Focus-Variation[1]integrates the small depth of focus of an optical system with vertical scanning to give color and topographical data from the variation of focus. The key component of the system is a precision optic that contains a variety of lens systems that can be fitted with different objectives, enabling measurements with different resolution.
当使用光束分裂的镜子时，将从白光源传来的灯插入系统的光路径，然后通过物镜将其聚焦在样品上。根据样品的版式，一旦通过物镜击中样品后，相同的光被反射到各个方向中。
If diffuse reflective properties are shown by the topography, then the light will be reflected equally strong into each direction. With regard to specular reflections, the light is scattered predominantly into one direction. All the rays arising from the specimen and hitting the objective lens are bundled in the optics and collected by a light sensitive sensor placed at the back of the beam splitting mirror. Only small areas of the object can be clearly imaged because of the small depth of field of the optics.
In order to completely detect the surface with full depth of field, the precision optic is vertically moved along the optical axis while continuously capturing the data from the surface. This way, each area of the object is clearly focused. Algorithms transform the acquired sensor data into 3D data and a true color image with full depth of field. This is obtained by examining the focus variation along the vertical axis.
InfiniteFocus是基于焦点变化的操作原理的3D测量设备。使用此测量设备时，会出现以下技术规范：
垂直分辨率可以低至10 nm，并且依赖于选定的目标。垂直扫描范围取决于物镜的工作距离，范围为4.5至23.5 mm。与常规方法相比，垂直分辨率是无关的扫描高度，并导致垂直分辨率动态1：500000。
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The used objective determines the XY range, which usually ranges from 0.16 mm x 0.16 mm to 5.63 mm x 5.63 mm for one measurement. The XY range can be exceeded up to 100 x 100 mm by using a motorized XY stage and special algorithms.
与其他仅限于同轴照明的光学技术相比，最大可测量的斜率角不仅取决于物镜的数值光圈。Focus-Variation可以使用许多不同的照明源（例如环光）使用，从而实现了超过87°的斜率角度的测量。焦点变化适用于具有大量不同光反射率值的表面。
由于光学技术在使用光方面具有很高的灵活性，因此即使在相同的视野中，也可以避免典型的限制，例如测量具有较大反射特性的表面。从光泽到弥散反射的样本可能有所不同，从光滑到粗糙的表面特性以及从均质到复合材料。焦点变差克服了通过照明的组合，控制综合偏振和传感器参数的组合来克服限制测量能力的方面。调制照明意味着照明的强度是变化而不是恒定的。
A signal generator can create the complex variation of the intensity. Through the continuously changing intensity, much more information is collected from the surface of the specimens.
除了扫描的高度数据之外，焦点变化还提供了具有完整景深的颜色图像，该图像已注册到3D点。这提供了光学彩色图像，该图像就测量场或独特的表面特征的识别和定位就可以简化测量。试样表面的光色图像及其深度信息之间的视觉相关性通常相互连接，因此是有意义的3D测量的重要方面。
由于所描述的方法取决于分析焦点的变化，因此仅与焦点在垂直扫描过程中发生足够变化的表面相关。满足此需求的表面，例如透明的样本或仅有局部粗糙度的组件，几乎是无法衡量的。焦点变化通常为在2 µm的LC处提供可重复的测量结果，其局部RA为0.009 µm
焦点变化技术用于进行高分辨率3D表面测量，以在实验室和生产中的研发活动中进行质量保证。主要应用是表面分析和表征，例如精确制造，工具和霉菌制造，汽车行业，摩擦学，腐蚀，医疗设备开发，电子设备和各种材料科学。欧洲杯足球竞彩欧洲杯线上买球由于其技术规格，焦点变化技术用于测量形式和粗糙度。
Focus-Variation in Comparison
Whenever micro geometric features and surface qualities have to be examined, accurate measurement solutions with high resolution are essential. Focus-Variation, compared to alternative optical technologies, closes the gap between classical surface metrology devices and typical 3D coordinate measuring technology.
配置文件投影仪
图像处理系统在内，包括配置文件投影仪是当前光学测量系统的前身，仍然适用于理解光学测量技术。配置文件投影仪扩大了组件的表面特性，并将图像投影到屏幕上。
将图像与通过图案匹配的合适参考进行比较。好处是可以在几秒钟内进行的测量，尽管几何特征的自动测量仅限于2D应用。对对象对齐的敏感性是一个主要缺点。基于其方向，可以实现不同的测量结果。
Structured Light
Structured light is based on a projector that illuminates the measurement object with a number of dark and bright stripes and then captures it with at least a single camera. The topography of the sample distorts the projector’s stripe pattern; this distorted pattern is recorded with a camera and the topography is finally calculated through image processing.
A main benefit provided by structured light is the high measurement speed obtained when measuring large surfaces. Hence, the technology is mainly used for measuring extremely large parts (e.g. bodywork). However, the technology is limited to high-resolution sub-µm depth measurements as, for instance, with roughness measurements. Moreover, factors like high sensitivity to varying surface characteristics and the low depth of field considerably limit the application range.
共聚焦测量
共聚焦测量由其高横向分辨率定义。Right at the focal point within the detector, an extra aperture is employed to block light from both below and above the focal plane, allowing light within the focal plane to pass through the detector.
通过检测最强的信号深度来测量深度。特别是，共聚焦系统适合测量可以在半导体几何形状或硅结构上找到的高光滑表面。高分辨率在Z中的好处伴随着对振动的敏感性。
White Light Interferometer (WLI)
WLI determines topographical features using interference effects. High vertical resolution is one major advantage. Although it can be difficult to measure rough surfaces, the method can be used for evaluating glass structure and lenses.
Focus-Variation
Focus-Ariation收集深度信息以及表面注册的真实颜色信息。纳米结构和微观结构的粗糙度均基于轮廓和区域。Real3D技术用于从不同角度测量复杂的几何形状，随后将其集成到完整的3D数据集中。
通过测量单个系统中的位置，粗糙度，形式和维度，焦点变化缩小了经典表面计量学和典型的3D坐标测量技术之间的差距。
与轮廓投影仪相比，仅测量组件的3D表面，而不是轮廓。虽然干涉仪和共聚焦系统能够测量系统焦点周围狭窄带中的强度调制或强度峰值，但焦点变化可以测量明显更大的面积的清晰度。因此，该技术对振动更具耐受性。
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[1]ISO 25178-6：几何产品规格（GPS） - 表面纹理：面积 - 第6部分：测量表面纹理，草稿的方法的分类。
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