200928300 九、發明說明： 【發明所屬之技術領域】 本發明是有關於一種外差干涉量測裝置，特別是有關 於一種量測光熱係數之裝置。 【先前技術】 ❹200928300 IX. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD The present invention relates to a heterodyne interference measuring device, and more particularly to a device for measuring photothermal coefficient. [Prior Art] ❹
光熱係數（Thermo-optic coefficients)係為光學材料之 折射係數(η)對溫度變化率，其值對於倍頻系統十分重要。 微小化是世界發展趨勢，元件大小往夸来尺度進 步’且光電系統積體化是必然方向，因此元件微小化後， 光熱係數成為光電系統重要考量因素。傳統方法為量測 光纖材料預形體，預形體做成菱形，量測其最小偏向角 以求出光熱係數。其量測為光纖製造材料為主，而非光 纖本身，無法直接量測光纖之光熱係數。且此法精確产 只到小數點後四位，精確度易受環境因子影響， ς 子於量測光熱係數時，須要極高標準之要求，對於 者來說造成實驗室或公司成本及人力之浪費。 / 另一習知，光熱係數之量測裝置所使用之 於 分複雜，量測者於量測光熱係數時須 1 路’十分不便。 王後雜之電 有鑑於習知技藝之各項問題，為了能夠 之，本發明人基於多年研究開發與諸多實務 ^決 -種外差干涉量縣置，以作為改善上述缺實= 5 200928300 式與依據。 【發明内容】 . 有鑑於此，本發明之目的就是在提供一種外差干涉 量測裝置，以解決量測光熱係數所面臨之困難度的問題。 根據本發明之目的，提出一種外差干涉量測裝置，其 係用以量測一待測物之光熱係數，此裝置包含一共振腔、 一雷射產生單元、一射頻產生單元、一電流輸入單元、一 ❹光檢測單元及一混波單元。共振腔應用一溫度控制單元以 改變共振腔之溫度，射頻產生單元係用以輸出一第一射頻 訊號及一第二射頻訊號，第一射頻訊號係用以驅動該雷射 產生單元，電流輸入單元係用以輸出一直流電流以驅動雷 射產生單元，光檢測單元係接收反射光並轉換反射光為一 射頻電壓訊號，混波單元用以混合射頻電壓訊號及第二射 頻訊號以產生一直流相位訊號。 茲為使貴審查委員對本發明之技術特徵及所達到 ^ 之功效有更進一步之瞭解與認識，謹佐以較佳之實施例 及配合詳細之說明如後。 【實施方式】 以下將參照相關圖示，說明依本發明較佳實施例之 外差干涉量測裝置，為使便於理解，下述實施例中之相同 元件係以相同之符號標示來說明。 請參閱第1圖，其係為本發明之外差干涉量測裝置 6 200928300 之實施例方塊圖。圖中，外差干涉量測裝置係用以量測 一待測物之光熱係數，此裝置包含一共振腔11、一雷射 ' 產生單元12、一射頻產生單元13、一電流輸入單元14、 - 一光檢測單元15及一混波單元16。共振腔11應用一溫 度控制單元111以改變共振腔U之溫度，雷射產生單元 12係射出一雷射光進入共振腔形成多光束干涉以產生一 反射光’此雷射光之功率包絡（enVel〇pe)P⑴可定義為： Ρ«~Ρ〇(1+ίη COScc|,f) ❹ p〇為僅有直流電流驅動時之平均光功率，m等於 (Ppeak-Ρθ )/P〇為光功率調變係數。雷射產生單元係利 用射頻產生單元13產生之雷射調制訊號以調制雷射光， 雷射產生單元12係為一半導體雷射產生器，此雷射調制 訊號係為一射頻訊號產生器之輸出。 射頻產生單元13係用以輸出一第一射頻訊號及一第 二射頻訊號，第一射頻訊號係用以驅動雷射產生單元 12，電流輸入單元14係用以輸出一直流電流與射頻訊號 同時驅動雷射產生單元12，當第一射頻訊號極小時，第 一射頻訊號係使雷射光具有一載波、一微小上旁波帶訊 號及一微小下旁波帶訊號，此載波、微小上旁波帶訊號 及微小下旁波帶訊號係經由共振腔形成多光束干涉產生 反射光。 此反射光之電場Er為： Ετ = l_r、-橡 =私 t)exp(-δ—i φ) 7 200928300 E〇為入射光電場強疳夕丨久aThe thermo-optic coefficients are the refractive index (η) versus temperature change rate of an optical material, and its value is important for a frequency doubling system. Miniaturization is the development trend of the world, and the size of components is going to be scaled forward. And the integration of photovoltaic systems is an inevitable direction. Therefore, after miniaturization of components, the photothermal coefficient becomes an important consideration for photovoltaic systems. The conventional method is to measure the preform of the optical fiber material, and the preform is made into a diamond shape, and the minimum deflection angle is measured to obtain the photothermal coefficient. The measurement is based on the fiber manufacturing material, not the fiber itself, and the photothermal coefficient of the fiber cannot be directly measured. Moreover, the accuracy of this method is only four decimal places. The accuracy is easily affected by environmental factors. When measuring the photothermal coefficient, the scorpion requires extremely high standards, which causes labor or labor costs for the laboratory or the company. waste. / Another conventional knowledge is that the photothermal coefficient measurement device is used in a complicated manner, and the measurementer must measure one photothermal coefficient by one step, which is very inconvenient. In order to be able to do so, the inventor has based on years of research and development and many practical measures to determine the above-mentioned lack of realism = 5 200928300 And basis. SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a heterodyne interference measuring device for solving the problem of measuring the difficulty of photothermal coefficient. According to the object of the present invention, a heterodyne interference measuring device is proposed for measuring the photothermal coefficient of a test object, the device comprising a resonant cavity, a laser generating unit, a radio frequency generating unit, and a current input. a unit, a light detecting unit and a mixing unit. The resonant cavity is applied with a temperature control unit for changing the temperature of the resonant cavity. The RF generating unit is configured to output a first RF signal and a second RF signal, and the first RF signal is used to drive the laser generating unit and the current input unit. The system is configured to output a DC current to drive the laser generating unit, the light detecting unit receives the reflected light and converts the reflected light into a RF voltage signal, and the mixing unit mixes the RF voltage signal and the second RF signal to generate a DC phase. Signal. For a better understanding of the technical features of the present invention and the efficacies of the present invention, the preferred embodiments and the detailed description are as follows. [Embodiment] Hereinafter, a heterodyne interference measuring apparatus according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. For the sake of understanding, the same elements in the following embodiments are denoted by the same reference numerals. Please refer to FIG. 1 , which is a block diagram of an embodiment of the heterodyne interference measuring device 6 200928300 of the present invention. In the figure, the heterodyne interference measuring device is used for measuring the photothermal coefficient of a test object, and the device comprises a resonant cavity 11, a laser 'generating unit 12, a radio frequency generating unit 13, a current input unit 14, - a light detecting unit 15 and a mixing unit 16. The resonant cavity 11 applies a temperature control unit 111 to change the temperature of the resonant cavity U. The laser generating unit 12 emits a laser beam into the resonant cavity to form multi-beam interference to generate a reflected light. The power envelope of the laser light (enVel〇pe) P(1) can be defined as: Ρ«~Ρ〇(1+ίη COScc|,f) ❹ p〇 is the average optical power when only DC current is driven, m is equal to (Ppeak-Ρθ)/P〇 is the optical power modulation coefficient. The laser generating unit utilizes a laser modulated signal generated by the RF generating unit 13 to modulate the laser light. The laser generating unit 12 is a semiconductor laser generator, and the laser modulated signal is an output of an RF signal generator. The RF generating unit 13 is configured to output a first RF signal and a second RF signal. The first RF signal is used to drive the laser generating unit 12, and the current input unit 14 is configured to output a DC current and a RF signal simultaneously. The laser generating unit 12, when the first RF signal is extremely small, the first RF signal causes the laser light to have a carrier, a small upper sideband signal and a small lower sideband signal, the carrier, the tiny upper sideband The signal and the tiny lower sideband signal form a multi-beam interference through the resonant cavity to generate reflected light. The electric field Er of this reflected light is: Ετ = l_r, - rubber = private t) exp(-δ - i φ) 7 200928300 E〇 is the incident light field strong 疳 丨 long a
其中，E〇 係為空氣到 ^行走一周之相 介質電場之, 位移。其中Among them, E〇 is the dielectric field of the air to the one-day walk, displacement. among them
η係為雷射光電場強度 L係為共振腔來回一周之長， 方向之折射係數。 光檢測單70 15更可包含一轉阻放放大器。告 ”檢測單元15，光檢測單元15係接收反：光並= 過一帶通濾波器18濾去雜訊，藉由轉阻放大器以轉換反 了光檢測電壓訊號，此光檢電壓訊號可類比為下 _=’賊毛D⑽咖雄^+幽+么_2偏必网㈣呌明 e_25°係為共振腔11對入射光中心波長之強度衰減， Q 5 :及占1係為上下旁波帶電場強度在共振腔11之衰減， ^係為雷射光共振腔11行走時之等效相位延遲。其中， 光檢測單元15係為一光檢器，把光變成電訊號。 光檢器電壓訊號係加入混波單元16之RF(radi〇 frequency)端，第二射頻訊號係經過一移相位單元ι41進 行相位移以輸出一 此移相位單元141可 為一 RC電路。混波單元16用以混合光檢測射頻電壓訊 號及第二射頻訊號，經一低通濾波器19以產生一直流相 位訊號，混波單元所輸出之直流相位訊號可為下列公式： 200928300 V(f) ^ e ' ¢(¢5 ^ - 2φ0 )sin 9]sm(〇)M〇sin(cdMr + 0j) 共振腔11係由待測物所組成，此共振腔u之溫度 變化係使反射光之相位產生變化，且此反射光之變化係 使直流相位訊號產生一相位移。The η system is the intensity of the laser light electric field. The L system is the refractive index of the length of the cavity and the length of the cavity. The light detecting unit 70 15 may further include a rotating impedance amplifier. The detecting unit 15 detects that the light detecting unit 15 receives the inverse: light and passes the bandpass filter 18 to filter out the noise. The transimpedance amplifier converts the inverted light detecting voltage signal, and the photodetecting voltage signal can be analogized to _=' thief hair D (10) café male ^ + sec + ○ _2 will be net (four) 呌 e e_25 ° is the resonance cavity 11 on the intensity of the incident light center wavelength attenuation, Q 5 : and 1 is the upper and lower sideband The electric field intensity is attenuated in the resonant cavity 11, and is the equivalent phase delay when the laser optical cavity 11 is traveling. The photodetecting unit 15 is a photodetector that turns the light into an electrical signal. The photodetector voltage signal system The RF signal is added to the RF (radi 〇 frequency) end of the mixing unit 16, and the second RF signal is phase-shifted by a phase shifting unit ι 41 to output a phase shifting unit 141 which can be an RC circuit. The mixing unit 16 is used to mix light. The RF voltage signal and the second RF signal are detected, and a DC signal is generated through a low pass filter 19, and the DC phase signal output by the mixing unit can be the following formula: 200928300 V(f) ^ e ' ¢ (¢5 ^ - 2φ0 )sin 9]sm(〇)M〇sin(cdMr + 0j) Resonant cavity 11 It consists of the object to be tested. The temperature change of the cavity u changes the phase of the reflected light, and the change of the reflected light causes a phase shift of the DC phase signal.
當入射光與共振腔11達到共振時，則nL=mA， m=l，2，3…’若改變共振腔u之溫度，則共振腔η之 折射率及長度亦隨之改變，因此當入射光頻率與下一個 共振腔11頻率相同時，則nL=(m+i)又，故可推得出下式： —(ΔΓ)£ + ?ιγ4£(ΔΓ) = Α 公式（一） 其中，η係為共振腔η折射係數，λ為雷射光光波 長，AT係為雷射光在共振腔增減一光波波長所須之溫 度，α為光束傳播軸方向之膨脹係數，[為共振腔來回長 度。 〇 朴由於折射率隨溫度改變而改變，故直流相位訊號亦 隨著共振腔11之溫度及長度而變化，當共振腔頻率與雷 射光頻率相同則直流相位訊號為零，故到下一個直流相 位訊號為零時，表示入射光與下一個共振腔u頻率相 同，依據電壓波形變化所需之溫度ΔΤ，代入上 即可得到欲求知的光熱係數。 a△式（） 以上所述僅為舉例性，而非為限制性者。任何未脫 f本發明之精神與範疇，而對其進行之等效修改或變 更，均應包含於後附之申請專利範圍中。 9 200928300 【圖式簡單說明】 第1圖係為本發明之外差干涉量測裝置之實施例方塊 、圖。 【主要元件符號說明】 11 :共振腔； 111 :溫度控制單元； 12 ： 雷射產生單元 13 ： 射頻產生單元 14 ： 電流輸入單元 141 :移相位單元； 15 :光檢測單元； 16 :混波單元； 17 :示波器； 18 :帶通濾波器；以及 19 :低通滤波器。 〇 10When the incident light and the resonant cavity 11 reach resonance, then nL=mA, m=l, 2, 3...' If the temperature of the resonant cavity u is changed, the refractive index and length of the resonant cavity η also change, so when incident When the optical frequency is the same as the frequency of the next resonant cavity 11, then nL = (m + i) again, so the following formula can be derived: - (ΔΓ) £ + ?ιγ4£(ΔΓ) = Α Equation (1) where η is the refractive index of the resonant cavity η, λ is the wavelength of the laser light, AT is the temperature required for the laser light to increase or decrease the wavelength of the light wave in the resonant cavity, and α is the expansion coefficient of the direction of the beam propagation axis. . Since the refractive index changes with temperature, the DC phase signal also changes with the temperature and length of the resonant cavity 11. When the resonant cavity frequency is the same as the laser light frequency, the DC phase signal is zero, so the next DC phase is reached. When the signal is zero, it means that the incident light has the same frequency as the next resonant cavity u. According to the temperature ΔΤ required for the voltage waveform change, the photothermal coefficient to be obtained can be obtained by substituting it. A Δ (() The above is merely illustrative and not limiting. Any changes or modifications to the spirit and scope of the invention are intended to be included in the scope of the appended claims. 9 200928300 [Simplified description of the drawings] Fig. 1 is a block diagram and a diagram showing an embodiment of the external interference measuring device of the present invention. [Main component symbol description] 11 : Resonant cavity; 111 : Temperature control unit; 12 : Laser generating unit 13 : RF generating unit 14 : Current input unit 141 : Phase shifting unit; 15 : Light detecting unit; 16 : Mixing unit ; 17 : oscilloscope; 18 : band pass filter; and 19 : low pass filter. 〇 10