JPS5975776A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To correct a flare, aperture effect, etc., which cause deterioration in display picture quality through an electric circuit by using a surface acoustic wave filter and a variable gain amplifier which have independently settable amplitude characteristics and phase characteristics in combination. CONSTITUTION:A video signal inputted to a video signal input terminal 17 is modulated to a carrier frequency that a filter with less phase distortion (e.g. surface acoustic wave filter denoted as SAW filter hereafter) requests, and divided into three frequency ranges by an SAW filter. Then, the signal is reconverted into a video signal of a base band by a demodulator 8 and its amplitude characteristics only are varied by the variable gain amplifier. In this case, the gain of an M range signal is unchanged and a large signal component between an L range and an H range varies with a control signal. Deterioration in picture quality due to a flare increases generally with screen brightness, so the control signal is obtained by detecting the screen brightness optically or by detecting the high voltage output power source of a high voltage power source (e.g. FBT) or a video output voltage.

Description

【発明の詳細な説明】 〔発明の利用分野〕 本発明は、投写形テレビジョン受像機のような特殊受像
機において、特に問題となるフレア、アパーチャー効果
等の光学系による画質劣化を、位相歪の少ないフィルタ
を用いた電気回路にＩり補償する手段に関するものであ
る。Detailed Description of the Invention [Field of Application of the Invention] The present invention solves the image quality deterioration caused by optical systems such as flare and aperture effects, which are particularly problematic in special receivers such as projection television receivers, by eliminating phase distortion. The present invention relates to means for compensating for I in an electric circuit using a filter with a small amount of noise.

〔従来技術〕[Prior art]

フレアの原因となる高輝度部分による蔭極線管（ＣＲＴ
）　　のノ・レーシヲンは、樋渡消二著「視覚とテレビ
ジョン」　（日本放送出版協会）Ｐ７８゜に詳細に書か
れている。ここでは、関係のある部分のみ引用し簡単に
説明する。A cathode ray tube (CRT) with high-brightness parts that cause flare
) is described in detail in Shoji Hiwatari's ``Vision and Television'' (Japan Broadcast Publishing Association), page 78. Here, only relevant parts will be quoted and briefly explained.

第１図はハレーション発生の原因を示す説明図である。FIG. 1 is an explanatory diagram showing the causes of halation.

第１図において、１は励起用電子ビ（）−ム、２は螢光
体、６はＣＲＴフェースプレート、４は光源、５はハレ
ーションが生じた場合の擬光源を示す。第１図において
角度Ｏは、光源４゜から出だ光が全反射する角度を示す
もので、フェースプレート６に用いる材料の屈折率に支
配さ。In FIG. 1, 1 is an excitation electron beam, 2 is a phosphor, 6 is a CRT face plate, 4 is a light source, and 5 is a pseudo light source when halation occurs. In FIG. 1, the angle O indicates the angle at which the light emitted from the light source 4° is totally reflected, and is governed by the refractive index of the material used for the face plate 6.

丸る。それゆえ、ハレーションが生ずる空間周波数は、
アパーチャー効果により低下する周波数よりもさらに低
い領域となる。これを、電気回路で用いる伝達関数の概
念を導入し、０ＴＦ（０ｐｔｉｃａｌ　Ｔｒａｎｓｆｅ
ｒＦｕｎｃｔｉｏｎ　）あるいはＭＴＦ（Ｍｏｄｕｌａ
ｔｉｏｎＴｒａｎｓｆｅｒＦｕｎｃｔｉｏｎ　）として
表現すると、第２、第６図に示す様に書ける０第２図に
おいて、Ａはビームが有限の大きさを持つため１だ生ず
るアパーチャー効果による高域周波数低下要因で、Ｂは
螢光体における散乱あるいは０にじみ“などでスポット
径が劣化する要因、Ｃけハレーションによるレスポンス
低下要因を示す○第３図は第２図の特性を横軸空間周波
数（あるいは解像度）、縦軸ＯＴＦで表わしだものであ
る。Round. Therefore, the spatial frequency at which halation occurs is
This is a region that is even lower than the frequency that decreases due to the aperture effect. By introducing the concept of transfer function used in electric circuits, we introduced the concept of 0TF (0ptical transfer function).
rFunction) or MTF (Modula
tionTransferFunction), it can be written as shown in Figures 2 and 6. In Figure 2, A is the high frequency reduction factor due to the aperture effect, which occurs because the beam has a finite size, and B is the firefly. Figure 3 shows the characteristics of Figure 2 with spatial frequency (or resolution) on the horizontal axis and OTF on the vertical axis. It is an expression.

まだ、第４図は、実際にセットに使われているＣＲＴの
実測値である。投写型テレビ（Ｐ　−ＴＶ）の場合は、
さらにレンズ等の光学系を通るため、第４図の高周波領
域のＯＴＦはさらに低下する。However, FIG. 4 shows actual measured values of a CRT actually used in a set. For projection television (P-TV),
Furthermore, since the light passes through an optical system such as a lens, the OTF in the high frequency region shown in FIG. 4 further decreases.

そのため、直流に近い低域部分と中高域周波数領域との
差はますます拡大され、画面は一面霧のかかったような
コントラストの甘いものとなる○ 一方、アパーチャー効果−による高域劣化°の補正は、
従来’Ｉ’Ｖ受像機などで多用され、第５図に示す回路
が開発され用いられて来た。第５図に示す回路は、２つ
のインダクタンスによりビデオ信号を２次微分するもの
で、画像輪郭部を強調し、アパーチャー効果による高域
周波数の低下を補償するものである。しかしながら、一
般のインダクタンス、容量等による周波数特性Ｃ゛操作
位相特性をも変化せしめ、画面上です／ギング等の副作
用が発生し、補正後において高品質画像を得る事は難し
かった。As a result, the difference between the low frequency region close to direct current and the mid-high frequency region is further expanded, and the screen becomes foggy and has poor contrast.On the other hand, the aperture effect compensates for the high frequency deterioration. teeth,
Conventionally, this circuit has been widely used in 'I'V receivers and the like, and the circuit shown in FIG. 5 has been developed and used. The circuit shown in FIG. 5 uses two inductances to perform second-order differentiation of a video signal, emphasizing image contours and compensating for a drop in high frequencies due to the aperture effect. However, it also changes the frequency characteristic C'operation phase characteristic due to general inductance, capacitance, etc., and side effects such as on-screen image/ging occur, making it difficult to obtain high-quality images after correction.

〔発明の目的〕[Purpose of the invention]

本発明の目的は、位相特性の良好なパントノ。 An object of the present invention is to provide a pantono with good phase characteristics.

スフイルタと可変利得増幅器と組み合せ、表示画質の品
質を劣化させるフレア、アパーチャー効果等を電気回路
で補正可能としたビデオ信号。A video signal that uses an electric circuit to correct flare and aperture effects that degrade display image quality by combining a filter and a variable gain amplifier.

処理回路を提供する事にある。Its purpose is to provide processing circuits.

〔発明の概要〕[Summary of the invention]

振幅特性と位相特性が独立に設定できる５ＡＷ（弾性表
面波）フィルタと可変利得増幅器との組合せで、上記問
題の解決を計った。We attempted to solve the above problem by combining a 5AW (surface acoustic wave) filter whose amplitude characteristics and phase characteristics can be set independently and a variable gain amplifier.

〔発明の実施例〕[Embodiments of the invention]

以下、具体的に図を用いて本発明を説明する。 The present invention will be specifically described below with reference to the drawings.

第６図に本発明の一実施例をブロック図で示す。FIG. 6 shows a block diagram of an embodiment of the present invention.

第６図において、６はビデオ信号をフィルタの要求する
周波数に変換するだめの変調器、７は位相歪の少ない周
波数帯域多分割型フィルり、８は復調器、９は高周波領
域可変利得増幅器、１０は中間周波数領域増幅器（利得
は固定でも良い）、１１は低周波傾城可変利得増幅器、
１２は高周波領域可変利得増幅器制御回路、１０は加算
器、１４は低周波可変利得増幅器制御回路、１５は高周
波側制御回路入力端子、１６は低周波側制御回路入力端
子、１７はビデオ信号入力端子、１８はビデオ信嶋出力
端子を示すＱ 第７図は、第６図の７に示すフィルタのベースバンド領
域における周波数特性を示す。第７図におけるｆＬは低
域カッ小オフ周波数、ｆＨは高域カットオフ周波数を示
し、Ｌ領域は低１＾１波領域、Ｍ領域は中間周波数領域
、Ｈ領域は高風波領域を示す。以下、本発明の動作を第
６図、第７図を用いて説明する。基本的な動作は、ビデ
オ信号入力端子１７に入力した映像信号は、位１相歪の
少ないフィルタ（例えば表面弾性波フィルター以下ＳＡ
Ｗと略す）が要求するキャリア周波数に変調され、ｓＡ
Ｗフィルタで第７図に示す６゜つの周波数領域に分割さ
れる。そのあと、復調器８でベースバンド領域のビデオ
信号にもどさ・れ、可変利得増幅器で振幅特性のみ変化
を受ける。このとき、Ｍ領域信号の利得は変化せず、Ｌ
領域、Ｈ領域の信号成分の大きさが、制御信号に応じて
変化する。このため、第６図に示しだ系の周波数特性は
、第７図に示したように、１０Ｍ領域の利得を基準に上
・下する。第６図９．１０゜１１の増幅器はインピーダ
ンス素子を用いて減衰器としても構成できることは先の
説明から明白である。In FIG. 6, 6 is a modulator for converting the video signal to the frequency required by the filter, 7 is a frequency band multi-division filter with little phase distortion, 8 is a demodulator, 9 is a high frequency domain variable gain amplifier, 10 is an intermediate frequency domain amplifier (the gain may be fixed); 11 is a low frequency tilting variable gain amplifier;
12 is a high frequency domain variable gain amplifier control circuit, 10 is an adder, 14 is a low frequency variable gain amplifier control circuit, 15 is a high frequency side control circuit input terminal, 16 is a low frequency side control circuit input terminal, 17 is a video signal input terminal , 18 indicates the video output terminal Q. FIG. 7 shows the frequency characteristics in the baseband region of the filter shown at 7 in FIG. 6. In FIG. 7, fL indicates the low cutoff frequency, fH indicates the high cutoff frequency, the L region indicates the low 1^1 wave region, the M region indicates the intermediate frequency region, and the H region indicates the high wind wave region. The operation of the present invention will be explained below with reference to FIGS. 6 and 7. The basic operation is that the video signal input to the video signal input terminal 17 is filtered through a filter with little phase distortion (for example, a surface acoustic wave filter or lower SA).
W) is modulated to the required carrier frequency, and sA
The signal is divided by the W filter into 6° frequency regions as shown in FIG. Thereafter, it is converted back to a baseband video signal by the demodulator 8, and only the amplitude characteristics are changed by the variable gain amplifier. At this time, the gain of the M region signal does not change and the L
The magnitude of the signal component in the region and the H region changes depending on the control signal. Therefore, the frequency characteristics of the system shown in FIG. 6 increase or decrease with respect to the gain in the 10M region, as shown in FIG. It is clear from the above description that the amplifier of FIG. 69.10.11 can also be constructed as an attenuator using an impedance element.

次に、可変利得増幅器９１１の利得を制御す仝。Next, the gain of variable gain amplifier 911 is controlled.

制御信号と制御回路について述べる。ここで、説明を簡
単にするだめ高周波領域可変利得増幅器９をＨＦ−Ａｍ
Ｐ、と略し、低周波領域可変利得増幅器１１をＬＦ−Ａ
ｍＰと略す。まず、Ｉ、、Ｆ−ＡｍＰの制御につい大述
べる。フレアによる画質劣化は一般に画面輝度の増加に
伴い増加するため、画面輝度を光学的に検出し制御信号
とするか、高圧電源（例えばＦＢＴ）の高圧出力電流、
あるいは映像出力電圧を検出し、制御電圧としても良い
○その際、平均的な増加に対応した制御電圧でもよいが
、ピーク値に対応する高速応答型の制御電圧発生機能を
第６図の１４にもたせる事もできる。一般には、画面輝
度に対応し、ＬＦ　−Ａｍ　ｐの利得と輝度の増加が逆
方向となればよい。両者の関係が線型かあるいは高次の
関数型を示すか・は、画像を見ながら最適状態に設定す
る事ができる。また、ＬＦ−Ａｍｐの利得変化幅も、先
に述べた様に検出し、自動的に変える事もできる力り観
視者が画面を見ながら好みに応じ手動の作用を付加する
事も容易である。The control signal and control circuit will be described. Here, for the sake of simplicity, the high frequency domain variable gain amplifier 9 will be replaced by HF-Am.
P, and the low frequency region variable gain amplifier 11 is referred to as LF-A.
Abbreviated as mP. First, we will briefly discuss the control of I,,F-AmP. Image quality deterioration due to flare generally increases as the screen brightness increases, so either the screen brightness is detected optically and used as a control signal, or the high-voltage output current of a high-voltage power supply (for example, FBT),
Alternatively, the video output voltage may be detected and used as the control voltage.In that case, a control voltage that corresponds to an average increase may be used, but a high-speed response control voltage generation function that corresponds to the peak value may be used as shown in 14 in Figure 6. You can also make it stand. In general, it is sufficient that the gain of LF-Amp and the increase in brightness are in opposite directions, corresponding to the screen brightness. Whether the relationship between the two is linear or exhibits a high-order functional type can be set to the optimal state while looking at the image. In addition, the range of gain change of the LF-Amp can be detected and automatically changed as mentioned above, making it easy for viewers to add manual effects according to their preference while looking at the screen. be.

次にＨＦ−Ａｍｐの制御信号について述べる。現在のＴ
Ｖ受像機を見ると、高域の周波数特性の調整は手動のも
のが多く、本発明においても手動動作は何ら問題とはな
らないが高域成分の多い画面、少ない画面を回路的に判
断し、画面内容に応じ制御する事も可能である。つ捷り
、・高域映像信号と低域映像信号の比率を求め、ある値
まではＨＦ−Ａｍｐの利得を増加させ、それ以上の比率
では利得を低下させることにより、自動的にＳ／Ｎおよ
び鮮鋭度の高い画像が得られる。Next, the control signal of the HF-Amp will be described. Current T
Looking at V-receivers, adjustment of high-frequency characteristics is often done manually, and manual operation is not a problem in the present invention, but it is necessary to use a circuit to determine which screens have more high-frequency components and which ones have less. It is also possible to control according to the screen content. - Determine the ratio of the high-frequency video signal and the low-frequency video signal, increase the gain of the HF-Amp up to a certain value, and decrease the gain at a higher ratio to automatically calculate the S/N. and images with high sharpness can be obtained.

〔発明の効果〕 最後に本発明の効果を具体的に述べる。〔Effect of the invention〕 Finally, the effects of the present invention will be specifically described.

（１）位相番の少ない（例えば５ＡＷ）フィルタを用い
る事により信号の位相特性が従来よりも著しく改善され
、リンギング、オーバーシーートなどの画質劣化の要因
が著しく改善される。(1) By using a filter with a small phase number (for example, 5AW), the phase characteristics of the signal are significantly improved compared to the conventional ones, and factors that cause image quality deterioration such as ringing and oversheeting are significantly improved.

（２）フレア対策アパーチャー補償など画質を劣化する
要因をＳＡＷフィルタを用いる事により１つのフィルタ
で構成でき、ＳＡＷフィルタを最適に設計することによ
りフィルタ間の遅延時間のずれを最小限におさえる事が
できる。(2) By using a SAW filter, factors that degrade image quality such as anti-flare aperture compensation can be configured with a single filter, and by optimally designing the SAW filter, it is possible to minimize the delay time difference between filters. can.

（６）遅延時間特性を互いに等しくしだ帯域分割型フィ
ルタ（ＳＡＷフィルタでは原理的に位相と振幅を独立し
て設計できるそめ、遅延時間特性を等しくすることは可
能である。）と可変利得増幅器を用いる車により、映像
信号の高域側、低域側をそれぞれ独立に調整できるだけ
でなく、画面の状態に応じた制御信号により、フレア補
償、アパーチャー補償の目動制御が可能となる。(6) Band-split filters with equal delay time characteristics (SAW filters can theoretically design phase and amplitude independently, so it is possible to have equal delay time characteristics) and variable gain amplifiers Not only can the high-frequency side and low-frequency side of the video signal be adjusted independently, but also the eye movement control of flare compensation and aperture compensation can be performed using control signals according to the screen condition.

（４）アパーチャー補償を行なうＨＦ−ＡｍＴ）の利得
を第８図に示す特性（直線特性を曲線とする事も可能）
とする事により、高域成分の多い映像内容の場合は、さ
らに鮮鋭度を良くする一方、ノイズの多い場合には高域
利得を減少させる事によｐ　Ｓ／Ｎのよい画面を得る事
ができる。(4) The gain of HF-AmT that performs aperture compensation is shown in Figure 8 (it is also possible to make the linear characteristic a curved line)
By doing this, in the case of video content with many high-frequency components, the sharpness is further improved, while in the case of a lot of noise, by reducing the high-frequency gain, it is possible to obtain a screen with a good pS/N. can.

以上が本発明による主ガ効果である。The above are the main effects of the present invention.

本発明の他の実施例として、第６図に示すブロック図で
、復調器８を出力端子１８の後にもってきて、加算回路
１６までをキャリアが重畳しでいる状態とする事も可能
であることは言うまで。As another embodiment of the present invention, in the block diagram shown in FIG. 6, it is also possible to place the demodulator 8 after the output terminal 18 so that carriers are superimposed up to the adder circuit 16. Suffice it to say.

もない。Nor.

本発明は、フレアによる画質劣化が特に問題となってい
る投写型ＴＶに適用可能であシ、補償量を電気回路で制
御できるだめ、補償の最適化が容易である。回路も集積
化する事にょシ、特性のバラツキを少なくする事ができ
るだけでなく、ＳＡＷフィルタと組み合せてコンパクト
化が可能となる。The present invention can be applied to projection type TVs where image quality deterioration due to flare is a particular problem, and since the amount of compensation can be controlled by an electric circuit, it is easy to optimize the compensation. By integrating the circuit, it is possible not only to reduce variations in characteristics, but also to make it more compact by combining it with a SAW filter.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図はフレア発生の原理説明図、第２図は、光学系の
伝送系を示すブロック図、第６図は第２図の特性図、第
４図は、一般セットのＯＴＦ特性図、第５図は一般ＴＶ
セットで使われているアパーチャー補償回路゛図、第６
図は本発明の一実施例を示すブロック図、第７図は本発
明で用い・るフィルタの特性図、第８図は本発明で用い
るアパーチャー補償用増幅器の利得特性を示すグラフ、
である。 ７・・・ＳＡＷフィルタ ９１１・・・可変利御増幅器 代理人弁理士　薄　１）利　、、４．％１に−」と１し
Ａよ 第　１　日 第１図 卿　４　図 ”’　　　　　　　　２００　　　３００　　４ｏＯ！
ｉｏｏ　　ｂｏｏ　’！ｏｏＢｏ。 角子ｉ（度（１７本） 第　与プFigure 1 is a diagram explaining the principle of flare generation, Figure 2 is a block diagram showing the transmission system of the optical system, Figure 6 is the characteristic diagram of Figure 2, Figure 4 is the OTF characteristic diagram of the general set, Figure 5 is a general TV
Aperture compensation circuit used in the set, Figure 6
FIG. 7 is a block diagram showing an embodiment of the present invention, FIG. 7 is a characteristic diagram of a filter used in the present invention, and FIG. 8 is a graph showing gain characteristics of an aperture compensation amplifier used in the present invention.
It is. 7...SAW Filter 911...Variable Interest Amplifier Patent Attorney Susuki 1) Ri 4. %1-'' and 1, A, 1st day, 1st figure, 4 figure''' 200 300 4oO!
ioo boo'! ooBo. Kakuji i (degrees (17))

Claims (1)

【特許請求の範囲】 １）入力ビデオ信号の帯域を少なくも高周波側帯域と低
周波側帯域に分割して出力するフィー・ルタと、該フィ
ルタから出力される高周波側帯域ビデオ信号と低周波側
帯域ビデオ信号をそれぞれ増幅して出力する第１および
第２の可変利得増幅器と、前記第１および第２の増幅器
の各利得をそれぞれ可変制御する制御信、１号を発生す
る第１および第２の制御信号発生手段と、前記第１およ
び第２の可変利得増幅器からの各出力を加算して出力す
る加算回路とを有して成ることを特徴とするビデオ信号
処理回路。 ２、特許請求の範囲第１項に記載のビデオ信号処理回路
において、低周波側信号を扱う第１の可変利得増幅器の
制御信号を、ビデオ信号を表示するブラウン管の輝度に
対応させたごとを特徴とするビデオ信号処理回路。 ３）特許請求の範囲第１項に記載のビデオ信号処理回路
において、高周波側信号を扱う第２゛の可変利得増幅器
の制御信号を、ビデオ信号の高域成分と低域成分の比を
取り、その比率がある値までは、前記高周波側可変利得
増幅器の増幅率が増大する方向とし、前記比率がおる値
以上の時は前記高周波側可変利得増幅器の利得をおさえ
る方向とした事を特徴とするビデオ信号処理回路。 ４）特許請求の範囲第１項乃至第３項のうちの任意の一
つに記載のビデオ信号処理回路において、フィルタ素子
として、その分割帯域の遅延時間特性をだがいにほぼ等
しくした弾性表面波フィルタを用いたことを特徴とする
ピ。 デオ信号処理回路。[Claims] 1) A filter that divides the band of an input video signal into at least a high frequency side band and a low frequency side band and outputs the divided band, and a high frequency side band video signal and a low frequency side output from the filter. first and second variable gain amplifiers that amplify and output band video signals, respectively; first and second variable gain amplifiers that generate control signals No. 1 that variably control the gains of the first and second amplifiers, respectively; 1. A video signal processing circuit comprising: a control signal generating means; and an adding circuit that adds and outputs the respective outputs from the first and second variable gain amplifiers. 2. The video signal processing circuit according to claim 1, characterized in that the control signal of the first variable gain amplifier that handles the low frequency side signal corresponds to the brightness of the cathode ray tube that displays the video signal. video signal processing circuit. 3) In the video signal processing circuit according to claim 1, the control signal of the second variable gain amplifier that handles the high frequency side signal is determined by taking the ratio of the high frequency component and the low frequency component of the video signal, The amplification factor of the high frequency side variable gain amplifier increases until the ratio reaches a certain value, and when the ratio exceeds a certain value, the gain of the high frequency side variable gain amplifier is suppressed. Video signal processing circuit. 4) In the video signal processing circuit according to any one of claims 1 to 3, the filter element is a surface acoustic wave whose divided bands have substantially equal delay time characteristics. Pi is characterized by using a filter. video signal processing circuit.