JPH06112895A - Analog optical picture transmitter - Google Patents
Analog optical picture transmitterInfo
- Publication number
- JPH06112895A JPH06112895A JP4257861A JP25786192A JPH06112895A JP H06112895 A JPH06112895 A JP H06112895A JP 4257861 A JP4257861 A JP 4257861A JP 25786192 A JP25786192 A JP 25786192A JP H06112895 A JPH06112895 A JP H06112895A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- frequency
- response
- frequency modulation
- pulse frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
- Optical Communication System (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明はアナログ光画像送信装置
に関し、特に画像信号以外の過大入力信号が画像信号入
力端子に入力しても、同時に伝送する音声信号に悪影響
を及ぼすことのないアナログ光画像送信装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog optical image transmitting apparatus, and more particularly to an analog optical image transmitting apparatus which does not adversely affect simultaneously transmitted audio signals even if an excessive input signal other than an image signal is inputted to an image signal input terminal. The present invention relates to an image transmission device.
【０００２】[0002]
【従来の技術】従来のアナログ光画像送信装置は、図２
のブロック図に示すように、画像信号入力端子１と音声
信号入力端子２と画像信号入力部端子１に接続されたダ
イオードリミタ８と音声信号入力端子２に接続された周
波数変調器６と結合部３とパルス周波数変調器４とレー
ザ駆動回路５とレーザダイオード９とを有している。2. Description of the Related Art A conventional analog optical image transmitter is shown in FIG.
As shown in the block diagram of FIG. 1, the image signal input terminal 1, the audio signal input terminal 2, the image signal input section, the diode limiter 8 connected to the terminal 1, the frequency modulator 6 connected to the audio signal input terminal 2, and the coupling section. 3, a pulse frequency modulator 4, a laser drive circuit 5, and a laser diode 9.
【０００３】ＮＴＳＣなどの画像信号Ｓ１は画像信号入
力端子１に入力される。また、音声信号Ｓ２は音声信号
入力端子２に入力される。音声信号Ｓ２は周波数変調器
７で周波数変調される。ダイオードリミタ８で振幅制限
された画像信号Ｓ１と周波数変調された音声信号Ｓ３は
結合部３で周波数分割多重される。この周波数分割多重
信号Ｓ４は、パルス周波数変調器４ａでパルス周波数変
調される。このパルス周波数変調された信号Ｓ６ａはレ
ーザ駆動回路５に入力される。レーザ駆動回路５の出力
Ｓ７ａはレーザダイオード６を駆動し、レーザダイオー
ド６は光出力する。An image signal S1 such as NTSC is input to an image signal input terminal 1. The audio signal S2 is input to the audio signal input terminal 2. The audio signal S2 is frequency-modulated by the frequency modulator 7. The image signal S1 whose amplitude is limited by the diode limiter 8 and the frequency-modulated audio signal S3 are frequency-division multiplexed by the coupling unit 3. The frequency division multiplexed signal S4 is pulse frequency modulated by the pulse frequency modulator 4a. The pulse frequency modulated signal S6a is input to the laser drive circuit 5. The output S7a of the laser drive circuit 5 drives the laser diode 6, and the laser diode 6 outputs light.
【０００４】[0004]
【発明が解決しようとする課題】この従来のアナログ光
画像送信装置では、入力される画像信号がマイクロ波伝
送路を用いた画像伝送装置の出力であると、マイクロ波
回線がビルなどでさえぎられた時、上記画像伝送装置か
らは通常の画像信号の電圧１ＶP-P よりはるかに大きい
白色雑音が出力される。この白色雑音が画像信号入力端
子部に入力されると、ダイオードリミタにより白色雑音
はクリップされる。しかし、クリップされた白色雑音の
振幅はダイオードの順方向電圧にほぼ等しくなるため、
この白色雑音の電圧はダイオードの順方向電圧約０．７
Ｖの整数倍になる。従って上記リミタにおいて画像信号
を通すために２個のダイオードを直列にすると、この電
圧は、１．４Ｖになり、画像信号１ＶP-P より０．４Ｖ
も大きくなる。また、画像信号は明るさにより平均値が
変動する。このため、ダイオード２個を直列にしたダイ
オードリミタに画像信号を通すと、画像信号が平均値変
動した時、画像信号波形が劣化することがある。したが
って、ダイオードリミタの直列ダイオードの数を増やす
だけでは白色雑音の振幅が大きくなり、パルス周波数変
調器が過変調状態になる。すると、同時に伝送している
周波数変調された音声信号のキャリアに画像信号のキャ
リアが漏れこんでしまい、復調後の音声信号が劣化して
聞こえなくなるという問題点があった。In this conventional analog optical image transmitting apparatus, if the input image signal is the output of the image transmitting apparatus using the microwave transmission line, the microwave line is blocked in a building or the like. At this time, the image transmission device outputs white noise much larger than the normal image signal voltage of 1 V PP . When this white noise is input to the image signal input terminal portion, the white noise is clipped by the diode limiter. However, the clipped white noise amplitude is approximately equal to the diode forward voltage, so
The voltage of this white noise is about 0.7 forward voltage of the diode.
It becomes an integral multiple of V. Therefore, if two diodes are connected in series to pass the image signal in the limiter, the voltage becomes 1.4V, which is 0.4V from the image signal 1V PP.
Also grows. Further, the average value of the image signal changes depending on the brightness. Therefore, when an image signal is passed through a diode limiter in which two diodes are connected in series, the image signal waveform may deteriorate when the average value of the image signal changes. Therefore, simply increasing the number of series diodes of the diode limiter increases the amplitude of white noise, and the pulse frequency modulator is in the overmodulation state. Then, the carrier of the image signal leaks into the carrier of the frequency-modulated audio signal that is being transmitted at the same time, and the demodulated audio signal is deteriorated and cannot be heard.
【０００５】[0005]
【課題を解決するための手段】本発明のアナログ光画像
送信装置は、画像信号入力端子からの画像信号を振幅制
限するダイオードリミタと、音声信号入力端子からの音
声信号に応答して前記音声信号の周波数変調信号を生じ
る周波数変調器と、前記振幅制限された画像信号と前記
周波数変調信号とを周波数分割多重し周波数分割多重信
号を生じる結合部と、前記振幅制限された画像信号から
同期信号のありなしを検出し前記同期信号が検出できな
いときには同期信号不検出信号を生じる同期信号検出部
と、前記周波数分割多重信号に応答してパルス周波数変
調信号を生じ前記同期信号不検出信号を受けると前記パ
ルス周波数変調信号の中心周波数を変化させるパルス周
波数変調器と、前記パルス周波数変調信号に応答してレ
ーザ駆動出力を生じるレーザ駆動回路と、前記レーザ駆
動出力に応答して光信号を生じるレーザダイオードとを
有している。SUMMARY OF THE INVENTION An analog optical image transmitter of the present invention comprises a diode limiter for limiting the amplitude of an image signal from an image signal input terminal, and the audio signal in response to the audio signal from the audio signal input terminal. A frequency modulator for generating a frequency-modulated signal, a coupling unit for frequency-division-multiplexing the amplitude-limited image signal and the frequency-modulated signal to generate a frequency-division-multiplexed signal, and a synchronization signal from the amplitude-limited image signal. A synchronization signal detection unit that detects a presence or absence and generates a synchronization signal non-detection signal when the synchronization signal cannot be detected, and a pulse signal that generates a pulse frequency modulation signal in response to the frequency division multiplexed signal and receives the synchronization signal non-detection signal. A pulse frequency modulator that changes the center frequency of the pulse frequency modulation signal, and a laser drive output is generated in response to the pulse frequency modulation signal. A laser driving circuit that has a laser diode to produce a light signal in response to the laser driving output.
【０００６】[0006]
【実施例】次に本発明について図面を参照して説明す
る。図１は本発明の一実施例のブロック図である。ＮＴ
ＳＣ信号に代表されるアナログの画像信号Ｓ１が画像信
号入力端子に入力される。この信号Ｓ１は、２個のダイ
オードを直列接続したダイオードリミタ８により、振幅
制限される。一方、音声信号Ｓ２が音声信号入力端子２
に入力される。この音声信号Ｓ２は周波数変調器７によ
り周波数変調される。ダイオードリミタ８からの画像信
号Ｓ１は、２分岐され、一方は結合器３に供給されて周
波数変調器７からの周波数変調信号Ｓ３と周波数分割多
重される。また、ダイオードリミタ８からの画像信号Ｓ
１の他方は同期信号検出部９に供給される。結合器３か
らの周波数分割多重信号Ｓ４は、パルス周波数変調器４
によってパルス周波数変調される。このパルス周波数変
調信号Ｓ６はレーザ駆動回路５を駆動し、レーザ駆動回
路５はこの信号Ｓ６に応答してレーザ駆動出力Ｓ７を生
ずる。レーザダイオード６はこのレーザ駆動出力Ｓ７に
応答して光信号を送出する。The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. NT
An analog image signal S1 represented by an SC signal is input to the image signal input terminal. The amplitude of this signal S1 is limited by the diode limiter 8 in which two diodes are connected in series. On the other hand, the audio signal S2 is the audio signal input terminal 2
Entered in. This audio signal S2 is frequency-modulated by the frequency modulator 7. The image signal S1 from the diode limiter 8 is branched into two, one of which is supplied to the combiner 3 and is frequency division multiplexed with the frequency modulation signal S3 from the frequency modulator 7. In addition, the image signal S from the diode limiter 8
The other one is supplied to the synchronization signal detector 9. The frequency division multiplexed signal S4 from the combiner 3 is supplied to the pulse frequency modulator 4
Is pulse frequency modulated. The pulse frequency modulation signal S6 drives the laser drive circuit 5, and the laser drive circuit 5 produces a laser drive output S7 in response to the signal S6. The laser diode 6 sends out an optical signal in response to the laser drive output S7.
【０００７】ここで、上記画像信号Ｓ１がＮＴＳＣ方式
の画像信号であると、パルス周波数変調信号Ｓ６のキャ
リアは、周波数変調信号Ｓ３のキャリアに洩れ込むこと
はない。しかし、上記画像信号Ｓ１が、マイクロ波回線
を伝送路とする画像伝送装置からの出力であると、上記
マイクロ波回線が断になると、上記ＮＴＳＣ画像信号よ
りはるかに大きい白色雑音が画像信号入力端子１に入力
される。この結果は、上述のとおり、パルス周波数変調
信号Ｓ６に過変調状態を生じ、このパルス周波数変調信
号Ｓ６のキャリアが周波数変調信号Ｓ３のキャリアに洩
れ込むことになり、上記光信号を復調後の音声信号に劣
化を生じることになる。If the image signal S1 is an NTSC type image signal, the carrier of the pulse frequency modulation signal S6 will not leak into the carrier of the frequency modulation signal S3. However, if the image signal S1 is an output from an image transmission device having a microwave line as a transmission line, when the microwave line is disconnected, white noise much larger than that of the NTSC image signal is generated in the image signal input terminal. Input to 1. As a result, as described above, the pulse frequency modulation signal S6 is overmodulated, and the carrier of the pulse frequency modulation signal S6 leaks into the carrier of the frequency modulation signal S3. The signal will be deteriorated.
【０００８】この実施例では、上述の不具合を生じない
ように、上記白色雑音が画像信号Ｓ１の同期信号より大
きいときには、パルス周波数変調信号Ｓ６の中心周波数
を周波数変調信号Ｓ３のキャリアに洩れ込まない周波数
に変化させている。即ち、同期信号検出部９は、供給さ
れた画像信号Ｓ１から同期信号を検出しないときには不
検出信号Ｓ５を生じ、パルス周波数変調器４は、この信
号Ｓ５に応答してパルス周波数変調信号Ｓ６の中心周波
数を周波数変調信号Ｓ３のキャリアに洩れ込まない高い
周波数に変化させる。なお、パルス周波数変調信号Ｓ６
の中心周波数（キャリア）を高く移動しても、音声信号
Ｓ２は周波数変調されているので良質の伝送を行うこと
ができる。In this embodiment, the center frequency of the pulse frequency modulation signal S6 does not leak into the carrier of the frequency modulation signal S3 when the white noise is larger than the synchronizing signal of the image signal S1 so as not to cause the above-mentioned problems. The frequency is changed. That is, the synchronization signal detection unit 9 generates the non-detection signal S5 when the synchronization signal is not detected from the supplied image signal S1, and the pulse frequency modulator 4 responds to the signal S5 and outputs the center of the pulse frequency modulation signal S6. The frequency is changed to a high frequency that does not leak into the carrier of the frequency modulation signal S3. The pulse frequency modulation signal S6
Even if the center frequency (carrier) of (1) is moved high, since the audio signal S2 is frequency-modulated, high-quality transmission can be performed.
【０００９】[0009]
【発明の効果】以上説明したように本発明は、画像信号
よりはるかに大きい白色雑音が重畳入力されているとき
には上記画像信号から同期信号を検出できないことを利
用し、同期信号検出部により上記画像信号から同期信号
のありなしを検出し、同期信号不検出のときには、パル
ス周波数変調信号の中心周波数を音声信号の周波数変調
波である周波数変調信号のキャリアに洩れ込まない高い
周波数に変化させるので大きな白色雑音が入力されても
音声信号の変調信号には悪影響を及ぼさないという効果
を有する。As described above, the present invention takes advantage of the fact that the sync signal cannot be detected from the image signal when the white noise, which is much larger than the image signal, is superposed and input. The presence or absence of a sync signal is detected from the signal, and when the sync signal is not detected, the center frequency of the pulse frequency modulation signal is changed to a high frequency that does not leak into the carrier of the frequency modulation signal that is the frequency modulation wave of the voice signal. Even if white noise is input, it has the effect of not adversely affecting the modulated signal of the audio signal.
【図１】本発明の一実施例のブロック図である。FIG. 1 is a block diagram of an embodiment of the present invention.
【図２】従来のアナログ光画像送信装置のブロック図で
ある。FIG. 2 is a block diagram of a conventional analog optical image transmission device.
１ 画像信号入力端子 ２ 音声信号入力端子 ３ 結合部 ４，４ａ パルス周波数変調器 ５ レーザ駆動回路 ６ レーザダイオード ７ 周波数変調器 ８ ダイオードリミタ ９ 同期信号検出部 1 image signal input terminal 2 audio signal input terminal 3 coupling section 4, 4a pulse frequency modulator 5 laser drive circuit 6 laser diode 7 frequency modulator 8 diode limiter 9 synchronization signal detection section
Claims (2)
制限するダイオードリミタと、音声信号入力端子からの
音声信号に応答して前記音声信号の周波数変調信号を生
じる周波数変調器と、前記振幅制限された画像信号と前
記周波数変調信号とを周波数分割多重し周波数分割多重
信号を生じる結合部と、前記振幅制限された画像信号か
ら同期信号のありなしを検出し前記同期信号が検出でき
ないときには同期信号不検出信号を生じる同期信号検出
部と、前記周波数分割多重信号に応答してパルス周波数
変調信号を生じ前記同期信号不検出信号を受けると前記
パルス周波数変調信号の中心周波数を変化させるパルス
周波数変調器と、前記パルス周波数変調信号に応答して
レーザ駆動出力を生じるレーザ駆動回路と、前記レーザ
駆動出力に応答して光信号を生じるレーザダイオードと
を有することを特徴とするアナログ光画像送信装置。1. A diode limiter that limits the amplitude of an image signal from an image signal input terminal, a frequency modulator that generates a frequency-modulated signal of the audio signal in response to the audio signal from the audio signal input terminal, and the amplitude limiter. A frequency division multiplex of the generated image signal and the frequency modulated signal to generate a frequency division multiplex signal, and a synchronization signal when the presence or absence of a synchronization signal is detected from the amplitude limited image signal and the synchronization signal cannot be detected. A synchronization signal detection unit that produces a non-detection signal, and a pulse frequency modulator that produces a pulse frequency modulation signal in response to the frequency division multiplexed signal and that changes the center frequency of the pulse frequency modulation signal when the synchronization signal non-detection signal is received. A laser drive circuit that produces a laser drive output in response to the pulse frequency modulation signal, and a laser drive circuit in response to the laser drive output. An analog optical image transmitting device, comprising: a laser diode that generates an optical signal.
る前記パルス周波数変調信号の中心周波数が、前記周波
数変調信号のキャリアより高いことを特徴とする請求項
１記載のアナログ光画像送信装置。2. The analog optical image transmitting apparatus according to claim 1, wherein a center frequency of the pulse frequency modulation signal which changes in response to the synchronization signal non-detection signal is higher than a carrier of the frequency modulation signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25786192A JP3259354B2 (en) | 1992-09-28 | 1992-09-28 | Analog optical image transmission device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25786192A JP3259354B2 (en) | 1992-09-28 | 1992-09-28 | Analog optical image transmission device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06112895A true JPH06112895A (en) | 1994-04-22 |
| JP3259354B2 JP3259354B2 (en) | 2002-02-25 |
Family
ID=17312195
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25786192A Expired - Fee Related JP3259354B2 (en) | 1992-09-28 | 1992-09-28 | Analog optical image transmission device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3259354B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008028730A (en) * | 2006-07-21 | 2008-02-07 | Toshiba Corp | Optical transmitter |
-
1992
- 1992-09-28 JP JP25786192A patent/JP3259354B2/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008028730A (en) * | 2006-07-21 | 2008-02-07 | Toshiba Corp | Optical transmitter |
| JP4714103B2 (en) * | 2006-07-21 | 2011-06-29 | 株式会社東芝 | Optical transmitter |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3259354B2 (en) | 2002-02-25 |
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