Effective cathode diameter (ECD) is an important index of low-light-level (LLL) image intensifier. The traditional evaluation method of this index is based on subjective observation. Professional testers observe the output image of image intensifier through microscope, and give the evaluation results according to the calibration target and their visual perception. The drawback is that the tester has to zoom the effective field of view and rotate the scale target to make evaluation, so the subjectivity is strong and the manpower is considerable. To address these problems, an objective evaluation method of ECD of LLL image intensifier is proposed, which realizes the digital measurement of the index. This method mainly composes of three parts: extracting effective anode edge (EAE), locating effective cathode center (ECC), and calculating ECD scale length. The anode output image of image intensifier is the target image. The specific implementations of this method comprise: first, extract EAE from the target image using the proposed edge extraction strategy. The square area containing the target central square (TCS) is the region of interest (ROI). Then, use the edge corner detection strategy based on neighborhood edge slope features to extract edge corners from ROI edge image. TCS corners are distinguished from other corners by their salient features, which are utilized to generate ECC. The pixel length of ECD is calculated by EAE and ECC. After that, compute the scale length of the circle diameter where the scale is located by using the proposed basic scale positioning strategy, and the conversion unit between pixels and millimeters is derived. Finally, deduce the scale length of ECD relying on the “pixel/mm” conversion unit and the pixel length of ECD. To verify the performance of this method, different types of image tubes are adopted for experiments. The results show that this method is robust to tube type, image brightness and effective anode field of view, and the calculated key parameters are in good agreement with the actual results. In addition, by comparing with the subjective evaluation method, the feasibility of this method is investigated. The results show that the objective evaluation results are consistent with the subjective judgment results, with a higher accuracy (0.001 mm). Moreover, the repeatability experimental results demonstrate that this method is more stable than the subjective evaluation method (the maximum deviation of evaluation results is 0.08 mm). In general, the presented objective evaluation method can be regarded as a reasonable alternative to the traditional ECD evaluation method for LLL image intensifier.

有效阴极直径 (ECD) 是弱光级 (LLL) 图像增强器的重要指标。该指标的传统评价方法是基于主观观察。专业测试人员通过显微镜观察图像增强器的输出图像，并根据校准目标和他们的视觉感知给出评估结果。缺点是测试者必须放大有效视场和旋转尺度目标进行评价，主观性强，人力可观。针对这些问题，提出了一种微光像增强器ECD的客观评价方法，实现了指标的数字化测量。该方法主要由三部分组成：提取有效阳极边缘（EAE）、定位有效阴极中心（ECC）、并计算 ECD 标尺长度。图像增强器的阳极输出图像为目标图像。该方法的具体实现包括：首先，利用提出的边缘提取策略从目标图像中提取EAE。包含目标中心正方形 (TCS) 的正方形区域是感兴趣区域 (ROI)。然后，使用基于邻域边缘斜率特征的边角检测策略从ROI边缘图像中提取边角。TCS 角通过其显着特征与其他角区分开来，这些特征用于生成 ECC。ECD 的像素长度由 EAE 和 ECC 计算。然后，利用提出的基本尺度定位策略，计算出尺度所在圆直径的尺度长度，推导出像素和毫米之间的转换单位。最后，依靠“pixel/mm”转换单位和ECD的像素长度推导出ECD的尺度长度。为了验证该方法的性能，采用不同类型的显像管进行实验。结果表明，该方法对管型、图像亮度和阳极有效视场具有鲁棒性，计算的关键参数与实际结果吻合较好。此外，通过与主观评价方法的比较，考察了该方法的可行性。结果表明，客观评价结果与主观判断结果一致，准确度更高（0.001 mm）。此外，重复性实验结果表明，该方法比主观评价方法更稳定（评价结果的最大偏差为0.08 mm）。一般来说，