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摘要:
为了提高可见光波段(0.3 μm~0.9 μm)高温标定的效率，提出了可见光波段高温标定的简化方法。本文提出了带有曝光时间变量的可见光波段的高温标定模型，通过大量实验发现，RGB相机各个通道的灰度值不仅随曝光时间递增呈线性变化，且随黑体辐射亮度的递增也呈线性变化，进而确定了可见光波段高温标定模型的具体形式。为了求解简化后的可见光波段高温标定模型中的未知数，在两个黑体辐射亮度下，分别采集两个曝光时间下的图像数据，接着，对图像数据进行处理，便可以得到任意曝光时间下的RGB相机高温标定曲线。最后，对本文提出的简化可见光波段高温标定方法与常规按曝光时间进行可见光波段高温标定法进行比较。实验结果表明：R、G、B通道计算值与标定值的相对误差最大值分别为3.38%、2.56%和−1.14%，且各通道的计算值与标定值的相对误差均未超过3.50%。本文提出的数学模型可以有效地简化传统的高温标定法，进而大大缩短了高温标定时间，提高了高温标定的标定效率。
Abstract:To improve the efficiency of high temperature calibration in the visible light band (0.3 μm~0.9 μm), a simplified method for high-temperature calibration is proposed. Firstly, a high-temperature calibration model in the visible light band with exposure time variable is proposed. Based on a large number of experimental data, it is found that the gray value of each channel of an RGB camera varies linearly not only with the increase of exposure time, but also with the increase of black-body radiation brightness. Thus, a specific form of high-temperature calibration model in the visible light band is determined. To solve the unknowns in the simplified high-temperature calibration model in the visible light band, image data at two different exposure times are collected under two levels of black-body radiation brightness, and then the image data is processed to obtain the high-temperature calibration curve of the RGB camera under any exposure time. Finally, the simplified visible light band high-temperature calibration method proposed in this article is compared to the conventional visible light band high-temperature calibration method based on exposure time. The experimental results show that the maximum relative error between the calculated value of the R channel, G channel, B channel and the calibrated values are 3.38%, 2.56%, −1.14%. Moreover, the relative error between the calculated and the calibrated values for each channel does not exceed 3.50%. The mathematical model proposed in this article can effectively simplify the conventional high-temperature calibration method, resulting in a reduced high-temperature calibration time and improving the calibration efficiency.
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Key words:
- visible light band /
- high temperature calibration /
- RGB camera /
- exposure time
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图 1 RGB相机高温标定实验装置
Figure 1. Experimental setup of high temperature calibration for RGB camera
图 2 相机各通道灰度均值随曝光时间的变化曲线
Figure 2. The mean gray values for each channel of camera varying with the exposure time
图 3 相机各通道灰度均值随黑体辐射亮度的变化曲线。(a) R通道；(b) G通道；(c) B通道
Figure 3. The mean gray values for each channel of the camera as a function of the brightness of the blackbody radiation. (a) R channel; (b) G channel; (c) B channel
表 1 在曝光时间一定的条件下RGB相机各通道的斜率与截距值
Table 1. The slope and intercept values of each channel of an RGB camera under certain exposure time
R通道曝光
时间/μsR通道斜率
/(DN·W−1·m2·sr)R通道
截距/DNG通道曝光
时间/μsG通道斜率
/(DN·W−1·m2·sr)G通道
截距/DNB通道曝光
时间/μsB通道斜率
/(DN·W−1·m2·sr)B通道
截距/DN145 2.17 50.58 276 2.52 50.74 137 0.84 53.08 364 5.44 52.79 480 4.37 53.10 444 2.72 55.12 545 8.14 54.70 575 5.24 54.06 534 3.27 55.90 
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表 2 简化标定的9个未知数
Table 2. 9 unknowns for simplified calibration
$ {K_{\rm{r}}} $
（W−1·m2·sr·μs−1）$ {B_{\rm{r}}} $
（W−1·m2·sr·μs−1）$ G_{\rm{r}}^{\rm{noise}} $
（DN）$ {K_{\rm{g}}} $
（W−1·m2·sr·μs−1）$ {B_{\rm{g}}} $
（W−1·m2·sr·μs−1）$ G_{\rm{g}}^{\rm{noise}} $
（DN）$ {K_{\rm{b}}} $
（W−1·m2·sr·μs−1）$ {B_{\rm{b}}} $
（W−1·m2·sr·μs−1）$ G_{\rm{b}}^{\rm{noise}} $
（DN）0.0149 0.0103 49.07 0.0091 0.0112 47.67 0.0061 0.0070 52.10
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表 3 计算值与标定值的相对误差
Table 3. Error between calculated and calibrated values
温度(K) 400 μs 500 μs R(％) G(％) B(％) R(％) G(％) B(％) 973.15 −1.11 0.43 −0.22 2.17 −0.57 0.73 1023.15 0.32 0.91 −0.57 3.38 −0.15 −0.40 1073.15 −0.06 2.56 1.01 0.63 0.38 1.10 1123.15 0.78 2.48 −1.14 −1.98 0.28 −0.89 1173.15 −0.05 2.49 0.03 −2.82 0.53 −0.20 1223.15 −0.18 1.09 0.62 1.15 −0.75 −0.83 1273.15 -- 0.23 0.72 -- −0.00 −0.04 1323.15 -- -- −0.45 -- -- −0.03
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