同源双光路能见度仪是一种基于数字摄像法的能见度仪。通过CCD传感器获取的光源亮度是光斑提取算法及能见度反演模型的重要组成部分,而背景光噪声严重影响能见度反演准确性。针对复杂背景光干扰下能见度反演出现的较大误差,运用幅度调制方法重新设计调制光源,并对CCD采集的图片进行解调,以有效消除背景光。实验结果表明:光源幅度调制方法能有效去除背景光,并可消除随机噪声和相机暗电流噪声;当调制点数范围为32~128时,图像去噪效果较好,去噪后光斑图像峰值信噪比大于30;在上述调制点范围内,点数越大,峰值信噪比越大,则均方根误差越小。调制点数范围为32~128时,所提方法能显著提高能见度反演精度。

Homologous dual-light-path visibility instrument is a visibility instrument based on digital camera method. The brightness of the light source obtained by the CCD sensor is an important part of the spot extraction algorithm and the visibility inversion model. The background light noise seriouly affects accuracy of visibility inversion. Aiming at the large error of visibility inversion under complex background light disturbance, we use the amplitude modulation method to redesign the modulated light source, and demodulate the CCD image so that the background light is eliminated effectively. The experimental results show that the light source amplitude modulation method can effectively remove the background light, the random noise, and the dark noise of the camera. When the modulation points are within 32 to 128, the image denoising effect is good and the peak signal-noise-ratio (PSNR) of the speckle image after denoising is greater than 30. In this modulation point range, the larger the number of modulation is, the larger the PSNR is and the smaller the root mean square error is. Inversion accuracy of the visibility is greatly improved in the range of the above modulation points, which means that the amplitude modulation method can significantly improve the accuracy of visibility inversion.