Visual Requirements for High-Fidelity Display 1
Visual Requirements for High-Fidelity Display 1
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高保真显示的视觉要求 1
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发表时间：
2003
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通讯作者：
M. Flynn
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作者：
M. Flynn
数字放射照相过程包括(a) x射线沿射线形成正射影的衰减，(b)用二维记录设备检测辐射束，(c)处理探测器信号以产生用于呈现的数字图像，以及(d)显示数字图像。该过程的表现通常被认为是根据对解释图像的人呈现重要解剖结构的能力。过程中任何限制对比度、模糊细节或添加噪点的步骤都可能限制解释过程。来自患者的图像信息可能会因产生模糊的大焦点或不适当的峰值电压而产生差的对比度而退化。调制传输特性差的探测器或在x射线信号中添加仪器噪声的探测器可能会降低图像记录的质量。数字图像的显示同样会给信号增加仪表噪声，并进一步限制调制传输。图像形成和射线照相记录过程通常能够记录非常精细的解剖结构，产生非常低的对比度。如果显示没有进一步的退化，这些信号的细节和对比度可以超过人类视觉系统的视觉敏锐度限制。在这种情况下，解译需要某种形式的放大，可以是几何放大，也可以是显示处理放大。本章讨论人类视觉系统的视敏度。眼睛可以检测到的最大空间频率被用来建议显示所需的最大空间频率（即最小图像元素尺寸[像素]和最大显示阵列尺寸）。检测标准测试目标的最小对比度用于解释如何校准显示设备以产生有效的灰度响应。利用全局适应眼的非线性特性，推导出在不同设备上显示数字图像时达到等效外观的条件。
The digital radiographic process involves (a) the attenuation of x rays along rays forming an orthographic projection, (b) the detection of the radiation beam by a two-dimensional recording device, (c) the processing of detector signals to produce a digital image for presentation, and (d) the display of the digital image. The performance of the process is typically considered in terms of the ability to present anatomic structures of importance to the person interpreting the image. Any steps in the process that limit contrast, blur detail, or add noise can limit the interpretative process. Image information from the patient is potentially degraded by large focal spots that produce blur or by inappropriate peak kilovoltage that produces poor contrast. The recording of images is potentially degraded by detectors with poor modulation transfer characteristics or by detectors that add instrument noise to the x-ray signal. Display of the digital image can similarly add instrument noise to the signal and further restrict modulation transfer. The image formation and radiographic recording processes are often capable of recording anatomic structures with very fine detail that produce very low contrast. If displayed with no further degradation, the detail and contrast in these signals can exceed the visual acuity limits of the human vision system. Interpretation in these circumstances requires some form of magnification, either geometric or produced by display processing. The visual acuity of the human vision system is considered in this chapter. The maximum spatial frequency that the eye can detect is used to suggest the maximum spatial frequency that is needed for a display (ie, the minimum picture element size [pixel] and maximum display array size). The minimum contrast to detect standard test targets is used to explain how display devices should be calibrated to produce an effective gray-scale response. The nonlinear characteristics of the globally adapted eye are used to derive conditions to achieve an equivalent appearance of a digital image when it is displayed on different devices.