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当
$f = 36\;{\rm{mm}}$ ,${R_t} = 25\;{\rm{mm}}$ ,$SNR = 7$ ,光斑半径分别取$r = 0.7\; {\rm{mm}}{\text{,}}0.8\; {\rm{mm}}{\text{,}}0.9\; {\rm{mm}}{\text{,}}1\; {\rm{mm}}$ 时,通过MATLAB仿真$\sigma ({E_\psi })$ 与${\psi _f}$ 的关系如图3所示。为更好地分析入射角
${\psi _f}$ 对方位角误差标准差$\sigma ({E_\psi })$ 的影响,根据仿真结果得表1。$\sigma ({E_\psi })$/mrad ${\psi _f}$/rad 0 0.005 0.01 0.015 0.02 r=0.7 mm 2.2445 2.3532 2.6280 2.9541 3.1742 r=0.8 mm 2.5758 2.6716 2.9236 3.2482 3.5453 r=0.9 mm 2.9097 2.9952 3.2263 3.5404 3.8634 r=1 mm 3.2465 3.3236 3.5360 3.8358 4.1659 Table 1. Relationship between
$\sigma ({E_\psi })$ and${\psi _f}$ 由图3知,方位角误差标准差
$\sigma ({E_\psi })$ 关于入射角${\psi _f} = 0$ 对称,当光斑半径$r$ 一定时,$\sigma ({E_\psi })$ 随着${\psi _f}$ 增大而增大,若${\psi _f} = 0$ ,$\sigma ({E_\psi })$ 取最小值,即激光导引头在锁定跟踪阶段,四象限探测器测角精度最大。由表1知,当$r = 1\;{\rm{mm}}$ 时,若${\psi _f} = 0.01\;{\rm{rad}}$ ,则$\sigma ({E_\psi }) = 3.536\;{\rm{mrad}}$ ,即漫反射激光以0.01 rad的角度进入导引头,则方位角误差标准差为3.536 mrad;而若${\psi _f} = 0$ ,则$\sigma ({E_\psi }) = $ 3.246 5 mrad,即激光导引头跟踪上目标时,方位角误差标准差约为3.246 5 mrad。当入射角${\psi _f}$ 一定时,$\sigma ({E_\psi })$ 随着$r$ 增大而增大,即增大光斑半径$r$ 会使方位角误差标准差$\sigma ({E_\psi })$ 增大,所以可通过调节导引头光学系统结构减小光斑半径,进而提高四象限探测器测角精度,但是光斑半径$r$ 减小,导引头视场范围也减小,所以在光学系统设计中,要综合四象限探测器测角精度和视场范围确定光斑半径以及光敏面半径。 -
激光制导过程中,从激光导引头探测到制导信号至导引头进入盲区,信噪比
$SNR$ 逐渐增大。当f = 36 mm,Rt = 25 mm,r = 1 mm,${\psi _f}$ 分别取${\psi _f} = $ 0 rad, 0.02 rad, 0.03 rad时,通过MATLAB仿真$\sigma ({E_\psi })$ 与$SNR$ 的关系如图4所示。为更好地分析信噪比
$SNR$ 对方位角误差标准差$\sigma ({E_\psi })$ 的影响,根据仿真结果得表2。$\sigma ({E_\psi })$/mrad SNR 10 30 50 70 90 ${\psi _f} = 0\;$ 2.272 6 0.757 5 0.4545 0.3247 0.2525 ${\psi _f} = 0.02\;$ 2.684 9 0.895 0 0.5370 0.3836 0.2983 ${\psi _f} = 0.03\;$ 3.120 6 1.040 2 0.6241 0.4458 0.3467 Table 2. Relationship between
$\sigma ({E_\psi })$ and$SNR$ 由图4知,当入射角
${\psi _f}$ 一定时,方位角误差标准差$\sigma ({E_\psi })$ 随着信噪比$SNR$ 增大而减小。由表2知,当${\psi _f} = 0.02\;{\rm{rad}}$ 时,若$SNR = 30$ ,则$\sigma ({E_\psi }) = 0.895\;{\rm{mrad}}$ ;若$SNR = 90$ ,则$\sigma ({E_\psi }) = 0.289 3\;{\rm{mrad}}$ 。即在激光制导过程中,当光斑半径r= 1 mm,漫反射激光以0.02 rad的角度进入激光导引头时,若$SNR = 30$ ,则方位角误差标准差为0.895 mrad;若信噪比$SNR = 90$ ,则方位角误差标准差为0.298 3 mrad。所以,当激光导引头参数和目标指示器参数确定的情况下,可根据不同作用距离处的信噪比分析四象限探测器测角精度;也可通过增大目标指示器单脉冲能量或降低导引头内部电路噪声干扰,从而提高四象限探测器在指定作用距离处的测角精度。
Modeling research on angle measurement accuracy of four-quadrant detector of laser seeker
doi: 10.3788/IRLA20190453
- Received Date: 2019-11-10
- Rev Recd Date: 2019-12-18
- Available Online: 2020-07-23
- Publish Date: 2020-07-23
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Key words:
- laser seeker /
- four quadrant detector /
- angle measurement accuracy /
- noise interference current
Abstract: The accuracy of the four-quadrant detector on the target directly affects the guidance precision of the laser guided weapon. Therefore, it is very important to study the accuracy of the four-quadrant detector. In this paper, the method of computation and simulation analysis was adopted, based on the uniform distribution of the pulse peak power density at the entrance of the seeker, and the noise interference current obeyed the Gaussian distribution, and the beam deflection angle error model of the laser seeker was established; however, the beam deflection angle error had random probability due to noise interference, so the mean and standard deviation of the beam deflection angle error were used as the measurement of the four-quadrant detector angle measurement accuracy. The relationship was established between the mean and standard deviation of the beam deflection angle error and the optical parameters of the seeker, the spot radius, the incident angle of the diffuse reflection laser, the noise interference current, and the pulse peak power density at the entrance of the seeker. Taking the standard deviation of the deflection angle of the seeker beam as an example, the simulation analysis was carried out in combination with the application background.