Analysis and Suppression of Stray Radiation in Uncooled Thermal Infrared Imaging Spectrometer

Xinlong Xie; Xiaoxiao Zhu; Jiacheng Zhu; Weimin Shen

doi:10.3788/AOS202242.1512006

Acta Optica Sinica, Volume. 42, Issue 15, 1512006(2022)

Analysis and Suppression of Stray Radiation in Uncooled Thermal Infrared Imaging Spectrometer

Xinlong Xie^1,2, Xiaoxiao Zhu^1,2, Jiacheng Zhu^1,2、**, and Weimin Shen^1,2、*

¹Key Lab of Modern Optical Technologies of Education Ministry of China, School of Optoelectronic Science and Engineering, Soochow University, Suzhou 215006, Jiangsu , China

²Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province, School of Optoelectronic Science and Engineering, Soochow University, Suzhou 215006, Jiangsu , China

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Figures & Tables(14)

Fig. 1. Light path diagram of spectrometer

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Fig. 2. MTF curve of spectrometer

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Fig. 3. Spot diagram of spectrometer

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Fig. 4. Structural model of optical machine

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Fig. 5. Working principle of infrared focal plane array

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Fig. 6. NETD of infrared focal plane array varying with F number of system

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$Diffraction efficiency of grating$

Fig. 7. Diffraction efficiency of grating

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Fig. 8. Total NETD varying with F number of system

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Fig. 9. Partition of image plane

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Fig. 10. Simulation results of using linear relationship between pixels to remove noise. (a) Image plane when signal is submerged; (b) image plane after denoising by algorithm; (c) ideal image plane

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Table 1. Parameter indexes of spectrometer
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Table 1. Parameter indexes of spectrometer
Parameter Value
F number 2
Focal length f /mm 60
Wavelength /μm 7-14
Spectral resolution /nm 100
Pixel size /μm 25
Field of view /（°） 3.48
Image size（mm×mm） 3.84×1.75

Table 2. Parameters of uncooled infrared focal plane array^[13]

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Table 2. Parameters of uncooled infrared focal plane array^[13]

Parameter	Value	Parameter	Value
Image array size（x_c×x_l）	384×288	Thermal capacity C	$4.34 \times 10^{- 10}$
Pixel area A /m²	$6.25 \times 10^{- 10}$	Thermal conduction $G$ /（W·K^-1）	$5 \times 10^{- 8}$
Pixel fill factor $β$	$0.7$	Temperature contrast $\frac{Δ P}{Δ T} /$ （W·K^-1·m^-2）	$2.426$
Bias voltage $U_{b i a s}$ /V	$2$	Boltzmann constant $k$ /（J·K^-1）	$1 \times 10^{- 23}$
Image read-out frequency $f_{i}$ /Hz	$50$	Absorption in wavelength range of 7-14 μm $ε$ _7-14	$0.90$
Transmission of system in wavelength range of 7-14 μm $ϕ$ _7-14	$0.7$	Uniformity correction frequency $f_{s}$ /Hz	$1.66 \times 10^{- 2}$
1/f noise constant $K$ /m³	$4.0 \times 10^{- 29}$	Resistance $R$ /Ω	$2.6 \times 10^{4}$
Volume of vanadium oxide material $υ$ /m³	$3.5 \times 10^{- 17}$	Temperature coefficient of resistance $α$	$0.02$
Total noise voltage of ROIC $V_{R O I C}$ /V	$1.4 \times 10^{- 6}$	Infrared modulation frequency $ω$ /Hz	$30$
Bolometer temperature T /K	300	Input referred noise voltage of ROIC V_amp /V	$0.8 \times 10^{- 6}$
Noise voltage of each analogue-to-digital converter V_ADC /V	$5.7 \times 10^{- 7}$	Current noise from ROIC input including bolometer bias current source I_ROIC /A	$8.0 \times 10^{- 11}$

Table 3. Optical properties of system components

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Table 3. Optical properties of system components

Component		Treatment method
Component		Brighten surface	Blacken surface	Surface with black nickel
Baffle（300 K）	Vanes	Reflectivity：0.98，absorptivity：0.01，scattering rate：0.01
Foreoptics（300 K）	M1	Reflectivity：0.95，absorptivity：0.03，scattering rate：0.02
	M2
	M3
	Mechanical wall	Reflectivity：0.94， absorptivity：0.05， scattering rate：0.01	Reflectivity：0.05， absorptivity：0.90， scattering rate：0.05	Reflectivity：0.40， absorptivity：0.20， scattering rate：0.40
Slit（193 K）		Reflectivity：0.05，absorptivity：0.90，scattering：0.05
Spectrometer（300 K）	Spherical mirror	Reflectivity：0.95，absorptivity：0.03，scattering rate：0.02
	Convex grating	Reflectivity：0.90，absorptivity：0.10 （order：1，grating constant：0.74 mm）
	Mechanical wall	Absorptivity：0.05， reflectivity：0.94， scattering rate：0.01	Absorptivity：0.90， reflectivity：0.05， scattering rate：0.05	Absorptivity：0.20， reflectivity：0.40， scattering rate：0.40

Table 4. Analysis result of stray radiation

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Table 4. Analysis result of stray radiation

Stray light source	Stray radiation of blacken surface /（W·mm^-2）	Stray radiation of surface with black nickel /（W·mm^-2）	Stray radiation of polished surface /（W·mm^-2）
Foreoptics	3.930×10^-9	5.330×10^-10	9.362×10^-9
Slit	7.940×10^-7	1.570×10^-6	4.370×10^-6
Spectrometer	1.710×10^-4	1.290×10^-4	5.910×10^-5
Grating	7.820×10^-7	2.830×10^-6	1.160×10^-5

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Xinlong Xie, Xiaoxiao Zhu, Jiacheng Zhu, Weimin Shen. Analysis and Suppression of Stray Radiation in Uncooled Thermal Infrared Imaging Spectrometer[J]. Acta Optica Sinica, 2022, 42(15): 1512006

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