JP2000324363A - Gradation correction device - Google Patents
Gradation correction deviceInfo
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- JP2000324363A JP2000324363A JP11130893A JP13089399A JP2000324363A JP 2000324363 A JP2000324363 A JP 2000324363A JP 11130893 A JP11130893 A JP 11130893A JP 13089399 A JP13089399 A JP 13089399A JP 2000324363 A JP2000324363 A JP 2000324363A
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- gradation
- level
- input signal
- division
- correction
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ビデオカメラなど
に用いられる階調補正装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation correction device used for a video camera or the like.
【０００２】[0002]
【従来の技術】従来の階調補正装置としては特願平９−
０１２８４４号公報に記載されたものが知られている。2. Description of the Related Art As a conventional gradation correcting apparatus, Japanese Patent Application No. 9-90, filed on Jan. 19, 1993.
The one described in JP-A-012844 is known.
【０００３】図９に従来の階調補正装置の構成図を示
す。図９において、１は入力端子、３は信号レベル検出
手段、４はヒストグラム検出手段、５は階調特性設定手
段、６は階調補正手段、９は出力端子である。FIG. 9 shows a configuration diagram of a conventional tone correction device. In FIG. 9, 1 is an input terminal, 3 is a signal level detecting means, 4 is a histogram detecting means, 5 is a gradation characteristic setting means, 6 is a gradation correcting means, and 9 is an output terminal.
【０００４】従来の階調補正装置では、入力端子１より
入力した入力信号を信号レベル検出手段３でレベル検出
し、ヒストグラム検出手段４で入力信号の１画面分に相
当する輝度値のヒストグラムを算出し、階調特性設定手
段５で入力信号の輝度値の分布の度合いに応じて、傾き
が変わるような階調特性を算出し、階調補正手段６で階
調特性設定手段５で算出した階調特性により階調補正し
て出力端子９より出力する。In the conventional tone correction device, the level of an input signal input from an input terminal 1 is detected by a signal level detecting means 3, and a histogram of a luminance value corresponding to one screen of the input signal is calculated by a histogram detecting means 4. Then, the gradation characteristic setting means 5 calculates a gradation characteristic whose inclination changes according to the degree of distribution of the luminance value of the input signal, and the gradation correction means 6 calculates the gradation characteristic calculated by the gradation characteristic setting means 5. The tone is corrected by the tone characteristics and output from the output terminal 9.
【０００５】ここで、信号レベル検出手段３では入力信
号を等間隔の複数のレベルに分割し、そのレベルごとに
輝度値の分布を検出している。Here, the signal level detecting means 3 divides the input signal into a plurality of equally-spaced levels, and detects a luminance value distribution for each level.
【０００６】図１０に従来の階調補正装置のヒストグラ
ム分布及び階調補正特性を示す。図１０において、
（ａ）はヒストグラムで横軸は入力信号の分割レベル、
縦軸は入力信号の各信号レベルに対応する頻度分布（ヒ
ストグラム）である。（ｂ）は階調補正特性で、横軸は
入力信号レベル、縦軸は出力信号レベルである。（ｃ）
はガンマ補正特性で、横軸は入力信号レベル、縦軸は出
力信号レベルである。（ｄ）は階調補正特性とガンマ補
正特性を含めた総合階調特性である。FIG. 10 shows a histogram distribution and a gradation correction characteristic of a conventional gradation correction device. In FIG.
(A) is a histogram, the horizontal axis is the division level of the input signal,
The vertical axis is a frequency distribution (histogram) corresponding to each signal level of the input signal. (B) is a gradation correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. (C)
Is the gamma correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. (D) is an overall gradation characteristic including a gradation correction characteristic and a gamma correction characteristic.
【０００７】なお、ガンマ補正処理は階調補正装置の出
力信号に対して、カメラの信号処理で行われる処理であ
り、対応するブロックは図９には記載されていない。Note that the gamma correction process is a process performed by a camera signal process on the output signal of the tone correction device, and the corresponding block is not shown in FIG.
【０００８】図１０（ａ）は低輝度部と高輝度部に分布
が集中している状態を表している。図１０（ｂ）では、
図１０（ａ）で頻度の多かった分割レベルに相当する入
力信号レベルに対応する階調補正特性の傾きが急になる
ように設定されており、頻度の多かった分割レベルのコ
ントラストが強調される。また、逆に図１０（ａ）で頻
度の少なかった分割レベルに相当する入力信号レベルに
対応する階調補正特性の傾きは緩やかになるように設定
される。FIG. 10A shows a state in which the distribution is concentrated in the low luminance portion and the high luminance portion. In FIG. 10B,
In FIG. 10A, the gradient of the gradation correction characteristic corresponding to the input signal level corresponding to the frequent division level is set to be steep, and the contrast of the frequent division level is emphasized. . Conversely, the slope of the gradation correction characteristic corresponding to the input signal level corresponding to the less frequently divided level in FIG. 10A is set to be gentle.
【０００９】[0009]
【発明が解決しようとする課題】しかしながら、上記の
ような構成では、ビデオカメラのように、ガンマ補正
や、ニー補正を施すような機器においては、ガンマ補正
により信号レベルのうち低輝度部の階調特性は強調さ
れ、高輝度部の階調特性は抑圧されるので、最適な階調
補正特性を得ることができないという課題がある。However, in the above configuration, in a device such as a video camera that performs gamma correction or knee correction, the level of the low-luminance portion of the signal level is reduced by the gamma correction. Since the tone characteristics are emphasized and the tone characteristics of the high-luminance portion are suppressed, there is a problem that an optimal tone correction characteristic cannot be obtained.
【００１０】また、低輝度部は、ガンマ補正により３倍
から４倍のゲインがかかるため、特に入力信号レベルの
分割数が少ない場合には出力信号の低輝度部の補正レベ
ルの間隔が相対的に広くなり、階調補正を最適に調整す
るのは困難になるという課題がある。In addition, since the low-brightness part has a gain of three to four times due to gamma correction, especially when the number of divisions of the input signal level is small, the interval between the correction levels of the low-brightness part of the output signal is relatively small. Therefore, there is a problem that it is difficult to optimally adjust the gradation correction.
【００１１】また、高輝度部はニー補正により傾きが極
端に抑圧されるため、検出したヒストグラムのデータ通
り補正したのでは、高輝度部が階調不足になるという課
題がある。In addition, since the inclination of the high luminance portion is extremely suppressed by the knee correction, there is a problem that if the correction is performed according to the data of the detected histogram, the gradation of the high luminance portion becomes insufficient.
【００１２】したがって、本発明の目的は、最適な階調
補正特性を得ることができる階調補正装置を提供するこ
とである。Accordingly, it is an object of the present invention to provide a gradation correction device capable of obtaining an optimum gradation correction characteristic.
【００１３】[0013]
【課題を解決するための手段】請求項１記載の階調補正
装置は、入力信号レベルの分布範囲を複数の分割レベル
に分割し入力信号がどの分割レベルに入っているかを検
出する信号レベル検出手段と、分割レベルごとの入力信
号の分布であるヒストグラムを検出するヒストグラム検
出手段と、ヒストグラムに応じて分布の多いレベルの傾
きが急になるように階調特性を設定する階調特性設定手
段と、階調特性設定手段で設定された階調特性に応じ
て、入力信号に非線形な階調補正を施す階調補正手段
と、信号レベル検出手段で用いられる分割レベルの間隔
が入力信号に対し非均一になるように、分割レベルの間
隔を調整する分割レベル調整手段とを備えたものであ
る。According to a first aspect of the present invention, there is provided a gradation correction apparatus for dividing a distribution range of an input signal level into a plurality of division levels and detecting which division level the input signal falls into. Means, a histogram detecting means for detecting a histogram which is a distribution of the input signal for each division level, and a gradation characteristic setting means for setting a gradation characteristic so that a gradient having a large distribution is steep according to the histogram. A tone correction means for performing non-linear tone correction on an input signal in accordance with a tone characteristic set by a tone characteristic setting means, and an interval between division levels used by a signal level detection means being different from the input signal. Division level adjusting means for adjusting the interval between division levels so as to be uniform.
【００１４】請求項１記載の階調補正装置によれば、信
号レベル検出手段で入力信号レベルの分布範囲を複数の
分割レベルに分割し入力信号がどの分割レベルに入って
いるかを検出し、分割レベル調整手段で信号レベル検出
手段で用いられる分割レベルの間隔が、入力信号に対し
非均一になるように分割レベルの間隔を調整し、ヒスト
グラム検出手段で分割レベルごとの入力信号の分布であ
るヒストグラムを検出し、階調特性設定手段でヒストグ
ラムに応じて分布の多いレベルの傾きが急になるように
階調特性を設定し、階調特性設定手段で設定された階調
特性に応じて、信号に非線形な階調補正を施すという作
用を有する。According to the first aspect of the present invention, the distribution range of the input signal level is divided into a plurality of division levels by the signal level detection means, and the division level of the input signal is detected. The level adjustment means adjusts the interval between the division levels so that the interval between the division levels used by the signal level detection means is non-uniform with respect to the input signal, and the histogram detection means shows the distribution of the input signal for each division level. Is detected by the gradation characteristic setting means, and the gradation characteristic is set so that the gradient of a level having a large distribution becomes steep in accordance with the histogram, and the signal is set in accordance with the gradation characteristic set by the gradation characteristic setting means. Has an effect of performing non-linear gradation correction on the image.
【００１５】したがって、例えばビデオカメラのよう
に、ガンマ補正や、ニー補正を施すような機器におい
て、ガンマ補正により信号レベルのうち低輝度部の階調
特性が強調される場合でも、例えば低輝度部の分割レベ
ル数を細かくとって低輝度部を重視した階調補正をする
等、最適な階調補正特性を得ることができる。Therefore, in a device such as a video camera that performs gamma correction or knee correction, even if the gradation characteristics of the low luminance portion of the signal level are emphasized by the gamma correction, for example, the low luminance portion Optimum gradation correction characteristics can be obtained, for example, by performing gradation correction with emphasis on low-luminance portions by taking the number of division levels into small values.
【００１６】請求項２記載の階調補正装置は、請求項１
において、分割レベル調整手段は分割レベルの間隔が入
力信号に対し非均一になるように設定する複数の分割レ
ベル設定手段で構成され、信号レベル検出手段は入力信
号を分割レベル調整手段で設定された分割レベルと比較
する複数の比較器を有するものである。According to a second aspect of the present invention, there is provided a gradation correcting apparatus.
, The division level adjusting means is constituted by a plurality of division level setting means for setting intervals of the division levels to be non-uniform with respect to the input signal, and the signal level detecting means sets the input signal by the division level adjusting means. It has a plurality of comparators for comparing with the division level.
【００１７】請求項２記載の階調補正装置によれば、請
求項１と同様な効果がある。According to the gradation correcting apparatus of the second aspect, the same effect as that of the first aspect is obtained.
【００１８】請求項３記載の階調補正装置は、入力信号
に対して非線形な出力特性を持つ補助的階調補正手段
と、この補助的階調補正手段の出力信号を入力信号とし
て、入力信号のレベルの分布範囲を複数の分割レベルに
分割し入力信号がどの分割レベルに入っているかを検出
する信号レベル検出手段と、分割レベルごとの入力信号
の分布であるヒストグラムを検出するヒストグラム検出
手段と、ヒストグラムに応じて分布の多いレベルの傾き
が急になるように階調特性を設定する階調特性設定手段
と、階調特性設定手段で設定された階調特性に応じて、
入力信号に非線形な階調補正を施す階調補正手段とを備
えたものである。According to a third aspect of the present invention, there is provided a gradation correcting apparatus, wherein an auxiliary gradation correcting means having a non-linear output characteristic with respect to an input signal, and an output signal of the auxiliary gradation correcting means as an input signal. Signal level detection means for dividing the distribution range of the level into a plurality of division levels and detecting which division level the input signal is in, and histogram detection means for detecting a histogram which is the distribution of the input signal for each division level A tone characteristic setting means for setting a tone characteristic so that the gradient of a level having a large distribution according to the histogram becomes steep; and a tone characteristic set by the tone characteristic setting means,
And a gradation correcting means for performing non-linear gradation correction on the input signal.
【００１９】請求項３記載の階調補正装置によれば、補
助的階調補正手段を簡単な構成とすることができるた
め、小さな回路規模で請求項１と同様の階調補正特性を
得ることができる。According to the third aspect of the present invention, since the auxiliary tone correcting means can have a simple configuration, it is possible to obtain the same tone correcting characteristic as that of the first aspect with a small circuit scale. Can be.
【００２０】請求項４記載の階調補正装置は、入力信号
に対し、レベル補正を施す第１のレベル補正手段と、こ
の第１のレベル補正手段の出力信号を入力信号として、
この入力信号のレベルの分布範囲を複数の分割レベルに
分割し入力信号がどの分割レベルに入っているかを検出
する信号レベル検出手段と、分割レベルごとの入力信号
の分布であるヒストグラムを検出するヒストグラム検出
手段と、ヒストグラムに応じて分布の多いレベルの傾き
が急になるように階調特性を設定する階調特性設定手段
と、階調特性設定手段で設定された階調特性に応じて、
入力信号に非線形な階調補正を施す階調補正手段と、こ
の階調補正手段における階調補正処理の後の信号に対し
レベル補正を施す第２のレベル補正手段とを備えたもの
である。According to a fourth aspect of the present invention, there is provided a tone correction apparatus comprising: a first level correction unit for performing a level correction on an input signal; and an output signal of the first level correction unit as an input signal.
Signal level detecting means for dividing the distribution range of the level of the input signal into a plurality of division levels and detecting which division level the input signal belongs to, and a histogram for detecting a histogram which is a distribution of the input signal for each division level Detecting means, gradation characteristic setting means for setting gradation characteristics such that the gradient of a level having a large distribution according to the histogram becomes steep, and gradation characteristics set by the gradation characteristic setting means,
It is provided with a gradation correcting means for performing a non-linear gradation correction on an input signal, and a second level correcting means for performing a level correction on a signal after the gradation correction processing in the gradation correcting means.
【００２１】請求項４記載の階調補正装置によれば、信
号レベル検出手段の入力信号にオフセット値を加算する
ことによって折れ点を調整することにより、より自然な
階調特性を得ることができる。According to the tone correcting apparatus of the present invention, a more natural tone characteristic can be obtained by adjusting a break point by adding an offset value to an input signal of the signal level detecting means. .
【００２２】請求項５記載の階調補正装置は、請求項
１、請求項２、請求項３または請求項４において、階調
特性設定手段が特定の分割レベルの階調特性の傾きがヒ
ストグラムの分布に対して、より急峻になるように階調
特性を設定する重み付け手段を有するものである。According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect of the present invention, the gradation characteristic setting means determines that the gradient of the gradation characteristic at a specific division level is equal to that of the histogram. It has weighting means for setting gradation characteristics so that the distribution becomes steeper.
【００２３】請求項５記載の階調補正装置によれば、請
求項１、請求項２、請求項３または請求項４と同様な効
果のほか、重み付け手段で特定の信号レベルの階調特性
の傾きがヒストグラムの分布に対して、より急峻になる
ように階調特性を設定することによって、例えばビデオ
カメラのようにガンマ補正やニー補正を施すような機器
において、ガンマ補正により信号レベルのうち低輝度部
の階調特性が強調される場合でも最適な階調補正特性を
得ることができる。According to the tone correcting apparatus of the fifth aspect, in addition to the same effects as those of the first, second, third or fourth aspect, the weighting means can be used to obtain the tone characteristic of a specific signal level. By setting the gradation characteristics so that the slope becomes steeper with respect to the distribution of the histogram, in a device such as a video camera that performs gamma correction or knee correction, the signal level becomes lower due to gamma correction. Even when the gradation characteristics of the luminance section are emphasized, the optimum gradation correction characteristics can be obtained.
【００２４】[0024]
【発明の実施の形態】（実施の形態１）以下、本発明の
第１の実施の形態の階調補正装置について、図１および
図２を参照しながら説明する。(Embodiment 1) Hereinafter, a gradation correcting apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
【００２５】図１は、本発明の第１の実施の形態の階調
補正装置の構成を表す構成図である。階調補正の分割レ
ベル数は多ければ多いほど細かな階調補正が可能となる
が、それに対して回路規模は大きくなる。実際には１６
分割程度が望ましいが、説明を容易にするため、第１の
実施の形態では入力信号の分割レベル数を８とする。FIG. 1 is a configuration diagram showing a configuration of a gradation correction apparatus according to a first embodiment of the present invention. Finer gradation correction is possible as the number of gradation correction division levels increases, but the circuit scale increases. Actually 16
Although the degree of division is desirable, the number of division levels of the input signal is eight in the first embodiment for the sake of simplicity.
【００２６】図１において、１は入力端子、２は分割レ
ベル調整手段、３は信号レベル検出手段、４はヒストグ
ラム検出手段、５は階調特性設定手段、６は階調補正手
段、７ａ〜７ｈは分割レベル設定手段としてのレジス
タ、８ａ〜８ｈは比較器、９は出力端子、１０は信号レ
ベル判定回路、１１はマルチプレクサ、１２はレジスタ
（１２ａ〜１２ｈ）、１３はセレクタ、１４は加算器で
ある。In FIG. 1, 1 is an input terminal, 2 is a division level adjusting unit, 3 is a signal level detecting unit, 4 is a histogram detecting unit, 5 is a gradation characteristic setting unit, 6 is a gradation correcting unit, and 7a to 7h. Is a register as division level setting means, 8a to 8h are comparators, 9 is an output terminal, 10 is a signal level determination circuit, 11 is a multiplexer, 12 is a register (12a to 12h), 13 is a selector, and 14 is an adder. is there.
【００２７】入力端子１より入力された入力信号Ｓｉｎ
は信号レベル検出手段３に入力される。信号レベル検出
手段３は分割レベル調整手段２の分割レベル設定手段と
してのレジスタ７ａ〜７ｈに設定された８個の分割レベ
ルデータを入力し、比較器８ａ〜８ｈで入力信号Ｓｉｎ
と上記８個の分割レベルデータとを比較し、信号レベル
判定回路１０で入力信号が８個の分割レベルのうちどの
レベルに入っているかを判定し制御信号としてヒストグ
ラム検出手段４に伝える。The input signal Sin input from the input terminal 1
Is input to the signal level detecting means 3. The signal level detection means 3 inputs eight division level data set in the registers 7a to 7h as division level setting means of the division level adjustment means 2, and the comparators 8a to 8h input the signal Sin.
Is compared with the above eight division level data, the signal level judgment circuit 10 judges which of the eight division levels the input signal is in, and transmits it to the histogram detection means 4 as a control signal.
【００２８】ここで、レジスタ７ａ〜７ｈに設定する分
割レベルは入力信号の小さい方から最初の４分の１の範
囲を４分割し、次の４分の１の範囲を２分割し、残り２
分の１の範囲を２分割するように設定する。Here, the division levels set in the registers 7a to 7h are such that the first quarter range is divided into four from the smaller input signal, the next quarter range is divided into two, and the remaining two parts are divided into two.
It is set to divide the range of 1/2 into two.
【００２９】ヒストグラム検出手段４では、入力した制
御信号によりマルチプレクサ１１とセレクタ１３を制御
し、マルチプレクサ１１とセレクタ１３は８個のレジス
タ１２ａ〜１２ｈのうち入力した信号レベルに対応した
レジスタを選択する。加算器１４では選択されたレジス
タ１２ａ〜１２ｈのいずれかの出力信号に１を加算し、
再び同じレジスタ１２に格納する。この動作を１フィー
ルド期間にわたって行うことによって８個のレベルに対
応するヒストグラムデータH(０)からH(７)が得られる。In the histogram detecting means 4, the multiplexer 11 and the selector 13 are controlled by the input control signal, and the multiplexer 11 and the selector 13 select a register corresponding to the input signal level from the eight registers 12a to 12h. The adder 14 adds 1 to the output signal of one of the selected registers 12a to 12h,
It is stored in the same register 12 again. By performing this operation over one field period, histogram data H (0) to H (7) corresponding to eight levels are obtained.
【００３０】以上のようにして求められた８個のレベル
に対応するヒストグラムデータH(０）からH(７）は、テ
レビ信号の垂直ブランキング期間内に階調特性設定手段
５に転送される。The histogram data H (0) to H (7) corresponding to the eight levels obtained as described above are transferred to the gradation characteristic setting means 5 during the vertical blanking period of the television signal. .
【００３１】階調特性設定手段５内では、ヒストグラム
データH(０）からH(７）の累積積分値SH（０）からSH
（７）により階調補正特性を得て、階調補正手段６の階
調補正特性を設定する。累積積分値SH(n）は、H(n)を用
いて、SH(n）＝ΣH(k) k=0,1,2,・・・ ,nで表される。In the gradation characteristic setting means 5, the cumulative integrated values SH (0) to SH (0) of the histogram data H (0) to H (7) are obtained.
The gradation correction characteristic is obtained by (7), and the gradation correction characteristic of the gradation correction means 6 is set. The cumulative integral SH (n) is represented by SH (n) = ΣH (k) k = 0, 1, 2,..., N using H (n).
【００３２】階調補正手段６では階調特性設定手段５に
より設定された階調補正特性により入力端子１から入力
する入力信号Ｓｉｎに対して階調補正処理を施し出力信
号Ｓｏｕｔを出力端子９より出力する。The gradation correction means 6 performs gradation correction processing on the input signal Sin input from the input terminal 1 according to the gradation correction characteristics set by the gradation characteristic setting means 5, and outputs the output signal Sout from the output terminal 9. Output.
【００３３】出力信号Ｓｏｕｔはビデオカメラなどでは
図示しないガンマ補正回路により階調補正であるガンマ
補正処理が施されてカメラ出力として出力される。The output signal Sout is subjected to gamma correction processing for gradation correction by a gamma correction circuit (not shown) in a video camera or the like, and is output as a camera output.
【００３４】図２に第１の実施の形態の階調補正装置の
ヒストグラム分布及び階調補正特性を示す。図において
（ａ）はヒストグラムで横軸は入力信号の分割レベル、
縦軸は入力信号の各信号レベルに対応する頻度分布（ヒ
ストグラム）である。（ｂ）は階調補正特性で、横軸は
入力信号レベル、縦軸は出力信号レベルである。（ｃ）
はガンマ補正特性で、横軸は入力信号レベル、縦軸は出
力信号レベルである。（ｄ）は階調補正特性とガンマ補
正特性を含めた総合階調特性である。FIG. 2 shows a histogram distribution and gradation correction characteristics of the gradation correction device according to the first embodiment. In the figure, (a) is a histogram, the horizontal axis is the division level of the input signal,
The vertical axis is a frequency distribution (histogram) corresponding to each signal level of the input signal. (B) is a gradation correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. (C)
Is the gamma correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. (D) is an overall gradation characteristic including a gradation correction characteristic and a gamma correction characteristic.
【００３５】図２（ａ）のように低輝度部の分割数を細
かくとっているため、低輝度部を重視した階調補正とな
っている。これにより、図２（ｄ）の総合階調特性では
低輝度側の階調特性が図１１（ｄ）の従来の階調補正装
置の総合階調特性に比べてなめらかに補正されている。As shown in FIG. 2A, since the number of divisions of the low-luminance portion is made small, gradation correction is performed with emphasis on the low-luminance portion. As a result, in the total gradation characteristic of FIG. 2D, the gradation characteristic on the low luminance side is corrected more smoothly than the total gradation characteristic of the conventional gradation correction device of FIG. 11D.
【００３６】第１の実施の形態による本発明の効果は、
ビデオカメラのように、ガンマ補正や、ニー補正を施す
ような機器において、ガンマ補正により信号レベルのう
ち低輝度部の階調特性が強調される場合でも最適な階調
補正特性を得ることができるというものである。The effect of the present invention according to the first embodiment is as follows.
In a device such as a video camera that performs gamma correction or knee correction, an optimum gradation correction characteristic can be obtained even when the gamma correction emphasizes the gradation characteristic of a low-luminance part in the signal level. That is.
【００３７】（実施の形態２）実施の形態１で分割レベ
ルを設定したレジスタ７、信号レベルを検出した比較器
８は信号レベルの分割の数だけ必要となり回路規模が大
きくなる。(Embodiment 2) The register 7 in which the division level is set in the first embodiment and the comparators 8 which detect the signal level are required by the number of divisions of the signal level, and the circuit scale becomes large.
【００３８】第２の実施の形態による本発明の目的は、
第１の実施の形態に対してより簡単な構成で第１の実施
の形態と同様の効果を得ようと言うものである。The object of the present invention according to the second embodiment is as follows.
This is to obtain an effect similar to that of the first embodiment with a simpler configuration than that of the first embodiment.
【００３９】以下、本発明の第２の実施の形態の階調補
正装置について、図３および図４を参照しながら説明す
る。Hereinafter, a tone correction device according to a second embodiment of the present invention will be described with reference to FIGS.
【００４０】図３は第２の実施の形態の階調補正装置の
構成を示す構成図である。図３において、１４ａ、１４
ｂは加算器、１５は分割レベル調整手段である補助的な
階調補正手段、１６ａ、１６ｂは増幅器、１７は最小値
回路である。FIG. 3 is a configuration diagram showing the configuration of the tone correction device according to the second embodiment. In FIG. 3, 14a, 14
b is an adder, 15 is auxiliary gradation correction means as division level adjustment means, 16a and 16b are amplifiers, and 17 is a minimum value circuit.
【００４１】入力端子１に入力した入力信号Ｓｉｎは補
助的階調補正手段１５に入力される。The input signal Sin inputted to the input terminal 1 is inputted to the auxiliary gradation correcting means 15.
【００４２】補助的階調補正手段１５では入力信号Ｓｉ
ｎを増幅器１６ａで２倍した信号Ｓ０と、入力信号Ｓｉ
ｎに加算器１４ａでオフセット値off １が加算された信
号Ｓ１と、増幅器１６ｂで１／２倍し加算器１４ｂでオ
フセット値off ２が加算された信号Ｓ２が最小値回路１
７に入力され、３つの信号のうち最小のレベルを示す信
号が予備の階調補正が施された信号Ｓｉｎ２として出力
される。In the auxiliary gradation correcting means 15, the input signal Si
n is doubled by the amplifier 16a, and the input signal Si
The signal S1 obtained by adding the offset value off1 to the n by the adder 14a and the signal S2 obtained by multiplying the output signal by 1/2 by the amplifier 16b and adding the offset value off2 by the adder 14b are the minimum value circuit 1.
7, a signal indicating the minimum level among the three signals is output as a signal Sin2 subjected to preliminary gradation correction.
【００４３】ここで、オフセット値off １を入力信号の
分割範囲の１／４、オフセット値off ２を入力信号の分
割範囲の１／２とすると、Ｓｉｎ２の階調特性は図４
（ａ）のようになる。Here, assuming that the offset value off 1 is １ ／ of the input signal division range and the offset value off 2 is の of the input signal division range, the gradation characteristic of Sin 2 is as shown in FIG.
(A).
【００４４】次に補助的階調補正手段１５の出力信号Ｓ
ｉｎ２は信号レベル検出手段３に入力される。Next, the output signal S of the auxiliary gradation correction means 15
in2 is input to the signal level detection means 3.
【００４５】第２の実施の形態における信号レベル検出
手段３は入力信号レベルを８つのレベルに等間隔に分割
するように構成している。デジタル信号においては入力
信号の上位の３ビットにより８つのレベルの分割制御信
号を得ることができる。The signal level detecting means 3 in the second embodiment is configured to divide the input signal level into eight levels at equal intervals. In a digital signal, a division control signal of eight levels can be obtained by the upper three bits of the input signal.
【００４６】ヒストグラム検出手段４，階調特性設定手
段５、階調補正手段６の動作は第１の実施の形態に準じ
るので、ここでは省略する。The operations of the histogram detecting means 4, the gradation characteristic setting means 5, and the gradation correcting means 6 are the same as in the first embodiment, and will not be described here.
【００４７】図４に第２の実施の形態の階調補正装置の
ヒストグラム分布及び階調補正特性を示す。図４におい
て（ａ）は補助的階調補正手段の階調特性であり、横軸
は入力信号レベル、縦軸は出力信号レベルである。
（ｂ）はヒストグラムで横軸は入力信号の分割レベル、
縦軸は入力信号の各信号レベルに対応する頻度分布（ヒ
ストグラム）である。（ｃ）は階調補正特性で、横軸は
入力信号レベル、縦軸は出力信号レベルである。（ｄ）
は階調補正特性とガンマ補正特性を含めた総合階調特性
である。FIG. 4 shows a histogram distribution and gradation correction characteristics of the gradation correction device according to the second embodiment. In FIG. 4, (a) shows the gradation characteristics of the auxiliary gradation correction means, where the horizontal axis is the input signal level and the vertical axis is the output signal level.
(B) is a histogram, the horizontal axis is the division level of the input signal,
The vertical axis is a frequency distribution (histogram) corresponding to each signal level of the input signal. (C) is a gradation correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. (D)
Is a total gradation characteristic including a gradation correction characteristic and a gamma correction characteristic.
【００４８】入力信号Ｓｉｎに対し補助的階調補正手段
１５で低輝度部の信号を２倍にすることにより、入力信
号Ｓｉｎの４分の１の範囲に分布していた信号はＳｉｎ
２では２分の１の範囲に分布することになる。入力信号
Ｓｉｎの次の４分の１の範囲に分布していた信号はＳｉ
ｎ２では２分の１から４分の３の範囲に分布する。この
ように補助的階調補正手段１５で予備の階調補正を施す
ことにより、分割範囲を設定した第１の実施の形態と同
様の範囲をヒストグラムの検出に割り当てることができ
る。そのため、ヒストグラム検出手段４で得られるヒス
トグラムの値は分割の間隔が等間隔であるのに第１の実
施の形態と同じ値が得られ、第１の実施の形態と同様の
階調特性が得られる。By doubling the signal of the low-luminance portion with respect to the input signal Sin by the auxiliary gradation correcting means 15, the signal distributed in a quarter of the input signal Sin is reduced to Sin.
In the case of 2, it is distributed in a half range. The signal distributed in the next quarter of the input signal Sin is Si
In n2, it is distributed in the range of 1/2 to 3/4. By performing the preliminary gradation correction by the auxiliary gradation correction means 15 in this manner, the same range as in the first embodiment in which the divided range is set can be assigned to the detection of the histogram. Therefore, the values of the histogram obtained by the histogram detection means 4 are the same as those in the first embodiment even though the division intervals are equal, and the same gradation characteristics as those in the first embodiment are obtained. Can be
【００４９】第２の実施の形態による本発明の効果は、
補助的階調補正手段１５を簡単な構成とすることができ
るため、小さな回路規模で第１の実施の形態と同様の階
調補正特性を得ることができるというものである。The effect of the present invention according to the second embodiment is as follows.
Since the auxiliary gradation correcting means 15 can have a simple configuration, the same gradation correction characteristics as those of the first embodiment can be obtained with a small circuit scale.
【００５０】（実施の形態３）以下、本発明の第３の実
施の形態の階調補正装置について、図５および図６を参
照しながら説明する。(Embodiment 3) Hereinafter, a gradation correcting apparatus according to a third embodiment of the present invention will be described with reference to FIGS.
【００５１】第３の実施の形態による本発明の目的は、
低輝度部の階調特性の設定の自由度を上げ、最適な階調
特性を得るというものである。The object of the present invention according to the third embodiment is as follows.
The purpose is to increase the degree of freedom in setting the gradation characteristics of the low-luminance portion and obtain the optimum gradation characteristics.
【００５２】図５に第３の実施の形態の階調補正装置の
構成を示す。図５において、１は入力端子、２は分割レ
ベル調整手段、３は信号レベル検出手段、４はヒストグ
ラム検出手段、５は階調特性設定手段、６は階調補正手
段、９は出力端子、１４は第１のレベル補正手段として
の加算器、１８は第２のレベル補正手段としての減算器
である。FIG. 5 shows the configuration of a tone correction device according to the third embodiment. In FIG. 5, 1 is an input terminal, 2 is a division level adjustment unit, 3 is a signal level detection unit, 4 is a histogram detection unit, 5 is a gradation characteristic setting unit, 6 is a gradation correction unit, 9 is an output terminal, 14 is Is an adder as first level correction means, and 18 is a subtractor as second level correction means.
【００５３】入力端子１に入力された入力信号ははじめ
に分割レベル調整手段２に入力される。分割レベル調整
手段２では特定のオフセット値off１が第１のレベル補
正手段としての加算器１４で加算され、オフセット付き
の入力信号Ｓｉｎ２が出力される。ここで、オフセット
値ｏｆｆ１は１段目に相当する最も低いレベルの分割レ
ベルの幅より小さい値とする。The input signal input to the input terminal 1 is first input to the division level adjusting means 2. In the division level adjusting means 2, a specific offset value off1 is added by an adder 14 as a first level correcting means, and an input signal Sin2 with an offset is output. Here, the offset value off1 is set to a value smaller than the width of the division level of the lowest level corresponding to the first stage.
【００５４】次にオフセット付き入力信号Ｓｉｎ２は信
号レベル検出手段３に入力され、信号レベルが検出され
る。Next, the input signal Sin2 with offset is inputted to the signal level detecting means 3, and the signal level is detected.
【００５５】信号レベル検出手段３では、第２の実施の
形態と同様に等間隔の分割レベルで信号レベルを検出
し、ヒストグラム検出手段４でオフセット加算された入
力信号のヒストグラムが算出される。階調特性設定手段
５では、ヒストグラム検出手段４で検出されたヒストグ
ラム値に応じた階調特性を算出するが、最も低いレベル
の分割レベルに対応する信号に対しては階調補正を行わ
ず入力信号をそのまま出すように設定する。階調補正手
段６では、階調特性設定手段５で算出された階調補正特
性を入力し、階調補正された出力信号を出力する。The signal level detecting means 3 detects signal levels at equally spaced division levels as in the second embodiment, and the histogram of the input signal subjected to offset addition by the histogram detecting means 4 is calculated. The gradation characteristic setting means 5 calculates a gradation characteristic according to the histogram value detected by the histogram detection means 4, but inputs the signal corresponding to the lowest division level without performing gradation correction. Set to output the signal as it is. The gradation correction means 6 receives the gradation correction characteristics calculated by the gradation characteristic setting means 5 and outputs a gradation-corrected output signal.
【００５６】階調補正手段６の出力信号は分割レベル調
整手段２の第２のレベル補正手段としての減算器１８に
より、オフセット値off ２が減じられ、出力信号Ｓｏｕ
ｔとして出力端子９から出力される。The output value of the gradation correction means 6 is reduced by the offset value off 2 by the subtracter 18 as the second level correction means of the division level adjustment means 2, and the output signal Sou
Output from the output terminal 9 as t.
【００５７】図６に第３の実施の形態の階調補正装置の
ヒストグラム分布及び階調補正特性を示す。図６におい
て（ａ）は分割レベル調整手段２の加算器１４の出力信
号Ｓｉｎ２の階調特性であり、横軸は入力信号レベル、
縦軸は出力信号レベルである。（ｂ）はヒストグラムで
横軸は入力信号の分割レベル、縦軸は入力信号の各信号
レベルに対応する頻度分布（ヒストグラム）である。
（ｃ）は階調補正特性で、横軸は入力信号レベル、縦軸
は出力信号レベルである。（ｄ）は分割レベル調整手段
２の減算器１８の出力信号Ｓoutの階調特性であり、横
軸は入力信号レベル、縦軸は出力信号レベルである。
（ｅ）は階調補正特性とガンマ補正特性を含めた総合階
調特性である。FIG. 6 shows a histogram distribution and gradation correction characteristics of the gradation correction apparatus according to the third embodiment. In FIG. 6, (a) shows the gradation characteristics of the output signal Sin2 of the adder 14 of the division level adjusting means 2, where the horizontal axis is the input signal level,
The vertical axis is the output signal level. (B) is a histogram, in which the horizontal axis represents the division level of the input signal, and the vertical axis represents the frequency distribution (histogram) corresponding to each signal level of the input signal.
(C) is a gradation correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. (D) is the gradation characteristic of the output signal Sout of the subtractor 18 of the division level adjusting means 2, where the horizontal axis is the input signal level and the vertical axis is the output signal level.
(E) is an overall gradation characteristic including a gradation correction characteristic and a gamma correction characteristic.
【００５８】図６（ｃ）では最小の分割レベルの傾きは
１倍になっている。図６（ｄ）ではオフセット値ｏｆｆ
２を減じ、図６（ｃ）の特性を負側にシフトした形の特
性になっている。図６（ｅ）では、オフセット値に相当
するレベルだけ最小の分割レベルが小さくなった形で総
合特性が形成されている。In FIG. 6C, the gradient of the minimum division level is one. In FIG. 6D, the offset value off
By subtracting 2, the characteristic of FIG. 6C is shifted to the negative side. In FIG. 6E, the overall characteristic is formed in such a manner that the minimum division level is reduced by a level corresponding to the offset value.
【００５９】折れ線で階調補正を行う場合には、その折
れ点のレベルで階調特性の傾きが不連続になり、階調補
正後の画像の階調特性が不自然となる場合があるが、本
実施の形態のように入力信号にオフセット値を加算する
ことによって折れ点を調整することにより、より自然な
階調特性を得ることができる。When gradation correction is performed with a broken line, the gradient of the gradation characteristic becomes discontinuous at the level of the broken point, and the gradation characteristic of the image after the gradation correction may become unnatural. By adjusting a break point by adding an offset value to an input signal as in the present embodiment, a more natural gradation characteristic can be obtained.
【００６０】第３の実施の形態による本発明の効果は、
入力信号にオフセット値を加算することによって折れ点
を調整することにより、より自然な階調特性を得ること
ができるというものである。The effect of the present invention according to the third embodiment is as follows.
By adjusting a break point by adding an offset value to an input signal, a more natural gradation characteristic can be obtained.
【００６１】（実施の形態４）以下、本発明の第４の実
施の形態の階調補正装置について、図７および図８を参
照しながら説明する。(Embodiment 4) Hereinafter, a gradation correcting apparatus according to a fourth embodiment of the present invention will be described with reference to FIGS.
【００６２】第４の実施の形態による本発明の目的は、
重み付け手段で特定の信号レベルの階調特性の傾きがヒ
ストグラムの分布に対して、より急峻になるように階調
特性を設定することによって、ビデオカメラのように、
ガンマ補正や、ニー補正を施すような機器において、ガ
ンマ補正により信号レベルのうち低輝度部の階調特性が
強調される場合でも最適な階調補正特性を得ることであ
る。The object of the present invention according to the fourth embodiment is as follows.
By setting the gradation characteristic so that the slope of the gradation characteristic of a specific signal level becomes steeper with respect to the distribution of the histogram by the weighting means, as in a video camera,
In a device that performs gamma correction or knee correction, an optimum gradation correction characteristic is to be obtained even when gradation characteristics of a low luminance portion in a signal level are emphasized by gamma correction.
【００６３】図７は本発明の第４の実施の形態の階調補
正装置の構成を表す構成図である。図７において、１９
は重み付け手段、２０は階調特性算出手段である。FIG. 7 is a configuration diagram showing the configuration of a tone correction device according to a fourth embodiment of the present invention. In FIG. 7, 19
Is a weighting means, and 20 is a gradation characteristic calculating means.
【００６４】第４の実施の形態において分割レベル調整
手段２、信号レベル検出手段３、ヒストグラム検出手段
４の動作は第３の実施の形態に準じるので、ここでは省
略する。階調特性設定手段５は階調特性算出手段２０に
おいて第３の実施の形態と同様に階調補正特性を算出し
た後、算出した階調補正特性を重み付け手段１９に入力
する。重み付け手段１９では特定の信号レベルの階調特
性の傾きがヒストグラムの分布に対して、より急峻にな
るように階調特性を設定する。具体的には８分割された
信号レベルの階調補正特性に対し、各段の傾きが最下段
は１倍、次の３段は１／２倍、次の２段は１倍、次の２
段は２倍となるようなゲインをかける。In the fourth embodiment, the operations of the division level adjusting means 2, the signal level detecting means 3, and the histogram detecting means 4 are the same as those of the third embodiment, and will not be described here. The gradation characteristic setting means 5 calculates the gradation correction characteristic in the gradation characteristic calculation means 20 in the same manner as in the third embodiment, and inputs the calculated gradation correction characteristic to the weighting means 19. The weighting means 19 sets the gradation characteristics so that the gradient of the gradation characteristics at a specific signal level becomes steeper with respect to the histogram distribution. Specifically, with respect to the gradation correction characteristic of the signal level divided into eight, the inclination of each stage is 1 × at the lowest stage, 倍 × at the next 3 stages, 1 × at the next 2 stages, 1 × at the next 2 stages.
The stage applies a gain that is doubled.
【００６５】階調補正手段６では、階調特性設定手段５
で算出された階調補正特性を入力し、階調補正された出
力信号を出力する。In the gradation correcting means 6, the gradation characteristic setting means 5
Is input, and an output signal whose gradation has been corrected is output.
【００６６】階調補正手段６の出力信号は分割レベル調
整手段２の第２のレベル補正手段としての減算器１８に
より、オフセット値off２が減じられ、出力信号Ｓｏｕ
ｔとして出力端子９から出力される。The output value of the gradation correction means 6 is reduced by the offset value off2 by the subtracter 18 as the second level correction means of the division level adjustment means 2, and the output signal Sou
Output from the output terminal 9 as t.
【００６７】図８に第４の実施の形態の階調補正装置の
階調補正特性等を示す。図８において（ａ）は階調補正
特性で、横軸は入力信号レベル、縦軸は出力信号レベル
である。図８（ａ）では重み付け前の階調補正特性を波
線で示す。（ｂ）は階調補正特性とガンマ補正特性を含
めた総合階調特性である。FIG. 8 shows the gradation correction characteristics and the like of the gradation correction device according to the fourth embodiment. In FIG. 8, (a) is the gradation correction characteristic, the horizontal axis is the input signal level, and the vertical axis is the output signal level. In FIG. 8A, the gradation correction characteristics before weighting are indicated by broken lines. (B) is an overall gradation characteristic including a gradation correction characteristic and a gamma correction characteristic.
【００６８】図８（ａ）で重み付け処理により最下段の
傾きは１倍、次の３段の傾きは１／２倍に、次の２段の
傾きは１倍に、次の２段の傾きは２倍となっている。In FIG. 8A, the slope of the lowermost stage is one time, the slope of the next three stages is 1/2, the slope of the next two stages is one time, and the slope of the next two stages is determined by the weighting process. Is doubled.
【００６９】結果として、図８（ｂ）のように、ガンマ
補正後の総合特性で、高輝度部の階調特性が急峻になっ
ていることがわかる。As a result, as shown in FIG. 8B, it can be seen that the gradation characteristics of the high-luminance portion are steep in the overall characteristics after gamma correction.
【００７０】第４の実施の形態による本発明の効果は、
重み付け手段１９で特定の信号レベルの階調特性の傾き
がヒストグラムの分布に対して、より急峻になるように
階調特性を設定することによって、ビデオカメラのよう
に、ガンマ補正や、ニー補正を施すような機器におい
て、ガンマ補正により信号レベルのうち低輝度部の階調
特性が強調される場合でも最適な階調補正特性を得るこ
とができるというものである。The effect of the present invention according to the fourth embodiment is as follows.
By setting the gradation characteristics so that the gradient of the gradation characteristics at a specific signal level becomes steeper with respect to the histogram distribution by the weighting means 19, gamma correction and knee correction can be performed as in a video camera. In such a device, the optimum gradation correction characteristic can be obtained even when the gradation characteristic of the low luminance portion of the signal level is emphasized by the gamma correction.
【００７１】なお、第２の実施の形態から第４の実施の
形態で分割レベル調整手段２の分割レベルは固定値とし
て扱っているが、入力信号のダイナミックレンジやヒス
トグラムデータの分布の変化に対応して分割レベルを変
化させても良い。この場合はさらに細かな調整が可能と
なる。Although the division levels of the division level adjusting means 2 are treated as fixed values in the second to fourth embodiments, they correspond to changes in the dynamic range of input signals and the distribution of histogram data. Alternatively, the division level may be changed. In this case, finer adjustment is possible.
【００７２】また、第１の実施の形態から第４の実施の
形態で入力信号の分割レベル数を８としたが、それ以上
であってもそれ以下であっても良い。分割数を多くすれ
ば、相対的に回路規模が大きくなるが、より細かな調整
が可能となる。Further, in the first to fourth embodiments, the number of division levels of the input signal is set to 8, but may be more or less. Increasing the number of divisions relatively increases the circuit scale, but allows finer adjustment.
【００７３】また、第２の実施の形態における補助的階
調補正手段１５はゲインとオフセットを変えた３種類の
信号のうち最小のものを取り出す構成となっているが、
折れ線近似である必要はない。Further, the auxiliary gradation correcting means 15 in the second embodiment is configured to take out the smallest one of the three types of signals having different gains and offsets.
It need not be a line-line approximation.
【００７４】また、第１の実施の形態から第４の実施の
形態の分割レベル調整手段２は、組み合わせて使用する
ことができる。複数の分割レベル調整手段２を組み合わ
せれば、よりよい階調補正特性を得ることができる。例
えば、第２の実施の形態および第３の実施の形態の分割
レベル調整手段２の少なくとも一方を第１の実施の形態
に加えたり、第３の実施の形態の分割レベル調整手段２
を第２の実施の形態に加えることが考えられる。さらに
第４の実施の形態の階調特性設定手段５を第１の実施の
形態または第２の実施の形態に適用することが可能であ
る。Further, the division level adjusting means 2 of the first to fourth embodiments can be used in combination. By combining a plurality of division level adjusting means 2, better gradation correction characteristics can be obtained. For example, at least one of the division level adjustment units 2 of the second and third embodiments may be added to the first embodiment, or the division level adjustment unit 2 of the third embodiment may be added.
May be added to the second embodiment. Further, the gradation characteristic setting means 5 of the fourth embodiment can be applied to the first embodiment or the second embodiment.
【００７５】また、第４の実施の形態で重み付け手段１
９で階調補正特性に対して重み付け処理を行っている
が、ヒストグラム検出手段４から入力するヒストグラム
データに対して重み付け処理を施しても同様の効果が得
られる。Further, in the fourth embodiment, the weighting means 1
9, weighting processing is performed on the gradation correction characteristic. However, the same effect can be obtained by performing weighting processing on the histogram data input from the histogram detecting means 4.
【００７６】この重み付け手段１９を有する階調特性設
定手段５は、第１の実施の形態および第２の実施の形態
に適用することも可能である。また、第４の実施の形態
で重み付けの値は固定値として扱っているが、入力信号
のダイナミックレンジやヒストグラムデータの分布の変
化に対応して重み付け量を変化させても良い。この場合
はさらに細かな調整が可能となる。The gradation characteristic setting means 5 having the weighting means 19 can be applied to the first embodiment and the second embodiment. Although the weighting value is treated as a fixed value in the fourth embodiment, the weighting amount may be changed according to a change in the dynamic range of the input signal or the distribution of the histogram data. In this case, finer adjustment is possible.
【００７７】また、第４の実施の形態の重み付け量をカ
メラ信号処理で施されるガンマ補正特性と逆の特性とし
ても良い。そうすることによって、ガンマ補正による低
輝度部の強調と、高輝度部の抑圧をキャンセルすること
ができる。Further, the weighting amount of the fourth embodiment may be a characteristic opposite to the gamma correction characteristic performed in the camera signal processing. By doing so, it is possible to cancel the emphasis of the low-luminance part and the suppression of the high-luminance part by gamma correction.
【００７８】[0078]
【発明の効果】請求項１記載の階調補正装置によれば、
例えばビデオカメラのように、ガンマ補正や、ニー補正
を施すような機器において、ガンマ補正により信号レベ
ルのうち低輝度部の階調特性が強調される場合でも、例
えば低輝度部の分割レベル数を細かくとって低輝度部を
重視した階調補正をする等、最適な階調補正特性を得る
ことができる。According to the gradation correcting apparatus of the first aspect,
For example, in a device such as a video camera that performs gamma correction or knee correction, even if the gradation characteristics of the low luminance portion of the signal level are emphasized by the gamma correction, for example, the number of division levels of the low luminance portion is reduced. Optimum gradation correction characteristics can be obtained, for example, by performing fine gradation correction with emphasis on a low luminance portion.
【００７９】請求項２記載の階調補正装置によれば、請
求項１と同様な効果がある。According to the gradation correcting apparatus of the second aspect, the same effect as that of the first aspect can be obtained.
【００８０】請求項３記載の階調補正装置によれば、補
助的階調補正手段を簡単な構成とすることができるた
め、小さな回路規模で請求項１と同様の階調補正特性を
得ることができる。According to the third aspect of the present invention, since the auxiliary tone correcting means can have a simple configuration, it is possible to obtain the same tone correction characteristics as in the first aspect with a small circuit scale. Can be.
【００８１】請求項４記載の階調補正装置によれば、信
号レベル検出手段の入力信号にオフセット値を加算する
ことによって折れ点を調整することにより、より自然な
階調特性を得ることができる。According to the tone correcting apparatus of the present invention, a more natural tone characteristic can be obtained by adjusting a break point by adding an offset value to an input signal of the signal level detecting means. .
【００８２】請求項５記載の階調補正装置によれば、請
求項１、請求項２、請求項３または請求項４と同様な効
果のほか、重み付け手段で特定の信号レベルの階調特性
の傾きがヒストグラムの分布に対して、より急峻になる
ように階調特性を設定することによって、例えばビデオ
カメラのようにガンマ補正やニー補正を施すような機器
において、ガンマ補正により信号レベルのうち低輝度部
の階調特性が強調される場合でも最適な階調補正特性を
得ることができる。According to the gradation correcting apparatus of the fifth aspect, in addition to the same effects as those of the first, second, third, and fourth aspects, the weighting means can be used to obtain a gradation characteristic of a specific signal level. By setting the gradation characteristics so that the slope becomes steeper with respect to the distribution of the histogram, in a device such as a video camera that performs gamma correction or knee correction, the signal level becomes lower due to gamma correction. Even when the gradation characteristics of the luminance section are emphasized, the optimum gradation correction characteristics can be obtained.
【図１】この発明の第１の実施の形態の階調補正装置の
構成を表す構成図である。FIG. 1 is a configuration diagram illustrating a configuration of a gradation correction device according to a first embodiment of the present invention.
【図２】第１の実施の形態の階調補正装置の特性図を示
し、（ａ）はヒストグラム分布、（ｂ）は階調補正特
性、（ｃ）はガンマ補正特性、（ｄ）は総合階調特性で
ある。FIGS. 2A and 2B are characteristic diagrams of the gradation correction device according to the first embodiment, wherein FIG. 2A shows a histogram distribution, FIG. 2B shows a gradation correction characteristic, FIG. 2C shows a gamma correction characteristic, and FIG. This is a gradation characteristic.
【図３】第２の実施の形態の階調補正装置の構成を表す
構成図である。FIG. 3 is a configuration diagram illustrating a configuration of a gradation correction device according to a second embodiment.
【図４】第２の実施の形態の階調補正装置の特性図を示
し、（ａ）は補助階調補正特性、（ｂ）はヒストグラム
分布、（ｃ）は階調補正特性、（ｄ）は総合階調特性で
ある。4A and 4B are characteristic diagrams of a tone correction device according to a second embodiment, wherein FIG. 4A shows an auxiliary tone correction characteristic, FIG. 4B shows a histogram distribution, FIG. 4C shows a tone correction characteristic, and FIG. Is the total gradation characteristic.
【図５】第３の実施の形態の階調補正装置の構成を表す
構成図である。FIG. 5 is a configuration diagram illustrating a configuration of a gradation correction device according to a third embodiment.
【図６】第３の実施の形態の階調補正装置の特性図を示
し、（ａ）は出力信号Ｓｉｎ２の階調特性、（ｂ）はヒ
ストグラム分布、（ｃ）は階調補正特性、（ｄ）はＳｏ
ｕｔの階調特性、（ｅ）は総合階調特性である。FIGS. 6A and 6B are characteristic diagrams of the tone correction device according to the third embodiment, in which FIG. 6A shows the tone characteristics of the output signal Sin2, FIG. 6B shows the histogram distribution, FIG. d) is So
ut, and (e) are the total gradation characteristics.
【図７】第４の実施の形態の階調補正装置の構成を表す
構成図である。FIG. 7 is a configuration diagram illustrating a configuration of a tone correction device according to a fourth embodiment.
【図８】第４の実施の形態の階調補正装置の特性図を示
し、（ａ）は階調補正特性、（ｂ）は総合階調特性であ
る。FIGS. 8A and 8B are characteristic diagrams of a tone correction device according to a fourth embodiment, wherein FIG. 8A shows tone correction characteristics and FIG. 8B shows total tone characteristics.
【図９】従来の階調補正装置の構成を示す構成図であ
る。FIG. 9 is a configuration diagram showing a configuration of a conventional tone correction device.
【図１０】従来の階調補正装置の特性図を示し、（ａ）
はヒストグラム分布、（ｂ）は階調補正特性、（ｃ）は
ガンマ補正特性、（ｄ）は総合階調特性である。FIG. 10 shows a characteristic diagram of a conventional tone correction device, and FIG.
Is a histogram distribution, (b) is a gradation correction characteristic, (c) is a gamma correction characteristic, and (d) is a total gradation characteristic.
１ 入力端子 ２ 分割レベル調整手段 ３ 信号レベル検出手段 ４ ヒストグラム検出手段 ５ 階調特性設定手段 ６ 階調補正手段 ７ 分割レベル設定手段としてのレジスタ ８ 比較器 ９ 出力端子 １０ 信号レベル判定回路 １１ マルチプレクサ １２ レジスタ １３ セレクタ １４ 加算器 １５ 補助的階調補正手段 １６ 増幅器 １７ 最小値回路 １８ 減算器 １９ 重み付け手段 ２０ 階調特性算出手段 REFERENCE SIGNS LIST 1 input terminal 2 division level adjustment means 3 signal level detection means 4 histogram detection means 5 gradation characteristic setting means 6 gradation correction means 7 register as division level setting means 8 comparator 9 output terminal 10 signal level judgment circuit 11 multiplexer 12 Register 13 Selector 14 Adder 15 Auxiliary tone correction means 16 Amplifier 17 Minimum value circuit 18 Subtractor 19 Weighting means 20 Tone characteristic calculation means
───────────────────────────────────────────────────── フロントページの続き (72)発明者 米山 匡幸 大阪府門真市大字門真1006番地 松下電器 産業株式会社内 Ｆターム(参考） 5C021 PA02 PA17 PA53 PA66 RA00 RB03 RC06 XA01 XA31 ──────────────────────────────────────────────────続 き Continued on the front page (72) Masayuki Yoneyama, Inventor 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5C021 PA02 PA17 PA53 PA66 RA00 RB03 RC06 XA01 XA31
Claims (5)
レベルに分割し入力信号がどの分割レベルに入っている
かを検出する信号レベル検出手段と、 前記分割レベルごとの前記入力信号の分布であるヒスト
グラムを検出するヒストグラム検出手段と、 前記ヒストグラムに応じて分布の多いレベルの傾きが急
になるように階調特性を設定する階調特性設定手段と、 前記階調特性設定手段で設定された階調特性に応じて、
前記入力信号に非線形な階調補正を施す階調補正手段
と、 前記信号レベル検出手段で用いられる前記分割レベルの
間隔が前記入力信号に対し非均一になるように、前記分
割レベルの間隔を調整する分割レベル調整手段とを備え
た階調補正装置。1. A signal level detecting means for dividing a distribution range of an input signal level into a plurality of division levels and detecting which division level the input signal is in, and a distribution of the input signal for each division level. Histogram detection means for detecting a histogram; gradation characteristic setting means for setting a gradation characteristic so that the gradient of a level having a large distribution according to the histogram is steep; and a floor set by the gradation characteristic setting means. Depending on the tonal characteristics,
A gradation correction unit for performing non-linear gradation correction on the input signal; and adjusting the interval between the division levels so that the interval between the division levels used in the signal level detection unit is non-uniform with respect to the input signal. And a division level adjusting unit.
が入力信号に対し非均一になるように設定する複数の分
割レベル設定手段で構成され、 信号レベル検出手段は入力信号を前記分割レベル調整手
段で設定された分割レベルと比較する複数の比較器を有
する請求項１記載の階調補正装置。2. The division level adjusting means comprises a plurality of division level setting means for setting an interval between division levels so as to be non-uniform with respect to an input signal, and the signal level detecting means converts an input signal into said division level adjusting means. 2. The gradation correction device according to claim 1, further comprising a plurality of comparators for comparing the division level set in the step (c).
つ補助的階調補正手段と、 前記補助的階調補正手段の出力信号を入力信号として、
この入力信号のレベルの分布範囲を複数の分割レベルに
分割し前記入力信号がどの分割レベルに入っているかを
検出する信号レベル検出手段と、 前記分割レベルごとの前記入力信号の分布であるヒスト
グラムを検出するヒストグラム検出手段と、 前記ヒストグラムに応じて分布の多いレベルの傾きが急
になるように階調特性を設定する階調特性設定手段と、 前記階調特性設定手段で設定された階調特性に応じて、
前記入力信号に非線形な階調補正を施す階調補正手段と
を備えた階調補正装置。3. An auxiliary gradation correction unit having a non-linear output characteristic with respect to an input signal, and an output signal of the auxiliary gradation correction unit as an input signal.
Signal level detection means for dividing the distribution range of the level of the input signal into a plurality of division levels and detecting which division level the input signal falls into; and a histogram which is a distribution of the input signal for each division level. Histogram detection means for detecting, gradation characteristic setting means for setting gradation characteristics such that the gradient of a level having a large distribution according to the histogram is steep, and gradation characteristics set by the gradation characteristic setting means In response to the,
A gradation correction unit that performs non-linear gradation correction on the input signal.
のレベル補正手段と、 この第１のレベル補正手段の出力信号を入力信号とし
て、この入力信号のレベルの分布範囲を複数の分割レベ
ルに分割し前記入力信号がどの分割レベルに入っている
かを検出する信号レベル検出手段と、 前記分割レベルごとの前記入力信号の分布であるヒスト
グラムを検出するヒストグラム検出手段と、 前記ヒストグラムに応じて分布の多いレベルの傾きが急
になるように階調特性を設定する階調特性設定手段と、 前記階調特性設定手段で設定された階調特性に応じて、
前記入力信号に非線形な階調補正を施す階調補正手段
と、 この階調補正手段における階調補正処理の後の信号に対
しレベル補正を施す第２のレベル補正手段とを備えた階
調補正装置。4. A first method for performing level correction on an input signal.
A level correction means, and using the output signal of the first level correction means as an input signal, dividing the distribution range of the level of the input signal into a plurality of division levels, and detecting which division level the input signal falls into Signal level detecting means, a histogram detecting means for detecting a histogram which is a distribution of the input signal for each of the division levels, and setting a gradation characteristic so that a gradient having a large distribution is steep according to the histogram. Tone characteristic setting means to perform, according to the tone characteristic set by the tone characteristic setting means,
A tone correction device comprising: tone correction means for performing non-linear tone correction on the input signal; and second level correction means for performing level correction on a signal after the tone correction processing by the tone correction means. apparatus.
階調特性の傾きがヒストグラムの分布に対して、より急
峻になるように階調特性を設定する重み付け手段を有す
る請求項１、請求項２、請求項３または請求項４記載の
階調補正装置。5. A gradation characteristic setting means comprising weighting means for setting a gradation characteristic so that a gradient of a gradation characteristic at a specific division level becomes steeper with respect to a histogram distribution. The tone correction device according to claim 2, 3, or 4.
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| JP13089399A JP4376352B2 (en) | 1999-05-12 | 1999-05-12 | Tone correction device |
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|---|---|---|---|
| JP13089399A JP4376352B2 (en) | 1999-05-12 | 1999-05-12 | Tone correction device |
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|---|---|
| JP2000324363A true JP2000324363A (en) | 2000-11-24 |
| JP4376352B2 JP4376352B2 (en) | 2009-12-02 |
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|---|---|---|---|
| JP13089399A Expired - Fee Related JP4376352B2 (en) | 1999-05-12 | 1999-05-12 | Tone correction device |
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| JP (1) | JP4376352B2 (en) |
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