value is fed to discriminators 17 ₀ , 17 ₁ , ... 17 ₁₅ , each of which determines the corresponding brightness level to determine whether it corresponds to one of the brightness levels. More specifically, it is assumed that the sum of the appearance frequencies in 1 frame is 255, and the brightness level is divided into 16 levels for detection. The discriminator 17 ₀ determines whether the brightness level corresponds to either level 0 or level 1, the discriminator 17 ₁ determines whether the brightness level corresponds to one of the levels 0 to 2. This operation continues until it is determined whether the brightness level corresponds to one of the levels from 0 to 16. Thus, it is determined whether each of all brightness levels corresponds to one of the levels from 0 to the desired level. If the brightness level corresponds to one of the given levels, then the appearance frequency is calculated using one of the subsequent first counters 19 ₀ , 19 ₁ , ... 19 ₁₅ .

Data corresponding to the occurrence frequencies calculated by the first counters 19 ₀ , 19 ₁ , ... 19 ₁₅ are supplied respectively to the inputs of the comparators 21 ₀ , 21 ₁ , ... 21 ₁₅ . To the other inputs of the comparators, a signal is output from the output 11 of the reference comparison value. Therefore, when the frequency of occurrence, counted by each of the first counters 19 ₀ , 19 ₁ , ... 19 ₁₅ , exceeds the reference value of the comparison, then the second counters 23 ₀ , 23 ₁ , ... 23 ₁₅ count and the first counts 19 ₀ , 19 ₁ , ... 19 ₁₅ set in the initial position.

If the reference comparison value supplied from output 11 of the reference comparison value exceeds the quotient of dividing a given number of samples in 1 frame by the number m of samples used to calculate the average value of the brightness levels by the average value calculator 10, then the equation below is applied and the value of the correction characteristic the point obtained at the second counter 23 becomes 255 (FFH).

Reference value of comparison = (The total number of image elements in 1 frame / m) FFH = w (The number of image elements in the horizontal direction) × h (The number of image elements in the vertical direction) - 16 ÷ 255.

It is assumed that the frequency of occurrence, counted by the second counters 23 ₀ , 23 ₁ , ... 23 ₁₅ , are as follows.

c0: Frequency of occurrence of levels in 00-10 (OF: hexadecimal notation), counted by the second counter 23 ₀ .

s1: Frequency of occurrence of levels in 00-20 (IF: hexadecimal notation), counted by the second counter 23 ₁ .

cE: Frequency of occurrence of levels 00-F0 (EF: hexadecimal notation), counted by the second counter 23 ₁₅ .

The appearance frequencies calculated by the second counters 23 ₀ , 23 ₁ , ... 23 ₁₅ , respectively, can be displayed as correcting characteristic points in a graphical representation of the brightness levels on the x-axis and the appearance frequencies on the y-axis according to Fig. 8.

Data on 16 levels obtained by summing each of the occurrence frequencies c0, c1, ... cЕ to the starting point 00, and the total number of occurrence frequencies (fixed value), are sent to linear interpolator 15, where the occurrence frequencies 00, c0, c1 ,. ..ce is connected in series with segments that are linearly interpolated to obtain a correction characteristic consisting of continuous segments.

The image quality corrector 16 processes the video signal supplied from the video signal output 12 to correct the image quality according to the correction characteristic obtained from the linear interpolator 15, with the formation of the corrected video signal at its output 18. More specifically, if the brightness level of the video signal supplied to the video signal input 12 is x, then the image quality correcting processing is done according to the correction characteristic, as a result of which the adjusted brightness level becomes equal to y, and the corrected video signal is removed from the video signal output 18.

In accordance with the first embodiment of the invention, the optimal correction characteristic, as shown above, can be obtained based on the frequency of occurrence of each brightness level, as a result of which it is possible to carry out corrective image quality processing in accordance with the state of this image.

According to a first embodiment of the invention, the number of samples for determining the average value using the average value calculator 10 is 16, the number of frames for receiving appearance frequency data using the appearance frequency counter is 1, and the number of brightness levels is 16. The present invention is not limited, however, to a specific case.

According to the first embodiment above, it is possible to obtain an optimal corrective characteristic in accordance with the frequency of occurrence of each brightness level, and therefore, corrective image processing can be performed in accordance with any type of image.

The following is a second embodiment of the invention, described with reference to Figures 9, 10 and 11.

The video signal input 12, the average value calculator 10, the appearance frequency counter 13, the image corrector 16, and the video signal output 18 shown in FIG. 9 are similar to the corresponding elements in the first embodiment according to FIGS. 6 and 7. The second embodiment is characterized by the presence of a correction curve generator 25, connected between the counter 13 of the frequency of occurrence and the corrector 16 image quality, while the shaper of the correction curve is configured to generate a new correction curve with publicly data frequency of the video signal which are obtained based on the video signal supplied to the input videosignalny 12 and the counter 13 counts the frequency of occurrence using the average value calculator 10, and according to a predetermined point, from terminal 27, predetermined data point.

The corrective curve generator 25 comprises a circuit configured to generate a Bezier curve passing through the starting point 00 and the ending point TF and based on a plurality of points characterizing the frequency of occurrence and provided by an alternately given point.

The purpose of the second embodiment of the invention is disclosed below.

(1). Assume that the video signal supplied to the video signal input 12 has a characteristic that causes the appearance frequency to be concentrated around the center similarly to case 1 of the appearance frequency distribution. In contrast to the case illustrated in FIG. 8, c0, c2, c4, c6, s8, cA, cC and cE corresponding to every second level 10, 30, 50, 70 are used as the appearance frequency data provided by the appearance frequency counter 13 , 90, BO and FO. These appearance frequencies data indicate that the appearance frequencies are at relatively low levels c0-c6 and c8-cE; while the appearance frequencies are at relatively high levels between c6 and c8.

T0, T2, T4, T6, T8, TA, TS and TE corresponding to levels 00, 20, 40, 60, 80, A0, C0 and E0, which are on a straight line connecting the starting point 00 and the ending point TF, respectively served as the set data to the input 27 of the set data.

Rearrangement of the indicated data in order of brightness gives T0, c0, T2, c2, T4, c4, T6, c6, T8, s8, TA, cA, TC, cC, TE and cE, which degenerate into a correction line containing segments, - depicted by a dotted line as in the first embodiment.

According to the second embodiment, if the Bezier curve passing through the starting point 00 and the ending point FF is formed by the correction curve generator 24 based on a plurality of points, including appearance frequency points and predetermined points arranged alternately, then it takes a 3-shaped shape, moreover, its part, characterizing relatively high levels of brightness, is slightly protruding upward, and its part, characterizing relatively low levels of brightness, is slightly reduced compared to the straight line represented the solid line in FIG. 10.

The image quality corrector 16 processes the video signal supplied from the video signal input 12 to adjust the image quality according to the correction curve provided by the correction curve generator 25, and allows to receive the corrected video signal at its output 18.

(2). Assume that the video signal supplied to the video signal input 12 has a characteristic represented by the appearance frequency distribution circuit 2, characterized by the predominance of relatively low brightness levels according to FIG. 2 (b). This case indicates that the occurrence frequencies are relatively low, respectively, within c0-c2 and c4-cE; wherein the appearance frequency is relatively high between c2 and c4.

Similarly to the above, when forming a Bezier line passing through the starting point 00 and the ending point TF and generated by the shaper 25 of the correction curve based on the given points rearranged in the order T0, c0, T2, c2, T4, c4, T6, c6, T8, TA , CA, TC, CC, TE and CE, it takes the form in which its part, representing high brightness levels, is almost straight, and its part, representing low brightness levels, is slightly reduced - in Fig. 11, this curve is represented by a solid line Compared to the straight line between the original endpoint 00 and endpoint TF.

The image quality corrector 16 processes the video signal coming from the output 16 to correct the image quality according to the correction curve provided by the correction curve generator 25 to obtain the corrected video signal at its output 18.

In the embodiment described above, the data defining the set points and coming from the output of the set point data 27 is selected from a straight line connecting the starting point 00 and the ending point TF, but the sampling method is not limited to this case. For example, as in the case of the characteristic line represented by the solid line in FIG. 10, the contrast between the bright part and the dark part of the image can be enhanced by fetching the specified points from a 3-shaped curve containing an upwardly extending part representing higher brightness levels and decreasing a part representing lower brightness levels; or the contrast between the bright part and the dark part can be attenuated with the help of predetermined points having the inverse characteristic.

This embodiment is not limited to the case where the appearance frequency data and the given point data are arranged alternately; for example, appearance frequency data and setpoint data can be rearranged in a 2: 1 ratio to highlight video data, or both can be rearranged in a 1: 2 ratio to highlight setpoint data.

In accordance with the foregoing, according to the second embodiment of the invention, the optimal correction characteristic can be obtained in accordance with the appearance frequency data for each brightness level to make image quality correction processing applicable for each image type. If necessary, by selecting any data points of the correction characteristic, the characteristic can be changed.

The following is a description of the image quality correction scheme in the framework of the third embodiment, with reference to FIGS. 8-12.

The elements shown in FIG. 12 are similar to the elements shown in FIG. 6 and have common numeric and alphabetic positions, as a result of which their description is not given.

12, reference numeral 12 denotes a video signal input; 10 - average value calculator; 13 - counter frequency of occurrence; 11 - input output of the reference value; 15 - linear interpolator; 16 - image quality corrector; 18 - output video signal; 31 - change controller.

The change controller 31 contains 15 change controllers 31 ₀ , 31 ₁ , ... 31 ₁₄ ; the controller 31 ₀ changes contains difference detectors 33 ₀ , the multiplier by a constant 35 ₀ , the adder 37 ₀ and the deceleration means 39 ₀ N-frame. The change controller 31 ₁ comprises difference detectors 33 ₁ , a multiplier by a constant 35 ₁ , an adder 37 ₁ and a deceleration means 39 _{1 of the} N-frame. Other controllers contain similar elements, in particular, the change controller 31 ₁₄ contains a difference detector 33 ₁₄ , a multiplier by a constant 35 ₁₄ , an adder 37 ₁₄ and a deceleration means 39 _{14 of the} N-frame.

The difference detectors 31 ₀ , 31 ₁ , ... 31 ₁₄ generate a difference value between the calculated values of the appearance frequencies taken from the second counters 23 ₀ , 23 ₁ , ... 23 ₁₄ , and the output values of the deceleration means 39 ₀ , 39 ₁ ,. ..39 ₁₄ N-frames. Constant multipliers 35 ₀ , 35 ₁ , ... 35 ₁₄ multiply the output values of the difference detectors 33 ₀ , 33 ₁ , ... 33 ₁₄ by a factor of 1 / X (X is an integer equal to 2 or greater, for example, X = 2) to obtain the product, the adders 37 ₀ , 37 ₁ , ... 37 ₁₄ summarize the output values of the constant multipliers 35 ₀ , 35 ₁ , ... 35 ₁₄ with the output values of the deceleration means 39 ₀ , 39 ₁ , ... 39 ₁₄ N-frame deceleration means 39 ₀ , 39 ₁ , ... 39 ₁₄ N-frames not only delay the sums received by adders 37 ₀ , 37 ₁ , ... 37 ₁₄ , by N frames to supply a signal at the output to difference detectors 33 ₀ , 33 ₁ , ... 33 ₁₄ and adders 37 ₀ , 33 ₁ , ... 34 ₁₄ , but also address their output signals to the linear interpolator 15. The value of the appearance frequency obtained at the output of the second counter 23 ₁₅ in the counter 13 appearance, directly to the linear interpolator 15 without using the controller 13 changes.

The purpose of the third embodiment having the structure disclosed above is described with reference to FIG. 14 and FIG. 18.

N may be any integer equal to or greater than one; m is any integer equal to or greater than 2; X - any number equal to or greater than 2. For convenience of explanation, the option is given when N = 1, m = 16 and X = 2.

(1). The video signals supplied to the video signal input 12 are processed by the average value calculator 10 and output sequentially as the average values of each of the 16 brightness levels.

(2). When applying the average value calculated by the average value calculator 10 to the appearance frequency counter 13, the latter functions similarly to the counter according to the first embodiment according to FIGS. 6 and 7.

For convenience, we assume that the values of the appearance frequencies taken from the second counters 23 ₀ , 23 ₁ , ... 23 ₁₄ are c0, c1, ... cE and cF, respectively. In this case, c0, c1, ... cE and cF characterize the occurrence frequencies explained below.

c0: Occurrence frequency calculated by the second counter 23 ₀ within levels 00-10 (10 is a hexadecimal value).

s1: Occurrence frequency calculated by the second counter 23 ₁ within the range of 00-20 (20 is a hexadecimal value).

cE: Occurrence frequency calculated by the second counter 23 ₁₄ within the levels 00-F0 (F0 is a hexadecimal value).

cF: Frequency of occurrence (constant value) counted by the second counter 23 ₁₅ within the range of 00-100 (100 is a hexadecimal value).

(3). When receiving 16-level data containing the frequency values of occurrence c0, c1, ... cF, taken from the second counters 23 ₀ , 23 ₁ , ... 23 ₁₅ , and the data of the starting point 00 summed with them, the change controller 31 controls the change each frequency of occurrence of c0, c1, ... cE and cF during a 1-frame period (case when N = 1) up to a certain amount of change during a multi-frame period (an example of the multiplicity of an N-frame) at the output, provided that cF will not change, being a constant value.

For example, if we assume that the frequency c0 of the second counter 23 ₀ becomes [2], [2], [2], [2], [2], [16], [16], [16], [16], [16], [16] and [16] according to Fig. 14 (a) and changes immediately to [16] from [2] during the FT frame period near point t6 according to part (b) of the same Fig., Thanks to the control function controller 31 changes, the frequency of occurrences will change from [2] to [9] during the 1-frame period FT immediately after point t7, which appears after the 1-frame period FT from point t6, and then changes to [13], [ 15] and [16], respectively, during 1-frame periods of directly behind the point t8, t9 and t10 until converging to the point [16]. That is, a fast change over one 1-frame period is controlled until smoother changes lasting over the 4-frame period.

The control function of the change controller 31 is explained with its subdivision into points 1 to 5 according to the circuit shown in FIG. 13.

For convenience, suppose that the frequency of occurrence (corrective characteristic point) of the second counter 23 ₀ is equal to P0 and the frequency of occurrence (corrective characteristic point) of the decelerator 39 _{0 of the} N-frame is PD0.

According to Fig. 14 (a), assuming that P0 changed to [16] from [12] during the 1-frame period FT around point t6, P0 = 16 and PD0 = 2 during the specified 1-frame period FT, and therefore the frequency of occurrence taken from the controller 31 ₀ changes becomes equal to [2].

In this case, the value (P0-PD0) at the output of the difference detector 33 ₀ becomes 14 (= 16-2); the value of (P0-PD0) × 1/2 at the output of the multiplier by the constant 35 ₀ is equal to 7 (= 14/2); the value of PD0 + (P0-PD0) 1/2 at the output of the adder 37 ₀ is 9 (= 2 + 7).

During the 1-frame period at point t7 immediately after the 1-frame period FT from point t6, the data received by a delay of 1 frame of the output signal of adder 37 ₀ forms the output signal (i.e., PD) of the decelerator 39 ₀ N-frame , and therefore, the value of the frequency of occurrence taken from the controller 31 changes becomes equal to [9].

In this case, the output signal (P0-PD0) of the difference detector 33 ₀ is equal to 7 (= 16-9); output signal (P0-PD0) × 1/2 of the constant multiplier 35 ₀ is equal to 4 (= 7/2, with rounding to decimal fractions); output signal PD0 + (P0-PD9) × 1/2 of adder 37 ₀ is 13 (= 9 + 4).

During the 1-frame period FT immediately after point t8, after a 1-frame period originating from point t7, similar to the case described in paragraph 2, the value of the appearance frequency taken from the change controller 31 becomes 13.

In this case, the output signal of the adder 37 ₀ becomes equal to 15 (= 13 + 2), similarly to the case given in the previous paragraph.

During the 1-frame period FT immediately after point t9, after the end of the 1-frame period TF, starting from point t8, similarly to the option described in the previous paragraph, the value of the appearance frequency taken from the controller 31 ₀ changes becomes equal to 15.

In this case, the output signal of the adder 37 ₀ , similar to the case given in the previous paragraph, becomes 16 (= 15 + 1).

During the 1-frame period FT immediately after point t10, after the end of the 1-frame period TF, starting from point t9, the value of the frequency of occurrence taken from the controller 31 ₀ changes becomes equal to [16], as in the case described in the previous paragraph .

In this case, the output signal of the adder 37, similarly to the case given in the previous paragraph, becomes 16 (= 16 + 0).

(4). Changes in the appearance frequencies c1, ... cE of the other second adders 37 _{0 are} also made smoother at the output due to the control effect of the controller 31 changes.

In the case of applying the above option for the circuit according to Fig.13, the values of the frequency of occurrence, taken from the second counters 21 ₁ , ... 23 ₁₄ , become equal to P1 (= c1), ... P14 (= cE), and when the output the values of the deceleration means 39 ₁ , ... 39 _{14 of the} N-frame become equal to PD1, ... PD14, and the values of P1, ... P14 change sharply during a certain 1-frame period, by changing the corresponding values of PD1, ... PD14 run to provide less dramatic changes over a multi-frame period.

(5). The values of changes in the frequencies of occurrence c0 (= P0), c1 (= P1), ... cE (= P14) from the second counters 23 ₀ , 23 ₁ , ... 23 ₁₄ , adjusted to less abrupt changes, are sent to a linear interpolator 15 , for linear interpolation of the change by connecting in series the adjusted occurrence frequencies 00, c0, c1, ... cE and cF with a straight line, in order to form a correction characteristic.

For example, compared with the variant when the correction characteristic obtained by the traditional linear interpolator without change controller 31, according to FIG. 6, has sharply changed similarly to the variant of the correction characteristic U1, shown as a dotted line, and the correction characteristic U2, shown by the solid line in FIG. 8, over a 1-frame period, then in the case of a circuit including a change controller 31 according to the present invention, a change from a correction characteristic U1 to a similar line U2 can be make it smoother over a multi-frame period.

That is, since changes in the frequency of occurrence of c0, c1, ... cE become smoother due to the function of the change controller 31, the correction characteristic generated by the linear interpolator 15 smoothly changes during a multi-frame period (for example, a period within 4-6 frames), and converges in U2.

In this case, the frequency of appearance of c0 smoothly changes over a 4-frame period, as was shown in paragraphs 1-5, while the frequencies of appearance of c1, ... cE smoothly change over a 4-frame period or in multi-frame periods, the number of frames in which 4 is not equal (for example, 5 or 6 frames), depending on the volume of changes.

In Fig. 8, the correction characteristic U1 corresponds to the correction characteristic, ranked from point t6 to point t7, point after a 1-frame period from point t6; and c0 (frequency of occurrence in the second counter 23 ₀ ) on the indicated correction characteristic U1 corresponds to the value [9] according to the case described in the previous paragraph.

(6). The image quality corrector 16 processes, adjusting the image quality, the video signal supplied to the video signal input 12, in accordance with the correction characteristic, to obtain the corrected video signal at its output 18. More specifically, if the brightness level of the video signal supplied to the video signal input 12 is x, then the processing for correcting the image quality is performed according to the correction characteristic, as a result of which the brightness level is adjusted to y, and the corrected video signal is obtained at the output 18.

According to a third embodiment of the invention, it is possible to perform not only operations for correcting image quality according to an optimal characteristic based on the frequency of occurrence of the brightness level of each image element in N frames, but also correcting image quality without degrading the image quality, eliminating a significant change in the distribution of the frequency of occurrence of the brightness level while switching the image or while displaying a moving image.

The following is a description of the image quality correction scheme within the fourth embodiment of the present invention with reference to FIG.

The circuit includes a video signal input 12, an average value calculator 10, an appearance frequency counter 13, an image quality corrector 16, a video signal output 18, and a change controller 31. These elements are similar to the elements according to the third embodiment illustrated in FIG. 12 and FIG. 13. The circuit according to the fourth embodiment is characterized in that the correction curve generator 25 replaces the linear interpolator 15 shown in FIG. 12.

The adjusting curve generator 26 is connected between the change controller 31 and the image quality corrector 16 and is configured to generate a new correction curve based on the appearance frequency, which is counted by the appearance frequency counter 13 and whose change is controlled by the change controller 31, and based on the data of the set point supplied from input 27 data of a given point.

The adjusting curve generator 25, in particular, is made in the form of a circuit that allows you to generate a Bezier curve passing through the starting point 00 and the ending point TF, based on multiple points that determine the frequency of occurrence and predetermined points located alternately.

A fourth embodiment is explained with reference to FIGS. 2, 9, 10 and 11.

(1). Assume that the frequencies of occurrence of the brightness level of the video signals input from the video signal input 12 tend to be grouped practically around the average value, as represented by the frequency distribution and shown in FIG. 2 (a).

The appearance frequencies c0, c2, c4, c6, s8, cA, cC and cE with the counter 13 of the appearance frequency are used in accordance with the brightness levels 10, 30, 50, 70, 90, B0, D0 and F0, which are arranged in such a way that each the second level is skipped similarly to the second embodiment shown in FIG. 2.

The values of T0, T2, T4, T6, T8, TA, TC and TE, respectively, corresponding to the levels 00, 20, 40, 60, 80, A0, C0 and E0 on a straight line connecting the starting point 00 and the ending point TF, are entered as set data from input 27 of the input data output.

In the traditional embodiment, when the change controller 31, as shown in FIG. 9, there is no S-shaped correction curve V (Bezier curve) of the correction shown by the solid line in FIG. 10, is obtained using the correction curve generator 25 based on multiple points bearing data on the frequency of occurrence: s0, s2, s4, s6, sA, ss and CE and data on the given points: T0, T2, T4, T6, T8, TA, TS and TE, which are located alternately; in this case, if the frequencies of occurrence of C0, c2, c4, c6, c8, cA, cC and CE change sharply, the correction curve also changes sharply from the correction curve VI to the correction curve V2 (V1 and V2 are not shown).

But in the case of the embodiment with the controller 31 of the changes depicted in FIG. 15, changes in the frequencies of occurrence of c0, c2, c4, c6, c8, cA, cC and cE for 1 frame are controlled to give them smoother changes in the continuation of the multi-frame period, as a result, the correction curve V generated by the correction curve generator 25 changes gradually as V1, V1 ₁ , V1 ₂ , ..., V2 frame by frame until it converges in V2 (V1 ₁ , V1 _{2 are} not shown).

The image quality controller 16 processes, for correcting the image quality, the video signal input to the video signal input 12 to obtain the corrected video signal at its output 18.

(2). Assume that the video signals supplied to the video signal input 12 have a distribution circuit 2 of the frequency of occurrence of the brightness level, which is characterized by a concentration of values within the lower level.

Similarly to the variant disclosed in the previous paragraph (1), according to the second embodiment, which does not include a change controller 31, a correction curve W (a Bezier curve) is generated using a correction curve generator 25 based on multiple points defining appearance frequency data: c0, c2, c4, c6, c8, cA, cC and cE, and data of a given point: T0, T2, T4, T6, T8, TA, TC and TE, which are located alternately; in this case, if the occurrence frequencies c0, c2, c4, c6, c8, cA, cC and cE, respectively, change sharply, then the correction curve W also changes sharply from W1 to W2 (W1 and W2 are not shown).

In the case of the fourth embodiment, comprising a controller 31 of changes, changes in the appearance data of c0, c2, c4, c6, s8, cA, cC and cE during the 1-frame period are controlled to make them smoother for a multi-frame period, resulting in the correction curve W also changes gradually from W1, W1 ₁ , W1 ₂ , ... W2 in each single-frame period until converging to W2 (W1 ₁ , W1 _{2 are} not shown).

The image quality controller 16 processes, for correcting the image quality, the video signal coming from the video signal input 12 according to the correction curve generated by the correction curve generator 25 to obtain a corrected video signal at its output 18.

According to a fourth embodiment, the data of the set point from the input 27 of the data of the set point is sampled based on a straight line connecting the starting point 00 and the ending point TF, but this option is not limited to this sample only; for example, the data of a given point can be sampled on the basis of an S-shaped curve in which the slightly protruding portion represents the upper levels, and the decreasing portion represents the lower levels, as shown in FIG. 10, to highlight the contrast between bright and dark areas, or for weakening the contrast between bright and dark areas by sampling given points with inverse characteristics.

The present invention is not limited to the case when the occurrence frequency data and the set point data are arranged alternately; video signal data can be extracted by setting the ratio between the appearance frequency data and the given point data equal to 2: 1, or the given point data can be extracted by setting the 1: 2 ratio or other ratios.

According to the fourth embodiment disclosed above, it is possible to perform not only the signal processing for correcting the image quality in accordance with the optimum correction characteristic based on the appearance frequency corresponding to each brightness level, it is also possible to perform this processing without an accompanying deterioration in image quality even in the case when the frequency the appearance of brightness levels of image elements vary significantly. In this case, an excessive change in the correction curve can be eliminated by selective use of the correction characteristics. The correction curve can also be changed in accordance with the requirements for image quality.

The third and fourth embodiments are explained on the basis of examples, providing means for calculating an average value to simplify the occurrence frequency counter, however, these embodiments are not limited to these examples; they also apply to cases where the means of calculating the mean is not used.

The image quality correction circuit according to the fifth embodiment is explained with reference to FIG. 16 and FIG.

In Fig. 16, numeral 12 denotes a video signal input; position 10 is an average value calculator for calculating an average value of values with the number of points m (m = an integer equal to 2 or greater); position 13 is the counter of the frequency of occurrence for sequentially counting the frequency of occurrence set to different values, starting from the 0-level N of the number of frames (any integer equal to 1 or greater); 29 — control circuit of the correction characteristic point for controlling the correction characteristic point by setting the upper limit value (an + w) and the lower limit value (an - w); at 48, a correction curve generator for generating a correction curve in accordance with controlled correction characteristic points; position 49 - input data of a given point for entering data of a given point; reference numeral 16 is an image quality corrector for correcting image quality according to a generated correction curve; position 18 - video signal output for outputting the corrected video signal.

The correction characteristic point control circuit 29 includes a control range comparator 43, a control range setting means 46, a control counter for determining a processing order and a correction characteristic point selector 47, a control range comparator 43 includes an upper limit comparator 41a for comparing the correction data of the uncorrected correction point (Pn) with an upper limit value (an + w) at this characteristic point and a lower limit comparator 42a for comparing Pn with the lower the limit value (an - w) at this characteristic point; the control range setting means 46 comprises upper limit setting means 44 a for setting an upper limit value (an + w) and a lower limit setting means 45 a for setting a lower limit value (an - w); wherein the correcting characteristic point selector 47 is a circuit for selecting the output x for the Pn counter 13 of the appearance frequency, the output y for the upper limit value (an + w) of the upper limit setting means 44a and the output z for the lower limit value (an + w) of the setting means 45a lower limit.

In this case, according to FIG. 17, a straight line connecting the starting point and the ending point in rectangular coordinates, where the x axis represents the output brightness level and the y axis represents the input brightness level, characterizes the ideal correction characteristic in the absence of deviations in the frequencies of the appearance of input levels of input video signals ; moreover, w represents a certain distribution range around the ideal characteristic an + w and an - w, respectively, represent predetermined control lines, depicted by dotted lines in Fig. 17 and characterizing the upper and lower limits, and running for some extent parallel to the ideal straight line.

The purpose of the correction circuit according to the fifth embodiment is explained below.

The video signals supplied to the video signal input 12 are processed by means 10 calculating the average value to calculate the average values of the brightness levels of each of the 16 image elements at different points, which must be output sequentially.

The indicated average value is found on the assumption that the total number of occurrence frequencies in the N number (N = any integer equal to 1 or greater) is 255, and there are 16 different brightness levels. Detected averages are counted by a frequency counter.

Correction characteristic point data Pn, for which no control is performed, from the occurrence frequency counter 13 is supplied not only to terminal x of the selector 47 of the correction characteristic point 47, but also to one of the inputs of the subsequent upper limit comparator 41a and the lower limit comparator 42a. The upper limit value an + w and the lower limit value an - w, corresponding to the data numbers Pn of the correction characteristic point taken from the control counter 40, are supplied to the other inputs of the upper limit comparator 41a and the lower limit comparator 42a, respectively. Therefore, in the case when Pn> an + w, then at the output of the upper limit comparator 41a, a signal is obtained for switching the contact at the selector 47 of the correction characteristic point; if Pn> an - w, then the output of the lower limit comparator 42a receives a signal for switching to the terminal z of the selector 47 of the correction characteristic point.

For example, according to the embodiment illustrated in FIG. 17, since Pn> an + w, where Pn is at a very high point y, the switching signal is removed from the upper limit comparator 41a to switch the contact of the correction characteristic selector 47 to the terminal y, and the value an + w from the upper limit setting means 44a is supplied to the correction curve generator 48. The correction curve generator 48 generates a corrected correction curve on the upper limit setting line P1 shown in FIG. 17 according to the value an + w taken from the upper limit setting means 44a for use as the address and data of a given point input from a given 49 points, and the corrected correction curve is fed to the corrector 16 image quality. The video signal coming from the video signal input 12 is corrected using the image quality corrector 16 according to the correction curve, and the corrected video signal is removed from the output 18. According to the above, the image quality deterioration can be prevented by controlling the point y, the distribution of the appearance frequencies of which has some variation in a given range.

According to the embodiment of FIG. 17, since Pn <an - w, where Pn is at a very low point z, the switching signal is taken from the lower limit comparator 42a to switch the contact of the correction characteristic selector 47 to the terminal z, and the value an - w from the output of the lower limit setting means 45 a, a correction curve is supplied to the shaper 48. The correction curve generator 48 generates a corrected correction curve at point P3 of the lower limit setting line shown in FIG. 17 according to the value of an-w taken from the lower limit setting means 45a for use as the address and data of a given point coming from input 49 data of a given point, and the corrected correction curve is fed to the corrector 16 image quality. The video signal supplied to the video signal input 12 is corrected using the image quality corrector 16 according to the corrected correction curve, and the corrected video signal is removed from the output 18. According to the above, image quality deterioration can be prevented by controlling the z point, the frequency distribution, the appearance of which has some variation in the given the limit.

Further, in the case an + w> Pn> an - w, where Pn is at the point x between the upper limit value and the lower limit value, the switching signal from the upper limit comparator 41a and the lower limit comparator 42a will not be output, and Pn from the output counter 13 appearances served on the shaper 48 of the correction curve. From the output of the shaper 48 of the correction curve, the uncorrected correction curve of the circuit is supplied to the image quality corrector 16, and the video signal from the video signal input 12 is supplied uncorrected to the output 18.

According to the foregoing, in accordance with the fifth embodiment of the invention, it is possible to prevent the formation of a correction characteristic having an excessive slope and a deterioration in image quality due to the slope of the appearance frequency characteristic to obtain an optimal correction characteristic.

The following is a description of a sixth embodiment of the invention according to FIGS. 18 and 19.

According to a fifth embodiment, regardless of the values of the correction characteristic points, it is assumed that the range of the upper limit values + w and the lower limit values -w is fixed.

In contrast, according to the sixth embodiment, when calculating the correction characteristic point based on the frequency of occurrence of the input video signal level in N number of frames, the upper limit and lower limit ranges are set for each correction characteristic point.

On Fig presents a diagram containing a video signal input 12, an average value calculator 10, an appearance frequency counter 13, an image quality corrector 16, a video signal output 18, a correction curve generator 48, and a given point data input 49. These elements are similar to the corresponding circuit elements according to the fifth embodiment. On the other hand, according to FIG. 19, the second embodiment is distinguished by generating a quadratic curve according to corrective characteristic points representing an upper limit value YHn and a lower limit value YLn equal to 0, respectively, at the starting point 0; moreover, the upper limit value YHn gradually increases relative to the straight line an to an intermediate position, and the lower limit value YLn again discretely decreases relative to the straight line an to the end point FF. As stated above, the straight line an connects the start point and end point FF on the correction curve and represents the ideal correction curve, where the appearance frequencies of the input levels of the input video signals are not inclined.

The following describes the purpose of the sixth embodiment of the invention.

For example, according to FIG. 19, since Pn> YH1, where the non-controlled Pn data of the correction characteristic point from the appearance frequency counter 13 is at a point at a high input level, the switching signal is removed from the upper limit comparator 41b to switch the contact of the correction characteristic selector 47 to terminal y; and a signal YH1 from the output of the upper limit comparator 44b is supplied to the correction curve generator 48. The correction curve generator 48 generates the corrected correction curve at point P1 of the set upper limit line shown in FIG. 19 according to the signal serving as the address from the output of the upper limit setting means 44b and based on the data of the set point from the data input 49 a given point, and the corrected correction curve obtained at its output is supplied to the image quality corrector 16. The corrector 16 of the image quality corrects the video signal from the video signal input 12 in accordance with the correction curve and allows you to receive the corrected video signal at its output 18. Thus, deterioration of image quality is prevented by controlling the point y, the distribution of the frequency, the appearance of which decreases within a given range.

Moreover, in the embodiment according to FIG. 19, since Pn <Y13, where Pn is at the low input level point z, the switching signal is removed from the output of the lower limit comparator 42b to switch the contact of the correction characteristic selector 47 to the terminal z; and YL3 from the output of the lower limit setting means 45b is supplied to the correction curve generator 48. The correction curve generator 48 generates the corrected correction curve at point P3 on the set upper limit line shown in FIG. 19 according to the signal serving as the address from the output of the lower limit setting means 45b, and based on the data of the set point from input 49 data of a given point, with receiving at its output a corrected correction curve supplied to the image quality corrector 16. The image quality corrector 16 corrects the video signal received at the video signal input 12 in accordance with the correction curve to obtain the corrected video signal at the output 18. Thus, deterioration of image quality is prevented by controlling the point y, the distribution of the frequency, the appearance of which decreases within a given range.

Further, in the case where YH2> Pn> YL2, where Pn is at the point x between the upper limit value and the lower limit value, as a result of which the switching signal will not be removed from the upper limit comparator 41a and the lower limit comparator 42a, and the Pn value from the output counter 13, the frequency of occurrence is served on the shaper 48 of the correction curve. From the output of the correction curve generator 48, the uncorrected correction curve is supplied to the image quality corrector 16, and the video signal supplied to input 12 is output 18 without correction.

According to the foregoing, in accordance with the sixth embodiment, it is possible to obtain an optimal correction characteristic consistent with the frequency of occurrence of each level, and also carry out processing to correct image quality for any image. In accordance with this embodiment, according to the correction characteristic point, it is possible not only to exclude an excessive change in the correction curve, but also to form a correction curve in accordance with the requirements of the invention.

According to the fifth and sixth embodiments, the number of samples for obtaining the average value using the average value calculator 10 is set to 16, the number of frames for receiving appearance frequency data from the appearance frequency counter 13 is set to 1; and the number of gradations of the brightness level is set to 16, however, the present invention is not limited to these specific examples.

Industrial applicability

The image quality correction scheme according to this invention is made not only with the possibility of obtaining the optimal correction characteristic according to the frequency of occurrence of each brightness level for processing in order to correct image quality of any kind, but also with the possibility of preventing excessive changes in the correction curve and with the possibility of changing the correction curve in accordance with the requirements of the invention. Even in the case of a significant change in the distribution of the frequency of occurrence of the brightness level during image switching or when moving images are displayed, these excessive changes and the consequent deterioration in image quality can be prevented using image quality correction processing according to the present invention.

Claims (34)

1. The image quality correction circuit containing a counter 13 of the frequency of occurrence of brightness levels to calculate the frequency of occurrence of multiple brightness levels, the selection of which is made from the video signals supplied to the video signal input 12, a linear interpolator 15 to generate a correction characteristic using interpolation based on points of the calculated value, taken from the output of the counter 13 occurrence frequencies, and the corrector 16 image quality for the correction of incoming video signals in accordance with the correcting character characteristic points. 2. The circuit according to claim 1, containing a change controller that controls the change in the calculated value of the counter of the appearance of the brightness level for a period of time exceeding the N-frame period by more than one time, and the counter of the appearance frequency is configured to count the frequency of occurrence of brightness levels of image elements input the video signal in N number of frames, where N is any integer equal to or greater than one, the interpolator is configured to generate a correction characteristic using linear interpolation based on the counted value obtained from the output of the controller changes, and image quality corrector configured to correct the input video signal in accordance with the correcting characteristic line generated by the interpolator. 3. The circuit according to claim 1, comprising a plurality of discriminators 17 for determining the frequency of occurrence of multiple brightness levels for each of the predetermined levels, a plurality of first counters 19 for counting the frequency of occurrence for each of the predefined levels determined by the discriminators 17, a plurality of comparators 21 for comparison the output signals of the first counters 19 with reference values supplied to the input 11 of the reference comparison value to establish the reading of the first counters 19 taking into account the output signals of comparison And a plurality of second counters 23 for counting the output signals of the comparators 21. 4. The circuit according to claim 2, in which the appearance frequency counter comprises a plurality of discriminators determining the correspondence of the brightness level of each image element of the input video signal to each of the multiple predetermined levels, a plurality of first counters for counting the number of determination operations performed by each discriminator, a plurality of comparators for comparing the calculated value taken from the first counter, with a predefined reference value in order to obtain the first counter, taking into account the result comparisons, and a plurality of second counters for counting the number of output signals of the comparator for use as a frequency of occurrence. 5. The circuit according to claim 2, in which the change controller contains a difference detector, a constant multiplier, an adder, and an N-frame decelerator, wherein a difference value is obtained at the output of the difference detector between the calculated value of the appearance frequency counter and the output value of the N- deceleration means frame, the constant multiplier is configured to multiply the value at the output of the difference detector by 1 / X, where X is any integer equal to or greater than 2, the adder is configured to sum the value at the output of the funds and deceleration of the N-frame with the value at the output of the multiplier by a constant, the means of decelerating the N-frame is configured to delay the value obtained at the output of the adder by N-frames for subsequent supply to the difference detector and adder, and to obtain a signal with controlled change. 6. The circuit according to claim 2, in which the change controller contains a difference detector, a constant multiplier, an adder, and an N-frame decelerator, and the output of the difference detector receives a signal corresponding to the difference between the calculated value of the second counter and the value from the output of the deceleration means N -frame, the constant multiplier is configured to multiply the value at the output of the N-frame decelerator by a factor of 1 / X, where X is an integer equal to or greater than 2, the adder is configured to sum the value by you As a multiplier by a constant with a value at the output of the N-frame slowdown means, the N-frame slowdown means is capable of delaying the signal corresponding to the sum received by the adder by N-frames for subsequent supply to the difference detector and adder, and to obtain a signal at the output with controlled change. 7. The circuit according to claim 3, in which the appearance frequency counter 13 comprises discriminators 17, first counters, comparators 21 and second counters 23, each of which contains 16 series-connected circuits. 8. An image quality correction circuit comprising an average value calculator 10 for calculating an average value of brightness levels of each of the multiple image elements sampled from the video signals supplied to the video signal input 12, an appearance frequency counter 13 for counting an appearance frequency of predetermined multiple brightness levels, processed by the calculator 10 of the average value, a linear interpolator 15 to form a correction characteristic by linear interpolation based on more than points of the calculated value, taken from the counter 13 of the appearance frequency, and the corrector 16 image quality for the correction of the supplied video signals according to the correction characteristic. 9. The circuit of claim 8, comprising a change controller, controlling the output by changing the calculated value of the appearance frequency counter during a period repeatedly exceeding the N-frame period, wherein the average value calculator is configured to calculate the average value of brightness levels m of image elements of the input video signal, where m is any integer greater than or equal to 2, the appearance frequency counter is configured to calculate brightness levels calculated by the average value calculator in the N-frame period for each of the multiple ranges of a given level, where N is an integer equal to or greater than 1, the linear interpolator is configured to generate a correction characteristic using linear interpolation based on the calculated value obtained from the output of the measurement controller, and the image quality corrector is configured to correct the input video signal in accordance with the correction curve generated by the shaper of the correction curve. 10. The circuit of claim 8, comprising a plurality of discriminators 17 for determining the occurrence frequencies of multiple brightness levels for each of the predetermined levels, a plurality of first counters 19 for counting the occurrence frequency for each of the predetermined levels determined by the discriminators 17, a plurality of comparators 21 for comparison the output signals of the first counters 19 with reference values supplied to the input 11 of the reference comparison value to establish the readings of the first counters 19 taking into account the output signals compared and a plurality of second counters 23 for counting the output signals of the comparators 21. 11. The circuit according to claim 9, in which the appearance frequency counter comprises a plurality of discriminators determining the correspondence of the brightness levels determined by the average value calculator to ranges of a given level, a plurality of first counters for counting the number of determination operations performed by each discriminator, a plurality of comparators for comparing the calculated values of the first counters with predefined reference values in order to obtain the first counter, taking into account the result of the comparison, and many second counters to count the number of output signals of the comparator for use as occurrence frequencies. 12. The circuit according to claim 9, in which the change controller contains a difference detector, a constant multiplier, an adder, and an N-frame decelerator, wherein a difference value is obtained at the output of the difference detector between the calculated value of the appearance frequency counter and the value of the output of the N- decelerator frame, the constant multiplier is configured to multiply the value at the output of the difference detector by 1 / X, where X is any integer equal to or greater than 2, the adder is configured to sum the value at the output of the means and slowing N-frame with the value at the output of multiplier by a constant deceleration means N is configured to delay the value obtained at the adder output to N-frame for subsequent supply to the difference detector and the adder, and for receiving the output signal with a controlled change. 13. The circuit according to claim 9, in which the change controller contains a difference detector, a constant multiplier, an adder, and an N-frame decelerator, wherein a difference value is obtained at the output of the difference detector between the calculated value of the second counter and the value of the output of the N-frame decelerator , a multiplier by a constant, configured to multiply the values at the output of the N-frame deceleration means by a factor of 1 / X, where X is an integer equal to or greater than 2, the adder is configured to sum the values at the output of the mind a cutter to a constant with the output value of the N-frame slowdown means, and the N-frame slowdown means is capable of delaying the total value received from the adder by N-frames for feeding to the difference detector and receiving a signal with a controlled change at the output. 14. The circuit of claim 10, in which the counter 13 of the appearance frequency contains discriminators 17, first counters, comparators 21 and second counters 23, each of which contains 16 series-connected circuits. 15. An image quality correction circuit comprising a counter 13 for counting the frequencies of occurrence of multiple brightness levels, the sampling of which is made from the video signals supplied to the video signal input 12, a correction curve generator 25 to generate a new correction curve based on the value received at the output of the appearance frequency counter 13 and corresponding to the point data, and based on previously entered point data entered along with the calculated point values, and the image quality corrector 16. 16. The circuit of claim 15, comprising a change controller that controls the change in the calculated value of the appearance frequency counter over a period repeatedly exceeding the N-frame period, the appearance frequency counter being configured to calculate the frequency of occurrence of brightness levels of image elements of input video signals in N frames, where N is any integer equal to or greater than 1, the shaper of the correction curve is configured to generate a new correction curve based on the calculated values, the floor changes to the output of the controller, and predefined values, and the image quality corrector is configured to correct the input video signal in accordance with the correction curve generated by the correction curve generator. 17. The circuit according to clause 15, in which the adjusting curve generator 25 is configured to generate a new characteristic by introducing either data on the point of the calculated value taken from the output of the counter 13 of the appearance frequency or introducing predefined data of the given point into other data, in particular between every second data, or between every second plural data. 18. The circuit of claim 15, wherein the correction curve generator comprises a circuit configured to generate a Bezier curve passing through the starting point and the ending point, based on the point data of the calculated value obtained at the output of the appearance frequency counter 13 and the predetermined point data wherein said data is selectively included in other data, in particular between every second data, or between every second plural data. 19. The circuit of claim 15, wherein the appearance frequency counter comprises a plurality of discriminators that determine the correspondence of the brightness level of each image element of the input video signal to each of the multiple predetermined levels, a plurality of first counters for counting the number of determination operations performed by each discriminator, and a plurality of comparators for comparing the calculated value taken from the first counter, with a predefined reference value in order to obtain the first counter, taking into account the result and comparisons, and many second counters for counting the number of output signals of the comparator to be used as the frequency of occurrence. 20. The circuit according to clause 16, in which the change controller contains a difference detector, a constant multiplier, an adder and an N-frame deceleration means, wherein a difference value is obtained at the output of the difference detector between the calculated value of the appearance frequency counter and the value of the output of the N- deceleration means frame, the constant multiplier is configured to multiply the value at the output of the difference detector by 1 / X, where X is any integer equal to or greater than 2, the adder is configured to sum the value at the output of the means VA deceleration of the N-frame with a value at the output of the multiplier by a constant, the means of decelerating the N-frame is configured to delay the value obtained at the output of the adder by N-frames for subsequent supply to the resonant detector and the adder, and to obtain a signal with controlled change. 21. The circuit according to clause 16, in which the change controller contains a difference detector, a constant multiplier, an adder and an N-frame decelerator, and the output of the difference detector receives a signal corresponding to the difference between the calculated value of the second counter and the value from the output of the deceleration means N -frame by a factor of 1 / X, where X is an integer equal to or greater than 2, the adder is configured to sum the values at the output of the multiplier by a constant with the value at the output of the N-frame slowdown means, N-slowdown means ra is arranged to delay the signal corresponding to the sum obtained by the adder for N-frame for subsequent supply to the difference detector and the adder, and for receiving the output signal with a controlled change. 22. An image quality correction circuit comprising an average value calculator 10 for calculating an average value of brightness levels of each of the multiple image elements of the video signal supplied to the video signal input 12, a counter 13 of occurrence frequencies of multiple brightness levels calculated by the average value calculator 10 for each predetermined level, a correction curve generator 25 for generating a new correction curve based on a value obtained at the output of the frequency counter 13 eniya and respective data on the points, and on the basis of predetermined data describing said point and introduced into the calculated values, and the image quality corrector 16 for correcting the video signal according to the correcting curve generated correcting curve generator 25. 23. The circuit according to claim 22, comprising a change controller, controlling the output by changing the calculated value of the appearance frequency counter during a period repeatedly exceeding the N-frame period, the average value calculator being configured to calculate the average value of the brightness levels m of the image elements of the input video signals, where m is any integer equal to or greater than 2, the appearance frequency counter is configured to count the frequency of occurrence of brightness levels calculated by the average value calculator An N-frame period for each of the multiple preset levels, where N is an integer equal to or greater than 1, the correction curve generator is configured to generate a new correction curve based on the calculated values received at the output of the change controller and predefined values, and the corrector image quality is made with the possibility of correction of the input video signal in accordance with the correction curve generated by the shaper of the correction curve. 24. The circuit according to claim 22, in which the adjusting curve generator 25 is configured to generate a new characteristic by introducing either data on the point of the calculated value taken from the output of the counter 13 of the appearance frequency or introducing predefined data of the given point into other data, in particular between every second data, or between every second plural data. 25. The circuit according to item 22, in which the generator 25 of the correction curve contains a circuit configured to generate a Bezier curve passing through the starting point and end point, based on the point data of the calculated value obtained at the output of the counter 13 of the frequency of occurrence and predefined data points, wherein said data is selectively inserted into other data, in particular between every second data, or between every second plural data. 26. The circuit according to claim 24, wherein the appearance frequency counter comprises a plurality of discriminators determining the correspondence of the brightness level of each image element of the input video signal to each of the multiple predetermined levels, a plurality of first counters for counting the number of determination operations performed by each discriminator, a plurality of comparators for comparing the calculated value taken from the first counter, with a predefined reference value in order to obtain the first counter, taking into account the result and comparisons, and many second counters for counting the number of output signals of the comparator to be used as the frequency of occurrence. 27. The circuit of claim 22, wherein the change controller comprises a difference detector, a constant multiplier, an adder, and an N-frame decelerator, wherein a difference value is obtained at the output of the difference detector between the calculated value of the appearance frequency counter and the value of the output of the N- decelerator frame; the constant multiplier is configured to multiply the value at the output of the difference detector by 1 / X, where X is any integer equal to or greater than 2; the adder is configured to sum the value at the output of the N-frame decelerator with the value at the output of the multiplier by a constant, the N-frame decelerator is configured to delay the value obtained at the output of the adder by N-frames for subsequent supply to the difference detector and adder, and to obtain a controlled change signal. 28. The image quality correction scheme according to claim 22, in which the change controller comprises a difference detector, a constant multiplier, an adder, and an N-frame decelerator, wherein the output of the difference detector receives a signal corresponding to the difference between the calculated value of the second counter and the output value means for slowing the N-frame; a multiplier by a constant multiplies the value at the output of the N-frame decelerator by a factor of 1 / X, where X is an integer equal to or greater than 2, the adder is capable of summing the value at the output of the multiplier by a constant with the value at the output of the N-frame decelerator ; the N-frame slowdown means is capable of delaying the signal corresponding to the sum received by the adder by N-frames for subsequent supply to the difference detector and adder, and for receiving a controlled change signal at the output. 29. An image quality correction circuit comprising an appearance frequency counter 13 for counting frequency appearance data of multiple brightness levels, the selection of which is made from the video signals supplied to the video signal input 12 for each predetermined level, the control circuit 29 of the correction characteristic characteristic point 29 for selectively receiving output the upper limit value, when the calculated value of the correction characteristic point, taken from the counter 13 of the frequency of occurrence, exceeds a predetermined the selected upper limit value, as well as selectively obtaining the lower limit value at the output when it is less than the lower limit value, a correction curve generator 48 for generating a correction curve in accordance with the output signal of the correction characteristic point control circuit 29, and an image quality corrector 16 for input correction to the input of the video signal in accordance with the correction characteristic generated by the shaper 48 of the correction curve. 30. The image quality correction scheme according to clause 29, in which the appearance frequency counter comprises an average value calculator for calculating an average value of brightness levels of multiple image elements of a video signal supplied to video signal input 12, and a counter for counting frequencies of occurrence of multiple brightness levels using a calculator 10 average value for each predetermined level. 31. The image quality correction scheme according to clause 29 or 30, in which the correction characteristic point control circuit 29 includes a control range comparator 43 for comparing the calculated value of the correction characteristic point and linearly varying upper limit value and lower limit value, the correcting characteristic point selector 47 for selection of the upper limit value, the lower limit value or the calculated value of the counter 13 of the frequency of occurrence in accordance with the output a control range comparator 43, and a control counter 40 for controlling the processing order of the correction characteristic point. 32. The image quality correction scheme of claim 31, wherein the control range comparator 43 includes an upper limit comparator 41a for comparing the calculated value (Pn) of the correction characteristic point and a linear variable upper limit value (an + w), and a lower limit comparator 42a for comparing the calculated value Pn of the correction characteristic point and the lower limit value (an-w), and the control range setting means 46 comprising the upper limit setting means 44a for setting the upper th limit value an + w, and the means 45a for setting the lower limit of the lower limit value (an-w). 33. The image quality correction scheme according to clause 29 or 30, in which the correction characteristic control circuit 29 comprises a control range comparator 43 for comparing the calculated value Pn of the correction characteristic point with upper limit values and lower limit values on the correction characteristics of the graph passing through the starting point and an end point that changes quadratically with respect to their intermediate parts, a correcting characteristic point selector 47 for selecting top its limit value, lower limit value or counted value of the counter 13 occurrence frequency, and a counter 40 for controlling the order of processing of correcting characteristic points. 34. The image quality correction scheme of claim 32, wherein the control range comparator 43 includes an upper limit comparator 41b for comparing the calculated value Pn of the correction characteristic point with a quadratically varying upper limit value YHn, and a lower limit comparator 42b for comparing the calculated value Pn of the correction characteristic points with a lower limit value YLn, wherein the control range setting means 46 comprises upper limit setting means 44b for setting the upper limit value YHn and means 45b for the lower limit value of the lower limit value YLn.

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