JPH0439039B2 - - Google Patents
Info
- Publication number
- JPH0439039B2 JPH0439039B2 JP61141289A JP14128986A JPH0439039B2 JP H0439039 B2 JPH0439039 B2 JP H0439039B2 JP 61141289 A JP61141289 A JP 61141289A JP 14128986 A JP14128986 A JP 14128986A JP H0439039 B2 JPH0439039 B2 JP H0439039B2
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- signal
- laser
- light
- beat 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.)
- Expired - Lifetime
Links
- 230000035559 beat frequency Effects 0.000 claims description 26
- 238000001514 detection method Methods 0.000 claims description 9
- 230000001360 synchronised effect Effects 0.000 claims description 5
- 238000000034 method Methods 0.000 description 11
- 238000001228 spectrum Methods 0.000 description 11
- 238000010521 absorption reaction Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 8
- 230000003287 optical effect Effects 0.000 description 8
- 238000005259 measurement Methods 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000029553 photosynthesis Effects 0.000 description 1
- 238000010672 photosynthesis Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000010408 sweeping Methods 0.000 description 1
Landscapes
- Optical Radar Systems And Details Thereof (AREA)
Description
【発明の詳細な説明】
（産業上の利用分野）
この発明は、差分吸収方式のガス探知を目的と
した赤外線FM−CWレーザ・レーダに関し、特
に受信光の周波数のみならず振幅の検出が必要と
なるガス濃度検出のためのレーザ・レーダ用ヘテ
ロダイン受信機の改良に関するものである。[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to an infrared FM-CW laser/radar for the purpose of gas detection using a differential absorption method, and in particular, it is necessary to detect not only the frequency but also the amplitude of received light. This paper relates to the improvement of a laser/radar heterodyne receiver for gas concentration detection.
（概要）
この発明は、差分吸収方式のガス探知を目的と
した赤外線FM−CWレーザ・レーダにおいて、
ヘテロダイン受信機の性能向上を図るため、アナ
ログ掛算器を利用して特定期間の受信信号を周期
的に検出し、かつ反射対象物までの距離を算出す
る期間と、ガス塊の濃度を算出する期間とで、信
号検出経路に挿入したろ波器のモードを走査モー
ドと固定モードに帯域幅を切り換えて、高安定、
高感度の受信動作を達成するようにしたものであ
る。(Summary) This invention provides an infrared FM-CW laser/radar for gas detection using a differential absorption method.
In order to improve the performance of the heterodyne receiver, an analog multiplier is used to periodically detect the received signal during a specific period, and there is a period in which the distance to the reflected object is calculated, and a period in which the concentration of the gas mass is calculated. The mode of the filter inserted in the signal detection path can be switched between scanning mode and fixed mode to achieve high stability and
It is designed to achieve highly sensitive reception operation.
（従来の技術）
大気中の対象物、殊に特定のガス塊を探知する
方式として、赤外線レーザ・レーダを用いた差分
吸収方式の計測式が周知である。このレーザ．レ
ーダには、レーザ光をパルス状に出射して目標ガ
ス塊までの距離を測定するやり方と、周波数変調
したレーザ光を連続的に出射して受信光と送信光
とのビート周波数から反射物体までの距離を測定
するとともにその間のレーザ光の吸収量からガス
塊の濃度を知るFM−CW方式である。(Prior Art) As a method for detecting objects in the atmosphere, particularly specific gas masses, a differential absorption method using an infrared laser/radar is well known. This laser. Radar has two methods: emitting laser light in pulses to measure the distance to the target gas mass, and continuously emitting frequency-modulated laser light to measure the distance from the beat frequency of the received and transmitted light to the reflecting object. This is an FM-CW method that measures the distance between and determines the concentration of the gas mass from the amount of laser light absorbed between them.
第３図は、上記FM−CW（周波数変調した連続
波）形式の赤外線レーザ光を用いた差分吸収式レ
ーザ・レーダの動作原理を説明する図であつて、
レーザ・レーダ本体１より送信パワーPtで異な
る波長λ0，λ1の赤外線レーザ光を所定時間毎に交
互に切り換えて目標ガス塊２を含む空間に出射し
ている。各波長のレーザ光は、それぞれ所定の周
波数幅内を上下に掃引する形で周波数変調されて
おり、かつ本体１内ではこの送信光の一部をロー
カル光として分岐して反射物体３からの反射によ
る受信光（受信パワーPr）と混合することによ
りヘテロダイン方式でビート周波数を得るように
している。 FIG. 3 is a diagram illustrating the operating principle of a differential absorption laser/radar using the above-mentioned FM-CW (frequency modulated continuous wave) type infrared laser beam,
Infrared laser beams of different wavelengths λ 0 and λ 1 are alternately switched at predetermined time intervals and emitted from a laser/radar main body 1 into a space containing a target gas mass 2 with a transmission power Pt. The laser beams of each wavelength are frequency-modulated by sweeping up and down within a predetermined frequency width, and within the main body 1, a part of this transmitted light is branched as local light and reflected from a reflecting object 3. By mixing the received light (received power Pr) with the received light (received power Pr), the beat frequency is obtained in a heterodyne method.
第４図は、送信光と受信光と周波数関係を示す
図であつて、それらの差として取り出されるビー
ト周波数frが、第３図に示した反射物体３までの
距離d1の関数となる。すなわち、ローカル光とし
ての送信光と、反射物体３からの散乱反射による
受信光との周波数偏差は、送信光の反射位置が遠
くなるほど大きくなる関係にあるので、ビート周
波数frの受信信号のパワースペクトラムを解析す
ることにより、反射物体３までの距離d1を識別す
ることができる。 FIG. 4 is a diagram showing the frequency relationship between transmitted light and received light, and the beat frequency fr extracted as the difference between them is a function of the distance d 1 to the reflecting object 3 shown in FIG. 3. In other words, the frequency deviation between the transmitted light as local light and the received light due to scattered reflection from the reflecting object 3 increases as the reflection position of the transmitted light becomes farther away, so the power spectrum of the received signal at the beat frequency fr By analyzing , the distance d 1 to the reflecting object 3 can be identified.
ここで、探知すべきガス（例えばCO2）塊２の
赤外線透過（吸収）特性は、一般に第５図のよう
に特定の波長で透過率が急激に低下する特性を持
つ。従つて、その吸収波長λ1とその近辺の非吸収
波長λ0の２派をそれぞれ周波数変調して時分割で
交互に目標とするガス塊２に向け放射すると、各
波長について得られるビート周波数frの受信信号
のパワースペクトラムは第６図のようになる。つ
まり、波長λ0による計測時には、ビート周波数
fr1に対応した距離d1の位置で反射物体３による
レーザ光の反射が起こり、それが受信パワースペ
クトルのピークPrpとして観測される。ところ
が、波長λ1の吸収波長による計測時には、当該波
長が目標ガスで吸収されて反射分が減少し、距離
d1点での受信パワーのスペクトルのレベルは低下
する。かくして、ビート周波数fr1を解析識別す
ることによつて目標とするガス塊をはさんだ反射
物体までの距離を算出することができ、またレー
ザ・レーダからの送信光の波長をλ0に設定した時
のビート周波数fr1の受信信号パワーと送信光の
波長をλ1に設定した時のビート周波数fr1の受信
信号パワーとを比較演算することにより、当該ガ
ス塊による吸収量の差からガス塊の濃度を測定す
ることができる。 Here, the infrared transmission (absorption) characteristics of the gas (for example, CO 2 ) lump 2 to be detected generally have a characteristic in which the transmittance decreases rapidly at a specific wavelength, as shown in FIG. Therefore, if the absorption wavelength λ 1 and the nearby non-absorption wavelength λ 0 are frequency-modulated and radiated alternately to the target gas mass 2 in a time-sharing manner, the beat frequency fr obtained for each wavelength is The power spectrum of the received signal is as shown in FIG. In other words, when measuring at wavelength λ 0 , the beat frequency is
Reflection of the laser beam by the reflecting object 3 occurs at a distance d 1 corresponding to fr 1 , and this is observed as a peak Prp in the received power spectrum. However, when measuring using the absorption wavelength of wavelength λ 1 , the wavelength is absorbed by the target gas, the reflected amount is reduced, and the distance is reduced.
d The level of the received power spectrum at one point decreases. In this way, by analyzing and identifying the beat frequency fr 1 , we were able to calculate the distance to the reflecting object that sandwiched the target gas mass, and also set the wavelength of the transmitted light from the laser/radar to λ 0 . By comparing the received signal power at the beat frequency fr 1 when the wavelength of the transmitted light is set to λ 1 and the received signal power at the beat frequency fr 1 when the wavelength of the transmitted light is set to λ 1 , the gas mass is determined from the difference in the amount absorbed by the gas mass. The concentration of can be measured.
（発明が解決しようとする問題点）
ところで、上記のようなFM−CW方式のレー
ザ・レーダにおいては、第４図のように完全にリ
ニアなFM変調が実際には困難であり、実調特性
の直線性が悪いので、変調周期の特定期間（比較
的直線性の良い部分）を切り出してその間での受
信周波数のパワースペクトラムを計測するのが一
般的である。このために従来はアナログスイツチ
を用いて有効期間を切り出した後、ろ波・検波を
行う方式や、有効期間内のみＡ／Ｄ変換を実施し
てそのデータを離散フーリエ変換してパワースペ
クトラムを算出するやり方をとつていた。しかし
アナログスイツチを用いる方法は、サイドローブ
が大きくなる不都合があるほか、スイツチのオ
ン・オフに伴うスパイク雑音がろ波器を通過して
Ｓ／Ｎが劣化する問題があつた。またＡ／Ｄ変換
方式は、Ａ／Ｄ変換器の分解能によりダイナミツ
クレンジが制限される問題があつた。(Problems to be Solved by the Invention) By the way, in the FM-CW type laser/radar as described above, it is actually difficult to achieve completely linear FM modulation as shown in Figure 4, and the actual tuning characteristics Since linearity is poor, it is common to cut out a specific period of the modulation cycle (a portion with relatively good linearity) and measure the power spectrum of the received frequency during that period. To do this, conventional methods used an analog switch to cut out the valid period and then filtered and detected it, or performed A/D conversion only during the valid period and performed discrete Fourier transform on the data to calculate the power spectrum. I had learned how to do it. However, the method using an analog switch has the disadvantage that side lobes become large, and there is also the problem that spike noise accompanying the on/off of the switch passes through a filter, degrading the S/N ratio. Further, the A/D conversion method has a problem in that the dynamic range is limited by the resolution of the A/D converter.
一方、上記のような送信光と受信光のビート周
波数frの受信パワースペクトラムを解析するレー
ザ・レーダ用のヘテロダイン受信機としては、広
い帯域にわたつて高い感度が要求されるけれど
も、通常受信機の感度と帯域とは逆比例の関係に
あつて両立し難い問題である。 On the other hand, a heterodyne receiver for laser/radar that analyzes the received power spectrum of the beat frequency fr of transmitted light and received light as described above requires high sensitivity over a wide band, but the receiver's normal Sensitivity and bandwidth are inversely proportional and are difficult to reconcile.
そこでこの発明は、差分吸収方式による大気中
のガス探知を目的としたFM−CWレーザ・レー
ダにおいて高精度で目標ガス塊の情報を含んだ反
射信号光を受信・解析することのできるレーザ・
レーダ用ヘテロダイン受信機の提供を目的とする
ものである。 Therefore, the present invention has developed a laser system that can receive and analyze reflected signal light containing information about a target gas mass with high precision in an FM-CW laser/radar aimed at gas detection in the atmosphere using a differential absorption method.
The purpose of this invention is to provide a heterodyne receiver for radar.
（問題点を解決するための手段）
簡単に述べるとこの発明は、レーザ光に対する
FMの変調周期に同期した所定パターンの窓関数
を発生させ、その窓関数パターンをゲート信号と
して受信光と送信光より得たビート周波数信号の
通過期間を制限する点と、その信号経路に挿入し
た帯域ろ波器の中心周波数を走査モードと固定モ
ードに切り換えて受信光のパワースペクトルの計
測を行うようにした点を特徴とするものである。(Means for Solving the Problems) Briefly stated, this invention provides solutions for laser light.
A window function with a predetermined pattern synchronized with the FM modulation period is generated, and the window function pattern is used as a gate signal to limit the passage period of the beat frequency signal obtained from the received light and the transmitted light, and it is inserted into the signal path. This method is characterized in that the power spectrum of received light is measured by switching the center frequency of the bandpass filter between scanning mode and fixed mode.
（作用）
すなわち、受信光と送信光とのビート周波数信
号の受信経路にアナログ掛算器を挿入して、所定
の窓関数パターンを持つたゲート信号との積をと
ることにより、変調周期の特定期間の信号のみを
雑音の発生なしに周期的に取り出すことができ
る。そして、まず目標ガス塊と探知と、反射物体
までの距離を識別するため特定期間で通過した受
信信号のビート周波数frを帯域ろ波器の通過帯域
を走査することによつて解析し、２波長間での受
信パワーの差が最も大きく現われる点に、当該ろ
波器の中心周波数を固定する。ついでこの固定モ
ードにおいて２波長間の受信パワーの差を積算す
ることにより高精度の計測を実施することができ
る。(Function) In other words, by inserting an analog multiplier into the receiving path of the beat frequency signal of the received light and the transmitted light, and multiplying the received light and the gate signal with a predetermined window function pattern, the specific period of the modulation period can be adjusted. can be extracted periodically without generating noise. First, in order to identify the target gas mass, detection, and distance to the reflecting object, the beat frequency fr of the received signal that has passed in a specific period is analyzed by scanning the passband of the bandpass filter, and the two wavelengths are analyzed. The center frequency of the filter is fixed at the point where the difference in received power between the filters is the largest. Next, in this fixed mode, highly accurate measurement can be performed by integrating the difference in received power between the two wavelengths.
（実施例）
第１図は、この発明によるFM−CWレーザ・
レーダ用へテロダイン受信機の１実施例構成を示
す要部ブロツク図である。(Example) Figure 1 shows the FM-CW laser according to the present invention.
1 is a block diagram of main parts showing the configuration of an embodiment of a radar heterodyne receiver. FIG.
炭酸ガスレーザのような赤外線レーザ光源１０
の光軸上に、変調用発振源１１に連なる光学変調
器１２が設けられ、変調されたレーザ光である送
信光Ltがビームスプリツタ１３を通して目標空
間へ放射されるようになつている。ビームスピリ
ツタ１３で分岐された送信光の一部はローカル光
として光合成ミラー１４で目標空間からの反射に
よる受信光Lrと混合されて、赤外線検知器１５
に入り、両光信号の周波数差に相当するビート周
波数成分をもつた電気信号である受信信号Risに
変換される。この受信信号Risは増幅器１６で増
幅された後、この発明の特徴とするアナログ掛算
器１７の一方の入力Ｘに加えられる。アナログ掛
算器１７の他方の入力Ｙには、上記受信信号Ris
の通過タイミングを規制する所定パターンのゲー
ト信号Gsを発生するための回路１８が接続され
ている。そしてこのゲート信号発生回路１８は、
上記変調用発振源１１と変調周期に同期したタイ
ミングで所定のアドレスを発生するためのタイミ
ング・アドレス発生回路１９と、指定されたアド
レスごとに複数の窓関数のパターンを記憶した
ROM（読みだし専用メモリ）２０、およびPOM
２０からの読みだしデータを逐次アナログ電圧に
変換してROMの記憶内容に応じた所定の窓関数
パターンのアナログゲート信号Gsを発生する
Ｄ／Ａ変換器２１を含んでいる。 Infrared laser light source 10 such as a carbon dioxide laser
An optical modulator 12 connected to a modulating oscillation source 11 is provided on the optical axis of the optical modulator 12, and the transmitted light Lt, which is modulated laser light, is radiated into the target space through a beam splitter 13. A part of the transmitted light branched by the beam spiriter 13 is mixed as local light with the received light Lr reflected from the target space by the light combining mirror 14, and then sent to the infrared detector 15.
The received signal Ris is converted into a received signal Ris, which is an electrical signal with a beat frequency component corresponding to the frequency difference between the two optical signals. This received signal Ris is amplified by an amplifier 16 and then applied to one input X of an analog multiplier 17, which is a feature of the present invention. The other input Y of the analog multiplier 17 receives the received signal Ris.
A circuit 18 is connected to generate a gate signal Gs of a predetermined pattern that regulates the timing of passage of the gate signal Gs. This gate signal generation circuit 18 is
A timing address generation circuit 19 for generating a predetermined address at a timing synchronized with the modulation oscillation source 11 and the modulation cycle, and a plurality of window function patterns stored for each specified address.
ROM (read-only memory) 20, and POM
It includes a D/A converter 21 that sequentially converts read data from 20 into an analog voltage and generates an analog gate signal Gs of a predetermined window function pattern according to the contents stored in the ROM.
ここで第２図は、上記送信光Ltの周波数変調
の模様とアナログゲート信号Gsとの関係を示す
タイミングチヤートで、送信光の光周波数はレー
ザ光の波長λ0又はλ1に対応する周波数f0又はf1を
中心として所定の変調幅内での線ftのように周期
的に変化している。この変調周期の中で最も変調
特性の安定した中心周波数付近の特定期間τを取
り出して信号処理をするため、この発明では前述
のようなゲート信号発生回路１８を設けて第２図
のGsで示すようなゲート信号を作つている。 Here, FIG. 2 is a timing chart showing the relationship between the frequency modulation pattern of the transmitted light Lt and the analog gate signal Gs, and the optical frequency of the transmitted light is the frequency f corresponding to the wavelength λ 0 or λ 1 of the laser light. It changes periodically like a line ft within a predetermined modulation width around 0 or f1 . In order to perform signal processing by extracting a specific period τ around the center frequency where the modulation characteristics are most stable in this modulation period, the present invention provides the gate signal generation circuit 18 as described above, as shown by Gs in FIG. I am creating a gate signal like this.
各部の同期をとるためのクロツク信号CLは前
記タイミング・アドレス発生回路１９で作成され
て前記変調用発振源１１に加えられていて、ゲー
ト信号の発生タイミングはレーザ光に対する変調
周期と同期をとられており、またゲート信号のパ
ターンはROM２０に対するアドレス指定を変更
することにより任意に（例えばサイドローブが最
小となるように）変更できるようになつている。
かくして、掛算器１７の出力にはビート周波数成
分の受信信号Risと所定の窓関数パターンのゲー
ト信号Gsとの積の信号Ris′が特定のタイミングで
出力される形となる。 A clock signal CL for synchronizing each part is generated by the timing address generation circuit 19 and applied to the modulation oscillation source 11, and the timing of generation of the gate signal is synchronized with the modulation cycle of the laser beam. Furthermore, the pattern of the gate signal can be changed arbitrarily (for example, so that the side lobe is minimized) by changing the address designation for the ROM 20.
Thus, the multiplier 17 outputs a signal Ris', which is the product of the received signal Ris of the beat frequency component and the gate signal Gs of a predetermined window function pattern, at a specific timing.
再び第１図を参照すると、掛算器１７の出力側
には中心周波数可変型の帯域ろ波器２２が接続さ
れている。この帯域ろ波器２２にはモード制御回
路２３が接続され、その通過帯域の中心周波数を
信号処理回路２６からの制御信号に基づいて走査
モードと固定モードに切り換えできるようになつ
ている。すなわち、走査モードにおいては受信信
号のビート周波数frを距離分解可能な範囲にわた
つてろ波器２２の通過帯域の中心周波数を走査す
る。そして、その間の受信パワーを周波数対応で
測定すべく、ろ波器の出力を次の検波回路２４と
Ａ／Ｄ変換器２５を通して信号処理回路２６に入
れ、第６図について先に説明したような受信信号
のパワースペクトラムの関係から、反射物体まで
の距離を算出する。なお、ろ波器２２の出力以降
は信号処理回路２６を含めて通常のスペクトルア
ナライザで構成しても良い。なお、前記クロツク
信号CLはモード制御回路２３及びＡ／Ｄ変換器
２５にも加えられている。 Referring again to FIG. 1, a variable center frequency bandpass filter 22 is connected to the output side of the multiplier 17. A mode control circuit 23 is connected to the bandpass filter 22, and the center frequency of its passband can be switched between a scanning mode and a fixed mode based on a control signal from a signal processing circuit 26. That is, in the scanning mode, the center frequency of the passband of the filter 22 is scanned over a range in which the beat frequency fr of the received signal can be resolved by distance. Then, in order to measure the received power during that period according to the frequency, the output of the filter is inputted to the signal processing circuit 26 through the next detection circuit 24 and the A/D converter 25, and the output power is inputted to the signal processing circuit 26 as described above with reference to FIG. The distance to the reflecting object is calculated from the power spectrum relationship of the received signal. Note that the signal processing circuit 26 and the signal processing circuit 26 subsequent to the output of the filter 22 may be configured with a normal spectrum analyzer. Note that the clock signal CL is also applied to the mode control circuit 23 and the A/D converter 25.
走査モードでの数回のデータ取り込みで反射物
体までの距離を算出した後、その距離識別信号を
制御信号としてモード制御回路２３に与えてろ波
器２２の中心周波数を反射物体までの距離に対応
したビート周波数fr1に固定する。このような制
御は電子同調型のろ波器を用い、距離識別信号を
制御電圧に変換して供給することにより容易に実
現できる。ろ波器２２を固定モードに切り換えた
後その出力には、レーザ光の周波数変調周期に同
期した上記ゲート信号Gsとタイミング毎に反射
物体からの反射に基づくビート周波数fr1の信号
のみがとり出される。かくしてレーザ光の波長を
λ0，λ1と交互に切り換えて、それぞれの波長での
目標ガス塊により吸収量を示す受信パワー（受信
信号の振幅）のデータを多数回（100〜1000回）
取り込み、このデータを信号処理回路２６で積算
して目標ガス塊の濃度を求めることができる。 After calculating the distance to the reflecting object by acquiring data several times in the scanning mode, the distance identification signal is given to the mode control circuit 23 as a control signal to make the center frequency of the filter 22 correspond to the distance to the reflecting object. Fix the beat frequency fr to 1 . Such control can be easily realized by using an electronically tuned filter and converting the distance identification signal into a control voltage and supplying it. After switching the filter 22 to the fixed mode, only the gate signal Gs synchronized with the frequency modulation period of the laser beam and a signal with a beat frequency fr 1 based on the reflection from the reflecting object at each timing are extracted as its output. It will be done. In this way, the wavelength of the laser beam is alternately switched to λ 0 and λ 1 , and data on the received power (amplitude of the received signal) indicating the amount absorbed by the target gas mass at each wavelength is collected many times (100 to 1000 times).
The concentration of the target gas mass can be determined by importing the data and integrating the data in the signal processing circuit 26.
（効果）
一般に、この発明の対象とするようなFM−
CWレーザ・レーダを用いて特定ガス塊の濃度を
実施するには、受信パワーを精密に測定すればよ
いのであるが、反射物体との間に介在するガス塊
は不安定であつて受信パワーは原理的にスペクト
ルゆらぎを有している。従つて測定精度を上げる
には多数回のデータ取得と積算が不可決である
が、受信周波数（ビート周波数）を走査すると同
時に、受信信号の積算を実施することは、測定に
長時間を要することとなつて現実的でない。この
点この発明では、数回の走査で反射物体までの距
離（ビート周波数）を識別した後、その周波数に
帯域ろ波器の中心周波数を固定することによつて
濃度測定のためのデータを狭い帯域で取り込むよ
うにしているので、信号の処理を高感度かつ高速
度で実行することができる。またこの発明によれ
ば、ゲート信号のパターンを与える窓関数を
ROMの記憶内容から任意に選択することができ
るので、サイドローブの発生を低くおさえること
ができる他、スパイク雑音の障害もないので、精
度の高い計測が可能となる。(Effect) In general, FM-
In order to measure the concentration of a specific gas mass using a CW laser/radar, it is sufficient to precisely measure the received power, but the gas mass interposed between it and the reflecting object is unstable, and the received power is In principle, it has spectral fluctuation. Therefore, in order to improve measurement accuracy, it is necessary to acquire and integrate data multiple times, but scanning the receiving frequency (beat frequency) and integrating the received signal at the same time requires a long time for measurement. That's not realistic. In this regard, in this invention, after identifying the distance (beat frequency) to the reflecting object through several scans, the center frequency of the bandpass filter is fixed at that frequency, thereby narrowing the data for concentration measurement. Since the signal is captured in the band, signal processing can be performed with high sensitivity and high speed. Further, according to the present invention, the window function that provides the pattern of the gate signal is
Since it is possible to arbitrarily select from the contents stored in the ROM, the generation of side lobes can be kept low, and since there is no interference from spike noise, highly accurate measurement is possible.
第１図はこの発明によるFM−CWレーザ・レ
ーダ用ヘテロダイン受信機の１実施例構成を示す
ブロツク図、第２図はレーザ光の周波数変調の模
様とゲート信号の関係を示すタイムチヤート、第
３図はFM−CWレーザ・レーダの動作原理を説
明するための説明図、第４図は周波数変調された
送信光周波数と受信光周波数の関係を示すタイム
チヤート、第５図はレーザ波長とガスに対するレ
ーザ光の透過率の関係を示す線図、第６図は受信
信号のビート周波数と受信信号のパワースペクト
ラムの関係を示す線図である。
１……レーザ・レーダ本体、２……目標ガス
塊、３……反射物体、１０……赤外線レーザ光
源、１１……変調用発振源、１２……光学変調
器、１３……ビームスプリツタ、１４……光合成
ミラー、１５……赤外線検知器、１６……増幅
器、１７……アナログ掛算器、１８……ゲート信
号発生回路、２２……帯域ろ波器、２３……モー
ド制御回路、２４……検波回路、２５……Ａ／Ｄ
変換器、２６……信号処理回路、Lt……送信光、
Lr……受信光。
Fig. 1 is a block diagram showing the configuration of one embodiment of a heterodyne receiver for FM-CW laser/radar according to the present invention, Fig. 2 is a time chart showing the relationship between the frequency modulation pattern of laser light and the gate signal, and Fig. 3 The figure is an explanatory diagram to explain the operating principle of FM-CW laser/radar, Figure 4 is a time chart showing the relationship between frequency-modulated transmitting optical frequency and receiving optical frequency, and Figure 5 is a diagram showing the relationship between laser wavelength and gas. A diagram showing the relationship between the transmittance of laser light, and FIG. 6 is a diagram showing the relationship between the beat frequency of the received signal and the power spectrum of the received signal. DESCRIPTION OF SYMBOLS 1... Laser/radar main body, 2... Target gas mass, 3... Reflective object, 10... Infrared laser light source, 11... Oscillation source for modulation, 12... Optical modulator, 13... Beam splitter, 14...Photosynthesis mirror, 15...Infrared detector, 16...Amplifier, 17...Analog multiplier, 18...Gate signal generation circuit, 22...Band filter, 23...Mode control circuit, 24... ...Detection circuit, 25...A/D
Converter, 26...Signal processing circuit, Lt...Transmission light,
Lr...Received light.
Claims (1)
続的に出射し、その反射光を受信して送信光と混
合することにより送信光と受信光とのビート周波
数を検出するレーザ・レーダ用ヘテロダイン受信
機において、前記ビート周波数信号の信号経路中
に、当該ビート周波数信号を一方の入力とするア
ナログ掛算器と、この出力を受ける周波数可変型
の帯域ろ波器を挿入し、かつ前記アナログ掛算器
の他方の入力に上記周波数変調の繰り返し周期に
同期した所定のパターンのゲート信号を供給する
回路を接続するとともに、前記帯域ろ波器の中心
周波数を走査モードと固定モードに切り換える制
御回路を付設し、走査モードで検出された反射対
象物までの距離に応じたビート周波数の検出信号
を前記制御回路に与えて前記帯域ろ波器の中心周
波数を当該ビート周波数に固定することにより固
定モードに切り換えることを特徴とするレーザ・
レーダ用ヘテロダイン受信機。1. A heterodyne receiver for laser/radar that continuously emits frequency-modulated laser light as transmitted light, receives the reflected light, and mixes it with the transmitted light to detect the beat frequency of the transmitted light and received light. In the signal path of the beat frequency signal, an analog multiplier that receives the beat frequency signal as one input, and a variable frequency bandpass filter that receives the output thereof are inserted, and the other of the analog multipliers A circuit for supplying a gate signal of a predetermined pattern synchronized with the repetition period of the frequency modulation is connected to the input of the filter, and a control circuit for switching the center frequency of the bandpass filter between a scanning mode and a fixed mode is attached. Switching to the fixed mode is performed by giving a detection signal of a beat frequency corresponding to the distance to the reflecting object detected in the mode to the control circuit and fixing the center frequency of the bandpass filter to the beat frequency. Laser
Heterodyne receiver for radar.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61141289A JPS62298789A (en) | 1986-06-19 | 1986-06-19 | Heterodyne receiver for laser radar |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61141289A JPS62298789A (en) | 1986-06-19 | 1986-06-19 | Heterodyne receiver for laser radar |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62298789A JPS62298789A (en) | 1987-12-25 |
| JPH0439039B2 true JPH0439039B2 (en) | 1992-06-26 |
Family
ID=15288422
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61141289A Granted JPS62298789A (en) | 1986-06-19 | 1986-06-19 | Heterodyne receiver for laser radar |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62298789A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2024516584A (en) * | 2021-04-16 | 2024-04-16 | ｓａｎｔｅｃ Ｈｏｌｄｉｎｇｓ株式会社 | Systems and methods for LIDAR sensing |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11016195B2 (en) * | 2019-04-26 | 2021-05-25 | Mouro Labs, S.L. | Apparatus and method for managing coherent detection from multiple apertures in a LiDAR system |
| CN116964488A (en) * | 2021-02-26 | 2023-10-27 | 三菱电机株式会社 | lidar device |
-
1986
- 1986-06-19 JP JP61141289A patent/JPS62298789A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2024516584A (en) * | 2021-04-16 | 2024-04-16 | ｓａｎｔｅｃ Ｈｏｌｄｉｎｇｓ株式会社 | Systems and methods for LIDAR sensing |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62298789A (en) | 1987-12-25 |
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