一种面阵成像光谱相机空间分辨力的精确测量方法

储松南, 刘海涛, 胡奇琪, 等. 一种面阵成像光谱相机空间分辨力的精确测量方法[J]. 光电工程, 2019, 46(11): 180458. doi: 10.12086/oee.2019.180458
引用本文: 储松南, 刘海涛, 胡奇琪, 等. 一种面阵成像光谱相机空间分辨力的精确测量方法[J]. 光电工程, 2019, 46(11): 180458. doi: 10.12086/oee.2019.180458
Chu Songnan, Liu Haitao, Hu Qiqi, et al. An accurate measurement method for the spatial resolution of area array spectral imaging equipment[J]. Opto-Electronic Engineering, 2019, 46(11): 180458. doi: 10.12086/oee.2019.180458
Citation: Chu Songnan, Liu Haitao, Hu Qiqi, et al. An accurate measurement method for the spatial resolution of area array spectral imaging equipment[J]. Opto-Electronic Engineering, 2019, 46(11): 180458. doi: 10.12086/oee.2019.180458

一种面阵成像光谱相机空间分辨力的精确测量方法

  • 基金项目:
    国家重点研发计划基金资助项目(2017YFC0803806);现场物证溯源技术国家工程实验室开放课题基金资助项目(2017NELKFKT04)
详细信息
    作者简介:
    通讯作者: 骆永全(1974-),男,硕士,研究员,主要从事光束精密控制的研究。E-mail: uestcaep@126.com
  • 中图分类号: TB872

An accurate measurement method for the spatial resolution of area array spectral imaging equipment

  • Fund Project: Supported by National Key R & D Program of China (2017YFC0803806) and National Engineering Laboratory for Forensic Science Open Object Fund (2017NELKFKT04)
More Information
  • 目前在光谱成像领域建立由空间分辨力的量化测量方法,但在探测器分辨能力不足时,其存在测量时成像位置不同带来测量结果不同的现象。本文提出了一种适用于面阵成像光谱相机空间分辨力的精密测量方法,其基于黑白线对在精密平移下的光谱图像,绘制出单个像素的灰度随位移的变化曲线,理论上通过曲线的分割可获得各种可能成像位置下灰度随像素的分布结果,在实际操作时可仅通过一种曲线分割取点,直接得到各成像位置均能分辨的线对密度值。该方法有效地避免了现有方法在探测器分辨能力不足时的缺陷,通过对一台面成像光谱相机的实验测量验证了其可行性。

  • Overview: Spatial resolution is an important performance parameter of digital imaging equipment. At present, the commonly used laboratory measurement method for human eyes is to interpret the image of the spatial resolution testing board. In the field of spectral imaging, a quantitative measurement method of spatial resolution based on data processing has been established. The spectral image of black-white line pair resolution testing board is taken in this method. If the ratio of the adjacent gray peak value and gray valley value (PVR) corresponding to the black-white line pair on the image is larger than $\sqrt 2 $, the line pair can be distinguished. However, when the detector is not capable of resolving the targets, the method has the phenomenon of different measurement results caused by different imaging locations, which will make the results obtained by different experiments difficult to be consistent. In order to solve the above problems, this paper proposes an accurate measurement method for the spatial resolution of the camera of array spectral imaging. By taking a series of spectral images of black-white line pairs under continuous precision displacement, the curve of variation of gray level with displacement of two adjacent pixels in the translation direction is drawn. If the difference in pixel sizes is ignored, the spacing between two curves in the translation direction corresponds to the imaging range value of a single pixel. With arbitrary points as the starting point and with the imaging range value of a single pixel as the space to segment the smooth gray level curve of a single pixel varying with displacement, the distribution results of gray level with pixel in various possible imaging locations can be obtained theoretically. Then, the minimum value of PVR value is found. If the minimum value is greater than $\sqrt 2 $, the black-white line pair can be distinguished at all imaging locations. If the minimum value is less than $\sqrt 2 $, the black-white line pair cannot be distinguished at the some imaging locations. As the gray level distribution of the black-white line pair image is close to sinusoidal distribution near Nyquist frequency, the moving step of imaging can be reduced by curve fitting, and the curve of pixel gray level changing with displacement is more smooth. Then, the paper proves that a simple curve segmentation method can directly obtain the minimum PVR value, which significantly reduces the data processing capacity of this method. At last, the feasibility and correctness of the method are verified by the experimental measurement for an area array spectral imaging equipment. This method can effectively avoid the defects of existing methods when the resolution of detector is insufficient, the data processing is relatively simple, and the results are reliable, which is conducive to maintaining the consistency of the measurement results of spatial resolution between different experiments. In addition, this method can also be applied to the accurate measurement of the modulation transfer function of the array imaging system, so as to quickly find the measurement target matching the Nyquist frequency of the system.

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  • 图 1  Nyquist极限频率时三种典型成像结果

    Figure 1.  Three types of typical imging result at Nyquist frequency

    图 2  精密平移下黑白线对的成像结果

    Figure 2.  Imaging results of blackwhite lines with accurate shift

    图 3  尺寸对应关系

    Figure 3.  Dimensional relevance

    图 4  曲线对应分割示例

    Figure 4.  Example for curve division

    图 5  PVR取最小值的曲线分割

    Figure 5.  Curve division for PVR minimum

    图 6  典型情况

    Figure 6.  Typical results

    图 7  图 6对应的分割点右移

    Figure 7.  The results of division points in figure 6 moving to the right

    图 8  测试分辨力板

    Figure 8.  The resolution board for testing

    图 9  成像结果及与黑白线对的对应关系

    Figure 9.  The imaging results and the correspondence of blackwhite lines

    图 10  相邻像素的灰度随位移的变化。(a) 18 lp/mm;(b) 20 lp/mm

    Figure 10.  Gray level variation of adjacent pixels with shift. (a) 18 lp/mm; (b) 20 lp/mm

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出版历程
收稿日期:  2018-09-05
修回日期:  2019-02-22
刊出日期:  2019-11-01

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