1. Short-Wave Infrared Dual Band Laser Countermeasure System
各位評審委員早 學生賴暉凱 指導教授是陳德請博士 今天要報告的題目是
“短波紅外線雙波段雷射反制系統”
Reporter：Huei-Kai Lai
Adviser ：Dr. Der-Chin Chen
2013 / 12 /19

2. Outline Abstract Motivation Literature Reviews
Electro-Optical Countermeasures
In-Band and Out-of-Band technique
Jamming Methods on Laser Rangefinder
Classification of Deception Jamming Methods
Active Positive Deviation Jamming
Passive Positive Deviation Jamming
Pulsed Time of Flight Laser Range Finder
Laser Ranging Equation
Estimation Effective Range
Effects of Atmospheric Attenuation
Estimation of Counter Distance
Estimation of Detecting Distance

3. Outline System Structure Experimental Results and analysis
Analyze Time-of-Flight Signal
The Countermeasure System Structure of Laser Range Finder
Infrared Receiver-Photodiode
Infrared Receiver-Transimpedance Amplifier (TIA)
Infrared Receiver-Auto Gain Control
Recognition circuit -Inverting Schmitt Trigger
Recognition circuit-Pulse Stretching
Recognition circuit -Frequency to Voltage
Analog to Digital Converter + MCU + LCM
Laser Diode Laser Driver
Experimental Results and analysis
Conclusion and Future Work
Reference

4. Abstract
The purpose of this research is to construct the countermeasure system of laser range finder. By realizing the mode of laser range finder and analyzing the system architecture to find out the mechanism of counter measurement. The direct way is receiving and duplicating the signal from laser rangefinder, and return interfering signals with the same frequency back through the original optical axis. It will make laser range finder get misjudgment.
Laser range finder countermeasure system architecture and circuit design have been established. For 905 nm pulsed laser range finder, laser countermeasure system can copy the ranging signal successfully, and makes laser rangefinder ranging error has occurred.
Keywords：Laser range finder, Countermeasure, Laser diode 摘要
本文研究目的主要在建構雷射測距儀反制系統。透過了解及探討雷射測距的測距模式及其系統架構，分析並找出測距反制機制。
本研究採用反制方法為接收並複製對方之測距信號，沿著原光路送回相同頻率的信號，以足夠雷射強度使對方測距儀造成誤判。
目前完成 905nm脈衝式雷射測距反制系統架構及電路設計，針對脈衝式雷射測距儀進行測試，系統已可成功複製測距信號，並使測距儀測距發生錯誤。

5. Motivation
With the Optics, Semiconductor and Electronic technology have greatly advanced, the foundation of laser range finder has an extremely advancement as well. It is widely used in civil engineering and architecture, traffic, aviation and Industrial production…etc.
It also provides people accurate and quick information about distance of data. In addition to those fields, laser range finder also widely used in military. Therefore, in order to ensure the safety of the chariot, laser range finder countermeasure system emerges as a result. 動機
雷射測距儀是現代最先進且精確度高的測距系統，隨著半導體、電子元件和光學技術的發達及各式新型的光電元件和製程技術的進步，提高了雷射測距儀的精確度和便攜性。
雷射測距儀亦多方使用在軍事用途上，常使用的雷射波段為短波紅外線，但隨著資訊安全和軍事需求下，如何在雷射測距的範圍下有效地匿蹤，甚至主動造成干擾成為目前重要的研究課題。

6. Literature Reviews：Electro-Optical Countermeasures
The countermeasure of laser range finder is only a part of Electro-Optical Countermeasures. With the rapid development of laser and infrared technology, Electro-Optical countermeasures technology in the military confrontation is widely used.
文獻回顧
雷射測距的干擾僅是光電對抗(Electro-Optical Countermeasures)領域中的一個分支。隨著雷射及紅外技術迅速發展，光電對抗技術在軍事上得到廣泛的運用，以下簡述何謂光電對抗及其分類。
What is the definition and classification of Electro-Optical countermeasures?

7. Literature Reviews：In-Band and Out-of-Band technique
It is necessary for in-band technique to be successful , it has to be satisfied at least these conditions :
The target sensor to be looking at the countermeasure system.
The target’s optical train must be transparent to the incident laser wavelength, i.e. the laser energy must pass to the detector.
對抗的機制分為二種，帶內(In band)及帶外(Out of band)技術，要成
功運用帶內技術必須至少滿足二個條件：
目標的Sensor必須對著干擾系統
發射之光源波長必須相同，即雷射的能量可被感測器接收。
In-Band
Laser Input
Out-of-Band
Fig.1 In-band and Out-of-Band defeat mechanism.

8. Literature Reviews：Jamming methods on Laser Rangefinder
Table.1 Jamming methods on laser
rangefinder.
Jamming Methods on Laser Range Finder
Passive
Active
雷射測距儀的干擾研究極為重要，一些國家已研製出相應的干擾設備，可分為主動式與被動式
被動式：即是在被測物體上塗抹、加裝或散佈…等特殊材料使反射信號強度衰減至測距儀無法偵測而失去功用
主動式：亦可分為二種－有源型及無源型。
有源型分為(1)正偏差同步轉發式(2)負偏差高重頻脈波式(3)高功率致盲(摧毀)式。
Material
Without Light Source
With Light Source
High-Power
Negative
Deviation
Positive
Deviation

9. Active Positive Deviation Jamming System
Laser detector
Convergent
lens 1
Electric delay
circuit
正偏差同步轉發式
雷射探測器置於會聚透鏡1的焦平面上以便有效地接收雷射能量。雷射探測器的輸出端接電子延遲線路的輸入端，電子延遲線路的輸出端接雷射探測器的觸發器。干擾雷射脈衝由會聚透鏡發射出去。雷射器的光軸應平行於會聚透鏡的光軸，且會聚透鏡1和2的光軸也互相平行，這樣使干擾脈衝能按原方向發射回去。由於這種雷射干擾機發出的干擾脈衝信號總是慢於實際目標的回波脈衝信號，因此只能進行正距離測距欺騙。
Convergent
lens 2
Laser
generator
Fig.2 Active jamming system.
This laser jammer system transmits the pulse signal which is always slower than the reflected pulse signal of actual target , it can only get positive deviation jamming.

10. Delaying Fiber Jamming System
Germany has developed a countermeasure system of laser range finder that uses delaying fiber technology, as shown in Fig.3.
Convergent lens
Fiber coupler
無源型：
如圖3所示。
德國研製成功一種無源光纖雷射測距干擾系統，採用光纖二次延遲技術。當平臺受到敵方雷射測距信號照射後，由光纖經極短的二次延遲後，按原路反射回去，使敵方測距機在設定的距離範圍內探測到的是產生測距正偏差的干擾信號
Fiber coupling element
Delay fiber
Reflector
Fig.3 The delaying fiber jamming system.

11. The Mode of Laser Range Finder
Interference
Triangulation
Time-of-Flight
Pulsed
Phase-shift
MCW
雷射測距的方法可以歸為三類：干涉式、三角式、飛行時間式。其中飛行時間式是根據雷射飛行時間來得到目標物距離，
據所發射 雷射調變狀態的不同，
可分為脈衝雷射測距和
相位式雷射測距和調頻式雷射測距。

12. Pulsed TOF
Transmitter
MCU
&
Processor
Timer
脈衝式雷射測距儀
當計時器開始計時，同時發射器朝向待測物發射一個高功率的雷射脈衝，經過目標物的反射，最後等待接收器接收到由待測物反射回來的雷射脈衝信號，即停止計時，根據光脈衝來回所需的時間即可算出距離。
Receiver d
Fig.5 Pulsed Time-of-Flight laser range finder.
When the speed of light is known, by calculating the number of the clock which travel between the system and target, the distance can be obtained.
…………Eq.1

13. Laser Ranging Equationτα ρ
Laser Pt
Detector Pr Ar Al O N θ R ƞt ƞr
假設接收光學系統的穿透率為 ，則光偵測器光敏元所接收到的雷射功率為
Fig.7 Relationship between ranging system and the target diagram.
…………Eq.4
…………Eq.5

14. Estimating Effective RangeP0
Photo Detector θ φ Kt Kr Pr D
Laser
Fig.8 Relationship between laser countermeasure system and laser range finder.
此距離估算方程式來自測距方程式，僅考慮雷射反制系統與被反制系統之間的關係。
P0為雷射發射功率，Kt及Kr分別為發射接收鏡組穿透率，Tσ為雷射之大氣穿透率，φ為發射端光軸與接收端光軸之夾角，At為目標面積，即可接收之面積，Ar則為光在目標處所照射之面積。
The maximum ranging distance：
Receiving Power of Photo Detector：
…………Eq.6
…………Eq.9
The distance can be calculated by Eq.7：
…………Eq.7

15. Effects of Atmospheric Attenuation
對於905 nm雷射而言，能見度為2 km的情形下，經過4 km的傳輸距離後，大氣的穿透率幾乎為0；而能見度為20 km時，經過20 km的傳輸後，大氣穿透率約還有10%。因此可得，當能見度一定時，大氣穿透率隨傳輸距離的增加而衰減；當傳輸距離一定時，隨著能見度提高，大氣穿透率亦隨著上升。
Fig.9 Relationship between 905 nm laser atmosphere transmittance and visibility
and transmission range.
…………Eq.10

16. Estimation of Counter Distance
For APD Photodiode:
Table.1 The parameters of estimation of counter distance
Visibility =20 km ( Tσ = e R )
Laser countermeasure system transmitter
Laser range finder
receiver λ
905 nm
Prmin
3.16*10-11 W Kt Kr
80 % P0
0.5 mW D
26 mm θ
30° φ 0°
反制距離估算
Table1 反制距離計算時的參數 假設在V=10 km的情況下
雷射反制裝置發射端在無發射鏡組的狀態下 雷射波長為905 nm 輸出功率為0.5mW 取較大發散角約30度
考慮垂直入射的狀況
雷射測距儀接收端部分 假設接收鏡組織穿透率為80% 接收物鏡直徑為 26 mm
其中Pmin 由光檢知器之NEP值決定
By Eq.9 maximum counter range:
…………Eq.11
For Table 1. Parameters:

17. Estimation of Counter Distance
圖10為在不同能見度條件下，不同雷射功率所對應的最大反制作用距離。四條曲線分別對應大氣能見度為2 km、5 km、10 km及20 km。從圖10中可以看出，隨著雷射功率的增加，系統之作用距離增大；隨著能見度的降低，系統作用距離減小，當大氣條件較差時，增加雷射功率對作用距離提高作用不大。
Fig.10 Relationship between operating range and laser power and visibility.

18. Estimation of Detecting Distance
Transmitting power of laser range finder must know before estimate detecting range by Eq.4.
Table 2 Parameters of laser range finder
Laser range finder (Rmax=1000m)
Transmitter
Receiver λ
905 nm
Prmin
3.162*10-11 W Kt
 80% Kr
80%
Tσ (V=10 km)
81.485% D
26 mm φ 0° Ar
5.309*10-4 m2 ρ
60%
計算偵測距離前，必須先知道測距儀的發射功率，已最遠測距為1000公尺之測距儀為例
假設在能見度10 km (Tσ=e R)的情況下，接收鏡組及發射鏡組穿透率皆為80 %，目標物體反射率為60 %，接收光學系統之物鏡直徑為26 mm，其面積Ar為5.309*10-4 m2，考慮垂直入射φ=0°，Prmin同樣以3.162*10-11 W取之，將上述參數代入測距方程式，算出P0約為1W

19. Estimation of Detecting Distance
…………Eq.12
Table 3 The parameters of estimation of detecting distance
Visibility =10 km ( Tσ = e R )
Laser range finder transmitter
Laser countermeasure system receiver λ
905 nm
Prmin
4.23*10-10 W Kt
 80% Kr P0
1 W D θ 1° AΦ
4*10-6 m2 φ 0°
LAPD-2000 PIN Photodiode：
得到測距儀之發射功率後，由表3雷射測距儀發射端及反制系統接收端參數如所示：
雷射測距儀發射端參數為 雷射波長為905 nm 發射組穿透率80% 準值後發散角為1度
考慮垂直入射的狀況
反制系統接收端部分 光偵測器以LAPD-2000為例光敏面元直徑為2mm 面積Aㄈ哀為4*10-6
由於此光偵測器定無給出其頻寬 因此利用此光偵測器量測脈衝雷射之上升時間來推算
上升時間約為60us 換算出頻寬為16MHz
Pmin 由光檢知器之NEP值決定
Eq.9 rewrites as：
…………Eq.13

20. System Structure
This study constructed laser countermeasures system, the first step must be set out basic requirements. They are as follows:
(a) Dual-band receiver and transmitter: 905 nm, 1550 nm
(b) Detect and counter the distance over 1000 m.
TOF pulsed laser range finders measure the distance more than 1000 m. Therefore, this mode of laser range finder become
the counter object.
In-Band mechanism to be a starting point, designing an active-positive deviation counter system.
針對市面上雷射測距儀主要使用之雷射發射波段及偵測距離，定出基本規格，主要規格如下：
A 雙波段發射與接收
B偵測距離與反制距離超過1000
此系統將以帶內( In-band )機制為出發點，設計一有源正偏差同步轉發式雷射測距反制系統。

21. Analyze Time-of-Flight signal
Reflected
beam
Measuring LD PD
Jamming
Fig.11 Analysis of pulsed signal.

22. The Countermeasures System Structure of Laser Range Finder
(1) Infrared Receiver
(3) Processer
PIN Photo
Detector
TIA ＋
AGC
Schmitt Trigger
F to V
Converter
905 nm
1550 nm
(2) Repeater
MCU ＋
ADC
Duplicate
Circuit
Memory
(4) Infrared Transmitter
Laser Diodes
Laser
Drivers
Alarm
&
Display
905 nm
1550 nm
Fig.12 Laser counter measurement structure diagram.

23. Max. Reverse Voltage (V)
Infrared Receiver
Wavelength (nm)
Responsivity (A/W)
Table 4. Specifications of LAPD-2000
LAPD-2000
Max. Reverse Voltage (V) 20
Active Diameter (mm) 2
Wavelength Range (um)  
Dark (nA) 10
Capacitance (pF)
@-5V
200
Responsivity
(A/W)
0.65 μm
0.05
0.85 μm
0.20
1.31 μm
0.90
1.55 μm
0.95
nm (pW/(Hz)1/2)
0.04
Fig.13 Spectral response of LAPD-2000.
Fig.14 Dark capacitance of LAPD-2000.

24. Infrared Receiver-Transimpedance Amplifier (TIA)
式中CD為光二極體之電容，CDIFF為差動輸入電容，CCM為共模輸入電容。
Fig.16 Compensation Capacitance v.s. Feedback Resistance.
Fig.15 Transimpedance Analysis Circuit.
…………Eq.11
…………Eq.12
Fig.17 Bandwidth v.s. Feedback Resistance.

25. Infrared Receiver-Auto Gain Control
Fig.18 Auto gain control Circuit.
AD603 voltage Input range：250 mV~1.4V
According to TIA, output voltage is：
By Eq. 9：

26. Recognition circuit -Inverting Schmitt Trigger
Recognition circuit consists of inverting schmitt trigger、pulse stretching、frequency to voltage 、analog to digital Converter and MCU.
There are two reasons for using inverting schmitt trigger：
(1) Pulse stretching circuit input should be negative-
edge-triggered.
(2)To be the input signals of laser driver circuit.
使用反向史密特觸發器的原因在於可使前級訊號轉換成完整之方波，而反向的目的有二：(1)後級的脈衝展寬電路輸入必須是負源觸發(2)作為雷射驅動調制訊號 VH VN VP VO VI
VP >3V
Fig.19 Transfer characteristic.

27. Recognition circuit-Pulse Stretching
Vcc
(8)Vcc
(4)Reset
(7)Discharge
(6)Threshold
(2)Trigger
(1)GND
(3)Output
(5)Control
Voltage R VC + _ Vo
0.01μF
Vtrigger C
Pulse 100 Hz
Duty 5% 100 Hz
2.5 ms
Duty 95% 1.9 kHz
Fig.20 Monostable mutlivibrator circuit.
…………Eq.12

28. Recognition circuit -Frequency to Voltage
Fig.21 Frequency to voltage converter circuit.
Fig.22 Frequency to voltage transfer diagram

29. Analog to Digital Converter + MCU + LCM
Fig.23 ADC+MCU+LCM circuit

30. Laser Diode Laser Driver
Table 5 Electrical and Optical Characteristics of 980nm laser diode
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
Threshold Current
Ith - 12 20 mA
Operating Current
Iop
Po=25mW 44 70
Operating Voltage
Vop 1
1.5
2.1
Volt
Slope Efficiency η
20mW-10mW
I20mW-I10mW
0.5
0.8
mW/mA
Monitor Current Im
0.1
0.2
Beam Divergence
Parallel
θ// 8 13 18
deg.
(FWHM)
Perpendicular θ⊥ 25 30 35
Lasing Wavelength λ
970
980
990 nm

31. Laser Diode Laser Driver
Fig.24 Optical Output Power v.s. Forward Current
Fig.25 Laser driver circuit

32. Experimental Results and analysis
Fig.26 Bushnell 905 nm laser range finder.
(b)
Fig.28 Transmitting wavefront of 905 nm laser range
finder.
Fig.27 Spectrogram of 905nm laser range finder.

33. Experimental Results and analysis
Laser Rangefinder
Laser Countermeasure System
Fig.30 Wavefronts of Photodiode
and output of SN75451 R
Fig.29 Experimental architecture of laser counter measurement.
Fig.31 Δt between Photodiode
and Voltage output of SN75451
Fig.32 Countermeasure system laser out signal and Voltage output of SN75451

34. Conclusion & Future Work
Presently it has established laser countermeasure system for 905 nm pulsed laser range finder.
Laser countermeasure system using laser diode with wavelength of 980 nm by point-to-point testing, and the experimental results shows that this system can interference laser range finder.
Future Work
(1) Add 1550 nm laser diode into countermeasure system.
(2) Use high power pulsed laser diode and APD photodiode.
(3) Receiver and Transmitter lens.
(4) Calculate time delay.
(5) Test More laser range finder.
此系統主要針對脈衝式雷射測距儀進行反制，目前實驗以點對點近距離的方式進行測試，使用雷射波段為980 nm，可辨識的雷射重頻率為1.9kHz由實驗結果可知反制系統可有效干擾雷射測距儀
1.目前尚未達到雙段波雷射反制系統，未來將加入1550 nm
如欲增加可偵測的距離，可使用靈敏度更高的APD光檢知器，並於檢知器前加入接收鏡組
由於實驗目前可測試的雷射測距儀不多，未來希望可建立出不同型號測距儀之測距頻率資料庫，測試其實用性。